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Revision 1.306 by root, Mon Oct 18 07:36:05 2010 UTC vs.
Revision 1.440 by root, Tue Jan 31 09:31:43 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
…		…
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	Familiarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		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 (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
171		182
172	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
173		184
174	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
176	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
177		194
178	=item int ev_version_major ()	195	=item int ev_version_major ()
179		196
180	=item int ev_version_minor ()	197	=item int ev_version_minor ()
181		198
…		…
192	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	211	not a problem.
195		212
196	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
198		216
199	assert (("libev version mismatch",	217	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
202		220
…		…
213	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
215		233
216	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
217		235
218	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
224		243
225	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
226		245
227	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
232		251
233	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
234		253
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		255
237	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	285	}
267		286
268	...	287	...
269	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
270		289
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		291
273	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
274	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
275	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	307	}
289		308
290	...	309	...
291	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
292		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
293	=back	325	=back
294		326
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		328
297	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
298	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
299	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
300		332
301	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
302	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
303	not.	335	do not.
304		336
305	=over 4	337	=over 4
306		338
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		340
309	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
310	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
311	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
312	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".
313		351
314	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
315	function.	353	function (or via the C<EV_DEFAULT> macro).
316		354
317	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
318	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
319	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).
320		359
321	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,
322	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
323	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
324	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
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	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.
327		384
328	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
329	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>).
330		387
331	The following flags are supported:	388	The following flags are supported:
…		…
341		398
342	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
343	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
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	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
346	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
347	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).
348		407
349	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
350		409
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
…		…
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 sequence
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	without a system call and thus I<very> fast, but my GNU/Linux system also has
359	C<pthread_atfork> which is even faster).	418	C<pthread_atfork> which is even faster).
360		419
361	The big advantage of this flag is that you can forget about fork (and	420	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	421	forget about forgetting to tell libev about forking, although you still
363	flag.	422	have to ignore C<SIGPIPE>) when you use this flag.
364		423
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	424	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	425	environment variable.
367		426
368	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
369		428
370	When this flag is specified, then libev will not attempt to use the	429	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	430	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	431	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.	432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		433
375	=item C<EVFLAG_SIGNALFD>	434	=item C<EVFLAG_SIGNALFD>
376		435
377	When this flag is specified, then libev will attempt to use the	436	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	437	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	438	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	439	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	440	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	441	threads that are not interested in handling them.
383		442
384	Signalfd will not be used by default as this changes your signal mask, and	443	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	444	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
387		461
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		463
390	This is your standard select(2) backend. Not I<completely> standard, as	464	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,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		494
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	496	kernels).
423		497
424	For few fds, this backend is a bit little slower than poll and select,	498	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	499	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),	500	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).	501	fd), epoll scales either O(1) or O(active_fds).
428		502
429	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(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	509	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	510	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	511	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	512	and is of course hard to detect.
437		513
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	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	515	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	516	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	517	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	518	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	524	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
447		530
448	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
488		571
489	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
490	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
491	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
493	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
495	cases	578	drops fds silently in similarly hard-to-detect cases.
496		579
497	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
498		581
499	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
500	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		601
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
521		604
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	608	might perform better.
530		609
531	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
535		624
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
538		627
539	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
540		629
541	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		633
545	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		643
547	=back	644	=back
548		645
549	If one or more of the backend flags are or'ed into the flags value,	646	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	647	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	648	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	649	()> will be tried.
553		650
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common 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.	651	Example: Try to create a event loop that uses epoll and nothing else.
581		652
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	654	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
585		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
586	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
587		663
588	Destroys the default loop (frees all memory and kernel state etc.). None	664	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	665	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	666	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	667	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	668	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		670	for example).
594		671
595	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
598		675
599	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
603		684
604	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
605		686
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610
611	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations
612	to reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
613	name, you can call it anytime, but it makes most sense after forking, in	689	the name, you can call it anytime you are allowed to start or stop
614	the child process (or both child and parent, but that again makes little	690	watchers (except inside an C<ev_prepare> callback), but it makes most
615	sense). You I<must> call it in the child before using any of the libev	691	sense after forking, in the child process. You I<must> call it (or use
616	functions, and it will only take effect at the next C<ev_loop> iteration.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
617		693
		694	In addition, if you want to reuse a loop (via this function or
		695	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		696
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	697	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	698	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	699	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	700	during fork.
622		701
623	On the other hand, you only need to call this function in the child	702	On the other hand, you only need to call this function in the child
624	process if and only if you want to use the event loop in the child. If you	703	process if and only if you want to use the event loop in the child. If
625	just fork+exec or create a new loop in the child, you don't have to call	704	you just fork+exec or create a new loop in the child, you don't have to
626	it at all.	705	call it at all (in fact, C<epoll> is so badly broken that it makes a
		706	difference, but libev will usually detect this case on its own and do a
		707	costly reset of the backend).
627		708
628	The function itself is quite fast and it's usually not a problem to call	709	The function itself is quite fast and it's usually not a problem to call
629	it just in case after a fork. To make this easy, the function will fit in	710	it just in case after a fork.
630	quite nicely into a call to C<pthread_atfork>:
631		711
		712	Example: Automate calling C<ev_loop_fork> on the default loop when
		713	using pthreads.
		714
		715	static void
		716	post_fork_child (void)
		717	{
		718	ev_loop_fork (EV_DEFAULT);
		719	}
		720
		721	...
632	pthread_atfork (0, 0, ev_default_fork);	722	pthread_atfork (0, 0, post_fork_child);
633
634	=item ev_loop_fork (loop)
635
636	Like C<ev_default_fork>, but acts on an event loop created by
637	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
638	after fork that you want to re-use in the child, and how you keep track of
639	them is entirely your own problem.
640		723
641	=item int ev_is_default_loop (loop)	724	=item int ev_is_default_loop (loop)
642		725
643	Returns true when the given loop is, in fact, the default loop, and false	726	Returns true when the given loop is, in fact, the default loop, and false
644	otherwise.	727	otherwise.
645		728
646	=item unsigned int ev_iteration (loop)	729	=item unsigned int ev_iteration (loop)
647		730
648	Returns the current iteration count for the loop, which is identical to	731	Returns the current iteration count for the event loop, which is identical
649	the number of times libev did poll for new events. It starts at C<0> and	732	to the number of times libev did poll for new events. It starts at C<0>
650	happily wraps around with enough iterations.	733	and happily wraps around with enough iterations.
651		734
652	This value can sometimes be useful as a generation counter of sorts (it	735	This value can sometimes be useful as a generation counter of sorts (it
653	"ticks" the number of loop iterations), as it roughly corresponds with	736	"ticks" the number of loop iterations), as it roughly corresponds with
654	C<ev_prepare> and C<ev_check> calls - and is incremented between the	737	C<ev_prepare> and C<ev_check> calls - and is incremented between the
655	prepare and check phases.	738	prepare and check phases.
656		739
657	=item unsigned int ev_depth (loop)	740	=item unsigned int ev_depth (loop)
658		741
659	Returns the number of times C<ev_loop> was entered minus the number of	742	Returns the number of times C<ev_run> was entered minus the number of
660	times C<ev_loop> was exited, in other words, the recursion depth.	743	times C<ev_run> was exited normally, in other words, the recursion depth.
661		744
662	Outside C<ev_loop>, this number is zero. In a callback, this number is	745	Outside C<ev_run>, this number is zero. In a callback, this number is
663	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	746	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
664	in which case it is higher.	747	in which case it is higher.
665		748
666	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	749	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
667	etc.), doesn't count as "exit" - consider this as a hint to avoid such	750	throwing an exception etc.), doesn't count as "exit" - consider this
668	ungentleman behaviour unless it's really convenient.	751	as a hint to avoid such ungentleman-like behaviour unless it's really
		752	convenient, in which case it is fully supported.
669		753
670	=item unsigned int ev_backend (loop)	754	=item unsigned int ev_backend (loop)
671		755
672	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	756	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
673	use.	757	use.
…		…
682		766
683	=item ev_now_update (loop)	767	=item ev_now_update (loop)
684		768
685	Establishes the current time by querying the kernel, updating the time	769	Establishes the current time by querying the kernel, updating the time
686	returned by C<ev_now ()> in the progress. This is a costly operation and	770	returned by C<ev_now ()> in the progress. This is a costly operation and
687	is usually done automatically within C<ev_loop ()>.	771	is usually done automatically within C<ev_run ()>.
688		772
689	This function is rarely useful, but when some event callback runs for a	773	This function is rarely useful, but when some event callback runs for a
690	very long time without entering the event loop, updating libev's idea of	774	very long time without entering the event loop, updating libev's idea of
691	the current time is a good idea.	775	the current time is a good idea.
692		776
693	See also L<The special problem of time updates> in the C<ev_timer> section.	777	See also L</The special problem of time updates> in the C<ev_timer> section.
694		778
695	=item ev_suspend (loop)	779	=item ev_suspend (loop)
696		780
697	=item ev_resume (loop)	781	=item ev_resume (loop)
698		782
699	These two functions suspend and resume a loop, for use when the loop is	783	These two functions suspend and resume an event loop, for use when the
700	not used for a while and timeouts should not be processed.	784	loop is not used for a while and timeouts should not be processed.
701		785
702	A typical use case would be an interactive program such as a game: When	786	A typical use case would be an interactive program such as a game: When
703	the user presses C<^Z> to suspend the game and resumes it an hour later it	787	the user presses C<^Z> to suspend the game and resumes it an hour later it
704	would be best to handle timeouts as if no time had actually passed while	788	would be best to handle timeouts as if no time had actually passed while
705	the program was suspended. This can be achieved by calling C<ev_suspend>	789	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
716	without a previous call to C<ev_suspend>.	800	without a previous call to C<ev_suspend>.
717		801
718	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	802	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
719	event loop time (see C<ev_now_update>).	803	event loop time (see C<ev_now_update>).
720		804
721	=item ev_loop (loop, int flags)	805	=item bool ev_run (loop, int flags)
722		806
723	Finally, this is it, the event handler. This function usually is called	807	Finally, this is it, the event handler. This function usually is called
724	after you have initialised all your watchers and you want to start	808	after you have initialised all your watchers and you want to start
725	handling events.	809	handling events. It will ask the operating system for any new events, call
		810	the watcher callbacks, and then repeat the whole process indefinitely: This
		811	is why event loops are called I<loops>.
726		812
727	If the flags argument is specified as C<0>, it will not return until	813	If the flags argument is specified as C<0>, it will keep handling events
728	either no event watchers are active anymore or C<ev_unloop> was called.	814	until either no event watchers are active anymore or C<ev_break> was
		815	called.
729		816
		817	The return value is false if there are no more active watchers (which
		818	usually means "all jobs done" or "deadlock"), and true in all other cases
		819	(which usually means " you should call C<ev_run> again").
		820
730	Please note that an explicit C<ev_unloop> is usually better than	821	Please note that an explicit C<ev_break> is usually better than
731	relying on all watchers to be stopped when deciding when a program has	822	relying on all watchers to be stopped when deciding when a program has
732	finished (especially in interactive programs), but having a program	823	finished (especially in interactive programs), but having a program
733	that automatically loops as long as it has to and no longer by virtue	824	that automatically loops as long as it has to and no longer by virtue
734	of relying on its watchers stopping correctly, that is truly a thing of	825	of relying on its watchers stopping correctly, that is truly a thing of
735	beauty.	826	beauty.
736		827
		828	This function is I<mostly> exception-safe - you can break out of a
		829	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		830	exception and so on. This does not decrement the C<ev_depth> value, nor
		831	will it clear any outstanding C<EVBREAK_ONE> breaks.
		832
737	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	833	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
738	those events and any already outstanding ones, but will not block your	834	those events and any already outstanding ones, but will not wait and
739	process in case there are no events and will return after one iteration of	835	block your process in case there are no events and will return after one
740	the loop.	836	iteration of the loop. This is sometimes useful to poll and handle new
		837	events while doing lengthy calculations, to keep the program responsive.
741		838
742	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	839	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
743	necessary) and will handle those and any already outstanding ones. It	840	necessary) and will handle those and any already outstanding ones. It
744	will block your process until at least one new event arrives (which could	841	will block your process until at least one new event arrives (which could
745	be an event internal to libev itself, so there is no guarantee that a	842	be an event internal to libev itself, so there is no guarantee that a
746	user-registered callback will be called), and will return after one	843	user-registered callback will be called), and will return after one
747	iteration of the loop.	844	iteration of the loop.
748		845
749	This is useful if you are waiting for some external event in conjunction	846	This is useful if you are waiting for some external event in conjunction
750	with something not expressible using other libev watchers (i.e. "roll your	847	with something not expressible using other libev watchers (i.e. "roll your
751	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	848	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
752	usually a better approach for this kind of thing.	849	usually a better approach for this kind of thing.
753		850
754	Here are the gory details of what C<ev_loop> does:	851	Here are the gory details of what C<ev_run> does (this is for your
		852	understanding, not a guarantee that things will work exactly like this in
		853	future versions):
755		854
		855	- Increment loop depth.
		856	- Reset the ev_break status.
756	- Before the first iteration, call any pending watchers.	857	- Before the first iteration, call any pending watchers.
		858	LOOP:
757	* If EVFLAG_FORKCHECK was used, check for a fork.	859	- If EVFLAG_FORKCHECK was used, check for a fork.
758	- If a fork was detected (by any means), queue and call all fork watchers.	860	- If a fork was detected (by any means), queue and call all fork watchers.
759	- Queue and call all prepare watchers.	861	- Queue and call all prepare watchers.
		862	- If ev_break was called, goto FINISH.
760	- If we have been forked, detach and recreate the kernel state	863	- If we have been forked, detach and recreate the kernel state
761	as to not disturb the other process.	864	as to not disturb the other process.
762	- Update the kernel state with all outstanding changes.	865	- Update the kernel state with all outstanding changes.
763	- Update the "event loop time" (ev_now ()).	866	- Update the "event loop time" (ev_now ()).
764	- Calculate for how long to sleep or block, if at all	867	- Calculate for how long to sleep or block, if at all
765	(active idle watchers, EVLOOP_NONBLOCK or not having	868	(active idle watchers, EVRUN_NOWAIT or not having
766	any active watchers at all will result in not sleeping).	869	any active watchers at all will result in not sleeping).
767	- Sleep if the I/O and timer collect interval say so.	870	- Sleep if the I/O and timer collect interval say so.
		871	- Increment loop iteration counter.
768	- Block the process, waiting for any events.	872	- Block the process, waiting for any events.
769	- Queue all outstanding I/O (fd) events.	873	- Queue all outstanding I/O (fd) events.
770	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	874	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
771	- Queue all expired timers.	875	- Queue all expired timers.
772	- Queue all expired periodics.	876	- Queue all expired periodics.
773	- Unless any events are pending now, queue all idle watchers.	877	- Queue all idle watchers with priority higher than that of pending events.
774	- Queue all check watchers.	878	- Queue all check watchers.
775	- Call all queued watchers in reverse order (i.e. check watchers first).	879	- Call all queued watchers in reverse order (i.e. check watchers first).
776	Signals and child watchers are implemented as I/O watchers, and will	880	Signals and child watchers are implemented as I/O watchers, and will
777	be handled here by queueing them when their watcher gets executed.	881	be handled here by queueing them when their watcher gets executed.
778	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	882	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
779	were used, or there are no active watchers, return, otherwise	883	were used, or there are no active watchers, goto FINISH, otherwise
780	continue with step *.	884	continue with step LOOP.
		885	FINISH:
		886	- Reset the ev_break status iff it was EVBREAK_ONE.
		887	- Decrement the loop depth.
		888	- Return.
781		889
782	Example: Queue some jobs and then loop until no events are outstanding	890	Example: Queue some jobs and then loop until no events are outstanding
783	anymore.	891	anymore.
784		892
785	... queue jobs here, make sure they register event watchers as long	893	... queue jobs here, make sure they register event watchers as long
786	... as they still have work to do (even an idle watcher will do..)	894	... as they still have work to do (even an idle watcher will do..)
787	ev_loop (my_loop, 0);	895	ev_run (my_loop, 0);
788	... jobs done or somebody called unloop. yeah!	896	... jobs done or somebody called break. yeah!
789		897
790	=item ev_unloop (loop, how)	898	=item ev_break (loop, how)
791		899
792	Can be used to make a call to C<ev_loop> return early (but only after it	900	Can be used to make a call to C<ev_run> return early (but only after it
793	has processed all outstanding events). The C<how> argument must be either	901	has processed all outstanding events). The C<how> argument must be either
794	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	902	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
795	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	903	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
796		904
797	This "unloop state" will be cleared when entering C<ev_loop> again.	905	This "break state" will be cleared on the next call to C<ev_run>.
798		906
799	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	907	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		908	which case it will have no effect.
800		909
801	=item ev_ref (loop)	910	=item ev_ref (loop)
802		911
803	=item ev_unref (loop)	912	=item ev_unref (loop)
804		913
805	Ref/unref can be used to add or remove a reference count on the event	914	Ref/unref can be used to add or remove a reference count on the event
806	loop: Every watcher keeps one reference, and as long as the reference	915	loop: Every watcher keeps one reference, and as long as the reference
807	count is nonzero, C<ev_loop> will not return on its own.	916	count is nonzero, C<ev_run> will not return on its own.
