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Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC vs.
Revision 1.358 by sf-exg, Tue Jan 11 08:43:48 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	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
168	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
169	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>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	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
174	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
…		…
191	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
192	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
193	not a problem.	203	not a problem.
194		204
195	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
196	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
197		208
198	assert (("libev version mismatch",	209	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
201		212
…		…
212	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
214		225
215	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
216		227
217	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
218	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
219	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
220	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
221	(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
222	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
223		235
224	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
225		237
226	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
227	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
231		243
232	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
233		245
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		247
236	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	277	}
266		278
267	...	279	...
268	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
269		281
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		283
272	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
273	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
274	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	299	}
288		300
289	...	301	...
290	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
291		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
292	=back	317	=back
293		318
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		320
296	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
297	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
298	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
299		324
300	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
301	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
302	not.	327	do not.
303		328
304	=over 4	329	=over 4
305		330
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		332
308	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
309	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
310	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
311	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".
312		343
313	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
314	function.	345	function (or via the C<EV_DEFAULT> macro).
315		346
316	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
317	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
318	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).
319		351
320	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,
321	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
322	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
323	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
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	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.
326		376
327	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
328	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>).
329		379
330	The following flags are supported:	380	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
346	around bugs.	396	around bugs.
347		397
348	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
349		399
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		402
354	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
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_NOSIGFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will not 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 is	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	428	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	429	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
382		448
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		450
385	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
386	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
422	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
423		489
424	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
425	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
426	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
427	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
428	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
429	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
430	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
431	hard to detect.	499	and is of course hard to detect.
432		500
433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
434	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
435	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
436	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
437	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
438	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
439	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
440		514
441	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
442	will result in some caching, there is still a system call per such	516	will result in some caching, there is still a system call per such
443	incident (because the same I<file descriptor> could point to a different	517	incident (because the same I<file descriptor> could point to a different
444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
511		585
512	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
513	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
514		588
515	Please note that Solaris event ports can deliver a lot of spurious
516	notifications, so you need to use non-blocking I/O or other means to avoid
517	blocking when no data (or space) is available.
518
519	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
520	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
522	might perform better.	592	might perform better.
523		593
524	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
525	notifications, this backend actually performed fully to specification
526	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
527	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
528		608
529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
530	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
531		611
532	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
533		613
534	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
536	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
537		617
538	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
539		627
540	=back	628	=back
541		629
542	If one or more of the backend flags are or'ed into the flags value,	630	If one or more of the backend flags are or'ed into the flags value,
543	then only these backends will be tried (in the reverse order as listed	631	then only these backends will be tried (in the reverse order as listed
544	here). If none are specified, all backends in C<ev_recommended_backends	632	here). If none are specified, all backends in C<ev_recommended_backends
545	()> will be tried.	633	()> will be tried.
546		634
547	Example: This is the most typical usage.
548
549	if (!ev_default_loop (0))
550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
551
552	Example: Restrict libev to the select and poll backends, and do not allow
553	environment settings to be taken into account:
554
555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
556
557	Example: Use whatever libev has to offer, but make sure that kqueue is
558	used if available (warning, breaks stuff, best use only with your own
559	private event loop and only if you know the OS supports your types of
560	fds):
561
562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
563
564	=item struct ev_loop *ev_loop_new (unsigned int flags)
565
566	Similar to C<ev_default_loop>, but always creates a new event loop that is
567	always distinct from the default loop. Unlike the default loop, it cannot
568	handle signal and child watchers, and attempts to do so will be greeted by
569	undefined behaviour (or a failed assertion if assertions are enabled).
570
571	Note that this function I<is> thread-safe, and the recommended way to use
572	libev with threads is indeed to create one loop per thread, and using the
573	default loop in the "main" or "initial" thread.
574
575	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
576		636
577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
578	if (!epoller)	638	if (!epoller)
579	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
580		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
581	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
582		647
583	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
584	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
585	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
586	responsibility to either stop all watchers cleanly yourself I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
587	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
588	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
590		655
591	Note that certain global state, such as signal state (and installed signal	656	Note that certain global state, such as signal state (and installed signal
592	handlers), will not be freed by this function, and related watchers (such	657	handlers), will not be freed by this function, and related watchers (such
593	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
594		659
595	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
596	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
597	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
598	C<ev_loop_new> and C<ev_loop_destroy>.	667	and C<ev_loop_destroy>.
599		668
600	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
601		670
602	Like C<ev_default_destroy>, but destroys an event loop created by an
603	earlier call to C<ev_loop_new>.
604
605	=item ev_default_fork ()
606
607	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
608	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
609	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
610	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
611	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
612	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
613		681
614	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
615	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
616	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
617		688
618	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
619	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
620	quite nicely into a call to C<pthread_atfork>:
621		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
622	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
623
624	=item ev_loop_fork (loop)
625
626	Like C<ev_default_fork>, but acts on an event loop created by
627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
628	after fork that you want to re-use in the child, and how you do this is
629	entirely your own problem.
630		703
631	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
632		705
633	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
634	otherwise.	707	otherwise.
635		708
636	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
637		710
638	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
639	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
640	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
641		714
642	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
643	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
644	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
645		719
646	=item unsigned int ev_loop_depth (loop)	720	=item unsigned int ev_depth (loop)
647		721
648	Returns the number of times C<ev_loop> was entered minus the number of	722	Returns the number of times C<ev_run> was entered minus the number of
649	times C<ev_loop> was exited, in other words, the recursion depth.	723	times C<ev_run> was exited normally, in other words, the recursion depth.
650		724
651	Outside C<ev_loop>, this number is zero. In a callback, this number is	725	Outside C<ev_run>, this number is zero. In a callback, this number is
652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
653	in which case it is higher.	727	in which case it is higher.
654		728
655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
656	etc.), doesn't count as exit.	730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
657		733
658	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
659		735
660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
661	use.	737	use.
…		…
670		746
671	=item ev_now_update (loop)	747	=item ev_now_update (loop)
672		748
673	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
674	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
675	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
676		752
677	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
678	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
679	the current time is a good idea.	755	the current time is a good idea.
680		756
…		…
682		758
683	=item ev_suspend (loop)	759	=item ev_suspend (loop)
684		760
685	=item ev_resume (loop)	761	=item ev_resume (loop)
686		762
687	These two functions suspend and resume a loop, for use when the loop is	763	These two functions suspend and resume an event loop, for use when the
688	not used for a while and timeouts should not be processed.	764	loop is not used for a while and timeouts should not be processed.
689		765
690	A typical use case would be an interactive program such as a game: When	766	A typical use case would be an interactive program such as a game: When
691	the user presses C<^Z> to suspend the game and resumes it an hour later it	767	the user presses C<^Z> to suspend the game and resumes it an hour later it
692	would be best to handle timeouts as if no time had actually passed while	768	would be best to handle timeouts as if no time had actually passed while
693	the program was suspended. This can be achieved by calling C<ev_suspend>	769	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
695	C<ev_resume> directly afterwards to resume timer processing.	771	C<ev_resume> directly afterwards to resume timer processing.
696		772
697	Effectively, all C<ev_timer> watchers will be delayed by the time spend	773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
699	will be rescheduled (that is, they will lose any events that would have	775	will be rescheduled (that is, they will lose any events that would have
700	occured while suspended).	776	occurred while suspended).
701		777
702	After calling C<ev_suspend> you B<must not> call I<any> function on the	778	After calling C<ev_suspend> you B<must not> call I<any> function on the
703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
704	without a previous call to C<ev_suspend>.	780	without a previous call to C<ev_suspend>.
705		781
706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
707	event loop time (see C<ev_now_update>).	783	event loop time (see C<ev_now_update>).
708		784
709	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
710		786
711	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
712	after you have initialised all your watchers and you want to start	788	after you have initialised all your watchers and you want to start
713	handling events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
714		792
715	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
716	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
717		796
718	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
719	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
720	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
721	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
722	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
723	beauty.	802	beauty.
724		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
726	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
727	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
728	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
729		814
730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
731	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
732	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
733	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
734	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
735	iteration of the loop.	820	iteration of the loop.
736		821
737	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
738	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
740	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
741		826
742	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
743		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
747	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	838	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
755	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
756	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
759	- Queue all expired timers.	849	- Queue all expired timers.
760	- Queue all expired periodics.	850	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	852	- Queue all check watchers.
763	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
764	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
765	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
767	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
768	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
769		863
770	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
771	anymore.	865	anymore.
772		866
773	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
774	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
775	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
777		871
778	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
779		873
780	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
781	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
784		878
785	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
786		880
787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
788		883
789	=item ev_ref (loop)	884	=item ev_ref (loop)
790		885
791	=item ev_unref (loop)	886	=item ev_unref (loop)
792		887
793	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
794	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
795	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
796		891
797	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
798	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
799	stopping it.	895	before stopping it.
800		896
801	As an example, libev itself uses this for its internal signal pipe: It	897	As an example, libev itself uses this for its internal signal pipe: It
802	is not visible to the libev user and should not keep C<ev_loop> from	898	is not visible to the libev user and should not keep C<ev_run> from
803	exiting if no event watchers registered by it are active. It is also an	899	exiting if no event watchers registered by it are active. It is also an
804	excellent way to do this for generic recurring timers or from within	900	excellent way to do this for generic recurring timers or from within
805	third-party libraries. Just remember to I<unref after start> and I<ref	901	third-party libraries. Just remember to I<unref after start> and I<ref
806	before stop> (but only if the watcher wasn't active before, or was active	902	before stop> (but only if the watcher wasn't active before, or was active
807	before, respectively. Note also that libev might stop watchers itself	903	before, respectively. Note also that libev might stop watchers itself
808	(e.g. non-repeating timers) in which case you have to C<ev_ref>	904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
809	in the callback).	905	in the callback).
810		906
811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
812	running when nothing else is active.	908	running when nothing else is active.
813		909
814	ev_signal exitsig;	910	ev_signal exitsig;
815	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
816	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
817	evf_unref (loop);	913	ev_unref (loop);
818		914
819	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
820		916
821	ev_ref (loop);	917	ev_ref (loop);
822	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
861	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
862	as this approaches the timing granularity of most systems. Note that if	958	as this approaches the timing granularity of most systems. Note that if
863	you do transactions with the outside world and you can't increase the	959	you do transactions with the outside world and you can't increase the
864	parallelity, then this setting will limit your transaction rate (if you	960	parallelity, then this setting will limit your transaction rate (if you
865	need to poll once per transaction and the I/O collect interval is 0.01,	961	need to poll once per transaction and the I/O collect interval is 0.01,
866	then you can't do more than 100 transations per second).	962	then you can't do more than 100 transactions per second).
867		963
868	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
869	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
870	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
871	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
…		…
879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
880		976
881	=item ev_invoke_pending (loop)	977	=item ev_invoke_pending (loop)
882		978
883	This call will simply invoke all pending watchers while resetting their	979	This call will simply invoke all pending watchers while resetting their
884	pending state. Normally, C<ev_loop> does this automatically when required,	980	pending state. Normally, C<ev_run> does this automatically when required,
885	but when overriding the invoke callback this call comes handy.	981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
886		986
887	=item int ev_pending_count (loop)	987	=item int ev_pending_count (loop)
888		988
889	Returns the number of pending watchers - zero indicates that no watchers	989	Returns the number of pending watchers - zero indicates that no watchers
890	are pending.	990	are pending.
891		991
892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
893		993
894	This overrides the invoke pending functionality of the loop: Instead of	994	This overrides the invoke pending functionality of the loop: Instead of
895	invoking all pending watchers when there are any, C<ev_loop> will call	995	invoking all pending watchers when there are any, C<ev_run> will call
896	this callback instead. This is useful, for example, when you want to	996	this callback instead. This is useful, for example, when you want to
897	invoke the actual watchers inside another context (another thread etc.).	997	invoke the actual watchers inside another context (another thread etc.).
898		998
899	If you want to reset the callback, use C<ev_invoke_pending> as new	999	If you want to reset the callback, use C<ev_invoke_pending> as new
900	callback.	1000	callback.
…		…
903		1003
904	Sometimes you want to share the same loop between multiple threads. This	1004	Sometimes you want to share the same loop between multiple threads. This
905	can be done relatively simply by putting mutex_lock/unlock calls around	1005	can be done relatively simply by putting mutex_lock/unlock calls around
906	each call to a libev function.	1006	each call to a libev function.
907		1007
908	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1008	However, C<ev_run> can run an indefinite time, so it is not feasible
909	wait for it to return. One way around this is to wake up the loop via	1009	to wait for it to return. One way around this is to wake up the event
910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
911	and I<acquire> callbacks on the loop.	1011	I<release> and I<acquire> callbacks on the loop.
912		1012
913	When set, then C<release> will be called just before the thread is	1013	When set, then C<release> will be called just before the thread is
914	suspended waiting for new events, and C<acquire> is called just	1014	suspended waiting for new events, and C<acquire> is called just
915	afterwards.	1015	afterwards.
