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Revision 1.362 by root, Sun Jan 30 21:10:13 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	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
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	Familiarity 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	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
387		451
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		453
390	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	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).	491	epoll scales either O(1) or O(active_fds).
428		492
429	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(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	499	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	500	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	501	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	502	and is of course hard to detect.
437		503
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	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	505	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	506	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
442	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
443	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
445		517
446	While stopping, setting and starting an I/O watcher in the same iteration	518	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	519	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	520	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	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		588
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	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)).	590	it's really slow, but it still scales very well (O(active_fds)).
519		591
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	592	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	593	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	595	might perform better.
528		596
529	On the positive side, with the exception of the spurious readiness	597	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	598	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
533		611
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
536		614
537	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
538		616
539	Try all backends (even potentially broken ones that wouldn't be tried	617	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	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		620
543	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		630
545	=back	631	=back
546		632
547	If one or more of the backend flags are or'ed into the flags value,	633	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	634	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	635	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	636	()> will be tried.
551		637
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.	638	Example: Try to create a event loop that uses epoll and nothing else.
579		639
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	641	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
583		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
584	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
585		650
586	Destroys the default loop (frees all memory and kernel state etc.). None	651	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	652	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	653	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,	654	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	655	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).	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		657	for example).
592		658
593	Note that certain global state, such as signal state (and installed signal	659	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	660	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
596		662
597	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	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	669	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>.	670	and C<ev_loop_destroy>.
601		671
602	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
603		673
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	674	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	675	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	676	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	677	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	678	child before resuming or calling C<ev_run>.
614	functions, and it will only take effect at the next C<ev_loop> iteration.
615		679
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	680	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	681	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	682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	683	during fork.
620		684
621	On the other hand, you only need to call this function in the child	685	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	686	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	687	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
625		691
626	The function itself is quite fast and it's usually not a problem to call	692	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	693	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
630	pthread_atfork (0, 0, ev_default_fork);	705	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		706
639	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
640		708
641	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	710	otherwise.
643		711
644	=item unsigned int ev_iteration (loop)	712	=item unsigned int ev_iteration (loop)
645		713
646	Returns the current iteration count for the loop, which is identical to	714	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	715	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
649		717
650	This value can sometimes be useful as a generation counter of sorts (it	718	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	719	"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	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	721	prepare and check phases.
654		722
655	=item unsigned int ev_depth (loop)	723	=item unsigned int ev_depth (loop)
656		724
657	Returns the number of times C<ev_loop> was entered minus the number of	725	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.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
659		727
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	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),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	730	in which case it is higher.
663		731
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	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	733	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
667		736
668	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
669		738
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	740	use.
…		…
680		749
681	=item ev_now_update (loop)	750	=item ev_now_update (loop)
682		751
683	Establishes the current time by querying the kernel, updating the time	752	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	753	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
686		755
687	This function is rarely useful, but when some event callback runs for a	756	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	757	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	758	the current time is a good idea.
690		759
…		…
692		761
693	=item ev_suspend (loop)	762	=item ev_suspend (loop)
694		763
695	=item ev_resume (loop)	764	=item ev_resume (loop)
696		765
697	These two functions suspend and resume a loop, for use when the loop is	766	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.	767	loop is not used for a while and timeouts should not be processed.
699		768
700	A typical use case would be an interactive program such as a game: When	769	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	770	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	771	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>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
714	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
715		784
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
718		787
719	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
720		789
721	Finally, this is it, the event handler. This function usually is called	790	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	791	after you have initialised all your watchers and you want to start
723	handling events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
724		795
725	If the flags argument is specified as C<0>, it will not return until	796	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.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
727		799
728	Please note that an explicit C<ev_unloop> is usually better than	800	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	801	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	803	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	804	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	805	beauty.
734		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	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	813	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	814	block your process in case there are no events and will return after one
738	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
739		817
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	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	819	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	820	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	821	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	822	user-registered callback will be called), and will return after one
745	iteration of the loop.	823	iteration of the loop.
746		824
747	This is useful if you are waiting for some external event in conjunction	825	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	826	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	827	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.	828	usually a better approach for this kind of thing.
751		829
752	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
753		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	841	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	852	- Queue all expired timers.
770	- Queue all expired periodics.	853	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	855	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- 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	857	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
779		866
780	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	868	anymore.
782		869
783	... queue jobs here, make sure they register event watchers as long	870	... 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..)	871	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
787		874
788	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
789		876
790	Can be used to make a call to C<ev_loop> return early (but only after it	877	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	878	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	879	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.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		881
795	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
796		883
797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
798		886
799	=item ev_ref (loop)	887	=item ev_ref (loop)
800		888
801	=item ev_unref (loop)	889	=item ev_unref (loop)
802		890
803	Ref/unref can be used to add or remove a reference count on the event	891	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	892	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.	893	count is nonzero, C<ev_run> will not return on its own.
806		894
807	This is useful when you have a watcher that you never intend to	895	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	896	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>	897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	898	before stopping it.
811		899
812	As an example, libev itself uses this for its internal signal pipe: It	900	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	901	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	902	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	903	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	904	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	905	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	906	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>	907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	908	in the callback).
821		909
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	911	running when nothing else is active.
824		912
825	ev_signal exitsig;	913	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	916	ev_unref (loop);
829		917
830	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
831		919
832	ev_ref (loop);	920	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		979
892	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
893		981
894	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		989
898	=item int ev_pending_count (loop)	990	=item int ev_pending_count (loop)
899		991
900	Returns the number of pending watchers - zero indicates that no watchers	992	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	993	are pending.
902		994
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		996
905	This overrides the invoke pending functionality of the loop: Instead of	997	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	998	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	999	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
909		1001
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1002	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1003	callback.
…		…
914		1006
915	Sometimes you want to share the same loop between multiple threads. This	1007	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	1008	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1009	each call to a libev function.
918		1010
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1011	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	1012	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>	1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
923		1015
924	When set, then C<release> will be called just before the thread is	1016	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	1017	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1018	afterwards.
927		1019
…		…
930		1022
931	While event loop modifications are allowed between invocations of	1023	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1024	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	1025	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	1026	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	1027	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.	1028	to take note of any changes you made.
937		1029
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1030	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1031	invocations of C<release> and C<acquire>.
940		1032
941	See also the locking example in the C<THREADS> section later in this	1033	See also the locking example in the C<THREADS> section later in this
942	document.	1034	document.
943		1035
944	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
945		1037
946	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
947		1039
948	Set and retrieve a single C<void *> associated with a loop. When	1040	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	1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1042	C<0>.
951		1043
952	These two functions can be used to associate arbitrary data with a loop,	1044	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	1045	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	1046	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1047	any other purpose as well.
956		1048
957	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
958		1050
959	This function only does something when C<EV_VERIFY> support has been	1051	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	1052	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	1053	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	1054	is found to be inconsistent, it will print an error message to standard
…		…
973		1065
974	In the following description, uppercase C<TYPE> in names stands for the	1066	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	1067	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.	1068	watchers and C<ev_io_start> for I/O watchers.