808		917
809	This is useful when you have a watcher that you never intend to	918	This is useful when you have a watcher that you never intend to
810	unregister, but that nevertheless should not keep C<ev_loop> from	919	unregister, but that nevertheless should not keep C<ev_run> from
811	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	920	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
812	before stopping it.	921	before stopping it.
813		922
814	As an example, libev itself uses this for its internal signal pipe: It	923	As an example, libev itself uses this for its internal signal pipe: It
815	is not visible to the libev user and should not keep C<ev_loop> from	924	is not visible to the libev user and should not keep C<ev_run> from
816	exiting if no event watchers registered by it are active. It is also an	925	exiting if no event watchers registered by it are active. It is also an
817	excellent way to do this for generic recurring timers or from within	926	excellent way to do this for generic recurring timers or from within
818	third-party libraries. Just remember to I<unref after start> and I<ref	927	third-party libraries. Just remember to I<unref after start> and I<ref
819	before stop> (but only if the watcher wasn't active before, or was active	928	before stop> (but only if the watcher wasn't active before, or was active
820	before, respectively. Note also that libev might stop watchers itself	929	before, respectively. Note also that libev might stop watchers itself
821	(e.g. non-repeating timers) in which case you have to C<ev_ref>	930	(e.g. non-repeating timers) in which case you have to C<ev_ref>
822	in the callback).	931	in the callback).
823		932
824	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	933	Example: Create a signal watcher, but keep it from keeping C<ev_run>
825	running when nothing else is active.	934	running when nothing else is active.
826		935
827	ev_signal exitsig;	936	ev_signal exitsig;
828	ev_signal_init (&exitsig, sig_cb, SIGINT);	937	ev_signal_init (&exitsig, sig_cb, SIGINT);
829	ev_signal_start (loop, &exitsig);	938	ev_signal_start (loop, &exitsig);
830	evf_unref (loop);	939	ev_unref (loop);
831		940
832	Example: For some weird reason, unregister the above signal handler again.	941	Example: For some weird reason, unregister the above signal handler again.
833		942
834	ev_ref (loop);	943	ev_ref (loop);
835	ev_signal_stop (loop, &exitsig);	944	ev_signal_stop (loop, &exitsig);
…		…
855	overhead for the actual polling but can deliver many events at once.	964	overhead for the actual polling but can deliver many events at once.
856		965
857	By setting a higher I<io collect interval> you allow libev to spend more	966	By setting a higher I<io collect interval> you allow libev to spend more
858	time collecting I/O events, so you can handle more events per iteration,	967	time collecting I/O events, so you can handle more events per iteration,
859	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	968	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
860	C<ev_timer>) will be not affected. Setting this to a non-null value will	969	C<ev_timer>) will not be affected. Setting this to a non-null value will
861	introduce an additional C<ev_sleep ()> call into most loop iterations. The	970	introduce an additional C<ev_sleep ()> call into most loop iterations. The
862	sleep time ensures that libev will not poll for I/O events more often then	971	sleep time ensures that libev will not poll for I/O events more often then
863	once per this interval, on average.	972	once per this interval, on average (as long as the host time resolution is
		973	good enough).
864		974
865	Likewise, by setting a higher I<timeout collect interval> you allow libev	975	Likewise, by setting a higher I<timeout collect interval> you allow libev
866	to spend more time collecting timeouts, at the expense of increased	976	to spend more time collecting timeouts, at the expense of increased
867	latency/jitter/inexactness (the watcher callback will be called	977	latency/jitter/inexactness (the watcher callback will be called
868	later). C<ev_io> watchers will not be affected. Setting this to a non-null	978	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
892	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1002	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
893		1003
894	=item ev_invoke_pending (loop)	1004	=item ev_invoke_pending (loop)
895		1005
896	This call will simply invoke all pending watchers while resetting their	1006	This call will simply invoke all pending watchers while resetting their
897	pending state. Normally, C<ev_loop> does this automatically when required,	1007	pending state. Normally, C<ev_run> does this automatically when required,
898	but when overriding the invoke callback this call comes handy.	1008	but when overriding the invoke callback this call comes handy. This
		1009	function can be invoked from a watcher - this can be useful for example
		1010	when you want to do some lengthy calculation and want to pass further
		1011	event handling to another thread (you still have to make sure only one
		1012	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
899		1013
900	=item int ev_pending_count (loop)	1014	=item int ev_pending_count (loop)
901		1015
902	Returns the number of pending watchers - zero indicates that no watchers	1016	Returns the number of pending watchers - zero indicates that no watchers
903	are pending.	1017	are pending.
904		1018
905	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1019	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
906		1020
907	This overrides the invoke pending functionality of the loop: Instead of	1021	This overrides the invoke pending functionality of the loop: Instead of
908	invoking all pending watchers when there are any, C<ev_loop> will call	1022	invoking all pending watchers when there are any, C<ev_run> will call
909	this callback instead. This is useful, for example, when you want to	1023	this callback instead. This is useful, for example, when you want to
910	invoke the actual watchers inside another context (another thread etc.).	1024	invoke the actual watchers inside another context (another thread etc.).
911		1025
912	If you want to reset the callback, use C<ev_invoke_pending> as new	1026	If you want to reset the callback, use C<ev_invoke_pending> as new
913	callback.	1027	callback.
914		1028
915	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1029	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
916		1030
917	Sometimes you want to share the same loop between multiple threads. This	1031	Sometimes you want to share the same loop between multiple threads. This
918	can be done relatively simply by putting mutex_lock/unlock calls around	1032	can be done relatively simply by putting mutex_lock/unlock calls around
919	each call to a libev function.	1033	each call to a libev function.
920		1034
921	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1035	However, C<ev_run> can run an indefinite time, so it is not feasible
922	wait for it to return. One way around this is to wake up the loop via	1036	to wait for it to return. One way around this is to wake up the event
923	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1037	loop via C<ev_break> and C<ev_async_send>, another way is to set these
924	and I<acquire> callbacks on the loop.	1038	I<release> and I<acquire> callbacks on the loop.
925		1039
926	When set, then C<release> will be called just before the thread is	1040	When set, then C<release> will be called just before the thread is
927	suspended waiting for new events, and C<acquire> is called just	1041	suspended waiting for new events, and C<acquire> is called just
928	afterwards.	1042	afterwards.
929		1043
…		…
932		1046
933	While event loop modifications are allowed between invocations of	1047	While event loop modifications are allowed between invocations of
934	C<release> and C<acquire> (that's their only purpose after all), no	1048	C<release> and C<acquire> (that's their only purpose after all), no
935	modifications done will affect the event loop, i.e. adding watchers will	1049	modifications done will affect the event loop, i.e. adding watchers will
936	have no effect on the set of file descriptors being watched, or the time	1050	have no effect on the set of file descriptors being watched, or the time
937	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1051	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
938	to take note of any changes you made.	1052	to take note of any changes you made.
939		1053
940	In theory, threads executing C<ev_loop> will be async-cancel safe between	1054	In theory, threads executing C<ev_run> will be async-cancel safe between
941	invocations of C<release> and C<acquire>.	1055	invocations of C<release> and C<acquire>.
942		1056
943	See also the locking example in the C<THREADS> section later in this	1057	See also the locking example in the C<THREADS> section later in this
944	document.	1058	document.
945		1059
946	=item ev_set_userdata (loop, void *data)	1060	=item ev_set_userdata (loop, void *data)
947		1061
948	=item ev_userdata (loop)	1062	=item void *ev_userdata (loop)
949		1063
950	Set and retrieve a single C<void *> associated with a loop. When	1064	Set and retrieve a single C<void *> associated with a loop. When
951	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1065	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
952	C<0.>	1066	C<0>.
953		1067
954	These two functions can be used to associate arbitrary data with a loop,	1068	These two functions can be used to associate arbitrary data with a loop,
955	and are intended solely for the C<invoke_pending_cb>, C<release> and	1069	and are intended solely for the C<invoke_pending_cb>, C<release> and
956	C<acquire> callbacks described above, but of course can be (ab-)used for	1070	C<acquire> callbacks described above, but of course can be (ab-)used for
957	any other purpose as well.	1071	any other purpose as well.
958		1072
959	=item ev_loop_verify (loop)	1073	=item ev_verify (loop)
960		1074
961	This function only does something when C<EV_VERIFY> support has been	1075	This function only does something when C<EV_VERIFY> support has been
962	compiled in, which is the default for non-minimal builds. It tries to go	1076	compiled in, which is the default for non-minimal builds. It tries to go
963	through all internal structures and checks them for validity. If anything	1077	through all internal structures and checks them for validity. If anything
964	is found to be inconsistent, it will print an error message to standard	1078	is found to be inconsistent, it will print an error message to standard
…		…
975		1089
976	In the following description, uppercase C<TYPE> in names stands for the	1090	In the following description, uppercase C<TYPE> in names stands for the
977	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1091	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
978	watchers and C<ev_io_start> for I/O watchers.	1092	watchers and C<ev_io_start> for I/O watchers.
979		1093
980	A watcher is a structure that you create and register to record your	1094	A watcher is an opaque structure that you allocate and register to record
981	interest in some event. For instance, if you want to wait for STDIN to	1095	your interest in some event. To make a concrete example, imagine you want
982	become readable, you would create an C<ev_io> watcher for that:	1096	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1097	for that:
983		1098
984	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
985	{	1100	{
986	ev_io_stop (w);	1101	ev_io_stop (w);
987	ev_unloop (loop, EVUNLOOP_ALL);	1102	ev_break (loop, EVBREAK_ALL);
988	}	1103	}
989		1104
990	struct ev_loop *loop = ev_default_loop (0);	1105	struct ev_loop *loop = ev_default_loop (0);
991		1106
992	ev_io stdin_watcher;	1107	ev_io stdin_watcher;
993		1108
994	ev_init (&stdin_watcher, my_cb);	1109	ev_init (&stdin_watcher, my_cb);
995	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1110	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
996	ev_io_start (loop, &stdin_watcher);	1111	ev_io_start (loop, &stdin_watcher);
997		1112
998	ev_loop (loop, 0);	1113	ev_run (loop, 0);
999		1114
1000	As you can see, you are responsible for allocating the memory for your	1115	As you can see, you are responsible for allocating the memory for your
1001	watcher structures (and it is I<usually> a bad idea to do this on the	1116	watcher structures (and it is I<usually> a bad idea to do this on the
1002	stack).	1117	stack).
1003		1118
1004	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1119	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1005	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1120	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1006		1121
1007	Each watcher structure must be initialised by a call to C<ev_init	1122	Each watcher structure must be initialised by a call to C<ev_init (watcher
1008	(watcher *, callback)>, which expects a callback to be provided. This	1123	*, callback)>, which expects a callback to be provided. This callback is
1009	callback gets invoked each time the event occurs (or, in the case of I/O	1124	invoked each time the event occurs (or, in the case of I/O watchers, each
1010	watchers, each time the event loop detects that the file descriptor given	1125	time the event loop detects that the file descriptor given is readable
1011	is readable and/or writable).	1126	and/or writable).
1012		1127
1013	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1128	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1014	macro to configure it, with arguments specific to the watcher type. There	1129	macro to configure it, with arguments specific to the watcher type. There
1015	is also a macro to combine initialisation and setting in one call: C<<	1130	is also a macro to combine initialisation and setting in one call: C<<
1016	ev_TYPE_init (watcher *, callback, ...) >>.	1131	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1067		1182
1068	=item C<EV_PREPARE>	1183	=item C<EV_PREPARE>
1069		1184
1070	=item C<EV_CHECK>	1185	=item C<EV_CHECK>
1071		1186
1072	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1187	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1073	to gather new events, and all C<ev_check> watchers are invoked just after	1188	gather new events, and all C<ev_check> watchers are queued (not invoked)
1074	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1189	just after C<ev_run> has gathered them, but before it queues any callbacks
		1190	for any received events. That means C<ev_prepare> watchers are the last
		1191	watchers invoked before the event loop sleeps or polls for new events, and
		1192	C<ev_check> watchers will be invoked before any other watchers of the same
		1193	or lower priority within an event loop iteration.
		1194
1075	received events. Callbacks of both watcher types can start and stop as	1195	Callbacks of both watcher types can start and stop as many watchers as
1076	many watchers as they want, and all of them will be taken into account	1196	they want, and all of them will be taken into account (for example, a
1077	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1197	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1078	C<ev_loop> from blocking).	1198	blocking).
1079		1199
1080	=item C<EV_EMBED>	1200	=item C<EV_EMBED>
1081		1201
1082	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1202	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1083		1203
1084	=item C<EV_FORK>	1204	=item C<EV_FORK>
1085		1205
1086	The event loop has been resumed in the child process after fork (see	1206	The event loop has been resumed in the child process after fork (see
1087	C<ev_fork>).	1207	C<ev_fork>).
		1208
		1209	=item C<EV_CLEANUP>
		1210
		1211	The event loop is about to be destroyed (see C<ev_cleanup>).
1088		1212
1089	=item C<EV_ASYNC>	1213	=item C<EV_ASYNC>
1090		1214
1091	The given async watcher has been asynchronously notified (see C<ev_async>).	1215	The given async watcher has been asynchronously notified (see C<ev_async>).
1092		1216
…		…
1202		1326
1203	=item callback ev_cb (ev_TYPE *watcher)	1327	=item callback ev_cb (ev_TYPE *watcher)
1204		1328
1205	Returns the callback currently set on the watcher.	1329	Returns the callback currently set on the watcher.
1206		1330
1207	=item ev_cb_set (ev_TYPE *watcher, callback)	1331	=item ev_set_cb (ev_TYPE *watcher, callback)
1208		1332
1209	Change the callback. You can change the callback at virtually any time	1333	Change the callback. You can change the callback at virtually any time
1210	(modulo threads).	1334	(modulo threads).
1211		1335
1212	=item ev_set_priority (ev_TYPE *watcher, int priority)	1336	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1230	or might not have been clamped to the valid range.	1354	or might not have been clamped to the valid range.
1231		1355
1232	The default priority used by watchers when no priority has been set is	1356	The default priority used by watchers when no priority has been set is
1233	always C<0>, which is supposed to not be too high and not be too low :).	1357	always C<0>, which is supposed to not be too high and not be too low :).
1234		1358
1235	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1359	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1236	priorities.	1360	priorities.
1237		1361
1238	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1362	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1239		1363
1240	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1364	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1265	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1389	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1266	functions that do not need a watcher.	1390	functions that do not need a watcher.
1267		1391
1268	=back	1392	=back
1269		1393
		1394	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1395	OWN COMPOSITE WATCHERS> idioms.
1270		1396
1271	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1397	=head2 WATCHER STATES
1272		1398
1273	Each watcher has, by default, a member C<void *data> that you can change	1399	There are various watcher states mentioned throughout this manual -
1274	and read at any time: libev will completely ignore it. This can be used	1400	active, pending and so on. In this section these states and the rules to
1275	to associate arbitrary data with your watcher. If you need more data and	1401	transition between them will be described in more detail - and while these
1276	don't want to allocate memory and store a pointer to it in that data	1402	rules might look complicated, they usually do "the right thing".
1277	member, you can also "subclass" the watcher type and provide your own
1278	data:
1279		1403
1280	struct my_io	1404	=over 4
1281	{
1282	ev_io io;
1283	int otherfd;
1284	void *somedata;
1285	struct whatever *mostinteresting;
1286	};
1287		1405
1288	...	1406	=item initialised
1289	struct my_io w;
1290	ev_io_init (&w.io, my_cb, fd, EV_READ);
1291		1407
1292	And since your callback will be called with a pointer to the watcher, you	1408	Before a watcher can be registered with the event loop it has to be
1293	can cast it back to your own type:	1409	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1410	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1294		1411
1295	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1412	In this state it is simply some block of memory that is suitable for
1296	{	1413	use in an event loop. It can be moved around, freed, reused etc. at
1297	struct my_io *w = (struct my_io *)w_;	1414	will - as long as you either keep the memory contents intact, or call
1298	...	1415	C<ev_TYPE_init> again.
1299	}
1300		1416
1301	More interesting and less C-conformant ways of casting your callback type	1417	=item started/running/active
1302	instead have been omitted.
1303		1418
1304	Another common scenario is to use some data structure with multiple	1419	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1305	embedded watchers:	1420	property of the event loop, and is actively waiting for events. While in
		1421	this state it cannot be accessed (except in a few documented ways), moved,
		1422	freed or anything else - the only legal thing is to keep a pointer to it,
		1423	and call libev functions on it that are documented to work on active watchers.
