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Revision 1.282 by root, Wed Mar 10 08:19:39 2010 UTC vs.
Revision 1.441 by root, Thu Jul 13 10:46:52 2017 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
134	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	146	time differences (e.g. delays) throughout libev.
136		147
137	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
138		149
139	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	151	and internal errors (bugs).
…		…
164		175
165	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
166		177
167	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
168	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
169	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>.
170		182
171	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
172		184
173	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
174	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
175	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 >>).
176		194
177	=item int ev_version_major ()	195	=item int ev_version_major ()
178		196
179	=item int ev_version_minor ()	197	=item int ev_version_minor ()
180		198
…		…
191	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
192	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
193	not a problem.	211	not a problem.
194		212
195	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
196	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
197		216
198	assert (("libev version mismatch",	217	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
201		220
…		…
212	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
214		233
215	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
216		235
217	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
218	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
219	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
220	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
221	(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
222	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
223		243
224	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
225		245
226	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
227	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
231		251
232	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
233		253
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
235		255
236	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	285	}
266		286
267	...	287	...
268	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
269		289
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
271		291
272	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	307	}
288		308
289	...	309	...
290	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
291		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
292	=back	325	=back
293		326
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		328
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
299		332
300	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
302	not.	335	do not.
303		336
304	=over 4	337	=over 4
305		338
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		340
308	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
312		351
313	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
314	function.	353	function (or via the C<EV_DEFAULT> macro).
315		354
316	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
319		359
320	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
326		384
327	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		387
330	The following flags are supported:	388	The following flags are supported:
…		…
340		398
341	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
342	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
344	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
345	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
346	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
347		407
348	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
349		409
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	411	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		412
354	This works by calling C<getpid ()> on every iteration of the loop,	413	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	414	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	415	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	416	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	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
360		420
361	The big advantage of this flag is that you can forget about fork (and	421	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	422	forget about forgetting to tell libev about forking, although you still
363	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
364		424
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	426	environment variable.
367		427
368	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
369		429
370	When this flag is specified, then libev will not attempt to use the	430	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	431	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	432	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.	433	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		434
375	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
376		436
377	When this flag is specified, then libev will attempt to use the	437	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	438	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	439	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	440	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	441	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	442	threads that are not interested in handling them.
383		443
384	Signalfd will not be used by default as this changes your signal mask, and	444	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	445	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
387		462
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		464
390	This is your standard select(2) backend. Not I<completely> standard, as	465	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,	466	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		495
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	497	kernels).
423		498
424	For few fds, this backend is a bit little slower than poll and select,	499	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	500	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),	501	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).	502	fd), epoll scales either O(1) or O(active_fds).
428		503
429	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	507	descriptor (and unnecessary guessing of parameters), problems with dup,
		508	returning before the timeout value, resulting in additional iterations
		509	(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	510	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	511	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	512	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	513	and is of course hard to detect.
437		514
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	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	516	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	517	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	518	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	519	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
		525	not least, it also refuses to work with some file descriptors which work
		526	perfectly fine with C<select> (files, many character devices...).
		527
		528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
445		531
446	While stopping, setting and starting an I/O watcher in the same iteration	532	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	533	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	534	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	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
486		572
487	It scales in the same way as the epoll backend, but the interface to the	573	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	574	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	575	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	576	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	577	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	578	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	579	drops fds silently in similarly hard-to-detect cases.
494		580
495	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
496		582
497	While nominally embeddable in other event loops, this doesn't work	583	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	584	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		602
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	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)).	604	it's really slow, but it still scales very well (O(active_fds)).
519		605
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	606	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	607	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	609	might perform better.
528		610
529	On the positive side, with the exception of the spurious readiness	611	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	612	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
533		625
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
536		628
537	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
538		630
539	Try all backends (even potentially broken ones that wouldn't be tried	631	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	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		634
543	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		644
545	=back	645	=back
546		646
547	If one or more of the backend flags are or'ed into the flags value,	647	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	648	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	649	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	650	()> will be tried.
551		651
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. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	652	Example: Try to create a event loop that uses epoll and nothing else.
581		653
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	655	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
585		657
		658	Example: Use whatever libev has to offer, but make sure that kqueue is
		659	used if available.
		660
		661	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		662
586	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
587		664
588	Destroys the default loop again (frees all memory and kernel state	665	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	666	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	667	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	668	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	669	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	670	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		672
596	Note that certain global state, such as signal state (and installed signal	673	Note that certain global state, such as signal state (and installed signal
597	handlers), will not be freed by this function, and related watchers (such	674	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
599		676
600	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	678	C<ev_loop_new>, but it can also be used on the default loop returned by
		679	C<ev_default_loop>, in which case it is not thread-safe.
		680
		681	Note that it is not advisable to call this function on the default loop
		682	except in the rare occasion where you really need to free its resources.
602	pipe fds. If you need dynamically allocated loops it is better to use	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
603	C<ev_loop_new> and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
604		685
605	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
606		687
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	688	This function sets a flag that causes subsequent C<ev_run> iterations
613	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
614	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
615	the child process (or both child and parent, but that again makes little	691	watchers (except inside an C<ev_prepare> callback), but it makes most
616	sense). You I<must> call it in the child before using any of the libev	692	sense after forking, in the child process. You I<must> call it (or use
617	functions, and it will only take effect at the next C<ev_loop> iteration.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
		698	Again, you I<have> to call it on I<any> loop that you want to re-use after
		699	a fork, I<even if you do not plan to use the loop in the parent>. This is
		700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		701	during fork.
618		702
619	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
620	process if and only if you want to use the event library in the child. If	704	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	705	you just fork+exec or create a new loop in the child, you don't have to
		706	call it at all (in fact, C<epoll> is so badly broken that it makes a
		707	difference, but libev will usually detect this case on its own and do a
		708	costly reset of the backend).
622		709
623	The function itself is quite fast and it's usually not a problem to call	710	The function itself is quite fast and it's usually not a problem to call
624	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		712
		713	Example: Automate calling C<ev_loop_fork> on the default loop when
		714	using pthreads.
		715
		716	static void
		717	post_fork_child (void)
		718	{
		719	ev_loop_fork (EV_DEFAULT);
		720	}
		721
		722	...
627	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		724
636	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
637		726
638	Returns true when the given loop is, in fact, the default loop, and false	727	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	728	otherwise.
640		729
641	=item unsigned int ev_loop_count (loop)	730	=item unsigned int ev_iteration (loop)
642		731
643	Returns the count of loop iterations for the loop, which is identical to	732	Returns the current iteration count for the event loop, which is identical
644	the number of times libev did poll for new events. It starts at C<0> and	733	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	734	and happily wraps around with enough iterations.
646		735
647	This value can sometimes be useful as a generation counter of sorts (it	736	This value can sometimes be useful as a generation counter of sorts (it
648	"ticks" the number of loop iterations), as it roughly corresponds with	737	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	738	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		739	prepare and check phases.
650		740
651	=item unsigned int ev_loop_depth (loop)	741	=item unsigned int ev_depth (loop)
652		742
653	Returns the number of times C<ev_loop> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
654	times C<ev_loop> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
655		745
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	748	in which case it is higher.
659		749
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	751	throwing an exception etc.), doesn't count as "exit" - consider this
		752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
662		754
663	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
664		756
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	758	use.
…		…
675		767
676	=item ev_now_update (loop)	768	=item ev_now_update (loop)
677		769
678	Establishes the current time by querying the kernel, updating the time	770	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	771	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	772	is usually done automatically within C<ev_run ()>.
681		773
682	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
683	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	776	the current time is a good idea.
685		777
686	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
687		779
688	=item ev_suspend (loop)	780	=item ev_suspend (loop)
689		781
690	=item ev_resume (loop)	782	=item ev_resume (loop)
691		783
692	These two functions suspend and resume a loop, for use when the loop is	784	These two functions suspend and resume an event loop, for use when the
693	not used for a while and timeouts should not be processed.	785	loop is not used for a while and timeouts should not be processed.
694		786
695	A typical use case would be an interactive program such as a game: When	787	A typical use case would be an interactive program such as a game: When
696	the user presses C<^Z> to suspend the game and resumes it an hour later it	788	the user presses C<^Z> to suspend the game and resumes it an hour later it
697	would be best to handle timeouts as if no time had actually passed while	789	would be best to handle timeouts as if no time had actually passed while
698	the program was suspended. This can be achieved by calling C<ev_suspend>	790	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	792	C<ev_resume> directly afterwards to resume timer processing.
701		793
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	794	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	795	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	796	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	797	occurred while suspended).
706		798
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	799	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	800	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
710		802
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
713		805
714	=item ev_loop (loop, int flags)	806	=item bool ev_run (loop, int flags)
715		807
716	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
717	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
718	handling events.	810	handling events. It will ask the operating system for any new events, call
		811	the watcher callbacks, and then repeat the whole process indefinitely: This
		812	is why event loops are called I<loops>.
719		813
720	If the flags argument is specified as C<0>, it will not return until	814	If the flags argument is specified as C<0>, it will keep handling events
721	either no event watchers are active anymore or C<ev_unloop> was called.	815	until either no event watchers are active anymore or C<ev_break> was
		816	called.
722		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
		821
723	Please note that an explicit C<ev_unloop> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
724	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
727	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	827	beauty.
729		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
731	those events and any already outstanding ones, but will not block your	835	those events and any already outstanding ones, but will not wait and
732	process in case there are no events and will return after one iteration of	836	block your process in case there are no events and will return after one
733	the loop.	837	iteration of the loop. This is sometimes useful to poll and handle new
		838	events while doing lengthy calculations, to keep the program responsive.
734		839
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	840	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
736	necessary) and will handle those and any already outstanding ones. It	841	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	842	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	843	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	844	user-registered callback will be called), and will return after one
740	iteration of the loop.	845	iteration of the loop.
741		846
742	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
743	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
745	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
746		851
747	Here are the gory details of what C<ev_loop> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
748		855
		856	- Increment loop depth.
		857	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
		859	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	860	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	861	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	862	- Queue and call all prepare watchers.
		863	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	864	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	865	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	866	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	867	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	868	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	869	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	870	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	871	- Sleep if the I/O and timer collect interval say so.
		872	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	873	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	874	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	875	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	876	- Queue all expired timers.
765	- Queue all expired periodics.	877	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	878	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	879	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	880	- Call all queued watchers in reverse order (i.e. check watchers first).
769	Signals and child watchers are implemented as I/O watchers, and will	881	Signals and child watchers are implemented as I/O watchers, and will
770	be handled here by queueing them when their watcher gets executed.	882	be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	883	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	884	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	885	continue with step LOOP.
		886	FINISH:
		887	- Reset the ev_break status iff it was EVBREAK_ONE.
		888	- Decrement the loop depth.
		889	- Return.
774		890
775	Example: Queue some jobs and then loop until no events are outstanding	891	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	892	anymore.
777		893
778	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	896	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
782		898
783	=item ev_unloop (loop, how)	899	=item ev_break (loop, how)
784		900
785	Can be used to make a call to C<ev_loop> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
786	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		905
790	This "unloop state" will be cleared when entering C<ev_loop> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
791		907
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
793		910
794	=item ev_ref (loop)	911	=item ev_ref (loop)
795		912
796	=item ev_unref (loop)	913	=item ev_unref (loop)
797		914
798	Ref/unref can be used to add or remove a reference count on the event	915	Ref/unref can be used to add or remove a reference count on the event
799	loop: Every watcher keeps one reference, and as long as the reference	916	loop: Every watcher keeps one reference, and as long as the reference
800	count is nonzero, C<ev_loop> will not return on its own.	917	count is nonzero, C<ev_run> will not return on its own.
801		918
802	This is useful when you have a watcher that you never intend to	919	This is useful when you have a watcher that you never intend to
803	unregister, but that nevertheless should not keep C<ev_loop> from	920	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	921	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	922	before stopping it.
806		923
807	As an example, libev itself uses this for its internal signal pipe: It	924	As an example, libev itself uses this for its internal signal pipe: It
808	is not visible to the libev user and should not keep C<ev_loop> from	925	is not visible to the libev user and should not keep C<ev_run> from
809	exiting if no event watchers registered by it are active. It is also an	926	exiting if no event watchers registered by it are active. It is also an
810	excellent way to do this for generic recurring timers or from within	927	excellent way to do this for generic recurring timers or from within
811	third-party libraries. Just remember to I<unref after start> and I<ref	928	third-party libraries. Just remember to I<unref after start> and I<ref
812	before stop> (but only if the watcher wasn't active before, or was active	929	before stop> (but only if the watcher wasn't active before, or was active
813	before, respectively. Note also that libev might stop watchers itself	930	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	931	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	932	in the callback).
816		933
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	934	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	935	running when nothing else is active.
819		936
820	ev_signal exitsig;	937	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	940	ev_unref (loop);
824		941
825	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
826		943
827	ev_ref (loop);	944	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
848	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
849		966
850	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
851	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
853	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
854	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
855	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
856	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
857		975
858	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
859	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
860	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
861	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	985	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	986	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	987	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	988	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	989	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	990	then you can't do more than 100 transactions per second).
873		991
874	Setting the I<timeout collect interval> can improve the opportunity for	992	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	993	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	994	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	995	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1003	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		1004
887	=item ev_invoke_pending (loop)	1005	=item ev_invoke_pending (loop)
888		1006
889	This call will simply invoke all pending watchers while resetting their	1007	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	1008	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	1009	but when overriding the invoke callback this call comes handy. This
		1010	function can be invoked from a watcher - this can be useful for example
		1011	when you want to do some lengthy calculation and want to pass further
		1012	event handling to another thread (you still have to make sure only one
		1013	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		1014
893	=item int ev_pending_count (loop)	1015	=item int ev_pending_count (loop)
894		1016
895	Returns the number of pending watchers - zero indicates that no watchers	1017	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	1018	are pending.
