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Revision 1.296 by root, Tue Jun 29 10:51:18 2010 UTC vs.
Revision 1.358 by sf-exg, Tue Jan 11 08:43:48 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	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	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	138	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	139	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	140	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.	141	any calculations on it, you should treat it as some floating point value.
134		142
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	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	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
171		180
172	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
173		182
174	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
175	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
192	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	203	not a problem.
195		204
196	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
198		208
199	assert (("libev version mismatch",	209	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
202		212
…		…
213	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
215		225
216	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
217		227
218	Return the set of all backends compiled into this binary of libev and also	228	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	229	also recommended for this platform, meaning it will work for most file
		230	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	231	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	232	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	233	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.	234	probe for if you specify no backends explicitly.
224		235
225	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
226		237
227	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	239	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	240	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
232		243
233	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
234		245
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
236		247
237	Sets the allocation function to use (the prototype is similar - the	248	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	249	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	250	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	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	277	}
267		278
268	...	279	...
269	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
270		281
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
272		283
273	Set the callback function to call on a retryable system call error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	286	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	287	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	299	}
289		300
290	...	301	...
291	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
292		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
293	=back	317	=back
294		318
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		320
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	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>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
300		324
301	The library knows two types of such loops, the I<default> loop, which	325	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	326	supports child process events, and dynamically created event loops which
303	not.	327	do not.
304		328
305	=over 4	329	=over 4
306		330
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		332
309	This will initialise the default event loop if it hasn't been initialised	333	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	334	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	335	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).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
313		343
314	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
315	function.	345	function (or via the C<EV_DEFAULT> macro).
316		346
317	Note that this function is I<not> thread-safe, so if you want to use it	347	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,	348	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
320		351
321	The default loop is the only loop that can handle C<ev_signal> and	352	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	353	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	354	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	355	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	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
327		376
328	The flags argument can be used to specify special behaviour or specific	377	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>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		379
331	The following flags are supported:	380	The following flags are supported:
…		…
366	environment variable.	415	environment variable.
367		416
368	=item C<EVFLAG_NOINOTIFY>	417	=item C<EVFLAG_NOINOTIFY>
369		418
370	When this flag is specified, then libev will not attempt to use the	419	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	420	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	421	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.	422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		423
375	=item C<EVFLAG_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	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	427	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	428	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	429	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	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	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	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
387		448
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		450
390	This is your standard select(2) backend. Not I<completely> standard, as	451	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,	452	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
427	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
428		489
429	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(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	496	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	497	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	498	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	499	and is of course hard to detect.
437		500
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
439	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
440	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
442	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
443	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
445		514
446	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	516	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	517	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		585
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
519		588
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	592	might perform better.
528		593
529	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
533		608
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
536		611
537	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
538		613
539	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		617
543	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		627
545	=back	628	=back
546		629
547	If one or more of the backend flags are or'ed into the flags value,	630	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	631	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	632	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	633	()> will be tried.
551		634
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
579		636
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	638	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
583		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
584	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
585		647
586	Destroys the default loop (frees all memory and kernel state etc.). None	648	Destroys an event loop object (frees all memory and kernel state
587	of the active event watchers will be stopped in the normal sense, so	649	etc.). None of the active event watchers will be stopped in the normal
588	e.g. C<ev_is_active> might still return true. It is your responsibility to	650	sense, so e.g. C<ev_is_active> might still return true. It is your
589	either stop all watchers cleanly yourself I<before> calling this function,	651	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	652	calling this function, or cope with the fact afterwards (which is usually
591	can just ignore the watchers and/or C<free ()> them for example).	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		654	for example).
592		655
593	Note that certain global state, such as signal state (and installed signal	656	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	657	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
596		659
597	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	667	and C<ev_loop_destroy>.
601		668
602	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
603		670
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
610	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
611	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
612	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
613	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
614	functions, and it will only take effect at the next C<ev_loop> iteration.
615		676
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	677	Again, you I<have> to call it on I<any> loop that you want to re-use after
617	a fork, I<even if you do not plan to use the loop in the parent>. This is	678	a fork, I<even if you do not plan to use the loop in the parent>. This is
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	680	during fork.
620		681
621	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	683	process if and only if you want to use the event loop in the child. If
623	just fork+exec or create a new loop in the child, you don't have to call	684	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
625		688
626	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
630	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		703
639	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
640		705
641	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	707	otherwise.
643		708
644	=item unsigned int ev_iteration (loop)	709	=item unsigned int ev_iteration (loop)
645		710
646	Returns the current iteration count for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
647	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
649		714
650	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
652	C<ev_prepare> and C<ev_check> calls - and is incremented between the	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	718	prepare and check phases.
654		719
655	=item unsigned int ev_depth (loop)	720	=item unsigned int ev_depth (loop)
656		721
657	Returns the number of times C<ev_loop> was entered minus the number of	722	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	723	times C<ev_run> was exited normally, in other words, the recursion depth.
659		724
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	725	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	727	in which case it is higher.
663		728
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	etc.), doesn't count as "exit" - consider this as a hint to avoid such	730	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
667		733
668	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
669		735
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	737	use.
…		…
680		746
681	=item ev_now_update (loop)	747	=item ev_now_update (loop)
682		748
683	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
684	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
686		752
687	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	755	the current time is a good idea.
690		756
…		…
692		758
693	=item ev_suspend (loop)	759	=item ev_suspend (loop)
694		760
695	=item ev_resume (loop)	761	=item ev_resume (loop)
696		762
697	These two functions suspend and resume a loop, for use when the loop is	763	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	764	loop is not used for a while and timeouts should not be processed.
699		765
700	A typical use case would be an interactive program such as a game: When	766	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	767	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	768	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	769	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
705	C<ev_resume> directly afterwards to resume timer processing.	771	C<ev_resume> directly afterwards to resume timer processing.
706		772
707	Effectively, all C<ev_timer> watchers will be delayed by the time spend	773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
709	will be rescheduled (that is, they will lose any events that would have	775	will be rescheduled (that is, they will lose any events that would have
710	occured while suspended).	776	occurred while suspended).
711		777
712	After calling C<ev_suspend> you B<must not> call I<any> function on the	778	After calling C<ev_suspend> you B<must not> call I<any> function on the
713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
714	without a previous call to C<ev_suspend>.	780	without a previous call to C<ev_suspend>.
715		781
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	783	event loop time (see C<ev_now_update>).
718		784
719	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
720		786
721	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	788	after you have initialised all your watchers and you want to start
723	handling events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
724		792
725	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
727		796
728	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	802	beauty.
734		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
738	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
739		814
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
742	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
743	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
744	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
745	iteration of the loop.	820	iteration of the loop.
746		821
747	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
751		826
752	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
753		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	838	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	849	- Queue all expired timers.
770	- Queue all expired periodics.	850	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	852	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
779		863
780	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	865	anymore.
782		866
783	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
784	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
787		871
788	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
789		873
790	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		878
795	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
796		880
797	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
798		883
799	=item ev_ref (loop)	884	=item ev_ref (loop)
800		885
801	=item ev_unref (loop)	886	=item ev_unref (loop)
802		887
803	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
806		891
807	This is useful when you have a watcher that you never intend to	892	This is useful when you have a watcher that you never intend to
808	unregister, but that nevertheless should not keep C<ev_loop> from	893	unregister, but that nevertheless should not keep C<ev_run> from
809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	895	before stopping it.
811		896
812	As an example, libev itself uses this for its internal signal pipe: It	897	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	898	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	899	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	900	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	901	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	902	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	903	before, respectively. Note also that libev might stop watchers itself
819	(e.g. non-repeating timers) in which case you have to C<ev_ref>	904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	905	in the callback).
821		906
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	908	running when nothing else is active.
824		909
825	ev_signal exitsig;	910	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	913	ev_unref (loop);
829		914
830	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
831		916
832	ev_ref (loop);	917	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
872	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
873	as this approaches the timing granularity of most systems. Note that if	958	as this approaches the timing granularity of most systems. Note that if
874	you do transactions with the outside world and you can't increase the	959	you do transactions with the outside world and you can't increase the
875	parallelity, then this setting will limit your transaction rate (if you	960	parallelity, then this setting will limit your transaction rate (if you
876	need to poll once per transaction and the I/O collect interval is 0.01,	961	need to poll once per transaction and the I/O collect interval is 0.01,
877	then you can't do more than 100 transations per second).	962	then you can't do more than 100 transactions per second).
878		963
879	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
880	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
881	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
882	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		976
892	=item ev_invoke_pending (loop)	977	=item ev_invoke_pending (loop)
893		978
894	This call will simply invoke all pending watchers while resetting their	979	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	980	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		986
898	=item int ev_pending_count (loop)	987	=item int ev_pending_count (loop)
899		988
900	Returns the number of pending watchers - zero indicates that no watchers	989	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	990	are pending.
902		991
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		993
905	This overrides the invoke pending functionality of the loop: Instead of	994	This overrides the invoke pending functionality of the loop: Instead of
906	invoking all pending watchers when there are any, C<ev_loop> will call	995	invoking all pending watchers when there are any, C<ev_run> will call
907	this callback instead. This is useful, for example, when you want to	996	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	997	invoke the actual watchers inside another context (another thread etc.).
909		998
910	If you want to reset the callback, use C<ev_invoke_pending> as new	999	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1000	callback.
…		…
914		1003
915	Sometimes you want to share the same loop between multiple threads. This	1004	Sometimes you want to share the same loop between multiple threads. This
916	can be done relatively simply by putting mutex_lock/unlock calls around	1005	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1006	each call to a libev function.