1306		1424
1307	struct my_biggy	1425	=item pending
1308	{
1309	int some_data;
1310	ev_timer t1;
1311	ev_timer t2;
1312	}
1313		1426
1314	In this case getting the pointer to C<my_biggy> is a bit more	1427	If a watcher is active and libev determines that an event it is interested
1315	complicated: Either you store the address of your C<my_biggy> struct	1428	in has occurred (such as a timer expiring), it will become pending. It will
1316	in the C<data> member of the watcher (for woozies), or you need to use	1429	stay in this pending state until either it is stopped or its callback is
1317	some pointer arithmetic using C<offsetof> inside your watchers (for real	1430	about to be invoked, so it is not normally pending inside the watcher
1318	programmers):	1431	callback.
1319		1432
1320	#include <stddef.h>	1433	The watcher might or might not be active while it is pending (for example,
		1434	an expired non-repeating timer can be pending but no longer active). If it
		1435	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1436	but it is still property of the event loop at this time, so cannot be
		1437	moved, freed or reused. And if it is active the rules described in the
		1438	previous item still apply.
1321		1439
1322	static void	1440	It is also possible to feed an event on a watcher that is not active (e.g.
1323	t1_cb (EV_P_ ev_timer *w, int revents)	1441	via C<ev_feed_event>), in which case it becomes pending without being
1324	{	1442	active.
1325	struct my_biggy big = (struct my_biggy *)
1326	(((char *)w) - offsetof (struct my_biggy, t1));
1327	}
1328		1443
1329	static void	1444	=item stopped
1330	t2_cb (EV_P_ ev_timer *w, int revents)	1445
1331	{	1446	A watcher can be stopped implicitly by libev (in which case it might still
1332	struct my_biggy big = (struct my_biggy *)	1447	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1333	(((char *)w) - offsetof (struct my_biggy, t2));	1448	latter will clear any pending state the watcher might be in, regardless
1334	}	1449	of whether it was active or not, so stopping a watcher explicitly before
		1450	freeing it is often a good idea.
		1451
		1452	While stopped (and not pending) the watcher is essentially in the
		1453	initialised state, that is, it can be reused, moved, modified in any way
		1454	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1455	it again).
		1456
		1457	=back
1335		1458
1336	=head2 WATCHER PRIORITY MODELS	1459	=head2 WATCHER PRIORITY MODELS
1337		1460
1338	Many event loops support I<watcher priorities>, which are usually small	1461	Many event loops support I<watcher priorities>, which are usually small
1339	integers that influence the ordering of event callback invocation	1462	integers that influence the ordering of event callback invocation
…		…
1466	In general you can register as many read and/or write event watchers per	1589	In general you can register as many read and/or write event watchers per
1467	fd as you want (as long as you don't confuse yourself). Setting all file	1590	fd as you want (as long as you don't confuse yourself). Setting all file
1468	descriptors to non-blocking mode is also usually a good idea (but not	1591	descriptors to non-blocking mode is also usually a good idea (but not
1469	required if you know what you are doing).	1592	required if you know what you are doing).
1470		1593
1471	If you cannot use non-blocking mode, then force the use of a
1472	known-to-be-good backend (at the time of this writing, this includes only
1473	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1474	descriptors for which non-blocking operation makes no sense (such as
1475	files) - libev doesn't guarantee any specific behaviour in that case.
1476
1477	Another thing you have to watch out for is that it is quite easy to	1594	Another thing you have to watch out for is that it is quite easy to
1478	receive "spurious" readiness notifications, that is your callback might	1595	receive "spurious" readiness notifications, that is, your callback might
1479	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1596	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1480	because there is no data. Not only are some backends known to create a	1597	because there is no data. It is very easy to get into this situation even
1481	lot of those (for example Solaris ports), it is very easy to get into	1598	with a relatively standard program structure. Thus it is best to always
1482	this situation even with a relatively standard program structure. Thus	1599	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1483	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1484	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1600	preferable to a program hanging until some data arrives.
1485		1601
1486	If you cannot run the fd in non-blocking mode (for example you should	1602	If you cannot run the fd in non-blocking mode (for example you should
1487	not play around with an Xlib connection), then you have to separately	1603	not play around with an Xlib connection), then you have to separately
1488	re-test whether a file descriptor is really ready with a known-to-be good	1604	re-test whether a file descriptor is really ready with a known-to-be good
1489	interface such as poll (fortunately in our Xlib example, Xlib already	1605	interface such as poll (fortunately in the case of Xlib, it already does
1490	does this on its own, so its quite safe to use). Some people additionally	1606	this on its own, so its quite safe to use). Some people additionally
1491	use C<SIGALRM> and an interval timer, just to be sure you won't block	1607	use C<SIGALRM> and an interval timer, just to be sure you won't block
1492	indefinitely.	1608	indefinitely.
1493		1609
1494	But really, best use non-blocking mode.	1610	But really, best use non-blocking mode.
1495		1611
…		…
1523		1639
1524	There is no workaround possible except not registering events	1640	There is no workaround possible except not registering events
1525	for potentially C<dup ()>'ed file descriptors, or to resort to	1641	for potentially C<dup ()>'ed file descriptors, or to resort to
1526	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1642	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1527		1643
		1644	=head3 The special problem of files
		1645
		1646	Many people try to use C<select> (or libev) on file descriptors
		1647	representing files, and expect it to become ready when their program
		1648	doesn't block on disk accesses (which can take a long time on their own).
		1649
		1650	However, this cannot ever work in the "expected" way - you get a readiness
		1651	notification as soon as the kernel knows whether and how much data is
		1652	there, and in the case of open files, that's always the case, so you
		1653	always get a readiness notification instantly, and your read (or possibly
		1654	write) will still block on the disk I/O.
		1655
		1656	Another way to view it is that in the case of sockets, pipes, character
		1657	devices and so on, there is another party (the sender) that delivers data
		1658	on its own, but in the case of files, there is no such thing: the disk
		1659	will not send data on its own, simply because it doesn't know what you
		1660	wish to read - you would first have to request some data.
		1661
		1662	Since files are typically not-so-well supported by advanced notification
		1663	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1664	to files, even though you should not use it. The reason for this is
		1665	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1666	usually a tty, often a pipe, but also sometimes files or special devices
		1667	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1668	F</dev/urandom>), and even though the file might better be served with
		1669	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1670	it "just works" instead of freezing.
		1671
		1672	So avoid file descriptors pointing to files when you know it (e.g. use
		1673	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1674	when you rarely read from a file instead of from a socket, and want to
		1675	reuse the same code path.
		1676
1528	=head3 The special problem of fork	1677	=head3 The special problem of fork
1529		1678
1530	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1679	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1531	useless behaviour. Libev fully supports fork, but needs to be told about	1680	useless behaviour. Libev fully supports fork, but needs to be told about
1532	it in the child.	1681	it in the child if you want to continue to use it in the child.
1533		1682
1534	To support fork in your programs, you either have to call	1683	To support fork in your child processes, you have to call C<ev_loop_fork
1535	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1684	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1536	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1685	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1537	C<EVBACKEND_POLL>.
1538		1686
1539	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1540		1688
1541	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1689	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1542	when writing to a pipe whose other end has been closed, your program gets	1690	when writing to a pipe whose other end has been closed, your program gets
…		…
1624	...	1772	...
1625	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1626	ev_io stdin_readable;	1774	ev_io stdin_readable;
1627	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1628	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1629	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1630		1778
1631		1779
1632	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1633		1781
1634	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1640	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1641	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1642		1790
1643	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1644	passed (not I<at>, so on systems with very low-resolution clocks this	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1645	might introduce a small delay). If multiple timers become ready during the	1793	might introduce a small delay, see "the special problem of being too
		1794	early", below). If multiple timers become ready during the same loop
1646	same loop iteration then the ones with earlier time-out values are invoked	1795	iteration then the ones with earlier time-out values are invoked before
1647	before ones of the same priority with later time-out values (but this is	1796	ones of the same priority with later time-out values (but this is no
1648	no longer true when a callback calls C<ev_loop> recursively).	1797	longer true when a callback calls C<ev_run> recursively).
1649		1798
1650	=head3 Be smart about timeouts	1799	=head3 Be smart about timeouts
1651		1800
1652	Many real-world problems involve some kind of timeout, usually for error	1801	Many real-world problems involve some kind of timeout, usually for error
1653	recovery. A typical example is an HTTP request - if the other side hangs,	1802	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1728		1877
1729	In this case, it would be more efficient to leave the C<ev_timer> alone,	1878	In this case, it would be more efficient to leave the C<ev_timer> alone,
1730	but remember the time of last activity, and check for a real timeout only	1879	but remember the time of last activity, and check for a real timeout only
1731	within the callback:	1880	within the callback:
1732		1881
		1882	ev_tstamp timeout = 60.;
1733	ev_tstamp last_activity; // time of last activity	1883	ev_tstamp last_activity; // time of last activity
		1884	ev_timer timer;
1734		1885
1735	static void	1886	static void
1736	callback (EV_P_ ev_timer *w, int revents)	1887	callback (EV_P_ ev_timer *w, int revents)
1737	{	1888	{
1738	ev_tstamp now = ev_now (EV_A);	1889	// calculate when the timeout would happen
1739	ev_tstamp timeout = last_activity + 60.;	1890	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1740		1891
1741	// if last_activity + 60. is older than now, we did time out	1892	// if negative, it means we the timeout already occurred
1742	if (timeout < now)	1893	if (after < 0.)
1743	{	1894	{
1744	// timeout occurred, take action	1895	// timeout occurred, take action
1745	}	1896	}
1746	else	1897	else
1747	{	1898	{
1748	// callback was invoked, but there was some activity, re-arm	1899	// callback was invoked, but there was some recent
1749	// the watcher to fire in last_activity + 60, which is	1900	// activity. simply restart the timer to time out
1750	// guaranteed to be in the future, so "again" is positive:	1901	// after "after" seconds, which is the earliest time
1751	w->repeat = timeout - now;	1902	// the timeout can occur.
		1903	ev_timer_set (w, after, 0.);
1752	ev_timer_again (EV_A_ w);	1904	ev_timer_start (EV_A_ w);
1753	}	1905	}
1754	}	1906	}
1755		1907
1756	To summarise the callback: first calculate the real timeout (defined	1908	To summarise the callback: first calculate in how many seconds the
1757	as "60 seconds after the last activity"), then check if that time has	1909	timeout will occur (by calculating the absolute time when it would occur,
1758	been reached, which means something I<did>, in fact, time out. Otherwise	1910	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1759	the callback was invoked too early (C<timeout> is in the future), so	1911	(EV_A)> from that).
1760	re-schedule the timer to fire at that future time, to see if maybe we have
1761	a timeout then.
1762		1912
1763	Note how C<ev_timer_again> is used, taking advantage of the	1913	If this value is negative, then we are already past the timeout, i.e. we
1764	C<ev_timer_again> optimisation when the timer is already running.	1914	timed out, and need to do whatever is needed in this case.
		1915
		1916	Otherwise, we now the earliest time at which the timeout would trigger,
		1917	and simply start the timer with this timeout value.
		1918
		1919	In other words, each time the callback is invoked it will check whether
		1920	the timeout occurred. If not, it will simply reschedule itself to check
		1921	again at the earliest time it could time out. Rinse. Repeat.
1765		1922
1766	This scheme causes more callback invocations (about one every 60 seconds	1923	This scheme causes more callback invocations (about one every 60 seconds
1767	minus half the average time between activity), but virtually no calls to	1924	minus half the average time between activity), but virtually no calls to
1768	libev to change the timeout.	1925	libev to change the timeout.
1769		1926
1770	To start the timer, simply initialise the watcher and set C<last_activity>	1927	To start the machinery, simply initialise the watcher and set
1771	to the current time (meaning we just have some activity :), then call the	1928	C<last_activity> to the current time (meaning there was some activity just
1772	callback, which will "do the right thing" and start the timer:	1929	now), then call the callback, which will "do the right thing" and start
		1930	the timer:
1773		1931
		1932	last_activity = ev_now (EV_A);
1774	ev_init (timer, callback);	1933	ev_init (&timer, callback);
1775	last_activity = ev_now (loop);	1934	callback (EV_A_ &timer, 0);
1776	callback (loop, timer, EV_TIMER);
1777		1935
1778	And when there is some activity, simply store the current time in	1936	When there is some activity, simply store the current time in
1779	C<last_activity>, no libev calls at all:	1937	C<last_activity>, no libev calls at all:
1780		1938
		1939	if (activity detected)
1781	last_activity = ev_now (loop);	1940	last_activity = ev_now (EV_A);
		1941
		1942	When your timeout value changes, then the timeout can be changed by simply
		1943	providing a new value, stopping the timer and calling the callback, which
		1944	will again do the right thing (for example, time out immediately :).
		1945
		1946	timeout = new_value;
		1947	ev_timer_stop (EV_A_ &timer);
		1948	callback (EV_A_ &timer, 0);
1782		1949
1783	This technique is slightly more complex, but in most cases where the	1950	This technique is slightly more complex, but in most cases where the
1784	time-out is unlikely to be triggered, much more efficient.	1951	time-out is unlikely to be triggered, much more efficient.
1785
1786	Changing the timeout is trivial as well (if it isn't hard-coded in the
1787	callback :) - just change the timeout and invoke the callback, which will
1788	fix things for you.
1789		1952
1790	=item 4. Wee, just use a double-linked list for your timeouts.	1953	=item 4. Wee, just use a double-linked list for your timeouts.
1791		1954
1792	If there is not one request, but many thousands (millions...), all	1955	If there is not one request, but many thousands (millions...), all
1793	employing some kind of timeout with the same timeout value, then one can	1956	employing some kind of timeout with the same timeout value, then one can
…		…
1820	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1983	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1821	rather complicated, but extremely efficient, something that really pays	1984	rather complicated, but extremely efficient, something that really pays
1822	off after the first million or so of active timers, i.e. it's usually	1985	off after the first million or so of active timers, i.e. it's usually
1823	overkill :)	1986	overkill :)
1824		1987
		1988	=head3 The special problem of being too early
		1989
		1990	If you ask a timer to call your callback after three seconds, then
		1991	you expect it to be invoked after three seconds - but of course, this
		1992	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1993	guaranteed to any precision by libev - imagine somebody suspending the
		1994	process with a STOP signal for a few hours for example.
		1995
		1996	So, libev tries to invoke your callback as soon as possible I<after> the
		1997	delay has occurred, but cannot guarantee this.
		1998
		1999	A less obvious failure mode is calling your callback too early: many event
		2000	loops compare timestamps with a "elapsed delay >= requested delay", but
		2001	this can cause your callback to be invoked much earlier than you would
		2002	expect.
		2003
		2004	To see why, imagine a system with a clock that only offers full second
		2005	resolution (think windows if you can't come up with a broken enough OS
		2006	yourself). If you schedule a one-second timer at the time 500.9, then the
		2007	event loop will schedule your timeout to elapse at a system time of 500
		2008	(500.9 truncated to the resolution) + 1, or 501.
		2009
		2010	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2011	501" and invoke the callback 0.1s after it was started, even though a
		2012	one-second delay was requested - this is being "too early", despite best
		2013	intentions.
		2014
		2015	This is the reason why libev will never invoke the callback if the elapsed
		2016	delay equals the requested delay, but only when the elapsed delay is
		2017	larger than the requested delay. In the example above, libev would only invoke
		2018	the callback at system time 502, or 1.1s after the timer was started.
		2019
		2020	So, while libev cannot guarantee that your callback will be invoked
		2021	exactly when requested, it I<can> and I<does> guarantee that the requested
		2022	delay has actually elapsed, or in other words, it always errs on the "too
		2023	late" side of things.
		2024
1825	=head3 The special problem of time updates	2025	=head3 The special problem of time updates
1826		2026
1827	Establishing the current time is a costly operation (it usually takes at	2027	Establishing the current time is a costly operation (it usually takes
1828	least two system calls): EV therefore updates its idea of the current	2028	at least one system call): EV therefore updates its idea of the current
1829	time only before and after C<ev_loop> collects new events, which causes a	2029	time only before and after C<ev_run> collects new events, which causes a
1830	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2030	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1831	lots of events in one iteration.	2031	lots of events in one iteration.
1832		2032
1833	The relative timeouts are calculated relative to the C<ev_now ()>	2033	The relative timeouts are calculated relative to the C<ev_now ()>
1834	time. This is usually the right thing as this timestamp refers to the time	2034	time. This is usually the right thing as this timestamp refers to the time
1835	of the event triggering whatever timeout you are modifying/starting. If	2035	of the event triggering whatever timeout you are modifying/starting. If
1836	you suspect event processing to be delayed and you I<need> to base the	2036	you suspect event processing to be delayed and you I<need> to base the
1837	timeout on the current time, use something like this to adjust for this:	2037	timeout on the current time, use something like the following to adjust
		2038	for it:
1838		2039
1839	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2040	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1840		2041
1841	If the event loop is suspended for a long time, you can also force an	2042	If the event loop is suspended for a long time, you can also force an
1842	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2043	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1843	()>.	2044	()>, although that will push the event time of all outstanding events
		2045	further into the future.
		2046
		2047	=head3 The special problem of unsynchronised clocks
		2048
		2049	Modern systems have a variety of clocks - libev itself uses the normal
		2050	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2051	jumps).
