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Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC vs.
Revision 1.362 by root, Sun Jan 30 21:10:13 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
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	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
382		451
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		453
385	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
386	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
422	epoll scales either O(1) or O(active_fds).	491	epoll scales either O(1) or O(active_fds).
423		492
424	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
425	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
426	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
427	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
428	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
429	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
430	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
431	hard to detect.	502	and is of course hard to detect.
432		503
433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
434	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
435	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
436	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
437	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
438	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
439	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
440		517
441	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
442	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
443	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
511		588
512	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
513	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
514		591
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	592	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	593	file descriptor per loop iteration. For small and medium numbers of file
521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
522	might perform better.	595	might perform better.
523		596
524	On the positive side, with the exception of the spurious readiness	597	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	598	specification in all tests and is fully embeddable, which is a rare feat
527	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
528		611
529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
530	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
531		614
532	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
533		616
534	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
536	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
537		620
538	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
539		630
540	=back	631	=back
541		632
542	If one or more of the backend flags are or'ed into the flags value,	633	If one or more of the backend flags are or'ed into the flags value,
543	then only these backends will be tried (in the reverse order as listed	634	then only these backends will be tried (in the reverse order as listed
544	here). If none are specified, all backends in C<ev_recommended_backends	635	here). If none are specified, all backends in C<ev_recommended_backends
545	()> will be tried.	636	()> will be tried.
546		637
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.	638	Example: Try to create a event loop that uses epoll and nothing else.
576		639
577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
578	if (!epoller)	641	if (!epoller)
579	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
580		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
581	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
582		650
583	Destroys the default loop again (frees all memory and kernel state	651	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	652	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	653	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>	654	responsibility to either stop all watchers cleanly yourself I<before>
587	calling this function, or cope with the fact afterwards (which is usually	655	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	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
590		658
591	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
592	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
593	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
594		662
595	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
596	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
597	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
598	C<ev_loop_new> and C<ev_loop_destroy>.	670	and C<ev_loop_destroy>.
599		671
600	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
601		673
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	674	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	675	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	676	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	677	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	678	child before resuming or calling C<ev_run>.
612	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
613		684
614	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
615	process if and only if you want to use the event library in the child. If	686	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.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
617		691
618	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
619	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
620	quite nicely into a call to C<pthread_atfork>:
621		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
622	pthread_atfork (0, 0, ev_default_fork);	705	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		706
631	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
632		708
633	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
634	otherwise.	710	otherwise.
635		711
636	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
637		713
638	Returns the count of loop iterations for the loop, which is identical to	714	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	715	to the number of times libev did poll for new events. It starts at C<0>
640	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
641		717
642	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
643	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
644	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
645		722
646	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
647		724
648	Returns the number of times C<ev_loop> was entered minus the number of	725	Returns the number of times C<ev_run> was entered minus the number of
649	times C<ev_loop> was exited, in other words, the recursion depth.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
650		727
651	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	Outside C<ev_run>, this number is zero. In a callback, this number is
652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
653	in which case it is higher.	730	in which case it is higher.
654		731
655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
656	etc.), doesn't count as exit.	733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
657		736
658	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
659		738
660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
661	use.	740	use.
…		…
670		749
671	=item ev_now_update (loop)	750	=item ev_now_update (loop)
672		751
673	Establishes the current time by querying the kernel, updating the time	752	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	753	returned by C<ev_now ()> in the progress. This is a costly operation and
675	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
676		755
677	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
678	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
679	the current time is a good idea.	758	the current time is a good idea.
680		759
…		…
682		761
683	=item ev_suspend (loop)	762	=item ev_suspend (loop)
684		763
685	=item ev_resume (loop)	764	=item ev_resume (loop)
686		765
687	These two functions suspend and resume a loop, for use when the loop is	766	These two functions suspend and resume an event loop, for use when the
688	not used for a while and timeouts should not be processed.	767	loop is not used for a while and timeouts should not be processed.
689		768
690	A typical use case would be an interactive program such as a game: When	769	A typical use case would be an interactive program such as a game: When
691	the user presses C<^Z> to suspend the game and resumes it an hour later it	770	the user presses C<^Z> to suspend the game and resumes it an hour later it
692	would be best to handle timeouts as if no time had actually passed while	771	would be best to handle timeouts as if no time had actually passed while
693	the program was suspended. This can be achieved by calling C<ev_suspend>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
695	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
696		775
697	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	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	777	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	778	will be rescheduled (that is, they will lose any events that would have
700	occured while suspended).	779	occurred while suspended).
701		780
702	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	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>	782	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>.	783	without a previous call to C<ev_suspend>.
705		784
706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
707	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
708		787
709	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
710		789
711	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
712	after you have initialised all your watchers and you want to start	791	after you have initialised all your watchers and you want to start
713	handling events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
714		795
715	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
716	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
717		799
718	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
719	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
720	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
721	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
722	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
723	beauty.	805	beauty.
724		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
726	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
727	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
728	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
729		817
730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
731	necessary) and will handle those and any already outstanding ones. It	819	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	820	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	821	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	822	user-registered callback will be called), and will return after one
735	iteration of the loop.	823	iteration of the loop.
736		824
737	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
738	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
740	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
741		829
742	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
743		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
747	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	841	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
755	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
756	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
759	- Queue all expired timers.	852	- Queue all expired timers.
760	- Queue all expired periodics.	853	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	855	- Queue all check watchers.
763	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- Call all queued watchers in reverse order (i.e. check watchers first).
764	Signals and child watchers are implemented as I/O watchers, and will	857	Signals and child watchers are implemented as I/O watchers, and will
765	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
767	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
768	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
769		866
770	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
771	anymore.	868	anymore.
772		869
773	... queue jobs here, make sure they register event watchers as long	870	... 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..)	871	... as they still have work to do (even an idle watcher will do..)
775	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
777		874
778	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
779		876
780	Can be used to make a call to C<ev_loop> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
781	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	879	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
784		881
785	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
786		883
787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
788		886
789	=item ev_ref (loop)	887	=item ev_ref (loop)
790		888
791	=item ev_unref (loop)	889	=item ev_unref (loop)
792		890
793	Ref/unref can be used to add or remove a reference count on the event	891	Ref/unref can be used to add or remove a reference count on the event
794	loop: Every watcher keeps one reference, and as long as the reference	892	loop: Every watcher keeps one reference, and as long as the reference
795	count is nonzero, C<ev_loop> will not return on its own.	893	count is nonzero, C<ev_run> will not return on its own.
796		894
797	If you have a watcher you never unregister that should not keep C<ev_loop>	895	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	896	unregister, but that nevertheless should not keep C<ev_run> from
		897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
799	stopping it.	898	before stopping it.
800		899
801	As an example, libev itself uses this for its internal signal pipe: It	900	As an example, libev itself uses this for its internal signal pipe: It
802	is not visible to the libev user and should not keep C<ev_loop> from	901	is not visible to the libev user and should not keep C<ev_run> from
803	exiting if no event watchers registered by it are active. It is also an	902	exiting if no event watchers registered by it are active. It is also an
804	excellent way to do this for generic recurring timers or from within	903	excellent way to do this for generic recurring timers or from within
805	third-party libraries. Just remember to I<unref after start> and I<ref	904	third-party libraries. Just remember to I<unref after start> and I<ref
806	before stop> (but only if the watcher wasn't active before, or was active	905	before stop> (but only if the watcher wasn't active before, or was active
807	before, respectively. Note also that libev might stop watchers itself	906	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>	907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
809	in the callback).	908	in the callback).
810		909
811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
812	running when nothing else is active.	911	running when nothing else is active.
813		912
814	ev_signal exitsig;	913	ev_signal exitsig;
815	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
816	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
817	evf_unref (loop);	916	ev_unref (loop);
818		917
819	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
820		919
821	ev_ref (loop);	920	ev_ref (loop);
822	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
861	usually doesn't make much sense to set it to a lower value than C<0.01>,	960	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	961	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	962	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	963	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,	964	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).	965	then you can't do more than 100 transactions per second).