897		1019
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1020	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		1021
900	This overrides the invoke pending functionality of the loop: Instead of	1022	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	1023	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	1024	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
904		1026
905	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1028	callback.
907		1029
908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
909		1031
910	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
911	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1034	each call to a libev function.
913		1035
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
915	wait for it to return. One way around this is to wake up the loop via	1037	to wait for it to return. One way around this is to wake up the event
916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
918		1040
919	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
920	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1043	afterwards.
922		1044
…		…
925		1047
926	While event loop modifications are allowed between invocations of	1048	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1049	C<release> and C<acquire> (that's their only purpose after all), no
928	modifications done will affect the event loop, i.e. adding watchers will	1050	modifications done will affect the event loop, i.e. adding watchers will
929	have no effect on the set of file descriptors being watched, or the time	1051	have no effect on the set of file descriptors being watched, or the time
930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1052	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
931	to take note of any changes you made.	1053	to take note of any changes you made.
932		1054
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1055	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1056	invocations of C<release> and C<acquire>.
935		1057
936	See also the locking example in the C<THREADS> section later in this	1058	See also the locking example in the C<THREADS> section later in this
937	document.	1059	document.
938		1060
939	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
940		1062
941	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
942		1064
943	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1067	C<0>.
946		1068
947	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
948	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
949	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1072	any other purpose as well.
951		1073
952	=item ev_loop_verify (loop)	1074	=item ev_verify (loop)
953		1075
954	This function only does something when C<EV_VERIFY> support has been	1076	This function only does something when C<EV_VERIFY> support has been
955	compiled in, which is the default for non-minimal builds. It tries to go	1077	compiled in, which is the default for non-minimal builds. It tries to go
956	through all internal structures and checks them for validity. If anything	1078	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1079	is found to be inconsistent, it will print an error message to standard
…		…
968		1090
969	In the following description, uppercase C<TYPE> in names stands for the	1091	In the following description, uppercase C<TYPE> in names stands for the
970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1092	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
971	watchers and C<ev_io_start> for I/O watchers.	1093	watchers and C<ev_io_start> for I/O watchers.
972		1094
973	A watcher is a structure that you create and register to record your	1095	A watcher is an opaque structure that you allocate and register to record
974	interest in some event. For instance, if you want to wait for STDIN to	1096	your interest in some event. To make a concrete example, imagine you want
975	become readable, you would create an C<ev_io> watcher for that:	1097	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1098	for that:
976		1099
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1100	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1101	{
979	ev_io_stop (w);	1102	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1103	ev_break (loop, EVBREAK_ALL);
981	}	1104	}
982		1105
983	struct ev_loop *loop = ev_default_loop (0);	1106	struct ev_loop *loop = ev_default_loop (0);
984		1107
985	ev_io stdin_watcher;	1108	ev_io stdin_watcher;
986		1109
987	ev_init (&stdin_watcher, my_cb);	1110	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1111	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1112	ev_io_start (loop, &stdin_watcher);
990		1113
991	ev_loop (loop, 0);	1114	ev_run (loop, 0);
992		1115
993	As you can see, you are responsible for allocating the memory for your	1116	As you can see, you are responsible for allocating the memory for your
994	watcher structures (and it is I<usually> a bad idea to do this on the	1117	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1118	stack).
996		1119
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1120	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1121	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1122
1000	Each watcher structure must be initialised by a call to C<ev_init	1123	Each watcher structure must be initialised by a call to C<ev_init (watcher
1001	(watcher *, callback)>, which expects a callback to be provided. This	1124	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1125	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1126	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1127	and/or writable).
1005		1128
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1129	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1007	macro to configure it, with arguments specific to the watcher type. There	1130	macro to configure it, with arguments specific to the watcher type. There
1008	is also a macro to combine initialisation and setting in one call: C<<	1131	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1132	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1155	=item C<EV_WRITE>
1033		1156
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1157	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1158	writable.
1036		1159
1037	=item C<EV_TIMEOUT>	1160	=item C<EV_TIMER>
1038		1161
1039	The C<ev_timer> watcher has timed out.	1162	The C<ev_timer> watcher has timed out.
1040		1163
1041	=item C<EV_PERIODIC>	1164	=item C<EV_PERIODIC>
1042		1165
…		…
1060		1183
1061	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1062		1185
1063	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1064		1187
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1066	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1067	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1068	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1069	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1070	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1071	C<ev_loop> from blocking).	1199	blocking).
1072		1200
1073	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1074		1202
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1204
1077	=item C<EV_FORK>	1205	=item C<EV_FORK>
1078		1206
1079	The event loop has been resumed in the child process after fork (see	1207	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1208	C<ev_fork>).
		1209
		1210	=item C<EV_CLEANUP>
		1211
		1212	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1213
1082	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1083		1215
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1216	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1217
…		…
1195		1327
1196	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1197		1329
1198	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1199		1331
1200	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1201		1333
1202	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1203	(modulo threads).	1335	(modulo threads).
1204		1336
1205	=item ev_set_priority (ev_TYPE *watcher, int priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1223	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1224		1356
1225	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1226	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1227		1359
1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1229	priorities.	1361	priorities.
1230		1362
1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1232		1364
1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1391	functions that do not need a watcher.
1260		1392
1261	=back	1393	=back
1262		1394
		1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1396	OWN COMPOSITE WATCHERS> idioms.
1263		1397
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1398	=head2 WATCHER STATES
1265		1399
1266	Each watcher has, by default, a member C<void *data> that you can change	1400	There are various watcher states mentioned throughout this manual -
1267	and read at any time: libev will completely ignore it. This can be used	1401	active, pending and so on. In this section these states and the rules to
1268	to associate arbitrary data with your watcher. If you need more data and	1402	transition between them will be described in more detail - and while these
1269	don't want to allocate memory and store a pointer to it in that data	1403	rules might look complicated, they usually do "the right thing".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1404
1273	struct my_io	1405	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1406
1281	...	1407	=item initialised
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1408
1285	And since your callback will be called with a pointer to the watcher, you	1409	Before a watcher can be registered with the event loop it has to be
1286	can cast it back to your own type:	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1287		1412
1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1413	In this state it is simply some block of memory that is suitable for
1289	{	1414	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1415	will - as long as you either keep the memory contents intact, or call
1291	...	1416	C<ev_TYPE_init> again.
1292	}
1293		1417
1294	More interesting and less C-conformant ways of casting your callback type	1418	=item started/running/active
1295	instead have been omitted.
1296		1419
1297	Another common scenario is to use some data structure with multiple	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1298	embedded watchers:	1421	property of the event loop, and is actively waiting for events. While in
		1422	this state it cannot be accessed (except in a few documented ways), moved,
		1423	freed or anything else - the only legal thing is to keep a pointer to it,
		1424	and call libev functions on it that are documented to work on active watchers.
1299		1425
1300	struct my_biggy	1426	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1427
1307	In this case getting the pointer to C<my_biggy> is a bit more	1428	If a watcher is active and libev determines that an event it is interested
1308	complicated: Either you store the address of your C<my_biggy> struct	1429	in has occurred (such as a timer expiring), it will become pending. It will
1309	in the C<data> member of the watcher (for woozies), or you need to use	1430	stay in this pending state until either it is stopped or its callback is
1310	some pointer arithmetic using C<offsetof> inside your watchers (for real	1431	about to be invoked, so it is not normally pending inside the watcher
1311	programmers):	1432	callback.
1312		1433
1313	#include <stddef.h>	1434	The watcher might or might not be active while it is pending (for example,
		1435	an expired non-repeating timer can be pending but no longer active). If it
		1436	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1437	but it is still property of the event loop at this time, so cannot be
		1438	moved, freed or reused. And if it is active the rules described in the
		1439	previous item still apply.
1314		1440
1315	static void	1441	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1442	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1443	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1444
1322	static void	1445	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1446
1324	{	1447	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1448	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1449	latter will clear any pending state the watcher might be in, regardless
1327	}	1450	of whether it was active or not, so stopping a watcher explicitly before
		1451	freeing it is often a good idea.
		1452
		1453	While stopped (and not pending) the watcher is essentially in the
		1454	initialised state, that is, it can be reused, moved, modified in any way
		1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
		1457
		1458	=back
1328		1459
1329	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1330		1461
1331	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1375		1506
1376	For example, to emulate how many other event libraries handle priorities,	1507	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1508	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1509	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1510	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1511	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1512	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1513	workable.
1383		1514
1384	Usually, however, the lock-out model implemented that way will perform	1515	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1516	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1530	{
1400	// stop the I/O watcher, we received the event, but	1531	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1532	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1533	ev_io_stop (EV_A_ w);
1403		1534
1404	// start the idle watcher to ahndle the actual event.	1535	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1536	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1537	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1538	ev_idle_start (EV_A_ &idle);
1408	}	1539	}
1409		1540
…		…
1459	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1460	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1461	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1593	required if you know what you are doing).
1463		1594
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1478		1602
1479	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1480	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1481	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1482	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1483	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1484	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1609	indefinitely.
1486		1610
1487	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1488		1612
…		…
1516		1640
1517	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1521	=head3 The special problem of fork	1678	=head3 The special problem of fork
1522		1679
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1524	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1525	it in the child.	1682	it in the child if you want to continue to use it in the child.
1526		1683
1527	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1528	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1687
1532	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1533		1689
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1535	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1538		1694
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1695	So when you encounter spurious, unexplained daemon exits, make sure you
1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1696	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541	somewhere, as that would have given you a big clue).	1697	somewhere, as that would have given you a big clue).
1542		1698
		1699	=head3 The special problem of accept()ing when you can't
		1700
		1701	Many implementations of the POSIX C<accept> function (for example,
		1702	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1703	connection from the pending queue in all error cases.
		1704
		1705	For example, larger servers often run out of file descriptors (because
		1706	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1707	rejecting the connection, leading to libev signalling readiness on
		1708	the next iteration again (the connection still exists after all), and
		1709	typically causing the program to loop at 100% CPU usage.
		1710
		1711	Unfortunately, the set of errors that cause this issue differs between
		1712	operating systems, there is usually little the app can do to remedy the
		1713	situation, and no known thread-safe method of removing the connection to
		1714	cope with overload is known (to me).
		1715
		1716	One of the easiest ways to handle this situation is to just ignore it
		1717	- when the program encounters an overload, it will just loop until the
		1718	situation is over. While this is a form of busy waiting, no OS offers an
		1719	event-based way to handle this situation, so it's the best one can do.
		1720
		1721	A better way to handle the situation is to log any errors other than
		1722	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1723	messages, and continue as usual, which at least gives the user an idea of
		1724	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1725	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1726	usage.
		1727
		1728	If your program is single-threaded, then you could also keep a dummy file
		1729	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1730	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1731	close that fd, and create a new dummy fd. This will gracefully refuse
		1732	clients under typical overload conditions.
		1733
		1734	The last way to handle it is to simply log the error and C<exit>, as
		1735	is often done with C<malloc> failures, but this results in an easy
		1736	opportunity for a DoS attack.
1543		1737
1544	=head3 Watcher-Specific Functions	1738	=head3 Watcher-Specific Functions
1545		1739
1546	=over 4	1740	=over 4
1547		1741
…		…
1579	...	1773	...
1580	struct ev_loop *loop = ev_default_init (0);	1774	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1775	ev_io stdin_readable;
1582	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1776	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1583	ev_io_start (loop, &stdin_readable);	1777	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1778	ev_run (loop, 0);
1585		1779
1586		1780
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1781	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1782
1589	Timer watchers are simple relative timers that generate an event after a	1783	Timer watchers are simple relative timers that generate an event after a
…		…
1595	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1596	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1597		1791
1598	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1599	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1600	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1601	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1602	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1603	no longer true when a callback calls C<ev_loop> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1604		1799
1605	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1606		1801
1607	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1608	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1683		1878
1684	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1685	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1686	within the callback:	1881	within the callback:
1687		1882
		1883	ev_tstamp timeout = 60.;
1688	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1689		1886
1690	static void	1887	static void
1691	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1692	{	1889	{
1693	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1694	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1695		1892
1696	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1697	if (timeout < now)	1894	if (after < 0.)
1698	{	1895	{
1699	// timeout occured, take action	1896	// timeout occurred, take action
1700	}	1897	}
1701	else	1898	else
1702	{	1899	{
1703	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1704	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1705	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1706	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1707	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1708	}	1906	}
1709	}	1907	}
1710		1908
1711	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1712	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1713	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1714	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1715	re-schedule the timer to fire at that future time, to see if maybe we have
1716	a timeout then.
1717		1913
1718	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1719	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1720		1923
1721	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1722	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1723	libev to change the timeout.	1926	libev to change the timeout.
1724		1927
1725	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1726	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1727	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1728		1932
		1933	last_activity = ev_now (EV_A);
1729	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1730	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1731	callback (loop, timer, EV_TIMEOUT);
1732		1936
1733	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1734	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1735		1939
		1940	if (activity detected)
1736	last_actiivty = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1737		1950
1738	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1739	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1740
1741	Changing the timeout is trivial as well (if it isn't hard-coded in the
1742	callback :) - just change the timeout and invoke the callback, which will
1743	fix things for you.
1744		1953
1745	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1746		1955
1747	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1748	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1775	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1776	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1777	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1778	overkill :)	1987	overkill :)
1779		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1780	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1781		2027
1782	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1783	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1784	time only before and after C<ev_loop> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1785	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1786	lots of events in one iteration.	2032	lots of events in one iteration.