		2052
		2053	Neither of these clocks is synchronised with each other or any other clock
		2054	on the system, so C<ev_time ()> might return a considerably different time
		2055	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2056	a call to C<gettimeofday> might return a second count that is one higher
		2057	than a directly following call to C<time>.
		2058
		2059	The moral of this is to only compare libev-related timestamps with
		2060	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2061	a second or so.
		2062
		2063	One more problem arises due to this lack of synchronisation: if libev uses
		2064	the system monotonic clock and you compare timestamps from C<ev_time>
		2065	or C<ev_now> from when you started your timer and when your callback is
		2066	invoked, you will find that sometimes the callback is a bit "early".
		2067
		2068	This is because C<ev_timer>s work in real time, not wall clock time, so
		2069	libev makes sure your callback is not invoked before the delay happened,
		2070	I<measured according to the real time>, not the system clock.
		2071
		2072	If your timeouts are based on a physical timescale (e.g. "time out this
		2073	connection after 100 seconds") then this shouldn't bother you as it is
		2074	exactly the right behaviour.
		2075
		2076	If you want to compare wall clock/system timestamps to your timers, then
		2077	you need to use C<ev_periodic>s, as these are based on the wall clock
		2078	time, where your comparisons will always generate correct results.
1844		2079
1845	=head3 The special problems of suspended animation	2080	=head3 The special problems of suspended animation
1846		2081
1847	When you leave the server world it is quite customary to hit machines that	2082	When you leave the server world it is quite customary to hit machines that
1848	can suspend/hibernate - what happens to the clocks during such a suspend?	2083	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1892	keep up with the timer (because it takes longer than those 10 seconds to	2127	keep up with the timer (because it takes longer than those 10 seconds to
1893	do stuff) the timer will not fire more than once per event loop iteration.	2128	do stuff) the timer will not fire more than once per event loop iteration.
1894		2129
1895	=item ev_timer_again (loop, ev_timer *)	2130	=item ev_timer_again (loop, ev_timer *)
1896		2131
1897	This will act as if the timer timed out and restart it again if it is	2132	This will act as if the timer timed out, and restarts it again if it is
1898	repeating. The exact semantics are:	2133	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2134	timeout to the C<repeat> value and calling C<ev_timer_start>.
1899		2135
		2136	The exact semantics are as in the following rules, all of which will be
		2137	applied to the watcher:
		2138
		2139	=over 4
		2140
1900	If the timer is pending, its pending status is cleared.	2141	=item If the timer is pending, the pending status is always cleared.
1901		2142
1902	If the timer is started but non-repeating, stop it (as if it timed out).	2143	=item If the timer is started but non-repeating, stop it (as if it timed
		2144	out, without invoking it).
1903		2145
1904	If the timer is repeating, either start it if necessary (with the	2146	=item If the timer is repeating, make the C<repeat> value the new timeout
1905	C<repeat> value), or reset the running timer to the C<repeat> value.	2147	and start the timer, if necessary.
1906		2148
		2149	=back
		2150
1907	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2151	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1908	usage example.	2152	usage example.
1909		2153
1910	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2154	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1911		2155
1912	Returns the remaining time until a timer fires. If the timer is active,	2156	Returns the remaining time until a timer fires. If the timer is active,
…		…
1951	}	2195	}
1952		2196
1953	ev_timer mytimer;	2197	ev_timer mytimer;
1954	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2198	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1955	ev_timer_again (&mytimer); /* start timer */	2199	ev_timer_again (&mytimer); /* start timer */
1956	ev_loop (loop, 0);	2200	ev_run (loop, 0);
1957		2201
1958	// and in some piece of code that gets executed on any "activity":	2202	// and in some piece of code that gets executed on any "activity":
1959	// reset the timeout to start ticking again at 10 seconds	2203	// reset the timeout to start ticking again at 10 seconds
1960	ev_timer_again (&mytimer);	2204	ev_timer_again (&mytimer);
1961		2205
…		…
1965	Periodic watchers are also timers of a kind, but they are very versatile	2209	Periodic watchers are also timers of a kind, but they are very versatile
1966	(and unfortunately a bit complex).	2210	(and unfortunately a bit complex).
1967		2211
1968	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2212	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1969	relative time, the physical time that passes) but on wall clock time	2213	relative time, the physical time that passes) but on wall clock time
1970	(absolute time, the thing you can read on your calender or clock). The	2214	(absolute time, the thing you can read on your calendar or clock). The
1971	difference is that wall clock time can run faster or slower than real	2215	difference is that wall clock time can run faster or slower than real
1972	time, and time jumps are not uncommon (e.g. when you adjust your	2216	time, and time jumps are not uncommon (e.g. when you adjust your
1973	wrist-watch).	2217	wrist-watch).
1974		2218
1975	You can tell a periodic watcher to trigger after some specific point	2219	You can tell a periodic watcher to trigger after some specific point
…		…
1987		2231
1988	As with timers, the callback is guaranteed to be invoked only when the	2232	As with timers, the callback is guaranteed to be invoked only when the
1989	point in time where it is supposed to trigger has passed. If multiple	2233	point in time where it is supposed to trigger has passed. If multiple
1990	timers become ready during the same loop iteration then the ones with	2234	timers become ready during the same loop iteration then the ones with
1991	earlier time-out values are invoked before ones with later time-out values	2235	earlier time-out values are invoked before ones with later time-out values
1992	(but this is no longer true when a callback calls C<ev_loop> recursively).	2236	(but this is no longer true when a callback calls C<ev_run> recursively).
1993		2237
1994	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1995		2239
1996	=over 4	2240	=over 4
1997		2241
…		…
2032		2276
2033	Another way to think about it (for the mathematically inclined) is that	2277	Another way to think about it (for the mathematically inclined) is that
2034	C<ev_periodic> will try to run the callback in this mode at the next possible	2278	C<ev_periodic> will try to run the callback in this mode at the next possible
2035	time where C<time = offset (mod interval)>, regardless of any time jumps.	2279	time where C<time = offset (mod interval)>, regardless of any time jumps.
2036		2280
2037	For numerical stability it is preferable that the C<offset> value is near	2281	The C<interval> I<MUST> be positive, and for numerical stability, the
2038	C<ev_now ()> (the current time), but there is no range requirement for	2282	interval value should be higher than C<1/8192> (which is around 100
2039	this value, and in fact is often specified as zero.	2283	microseconds) and C<offset> should be higher than C<0> and should have
		2284	at most a similar magnitude as the current time (say, within a factor of
		2285	ten). Typical values for offset are, in fact, C<0> or something between
		2286	C<0> and C<interval>, which is also the recommended range.
2040		2287
2041	Note also that there is an upper limit to how often a timer can fire (CPU	2288	Note also that there is an upper limit to how often a timer can fire (CPU
2042	speed for example), so if C<interval> is very small then timing stability	2289	speed for example), so if C<interval> is very small then timing stability
2043	will of course deteriorate. Libev itself tries to be exact to be about one	2290	will of course deteriorate. Libev itself tries to be exact to be about one
2044	millisecond (if the OS supports it and the machine is fast enough).	2291	millisecond (if the OS supports it and the machine is fast enough).
…		…
2152		2399
2153	ev_periodic hourly_tick;	2400	ev_periodic hourly_tick;
2154	ev_periodic_init (&hourly_tick, clock_cb,	2401	ev_periodic_init (&hourly_tick, clock_cb,
2155	fmod (ev_now (loop), 3600.), 3600., 0);	2402	fmod (ev_now (loop), 3600.), 3600., 0);
2156	ev_periodic_start (loop, &hourly_tick);	2403	ev_periodic_start (loop, &hourly_tick);
2157		2404
2158		2405
2159	=head2 C<ev_signal> - signal me when a signal gets signalled!	2406	=head2 C<ev_signal> - signal me when a signal gets signalled!
2160		2407
2161	Signal watchers will trigger an event when the process receives a specific	2408	Signal watchers will trigger an event when the process receives a specific
2162	signal one or more times. Even though signals are very asynchronous, libev	2409	signal one or more times. Even though signals are very asynchronous, libev
2163	will try it's best to deliver signals synchronously, i.e. as part of the	2410	will try its best to deliver signals synchronously, i.e. as part of the
2164	normal event processing, like any other event.	2411	normal event processing, like any other event.
2165		2412
2166	If you want signals to be delivered truly asynchronously, just use	2413	If you want signals to be delivered truly asynchronously, just use
2167	C<sigaction> as you would do without libev and forget about sharing	2414	C<sigaction> as you would do without libev and forget about sharing
2168	the signal. You can even use C<ev_async> from a signal handler to	2415	the signal. You can even use C<ev_async> from a signal handler to
…		…
2172	only within the same loop, i.e. you can watch for C<SIGINT> in your	2419	only within the same loop, i.e. you can watch for C<SIGINT> in your
2173	default loop and for C<SIGIO> in another loop, but you cannot watch for	2420	default loop and for C<SIGIO> in another loop, but you cannot watch for
2174	C<SIGINT> in both the default loop and another loop at the same time. At	2421	C<SIGINT> in both the default loop and another loop at the same time. At
2175	the moment, C<SIGCHLD> is permanently tied to the default loop.	2422	the moment, C<SIGCHLD> is permanently tied to the default loop.
2176		2423
2177	When the first watcher gets started will libev actually register something	2424	Only after the first watcher for a signal is started will libev actually
2178	with the kernel (thus it coexists with your own signal handlers as long as	2425	register something with the kernel. It thus coexists with your own signal
2179	you don't register any with libev for the same signal).	2426	handlers as long as you don't register any with libev for the same signal.
2180		2427
2181	If possible and supported, libev will install its handlers with	2428	If possible and supported, libev will install its handlers with
2182	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2429	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2183	not be unduly interrupted. If you have a problem with system calls getting	2430	not be unduly interrupted. If you have a problem with system calls getting
2184	interrupted by signals you can block all signals in an C<ev_check> watcher	2431	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2187	=head3 The special problem of inheritance over fork/execve/pthread_create	2434	=head3 The special problem of inheritance over fork/execve/pthread_create
2188		2435
2189	Both the signal mask (C<sigprocmask>) and the signal disposition	2436	Both the signal mask (C<sigprocmask>) and the signal disposition
2190	(C<sigaction>) are unspecified after starting a signal watcher (and after	2437	(C<sigaction>) are unspecified after starting a signal watcher (and after
2191	stopping it again), that is, libev might or might not block the signal,	2438	stopping it again), that is, libev might or might not block the signal,
2192	and might or might not set or restore the installed signal handler.	2439	and might or might not set or restore the installed signal handler (but
		2440	see C<EVFLAG_NOSIGMASK>).
2193		2441
2194	While this does not matter for the signal disposition (libev never	2442	While this does not matter for the signal disposition (libev never
2195	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2443	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2196	C<execve>), this matters for the signal mask: many programs do not expect	2444	C<execve>), this matters for the signal mask: many programs do not expect
2197	certain signals to be blocked.	2445	certain signals to be blocked.
…		…
2211		2459
2212	So I can't stress this enough: I<If you do not reset your signal mask when	2460	So I can't stress this enough: I<If you do not reset your signal mask when
2213	you expect it to be empty, you have a race condition in your code>. This	2461	you expect it to be empty, you have a race condition in your code>. This
2214	is not a libev-specific thing, this is true for most event libraries.	2462	is not a libev-specific thing, this is true for most event libraries.
2215		2463
		2464	=head3 The special problem of threads signal handling
		2465
		2466	POSIX threads has problematic signal handling semantics, specifically,
		2467	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2468	threads in a process block signals, which is hard to achieve.
		2469
		2470	When you want to use sigwait (or mix libev signal handling with your own
		2471	for the same signals), you can tackle this problem by globally blocking
		2472	all signals before creating any threads (or creating them with a fully set
		2473	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2474	loops. Then designate one thread as "signal receiver thread" which handles
		2475	these signals. You can pass on any signals that libev might be interested
		2476	in by calling C<ev_feed_signal>.
		2477
2216	=head3 Watcher-Specific Functions and Data Members	2478	=head3 Watcher-Specific Functions and Data Members
2217		2479
2218	=over 4	2480	=over 4
2219		2481
2220	=item ev_signal_init (ev_signal *, callback, int signum)	2482	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2235	Example: Try to exit cleanly on SIGINT.	2497	Example: Try to exit cleanly on SIGINT.
2236		2498
2237	static void	2499	static void
2238	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2500	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2239	{	2501	{
2240	ev_unloop (loop, EVUNLOOP_ALL);	2502	ev_break (loop, EVBREAK_ALL);
2241	}	2503	}
2242		2504
2243	ev_signal signal_watcher;	2505	ev_signal signal_watcher;
2244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2506	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2245	ev_signal_start (loop, &signal_watcher);	2507	ev_signal_start (loop, &signal_watcher);
…		…
2354		2616
2355	=head2 C<ev_stat> - did the file attributes just change?	2617	=head2 C<ev_stat> - did the file attributes just change?
2356		2618
2357	This watches a file system path for attribute changes. That is, it calls	2619	This watches a file system path for attribute changes. That is, it calls
2358	C<stat> on that path in regular intervals (or when the OS says it changed)	2620	C<stat> on that path in regular intervals (or when the OS says it changed)
2359	and sees if it changed compared to the last time, invoking the callback if	2621	and sees if it changed compared to the last time, invoking the callback
2360	it did.	2622	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2623	happen after the watcher has been started will be reported.
2361		2624
2362	The path does not need to exist: changing from "path exists" to "path does	2625	The path does not need to exist: changing from "path exists" to "path does
2363	not exist" is a status change like any other. The condition "path does not	2626	not exist" is a status change like any other. The condition "path does not
2364	exist" (or more correctly "path cannot be stat'ed") is signified by the	2627	exist" (or more correctly "path cannot be stat'ed") is signified by the
2365	C<st_nlink> field being zero (which is otherwise always forced to be at	2628	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2595	Apart from keeping your process non-blocking (which is a useful	2858	Apart from keeping your process non-blocking (which is a useful
2596	effect on its own sometimes), idle watchers are a good place to do	2859	effect on its own sometimes), idle watchers are a good place to do
2597	"pseudo-background processing", or delay processing stuff to after the	2860	"pseudo-background processing", or delay processing stuff to after the
2598	event loop has handled all outstanding events.	2861	event loop has handled all outstanding events.
2599		2862
		2863	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2864
		2865	As long as there is at least one active idle watcher, libev will never
		2866	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2867	For this to work, the idle watcher doesn't need to be invoked at all - the
		2868	lowest priority will do.
		2869
		2870	This mode of operation can be useful together with an C<ev_check> watcher,
		2871	to do something on each event loop iteration - for example to balance load
		2872	between different connections.
		2873
		2874	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2875	example.
		2876
2600	=head3 Watcher-Specific Functions and Data Members	2877	=head3 Watcher-Specific Functions and Data Members
2601		2878
2602	=over 4	2879	=over 4
2603		2880
2604	=item ev_idle_init (ev_idle *, callback)	2881	=item ev_idle_init (ev_idle *, callback)
…		…
2615	callback, free it. Also, use no error checking, as usual.	2892	callback, free it. Also, use no error checking, as usual.
2616		2893
2617	static void	2894	static void
2618	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2895	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2619	{	2896	{
		2897	// stop the watcher
		2898	ev_idle_stop (loop, w);
		2899
		2900	// now we can free it
2620	free (w);	2901	free (w);
		2902
2621	// now do something you wanted to do when the program has	2903	// now do something you wanted to do when the program has
2622	// no longer anything immediate to do.	2904	// no longer anything immediate to do.
2623	}	2905	}
2624		2906
2625	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2907	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2627	ev_idle_start (loop, idle_watcher);	2909	ev_idle_start (loop, idle_watcher);
2628		2910
2629		2911
2630	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2912	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2631		2913
2632	Prepare and check watchers are usually (but not always) used in pairs:	2914	Prepare and check watchers are often (but not always) used in pairs:
2633	prepare watchers get invoked before the process blocks and check watchers	2915	prepare watchers get invoked before the process blocks and check watchers
2634	afterwards.	2916	afterwards.
2635		2917
2636	You I<must not> call C<ev_loop> or similar functions that enter	2918	You I<must not> call C<ev_run> (or similar functions that enter the
2637	the current event loop from either C<ev_prepare> or C<ev_check>	2919	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2638	watchers. Other loops than the current one are fine, however. The	2920	C<ev_check> watchers. Other loops than the current one are fine,
2639	rationale behind this is that you do not need to check for recursion in	2921	however. The rationale behind this is that you do not need to check
2640	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2922	for recursion in those watchers, i.e. the sequence will always be
2641	C<ev_check> so if you have one watcher of each kind they will always be	2923	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2642	called in pairs bracketing the blocking call.	2924	kind they will always be called in pairs bracketing the blocking call.