867		966
868	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
869	saving power, as the program will "bundle" timer callback invocations that	968	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	969	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	970	times the process sleeps and wakes up again. Another useful technique to
…		…
879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
880		979
881	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
882		981
883	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
884	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
885	but when overriding the invoke callback this call comes handy.	984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
886		989
887	=item int ev_pending_count (loop)	990	=item int ev_pending_count (loop)
888		991
889	Returns the number of pending watchers - zero indicates that no watchers	992	Returns the number of pending watchers - zero indicates that no watchers
890	are pending.	993	are pending.
891		994
892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
893		996
894	This overrides the invoke pending functionality of the loop: Instead of	997	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	998	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	999	this callback instead. This is useful, for example, when you want to
897	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
898		1001
899	If you want to reset the callback, use C<ev_invoke_pending> as new	1002	If you want to reset the callback, use C<ev_invoke_pending> as new
900	callback.	1003	callback.
…		…
903		1006
904	Sometimes you want to share the same loop between multiple threads. This	1007	Sometimes you want to share the same loop between multiple threads. This
905	can be done relatively simply by putting mutex_lock/unlock calls around	1008	can be done relatively simply by putting mutex_lock/unlock calls around
906	each call to a libev function.	1009	each call to a libev function.
907		1010
908	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1011	However, C<ev_run> can run an indefinite time, so it is not feasible
909	wait for it to return. One way around this is to wake up the loop via	1012	to wait for it to return. One way around this is to wake up the event
910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
911	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
912		1015
913	When set, then C<release> will be called just before the thread is	1016	When set, then C<release> will be called just before the thread is
914	suspended waiting for new events, and C<acquire> is called just	1017	suspended waiting for new events, and C<acquire> is called just
915	afterwards.	1018	afterwards.
916		1019
…		…
919		1022
920	While event loop modifications are allowed between invocations of	1023	While event loop modifications are allowed between invocations of
921	C<release> and C<acquire> (that's their only purpose after all), no	1024	C<release> and C<acquire> (that's their only purpose after all), no
922	modifications done will affect the event loop, i.e. adding watchers will	1025	modifications done will affect the event loop, i.e. adding watchers will
923	have no effect on the set of file descriptors being watched, or the time	1026	have no effect on the set of file descriptors being watched, or the time
924	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
925	to take note of any changes you made.	1028	to take note of any changes you made.
926		1029
927	In theory, threads executing C<ev_loop> will be async-cancel safe between	1030	In theory, threads executing C<ev_run> will be async-cancel safe between
928	invocations of C<release> and C<acquire>.	1031	invocations of C<release> and C<acquire>.
929		1032
930	See also the locking example in the C<THREADS> section later in this	1033	See also the locking example in the C<THREADS> section later in this
931	document.	1034	document.
932		1035
933	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
934		1037
935	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
936		1039
937	Set and retrieve a single C<void *> associated with a loop. When	1040	Set and retrieve a single C<void *> associated with a loop. When
938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
939	C<0.>	1042	C<0>.
940		1043
941	These two functions can be used to associate arbitrary data with a loop,	1044	These two functions can be used to associate arbitrary data with a loop,
942	and are intended solely for the C<invoke_pending_cb>, C<release> and	1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
943	C<acquire> callbacks described above, but of course can be (ab-)used for	1046	C<acquire> callbacks described above, but of course can be (ab-)used for
944	any other purpose as well.	1047	any other purpose as well.
945		1048
946	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
947		1050
948	This function only does something when C<EV_VERIFY> support has been	1051	This function only does something when C<EV_VERIFY> support has been
949	compiled in, which is the default for non-minimal builds. It tries to go	1052	compiled in, which is the default for non-minimal builds. It tries to go
950	through all internal structures and checks them for validity. If anything	1053	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	1054	is found to be inconsistent, it will print an error message to standard
…		…
962		1065
963	In the following description, uppercase C<TYPE> in names stands for the	1066	In the following description, uppercase C<TYPE> in names stands for the
964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
965	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
966		1069
967	A watcher is a structure that you create and register to record your	1070	A watcher is an opaque structure that you allocate and register to record
968	interest in some event. For instance, if you want to wait for STDIN to	1071	your interest in some event. To make a concrete example, imagine you want
969	become readable, you would create an C<ev_io> watcher for that:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
970		1074
971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
972	{	1076	{
973	ev_io_stop (w);	1077	ev_io_stop (w);
974	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
975	}	1079	}
976		1080
977	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
978		1082
979	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
980		1084
981	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
983	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
984		1088
985	ev_loop (loop, 0);	1089	ev_run (loop, 0);
986		1090
987	As you can see, you are responsible for allocating the memory for your	1091	As you can see, you are responsible for allocating the memory for your
988	watcher structures (and it is I<usually> a bad idea to do this on the	1092	watcher structures (and it is I<usually> a bad idea to do this on the
989	stack).	1093	stack).
990		1094
991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
993		1097
994	Each watcher structure must be initialised by a call to C<ev_init	1098	Each watcher structure must be initialised by a call to C<ev_init (watcher
995	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, 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	1100	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	1101	time the event loop detects that the file descriptor given is readable
998	is readable and/or writable).	1102	and/or writable).
999		1103
1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1104	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1001	macro to configure it, with arguments specific to the watcher type. There	1105	macro to configure it, with arguments specific to the watcher type. There
1002	is also a macro to combine initialisation and setting in one call: C<<	1106	is also a macro to combine initialisation and setting in one call: C<<
1003	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1026	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
1027		1131
1028	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
1029	writable.	1133	writable.
1030		1134
1031	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
1032		1136
1033	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
1034		1138
1035	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
1036		1140
…		…
1054		1158
1055	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1056		1160
1057	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1058		1162
1059	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1060	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
1061	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
1062	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
1063	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
1064	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1065	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1066		1170
1067	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1068		1172
1069	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1070		1174
1071	=item C<EV_FORK>	1175	=item C<EV_FORK>
1072		1176
1073	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
1074	C<ev_fork>).	1178	C<ev_fork>).
		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
1075		1183
1076	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1077		1185
1078	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
1079		1187
…		…
1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1253	functions that do not need a watcher.	1361	functions that do not need a watcher.
1254		1362
1255	=back	1363	=back
1256		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1257		1367
1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1259		1369
1260	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1261	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1262	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1263	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1264	member, you can also "subclass" the watcher type and provide your own
1265	data:
1266		1374
1267	struct my_io	1375	=over 4
1268	{
1269	ev_io io;
1270	int otherfd;
1271	void *somedata;
1272	struct whatever *mostinteresting;
1273	};
1274		1376
1275	...	1377	=item initialiased
1276	struct my_io w;
1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1278		1378
1279	And since your callback will be called with a pointer to the watcher, you	1379	Before a watcher can be registered with the event looop it has to be
1280	can cast it back to your own type:	1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1281		1382
1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1383	In this state it is simply some block of memory that is suitable for
1283	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1284	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1285	...	1386	C<ev_TYPE_init> again.
1286	}
1287		1387
1288	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1289	instead have been omitted.
1290		1389
1291	Another common scenario is to use some data structure with multiple	1390	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1292	embedded watchers:	1391	property of the event loop, and is actively waiting for events. While in
		1392	this state it cannot be accessed (except in a few documented ways), moved,
		1393	freed or anything else - the only legal thing is to keep a pointer to it,
		1394	and call libev functions on it that are documented to work on active watchers.
1293		1395
1294	struct my_biggy	1396	=item pending
1295	{
1296	int some_data;
1297	ev_timer t1;
1298	ev_timer t2;
1299	}
1300		1397
1301	In this case getting the pointer to C<my_biggy> is a bit more	1398	If a watcher is active and libev determines that an event it is interested
1302	complicated: Either you store the address of your C<my_biggy> struct	1399	in has occurred (such as a timer expiring), it will become pending. It will
1303	in the C<data> member of the watcher (for woozies), or you need to use	1400	stay in this pending state until either it is stopped or its callback is
1304	some pointer arithmetic using C<offsetof> inside your watchers (for real	1401	about to be invoked, so it is not normally pending inside the watcher
1305	programmers):	1402	callback.