918		1007
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1008	However, C<ev_run> can run an indefinite time, so it is not feasible
920	wait for it to return. One way around this is to wake up the loop via	1009	to wait for it to return. One way around this is to wake up the event
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1011	I<release> and I<acquire> callbacks on the loop.
923		1012
924	When set, then C<release> will be called just before the thread is	1013	When set, then C<release> will be called just before the thread is
925	suspended waiting for new events, and C<acquire> is called just	1014	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1015	afterwards.
927		1016
…		…
930		1019
931	While event loop modifications are allowed between invocations of	1020	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1021	C<release> and C<acquire> (that's their only purpose after all), no
933	modifications done will affect the event loop, i.e. adding watchers will	1022	modifications done will affect the event loop, i.e. adding watchers will
934	have no effect on the set of file descriptors being watched, or the time	1023	have no effect on the set of file descriptors being watched, or the time
935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
936	to take note of any changes you made.	1025	to take note of any changes you made.
937		1026
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1027	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1028	invocations of C<release> and C<acquire>.
940		1029
941	See also the locking example in the C<THREADS> section later in this	1030	See also the locking example in the C<THREADS> section later in this
942	document.	1031	document.
943		1032
944	=item ev_set_userdata (loop, void *data)	1033	=item ev_set_userdata (loop, void *data)
945		1034
946	=item ev_userdata (loop)	1035	=item void *ev_userdata (loop)
947		1036
948	Set and retrieve a single C<void *> associated with a loop. When	1037	Set and retrieve a single C<void *> associated with a loop. When
949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1039	C<0>.
951		1040
952	These two functions can be used to associate arbitrary data with a loop,	1041	These two functions can be used to associate arbitrary data with a loop,
953	and are intended solely for the C<invoke_pending_cb>, C<release> and	1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
954	C<acquire> callbacks described above, but of course can be (ab-)used for	1043	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1044	any other purpose as well.
956		1045
957	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
958		1047
959	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
962	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
973		1062
974	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
977		1066
978	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
981		1071
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1073	{
984	ev_io_stop (w);	1074	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
986	}	1076	}
987		1077
988	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
989		1079
990	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
991		1081
992	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
995		1085
996	ev_loop (loop, 0);	1086	ev_run (loop, 0);
997		1087
998	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1090	stack).
1001		1091
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1094
1005	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
1007	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
1008	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1099	and/or writable).
1010		1100
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1155
1066	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
1067		1157
1068	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
1069		1159
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
1073	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
1074	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1076	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
1077		1167
1078	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
1079		1169
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1171
1082	=item C<EV_FORK>	1172	=item C<EV_FORK>
1083		1173
1084	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1175	C<ev_fork>).
		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1180
1087	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
1088		1182
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1184
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1358	functions that do not need a watcher.
1265		1359
1266	=back	1360	=back
1267		1361
		1362	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1363	OWN COMPOSITE WATCHERS> idioms.
1268		1364
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1365	=head2 WATCHER STATES
1270		1366
1271	Each watcher has, by default, a member C<void *data> that you can change	1367	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1368	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1369	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1370	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1371
1278	struct my_io	1372	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1373
1286	...	1374	=item initialiased
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1375
1290	And since your callback will be called with a pointer to the watcher, you	1376	Before a watcher can be registered with the event looop it has to be
1291	can cast it back to your own type:	1377	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1378	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1379
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1380	In this state it is simply some block of memory that is suitable for use
1294	{	1381	in an event loop. It can be moved around, freed, reused etc. at will.
1295	struct my_io *w = (struct my_io *)w_;
1296	...
1297	}
1298		1382
1299	More interesting and less C-conformant ways of casting your callback type	1383	=item started/running/active
1300	instead have been omitted.
1301		1384
1302	Another common scenario is to use some data structure with multiple	1385	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1386	property of the event loop, and is actively waiting for events. While in
		1387	this state it cannot be accessed (except in a few documented ways), moved,
		1388	freed or anything else - the only legal thing is to keep a pointer to it,
		1389	and call libev functions on it that are documented to work on active watchers.
1304		1390
1305	struct my_biggy	1391	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1392
1312	In this case getting the pointer to C<my_biggy> is a bit more	1393	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1394	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1395	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1396	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1397	callback.
1317		1398
1318	#include <stddef.h>	1399	The watcher might or might not be active while it is pending (for example,
		1400	an expired non-repeating timer can be pending but no longer active). If it
		1401	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1402	but it is still property of the event loop at this time, so cannot be
		1403	moved, freed or reused. And if it is active the rules described in the
		1404	previous item still apply.
1319		1405
1320	static void	1406	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1407	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1408	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1409
1327	static void	1410	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1411
1329	{	1412	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1413	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1414	latter will clear any pending state the watcher might be in, regardless
1332	}	1415	of whether it was active or not, so stopping a watcher explicitly before
		1416	freeing it is often a good idea.
		1417
		1418	While stopped (and not pending) the watcher is essentially in the
		1419	initialised state, that is it can be reused, moved, modified in any way
		1420	you wish.
		1421
		1422	=back
1333		1423
1334	=head2 WATCHER PRIORITY MODELS	1424	=head2 WATCHER PRIORITY MODELS
1335		1425
1336	Many event loops support I<watcher priorities>, which are usually small	1426	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1427	integers that influence the ordering of event callback invocation
…		…
1380		1470
1381	For example, to emulate how many other event libraries handle priorities,	1471	For example, to emulate how many other event libraries handle priorities,
1382	you can associate an C<ev_idle> watcher to each such watcher, and in	1472	you can associate an C<ev_idle> watcher to each such watcher, and in
1383	the normal watcher callback, you just start the idle watcher. The real	1473	the normal watcher callback, you just start the idle watcher. The real
1384	processing is done in the idle watcher callback. This causes libev to	1474	processing is done in the idle watcher callback. This causes libev to
1385	continously poll and process kernel event data for the watcher, but when	1475	continuously poll and process kernel event data for the watcher, but when
1386	the lock-out case is known to be rare (which in turn is rare :), this is	1476	the lock-out case is known to be rare (which in turn is rare :), this is
1387	workable.	1477	workable.
1388		1478
1389	Usually, however, the lock-out model implemented that way will perform	1479	Usually, however, the lock-out model implemented that way will perform
1390	miserably under the type of load it was designed to handle. In that case,	1480	miserably under the type of load it was designed to handle. In that case,
…		…
1464	In general you can register as many read and/or write event watchers per	1554	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1555	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1556	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1557	required if you know what you are doing).
1468		1558
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarentee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1559	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is, your callback might
1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1478	because there is no data. Not only are some backends known to create a	1562	because there is no data. It is very easy to get into this situation even
1479	lot of those (for example Solaris ports), it is very easy to get into	1563	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1564	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1565	preferable to a program hanging until some data arrives.
1483		1566
1484	If you cannot run the fd in non-blocking mode (for example you should	1567	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1568	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1569	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1570	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1571	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1572	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1573	indefinitely.
1491		1574
1492	But really, best use non-blocking mode.	1575	But really, best use non-blocking mode.
1493		1576
…		…
1521		1604
1522	There is no workaround possible except not registering events	1605	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1606	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1608
		1609	=head3 The special problem of files
		1610
		1611	Many people try to use C<select> (or libev) on file descriptors
		1612	representing files, and expect it to become ready when their program
		1613	doesn't block on disk accesses (which can take a long time on their own).
		1614
		1615	However, this cannot ever work in the "expected" way - you get a readiness
		1616	notification as soon as the kernel knows whether and how much data is
		1617	there, and in the case of open files, that's always the case, so you
		1618	always get a readiness notification instantly, and your read (or possibly
		1619	write) will still block on the disk I/O.
		1620
		1621	Another way to view it is that in the case of sockets, pipes, character
		1622	devices and so on, there is another party (the sender) that delivers data
		1623	on its own, but in the case of files, there is no such thing: the disk
		1624	will not send data on its own, simply because it doesn't know what you
		1625	wish to read - you would first have to request some data.
		1626
		1627	Since files are typically not-so-well supported by advanced notification
		1628	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1629	to files, even though you should not use it. The reason for this is
		1630	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1631	usually a tty, often a pipe, but also sometimes files or special devices
		1632	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1633	F</dev/urandom>), and even though the file might better be served with
		1634	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1635	it "just works" instead of freezing.
		1636
		1637	So avoid file descriptors pointing to files when you know it (e.g. use
		1638	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1639	when you rarely read from a file instead of from a socket, and want to
		1640	reuse the same code path.
		1641
1526	=head3 The special problem of fork	1642	=head3 The special problem of fork
1527		1643
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1644	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1645	useless behaviour. Libev fully supports fork, but needs to be told about
1530	it in the child.	1646	it in the child if you want to continue to use it in the child.
1531		1647
1532	To support fork in your programs, you either have to call	1648	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1649	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1650	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1651
1537	=head3 The special problem of SIGPIPE	1652	=head3 The special problem of SIGPIPE
1538		1653
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1654	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1655	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1737	...
1623	struct ev_loop *loop = ev_default_init (0);	1738	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1739	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1740	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1741	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1742	ev_run (loop, 0);
1628		1743
1629		1744
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1745	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1746
1632	Timer watchers are simple relative timers that generate an event after a	1747	Timer watchers are simple relative timers that generate an event after a
…		…
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1756	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1757	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1758	might introduce a small delay). If multiple timers become ready during the
1644	same loop iteration then the ones with earlier time-out values are invoked	1759	same loop iteration then the ones with earlier time-out values are invoked
1645	before ones of the same priority with later time-out values (but this is	1760	before ones of the same priority with later time-out values (but this is
1646	no longer true when a callback calls C<ev_loop> recursively).	1761	no longer true when a callback calls C<ev_run> recursively).
