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Revision 1.448 by root, Sun Jun 23 02:02:24 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
78	with libev.	80	with libev.
79		81
80	Familiarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
82		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
87	these event sources and provide your program with events.	97	these event sources and provide your program with events.
…		…
95	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
171		182
172	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
173		184
174	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
176	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
177		194
178	=item int ev_version_major ()	195	=item int ev_version_major ()
179		196
180	=item int ev_version_minor ()	197	=item int ev_version_minor ()
181		198
…		…
192	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	211	not a problem.
195		212
196	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
198		216
199	assert (("libev version mismatch",	217	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
202		220
…		…
213	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
215		233
216	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
217		235
218	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
224		243
225	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
226		245
227	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
232		251
233	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
234		253
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		255
237	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
246		265
247	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
248	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
249	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
250		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
251	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
252	retries (example requires a standards-compliant C<realloc>).	285	retries.
253		286
254	static void *	287	static void *
255	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
256	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
257	for (;;)	296	for (;;)
258	{	297	{
259	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
260		299
261	if (newptr)	300	if (newptr)
…		…
266	}	305	}
267		306
268	...	307	...
269	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
270		309
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		311
273	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	315	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	327	}
289		328
290	...	329	...
291	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
292		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
293	=back	345	=back
294		346
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		348
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	is I<not> optional in this case, as there is also an C<ev_loop>	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
300		352
301	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
303	not.	355	do not.
304		356
305	=over 4	357	=over 4
306		358
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		360
309	This will initialise the default event loop if it hasn't been initialised	361	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	362	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	363	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
313		371
314	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
315	function.	373	function (or via the C<EV_DEFAULT> macro).
316		374
317	Note that this function is I<not> thread-safe, so if you want to use it	375	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	376	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
320		379
321	The default loop is the only loop that can handle C<ev_signal> and	380	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	381	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	382	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	383	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
327		404
328	The flags argument can be used to specify special behaviour or specific	405	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		407
331	The following flags are supported:	408	The following flags are supported:
…		…
341		418
342	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
343	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
346	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
347	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
348		427
349	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
350		429
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	431	make libev check for a fork in each iteration by enabling this flag.
353		432
354	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
360		440
361	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
363	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
364		444
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	446	environment variable.
367		447
368	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
369		449
370	When this flag is specified, then libev will not attempt to use the	450	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	452	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		454
375	=item C<EVFLAG_SIGNALFD>	455	=item C<EVFLAG_SIGNALFD>
376		456
377	When this flag is specified, then libev will attempt to use the	457	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	459	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	460	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	461	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	462	threads that are not interested in handling them.
383		463
384	Signalfd will not be used by default as this changes your signal mask, and	464	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	465	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
387		482
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		484
390	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		515
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	517	kernels).
423		518
424	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
428		523
429	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	533	and is of course hard to detect.
437		534
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
		545	not least, it also refuses to work with some file descriptors which work
		546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
445		551
446	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
462	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
463	the usage. So sad.	569	the usage. So sad.
464		570
465	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
466	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from
		590	the epoll set), and generally sounds too good to be true. Because, this
		591	being the linux kernel, of course it suffers from a whole new set of
		592	limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to a system wide
		596	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		597	currently requires C<61> of this number. If no aio requests are left, this
		598	backend will be skipped during initialisation.
		599
		600	Most problematic in practise, however, is that not all file descriptors
		601	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		602	files, F</dev/null> and a few others are supported, but ttys do not work
		603	(probably because of a bug), so this is not (yet?) a generic event polling
		604	interface.
		605
		606	To work around this latter problem, the current version of libev uses
		607	epoll as a fallback for file deescriptor types that do not work. Epoll
		608	is used in, kind of, slow mode that hopefully avoids most of its design
		609	problems.
467		610
468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	611	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
469	C<EVBACKEND_POLL>.	612	C<EVBACKEND_POLL>.
470		613
471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	614	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
486		629
487	It scales in the same way as the epoll backend, but the interface to the	630	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	631	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	632	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	633	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	634	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	635	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	636	drops fds silently in similarly hard-to-detect cases.
494		637
495	This backend usually performs well under most conditions.	638	This backend usually performs well under most conditions.
496		639
497	While nominally embeddable in other event loops, this doesn't work	640	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	641	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	658	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		659
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	660	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	661	it's really slow, but it still scales very well (O(active_fds)).
519		662
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	663	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	664	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	665	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	666	might perform better.
528		667
529	On the positive side, with the exception of the spurious readiness	668	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	669	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	670	among the OS-specific backends (I vastly prefer correctness over speed
		671	hacks).
		672
		673	On the negative side, the interface is I<bizarre> - so bizarre that
		674	even sun itself gets it wrong in their code examples: The event polling
		675	function sometimes returns events to the caller even though an error
		676	occurred, but with no indication whether it has done so or not (yes, it's
		677	even documented that way) - deadly for edge-triggered interfaces where you
		678	absolutely have to know whether an event occurred or not because you have
		679	to re-arm the watcher.
		680
		681	Fortunately libev seems to be able to work around these idiocies.
533		682
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	683	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	684	C<EVBACKEND_POLL>.
536		685
537	=item C<EVBACKEND_ALL>	686	=item C<EVBACKEND_ALL>
538		687
539	Try all backends (even potentially broken ones that wouldn't be tried	688	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	689	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	690	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		691
543	It is definitely not recommended to use this flag.	692	It is definitely not recommended to use this flag, use whatever
		693	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		694	at all.
		695
		696	=item C<EVBACKEND_MASK>
		697
		698	Not a backend at all, but a mask to select all backend bits from a
		699	C<flags> value, in case you want to mask out any backends from a flags
		700	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		701
545	=back	702	=back
546		703
547	If one or more of the backend flags are or'ed into the flags value,	704	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	705	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	706	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	707	()> will be tried.
551		708
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	709	Example: Try to create a event loop that uses epoll and nothing else.
579		710
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	711	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	712	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	713	fatal ("no epoll found here, maybe it hides under your chair");
583		714
		715	Example: Use whatever libev has to offer, but make sure that kqueue is
		716	used if available.
		717
		718	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		719
		720	Example: Similarly, on linux, you mgiht want to take advantage of the
		721	linux aio backend if possible, but fall back to something else if that
		722	isn't available.
		723
		724	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		725
584	=item ev_default_destroy ()	726	=item ev_loop_destroy (loop)
585		727
586	Destroys the default loop (frees all memory and kernel state etc.). None	728	Destroys an event loop object (frees all memory and kernel state
587	of the active event watchers will be stopped in the normal sense, so	729	etc.). None of the active event watchers will be stopped in the normal
588	e.g. C<ev_is_active> might still return true. It is your responsibility to	730	sense, so e.g. C<ev_is_active> might still return true. It is your
589	either stop all watchers cleanly yourself I<before> calling this function,	731	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	732	calling this function, or cope with the fact afterwards (which is usually
591	can just ignore the watchers and/or C<free ()> them for example).	733	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		734	for example).
592		735
593	Note that certain global state, such as signal state (and installed signal	736	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	737	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	738	as signal and child watchers) would need to be stopped manually.
596		739
597	In general it is not advisable to call this function except in the	740	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	741	C<ev_loop_new>, but it can also be used on the default loop returned by
		742	C<ev_default_loop>, in which case it is not thread-safe.
		743
		744	Note that it is not advisable to call this function on the default loop
		745	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	746	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	747	and C<ev_loop_destroy>.
601		748
602	=item ev_loop_destroy (loop)	749	=item ev_loop_fork (loop)
603		750
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	This function sets a flag that causes subsequent C<ev_loop> iterations	751	This function sets a flag that causes subsequent C<ev_run> iterations
610	to reinitialise the kernel state for backends that have one. Despite the	752	to reinitialise the kernel state for backends that have one. Despite
611	name, you can call it anytime, but it makes most sense after forking, in	753	the name, you can call it anytime you are allowed to start or stop
612	the child process (or both child and parent, but that again makes little	754	watchers (except inside an C<ev_prepare> callback), but it makes most
613	sense). You I<must> call it in the child before using any of the libev	755	sense after forking, in the child process. You I<must> call it (or use
614	functions, and it will only take effect at the next C<ev_loop> iteration.	756	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
615		757
		758	In addition, if you want to reuse a loop (via this function or
		759	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		760
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	761	Again, you I<have> to call it on I<any> loop that you want to re-use after
617	a fork, I<even if you do not plan to use the loop in the parent>. This is	762	a fork, I<even if you do not plan to use the loop in the parent>. This is
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	763	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	764	during fork.
620		765
621	On the other hand, you only need to call this function in the child	766	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	767	process if and only if you want to use the event loop in the child. If
623	just fork+exec or create a new loop in the child, you don't have to call	768	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	769	call it at all (in fact, C<epoll> is so badly broken that it makes a
		770	difference, but libev will usually detect this case on its own and do a
		771	costly reset of the backend).
625		772
626	The function itself is quite fast and it's usually not a problem to call	773	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	774	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		775
		776	Example: Automate calling C<ev_loop_fork> on the default loop when
		777	using pthreads.
		778
		779	static void
		780	post_fork_child (void)
		781	{
		782	ev_loop_fork (EV_DEFAULT);
		783	}
		784
		785	...
630	pthread_atfork (0, 0, ev_default_fork);	786	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		787
639	=item int ev_is_default_loop (loop)	788	=item int ev_is_default_loop (loop)
640		789
641	Returns true when the given loop is, in fact, the default loop, and false	790	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	791	otherwise.
643		792
644	=item unsigned int ev_iteration (loop)	793	=item unsigned int ev_iteration (loop)
645		794
646	Returns the current iteration count for the loop, which is identical to	795	Returns the current iteration count for the event loop, which is identical
647	the number of times libev did poll for new events. It starts at C<0> and	796	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	797	and happily wraps around with enough iterations.
649		798
650	This value can sometimes be useful as a generation counter of sorts (it	799	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	800	"ticks" the number of loop iterations), as it roughly corresponds with
652	C<ev_prepare> and C<ev_check> calls - and is incremented between the	801	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	802	prepare and check phases.
654		803
655	=item unsigned int ev_depth (loop)	804	=item unsigned int ev_depth (loop)
656		805
657	Returns the number of times C<ev_loop> was entered minus the number of	806	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	807	times C<ev_run> was exited normally, in other words, the recursion depth.
659		808
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	809	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	810	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	811	in which case it is higher.
663		812
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	813	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	etc.), doesn't count as "exit" - consider this as a hint to avoid such	814	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	815	as a hint to avoid such ungentleman-like behaviour unless it's really
		816	convenient, in which case it is fully supported.
667		817
668	=item unsigned int ev_backend (loop)	818	=item unsigned int ev_backend (loop)
669		819
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	820	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	821	use.
…		…
680		830
681	=item ev_now_update (loop)	831	=item ev_now_update (loop)
682		832
683	Establishes the current time by querying the kernel, updating the time	833	Establishes the current time by querying the kernel, updating the time
684	returned by C<ev_now ()> in the progress. This is a costly operation and	834	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	835	is usually done automatically within C<ev_run ()>.
686		836
687	This function is rarely useful, but when some event callback runs for a	837	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	838	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	839	the current time is a good idea.
690		840
691	See also L<The special problem of time updates> in the C<ev_timer> section.	841	See also L</The special problem of time updates> in the C<ev_timer> section.
692		842
693	=item ev_suspend (loop)	843	=item ev_suspend (loop)
694		844
695	=item ev_resume (loop)	845	=item ev_resume (loop)
696		846
697	These two functions suspend and resume a loop, for use when the loop is	847	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	848	loop is not used for a while and timeouts should not be processed.
699		849
700	A typical use case would be an interactive program such as a game: When	850	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	851	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	852	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	853	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
714	without a previous call to C<ev_suspend>.	864	without a previous call to C<ev_suspend>.
715		865
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	866	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	867	event loop time (see C<ev_now_update>).
718		868
719	=item ev_loop (loop, int flags)	869	=item bool ev_run (loop, int flags)
720		870
721	Finally, this is it, the event handler. This function usually is called	871	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	872	after you have initialised all your watchers and you want to start
723	handling events.	873	handling events. It will ask the operating system for any new events, call
		874	the watcher callbacks, and then repeat the whole process indefinitely: This
		875	is why event loops are called I<loops>.
724		876
725	If the flags argument is specified as C<0>, it will not return until	877	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	878	until either no event watchers are active anymore or C<ev_break> was
		879	called.
727		880
		881	The return value is false if there are no more active watchers (which
		882	usually means "all jobs done" or "deadlock"), and true in all other cases
		883	(which usually means " you should call C<ev_run> again").
		884
728	Please note that an explicit C<ev_unloop> is usually better than	885	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	886	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	887	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	888	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	889	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	890	beauty.
734		891
		892	This function is I<mostly> exception-safe - you can break out of a
		893	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		894	exception and so on. This does not decrement the C<ev_depth> value, nor
		895	will it clear any outstanding C<EVBREAK_ONE> breaks.
		896
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	897	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	898	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	899	block your process in case there are no events and will return after one
738	the loop.	900	iteration of the loop. This is sometimes useful to poll and handle new
		901	events while doing lengthy calculations, to keep the program responsive.
739		902
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	903	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	904	necessary) and will handle those and any already outstanding ones. It
742	will block your process until at least one new event arrives (which could	905	will block your process until at least one new event arrives (which could
743	be an event internal to libev itself, so there is no guarantee that a	906	be an event internal to libev itself, so there is no guarantee that a
744	user-registered callback will be called), and will return after one	907	user-registered callback will be called), and will return after one
745	iteration of the loop.	908	iteration of the loop.
746		909
747	This is useful if you are waiting for some external event in conjunction	910	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	911	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	912	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	913	usually a better approach for this kind of thing.
751		914
752	Here are the gory details of what C<ev_loop> does:	915	Here are the gory details of what C<ev_run> does (this is for your
		916	understanding, not a guarantee that things will work exactly like this in
		917	future versions):
753		918
		919	- Increment loop depth.
		920	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	921	- Before the first iteration, call any pending watchers.
		922	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	923	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	924	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	925	- Queue and call all prepare watchers.
		926	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	927	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	928	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	929	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	930	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	931	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	932	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	933	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	934	- Sleep if the I/O and timer collect interval say so.
		935	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	936	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	937	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	938	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	939	- Queue all expired timers.
770	- Queue all expired periodics.	940	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	941	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	942	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	943	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	944	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	945	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	946	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	947	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	948	continue with step LOOP.
		949	FINISH:
		950	- Reset the ev_break status iff it was EVBREAK_ONE.
		951	- Decrement the loop depth.
		952	- Return.
779		953
780	Example: Queue some jobs and then loop until no events are outstanding	954	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	955	anymore.
782		956
783	... queue jobs here, make sure they register event watchers as long	957	... queue jobs here, make sure they register event watchers as long
784	... as they still have work to do (even an idle watcher will do..)	958	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	959	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	960	... jobs done or somebody called break. yeah!
787		961
788	=item ev_unloop (loop, how)	962	=item ev_break (loop, how)
789		963
790	Can be used to make a call to C<ev_loop> return early (but only after it	964	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	965	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	966	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	967	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		968
795	This "unloop state" will be cleared when entering C<ev_loop> again.	969	This "break state" will be cleared on the next call to C<ev_run>.
796		970
797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	971	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		972	which case it will have no effect.