1306		1403
1307	#include <stddef.h>	1404	The watcher might or might not be active while it is pending (for example,
		1405	an expired non-repeating timer can be pending but no longer active). If it
		1406	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1407	but it is still property of the event loop at this time, so cannot be
		1408	moved, freed or reused. And if it is active the rules described in the
		1409	previous item still apply.
1308		1410
1309	static void	1411	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)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1311	{	1413	active.
1312	struct my_biggy big = (struct my_biggy *)
1313	(((char *)w) - offsetof (struct my_biggy, t1));
1314	}
1315		1414
1316	static void	1415	=item stopped
1317	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1318	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1319	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1320	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1321	}	1420	of whether it was active or not, so stopping a watcher explicitly before
		1421	freeing it is often a good idea.
		1422
		1423	While stopped (and not pending) the watcher is essentially in the
		1424	initialised state, that is, it can be reused, moved, modified in any way
		1425	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1426	it again).
		1427
		1428	=back
1322		1429
1323	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1324		1431
1325	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1326	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1369		1476
1370	For example, to emulate how many other event libraries handle priorities,	1477	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	1478	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	1479	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	1480	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	1481	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	1482	the lock-out case is known to be rare (which in turn is rare :), this is
1376	workable.	1483	workable.
1377		1484
1378	Usually, however, the lock-out model implemented that way will perform	1485	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,	1486	miserably under the type of load it was designed to handle. In that case,
…		…
1393	{	1500	{
1394	// stop the I/O watcher, we received the event, but	1501	// stop the I/O watcher, we received the event, but
1395	// are not yet ready to handle it.	1502	// are not yet ready to handle it.
1396	ev_io_stop (EV_A_ w);	1503	ev_io_stop (EV_A_ w);
1397		1504
1398	// start the idle watcher to ahndle the actual event.	1505	// start the idle watcher to handle the actual event.
1399	// it will not be executed as long as other watchers	1506	// it will not be executed as long as other watchers
1400	// with the default priority are receiving events.	1507	// with the default priority are receiving events.
1401	ev_idle_start (EV_A_ &idle);	1508	ev_idle_start (EV_A_ &idle);
1402	}	1509	}
1403		1510
…		…
1453	In general you can register as many read and/or write event watchers per	1560	In general you can register as many read and/or write event watchers per
1454	fd as you want (as long as you don't confuse yourself). Setting all file	1561	fd as you want (as long as you don't confuse yourself). Setting all file
1455	descriptors to non-blocking mode is also usually a good idea (but not	1562	descriptors to non-blocking mode is also usually a good idea (but not
1456	required if you know what you are doing).	1563	required if you know what you are doing).
1457		1564
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	1565	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	1566	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	1567	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	1568	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	1569	with a relatively standard program structure. Thus it is best to always
1469	this situation even with a relatively standard program structure. Thus	1570	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
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.	1571	preferable to a program hanging until some data arrives.
1472		1572
1473	If you cannot run the fd in non-blocking mode (for example you should	1573	If you cannot run the fd in non-blocking mode (for example you should
1474	not play around with an Xlib connection), then you have to separately	1574	not play around with an Xlib connection), then you have to separately
1475	re-test whether a file descriptor is really ready with a known-to-be good	1575	re-test whether a file descriptor is really ready with a known-to-be good
1476	interface such as poll (fortunately in our Xlib example, Xlib already	1576	interface such as poll (fortunately in the case of Xlib, it already does
1477	does this on its own, so its quite safe to use). Some people additionally	1577	this on its own, so its quite safe to use). Some people additionally
1478	use C<SIGALRM> and an interval timer, just to be sure you won't block	1578	use C<SIGALRM> and an interval timer, just to be sure you won't block
1479	indefinitely.	1579	indefinitely.
1480		1580
1481	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1482		1582
…		…
1510		1610
1511	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1512	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1513	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1514		1614
		1615	=head3 The special problem of files
		1616
		1617	Many people try to use C<select> (or libev) on file descriptors
		1618	representing files, and expect it to become ready when their program
		1619	doesn't block on disk accesses (which can take a long time on their own).
		1620
		1621	However, this cannot ever work in the "expected" way - you get a readiness
		1622	notification as soon as the kernel knows whether and how much data is
		1623	there, and in the case of open files, that's always the case, so you
		1624	always get a readiness notification instantly, and your read (or possibly
		1625	write) will still block on the disk I/O.
		1626
		1627	Another way to view it is that in the case of sockets, pipes, character
		1628	devices and so on, there is another party (the sender) that delivers data
		1629	on its own, but in the case of files, there is no such thing: the disk
		1630	will not send data on its own, simply because it doesn't know what you
		1631	wish to read - you would first have to request some data.
		1632
		1633	Since files are typically not-so-well supported by advanced notification
		1634	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1635	to files, even though you should not use it. The reason for this is
		1636	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1637	usually a tty, often a pipe, but also sometimes files or special devices
		1638	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1639	F</dev/urandom>), and even though the file might better be served with
		1640	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1641	it "just works" instead of freezing.
		1642
		1643	So avoid file descriptors pointing to files when you know it (e.g. use
		1644	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1645	when you rarely read from a file instead of from a socket, and want to
		1646	reuse the same code path.
		1647
1515	=head3 The special problem of fork	1648	=head3 The special problem of fork
1516		1649
1517	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1650	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1518	useless behaviour. Libev fully supports fork, but needs to be told about	1651	useless behaviour. Libev fully supports fork, but needs to be told about
1519	it in the child.	1652	it in the child if you want to continue to use it in the child.
1520		1653
1521	To support fork in your programs, you either have to call	1654	To support fork in your child processes, you have to call C<ev_loop_fork
1522	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1655	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524	C<EVBACKEND_POLL>.
1525		1657
1526	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1527		1659
1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1660	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1529	when writing to a pipe whose other end has been closed, your program gets	1661	when writing to a pipe whose other end has been closed, your program gets
…		…
1532		1664
1533	So when you encounter spurious, unexplained daemon exits, make sure you	1665	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	1666	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).	1667	somewhere, as that would have given you a big clue).
1536		1668
		1669	=head3 The special problem of accept()ing when you can't
		1670
		1671	Many implementations of the POSIX C<accept> function (for example,
		1672	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1673	connection from the pending queue in all error cases.
		1674
		1675	For example, larger servers often run out of file descriptors (because
		1676	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1677	rejecting the connection, leading to libev signalling readiness on
		1678	the next iteration again (the connection still exists after all), and
		1679	typically causing the program to loop at 100% CPU usage.
		1680
		1681	Unfortunately, the set of errors that cause this issue differs between
		1682	operating systems, there is usually little the app can do to remedy the
		1683	situation, and no known thread-safe method of removing the connection to
		1684	cope with overload is known (to me).
		1685
		1686	One of the easiest ways to handle this situation is to just ignore it
		1687	- when the program encounters an overload, it will just loop until the
		1688	situation is over. While this is a form of busy waiting, no OS offers an
		1689	event-based way to handle this situation, so it's the best one can do.
		1690
		1691	A better way to handle the situation is to log any errors other than
		1692	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1693	messages, and continue as usual, which at least gives the user an idea of
		1694	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1695	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1696	usage.
		1697
		1698	If your program is single-threaded, then you could also keep a dummy file
		1699	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1700	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1701	close that fd, and create a new dummy fd. This will gracefully refuse
		1702	clients under typical overload conditions.
		1703
		1704	The last way to handle it is to simply log the error and C<exit>, as
		1705	is often done with C<malloc> failures, but this results in an easy
		1706	opportunity for a DoS attack.
1537		1707
1538	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1539		1709
1540	=over 4	1710	=over 4
1541		1711
…		…
1573	...	1743	...