916		1016
…		…
919		1019
920	While event loop modifications are allowed between invocations of	1020	While event loop modifications are allowed between invocations of
921	C<release> and C<acquire> (that's their only purpose after all), no	1021	C<release> and C<acquire> (that's their only purpose after all), no
922	modifications done will affect the event loop, i.e. adding watchers will	1022	modifications done will affect the event loop, i.e. adding watchers will
923	have no effect on the set of file descriptors being watched, or the time	1023	have no effect on the set of file descriptors being watched, or the time
924	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
925	to take note of any changes you made.	1025	to take note of any changes you made.
926		1026
927	In theory, threads executing C<ev_loop> will be async-cancel safe between	1027	In theory, threads executing C<ev_run> will be async-cancel safe between
928	invocations of C<release> and C<acquire>.	1028	invocations of C<release> and C<acquire>.
929		1029
930	See also the locking example in the C<THREADS> section later in this	1030	See also the locking example in the C<THREADS> section later in this
931	document.	1031	document.
932		1032
933	=item ev_set_userdata (loop, void *data)	1033	=item ev_set_userdata (loop, void *data)
934		1034
935	=item ev_userdata (loop)	1035	=item void *ev_userdata (loop)
936		1036
937	Set and retrieve a single C<void *> associated with a loop. When	1037	Set and retrieve a single C<void *> associated with a loop. When
938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
939	C<0.>	1039	C<0>.
940		1040
941	These two functions can be used to associate arbitrary data with a loop,	1041	These two functions can be used to associate arbitrary data with a loop,
942	and are intended solely for the C<invoke_pending_cb>, C<release> and	1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
943	C<acquire> callbacks described above, but of course can be (ab-)used for	1043	C<acquire> callbacks described above, but of course can be (ab-)used for
944	any other purpose as well.	1044	any other purpose as well.
945		1045
946	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
947		1047
948	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
949	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
950	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
951	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
962		1062
963	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
965	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
966		1066
967	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
968	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
969	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
970		1071
971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
972	{	1073	{
973	ev_io_stop (w);	1074	ev_io_stop (w);
974	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
975	}	1076	}
976		1077
977	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
978		1079
979	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
980		1081
981	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
983	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
984		1085
985	ev_loop (loop, 0);	1086	ev_run (loop, 0);
986		1087
987	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
988	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
989	stack).	1090	stack).
990		1091
991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
993		1094
994	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
995	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
996	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
997	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
998	is readable and/or writable).	1099	and/or writable).
999		1100
1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1001	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
1002	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
1003	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1026	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
1027		1128
1028	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
1029	writable.	1130	writable.
1030		1131
1031	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
1032		1133
1033	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
1034		1135
1035	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
1036		1137
…		…
1054		1155
1055	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
1056		1157
1057	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
1058		1159
1059	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1060	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
1061	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
1062	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
1063	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
1064	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1065	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
1066		1167
1067	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
1068		1169
1069	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1070		1171
1071	=item C<EV_FORK>	1172	=item C<EV_FORK>
1072		1173
1073	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
1074	C<ev_fork>).	1175	C<ev_fork>).
		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
1075		1180
1076	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
1077		1182
1078	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
1079		1184
…		…
1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1253	functions that do not need a watcher.	1358	functions that do not need a watcher.
1254		1359
1255	=back	1360	=back
1256		1361
		1362	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1363	OWN COMPOSITE WATCHERS> idioms.
1257		1364
1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1365	=head2 WATCHER STATES
1259		1366
1260	Each watcher has, by default, a member C<void *data> that you can change	1367	There are various watcher states mentioned throughout this manual -
1261	and read at any time: libev will completely ignore it. This can be used	1368	active, pending and so on. In this section these states and the rules to
1262	to associate arbitrary data with your watcher. If you need more data and	1369	transition between them will be described in more detail - and while these
1263	don't want to allocate memory and store a pointer to it in that data	1370	rules might look complicated, they usually do "the right thing".
1264	member, you can also "subclass" the watcher type and provide your own
1265	data:
1266		1371
1267	struct my_io	1372	=over 4
1268	{
1269	ev_io io;
1270	int otherfd;
1271	void *somedata;
1272	struct whatever *mostinteresting;
1273	};
1274		1373
1275	...	1374	=item initialiased
1276	struct my_io w;
1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1278		1375
1279	And since your callback will be called with a pointer to the watcher, you	1376	Before a watcher can be registered with the event looop it has to be
1280	can cast it back to your own type:	1377	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1378	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1281		1379
1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1380	In this state it is simply some block of memory that is suitable for use
1283	{	1381	in an event loop. It can be moved around, freed, reused etc. at will.
1284	struct my_io *w = (struct my_io *)w_;
1285	...
1286	}
1287		1382
1288	More interesting and less C-conformant ways of casting your callback type	1383	=item started/running/active
1289	instead have been omitted.
1290		1384
1291	Another common scenario is to use some data structure with multiple	1385	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1292	embedded watchers:	1386	property of the event loop, and is actively waiting for events. While in
		1387	this state it cannot be accessed (except in a few documented ways), moved,
		1388	freed or anything else - the only legal thing is to keep a pointer to it,
		1389	and call libev functions on it that are documented to work on active watchers.
1293		1390
1294	struct my_biggy	1391	=item pending
1295	{
1296	int some_data;
1297	ev_timer t1;
1298	ev_timer t2;
1299	}
1300		1392
1301	In this case getting the pointer to C<my_biggy> is a bit more	1393	If a watcher is active and libev determines that an event it is interested
1302	complicated: Either you store the address of your C<my_biggy> struct	1394	in has occurred (such as a timer expiring), it will become pending. It will
1303	in the C<data> member of the watcher (for woozies), or you need to use	1395	stay in this pending state until either it is stopped or its callback is
1304	some pointer arithmetic using C<offsetof> inside your watchers (for real	1396	about to be invoked, so it is not normally pending inside the watcher
1305	programmers):	1397	callback.
1306		1398
1307	#include <stddef.h>	1399	The watcher might or might not be active while it is pending (for example,
		1400	an expired non-repeating timer can be pending but no longer active). If it
		1401	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1402	but it is still property of the event loop at this time, so cannot be
		1403	moved, freed or reused. And if it is active the rules described in the
		1404	previous item still apply.
1308		1405
1309	static void	1406	It is also possible to feed an event on a watcher that is not active (e.g.
1310	t1_cb (EV_P_ ev_timer *w, int revents)	1407	via C<ev_feed_event>), in which case it becomes pending without being
1311	{	1408	active.
1312	struct my_biggy big = (struct my_biggy *)
1313	(((char *)w) - offsetof (struct my_biggy, t1));
1314	}
1315		1409
1316	static void	1410	=item stopped
1317	t2_cb (EV_P_ ev_timer *w, int revents)	1411
1318	{	1412	A watcher can be stopped implicitly by libev (in which case it might still
1319	struct my_biggy big = (struct my_biggy *)	1413	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1320	(((char *)w) - offsetof (struct my_biggy, t2));	1414	latter will clear any pending state the watcher might be in, regardless
1321	}	1415	of whether it was active or not, so stopping a watcher explicitly before
		1416	freeing it is often a good idea.
		1417
		1418	While stopped (and not pending) the watcher is essentially in the
		1419	initialised state, that is it can be reused, moved, modified in any way
		1420	you wish.
		1421
		1422	=back
1322		1423
1323	=head2 WATCHER PRIORITY MODELS	1424	=head2 WATCHER PRIORITY MODELS
1324		1425
1325	Many event loops support I<watcher priorities>, which are usually small	1426	Many event loops support I<watcher priorities>, which are usually small
1326	integers that influence the ordering of event callback invocation	1427	integers that influence the ordering of event callback invocation
…		…
1369		1470
1370	For example, to emulate how many other event libraries handle priorities,	1471	For example, to emulate how many other event libraries handle priorities,
1371	you can associate an C<ev_idle> watcher to each such watcher, and in	1472	you can associate an C<ev_idle> watcher to each such watcher, and in
1372	the normal watcher callback, you just start the idle watcher. The real	1473	the normal watcher callback, you just start the idle watcher. The real
1373	processing is done in the idle watcher callback. This causes libev to	1474	processing is done in the idle watcher callback. This causes libev to
1374	continously poll and process kernel event data for the watcher, but when	1475	continuously poll and process kernel event data for the watcher, but when
1375	the lock-out case is known to be rare (which in turn is rare :), this is	1476	the lock-out case is known to be rare (which in turn is rare :), this is
1376	workable.	1477	workable.
1377		1478
1378	Usually, however, the lock-out model implemented that way will perform	1479	Usually, however, the lock-out model implemented that way will perform
1379	miserably under the type of load it was designed to handle. In that case,	1480	miserably under the type of load it was designed to handle. In that case,
…		…
1393	{	1494	{
1394	// stop the I/O watcher, we received the event, but	1495	// stop the I/O watcher, we received the event, but
1395	// are not yet ready to handle it.	1496	// are not yet ready to handle it.
1396	ev_io_stop (EV_A_ w);	1497	ev_io_stop (EV_A_ w);
1397		1498
1398	// start the idle watcher to ahndle the actual event.	1499	// start the idle watcher to handle the actual event.
1399	// it will not be executed as long as other watchers	1500	// it will not be executed as long as other watchers
1400	// with the default priority are receiving events.	1501	// with the default priority are receiving events.
1401	ev_idle_start (EV_A_ &idle);	1502	ev_idle_start (EV_A_ &idle);
1402	}	1503	}
1403		1504
…		…
1453	In general you can register as many read and/or write event watchers per	1554	In general you can register as many read and/or write event watchers per
1454	fd as you want (as long as you don't confuse yourself). Setting all file	1555	fd as you want (as long as you don't confuse yourself). Setting all file
1455	descriptors to non-blocking mode is also usually a good idea (but not	1556	descriptors to non-blocking mode is also usually a good idea (but not
1456	required if you know what you are doing).	1557	required if you know what you are doing).
1457		1558
1458	If you cannot use non-blocking mode, then force the use of a
1459	known-to-be-good backend (at the time of this writing, this includes only
1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1461	descriptors for which non-blocking operation makes no sense (such as
1462	files) - libev doesn't guarentee any specific behaviour in that case.
1463
1464	Another thing you have to watch out for is that it is quite easy to	1559	Another thing you have to watch out for is that it is quite easy to
1465	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is, your callback might
1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1467	because there is no data. Not only are some backends known to create a	1562	because there is no data. It is very easy to get into this situation even
1468	lot of those (for example Solaris ports), it is very easy to get into	1563	with a relatively standard program structure. Thus it is best to always
1469	this situation even with a relatively standard program structure. Thus	1564	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1565	preferable to a program hanging until some data arrives.
1472		1566
1473	If you cannot run the fd in non-blocking mode (for example you should	1567	If you cannot run the fd in non-blocking mode (for example you should
1474	not play around with an Xlib connection), then you have to separately	1568	not play around with an Xlib connection), then you have to separately
1475	re-test whether a file descriptor is really ready with a known-to-be good	1569	re-test whether a file descriptor is really ready with a known-to-be good
1476	interface such as poll (fortunately in our Xlib example, Xlib already	1570	interface such as poll (fortunately in the case of Xlib, it already does
1477	does this on its own, so its quite safe to use). Some people additionally	1571	this on its own, so its quite safe to use). Some people additionally
1478	use C<SIGALRM> and an interval timer, just to be sure you won't block	1572	use C<SIGALRM> and an interval timer, just to be sure you won't block
1479	indefinitely.	1573	indefinitely.
1480		1574
1481	But really, best use non-blocking mode.	1575	But really, best use non-blocking mode.
1482		1576
…		…
1510		1604
1511	There is no workaround possible except not registering events	1605	There is no workaround possible except not registering events
1512	for potentially C<dup ()>'ed file descriptors, or to resort to	1606	for potentially C<dup ()>'ed file descriptors, or to resort to
1513	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1514		1608
		1609	=head3 The special problem of files
		1610
		1611	Many people try to use C<select> (or libev) on file descriptors
		1612	representing files, and expect it to become ready when their program
		1613	doesn't block on disk accesses (which can take a long time on their own).
		1614
		1615	However, this cannot ever work in the "expected" way - you get a readiness
		1616	notification as soon as the kernel knows whether and how much data is
		1617	there, and in the case of open files, that's always the case, so you
		1618	always get a readiness notification instantly, and your read (or possibly
		1619	write) will still block on the disk I/O.
		1620
		1621	Another way to view it is that in the case of sockets, pipes, character
		1622	devices and so on, there is another party (the sender) that delivers data
		1623	on its own, but in the case of files, there is no such thing: the disk
		1624	will not send data on its own, simply because it doesn't know what you
		1625	wish to read - you would first have to request some data.
		1626
		1627	Since files are typically not-so-well supported by advanced notification
		1628	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1629	to files, even though you should not use it. The reason for this is
		1630	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1631	usually a tty, often a pipe, but also sometimes files or special devices
		1632	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1633	F</dev/urandom>), and even though the file might better be served with
		1634	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1635	it "just works" instead of freezing.
		1636
		1637	So avoid file descriptors pointing to files when you know it (e.g. use
		1638	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1639	when you rarely read from a file instead of from a socket, and want to
		1640	reuse the same code path.
		1641
1515	=head3 The special problem of fork	1642	=head3 The special problem of fork
1516		1643
1517	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1644	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1518	useless behaviour. Libev fully supports fork, but needs to be told about	1645	useless behaviour. Libev fully supports fork, but needs to be told about
1519	it in the child.	1646	it in the child if you want to continue to use it in the child.