1647		1762
1648	=head3 Be smart about timeouts	1763	=head3 Be smart about timeouts
1649		1764
1650	Many real-world problems involve some kind of timeout, usually for error	1765	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1766	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1737	ev_tstamp timeout = last_activity + 60.;	1852	ev_tstamp timeout = last_activity + 60.;
1738		1853
1739	// if last_activity + 60. is older than now, we did time out	1854	// if last_activity + 60. is older than now, we did time out
1740	if (timeout < now)	1855	if (timeout < now)
1741	{	1856	{
1742	// timeout occured, take action	1857	// timeout occurred, take action
1743	}	1858	}
1744	else	1859	else
1745	{	1860	{
1746	// callback was invoked, but there was some activity, re-arm	1861	// callback was invoked, but there was some activity, re-arm
1747	// the watcher to fire in last_activity + 60, which is	1862	// the watcher to fire in last_activity + 60, which is
…		…
1822		1937
1823	=head3 The special problem of time updates	1938	=head3 The special problem of time updates
1824		1939
1825	Establishing the current time is a costly operation (it usually takes at	1940	Establishing the current time is a costly operation (it usually takes at
1826	least two system calls): EV therefore updates its idea of the current	1941	least two system calls): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	1942	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1943	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	1944	lots of events in one iteration.
1830		1945
1831	The relative timeouts are calculated relative to the C<ev_now ()>	1946	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	1947	time. This is usually the right thing as this timestamp refers to the time
…		…
1949	}	2064	}
1950		2065
1951	ev_timer mytimer;	2066	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2067	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2068	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2069	ev_run (loop, 0);
1955		2070
1956	// and in some piece of code that gets executed on any "activity":	2071	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2072	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2073	ev_timer_again (&mytimer);
1959		2074
…		…
1985		2100
1986	As with timers, the callback is guaranteed to be invoked only when the	2101	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2102	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2103	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2104	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2105	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2106
1992	=head3 Watcher-Specific Functions and Data Members	2107	=head3 Watcher-Specific Functions and Data Members
1993		2108
1994	=over 4	2109	=over 4
1995		2110
…		…
2123	Example: Call a callback every hour, or, more precisely, whenever the	2238	Example: Call a callback every hour, or, more precisely, whenever the
2124	system time is divisible by 3600. The callback invocation times have	2239	system time is divisible by 3600. The callback invocation times have
2125	potentially a lot of jitter, but good long-term stability.	2240	potentially a lot of jitter, but good long-term stability.
2126		2241
2127	static void	2242	static void
2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2243	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2129	{	2244	{
2130	... its now a full hour (UTC, or TAI or whatever your clock follows)	2245	... its now a full hour (UTC, or TAI or whatever your clock follows)
2131	}	2246	}
2132		2247
2133	ev_periodic hourly_tick;	2248	ev_periodic hourly_tick;
…		…
2156		2271
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2272	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2273
2159	Signal watchers will trigger an event when the process receives a specific	2274	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2275	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2276	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2277	normal event processing, like any other event.
2163		2278
2164	If you want signals to be delivered truly asynchronously, just use	2279	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2280	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2281	the signal. You can even use C<ev_async> from a signal handler to
…		…
2209		2324
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2325	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2326	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2327	is not a libev-specific thing, this is true for most event libraries.
2213		2328
		2329	=head3 The special problem of threads signal handling
		2330
		2331	POSIX threads has problematic signal handling semantics, specifically,
		2332	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2333	threads in a process block signals, which is hard to achieve.
		2334
		2335	When you want to use sigwait (or mix libev signal handling with your own
		2336	for the same signals), you can tackle this problem by globally blocking
		2337	all signals before creating any threads (or creating them with a fully set
		2338	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2339	loops. Then designate one thread as "signal receiver thread" which handles
		2340	these signals. You can pass on any signals that libev might be interested
		2341	in by calling C<ev_feed_signal>.
		2342
2214	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
2215		2344
2216	=over 4	2345	=over 4
2217		2346
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2347	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2362	Example: Try to exit cleanly on SIGINT.
2234		2363
2235	static void	2364	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2365	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2366	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2367	ev_break (loop, EVBREAK_ALL);
2239	}	2368	}
2240		2369
2241	ev_signal signal_watcher;	2370	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2371	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2372	ev_signal_start (loop, &signal_watcher);
…		…
2629		2758
2630	Prepare and check watchers are usually (but not always) used in pairs:	2759	Prepare and check watchers are usually (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2760	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2761	afterwards.
2633		2762
2634	You I<must not> call C<ev_loop> or similar functions that enter	2763	You I<must not> call C<ev_run> or similar functions that enter
2635	the current event loop from either C<ev_prepare> or C<ev_check>	2764	the current event loop from either C<ev_prepare> or C<ev_check>
2636	watchers. Other loops than the current one are fine, however. The	2765	watchers. Other loops than the current one are fine, however. The
2637	rationale behind this is that you do not need to check for recursion in	2766	rationale behind this is that you do not need to check for recursion in
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2767	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2639	C<ev_check> so if you have one watcher of each kind they will always be	2768	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2807		2936
2808	if (timeout >= 0)	2937	if (timeout >= 0)
2809	// create/start timer	2938	// create/start timer
2810		2939
2811	// poll	2940	// poll
2812	ev_loop (EV_A_ 0);	2941	ev_run (EV_A_ 0);
2813		2942
2814	// stop timer again	2943	// stop timer again
2815	if (timeout >= 0)	2944	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	2945	ev_timer_stop (EV_A_ &to);
2817		2946
…		…
2895	if you do not want that, you need to temporarily stop the embed watcher).	3024	if you do not want that, you need to temporarily stop the embed watcher).
2896		3025
2897	=item ev_embed_sweep (loop, ev_embed *)	3026	=item ev_embed_sweep (loop, ev_embed *)
2898		3027
2899	Make a single, non-blocking sweep over the embedded loop. This works	3028	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3029	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3030	appropriate way for embedded loops.
2902		3031
2903	=item struct ev_loop *other [read-only]	3032	=item struct ev_loop *other [read-only]
2904		3033
2905	The embedded event loop.	3034	The embedded event loop.
…		…
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3094	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2966	handlers will be invoked, too, of course.	3095	handlers will be invoked, too, of course.
2967		3096
2968	=head3 The special problem of life after fork - how is it possible?	3097	=head3 The special problem of life after fork - how is it possible?
2969		3098
2970	Most uses of C<fork()> consist of forking, then some simple calls to ste	3099	Most uses of C<fork()> consist of forking, then some simple calls to set
2971	up/change the process environment, followed by a call to C<exec()>. This	3100	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3101	sequence should be handled by libev without any problems.
2973		3102
2974	This changes when the application actually wants to do event handling	3103	This changes when the application actually wants to do event handling
2975	in the child, or both parent in child, in effect "continuing" after the	3104	in the child, or both parent in child, in effect "continuing" after the
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3120	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3121	signal watchers).
2993		3122
2994	When this is not possible, or you want to use the default loop for	3123	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3124	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3125	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3126	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3127	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3128	those watchers. Note also that in that case, you have to re-register any
		3129	signal watchers.
3000		3130
3001	=head3 Watcher-Specific Functions and Data Members	3131	=head3 Watcher-Specific Functions and Data Members
3002		3132
3003	=over 4	3133	=over 4
3004		3134
3005	=item ev_fork_init (ev_signal *, callback)	3135	=item ev_fork_init (ev_fork *, callback)
3006		3136
3007	Initialises and configures the fork watcher - it has no parameters of any	3137	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3138	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3139	really.
3010		3140
3011	=back	3141	=back
3012		3142
3013		3143
		3144	=head2 C<ev_cleanup> - even the best things end
		3145
		3146	Cleanup watchers are called just before the event loop is being destroyed
		3147	by a call to C<ev_loop_destroy>.
		3148
		3149	While there is no guarantee that the event loop gets destroyed, cleanup
		3150	watchers provide a convenient method to install cleanup hooks for your
		3151	program, worker threads and so on - you just to make sure to destroy the
		3152	loop when you want them to be invoked.
		3153
		3154	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3155	all other watchers, they do not keep a reference to the event loop (which
		3156	makes a lot of sense if you think about it). Like all other watchers, you
		3157	can call libev functions in the callback, except C<ev_cleanup_start>.
		3158
		3159	=head3 Watcher-Specific Functions and Data Members
		3160
		3161	=over 4
		3162
		3163	=item ev_cleanup_init (ev_cleanup *, callback)
		3164
		3165	Initialises and configures the cleanup watcher - it has no parameters of
		3166	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3167	pointless, I assure you.
		3168
		3169	=back
		3170
		3171	Example: Register an atexit handler to destroy the default loop, so any
		3172	cleanup functions are called.
		3173
		3174	static void
		3175	program_exits (void)
		3176	{
		3177	ev_loop_destroy (EV_DEFAULT_UC);
		3178	}
		3179
		3180	...
		3181	atexit (program_exits);
		3182
		3183
3014	=head2 C<ev_async> - how to wake up another event loop	3184	=head2 C<ev_async> - how to wake up an event loop
3015		3185
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3186	In general, you cannot use an C<ev_run> from multiple threads or other
3017	asynchronous sources such as signal handlers (as opposed to multiple event	3187	asynchronous sources such as signal handlers (as opposed to multiple event
3018	loops - those are of course safe to use in different threads).	3188	loops - those are of course safe to use in different threads).
3019		3189
3020	Sometimes, however, you need to wake up another event loop you do not	3190	Sometimes, however, you need to wake up an event loop you do not control,
3021	control, for example because it belongs to another thread. This is what	3191	for example because it belongs to another thread. This is what C<ev_async>
3022	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3192	watchers do: as long as the C<ev_async> watcher is active, you can signal
3023	can signal it by calling C<ev_async_send>, which is thread- and signal	3193	it by calling C<ev_async_send>, which is thread- and signal safe.