798		973
799	=item ev_ref (loop)	974	=item ev_ref (loop)
800		975
801	=item ev_unref (loop)	976	=item ev_unref (loop)
802		977
803	Ref/unref can be used to add or remove a reference count on the event	978	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	979	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	980	count is nonzero, C<ev_run> will not return on its own.
806		981
807	This is useful when you have a watcher that you never intend to	982	This is useful when you have a watcher that you never intend to
808	unregister, but that nevertheless should not keep C<ev_loop> from	983	unregister, but that nevertheless should not keep C<ev_run> from
809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	984	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	985	before stopping it.
811		986
812	As an example, libev itself uses this for its internal signal pipe: It	987	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	988	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	989	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	990	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	991	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	992	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	993	before, respectively. Note also that libev might stop watchers itself
819	(e.g. non-repeating timers) in which case you have to C<ev_ref>	994	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	995	in the callback).
821		996
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	997	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	998	running when nothing else is active.
824		999
825	ev_signal exitsig;	1000	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	1001	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	1002	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	1003	ev_unref (loop);
829		1004
830	Example: For some weird reason, unregister the above signal handler again.	1005	Example: For some weird reason, unregister the above signal handler again.
831		1006
832	ev_ref (loop);	1007	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	1008	ev_signal_stop (loop, &exitsig);
…		…
853	overhead for the actual polling but can deliver many events at once.	1028	overhead for the actual polling but can deliver many events at once.
854		1029
855	By setting a higher I<io collect interval> you allow libev to spend more	1030	By setting a higher I<io collect interval> you allow libev to spend more
856	time collecting I/O events, so you can handle more events per iteration,	1031	time collecting I/O events, so you can handle more events per iteration,
857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1032	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
858	C<ev_timer>) will be not affected. Setting this to a non-null value will	1033	C<ev_timer>) will not be affected. Setting this to a non-null value will
859	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1034	introduce an additional C<ev_sleep ()> call into most loop iterations. The
860	sleep time ensures that libev will not poll for I/O events more often then	1035	sleep time ensures that libev will not poll for I/O events more often then
861	once per this interval, on average.	1036	once per this interval, on average (as long as the host time resolution is
		1037	good enough).
862		1038
863	Likewise, by setting a higher I<timeout collect interval> you allow libev	1039	Likewise, by setting a higher I<timeout collect interval> you allow libev
864	to spend more time collecting timeouts, at the expense of increased	1040	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	1041	latency/jitter/inexactness (the watcher callback will be called
866	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1042	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1066	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		1067
892	=item ev_invoke_pending (loop)	1068	=item ev_invoke_pending (loop)
893		1069
894	This call will simply invoke all pending watchers while resetting their	1070	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	1071	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	1072	but when overriding the invoke callback this call comes handy. This
		1073	function can be invoked from a watcher - this can be useful for example
		1074	when you want to do some lengthy calculation and want to pass further
		1075	event handling to another thread (you still have to make sure only one
		1076	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		1077
898	=item int ev_pending_count (loop)	1078	=item int ev_pending_count (loop)
899		1079
900	Returns the number of pending watchers - zero indicates that no watchers	1080	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1081	are pending.
902		1082
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1083	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		1084
905	This overrides the invoke pending functionality of the loop: Instead of	1085	This overrides the invoke pending functionality of the loop: Instead of
906	invoking all pending watchers when there are any, C<ev_loop> will call	1086	invoking all pending watchers when there are any, C<ev_run> will call
907	this callback instead. This is useful, for example, when you want to	1087	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1088	invoke the actual watchers inside another context (another thread etc.).
909		1089
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1090	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1091	callback.
912		1092
913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1093	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
914		1094
915	Sometimes you want to share the same loop between multiple threads. This	1095	Sometimes you want to share the same loop between multiple threads. This
916	can be done relatively simply by putting mutex_lock/unlock calls around	1096	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1097	each call to a libev function.
918		1098
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1099	However, C<ev_run> can run an indefinite time, so it is not feasible
920	wait for it to return. One way around this is to wake up the loop via	1100	to wait for it to return. One way around this is to wake up the event
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1101	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1102	I<release> and I<acquire> callbacks on the loop.
923		1103
924	When set, then C<release> will be called just before the thread is	1104	When set, then C<release> will be called just before the thread is
925	suspended waiting for new events, and C<acquire> is called just	1105	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1106	afterwards.
927		1107
…		…
930		1110
931	While event loop modifications are allowed between invocations of	1111	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1112	C<release> and C<acquire> (that's their only purpose after all), no
933	modifications done will affect the event loop, i.e. adding watchers will	1113	modifications done will affect the event loop, i.e. adding watchers will
934	have no effect on the set of file descriptors being watched, or the time	1114	have no effect on the set of file descriptors being watched, or the time
935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1115	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
936	to take note of any changes you made.	1116	to take note of any changes you made.
937		1117
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1118	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1119	invocations of C<release> and C<acquire>.
940		1120
941	See also the locking example in the C<THREADS> section later in this	1121	See also the locking example in the C<THREADS> section later in this
942	document.	1122	document.
943		1123
944	=item ev_set_userdata (loop, void *data)	1124	=item ev_set_userdata (loop, void *data)
945		1125
946	=item ev_userdata (loop)	1126	=item void *ev_userdata (loop)
947		1127
948	Set and retrieve a single C<void *> associated with a loop. When	1128	Set and retrieve a single C<void *> associated with a loop. When
949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1129	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1130	C<0>.
951		1131
952	These two functions can be used to associate arbitrary data with a loop,	1132	These two functions can be used to associate arbitrary data with a loop,
953	and are intended solely for the C<invoke_pending_cb>, C<release> and	1133	and are intended solely for the C<invoke_pending_cb>, C<release> and
954	C<acquire> callbacks described above, but of course can be (ab-)used for	1134	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1135	any other purpose as well.
956		1136
957	=item ev_loop_verify (loop)	1137	=item ev_verify (loop)
958		1138
959	This function only does something when C<EV_VERIFY> support has been	1139	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1140	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1141	through all internal structures and checks them for validity. If anything
962	is found to be inconsistent, it will print an error message to standard	1142	is found to be inconsistent, it will print an error message to standard
…		…
973		1153
974	In the following description, uppercase C<TYPE> in names stands for the	1154	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1155	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1156	watchers and C<ev_io_start> for I/O watchers.
977		1157
978	A watcher is a structure that you create and register to record your	1158	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1159	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1160	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1161	for that:
981		1162
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1163	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1164	{
984	ev_io_stop (w);	1165	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1166	ev_break (loop, EVBREAK_ALL);
986	}	1167	}
987		1168
988	struct ev_loop *loop = ev_default_loop (0);	1169	struct ev_loop *loop = ev_default_loop (0);
989		1170
990	ev_io stdin_watcher;	1171	ev_io stdin_watcher;
991		1172
992	ev_init (&stdin_watcher, my_cb);	1173	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1174	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1175	ev_io_start (loop, &stdin_watcher);
995		1176
996	ev_loop (loop, 0);	1177	ev_run (loop, 0);
997		1178
998	As you can see, you are responsible for allocating the memory for your	1179	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1180	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1181	stack).
1001		1182
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1183	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1184	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1185
1005	Each watcher structure must be initialised by a call to C<ev_init	1186	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1187	*, callback)>, which expects a callback to be provided. This callback is
1007	callback gets invoked each time the event occurs (or, in the case of I/O	1188	invoked each time the event occurs (or, in the case of I/O watchers, each
1008	watchers, each time the event loop detects that the file descriptor given	1189	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1190	and/or writable).
1010		1191
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1192	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1193	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1194	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1195	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1246
1066	=item C<EV_PREPARE>	1247	=item C<EV_PREPARE>
1067		1248
1068	=item C<EV_CHECK>	1249	=item C<EV_CHECK>
1069		1250
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1251	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1252	gather new events, and all C<ev_check> watchers are queued (not invoked)
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1253	just after C<ev_run> has gathered them, but before it queues any callbacks
		1254	for any received events. That means C<ev_prepare> watchers are the last
		1255	watchers invoked before the event loop sleeps or polls for new events, and
		1256	C<ev_check> watchers will be invoked before any other watchers of the same
		1257	or lower priority within an event loop iteration.
		1258
1073	received events. Callbacks of both watcher types can start and stop as	1259	Callbacks of both watcher types can start and stop as many watchers as
1074	many watchers as they want, and all of them will be taken into account	1260	they want, and all of them will be taken into account (for example, a
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1261	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1076	C<ev_loop> from blocking).	1262	blocking).
1077		1263
1078	=item C<EV_EMBED>	1264	=item C<EV_EMBED>
1079		1265
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1266	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1267
1082	=item C<EV_FORK>	1268	=item C<EV_FORK>
1083		1269
1084	The event loop has been resumed in the child process after fork (see	1270	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1271	C<ev_fork>).
		1272
		1273	=item C<EV_CLEANUP>
		1274
		1275	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1276
1087	=item C<EV_ASYNC>	1277	=item C<EV_ASYNC>
1088		1278
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1279	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1280
…		…
1200		1390
1201	=item callback ev_cb (ev_TYPE *watcher)	1391	=item callback ev_cb (ev_TYPE *watcher)
1202		1392
1203	Returns the callback currently set on the watcher.	1393	Returns the callback currently set on the watcher.
1204		1394
1205	=item ev_cb_set (ev_TYPE *watcher, callback)	1395	=item ev_set_cb (ev_TYPE *watcher, callback)
1206		1396
1207	Change the callback. You can change the callback at virtually any time	1397	Change the callback. You can change the callback at virtually any time
1208	(modulo threads).	1398	(modulo threads).
1209		1399
1210	=item ev_set_priority (ev_TYPE *watcher, int priority)	1400	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1228	or might not have been clamped to the valid range.	1418	or might not have been clamped to the valid range.
1229		1419
1230	The default priority used by watchers when no priority has been set is	1420	The default priority used by watchers when no priority has been set is
1231	always C<0>, which is supposed to not be too high and not be too low :).	1421	always C<0>, which is supposed to not be too high and not be too low :).
1232		1422
1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1423	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1234	priorities.	1424	priorities.
1235		1425
1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1426	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1237		1427
1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1428	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1453	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1454	functions that do not need a watcher.
1265		1455
1266	=back	1456	=back
1267		1457
		1458	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1459	OWN COMPOSITE WATCHERS> idioms.
1268		1460
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1461	=head2 WATCHER STATES
1270		1462
1271	Each watcher has, by default, a member C<void *data> that you can change	1463	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1464	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1465	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1466	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1467
1278	struct my_io	1468	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1469
1286	...	1470	=item initialised
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1471
1290	And since your callback will be called with a pointer to the watcher, you	1472	Before a watcher can be registered with the event loop it has to be
1291	can cast it back to your own type:	1473	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1474	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1475
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1476	In this state it is simply some block of memory that is suitable for
1294	{	1477	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1478	will - as long as you either keep the memory contents intact, or call
1296	...	1479	C<ev_TYPE_init> again.
1297	}
1298		1480
1299	More interesting and less C-conformant ways of casting your callback type	1481	=item started/running/active
1300	instead have been omitted.
1301		1482
1302	Another common scenario is to use some data structure with multiple	1483	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1484	property of the event loop, and is actively waiting for events. While in
		1485	this state it cannot be accessed (except in a few documented ways), moved,
		1486	freed or anything else - the only legal thing is to keep a pointer to it,
		1487	and call libev functions on it that are documented to work on active watchers.
1304		1488
1305	struct my_biggy	1489	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1490
1312	In this case getting the pointer to C<my_biggy> is a bit more	1491	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1492	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1493	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1494	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1495	callback.
1317		1496
1318	#include <stddef.h>	1497	The watcher might or might not be active while it is pending (for example,
		1498	an expired non-repeating timer can be pending but no longer active). If it
		1499	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1500	but it is still property of the event loop at this time, so cannot be
		1501	moved, freed or reused. And if it is active the rules described in the
		1502	previous item still apply.
1319		1503
1320	static void	1504	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1505	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1506	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1507
1327	static void	1508	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1509
1329	{	1510	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1511	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1512	latter will clear any pending state the watcher might be in, regardless
1332	}	1513	of whether it was active or not, so stopping a watcher explicitly before
		1514	freeing it is often a good idea.
		1515
		1516	While stopped (and not pending) the watcher is essentially in the
		1517	initialised state, that is, it can be reused, moved, modified in any way
		1518	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1519	it again).
		1520
		1521	=back
1333		1522
1334	=head2 WATCHER PRIORITY MODELS	1523	=head2 WATCHER PRIORITY MODELS
1335		1524
1336	Many event loops support I<watcher priorities>, which are usually small	1525	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1526	integers that influence the ordering of event callback invocation
…		…
1464	In general you can register as many read and/or write event watchers per	1653	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1654	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1655	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1656	required if you know what you are doing).
1468		1657
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarantee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1658	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1659	receive "spurious" readiness notifications, that is, your callback might
1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1660	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1478	because there is no data. Not only are some backends known to create a	1661	because there is no data. It is very easy to get into this situation even
1479	lot of those (for example Solaris ports), it is very easy to get into	1662	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1663	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1664	preferable to a program hanging until some data arrives.
1483		1665
1484	If you cannot run the fd in non-blocking mode (for example you should	1666	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1667	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1668	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1669	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1670	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1671	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1672	indefinitely.
1491		1673
1492	But really, best use non-blocking mode.	1674	But really, best use non-blocking mode.
1493		1675
1494	=head3 The special problem of disappearing file descriptors	1676	=head3 The special problem of disappearing file descriptors
1495		1677
1496	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1678	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1497	descriptor (either due to calling C<close> explicitly or any other means,	1679	a file descriptor (either due to calling C<close> explicitly or any other
1498	such as C<dup2>). The reason is that you register interest in some file	1680	means, such as C<dup2>). The reason is that you register interest in some
1499	descriptor, but when it goes away, the operating system will silently drop	1681	file descriptor, but when it goes away, the operating system will silently
1500	this interest. If another file descriptor with the same number then is	1682	drop this interest. If another file descriptor with the same number then
1501	registered with libev, there is no efficient way to see that this is, in	1683	is registered with libev, there is no efficient way to see that this is,
1502	fact, a different file descriptor.	1684	in fact, a different file descriptor.
1503		1685
1504	To avoid having to explicitly tell libev about such cases, libev follows	1686	To avoid having to explicitly tell libev about such cases, libev follows
1505	the following policy: Each time C<ev_io_set> is being called, libev	1687	the following policy: Each time C<ev_io_set> is being called, libev
1506	will assume that this is potentially a new file descriptor, otherwise	1688	will assume that this is potentially a new file descriptor, otherwise
1507	it is assumed that the file descriptor stays the same. That means that	1689	it is assumed that the file descriptor stays the same. That means that
…		…
1521		1703
1522	There is no workaround possible except not registering events	1704	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1705	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1706	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1707
		1708	=head3 The special problem of files
		1709
		1710	Many people try to use C<select> (or libev) on file descriptors
		1711	representing files, and expect it to become ready when their program
		1712	doesn't block on disk accesses (which can take a long time on their own).
		1713
		1714	However, this cannot ever work in the "expected" way - you get a readiness
		1715	notification as soon as the kernel knows whether and how much data is
		1716	there, and in the case of open files, that's always the case, so you
		1717	always get a readiness notification instantly, and your read (or possibly
		1718	write) will still block on the disk I/O.
		1719
		1720	Another way to view it is that in the case of sockets, pipes, character
		1721	devices and so on, there is another party (the sender) that delivers data
		1722	on its own, but in the case of files, there is no such thing: the disk
		1723	will not send data on its own, simply because it doesn't know what you
		1724	wish to read - you would first have to request some data.