1520		1647
1521	To support fork in your programs, you either have to call	1648	To support fork in your child processes, you have to call C<ev_loop_fork
1522	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1649	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1650	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524	C<EVBACKEND_POLL>.
1525		1651
1526	=head3 The special problem of SIGPIPE	1652	=head3 The special problem of SIGPIPE
1527		1653
1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1654	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1529	when writing to a pipe whose other end has been closed, your program gets	1655	when writing to a pipe whose other end has been closed, your program gets
…		…
1532		1658
1533	So when you encounter spurious, unexplained daemon exits, make sure you	1659	So when you encounter spurious, unexplained daemon exits, make sure you
1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1660	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1535	somewhere, as that would have given you a big clue).	1661	somewhere, as that would have given you a big clue).
1536		1662
		1663	=head3 The special problem of accept()ing when you can't
		1664
		1665	Many implementations of the POSIX C<accept> function (for example,
		1666	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1667	connection from the pending queue in all error cases.
		1668
		1669	For example, larger servers often run out of file descriptors (because
		1670	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1671	rejecting the connection, leading to libev signalling readiness on
		1672	the next iteration again (the connection still exists after all), and
		1673	typically causing the program to loop at 100% CPU usage.
		1674
		1675	Unfortunately, the set of errors that cause this issue differs between
		1676	operating systems, there is usually little the app can do to remedy the
		1677	situation, and no known thread-safe method of removing the connection to
		1678	cope with overload is known (to me).
		1679
		1680	One of the easiest ways to handle this situation is to just ignore it
		1681	- when the program encounters an overload, it will just loop until the
		1682	situation is over. While this is a form of busy waiting, no OS offers an
		1683	event-based way to handle this situation, so it's the best one can do.
		1684
		1685	A better way to handle the situation is to log any errors other than
		1686	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1687	messages, and continue as usual, which at least gives the user an idea of
		1688	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1689	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1690	usage.
		1691
		1692	If your program is single-threaded, then you could also keep a dummy file
		1693	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1694	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1695	close that fd, and create a new dummy fd. This will gracefully refuse
		1696	clients under typical overload conditions.
		1697
		1698	The last way to handle it is to simply log the error and C<exit>, as
		1699	is often done with C<malloc> failures, but this results in an easy
		1700	opportunity for a DoS attack.
1537		1701
1538	=head3 Watcher-Specific Functions	1702	=head3 Watcher-Specific Functions
1539		1703
1540	=over 4	1704	=over 4
1541		1705
…		…
1573	...	1737	...
1574	struct ev_loop *loop = ev_default_init (0);	1738	struct ev_loop *loop = ev_default_init (0);
1575	ev_io stdin_readable;	1739	ev_io stdin_readable;
1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1740	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1577	ev_io_start (loop, &stdin_readable);	1741	ev_io_start (loop, &stdin_readable);
1578	ev_loop (loop, 0);	1742	ev_run (loop, 0);
1579		1743
1580		1744
1581	=head2 C<ev_timer> - relative and optionally repeating timeouts	1745	=head2 C<ev_timer> - relative and optionally repeating timeouts
1582		1746
1583	Timer watchers are simple relative timers that generate an event after a	1747	Timer watchers are simple relative timers that generate an event after a
…		…
1592	The callback is guaranteed to be invoked only I<after> its timeout has	1756	The callback is guaranteed to be invoked only I<after> its timeout has
1593	passed (not I<at>, so on systems with very low-resolution clocks this	1757	passed (not I<at>, so on systems with very low-resolution clocks this
1594	might introduce a small delay). If multiple timers become ready during the	1758	might introduce a small delay). If multiple timers become ready during the
1595	same loop iteration then the ones with earlier time-out values are invoked	1759	same loop iteration then the ones with earlier time-out values are invoked
1596	before ones of the same priority with later time-out values (but this is	1760	before ones of the same priority with later time-out values (but this is
1597	no longer true when a callback calls C<ev_loop> recursively).	1761	no longer true when a callback calls C<ev_run> recursively).
1598		1762
1599	=head3 Be smart about timeouts	1763	=head3 Be smart about timeouts
1600		1764
1601	Many real-world problems involve some kind of timeout, usually for error	1765	Many real-world problems involve some kind of timeout, usually for error
1602	recovery. A typical example is an HTTP request - if the other side hangs,	1766	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1688	ev_tstamp timeout = last_activity + 60.;	1852	ev_tstamp timeout = last_activity + 60.;
1689		1853
1690	// if last_activity + 60. is older than now, we did time out	1854	// if last_activity + 60. is older than now, we did time out
1691	if (timeout < now)	1855	if (timeout < now)
1692	{	1856	{
1693	// timeout occured, take action	1857	// timeout occurred, take action
1694	}	1858	}
1695	else	1859	else
1696	{	1860	{
1697	// callback was invoked, but there was some activity, re-arm	1861	// callback was invoked, but there was some activity, re-arm
1698	// the watcher to fire in last_activity + 60, which is	1862	// the watcher to fire in last_activity + 60, which is
…		…
1720	to the current time (meaning we just have some activity :), then call the	1884	to the current time (meaning we just have some activity :), then call the
1721	callback, which will "do the right thing" and start the timer:	1885	callback, which will "do the right thing" and start the timer:
1722		1886
1723	ev_init (timer, callback);	1887	ev_init (timer, callback);
1724	last_activity = ev_now (loop);	1888	last_activity = ev_now (loop);
1725	callback (loop, timer, EV_TIMEOUT);	1889	callback (loop, timer, EV_TIMER);
1726		1890
1727	And when there is some activity, simply store the current time in	1891	And when there is some activity, simply store the current time in
1728	C<last_activity>, no libev calls at all:	1892	C<last_activity>, no libev calls at all:
1729		1893
1730	last_actiivty = ev_now (loop);	1894	last_activity = ev_now (loop);
1731		1895
1732	This technique is slightly more complex, but in most cases where the	1896	This technique is slightly more complex, but in most cases where the
1733	time-out is unlikely to be triggered, much more efficient.	1897	time-out is unlikely to be triggered, much more efficient.
1734		1898
1735	Changing the timeout is trivial as well (if it isn't hard-coded in the	1899	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1773		1937
1774	=head3 The special problem of time updates	1938	=head3 The special problem of time updates
1775		1939
1776	Establishing the current time is a costly operation (it usually takes at	1940	Establishing the current time is a costly operation (it usually takes at
1777	least two system calls): EV therefore updates its idea of the current	1941	least two system calls): EV therefore updates its idea of the current
1778	time only before and after C<ev_loop> collects new events, which causes a	1942	time only before and after C<ev_run> collects new events, which causes a
1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1943	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1780	lots of events in one iteration.	1944	lots of events in one iteration.
1781		1945
1782	The relative timeouts are calculated relative to the C<ev_now ()>	1946	The relative timeouts are calculated relative to the C<ev_now ()>
1783	time. This is usually the right thing as this timestamp refers to the time	1947	time. This is usually the right thing as this timestamp refers to the time
…		…
1861	Returns the remaining time until a timer fires. If the timer is active,	2025	Returns the remaining time until a timer fires. If the timer is active,
1862	then this time is relative to the current event loop time, otherwise it's	2026	then this time is relative to the current event loop time, otherwise it's
1863	the timeout value currently configured.	2027	the timeout value currently configured.
1864		2028
1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2029	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2030	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1867	will return C<4>. When the timer expires and is restarted, it will return	2031	will return C<4>. When the timer expires and is restarted, it will return
1868	roughly C<7> (likely slightly less as callback invocation takes some time,	2032	roughly C<7> (likely slightly less as callback invocation takes some time,
1869	too), and so on.	2033	too), and so on.
1870		2034
1871	=item ev_tstamp repeat [read-write]	2035	=item ev_tstamp repeat [read-write]
…		…
1900	}	2064	}
1901		2065
1902	ev_timer mytimer;	2066	ev_timer mytimer;
1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2067	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1904	ev_timer_again (&mytimer); /* start timer */	2068	ev_timer_again (&mytimer); /* start timer */
1905	ev_loop (loop, 0);	2069	ev_run (loop, 0);
1906		2070
1907	// and in some piece of code that gets executed on any "activity":	2071	// and in some piece of code that gets executed on any "activity":
1908	// reset the timeout to start ticking again at 10 seconds	2072	// reset the timeout to start ticking again at 10 seconds
1909	ev_timer_again (&mytimer);	2073	ev_timer_again (&mytimer);
1910		2074
…		…
1936		2100
1937	As with timers, the callback is guaranteed to be invoked only when the	2101	As with timers, the callback is guaranteed to be invoked only when the
1938	point in time where it is supposed to trigger has passed. If multiple	2102	point in time where it is supposed to trigger has passed. If multiple
1939	timers become ready during the same loop iteration then the ones with	2103	timers become ready during the same loop iteration then the ones with
1940	earlier time-out values are invoked before ones with later time-out values	2104	earlier time-out values are invoked before ones with later time-out values
1941	(but this is no longer true when a callback calls C<ev_loop> recursively).	2105	(but this is no longer true when a callback calls C<ev_run> recursively).
1942		2106
1943	=head3 Watcher-Specific Functions and Data Members	2107	=head3 Watcher-Specific Functions and Data Members
1944		2108
1945	=over 4	2109	=over 4
1946		2110
…		…
2074	Example: Call a callback every hour, or, more precisely, whenever the	2238	Example: Call a callback every hour, or, more precisely, whenever the
2075	system time is divisible by 3600. The callback invocation times have	2239	system time is divisible by 3600. The callback invocation times have
2076	potentially a lot of jitter, but good long-term stability.	2240	potentially a lot of jitter, but good long-term stability.
2077		2241
2078	static void	2242	static void
2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2243	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2080	{	2244	{
2081	... its now a full hour (UTC, or TAI or whatever your clock follows)	2245	... its now a full hour (UTC, or TAI or whatever your clock follows)
2082	}	2246	}
2083		2247
2084	ev_periodic hourly_tick;	2248	ev_periodic hourly_tick;
…		…
2107		2271
2108	=head2 C<ev_signal> - signal me when a signal gets signalled!	2272	=head2 C<ev_signal> - signal me when a signal gets signalled!
2109		2273
2110	Signal watchers will trigger an event when the process receives a specific	2274	Signal watchers will trigger an event when the process receives a specific
2111	signal one or more times. Even though signals are very asynchronous, libev	2275	signal one or more times. Even though signals are very asynchronous, libev
2112	will try it's best to deliver signals synchronously, i.e. as part of the	2276	will try its best to deliver signals synchronously, i.e. as part of the
2113	normal event processing, like any other event.	2277	normal event processing, like any other event.
2114		2278
2115	If you want signals to be delivered truly asynchronously, just use	2279	If you want signals to be delivered truly asynchronously, just use
2116	C<sigaction> as you would do without libev and forget about sharing	2280	C<sigaction> as you would do without libev and forget about sharing
2117	the signal. You can even use C<ev_async> from a signal handler to	2281	the signal. You can even use C<ev_async> from a signal handler to
…		…
2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2295	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2132	not be unduly interrupted. If you have a problem with system calls getting	2296	not be unduly interrupted. If you have a problem with system calls getting
2133	interrupted by signals you can block all signals in an C<ev_check> watcher	2297	interrupted by signals you can block all signals in an C<ev_check> watcher
2134	and unblock them in an C<ev_prepare> watcher.	2298	and unblock them in an C<ev_prepare> watcher.
2135		2299
2136	=head3 The special problem of inheritance over execve	2300	=head3 The special problem of inheritance over fork/execve/pthread_create
2137		2301
2138	Both the signal mask (C<sigprocmask>) and the signal disposition	2302	Both the signal mask (C<sigprocmask>) and the signal disposition
2139	(C<sigaction>) are unspecified after starting a signal watcher (and after	2303	(C<sigaction>) are unspecified after starting a signal watcher (and after
2140	stopping it again), that is, libev might or might not block the signal,	2304	stopping it again), that is, libev might or might not block the signal,
2141	and might or might not set or restore the installed signal handler.	2305	and might or might not set or restore the installed signal handler.
…		…
2151		2315
2152	The simplest way to ensure that the signal mask is reset in the child is	2316	The simplest way to ensure that the signal mask is reset in the child is
2153	to install a fork handler with C<pthread_atfork> that resets it. That will	2317	to install a fork handler with C<pthread_atfork> that resets it. That will
2154	catch fork calls done by libraries (such as the libc) as well.	2318	catch fork calls done by libraries (such as the libc) as well.
2155		2319
2156	In current versions of libev, you can also ensure that the signal mask is	2320	In current versions of libev, the signal will not be blocked indefinitely
2157	not blocking any signals (except temporarily, so thread users watch out)	2321	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This	2322	the window of opportunity for problems, it will not go away, as libev
2159	is not guaranteed for future versions, however.	2323	I<has> to modify the signal mask, at least temporarily.
		2324
		2325	So I can't stress this enough: I<If you do not reset your signal mask when
		2326	you expect it to be empty, you have a race condition in your code>. This
		2327	is not a libev-specific thing, this is true for most event libraries.