2643		2925
2644	Their main purpose is to integrate other event mechanisms into libev and	2926	Their main purpose is to integrate other event mechanisms into libev and
2645	their use is somewhat advanced. They could be used, for example, to track	2927	their use is somewhat advanced. They could be used, for example, to track
2646	variable changes, implement your own watchers, integrate net-snmp or a	2928	variable changes, implement your own watchers, integrate net-snmp or a
2647	coroutine library and lots more. They are also occasionally useful if	2929	coroutine library and lots more. They are also occasionally useful if
…		…
2665	with priority higher than or equal to the event loop and one coroutine	2947	with priority higher than or equal to the event loop and one coroutine
2666	of lower priority, but only once, using idle watchers to keep the event	2948	of lower priority, but only once, using idle watchers to keep the event
2667	loop from blocking if lower-priority coroutines are active, thus mapping	2949	loop from blocking if lower-priority coroutines are active, thus mapping
2668	low-priority coroutines to idle/background tasks).	2950	low-priority coroutines to idle/background tasks).
2669		2951
2670	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2952	When used for this purpose, it is recommended to give C<ev_check> watchers
2671	priority, to ensure that they are being run before any other watchers	2953	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2672	after the poll (this doesn't matter for C<ev_prepare> watchers).	2954	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2955	watchers).
2673		2956
2674	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2957	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2675	activate ("feed") events into libev. While libev fully supports this, they	2958	activate ("feed") events into libev. While libev fully supports this, they
2676	might get executed before other C<ev_check> watchers did their job. As	2959	might get executed before other C<ev_check> watchers did their job. As
2677	C<ev_check> watchers are often used to embed other (non-libev) event	2960	C<ev_check> watchers are often used to embed other (non-libev) event
2678	loops those other event loops might be in an unusable state until their	2961	loops those other event loops might be in an unusable state until their
2679	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2962	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2680	others).	2963	others).
		2964
		2965	=head3 Abusing an C<ev_check> watcher for its side-effect
		2966
		2967	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2968	useful because they are called once per event loop iteration. For
		2969	example, if you want to handle a large number of connections fairly, you
		2970	normally only do a bit of work for each active connection, and if there
		2971	is more work to do, you wait for the next event loop iteration, so other
		2972	connections have a chance of making progress.
		2973
		2974	Using an C<ev_check> watcher is almost enough: it will be called on the
		2975	next event loop iteration. However, that isn't as soon as possible -
		2976	without external events, your C<ev_check> watcher will not be invoked.
		2977
		2978	This is where C<ev_idle> watchers come in handy - all you need is a
		2979	single global idle watcher that is active as long as you have one active
		2980	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2981	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2982	invoked. Neither watcher alone can do that.
2681		2983
2682	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2683		2985
2684	=over 4	2986	=over 4
2685		2987
…		…
2809		3111
2810	if (timeout >= 0)	3112	if (timeout >= 0)
2811	// create/start timer	3113	// create/start timer
2812		3114
2813	// poll	3115	// poll
2814	ev_loop (EV_A_ 0);	3116	ev_run (EV_A_ 0);
2815		3117
2816	// stop timer again	3118	// stop timer again
2817	if (timeout >= 0)	3119	if (timeout >= 0)
2818	ev_timer_stop (EV_A_ &to);	3120	ev_timer_stop (EV_A_ &to);
2819		3121
…		…
2886		3188
2887	=over 4	3189	=over 4
2888		3190
2889	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3191	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2890		3192
2891	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3193	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2892		3194
2893	Configures the watcher to embed the given loop, which must be	3195	Configures the watcher to embed the given loop, which must be
2894	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3196	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2895	invoked automatically, otherwise it is the responsibility of the callback	3197	invoked automatically, otherwise it is the responsibility of the callback
2896	to invoke it (it will continue to be called until the sweep has been done,	3198	to invoke it (it will continue to be called until the sweep has been done,
2897	if you do not want that, you need to temporarily stop the embed watcher).	3199	if you do not want that, you need to temporarily stop the embed watcher).
2898		3200
2899	=item ev_embed_sweep (loop, ev_embed *)	3201	=item ev_embed_sweep (loop, ev_embed *)
2900		3202
2901	Make a single, non-blocking sweep over the embedded loop. This works	3203	Make a single, non-blocking sweep over the embedded loop. This works
2902	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3204	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2903	appropriate way for embedded loops.	3205	appropriate way for embedded loops.
2904		3206
2905	=item struct ev_loop *other [read-only]	3207	=item struct ev_loop *other [read-only]
2906		3208
2907	The embedded event loop.	3209	The embedded event loop.
…		…
2917	used).	3219	used).
2918		3220
2919	struct ev_loop *loop_hi = ev_default_init (0);	3221	struct ev_loop *loop_hi = ev_default_init (0);
2920	struct ev_loop *loop_lo = 0;	3222	struct ev_loop *loop_lo = 0;
2921	ev_embed embed;	3223	ev_embed embed;
2922		3224
2923	// see if there is a chance of getting one that works	3225	// see if there is a chance of getting one that works
2924	// (remember that a flags value of 0 means autodetection)	3226	// (remember that a flags value of 0 means autodetection)
2925	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3227	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2926	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3228	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2927	: 0;	3229	: 0;
…		…
2941	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3243	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2942		3244
2943	struct ev_loop *loop = ev_default_init (0);	3245	struct ev_loop *loop = ev_default_init (0);
2944	struct ev_loop *loop_socket = 0;	3246	struct ev_loop *loop_socket = 0;
2945	ev_embed embed;	3247	ev_embed embed;
2946		3248
2947	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3249	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2948	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3250	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2949	{	3251	{
2950	ev_embed_init (&embed, 0, loop_socket);	3252	ev_embed_init (&embed, 0, loop_socket);
2951	ev_embed_start (loop, &embed);	3253	ev_embed_start (loop, &embed);
…		…
2959		3261
2960	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3262	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2961		3263
2962	Fork watchers are called when a C<fork ()> was detected (usually because	3264	Fork watchers are called when a C<fork ()> was detected (usually because
2963	whoever is a good citizen cared to tell libev about it by calling	3265	whoever is a good citizen cared to tell libev about it by calling
2964	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3266	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2965	event loop blocks next and before C<ev_check> watchers are being called,	3267	and before C<ev_check> watchers are being called, and only in the child
2966	and only in the child after the fork. If whoever good citizen calling	3268	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2967	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3269	and calls it in the wrong process, the fork handlers will be invoked, too,
2968	handlers will be invoked, too, of course.	3270	of course.
2969		3271
2970	=head3 The special problem of life after fork - how is it possible?	3272	=head3 The special problem of life after fork - how is it possible?
2971		3273
2972	Most uses of C<fork()> consist of forking, then some simple calls to set	3274	Most uses of C<fork ()> consist of forking, then some simple calls to set
2973	up/change the process environment, followed by a call to C<exec()>. This	3275	up/change the process environment, followed by a call to C<exec()>. This
2974	sequence should be handled by libev without any problems.	3276	sequence should be handled by libev without any problems.
2975		3277
2976	This changes when the application actually wants to do event handling	3278	This changes when the application actually wants to do event handling
2977	in the child, or both parent in child, in effect "continuing" after the	3279	in the child, or both parent in child, in effect "continuing" after the
…		…
2993	disadvantage of having to use multiple event loops (which do not support	3295	disadvantage of having to use multiple event loops (which do not support
2994	signal watchers).	3296	signal watchers).
2995		3297
2996	When this is not possible, or you want to use the default loop for	3298	When this is not possible, or you want to use the default loop for
2997	other reasons, then in the process that wants to start "fresh", call	3299	other reasons, then in the process that wants to start "fresh", call
2998	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3300	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2999	the default loop will "orphan" (not stop) all registered watchers, so you	3301	Destroying the default loop will "orphan" (not stop) all registered
3000	have to be careful not to execute code that modifies those watchers. Note	3302	watchers, so you have to be careful not to execute code that modifies
3001	also that in that case, you have to re-register any signal watchers.	3303	those watchers. Note also that in that case, you have to re-register any
		3304	signal watchers.
3002		3305
3003	=head3 Watcher-Specific Functions and Data Members	3306	=head3 Watcher-Specific Functions and Data Members
3004		3307
3005	=over 4	3308	=over 4
3006		3309
3007	=item ev_fork_init (ev_signal *, callback)	3310	=item ev_fork_init (ev_fork *, callback)
3008		3311
3009	Initialises and configures the fork watcher - it has no parameters of any	3312	Initialises and configures the fork watcher - it has no parameters of any
3010	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3313	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3011	believe me.	3314	really.
3012		3315
3013	=back	3316	=back
		3317
		3318
		3319	=head2 C<ev_cleanup> - even the best things end
		3320
		3321	Cleanup watchers are called just before the event loop is being destroyed
		3322	by a call to C<ev_loop_destroy>.
		3323
		3324	While there is no guarantee that the event loop gets destroyed, cleanup
		3325	watchers provide a convenient method to install cleanup hooks for your
		3326	program, worker threads and so on - you just to make sure to destroy the
		3327	loop when you want them to be invoked.
		3328
		3329	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3330	all other watchers, they do not keep a reference to the event loop (which
		3331	makes a lot of sense if you think about it). Like all other watchers, you
		3332	can call libev functions in the callback, except C<ev_cleanup_start>.
		3333
		3334	=head3 Watcher-Specific Functions and Data Members
		3335
		3336	=over 4
		3337
		3338	=item ev_cleanup_init (ev_cleanup *, callback)
		3339
		3340	Initialises and configures the cleanup watcher - it has no parameters of
		3341	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3342	pointless, I assure you.
		3343
		3344	=back
		3345
		3346	Example: Register an atexit handler to destroy the default loop, so any
		3347	cleanup functions are called.
		3348
		3349	static void
		3350	program_exits (void)
		3351	{
		3352	ev_loop_destroy (EV_DEFAULT_UC);
		3353	}
		3354
		3355	...
		3356	atexit (program_exits);
3014		3357
3015		3358
3016	=head2 C<ev_async> - how to wake up an event loop	3359	=head2 C<ev_async> - how to wake up an event loop
3017		3360
3018	In general, you cannot use an C<ev_loop> from multiple threads or other	3361	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3025	it by calling C<ev_async_send>, which is thread- and signal safe.	3368	it by calling C<ev_async_send>, which is thread- and signal safe.
3026		3369
3027	This functionality is very similar to C<ev_signal> watchers, as signals,	3370	This functionality is very similar to C<ev_signal> watchers, as signals,
3028	too, are asynchronous in nature, and signals, too, will be compressed	3371	too, are asynchronous in nature, and signals, too, will be compressed
3029	(i.e. the number of callback invocations may be less than the number of	3372	(i.e. the number of callback invocations may be less than the number of
3030	C<ev_async_sent> calls).	3373	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3031		3374	of "global async watchers" by using a watcher on an otherwise unused
3032	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3375	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3033	just the default loop.	3376	even without knowing which loop owns the signal.
3034		3377
3035	=head3 Queueing	3378	=head3 Queueing
3036		3379
3037	C<ev_async> does not support queueing of data in any way. The reason	3380	C<ev_async> does not support queueing of data in any way. The reason
3038	is that the author does not know of a simple (or any) algorithm for a	3381	is that the author does not know of a simple (or any) algorithm for a
…		…
3130	trust me.	3473	trust me.
3131		3474
3132	=item ev_async_send (loop, ev_async *)	3475	=item ev_async_send (loop, ev_async *)
3133		3476
3134	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3477	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3135	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3478	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3479	returns.
		3480
3136	C<ev_feed_event>, this call is safe to do from other threads, signal or	3481	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3137	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3482	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3138	section below on what exactly this means).	3483	embedding section below on what exactly this means).
3139		3484
3140	Note that, as with other watchers in libev, multiple events might get	3485	Note that, as with other watchers in libev, multiple events might get
3141	compressed into a single callback invocation (another way to look at this	3486	compressed into a single callback invocation (another way to look at
3142	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3487	this is that C<ev_async> watchers are level-triggered: they are set on
3143	reset when the event loop detects that).	3488	C<ev_async_send>, reset when the event loop detects that).
3144		3489
3145	This call incurs the overhead of a system call only once per event loop	3490	This call incurs the overhead of at most one extra system call per event
3146	iteration, so while the overhead might be noticeable, it doesn't apply to	3491	loop iteration, if the event loop is blocked, and no syscall at all if
3147	repeated calls to C<ev_async_send> for the same event loop.	3492	the event loop (or your program) is processing events. That means that
		3493	repeated calls are basically free (there is no need to avoid calls for
		3494	performance reasons) and that the overhead becomes smaller (typically
		3495	zero) under load.
3148		3496
3149	=item bool = ev_async_pending (ev_async *)	3497	=item bool = ev_async_pending (ev_async *)
3150		3498
3151	Returns a non-zero value when C<ev_async_send> has been called on the	3499	Returns a non-zero value when C<ev_async_send> has been called on the
3152	watcher but the event has not yet been processed (or even noted) by the	3500	watcher but the event has not yet been processed (or even noted) by the
…		…
3207	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3555	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3208		3556
3209	=item ev_feed_fd_event (loop, int fd, int revents)	3557	=item ev_feed_fd_event (loop, int fd, int revents)
3210		3558
3211	Feed an event on the given fd, as if a file descriptor backend detected	3559	Feed an event on the given fd, as if a file descriptor backend detected
3212	the given events it.	3560	the given events.
3213		3561
3214	=item ev_feed_signal_event (loop, int signum)	3562	=item ev_feed_signal_event (loop, int signum)
3215		3563
3216	Feed an event as if the given signal occurred (C<loop> must be the default	3564	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3217	loop!).	3565	which is async-safe.
3218		3566
3219	=back	3567	=back
		3568
		3569
		3570	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3571
		3572	This section explains some common idioms that are not immediately
		3573	obvious. Note that examples are sprinkled over the whole manual, and this
		3574	section only contains stuff that wouldn't fit anywhere else.
		3575
		3576	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3577
		3578	Each watcher has, by default, a C<void *data> member that you can read
		3579	or modify at any time: libev will completely ignore it. This can be used
		3580	to associate arbitrary data with your watcher. If you need more data and
		3581	don't want to allocate memory separately and store a pointer to it in that
		3582	data member, you can also "subclass" the watcher type and provide your own
		3583	data:
		3584
		3585	struct my_io
		3586	{
		3587	ev_io io;
		3588	int otherfd;
		3589	void *somedata;
		3590	struct whatever *mostinteresting;
		3591	};
		3592
		3593	...
		3594	struct my_io w;
		3595	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3596
		3597	And since your callback will be called with a pointer to the watcher, you
		3598	can cast it back to your own type:
		3599
		3600	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3601	{
		3602	struct my_io *w = (struct my_io *)w_;
		3603	...
		3604	}
		3605
		3606	More interesting and less C-conformant ways of casting your callback
		3607	function type instead have been omitted.
		3608
		3609	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3610
		3611	Another common scenario is to use some data structure with multiple
		3612	embedded watchers, in effect creating your own watcher that combines
		3613	multiple libev event sources into one "super-watcher":
		3614
		3615	struct my_biggy
		3616	{
		3617	int some_data;
		3618	ev_timer t1;
		3619	ev_timer t2;
		3620	}
		3621
		3622	In this case getting the pointer to C<my_biggy> is a bit more
		3623	complicated: Either you store the address of your C<my_biggy> struct in
		3624	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3625	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3626	real programmers):
		3627
		3628	#include <stddef.h>
		3629
		3630	static void
		3631	t1_cb (EV_P_ ev_timer *w, int revents)
		3632	{
		3633	struct my_biggy big = (struct my_biggy *)
		3634	(((char *)w) - offsetof (struct my_biggy, t1));
		3635	}
		3636
		3637	static void
		3638	t2_cb (EV_P_ ev_timer *w, int revents)
		3639	{
		3640	struct my_biggy big = (struct my_biggy *)
		3641	(((char *)w) - offsetof (struct my_biggy, t2));
		3642	}
		3643
		3644	=head2 AVOIDING FINISHING BEFORE RETURNING
		3645
		3646	Often you have structures like this in event-based programs:
		3647
		3648	callback ()
		3649	{
		3650	free (request);
		3651	}
		3652
		3653	request = start_new_request (..., callback);
		3654
		3655	The intent is to start some "lengthy" operation. The C<request> could be
		3656	used to cancel the operation, or do other things with it.
		3657
		3658	It's not uncommon to have code paths in C<start_new_request> that
		3659	immediately invoke the callback, for example, to report errors. Or you add
		3660	some caching layer that finds that it can skip the lengthy aspects of the
		3661	operation and simply invoke the callback with the result.
		3662
		3663	The problem here is that this will happen I<before> C<start_new_request>
		3664	has returned, so C<request> is not set.
		3665
		3666	Even if you pass the request by some safer means to the callback, you
		3667	might want to do something to the request after starting it, such as
		3668	canceling it, which probably isn't working so well when the callback has
		3669	already been invoked.
		3670
		3671	A common way around all these issues is to make sure that
		3672	C<start_new_request> I<always> returns before the callback is invoked. If
		3673	C<start_new_request> immediately knows the result, it can artificially
		3674	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3675	example, or more sneakily, by reusing an existing (stopped) watcher and
		3676	pushing it into the pending queue:
		3677
		3678	ev_set_cb (watcher, callback);
		3679	ev_feed_event (EV_A_ watcher, 0);
		3680
		3681	This way, C<start_new_request> can safely return before the callback is
		3682	invoked, while not delaying callback invocation too much.