1787		2033
1788	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1789	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1790	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1791	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1792	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1793		2040
1794	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1795		2042
1796	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1797	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1798	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
1799		2080
1800	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1801		2082
1802	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
1803	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1847	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1848	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1849		2130
1850	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1851		2132
1852	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
1853	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
1854		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
1855	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1856		2143
1857	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
1858		2146
1859	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
1860	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1861		2149
		2150	=back
		2151
1862	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1863	usage example.	2153	usage example.
1864		2154
1865	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1866		2156
1867	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
1906	}	2196	}
1907		2197
1908	ev_timer mytimer;	2198	ev_timer mytimer;
1909	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2199	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1910	ev_timer_again (&mytimer); /* start timer */	2200	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2201	ev_run (loop, 0);
1912		2202
1913	// and in some piece of code that gets executed on any "activity":	2203	// and in some piece of code that gets executed on any "activity":
1914	// reset the timeout to start ticking again at 10 seconds	2204	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2205	ev_timer_again (&mytimer);
1916		2206
…		…
1920	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
1921	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
1922		2212
1923	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1924	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
1925	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
1926	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
1927	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
1928	wrist-watch).	2218	wrist-watch).
1929		2219
1930	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
1942		2232
1943	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
1944	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
1945	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
1946	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
1947	(but this is no longer true when a callback calls C<ev_loop> recursively).	2237	(but this is no longer true when a callback calls C<ev_run> recursively).
1948		2238
1949	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1950		2240
1951	=over 4	2241	=over 4
1952		2242
…		…
1987		2277
1988	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
1989	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
1990	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
1991		2281
1992	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
1993	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
1994	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
1995		2288
1996	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
1997	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
1998	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
1999	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2373	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2374	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2375	potentially a lot of jitter, but good long-term stability.
2083		2376
2084	static void	2377	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2378	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2379	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2380	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2381	}
2089		2382
2090	ev_periodic hourly_tick;	2383	ev_periodic hourly_tick;
…		…
2107		2400
2108	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2109	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2110	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2111	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2112		2405
2113		2406
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2408
2116	Signal watchers will trigger an event when the process receives a specific	2409	Signal watchers will trigger an event when the process receives a specific
2117	signal one or more times. Even though signals are very asynchronous, libev	2410	signal one or more times. Even though signals are very asynchronous, libev
2118	will try it's best to deliver signals synchronously, i.e. as part of the	2411	will try its best to deliver signals synchronously, i.e. as part of the
2119	normal event processing, like any other event.	2412	normal event processing, like any other event.
2120		2413
2121	If you want signals to be delivered truly asynchronously, just use	2414	If you want signals to be delivered truly asynchronously, just use
2122	C<sigaction> as you would do without libev and forget about sharing	2415	C<sigaction> as you would do without libev and forget about sharing
2123	the signal. You can even use C<ev_async> from a signal handler to	2416	the signal. You can even use C<ev_async> from a signal handler to
…		…
2127	only within the same loop, i.e. you can watch for C<SIGINT> in your	2420	only within the same loop, i.e. you can watch for C<SIGINT> in your
2128	default loop and for C<SIGIO> in another loop, but you cannot watch for	2421	default loop and for C<SIGIO> in another loop, but you cannot watch for
2129	C<SIGINT> in both the default loop and another loop at the same time. At	2422	C<SIGINT> in both the default loop and another loop at the same time. At
2130	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2131		2424
2132	When the first watcher gets started will libev actually register something	2425	Only after the first watcher for a signal is started will libev actually
2133	with the kernel (thus it coexists with your own signal handlers as long as	2426	register something with the kernel. It thus coexists with your own signal
2134	you don't register any with libev for the same signal).	2427	handlers as long as you don't register any with libev for the same signal.
2135		2428
2136	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2137	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2138	not be unduly interrupted. If you have a problem with system calls getting	2431	not be unduly interrupted. If you have a problem with system calls getting
2139	interrupted by signals you can block all signals in an C<ev_check> watcher	2432	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2142	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2143		2436
2144	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2145	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2146	stopping it again), that is, libev might or might not block the signal,	2439	stopping it again), that is, libev might or might not block the signal,
2147	and might or might not set or restore the installed signal handler.	2440	and might or might not set or restore the installed signal handler (but
		2441	see C<EVFLAG_NOSIGMASK>).
2148		2442
2149	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2444	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2151	C<execve>), this matters for the signal mask: many programs do not expect	2445	C<execve>), this matters for the signal mask: many programs do not expect
2152	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2166		2460
2167	So I can't stress this enough: I<If you do not reset your signal mask when	2461	So I can't stress this enough: I<If you do not reset your signal mask when
2168	you expect it to be empty, you have a race condition in your code>. This	2462	you expect it to be empty, you have a race condition in your code>. This
2169	is not a libev-specific thing, this is true for most event libraries.	2463	is not a libev-specific thing, this is true for most event libraries.
2170		2464
		2465	=head3 The special problem of threads signal handling
		2466
		2467	POSIX threads has problematic signal handling semantics, specifically,
		2468	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2469	threads in a process block signals, which is hard to achieve.
		2470
		2471	When you want to use sigwait (or mix libev signal handling with your own
		2472	for the same signals), you can tackle this problem by globally blocking
		2473	all signals before creating any threads (or creating them with a fully set
		2474	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2475	loops. Then designate one thread as "signal receiver thread" which handles
		2476	these signals. You can pass on any signals that libev might be interested
		2477	in by calling C<ev_feed_signal>.
		2478
2171	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2172		2480
2173	=over 4	2481	=over 4
2174		2482
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2483	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2498	Example: Try to exit cleanly on SIGINT.
2191		2499
2192	static void	2500	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2501	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2502	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2503	ev_break (loop, EVBREAK_ALL);
2196	}	2504	}
2197		2505
2198	ev_signal signal_watcher;	2506	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2507	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2508	ev_signal_start (loop, &signal_watcher);
…		…
2309		2617
2310	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2311		2619
2312	This watches a file system path for attribute changes. That is, it calls	2620	This watches a file system path for attribute changes. That is, it calls
2313	C<stat> on that path in regular intervals (or when the OS says it changed)	2621	C<stat> on that path in regular intervals (or when the OS says it changed)
2314	and sees if it changed compared to the last time, invoking the callback if	2622	and sees if it changed compared to the last time, invoking the callback
2315	it did.	2623	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2624	happen after the watcher has been started will be reported.
2316		2625
2317	The path does not need to exist: changing from "path exists" to "path does	2626	The path does not need to exist: changing from "path exists" to "path does
2318	not exist" is a status change like any other. The condition "path does not	2627	not exist" is a status change like any other. The condition "path does not
2319	exist" (or more correctly "path cannot be stat'ed") is signified by the	2628	exist" (or more correctly "path cannot be stat'ed") is signified by the
2320	C<st_nlink> field being zero (which is otherwise always forced to be at	2629	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2550	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2551	effect on its own sometimes), idle watchers are a good place to do	2860	effect on its own sometimes), idle watchers are a good place to do
2552	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2553	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2554		2863
		2864	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2865
		2866	As long as there is at least one active idle watcher, libev will never
		2867	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2868	For this to work, the idle watcher doesn't need to be invoked at all - the
		2869	lowest priority will do.
		2870
		2871	This mode of operation can be useful together with an C<ev_check> watcher,
		2872	to do something on each event loop iteration - for example to balance load
		2873	between different connections.
		2874
		2875	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2876	example.
		2877
2555	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2556		2879
2557	=over 4	2880	=over 4
2558		2881
2559	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2570	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2571		2894
2572	static void	2895	static void
2573	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2896	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2574	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2575	free (w);	2902	free (w);
		2903
2576	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2577	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2578	}	2906	}
2579		2907
2580	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2582	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2583		2911
2584		2912
2585	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2913	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2586		2914
2587	Prepare and check watchers are usually (but not always) used in pairs:	2915	Prepare and check watchers are often (but not always) used in pairs:
2588	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2917	afterwards.
2590		2918
2591	You I<must not> call C<ev_loop> or similar functions that enter	2919	You I<must not> call C<ev_run> (or similar functions that enter the
2592	the current event loop from either C<ev_prepare> or C<ev_check>	2920	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2593	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2594	rationale behind this is that you do not need to check for recursion in	2922	however. The rationale behind this is that you do not need to check
2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2923	for recursion in those watchers, i.e. the sequence will always be
2596	C<ev_check> so if you have one watcher of each kind they will always be	2924	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2597	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2598		2926
2599	Their main purpose is to integrate other event mechanisms into libev and	2927	Their main purpose is to integrate other event mechanisms into libev and
2600	their use is somewhat advanced. They could be used, for example, to track	2928	their use is somewhat advanced. They could be used, for example, to track
2601	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2602	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2620	with priority higher than or equal to the event loop and one coroutine	2948	with priority higher than or equal to the event loop and one coroutine
2621	of lower priority, but only once, using idle watchers to keep the event	2949	of lower priority, but only once, using idle watchers to keep the event
2622	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2623	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2624		2952
2625	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2953	When used for this purpose, it is recommended to give C<ev_check> watchers
2626	priority, to ensure that they are being run before any other watchers	2954	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2627	after the poll (this doesn't matter for C<ev_prepare> watchers).	2955	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2956	watchers).
2628		2957
2629	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2958	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2630	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2631	might get executed before other C<ev_check> watchers did their job. As	2960	might get executed before other C<ev_check> watchers did their job. As
2632	C<ev_check> watchers are often used to embed other (non-libev) event	2961	C<ev_check> watchers are often used to embed other (non-libev) event
2633	loops those other event loops might be in an unusable state until their	2962	loops those other event loops might be in an unusable state until their
2634	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2963	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2635	others).	2964	others).
		2965
		2966	=head3 Abusing an C<ev_check> watcher for its side-effect
		2967
		2968	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2969	useful because they are called once per event loop iteration. For
		2970	example, if you want to handle a large number of connections fairly, you
		2971	normally only do a bit of work for each active connection, and if there
		2972	is more work to do, you wait for the next event loop iteration, so other
		2973	connections have a chance of making progress.
		2974
		2975	Using an C<ev_check> watcher is almost enough: it will be called on the
		2976	next event loop iteration. However, that isn't as soon as possible -
		2977	without external events, your C<ev_check> watcher will not be invoked.
		2978
		2979	This is where C<ev_idle> watchers come in handy - all you need is a
		2980	single global idle watcher that is active as long as you have one active
		2981	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2982	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2983	invoked. Neither watcher alone can do that.
2636		2984
2637	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2638		2986
2639	=over 4	2987	=over 4
2640		2988
…		…
2764		3112
2765	if (timeout >= 0)	3113	if (timeout >= 0)
2766	// create/start timer	3114	// create/start timer
2767		3115
2768	// poll	3116	// poll
2769	ev_loop (EV_A_ 0);	3117	ev_run (EV_A_ 0);
2770		3118
2771	// stop timer again	3119	// stop timer again
2772	if (timeout >= 0)	3120	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	3121	ev_timer_stop (EV_A_ &to);
2774		3122
…		…
2841		3189
2842	=over 4	3190	=over 4
2843		3191
2844	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3192	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2845		3193
2846	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3194	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2847		3195
2848	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
2849	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2850	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
2851	to invoke it (it will continue to be called until the sweep has been done,	3199	to invoke it (it will continue to be called until the sweep has been done,
2852	if you do not want that, you need to temporarily stop the embed watcher).	3200	if you do not want that, you need to temporarily stop the embed watcher).
2853		3201
2854	=item ev_embed_sweep (loop, ev_embed *)	3202	=item ev_embed_sweep (loop, ev_embed *)
2855		3203
2856	Make a single, non-blocking sweep over the embedded loop. This works	3204	Make a single, non-blocking sweep over the embedded loop. This works
2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3205	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2858	appropriate way for embedded loops.	3206	appropriate way for embedded loops.
2859		3207
2860	=item struct ev_loop *other [read-only]	3208	=item struct ev_loop *other [read-only]
2861		3209
2862	The embedded event loop.	3210	The embedded event loop.
…		…
2872	used).	3220	used).
2873		3221
2874	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
2875	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
2876	ev_embed embed;	3224	ev_embed embed;
2877		3225
2878	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
2879	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
2880	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2881	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2882	: 0;	3230	: 0;
…		…
2896	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2897		3245
2898	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
2899	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
2900	ev_embed embed;	3248	ev_embed embed;
2901		3249
2902	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2903	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2904	{	3252	{
2905	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
2906	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
2914		3262
2915	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2916		3264
2917	Fork watchers are called when a C<fork ()> was detected (usually because	3265	Fork watchers are called when a C<fork ()> was detected (usually because
2918	whoever is a good citizen cared to tell libev about it by calling	3266	whoever is a good citizen cared to tell libev about it by calling
2919	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3267	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2920	event loop blocks next and before C<ev_check> watchers are being called,	3268	and before C<ev_check> watchers are being called, and only in the child
2921	and only in the child after the fork. If whoever good citizen calling	3269	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3270	and calls it in the wrong process, the fork handlers will be invoked, too,
2923	handlers will be invoked, too, of course.	3271	of course.
2924		3272
2925	=head3 The special problem of life after fork - how is it possible?	3273	=head3 The special problem of life after fork - how is it possible?
2926		3274
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3275	Most uses of C<fork ()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3276	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
2930		3278
2931	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3280	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	disadvantage of having to use multiple event loops (which do not support	3296	disadvantage of having to use multiple event loops (which do not support
2949	signal watchers).	3297	signal watchers).
2950		3298
2951	When this is not possible, or you want to use the default loop for	3299	When this is not possible, or you want to use the default loop for
2952	other reasons, then in the process that wants to start "fresh", call	3300	other reasons, then in the process that wants to start "fresh", call
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3301	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3302	Destroying the default loop will "orphan" (not stop) all registered
2955	have to be careful not to execute code that modifies those watchers. Note	3303	watchers, so you have to be careful not to execute code that modifies
2956	also that in that case, you have to re-register any signal watchers.	3304	those watchers. Note also that in that case, you have to re-register any
		3305	signal watchers.