977		1069
978	A watcher is a structure that you create and register to record your	1070	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	1071	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:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
981		1074
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1076	{
984	ev_io_stop (w);	1077	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
986	}	1079	}
987		1080
988	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
989		1082
990	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
991		1084
992	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
995		1088
996	ev_loop (loop, 0);	1089	ev_run (loop, 0);
997		1090
998	As you can see, you are responsible for allocating the memory for your	1091	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	1092	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1093	stack).
1001		1094
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1095	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).	1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1097
1005	Each watcher structure must be initialised by a call to C<ev_init	1098	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	1099	*, 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	1100	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	1101	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1102	and/or writable).
1010		1103
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1104	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	1105	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<<	1106	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1158
1066	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1067		1160
1068	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1069		1162
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	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	1164	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	1165	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	1166	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	1167	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	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1076	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1077		1170
1078	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1079		1172
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1174
1082	=item C<EV_FORK>	1175	=item C<EV_FORK>
1083		1176
1084	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1178	C<ev_fork>).
		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1183
1087	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1088		1185
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1187
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1361	functions that do not need a watcher.
1265		1362
1266	=back	1363	=back
1267		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1268		1367
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1270		1369
1271	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1371	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	1372	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	1373	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		1374
1278	struct my_io	1375	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1376
1286	...	1377	=item initialiased
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1378
1290	And since your callback will be called with a pointer to the watcher, you	1379	Before a watcher can be registered with the event looop it has to be
1291	can cast it back to your own type:	1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1382
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1383	In this state it is simply some block of memory that is suitable for
1294	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1296	...	1386	C<ev_TYPE_init> again.
1297	}
1298		1387
1299	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1300	instead have been omitted.
1301		1389
1302	Another common scenario is to use some data structure with multiple	1390	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1391	property of the event loop, and is actively waiting for events. While in
		1392	this state it cannot be accessed (except in a few documented ways), moved,
		1393	freed or anything else - the only legal thing is to keep a pointer to it,
		1394	and call libev functions on it that are documented to work on active watchers.
1304		1395
1305	struct my_biggy	1396	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1397
1312	In this case getting the pointer to C<my_biggy> is a bit more	1398	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	1399	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	1400	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	1401	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1402	callback.
1317		1403
1318	#include <stddef.h>	1404	The watcher might or might not be active while it is pending (for example,
		1405	an expired non-repeating timer can be pending but no longer active). If it
		1406	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1407	but it is still property of the event loop at this time, so cannot be
		1408	moved, freed or reused. And if it is active the rules described in the
		1409	previous item still apply.
1319		1410
1320	static void	1411	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)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1413	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1414
1327	static void	1415	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1329	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1332	}	1420	of whether it was active or not, so stopping a watcher explicitly before
		1421	freeing it is often a good idea.
		1422
		1423	While stopped (and not pending) the watcher is essentially in the
		1424	initialised state, that is, it can be reused, moved, modified in any way
		1425	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1426	it again).
		1427
		1428	=back
1333		1429
1334	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1335		1431
1336	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1464	In general you can register as many read and/or write event watchers per	1560	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	1561	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	1562	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1563	required if you know what you are doing).
1468		1564
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarantee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1565	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	1566	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	1567	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	1568	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	1569	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1570	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.	1571	preferable to a program hanging until some data arrives.
1483		1572
1484	If you cannot run the fd in non-blocking mode (for example you should	1573	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	1574	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	1575	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	1576	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	1577	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	1578	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1579	indefinitely.
1491		1580
1492	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1493		1582
…		…
1521		1610
1522	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1614
		1615	=head3 The special problem of files
		1616
		1617	Many people try to use C<select> (or libev) on file descriptors
		1618	representing files, and expect it to become ready when their program
		1619	doesn't block on disk accesses (which can take a long time on their own).
		1620
		1621	However, this cannot ever work in the "expected" way - you get a readiness
		1622	notification as soon as the kernel knows whether and how much data is
		1623	there, and in the case of open files, that's always the case, so you
		1624	always get a readiness notification instantly, and your read (or possibly
		1625	write) will still block on the disk I/O.
		1626
		1627	Another way to view it is that in the case of sockets, pipes, character
		1628	devices and so on, there is another party (the sender) that delivers data
		1629	on its own, but in the case of files, there is no such thing: the disk
		1630	will not send data on its own, simply because it doesn't know what you
		1631	wish to read - you would first have to request some data.
		1632
		1633	Since files are typically not-so-well supported by advanced notification
		1634	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1635	to files, even though you should not use it. The reason for this is
		1636	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1637	usually a tty, often a pipe, but also sometimes files or special devices
		1638	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1639	F</dev/urandom>), and even though the file might better be served with
		1640	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1641	it "just works" instead of freezing.
		1642
		1643	So avoid file descriptors pointing to files when you know it (e.g. use
		1644	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1645	when you rarely read from a file instead of from a socket, and want to
		1646	reuse the same code path.
		1647
1526	=head3 The special problem of fork	1648	=head3 The special problem of fork
1527		1649
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1650	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	1651	useless behaviour. Libev fully supports fork, but needs to be told about
1530	it in the child.	1652	it in the child if you want to continue to use it in the child.
1531		1653
1532	To support fork in your programs, you either have to call	1654	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,	1655	()> 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	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1657
1537	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1538		1659
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1660	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	1661	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1743	...
1623	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1745	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1746	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1628		1749
1629		1750
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1752
1632	Timer watchers are simple relative timers that generate an event after a	1753	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	1762	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	1763	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	1764	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	1765	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	1766	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).	1767	no longer true when a callback calls C<ev_run> recursively).
1647		1768
1648	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1649		1770
1650	Many real-world problems involve some kind of timeout, usually for error	1771	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,	1772	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1822		1943
1823	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1824		1945
1825	Establishing the current time is a costly operation (it usually takes at	1946	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	1947	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	1948	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	1949	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	1950	lots of events in one iteration.
1830		1951
1831	The relative timeouts are calculated relative to the C<ev_now ()>	1952	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	1953	time. This is usually the right thing as this timestamp refers to the time
…		…
1949	}	2070	}
1950		2071
1951	ev_timer mytimer;	2072	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2073	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1955		2076
1956	// and in some piece of code that gets executed on any "activity":	2077	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1959		2080
…		…
1985		2106
1986	As with timers, the callback is guaranteed to be invoked only when the	2107	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	2108	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	2109	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	2110	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).	2111	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2112
1992	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1993		2114
1994	=over 4	2115	=over 4
1995		2116
…		…
2156		2277
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2279
2159	Signal watchers will trigger an event when the process receives a specific	2280	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	2281	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	2282	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2283	normal event processing, like any other event.