		1725
		1726	Since files are typically not-so-well supported by advanced notification
		1727	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1728	to files, even though you should not use it. The reason for this is
		1729	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1730	usually a tty, often a pipe, but also sometimes files or special devices
		1731	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1732	F</dev/urandom>), and even though the file might better be served with
		1733	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1734	it "just works" instead of freezing.
		1735
		1736	So avoid file descriptors pointing to files when you know it (e.g. use
		1737	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1738	when you rarely read from a file instead of from a socket, and want to
		1739	reuse the same code path.
		1740
1526	=head3 The special problem of fork	1741	=head3 The special problem of fork
1527		1742
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1743	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1744	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1530	it in the child.	1745	to be told about it in the child if you want to continue to use it in the
		1746	child.
1531		1747
1532	To support fork in your programs, you either have to call	1748	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1749	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1750	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1751
1537	=head3 The special problem of SIGPIPE	1752	=head3 The special problem of SIGPIPE
1538		1753
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1754	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1755	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1837	...
1623	struct ev_loop *loop = ev_default_init (0);	1838	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1839	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1840	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1841	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1842	ev_run (loop, 0);
1628		1843
1629		1844
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1845	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1846
1632	Timer watchers are simple relative timers that generate an event after a	1847	Timer watchers are simple relative timers that generate an event after a
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1853	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1854	monotonic clock option helps a lot here).
1640		1855
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1856	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1857	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1858	might introduce a small delay, see "the special problem of being too
		1859	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1860	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1861	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1862	longer true when a callback calls C<ev_run> recursively).
1647		1863
1648	=head3 Be smart about timeouts	1864	=head3 Be smart about timeouts
1649		1865
1650	Many real-world problems involve some kind of timeout, usually for error	1866	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1867	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1942
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1943	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1944	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1945	within the callback:
1730		1946
		1947	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1948	ev_tstamp last_activity; // time of last activity
		1949	ev_timer timer;
1732		1950
1733	static void	1951	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1952	callback (EV_P_ ev_timer *w, int revents)
1735	{	1953	{
1736	ev_tstamp now = ev_now (EV_A);	1954	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1955	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1956
1739	// if last_activity + 60. is older than now, we did time out	1957	// if negative, it means we the timeout already occurred
1740	if (timeout < now)	1958	if (after < 0.)
1741	{	1959	{
1742	// timeout occurred, take action	1960	// timeout occurred, take action
1743	}	1961	}
1744	else	1962	else
1745	{	1963	{
1746	// callback was invoked, but there was some activity, re-arm	1964	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1965	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1966	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1967	// the timeout can occur.
		1968	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1969	ev_timer_start (EV_A_ w);
1751	}	1970	}
1752	}	1971	}
1753		1972
1754	To summarise the callback: first calculate the real timeout (defined	1973	To summarise the callback: first calculate in how many seconds the
1755	as "60 seconds after the last activity"), then check if that time has	1974	timeout will occur (by calculating the absolute time when it would occur,
1756	been reached, which means something I<did>, in fact, time out. Otherwise	1975	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1757	the callback was invoked too early (C<timeout> is in the future), so	1976	(EV_A)> from that).
1758	re-schedule the timer to fire at that future time, to see if maybe we have
1759	a timeout then.
1760		1977
1761	Note how C<ev_timer_again> is used, taking advantage of the	1978	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1979	timed out, and need to do whatever is needed in this case.
		1980
		1981	Otherwise, we now the earliest time at which the timeout would trigger,
		1982	and simply start the timer with this timeout value.
		1983
		1984	In other words, each time the callback is invoked it will check whether
		1985	the timeout occurred. If not, it will simply reschedule itself to check
		1986	again at the earliest time it could time out. Rinse. Repeat.
1763		1987
1764	This scheme causes more callback invocations (about one every 60 seconds	1988	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1989	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1990	libev to change the timeout.
1767		1991
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1992	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1993	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1994	now), then call the callback, which will "do the right thing" and start
		1995	the timer:
1771		1996
		1997	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	1998	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	1999	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		2000
1776	And when there is some activity, simply store the current time in	2001	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	2002	C<last_activity>, no libev calls at all:
1778		2003
		2004	if (activity detected)
1779	last_activity = ev_now (loop);	2005	last_activity = ev_now (EV_A);
		2006
		2007	When your timeout value changes, then the timeout can be changed by simply
		2008	providing a new value, stopping the timer and calling the callback, which
		2009	will again do the right thing (for example, time out immediately :).
		2010
		2011	timeout = new_value;
		2012	ev_timer_stop (EV_A_ &timer);
		2013	callback (EV_A_ &timer, 0);
1780		2014
1781	This technique is slightly more complex, but in most cases where the	2015	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	2016	time-out is unlikely to be triggered, much more efficient.
1783
1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
1785	callback :) - just change the timeout and invoke the callback, which will
1786	fix things for you.
1787		2017
1788	=item 4. Wee, just use a double-linked list for your timeouts.	2018	=item 4. Wee, just use a double-linked list for your timeouts.
1789		2019
1790	If there is not one request, but many thousands (millions...), all	2020	If there is not one request, but many thousands (millions...), all
1791	employing some kind of timeout with the same timeout value, then one can	2021	employing some kind of timeout with the same timeout value, then one can
…		…
1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2048	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1819	rather complicated, but extremely efficient, something that really pays	2049	rather complicated, but extremely efficient, something that really pays
1820	off after the first million or so of active timers, i.e. it's usually	2050	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	2051	overkill :)
1822		2052
		2053	=head3 The special problem of being too early
		2054
		2055	If you ask a timer to call your callback after three seconds, then
		2056	you expect it to be invoked after three seconds - but of course, this
		2057	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2058	guaranteed to any precision by libev - imagine somebody suspending the
		2059	process with a STOP signal for a few hours for example.
		2060
		2061	So, libev tries to invoke your callback as soon as possible I<after> the
		2062	delay has occurred, but cannot guarantee this.
		2063
		2064	A less obvious failure mode is calling your callback too early: many event
		2065	loops compare timestamps with a "elapsed delay >= requested delay", but
		2066	this can cause your callback to be invoked much earlier than you would
		2067	expect.
		2068
		2069	To see why, imagine a system with a clock that only offers full second
		2070	resolution (think windows if you can't come up with a broken enough OS
		2071	yourself). If you schedule a one-second timer at the time 500.9, then the
		2072	event loop will schedule your timeout to elapse at a system time of 500
		2073	(500.9 truncated to the resolution) + 1, or 501.
		2074
		2075	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2076	501" and invoke the callback 0.1s after it was started, even though a
		2077	one-second delay was requested - this is being "too early", despite best
		2078	intentions.
		2079
		2080	This is the reason why libev will never invoke the callback if the elapsed
		2081	delay equals the requested delay, but only when the elapsed delay is
		2082	larger than the requested delay. In the example above, libev would only invoke
		2083	the callback at system time 502, or 1.1s after the timer was started.
		2084
		2085	So, while libev cannot guarantee that your callback will be invoked
		2086	exactly when requested, it I<can> and I<does> guarantee that the requested
		2087	delay has actually elapsed, or in other words, it always errs on the "too
		2088	late" side of things.
		2089
1823	=head3 The special problem of time updates	2090	=head3 The special problem of time updates
1824		2091
1825	Establishing the current time is a costly operation (it usually takes at	2092	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2093	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2094	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2095	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2096	lots of events in one iteration.
1830		2097
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2098	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	2099	time. This is usually the right thing as this timestamp refers to the time
1833	of the event triggering whatever timeout you are modifying/starting. If	2100	of the event triggering whatever timeout you are modifying/starting. If
1834	you suspect event processing to be delayed and you I<need> to base the	2101	you suspect event processing to be delayed and you I<need> to base the
1835	timeout on the current time, use something like this to adjust for this:	2102	timeout on the current time, use something like the following to adjust
		2103	for it:
1836		2104
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2105	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1838		2106
1839	If the event loop is suspended for a long time, you can also force an	2107	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2108	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2109	()>, although that will push the event time of all outstanding events
		2110	further into the future.
		2111
		2112	=head3 The special problem of unsynchronised clocks
		2113
		2114	Modern systems have a variety of clocks - libev itself uses the normal
		2115	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2116	jumps).
		2117
		2118	Neither of these clocks is synchronised with each other or any other clock
		2119	on the system, so C<ev_time ()> might return a considerably different time
		2120	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2121	a call to C<gettimeofday> might return a second count that is one higher
		2122	than a directly following call to C<time>.
		2123
		2124	The moral of this is to only compare libev-related timestamps with
		2125	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2126	a second or so.
		2127
		2128	One more problem arises due to this lack of synchronisation: if libev uses
		2129	the system monotonic clock and you compare timestamps from C<ev_time>
		2130	or C<ev_now> from when you started your timer and when your callback is
		2131	invoked, you will find that sometimes the callback is a bit "early".
		2132
		2133	This is because C<ev_timer>s work in real time, not wall clock time, so
		2134	libev makes sure your callback is not invoked before the delay happened,
		2135	I<measured according to the real time>, not the system clock.
		2136
		2137	If your timeouts are based on a physical timescale (e.g. "time out this
		2138	connection after 100 seconds") then this shouldn't bother you as it is
		2139	exactly the right behaviour.
		2140
		2141	If you want to compare wall clock/system timestamps to your timers, then
		2142	you need to use C<ev_periodic>s, as these are based on the wall clock
		2143	time, where your comparisons will always generate correct results.
1842		2144
1843	=head3 The special problems of suspended animation	2145	=head3 The special problems of suspended animation
1844		2146
1845	When you leave the server world it is quite customary to hit machines that	2147	When you leave the server world it is quite customary to hit machines that
1846	can suspend/hibernate - what happens to the clocks during such a suspend?	2148	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1876		2178
1877	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2179	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1878		2180
1879	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2181	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1880		2182
1881	Configure the timer to trigger after C<after> seconds. If C<repeat>	2183	Configure the timer to trigger after C<after> seconds (fractional and
1882	is C<0.>, then it will automatically be stopped once the timeout is	2184	negative values are supported). If C<repeat> is C<0.>, then it will
1883	reached. If it is positive, then the timer will automatically be	2185	automatically be stopped once the timeout is reached. If it is positive,
1884	configured to trigger again C<repeat> seconds later, again, and again,	2186	then the timer will automatically be configured to trigger again C<repeat>
1885	until stopped manually.	2187	seconds later, again, and again, until stopped manually.
1886		2188
1887	The timer itself will do a best-effort at avoiding drift, that is, if	2189	The timer itself will do a best-effort at avoiding drift, that is, if
1888	you configure a timer to trigger every 10 seconds, then it will normally	2190	you configure a timer to trigger every 10 seconds, then it will normally
1889	trigger at exactly 10 second intervals. If, however, your program cannot	2191	trigger at exactly 10 second intervals. If, however, your program cannot
1890	keep up with the timer (because it takes longer than those 10 seconds to	2192	keep up with the timer (because it takes longer than those 10 seconds to
1891	do stuff) the timer will not fire more than once per event loop iteration.	2193	do stuff) the timer will not fire more than once per event loop iteration.
1892		2194
1893	=item ev_timer_again (loop, ev_timer *)	2195	=item ev_timer_again (loop, ev_timer *)
1894		2196
1895	This will act as if the timer timed out and restart it again if it is	2197	This will act as if the timer timed out, and restarts it again if it is
1896	repeating. The exact semantics are:	2198	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2199	timeout to the C<repeat> value and calling C<ev_timer_start>.
1897		2200
		2201	The exact semantics are as in the following rules, all of which will be
		2202	applied to the watcher:
		2203
		2204	=over 4
		2205
1898	If the timer is pending, its pending status is cleared.	2206	=item If the timer is pending, the pending status is always cleared.
1899		2207
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2208	=item If the timer is started but non-repeating, stop it (as if it timed
		2209	out, without invoking it).
1901		2210
1902	If the timer is repeating, either start it if necessary (with the	2211	=item If the timer is repeating, make the C<repeat> value the new timeout
1903	C<repeat> value), or reset the running timer to the C<repeat> value.	2212	and start the timer, if necessary.
1904		2213
		2214	=back
		2215
1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2216	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1906	usage example.	2217	usage example.
1907		2218
1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2219	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1909		2220
1910	Returns the remaining time until a timer fires. If the timer is active,	2221	Returns the remaining time until a timer fires. If the timer is active,
…		…
1949	}	2260	}
1950		2261
1951	ev_timer mytimer;	2262	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2263	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2264	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2265	ev_run (loop, 0);
1955		2266
1956	// and in some piece of code that gets executed on any "activity":	2267	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2268	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2269	ev_timer_again (&mytimer);
1959		2270
…		…
1963	Periodic watchers are also timers of a kind, but they are very versatile	2274	Periodic watchers are also timers of a kind, but they are very versatile
1964	(and unfortunately a bit complex).	2275	(and unfortunately a bit complex).
1965		2276
1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2277	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1967	relative time, the physical time that passes) but on wall clock time	2278	relative time, the physical time that passes) but on wall clock time
1968	(absolute time, the thing you can read on your calender or clock). The	2279	(absolute time, the thing you can read on your calendar or clock). The
1969	difference is that wall clock time can run faster or slower than real	2280	difference is that wall clock time can run faster or slower than real
1970	time, and time jumps are not uncommon (e.g. when you adjust your	2281	time, and time jumps are not uncommon (e.g. when you adjust your
1971	wrist-watch).	2282	wrist-watch).
1972		2283
1973	You can tell a periodic watcher to trigger after some specific point	2284	You can tell a periodic watcher to trigger after some specific point
…		…
1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2289	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1979	it, as it uses a relative timeout).	2290	it, as it uses a relative timeout).
1980		2291
1981	C<ev_periodic> watchers can also be used to implement vastly more complex	2292	C<ev_periodic> watchers can also be used to implement vastly more complex
1982	timers, such as triggering an event on each "midnight, local time", or	2293	timers, such as triggering an event on each "midnight, local time", or
1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2294	other complicated rules. This cannot easily be done with C<ev_timer>
1984	those cannot react to time jumps.	2295	watchers, as those cannot react to time jumps.
1985		2296
1986	As with timers, the callback is guaranteed to be invoked only when the	2297	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2298	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2299	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2300	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2301	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2302
1992	=head3 Watcher-Specific Functions and Data Members	2303	=head3 Watcher-Specific Functions and Data Members
1993		2304
1994	=over 4	2305	=over 4
1995		2306
…		…
2030		2341
2031	Another way to think about it (for the mathematically inclined) is that	2342	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2343	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2344	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2345
2035	For numerical stability it is preferable that the C<offset> value is near	2346	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2347	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2348	microseconds) and C<offset> should be higher than C<0> and should have
		2349	at most a similar magnitude as the current time (say, within a factor of
		2350	ten). Typical values for offset are, in fact, C<0> or something between
		2351	C<0> and C<interval>, which is also the recommended range.
2038		2352
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2353	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2354	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2355	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2356	millisecond (if the OS supports it and the machine is fast enough).
…		…
2072		2386
2073	NOTE: I<< This callback must always return a time that is higher than or	2387	NOTE: I<< This callback must always return a time that is higher than or
2074	equal to the passed C<now> value >>.	2388	equal to the passed C<now> value >>.