2957		3306
2958	=head3 Watcher-Specific Functions and Data Members	3307	=head3 Watcher-Specific Functions and Data Members
2959		3308
2960	=over 4	3309	=over 4
2961		3310
2962	=item ev_fork_init (ev_signal *, callback)	3311	=item ev_fork_init (ev_fork *, callback)
2963		3312
2964	Initialises and configures the fork watcher - it has no parameters of any	3313	Initialises and configures the fork watcher - it has no parameters of any
2965	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3314	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2966	believe me.	3315	really.
2967		3316
2968	=back	3317	=back
2969		3318
2970		3319
		3320	=head2 C<ev_cleanup> - even the best things end
		3321
		3322	Cleanup watchers are called just before the event loop is being destroyed
		3323	by a call to C<ev_loop_destroy>.
		3324
		3325	While there is no guarantee that the event loop gets destroyed, cleanup
		3326	watchers provide a convenient method to install cleanup hooks for your
		3327	program, worker threads and so on - you just to make sure to destroy the
		3328	loop when you want them to be invoked.
		3329
		3330	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3331	all other watchers, they do not keep a reference to the event loop (which
		3332	makes a lot of sense if you think about it). Like all other watchers, you
		3333	can call libev functions in the callback, except C<ev_cleanup_start>.
		3334
		3335	=head3 Watcher-Specific Functions and Data Members
		3336
		3337	=over 4
		3338
		3339	=item ev_cleanup_init (ev_cleanup *, callback)
		3340
		3341	Initialises and configures the cleanup watcher - it has no parameters of
		3342	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3343	pointless, I assure you.
		3344
		3345	=back
		3346
		3347	Example: Register an atexit handler to destroy the default loop, so any
		3348	cleanup functions are called.
		3349
		3350	static void
		3351	program_exits (void)
		3352	{
		3353	ev_loop_destroy (EV_DEFAULT_UC);
		3354	}
		3355
		3356	...
		3357	atexit (program_exits);
		3358
		3359
2971	=head2 C<ev_async> - how to wake up another event loop	3360	=head2 C<ev_async> - how to wake up an event loop
2972		3361
2973	In general, you cannot use an C<ev_loop> from multiple threads or other	3362	In general, you cannot use an C<ev_loop> from multiple threads or other
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3363	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3364	loops - those are of course safe to use in different threads).
2976		3365
2977	Sometimes, however, you need to wake up another event loop you do not	3366	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3367	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3368	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3369	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3370
2983	This functionality is very similar to C<ev_signal> watchers, as signals,	3371	This functionality is very similar to C<ev_signal> watchers, as signals,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
2985	(i.e. the number of callback invocations may be less than the number of	3373	(i.e. the number of callback invocations may be less than the number of
2986	C<ev_async_sent> calls).	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2987		3375	of "global async watchers" by using a watcher on an otherwise unused
2988	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3376	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2989	just the default loop.	3377	even without knowing which loop owns the signal.
2990		3378
2991	=head3 Queueing	3379	=head3 Queueing
2992		3380
2993	C<ev_async> does not support queueing of data in any way. The reason	3381	C<ev_async> does not support queueing of data in any way. The reason
2994	is that the author does not know of a simple (or any) algorithm for a	3382	is that the author does not know of a simple (or any) algorithm for a
…		…
3086	trust me.	3474	trust me.
3087		3475
3088	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3089		3477
3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3478	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3479	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3480	returns.
		3481
3092	C<ev_feed_event>, this call is safe to do from other threads, signal or	3482	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3483	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3094	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3095		3485
3096	Note that, as with other watchers in libev, multiple events might get	3486	Note that, as with other watchers in libev, multiple events might get
3097	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3488	this is that C<ev_async> watchers are level-triggered: they are set on
3099	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3100		3490
3101	This call incurs the overhead of a system call only once per event loop	3491	This call incurs the overhead of at most one extra system call per event
3102	iteration, so while the overhead might be noticeable, it doesn't apply to	3492	loop iteration, if the event loop is blocked, and no syscall at all if
3103	repeated calls to C<ev_async_send> for the same event loop.	3493	the event loop (or your program) is processing events. That means that
		3494	repeated calls are basically free (there is no need to avoid calls for
		3495	performance reasons) and that the overhead becomes smaller (typically
		3496	zero) under load.
3104		3497
3105	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3106		3499
3107	Returns a non-zero value when C<ev_async_send> has been called on the	3500	Returns a non-zero value when C<ev_async_send> has been called on the
3108	watcher but the event has not yet been processed (or even noted) by the	3501	watcher but the event has not yet been processed (or even noted) by the
…		…
3141		3534
3142	If C<timeout> is less than 0, then no timeout watcher will be	3535	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3536	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3537	repeat = 0) will be started. C<0> is a valid timeout.
3145		3538
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3539	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3540	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3541	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3542	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3543	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3544	events precedence.
3152		3545
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3546	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3547
3155	static void stdin_ready (int revents, void *arg)	3548	static void stdin_ready (int revents, void *arg)
3156	{	3549	{
3157	if (revents & EV_READ)	3550	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3551	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3552	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3553	/* doh, nothing entered */;
3161	}	3554	}
3162		3555
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3557
3165	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3166		3559
3167	Feed an event on the given fd, as if a file descriptor backend detected	3560	Feed an event on the given fd, as if a file descriptor backend detected
3168	the given events it.	3561	the given events.
3169		3562
3170	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3171		3564
3172	Feed an event as if the given signal occurred (C<loop> must be the default	3565	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3173	loop!).	3566	which is async-safe.
3174		3567
3175	=back	3568	=back
		3569
		3570
		3571	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3572
		3573	This section explains some common idioms that are not immediately
		3574	obvious. Note that examples are sprinkled over the whole manual, and this
		3575	section only contains stuff that wouldn't fit anywhere else.
		3576
		3577	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3578
		3579	Each watcher has, by default, a C<void *data> member that you can read
		3580	or modify at any time: libev will completely ignore it. This can be used
		3581	to associate arbitrary data with your watcher. If you need more data and
		3582	don't want to allocate memory separately and store a pointer to it in that
		3583	data member, you can also "subclass" the watcher type and provide your own
		3584	data:
		3585
		3586	struct my_io
		3587	{
		3588	ev_io io;
		3589	int otherfd;
		3590	void *somedata;
		3591	struct whatever *mostinteresting;
		3592	};
		3593
		3594	...
		3595	struct my_io w;
		3596	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3597
		3598	And since your callback will be called with a pointer to the watcher, you
		3599	can cast it back to your own type:
		3600
		3601	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3602	{
		3603	struct my_io *w = (struct my_io *)w_;
		3604	...
		3605	}
		3606
		3607	More interesting and less C-conformant ways of casting your callback
		3608	function type instead have been omitted.
		3609
		3610	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3611
		3612	Another common scenario is to use some data structure with multiple
		3613	embedded watchers, in effect creating your own watcher that combines
		3614	multiple libev event sources into one "super-watcher":
		3615
		3616	struct my_biggy
		3617	{
		3618	int some_data;
		3619	ev_timer t1;
		3620	ev_timer t2;
		3621	}
		3622
		3623	In this case getting the pointer to C<my_biggy> is a bit more
		3624	complicated: Either you store the address of your C<my_biggy> struct in
		3625	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3626	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3627	real programmers):
		3628
		3629	#include <stddef.h>
		3630
		3631	static void
		3632	t1_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t1));
		3636	}
		3637
		3638	static void
		3639	t2_cb (EV_P_ ev_timer *w, int revents)
		3640	{
		3641	struct my_biggy big = (struct my_biggy *)
		3642	(((char *)w) - offsetof (struct my_biggy, t2));
		3643	}
		3644
		3645	=head2 AVOIDING FINISHING BEFORE RETURNING
		3646
		3647	Often you have structures like this in event-based programs:
		3648
		3649	callback ()
		3650	{
		3651	free (request);
		3652	}
		3653
		3654	request = start_new_request (..., callback);
		3655
		3656	The intent is to start some "lengthy" operation. The C<request> could be
		3657	used to cancel the operation, or do other things with it.
		3658
		3659	It's not uncommon to have code paths in C<start_new_request> that
		3660	immediately invoke the callback, for example, to report errors. Or you add
		3661	some caching layer that finds that it can skip the lengthy aspects of the
		3662	operation and simply invoke the callback with the result.
		3663
		3664	The problem here is that this will happen I<before> C<start_new_request>
		3665	has returned, so C<request> is not set.
		3666
		3667	Even if you pass the request by some safer means to the callback, you
		3668	might want to do something to the request after starting it, such as
		3669	canceling it, which probably isn't working so well when the callback has
		3670	already been invoked.
		3671
		3672	A common way around all these issues is to make sure that
		3673	C<start_new_request> I<always> returns before the callback is invoked. If
		3674	C<start_new_request> immediately knows the result, it can artificially
		3675	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3676	example, or more sneakily, by reusing an existing (stopped) watcher and
		3677	pushing it into the pending queue:
		3678
		3679	ev_set_cb (watcher, callback);
		3680	ev_feed_event (EV_A_ watcher, 0);
		3681
		3682	This way, C<start_new_request> can safely return before the callback is
		3683	invoked, while not delaying callback invocation too much.
		3684
		3685	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3686
		3687	Often (especially in GUI toolkits) there are places where you have
		3688	I<modal> interaction, which is most easily implemented by recursively
		3689	invoking C<ev_run>.
		3690
		3691	This brings the problem of exiting - a callback might want to finish the
		3692	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3693	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3694	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3695	other combination: In these cases, a simple C<ev_break> will not work.
		3696
		3697	The solution is to maintain "break this loop" variable for each C<ev_run>
		3698	invocation, and use a loop around C<ev_run> until the condition is
		3699	triggered, using C<EVRUN_ONCE>:
		3700
		3701	// main loop
		3702	int exit_main_loop = 0;
		3703
		3704	while (!exit_main_loop)
		3705	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3706
		3707	// in a modal watcher
		3708	int exit_nested_loop = 0;
		3709
		3710	while (!exit_nested_loop)
		3711	ev_run (EV_A_ EVRUN_ONCE);
		3712
		3713	To exit from any of these loops, just set the corresponding exit variable:
		3714
		3715	// exit modal loop
		3716	exit_nested_loop = 1;
		3717
		3718	// exit main program, after modal loop is finished
		3719	exit_main_loop = 1;
		3720
		3721	// exit both
		3722	exit_main_loop = exit_nested_loop = 1;
		3723
		3724	=head2 THREAD LOCKING EXAMPLE
		3725
		3726	Here is a fictitious example of how to run an event loop in a different
		3727	thread from where callbacks are being invoked and watchers are
		3728	created/added/removed.
		3729
		3730	For a real-world example, see the C<EV::Loop::Async> perl module,
		3731	which uses exactly this technique (which is suited for many high-level
		3732	languages).
		3733
		3734	The example uses a pthread mutex to protect the loop data, a condition
		3735	variable to wait for callback invocations, an async watcher to notify the
		3736	event loop thread and an unspecified mechanism to wake up the main thread.
		3737
		3738	First, you need to associate some data with the event loop:
		3739
		3740	typedef struct {
		3741	mutex_t lock; /* global loop lock */
		3742	ev_async async_w;
		3743	thread_t tid;
		3744	cond_t invoke_cv;
		3745	} userdata;
		3746
		3747	void prepare_loop (EV_P)
		3748	{
		3749	// for simplicity, we use a static userdata struct.
		3750	static userdata u;
		3751
		3752	ev_async_init (&u->async_w, async_cb);
		3753	ev_async_start (EV_A_ &u->async_w);
		3754
		3755	pthread_mutex_init (&u->lock, 0);
		3756	pthread_cond_init (&u->invoke_cv, 0);
		3757
		3758	// now associate this with the loop
		3759	ev_set_userdata (EV_A_ u);
		3760	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3761	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3762
		3763	// then create the thread running ev_run
		3764	pthread_create (&u->tid, 0, l_run, EV_A);
		3765	}
		3766
		3767	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3768	solely to wake up the event loop so it takes notice of any new watchers
		3769	that might have been added:
		3770
		3771	static void
		3772	async_cb (EV_P_ ev_async *w, int revents)
		3773	{
		3774	// just used for the side effects
		3775	}
		3776
		3777	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3778	protecting the loop data, respectively.