3024	safe.
3025		3194
3026	This functionality is very similar to C<ev_signal> watchers, as signals,	3195	This functionality is very similar to C<ev_signal> watchers, as signals,
3027	too, are asynchronous in nature, and signals, too, will be compressed	3196	too, are asynchronous in nature, and signals, too, will be compressed
3028	(i.e. the number of callback invocations may be less than the number of	3197	(i.e. the number of callback invocations may be less than the number of
3029	C<ev_async_sent> calls).	3198	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3199	of "global async watchers" by using a watcher on an otherwise unused
		3200	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3201	even without knowing which loop owns the signal.
3030		3202
3031	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3203	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3032	just the default loop.	3204	just the default loop.
3033		3205
3034	=head3 Queueing	3206	=head3 Queueing
…		…
3210	Feed an event on the given fd, as if a file descriptor backend detected	3382	Feed an event on the given fd, as if a file descriptor backend detected
3211	the given events it.	3383	the given events it.
3212		3384
3213	=item ev_feed_signal_event (loop, int signum)	3385	=item ev_feed_signal_event (loop, int signum)
3214		3386
3215	Feed an event as if the given signal occurred (C<loop> must be the default	3387	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3216	loop!).	3388	which is async-safe.
3217		3389
3218	=back	3390	=back
		3391
		3392
		3393	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3394
		3395	This section explains some common idioms that are not immediately
		3396	obvious. Note that examples are sprinkled over the whole manual, and this
		3397	section only contains stuff that wouldn't fit anywhere else.
		3398
		3399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3400
		3401	Each watcher has, by default, a C<void *data> member that you can read
		3402	or modify at any time: libev will completely ignore it. This can be used
		3403	to associate arbitrary data with your watcher. If you need more data and
		3404	don't want to allocate memory separately and store a pointer to it in that
		3405	data member, you can also "subclass" the watcher type and provide your own
		3406	data:
		3407
		3408	struct my_io
		3409	{
		3410	ev_io io;
		3411	int otherfd;
		3412	void *somedata;
		3413	struct whatever *mostinteresting;
		3414	};
		3415
		3416	...
		3417	struct my_io w;
		3418	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3419
		3420	And since your callback will be called with a pointer to the watcher, you
		3421	can cast it back to your own type:
		3422
		3423	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3424	{
		3425	struct my_io *w = (struct my_io *)w_;
		3426	...
		3427	}
		3428
		3429	More interesting and less C-conformant ways of casting your callback
		3430	function type instead have been omitted.
		3431
		3432	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3433
		3434	Another common scenario is to use some data structure with multiple
		3435	embedded watchers, in effect creating your own watcher that combines
		3436	multiple libev event sources into one "super-watcher":
		3437
		3438	struct my_biggy
		3439	{
		3440	int some_data;
		3441	ev_timer t1;
		3442	ev_timer t2;
		3443	}
		3444
		3445	In this case getting the pointer to C<my_biggy> is a bit more
		3446	complicated: Either you store the address of your C<my_biggy> struct in
		3447	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3448	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3449	real programmers):
		3450
		3451	#include <stddef.h>
		3452
		3453	static void
		3454	t1_cb (EV_P_ ev_timer *w, int revents)
		3455	{
		3456	struct my_biggy big = (struct my_biggy *)
		3457	(((char *)w) - offsetof (struct my_biggy, t1));
		3458	}
		3459
		3460	static void
		3461	t2_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t2));
		3465	}
		3466
		3467	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3468
		3469	Often (especially in GUI toolkits) there are places where you have
		3470	I<modal> interaction, which is most easily implemented by recursively
		3471	invoking C<ev_run>.
		3472
		3473	This brings the problem of exiting - a callback might want to finish the
		3474	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3475	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3476	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3477	other combination: In these cases, C<ev_break> will not work alone.
		3478
		3479	The solution is to maintain "break this loop" variable for each C<ev_run>
		3480	invocation, and use a loop around C<ev_run> until the condition is
		3481	triggered, using C<EVRUN_ONCE>:
		3482
		3483	// main loop
		3484	int exit_main_loop = 0;
		3485
		3486	while (!exit_main_loop)
		3487	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3488
		3489	// in a model watcher
		3490	int exit_nested_loop = 0;
		3491
		3492	while (!exit_nested_loop)
		3493	ev_run (EV_A_ EVRUN_ONCE);
		3494
		3495	To exit from any of these loops, just set the corresponding exit variable:
		3496
		3497	// exit modal loop
		3498	exit_nested_loop = 1;
		3499
		3500	// exit main program, after modal loop is finished
		3501	exit_main_loop = 1;
		3502
		3503	// exit both
		3504	exit_main_loop = exit_nested_loop = 1;
		3505
		3506	=head2 THREAD LOCKING EXAMPLE
		3507
		3508	Here is a fictitious example of how to run an event loop in a different
		3509	thread than where callbacks are being invoked and watchers are
		3510	created/added/removed.
		3511
		3512	For a real-world example, see the C<EV::Loop::Async> perl module,
		3513	which uses exactly this technique (which is suited for many high-level
		3514	languages).
		3515
		3516	The example uses a pthread mutex to protect the loop data, a condition
		3517	variable to wait for callback invocations, an async watcher to notify the
		3518	event loop thread and an unspecified mechanism to wake up the main thread.
		3519
		3520	First, you need to associate some data with the event loop:
		3521
		3522	typedef struct {
		3523	mutex_t lock; /* global loop lock */
		3524	ev_async async_w;
		3525	thread_t tid;
		3526	cond_t invoke_cv;
		3527	} userdata;
		3528
		3529	void prepare_loop (EV_P)
		3530	{
		3531	// for simplicity, we use a static userdata struct.
		3532	static userdata u;
		3533
		3534	ev_async_init (&u->async_w, async_cb);
		3535	ev_async_start (EV_A_ &u->async_w);
		3536
		3537	pthread_mutex_init (&u->lock, 0);
		3538	pthread_cond_init (&u->invoke_cv, 0);
		3539
		3540	// now associate this with the loop
		3541	ev_set_userdata (EV_A_ u);
		3542	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3543	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3544
		3545	// then create the thread running ev_loop
		3546	pthread_create (&u->tid, 0, l_run, EV_A);
		3547	}
		3548
		3549	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3550	solely to wake up the event loop so it takes notice of any new watchers
		3551	that might have been added:
		3552
		3553	static void
		3554	async_cb (EV_P_ ev_async *w, int revents)
		3555	{
		3556	// just used for the side effects
		3557	}
		3558
		3559	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3560	protecting the loop data, respectively.
		3561
		3562	static void
		3563	l_release (EV_P)
		3564	{
		3565	userdata *u = ev_userdata (EV_A);
		3566	pthread_mutex_unlock (&u->lock);
		3567	}
		3568
		3569	static void
		3570	l_acquire (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_lock (&u->lock);
		3574	}
		3575
		3576	The event loop thread first acquires the mutex, and then jumps straight
		3577	into C<ev_run>:
		3578
		3579	void *
		3580	l_run (void *thr_arg)
		3581	{
		3582	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3583
		3584	l_acquire (EV_A);
		3585	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3586	ev_run (EV_A_ 0);
		3587	l_release (EV_A);
		3588
		3589	return 0;
		3590	}
		3591
		3592	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3593	signal the main thread via some unspecified mechanism (signals? pipe
		3594	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3595	have been called (in a while loop because a) spurious wakeups are possible
		3596	and b) skipping inter-thread-communication when there are no pending
		3597	watchers is very beneficial):
		3598
		3599	static void
		3600	l_invoke (EV_P)
		3601	{
		3602	userdata *u = ev_userdata (EV_A);
		3603
		3604	while (ev_pending_count (EV_A))
		3605	{
		3606	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3607	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3608	}
		3609	}
		3610
		3611	Now, whenever the main thread gets told to invoke pending watchers, it
		3612	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3613	thread to continue:
		3614
		3615	static void
		3616	real_invoke_pending (EV_P)
		3617	{
		3618	userdata *u = ev_userdata (EV_A);
		3619
		3620	pthread_mutex_lock (&u->lock);
		3621	ev_invoke_pending (EV_A);
		3622	pthread_cond_signal (&u->invoke_cv);
		3623	pthread_mutex_unlock (&u->lock);
		3624	}
		3625
		3626	Whenever you want to start/stop a watcher or do other modifications to an
		3627	event loop, you will now have to lock:
		3628
		3629	ev_timer timeout_watcher;
		3630	userdata *u = ev_userdata (EV_A);
		3631
		3632	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_timer_start (EV_A_ &timeout_watcher);
		3636	ev_async_send (EV_A_ &u->async_w);
		3637	pthread_mutex_unlock (&u->lock);
		3638
		3639	Note that sending the C<ev_async> watcher is required because otherwise
		3640	an event loop currently blocking in the kernel will have no knowledge
		3641	about the newly added timer. By waking up the loop it will pick up any new
		3642	watchers in the next event loop iteration.
		3643
		3644	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3645
		3646	While the overhead of a callback that e.g. schedules a thread is small, it
		3647	is still an overhead. If you embed libev, and your main usage is with some
		3648	kind of threads or coroutines, you might want to customise libev so that
		3649	doesn't need callbacks anymore.
		3650
		3651	Imagine you have coroutines that you can switch to using a function
		3652	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3653	and that due to some magic, the currently active coroutine is stored in a
		3654	global called C<current_coro>. Then you can build your own "wait for libev
		3655	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3656	the differing C<;> conventions):
		3657
		3658	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3659	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3660
		3661	That means instead of having a C callback function, you store the
		3662	coroutine to switch to in each watcher, and instead of having libev call
		3663	your callback, you instead have it switch to that coroutine.