2075		2389
2076	This can be used to create very complex timers, such as a timer that	2390	This can be used to create very complex timers, such as a timer that
2077	triggers on "next midnight, local time". To do this, you would calculate the	2391	triggers on "next midnight, local time". To do this, you would calculate
2078	next midnight after C<now> and return the timestamp value for this. How	2392	the next midnight after C<now> and return the timestamp value for
2079	you do this is, again, up to you (but it is not trivial, which is the main	2393	this. Here is a (completely untested, no error checking) example on how to
2080	reason I omitted it as an example).	2394	do this:
		2395
		2396	#include <time.h>
		2397
		2398	static ev_tstamp
		2399	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2400	{
		2401	time_t tnow = (time_t)now;
		2402	struct tm tm;
		2403	localtime_r (&tnow, &tm);
		2404
		2405	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2406	++tm.tm_mday; // midnight next day
		2407
		2408	return mktime (&tm);
		2409	}
		2410
		2411	Note: this code might run into trouble on days that have more then two
		2412	midnights (beginning and end).
2081		2413
2082	=back	2414	=back
2083		2415
2084	=item ev_periodic_again (loop, ev_periodic *)	2416	=item ev_periodic_again (loop, ev_periodic *)
2085		2417
…		…
2150		2482
2151	ev_periodic hourly_tick;	2483	ev_periodic hourly_tick;
2152	ev_periodic_init (&hourly_tick, clock_cb,	2484	ev_periodic_init (&hourly_tick, clock_cb,
2153	fmod (ev_now (loop), 3600.), 3600., 0);	2485	fmod (ev_now (loop), 3600.), 3600., 0);
2154	ev_periodic_start (loop, &hourly_tick);	2486	ev_periodic_start (loop, &hourly_tick);
2155		2487
2156		2488
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2489	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2490
2159	Signal watchers will trigger an event when the process receives a specific	2491	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2492	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2493	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2494	normal event processing, like any other event.
2163		2495
2164	If you want signals to be delivered truly asynchronously, just use	2496	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2497	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2498	the signal. You can even use C<ev_async> from a signal handler to
…		…
2170	only within the same loop, i.e. you can watch for C<SIGINT> in your	2502	only within the same loop, i.e. you can watch for C<SIGINT> in your
2171	default loop and for C<SIGIO> in another loop, but you cannot watch for	2503	default loop and for C<SIGIO> in another loop, but you cannot watch for
2172	C<SIGINT> in both the default loop and another loop at the same time. At	2504	C<SIGINT> in both the default loop and another loop at the same time. At
2173	the moment, C<SIGCHLD> is permanently tied to the default loop.	2505	the moment, C<SIGCHLD> is permanently tied to the default loop.
2174		2506
2175	When the first watcher gets started will libev actually register something	2507	Only after the first watcher for a signal is started will libev actually
2176	with the kernel (thus it coexists with your own signal handlers as long as	2508	register something with the kernel. It thus coexists with your own signal
2177	you don't register any with libev for the same signal).	2509	handlers as long as you don't register any with libev for the same signal.
2178		2510
2179	If possible and supported, libev will install its handlers with	2511	If possible and supported, libev will install its handlers with
2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2512	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2181	not be unduly interrupted. If you have a problem with system calls getting	2513	not be unduly interrupted. If you have a problem with system calls getting
2182	interrupted by signals you can block all signals in an C<ev_check> watcher	2514	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2517	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2518
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2519	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2520	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2521	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2522	and might or might not set or restore the installed signal handler (but
		2523	see C<EVFLAG_NOSIGMASK>).
2191		2524
2192	While this does not matter for the signal disposition (libev never	2525	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2526	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2527	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2528	certain signals to be blocked.
…		…
2209		2542
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2543	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2544	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2545	is not a libev-specific thing, this is true for most event libraries.
2213		2546
		2547	=head3 The special problem of threads signal handling
		2548
		2549	POSIX threads has problematic signal handling semantics, specifically,
		2550	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2551	threads in a process block signals, which is hard to achieve.
		2552
		2553	When you want to use sigwait (or mix libev signal handling with your own
		2554	for the same signals), you can tackle this problem by globally blocking
		2555	all signals before creating any threads (or creating them with a fully set
		2556	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2557	loops. Then designate one thread as "signal receiver thread" which handles
		2558	these signals. You can pass on any signals that libev might be interested
		2559	in by calling C<ev_feed_signal>.
		2560
2214	=head3 Watcher-Specific Functions and Data Members	2561	=head3 Watcher-Specific Functions and Data Members
2215		2562
2216	=over 4	2563	=over 4
2217		2564
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2565	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2580	Example: Try to exit cleanly on SIGINT.
2234		2581
2235	static void	2582	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2583	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2584	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2585	ev_break (loop, EVBREAK_ALL);
2239	}	2586	}
2240		2587
2241	ev_signal signal_watcher;	2588	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2589	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2590	ev_signal_start (loop, &signal_watcher);
…		…
2352		2699
2353	=head2 C<ev_stat> - did the file attributes just change?	2700	=head2 C<ev_stat> - did the file attributes just change?
2354		2701
2355	This watches a file system path for attribute changes. That is, it calls	2702	This watches a file system path for attribute changes. That is, it calls
2356	C<stat> on that path in regular intervals (or when the OS says it changed)	2703	C<stat> on that path in regular intervals (or when the OS says it changed)
2357	and sees if it changed compared to the last time, invoking the callback if	2704	and sees if it changed compared to the last time, invoking the callback
2358	it did.	2705	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2706	happen after the watcher has been started will be reported.
2359		2707
2360	The path does not need to exist: changing from "path exists" to "path does	2708	The path does not need to exist: changing from "path exists" to "path does
2361	not exist" is a status change like any other. The condition "path does not	2709	not exist" is a status change like any other. The condition "path does not
2362	exist" (or more correctly "path cannot be stat'ed") is signified by the	2710	exist" (or more correctly "path cannot be stat'ed") is signified by the
2363	C<st_nlink> field being zero (which is otherwise always forced to be at	2711	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2593	Apart from keeping your process non-blocking (which is a useful	2941	Apart from keeping your process non-blocking (which is a useful
2594	effect on its own sometimes), idle watchers are a good place to do	2942	effect on its own sometimes), idle watchers are a good place to do
2595	"pseudo-background processing", or delay processing stuff to after the	2943	"pseudo-background processing", or delay processing stuff to after the
2596	event loop has handled all outstanding events.	2944	event loop has handled all outstanding events.
2597		2945
		2946	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2947
		2948	As long as there is at least one active idle watcher, libev will never
		2949	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2950	For this to work, the idle watcher doesn't need to be invoked at all - the
		2951	lowest priority will do.
		2952
		2953	This mode of operation can be useful together with an C<ev_check> watcher,
		2954	to do something on each event loop iteration - for example to balance load
		2955	between different connections.
		2956
		2957	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2958	example.
		2959
2598	=head3 Watcher-Specific Functions and Data Members	2960	=head3 Watcher-Specific Functions and Data Members
2599		2961
2600	=over 4	2962	=over 4
2601		2963
2602	=item ev_idle_init (ev_idle *, callback)	2964	=item ev_idle_init (ev_idle *, callback)
…		…
2613	callback, free it. Also, use no error checking, as usual.	2975	callback, free it. Also, use no error checking, as usual.
2614		2976
2615	static void	2977	static void
2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2978	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2617	{	2979	{
		2980	// stop the watcher
		2981	ev_idle_stop (loop, w);
		2982
		2983	// now we can free it
2618	free (w);	2984	free (w);
		2985
2619	// now do something you wanted to do when the program has	2986	// now do something you wanted to do when the program has
2620	// no longer anything immediate to do.	2987	// no longer anything immediate to do.
2621	}	2988	}
2622		2989
2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2990	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2625	ev_idle_start (loop, idle_watcher);	2992	ev_idle_start (loop, idle_watcher);
2626		2993
2627		2994
2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2995	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2629		2996
2630	Prepare and check watchers are usually (but not always) used in pairs:	2997	Prepare and check watchers are often (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2998	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2999	afterwards.
2633		3000
2634	You I<must not> call C<ev_loop> or similar functions that enter	3001	You I<must not> call C<ev_run> (or similar functions that enter the
2635	the current event loop from either C<ev_prepare> or C<ev_check>	3002	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2636	watchers. Other loops than the current one are fine, however. The	3003	C<ev_check> watchers. Other loops than the current one are fine,
2637	rationale behind this is that you do not need to check for recursion in	3004	however. The rationale behind this is that you do not need to check
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3005	for recursion in those watchers, i.e. the sequence will always be
2639	C<ev_check> so if you have one watcher of each kind they will always be	3006	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2640	called in pairs bracketing the blocking call.	3007	kind they will always be called in pairs bracketing the blocking call.
2641		3008
2642	Their main purpose is to integrate other event mechanisms into libev and	3009	Their main purpose is to integrate other event mechanisms into libev and
2643	their use is somewhat advanced. They could be used, for example, to track	3010	their use is somewhat advanced. They could be used, for example, to track
2644	variable changes, implement your own watchers, integrate net-snmp or a	3011	variable changes, implement your own watchers, integrate net-snmp or a
2645	coroutine library and lots more. They are also occasionally useful if	3012	coroutine library and lots more. They are also occasionally useful if
…		…
2663	with priority higher than or equal to the event loop and one coroutine	3030	with priority higher than or equal to the event loop and one coroutine
2664	of lower priority, but only once, using idle watchers to keep the event	3031	of lower priority, but only once, using idle watchers to keep the event
2665	loop from blocking if lower-priority coroutines are active, thus mapping	3032	loop from blocking if lower-priority coroutines are active, thus mapping
2666	low-priority coroutines to idle/background tasks).	3033	low-priority coroutines to idle/background tasks).
2667		3034
2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3035	When used for this purpose, it is recommended to give C<ev_check> watchers
2669	priority, to ensure that they are being run before any other watchers	3036	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2670	after the poll (this doesn't matter for C<ev_prepare> watchers).	3037	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3038	watchers).
2671		3039
2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2673	activate ("feed") events into libev. While libev fully supports this, they	3041	activate ("feed") events into libev. While libev fully supports this, they
2674	might get executed before other C<ev_check> watchers did their job. As	3042	might get executed before other C<ev_check> watchers did their job. As
2675	C<ev_check> watchers are often used to embed other (non-libev) event	3043	C<ev_check> watchers are often used to embed other (non-libev) event
2676	loops those other event loops might be in an unusable state until their	3044	loops those other event loops might be in an unusable state until their
2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2678	others).	3046	others).
		3047
		3048	=head3 Abusing an C<ev_check> watcher for its side-effect
		3049
		3050	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3051	useful because they are called once per event loop iteration. For
		3052	example, if you want to handle a large number of connections fairly, you
		3053	normally only do a bit of work for each active connection, and if there
		3054	is more work to do, you wait for the next event loop iteration, so other
		3055	connections have a chance of making progress.
		3056
		3057	Using an C<ev_check> watcher is almost enough: it will be called on the
		3058	next event loop iteration. However, that isn't as soon as possible -
		3059	without external events, your C<ev_check> watcher will not be invoked.
		3060
		3061	This is where C<ev_idle> watchers come in handy - all you need is a
		3062	single global idle watcher that is active as long as you have one active
		3063	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3064	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3065	invoked. Neither watcher alone can do that.
2679		3066
2680	=head3 Watcher-Specific Functions and Data Members	3067	=head3 Watcher-Specific Functions and Data Members
2681		3068
2682	=over 4	3069	=over 4
2683		3070
…		…
2807		3194
2808	if (timeout >= 0)	3195	if (timeout >= 0)
2809	// create/start timer	3196	// create/start timer
2810		3197
2811	// poll	3198	// poll
2812	ev_loop (EV_A_ 0);	3199	ev_run (EV_A_ 0);
2813		3200
2814	// stop timer again	3201	// stop timer again
2815	if (timeout >= 0)	3202	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3203	ev_timer_stop (EV_A_ &to);
2817		3204
…		…
2884		3271
2885	=over 4	3272	=over 4
2886		3273
2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3274	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2888		3275
2889	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3276	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2890		3277
2891	Configures the watcher to embed the given loop, which must be	3278	Configures the watcher to embed the given loop, which must be
2892	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3279	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2893	invoked automatically, otherwise it is the responsibility of the callback	3280	invoked automatically, otherwise it is the responsibility of the callback
2894	to invoke it (it will continue to be called until the sweep has been done,	3281	to invoke it (it will continue to be called until the sweep has been done,
2895	if you do not want that, you need to temporarily stop the embed watcher).	3282	if you do not want that, you need to temporarily stop the embed watcher).
2896		3283
2897	=item ev_embed_sweep (loop, ev_embed *)	3284	=item ev_embed_sweep (loop, ev_embed *)
2898		3285
2899	Make a single, non-blocking sweep over the embedded loop. This works	3286	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3287	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3288	appropriate way for embedded loops.
2902		3289
2903	=item struct ev_loop *other [read-only]	3290	=item struct ev_loop *other [read-only]
2904		3291
2905	The embedded event loop.	3292	The embedded event loop.
…		…
2915	used).	3302	used).
2916		3303
2917	struct ev_loop *loop_hi = ev_default_init (0);	3304	struct ev_loop *loop_hi = ev_default_init (0);
2918	struct ev_loop *loop_lo = 0;	3305	struct ev_loop *loop_lo = 0;
2919	ev_embed embed;	3306	ev_embed embed;
2920		3307
2921	// see if there is a chance of getting one that works	3308	// see if there is a chance of getting one that works
2922	// (remember that a flags value of 0 means autodetection)	3309	// (remember that a flags value of 0 means autodetection)
2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3310	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3311	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2925	: 0;	3312	: 0;
…		…
2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3326	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2940		3327
2941	struct ev_loop *loop = ev_default_init (0);	3328	struct ev_loop *loop = ev_default_init (0);
2942	struct ev_loop *loop_socket = 0;	3329	struct ev_loop *loop_socket = 0;
2943	ev_embed embed;	3330	ev_embed embed;
2944		3331
2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3332	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3333	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2947	{	3334	{
2948	ev_embed_init (&embed, 0, loop_socket);	3335	ev_embed_init (&embed, 0, loop_socket);
2949	ev_embed_start (loop, &embed);	3336	ev_embed_start (loop, &embed);
…		…
2957		3344
2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3345	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2959		3346
2960	Fork watchers are called when a C<fork ()> was detected (usually because	3347	Fork watchers are called when a C<fork ()> was detected (usually because
2961	whoever is a good citizen cared to tell libev about it by calling	3348	whoever is a good citizen cared to tell libev about it by calling
2962	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3349	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2963	event loop blocks next and before C<ev_check> watchers are being called,	3350	and before C<ev_check> watchers are being called, and only in the child
2964	and only in the child after the fork. If whoever good citizen calling	3351	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3352	and calls it in the wrong process, the fork handlers will be invoked, too,
2966	handlers will be invoked, too, of course.	3353	of course.
2967		3354
2968	=head3 The special problem of life after fork - how is it possible?	3355	=head3 The special problem of life after fork - how is it possible?
2969		3356
2970	Most uses of C<fork()> consist of forking, then some simple calls to set	3357	Most uses of C<fork ()> consist of forking, then some simple calls to set
2971	up/change the process environment, followed by a call to C<exec()>. This	3358	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3359	sequence should be handled by libev without any problems.
2973		3360
2974	This changes when the application actually wants to do event handling	3361	This changes when the application actually wants to do event handling
2975	in the child, or both parent in child, in effect "continuing" after the	3362	in the child, or both parent in child, in effect "continuing" after the
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3378	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3379	signal watchers).