2163		2284
2164	If you want signals to be delivered truly asynchronously, just use	2285	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2286	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	2287	the signal. You can even use C<ev_async> from a signal handler to
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2306	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2307
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2308	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2309	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2310	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2311	and might or might not set or restore the installed signal handler (but
		2312	see C<EVFLAG_NOSIGMASK>).
2191		2313
2192	While this does not matter for the signal disposition (libev never	2314	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2315	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2316	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2317	certain signals to be blocked.
…		…
2209		2331
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2332	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	2333	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.	2334	is not a libev-specific thing, this is true for most event libraries.
2213		2335
		2336	=head3 The special problem of threads signal handling
		2337
		2338	POSIX threads has problematic signal handling semantics, specifically,
		2339	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2340	threads in a process block signals, which is hard to achieve.
		2341
		2342	When you want to use sigwait (or mix libev signal handling with your own
		2343	for the same signals), you can tackle this problem by globally blocking
		2344	all signals before creating any threads (or creating them with a fully set
		2345	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2346	loops. Then designate one thread as "signal receiver thread" which handles
		2347	these signals. You can pass on any signals that libev might be interested
		2348	in by calling C<ev_feed_signal>.
		2349
2214	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
2215		2351
2216	=over 4	2352	=over 4
2217		2353
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2354	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
2234		2370
2235	static void	2371	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2373	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
2239	}	2375	}
2240		2376
2241	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
2629		2765
2630	Prepare and check watchers are usually (but not always) used in pairs:	2766	Prepare and check watchers are usually (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2768	afterwards.
2633		2769
2634	You I<must not> call C<ev_loop> or similar functions that enter	2770	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>	2771	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	2772	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	2773	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,	2774	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	2775	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2807		2943
2808	if (timeout >= 0)	2944	if (timeout >= 0)
2809	// create/start timer	2945	// create/start timer
2810		2946
2811	// poll	2947	// poll
2812	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2813		2949
2814	// stop timer again	2950	// stop timer again
2815	if (timeout >= 0)	2951	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2817		2953
…		…
2895	if you do not want that, you need to temporarily stop the embed watcher).	3031	if you do not want that, you need to temporarily stop the embed watcher).
2896		3032
2897	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2898		3034
2899	Make a single, non-blocking sweep over the embedded loop. This works	3035	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	3036	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2902		3038
2903	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2904		3040
2905	The embedded event loop.	3041	The embedded event loop.
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3127	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3128	signal watchers).
2993		3129
2994	When this is not possible, or you want to use the default loop for	3130	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	3131	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3132	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	3133	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3134	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.	3135	those watchers. Note also that in that case, you have to re-register any
		3136	signal watchers.
3000		3137
3001	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
3002		3139
3003	=over 4	3140	=over 4
3004		3141
3005	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
3006		3143
3007	Initialises and configures the fork watcher - it has no parameters of any	3144	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,	3145	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3146	really.
3010		3147
3011	=back	3148	=back
3012		3149
3013		3150
		3151	=head2 C<ev_cleanup> - even the best things end
		3152
		3153	Cleanup watchers are called just before the event loop is being destroyed
		3154	by a call to C<ev_loop_destroy>.
		3155
		3156	While there is no guarantee that the event loop gets destroyed, cleanup
		3157	watchers provide a convenient method to install cleanup hooks for your
		3158	program, worker threads and so on - you just to make sure to destroy the
		3159	loop when you want them to be invoked.
		3160
		3161	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3162	all other watchers, they do not keep a reference to the event loop (which
		3163	makes a lot of sense if you think about it). Like all other watchers, you
		3164	can call libev functions in the callback, except C<ev_cleanup_start>.
		3165
		3166	=head3 Watcher-Specific Functions and Data Members
		3167
		3168	=over 4
		3169
		3170	=item ev_cleanup_init (ev_cleanup *, callback)
		3171
		3172	Initialises and configures the cleanup watcher - it has no parameters of
		3173	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3174	pointless, I assure you.
		3175
		3176	=back
		3177
		3178	Example: Register an atexit handler to destroy the default loop, so any
		3179	cleanup functions are called.
		3180
		3181	static void
		3182	program_exits (void)
		3183	{
		3184	ev_loop_destroy (EV_DEFAULT_UC);
		3185	}
		3186
		3187	...
		3188	atexit (program_exits);
		3189
		3190
3014	=head2 C<ev_async> - how to wake up an event loop	3191	=head2 C<ev_async> - how to wake up an event loop
3015		3192
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	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	3194	asynchronous sources such as signal handlers (as opposed to multiple event
3018	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
3019		3196
3020	Sometimes, however, you need to wake up an event loop you do not control,	3197	Sometimes, however, you need to wake up an event loop you do not control,
3021	for example because it belongs to another thread. This is what C<ev_async>	3198	for example because it belongs to another thread. This is what C<ev_async>
…		…
3023	it by calling C<ev_async_send>, which is thread- and signal safe.	3200	it by calling C<ev_async_send>, which is thread- and signal safe.
3024		3201
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3202	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3203	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3204	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3205	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3206	of "global async watchers" by using a watcher on an otherwise unused
		3207	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3208	even without knowing which loop owns the signal.
3029		3209
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3210	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3031	just the default loop.	3211	just the default loop.
3032		3212
3033	=head3 Queueing	3213	=head3 Queueing
…		…
3209	Feed an event on the given fd, as if a file descriptor backend detected	3389	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3390	the given events it.
3211		3391
3212	=item ev_feed_signal_event (loop, int signum)	3392	=item ev_feed_signal_event (loop, int signum)
3213		3393
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3394	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3395	which is async-safe.
3216		3396
3217	=back	3397	=back
		3398
		3399
		3400	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3401
		3402	This section explains some common idioms that are not immediately
		3403	obvious. Note that examples are sprinkled over the whole manual, and this
		3404	section only contains stuff that wouldn't fit anywhere else.
		3405
		3406	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3407
		3408	Each watcher has, by default, a C<void *data> member that you can read
		3409	or modify at any time: libev will completely ignore it. This can be used
		3410	to associate arbitrary data with your watcher. If you need more data and
		3411	don't want to allocate memory separately and store a pointer to it in that
		3412	data member, you can also "subclass" the watcher type and provide your own
		3413	data:
		3414
		3415	struct my_io
		3416	{
		3417	ev_io io;
		3418	int otherfd;
		3419	void *somedata;
		3420	struct whatever *mostinteresting;
		3421	};
		3422
		3423	...
		3424	struct my_io w;
		3425	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3426
		3427	And since your callback will be called with a pointer to the watcher, you
		3428	can cast it back to your own type:
		3429
		3430	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3431	{
		3432	struct my_io *w = (struct my_io *)w_;
		3433	...
		3434	}
		3435
		3436	More interesting and less C-conformant ways of casting your callback
		3437	function type instead have been omitted.