		2328
		2329	=head3 The special problem of threads signal handling
		2330
		2331	POSIX threads has problematic signal handling semantics, specifically,
		2332	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2333	threads in a process block signals, which is hard to achieve.
		2334
		2335	When you want to use sigwait (or mix libev signal handling with your own
		2336	for the same signals), you can tackle this problem by globally blocking
		2337	all signals before creating any threads (or creating them with a fully set
		2338	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2339	loops. Then designate one thread as "signal receiver thread" which handles
		2340	these signals. You can pass on any signals that libev might be interested
		2341	in by calling C<ev_feed_signal>.
2160		2342
2161	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
2162		2344
2163	=over 4	2345	=over 4
2164		2346
…		…
2180	Example: Try to exit cleanly on SIGINT.	2362	Example: Try to exit cleanly on SIGINT.
2181		2363
2182	static void	2364	static void
2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2365	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2184	{	2366	{
2185	ev_unloop (loop, EVUNLOOP_ALL);	2367	ev_break (loop, EVBREAK_ALL);
2186	}	2368	}
2187		2369
2188	ev_signal signal_watcher;	2370	ev_signal signal_watcher;
2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2371	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2190	ev_signal_start (loop, &signal_watcher);	2372	ev_signal_start (loop, &signal_watcher);
…		…
2576		2758
2577	Prepare and check watchers are usually (but not always) used in pairs:	2759	Prepare and check watchers are usually (but not always) used in pairs:
2578	prepare watchers get invoked before the process blocks and check watchers	2760	prepare watchers get invoked before the process blocks and check watchers
2579	afterwards.	2761	afterwards.
2580		2762
2581	You I<must not> call C<ev_loop> or similar functions that enter	2763	You I<must not> call C<ev_run> or similar functions that enter
2582	the current event loop from either C<ev_prepare> or C<ev_check>	2764	the current event loop from either C<ev_prepare> or C<ev_check>
2583	watchers. Other loops than the current one are fine, however. The	2765	watchers. Other loops than the current one are fine, however. The
2584	rationale behind this is that you do not need to check for recursion in	2766	rationale behind this is that you do not need to check for recursion in
2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2767	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2586	C<ev_check> so if you have one watcher of each kind they will always be	2768	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2754		2936
2755	if (timeout >= 0)	2937	if (timeout >= 0)
2756	// create/start timer	2938	// create/start timer
2757		2939
2758	// poll	2940	// poll
2759	ev_loop (EV_A_ 0);	2941	ev_run (EV_A_ 0);
2760		2942
2761	// stop timer again	2943	// stop timer again
2762	if (timeout >= 0)	2944	if (timeout >= 0)
2763	ev_timer_stop (EV_A_ &to);	2945	ev_timer_stop (EV_A_ &to);
2764		2946
…		…
2842	if you do not want that, you need to temporarily stop the embed watcher).	3024	if you do not want that, you need to temporarily stop the embed watcher).
2843		3025
2844	=item ev_embed_sweep (loop, ev_embed *)	3026	=item ev_embed_sweep (loop, ev_embed *)
2845		3027
2846	Make a single, non-blocking sweep over the embedded loop. This works	3028	Make a single, non-blocking sweep over the embedded loop. This works
2847	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3029	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2848	appropriate way for embedded loops.	3030	appropriate way for embedded loops.
2849		3031
2850	=item struct ev_loop *other [read-only]	3032	=item struct ev_loop *other [read-only]
2851		3033
2852	The embedded event loop.	3034	The embedded event loop.
…		…
2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3094	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2913	handlers will be invoked, too, of course.	3095	handlers will be invoked, too, of course.
2914		3096
2915	=head3 The special problem of life after fork - how is it possible?	3097	=head3 The special problem of life after fork - how is it possible?
2916		3098
2917	Most uses of C<fork()> consist of forking, then some simple calls to ste	3099	Most uses of C<fork()> consist of forking, then some simple calls to set
2918	up/change the process environment, followed by a call to C<exec()>. This	3100	up/change the process environment, followed by a call to C<exec()>. This
2919	sequence should be handled by libev without any problems.	3101	sequence should be handled by libev without any problems.
2920		3102
2921	This changes when the application actually wants to do event handling	3103	This changes when the application actually wants to do event handling
2922	in the child, or both parent in child, in effect "continuing" after the	3104	in the child, or both parent in child, in effect "continuing" after the
…		…
2938	disadvantage of having to use multiple event loops (which do not support	3120	disadvantage of having to use multiple event loops (which do not support
2939	signal watchers).	3121	signal watchers).
2940		3122
2941	When this is not possible, or you want to use the default loop for	3123	When this is not possible, or you want to use the default loop for
2942	other reasons, then in the process that wants to start "fresh", call	3124	other reasons, then in the process that wants to start "fresh", call
2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3125	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2944	the default loop will "orphan" (not stop) all registered watchers, so you	3126	Destroying the default loop will "orphan" (not stop) all registered
2945	have to be careful not to execute code that modifies those watchers. Note	3127	watchers, so you have to be careful not to execute code that modifies
2946	also that in that case, you have to re-register any signal watchers.	3128	those watchers. Note also that in that case, you have to re-register any
		3129	signal watchers.
2947		3130
2948	=head3 Watcher-Specific Functions and Data Members	3131	=head3 Watcher-Specific Functions and Data Members
2949		3132
2950	=over 4	3133	=over 4
2951		3134
2952	=item ev_fork_init (ev_signal *, callback)	3135	=item ev_fork_init (ev_fork *, callback)
2953		3136
2954	Initialises and configures the fork watcher - it has no parameters of any	3137	Initialises and configures the fork watcher - it has no parameters of any
2955	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3138	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2956	believe me.	3139	really.
2957		3140
2958	=back	3141	=back
2959		3142
2960		3143
		3144	=head2 C<ev_cleanup> - even the best things end
		3145
		3146	Cleanup watchers are called just before the event loop is being destroyed
		3147	by a call to C<ev_loop_destroy>.
		3148
		3149	While there is no guarantee that the event loop gets destroyed, cleanup
		3150	watchers provide a convenient method to install cleanup hooks for your
		3151	program, worker threads and so on - you just to make sure to destroy the
		3152	loop when you want them to be invoked.
		3153
		3154	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3155	all other watchers, they do not keep a reference to the event loop (which
		3156	makes a lot of sense if you think about it). Like all other watchers, you
		3157	can call libev functions in the callback, except C<ev_cleanup_start>.
		3158
		3159	=head3 Watcher-Specific Functions and Data Members
		3160
		3161	=over 4
		3162
		3163	=item ev_cleanup_init (ev_cleanup *, callback)
		3164
		3165	Initialises and configures the cleanup watcher - it has no parameters of
		3166	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3167	pointless, I assure you.
		3168
		3169	=back
		3170
		3171	Example: Register an atexit handler to destroy the default loop, so any
		3172	cleanup functions are called.
		3173
		3174	static void
		3175	program_exits (void)
		3176	{
		3177	ev_loop_destroy (EV_DEFAULT_UC);
		3178	}
		3179
		3180	...
		3181	atexit (program_exits);
		3182
		3183
2961	=head2 C<ev_async> - how to wake up another event loop	3184	=head2 C<ev_async> - how to wake up an event loop
2962		3185
2963	In general, you cannot use an C<ev_loop> from multiple threads or other	3186	In general, you cannot use an C<ev_run> from multiple threads or other
2964	asynchronous sources such as signal handlers (as opposed to multiple event	3187	asynchronous sources such as signal handlers (as opposed to multiple event
2965	loops - those are of course safe to use in different threads).	3188	loops - those are of course safe to use in different threads).
2966		3189
2967	Sometimes, however, you need to wake up another event loop you do not	3190	Sometimes, however, you need to wake up an event loop you do not control,
2968	control, for example because it belongs to another thread. This is what	3191	for example because it belongs to another thread. This is what C<ev_async>
2969	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3192	watchers do: as long as the C<ev_async> watcher is active, you can signal
2970	can signal it by calling C<ev_async_send>, which is thread- and signal	3193	it by calling C<ev_async_send>, which is thread- and signal safe.
2971	safe.
2972		3194
2973	This functionality is very similar to C<ev_signal> watchers, as signals,	3195	This functionality is very similar to C<ev_signal> watchers, as signals,
2974	too, are asynchronous in nature, and signals, too, will be compressed	3196	too, are asynchronous in nature, and signals, too, will be compressed
2975	(i.e. the number of callback invocations may be less than the number of	3197	(i.e. the number of callback invocations may be less than the number of
2976	C<ev_async_sent> calls).	3198	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3199	of "global async watchers" by using a watcher on an otherwise unused
		3200	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3201	even without knowing which loop owns the signal.
2977		3202
2978	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3203	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2979	just the default loop.	3204	just the default loop.
2980		3205
2981	=head3 Queueing	3206	=head3 Queueing
…		…
3131		3356
3132	If C<timeout> is less than 0, then no timeout watcher will be	3357	If C<timeout> is less than 0, then no timeout watcher will be
3133	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3358	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3134	repeat = 0) will be started. C<0> is a valid timeout.	3359	repeat = 0) will be started. C<0> is a valid timeout.
3135		3360
3136	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3361	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3137	passed an C<revents> set like normal event callbacks (a combination of	3362	passed an C<revents> set like normal event callbacks (a combination of
3138	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3363	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3139	value passed to C<ev_once>. Note that it is possible to receive I<both>	3364	value passed to C<ev_once>. Note that it is possible to receive I<both>
3140	a timeout and an io event at the same time - you probably should give io	3365	a timeout and an io event at the same time - you probably should give io
3141	events precedence.	3366	events precedence.
3142		3367
3143	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3368	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3144		3369
3145	static void stdin_ready (int revents, void *arg)	3370	static void stdin_ready (int revents, void *arg)
3146	{	3371	{
3147	if (revents & EV_READ)	3372	if (revents & EV_READ)
3148	/* stdin might have data for us, joy! */;	3373	/* stdin might have data for us, joy! */;
3149	else if (revents & EV_TIMEOUT)	3374	else if (revents & EV_TIMER)
3150	/* doh, nothing entered */;	3375	/* doh, nothing entered */;
3151	}	3376	}
3152		3377
3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3378	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3154		3379
…		…
3157	Feed an event on the given fd, as if a file descriptor backend detected	3382	Feed an event on the given fd, as if a file descriptor backend detected
3158	the given events it.	3383	the given events it.
3159		3384
3160	=item ev_feed_signal_event (loop, int signum)	3385	=item ev_feed_signal_event (loop, int signum)
3161		3386
3162	Feed an event as if the given signal occurred (C<loop> must be the default	3387	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3163	loop!).	3388	which is async-safe.
3164		3389
3165	=back	3390	=back
		3391
		3392
		3393	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3394
		3395	This section explains some common idioms that are not immediately
		3396	obvious. Note that examples are sprinkled over the whole manual, and this
		3397	section only contains stuff that wouldn't fit anywhere else.
		3398
		3399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3400
		3401	Each watcher has, by default, a C<void *data> member that you can read
		3402	or modify at any time: libev will completely ignore it. This can be used
		3403	to associate arbitrary data with your watcher. If you need more data and
		3404	don't want to allocate memory separately and store a pointer to it in that
		3405	data member, you can also "subclass" the watcher type and provide your own
		3406	data:
		3407
		3408	struct my_io
		3409	{
		3410	ev_io io;
		3411	int otherfd;
		3412	void *somedata;
		3413	struct whatever *mostinteresting;
		3414	};
		3415
		3416	...
		3417	struct my_io w;
		3418	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3419
		3420	And since your callback will be called with a pointer to the watcher, you
		3421	can cast it back to your own type:
		3422
		3423	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3424	{
		3425	struct my_io *w = (struct my_io *)w_;
		3426	...
		3427	}
		3428
		3429	More interesting and less C-conformant ways of casting your callback
		3430	function type instead have been omitted.
		3431
		3432	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3433
		3434	Another common scenario is to use some data structure with multiple
		3435	embedded watchers, in effect creating your own watcher that combines
		3436	multiple libev event sources into one "super-watcher":
		3437
		3438	struct my_biggy
		3439	{
		3440	int some_data;
		3441	ev_timer t1;
		3442	ev_timer t2;
		3443	}
		3444
		3445	In this case getting the pointer to C<my_biggy> is a bit more
		3446	complicated: Either you store the address of your C<my_biggy> struct in
		3447	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3448	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3449	real programmers):
		3450
		3451	#include <stddef.h>
		3452
		3453	static void
		3454	t1_cb (EV_P_ ev_timer *w, int revents)
		3455	{
		3456	struct my_biggy big = (struct my_biggy *)
		3457	(((char *)w) - offsetof (struct my_biggy, t1));
		3458	}
		3459
		3460	static void
		3461	t2_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t2));
		3465	}
		3466
		3467	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3468
		3469	Often (especially in GUI toolkits) there are places where you have
		3470	I<modal> interaction, which is most easily implemented by recursively
		3471	invoking C<ev_run>.
		3472
		3473	This brings the problem of exiting - a callback might want to finish the
		3474	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3475	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3476	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3477	other combination: In these cases, C<ev_break> will not work alone.