2993		3380
2994	When this is not possible, or you want to use the default loop for	3381	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3382	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3383	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3384	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3385	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3386	those watchers. Note also that in that case, you have to re-register any
		3387	signal watchers.
3000		3388
3001	=head3 Watcher-Specific Functions and Data Members	3389	=head3 Watcher-Specific Functions and Data Members
3002		3390
3003	=over 4	3391	=over 4
3004		3392
3005	=item ev_fork_init (ev_signal *, callback)	3393	=item ev_fork_init (ev_fork *, callback)
3006		3394
3007	Initialises and configures the fork watcher - it has no parameters of any	3395	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3396	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3397	really.
3010		3398
3011	=back	3399	=back
		3400
		3401
		3402	=head2 C<ev_cleanup> - even the best things end
		3403
		3404	Cleanup watchers are called just before the event loop is being destroyed
		3405	by a call to C<ev_loop_destroy>.
		3406
		3407	While there is no guarantee that the event loop gets destroyed, cleanup
		3408	watchers provide a convenient method to install cleanup hooks for your
		3409	program, worker threads and so on - you just to make sure to destroy the
		3410	loop when you want them to be invoked.
		3411
		3412	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3413	all other watchers, they do not keep a reference to the event loop (which
		3414	makes a lot of sense if you think about it). Like all other watchers, you
		3415	can call libev functions in the callback, except C<ev_cleanup_start>.
		3416
		3417	=head3 Watcher-Specific Functions and Data Members
		3418
		3419	=over 4
		3420
		3421	=item ev_cleanup_init (ev_cleanup *, callback)
		3422
		3423	Initialises and configures the cleanup watcher - it has no parameters of
		3424	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3425	pointless, I assure you.
		3426
		3427	=back
		3428
		3429	Example: Register an atexit handler to destroy the default loop, so any
		3430	cleanup functions are called.
		3431
		3432	static void
		3433	program_exits (void)
		3434	{
		3435	ev_loop_destroy (EV_DEFAULT_UC);
		3436	}
		3437
		3438	...
		3439	atexit (program_exits);
3012		3440
3013		3441
3014	=head2 C<ev_async> - how to wake up an event loop	3442	=head2 C<ev_async> - how to wake up an event loop
3015		3443
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3444	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3023	it by calling C<ev_async_send>, which is thread- and signal safe.	3451	it by calling C<ev_async_send>, which is thread- and signal safe.
3024		3452
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3453	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3454	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3455	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3456	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3029		3457	of "global async watchers" by using a watcher on an otherwise unused
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3458	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3031	just the default loop.	3459	even without knowing which loop owns the signal.
3032		3460
3033	=head3 Queueing	3461	=head3 Queueing
3034		3462
3035	C<ev_async> does not support queueing of data in any way. The reason	3463	C<ev_async> does not support queueing of data in any way. The reason
3036	is that the author does not know of a simple (or any) algorithm for a	3464	is that the author does not know of a simple (or any) algorithm for a
…		…
3128	trust me.	3556	trust me.
3129		3557
3130	=item ev_async_send (loop, ev_async *)	3558	=item ev_async_send (loop, ev_async *)
3131		3559
3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3560	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3561	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3562	returns.
		3563
3134	C<ev_feed_event>, this call is safe to do from other threads, signal or	3564	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3565	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3136	section below on what exactly this means).	3566	embedding section below on what exactly this means).
3137		3567
3138	Note that, as with other watchers in libev, multiple events might get	3568	Note that, as with other watchers in libev, multiple events might get
3139	compressed into a single callback invocation (another way to look at this	3569	compressed into a single callback invocation (another way to look at
3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3570	this is that C<ev_async> watchers are level-triggered: they are set on
3141	reset when the event loop detects that).	3571	C<ev_async_send>, reset when the event loop detects that).
3142		3572
3143	This call incurs the overhead of a system call only once per event loop	3573	This call incurs the overhead of at most one extra system call per event
3144	iteration, so while the overhead might be noticeable, it doesn't apply to	3574	loop iteration, if the event loop is blocked, and no syscall at all if
3145	repeated calls to C<ev_async_send> for the same event loop.	3575	the event loop (or your program) is processing events. That means that
		3576	repeated calls are basically free (there is no need to avoid calls for
		3577	performance reasons) and that the overhead becomes smaller (typically
		3578	zero) under load.
3146		3579
3147	=item bool = ev_async_pending (ev_async *)	3580	=item bool = ev_async_pending (ev_async *)
3148		3581
3149	Returns a non-zero value when C<ev_async_send> has been called on the	3582	Returns a non-zero value when C<ev_async_send> has been called on the
3150	watcher but the event has not yet been processed (or even noted) by the	3583	watcher but the event has not yet been processed (or even noted) by the
…		…
3167		3600
3168	There are some other functions of possible interest. Described. Here. Now.	3601	There are some other functions of possible interest. Described. Here. Now.
3169		3602
3170	=over 4	3603	=over 4
3171		3604
3172	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3605	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3173		3606
3174	This function combines a simple timer and an I/O watcher, calls your	3607	This function combines a simple timer and an I/O watcher, calls your
3175	callback on whichever event happens first and automatically stops both	3608	callback on whichever event happens first and automatically stops both
3176	watchers. This is useful if you want to wait for a single event on an fd	3609	watchers. This is useful if you want to wait for a single event on an fd
3177	or timeout without having to allocate/configure/start/stop/free one or	3610	or timeout without having to allocate/configure/start/stop/free one or
…		…
3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3638	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3206		3639
3207	=item ev_feed_fd_event (loop, int fd, int revents)	3640	=item ev_feed_fd_event (loop, int fd, int revents)
3208		3641
3209	Feed an event on the given fd, as if a file descriptor backend detected	3642	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3643	the given events.
3211		3644
3212	=item ev_feed_signal_event (loop, int signum)	3645	=item ev_feed_signal_event (loop, int signum)
3213		3646
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3647	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3648	which is async-safe.
3216		3649
3217	=back	3650	=back
		3651
		3652
		3653	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3654
		3655	This section explains some common idioms that are not immediately
		3656	obvious. Note that examples are sprinkled over the whole manual, and this
		3657	section only contains stuff that wouldn't fit anywhere else.
		3658
		3659	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3660
		3661	Each watcher has, by default, a C<void *data> member that you can read
		3662	or modify at any time: libev will completely ignore it. This can be used
		3663	to associate arbitrary data with your watcher. If you need more data and
		3664	don't want to allocate memory separately and store a pointer to it in that
		3665	data member, you can also "subclass" the watcher type and provide your own
		3666	data:
		3667
		3668	struct my_io
		3669	{
		3670	ev_io io;
		3671	int otherfd;
		3672	void *somedata;
		3673	struct whatever *mostinteresting;
		3674	};
		3675
		3676	...
		3677	struct my_io w;
		3678	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3679
		3680	And since your callback will be called with a pointer to the watcher, you
		3681	can cast it back to your own type:
		3682
		3683	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3684	{
		3685	struct my_io *w = (struct my_io *)w_;
		3686	...
		3687	}
		3688
		3689	More interesting and less C-conformant ways of casting your callback
		3690	function type instead have been omitted.
		3691
		3692	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3693
		3694	Another common scenario is to use some data structure with multiple
		3695	embedded watchers, in effect creating your own watcher that combines
		3696	multiple libev event sources into one "super-watcher":
		3697
		3698	struct my_biggy
		3699	{
		3700	int some_data;
		3701	ev_timer t1;
		3702	ev_timer t2;
		3703	}
		3704
		3705	In this case getting the pointer to C<my_biggy> is a bit more
		3706	complicated: Either you store the address of your C<my_biggy> struct in
		3707	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3708	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3709	real programmers):
		3710
		3711	#include <stddef.h>
		3712
		3713	static void
		3714	t1_cb (EV_P_ ev_timer *w, int revents)
		3715	{
		3716	struct my_biggy big = (struct my_biggy *)
		3717	(((char *)w) - offsetof (struct my_biggy, t1));
		3718	}
		3719
		3720	static void
		3721	t2_cb (EV_P_ ev_timer *w, int revents)
		3722	{
		3723	struct my_biggy big = (struct my_biggy *)
		3724	(((char *)w) - offsetof (struct my_biggy, t2));
		3725	}
		3726
		3727	=head2 AVOIDING FINISHING BEFORE RETURNING
		3728
		3729	Often you have structures like this in event-based programs:
		3730
		3731	callback ()
		3732	{
		3733	free (request);
		3734	}
		3735
		3736	request = start_new_request (..., callback);
		3737
		3738	The intent is to start some "lengthy" operation. The C<request> could be
		3739	used to cancel the operation, or do other things with it.
		3740
		3741	It's not uncommon to have code paths in C<start_new_request> that
		3742	immediately invoke the callback, for example, to report errors. Or you add
		3743	some caching layer that finds that it can skip the lengthy aspects of the
		3744	operation and simply invoke the callback with the result.
		3745
		3746	The problem here is that this will happen I<before> C<start_new_request>
		3747	has returned, so C<request> is not set.
		3748
		3749	Even if you pass the request by some safer means to the callback, you
		3750	might want to do something to the request after starting it, such as
		3751	canceling it, which probably isn't working so well when the callback has
		3752	already been invoked.
		3753
		3754	A common way around all these issues is to make sure that
		3755	C<start_new_request> I<always> returns before the callback is invoked. If
		3756	C<start_new_request> immediately knows the result, it can artificially
		3757	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3758	example, or more sneakily, by reusing an existing (stopped) watcher and
		3759	pushing it into the pending queue:
		3760
		3761	ev_set_cb (watcher, callback);
		3762	ev_feed_event (EV_A_ watcher, 0);
		3763
		3764	This way, C<start_new_request> can safely return before the callback is
		3765	invoked, while not delaying callback invocation too much.
		3766
		3767	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3768
		3769	Often (especially in GUI toolkits) there are places where you have
		3770	I<modal> interaction, which is most easily implemented by recursively
		3771	invoking C<ev_run>.
		3772
		3773	This brings the problem of exiting - a callback might want to finish the
		3774	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3775	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3776	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3777	other combination: In these cases, a simple C<ev_break> will not work.
		3778
		3779	The solution is to maintain "break this loop" variable for each C<ev_run>
		3780	invocation, and use a loop around C<ev_run> until the condition is
		3781	triggered, using C<EVRUN_ONCE>:
		3782
		3783	// main loop
		3784	int exit_main_loop = 0;
		3785
		3786	while (!exit_main_loop)
		3787	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3788
		3789	// in a modal watcher
		3790	int exit_nested_loop = 0;
		3791
		3792	while (!exit_nested_loop)
		3793	ev_run (EV_A_ EVRUN_ONCE);
		3794
		3795	To exit from any of these loops, just set the corresponding exit variable:
		3796
		3797	// exit modal loop
		3798	exit_nested_loop = 1;
		3799
		3800	// exit main program, after modal loop is finished
		3801	exit_main_loop = 1;
		3802
		3803	// exit both
		3804	exit_main_loop = exit_nested_loop = 1;
		3805
		3806	=head2 THREAD LOCKING EXAMPLE
		3807
		3808	Here is a fictitious example of how to run an event loop in a different
		3809	thread from where callbacks are being invoked and watchers are
		3810	created/added/removed.
		3811
		3812	For a real-world example, see the C<EV::Loop::Async> perl module,
		3813	which uses exactly this technique (which is suited for many high-level
		3814	languages).
		3815
		3816	The example uses a pthread mutex to protect the loop data, a condition
		3817	variable to wait for callback invocations, an async watcher to notify the
		3818	event loop thread and an unspecified mechanism to wake up the main thread.
		3819
		3820	First, you need to associate some data with the event loop:
		3821
		3822	typedef struct {
		3823	mutex_t lock; /* global loop lock */
		3824	ev_async async_w;
		3825	thread_t tid;
		3826	cond_t invoke_cv;
		3827	} userdata;
		3828
		3829	void prepare_loop (EV_P)
		3830	{
		3831	// for simplicity, we use a static userdata struct.
		3832	static userdata u;
		3833
		3834	ev_async_init (&u->async_w, async_cb);
		3835	ev_async_start (EV_A_ &u->async_w);
		3836
		3837	pthread_mutex_init (&u->lock, 0);
		3838	pthread_cond_init (&u->invoke_cv, 0);
		3839
		3840	// now associate this with the loop
		3841	ev_set_userdata (EV_A_ u);
		3842	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3843	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3844
		3845	// then create the thread running ev_run
		3846	pthread_create (&u->tid, 0, l_run, EV_A);
		3847	}
		3848
		3849	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3850	solely to wake up the event loop so it takes notice of any new watchers
		3851	that might have been added:
		3852
		3853	static void
		3854	async_cb (EV_P_ ev_async *w, int revents)
		3855	{
		3856	// just used for the side effects
		3857	}
		3858
		3859	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3860	protecting the loop data, respectively.
		3861
		3862	static void
		3863	l_release (EV_P)
		3864	{
		3865	userdata *u = ev_userdata (EV_A);
		3866	pthread_mutex_unlock (&u->lock);
		3867	}
		3868
		3869	static void
		3870	l_acquire (EV_P)
		3871	{
		3872	userdata *u = ev_userdata (EV_A);
		3873	pthread_mutex_lock (&u->lock);
		3874	}
		3875
		3876	The event loop thread first acquires the mutex, and then jumps straight
		3877	into C<ev_run>:
		3878
		3879	void *
		3880	l_run (void *thr_arg)
		3881	{
		3882	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3883
		3884	l_acquire (EV_A);
		3885	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3886	ev_run (EV_A_ 0);
		3887	l_release (EV_A);
		3888
		3889	return 0;
		3890	}
		3891
		3892	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3893	signal the main thread via some unspecified mechanism (signals? pipe
		3894	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3895	have been called (in a while loop because a) spurious wakeups are possible
		3896	and b) skipping inter-thread-communication when there are no pending
		3897	watchers is very beneficial):
		3898
		3899	static void
		3900	l_invoke (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903
		3904	while (ev_pending_count (EV_A))
		3905	{
		3906	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3907	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3908	}
		3909	}
		3910
		3911	Now, whenever the main thread gets told to invoke pending watchers, it
		3912	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3913	thread to continue:
		3914
		3915	static void
		3916	real_invoke_pending (EV_P)
		3917	{
		3918	userdata *u = ev_userdata (EV_A);
		3919
		3920	pthread_mutex_lock (&u->lock);
		3921	ev_invoke_pending (EV_A);
		3922	pthread_cond_signal (&u->invoke_cv);
		3923	pthread_mutex_unlock (&u->lock);
		3924	}
		3925
		3926	Whenever you want to start/stop a watcher or do other modifications to an
		3927	event loop, you will now have to lock:
		3928
		3929	ev_timer timeout_watcher;
		3930	userdata *u = ev_userdata (EV_A);
		3931
		3932	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3933
		3934	pthread_mutex_lock (&u->lock);
		3935	ev_timer_start (EV_A_ &timeout_watcher);
		3936	ev_async_send (EV_A_ &u->async_w);
		3937	pthread_mutex_unlock (&u->lock);
		3938
		3939	Note that sending the C<ev_async> watcher is required because otherwise
		3940	an event loop currently blocking in the kernel will have no knowledge
		3941	about the newly added timer. By waking up the loop it will pick up any new
		3942	watchers in the next event loop iteration.