		3438
		3439	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3440
		3441	Another common scenario is to use some data structure with multiple
		3442	embedded watchers, in effect creating your own watcher that combines
		3443	multiple libev event sources into one "super-watcher":
		3444
		3445	struct my_biggy
		3446	{
		3447	int some_data;
		3448	ev_timer t1;
		3449	ev_timer t2;
		3450	}
		3451
		3452	In this case getting the pointer to C<my_biggy> is a bit more
		3453	complicated: Either you store the address of your C<my_biggy> struct in
		3454	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3455	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3456	real programmers):
		3457
		3458	#include <stddef.h>
		3459
		3460	static void
		3461	t1_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t1));
		3465	}
		3466
		3467	static void
		3468	t2_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t2));
		3472	}
		3473
		3474	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3475
		3476	Often (especially in GUI toolkits) there are places where you have
		3477	I<modal> interaction, which is most easily implemented by recursively
		3478	invoking C<ev_run>.
		3479
		3480	This brings the problem of exiting - a callback might want to finish the
		3481	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3482	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3483	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3484	other combination: In these cases, C<ev_break> will not work alone.
		3485
		3486	The solution is to maintain "break this loop" variable for each C<ev_run>
		3487	invocation, and use a loop around C<ev_run> until the condition is
		3488	triggered, using C<EVRUN_ONCE>:
		3489
		3490	// main loop
		3491	int exit_main_loop = 0;
		3492
		3493	while (!exit_main_loop)
		3494	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3495
		3496	// in a model watcher
		3497	int exit_nested_loop = 0;
		3498
		3499	while (!exit_nested_loop)
		3500	ev_run (EV_A_ EVRUN_ONCE);
		3501
		3502	To exit from any of these loops, just set the corresponding exit variable:
		3503
		3504	// exit modal loop
		3505	exit_nested_loop = 1;
		3506
		3507	// exit main program, after modal loop is finished
		3508	exit_main_loop = 1;
		3509
		3510	// exit both
		3511	exit_main_loop = exit_nested_loop = 1;
		3512
		3513	=head2 THREAD LOCKING EXAMPLE
		3514
		3515	Here is a fictitious example of how to run an event loop in a different
		3516	thread from where callbacks are being invoked and watchers are
		3517	created/added/removed.
		3518
		3519	For a real-world example, see the C<EV::Loop::Async> perl module,
		3520	which uses exactly this technique (which is suited for many high-level
		3521	languages).
		3522
		3523	The example uses a pthread mutex to protect the loop data, a condition
		3524	variable to wait for callback invocations, an async watcher to notify the
		3525	event loop thread and an unspecified mechanism to wake up the main thread.
		3526
		3527	First, you need to associate some data with the event loop:
		3528
		3529	typedef struct {
		3530	mutex_t lock; /* global loop lock */
		3531	ev_async async_w;
		3532	thread_t tid;
		3533	cond_t invoke_cv;
		3534	} userdata;
		3535
		3536	void prepare_loop (EV_P)
		3537	{
		3538	// for simplicity, we use a static userdata struct.
		3539	static userdata u;
		3540
		3541	ev_async_init (&u->async_w, async_cb);
		3542	ev_async_start (EV_A_ &u->async_w);
		3543
		3544	pthread_mutex_init (&u->lock, 0);
		3545	pthread_cond_init (&u->invoke_cv, 0);
		3546
		3547	// now associate this with the loop
		3548	ev_set_userdata (EV_A_ u);
		3549	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3550	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3551
		3552	// then create the thread running ev_run
		3553	pthread_create (&u->tid, 0, l_run, EV_A);
		3554	}
		3555
		3556	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3557	solely to wake up the event loop so it takes notice of any new watchers
		3558	that might have been added:
		3559
		3560	static void
		3561	async_cb (EV_P_ ev_async *w, int revents)
		3562	{
		3563	// just used for the side effects
		3564	}
		3565
		3566	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3567	protecting the loop data, respectively.
		3568
		3569	static void
		3570	l_release (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_unlock (&u->lock);
		3574	}
		3575
		3576	static void
		3577	l_acquire (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_lock (&u->lock);
		3581	}
		3582
		3583	The event loop thread first acquires the mutex, and then jumps straight
		3584	into C<ev_run>:
		3585
		3586	void *
		3587	l_run (void *thr_arg)
		3588	{
		3589	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3590
		3591	l_acquire (EV_A);
		3592	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3593	ev_run (EV_A_ 0);
		3594	l_release (EV_A);
		3595
		3596	return 0;
		3597	}
		3598
		3599	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3600	signal the main thread via some unspecified mechanism (signals? pipe
		3601	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3602	have been called (in a while loop because a) spurious wakeups are possible
		3603	and b) skipping inter-thread-communication when there are no pending
		3604	watchers is very beneficial):
		3605
		3606	static void
		3607	l_invoke (EV_P)
		3608	{
		3609	userdata *u = ev_userdata (EV_A);
		3610
		3611	while (ev_pending_count (EV_A))
		3612	{
		3613	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3614	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3615	}
		3616	}
		3617
		3618	Now, whenever the main thread gets told to invoke pending watchers, it
		3619	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3620	thread to continue:
		3621
		3622	static void
		3623	real_invoke_pending (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	pthread_mutex_lock (&u->lock);
		3628	ev_invoke_pending (EV_A);
		3629	pthread_cond_signal (&u->invoke_cv);
		3630	pthread_mutex_unlock (&u->lock);
		3631	}
		3632
		3633	Whenever you want to start/stop a watcher or do other modifications to an
		3634	event loop, you will now have to lock:
		3635
		3636	ev_timer timeout_watcher;
		3637	userdata *u = ev_userdata (EV_A);
		3638
		3639	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3640
		3641	pthread_mutex_lock (&u->lock);
		3642	ev_timer_start (EV_A_ &timeout_watcher);
		3643	ev_async_send (EV_A_ &u->async_w);
		3644	pthread_mutex_unlock (&u->lock);
		3645
		3646	Note that sending the C<ev_async> watcher is required because otherwise
		3647	an event loop currently blocking in the kernel will have no knowledge
		3648	about the newly added timer. By waking up the loop it will pick up any new
		3649	watchers in the next event loop iteration.
		3650
		3651	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3652
		3653	While the overhead of a callback that e.g. schedules a thread is small, it
		3654	is still an overhead. If you embed libev, and your main usage is with some
		3655	kind of threads or coroutines, you might want to customise libev so that
		3656	doesn't need callbacks anymore.
		3657
		3658	Imagine you have coroutines that you can switch to using a function
		3659	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3660	and that due to some magic, the currently active coroutine is stored in a
		3661	global called C<current_coro>. Then you can build your own "wait for libev
		3662	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3663	the differing C<;> conventions):
		3664
		3665	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3666	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3667
		3668	That means instead of having a C callback function, you store the
		3669	coroutine to switch to in each watcher, and instead of having libev call
		3670	your callback, you instead have it switch to that coroutine.