1574	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1575	ev_io stdin_readable;	1745	ev_io stdin_readable;
1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1746	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1577	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1578	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1579		1749
1580		1750
1581	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1582		1752
1583	Timer watchers are simple relative timers that generate an event after a	1753	Timer watchers are simple relative timers that generate an event after a
…		…
1592	The callback is guaranteed to be invoked only I<after> its timeout has	1762	The callback is guaranteed to be invoked only I<after> its timeout has
1593	passed (not I<at>, so on systems with very low-resolution clocks this	1763	passed (not I<at>, so on systems with very low-resolution clocks this
1594	might introduce a small delay). If multiple timers become ready during the	1764	might introduce a small delay). If multiple timers become ready during the
1595	same loop iteration then the ones with earlier time-out values are invoked	1765	same loop iteration then the ones with earlier time-out values are invoked
1596	before ones of the same priority with later time-out values (but this is	1766	before ones of the same priority with later time-out values (but this is
1597	no longer true when a callback calls C<ev_loop> recursively).	1767	no longer true when a callback calls C<ev_run> recursively).
1598		1768
1599	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1600		1770
1601	Many real-world problems involve some kind of timeout, usually for error	1771	Many real-world problems involve some kind of timeout, usually for error
1602	recovery. A typical example is an HTTP request - if the other side hangs,	1772	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1688	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1689		1859
1690	// if last_activity + 60. is older than now, we did time out	1860	// if last_activity + 60. is older than now, we did time out
1691	if (timeout < now)	1861	if (timeout < now)
1692	{	1862	{
1693	// timeout occured, take action	1863	// timeout occurred, take action
1694	}	1864	}
1695	else	1865	else
1696	{	1866	{
1697	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1698	// the watcher to fire in last_activity + 60, which is	1868	// the watcher to fire in last_activity + 60, which is
…		…
1720	to the current time (meaning we just have some activity :), then call the	1890	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:	1891	callback, which will "do the right thing" and start the timer:
1722		1892
1723	ev_init (timer, callback);	1893	ev_init (timer, callback);
1724	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1725	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1726		1896
1727	And when there is some activity, simply store the current time in	1897	And when there is some activity, simply store the current time in
1728	C<last_activity>, no libev calls at all:	1898	C<last_activity>, no libev calls at all:
1729		1899
1730	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1731		1901
1732	This technique is slightly more complex, but in most cases where the	1902	This technique is slightly more complex, but in most cases where the
1733	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1734		1904
1735	Changing the timeout is trivial as well (if it isn't hard-coded in the	1905	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1773		1943
1774	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1775		1945
1776	Establishing the current time is a costly operation (it usually takes at	1946	Establishing the current time is a costly operation (it usually takes at
1777	least two system calls): EV therefore updates its idea of the current	1947	least two system calls): EV therefore updates its idea of the current
1778	time only before and after C<ev_loop> collects new events, which causes a	1948	time only before and after C<ev_run> collects new events, which causes a
1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1949	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1780	lots of events in one iteration.	1950	lots of events in one iteration.
1781		1951
1782	The relative timeouts are calculated relative to the C<ev_now ()>	1952	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	1953	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,	2031	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	2032	then this time is relative to the current event loop time, otherwise it's
1863	the timeout value currently configured.	2033	the timeout value currently configured.
1864		2034
1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2035	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>	2036	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	2037	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,	2038	roughly C<7> (likely slightly less as callback invocation takes some time,
1869	too), and so on.	2039	too), and so on.
1870		2040
1871	=item ev_tstamp repeat [read-write]	2041	=item ev_tstamp repeat [read-write]
…		…
1900	}	2070	}
1901		2071
1902	ev_timer mytimer;	2072	ev_timer mytimer;
1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2073	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1904	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1905	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1906		2076
1907	// and in some piece of code that gets executed on any "activity":	2077	// and in some piece of code that gets executed on any "activity":
1908	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1909	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1910		2080
…		…
1936		2106
1937	As with timers, the callback is guaranteed to be invoked only when the	2107	As with timers, the callback is guaranteed to be invoked only when the
1938	point in time where it is supposed to trigger has passed. If multiple	2108	point in time where it is supposed to trigger has passed. If multiple
1939	timers become ready during the same loop iteration then the ones with	2109	timers become ready during the same loop iteration then the ones with
1940	earlier time-out values are invoked before ones with later time-out values	2110	earlier time-out values are invoked before ones with later time-out values
1941	(but this is no longer true when a callback calls C<ev_loop> recursively).	2111	(but this is no longer true when a callback calls C<ev_run> recursively).
1942		2112
1943	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1944		2114
1945	=over 4	2115	=over 4
1946		2116
…		…
2074	Example: Call a callback every hour, or, more precisely, whenever the	2244	Example: Call a callback every hour, or, more precisely, whenever the
2075	system time is divisible by 3600. The callback invocation times have	2245	system time is divisible by 3600. The callback invocation times have
2076	potentially a lot of jitter, but good long-term stability.	2246	potentially a lot of jitter, but good long-term stability.
2077		2247
2078	static void	2248	static void
2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2249	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2080	{	2250	{
2081	... its now a full hour (UTC, or TAI or whatever your clock follows)	2251	... its now a full hour (UTC, or TAI or whatever your clock follows)
2082	}	2252	}
2083		2253
2084	ev_periodic hourly_tick;	2254	ev_periodic hourly_tick;
…		…
2107		2277
2108	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
2109		2279
2110	Signal watchers will trigger an event when the process receives a specific	2280	Signal watchers will trigger an event when the process receives a specific
2111	signal one or more times. Even though signals are very asynchronous, libev	2281	signal one or more times. Even though signals are very asynchronous, libev
2112	will try it's best to deliver signals synchronously, i.e. as part of the	2282	will try its best to deliver signals synchronously, i.e. as part of the
2113	normal event processing, like any other event.	2283	normal event processing, like any other event.
2114		2284
2115	If you want signals to be delivered truly asynchronously, just use	2285	If you want signals to be delivered truly asynchronously, just use
2116	C<sigaction> as you would do without libev and forget about sharing	2286	C<sigaction> as you would do without libev and forget about sharing
2117	the signal. You can even use C<ev_async> from a signal handler to	2287	the signal. You can even use C<ev_async> from a signal handler to
…		…
2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2301	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	2302	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	2303	interrupted by signals you can block all signals in an C<ev_check> watcher
2134	and unblock them in an C<ev_prepare> watcher.	2304	and unblock them in an C<ev_prepare> watcher.
2135		2305
2136	=head3 The special problem of inheritance over execve	2306	=head3 The special problem of inheritance over fork/execve/pthread_create
2137		2307
2138	Both the signal mask (C<sigprocmask>) and the signal disposition	2308	Both the signal mask (C<sigprocmask>) and the signal disposition
2139	(C<sigaction>) are unspecified after starting a signal watcher (and after	2309	(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,	2310	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.	2311	and might or might not set or restore the installed signal handler (but
		2312	see C<EVFLAG_NOSIGMASK>).
2142		2313
2143	While this does not matter for the signal disposition (libev never	2314	While this does not matter for the signal disposition (libev never
2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2315	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2145	C<execve>), this matters for the signal mask: many programs do not expect	2316	C<execve>), this matters for the signal mask: many programs do not expect
2146	certain signals to be blocked.	2317	certain signals to be blocked.
…		…
2151		2322
2152	The simplest way to ensure that the signal mask is reset in the child is	2323	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	2324	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.	2325	catch fork calls done by libraries (such as the libc) as well.
2155		2326
2156	In current versions of libev, you can also ensure that the signal mask is	2327	In current versions of libev, the signal will not be blocked indefinitely
2157	not blocking any signals (except temporarily, so thread users watch out)	2328	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	2329	the window of opportunity for problems, it will not go away, as libev
2159	is not guaranteed for future versions, however.	2330	I<has> to modify the signal mask, at least temporarily.
		2331
		2332	So I can't stress this enough: I<If you do not reset your signal mask when
		2333	you expect it to be empty, you have a race condition in your code>. This
		2334	is not a libev-specific thing, this is true for most event libraries.
		2335
		2336	=head3 The special problem of threads signal handling
		2337
		2338	POSIX threads has problematic signal handling semantics, specifically,
		2339	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2340	threads in a process block signals, which is hard to achieve.