		3943
		3944	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3945
		3946	While the overhead of a callback that e.g. schedules a thread is small, it
		3947	is still an overhead. If you embed libev, and your main usage is with some
		3948	kind of threads or coroutines, you might want to customise libev so that
		3949	doesn't need callbacks anymore.
		3950
		3951	Imagine you have coroutines that you can switch to using a function
		3952	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3953	and that due to some magic, the currently active coroutine is stored in a
		3954	global called C<current_coro>. Then you can build your own "wait for libev
		3955	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3956	the differing C<;> conventions):
		3957
		3958	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3959	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3960
		3961	That means instead of having a C callback function, you store the
		3962	coroutine to switch to in each watcher, and instead of having libev call
		3963	your callback, you instead have it switch to that coroutine.
		3964
		3965	A coroutine might now wait for an event with a function called
		3966	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3967	matter when, or whether the watcher is active or not when this function is
		3968	called):
		3969
		3970	void
		3971	wait_for_event (ev_watcher *w)
		3972	{
		3973	ev_set_cb (w, current_coro);
		3974	switch_to (libev_coro);
		3975	}
		3976
		3977	That basically suspends the coroutine inside C<wait_for_event> and
		3978	continues the libev coroutine, which, when appropriate, switches back to
		3979	this or any other coroutine.
		3980
		3981	You can do similar tricks if you have, say, threads with an event queue -
		3982	instead of storing a coroutine, you store the queue object and instead of
		3983	switching to a coroutine, you push the watcher onto the queue and notify
		3984	any waiters.
		3985
		3986	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3987	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3988
		3989	// my_ev.h
		3990	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3991	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3992	#include "../libev/ev.h"
		3993
		3994	// my_ev.c
		3995	#define EV_H "my_ev.h"
		3996	#include "../libev/ev.c"
		3997
		3998	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3999	F<my_ev.c> into your project. When properly specifying include paths, you
		4000	can even use F<ev.h> as header file name directly.
3218		4001
3219		4002
3220	=head1 LIBEVENT EMULATION	4003	=head1 LIBEVENT EMULATION
3221		4004
3222	Libev offers a compatibility emulation layer for libevent. It cannot	4005	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	4006	emulate the internals of libevent, so here are some usage hints:
3224		4007
3225	=over 4	4008	=over 4
		4009
		4010	=item * Only the libevent-1.4.1-beta API is being emulated.
		4011
		4012	This was the newest libevent version available when libev was implemented,
		4013	and is still mostly unchanged in 2010.
3226		4014
3227	=item * Use it by including <event.h>, as usual.	4015	=item * Use it by including <event.h>, as usual.
3228		4016
3229	=item * The following members are fully supported: ev_base, ev_callback,	4017	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	4018	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	4024	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	4025	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	4026	is an ev_pri field.
3239		4027
3240	=item * In libevent, the last base created gets the signals, in libev, the	4028	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	4029	base that registered the signal gets the signals.
3242		4030
3243	=item * Other members are not supported.	4031	=item * Other members are not supported.
3244		4032
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4033	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	4034	to use the libev header file and library.
3247		4035
3248	=back	4036	=back
3249		4037
3250	=head1 C++ SUPPORT	4038	=head1 C++ SUPPORT
		4039
		4040	=head2 C API
		4041
		4042	The normal C API should work fine when used from C++: both ev.h and the
		4043	libev sources can be compiled as C++. Therefore, code that uses the C API
		4044	will work fine.
		4045
		4046	Proper exception specifications might have to be added to callbacks passed
		4047	to libev: exceptions may be thrown only from watcher callbacks, all other
		4048	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4049	callbacks) must not throw exceptions, and might need a C<noexcept>
		4050	specification. If you have code that needs to be compiled as both C and
		4051	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4052
		4053	static void
		4054	fatal_error (const char *msg) EV_NOEXCEPT
		4055	{
		4056	perror (msg);
		4057	abort ();
		4058	}
		4059
		4060	...
		4061	ev_set_syserr_cb (fatal_error);
		4062
		4063	The only API functions that can currently throw exceptions are C<ev_run>,
		4064	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4065	because it runs cleanup watchers).
		4066
		4067	Throwing exceptions in watcher callbacks is only supported if libev itself
		4068	is compiled with a C++ compiler or your C and C++ environments allow
		4069	throwing exceptions through C libraries (most do).
		4070
		4071	=head2 C++ API
3251		4072
3252	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4073	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3253	you to use some convenience methods to start/stop watchers and also change	4074	you to use some convenience methods to start/stop watchers and also change
3254	the callback model to a model using method callbacks on objects.	4075	the callback model to a model using method callbacks on objects.
3255		4076
3256	To use it,	4077	To use it,
3257		4078
3258	#include <ev++.h>	4079	#include <ev++.h>
3259		4080
3260	This automatically includes F<ev.h> and puts all of its definitions (many	4081	This automatically includes F<ev.h> and puts all of its definitions (many
3261	of them macros) into the global namespace. All C++ specific things are	4082	of them macros) into the global namespace. All C++ specific things are
3262	put into the C<ev> namespace. It should support all the same embedding	4083	put into the C<ev> namespace. It should support all the same embedding
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	4086	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	4087	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	4088	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	4089	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		4090
3270	Currently, functions, and static and non-static member functions can be	4091	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	4092	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	4093	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	4094	you need support for other types of functors please contact the author
3274	it).	4095	(preferably after implementing it).
		4096
		4097	For all this to work, your C++ compiler either has to use the same calling
		4098	conventions as your C compiler (for static member functions), or you have
		4099	to embed libev and compile libev itself as C++.
3275		4100
3276	Here is a list of things available in the C<ev> namespace:	4101	Here is a list of things available in the C<ev> namespace:
3277		4102
3278	=over 4	4103	=over 4
3279		4104
…		…
3289	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4114	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3290		4115
3291	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4116	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3292	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4117	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3293	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4118	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3294	defines by many implementations.	4119	defined by many implementations.
3295		4120
3296	All of those classes have these methods:	4121	All of those classes have these methods:
3297		4122
3298	=over 4	4123	=over 4
3299		4124
…		…
3361	void operator() (ev::io &w, int revents)	4186	void operator() (ev::io &w, int revents)
3362	{	4187	{
3363	...	4188	...
3364	}	4189	}
3365	}	4190	}
3366		4191
3367	myfunctor f;	4192	myfunctor f;
3368		4193
3369	ev::io w;	4194	ev::io w;
3370	w.set (&f);	4195	w.set (&f);
3371		4196
…		…
3389	Associates a different C<struct ev_loop> with this watcher. You can only	4214	Associates a different C<struct ev_loop> with this watcher. You can only
3390	do this when the watcher is inactive (and not pending either).	4215	do this when the watcher is inactive (and not pending either).
3391		4216
3392	=item w->set ([arguments])	4217	=item w->set ([arguments])
3393		4218
3394	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4219	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4220	with the same arguments. Either this method or a suitable start method
3395	called at least once. Unlike the C counterpart, an active watcher gets	4221	must be called at least once. Unlike the C counterpart, an active watcher
3396	automatically stopped and restarted when reconfiguring it with this	4222	gets automatically stopped and restarted when reconfiguring it with this
3397	method.	4223	method.
		4224
		4225	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4226	clashing with the C<set (loop)> method.
3398		4227
3399	=item w->start ()	4228	=item w->start ()
3400		4229
3401	Starts the watcher. Note that there is no C<loop> argument, as the	4230	Starts the watcher. Note that there is no C<loop> argument, as the
3402	constructor already stores the event loop.	4231	constructor already stores the event loop.
3403		4232
		4233	=item w->start ([arguments])
		4234
		4235	Instead of calling C<set> and C<start> methods separately, it is often
		4236	convenient to wrap them in one call. Uses the same type of arguments as
		4237	the configure C<set> method of the watcher.
		4238
3404	=item w->stop ()	4239	=item w->stop ()
3405		4240
3406	Stops the watcher if it is active. Again, no C<loop> argument.	4241	Stops the watcher if it is active. Again, no C<loop> argument.
3407		4242
3408	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4243	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3420		4255
3421	=back	4256	=back
3422		4257
3423	=back	4258	=back
3424		4259
3425	Example: Define a class with an IO and idle watcher, start one of them in	4260	Example: Define a class with two I/O and idle watchers, start the I/O
3426	the constructor.	4261	watchers in the constructor.
3427		4262
3428	class myclass	4263	class myclass
3429	{	4264	{
3430	ev::io io ; void io_cb (ev::io &w, int revents);	4265	ev::io io ; void io_cb (ev::io &w, int revents);
		4266	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3431	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4267	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3432		4268
3433	myclass (int fd)	4269	myclass (int fd)
3434	{	4270	{
3435	io .set <myclass, &myclass::io_cb > (this);	4271	io .set <myclass, &myclass::io_cb > (this);
		4272	io2 .set <myclass, &myclass::io2_cb > (this);
3436	idle.set <myclass, &myclass::idle_cb> (this);	4273	idle.set <myclass, &myclass::idle_cb> (this);
3437		4274
3438	io.start (fd, ev::READ);	4275	io.set (fd, ev::WRITE); // configure the watcher
		4276	io.start (); // start it whenever convenient
		4277
		4278	io2.start (fd, ev::READ); // set + start in one call
3439	}	4279	}
3440	};	4280	};
3441		4281
3442		4282
3443	=head1 OTHER LANGUAGE BINDINGS	4283	=head1 OTHER LANGUAGE BINDINGS
…		…
3482	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4322	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3483		4323
3484	=item D	4324	=item D
3485		4325
3486	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4326	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3487	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4327	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3488		4328
3489	=item Ocaml	4329	=item Ocaml
3490		4330
3491	Erkki Seppala has written Ocaml bindings for libev, to be found at	4331	Erkki Seppala has written Ocaml bindings for libev, to be found at
3492	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4332	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3495		4335
3496	Brian Maher has written a partial interface to libev for lua (at the	4336	Brian Maher has written a partial interface to libev for lua (at the
3497	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4337	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3498	L<http://github.com/brimworks/lua-ev>.	4338	L<http://github.com/brimworks/lua-ev>.
3499		4339
		4340	=item Javascript
		4341
		4342	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4343
		4344	=item Others
		4345
		4346	There are others, and I stopped counting.
		4347
3500	=back	4348	=back
3501		4349
3502		4350
3503	=head1 MACRO MAGIC	4351	=head1 MACRO MAGIC
3504		4352
…		…
3517	loop argument"). The C<EV_A> form is used when this is the sole argument,	4365	loop argument"). The C<EV_A> form is used when this is the sole argument,
3518	C<EV_A_> is used when other arguments are following. Example:	4366	C<EV_A_> is used when other arguments are following. Example:
3519		4367
3520	ev_unref (EV_A);	4368	ev_unref (EV_A);
3521	ev_timer_add (EV_A_ watcher);	4369	ev_timer_add (EV_A_ watcher);
3522	ev_loop (EV_A_ 0);	4370	ev_run (EV_A_ 0);
3523		4371
3524	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4372	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3525	which is often provided by the following macro.	4373	which is often provided by the following macro.
3526		4374
3527	=item C<EV_P>, C<EV_P_>	4375	=item C<EV_P>, C<EV_P_>
…		…
3540	suitable for use with C<EV_A>.	4388	suitable for use with C<EV_A>.
3541		4389
3542	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4390	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3543		4391
3544	Similar to the other two macros, this gives you the value of the default	4392	Similar to the other two macros, this gives you the value of the default
3545	loop, if multiple loops are supported ("ev loop default").	4393	loop, if multiple loops are supported ("ev loop default"). The default loop
		4394	will be initialised if it isn't already initialised.
		4395
		4396	For non-multiplicity builds, these macros do nothing, so you always have
		4397	to initialise the loop somewhere.
3546		4398
3547	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4399	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3548		4400
3549	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4401	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3550	default loop has been initialised (C<UC> == unchecked). Their behaviour	4402	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3567	}	4419	}
3568		4420
3569	ev_check check;	4421	ev_check check;
3570	ev_check_init (&check, check_cb);	4422	ev_check_init (&check, check_cb);
3571	ev_check_start (EV_DEFAULT_ &check);	4423	ev_check_start (EV_DEFAULT_ &check);
3572	ev_loop (EV_DEFAULT_ 0);	4424	ev_run (EV_DEFAULT_ 0);
3573		4425
3574	=head1 EMBEDDING	4426	=head1 EMBEDDING
3575		4427
3576	Libev can (and often is) directly embedded into host	4428	Libev can (and often is) directly embedded into host
3577	applications. Examples of applications that embed it include the Deliantra	4429	applications. Examples of applications that embed it include the Deliantra
…		…
3617	ev_vars.h	4469	ev_vars.h
3618	ev_wrap.h	4470	ev_wrap.h
3619		4471
3620	ev_win32.c required on win32 platforms only	4472	ev_win32.c required on win32 platforms only
3621		4473
3622	ev_select.c only when select backend is enabled (which is enabled by default)	4474	ev_select.c only when select backend is enabled
3623	ev_poll.c only when poll backend is enabled (disabled by default)	4475	ev_poll.c only when poll backend is enabled
3624	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4476	ev_epoll.c only when the epoll backend is enabled
		4477	ev_linuxaio.c only when the linux aio backend is enabled
3625	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4478	ev_kqueue.c only when the kqueue backend is enabled
3626	ev_port.c only when the solaris port backend is enabled (disabled by default)	4479	ev_port.c only when the solaris port backend is enabled
3627		4480
3628	F<ev.c> includes the backend files directly when enabled, so you only need	4481	F<ev.c> includes the backend files directly when enabled, so you only need
3629	to compile this single file.	4482	to compile this single file.
3630		4483
3631	=head3 LIBEVENT COMPATIBILITY API	4484	=head3 LIBEVENT COMPATIBILITY API
…		…
3669	users of libev and the libev code itself must be compiled with compatible	4522	users of libev and the libev code itself must be compiled with compatible
3670	settings.	4523	settings.
3671		4524
3672	=over 4	4525	=over 4
3673		4526
		4527	=item EV_COMPAT3 (h)
		4528
		4529	Backwards compatibility is a major concern for libev. This is why this
		4530	release of libev comes with wrappers for the functions and symbols that
		4531	have been renamed between libev version 3 and 4.
		4532
		4533	You can disable these wrappers (to test compatibility with future
		4534	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4535	sources. This has the additional advantage that you can drop the C<struct>
		4536	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4537	typedef in that case.
		4538
		4539	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4540	and in some even more future version the compatibility code will be
		4541	removed completely.
		4542
3674	=item EV_STANDALONE (h)	4543	=item EV_STANDALONE (h)
3675		4544
3676	Must always be C<1> if you do not use autoconf configuration, which	4545	Must always be C<1> if you do not use autoconf configuration, which
3677	keeps libev from including F<config.h>, and it also defines dummy	4546	keeps libev from including F<config.h>, and it also defines dummy
3678	implementations for some libevent functions (such as logging, which is not	4547	implementations for some libevent functions (such as logging, which is not
3679	supported). It will also not define any of the structs usually found in	4548	supported). It will also not define any of the structs usually found in
3680	F<event.h> that are not directly supported by the libev core alone.	4549	F<event.h> that are not directly supported by the libev core alone.
3681		4550
3682	In standalone mode, libev will still try to automatically deduce the	4551	In standalone mode, libev will still try to automatically deduce the
3683	configuration, but has to be more conservative.	4552	configuration, but has to be more conservative.