		3683
		3684	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3685
		3686	Often (especially in GUI toolkits) there are places where you have
		3687	I<modal> interaction, which is most easily implemented by recursively
		3688	invoking C<ev_run>.
		3689
		3690	This brings the problem of exiting - a callback might want to finish the
		3691	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3692	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3693	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3694	other combination: In these cases, a simple C<ev_break> will not work.
		3695
		3696	The solution is to maintain "break this loop" variable for each C<ev_run>
		3697	invocation, and use a loop around C<ev_run> until the condition is
		3698	triggered, using C<EVRUN_ONCE>:
		3699
		3700	// main loop
		3701	int exit_main_loop = 0;
		3702
		3703	while (!exit_main_loop)
		3704	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3705
		3706	// in a modal watcher
		3707	int exit_nested_loop = 0;
		3708
		3709	while (!exit_nested_loop)
		3710	ev_run (EV_A_ EVRUN_ONCE);
		3711
		3712	To exit from any of these loops, just set the corresponding exit variable:
		3713
		3714	// exit modal loop
		3715	exit_nested_loop = 1;
		3716
		3717	// exit main program, after modal loop is finished
		3718	exit_main_loop = 1;
		3719
		3720	// exit both
		3721	exit_main_loop = exit_nested_loop = 1;
		3722
		3723	=head2 THREAD LOCKING EXAMPLE
		3724
		3725	Here is a fictitious example of how to run an event loop in a different
		3726	thread from where callbacks are being invoked and watchers are
		3727	created/added/removed.
		3728
		3729	For a real-world example, see the C<EV::Loop::Async> perl module,
		3730	which uses exactly this technique (which is suited for many high-level
		3731	languages).
		3732
		3733	The example uses a pthread mutex to protect the loop data, a condition
		3734	variable to wait for callback invocations, an async watcher to notify the
		3735	event loop thread and an unspecified mechanism to wake up the main thread.
		3736
		3737	First, you need to associate some data with the event loop:
		3738
		3739	typedef struct {
		3740	mutex_t lock; /* global loop lock */
		3741	ev_async async_w;
		3742	thread_t tid;
		3743	cond_t invoke_cv;
		3744	} userdata;
		3745
		3746	void prepare_loop (EV_P)
		3747	{
		3748	// for simplicity, we use a static userdata struct.
		3749	static userdata u;
		3750
		3751	ev_async_init (&u->async_w, async_cb);
		3752	ev_async_start (EV_A_ &u->async_w);
		3753
		3754	pthread_mutex_init (&u->lock, 0);
		3755	pthread_cond_init (&u->invoke_cv, 0);
		3756
		3757	// now associate this with the loop
		3758	ev_set_userdata (EV_A_ u);
		3759	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3760	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3761
		3762	// then create the thread running ev_run
		3763	pthread_create (&u->tid, 0, l_run, EV_A);
		3764	}
		3765
		3766	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3767	solely to wake up the event loop so it takes notice of any new watchers
		3768	that might have been added:
		3769
		3770	static void
		3771	async_cb (EV_P_ ev_async *w, int revents)
		3772	{
		3773	// just used for the side effects
		3774	}
		3775
		3776	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3777	protecting the loop data, respectively.
		3778
		3779	static void
		3780	l_release (EV_P)
		3781	{
		3782	userdata *u = ev_userdata (EV_A);
		3783	pthread_mutex_unlock (&u->lock);
		3784	}
		3785
		3786	static void
		3787	l_acquire (EV_P)
		3788	{
		3789	userdata *u = ev_userdata (EV_A);
		3790	pthread_mutex_lock (&u->lock);
		3791	}
		3792
		3793	The event loop thread first acquires the mutex, and then jumps straight
		3794	into C<ev_run>:
		3795
		3796	void *
		3797	l_run (void *thr_arg)
		3798	{
		3799	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3800
		3801	l_acquire (EV_A);
		3802	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3803	ev_run (EV_A_ 0);
		3804	l_release (EV_A);
		3805
		3806	return 0;
		3807	}
		3808
		3809	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3810	signal the main thread via some unspecified mechanism (signals? pipe
		3811	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3812	have been called (in a while loop because a) spurious wakeups are possible
		3813	and b) skipping inter-thread-communication when there are no pending
		3814	watchers is very beneficial):
		3815
		3816	static void
		3817	l_invoke (EV_P)
		3818	{
		3819	userdata *u = ev_userdata (EV_A);
		3820
		3821	while (ev_pending_count (EV_A))
		3822	{
		3823	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3824	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3825	}
		3826	}
		3827
		3828	Now, whenever the main thread gets told to invoke pending watchers, it
		3829	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3830	thread to continue:
		3831
		3832	static void
		3833	real_invoke_pending (EV_P)
		3834	{
		3835	userdata *u = ev_userdata (EV_A);
		3836
		3837	pthread_mutex_lock (&u->lock);
		3838	ev_invoke_pending (EV_A);
		3839	pthread_cond_signal (&u->invoke_cv);
		3840	pthread_mutex_unlock (&u->lock);
		3841	}
		3842
		3843	Whenever you want to start/stop a watcher or do other modifications to an
		3844	event loop, you will now have to lock:
		3845
		3846	ev_timer timeout_watcher;
		3847	userdata *u = ev_userdata (EV_A);
		3848
		3849	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3850
		3851	pthread_mutex_lock (&u->lock);
		3852	ev_timer_start (EV_A_ &timeout_watcher);
		3853	ev_async_send (EV_A_ &u->async_w);
		3854	pthread_mutex_unlock (&u->lock);
		3855
		3856	Note that sending the C<ev_async> watcher is required because otherwise
		3857	an event loop currently blocking in the kernel will have no knowledge
		3858	about the newly added timer. By waking up the loop it will pick up any new
		3859	watchers in the next event loop iteration.
		3860
		3861	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3862
		3863	While the overhead of a callback that e.g. schedules a thread is small, it
		3864	is still an overhead. If you embed libev, and your main usage is with some
		3865	kind of threads or coroutines, you might want to customise libev so that
		3866	doesn't need callbacks anymore.
		3867
		3868	Imagine you have coroutines that you can switch to using a function
		3869	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3870	and that due to some magic, the currently active coroutine is stored in a
		3871	global called C<current_coro>. Then you can build your own "wait for libev
		3872	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3873	the differing C<;> conventions):
		3874
		3875	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3876	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3877
		3878	That means instead of having a C callback function, you store the
		3879	coroutine to switch to in each watcher, and instead of having libev call
		3880	your callback, you instead have it switch to that coroutine.
		3881
		3882	A coroutine might now wait for an event with a function called
		3883	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3884	matter when, or whether the watcher is active or not when this function is
		3885	called):
		3886
		3887	void
		3888	wait_for_event (ev_watcher *w)
		3889	{
		3890	ev_set_cb (w, current_coro);
		3891	switch_to (libev_coro);
		3892	}
		3893
		3894	That basically suspends the coroutine inside C<wait_for_event> and
		3895	continues the libev coroutine, which, when appropriate, switches back to
		3896	this or any other coroutine.
		3897
		3898	You can do similar tricks if you have, say, threads with an event queue -
		3899	instead of storing a coroutine, you store the queue object and instead of
		3900	switching to a coroutine, you push the watcher onto the queue and notify
		3901	any waiters.
		3902
		3903	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3904	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3905
		3906	// my_ev.h
		3907	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3908	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3909	#include "../libev/ev.h"
		3910
		3911	// my_ev.c
		3912	#define EV_H "my_ev.h"
		3913	#include "../libev/ev.c"
		3914
		3915	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3916	F<my_ev.c> into your project. When properly specifying include paths, you
		3917	can even use F<ev.h> as header file name directly.
3220		3918
3221		3919
3222	=head1 LIBEVENT EMULATION	3920	=head1 LIBEVENT EMULATION
3223		3921
3224	Libev offers a compatibility emulation layer for libevent. It cannot	3922	Libev offers a compatibility emulation layer for libevent. It cannot
3225	emulate the internals of libevent, so here are some usage hints:	3923	emulate the internals of libevent, so here are some usage hints:
3226		3924
3227	=over 4	3925	=over 4
		3926
		3927	=item * Only the libevent-1.4.1-beta API is being emulated.
		3928
		3929	This was the newest libevent version available when libev was implemented,
		3930	and is still mostly unchanged in 2010.
3228		3931
3229	=item * Use it by including <event.h>, as usual.	3932	=item * Use it by including <event.h>, as usual.
3230		3933
3231	=item * The following members are fully supported: ev_base, ev_callback,	3934	=item * The following members are fully supported: ev_base, ev_callback,
3232	ev_arg, ev_fd, ev_res, ev_events.	3935	ev_arg, ev_fd, ev_res, ev_events.
…		…
3238	=item * Priorities are not currently supported. Initialising priorities	3941	=item * Priorities are not currently supported. Initialising priorities
3239	will fail and all watchers will have the same priority, even though there	3942	will fail and all watchers will have the same priority, even though there
3240	is an ev_pri field.	3943	is an ev_pri field.
3241		3944
3242	=item * In libevent, the last base created gets the signals, in libev, the	3945	=item * In libevent, the last base created gets the signals, in libev, the
3243	first base created (== the default loop) gets the signals.	3946	base that registered the signal gets the signals.
3244		3947
3245	=item * Other members are not supported.	3948	=item * Other members are not supported.
3246		3949
3247	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3950	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3248	to use the libev header file and library.	3951	to use the libev header file and library.
3249		3952
3250	=back	3953	=back
3251		3954
3252	=head1 C++ SUPPORT	3955	=head1 C++ SUPPORT
		3956
		3957	=head2 C API
		3958
		3959	The normal C API should work fine when used from C++: both ev.h and the
		3960	libev sources can be compiled as C++. Therefore, code that uses the C API
		3961	will work fine.
		3962
		3963	Proper exception specifications might have to be added to callbacks passed
		3964	to libev: exceptions may be thrown only from watcher callbacks, all
		3965	other callbacks (allocator, syserr, loop acquire/release and periodic
		3966	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3967	()> specification. If you have code that needs to be compiled as both C
		3968	and C++ you can use the C<EV_THROW> macro for this:
		3969
		3970	static void
		3971	fatal_error (const char *msg) EV_THROW
		3972	{
		3973	perror (msg);
		3974	abort ();
		3975	}
		3976
		3977	...
		3978	ev_set_syserr_cb (fatal_error);
		3979
		3980	The only API functions that can currently throw exceptions are C<ev_run>,
		3981	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3982	because it runs cleanup watchers).
		3983
		3984	Throwing exceptions in watcher callbacks is only supported if libev itself
		3985	is compiled with a C++ compiler or your C and C++ environments allow
		3986	throwing exceptions through C libraries (most do).
		3987
		3988	=head2 C++ API
3253		3989
3254	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3990	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3255	you to use some convenience methods to start/stop watchers and also change	3991	you to use some convenience methods to start/stop watchers and also change
3256	the callback model to a model using method callbacks on objects.	3992	the callback model to a model using method callbacks on objects.
3257		3993
3258	To use it,	3994	To use it,
3259		3995
3260	#include <ev++.h>	3996	#include <ev++.h>
3261		3997
3262	This automatically includes F<ev.h> and puts all of its definitions (many	3998	This automatically includes F<ev.h> and puts all of its definitions (many
3263	of them macros) into the global namespace. All C++ specific things are	3999	of them macros) into the global namespace. All C++ specific things are
3264	put into the C<ev> namespace. It should support all the same embedding	4000	put into the C<ev> namespace. It should support all the same embedding
…		…
3267	Care has been taken to keep the overhead low. The only data member the C++	4003	Care has been taken to keep the overhead low. The only data member the C++
3268	classes add (compared to plain C-style watchers) is the event loop pointer	4004	classes add (compared to plain C-style watchers) is the event loop pointer
3269	that the watcher is associated with (or no additional members at all if	4005	that the watcher is associated with (or no additional members at all if
3270	you disable C<EV_MULTIPLICITY> when embedding libev).	4006	you disable C<EV_MULTIPLICITY> when embedding libev).
3271		4007
3272	Currently, functions, and static and non-static member functions can be	4008	Currently, functions, static and non-static member functions and classes
3273	used as callbacks. Other types should be easy to add as long as they only	4009	with C<operator ()> can be used as callbacks. Other types should be easy
3274	need one additional pointer for context. If you need support for other	4010	to add as long as they only need one additional pointer for context. If
3275	types of functors please contact the author (preferably after implementing	4011	you need support for other types of functors please contact the author
3276	it).	4012	(preferably after implementing it).
		4013
		4014	For all this to work, your C++ compiler either has to use the same calling
		4015	conventions as your C compiler (for static member functions), or you have
		4016	to embed libev and compile libev itself as C++.
3277		4017
3278	Here is a list of things available in the C<ev> namespace:	4018	Here is a list of things available in the C<ev> namespace:
3279		4019
3280	=over 4	4020	=over 4
3281		4021
…		…
3291	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4031	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3292		4032
3293	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4033	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3294	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4034	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3295	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4035	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3296	defines by many implementations.	4036	defined by many implementations.
3297		4037
3298	All of those classes have these methods:	4038	All of those classes have these methods:
3299		4039
3300	=over 4	4040	=over 4
3301		4041
…		…
3363	void operator() (ev::io &w, int revents)	4103	void operator() (ev::io &w, int revents)
3364	{	4104	{
3365	...	4105	...
3366	}	4106	}
3367	}	4107	}
3368		4108
3369	myfunctor f;	4109	myfunctor f;
3370		4110
3371	ev::io w;	4111	ev::io w;
3372	w.set (&f);	4112	w.set (&f);
3373		4113
…		…
3391	Associates a different C<struct ev_loop> with this watcher. You can only	4131	Associates a different C<struct ev_loop> with this watcher. You can only
3392	do this when the watcher is inactive (and not pending either).	4132	do this when the watcher is inactive (and not pending either).
3393		4133
3394	=item w->set ([arguments])	4134	=item w->set ([arguments])
3395		4135
3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4136	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4137	with the same arguments. Either this method or a suitable start method
3397	called at least once. Unlike the C counterpart, an active watcher gets	4138	must be called at least once. Unlike the C counterpart, an active watcher
3398	automatically stopped and restarted when reconfiguring it with this	4139	gets automatically stopped and restarted when reconfiguring it with this
3399	method.	4140	method.
		4141
		4142	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4143	clashing with the C<set (loop)> method.
3400		4144
3401	=item w->start ()	4145	=item w->start ()
3402		4146
3403	Starts the watcher. Note that there is no C<loop> argument, as the	4147	Starts the watcher. Note that there is no C<loop> argument, as the
3404	constructor already stores the event loop.	4148	constructor already stores the event loop.
3405		4149
		4150	=item w->start ([arguments])
		4151
		4152	Instead of calling C<set> and C<start> methods separately, it is often
		4153	convenient to wrap them in one call. Uses the same type of arguments as
		4154	the configure C<set> method of the watcher.
		4155
3406	=item w->stop ()	4156	=item w->stop ()
3407		4157
3408	Stops the watcher if it is active. Again, no C<loop> argument.	4158	Stops the watcher if it is active. Again, no C<loop> argument.
3409		4159
3410	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4160	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3422		4172
3423	=back	4173	=back
3424		4174
3425	=back	4175	=back
3426		4176
3427	Example: Define a class with an IO and idle watcher, start one of them in	4177	Example: Define a class with two I/O and idle watchers, start the I/O
3428	the constructor.	4178	watchers in the constructor.
3429		4179
3430	class myclass	4180	class myclass
3431	{	4181	{
3432	ev::io io ; void io_cb (ev::io &w, int revents);	4182	ev::io io ; void io_cb (ev::io &w, int revents);
		4183	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3434		4185
3435	myclass (int fd)	4186	myclass (int fd)
3436	{	4187	{
3437	io .set <myclass, &myclass::io_cb > (this);	4188	io .set <myclass, &myclass::io_cb > (this);
		4189	io2 .set <myclass, &myclass::io2_cb > (this);
3438	idle.set <myclass, &myclass::idle_cb> (this);	4190	idle.set <myclass, &myclass::idle_cb> (this);
3439		4191
3440	io.start (fd, ev::READ);	4192	io.set (fd, ev::WRITE); // configure the watcher
		4193	io.start (); // start it whenever convenient
		4194
		4195	io2.start (fd, ev::READ); // set + start in one call
3441	}	4196	}
3442	};	4197	};
3443		4198
3444		4199
3445	=head1 OTHER LANGUAGE BINDINGS	4200	=head1 OTHER LANGUAGE BINDINGS
…		…
3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4239	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3485		4240
3486	=item D	4241	=item D
3487		4242
3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4243	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4244	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3490		4245
3491	=item Ocaml	4246	=item Ocaml
3492		4247
3493	Erkki Seppala has written Ocaml bindings for libev, to be found at	4248	Erkki Seppala has written Ocaml bindings for libev, to be found at
3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4249	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3497		4252
3498	Brian Maher has written a partial interface to libev for lua (at the	4253	Brian Maher has written a partial interface to libev for lua (at the
3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4254	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3500	L<http://github.com/brimworks/lua-ev>.	4255	L<http://github.com/brimworks/lua-ev>.