		3779
		3780	static void
		3781	l_release (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_unlock (&u->lock);
		3785	}
		3786
		3787	static void
		3788	l_acquire (EV_P)
		3789	{
		3790	userdata *u = ev_userdata (EV_A);
		3791	pthread_mutex_lock (&u->lock);
		3792	}
		3793
		3794	The event loop thread first acquires the mutex, and then jumps straight
		3795	into C<ev_run>:
		3796
		3797	void *
		3798	l_run (void *thr_arg)
		3799	{
		3800	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3801
		3802	l_acquire (EV_A);
		3803	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3804	ev_run (EV_A_ 0);
		3805	l_release (EV_A);
		3806
		3807	return 0;
		3808	}
		3809
		3810	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3811	signal the main thread via some unspecified mechanism (signals? pipe
		3812	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3813	have been called (in a while loop because a) spurious wakeups are possible
		3814	and b) skipping inter-thread-communication when there are no pending
		3815	watchers is very beneficial):
		3816
		3817	static void
		3818	l_invoke (EV_P)
		3819	{
		3820	userdata *u = ev_userdata (EV_A);
		3821
		3822	while (ev_pending_count (EV_A))
		3823	{
		3824	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3825	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3826	}
		3827	}
		3828
		3829	Now, whenever the main thread gets told to invoke pending watchers, it
		3830	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3831	thread to continue:
		3832
		3833	static void
		3834	real_invoke_pending (EV_P)
		3835	{
		3836	userdata *u = ev_userdata (EV_A);
		3837
		3838	pthread_mutex_lock (&u->lock);
		3839	ev_invoke_pending (EV_A);
		3840	pthread_cond_signal (&u->invoke_cv);
		3841	pthread_mutex_unlock (&u->lock);
		3842	}
		3843
		3844	Whenever you want to start/stop a watcher or do other modifications to an
		3845	event loop, you will now have to lock:
		3846
		3847	ev_timer timeout_watcher;
		3848	userdata *u = ev_userdata (EV_A);
		3849
		3850	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3851
		3852	pthread_mutex_lock (&u->lock);
		3853	ev_timer_start (EV_A_ &timeout_watcher);
		3854	ev_async_send (EV_A_ &u->async_w);
		3855	pthread_mutex_unlock (&u->lock);
		3856
		3857	Note that sending the C<ev_async> watcher is required because otherwise
		3858	an event loop currently blocking in the kernel will have no knowledge
		3859	about the newly added timer. By waking up the loop it will pick up any new
		3860	watchers in the next event loop iteration.
		3861
		3862	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3863
		3864	While the overhead of a callback that e.g. schedules a thread is small, it
		3865	is still an overhead. If you embed libev, and your main usage is with some
		3866	kind of threads or coroutines, you might want to customise libev so that
		3867	doesn't need callbacks anymore.
		3868
		3869	Imagine you have coroutines that you can switch to using a function
		3870	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3871	and that due to some magic, the currently active coroutine is stored in a
		3872	global called C<current_coro>. Then you can build your own "wait for libev
		3873	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3874	the differing C<;> conventions):
		3875
		3876	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3877	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3878
		3879	That means instead of having a C callback function, you store the
		3880	coroutine to switch to in each watcher, and instead of having libev call
		3881	your callback, you instead have it switch to that coroutine.
		3882
		3883	A coroutine might now wait for an event with a function called
		3884	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3885	matter when, or whether the watcher is active or not when this function is
		3886	called):
		3887
		3888	void
		3889	wait_for_event (ev_watcher *w)
		3890	{
		3891	ev_set_cb (w, current_coro);
		3892	switch_to (libev_coro);
		3893	}
		3894
		3895	That basically suspends the coroutine inside C<wait_for_event> and
		3896	continues the libev coroutine, which, when appropriate, switches back to
		3897	this or any other coroutine.
		3898
		3899	You can do similar tricks if you have, say, threads with an event queue -
		3900	instead of storing a coroutine, you store the queue object and instead of
		3901	switching to a coroutine, you push the watcher onto the queue and notify
		3902	any waiters.
		3903
		3904	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3905	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3906
		3907	// my_ev.h
		3908	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3909	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3910	#include "../libev/ev.h"
		3911
		3912	// my_ev.c
		3913	#define EV_H "my_ev.h"
		3914	#include "../libev/ev.c"
		3915
		3916	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3917	F<my_ev.c> into your project. When properly specifying include paths, you
		3918	can even use F<ev.h> as header file name directly.
3176		3919
3177		3920
3178	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3179		3922
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3924	emulate the internals of libevent, so here are some usage hints:
3182		3925
3183	=over 4	3926	=over 4
		3927
		3928	=item * Only the libevent-1.4.1-beta API is being emulated.
		3929
		3930	This was the newest libevent version available when libev was implemented,
		3931	and is still mostly unchanged in 2010.
3184		3932
3185	=item * Use it by including <event.h>, as usual.	3933	=item * Use it by including <event.h>, as usual.
3186		3934
3187	=item * The following members are fully supported: ev_base, ev_callback,	3935	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3936	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3942	=item * Priorities are not currently supported. Initialising priorities
3195	will fail and all watchers will have the same priority, even though there	3943	will fail and all watchers will have the same priority, even though there
3196	is an ev_pri field.	3944	is an ev_pri field.
3197		3945
3198	=item * In libevent, the last base created gets the signals, in libev, the	3946	=item * In libevent, the last base created gets the signals, in libev, the
3199	first base created (== the default loop) gets the signals.	3947	base that registered the signal gets the signals.
3200		3948
3201	=item * Other members are not supported.	3949	=item * Other members are not supported.
3202		3950
3203	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3951	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3204	to use the libev header file and library.	3952	to use the libev header file and library.
3205		3953
3206	=back	3954	=back
3207		3955
3208	=head1 C++ SUPPORT	3956	=head1 C++ SUPPORT
		3957
		3958	=head2 C API
		3959
		3960	The normal C API should work fine when used from C++: both ev.h and the
		3961	libev sources can be compiled as C++. Therefore, code that uses the C API
		3962	will work fine.
		3963
		3964	Proper exception specifications might have to be added to callbacks passed
		3965	to libev: exceptions may be thrown only from watcher callbacks, all
		3966	other callbacks (allocator, syserr, loop acquire/release and periodic
		3967	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3968	()> specification. If you have code that needs to be compiled as both C
		3969	and C++ you can use the C<EV_THROW> macro for this:
		3970
		3971	static void
		3972	fatal_error (const char *msg) EV_THROW
		3973	{
		3974	perror (msg);
		3975	abort ();
		3976	}
		3977
		3978	...
		3979	ev_set_syserr_cb (fatal_error);
		3980
		3981	The only API functions that can currently throw exceptions are C<ev_run>,
		3982	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3983	because it runs cleanup watchers).
		3984
		3985	Throwing exceptions in watcher callbacks is only supported if libev itself
		3986	is compiled with a C++ compiler or your C and C++ environments allow
		3987	throwing exceptions through C libraries (most do).
		3988
		3989	=head2 C++ API
3209		3990
3210	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3991	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3211	you to use some convenience methods to start/stop watchers and also change	3992	you to use some convenience methods to start/stop watchers and also change
3212	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3213		3994
3214	To use it,	3995	To use it,
3215		3996
3216	#include <ev++.h>	3997	#include <ev++.h>
3217		3998
3218	This automatically includes F<ev.h> and puts all of its definitions (many	3999	This automatically includes F<ev.h> and puts all of its definitions (many
3219	of them macros) into the global namespace. All C++ specific things are	4000	of them macros) into the global namespace. All C++ specific things are
3220	put into the C<ev> namespace. It should support all the same embedding	4001	put into the C<ev> namespace. It should support all the same embedding
…		…
3223	Care has been taken to keep the overhead low. The only data member the C++	4004	Care has been taken to keep the overhead low. The only data member the C++
3224	classes add (compared to plain C-style watchers) is the event loop pointer	4005	classes add (compared to plain C-style watchers) is the event loop pointer
3225	that the watcher is associated with (or no additional members at all if	4006	that the watcher is associated with (or no additional members at all if
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	4007	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		4008
3228	Currently, functions, and static and non-static member functions can be	4009	Currently, functions, static and non-static member functions and classes
3229	used as callbacks. Other types should be easy to add as long as they only	4010	with C<operator ()> can be used as callbacks. Other types should be easy
3230	need one additional pointer for context. If you need support for other	4011	to add as long as they only need one additional pointer for context. If
3231	types of functors please contact the author (preferably after implementing	4012	you need support for other types of functors please contact the author
3232	it).	4013	(preferably after implementing it).
		4014
		4015	For all this to work, your C++ compiler either has to use the same calling
		4016	conventions as your C compiler (for static member functions), or you have
		4017	to embed libev and compile libev itself as C++.
3233		4018
3234	Here is a list of things available in the C<ev> namespace:	4019	Here is a list of things available in the C<ev> namespace:
3235		4020
3236	=over 4	4021	=over 4
3237		4022
…		…
3247	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4032	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3248		4033
3249	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4034	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3250	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4035	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3251	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4036	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3252	defines by many implementations.	4037	defined by many implementations.
3253		4038
3254	All of those classes have these methods:	4039	All of those classes have these methods:
3255		4040
3256	=over 4	4041	=over 4
3257		4042
…		…
3298	myclass obj;	4083	myclass obj;
3299	ev::io iow;	4084	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	4085	iow.set <myclass, &myclass::io_cb> (&obj);
3301		4086
3302	=item w->set (object *)	4087	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		4088
3306	This is a variation of a method callback - leaving out the method to call	4089	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	4090	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	4091	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	4092	the time. Incidentally, you can then also leave out the template argument
…		…
3321	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3322	{	4105	{
3323	...	4106	...
3324	}	4107	}
3325	}	4108	}
3326		4109
3327	myfunctor f;	4110	myfunctor f;
3328		4111
3329	ev::io w;	4112	ev::io w;
3330	w.set (&f);	4113	w.set (&f);
3331		4114
…		…
3349	Associates a different C<struct ev_loop> with this watcher. You can only	4132	Associates a different C<struct ev_loop> with this watcher. You can only
3350	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3351		4134
3352	=item w->set ([arguments])	4135	=item w->set ([arguments])
3353		4136
3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4137	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4138	with the same arguments. Either this method or a suitable start method
3355	called at least once. Unlike the C counterpart, an active watcher gets	4139	must be called at least once. Unlike the C counterpart, an active watcher
3356	automatically stopped and restarted when reconfiguring it with this	4140	gets automatically stopped and restarted when reconfiguring it with this
3357	method.	4141	method.
		4142
		4143	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4144	clashing with the C<set (loop)> method.
3358		4145
3359	=item w->start ()	4146	=item w->start ()
3360		4147
3361	Starts the watcher. Note that there is no C<loop> argument, as the	4148	Starts the watcher. Note that there is no C<loop> argument, as the
3362	constructor already stores the event loop.	4149	constructor already stores the event loop.
3363		4150
		4151	=item w->start ([arguments])
		4152
		4153	Instead of calling C<set> and C<start> methods separately, it is often
		4154	convenient to wrap them in one call. Uses the same type of arguments as
		4155	the configure C<set> method of the watcher.
		4156
3364	=item w->stop ()	4157	=item w->stop ()
3365		4158
3366	Stops the watcher if it is active. Again, no C<loop> argument.	4159	Stops the watcher if it is active. Again, no C<loop> argument.
3367		4160
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4161	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		4173
3381	=back	4174	=back
3382		4175
3383	=back	4176	=back
3384		4177
3385	Example: Define a class with an IO and idle watcher, start one of them in	4178	Example: Define a class with two I/O and idle watchers, start the I/O
3386	the constructor.	4179	watchers in the constructor.
3387		4180
3388	class myclass	4181	class myclass
3389	{	4182	{
3390	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
		4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		4186
3393	myclass (int fd)	4187	myclass (int fd)
3394	{	4188	{
3395	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
		4190	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	4191	idle.set <myclass, &myclass::idle_cb> (this);
3397		4192
3398	io.start (fd, ev::READ);	4193	io.set (fd, ev::WRITE); // configure the watcher
		4194	io.start (); // start it whenever convenient
		4195
		4196	io2.start (fd, ev::READ); // set + start in one call
3399	}	4197	}
3400	};	4198	};
3401		4199
3402		4200
3403	=head1 OTHER LANGUAGE BINDINGS	4201	=head1 OTHER LANGUAGE BINDINGS
…		…
3442	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3443		4241
3444	=item D	4242	=item D
3445		4243
3446	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4244	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3447	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4245	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3448		4246
3449	=item Ocaml	4247	=item Ocaml
3450		4248
3451	Erkki Seppala has written Ocaml bindings for libev, to be found at	4249	Erkki Seppala has written Ocaml bindings for libev, to be found at
3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3455		4253
3456	Brian Maher has written a partial interface to libev for lua (at the	4254	Brian Maher has written a partial interface to libev for lua (at the
3457	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4255	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3458	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3459		4257
		4258	=item Javascript
		4259
		4260	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4261
		4262	=item Others
		4263
		4264	There are others, and I stopped counting.
		4265
3460	=back	4266	=back
3461		4267
3462		4268
3463	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3464		4270
…		…
3477	loop argument"). The C<EV_A> form is used when this is the sole argument,	4283	loop argument"). The C<EV_A> form is used when this is the sole argument,
3478	C<EV_A_> is used when other arguments are following. Example:	4284	C<EV_A_> is used when other arguments are following. Example:
3479		4285
3480	ev_unref (EV_A);	4286	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	4287	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	4288	ev_run (EV_A_ 0);
3483		4289
3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4290	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3485	which is often provided by the following macro.	4291	which is often provided by the following macro.
3486		4292
3487	=item C<EV_P>, C<EV_P_>	4293	=item C<EV_P>, C<EV_P_>
…		…
3500	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3501		4307
3502	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3503		4309
3504	Similar to the other two macros, this gives you the value of the default	4310	Similar to the other two macros, this gives you the value of the default
3505	loop, if multiple loops are supported ("ev loop default").	4311	loop, if multiple loops are supported ("ev loop default"). The default loop
		4312	will be initialised if it isn't already initialised.
		4313
		4314	For non-multiplicity builds, these macros do nothing, so you always have
		4315	to initialise the loop somewhere.
3506		4316
3507	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3508		4318
3509	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4319	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3510	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3527	}	4337	}
3528		4338
3529	ev_check check;	4339	ev_check check;
3530	ev_check_init (&check, check_cb);	4340	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4341	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4342	ev_run (EV_DEFAULT_ 0);
3533		4343
3534	=head1 EMBEDDING	4344	=head1 EMBEDDING
3535		4345
3536	Libev can (and often is) directly embedded into host	4346	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4347	applications. Examples of applications that embed it include the Deliantra
…		…
3577	ev_vars.h	4387	ev_vars.h
3578	ev_wrap.h	4388	ev_wrap.h
3579		4389
3580	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
3581		4391
3582	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
3583	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
3584	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
3585	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
3586	ev_port.c only when the solaris port backend is enabled (disabled by default)	4396	ev_port.c only when the solaris port backend is enabled
3587		4397
3588	F<ev.c> includes the backend files directly when enabled, so you only need	4398	F<ev.c> includes the backend files directly when enabled, so you only need
3589	to compile this single file.	4399	to compile this single file.