		3671
		3672	A coroutine might now wait for an event with a function called
		3673	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3674	matter when, or whether the watcher is active or not when this function is
		3675	called):
		3676
		3677	void
		3678	wait_for_event (ev_watcher *w)
		3679	{
		3680	ev_cb_set (w) = current_coro;
		3681	switch_to (libev_coro);
		3682	}
		3683
		3684	That basically suspends the coroutine inside C<wait_for_event> and
		3685	continues the libev coroutine, which, when appropriate, switches back to
		3686	this or any other coroutine. I am sure if you sue this your own :)
		3687
		3688	You can do similar tricks if you have, say, threads with an event queue -
		3689	instead of storing a coroutine, you store the queue object and instead of
		3690	switching to a coroutine, you push the watcher onto the queue and notify
		3691	any waiters.
		3692
		3693	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3694	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3695
		3696	// my_ev.h
		3697	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3698	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3699	#include "../libev/ev.h"
		3700
		3701	// my_ev.c
		3702	#define EV_H "my_ev.h"
		3703	#include "../libev/ev.c"
		3704
		3705	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3706	F<my_ev.c> into your project. When properly specifying include paths, you
		3707	can even use F<ev.h> as header file name directly.
3218		3708
3219		3709
3220	=head1 LIBEVENT EMULATION	3710	=head1 LIBEVENT EMULATION
3221		3711
3222	Libev offers a compatibility emulation layer for libevent. It cannot	3712	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	3713	emulate the internals of libevent, so here are some usage hints:
3224		3714
3225	=over 4	3715	=over 4
		3716
		3717	=item * Only the libevent-1.4.1-beta API is being emulated.
		3718
		3719	This was the newest libevent version available when libev was implemented,
		3720	and is still mostly unchanged in 2010.
3226		3721
3227	=item * Use it by including <event.h>, as usual.	3722	=item * Use it by including <event.h>, as usual.
3228		3723
3229	=item * The following members are fully supported: ev_base, ev_callback,	3724	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	3725	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	3731	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	3732	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	3733	is an ev_pri field.
3239		3734
3240	=item * In libevent, the last base created gets the signals, in libev, the	3735	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	3736	base that registered the signal gets the signals.
3242		3737
3243	=item * Other members are not supported.	3738	=item * Other members are not supported.
3244		3739
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3740	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	3741	to use the libev header file and library.
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	3760	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	3761	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	3762	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	3763	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		3764
3270	Currently, functions, and static and non-static member functions can be	3765	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	3766	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	3767	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	3768	you need support for other types of functors please contact the author
3274	it).	3769	(preferably after implementing it).
3275		3770
3276	Here is a list of things available in the C<ev> namespace:	3771	Here is a list of things available in the C<ev> namespace:
3277		3772
3278	=over 4	3773	=over 4
3279		3774
…		…
3389	Associates a different C<struct ev_loop> with this watcher. You can only	3884	Associates a different C<struct ev_loop> with this watcher. You can only
3390	do this when the watcher is inactive (and not pending either).	3885	do this when the watcher is inactive (and not pending either).
3391		3886
3392	=item w->set ([arguments])	3887	=item w->set ([arguments])
3393		3888
3394	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3889	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3395	called at least once. Unlike the C counterpart, an active watcher gets	3890	method or a suitable start method must be called at least once. Unlike the
3396	automatically stopped and restarted when reconfiguring it with this	3891	C counterpart, an active watcher gets automatically stopped and restarted
3397	method.	3892	when reconfiguring it with this method.
3398		3893
3399	=item w->start ()	3894	=item w->start ()
3400		3895
3401	Starts the watcher. Note that there is no C<loop> argument, as the	3896	Starts the watcher. Note that there is no C<loop> argument, as the
3402	constructor already stores the event loop.	3897	constructor already stores the event loop.
3403		3898
		3899	=item w->start ([arguments])
		3900
		3901	Instead of calling C<set> and C<start> methods separately, it is often
		3902	convenient to wrap them in one call. Uses the same type of arguments as
		3903	the configure C<set> method of the watcher.
		3904
3404	=item w->stop ()	3905	=item w->stop ()
3405		3906
3406	Stops the watcher if it is active. Again, no C<loop> argument.	3907	Stops the watcher if it is active. Again, no C<loop> argument.
3407		3908
3408	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3909	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3420		3921
3421	=back	3922	=back
3422		3923
3423	=back	3924	=back
3424		3925
3425	Example: Define a class with an IO and idle watcher, start one of them in	3926	Example: Define a class with two I/O and idle watchers, start the I/O
3426	the constructor.	3927	watchers in the constructor.
3427		3928
3428	class myclass	3929	class myclass
3429	{	3930	{
3430	ev::io io ; void io_cb (ev::io &w, int revents);	3931	ev::io io ; void io_cb (ev::io &w, int revents);
		3932	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3431	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3933	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3432		3934
3433	myclass (int fd)	3935	myclass (int fd)
3434	{	3936	{
3435	io .set <myclass, &myclass::io_cb > (this);	3937	io .set <myclass, &myclass::io_cb > (this);
		3938	io2 .set <myclass, &myclass::io2_cb > (this);
3436	idle.set <myclass, &myclass::idle_cb> (this);	3939	idle.set <myclass, &myclass::idle_cb> (this);
3437		3940
3438	io.start (fd, ev::READ);	3941	io.set (fd, ev::WRITE); // configure the watcher
		3942	io.start (); // start it whenever convenient
		3943
		3944	io2.start (fd, ev::READ); // set + start in one call
3439	}	3945	}
3440	};	3946	};
3441		3947
3442		3948
3443	=head1 OTHER LANGUAGE BINDINGS	3949	=head1 OTHER LANGUAGE BINDINGS
…		…
3517	loop argument"). The C<EV_A> form is used when this is the sole argument,	4023	loop argument"). The C<EV_A> form is used when this is the sole argument,
3518	C<EV_A_> is used when other arguments are following. Example:	4024	C<EV_A_> is used when other arguments are following. Example:
3519		4025
3520	ev_unref (EV_A);	4026	ev_unref (EV_A);
3521	ev_timer_add (EV_A_ watcher);	4027	ev_timer_add (EV_A_ watcher);
3522	ev_loop (EV_A_ 0);	4028	ev_run (EV_A_ 0);
3523		4029
3524	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4030	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3525	which is often provided by the following macro.	4031	which is often provided by the following macro.
3526		4032
3527	=item C<EV_P>, C<EV_P_>	4033	=item C<EV_P>, C<EV_P_>
…		…
3567	}	4073	}
3568		4074
3569	ev_check check;	4075	ev_check check;
3570	ev_check_init (&check, check_cb);	4076	ev_check_init (&check, check_cb);
3571	ev_check_start (EV_DEFAULT_ &check);	4077	ev_check_start (EV_DEFAULT_ &check);
3572	ev_loop (EV_DEFAULT_ 0);	4078	ev_run (EV_DEFAULT_ 0);
3573		4079
3574	=head1 EMBEDDING	4080	=head1 EMBEDDING
3575		4081
3576	Libev can (and often is) directly embedded into host	4082	Libev can (and often is) directly embedded into host
3577	applications. Examples of applications that embed it include the Deliantra	4083	applications. Examples of applications that embed it include the Deliantra
…		…
3668	to a compiled library. All other symbols change the ABI, which means all	4174	to a compiled library. All other symbols change the ABI, which means all
3669	users of libev and the libev code itself must be compiled with compatible	4175	users of libev and the libev code itself must be compiled with compatible
3670	settings.	4176	settings.