		2341
		2342	When you want to use sigwait (or mix libev signal handling with your own
		2343	for the same signals), you can tackle this problem by globally blocking
		2344	all signals before creating any threads (or creating them with a fully set
		2345	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2346	loops. Then designate one thread as "signal receiver thread" which handles
		2347	these signals. You can pass on any signals that libev might be interested
		2348	in by calling C<ev_feed_signal>.
2160		2349
2161	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
2162		2351
2163	=over 4	2352	=over 4
2164		2353
…		…
2180	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
2181		2370
2182	static void	2371	static void
2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2184	{	2373	{
2185	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
2186	}	2375	}
2187		2376
2188	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2190	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
2576		2765
2577	Prepare and check watchers are usually (but not always) used in pairs:	2766	Prepare and check watchers are usually (but not always) used in pairs:
2578	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2579	afterwards.	2768	afterwards.
2580		2769
2581	You I<must not> call C<ev_loop> or similar functions that enter	2770	You I<must not> call C<ev_run> or similar functions that enter
2582	the current event loop from either C<ev_prepare> or C<ev_check>	2771	the current event loop from either C<ev_prepare> or C<ev_check>
2583	watchers. Other loops than the current one are fine, however. The	2772	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	2773	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,	2774	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	2775	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2754		2943
2755	if (timeout >= 0)	2944	if (timeout >= 0)
2756	// create/start timer	2945	// create/start timer
2757		2946
2758	// poll	2947	// poll
2759	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2760		2949
2761	// stop timer again	2950	// stop timer again
2762	if (timeout >= 0)	2951	if (timeout >= 0)
2763	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2764		2953
…		…
2842	if you do not want that, you need to temporarily stop the embed watcher).	3031	if you do not want that, you need to temporarily stop the embed watcher).
2843		3032
2844	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2845		3034
2846	Make a single, non-blocking sweep over the embedded loop. This works	3035	Make a single, non-blocking sweep over the embedded loop. This works
2847	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3036	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2848	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2849		3038
2850	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2851		3040
2852	The embedded event loop.	3041	The embedded event loop.
…		…
2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3101	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2913	handlers will be invoked, too, of course.	3102	handlers will be invoked, too, of course.
2914		3103
2915	=head3 The special problem of life after fork - how is it possible?	3104	=head3 The special problem of life after fork - how is it possible?
2916		3105
2917	Most uses of C<fork()> consist of forking, then some simple calls to ste	3106	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	3107	up/change the process environment, followed by a call to C<exec()>. This
2919	sequence should be handled by libev without any problems.	3108	sequence should be handled by libev without any problems.
2920		3109
2921	This changes when the application actually wants to do event handling	3110	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	3111	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	3127	disadvantage of having to use multiple event loops (which do not support
2939	signal watchers).	3128	signal watchers).
2940		3129
2941	When this is not possible, or you want to use the default loop for	3130	When this is not possible, or you want to use the default loop for
2942	other reasons, then in the process that wants to start "fresh", call	3131	other reasons, then in the process that wants to start "fresh", call
2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3132	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	3133	Destroying the default loop will "orphan" (not stop) all registered
2945	have to be careful not to execute code that modifies those watchers. Note	3134	watchers, so you have to be careful not to execute code that modifies
2946	also that in that case, you have to re-register any signal watchers.	3135	those watchers. Note also that in that case, you have to re-register any
		3136	signal watchers.
2947		3137
2948	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
2949		3139
2950	=over 4	3140	=over 4
2951		3141
2952	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
2953		3143
2954	Initialises and configures the fork watcher - it has no parameters of any	3144	Initialises and configures the fork watcher - it has no parameters of any
2955	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3145	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2956	believe me.	3146	really.
2957		3147
2958	=back	3148	=back
2959		3149
2960		3150
		3151	=head2 C<ev_cleanup> - even the best things end
		3152
		3153	Cleanup watchers are called just before the event loop is being destroyed
		3154	by a call to C<ev_loop_destroy>.
		3155
		3156	While there is no guarantee that the event loop gets destroyed, cleanup
		3157	watchers provide a convenient method to install cleanup hooks for your
		3158	program, worker threads and so on - you just to make sure to destroy the
		3159	loop when you want them to be invoked.
		3160
		3161	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3162	all other watchers, they do not keep a reference to the event loop (which
		3163	makes a lot of sense if you think about it). Like all other watchers, you
		3164	can call libev functions in the callback, except C<ev_cleanup_start>.
		3165
		3166	=head3 Watcher-Specific Functions and Data Members
		3167
		3168	=over 4
		3169
		3170	=item ev_cleanup_init (ev_cleanup *, callback)
		3171
		3172	Initialises and configures the cleanup watcher - it has no parameters of
		3173	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3174	pointless, I assure you.
		3175
		3176	=back
		3177
		3178	Example: Register an atexit handler to destroy the default loop, so any
		3179	cleanup functions are called.
		3180
		3181	static void
		3182	program_exits (void)
		3183	{
		3184	ev_loop_destroy (EV_DEFAULT_UC);
		3185	}
		3186
		3187	...
		3188	atexit (program_exits);
		3189
		3190
2961	=head2 C<ev_async> - how to wake up another event loop	3191	=head2 C<ev_async> - how to wake up an event loop
2962		3192
2963	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	In general, you cannot use an C<ev_run> from multiple threads or other
2964	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
2965	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
2966		3196
2967	Sometimes, however, you need to wake up another event loop you do not	3197	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	3198	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	3199	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	3200	it by calling C<ev_async_send>, which is thread- and signal safe.
2971	safe.
2972		3201
2973	This functionality is very similar to C<ev_signal> watchers, as signals,	3202	This functionality is very similar to C<ev_signal> watchers, as signals,
2974	too, are asynchronous in nature, and signals, too, will be compressed	3203	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	3204	(i.e. the number of callback invocations may be less than the number of
2976	C<ev_async_sent> calls).	3205	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3206	of "global async watchers" by using a watcher on an otherwise unused
		3207	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3208	even without knowing which loop owns the signal.
2977		3209
2978	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3210	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2979	just the default loop.	3211	just the default loop.
2980		3212
2981	=head3 Queueing	3213	=head3 Queueing
…		…
3131		3363
3132	If C<timeout> is less than 0, then no timeout watcher will be	3364	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	3365	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3134	repeat = 0) will be started. C<0> is a valid timeout.	3366	repeat = 0) will be started. C<0> is a valid timeout.
3135		3367
3136	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3368	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	3369	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>	3370	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>	3371	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	3372	a timeout and an io event at the same time - you probably should give io
3141	events precedence.	3373	events precedence.
3142		3374
3143	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3375	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3144		3376
3145	static void stdin_ready (int revents, void *arg)	3377	static void stdin_ready (int revents, void *arg)
3146	{	3378	{
3147	if (revents & EV_READ)	3379	if (revents & EV_READ)
3148	/* stdin might have data for us, joy! */;	3380	/* stdin might have data for us, joy! */;
3149	else if (revents & EV_TIMEOUT)	3381	else if (revents & EV_TIMER)
3150	/* doh, nothing entered */;	3382	/* doh, nothing entered */;
3151	}	3383	}
3152		3384
3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3385	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3154		3386
…		…
3157	Feed an event on the given fd, as if a file descriptor backend detected	3389	Feed an event on the given fd, as if a file descriptor backend detected
3158	the given events it.	3390	the given events it.
3159		3391
3160	=item ev_feed_signal_event (loop, int signum)	3392	=item ev_feed_signal_event (loop, int signum)
3161		3393
3162	Feed an event as if the given signal occurred (C<loop> must be the default	3394	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3163	loop!).	3395	which is async-safe.
3164		3396
3165	=back	3397	=back
		3398
		3399
		3400	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3401
		3402	This section explains some common idioms that are not immediately
		3403	obvious. Note that examples are sprinkled over the whole manual, and this
		3404	section only contains stuff that wouldn't fit anywhere else.