3590		4400
3591	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
3622	define before including (or compiling) any of its files. The default in	4432	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4433	the absence of autoconf is documented for every option.
3624		4434
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4435	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4436	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4437	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4438	to a compiled library. All other symbols change the ABI, which means all
3629	users of libev and the libev code itself must be compiled with compatible	4439	users of libev and the libev code itself must be compiled with compatible
3630	settings.	4440	settings.
3631		4441
3632	=over 4	4442	=over 4
		4443
		4444	=item EV_COMPAT3 (h)
		4445
		4446	Backwards compatibility is a major concern for libev. This is why this
		4447	release of libev comes with wrappers for the functions and symbols that
		4448	have been renamed between libev version 3 and 4.
		4449
		4450	You can disable these wrappers (to test compatibility with future
		4451	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4452	sources. This has the additional advantage that you can drop the C<struct>
		4453	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4454	typedef in that case.
		4455
		4456	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4457	and in some even more future version the compatibility code will be
		4458	removed completely.
3633		4459
3634	=item EV_STANDALONE (h)	4460	=item EV_STANDALONE (h)
3635		4461
3636	Must always be C<1> if you do not use autoconf configuration, which	4462	Must always be C<1> if you do not use autoconf configuration, which
3637	keeps libev from including F<config.h>, and it also defines dummy	4463	keeps libev from including F<config.h>, and it also defines dummy
…		…
3639	supported). It will also not define any of the structs usually found in	4465	supported). It will also not define any of the structs usually found in
3640	F<event.h> that are not directly supported by the libev core alone.	4466	F<event.h> that are not directly supported by the libev core alone.
3641		4467
3642	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
3643	configuration, but has to be more conservative.	4469	configuration, but has to be more conservative.
		4470
		4471	=item EV_USE_FLOOR
		4472
		4473	If defined to be C<1>, libev will use the C<floor ()> function for its
		4474	periodic reschedule calculations, otherwise libev will fall back on a
		4475	portable (slower) implementation. If you enable this, you usually have to
		4476	link against libm or something equivalent. Enabling this when the C<floor>
		4477	function is not available will fail, so the safe default is to not enable
		4478	this.
3644		4479
3645	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
3646		4481
3647	If defined to be C<1>, libev will try to detect the availability of the	4482	If defined to be C<1>, libev will try to detect the availability of the
3648	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3733		4568
3734	If programs implement their own fd to handle mapping on win32, then this	4569	If programs implement their own fd to handle mapping on win32, then this
3735	macro can be used to override the C<close> function, useful to unregister	4570	macro can be used to override the C<close> function, useful to unregister
3736	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
3737	the underlying OS handle.	4572	the underlying OS handle.
		4573
		4574	=item EV_USE_WSASOCKET
		4575
		4576	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4577	communication socket, which works better in some environments. Otherwise,
		4578	the normal C<socket> function will be used, which works better in other
		4579	environments.
3738		4580
3739	=item EV_USE_POLL	4581	=item EV_USE_POLL
3740		4582
3741	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4583	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3742	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3778	If defined to be C<1>, libev will compile in support for the Linux inotify	4620	If defined to be C<1>, libev will compile in support for the Linux inotify
3779	interface to speed up C<ev_stat> watchers. Its actual availability will	4621	interface to speed up C<ev_stat> watchers. Its actual availability will
3780	be detected at runtime. If undefined, it will be enabled if the headers	4622	be detected at runtime. If undefined, it will be enabled if the headers
3781	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3782		4624
		4625	=item EV_NO_SMP
		4626
		4627	If defined to be C<1>, libev will assume that memory is always coherent
		4628	between threads, that is, threads can be used, but threads never run on
		4629	different cpus (or different cpu cores). This reduces dependencies
		4630	and makes libev faster.
		4631
		4632	=item EV_NO_THREADS
		4633
		4634	If defined to be C<1>, libev will assume that it will never be called from
		4635	different threads (that includes signal handlers), which is a stronger
		4636	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4637	libev faster.
		4638
3783	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
3784		4640
3785	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4641	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3786	access is atomic with respect to other threads or signal contexts. No such	4642	access is atomic with respect to other threads or signal contexts. No
3787	type is easily found in the C language, so you can provide your own type	4643	such type is easily found in the C language, so you can provide your own
3788	that you know is safe for your purposes. It is used both for signal handler "locking"	4644	type that you know is safe for your purposes. It is used both for signal
3789	as well as for signal and thread safety in C<ev_async> watchers.	4645	handler "locking" as well as for signal and thread safety in C<ev_async>
		4646	watchers.
3790		4647
3791	In the absence of this define, libev will use C<sig_atomic_t volatile>	4648	In the absence of this define, libev will use C<sig_atomic_t volatile>
3792	(from F<signal.h>), which is usually good enough on most platforms.	4649	(from F<signal.h>), which is usually good enough on most platforms.
3793		4650
3794	=item EV_H (h)	4651	=item EV_H (h)
…		…
3821	will have the C<struct ev_loop *> as first argument, and you can create	4678	will have the C<struct ev_loop *> as first argument, and you can create
3822	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
3823	for multiple event loops and there is no first event loop pointer	4680	for multiple event loops and there is no first event loop pointer
3824	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
3825		4682
		4683	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4684	default loop when multiplicity is switched off - you always have to
		4685	initialise the loop manually in this case.
		4686
3826	=item EV_MINPRI	4687	=item EV_MINPRI
3827		4688
3828	=item EV_MAXPRI	4689	=item EV_MAXPRI
3829		4690
3830	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4691	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3838	fine.	4699	fine.
3839		4700
3840	If your embedding application does not need any priorities, defining these	4701	If your embedding application does not need any priorities, defining these
3841	both to C<0> will save some memory and CPU.	4702	both to C<0> will save some memory and CPU.
3842		4703
3843	=item EV_PERIODIC_ENABLE	4704	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4705	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4706	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844		4707
3845	If undefined or defined to be C<1>, then periodic timers are supported. If	4708	If undefined or defined to be C<1> (and the platform supports it), then
3846	defined to be C<0>, then they are not. Disabling them saves a few kB of	4709	the respective watcher type is supported. If defined to be C<0>, then it
3847	code.	4710	is not. Disabling watcher types mainly saves code size.
3848		4711
3849	=item EV_IDLE_ENABLE	4712	=item EV_FEATURES
3850
3851	If undefined or defined to be C<1>, then idle watchers are supported. If
3852	defined to be C<0>, then they are not. Disabling them saves a few kB of
3853	code.
3854
3855	=item EV_EMBED_ENABLE
3856
3857	If undefined or defined to be C<1>, then embed watchers are supported. If
3858	defined to be C<0>, then they are not. Embed watchers rely on most other
3859	watcher types, which therefore must not be disabled.
3860
3861	=item EV_STAT_ENABLE
3862
3863	If undefined or defined to be C<1>, then stat watchers are supported. If
3864	defined to be C<0>, then they are not.
3865
3866	=item EV_FORK_ENABLE
3867
3868	If undefined or defined to be C<1>, then fork watchers are supported. If
3869	defined to be C<0>, then they are not.
3870
3871	=item EV_SIGNAL_ENABLE
3872
3873	If undefined or defined to be C<1>, then signal watchers are supported. If
3874	defined to be C<0>, then they are not.
3875
3876	=item EV_ASYNC_ENABLE
3877
3878	If undefined or defined to be C<1>, then async watchers are supported. If
3879	defined to be C<0>, then they are not.
3880
3881	=item EV_CHILD_ENABLE
3882
3883	If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884	child watchers are supported. If defined to be C<0>, then they are not.
3885
3886	=item EV_MINIMAL
3887		4713
3888	If you need to shave off some kilobytes of code at the expense of some	4714	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), define this symbol to C<1>. Currently this	4715	speed (but with the full API), you can define this symbol to request
3890	is used to override some inlining decisions, saves roughly 30% code size	4716	certain subsets of functionality. The default is to enable all features
3891	on amd64. It also selects a much smaller 2-heap for timer management over	4717	that can be enabled on the platform.
3892	the default 4-heap.
3893		4718
3894	You can save even more by disabling watcher types you do not need	4719	A typical way to use this symbol is to define it to C<0> (or to a bitset
3895	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4720	with some broad features you want) and then selectively re-enable
3896	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4721	additional parts you want, for example if you want everything minimal,
3897	eventfd and signalfd will further help, and disabling backends one doesn't	4722	but multiple event loop support, async and child watchers and the poll
3898	need (e.g. poll, epoll, kqueue, ports) will help further.	4723	backend, use this:
3899		4724
3900	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4725	#define EV_FEATURES 0
3901	provide a bare-bones event library. See C<ev.h> for details on what parts
3902	of the API are still available, and do not complain if this subset changes
3903	over time.
3904
3905	This example set of settings reduces the compiled size of libev from 24Kb
3906	to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907	an effect on the amount of memory used). With an intelligent-enough linker
3908	further unused functions might be left out as well automatically.
3909
3910	// tuning and API changes
3911	#define EV_MINIMAL 2
3912	#define EV_MULTIPLICITY 0	4726	#define EV_MULTIPLICITY 1
3913	#define EV_MINPRI 0
3914	#define EV_MAXPRI 0
3915
3916	// OS-specific backends
3917	#define EV_USE_INOTIFY 0
3918	#define EV_USE_EVENTFD 0
3919	#define EV_USE_SIGNALFD 0
3920	#define EV_USE_REALTIME 0
3921	#define EV_USE_MONOTONIC 0
3922	#define EV_USE_CLOCK_SYSCALL 0
3923
3924	// disable all backends except select
3925	#define EV_USE_POLL 0	4727	#define EV_USE_POLL 1
3926	#define EV_USE_PORT 0
3927	#define EV_USE_KQUEUE 0
3928	#define EV_USE_EPOLL 0
3929
3930	// disable all watcher types that cna be disabled
3931	#define EV_STAT_ENABLE 0
3932	#define EV_PERIODIC_ENABLE 0
3933	#define EV_IDLE_ENABLE 0
3934	#define EV_FORK_ENABLE 0
3935	#define EV_SIGNAL_ENABLE 0
3936	#define EV_CHILD_ENABLE 0	4728	#define EV_CHILD_ENABLE 1
3937	#define EV_ASYNC_ENABLE 0	4729	#define EV_ASYNC_ENABLE 1
3938	#define EV_EMBED_ENABLE 0	4730
		4731	The actual value is a bitset, it can be a combination of the following
		4732	values (by default, all of these are enabled):
		4733
		4734	=over 4
		4735
		4736	=item C<1> - faster/larger code
		4737
		4738	Use larger code to speed up some operations.
		4739
		4740	Currently this is used to override some inlining decisions (enlarging the
		4741	code size by roughly 30% on amd64).
		4742
		4743	When optimising for size, use of compiler flags such as C<-Os> with
		4744	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4745	assertions.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
		4749
		4750	=item C<2> - faster/larger data structures
		4751
		4752	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4753	hash table sizes and so on. This will usually further increase code size
		4754	and can additionally have an effect on the size of data structures at
		4755	runtime.
		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
		4760	=item C<4> - full API configuration
		4761
		4762	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4764
		4765	=item C<8> - full API
		4766
		4767	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4768	details on which parts of the API are still available without this
		4769	feature, and do not complain if this subset changes over time.
		4770
		4771	=item C<16> - enable all optional watcher types
		4772
		4773	Enables all optional watcher types. If you want to selectively enable
		4774	only some watcher types other than I/O and timers (e.g. prepare,
		4775	embed, async, child...) you can enable them manually by defining
		4776	C<EV_watchertype_ENABLE> to C<1> instead.
		4777
		4778	=item C<32> - enable all backends
		4779
		4780	This enables all backends - without this feature, you need to enable at
		4781	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4782
		4783	=item C<64> - enable OS-specific "helper" APIs
		4784
		4785	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4786	default.
		4787
		4788	=back
		4789
		4790	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4791	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4792	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4793	watchers, timers and monotonic clock support.
		4794
		4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4796	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4797	your program might be left out as well - a binary starting a timer and an
		4798	I/O watcher then might come out at only 5Kb.
		4799
		4800	=item EV_API_STATIC
		4801
		4802	If this symbol is defined (by default it is not), then all identifiers
		4803	will have static linkage. This means that libev will not export any
		4804	identifiers, and you cannot link against libev anymore. This can be useful
		4805	when you embed libev, only want to use libev functions in a single file,
		4806	and do not want its identifiers to be visible.
		4807
		4808	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4809	wants to use libev.
		4810
		4811	This option only works when libev is compiled with a C compiler, as C++
		4812	doesn't support the required declaration syntax.
3939		4813
3940	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
3941		4815
3942	If this is set to C<1> at compiletime, then libev will avoid using stdio	4816	If this is set to C<1> at compiletime, then libev will avoid using stdio
3943	functions (printf, scanf, perror etc.). This will increase the codesize	4817	functions (printf, scanf, perror etc.). This will increase the code size
3944	somewhat, but if your program doesn't otherwise depend on stdio and your	4818	somewhat, but if your program doesn't otherwise depend on stdio and your
3945	libc allows it, this avoids linking in the stdio library which is quite	4819	libc allows it, this avoids linking in the stdio library which is quite
3946	big.	4820	big.