3671		4177
3672	=over 4	4178	=over 4
		4179
		4180	=item EV_COMPAT3 (h)
		4181
		4182	Backwards compatibility is a major concern for libev. This is why this
		4183	release of libev comes with wrappers for the functions and symbols that
		4184	have been renamed between libev version 3 and 4.
		4185
		4186	You can disable these wrappers (to test compatibility with future
		4187	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4188	sources. This has the additional advantage that you can drop the C<struct>
		4189	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4190	typedef in that case.
		4191
		4192	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4193	and in some even more future version the compatibility code will be
		4194	removed completely.
3673		4195
3674	=item EV_STANDALONE (h)	4196	=item EV_STANDALONE (h)
3675		4197
3676	Must always be C<1> if you do not use autoconf configuration, which	4198	Must always be C<1> if you do not use autoconf configuration, which
3677	keeps libev from including F<config.h>, and it also defines dummy	4199	keeps libev from including F<config.h>, and it also defines dummy
…		…
4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4549	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4028	will be C<0>.	4550	will be C<0>.
4029		4551
4030	=item EV_VERIFY	4552	=item EV_VERIFY
4031		4553
4032	Controls how much internal verification (see C<ev_loop_verify ()>) will	4554	Controls how much internal verification (see C<ev_verify ()>) will
4033	be done: If set to C<0>, no internal verification code will be compiled	4555	be done: If set to C<0>, no internal verification code will be compiled
4034	in. If set to C<1>, then verification code will be compiled in, but not	4556	in. If set to C<1>, then verification code will be compiled in, but not
4035	called. If set to C<2>, then the internal verification code will be	4557	called. If set to C<2>, then the internal verification code will be
4036	called once per loop, which can slow down libev. If set to C<3>, then the	4558	called once per loop, which can slow down libev. If set to C<3>, then the
4037	verification code will be called very frequently, which will slow down	4559	verification code will be called very frequently, which will slow down
…		…
4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4642	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4121		4643
4122	#include "ev_cpp.h"	4644	#include "ev_cpp.h"
4123	#include "ev.c"	4645	#include "ev.c"
4124		4646
4125	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4647	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4126		4648
4127	=head2 THREADS AND COROUTINES	4649	=head2 THREADS AND COROUTINES
4128		4650
4129	=head3 THREADS	4651	=head3 THREADS
4130		4652
…		…
4181	default loop and triggering an C<ev_async> watcher from the default loop	4703	default loop and triggering an C<ev_async> watcher from the default loop
4182	watcher callback into the event loop interested in the signal.	4704	watcher callback into the event loop interested in the signal.
4183		4705
4184	=back	4706	=back
4185		4707
4186	=head4 THREAD LOCKING EXAMPLE	4708	See also L<THREAD LOCKING EXAMPLE>.
4187
4188	Here is a fictitious example of how to run an event loop in a different
4189	thread than where callbacks are being invoked and watchers are
4190	created/added/removed.
4191
4192	For a real-world example, see the C<EV::Loop::Async> perl module,
4193	which uses exactly this technique (which is suited for many high-level
4194	languages).
4195
4196	The example uses a pthread mutex to protect the loop data, a condition
4197	variable to wait for callback invocations, an async watcher to notify the
4198	event loop thread and an unspecified mechanism to wake up the main thread.
4199
4200	First, you need to associate some data with the event loop:
4201
4202	typedef struct {
4203	mutex_t lock; /* global loop lock */
4204	ev_async async_w;
4205	thread_t tid;
4206	cond_t invoke_cv;
4207	} userdata;
4208
4209	void prepare_loop (EV_P)
4210	{
4211	// for simplicity, we use a static userdata struct.
4212	static userdata u;
4213
4214	ev_async_init (&u->async_w, async_cb);
4215	ev_async_start (EV_A_ &u->async_w);
4216
4217	pthread_mutex_init (&u->lock, 0);
4218	pthread_cond_init (&u->invoke_cv, 0);
4219
4220	// now associate this with the loop
4221	ev_set_userdata (EV_A_ u);
4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4224
4225	// then create the thread running ev_loop
4226	pthread_create (&u->tid, 0, l_run, EV_A);
4227	}
4228
4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
4230	solely to wake up the event loop so it takes notice of any new watchers
4231	that might have been added:
4232
4233	static void
4234	async_cb (EV_P_ ev_async *w, int revents)
4235	{
4236	// just used for the side effects
4237	}
4238
4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4240	protecting the loop data, respectively.
4241
4242	static void
4243	l_release (EV_P)
4244	{
4245	userdata *u = ev_userdata (EV_A);
4246	pthread_mutex_unlock (&u->lock);
4247	}
4248
4249	static void
4250	l_acquire (EV_P)
4251	{
4252	userdata *u = ev_userdata (EV_A);
4253	pthread_mutex_lock (&u->lock);
4254	}
4255
4256	The event loop thread first acquires the mutex, and then jumps straight
4257	into C<ev_loop>:
4258
4259	void *
4260	l_run (void *thr_arg)
4261	{
4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4263
4264	l_acquire (EV_A);
4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4266	ev_loop (EV_A_ 0);
4267	l_release (EV_A);
4268
4269	return 0;
4270	}
4271
4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
4273	signal the main thread via some unspecified mechanism (signals? pipe
4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4275	have been called (in a while loop because a) spurious wakeups are possible
4276	and b) skipping inter-thread-communication when there are no pending
4277	watchers is very beneficial):
4278
4279	static void
4280	l_invoke (EV_P)
4281	{
4282	userdata *u = ev_userdata (EV_A);
4283
4284	while (ev_pending_count (EV_A))
4285	{
4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
4288	}
4289	}
4290
4291	Now, whenever the main thread gets told to invoke pending watchers, it
4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4293	thread to continue:
4294
4295	static void
4296	real_invoke_pending (EV_P)
4297	{
4298	userdata *u = ev_userdata (EV_A);
4299
4300	pthread_mutex_lock (&u->lock);
4301	ev_invoke_pending (EV_A);
4302	pthread_cond_signal (&u->invoke_cv);
4303	pthread_mutex_unlock (&u->lock);
4304	}
4305
4306	Whenever you want to start/stop a watcher or do other modifications to an
4307	event loop, you will now have to lock:
4308
4309	ev_timer timeout_watcher;
4310	userdata *u = ev_userdata (EV_A);
4311
4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4313
4314	pthread_mutex_lock (&u->lock);
4315	ev_timer_start (EV_A_ &timeout_watcher);
4316	ev_async_send (EV_A_ &u->async_w);
4317	pthread_mutex_unlock (&u->lock);
4318
4319	Note that sending the C<ev_async> watcher is required because otherwise
4320	an event loop currently blocking in the kernel will have no knowledge
4321	about the newly added timer. By waking up the loop it will pick up any new
4322	watchers in the next event loop iteration.