		3664
		3665	A coroutine might now wait for an event with a function called
		3666	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3667	matter when, or whether the watcher is active or not when this function is
		3668	called):
		3669
		3670	void
		3671	wait_for_event (ev_watcher *w)
		3672	{
		3673	ev_cb_set (w) = current_coro;
		3674	switch_to (libev_coro);
		3675	}
		3676
		3677	That basically suspends the coroutine inside C<wait_for_event> and
		3678	continues the libev coroutine, which, when appropriate, switches back to
		3679	this or any other coroutine. I am sure if you sue this your own :)
		3680
		3681	You can do similar tricks if you have, say, threads with an event queue -
		3682	instead of storing a coroutine, you store the queue object and instead of
		3683	switching to a coroutine, you push the watcher onto the queue and notify
		3684	any waiters.
		3685
		3686	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3687	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3688
		3689	// my_ev.h
		3690	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3691	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3692	#include "../libev/ev.h"
		3693
		3694	// my_ev.c
		3695	#define EV_H "my_ev.h"
		3696	#include "../libev/ev.c"
		3697
		3698	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3699	F<my_ev.c> into your project. When properly specifying include paths, you
		3700	can even use F<ev.h> as header file name directly.
3219		3701
3220		3702
3221	=head1 LIBEVENT EMULATION	3703	=head1 LIBEVENT EMULATION
3222		3704
3223	Libev offers a compatibility emulation layer for libevent. It cannot	3705	Libev offers a compatibility emulation layer for libevent. It cannot
3224	emulate the internals of libevent, so here are some usage hints:	3706	emulate the internals of libevent, so here are some usage hints:
3225		3707
3226	=over 4	3708	=over 4
		3709
		3710	=item * Only the libevent-1.4.1-beta API is being emulated.
		3711
		3712	This was the newest libevent version available when libev was implemented,
		3713	and is still mostly unchanged in 2010.
3227		3714
3228	=item * Use it by including <event.h>, as usual.	3715	=item * Use it by including <event.h>, as usual.
3229		3716
3230	=item * The following members are fully supported: ev_base, ev_callback,	3717	=item * The following members are fully supported: ev_base, ev_callback,
3231	ev_arg, ev_fd, ev_res, ev_events.	3718	ev_arg, ev_fd, ev_res, ev_events.
…		…
3237	=item * Priorities are not currently supported. Initialising priorities	3724	=item * Priorities are not currently supported. Initialising priorities
3238	will fail and all watchers will have the same priority, even though there	3725	will fail and all watchers will have the same priority, even though there
3239	is an ev_pri field.	3726	is an ev_pri field.
3240		3727
3241	=item * In libevent, the last base created gets the signals, in libev, the	3728	=item * In libevent, the last base created gets the signals, in libev, the
3242	first base created (== the default loop) gets the signals.	3729	base that registered the signal gets the signals.
3243		3730
3244	=item * Other members are not supported.	3731	=item * Other members are not supported.
3245		3732
3246	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3733	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3247	to use the libev header file and library.	3734	to use the libev header file and library.
…		…
3266	Care has been taken to keep the overhead low. The only data member the C++	3753	Care has been taken to keep the overhead low. The only data member the C++
3267	classes add (compared to plain C-style watchers) is the event loop pointer	3754	classes add (compared to plain C-style watchers) is the event loop pointer
3268	that the watcher is associated with (or no additional members at all if	3755	that the watcher is associated with (or no additional members at all if
3269	you disable C<EV_MULTIPLICITY> when embedding libev).	3756	you disable C<EV_MULTIPLICITY> when embedding libev).
3270		3757
3271	Currently, functions, and static and non-static member functions can be	3758	Currently, functions, static and non-static member functions and classes
3272	used as callbacks. Other types should be easy to add as long as they only	3759	with C<operator ()> can be used as callbacks. Other types should be easy
3273	need one additional pointer for context. If you need support for other	3760	to add as long as they only need one additional pointer for context. If
3274	types of functors please contact the author (preferably after implementing	3761	you need support for other types of functors please contact the author
3275	it).	3762	(preferably after implementing it).
3276		3763
3277	Here is a list of things available in the C<ev> namespace:	3764	Here is a list of things available in the C<ev> namespace:
3278		3765
3279	=over 4	3766	=over 4
3280		3767
…		…
3341	myclass obj;	3828	myclass obj;
3342	ev::io iow;	3829	ev::io iow;
3343	iow.set <myclass, &myclass::io_cb> (&obj);	3830	iow.set <myclass, &myclass::io_cb> (&obj);
3344		3831
3345	=item w->set (object *)	3832	=item w->set (object *)
3346
3347	This is an B<experimental> feature that might go away in a future version.
3348		3833
3349	This is a variation of a method callback - leaving out the method to call	3834	This is a variation of a method callback - leaving out the method to call
3350	will default the method to C<operator ()>, which makes it possible to use	3835	will default the method to C<operator ()>, which makes it possible to use
3351	functor objects without having to manually specify the C<operator ()> all	3836	functor objects without having to manually specify the C<operator ()> all
3352	the time. Incidentally, you can then also leave out the template argument	3837	the time. Incidentally, you can then also leave out the template argument
…		…
3392	Associates a different C<struct ev_loop> with this watcher. You can only	3877	Associates a different C<struct ev_loop> with this watcher. You can only
3393	do this when the watcher is inactive (and not pending either).	3878	do this when the watcher is inactive (and not pending either).
3394		3879
3395	=item w->set ([arguments])	3880	=item w->set ([arguments])
3396		3881
3397	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3882	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3398	called at least once. Unlike the C counterpart, an active watcher gets	3883	method or a suitable start method must be called at least once. Unlike the
3399	automatically stopped and restarted when reconfiguring it with this	3884	C counterpart, an active watcher gets automatically stopped and restarted
3400	method.	3885	when reconfiguring it with this method.
3401		3886
3402	=item w->start ()	3887	=item w->start ()
3403		3888
3404	Starts the watcher. Note that there is no C<loop> argument, as the	3889	Starts the watcher. Note that there is no C<loop> argument, as the
3405	constructor already stores the event loop.	3890	constructor already stores the event loop.
3406		3891
		3892	=item w->start ([arguments])
		3893
		3894	Instead of calling C<set> and C<start> methods separately, it is often
		3895	convenient to wrap them in one call. Uses the same type of arguments as
		3896	the configure C<set> method of the watcher.
		3897
3407	=item w->stop ()	3898	=item w->stop ()
3408		3899
3409	Stops the watcher if it is active. Again, no C<loop> argument.	3900	Stops the watcher if it is active. Again, no C<loop> argument.
3410		3901
3411	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3902	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3423		3914
3424	=back	3915	=back
3425		3916
3426	=back	3917	=back
3427		3918
3428	Example: Define a class with an IO and idle watcher, start one of them in	3919	Example: Define a class with two I/O and idle watchers, start the I/O
3429	the constructor.	3920	watchers in the constructor.
3430		3921
3431	class myclass	3922	class myclass
3432	{	3923	{
3433	ev::io io ; void io_cb (ev::io &w, int revents);	3924	ev::io io ; void io_cb (ev::io &w, int revents);
		3925	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3434	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3926	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3435		3927
3436	myclass (int fd)	3928	myclass (int fd)
3437	{	3929	{
3438	io .set <myclass, &myclass::io_cb > (this);	3930	io .set <myclass, &myclass::io_cb > (this);
		3931	io2 .set <myclass, &myclass::io2_cb > (this);
3439	idle.set <myclass, &myclass::idle_cb> (this);	3932	idle.set <myclass, &myclass::idle_cb> (this);
3440		3933
3441	io.start (fd, ev::READ);	3934	io.set (fd, ev::WRITE); // configure the watcher
		3935	io.start (); // start it whenever convenient
		3936
		3937	io2.start (fd, ev::READ); // set + start in one call
3442	}	3938	}
3443	};	3939	};
3444		3940
3445		3941
3446	=head1 OTHER LANGUAGE BINDINGS	3942	=head1 OTHER LANGUAGE BINDINGS
…		…
3520	loop argument"). The C<EV_A> form is used when this is the sole argument,	4016	loop argument"). The C<EV_A> form is used when this is the sole argument,
3521	C<EV_A_> is used when other arguments are following. Example:	4017	C<EV_A_> is used when other arguments are following. Example:
3522		4018
3523	ev_unref (EV_A);	4019	ev_unref (EV_A);
3524	ev_timer_add (EV_A_ watcher);	4020	ev_timer_add (EV_A_ watcher);
3525	ev_loop (EV_A_ 0);	4021	ev_run (EV_A_ 0);
3526		4022
3527	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4023	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3528	which is often provided by the following macro.	4024	which is often provided by the following macro.
3529		4025
3530	=item C<EV_P>, C<EV_P_>	4026	=item C<EV_P>, C<EV_P_>
…		…
3570	}	4066	}
3571		4067
3572	ev_check check;	4068	ev_check check;
3573	ev_check_init (&check, check_cb);	4069	ev_check_init (&check, check_cb);
3574	ev_check_start (EV_DEFAULT_ &check);	4070	ev_check_start (EV_DEFAULT_ &check);
3575	ev_loop (EV_DEFAULT_ 0);	4071	ev_run (EV_DEFAULT_ 0);
3576		4072
3577	=head1 EMBEDDING	4073	=head1 EMBEDDING
3578		4074
3579	Libev can (and often is) directly embedded into host	4075	Libev can (and often is) directly embedded into host
3580	applications. Examples of applications that embed it include the Deliantra	4076	applications. Examples of applications that embed it include the Deliantra
…		…
3671	to a compiled library. All other symbols change the ABI, which means all	4167	to a compiled library. All other symbols change the ABI, which means all
3672	users of libev and the libev code itself must be compiled with compatible	4168	users of libev and the libev code itself must be compiled with compatible
3673	settings.	4169	settings.