3947		4821
3948	Note that error messages might become less precise when this option is	4822	Note that error messages might become less precise when this option is
…		…
3952		4826
3953	The highest supported signal number, +1 (or, the number of	4827	The highest supported signal number, +1 (or, the number of
3954	signals): Normally, libev tries to deduce the maximum number of signals	4828	signals): Normally, libev tries to deduce the maximum number of signals
3955	automatically, but sometimes this fails, in which case it can be	4829	automatically, but sometimes this fails, in which case it can be
3956	specified. Also, using a lower number than detected (C<32> should be	4830	specified. Also, using a lower number than detected (C<32> should be
3957	good for about any system in existance) can save some memory, as libev	4831	good for about any system in existence) can save some memory, as libev
3958	statically allocates some 12-24 bytes per signal number.	4832	statically allocates some 12-24 bytes per signal number.
3959		4833
3960	=item EV_PID_HASHSIZE	4834	=item EV_PID_HASHSIZE
3961		4835
3962	C<ev_child> watchers use a small hash table to distribute workload by	4836	C<ev_child> watchers use a small hash table to distribute workload by
3963	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4837	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964	than enough. If you need to manage thousands of children you might want to	4838	usually more than enough. If you need to manage thousands of children you
3965	increase this value (I<must> be a power of two).	4839	might want to increase this value (I<must> be a power of two).
3966		4840
3967	=item EV_INOTIFY_HASHSIZE	4841	=item EV_INOTIFY_HASHSIZE
3968		4842
3969	C<ev_stat> watchers use a small hash table to distribute workload by	4843	C<ev_stat> watchers use a small hash table to distribute workload by
3970	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4844	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971	usually more than enough. If you need to manage thousands of C<ev_stat>	4845	disabled), usually more than enough. If you need to manage thousands of
3972	watchers you might want to increase this value (I<must> be a power of	4846	C<ev_stat> watchers you might want to increase this value (I<must> be a
3973	two).	4847	power of two).
3974		4848
3975	=item EV_USE_4HEAP	4849	=item EV_USE_4HEAP
3976		4850
3977	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4851	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4852	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4853	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980	faster performance with many (thousands) of watchers.	4854	faster performance with many (thousands) of watchers.
3981		4855
3982	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4856	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983	(disabled).	4857	will be C<0>.
3984		4858
3985	=item EV_HEAP_CACHE_AT	4859	=item EV_HEAP_CACHE_AT
3986		4860
3987	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4861	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4862	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4863	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4864	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991	but avoids random read accesses on heap changes. This improves performance	4865	but avoids random read accesses on heap changes. This improves performance
3992	noticeably with many (hundreds) of watchers.	4866	noticeably with many (hundreds) of watchers.
3993		4867
3994	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4868	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995	(disabled).	4869	will be C<0>.
3996		4870
3997	=item EV_VERIFY	4871	=item EV_VERIFY
3998		4872
3999	Controls how much internal verification (see C<ev_loop_verify ()>) will	4873	Controls how much internal verification (see C<ev_verify ()>) will
4000	be done: If set to C<0>, no internal verification code will be compiled	4874	be done: If set to C<0>, no internal verification code will be compiled
4001	in. If set to C<1>, then verification code will be compiled in, but not	4875	in. If set to C<1>, then verification code will be compiled in, but not
4002	called. If set to C<2>, then the internal verification code will be	4876	called. If set to C<2>, then the internal verification code will be
4003	called once per loop, which can slow down libev. If set to C<3>, then the	4877	called once per loop, which can slow down libev. If set to C<3>, then the
4004	verification code will be called very frequently, which will slow down	4878	verification code will be called very frequently, which will slow down
4005	libev considerably.	4879	libev considerably.
4006		4880
4007	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4881	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008	C<0>.	4882	will be C<0>.
4009		4883
4010	=item EV_COMMON	4884	=item EV_COMMON
4011		4885
4012	By default, all watchers have a C<void *data> member. By redefining	4886	By default, all watchers have a C<void *data> member. By redefining
4013	this macro to a something else you can include more and other types of	4887	this macro to something else you can include more and other types of
4014	members. You have to define it each time you include one of the files,	4888	members. You have to define it each time you include one of the files,
4015	though, and it must be identical each time.	4889	though, and it must be identical each time.
4016		4890
4017	For example, the perl EV module uses something like this:	4891	For example, the perl EV module uses something like this:
4018		4892
…		…
4071	file.	4945	file.
4072		4946
4073	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4947	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074	that everybody includes and which overrides some configure choices:	4948	that everybody includes and which overrides some configure choices:
4075		4949
4076	#define EV_MINIMAL 1	4950	#define EV_FEATURES 8
4077	#define EV_USE_POLL 0	4951	#define EV_USE_SELECT 1
4078	#define EV_MULTIPLICITY 0
4079	#define EV_PERIODIC_ENABLE 0	4952	#define EV_PREPARE_ENABLE 1
		4953	#define EV_IDLE_ENABLE 1
4080	#define EV_STAT_ENABLE 0	4954	#define EV_SIGNAL_ENABLE 1
4081	#define EV_FORK_ENABLE 0	4955	#define EV_CHILD_ENABLE 1
		4956	#define EV_USE_STDEXCEPT 0
4082	#define EV_CONFIG_H <config.h>	4957	#define EV_CONFIG_H <config.h>
4083	#define EV_MINPRI 0
4084	#define EV_MAXPRI 0
4085		4958
4086	#include "ev++.h"	4959	#include "ev++.h"
4087		4960
4088	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4961	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089		4962
4090	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4091	#include "ev.c"	4964	#include "ev.c"
4092		4965
4093	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4094		4967
4095	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4096		4969
4097	=head3 THREADS	4970	=head3 THREADS
4098		4971
…		…
4149	default loop and triggering an C<ev_async> watcher from the default loop	5022	default loop and triggering an C<ev_async> watcher from the default loop
4150	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4151		5024
4152	=back	5025	=back
4153		5026
4154	=head4 THREAD LOCKING EXAMPLE	5027	See also L</THREAD LOCKING EXAMPLE>.
4155
4156	Here is a fictitious example of how to run an event loop in a different
4157	thread than where callbacks are being invoked and watchers are
4158	created/added/removed.
4159
4160	For a real-world example, see the C<EV::Loop::Async> perl module,
4161	which uses exactly this technique (which is suited for many high-level
4162	languages).
4163
4164	The example uses a pthread mutex to protect the loop data, a condition
4165	variable to wait for callback invocations, an async watcher to notify the
4166	event loop thread and an unspecified mechanism to wake up the main thread.
4167
4168	First, you need to associate some data with the event loop:
4169
4170	typedef struct {
4171	mutex_t lock; /* global loop lock */
4172	ev_async async_w;
4173	thread_t tid;
4174	cond_t invoke_cv;
4175	} userdata;
4176
4177	void prepare_loop (EV_P)
4178	{
4179	// for simplicity, we use a static userdata struct.
4180	static userdata u;
4181
4182	ev_async_init (&u->async_w, async_cb);
4183	ev_async_start (EV_A_ &u->async_w);
4184
4185	pthread_mutex_init (&u->lock, 0);
4186	pthread_cond_init (&u->invoke_cv, 0);
4187
4188	// now associate this with the loop
4189	ev_set_userdata (EV_A_ u);
4190	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4191	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4192
4193	// then create the thread running ev_loop
4194	pthread_create (&u->tid, 0, l_run, EV_A);
4195	}
4196
4197	The callback for the C<ev_async> watcher does nothing: the watcher is used
4198	solely to wake up the event loop so it takes notice of any new watchers
4199	that might have been added:
4200
4201	static void
4202	async_cb (EV_P_ ev_async *w, int revents)
4203	{
4204	// just used for the side effects
4205	}
4206
4207	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4208	protecting the loop data, respectively.
4209
4210	static void
4211	l_release (EV_P)
4212	{
4213	userdata *u = ev_userdata (EV_A);
4214	pthread_mutex_unlock (&u->lock);
4215	}
4216
4217	static void
4218	l_acquire (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221	pthread_mutex_lock (&u->lock);
4222	}
4223
4224	The event loop thread first acquires the mutex, and then jumps straight
4225	into C<ev_loop>:
4226
4227	void *
4228	l_run (void *thr_arg)
4229	{
4230	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4231
4232	l_acquire (EV_A);
4233	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4234	ev_loop (EV_A_ 0);
4235	l_release (EV_A);
4236
4237	return 0;
4238	}
4239
4240	Instead of invoking all pending watchers, the C<l_invoke> callback will
4241	signal the main thread via some unspecified mechanism (signals? pipe
4242	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4243	have been called (in a while loop because a) spurious wakeups are possible
4244	and b) skipping inter-thread-communication when there are no pending
4245	watchers is very beneficial):
4246
4247	static void
4248	l_invoke (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251
4252	while (ev_pending_count (EV_A))
4253	{
4254	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4255	pthread_cond_wait (&u->invoke_cv, &u->lock);
4256	}
4257	}
4258
4259	Now, whenever the main thread gets told to invoke pending watchers, it
4260	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4261	thread to continue:
4262
4263	static void
4264	real_invoke_pending (EV_P)
4265	{
4266	userdata *u = ev_userdata (EV_A);
4267
4268	pthread_mutex_lock (&u->lock);
4269	ev_invoke_pending (EV_A);
4270	pthread_cond_signal (&u->invoke_cv);
4271	pthread_mutex_unlock (&u->lock);
4272	}
4273
4274	Whenever you want to start/stop a watcher or do other modifications to an
4275	event loop, you will now have to lock:
4276
4277	ev_timer timeout_watcher;
4278	userdata *u = ev_userdata (EV_A);
4279
4280	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4281
4282	pthread_mutex_lock (&u->lock);
4283	ev_timer_start (EV_A_ &timeout_watcher);
4284	ev_async_send (EV_A_ &u->async_w);
4285	pthread_mutex_unlock (&u->lock);
4286
4287	Note that sending the C<ev_async> watcher is required because otherwise
4288	an event loop currently blocking in the kernel will have no knowledge
4289	about the newly added timer. By waking up the loop it will pick up any new
4290	watchers in the next event loop iteration.
4291		5028
4292	=head3 COROUTINES	5029	=head3 COROUTINES
4293		5030
4294	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4295	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
4296	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5033	coroutines (e.g. you can call C<ev_run> on the same loop from two
4297	different coroutines, and switch freely between both coroutines running	5034	different coroutines, and switch freely between both coroutines running
4298	the loop, as long as you don't confuse yourself). The only exception is	5035	the loop, as long as you don't confuse yourself). The only exception is
4299	that you must not do this from C<ev_periodic> reschedule callbacks.	5036	that you must not do this from C<ev_periodic> reschedule callbacks.
4300		5037
4301	Care has been taken to ensure that libev does not keep local state inside	5038	Care has been taken to ensure that libev does not keep local state inside
4302	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5039	C<ev_run>, and other calls do not usually allow for coroutine switches as
4303	they do not call any callbacks.	5040	they do not call any callbacks.
4304		5041
4305	=head2 COMPILER WARNINGS	5042	=head2 COMPILER WARNINGS
4306		5043
4307	Depending on your compiler and compiler settings, you might get no or a	5044	Depending on your compiler and compiler settings, you might get no or a
…		…
4318	maintainable.	5055	maintainable.
4319		5056
4320	And of course, some compiler warnings are just plain stupid, or simply	5057	And of course, some compiler warnings are just plain stupid, or simply
4321	wrong (because they don't actually warn about the condition their message	5058	wrong (because they don't actually warn about the condition their message
4322	seems to warn about). For example, certain older gcc versions had some	5059	seems to warn about). For example, certain older gcc versions had some
4323	warnings that resulted an extreme number of false positives. These have	5060	warnings that resulted in an extreme number of false positives. These have
4324	been fixed, but some people still insist on making code warn-free with	5061	been fixed, but some people still insist on making code warn-free with
4325	such buggy versions.	5062	such buggy versions.
4326		5063
4327	While libev is written to generate as few warnings as possible,	5064	While libev is written to generate as few warnings as possible,
4328	"warn-free" code is not a goal, and it is recommended not to build libev	5065	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4364	I suggest using suppression lists.	5101	I suggest using suppression lists.
4365		5102
4366		5103
4367	=head1 PORTABILITY NOTES	5104	=head1 PORTABILITY NOTES
4368		5105
		5106	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5107
		5108	GNU/Linux is the only common platform that supports 64 bit file/large file
		5109	interfaces but I<disables> them by default.
		5110
		5111	That means that libev compiled in the default environment doesn't support
		5112	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5113
		5114	Unfortunately, many programs try to work around this GNU/Linux issue
		5115	by enabling the large file API, which makes them incompatible with the
		5116	standard libev compiled for their system.
		5117
		5118	Likewise, libev cannot enable the large file API itself as this would
		5119	suddenly make it incompatible to the default compile time environment,
		5120	i.e. all programs not using special compile switches.
		5121
		5122	=head2 OS/X AND DARWIN BUGS
		5123
		5124	The whole thing is a bug if you ask me - basically any system interface
		5125	you touch is broken, whether it is locales, poll, kqueue or even the
		5126	OpenGL drivers.
		5127
		5128	=head3 C<kqueue> is buggy
		5129
		5130	The kqueue syscall is broken in all known versions - most versions support
		5131	only sockets, many support pipes.
		5132
		5133	Libev tries to work around this by not using C<kqueue> by default on this
		5134	rotten platform, but of course you can still ask for it when creating a
		5135	loop - embedding a socket-only kqueue loop into a select-based one is
		5136	probably going to work well.
		5137
		5138	=head3 C<poll> is buggy
		5139
		5140	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5141	implementation by something calling C<kqueue> internally around the 10.5.6
		5142	release, so now C<kqueue> I<and> C<poll> are broken.