		3478
		3479	The solution is to maintain "break this loop" variable for each C<ev_run>
		3480	invocation, and use a loop around C<ev_run> until the condition is
		3481	triggered, using C<EVRUN_ONCE>:
		3482
		3483	// main loop
		3484	int exit_main_loop = 0;
		3485
		3486	while (!exit_main_loop)
		3487	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3488
		3489	// in a model watcher
		3490	int exit_nested_loop = 0;
		3491
		3492	while (!exit_nested_loop)
		3493	ev_run (EV_A_ EVRUN_ONCE);
		3494
		3495	To exit from any of these loops, just set the corresponding exit variable:
		3496
		3497	// exit modal loop
		3498	exit_nested_loop = 1;
		3499
		3500	// exit main program, after modal loop is finished
		3501	exit_main_loop = 1;
		3502
		3503	// exit both
		3504	exit_main_loop = exit_nested_loop = 1;
		3505
		3506	=head2 THREAD LOCKING EXAMPLE
		3507
		3508	Here is a fictitious example of how to run an event loop in a different
		3509	thread than where callbacks are being invoked and watchers are
		3510	created/added/removed.
		3511
		3512	For a real-world example, see the C<EV::Loop::Async> perl module,
		3513	which uses exactly this technique (which is suited for many high-level
		3514	languages).
		3515
		3516	The example uses a pthread mutex to protect the loop data, a condition
		3517	variable to wait for callback invocations, an async watcher to notify the
		3518	event loop thread and an unspecified mechanism to wake up the main thread.
		3519
		3520	First, you need to associate some data with the event loop:
		3521
		3522	typedef struct {
		3523	mutex_t lock; /* global loop lock */
		3524	ev_async async_w;
		3525	thread_t tid;
		3526	cond_t invoke_cv;
		3527	} userdata;
		3528
		3529	void prepare_loop (EV_P)
		3530	{
		3531	// for simplicity, we use a static userdata struct.
		3532	static userdata u;
		3533
		3534	ev_async_init (&u->async_w, async_cb);
		3535	ev_async_start (EV_A_ &u->async_w);
		3536
		3537	pthread_mutex_init (&u->lock, 0);
		3538	pthread_cond_init (&u->invoke_cv, 0);
		3539
		3540	// now associate this with the loop
		3541	ev_set_userdata (EV_A_ u);
		3542	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3543	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3544
		3545	// then create the thread running ev_loop
		3546	pthread_create (&u->tid, 0, l_run, EV_A);
		3547	}
		3548
		3549	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3550	solely to wake up the event loop so it takes notice of any new watchers
		3551	that might have been added:
		3552
		3553	static void
		3554	async_cb (EV_P_ ev_async *w, int revents)
		3555	{
		3556	// just used for the side effects
		3557	}
		3558
		3559	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3560	protecting the loop data, respectively.
		3561
		3562	static void
		3563	l_release (EV_P)
		3564	{
		3565	userdata *u = ev_userdata (EV_A);
		3566	pthread_mutex_unlock (&u->lock);
		3567	}
		3568
		3569	static void
		3570	l_acquire (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_lock (&u->lock);
		3574	}
		3575
		3576	The event loop thread first acquires the mutex, and then jumps straight
		3577	into C<ev_run>:
		3578
		3579	void *
		3580	l_run (void *thr_arg)
		3581	{
		3582	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3583
		3584	l_acquire (EV_A);
		3585	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3586	ev_run (EV_A_ 0);
		3587	l_release (EV_A);
		3588
		3589	return 0;
		3590	}
		3591
		3592	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3593	signal the main thread via some unspecified mechanism (signals? pipe
		3594	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3595	have been called (in a while loop because a) spurious wakeups are possible
		3596	and b) skipping inter-thread-communication when there are no pending
		3597	watchers is very beneficial):
		3598
		3599	static void
		3600	l_invoke (EV_P)
		3601	{
		3602	userdata *u = ev_userdata (EV_A);
		3603
		3604	while (ev_pending_count (EV_A))
		3605	{
		3606	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3607	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3608	}
		3609	}
		3610
		3611	Now, whenever the main thread gets told to invoke pending watchers, it
		3612	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3613	thread to continue:
		3614
		3615	static void
		3616	real_invoke_pending (EV_P)
		3617	{
		3618	userdata *u = ev_userdata (EV_A);
		3619
		3620	pthread_mutex_lock (&u->lock);
		3621	ev_invoke_pending (EV_A);
		3622	pthread_cond_signal (&u->invoke_cv);
		3623	pthread_mutex_unlock (&u->lock);
		3624	}
		3625
		3626	Whenever you want to start/stop a watcher or do other modifications to an
		3627	event loop, you will now have to lock:
		3628
		3629	ev_timer timeout_watcher;
		3630	userdata *u = ev_userdata (EV_A);
		3631
		3632	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_timer_start (EV_A_ &timeout_watcher);
		3636	ev_async_send (EV_A_ &u->async_w);
		3637	pthread_mutex_unlock (&u->lock);
		3638
		3639	Note that sending the C<ev_async> watcher is required because otherwise
		3640	an event loop currently blocking in the kernel will have no knowledge
		3641	about the newly added timer. By waking up the loop it will pick up any new
		3642	watchers in the next event loop iteration.
		3643
		3644	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3645
		3646	While the overhead of a callback that e.g. schedules a thread is small, it
		3647	is still an overhead. If you embed libev, and your main usage is with some
		3648	kind of threads or coroutines, you might want to customise libev so that
		3649	doesn't need callbacks anymore.
		3650
		3651	Imagine you have coroutines that you can switch to using a function
		3652	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3653	and that due to some magic, the currently active coroutine is stored in a
		3654	global called C<current_coro>. Then you can build your own "wait for libev
		3655	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3656	the differing C<;> conventions):
		3657
		3658	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3659	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3660
		3661	That means instead of having a C callback function, you store the
		3662	coroutine to switch to in each watcher, and instead of having libev call
		3663	your callback, you instead have it switch to that coroutine.
		3664
		3665	A coroutine might now wait for an event with a function called
		3666	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3667	matter when, or whether the watcher is active or not when this function is
		3668	called):
		3669
		3670	void
		3671	wait_for_event (ev_watcher *w)
		3672	{
		3673	ev_cb_set (w) = current_coro;
		3674	switch_to (libev_coro);
		3675	}
		3676
		3677	That basically suspends the coroutine inside C<wait_for_event> and
		3678	continues the libev coroutine, which, when appropriate, switches back to
		3679	this or any other coroutine. I am sure if you sue this your own :)
		3680
		3681	You can do similar tricks if you have, say, threads with an event queue -
		3682	instead of storing a coroutine, you store the queue object and instead of
		3683	switching to a coroutine, you push the watcher onto the queue and notify
		3684	any waiters.
		3685
		3686	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3687	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3688
		3689	// my_ev.h
		3690	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3691	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3692	#include "../libev/ev.h"
		3693
		3694	// my_ev.c
		3695	#define EV_H "my_ev.h"
		3696	#include "../libev/ev.c"
		3697
		3698	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3699	F<my_ev.c> into your project. When properly specifying include paths, you
		3700	can even use F<ev.h> as header file name directly.
3166		3701
3167		3702
3168	=head1 LIBEVENT EMULATION	3703	=head1 LIBEVENT EMULATION
3169		3704
3170	Libev offers a compatibility emulation layer for libevent. It cannot	3705	Libev offers a compatibility emulation layer for libevent. It cannot
3171	emulate the internals of libevent, so here are some usage hints:	3706	emulate the internals of libevent, so here are some usage hints:
3172		3707
3173	=over 4	3708	=over 4
		3709
		3710	=item * Only the libevent-1.4.1-beta API is being emulated.
		3711
		3712	This was the newest libevent version available when libev was implemented,
		3713	and is still mostly unchanged in 2010.
3174		3714
3175	=item * Use it by including <event.h>, as usual.	3715	=item * Use it by including <event.h>, as usual.
3176		3716
3177	=item * The following members are fully supported: ev_base, ev_callback,	3717	=item * The following members are fully supported: ev_base, ev_callback,
3178	ev_arg, ev_fd, ev_res, ev_events.	3718	ev_arg, ev_fd, ev_res, ev_events.
…		…
3184	=item * Priorities are not currently supported. Initialising priorities	3724	=item * Priorities are not currently supported. Initialising priorities
3185	will fail and all watchers will have the same priority, even though there	3725	will fail and all watchers will have the same priority, even though there
3186	is an ev_pri field.	3726	is an ev_pri field.
3187		3727
3188	=item * In libevent, the last base created gets the signals, in libev, the	3728	=item * In libevent, the last base created gets the signals, in libev, the
3189	first base created (== the default loop) gets the signals.	3729	base that registered the signal gets the signals.
3190		3730
3191	=item * Other members are not supported.	3731	=item * Other members are not supported.
3192		3732
3193	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3733	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3194	to use the libev header file and library.	3734	to use the libev header file and library.
…		…
3213	Care has been taken to keep the overhead low. The only data member the C++	3753	Care has been taken to keep the overhead low. The only data member the C++
3214	classes add (compared to plain C-style watchers) is the event loop pointer	3754	classes add (compared to plain C-style watchers) is the event loop pointer
3215	that the watcher is associated with (or no additional members at all if	3755	that the watcher is associated with (or no additional members at all if
3216	you disable C<EV_MULTIPLICITY> when embedding libev).	3756	you disable C<EV_MULTIPLICITY> when embedding libev).
3217		3757
3218	Currently, functions, and static and non-static member functions can be	3758	Currently, functions, static and non-static member functions and classes
3219	used as callbacks. Other types should be easy to add as long as they only	3759	with C<operator ()> can be used as callbacks. Other types should be easy
3220	need one additional pointer for context. If you need support for other	3760	to add as long as they only need one additional pointer for context. If
3221	types of functors please contact the author (preferably after implementing	3761	you need support for other types of functors please contact the author
3222	it).	3762	(preferably after implementing it).
3223		3763
3224	Here is a list of things available in the C<ev> namespace:	3764	Here is a list of things available in the C<ev> namespace:
3225		3765
3226	=over 4	3766	=over 4
3227		3767
…		…
3288	myclass obj;	3828	myclass obj;
3289	ev::io iow;	3829	ev::io iow;
3290	iow.set <myclass, &myclass::io_cb> (&obj);	3830	iow.set <myclass, &myclass::io_cb> (&obj);
3291		3831
3292	=item w->set (object *)	3832	=item w->set (object *)
3293
3294	This is an B<experimental> feature that might go away in a future version.
3295		3833
3296	This is a variation of a method callback - leaving out the method to call	3834	This is a variation of a method callback - leaving out the method to call
3297	will default the method to C<operator ()>, which makes it possible to use	3835	will default the method to C<operator ()>, which makes it possible to use
3298	functor objects without having to manually specify the C<operator ()> all	3836	functor objects without having to manually specify the C<operator ()> all
3299	the time. Incidentally, you can then also leave out the template argument	3837	the time. Incidentally, you can then also leave out the template argument
…		…
3339	Associates a different C<struct ev_loop> with this watcher. You can only	3877	Associates a different C<struct ev_loop> with this watcher. You can only
3340	do this when the watcher is inactive (and not pending either).	3878	do this when the watcher is inactive (and not pending either).
3341		3879
3342	=item w->set ([arguments])	3880	=item w->set ([arguments])
3343		3881
3344	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3882	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3345	called at least once. Unlike the C counterpart, an active watcher gets	3883	method or a suitable start method must be called at least once. Unlike the
3346	automatically stopped and restarted when reconfiguring it with this	3884	C counterpart, an active watcher gets automatically stopped and restarted
3347	method.	3885	when reconfiguring it with this method.
3348		3886
3349	=item w->start ()	3887	=item w->start ()
3350		3888
3351	Starts the watcher. Note that there is no C<loop> argument, as the	3889	Starts the watcher. Note that there is no C<loop> argument, as the
3352	constructor already stores the event loop.	3890	constructor already stores the event loop.
3353		3891
		3892	=item w->start ([arguments])
		3893
		3894	Instead of calling C<set> and C<start> methods separately, it is often
		3895	convenient to wrap them in one call. Uses the same type of arguments as
		3896	the configure C<set> method of the watcher.
		3897
3354	=item w->stop ()	3898	=item w->stop ()
3355		3899
3356	Stops the watcher if it is active. Again, no C<loop> argument.	3900	Stops the watcher if it is active. Again, no C<loop> argument.
3357		3901
3358	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3902	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3370		3914
3371	=back	3915	=back
3372		3916
3373	=back	3917	=back
3374		3918
3375	Example: Define a class with an IO and idle watcher, start one of them in	3919	Example: Define a class with two I/O and idle watchers, start the I/O
3376	the constructor.	3920	watchers in the constructor.