3674		4170
3675	=over 4	4171	=over 4
		4172
		4173	=item EV_COMPAT3 (h)
		4174
		4175	Backwards compatibility is a major concern for libev. This is why this
		4176	release of libev comes with wrappers for the functions and symbols that
		4177	have been renamed between libev version 3 and 4.
		4178
		4179	You can disable these wrappers (to test compatibility with future
		4180	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4181	sources. This has the additional advantage that you can drop the C<struct>
		4182	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4183	typedef in that case.
		4184
		4185	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4186	and in some even more future version the compatibility code will be
		4187	removed completely.
3676		4188
3677	=item EV_STANDALONE (h)	4189	=item EV_STANDALONE (h)
3678		4190
3679	Must always be C<1> if you do not use autoconf configuration, which	4191	Must always be C<1> if you do not use autoconf configuration, which
3680	keeps libev from including F<config.h>, and it also defines dummy	4192	keeps libev from including F<config.h>, and it also defines dummy
…		…
3887	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4399	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3888	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4400	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3889		4401
3890	If undefined or defined to be C<1> (and the platform supports it), then	4402	If undefined or defined to be C<1> (and the platform supports it), then
3891	the respective watcher type is supported. If defined to be C<0>, then it	4403	the respective watcher type is supported. If defined to be C<0>, then it
3892	is not. Disabling watcher types mainly saves codesize.	4404	is not. Disabling watcher types mainly saves code size.
3893		4405
3894	=item EV_FEATURES	4406	=item EV_FEATURES
3895		4407
3896	If you need to shave off some kilobytes of code at the expense of some	4408	If you need to shave off some kilobytes of code at the expense of some
3897	speed (but with the full API), you can define this symbol to request	4409	speed (but with the full API), you can define this symbol to request
…		…
3917		4429
3918	=item C<1> - faster/larger code	4430	=item C<1> - faster/larger code
3919		4431
3920	Use larger code to speed up some operations.	4432	Use larger code to speed up some operations.
3921		4433
3922	Currently this is used to override some inlining decisions (enlarging the roughly	4434	Currently this is used to override some inlining decisions (enlarging the
3923	30% code size on amd64.	4435	code size by roughly 30% on amd64).
3924		4436
3925	When optimising for size, use of compiler flags such as C<-Os> with	4437	When optimising for size, use of compiler flags such as C<-Os> with
3926	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4438	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3927	assertions.	4439	assertions.
3928		4440
3929	=item C<2> - faster/larger data structures	4441	=item C<2> - faster/larger data structures
3930		4442
3931	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4443	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3932	hash table sizes and so on. This will usually further increase codesize	4444	hash table sizes and so on. This will usually further increase code size
3933	and can additionally have an effect on the size of data structures at	4445	and can additionally have an effect on the size of data structures at
3934	runtime.	4446	runtime.
3935		4447
3936	=item C<4> - full API configuration	4448	=item C<4> - full API configuration
3937		4449
…		…
3974	I/O watcher then might come out at only 5Kb.	4486	I/O watcher then might come out at only 5Kb.
3975		4487
3976	=item EV_AVOID_STDIO	4488	=item EV_AVOID_STDIO
3977		4489
3978	If this is set to C<1> at compiletime, then libev will avoid using stdio	4490	If this is set to C<1> at compiletime, then libev will avoid using stdio
3979	functions (printf, scanf, perror etc.). This will increase the codesize	4491	functions (printf, scanf, perror etc.). This will increase the code size
3980	somewhat, but if your program doesn't otherwise depend on stdio and your	4492	somewhat, but if your program doesn't otherwise depend on stdio and your
3981	libc allows it, this avoids linking in the stdio library which is quite	4493	libc allows it, this avoids linking in the stdio library which is quite
3982	big.	4494	big.
3983		4495
3984	Note that error messages might become less precise when this option is	4496	Note that error messages might become less precise when this option is
…		…
3988		4500
3989	The highest supported signal number, +1 (or, the number of	4501	The highest supported signal number, +1 (or, the number of
3990	signals): Normally, libev tries to deduce the maximum number of signals	4502	signals): Normally, libev tries to deduce the maximum number of signals
3991	automatically, but sometimes this fails, in which case it can be	4503	automatically, but sometimes this fails, in which case it can be
3992	specified. Also, using a lower number than detected (C<32> should be	4504	specified. Also, using a lower number than detected (C<32> should be
3993	good for about any system in existance) can save some memory, as libev	4505	good for about any system in existence) can save some memory, as libev
3994	statically allocates some 12-24 bytes per signal number.	4506	statically allocates some 12-24 bytes per signal number.
3995		4507
3996	=item EV_PID_HASHSIZE	4508	=item EV_PID_HASHSIZE
3997		4509
3998	C<ev_child> watchers use a small hash table to distribute workload by	4510	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4030	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4542	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4031	will be C<0>.	4543	will be C<0>.
4032		4544
4033	=item EV_VERIFY	4545	=item EV_VERIFY
4034		4546
4035	Controls how much internal verification (see C<ev_loop_verify ()>) will	4547	Controls how much internal verification (see C<ev_verify ()>) will
4036	be done: If set to C<0>, no internal verification code will be compiled	4548	be done: If set to C<0>, no internal verification code will be compiled
4037	in. If set to C<1>, then verification code will be compiled in, but not	4549	in. If set to C<1>, then verification code will be compiled in, but not
4038	called. If set to C<2>, then the internal verification code will be	4550	called. If set to C<2>, then the internal verification code will be
4039	called once per loop, which can slow down libev. If set to C<3>, then the	4551	called once per loop, which can slow down libev. If set to C<3>, then the
4040	verification code will be called very frequently, which will slow down	4552	verification code will be called very frequently, which will slow down
…		…
4044	will be C<0>.	4556	will be C<0>.
4045		4557
4046	=item EV_COMMON	4558	=item EV_COMMON
4047		4559
4048	By default, all watchers have a C<void *data> member. By redefining	4560	By default, all watchers have a C<void *data> member. By redefining
4049	this macro to a something else you can include more and other types of	4561	this macro to something else you can include more and other types of
4050	members. You have to define it each time you include one of the files,	4562	members. You have to define it each time you include one of the files,
4051	though, and it must be identical each time.	4563	though, and it must be identical each time.
4052		4564
4053	For example, the perl EV module uses something like this:	4565	For example, the perl EV module uses something like this:
4054		4566
…		…
4123	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4635	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4124		4636
4125	#include "ev_cpp.h"	4637	#include "ev_cpp.h"
4126	#include "ev.c"	4638	#include "ev.c"
4127		4639
4128	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4640	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4129		4641
4130	=head2 THREADS AND COROUTINES	4642	=head2 THREADS AND COROUTINES
4131		4643
4132	=head3 THREADS	4644	=head3 THREADS
4133		4645
…		…
4184	default loop and triggering an C<ev_async> watcher from the default loop	4696	default loop and triggering an C<ev_async> watcher from the default loop
4185	watcher callback into the event loop interested in the signal.	4697	watcher callback into the event loop interested in the signal.
4186		4698
4187	=back	4699	=back
4188		4700
4189	=head4 THREAD LOCKING EXAMPLE	4701	See also L<THREAD LOCKING EXAMPLE>.
4190
4191	Here is a fictitious example of how to run an event loop in a different
4192	thread than where callbacks are being invoked and watchers are
4193	created/added/removed.
4194
4195	For a real-world example, see the C<EV::Loop::Async> perl module,
4196	which uses exactly this technique (which is suited for many high-level
4197	languages).
4198
4199	The example uses a pthread mutex to protect the loop data, a condition
4200	variable to wait for callback invocations, an async watcher to notify the
4201	event loop thread and an unspecified mechanism to wake up the main thread.
4202
4203	First, you need to associate some data with the event loop:
4204
4205	typedef struct {
4206	mutex_t lock; /* global loop lock */
4207	ev_async async_w;
4208	thread_t tid;
4209	cond_t invoke_cv;
4210	} userdata;
4211
4212	void prepare_loop (EV_P)
4213	{
4214	// for simplicity, we use a static userdata struct.
4215	static userdata u;
4216
4217	ev_async_init (&u->async_w, async_cb);
4218	ev_async_start (EV_A_ &u->async_w);
4219
4220	pthread_mutex_init (&u->lock, 0);
4221	pthread_cond_init (&u->invoke_cv, 0);
4222
4223	// now associate this with the loop
4224	ev_set_userdata (EV_A_ u);
4225	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4226	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4227
4228	// then create the thread running ev_loop
4229	pthread_create (&u->tid, 0, l_run, EV_A);
4230	}
4231
4232	The callback for the C<ev_async> watcher does nothing: the watcher is used
4233	solely to wake up the event loop so it takes notice of any new watchers
4234	that might have been added:
4235
4236	static void
4237	async_cb (EV_P_ ev_async *w, int revents)
4238	{
4239	// just used for the side effects
4240	}
4241
4242	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4243	protecting the loop data, respectively.