3501		4256
		4257	=item Javascript
		4258
		4259	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4260
		4261	=item Others
		4262
		4263	There are others, and I stopped counting.
		4264
3502	=back	4265	=back
3503		4266
3504		4267
3505	=head1 MACRO MAGIC	4268	=head1 MACRO MAGIC
3506		4269
…		…
3519	loop argument"). The C<EV_A> form is used when this is the sole argument,	4282	loop argument"). The C<EV_A> form is used when this is the sole argument,
3520	C<EV_A_> is used when other arguments are following. Example:	4283	C<EV_A_> is used when other arguments are following. Example:
3521		4284
3522	ev_unref (EV_A);	4285	ev_unref (EV_A);
3523	ev_timer_add (EV_A_ watcher);	4286	ev_timer_add (EV_A_ watcher);
3524	ev_loop (EV_A_ 0);	4287	ev_run (EV_A_ 0);
3525		4288
3526	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4289	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3527	which is often provided by the following macro.	4290	which is often provided by the following macro.
3528		4291
3529	=item C<EV_P>, C<EV_P_>	4292	=item C<EV_P>, C<EV_P_>
…		…
3542	suitable for use with C<EV_A>.	4305	suitable for use with C<EV_A>.
3543		4306
3544	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4307	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3545		4308
3546	Similar to the other two macros, this gives you the value of the default	4309	Similar to the other two macros, this gives you the value of the default
3547	loop, if multiple loops are supported ("ev loop default").	4310	loop, if multiple loops are supported ("ev loop default"). The default loop
		4311	will be initialised if it isn't already initialised.
		4312
		4313	For non-multiplicity builds, these macros do nothing, so you always have
		4314	to initialise the loop somewhere.
3548		4315
3549	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4316	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3550		4317
3551	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4318	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3552	default loop has been initialised (C<UC> == unchecked). Their behaviour	4319	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3569	}	4336	}
3570		4337
3571	ev_check check;	4338	ev_check check;
3572	ev_check_init (&check, check_cb);	4339	ev_check_init (&check, check_cb);
3573	ev_check_start (EV_DEFAULT_ &check);	4340	ev_check_start (EV_DEFAULT_ &check);
3574	ev_loop (EV_DEFAULT_ 0);	4341	ev_run (EV_DEFAULT_ 0);
3575		4342
3576	=head1 EMBEDDING	4343	=head1 EMBEDDING
3577		4344
3578	Libev can (and often is) directly embedded into host	4345	Libev can (and often is) directly embedded into host
3579	applications. Examples of applications that embed it include the Deliantra	4346	applications. Examples of applications that embed it include the Deliantra
…		…
3619	ev_vars.h	4386	ev_vars.h
3620	ev_wrap.h	4387	ev_wrap.h
3621		4388
3622	ev_win32.c required on win32 platforms only	4389	ev_win32.c required on win32 platforms only
3623		4390
3624	ev_select.c only when select backend is enabled (which is enabled by default)	4391	ev_select.c only when select backend is enabled
3625	ev_poll.c only when poll backend is enabled (disabled by default)	4392	ev_poll.c only when poll backend is enabled
3626	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4393	ev_epoll.c only when the epoll backend is enabled
3627	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4394	ev_kqueue.c only when the kqueue backend is enabled
3628	ev_port.c only when the solaris port backend is enabled (disabled by default)	4395	ev_port.c only when the solaris port backend is enabled
3629		4396
3630	F<ev.c> includes the backend files directly when enabled, so you only need	4397	F<ev.c> includes the backend files directly when enabled, so you only need
3631	to compile this single file.	4398	to compile this single file.
3632		4399
3633	=head3 LIBEVENT COMPATIBILITY API	4400	=head3 LIBEVENT COMPATIBILITY API
…		…
3671	users of libev and the libev code itself must be compiled with compatible	4438	users of libev and the libev code itself must be compiled with compatible
3672	settings.	4439	settings.
3673		4440
3674	=over 4	4441	=over 4
3675		4442
		4443	=item EV_COMPAT3 (h)
		4444
		4445	Backwards compatibility is a major concern for libev. This is why this
		4446	release of libev comes with wrappers for the functions and symbols that
		4447	have been renamed between libev version 3 and 4.
		4448
		4449	You can disable these wrappers (to test compatibility with future
		4450	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4451	sources. This has the additional advantage that you can drop the C<struct>
		4452	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4453	typedef in that case.
		4454
		4455	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4456	and in some even more future version the compatibility code will be
		4457	removed completely.
		4458
3676	=item EV_STANDALONE (h)	4459	=item EV_STANDALONE (h)
3677		4460
3678	Must always be C<1> if you do not use autoconf configuration, which	4461	Must always be C<1> if you do not use autoconf configuration, which
3679	keeps libev from including F<config.h>, and it also defines dummy	4462	keeps libev from including F<config.h>, and it also defines dummy
3680	implementations for some libevent functions (such as logging, which is not	4463	implementations for some libevent functions (such as logging, which is not
3681	supported). It will also not define any of the structs usually found in	4464	supported). It will also not define any of the structs usually found in
3682	F<event.h> that are not directly supported by the libev core alone.	4465	F<event.h> that are not directly supported by the libev core alone.
3683		4466
3684	In standalone mode, libev will still try to automatically deduce the	4467	In standalone mode, libev will still try to automatically deduce the
3685	configuration, but has to be more conservative.	4468	configuration, but has to be more conservative.
		4469
		4470	=item EV_USE_FLOOR
		4471
		4472	If defined to be C<1>, libev will use the C<floor ()> function for its
		4473	periodic reschedule calculations, otherwise libev will fall back on a
		4474	portable (slower) implementation. If you enable this, you usually have to
		4475	link against libm or something equivalent. Enabling this when the C<floor>
		4476	function is not available will fail, so the safe default is to not enable
		4477	this.
3686		4478
3687	=item EV_USE_MONOTONIC	4479	=item EV_USE_MONOTONIC
3688		4480
3689	If defined to be C<1>, libev will try to detect the availability of the	4481	If defined to be C<1>, libev will try to detect the availability of the
3690	monotonic clock option at both compile time and runtime. Otherwise no	4482	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3775		4567
3776	If programs implement their own fd to handle mapping on win32, then this	4568	If programs implement their own fd to handle mapping on win32, then this
3777	macro can be used to override the C<close> function, useful to unregister	4569	macro can be used to override the C<close> function, useful to unregister
3778	file descriptors again. Note that the replacement function has to close	4570	file descriptors again. Note that the replacement function has to close
3779	the underlying OS handle.	4571	the underlying OS handle.
		4572
		4573	=item EV_USE_WSASOCKET
		4574
		4575	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4576	communication socket, which works better in some environments. Otherwise,
		4577	the normal C<socket> function will be used, which works better in other
		4578	environments.
3780		4579
3781	=item EV_USE_POLL	4580	=item EV_USE_POLL
3782		4581
3783	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4582	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3784	backend. Otherwise it will be enabled on non-win32 platforms. It	4583	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3820	If defined to be C<1>, libev will compile in support for the Linux inotify	4619	If defined to be C<1>, libev will compile in support for the Linux inotify
3821	interface to speed up C<ev_stat> watchers. Its actual availability will	4620	interface to speed up C<ev_stat> watchers. Its actual availability will
3822	be detected at runtime. If undefined, it will be enabled if the headers	4621	be detected at runtime. If undefined, it will be enabled if the headers
3823	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4622	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3824		4623
		4624	=item EV_NO_SMP
		4625
		4626	If defined to be C<1>, libev will assume that memory is always coherent
		4627	between threads, that is, threads can be used, but threads never run on
		4628	different cpus (or different cpu cores). This reduces dependencies
		4629	and makes libev faster.
		4630
		4631	=item EV_NO_THREADS
		4632
		4633	If defined to be C<1>, libev will assume that it will never be called from
		4634	different threads (that includes signal handlers), which is a stronger
		4635	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4636	libev faster.
		4637
3825	=item EV_ATOMIC_T	4638	=item EV_ATOMIC_T
3826		4639
3827	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4640	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3828	access is atomic with respect to other threads or signal contexts. No such	4641	access is atomic with respect to other threads or signal contexts. No
3829	type is easily found in the C language, so you can provide your own type	4642	such type is easily found in the C language, so you can provide your own
3830	that you know is safe for your purposes. It is used both for signal handler "locking"	4643	type that you know is safe for your purposes. It is used both for signal
3831	as well as for signal and thread safety in C<ev_async> watchers.	4644	handler "locking" as well as for signal and thread safety in C<ev_async>
		4645	watchers.
3832		4646
3833	In the absence of this define, libev will use C<sig_atomic_t volatile>	4647	In the absence of this define, libev will use C<sig_atomic_t volatile>
3834	(from F<signal.h>), which is usually good enough on most platforms.	4648	(from F<signal.h>), which is usually good enough on most platforms.
3835		4649
3836	=item EV_H (h)	4650	=item EV_H (h)
…		…
3863	will have the C<struct ev_loop *> as first argument, and you can create	4677	will have the C<struct ev_loop *> as first argument, and you can create
3864	additional independent event loops. Otherwise there will be no support	4678	additional independent event loops. Otherwise there will be no support
3865	for multiple event loops and there is no first event loop pointer	4679	for multiple event loops and there is no first event loop pointer
3866	argument. Instead, all functions act on the single default loop.	4680	argument. Instead, all functions act on the single default loop.
3867		4681
		4682	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4683	default loop when multiplicity is switched off - you always have to
		4684	initialise the loop manually in this case.
		4685
3868	=item EV_MINPRI	4686	=item EV_MINPRI
3869		4687
3870	=item EV_MAXPRI	4688	=item EV_MAXPRI
3871		4689
3872	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4690	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3908	#define EV_USE_POLL 1	4726	#define EV_USE_POLL 1
3909	#define EV_CHILD_ENABLE 1	4727	#define EV_CHILD_ENABLE 1
3910	#define EV_ASYNC_ENABLE 1	4728	#define EV_ASYNC_ENABLE 1
3911		4729
3912	The actual value is a bitset, it can be a combination of the following	4730	The actual value is a bitset, it can be a combination of the following
3913	values:	4731	values (by default, all of these are enabled):
3914		4732
3915	=over 4	4733	=over 4
3916		4734
3917	=item C<1> - faster/larger code	4735	=item C<1> - faster/larger code
3918		4736
…		…
3922	code size by roughly 30% on amd64).	4740	code size by roughly 30% on amd64).
3923		4741
3924	When optimising for size, use of compiler flags such as C<-Os> with	4742	When optimising for size, use of compiler flags such as C<-Os> with
3925	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4743	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3926	assertions.	4744	assertions.
		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
3927		4748
3928	=item C<2> - faster/larger data structures	4749	=item C<2> - faster/larger data structures
3929		4750
3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4751	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3931	hash table sizes and so on. This will usually further increase code size	4752	hash table sizes and so on. This will usually further increase code size
3932	and can additionally have an effect on the size of data structures at	4753	and can additionally have an effect on the size of data structures at
3933	runtime.	4754	runtime.
3934		4755
		4756	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4757	(e.g. gcc with C<-Os>).
		4758
3935	=item C<4> - full API configuration	4759	=item C<4> - full API configuration
3936		4760
3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4761	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3938	enables multiplicity (C<EV_MULTIPLICITY>=1).	4762	enables multiplicity (C<EV_MULTIPLICITY>=1).
3939		4763
…		…
3969		4793
3970	With an intelligent-enough linker (gcc+binutils are intelligent enough	4794	With an intelligent-enough linker (gcc+binutils are intelligent enough
3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4795	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3972	your program might be left out as well - a binary starting a timer and an	4796	your program might be left out as well - a binary starting a timer and an
3973	I/O watcher then might come out at only 5Kb.	4797	I/O watcher then might come out at only 5Kb.
		4798
		4799	=item EV_API_STATIC
		4800
		4801	If this symbol is defined (by default it is not), then all identifiers
		4802	will have static linkage. This means that libev will not export any
		4803	identifiers, and you cannot link against libev anymore. This can be useful
		4804	when you embed libev, only want to use libev functions in a single file,
		4805	and do not want its identifiers to be visible.
		4806
		4807	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4808	wants to use libev.
		4809
		4810	This option only works when libev is compiled with a C compiler, as C++
		4811	doesn't support the required declaration syntax.
3974		4812
3975	=item EV_AVOID_STDIO	4813	=item EV_AVOID_STDIO
3976		4814
3977	If this is set to C<1> at compiletime, then libev will avoid using stdio	4815	If this is set to C<1> at compiletime, then libev will avoid using stdio
3978	functions (printf, scanf, perror etc.). This will increase the code size	4816	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4867	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4030	will be C<0>.	4868	will be C<0>.
4031		4869
4032	=item EV_VERIFY	4870	=item EV_VERIFY
4033		4871
4034	Controls how much internal verification (see C<ev_loop_verify ()>) will	4872	Controls how much internal verification (see C<ev_verify ()>) will
4035	be done: If set to C<0>, no internal verification code will be compiled	4873	be done: If set to C<0>, no internal verification code will be compiled
4036	in. If set to C<1>, then verification code will be compiled in, but not	4874	in. If set to C<1>, then verification code will be compiled in, but not
4037	called. If set to C<2>, then the internal verification code will be	4875	called. If set to C<2>, then the internal verification code will be
4038	called once per loop, which can slow down libev. If set to C<3>, then the	4876	called once per loop, which can slow down libev. If set to C<3>, then the
4039	verification code will be called very frequently, which will slow down	4877	verification code will be called very frequently, which will slow down
…		…
4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4123		4961
4124	#include "ev_cpp.h"	4962	#include "ev_cpp.h"
4125	#include "ev.c"	4963	#include "ev.c"
4126		4964
4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4965	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4128		4966
4129	=head2 THREADS AND COROUTINES	4967	=head2 THREADS AND COROUTINES
4130		4968
4131	=head3 THREADS	4969	=head3 THREADS
4132		4970
…		…
4183	default loop and triggering an C<ev_async> watcher from the default loop	5021	default loop and triggering an C<ev_async> watcher from the default loop
4184	watcher callback into the event loop interested in the signal.	5022	watcher callback into the event loop interested in the signal.
4185		5023
4186	=back	5024	=back
4187		5025
4188	=head4 THREAD LOCKING EXAMPLE	5026	See also L</THREAD LOCKING EXAMPLE>.
4189
4190	Here is a fictitious example of how to run an event loop in a different
4191	thread than where callbacks are being invoked and watchers are
4192	created/added/removed.
4193
4194	For a real-world example, see the C<EV::Loop::Async> perl module,
4195	which uses exactly this technique (which is suited for many high-level
4196	languages).
4197
4198	The example uses a pthread mutex to protect the loop data, a condition
4199	variable to wait for callback invocations, an async watcher to notify the
4200	event loop thread and an unspecified mechanism to wake up the main thread.
4201
4202	First, you need to associate some data with the event loop:
4203
4204	typedef struct {
4205	mutex_t lock; /* global loop lock */
4206	ev_async async_w;
4207	thread_t tid;
4208	cond_t invoke_cv;
4209	} userdata;
4210
4211	void prepare_loop (EV_P)
4212	{
4213	// for simplicity, we use a static userdata struct.
4214	static userdata u;
4215
4216	ev_async_init (&u->async_w, async_cb);
4217	ev_async_start (EV_A_ &u->async_w);
4218
4219	pthread_mutex_init (&u->lock, 0);
4220	pthread_cond_init (&u->invoke_cv, 0);
4221
4222	// now associate this with the loop
4223	ev_set_userdata (EV_A_ u);
4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4226
4227	// then create the thread running ev_loop
4228	pthread_create (&u->tid, 0, l_run, EV_A);
4229	}
4230
4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
4232	solely to wake up the event loop so it takes notice of any new watchers
4233	that might have been added:
4234
4235	static void
4236	async_cb (EV_P_ ev_async *w, int revents)
4237	{
4238	// just used for the side effects
4239	}
4240
4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4242	protecting the loop data, respectively.