3377		3921
3378	class myclass	3922	class myclass
3379	{	3923	{
3380	ev::io io ; void io_cb (ev::io &w, int revents);	3924	ev::io io ; void io_cb (ev::io &w, int revents);
		3925	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3381	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3926	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3382		3927
3383	myclass (int fd)	3928	myclass (int fd)
3384	{	3929	{
3385	io .set <myclass, &myclass::io_cb > (this);	3930	io .set <myclass, &myclass::io_cb > (this);
		3931	io2 .set <myclass, &myclass::io2_cb > (this);
3386	idle.set <myclass, &myclass::idle_cb> (this);	3932	idle.set <myclass, &myclass::idle_cb> (this);
3387		3933
3388	io.start (fd, ev::READ);	3934	io.set (fd, ev::WRITE); // configure the watcher
		3935	io.start (); // start it whenever convenient
		3936
		3937	io2.start (fd, ev::READ); // set + start in one call
3389	}	3938	}
3390	};	3939	};
3391		3940
3392		3941
3393	=head1 OTHER LANGUAGE BINDINGS	3942	=head1 OTHER LANGUAGE BINDINGS
…		…
3441	Erkki Seppala has written Ocaml bindings for libev, to be found at	3990	Erkki Seppala has written Ocaml bindings for libev, to be found at
3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3991	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3443		3992
3444	=item Lua	3993	=item Lua
3445		3994
3446	Brian Maher has written a partial interface to libev	3995	Brian Maher has written a partial interface to libev for lua (at the
3447	for lua (only C<ev_io> and C<ev_timer>), to be found at	3996	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3448	L<http://github.com/brimworks/lua-ev>.	3997	L<http://github.com/brimworks/lua-ev>.
3449		3998
3450	=back	3999	=back
3451		4000
3452		4001
…		…
3467	loop argument"). The C<EV_A> form is used when this is the sole argument,	4016	loop argument"). The C<EV_A> form is used when this is the sole argument,
3468	C<EV_A_> is used when other arguments are following. Example:	4017	C<EV_A_> is used when other arguments are following. Example:
3469		4018
3470	ev_unref (EV_A);	4019	ev_unref (EV_A);
3471	ev_timer_add (EV_A_ watcher);	4020	ev_timer_add (EV_A_ watcher);
3472	ev_loop (EV_A_ 0);	4021	ev_run (EV_A_ 0);
3473		4022
3474	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4023	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3475	which is often provided by the following macro.	4024	which is often provided by the following macro.
3476		4025
3477	=item C<EV_P>, C<EV_P_>	4026	=item C<EV_P>, C<EV_P_>
…		…
3517	}	4066	}
3518		4067
3519	ev_check check;	4068	ev_check check;
3520	ev_check_init (&check, check_cb);	4069	ev_check_init (&check, check_cb);
3521	ev_check_start (EV_DEFAULT_ &check);	4070	ev_check_start (EV_DEFAULT_ &check);
3522	ev_loop (EV_DEFAULT_ 0);	4071	ev_run (EV_DEFAULT_ 0);
3523		4072
3524	=head1 EMBEDDING	4073	=head1 EMBEDDING
3525		4074
3526	Libev can (and often is) directly embedded into host	4075	Libev can (and often is) directly embedded into host
3527	applications. Examples of applications that embed it include the Deliantra	4076	applications. Examples of applications that embed it include the Deliantra
…		…
3607	libev.m4	4156	libev.m4
3608		4157
3609	=head2 PREPROCESSOR SYMBOLS/MACROS	4158	=head2 PREPROCESSOR SYMBOLS/MACROS
3610		4159
3611	Libev can be configured via a variety of preprocessor symbols you have to	4160	Libev can be configured via a variety of preprocessor symbols you have to
3612	define before including any of its files. The default in the absence of	4161	define before including (or compiling) any of its files. The default in
3613	autoconf is documented for every option.	4162	the absence of autoconf is documented for every option.
		4163
		4164	Symbols marked with "(h)" do not change the ABI, and can have different
		4165	values when compiling libev vs. including F<ev.h>, so it is permissible
		4166	to redefine them before including F<ev.h> without breaking compatibility
		4167	to a compiled library. All other symbols change the ABI, which means all
		4168	users of libev and the libev code itself must be compiled with compatible
		4169	settings.
3614		4170
3615	=over 4	4171	=over 4
3616		4172
		4173	=item EV_COMPAT3 (h)
		4174
		4175	Backwards compatibility is a major concern for libev. This is why this
		4176	release of libev comes with wrappers for the functions and symbols that
		4177	have been renamed between libev version 3 and 4.
		4178
		4179	You can disable these wrappers (to test compatibility with future
		4180	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4181	sources. This has the additional advantage that you can drop the C<struct>
		4182	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4183	typedef in that case.
		4184
		4185	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4186	and in some even more future version the compatibility code will be
		4187	removed completely.
		4188
3617	=item EV_STANDALONE	4189	=item EV_STANDALONE (h)
3618		4190
3619	Must always be C<1> if you do not use autoconf configuration, which	4191	Must always be C<1> if you do not use autoconf configuration, which
3620	keeps libev from including F<config.h>, and it also defines dummy	4192	keeps libev from including F<config.h>, and it also defines dummy
3621	implementations for some libevent functions (such as logging, which is not	4193	implementations for some libevent functions (such as logging, which is not
3622	supported). It will also not define any of the structs usually found in	4194	supported). It will also not define any of the structs usually found in
…		…
3772	as well as for signal and thread safety in C<ev_async> watchers.	4344	as well as for signal and thread safety in C<ev_async> watchers.
3773		4345
3774	In the absence of this define, libev will use C<sig_atomic_t volatile>	4346	In the absence of this define, libev will use C<sig_atomic_t volatile>
3775	(from F<signal.h>), which is usually good enough on most platforms.	4347	(from F<signal.h>), which is usually good enough on most platforms.
3776		4348
3777	=item EV_H	4349	=item EV_H (h)
3778		4350
3779	The name of the F<ev.h> header file used to include it. The default if	4351	The name of the F<ev.h> header file used to include it. The default if
3780	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4352	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3781	used to virtually rename the F<ev.h> header file in case of conflicts.	4353	used to virtually rename the F<ev.h> header file in case of conflicts.
3782		4354
3783	=item EV_CONFIG_H	4355	=item EV_CONFIG_H (h)
3784		4356
3785	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4357	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3786	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4358	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3787	C<EV_H>, above.	4359	C<EV_H>, above.
3788		4360
3789	=item EV_EVENT_H	4361	=item EV_EVENT_H (h)
3790		4362
3791	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4363	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3792	of how the F<event.h> header can be found, the default is C<"event.h">.	4364	of how the F<event.h> header can be found, the default is C<"event.h">.
3793		4365
3794	=item EV_PROTOTYPES	4366	=item EV_PROTOTYPES (h)
3795		4367
3796	If defined to be C<0>, then F<ev.h> will not define any function	4368	If defined to be C<0>, then F<ev.h> will not define any function
3797	prototypes, but still define all the structs and other symbols. This is	4369	prototypes, but still define all the structs and other symbols. This is
3798	occasionally useful if you want to provide your own wrapper functions	4370	occasionally useful if you want to provide your own wrapper functions
3799	around libev functions.	4371	around libev functions.
…		…
3821	fine.	4393	fine.
3822		4394
3823	If your embedding application does not need any priorities, defining these	4395	If your embedding application does not need any priorities, defining these
3824	both to C<0> will save some memory and CPU.	4396	both to C<0> will save some memory and CPU.
3825		4397
3826	=item EV_PERIODIC_ENABLE	4398	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4399	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4400	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3827		4401
3828	If undefined or defined to be C<1>, then periodic timers are supported. If	4402	If undefined or defined to be C<1> (and the platform supports it), then
3829	defined to be C<0>, then they are not. Disabling them saves a few kB of	4403	the respective watcher type is supported. If defined to be C<0>, then it
3830	code.	4404	is not. Disabling watcher types mainly saves code size.
3831		4405
3832	=item EV_IDLE_ENABLE	4406	=item EV_FEATURES
3833
3834	If undefined or defined to be C<1>, then idle watchers are supported. If
3835	defined to be C<0>, then they are not. Disabling them saves a few kB of
3836	code.
3837
3838	=item EV_EMBED_ENABLE
3839
3840	If undefined or defined to be C<1>, then embed watchers are supported. If
3841	defined to be C<0>, then they are not. Embed watchers rely on most other
3842	watcher types, which therefore must not be disabled.
3843
3844	=item EV_STAT_ENABLE
3845
3846	If undefined or defined to be C<1>, then stat watchers are supported. If
3847	defined to be C<0>, then they are not.
3848
3849	=item EV_FORK_ENABLE
3850
3851	If undefined or defined to be C<1>, then fork watchers are supported. If
3852	defined to be C<0>, then they are not.
3853
3854	=item EV_ASYNC_ENABLE
3855
3856	If undefined or defined to be C<1>, then async watchers are supported. If
3857	defined to be C<0>, then they are not.
3858
3859	=item EV_MINIMAL
3860		4407
3861	If you need to shave off some kilobytes of code at the expense of some	4408	If you need to shave off some kilobytes of code at the expense of some
3862	speed (but with the full API), define this symbol to C<1>. Currently this	4409	speed (but with the full API), you can define this symbol to request
3863	is used to override some inlining decisions, saves roughly 30% code size	4410	certain subsets of functionality. The default is to enable all features
3864	on amd64. It also selects a much smaller 2-heap for timer management over	4411	that can be enabled on the platform.
3865	the default 4-heap.
3866		4412
3867	You can save even more by disabling watcher types you do not need	4413	A typical way to use this symbol is to define it to C<0> (or to a bitset
3868	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4414	with some broad features you want) and then selectively re-enable
3869	(C<-DNDEBUG>) will usually reduce code size a lot.	4415	additional parts you want, for example if you want everything minimal,
		4416	but multiple event loop support, async and child watchers and the poll
		4417	backend, use this:
3870		4418
3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4419	#define EV_FEATURES 0
3872	provide a bare-bones event library. See C<ev.h> for details on what parts	4420	#define EV_MULTIPLICITY 1
3873	of the API are still available, and do not complain if this subset changes	4421	#define EV_USE_POLL 1
3874	over time.	4422	#define EV_CHILD_ENABLE 1
		4423	#define EV_ASYNC_ENABLE 1
		4424
		4425	The actual value is a bitset, it can be a combination of the following
		4426	values:
		4427
		4428	=over 4
		4429
		4430	=item C<1> - faster/larger code
		4431
		4432	Use larger code to speed up some operations.
		4433
		4434	Currently this is used to override some inlining decisions (enlarging the
		4435	code size by roughly 30% on amd64).
		4436
		4437	When optimising for size, use of compiler flags such as C<-Os> with
		4438	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4439	assertions.
		4440
		4441	=item C<2> - faster/larger data structures
		4442
		4443	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4444	hash table sizes and so on. This will usually further increase code size
		4445	and can additionally have an effect on the size of data structures at
		4446	runtime.
		4447
		4448	=item C<4> - full API configuration
		4449
		4450	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4451	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4452
		4453	=item C<8> - full API
		4454
		4455	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4456	details on which parts of the API are still available without this
		4457	feature, and do not complain if this subset changes over time.
		4458
		4459	=item C<16> - enable all optional watcher types
		4460
		4461	Enables all optional watcher types. If you want to selectively enable
		4462	only some watcher types other than I/O and timers (e.g. prepare,
		4463	embed, async, child...) you can enable them manually by defining
		4464	C<EV_watchertype_ENABLE> to C<1> instead.
		4465
		4466	=item C<32> - enable all backends
		4467
		4468	This enables all backends - without this feature, you need to enable at
		4469	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4470
		4471	=item C<64> - enable OS-specific "helper" APIs
		4472
		4473	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4474	default.
		4475
		4476	=back
		4477
		4478	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4479	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4480	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4481	watchers, timers and monotonic clock support.
		4482
		4483	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4484	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4485	your program might be left out as well - a binary starting a timer and an
		4486	I/O watcher then might come out at only 5Kb.
		4487
		4488	=item EV_AVOID_STDIO
		4489
		4490	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4491	functions (printf, scanf, perror etc.). This will increase the code size
		4492	somewhat, but if your program doesn't otherwise depend on stdio and your
		4493	libc allows it, this avoids linking in the stdio library which is quite
		4494	big.
		4495
		4496	Note that error messages might become less precise when this option is
		4497	enabled.
3875		4498
3876	=item EV_NSIG	4499	=item EV_NSIG
3877		4500
3878	The highest supported signal number, +1 (or, the number of	4501	The highest supported signal number, +1 (or, the number of
3879	signals): Normally, libev tries to deduce the maximum number of signals	4502	signals): Normally, libev tries to deduce the maximum number of signals
3880	automatically, but sometimes this fails, in which case it can be	4503	automatically, but sometimes this fails, in which case it can be
3881	specified. Also, using a lower number than detected (C<32> should be	4504	specified. Also, using a lower number than detected (C<32> should be
3882	good for about any system in existance) can save some memory, as libev	4505	good for about any system in existence) can save some memory, as libev
3883	statically allocates some 12-24 bytes per signal number.	4506	statically allocates some 12-24 bytes per signal number.
3884		4507
3885	=item EV_PID_HASHSIZE	4508	=item EV_PID_HASHSIZE
3886		4509
3887	C<ev_child> watchers use a small hash table to distribute workload by	4510	C<ev_child> watchers use a small hash table to distribute workload by
3888	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4511	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3889	than enough. If you need to manage thousands of children you might want to	4512	usually more than enough. If you need to manage thousands of children you
3890	increase this value (I<must> be a power of two).	4513	might want to increase this value (I<must> be a power of two).