		3405
		3406	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3407
		3408	Each watcher has, by default, a C<void *data> member that you can read
		3409	or modify at any time: libev will completely ignore it. This can be used
		3410	to associate arbitrary data with your watcher. If you need more data and
		3411	don't want to allocate memory separately and store a pointer to it in that
		3412	data member, you can also "subclass" the watcher type and provide your own
		3413	data:
		3414
		3415	struct my_io
		3416	{
		3417	ev_io io;
		3418	int otherfd;
		3419	void *somedata;
		3420	struct whatever *mostinteresting;
		3421	};
		3422
		3423	...
		3424	struct my_io w;
		3425	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3426
		3427	And since your callback will be called with a pointer to the watcher, you
		3428	can cast it back to your own type:
		3429
		3430	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3431	{
		3432	struct my_io *w = (struct my_io *)w_;
		3433	...
		3434	}
		3435
		3436	More interesting and less C-conformant ways of casting your callback
		3437	function type instead have been omitted.
		3438
		3439	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3440
		3441	Another common scenario is to use some data structure with multiple
		3442	embedded watchers, in effect creating your own watcher that combines
		3443	multiple libev event sources into one "super-watcher":
		3444
		3445	struct my_biggy
		3446	{
		3447	int some_data;
		3448	ev_timer t1;
		3449	ev_timer t2;
		3450	}
		3451
		3452	In this case getting the pointer to C<my_biggy> is a bit more
		3453	complicated: Either you store the address of your C<my_biggy> struct in
		3454	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3455	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3456	real programmers):
		3457
		3458	#include <stddef.h>
		3459
		3460	static void
		3461	t1_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t1));
		3465	}
		3466
		3467	static void
		3468	t2_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t2));
		3472	}
		3473
		3474	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3475
		3476	Often (especially in GUI toolkits) there are places where you have
		3477	I<modal> interaction, which is most easily implemented by recursively
		3478	invoking C<ev_run>.
		3479
		3480	This brings the problem of exiting - a callback might want to finish the
		3481	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3482	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3483	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3484	other combination: In these cases, C<ev_break> will not work alone.
		3485
		3486	The solution is to maintain "break this loop" variable for each C<ev_run>
		3487	invocation, and use a loop around C<ev_run> until the condition is
		3488	triggered, using C<EVRUN_ONCE>:
		3489
		3490	// main loop
		3491	int exit_main_loop = 0;
		3492
		3493	while (!exit_main_loop)
		3494	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3495
		3496	// in a model watcher
		3497	int exit_nested_loop = 0;
		3498
		3499	while (!exit_nested_loop)
		3500	ev_run (EV_A_ EVRUN_ONCE);
		3501
		3502	To exit from any of these loops, just set the corresponding exit variable:
		3503
		3504	// exit modal loop
		3505	exit_nested_loop = 1;
		3506
		3507	// exit main program, after modal loop is finished
		3508	exit_main_loop = 1;
		3509
		3510	// exit both
		3511	exit_main_loop = exit_nested_loop = 1;
		3512
		3513	=head2 THREAD LOCKING EXAMPLE
		3514
		3515	Here is a fictitious example of how to run an event loop in a different
		3516	thread from where callbacks are being invoked and watchers are
		3517	created/added/removed.
		3518
		3519	For a real-world example, see the C<EV::Loop::Async> perl module,
		3520	which uses exactly this technique (which is suited for many high-level
		3521	languages).
		3522
		3523	The example uses a pthread mutex to protect the loop data, a condition
		3524	variable to wait for callback invocations, an async watcher to notify the
		3525	event loop thread and an unspecified mechanism to wake up the main thread.
		3526
		3527	First, you need to associate some data with the event loop:
		3528
		3529	typedef struct {
		3530	mutex_t lock; /* global loop lock */
		3531	ev_async async_w;
		3532	thread_t tid;
		3533	cond_t invoke_cv;
		3534	} userdata;
		3535
		3536	void prepare_loop (EV_P)
		3537	{
		3538	// for simplicity, we use a static userdata struct.
		3539	static userdata u;
		3540
		3541	ev_async_init (&u->async_w, async_cb);
		3542	ev_async_start (EV_A_ &u->async_w);
		3543
		3544	pthread_mutex_init (&u->lock, 0);
		3545	pthread_cond_init (&u->invoke_cv, 0);
		3546
		3547	// now associate this with the loop
		3548	ev_set_userdata (EV_A_ u);
		3549	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3550	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3551
		3552	// then create the thread running ev_run
		3553	pthread_create (&u->tid, 0, l_run, EV_A);
		3554	}
		3555
		3556	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3557	solely to wake up the event loop so it takes notice of any new watchers
		3558	that might have been added:
		3559
		3560	static void
		3561	async_cb (EV_P_ ev_async *w, int revents)
		3562	{
		3563	// just used for the side effects
		3564	}
		3565
		3566	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3567	protecting the loop data, respectively.
		3568
		3569	static void
		3570	l_release (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_unlock (&u->lock);
		3574	}
		3575
		3576	static void
		3577	l_acquire (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_lock (&u->lock);
		3581	}
		3582
		3583	The event loop thread first acquires the mutex, and then jumps straight
		3584	into C<ev_run>:
		3585
		3586	void *
		3587	l_run (void *thr_arg)
		3588	{
		3589	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3590
		3591	l_acquire (EV_A);
		3592	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3593	ev_run (EV_A_ 0);
		3594	l_release (EV_A);
		3595
		3596	return 0;
		3597	}
		3598
		3599	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3600	signal the main thread via some unspecified mechanism (signals? pipe
		3601	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3602	have been called (in a while loop because a) spurious wakeups are possible
		3603	and b) skipping inter-thread-communication when there are no pending
		3604	watchers is very beneficial):
		3605
		3606	static void
		3607	l_invoke (EV_P)
		3608	{
		3609	userdata *u = ev_userdata (EV_A);
		3610
		3611	while (ev_pending_count (EV_A))
		3612	{
		3613	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3614	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3615	}
		3616	}
		3617
		3618	Now, whenever the main thread gets told to invoke pending watchers, it
		3619	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3620	thread to continue:
		3621
		3622	static void
		3623	real_invoke_pending (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	pthread_mutex_lock (&u->lock);
		3628	ev_invoke_pending (EV_A);
		3629	pthread_cond_signal (&u->invoke_cv);
		3630	pthread_mutex_unlock (&u->lock);
		3631	}
		3632
		3633	Whenever you want to start/stop a watcher or do other modifications to an
		3634	event loop, you will now have to lock:
		3635
		3636	ev_timer timeout_watcher;
		3637	userdata *u = ev_userdata (EV_A);
		3638
		3639	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3640
		3641	pthread_mutex_lock (&u->lock);
		3642	ev_timer_start (EV_A_ &timeout_watcher);
		3643	ev_async_send (EV_A_ &u->async_w);
		3644	pthread_mutex_unlock (&u->lock);
		3645
		3646	Note that sending the C<ev_async> watcher is required because otherwise
		3647	an event loop currently blocking in the kernel will have no knowledge
		3648	about the newly added timer. By waking up the loop it will pick up any new
		3649	watchers in the next event loop iteration.
		3650
		3651	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3652
		3653	While the overhead of a callback that e.g. schedules a thread is small, it
		3654	is still an overhead. If you embed libev, and your main usage is with some
		3655	kind of threads or coroutines, you might want to customise libev so that
		3656	doesn't need callbacks anymore.
		3657
		3658	Imagine you have coroutines that you can switch to using a function
		3659	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3660	and that due to some magic, the currently active coroutine is stored in a
		3661	global called C<current_coro>. Then you can build your own "wait for libev
		3662	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3663	the differing C<;> conventions):
		3664
		3665	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3666	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3667
		3668	That means instead of having a C callback function, you store the
		3669	coroutine to switch to in each watcher, and instead of having libev call
		3670	your callback, you instead have it switch to that coroutine.
		3671
		3672	A coroutine might now wait for an event with a function called
		3673	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3674	matter when, or whether the watcher is active or not when this function is
		3675	called):
		3676
		3677	void
		3678	wait_for_event (ev_watcher *w)
		3679	{
		3680	ev_cb_set (w) = current_coro;
		3681	switch_to (libev_coro);
		3682	}
		3683
		3684	That basically suspends the coroutine inside C<wait_for_event> and
		3685	continues the libev coroutine, which, when appropriate, switches back to
		3686	this or any other coroutine. I am sure if you sue this your own :)
		3687
		3688	You can do similar tricks if you have, say, threads with an event queue -
		3689	instead of storing a coroutine, you store the queue object and instead of
		3690	switching to a coroutine, you push the watcher onto the queue and notify
		3691	any waiters.