		5143
		5144	Libev tries to work around this by not using C<poll> by default on
		5145	this rotten platform, but of course you can still ask for it when creating
		5146	a loop.
		5147
		5148	=head3 C<select> is buggy
		5149
		5150	All that's left is C<select>, and of course Apple found a way to fuck this
		5151	one up as well: On OS/X, C<select> actively limits the number of file
		5152	descriptors you can pass in to 1024 - your program suddenly crashes when
		5153	you use more.
		5154
		5155	There is an undocumented "workaround" for this - defining
		5156	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5157	work on OS/X.
		5158
		5159	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5160
		5161	=head3 C<errno> reentrancy
		5162
		5163	The default compile environment on Solaris is unfortunately so
		5164	thread-unsafe that you can't even use components/libraries compiled
		5165	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5166	defined by default. A valid, if stupid, implementation choice.
		5167
		5168	If you want to use libev in threaded environments you have to make sure
		5169	it's compiled with C<_REENTRANT> defined.
		5170
		5171	=head3 Event port backend
		5172
		5173	The scalable event interface for Solaris is called "event
		5174	ports". Unfortunately, this mechanism is very buggy in all major
		5175	releases. If you run into high CPU usage, your program freezes or you get
		5176	a large number of spurious wakeups, make sure you have all the relevant
		5177	and latest kernel patches applied. No, I don't know which ones, but there
		5178	are multiple ones to apply, and afterwards, event ports actually work
		5179	great.
		5180
		5181	If you can't get it to work, you can try running the program by setting
		5182	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5183	C<select> backends.
		5184
		5185	=head2 AIX POLL BUG
		5186
		5187	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5188	this by trying to avoid the poll backend altogether (i.e. it's not even
		5189	compiled in), which normally isn't a big problem as C<select> works fine
		5190	with large bitsets on AIX, and AIX is dead anyway.
		5191
4369	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5192	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5193
		5194	=head3 General issues
4370		5195
4371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5196	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372	requires, and its I/O model is fundamentally incompatible with the POSIX	5197	requires, and its I/O model is fundamentally incompatible with the POSIX
4373	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4376	e.g. cygwin.	5201	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5202	as every compiler comes with a slightly differently broken/incompatible
		5203	environment.
4377		5204
4378	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4379	re-implementation of the I/O system. If you are into these kinds of	5206	re-implementation of the I/O system. If you are into this kind of thing,
4380	things, then note that glib does exactly that for you in a very portable	5207	then note that glib does exactly that for you in a very portable way (note
4381	way (note also that glib is the slowest event library known to man).	5208	also that glib is the slowest event library known to man).
4382		5209
4383	There is no supported compilation method available on windows except	5210	There is no supported compilation method available on windows except
4384	embedding it into other applications.	5211	embedding it into other applications.
4385		5212
4386	Sensible signal handling is officially unsupported by Microsoft - libev	5213	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4414	you do I<not> compile the F<ev.c> or any other embedded source files!):	5241	you do I<not> compile the F<ev.c> or any other embedded source files!):
4415		5242
4416	#include "evwrap.h"	5243	#include "evwrap.h"
4417	#include "ev.c"	5244	#include "ev.c"
4418		5245
4419	=over 4
4420
4421	=item The winsocket select function	5246	=head3 The winsocket C<select> function
4422		5247
4423	The winsocket C<select> function doesn't follow POSIX in that it	5248	The winsocket C<select> function doesn't follow POSIX in that it
4424	requires socket I<handles> and not socket I<file descriptors> (it is	5249	requires socket I<handles> and not socket I<file descriptors> (it is
4425	also extremely buggy). This makes select very inefficient, and also	5250	also extremely buggy). This makes select very inefficient, and also
4426	requires a mapping from file descriptors to socket handles (the Microsoft	5251	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4435	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5260	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436		5261
4437	Note that winsockets handling of fd sets is O(n), so you can easily get a	5262	Note that winsockets handling of fd sets is O(n), so you can easily get a
4438	complexity in the O(n²) range when using win32.	5263	complexity in the O(n²) range when using win32.
4439		5264
4440	=item Limited number of file descriptors	5265	=head3 Limited number of file descriptors
4441		5266
4442	Windows has numerous arbitrary (and low) limits on things.	5267	Windows has numerous arbitrary (and low) limits on things.
4443		5268
4444	Early versions of winsocket's select only supported waiting for a maximum	5269	Early versions of winsocket's select only supported waiting for a maximum
4445	of C<64> handles (probably owning to the fact that all windows kernels	5270	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4460	runtime libraries. This might get you to about C<512> or C<2048> sockets	5285	runtime libraries. This might get you to about C<512> or C<2048> sockets
4461	(depending on windows version and/or the phase of the moon). To get more,	5286	(depending on windows version and/or the phase of the moon). To get more,
4462	you need to wrap all I/O functions and provide your own fd management, but	5287	you need to wrap all I/O functions and provide your own fd management, but
4463	the cost of calling select (O(n²)) will likely make this unworkable.	5288	the cost of calling select (O(n²)) will likely make this unworkable.
4464		5289
4465	=back
4466
4467	=head2 PORTABILITY REQUIREMENTS	5290	=head2 PORTABILITY REQUIREMENTS
4468		5291
4469	In addition to a working ISO-C implementation and of course the	5292	In addition to a working ISO-C implementation and of course the
4470	backend-specific APIs, libev relies on a few additional extensions:	5293	backend-specific APIs, libev relies on a few additional extensions:
4471		5294
…		…
4477	Libev assumes not only that all watcher pointers have the same internal	5300	Libev assumes not only that all watcher pointers have the same internal
4478	structure (guaranteed by POSIX but not by ISO C for example), but it also	5301	structure (guaranteed by POSIX but not by ISO C for example), but it also
4479	assumes that the same (machine) code can be used to call any watcher	5302	assumes that the same (machine) code can be used to call any watcher
4480	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4481	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
		5305
		5306	=item null pointers and integer zero are represented by 0 bytes
		5307
		5308	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5309	relies on this setting pointers and integers to null.
		5310
		5311	=item pointer accesses must be thread-atomic
		5312
		5313	Accessing a pointer value must be atomic, it must both be readable and
		5314	writable in one piece - this is the case on all current architectures.
4482		5315
4483	=item C<sig_atomic_t volatile> must be thread-atomic as well	5316	=item C<sig_atomic_t volatile> must be thread-atomic as well
4484		5317
4485	The type C<sig_atomic_t volatile> (or whatever is defined as	5318	The type C<sig_atomic_t volatile> (or whatever is defined as
4486	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5319	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4495	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4496	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4497	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4498		5331
4499	The most portable way to handle signals is to block signals in all threads	5332	The most portable way to handle signals is to block signals in all threads
4500	except the initial one, and run the default loop in the initial thread as	5333	except the initial one, and run the signal handling loop in the initial
4501	well.	5334	thread as well.
4502		5335
4503	=item C<long> must be large enough for common memory allocation sizes	5336	=item C<long> must be large enough for common memory allocation sizes
4504		5337
4505	To improve portability and simplify its API, libev uses C<long> internally	5338	To improve portability and simplify its API, libev uses C<long> internally
4506	instead of C<size_t> when allocating its data structures. On non-POSIX	5339	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4509	watchers.	5342	watchers.
4510		5343
4511	=item C<double> must hold a time value in seconds with enough accuracy	5344	=item C<double> must hold a time value in seconds with enough accuracy
4512		5345
4513	The type C<double> is used to represent timestamps. It is required to	5346	The type C<double> is used to represent timestamps. It is required to
4514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5347	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4515	enough for at least into the year 4000. This requirement is fulfilled by	5348	good enough for at least into the year 4000 with millisecond accuracy
		5349	(the design goal for libev). This requirement is overfulfilled by
4516	implementations implementing IEEE 754, which is basically all existing	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4517	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5352	With IEEE 754 doubles, you get microsecond accuracy until at least the
4518	2200.	5353	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5354	is either obsolete or somebody patched it to use C<long double> or
		5355	something like that, just kidding).
4519		5356
4520	=back	5357	=back
4521		5358
4522	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4523		5360
…		…
4585	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
4586		5423
4587	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
4588		5425
4589	Sending involves a system call I<iff> there were no other C<ev_async_send>	5426	Sending involves a system call I<iff> there were no other C<ev_async_send>
4590	calls in the current loop iteration. Checking for async and signal events	5427	calls in the current loop iteration and the loop is currently
		5428	blocked. Checking for async and signal events involves iterating over all
4591	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
4592		5430
4593	=back	5431	=back
4594		5432
4595		5433
		5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5435
		5436	The major version 4 introduced some incompatible changes to the API.
		5437
		5438	At the moment, the C<ev.h> header file provides compatibility definitions
		5439	for all changes, so most programs should still compile. The compatibility
		5440	layer might be removed in later versions of libev, so better update to the
		5441	new API early than late.
		5442
		5443	=over 4
		5444
		5445	=item C<EV_COMPAT3> backwards compatibility mechanism
		5446
		5447	The backward compatibility mechanism can be controlled by
		5448	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5449	section.
		5450
		5451	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5452
		5453	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5454
		5455	ev_loop_destroy (EV_DEFAULT_UC);
		5456	ev_loop_fork (EV_DEFAULT);
		5457
		5458	=item function/symbol renames
		5459
		5460	A number of functions and symbols have been renamed:
		5461
		5462	ev_loop => ev_run
		5463	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5464	EVLOOP_ONESHOT => EVRUN_ONCE
		5465
		5466	ev_unloop => ev_break
		5467	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5468	EVUNLOOP_ONE => EVBREAK_ONE
		5469	EVUNLOOP_ALL => EVBREAK_ALL
		5470
		5471	EV_TIMEOUT => EV_TIMER
		5472
		5473	ev_loop_count => ev_iteration
		5474	ev_loop_depth => ev_depth
		5475	ev_loop_verify => ev_verify
		5476
		5477	Most functions working on C<struct ev_loop> objects don't have an
		5478	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5479	associated constants have been renamed to not collide with the C<struct
		5480	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5481	as all other watcher types. Note that C<ev_loop_fork> is still called
		5482	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5483	typedef.
		5484
		5485	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5486
		5487	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5488	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5489	and work, but the library code will of course be larger.
		5490
		5491	=back
		5492
		5493
4596	=head1 GLOSSARY	5494	=head1 GLOSSARY
4597		5495
4598	=over 4	5496	=over 4
4599		5497
4600	=item active	5498	=item active
4601		5499
4602	A watcher is active as long as it has been started (has been attached to	5500	A watcher is active as long as it has been started and not yet stopped.
4603	an event loop) but not yet stopped (disassociated from the event loop).	5501	See L</WATCHER STATES> for details.
4604		5502
4605	=item application	5503	=item application
4606		5504
4607	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
		5506
		5507	=item backend
		5508
		5509	The part of the code dealing with the operating system interfaces.
4608		5510
4609	=item callback	5511	=item callback
4610		5512
4611	The address of a function that is called when some event has been	5513	The address of a function that is called when some event has been
4612	detected. Callbacks are being passed the event loop, the watcher that	5514	detected. Callbacks are being passed the event loop, the watcher that
4613	received the event, and the actual event bitset.	5515	received the event, and the actual event bitset.
4614		5516
4615	=item callback invocation	5517	=item callback/watcher invocation
4616		5518
4617	The act of calling the callback associated with a watcher.	5519	The act of calling the callback associated with a watcher.
4618		5520
4619	=item event	5521	=item event
4620		5522
4621	A change of state of some external event, such as data now being available	5523	A change of state of some external event, such as data now being available
4622	for reading on a file descriptor, time having passed or simply not having	5524	for reading on a file descriptor, time having passed or simply not having
4623	any other events happening anymore.	5525	any other events happening anymore.
4624		5526
4625	In libev, events are represented as single bits (such as C<EV_READ> or	5527	In libev, events are represented as single bits (such as C<EV_READ> or
4626	C<EV_TIMEOUT>).	5528	C<EV_TIMER>).
4627		5529
4628	=item event library	5530	=item event library
4629		5531
4630	A software package implementing an event model and loop.	5532	A software package implementing an event model and loop.
4631		5533
…		…
4639	The model used to describe how an event loop handles and processes	5541	The model used to describe how an event loop handles and processes
4640	watchers and events.	5542	watchers and events.
4641		5543
4642	=item pending	5544	=item pending
4643		5545
4644	A watcher is pending as soon as the corresponding event has been detected,	5546	A watcher is pending as soon as the corresponding event has been
4645	and stops being pending as soon as the watcher will be invoked or its	5547	detected. See L</WATCHER STATES> for details.
4646	pending status is explicitly cleared by the application.
4647
4648	A watcher can be pending, but not active. Stopping a watcher also clears
4649	its pending status.
4650		5548
4651	=item real time	5549	=item real time
4652		5550
4653	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
4654		5552
4655	=item wall-clock time	5553	=item wall-clock time
4656		5554
4657	The time and date as shown on clocks. Unlike real time, it can actually	5555	The time and date as shown on clocks. Unlike real time, it can actually
4658	be wrong and jump forwards and backwards, e.g. when the you adjust your	5556	be wrong and jump forwards and backwards, e.g. when you adjust your
4659	clock.	5557	clock.
4660		5558
4661	=item watcher	5559	=item watcher
4662		5560
4663	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
4664	to be started (attached to an event loop) before they can receive events.	5562	to be started (attached to an event loop) before they can receive events.
4665		5563
4666	=item watcher invocation
4667
4668	The act of calling the callback associated with a watcher.
4669
4670	=back	5564	=back
4671		5565
4672	=head1 AUTHOR	5566	=head1 AUTHOR
4673		5567
4674	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5568	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5569	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4675		5570

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