3891		4514
3892	=item EV_INOTIFY_HASHSIZE	4515	=item EV_INOTIFY_HASHSIZE
3893		4516
3894	C<ev_stat> watchers use a small hash table to distribute workload by	4517	C<ev_stat> watchers use a small hash table to distribute workload by
3895	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4518	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3896	usually more than enough. If you need to manage thousands of C<ev_stat>	4519	disabled), usually more than enough. If you need to manage thousands of
3897	watchers you might want to increase this value (I<must> be a power of	4520	C<ev_stat> watchers you might want to increase this value (I<must> be a
3898	two).	4521	power of two).
3899		4522
3900	=item EV_USE_4HEAP	4523	=item EV_USE_4HEAP
3901		4524
3902	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4525	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3903	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4526	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3904	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4527	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3905	faster performance with many (thousands) of watchers.	4528	faster performance with many (thousands) of watchers.
3906		4529
3907	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4530	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3908	(disabled).	4531	will be C<0>.
3909		4532
3910	=item EV_HEAP_CACHE_AT	4533	=item EV_HEAP_CACHE_AT
3911		4534
3912	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4535	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3913	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4536	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3914	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4537	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3915	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4538	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3916	but avoids random read accesses on heap changes. This improves performance	4539	but avoids random read accesses on heap changes. This improves performance
3917	noticeably with many (hundreds) of watchers.	4540	noticeably with many (hundreds) of watchers.
3918		4541
3919	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4542	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3920	(disabled).	4543	will be C<0>.
3921		4544
3922	=item EV_VERIFY	4545	=item EV_VERIFY
3923		4546
3924	Controls how much internal verification (see C<ev_loop_verify ()>) will	4547	Controls how much internal verification (see C<ev_verify ()>) will
3925	be done: If set to C<0>, no internal verification code will be compiled	4548	be done: If set to C<0>, no internal verification code will be compiled
3926	in. If set to C<1>, then verification code will be compiled in, but not	4549	in. If set to C<1>, then verification code will be compiled in, but not
3927	called. If set to C<2>, then the internal verification code will be	4550	called. If set to C<2>, then the internal verification code will be
3928	called once per loop, which can slow down libev. If set to C<3>, then the	4551	called once per loop, which can slow down libev. If set to C<3>, then the
3929	verification code will be called very frequently, which will slow down	4552	verification code will be called very frequently, which will slow down
3930	libev considerably.	4553	libev considerably.
3931		4554
3932	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4555	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3933	C<0>.	4556	will be C<0>.
3934		4557
3935	=item EV_COMMON	4558	=item EV_COMMON
3936		4559
3937	By default, all watchers have a C<void *data> member. By redefining	4560	By default, all watchers have a C<void *data> member. By redefining
3938	this macro to a something else you can include more and other types of	4561	this macro to something else you can include more and other types of
3939	members. You have to define it each time you include one of the files,	4562	members. You have to define it each time you include one of the files,
3940	though, and it must be identical each time.	4563	though, and it must be identical each time.
3941		4564
3942	For example, the perl EV module uses something like this:	4565	For example, the perl EV module uses something like this:
3943		4566
…		…
3996	file.	4619	file.
3997		4620
3998	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4621	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3999	that everybody includes and which overrides some configure choices:	4622	that everybody includes and which overrides some configure choices:
4000		4623
4001	#define EV_MINIMAL 1	4624	#define EV_FEATURES 8
4002	#define EV_USE_POLL 0	4625	#define EV_USE_SELECT 1
4003	#define EV_MULTIPLICITY 0
4004	#define EV_PERIODIC_ENABLE 0	4626	#define EV_PREPARE_ENABLE 1
		4627	#define EV_IDLE_ENABLE 1
4005	#define EV_STAT_ENABLE 0	4628	#define EV_SIGNAL_ENABLE 1
4006	#define EV_FORK_ENABLE 0	4629	#define EV_CHILD_ENABLE 1
		4630	#define EV_USE_STDEXCEPT 0
4007	#define EV_CONFIG_H <config.h>	4631	#define EV_CONFIG_H <config.h>
4008	#define EV_MINPRI 0
4009	#define EV_MAXPRI 0
4010		4632
4011	#include "ev++.h"	4633	#include "ev++.h"
4012		4634
4013	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4635	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4014		4636
4015	#include "ev_cpp.h"	4637	#include "ev_cpp.h"
4016	#include "ev.c"	4638	#include "ev.c"
4017		4639
4018	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4640	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4019		4641
4020	=head2 THREADS AND COROUTINES	4642	=head2 THREADS AND COROUTINES
4021		4643
4022	=head3 THREADS	4644	=head3 THREADS
4023		4645
…		…
4074	default loop and triggering an C<ev_async> watcher from the default loop	4696	default loop and triggering an C<ev_async> watcher from the default loop
4075	watcher callback into the event loop interested in the signal.	4697	watcher callback into the event loop interested in the signal.
4076		4698
4077	=back	4699	=back
4078		4700
4079	=head4 THREAD LOCKING EXAMPLE	4701	See also L<THREAD LOCKING EXAMPLE>.
4080
4081	Here is a fictitious example of how to run an event loop in a different
4082	thread than where callbacks are being invoked and watchers are
4083	created/added/removed.
4084
4085	For a real-world example, see the C<EV::Loop::Async> perl module,
4086	which uses exactly this technique (which is suited for many high-level
4087	languages).
4088
4089	The example uses a pthread mutex to protect the loop data, a condition
4090	variable to wait for callback invocations, an async watcher to notify the
4091	event loop thread and an unspecified mechanism to wake up the main thread.
4092
4093	First, you need to associate some data with the event loop:
4094
4095	typedef struct {
4096	mutex_t lock; /* global loop lock */
4097	ev_async async_w;
4098	thread_t tid;
4099	cond_t invoke_cv;
4100	} userdata;
4101
4102	void prepare_loop (EV_P)
4103	{
4104	// for simplicity, we use a static userdata struct.
4105	static userdata u;
4106
4107	ev_async_init (&u->async_w, async_cb);
4108	ev_async_start (EV_A_ &u->async_w);
4109
4110	pthread_mutex_init (&u->lock, 0);
4111	pthread_cond_init (&u->invoke_cv, 0);
4112
4113	// now associate this with the loop
4114	ev_set_userdata (EV_A_ u);
4115	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4116	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4117
4118	// then create the thread running ev_loop
4119	pthread_create (&u->tid, 0, l_run, EV_A);
4120	}
4121
4122	The callback for the C<ev_async> watcher does nothing: the watcher is used
4123	solely to wake up the event loop so it takes notice of any new watchers
4124	that might have been added:
4125
4126	static void
4127	async_cb (EV_P_ ev_async *w, int revents)
4128	{
4129	// just used for the side effects
4130	}
4131
4132	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4133	protecting the loop data, respectively.
4134
4135	static void
4136	l_release (EV_P)
4137	{
4138	userdata *u = ev_userdata (EV_A);
4139	pthread_mutex_unlock (&u->lock);
4140	}
4141
4142	static void
4143	l_acquire (EV_P)
4144	{
4145	userdata *u = ev_userdata (EV_A);
4146	pthread_mutex_lock (&u->lock);
4147	}
4148
4149	The event loop thread first acquires the mutex, and then jumps straight
4150	into C<ev_loop>:
4151
4152	void *
4153	l_run (void *thr_arg)
4154	{
4155	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4156
4157	l_acquire (EV_A);
4158	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4159	ev_loop (EV_A_ 0);
4160	l_release (EV_A);
4161
4162	return 0;
4163	}
4164
4165	Instead of invoking all pending watchers, the C<l_invoke> callback will
4166	signal the main thread via some unspecified mechanism (signals? pipe
4167	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4168	have been called (in a while loop because a) spurious wakeups are possible
4169	and b) skipping inter-thread-communication when there are no pending
4170	watchers is very beneficial):
4171
4172	static void
4173	l_invoke (EV_P)
4174	{
4175	userdata *u = ev_userdata (EV_A);
4176
4177	while (ev_pending_count (EV_A))
4178	{
4179	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4180	pthread_cond_wait (&u->invoke_cv, &u->lock);
4181	}
4182	}
4183
4184	Now, whenever the main thread gets told to invoke pending watchers, it
4185	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4186	thread to continue:
4187
4188	static void
4189	real_invoke_pending (EV_P)
4190	{
4191	userdata *u = ev_userdata (EV_A);
4192
4193	pthread_mutex_lock (&u->lock);
4194	ev_invoke_pending (EV_A);
4195	pthread_cond_signal (&u->invoke_cv);
4196	pthread_mutex_unlock (&u->lock);
4197	}
4198
4199	Whenever you want to start/stop a watcher or do other modifications to an
4200	event loop, you will now have to lock:
4201
4202	ev_timer timeout_watcher;
4203	userdata *u = ev_userdata (EV_A);
4204
4205	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4206
4207	pthread_mutex_lock (&u->lock);
4208	ev_timer_start (EV_A_ &timeout_watcher);
4209	ev_async_send (EV_A_ &u->async_w);
4210	pthread_mutex_unlock (&u->lock);
4211
4212	Note that sending the C<ev_async> watcher is required because otherwise
4213	an event loop currently blocking in the kernel will have no knowledge
4214	about the newly added timer. By waking up the loop it will pick up any new
4215	watchers in the next event loop iteration.
4216		4702
4217	=head3 COROUTINES	4703	=head3 COROUTINES
4218		4704
4219	Libev is very accommodating to coroutines ("cooperative threads"):	4705	Libev is very accommodating to coroutines ("cooperative threads"):
4220	libev fully supports nesting calls to its functions from different	4706	libev fully supports nesting calls to its functions from different
4221	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4707	coroutines (e.g. you can call C<ev_run> on the same loop from two
4222	different coroutines, and switch freely between both coroutines running	4708	different coroutines, and switch freely between both coroutines running
4223	the loop, as long as you don't confuse yourself). The only exception is	4709	the loop, as long as you don't confuse yourself). The only exception is
4224	that you must not do this from C<ev_periodic> reschedule callbacks.	4710	that you must not do this from C<ev_periodic> reschedule callbacks.
4225		4711
4226	Care has been taken to ensure that libev does not keep local state inside	4712	Care has been taken to ensure that libev does not keep local state inside
4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4713	C<ev_run>, and other calls do not usually allow for coroutine switches as
4228	they do not call any callbacks.	4714	they do not call any callbacks.
4229		4715
4230	=head2 COMPILER WARNINGS	4716	=head2 COMPILER WARNINGS
4231		4717
4232	Depending on your compiler and compiler settings, you might get no or a	4718	Depending on your compiler and compiler settings, you might get no or a
…		…
4243	maintainable.	4729	maintainable.
4244		4730
4245	And of course, some compiler warnings are just plain stupid, or simply	4731	And of course, some compiler warnings are just plain stupid, or simply
4246	wrong (because they don't actually warn about the condition their message	4732	wrong (because they don't actually warn about the condition their message
4247	seems to warn about). For example, certain older gcc versions had some	4733	seems to warn about). For example, certain older gcc versions had some
4248	warnings that resulted an extreme number of false positives. These have	4734	warnings that resulted in an extreme number of false positives. These have
4249	been fixed, but some people still insist on making code warn-free with	4735	been fixed, but some people still insist on making code warn-free with
4250	such buggy versions.	4736	such buggy versions.
4251		4737
4252	While libev is written to generate as few warnings as possible,	4738	While libev is written to generate as few warnings as possible,
4253	"warn-free" code is not a goal, and it is recommended not to build libev	4739	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4289	I suggest using suppression lists.	4775	I suggest using suppression lists.
4290		4776
4291		4777
4292	=head1 PORTABILITY NOTES	4778	=head1 PORTABILITY NOTES
4293		4779
		4780	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4781
		4782	GNU/Linux is the only common platform that supports 64 bit file/large file
		4783	interfaces but I<disables> them by default.
		4784
		4785	That means that libev compiled in the default environment doesn't support
		4786	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4787
		4788	Unfortunately, many programs try to work around this GNU/Linux issue
		4789	by enabling the large file API, which makes them incompatible with the
		4790	standard libev compiled for their system.
		4791
		4792	Likewise, libev cannot enable the large file API itself as this would
		4793	suddenly make it incompatible to the default compile time environment,
		4794	i.e. all programs not using special compile switches.
		4795
		4796	=head2 OS/X AND DARWIN BUGS
		4797
		4798	The whole thing is a bug if you ask me - basically any system interface
		4799	you touch is broken, whether it is locales, poll, kqueue or even the
		4800	OpenGL drivers.
		4801
		4802	=head3 C<kqueue> is buggy
		4803
		4804	The kqueue syscall is broken in all known versions - most versions support
		4805	only sockets, many support pipes.
		4806
		4807	Libev tries to work around this by not using C<kqueue> by default on this
		4808	rotten platform, but of course you can still ask for it when creating a
		4809	loop - embedding a socket-only kqueue loop into a select-based one is
		4810	probably going to work well.
		4811
		4812	=head3 C<poll> is buggy
		4813
		4814	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4815	implementation by something calling C<kqueue> internally around the 10.5.6
		4816	release, so now C<kqueue> I<and> C<poll> are broken.