		4553
		4554	=item EV_USE_FLOOR
		4555
		4556	If defined to be C<1>, libev will use the C<floor ()> function for its
		4557	periodic reschedule calculations, otherwise libev will fall back on a
		4558	portable (slower) implementation. If you enable this, you usually have to
		4559	link against libm or something equivalent. Enabling this when the C<floor>
		4560	function is not available will fail, so the safe default is to not enable
		4561	this.
3684		4562
3685	=item EV_USE_MONOTONIC	4563	=item EV_USE_MONOTONIC
3686		4564
3687	If defined to be C<1>, libev will try to detect the availability of the	4565	If defined to be C<1>, libev will try to detect the availability of the
3688	monotonic clock option at both compile time and runtime. Otherwise no	4566	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3774	If programs implement their own fd to handle mapping on win32, then this	4652	If programs implement their own fd to handle mapping on win32, then this
3775	macro can be used to override the C<close> function, useful to unregister	4653	macro can be used to override the C<close> function, useful to unregister
3776	file descriptors again. Note that the replacement function has to close	4654	file descriptors again. Note that the replacement function has to close
3777	the underlying OS handle.	4655	the underlying OS handle.
3778		4656
		4657	=item EV_USE_WSASOCKET
		4658
		4659	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4660	communication socket, which works better in some environments. Otherwise,
		4661	the normal C<socket> function will be used, which works better in other
		4662	environments.
		4663
3779	=item EV_USE_POLL	4664	=item EV_USE_POLL
3780		4665
3781	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4666	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3782	backend. Otherwise it will be enabled on non-win32 platforms. It	4667	backend. Otherwise it will be enabled on non-win32 platforms. It
3783	takes precedence over select.	4668	takes precedence over select.
…		…
3787	If defined to be C<1>, libev will compile in support for the Linux	4672	If defined to be C<1>, libev will compile in support for the Linux
3788	C<epoll>(7) backend. Its availability will be detected at runtime,	4673	C<epoll>(7) backend. Its availability will be detected at runtime,
3789	otherwise another method will be used as fallback. This is the preferred	4674	otherwise another method will be used as fallback. This is the preferred
3790	backend for GNU/Linux systems. If undefined, it will be enabled if the	4675	backend for GNU/Linux systems. If undefined, it will be enabled if the
3791	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4676	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4677
		4678	=item EV_USE_LINUXAIO
		4679
		4680	If defined to be C<1>, libev will compile in support for the Linux
		4681	aio backend. Due to it's currenbt limitations it has to be requested
		4682	explicitly. If undefined, it will be enabled on linux, otherwise
		4683	disabled.
3792		4684
3793	=item EV_USE_KQUEUE	4685	=item EV_USE_KQUEUE
3794		4686
3795	If defined to be C<1>, libev will compile in support for the BSD style	4687	If defined to be C<1>, libev will compile in support for the BSD style
3796	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4688	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3818	If defined to be C<1>, libev will compile in support for the Linux inotify	4710	If defined to be C<1>, libev will compile in support for the Linux inotify
3819	interface to speed up C<ev_stat> watchers. Its actual availability will	4711	interface to speed up C<ev_stat> watchers. Its actual availability will
3820	be detected at runtime. If undefined, it will be enabled if the headers	4712	be detected at runtime. If undefined, it will be enabled if the headers
3821	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4713	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3822		4714
		4715	=item EV_NO_SMP
		4716
		4717	If defined to be C<1>, libev will assume that memory is always coherent
		4718	between threads, that is, threads can be used, but threads never run on
		4719	different cpus (or different cpu cores). This reduces dependencies
		4720	and makes libev faster.
		4721
		4722	=item EV_NO_THREADS
		4723
		4724	If defined to be C<1>, libev will assume that it will never be called from
		4725	different threads (that includes signal handlers), which is a stronger
		4726	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4727	libev faster.
		4728
3823	=item EV_ATOMIC_T	4729	=item EV_ATOMIC_T
3824		4730
3825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4731	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3826	access is atomic with respect to other threads or signal contexts. No such	4732	access is atomic with respect to other threads or signal contexts. No
3827	type is easily found in the C language, so you can provide your own type	4733	such type is easily found in the C language, so you can provide your own
3828	that you know is safe for your purposes. It is used both for signal handler "locking"	4734	type that you know is safe for your purposes. It is used both for signal
3829	as well as for signal and thread safety in C<ev_async> watchers.	4735	handler "locking" as well as for signal and thread safety in C<ev_async>
		4736	watchers.
3830		4737
3831	In the absence of this define, libev will use C<sig_atomic_t volatile>	4738	In the absence of this define, libev will use C<sig_atomic_t volatile>
3832	(from F<signal.h>), which is usually good enough on most platforms.	4739	(from F<signal.h>), which is usually good enough on most platforms.
3833		4740
3834	=item EV_H (h)	4741	=item EV_H (h)
…		…
3861	will have the C<struct ev_loop *> as first argument, and you can create	4768	will have the C<struct ev_loop *> as first argument, and you can create
3862	additional independent event loops. Otherwise there will be no support	4769	additional independent event loops. Otherwise there will be no support
3863	for multiple event loops and there is no first event loop pointer	4770	for multiple event loops and there is no first event loop pointer
3864	argument. Instead, all functions act on the single default loop.	4771	argument. Instead, all functions act on the single default loop.
3865		4772
		4773	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4774	default loop when multiplicity is switched off - you always have to
		4775	initialise the loop manually in this case.
		4776
3866	=item EV_MINPRI	4777	=item EV_MINPRI
3867		4778
3868	=item EV_MAXPRI	4779	=item EV_MAXPRI
3869		4780
3870	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4781	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3906	#define EV_USE_POLL 1	4817	#define EV_USE_POLL 1
3907	#define EV_CHILD_ENABLE 1	4818	#define EV_CHILD_ENABLE 1
3908	#define EV_ASYNC_ENABLE 1	4819	#define EV_ASYNC_ENABLE 1
3909		4820
3910	The actual value is a bitset, it can be a combination of the following	4821	The actual value is a bitset, it can be a combination of the following
3911	values:	4822	values (by default, all of these are enabled):
3912		4823
3913	=over 4	4824	=over 4
3914		4825
3915	=item C<1> - faster/larger code	4826	=item C<1> - faster/larger code
3916		4827
…		…
3920	code size by roughly 30% on amd64).	4831	code size by roughly 30% on amd64).
3921		4832
3922	When optimising for size, use of compiler flags such as C<-Os> with	4833	When optimising for size, use of compiler flags such as C<-Os> with
3923	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4834	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3924	assertions.	4835	assertions.
		4836
		4837	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4838	(e.g. gcc with C<-Os>).
3925		4839
3926	=item C<2> - faster/larger data structures	4840	=item C<2> - faster/larger data structures
3927		4841
3928	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4842	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3929	hash table sizes and so on. This will usually further increase code size	4843	hash table sizes and so on. This will usually further increase code size
3930	and can additionally have an effect on the size of data structures at	4844	and can additionally have an effect on the size of data structures at
3931	runtime.	4845	runtime.
3932		4846
		4847	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4848	(e.g. gcc with C<-Os>).
		4849
3933	=item C<4> - full API configuration	4850	=item C<4> - full API configuration
3934		4851
3935	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4852	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3936	enables multiplicity (C<EV_MULTIPLICITY>=1).	4853	enables multiplicity (C<EV_MULTIPLICITY>=1).
3937		4854
…		…
3967		4884
3968	With an intelligent-enough linker (gcc+binutils are intelligent enough	4885	With an intelligent-enough linker (gcc+binutils are intelligent enough
3969	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4886	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3970	your program might be left out as well - a binary starting a timer and an	4887	your program might be left out as well - a binary starting a timer and an
3971	I/O watcher then might come out at only 5Kb.	4888	I/O watcher then might come out at only 5Kb.
		4889
		4890	=item EV_API_STATIC
		4891
		4892	If this symbol is defined (by default it is not), then all identifiers
		4893	will have static linkage. This means that libev will not export any
		4894	identifiers, and you cannot link against libev anymore. This can be useful
		4895	when you embed libev, only want to use libev functions in a single file,
		4896	and do not want its identifiers to be visible.
		4897
		4898	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4899	wants to use libev.
		4900
		4901	This option only works when libev is compiled with a C compiler, as C++
		4902	doesn't support the required declaration syntax.
3972		4903
3973	=item EV_AVOID_STDIO	4904	=item EV_AVOID_STDIO
3974		4905
3975	If this is set to C<1> at compiletime, then libev will avoid using stdio	4906	If this is set to C<1> at compiletime, then libev will avoid using stdio
3976	functions (printf, scanf, perror etc.). This will increase the code size	4907	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4958	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4028	will be C<0>.	4959	will be C<0>.
4029		4960
4030	=item EV_VERIFY	4961	=item EV_VERIFY
4031		4962
4032	Controls how much internal verification (see C<ev_loop_verify ()>) will	4963	Controls how much internal verification (see C<ev_verify ()>) will
4033	be done: If set to C<0>, no internal verification code will be compiled	4964	be done: If set to C<0>, no internal verification code will be compiled
4034	in. If set to C<1>, then verification code will be compiled in, but not	4965	in. If set to C<1>, then verification code will be compiled in, but not
4035	called. If set to C<2>, then the internal verification code will be	4966	called. If set to C<2>, then the internal verification code will be
4036	called once per loop, which can slow down libev. If set to C<3>, then the	4967	called once per loop, which can slow down libev. If set to C<3>, then the
4037	verification code will be called very frequently, which will slow down	4968	verification code will be called very frequently, which will slow down
…		…
4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5051	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4121		5052
4122	#include "ev_cpp.h"	5053	#include "ev_cpp.h"
4123	#include "ev.c"	5054	#include "ev.c"
4124		5055
4125	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5056	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4126		5057
4127	=head2 THREADS AND COROUTINES	5058	=head2 THREADS AND COROUTINES
4128		5059
4129	=head3 THREADS	5060	=head3 THREADS
4130		5061
…		…
4181	default loop and triggering an C<ev_async> watcher from the default loop	5112	default loop and triggering an C<ev_async> watcher from the default loop
4182	watcher callback into the event loop interested in the signal.	5113	watcher callback into the event loop interested in the signal.
4183		5114
4184	=back	5115	=back
4185		5116
4186	=head4 THREAD LOCKING EXAMPLE	5117	See also L</THREAD LOCKING EXAMPLE>.
4187
4188	Here is a fictitious example of how to run an event loop in a different
4189	thread than where callbacks are being invoked and watchers are
4190	created/added/removed.
4191
4192	For a real-world example, see the C<EV::Loop::Async> perl module,
4193	which uses exactly this technique (which is suited for many high-level
4194	languages).
4195
4196	The example uses a pthread mutex to protect the loop data, a condition
4197	variable to wait for callback invocations, an async watcher to notify the
4198	event loop thread and an unspecified mechanism to wake up the main thread.
4199
4200	First, you need to associate some data with the event loop:
4201
4202	typedef struct {
4203	mutex_t lock; /* global loop lock */
4204	ev_async async_w;
4205	thread_t tid;
4206	cond_t invoke_cv;
4207	} userdata;
4208
4209	void prepare_loop (EV_P)
4210	{
4211	// for simplicity, we use a static userdata struct.
4212	static userdata u;
4213
4214	ev_async_init (&u->async_w, async_cb);
4215	ev_async_start (EV_A_ &u->async_w);
4216
4217	pthread_mutex_init (&u->lock, 0);
4218	pthread_cond_init (&u->invoke_cv, 0);
4219
4220	// now associate this with the loop
4221	ev_set_userdata (EV_A_ u);
4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4224
4225	// then create the thread running ev_loop
4226	pthread_create (&u->tid, 0, l_run, EV_A);
4227	}
4228
4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
4230	solely to wake up the event loop so it takes notice of any new watchers
4231	that might have been added:
4232
4233	static void
4234	async_cb (EV_P_ ev_async *w, int revents)
4235	{
4236	// just used for the side effects
4237	}
4238
4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4240	protecting the loop data, respectively.
4241
4242	static void
4243	l_release (EV_P)
4244	{
4245	userdata *u = ev_userdata (EV_A);
4246	pthread_mutex_unlock (&u->lock);
4247	}
4248
4249	static void
4250	l_acquire (EV_P)
4251	{
4252	userdata *u = ev_userdata (EV_A);
4253	pthread_mutex_lock (&u->lock);
4254	}
4255
4256	The event loop thread first acquires the mutex, and then jumps straight
4257	into C<ev_loop>:
4258
4259	void *
4260	l_run (void *thr_arg)
4261	{
4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4263
4264	l_acquire (EV_A);
4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4266	ev_loop (EV_A_ 0);
4267	l_release (EV_A);
4268
4269	return 0;
4270	}
4271
4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
4273	signal the main thread via some unspecified mechanism (signals? pipe
4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4275	have been called (in a while loop because a) spurious wakeups are possible
4276	and b) skipping inter-thread-communication when there are no pending
4277	watchers is very beneficial):
4278
4279	static void
4280	l_invoke (EV_P)
4281	{
4282	userdata *u = ev_userdata (EV_A);
4283
4284	while (ev_pending_count (EV_A))
4285	{
4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
4288	}
4289	}
4290
4291	Now, whenever the main thread gets told to invoke pending watchers, it
4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4293	thread to continue:
4294
4295	static void
4296	real_invoke_pending (EV_P)
4297	{
4298	userdata *u = ev_userdata (EV_A);
4299
4300	pthread_mutex_lock (&u->lock);
4301	ev_invoke_pending (EV_A);
4302	pthread_cond_signal (&u->invoke_cv);
4303	pthread_mutex_unlock (&u->lock);
4304	}
4305
4306	Whenever you want to start/stop a watcher or do other modifications to an
4307	event loop, you will now have to lock:
4308
4309	ev_timer timeout_watcher;
4310	userdata *u = ev_userdata (EV_A);
4311
4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4313
4314	pthread_mutex_lock (&u->lock);
4315	ev_timer_start (EV_A_ &timeout_watcher);
4316	ev_async_send (EV_A_ &u->async_w);
4317	pthread_mutex_unlock (&u->lock);
4318
4319	Note that sending the C<ev_async> watcher is required because otherwise
4320	an event loop currently blocking in the kernel will have no knowledge
4321	about the newly added timer. By waking up the loop it will pick up any new
4322	watchers in the next event loop iteration.
4323		5118
4324	=head3 COROUTINES	5119	=head3 COROUTINES
4325		5120
4326	Libev is very accommodating to coroutines ("cooperative threads"):	5121	Libev is very accommodating to coroutines ("cooperative threads"):
4327	libev fully supports nesting calls to its functions from different	5122	libev fully supports nesting calls to its functions from different
4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5123	coroutines (e.g. you can call C<ev_run> on the same loop from two
4329	different coroutines, and switch freely between both coroutines running	5124	different coroutines, and switch freely between both coroutines running
4330	the loop, as long as you don't confuse yourself). The only exception is	5125	the loop, as long as you don't confuse yourself). The only exception is
4331	that you must not do this from C<ev_periodic> reschedule callbacks.	5126	that you must not do this from C<ev_periodic> reschedule callbacks.
4332		5127
4333	Care has been taken to ensure that libev does not keep local state inside	5128	Care has been taken to ensure that libev does not keep local state inside
4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5129	C<ev_run>, and other calls do not usually allow for coroutine switches as
4335	they do not call any callbacks.	5130	they do not call any callbacks.