4323		4709
4324	=head3 COROUTINES	4710	=head3 COROUTINES
4325		4711
4326	Libev is very accommodating to coroutines ("cooperative threads"):	4712	Libev is very accommodating to coroutines ("cooperative threads"):
4327	libev fully supports nesting calls to its functions from different	4713	libev fully supports nesting calls to its functions from different
4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4714	coroutines (e.g. you can call C<ev_run> on the same loop from two
4329	different coroutines, and switch freely between both coroutines running	4715	different coroutines, and switch freely between both coroutines running
4330	the loop, as long as you don't confuse yourself). The only exception is	4716	the loop, as long as you don't confuse yourself). The only exception is
4331	that you must not do this from C<ev_periodic> reschedule callbacks.	4717	that you must not do this from C<ev_periodic> reschedule callbacks.
4332		4718
4333	Care has been taken to ensure that libev does not keep local state inside	4719	Care has been taken to ensure that libev does not keep local state inside
4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4720	C<ev_run>, and other calls do not usually allow for coroutine switches as
4335	they do not call any callbacks.	4721	they do not call any callbacks.
4336		4722
4337	=head2 COMPILER WARNINGS	4723	=head2 COMPILER WARNINGS
4338		4724
4339	Depending on your compiler and compiler settings, you might get no or a	4725	Depending on your compiler and compiler settings, you might get no or a
…		…
4423	=head3 C<kqueue> is buggy	4809	=head3 C<kqueue> is buggy
4424		4810
4425	The kqueue syscall is broken in all known versions - most versions support	4811	The kqueue syscall is broken in all known versions - most versions support
4426	only sockets, many support pipes.	4812	only sockets, many support pipes.
4427		4813
		4814	Libev tries to work around this by not using C<kqueue> by default on this
		4815	rotten platform, but of course you can still ask for it when creating a
		4816	loop - embedding a socket-only kqueue loop into a select-based one is
		4817	probably going to work well.
		4818
4428	=head3 C<poll> is buggy	4819	=head3 C<poll> is buggy
4429		4820
4430	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4821	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4431	implementation by something calling C<kqueue> internally around the 10.5.6	4822	implementation by something calling C<kqueue> internally around the 10.5.6
4432	release, so now C<kqueue> I<and> C<poll> are broken.	4823	release, so now C<kqueue> I<and> C<poll> are broken.
4433		4824
4434	Libev tries to work around this by neither using C<kqueue> nor C<poll> by	4825	Libev tries to work around this by not using C<poll> by default on
4435	default on this rotten platform, but of course you cna still ask for them	4826	this rotten platform, but of course you can still ask for it when creating
4436	when creating a loop.	4827	a loop.
4437		4828
4438	=head3 C<select> is buggy	4829	=head3 C<select> is buggy
4439		4830
4440	All that's left is C<select>, and of course Apple found a way to fuck this	4831	All that's left is C<select>, and of course Apple found a way to fuck this
4441	one up as well: On OS/X, C<select> actively limits the number of file	4832	one up as well: On OS/X, C<select> actively limits the number of file
4442	descriptors you can pass in to 1024 - your program suddenyl crashes when	4833	descriptors you can pass in to 1024 - your program suddenly crashes when
4443	you use more.	4834	you use more.
4444		4835
4445	There is an undocumented "workaround" for this - defining	4836	There is an undocumented "workaround" for this - defining
4446	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>	4837	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4447	work on OS/X.	4838	work on OS/X.
…		…
4450		4841
4451	=head3 C<errno> reentrancy	4842	=head3 C<errno> reentrancy
4452		4843
4453	The default compile environment on Solaris is unfortunately so	4844	The default compile environment on Solaris is unfortunately so
4454	thread-unsafe that you can't even use components/libraries compiled	4845	thread-unsafe that you can't even use components/libraries compiled
4455	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4846	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4456	isn't defined by default.	4847	defined by default. A valid, if stupid, implementation choice.
4457		4848
4458	If you want to use libev in threaded environments you have to make sure	4849	If you want to use libev in threaded environments you have to make sure
4459	it's compiled with C<_REENTRANT> defined.	4850	it's compiled with C<_REENTRANT> defined.
4460		4851
4461	=head3 Event port backend	4852	=head3 Event port backend
4462		4853
4463	The scalable event interface for Solaris is called "event ports". Unfortunately,	4854	The scalable event interface for Solaris is called "event
4464	this mechanism is very buggy. If you run into high CPU usage, your program	4855	ports". Unfortunately, this mechanism is very buggy in all major
		4856	releases. If you run into high CPU usage, your program freezes or you get
4465	freezes or you get a large number of spurious wakeups, make sure you have	4857	a large number of spurious wakeups, make sure you have all the relevant
4466	all the relevant and latest kernel patches applied. No, I don't know which	4858	and latest kernel patches applied. No, I don't know which ones, but there
4467	ones, but there are multiple ones.	4859	are multiple ones to apply, and afterwards, event ports actually work
		4860	great.
4468		4861
4469	If you can't get it to work, you can try running the program with	4862	If you can't get it to work, you can try running the program by setting
4470	C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends.	4863	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4864	C<select> backends.
4471		4865
4472	=head2 AIX POLL BUG	4866	=head2 AIX POLL BUG
4473		4867
4474	AIX unfortunately has a broken C<poll.h> header. Libev works around	4868	AIX unfortunately has a broken C<poll.h> header. Libev works around
4475	this by trying to avoid the poll backend altogether (i.e. it's not even	4869	this by trying to avoid the poll backend altogether (i.e. it's not even
4476	compiled in), which normally isn't a big problem as C<select> works fine	4870	compiled in), which normally isn't a big problem as C<select> works fine
4477	with large bitsets, and AIX is dead anyway.	4871	with large bitsets on AIX, and AIX is dead anyway.
4478		4872
4479	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4873	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4480		4874
4481	=head3 General issues	4875	=head3 General issues
4482		4876
…		…
4588	structure (guaranteed by POSIX but not by ISO C for example), but it also	4982	structure (guaranteed by POSIX but not by ISO C for example), but it also
4589	assumes that the same (machine) code can be used to call any watcher	4983	assumes that the same (machine) code can be used to call any watcher
4590	callback: The watcher callbacks have different type signatures, but libev	4984	callback: The watcher callbacks have different type signatures, but libev
4591	calls them using an C<ev_watcher *> internally.	4985	calls them using an C<ev_watcher *> internally.
4592		4986
		4987	=item pointer accesses must be thread-atomic
		4988
		4989	Accessing a pointer value must be atomic, it must both be readable and
		4990	writable in one piece - this is the case on all current architectures.