4243
4244	static void
4245	l_release (EV_P)
4246	{
4247	userdata *u = ev_userdata (EV_A);
4248	pthread_mutex_unlock (&u->lock);
4249	}
4250
4251	static void
4252	l_acquire (EV_P)
4253	{
4254	userdata *u = ev_userdata (EV_A);
4255	pthread_mutex_lock (&u->lock);
4256	}
4257
4258	The event loop thread first acquires the mutex, and then jumps straight
4259	into C<ev_loop>:
4260
4261	void *
4262	l_run (void *thr_arg)
4263	{
4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4265
4266	l_acquire (EV_A);
4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4268	ev_loop (EV_A_ 0);
4269	l_release (EV_A);
4270
4271	return 0;
4272	}
4273
4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
4275	signal the main thread via some unspecified mechanism (signals? pipe
4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4277	have been called (in a while loop because a) spurious wakeups are possible
4278	and b) skipping inter-thread-communication when there are no pending
4279	watchers is very beneficial):
4280
4281	static void
4282	l_invoke (EV_P)
4283	{
4284	userdata *u = ev_userdata (EV_A);
4285
4286	while (ev_pending_count (EV_A))
4287	{
4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
4290	}
4291	}
4292
4293	Now, whenever the main thread gets told to invoke pending watchers, it
4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4295	thread to continue:
4296
4297	static void
4298	real_invoke_pending (EV_P)
4299	{
4300	userdata *u = ev_userdata (EV_A);
4301
4302	pthread_mutex_lock (&u->lock);
4303	ev_invoke_pending (EV_A);
4304	pthread_cond_signal (&u->invoke_cv);
4305	pthread_mutex_unlock (&u->lock);
4306	}
4307
4308	Whenever you want to start/stop a watcher or do other modifications to an
4309	event loop, you will now have to lock:
4310
4311	ev_timer timeout_watcher;
4312	userdata *u = ev_userdata (EV_A);
4313
4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4315
4316	pthread_mutex_lock (&u->lock);
4317	ev_timer_start (EV_A_ &timeout_watcher);
4318	ev_async_send (EV_A_ &u->async_w);
4319	pthread_mutex_unlock (&u->lock);
4320
4321	Note that sending the C<ev_async> watcher is required because otherwise
4322	an event loop currently blocking in the kernel will have no knowledge
4323	about the newly added timer. By waking up the loop it will pick up any new
4324	watchers in the next event loop iteration.
4325		5027
4326	=head3 COROUTINES	5028	=head3 COROUTINES
4327		5029
4328	Libev is very accommodating to coroutines ("cooperative threads"):	5030	Libev is very accommodating to coroutines ("cooperative threads"):
4329	libev fully supports nesting calls to its functions from different	5031	libev fully supports nesting calls to its functions from different
4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5032	coroutines (e.g. you can call C<ev_run> on the same loop from two
4331	different coroutines, and switch freely between both coroutines running	5033	different coroutines, and switch freely between both coroutines running
4332	the loop, as long as you don't confuse yourself). The only exception is	5034	the loop, as long as you don't confuse yourself). The only exception is
4333	that you must not do this from C<ev_periodic> reschedule callbacks.	5035	that you must not do this from C<ev_periodic> reschedule callbacks.
4334		5036
4335	Care has been taken to ensure that libev does not keep local state inside	5037	Care has been taken to ensure that libev does not keep local state inside
4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5038	C<ev_run>, and other calls do not usually allow for coroutine switches as
4337	they do not call any callbacks.	5039	they do not call any callbacks.
4338		5040
4339	=head2 COMPILER WARNINGS	5041	=head2 COMPILER WARNINGS
4340		5042
4341	Depending on your compiler and compiler settings, you might get no or a	5043	Depending on your compiler and compiler settings, you might get no or a
…		…
4425	=head3 C<kqueue> is buggy	5127	=head3 C<kqueue> is buggy
4426		5128
4427	The kqueue syscall is broken in all known versions - most versions support	5129	The kqueue syscall is broken in all known versions - most versions support
4428	only sockets, many support pipes.	5130	only sockets, many support pipes.
4429		5131
4430	Libev tries to work around this by not using C<kqueue> by default on	5132	Libev tries to work around this by not using C<kqueue> by default on this
4431	this rotten platform, but of course you can still ask for it when creating	5133	rotten platform, but of course you can still ask for it when creating a
4432	a loop.	5134	loop - embedding a socket-only kqueue loop into a select-based one is
		5135	probably going to work well.
4433		5136
4434	=head3 C<poll> is buggy	5137	=head3 C<poll> is buggy
4435		5138
4436	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5139	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4437	implementation by something calling C<kqueue> internally around the 10.5.6	5140	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4456		5159
4457	=head3 C<errno> reentrancy	5160	=head3 C<errno> reentrancy
4458		5161
4459	The default compile environment on Solaris is unfortunately so	5162	The default compile environment on Solaris is unfortunately so
4460	thread-unsafe that you can't even use components/libraries compiled	5163	thread-unsafe that you can't even use components/libraries compiled
4461	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5164	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4462	isn't defined by default.	5165	defined by default. A valid, if stupid, implementation choice.
4463		5166
4464	If you want to use libev in threaded environments you have to make sure	5167	If you want to use libev in threaded environments you have to make sure
4465	it's compiled with C<_REENTRANT> defined.	5168	it's compiled with C<_REENTRANT> defined.
4466		5169
4467	=head3 Event port backend	5170	=head3 Event port backend
4468		5171
4469	The scalable event interface for Solaris is called "event ports". Unfortunately,	5172	The scalable event interface for Solaris is called "event
4470	this mechanism is very buggy. If you run into high CPU usage, your program	5173	ports". Unfortunately, this mechanism is very buggy in all major
		5174	releases. If you run into high CPU usage, your program freezes or you get
4471	freezes or you get a large number of spurious wakeups, make sure you have	5175	a large number of spurious wakeups, make sure you have all the relevant
4472	all the relevant and latest kernel patches applied. No, I don't know which	5176	and latest kernel patches applied. No, I don't know which ones, but there
4473	ones, but there are multiple ones.	5177	are multiple ones to apply, and afterwards, event ports actually work
		5178	great.
4474		5179
4475	If you can't get it to work, you can try running the program by setting	5180	If you can't get it to work, you can try running the program by setting
4476	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	5181	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4477	C<select> backends.	5182	C<select> backends.
4478		5183
4479	=head2 AIX POLL BUG	5184	=head2 AIX POLL BUG
4480		5185
4481	AIX unfortunately has a broken C<poll.h> header. Libev works around	5186	AIX unfortunately has a broken C<poll.h> header. Libev works around
4482	this by trying to avoid the poll backend altogether (i.e. it's not even	5187	this by trying to avoid the poll backend altogether (i.e. it's not even
4483	compiled in), which normally isn't a big problem as C<select> works fine	5188	compiled in), which normally isn't a big problem as C<select> works fine
4484	with large bitsets, and AIX is dead anyway.	5189	with large bitsets on AIX, and AIX is dead anyway.
4485		5190
4486	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5191	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4487		5192
4488	=head3 General issues	5193	=head3 General issues
4489		5194
…		…
4491	requires, and its I/O model is fundamentally incompatible with the POSIX	5196	requires, and its I/O model is fundamentally incompatible with the POSIX
4492	model. Libev still offers limited functionality on this platform in	5197	model. Libev still offers limited functionality on this platform in
4493	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5198	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4494	descriptors. This only applies when using Win32 natively, not when using	5199	descriptors. This only applies when using Win32 natively, not when using
4495	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5200	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4496	as every compielr comes with a slightly differently broken/incompatible	5201	as every compiler comes with a slightly differently broken/incompatible
4497	environment.	5202	environment.
4498		5203
4499	Lifting these limitations would basically require the full	5204	Lifting these limitations would basically require the full
4500	re-implementation of the I/O system. If you are into this kind of thing,	5205	re-implementation of the I/O system. If you are into this kind of thing,
4501	then note that glib does exactly that for you in a very portable way (note	5206	then note that glib does exactly that for you in a very portable way (note
…		…
4595	structure (guaranteed by POSIX but not by ISO C for example), but it also	5300	structure (guaranteed by POSIX but not by ISO C for example), but it also
4596	assumes that the same (machine) code can be used to call any watcher	5301	assumes that the same (machine) code can be used to call any watcher
4597	callback: The watcher callbacks have different type signatures, but libev	5302	callback: The watcher callbacks have different type signatures, but libev
4598	calls them using an C<ev_watcher *> internally.	5303	calls them using an C<ev_watcher *> internally.
4599		5304
		5305	=item null pointers and integer zero are represented by 0 bytes
		5306
		5307	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5308	relies on this setting pointers and integers to null.
		5309
		5310	=item pointer accesses must be thread-atomic
		5311
		5312	Accessing a pointer value must be atomic, it must both be readable and
		5313	writable in one piece - this is the case on all current architectures.
		5314
4600	=item C<sig_atomic_t volatile> must be thread-atomic as well	5315	=item C<sig_atomic_t volatile> must be thread-atomic as well
4601		5316
4602	The type C<sig_atomic_t volatile> (or whatever is defined as	5317	The type C<sig_atomic_t volatile> (or whatever is defined as
4603	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5318	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4604	threads. This is not part of the specification for C<sig_atomic_t>, but is	5319	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4612	thread" or will block signals process-wide, both behaviours would	5327	thread" or will block signals process-wide, both behaviours would
4613	be compatible with libev. Interaction between C<sigprocmask> and	5328	be compatible with libev. Interaction between C<sigprocmask> and
4614	C<pthread_sigmask> could complicate things, however.	5329	C<pthread_sigmask> could complicate things, however.
4615		5330
4616	The most portable way to handle signals is to block signals in all threads	5331	The most portable way to handle signals is to block signals in all threads
4617	except the initial one, and run the default loop in the initial thread as	5332	except the initial one, and run the signal handling loop in the initial
4618	well.	5333	thread as well.
4619		5334
4620	=item C<long> must be large enough for common memory allocation sizes	5335	=item C<long> must be large enough for common memory allocation sizes
4621		5336
4622	To improve portability and simplify its API, libev uses C<long> internally	5337	To improve portability and simplify its API, libev uses C<long> internally
4623	instead of C<size_t> when allocating its data structures. On non-POSIX	5338	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4626	watchers.	5341	watchers.
4627		5342
4628	=item C<double> must hold a time value in seconds with enough accuracy	5343	=item C<double> must hold a time value in seconds with enough accuracy
4629		5344
4630	The type C<double> is used to represent timestamps. It is required to	5345	The type C<double> is used to represent timestamps. It is required to
4631	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5346	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4632	enough for at least into the year 4000. This requirement is fulfilled by	5347	good enough for at least into the year 4000 with millisecond accuracy
		5348	(the design goal for libev). This requirement is overfulfilled by
4633	implementations implementing IEEE 754, which is basically all existing	5349	implementations using IEEE 754, which is basically all existing ones.
		5350
4634	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5351	With IEEE 754 doubles, you get microsecond accuracy until at least the
4635	2200.	5352	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5353	is either obsolete or somebody patched it to use C<long double> or
		5354	something like that, just kidding).
4636		5355
4637	=back	5356	=back
4638		5357
4639	If you know of other additional requirements drop me a note.	5358	If you know of other additional requirements drop me a note.
4640		5359
…		…
4702	=item Processing ev_async_send: O(number_of_async_watchers)	5421	=item Processing ev_async_send: O(number_of_async_watchers)
4703		5422
4704	=item Processing signals: O(max_signal_number)	5423	=item Processing signals: O(max_signal_number)
4705		5424
4706	Sending involves a system call I<iff> there were no other C<ev_async_send>	5425	Sending involves a system call I<iff> there were no other C<ev_async_send>
4707	calls in the current loop iteration. Checking for async and signal events	5426	calls in the current loop iteration and the loop is currently
		5427	blocked. Checking for async and signal events involves iterating over all
4708	involves iterating over all running async watchers or all signal numbers.	5428	running async watchers or all signal numbers.
4709		5429
4710	=back	5430	=back
4711		5431
4712		5432
4713	=head1 PORTING FROM LIBEV 3.X TO 4.X	5433	=head1 PORTING FROM LIBEV 3.X TO 4.X
4714		5434
4715	The major version 4 introduced some minor incompatible changes to the API.	5435	The major version 4 introduced some incompatible changes to the API.
4716		5436
4717	At the moment, the C<ev.h> header file tries to implement superficial	5437	At the moment, the C<ev.h> header file provides compatibility definitions
4718	compatibility, so most programs should still compile. Those might be	5438	for all changes, so most programs should still compile. The compatibility
4719	removed in later versions of libev, so better update early than late.	5439	layer might be removed in later versions of libev, so better update to the
		5440	new API early than late.
4720		5441
4721	=over 4	5442	=over 4
4722		5443
4723	=item C<ev_loop_count> renamed to C<ev_iteration>	5444	=item C<EV_COMPAT3> backwards compatibility mechanism
4724		5445
4725	=item C<ev_loop_depth> renamed to C<ev_depth>	5446	The backward compatibility mechanism can be controlled by
		5447	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5448	section.
4726		5449
4727	=item C<ev_loop_verify> renamed to C<ev_verify>	5450	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5451
		5452	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5453
		5454	ev_loop_destroy (EV_DEFAULT_UC);
		5455	ev_loop_fork (EV_DEFAULT);
		5456
		5457	=item function/symbol renames
		5458
		5459	A number of functions and symbols have been renamed:
		5460
		5461	ev_loop => ev_run
		5462	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5463	EVLOOP_ONESHOT => EVRUN_ONCE
		5464
		5465	ev_unloop => ev_break
		5466	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5467	EVUNLOOP_ONE => EVBREAK_ONE
		5468	EVUNLOOP_ALL => EVBREAK_ALL
		5469
		5470	EV_TIMEOUT => EV_TIMER
		5471
		5472	ev_loop_count => ev_iteration
		5473	ev_loop_depth => ev_depth
		5474	ev_loop_verify => ev_verify
4728		5475
4729	Most functions working on C<struct ev_loop> objects don't have an	5476	Most functions working on C<struct ev_loop> objects don't have an
4730	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5477	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5478	associated constants have been renamed to not collide with the C<struct
		5479	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5480	as all other watcher types. Note that C<ev_loop_fork> is still called
4731	still called C<ev_loop_fork> because it would otherwise clash with the	5481	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4732	C<ev_fork> typedef.	5482	typedef.
4733
4734	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4735
4736	This is a simple rename - all other watcher types use their name
4737	as revents flag, and now C<ev_timer> does, too.
4738
4739	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4740	and continue to be present for the foreseeable future, so this is mostly a
4741	documentation change.
4742		5483
4743	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5484	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4744		5485
4745	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5486	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4746	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5487	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4753		5494
4754	=over 4	5495	=over 4
4755		5496
4756	=item active	5497	=item active
4757		5498
4758	A watcher is active as long as it has been started (has been attached to	5499	A watcher is active as long as it has been started and not yet stopped.
4759	an event loop) but not yet stopped (disassociated from the event loop).	5500	See L</WATCHER STATES> for details.
4760		5501
4761	=item application	5502	=item application
4762		5503
4763	In this document, an application is whatever is using libev.	5504	In this document, an application is whatever is using libev.
		5505
		5506	=item backend
		5507
		5508	The part of the code dealing with the operating system interfaces.
4764		5509
4765	=item callback	5510	=item callback
4766		5511
4767	The address of a function that is called when some event has been	5512	The address of a function that is called when some event has been
4768	detected. Callbacks are being passed the event loop, the watcher that	5513	detected. Callbacks are being passed the event loop, the watcher that
4769	received the event, and the actual event bitset.	5514	received the event, and the actual event bitset.
4770		5515
4771	=item callback invocation	5516	=item callback/watcher invocation
4772		5517
4773	The act of calling the callback associated with a watcher.	5518	The act of calling the callback associated with a watcher.
4774		5519
4775	=item event	5520	=item event
4776		5521
…		…
4795	The model used to describe how an event loop handles and processes	5540	The model used to describe how an event loop handles and processes
4796	watchers and events.	5541	watchers and events.
4797		5542
4798	=item pending	5543	=item pending
4799		5544
4800	A watcher is pending as soon as the corresponding event has been detected,	5545	A watcher is pending as soon as the corresponding event has been
4801	and stops being pending as soon as the watcher will be invoked or its	5546	detected. See L</WATCHER STATES> for details.
4802	pending status is explicitly cleared by the application.
4803
4804	A watcher can be pending, but not active. Stopping a watcher also clears
4805	its pending status.
4806		5547
4807	=item real time	5548	=item real time
4808		5549
4809	The physical time that is observed. It is apparently strictly monotonic :)	5550	The physical time that is observed. It is apparently strictly monotonic :)
4810		5551
4811	=item wall-clock time	5552	=item wall-clock time
4812		5553
4813	The time and date as shown on clocks. Unlike real time, it can actually	5554	The time and date as shown on clocks. Unlike real time, it can actually
4814	be wrong and jump forwards and backwards, e.g. when the you adjust your	5555	be wrong and jump forwards and backwards, e.g. when you adjust your
4815	clock.	5556	clock.
4816		5557
4817	=item watcher	5558	=item watcher
4818		5559
4819	A data structure that describes interest in certain events. Watchers need	5560	A data structure that describes interest in certain events. Watchers need
4820	to be started (attached to an event loop) before they can receive events.	5561	to be started (attached to an event loop) before they can receive events.
4821		5562
4822	=item watcher invocation
4823
4824	The act of calling the callback associated with a watcher.
4825
4826	=back	5563	=back
4827		5564
4828	=head1 AUTHOR	5565	=head1 AUTHOR
4829		5566
4830	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5567	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5568	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4831		5569

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