4244
4245	static void
4246	l_release (EV_P)
4247	{
4248	userdata *u = ev_userdata (EV_A);
4249	pthread_mutex_unlock (&u->lock);
4250	}
4251
4252	static void
4253	l_acquire (EV_P)
4254	{
4255	userdata *u = ev_userdata (EV_A);
4256	pthread_mutex_lock (&u->lock);
4257	}
4258
4259	The event loop thread first acquires the mutex, and then jumps straight
4260	into C<ev_loop>:
4261
4262	void *
4263	l_run (void *thr_arg)
4264	{
4265	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4266
4267	l_acquire (EV_A);
4268	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4269	ev_loop (EV_A_ 0);
4270	l_release (EV_A);
4271
4272	return 0;
4273	}
4274
4275	Instead of invoking all pending watchers, the C<l_invoke> callback will
4276	signal the main thread via some unspecified mechanism (signals? pipe
4277	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4278	have been called (in a while loop because a) spurious wakeups are possible
4279	and b) skipping inter-thread-communication when there are no pending
4280	watchers is very beneficial):
4281
4282	static void
4283	l_invoke (EV_P)
4284	{
4285	userdata *u = ev_userdata (EV_A);
4286
4287	while (ev_pending_count (EV_A))
4288	{
4289	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4290	pthread_cond_wait (&u->invoke_cv, &u->lock);
4291	}
4292	}
4293
4294	Now, whenever the main thread gets told to invoke pending watchers, it
4295	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4296	thread to continue:
4297
4298	static void
4299	real_invoke_pending (EV_P)
4300	{
4301	userdata *u = ev_userdata (EV_A);
4302
4303	pthread_mutex_lock (&u->lock);
4304	ev_invoke_pending (EV_A);
4305	pthread_cond_signal (&u->invoke_cv);
4306	pthread_mutex_unlock (&u->lock);
4307	}
4308
4309	Whenever you want to start/stop a watcher or do other modifications to an
4310	event loop, you will now have to lock:
4311
4312	ev_timer timeout_watcher;
4313	userdata *u = ev_userdata (EV_A);
4314
4315	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4316
4317	pthread_mutex_lock (&u->lock);
4318	ev_timer_start (EV_A_ &timeout_watcher);
4319	ev_async_send (EV_A_ &u->async_w);
4320	pthread_mutex_unlock (&u->lock);
4321
4322	Note that sending the C<ev_async> watcher is required because otherwise
4323	an event loop currently blocking in the kernel will have no knowledge
4324	about the newly added timer. By waking up the loop it will pick up any new
4325	watchers in the next event loop iteration.
4326		4702
4327	=head3 COROUTINES	4703	=head3 COROUTINES
4328		4704
4329	Libev is very accommodating to coroutines ("cooperative threads"):	4705	Libev is very accommodating to coroutines ("cooperative threads"):
4330	libev fully supports nesting calls to its functions from different	4706	libev fully supports nesting calls to its functions from different
4331	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4707	coroutines (e.g. you can call C<ev_run> on the same loop from two
4332	different coroutines, and switch freely between both coroutines running	4708	different coroutines, and switch freely between both coroutines running
4333	the loop, as long as you don't confuse yourself). The only exception is	4709	the loop, as long as you don't confuse yourself). The only exception is
4334	that you must not do this from C<ev_periodic> reschedule callbacks.	4710	that you must not do this from C<ev_periodic> reschedule callbacks.
4335		4711
4336	Care has been taken to ensure that libev does not keep local state inside	4712	Care has been taken to ensure that libev does not keep local state inside
4337	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4713	C<ev_run>, and other calls do not usually allow for coroutine switches as
4338	they do not call any callbacks.	4714	they do not call any callbacks.
4339		4715
4340	=head2 COMPILER WARNINGS	4716	=head2 COMPILER WARNINGS
4341		4717
4342	Depending on your compiler and compiler settings, you might get no or a	4718	Depending on your compiler and compiler settings, you might get no or a
…		…
4353	maintainable.	4729	maintainable.
4354		4730
4355	And of course, some compiler warnings are just plain stupid, or simply	4731	And of course, some compiler warnings are just plain stupid, or simply
4356	wrong (because they don't actually warn about the condition their message	4732	wrong (because they don't actually warn about the condition their message
4357	seems to warn about). For example, certain older gcc versions had some	4733	seems to warn about). For example, certain older gcc versions had some
4358	warnings that resulted an extreme number of false positives. These have	4734	warnings that resulted in an extreme number of false positives. These have
4359	been fixed, but some people still insist on making code warn-free with	4735	been fixed, but some people still insist on making code warn-free with
4360	such buggy versions.	4736	such buggy versions.
4361		4737
4362	While libev is written to generate as few warnings as possible,	4738	While libev is written to generate as few warnings as possible,
4363	"warn-free" code is not a goal, and it is recommended not to build libev	4739	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4399	I suggest using suppression lists.	4775	I suggest using suppression lists.
4400		4776
4401		4777
4402	=head1 PORTABILITY NOTES	4778	=head1 PORTABILITY NOTES
4403		4779
		4780	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4781
		4782	GNU/Linux is the only common platform that supports 64 bit file/large file
		4783	interfaces but I<disables> them by default.
		4784
		4785	That means that libev compiled in the default environment doesn't support
		4786	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4787
		4788	Unfortunately, many programs try to work around this GNU/Linux issue
		4789	by enabling the large file API, which makes them incompatible with the
		4790	standard libev compiled for their system.
		4791
		4792	Likewise, libev cannot enable the large file API itself as this would
		4793	suddenly make it incompatible to the default compile time environment,
		4794	i.e. all programs not using special compile switches.
		4795
		4796	=head2 OS/X AND DARWIN BUGS
		4797
		4798	The whole thing is a bug if you ask me - basically any system interface
		4799	you touch is broken, whether it is locales, poll, kqueue or even the
		4800	OpenGL drivers.
		4801
		4802	=head3 C<kqueue> is buggy
		4803
		4804	The kqueue syscall is broken in all known versions - most versions support
		4805	only sockets, many support pipes.
		4806
		4807	Libev tries to work around this by not using C<kqueue> by default on this
		4808	rotten platform, but of course you can still ask for it when creating a
		4809	loop - embedding a socket-only kqueue loop into a select-based one is
		4810	probably going to work well.
		4811
		4812	=head3 C<poll> is buggy
		4813
		4814	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4815	implementation by something calling C<kqueue> internally around the 10.5.6
		4816	release, so now C<kqueue> I<and> C<poll> are broken.
		4817
		4818	Libev tries to work around this by not using C<poll> by default on
		4819	this rotten platform, but of course you can still ask for it when creating
		4820	a loop.
		4821
		4822	=head3 C<select> is buggy
		4823
		4824	All that's left is C<select>, and of course Apple found a way to fuck this
		4825	one up as well: On OS/X, C<select> actively limits the number of file
		4826	descriptors you can pass in to 1024 - your program suddenly crashes when
		4827	you use more.
		4828
		4829	There is an undocumented "workaround" for this - defining
		4830	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4831	work on OS/X.
		4832
		4833	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4834
		4835	=head3 C<errno> reentrancy
		4836
		4837	The default compile environment on Solaris is unfortunately so
		4838	thread-unsafe that you can't even use components/libraries compiled
		4839	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4840	defined by default. A valid, if stupid, implementation choice.
		4841
		4842	If you want to use libev in threaded environments you have to make sure
		4843	it's compiled with C<_REENTRANT> defined.
		4844
		4845	=head3 Event port backend
		4846
		4847	The scalable event interface for Solaris is called "event
		4848	ports". Unfortunately, this mechanism is very buggy in all major
		4849	releases. If you run into high CPU usage, your program freezes or you get
		4850	a large number of spurious wakeups, make sure you have all the relevant
		4851	and latest kernel patches applied. No, I don't know which ones, but there
		4852	are multiple ones to apply, and afterwards, event ports actually work
		4853	great.
		4854
		4855	If you can't get it to work, you can try running the program by setting
		4856	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4857	C<select> backends.
		4858
		4859	=head2 AIX POLL BUG
		4860
		4861	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4862	this by trying to avoid the poll backend altogether (i.e. it's not even
		4863	compiled in), which normally isn't a big problem as C<select> works fine
		4864	with large bitsets on AIX, and AIX is dead anyway.
		4865
4404	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4866	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4867
		4868	=head3 General issues
4405		4869
4406	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4870	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4407	requires, and its I/O model is fundamentally incompatible with the POSIX	4871	requires, and its I/O model is fundamentally incompatible with the POSIX
4408	model. Libev still offers limited functionality on this platform in	4872	model. Libev still offers limited functionality on this platform in
4409	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4873	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4410	descriptors. This only applies when using Win32 natively, not when using	4874	descriptors. This only applies when using Win32 natively, not when using
4411	e.g. cygwin.	4875	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4876	as every compielr comes with a slightly differently broken/incompatible
		4877	environment.
4412		4878
4413	Lifting these limitations would basically require the full	4879	Lifting these limitations would basically require the full
4414	re-implementation of the I/O system. If you are into these kinds of	4880	re-implementation of the I/O system. If you are into this kind of thing,
4415	things, then note that glib does exactly that for you in a very portable	4881	then note that glib does exactly that for you in a very portable way (note
4416	way (note also that glib is the slowest event library known to man).	4882	also that glib is the slowest event library known to man).
4417		4883
4418	There is no supported compilation method available on windows except	4884	There is no supported compilation method available on windows except
4419	embedding it into other applications.	4885	embedding it into other applications.