		3692
		3693	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3694	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3695
		3696	// my_ev.h
		3697	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3698	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3699	#include "../libev/ev.h"
		3700
		3701	// my_ev.c
		3702	#define EV_H "my_ev.h"
		3703	#include "../libev/ev.c"
		3704
		3705	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3706	F<my_ev.c> into your project. When properly specifying include paths, you
		3707	can even use F<ev.h> as header file name directly.
3166		3708
3167		3709
3168	=head1 LIBEVENT EMULATION	3710	=head1 LIBEVENT EMULATION
3169		3711
3170	Libev offers a compatibility emulation layer for libevent. It cannot	3712	Libev offers a compatibility emulation layer for libevent. It cannot
3171	emulate the internals of libevent, so here are some usage hints:	3713	emulate the internals of libevent, so here are some usage hints:
3172		3714
3173	=over 4	3715	=over 4
		3716
		3717	=item * Only the libevent-1.4.1-beta API is being emulated.
		3718
		3719	This was the newest libevent version available when libev was implemented,
		3720	and is still mostly unchanged in 2010.
3174		3721
3175	=item * Use it by including <event.h>, as usual.	3722	=item * Use it by including <event.h>, as usual.
3176		3723
3177	=item * The following members are fully supported: ev_base, ev_callback,	3724	=item * The following members are fully supported: ev_base, ev_callback,
3178	ev_arg, ev_fd, ev_res, ev_events.	3725	ev_arg, ev_fd, ev_res, ev_events.
…		…
3184	=item * Priorities are not currently supported. Initialising priorities	3731	=item * Priorities are not currently supported. Initialising priorities
3185	will fail and all watchers will have the same priority, even though there	3732	will fail and all watchers will have the same priority, even though there
3186	is an ev_pri field.	3733	is an ev_pri field.
3187		3734
3188	=item * In libevent, the last base created gets the signals, in libev, the	3735	=item * In libevent, the last base created gets the signals, in libev, the
3189	first base created (== the default loop) gets the signals.	3736	base that registered the signal gets the signals.
3190		3737
3191	=item * Other members are not supported.	3738	=item * Other members are not supported.
3192		3739
3193	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3740	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3194	to use the libev header file and library.	3741	to use the libev header file and library.
…		…
3213	Care has been taken to keep the overhead low. The only data member the C++	3760	Care has been taken to keep the overhead low. The only data member the C++
3214	classes add (compared to plain C-style watchers) is the event loop pointer	3761	classes add (compared to plain C-style watchers) is the event loop pointer
3215	that the watcher is associated with (or no additional members at all if	3762	that the watcher is associated with (or no additional members at all if
3216	you disable C<EV_MULTIPLICITY> when embedding libev).	3763	you disable C<EV_MULTIPLICITY> when embedding libev).
3217		3764
3218	Currently, functions, and static and non-static member functions can be	3765	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	3766	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	3767	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	3768	you need support for other types of functors please contact the author
3222	it).	3769	(preferably after implementing it).
3223		3770
3224	Here is a list of things available in the C<ev> namespace:	3771	Here is a list of things available in the C<ev> namespace:
3225		3772
3226	=over 4	3773	=over 4
3227		3774
…		…
3288	myclass obj;	3835	myclass obj;
3289	ev::io iow;	3836	ev::io iow;
3290	iow.set <myclass, &myclass::io_cb> (&obj);	3837	iow.set <myclass, &myclass::io_cb> (&obj);
3291		3838
3292	=item w->set (object *)	3839	=item w->set (object *)
3293
3294	This is an B<experimental> feature that might go away in a future version.
3295		3840
3296	This is a variation of a method callback - leaving out the method to call	3841	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	3842	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	3843	functor objects without having to manually specify the C<operator ()> all
3299	the time. Incidentally, you can then also leave out the template argument	3844	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	3884	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).	3885	do this when the watcher is inactive (and not pending either).
3341		3886
3342	=item w->set ([arguments])	3887	=item w->set ([arguments])
3343		3888
3344	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3889	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3345	called at least once. Unlike the C counterpart, an active watcher gets	3890	method or a suitable start method must be called at least once. Unlike the
3346	automatically stopped and restarted when reconfiguring it with this	3891	C counterpart, an active watcher gets automatically stopped and restarted
3347	method.	3892	when reconfiguring it with this method.
3348		3893
3349	=item w->start ()	3894	=item w->start ()
3350		3895
3351	Starts the watcher. Note that there is no C<loop> argument, as the	3896	Starts the watcher. Note that there is no C<loop> argument, as the
3352	constructor already stores the event loop.	3897	constructor already stores the event loop.
3353		3898
		3899	=item w->start ([arguments])
		3900
		3901	Instead of calling C<set> and C<start> methods separately, it is often
		3902	convenient to wrap them in one call. Uses the same type of arguments as
		3903	the configure C<set> method of the watcher.
		3904
3354	=item w->stop ()	3905	=item w->stop ()
3355		3906
3356	Stops the watcher if it is active. Again, no C<loop> argument.	3907	Stops the watcher if it is active. Again, no C<loop> argument.
3357		3908
3358	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3909	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3370		3921
3371	=back	3922	=back
3372		3923
3373	=back	3924	=back
3374		3925
3375	Example: Define a class with an IO and idle watcher, start one of them in	3926	Example: Define a class with two I/O and idle watchers, start the I/O
3376	the constructor.	3927	watchers in the constructor.
3377		3928
3378	class myclass	3929	class myclass
3379	{	3930	{
3380	ev::io io ; void io_cb (ev::io &w, int revents);	3931	ev::io io ; void io_cb (ev::io &w, int revents);
		3932	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3381	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3933	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3382		3934
3383	myclass (int fd)	3935	myclass (int fd)
3384	{	3936	{
3385	io .set <myclass, &myclass::io_cb > (this);	3937	io .set <myclass, &myclass::io_cb > (this);
		3938	io2 .set <myclass, &myclass::io2_cb > (this);
3386	idle.set <myclass, &myclass::idle_cb> (this);	3939	idle.set <myclass, &myclass::idle_cb> (this);
3387		3940
3388	io.start (fd, ev::READ);	3941	io.set (fd, ev::WRITE); // configure the watcher
		3942	io.start (); // start it whenever convenient
		3943
		3944	io2.start (fd, ev::READ); // set + start in one call
3389	}	3945	}
3390	};	3946	};
3391		3947
3392		3948
3393	=head1 OTHER LANGUAGE BINDINGS	3949	=head1 OTHER LANGUAGE BINDINGS
…		…
3441	Erkki Seppala has written Ocaml bindings for libev, to be found at	3997	Erkki Seppala has written Ocaml bindings for libev, to be found at
3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3998	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3443		3999
3444	=item Lua	4000	=item Lua
3445		4001
3446	Brian Maher has written a partial interface to libev	4002	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	4003	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3448	L<http://github.com/brimworks/lua-ev>.	4004	L<http://github.com/brimworks/lua-ev>.
3449		4005
3450	=back	4006	=back
3451		4007
3452		4008
…		…
3467	loop argument"). The C<EV_A> form is used when this is the sole argument,	4023	loop argument"). The C<EV_A> form is used when this is the sole argument,
3468	C<EV_A_> is used when other arguments are following. Example:	4024	C<EV_A_> is used when other arguments are following. Example:
3469		4025
3470	ev_unref (EV_A);	4026	ev_unref (EV_A);
3471	ev_timer_add (EV_A_ watcher);	4027	ev_timer_add (EV_A_ watcher);
3472	ev_loop (EV_A_ 0);	4028	ev_run (EV_A_ 0);
3473		4029
3474	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4030	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3475	which is often provided by the following macro.	4031	which is often provided by the following macro.