4336		5131
4337	=head2 COMPILER WARNINGS	5132	=head2 COMPILER WARNINGS
4338		5133
4339	Depending on your compiler and compiler settings, you might get no or a	5134	Depending on your compiler and compiler settings, you might get no or a
…		…
4423	=head3 C<kqueue> is buggy	5218	=head3 C<kqueue> is buggy
4424		5219
4425	The kqueue syscall is broken in all known versions - most versions support	5220	The kqueue syscall is broken in all known versions - most versions support
4426	only sockets, many support pipes.	5221	only sockets, many support pipes.
4427		5222
		5223	Libev tries to work around this by not using C<kqueue> by default on this
		5224	rotten platform, but of course you can still ask for it when creating a
		5225	loop - embedding a socket-only kqueue loop into a select-based one is
		5226	probably going to work well.
		5227
4428	=head3 C<poll> is buggy	5228	=head3 C<poll> is buggy
4429		5229
4430	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5230	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4431	implementation by something calling C<kqueue> internally around the 10.5.6	5231	implementation by something calling C<kqueue> internally around the 10.5.6
4432	release, so now C<kqueue> I<and> C<poll> are broken.	5232	release, so now C<kqueue> I<and> C<poll> are broken.
4433		5233
4434	Libev tries to work around this by neither using C<kqueue> nor C<poll> by	5234	Libev tries to work around this by not using C<poll> by default on
4435	default on this rotten platform, but of course you cna still ask for them	5235	this rotten platform, but of course you can still ask for it when creating
4436	when creating a loop.	5236	a loop.
4437		5237
4438	=head3 C<select> is buggy	5238	=head3 C<select> is buggy
4439		5239
4440	All that's left is C<select>, and of course Apple found a way to fuck this	5240	All that's left is C<select>, and of course Apple found a way to fuck this
4441	one up as well: On OS/X, C<select> actively limits the number of file	5241	one up as well: On OS/X, C<select> actively limits the number of file
4442	descriptors you can pass in to 1024 - your program suddenyl crashes when	5242	descriptors you can pass in to 1024 - your program suddenly crashes when
4443	you use more.	5243	you use more.
4444		5244
4445	There is an undocumented "workaround" for this - defining	5245	There is an undocumented "workaround" for this - defining
4446	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>	5246	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4447	work on OS/X.	5247	work on OS/X.
…		…
4450		5250
4451	=head3 C<errno> reentrancy	5251	=head3 C<errno> reentrancy
4452		5252
4453	The default compile environment on Solaris is unfortunately so	5253	The default compile environment on Solaris is unfortunately so
4454	thread-unsafe that you can't even use components/libraries compiled	5254	thread-unsafe that you can't even use components/libraries compiled
4455	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5255	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4456	isn't defined by default.	5256	defined by default. A valid, if stupid, implementation choice.
4457		5257
4458	If you want to use libev in threaded environments you have to make sure	5258	If you want to use libev in threaded environments you have to make sure
4459	it's compiled with C<_REENTRANT> defined.	5259	it's compiled with C<_REENTRANT> defined.
4460		5260
4461	=head3 Event port backend	5261	=head3 Event port backend
4462		5262
4463	The scalable event interface for Solaris is called "event ports". Unfortunately,	5263	The scalable event interface for Solaris is called "event
4464	this mechanism is very buggy. If you run into high CPU usage, your program	5264	ports". Unfortunately, this mechanism is very buggy in all major
		5265	releases. If you run into high CPU usage, your program freezes or you get
4465	freezes or you get a large number of spurious wakeups, make sure you have	5266	a large number of spurious wakeups, make sure you have all the relevant
4466	all the relevant and latest kernel patches applied. No, I don't know which	5267	and latest kernel patches applied. No, I don't know which ones, but there
4467	ones, but there are multiple ones.	5268	are multiple ones to apply, and afterwards, event ports actually work
		5269	great.
4468		5270
4469	If you can't get it to work, you can try running the program with	5271	If you can't get it to work, you can try running the program by setting
4470	C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends.	5272	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5273	C<select> backends.
4471		5274
4472	=head2 AIX POLL BUG	5275	=head2 AIX POLL BUG
4473		5276
4474	AIX unfortunately has a broken C<poll.h> header. Libev works around	5277	AIX unfortunately has a broken C<poll.h> header. Libev works around
4475	this by trying to avoid the poll backend altogether (i.e. it's not even	5278	this by trying to avoid the poll backend altogether (i.e. it's not even
4476	compiled in), which normally isn't a big problem as C<select> works fine	5279	compiled in), which normally isn't a big problem as C<select> works fine
4477	with large bitsets, and AIX is dead anyway.	5280	with large bitsets on AIX, and AIX is dead anyway.
4478		5281
4479	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5282	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4480		5283
4481	=head3 General issues	5284	=head3 General issues
4482		5285
…		…
4484	requires, and its I/O model is fundamentally incompatible with the POSIX	5287	requires, and its I/O model is fundamentally incompatible with the POSIX
4485	model. Libev still offers limited functionality on this platform in	5288	model. Libev still offers limited functionality on this platform in
4486	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5289	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4487	descriptors. This only applies when using Win32 natively, not when using	5290	descriptors. This only applies when using Win32 natively, not when using
4488	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5291	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4489	as every compielr comes with a slightly differently broken/incompatible	5292	as every compiler comes with a slightly differently broken/incompatible
4490	environment.	5293	environment.
4491		5294
4492	Lifting these limitations would basically require the full	5295	Lifting these limitations would basically require the full
4493	re-implementation of the I/O system. If you are into this kind of thing,	5296	re-implementation of the I/O system. If you are into this kind of thing,
4494	then note that glib does exactly that for you in a very portable way (note	5297	then note that glib does exactly that for you in a very portable way (note
…		…
4588	structure (guaranteed by POSIX but not by ISO C for example), but it also	5391	structure (guaranteed by POSIX but not by ISO C for example), but it also
4589	assumes that the same (machine) code can be used to call any watcher	5392	assumes that the same (machine) code can be used to call any watcher
4590	callback: The watcher callbacks have different type signatures, but libev	5393	callback: The watcher callbacks have different type signatures, but libev
4591	calls them using an C<ev_watcher *> internally.	5394	calls them using an C<ev_watcher *> internally.
4592		5395
		5396	=item null pointers and integer zero are represented by 0 bytes
		5397
		5398	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5399	relies on this setting pointers and integers to null.
		5400
		5401	=item pointer accesses must be thread-atomic
		5402
		5403	Accessing a pointer value must be atomic, it must both be readable and
		5404	writable in one piece - this is the case on all current architectures.
		5405
4593	=item C<sig_atomic_t volatile> must be thread-atomic as well	5406	=item C<sig_atomic_t volatile> must be thread-atomic as well
4594		5407
4595	The type C<sig_atomic_t volatile> (or whatever is defined as	5408	The type C<sig_atomic_t volatile> (or whatever is defined as
4596	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5409	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4597	threads. This is not part of the specification for C<sig_atomic_t>, but is	5410	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4605	thread" or will block signals process-wide, both behaviours would	5418	thread" or will block signals process-wide, both behaviours would
4606	be compatible with libev. Interaction between C<sigprocmask> and	5419	be compatible with libev. Interaction between C<sigprocmask> and
4607	C<pthread_sigmask> could complicate things, however.	5420	C<pthread_sigmask> could complicate things, however.
4608		5421
4609	The most portable way to handle signals is to block signals in all threads	5422	The most portable way to handle signals is to block signals in all threads
4610	except the initial one, and run the default loop in the initial thread as	5423	except the initial one, and run the signal handling loop in the initial
4611	well.	5424	thread as well.
4612		5425
4613	=item C<long> must be large enough for common memory allocation sizes	5426	=item C<long> must be large enough for common memory allocation sizes
4614		5427
4615	To improve portability and simplify its API, libev uses C<long> internally	5428	To improve portability and simplify its API, libev uses C<long> internally
4616	instead of C<size_t> when allocating its data structures. On non-POSIX	5429	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4619	watchers.	5432	watchers.
4620		5433
4621	=item C<double> must hold a time value in seconds with enough accuracy	5434	=item C<double> must hold a time value in seconds with enough accuracy
4622		5435
4623	The type C<double> is used to represent timestamps. It is required to	5436	The type C<double> is used to represent timestamps. It is required to
4624	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5437	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4625	enough for at least into the year 4000. This requirement is fulfilled by	5438	good enough for at least into the year 4000 with millisecond accuracy
		5439	(the design goal for libev). This requirement is overfulfilled by
4626	implementations implementing IEEE 754, which is basically all existing	5440	implementations using IEEE 754, which is basically all existing ones.
		5441
4627	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5442	With IEEE 754 doubles, you get microsecond accuracy until at least the
4628	2200.	5443	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5444	is either obsolete or somebody patched it to use C<long double> or
		5445	something like that, just kidding).
4629		5446
4630	=back	5447	=back
4631		5448
4632	If you know of other additional requirements drop me a note.	5449	If you know of other additional requirements drop me a note.
4633		5450
…		…
4695	=item Processing ev_async_send: O(number_of_async_watchers)	5512	=item Processing ev_async_send: O(number_of_async_watchers)
4696		5513
4697	=item Processing signals: O(max_signal_number)	5514	=item Processing signals: O(max_signal_number)
4698		5515
4699	Sending involves a system call I<iff> there were no other C<ev_async_send>	5516	Sending involves a system call I<iff> there were no other C<ev_async_send>
4700	calls in the current loop iteration. Checking for async and signal events	5517	calls in the current loop iteration and the loop is currently
		5518	blocked. Checking for async and signal events involves iterating over all
4701	involves iterating over all running async watchers or all signal numbers.	5519	running async watchers or all signal numbers.
4702		5520
4703	=back	5521	=back
4704		5522
4705		5523
4706	=head1 PORTING FROM LIBEV 3.X TO 4.X	5524	=head1 PORTING FROM LIBEV 3.X TO 4.X
4707		5525
4708	The major version 4 introduced some minor incompatible changes to the API.	5526	The major version 4 introduced some incompatible changes to the API.
4709		5527
4710	At the moment, the C<ev.h> header file tries to implement superficial	5528	At the moment, the C<ev.h> header file provides compatibility definitions
4711	compatibility, so most programs should still compile. Those might be	5529	for all changes, so most programs should still compile. The compatibility
4712	removed in later versions of libev, so better update early than late.	5530	layer might be removed in later versions of libev, so better update to the
		5531	new API early than late.
4713		5532
4714	=over 4	5533	=over 4
4715		5534
4716	=item C<ev_loop_count> renamed to C<ev_iteration>	5535	=item C<EV_COMPAT3> backwards compatibility mechanism
4717		5536
4718	=item C<ev_loop_depth> renamed to C<ev_depth>	5537	The backward compatibility mechanism can be controlled by
		5538	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5539	section.
4719		5540
4720	=item C<ev_loop_verify> renamed to C<ev_verify>	5541	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5542
		5543	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5544
		5545	ev_loop_destroy (EV_DEFAULT_UC);
		5546	ev_loop_fork (EV_DEFAULT);
		5547
		5548	=item function/symbol renames
		5549
		5550	A number of functions and symbols have been renamed:
		5551
		5552	ev_loop => ev_run
		5553	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5554	EVLOOP_ONESHOT => EVRUN_ONCE
		5555
		5556	ev_unloop => ev_break
		5557	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5558	EVUNLOOP_ONE => EVBREAK_ONE
		5559	EVUNLOOP_ALL => EVBREAK_ALL
		5560
		5561	EV_TIMEOUT => EV_TIMER
		5562
		5563	ev_loop_count => ev_iteration
		5564	ev_loop_depth => ev_depth
		5565	ev_loop_verify => ev_verify
4721		5566
4722	Most functions working on C<struct ev_loop> objects don't have an	5567	Most functions working on C<struct ev_loop> objects don't have an
4723	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5568	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5569	associated constants have been renamed to not collide with the C<struct
		5570	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5571	as all other watcher types. Note that C<ev_loop_fork> is still called
4724	still called C<ev_loop_fork> because it would otherwise clash with the	5572	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4725	C<ev_fork> typedef.	5573	typedef.
4726
4727	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4728
4729	This is a simple rename - all other watcher types use their name
4730	as revents flag, and now C<ev_timer> does, too.
4731
4732	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4733	and continue to be present for the foreseeable future, so this is mostly a
4734	documentation change.
4735		5574
4736	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5575	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4737		5576
4738	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5577	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4739	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5578	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4746		5585
4747	=over 4	5586	=over 4
4748		5587
4749	=item active	5588	=item active
4750		5589
4751	A watcher is active as long as it has been started (has been attached to	5590	A watcher is active as long as it has been started and not yet stopped.
4752	an event loop) but not yet stopped (disassociated from the event loop).	5591	See L</WATCHER STATES> for details.
4753		5592
4754	=item application	5593	=item application
4755		5594
4756	In this document, an application is whatever is using libev.	5595	In this document, an application is whatever is using libev.
		5596
		5597	=item backend
		5598
		5599	The part of the code dealing with the operating system interfaces.
4757		5600
4758	=item callback	5601	=item callback
4759		5602
4760	The address of a function that is called when some event has been	5603	The address of a function that is called when some event has been
4761	detected. Callbacks are being passed the event loop, the watcher that	5604	detected. Callbacks are being passed the event loop, the watcher that
4762	received the event, and the actual event bitset.	5605	received the event, and the actual event bitset.
4763		5606
4764	=item callback invocation	5607	=item callback/watcher invocation
4765		5608
4766	The act of calling the callback associated with a watcher.	5609	The act of calling the callback associated with a watcher.
4767		5610
4768	=item event	5611	=item event
4769		5612
…		…
4788	The model used to describe how an event loop handles and processes	5631	The model used to describe how an event loop handles and processes
4789	watchers and events.	5632	watchers and events.
4790		5633
4791	=item pending	5634	=item pending
4792		5635
4793	A watcher is pending as soon as the corresponding event has been detected,	5636	A watcher is pending as soon as the corresponding event has been
4794	and stops being pending as soon as the watcher will be invoked or its	5637	detected. See L</WATCHER STATES> for details.
4795	pending status is explicitly cleared by the application.
4796
4797	A watcher can be pending, but not active. Stopping a watcher also clears
4798	its pending status.
4799		5638
4800	=item real time	5639	=item real time
4801		5640
4802	The physical time that is observed. It is apparently strictly monotonic :)	5641	The physical time that is observed. It is apparently strictly monotonic :)
4803		5642
4804	=item wall-clock time	5643	=item wall-clock time
4805		5644
4806	The time and date as shown on clocks. Unlike real time, it can actually	5645	The time and date as shown on clocks. Unlike real time, it can actually
4807	be wrong and jump forwards and backwards, e.g. when the you adjust your	5646	be wrong and jump forwards and backwards, e.g. when you adjust your
4808	clock.	5647	clock.
4809		5648
4810	=item watcher	5649	=item watcher
4811		5650
4812	A data structure that describes interest in certain events. Watchers need	5651	A data structure that describes interest in certain events. Watchers need
4813	to be started (attached to an event loop) before they can receive events.	5652	to be started (attached to an event loop) before they can receive events.
4814		5653
4815	=item watcher invocation
4816
4817	The act of calling the callback associated with a watcher.
4818
4819	=back	5654	=back
4820		5655
4821	=head1 AUTHOR	5656	=head1 AUTHOR
4822		5657
4823	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5658	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5659	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4824		5660

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