4420		4886
4421	Sensible signal handling is officially unsupported by Microsoft - libev	4887	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4449	you do I<not> compile the F<ev.c> or any other embedded source files!):	4915	you do I<not> compile the F<ev.c> or any other embedded source files!):
4450		4916
4451	#include "evwrap.h"	4917	#include "evwrap.h"
4452	#include "ev.c"	4918	#include "ev.c"
4453		4919
4454	=over 4
4455
4456	=item The winsocket select function	4920	=head3 The winsocket C<select> function
4457		4921
4458	The winsocket C<select> function doesn't follow POSIX in that it	4922	The winsocket C<select> function doesn't follow POSIX in that it
4459	requires socket I<handles> and not socket I<file descriptors> (it is	4923	requires socket I<handles> and not socket I<file descriptors> (it is
4460	also extremely buggy). This makes select very inefficient, and also	4924	also extremely buggy). This makes select very inefficient, and also
4461	requires a mapping from file descriptors to socket handles (the Microsoft	4925	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4470	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4934	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4471		4935
4472	Note that winsockets handling of fd sets is O(n), so you can easily get a	4936	Note that winsockets handling of fd sets is O(n), so you can easily get a
4473	complexity in the O(n²) range when using win32.	4937	complexity in the O(n²) range when using win32.
4474		4938
4475	=item Limited number of file descriptors	4939	=head3 Limited number of file descriptors
4476		4940
4477	Windows has numerous arbitrary (and low) limits on things.	4941	Windows has numerous arbitrary (and low) limits on things.
4478		4942
4479	Early versions of winsocket's select only supported waiting for a maximum	4943	Early versions of winsocket's select only supported waiting for a maximum
4480	of C<64> handles (probably owning to the fact that all windows kernels	4944	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4495	runtime libraries. This might get you to about C<512> or C<2048> sockets	4959	runtime libraries. This might get you to about C<512> or C<2048> sockets
4496	(depending on windows version and/or the phase of the moon). To get more,	4960	(depending on windows version and/or the phase of the moon). To get more,
4497	you need to wrap all I/O functions and provide your own fd management, but	4961	you need to wrap all I/O functions and provide your own fd management, but
4498	the cost of calling select (O(n²)) will likely make this unworkable.	4962	the cost of calling select (O(n²)) will likely make this unworkable.
4499		4963
4500	=back
4501
4502	=head2 PORTABILITY REQUIREMENTS	4964	=head2 PORTABILITY REQUIREMENTS
4503		4965
4504	In addition to a working ISO-C implementation and of course the	4966	In addition to a working ISO-C implementation and of course the
4505	backend-specific APIs, libev relies on a few additional extensions:	4967	backend-specific APIs, libev relies on a few additional extensions:
4506		4968
…		…
4512	Libev assumes not only that all watcher pointers have the same internal	4974	Libev assumes not only that all watcher pointers have the same internal
4513	structure (guaranteed by POSIX but not by ISO C for example), but it also	4975	structure (guaranteed by POSIX but not by ISO C for example), but it also
4514	assumes that the same (machine) code can be used to call any watcher	4976	assumes that the same (machine) code can be used to call any watcher
4515	callback: The watcher callbacks have different type signatures, but libev	4977	callback: The watcher callbacks have different type signatures, but libev
4516	calls them using an C<ev_watcher *> internally.	4978	calls them using an C<ev_watcher *> internally.
		4979
		4980	=item pointer accesses must be thread-atomic
		4981
		4982	Accessing a pointer value must be atomic, it must both be readable and
		4983	writable in one piece - this is the case on all current architectures.
4517		4984
4518	=item C<sig_atomic_t volatile> must be thread-atomic as well	4985	=item C<sig_atomic_t volatile> must be thread-atomic as well
4519		4986
4520	The type C<sig_atomic_t volatile> (or whatever is defined as	4987	The type C<sig_atomic_t volatile> (or whatever is defined as
4521	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4988	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4544	watchers.	5011	watchers.
4545		5012
4546	=item C<double> must hold a time value in seconds with enough accuracy	5013	=item C<double> must hold a time value in seconds with enough accuracy
4547		5014
4548	The type C<double> is used to represent timestamps. It is required to	5015	The type C<double> is used to represent timestamps. It is required to
4549	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5016	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4550	enough for at least into the year 4000. This requirement is fulfilled by	5017	good enough for at least into the year 4000 with millisecond accuracy
		5018	(the design goal for libev). This requirement is overfulfilled by
4551	implementations implementing IEEE 754, which is basically all existing	5019	implementations using IEEE 754, which is basically all existing ones. With
4552	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5020	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4553	2200.
4554		5021
4555	=back	5022	=back
4556		5023
4557	If you know of other additional requirements drop me a note.	5024	If you know of other additional requirements drop me a note.
4558		5025
…		…
4628	=back	5095	=back
4629		5096
4630		5097
4631	=head1 PORTING FROM LIBEV 3.X TO 4.X	5098	=head1 PORTING FROM LIBEV 3.X TO 4.X
4632		5099
4633	The major version 4 introduced some minor incompatible changes to the API.	5100	The major version 4 introduced some incompatible changes to the API.
4634		5101
4635	At the moment, the C<ev.h> header file tries to implement superficial	5102	At the moment, the C<ev.h> header file provides compatibility definitions
4636	compatibility, so most programs should still compile. Those might be	5103	for all changes, so most programs should still compile. The compatibility
4637	removed in later versions of libev, so better update early than late.	5104	layer might be removed in later versions of libev, so better update to the
		5105	new API early than late.
4638		5106
4639	=over 4	5107	=over 4
4640		5108
4641	=item C<ev_loop_count> renamed to C<ev_iteration>	5109	=item C<EV_COMPAT3> backwards compatibility mechanism
4642		5110
4643	=item C<ev_loop_depth> renamed to C<ev_depth>	5111	The backward compatibility mechanism can be controlled by
		5112	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5113	section.
4644		5114
4645	=item C<ev_loop_verify> renamed to C<ev_verify>	5115	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5116
		5117	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5118
		5119	ev_loop_destroy (EV_DEFAULT_UC);
		5120	ev_loop_fork (EV_DEFAULT);
		5121
		5122	=item function/symbol renames
		5123
		5124	A number of functions and symbols have been renamed:
		5125
		5126	ev_loop => ev_run
		5127	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5128	EVLOOP_ONESHOT => EVRUN_ONCE
		5129
		5130	ev_unloop => ev_break
		5131	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5132	EVUNLOOP_ONE => EVBREAK_ONE
		5133	EVUNLOOP_ALL => EVBREAK_ALL
		5134
		5135	EV_TIMEOUT => EV_TIMER
		5136
		5137	ev_loop_count => ev_iteration
		5138	ev_loop_depth => ev_depth
		5139	ev_loop_verify => ev_verify
4646		5140
4647	Most functions working on C<struct ev_loop> objects don't have an	5141	Most functions working on C<struct ev_loop> objects don't have an
4648	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5142	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5143	associated constants have been renamed to not collide with the C<struct
		5144	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5145	as all other watcher types. Note that C<ev_loop_fork> is still called
4649	still called C<ev_loop_fork> because it would otherwise clash with the	5146	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4650	C<ev_fork> typedef.	5147	typedef.
4651
4652	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4653
4654	This is a simple rename - all other watcher types use their name
4655	as revents flag, and now C<ev_timer> does, too.
4656
4657	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4658	and continue to be present for the forseeable future, so this is mostly a
4659	documentation change.
4660		5148
4661	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5149	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4662		5150
4663	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5151	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4664	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5152	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4671		5159
4672	=over 4	5160	=over 4
4673		5161
4674	=item active	5162	=item active
4675		5163
4676	A watcher is active as long as it has been started (has been attached to	5164	A watcher is active as long as it has been started and not yet stopped.
4677	an event loop) but not yet stopped (disassociated from the event loop).	5165	See L<WATCHER STATES> for details.
4678		5166
4679	=item application	5167	=item application
4680		5168
4681	In this document, an application is whatever is using libev.	5169	In this document, an application is whatever is using libev.
		5170
		5171	=item backend
		5172
		5173	The part of the code dealing with the operating system interfaces.
4682		5174
4683	=item callback	5175	=item callback
4684		5176
4685	The address of a function that is called when some event has been	5177	The address of a function that is called when some event has been
4686	detected. Callbacks are being passed the event loop, the watcher that	5178	detected. Callbacks are being passed the event loop, the watcher that
4687	received the event, and the actual event bitset.	5179	received the event, and the actual event bitset.
4688		5180
4689	=item callback invocation	5181	=item callback/watcher invocation
4690		5182
4691	The act of calling the callback associated with a watcher.	5183	The act of calling the callback associated with a watcher.
4692		5184
4693	=item event	5185	=item event
4694		5186
…		…
4713	The model used to describe how an event loop handles and processes	5205	The model used to describe how an event loop handles and processes
4714	watchers and events.	5206	watchers and events.
4715		5207
4716	=item pending	5208	=item pending
4717		5209
4718	A watcher is pending as soon as the corresponding event has been detected,	5210	A watcher is pending as soon as the corresponding event has been
4719	and stops being pending as soon as the watcher will be invoked or its	5211	detected. See L<WATCHER STATES> for details.
4720	pending status is explicitly cleared by the application.
4721
4722	A watcher can be pending, but not active. Stopping a watcher also clears
4723	its pending status.
4724		5212
4725	=item real time	5213	=item real time
4726		5214
4727	The physical time that is observed. It is apparently strictly monotonic :)	5215	The physical time that is observed. It is apparently strictly monotonic :)
4728		5216
…		…
4735	=item watcher	5223	=item watcher
4736		5224
4737	A data structure that describes interest in certain events. Watchers need	5225	A data structure that describes interest in certain events. Watchers need
4738	to be started (attached to an event loop) before they can receive events.	5226	to be started (attached to an event loop) before they can receive events.
4739		5227
4740	=item watcher invocation
4741
4742	The act of calling the callback associated with a watcher.
4743
4744	=back	5228	=back
4745		5229
4746	=head1 AUTHOR	5230	=head1 AUTHOR
4747		5231
4748	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5232	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5233	Magnusson and Emanuele Giaquinta.
4749		5234

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