		4817
		4818	Libev tries to work around this by not using C<poll> by default on
		4819	this rotten platform, but of course you can still ask for it when creating
		4820	a loop.
		4821
		4822	=head3 C<select> is buggy
		4823
		4824	All that's left is C<select>, and of course Apple found a way to fuck this
		4825	one up as well: On OS/X, C<select> actively limits the number of file
		4826	descriptors you can pass in to 1024 - your program suddenly crashes when
		4827	you use more.
		4828
		4829	There is an undocumented "workaround" for this - defining
		4830	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4831	work on OS/X.
		4832
		4833	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4834
		4835	=head3 C<errno> reentrancy
		4836
		4837	The default compile environment on Solaris is unfortunately so
		4838	thread-unsafe that you can't even use components/libraries compiled
		4839	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4840	defined by default. A valid, if stupid, implementation choice.
		4841
		4842	If you want to use libev in threaded environments you have to make sure
		4843	it's compiled with C<_REENTRANT> defined.
		4844
		4845	=head3 Event port backend
		4846
		4847	The scalable event interface for Solaris is called "event
		4848	ports". Unfortunately, this mechanism is very buggy in all major
		4849	releases. If you run into high CPU usage, your program freezes or you get
		4850	a large number of spurious wakeups, make sure you have all the relevant
		4851	and latest kernel patches applied. No, I don't know which ones, but there
		4852	are multiple ones to apply, and afterwards, event ports actually work
		4853	great.
		4854
		4855	If you can't get it to work, you can try running the program by setting
		4856	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4857	C<select> backends.
		4858
		4859	=head2 AIX POLL BUG
		4860
		4861	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4862	this by trying to avoid the poll backend altogether (i.e. it's not even
		4863	compiled in), which normally isn't a big problem as C<select> works fine
		4864	with large bitsets on AIX, and AIX is dead anyway.
		4865
4294	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4866	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4867
		4868	=head3 General issues
4295		4869
4296	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4870	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4297	requires, and its I/O model is fundamentally incompatible with the POSIX	4871	requires, and its I/O model is fundamentally incompatible with the POSIX
4298	model. Libev still offers limited functionality on this platform in	4872	model. Libev still offers limited functionality on this platform in
4299	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4873	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4300	descriptors. This only applies when using Win32 natively, not when using	4874	descriptors. This only applies when using Win32 natively, not when using
4301	e.g. cygwin.	4875	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4876	as every compielr comes with a slightly differently broken/incompatible
		4877	environment.
4302		4878
4303	Lifting these limitations would basically require the full	4879	Lifting these limitations would basically require the full
4304	re-implementation of the I/O system. If you are into these kinds of	4880	re-implementation of the I/O system. If you are into this kind of thing,
4305	things, then note that glib does exactly that for you in a very portable	4881	then note that glib does exactly that for you in a very portable way (note
4306	way (note also that glib is the slowest event library known to man).	4882	also that glib is the slowest event library known to man).
4307		4883
4308	There is no supported compilation method available on windows except	4884	There is no supported compilation method available on windows except
4309	embedding it into other applications.	4885	embedding it into other applications.
4310		4886
4311	Sensible signal handling is officially unsupported by Microsoft - libev	4887	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4339	you do I<not> compile the F<ev.c> or any other embedded source files!):	4915	you do I<not> compile the F<ev.c> or any other embedded source files!):
4340		4916
4341	#include "evwrap.h"	4917	#include "evwrap.h"
4342	#include "ev.c"	4918	#include "ev.c"
4343		4919
4344	=over 4
4345
4346	=item The winsocket select function	4920	=head3 The winsocket C<select> function
4347		4921
4348	The winsocket C<select> function doesn't follow POSIX in that it	4922	The winsocket C<select> function doesn't follow POSIX in that it
4349	requires socket I<handles> and not socket I<file descriptors> (it is	4923	requires socket I<handles> and not socket I<file descriptors> (it is
4350	also extremely buggy). This makes select very inefficient, and also	4924	also extremely buggy). This makes select very inefficient, and also
4351	requires a mapping from file descriptors to socket handles (the Microsoft	4925	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4360	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4934	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4361		4935
4362	Note that winsockets handling of fd sets is O(n), so you can easily get a	4936	Note that winsockets handling of fd sets is O(n), so you can easily get a
4363	complexity in the O(n²) range when using win32.	4937	complexity in the O(n²) range when using win32.
4364		4938
4365	=item Limited number of file descriptors	4939	=head3 Limited number of file descriptors
4366		4940
4367	Windows has numerous arbitrary (and low) limits on things.	4941	Windows has numerous arbitrary (and low) limits on things.
4368		4942
4369	Early versions of winsocket's select only supported waiting for a maximum	4943	Early versions of winsocket's select only supported waiting for a maximum
4370	of C<64> handles (probably owning to the fact that all windows kernels	4944	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4385	runtime libraries. This might get you to about C<512> or C<2048> sockets	4959	runtime libraries. This might get you to about C<512> or C<2048> sockets
4386	(depending on windows version and/or the phase of the moon). To get more,	4960	(depending on windows version and/or the phase of the moon). To get more,
4387	you need to wrap all I/O functions and provide your own fd management, but	4961	you need to wrap all I/O functions and provide your own fd management, but
4388	the cost of calling select (O(n²)) will likely make this unworkable.	4962	the cost of calling select (O(n²)) will likely make this unworkable.
4389		4963
4390	=back
4391
4392	=head2 PORTABILITY REQUIREMENTS	4964	=head2 PORTABILITY REQUIREMENTS
4393		4965
4394	In addition to a working ISO-C implementation and of course the	4966	In addition to a working ISO-C implementation and of course the
4395	backend-specific APIs, libev relies on a few additional extensions:	4967	backend-specific APIs, libev relies on a few additional extensions:
4396		4968
…		…
4402	Libev assumes not only that all watcher pointers have the same internal	4974	Libev assumes not only that all watcher pointers have the same internal
4403	structure (guaranteed by POSIX but not by ISO C for example), but it also	4975	structure (guaranteed by POSIX but not by ISO C for example), but it also
4404	assumes that the same (machine) code can be used to call any watcher	4976	assumes that the same (machine) code can be used to call any watcher
4405	callback: The watcher callbacks have different type signatures, but libev	4977	callback: The watcher callbacks have different type signatures, but libev
4406	calls them using an C<ev_watcher *> internally.	4978	calls them using an C<ev_watcher *> internally.
		4979
		4980	=item pointer accesses must be thread-atomic
		4981
		4982	Accessing a pointer value must be atomic, it must both be readable and
		4983	writable in one piece - this is the case on all current architectures.
4407		4984
4408	=item C<sig_atomic_t volatile> must be thread-atomic as well	4985	=item C<sig_atomic_t volatile> must be thread-atomic as well
4409		4986
4410	The type C<sig_atomic_t volatile> (or whatever is defined as	4987	The type C<sig_atomic_t volatile> (or whatever is defined as
4411	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4988	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4434	watchers.	5011	watchers.
4435		5012
4436	=item C<double> must hold a time value in seconds with enough accuracy	5013	=item C<double> must hold a time value in seconds with enough accuracy
4437		5014
4438	The type C<double> is used to represent timestamps. It is required to	5015	The type C<double> is used to represent timestamps. It is required to
4439	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5016	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4440	enough for at least into the year 4000. This requirement is fulfilled by	5017	good enough for at least into the year 4000 with millisecond accuracy
		5018	(the design goal for libev). This requirement is overfulfilled by
4441	implementations implementing IEEE 754, which is basically all existing	5019	implementations using IEEE 754, which is basically all existing ones. With
4442	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5020	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4443	2200.
4444		5021
4445	=back	5022	=back
4446		5023
4447	If you know of other additional requirements drop me a note.	5024	If you know of other additional requirements drop me a note.
4448		5025
…		…
4516	involves iterating over all running async watchers or all signal numbers.	5093	involves iterating over all running async watchers or all signal numbers.
4517		5094
4518	=back	5095	=back
4519		5096
4520		5097
		5098	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5099
		5100	The major version 4 introduced some incompatible changes to the API.
		5101
		5102	At the moment, the C<ev.h> header file provides compatibility definitions
		5103	for all changes, so most programs should still compile. The compatibility
		5104	layer might be removed in later versions of libev, so better update to the
		5105	new API early than late.
		5106
		5107	=over 4
		5108
		5109	=item C<EV_COMPAT3> backwards compatibility mechanism
		5110
		5111	The backward compatibility mechanism can be controlled by
		5112	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5113	section.
		5114
		5115	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5116
		5117	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5118
		5119	ev_loop_destroy (EV_DEFAULT_UC);
		5120	ev_loop_fork (EV_DEFAULT);
		5121
		5122	=item function/symbol renames
		5123
		5124	A number of functions and symbols have been renamed:
		5125
		5126	ev_loop => ev_run
		5127	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5128	EVLOOP_ONESHOT => EVRUN_ONCE
		5129
		5130	ev_unloop => ev_break
		5131	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5132	EVUNLOOP_ONE => EVBREAK_ONE
		5133	EVUNLOOP_ALL => EVBREAK_ALL
		5134
		5135	EV_TIMEOUT => EV_TIMER
		5136
		5137	ev_loop_count => ev_iteration
		5138	ev_loop_depth => ev_depth
		5139	ev_loop_verify => ev_verify
		5140
		5141	Most functions working on C<struct ev_loop> objects don't have an
		5142	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5143	associated constants have been renamed to not collide with the C<struct
		5144	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5145	as all other watcher types. Note that C<ev_loop_fork> is still called
		5146	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5147	typedef.
		5148
		5149	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5150
		5151	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5152	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5153	and work, but the library code will of course be larger.
		5154
		5155	=back
		5156
		5157
4521	=head1 GLOSSARY	5158	=head1 GLOSSARY
4522		5159
4523	=over 4	5160	=over 4
4524		5161
4525	=item active	5162	=item active
4526		5163
4527	A watcher is active as long as it has been started (has been attached to	5164	A watcher is active as long as it has been started and not yet stopped.
4528	an event loop) but not yet stopped (disassociated from the event loop).	5165	See L<WATCHER STATES> for details.
4529		5166
4530	=item application	5167	=item application
4531		5168
4532	In this document, an application is whatever is using libev.	5169	In this document, an application is whatever is using libev.
		5170
		5171	=item backend
		5172
		5173	The part of the code dealing with the operating system interfaces.
4533		5174
4534	=item callback	5175	=item callback
4535		5176
4536	The address of a function that is called when some event has been	5177	The address of a function that is called when some event has been
4537	detected. Callbacks are being passed the event loop, the watcher that	5178	detected. Callbacks are being passed the event loop, the watcher that
4538	received the event, and the actual event bitset.	5179	received the event, and the actual event bitset.
4539		5180
4540	=item callback invocation	5181	=item callback/watcher invocation
4541		5182
4542	The act of calling the callback associated with a watcher.	5183	The act of calling the callback associated with a watcher.
4543		5184
4544	=item event	5185	=item event
4545		5186
4546	A change of state of some external event, such as data now being available	5187	A change of state of some external event, such as data now being available
4547	for reading on a file descriptor, time having passed or simply not having	5188	for reading on a file descriptor, time having passed or simply not having
4548	any other events happening anymore.	5189	any other events happening anymore.
4549		5190
4550	In libev, events are represented as single bits (such as C<EV_READ> or	5191	In libev, events are represented as single bits (such as C<EV_READ> or
4551	C<EV_TIMEOUT>).	5192	C<EV_TIMER>).
4552		5193
4553	=item event library	5194	=item event library
4554		5195
4555	A software package implementing an event model and loop.	5196	A software package implementing an event model and loop.
4556		5197
…		…
4564	The model used to describe how an event loop handles and processes	5205	The model used to describe how an event loop handles and processes
4565	watchers and events.	5206	watchers and events.
4566		5207
4567	=item pending	5208	=item pending
4568		5209
4569	A watcher is pending as soon as the corresponding event has been detected,	5210	A watcher is pending as soon as the corresponding event has been
4570	and stops being pending as soon as the watcher will be invoked or its	5211	detected. See L<WATCHER STATES> for details.
4571	pending status is explicitly cleared by the application.
4572
4573	A watcher can be pending, but not active. Stopping a watcher also clears
4574	its pending status.
4575		5212
4576	=item real time	5213	=item real time
4577		5214
4578	The physical time that is observed. It is apparently strictly monotonic :)	5215	The physical time that is observed. It is apparently strictly monotonic :)
4579		5216
…		…
4586	=item watcher	5223	=item watcher
4587		5224
4588	A data structure that describes interest in certain events. Watchers need	5225	A data structure that describes interest in certain events. Watchers need
4589	to be started (attached to an event loop) before they can receive events.	5226	to be started (attached to an event loop) before they can receive events.
4590		5227
4591	=item watcher invocation
4592
4593	The act of calling the callback associated with a watcher.
4594
4595	=back	5228	=back
4596		5229
4597	=head1 AUTHOR	5230	=head1 AUTHOR
4598		5231
4599	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5232	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5233	Magnusson and Emanuele Giaquinta.
4600		5234

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