		4991
4593	=item C<sig_atomic_t volatile> must be thread-atomic as well	4992	=item C<sig_atomic_t volatile> must be thread-atomic as well
4594		4993
4595	The type C<sig_atomic_t volatile> (or whatever is defined as	4994	The type C<sig_atomic_t volatile> (or whatever is defined as
4596	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4995	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4597	threads. This is not part of the specification for C<sig_atomic_t>, but is	4996	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4619	watchers.	5018	watchers.
4620		5019
4621	=item C<double> must hold a time value in seconds with enough accuracy	5020	=item C<double> must hold a time value in seconds with enough accuracy
4622		5021
4623	The type C<double> is used to represent timestamps. It is required to	5022	The type C<double> is used to represent timestamps. It is required to
4624	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5023	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4625	enough for at least into the year 4000. This requirement is fulfilled by	5024	good enough for at least into the year 4000 with millisecond accuracy
		5025	(the design goal for libev). This requirement is overfulfilled by
4626	implementations implementing IEEE 754, which is basically all existing	5026	implementations using IEEE 754, which is basically all existing ones. With
4627	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5027	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4628	2200.
4629		5028
4630	=back	5029	=back
4631		5030
4632	If you know of other additional requirements drop me a note.	5031	If you know of other additional requirements drop me a note.
4633		5032
…		…
4703	=back	5102	=back
4704		5103
4705		5104
4706	=head1 PORTING FROM LIBEV 3.X TO 4.X	5105	=head1 PORTING FROM LIBEV 3.X TO 4.X
4707		5106
4708	The major version 4 introduced some minor incompatible changes to the API.	5107	The major version 4 introduced some incompatible changes to the API.
4709		5108
4710	At the moment, the C<ev.h> header file tries to implement superficial	5109	At the moment, the C<ev.h> header file provides compatibility definitions
4711	compatibility, so most programs should still compile. Those might be	5110	for all changes, so most programs should still compile. The compatibility
4712	removed in later versions of libev, so better update early than late.	5111	layer might be removed in later versions of libev, so better update to the
		5112	new API early than late.
4713		5113
4714	=over 4	5114	=over 4
4715		5115
4716	=item C<ev_loop_count> renamed to C<ev_iteration>	5116	=item C<EV_COMPAT3> backwards compatibility mechanism
4717		5117
4718	=item C<ev_loop_depth> renamed to C<ev_depth>	5118	The backward compatibility mechanism can be controlled by
		5119	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5120	section.
4719		5121
4720	=item C<ev_loop_verify> renamed to C<ev_verify>	5122	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5123
		5124	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5125
		5126	ev_loop_destroy (EV_DEFAULT_UC);
		5127	ev_loop_fork (EV_DEFAULT);
		5128
		5129	=item function/symbol renames
		5130
		5131	A number of functions and symbols have been renamed:
		5132
		5133	ev_loop => ev_run
		5134	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5135	EVLOOP_ONESHOT => EVRUN_ONCE
		5136
		5137	ev_unloop => ev_break
		5138	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5139	EVUNLOOP_ONE => EVBREAK_ONE
		5140	EVUNLOOP_ALL => EVBREAK_ALL
		5141
		5142	EV_TIMEOUT => EV_TIMER
		5143
		5144	ev_loop_count => ev_iteration
		5145	ev_loop_depth => ev_depth
		5146	ev_loop_verify => ev_verify
4721		5147
4722	Most functions working on C<struct ev_loop> objects don't have an	5148	Most functions working on C<struct ev_loop> objects don't have an
4723	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5149	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5150	associated constants have been renamed to not collide with the C<struct
		5151	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5152	as all other watcher types. Note that C<ev_loop_fork> is still called
4724	still called C<ev_loop_fork> because it would otherwise clash with the	5153	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4725	C<ev_fork> typedef.	5154	typedef.
4726
4727	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4728
4729	This is a simple rename - all other watcher types use their name
4730	as revents flag, and now C<ev_timer> does, too.
4731
4732	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4733	and continue to be present for the foreseeable future, so this is mostly a
4734	documentation change.
4735		5155
4736	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5156	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4737		5157
4738	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5158	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4739	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5159	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4746		5166
4747	=over 4	5167	=over 4
4748		5168
4749	=item active	5169	=item active
4750		5170
4751	A watcher is active as long as it has been started (has been attached to	5171	A watcher is active as long as it has been started and not yet stopped.
4752	an event loop) but not yet stopped (disassociated from the event loop).	5172	See L<WATCHER STATES> for details.
4753		5173
4754	=item application	5174	=item application
4755		5175
4756	In this document, an application is whatever is using libev.	5176	In this document, an application is whatever is using libev.
		5177
		5178	=item backend
		5179
		5180	The part of the code dealing with the operating system interfaces.
4757		5181
4758	=item callback	5182	=item callback
4759		5183
4760	The address of a function that is called when some event has been	5184	The address of a function that is called when some event has been
4761	detected. Callbacks are being passed the event loop, the watcher that	5185	detected. Callbacks are being passed the event loop, the watcher that
4762	received the event, and the actual event bitset.	5186	received the event, and the actual event bitset.
4763		5187
4764	=item callback invocation	5188	=item callback/watcher invocation
4765		5189
4766	The act of calling the callback associated with a watcher.	5190	The act of calling the callback associated with a watcher.
4767		5191
4768	=item event	5192	=item event
4769		5193
…		…
4788	The model used to describe how an event loop handles and processes	5212	The model used to describe how an event loop handles and processes
4789	watchers and events.	5213	watchers and events.
4790		5214
4791	=item pending	5215	=item pending
4792		5216
4793	A watcher is pending as soon as the corresponding event has been detected,	5217	A watcher is pending as soon as the corresponding event has been
4794	and stops being pending as soon as the watcher will be invoked or its	5218	detected. See L<WATCHER STATES> for details.
4795	pending status is explicitly cleared by the application.
4796
4797	A watcher can be pending, but not active. Stopping a watcher also clears
4798	its pending status.
4799		5219
4800	=item real time	5220	=item real time
4801		5221
4802	The physical time that is observed. It is apparently strictly monotonic :)	5222	The physical time that is observed. It is apparently strictly monotonic :)
4803		5223
…		…
4810	=item watcher	5230	=item watcher
4811		5231
4812	A data structure that describes interest in certain events. Watchers need	5232	A data structure that describes interest in certain events. Watchers need
4813	to be started (attached to an event loop) before they can receive events.	5233	to be started (attached to an event loop) before they can receive events.
4814		5234
4815	=item watcher invocation
4816
4817	The act of calling the callback associated with a watcher.
4818
4819	=back	5235	=back
4820		5236
4821	=head1 AUTHOR	5237	=head1 AUTHOR
4822		5238
4823	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5239	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5240	Magnusson and Emanuele Giaquinta.
4824		5241

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