3476		4032
3477	=item C<EV_P>, C<EV_P_>	4033	=item C<EV_P>, C<EV_P_>
…		…
3517	}	4073	}
3518		4074
3519	ev_check check;	4075	ev_check check;
3520	ev_check_init (&check, check_cb);	4076	ev_check_init (&check, check_cb);
3521	ev_check_start (EV_DEFAULT_ &check);	4077	ev_check_start (EV_DEFAULT_ &check);
3522	ev_loop (EV_DEFAULT_ 0);	4078	ev_run (EV_DEFAULT_ 0);
3523		4079
3524	=head1 EMBEDDING	4080	=head1 EMBEDDING
3525		4081
3526	Libev can (and often is) directly embedded into host	4082	Libev can (and often is) directly embedded into host
3527	applications. Examples of applications that embed it include the Deliantra	4083	applications. Examples of applications that embed it include the Deliantra
…		…
3607	libev.m4	4163	libev.m4
3608		4164
3609	=head2 PREPROCESSOR SYMBOLS/MACROS	4165	=head2 PREPROCESSOR SYMBOLS/MACROS
3610		4166
3611	Libev can be configured via a variety of preprocessor symbols you have to	4167	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	4168	define before including (or compiling) any of its files. The default in
3613	autoconf is documented for every option.	4169	the absence of autoconf is documented for every option.
		4170
		4171	Symbols marked with "(h)" do not change the ABI, and can have different
		4172	values when compiling libev vs. including F<ev.h>, so it is permissible
		4173	to redefine them before including F<ev.h> without breaking compatibility
		4174	to a compiled library. All other symbols change the ABI, which means all
		4175	users of libev and the libev code itself must be compiled with compatible
		4176	settings.
3614		4177
3615	=over 4	4178	=over 4
3616		4179
		4180	=item EV_COMPAT3 (h)
		4181
		4182	Backwards compatibility is a major concern for libev. This is why this
		4183	release of libev comes with wrappers for the functions and symbols that
		4184	have been renamed between libev version 3 and 4.
		4185
		4186	You can disable these wrappers (to test compatibility with future
		4187	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4188	sources. This has the additional advantage that you can drop the C<struct>
		4189	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4190	typedef in that case.
		4191
		4192	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4193	and in some even more future version the compatibility code will be
		4194	removed completely.
		4195
3617	=item EV_STANDALONE	4196	=item EV_STANDALONE (h)
3618		4197
3619	Must always be C<1> if you do not use autoconf configuration, which	4198	Must always be C<1> if you do not use autoconf configuration, which
3620	keeps libev from including F<config.h>, and it also defines dummy	4199	keeps libev from including F<config.h>, and it also defines dummy
3621	implementations for some libevent functions (such as logging, which is not	4200	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	4201	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.	4351	as well as for signal and thread safety in C<ev_async> watchers.
3773		4352
3774	In the absence of this define, libev will use C<sig_atomic_t volatile>	4353	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.	4354	(from F<signal.h>), which is usually good enough on most platforms.
3776		4355
3777	=item EV_H	4356	=item EV_H (h)
3778		4357
3779	The name of the F<ev.h> header file used to include it. The default if	4358	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	4359	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.	4360	used to virtually rename the F<ev.h> header file in case of conflicts.
3782		4361
3783	=item EV_CONFIG_H	4362	=item EV_CONFIG_H (h)
3784		4363
3785	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4364	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	4365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3787	C<EV_H>, above.	4366	C<EV_H>, above.
3788		4367
3789	=item EV_EVENT_H	4368	=item EV_EVENT_H (h)
3790		4369
3791	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4370	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">.	4371	of how the F<event.h> header can be found, the default is C<"event.h">.
3793		4372
3794	=item EV_PROTOTYPES	4373	=item EV_PROTOTYPES (h)
3795		4374
3796	If defined to be C<0>, then F<ev.h> will not define any function	4375	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	4376	prototypes, but still define all the structs and other symbols. This is
3798	occasionally useful if you want to provide your own wrapper functions	4377	occasionally useful if you want to provide your own wrapper functions
3799	around libev functions.	4378	around libev functions.
…		…
3821	fine.	4400	fine.
3822		4401
3823	If your embedding application does not need any priorities, defining these	4402	If your embedding application does not need any priorities, defining these
3824	both to C<0> will save some memory and CPU.	4403	both to C<0> will save some memory and CPU.
3825		4404
3826	=item EV_PERIODIC_ENABLE	4405	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4406	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4407	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3827		4408
3828	If undefined or defined to be C<1>, then periodic timers are supported. If	4409	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	4410	the respective watcher type is supported. If defined to be C<0>, then it
3830	code.	4411	is not. Disabling watcher types mainly saves code size.
3831		4412
3832	=item EV_IDLE_ENABLE	4413	=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		4414
3861	If you need to shave off some kilobytes of code at the expense of some	4415	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	4416	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	4417	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	4418	that can be enabled on the platform.
3865	the default 4-heap.
3866		4419
3867	You can save even more by disabling watcher types you do not need	4420	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>	4421	with some broad features you want) and then selectively re-enable
3869	(C<-DNDEBUG>) will usually reduce code size a lot.	4422	additional parts you want, for example if you want everything minimal,
		4423	but multiple event loop support, async and child watchers and the poll
		4424	backend, use this:
3870		4425
3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4426	#define EV_FEATURES 0
3872	provide a bare-bones event library. See C<ev.h> for details on what parts	4427	#define EV_MULTIPLICITY 1
3873	of the API are still available, and do not complain if this subset changes	4428	#define EV_USE_POLL 1
3874	over time.	4429	#define EV_CHILD_ENABLE 1
		4430	#define EV_ASYNC_ENABLE 1
		4431
		4432	The actual value is a bitset, it can be a combination of the following
		4433	values:
		4434
		4435	=over 4
		4436
		4437	=item C<1> - faster/larger code
		4438
		4439	Use larger code to speed up some operations.
		4440
		4441	Currently this is used to override some inlining decisions (enlarging the
		4442	code size by roughly 30% on amd64).
		4443
		4444	When optimising for size, use of compiler flags such as C<-Os> with
		4445	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4446	assertions.
		4447
		4448	=item C<2> - faster/larger data structures
		4449
		4450	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4451	hash table sizes and so on. This will usually further increase code size
		4452	and can additionally have an effect on the size of data structures at
		4453	runtime.
		4454
		4455	=item C<4> - full API configuration
		4456
		4457	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4458	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4459
		4460	=item C<8> - full API
		4461
		4462	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4463	details on which parts of the API are still available without this
		4464	feature, and do not complain if this subset changes over time.
		4465
		4466	=item C<16> - enable all optional watcher types
		4467
		4468	Enables all optional watcher types. If you want to selectively enable
		4469	only some watcher types other than I/O and timers (e.g. prepare,
		4470	embed, async, child...) you can enable them manually by defining
		4471	C<EV_watchertype_ENABLE> to C<1> instead.
		4472
		4473	=item C<32> - enable all backends
		4474
		4475	This enables all backends - without this feature, you need to enable at
		4476	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4477
		4478	=item C<64> - enable OS-specific "helper" APIs
		4479
		4480	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4481	default.
		4482
		4483	=back
		4484
		4485	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4486	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4487	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4488	watchers, timers and monotonic clock support.
		4489
		4490	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4491	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4492	your program might be left out as well - a binary starting a timer and an
		4493	I/O watcher then might come out at only 5Kb.
		4494
		4495	=item EV_AVOID_STDIO
		4496
		4497	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4498	functions (printf, scanf, perror etc.). This will increase the code size
		4499	somewhat, but if your program doesn't otherwise depend on stdio and your
		4500	libc allows it, this avoids linking in the stdio library which is quite
		4501	big.
		4502
		4503	Note that error messages might become less precise when this option is
		4504	enabled.
3875		4505
3876	=item EV_NSIG	4506	=item EV_NSIG
3877		4507
3878	The highest supported signal number, +1 (or, the number of	4508	The highest supported signal number, +1 (or, the number of
3879	signals): Normally, libev tries to deduce the maximum number of signals	4509	signals): Normally, libev tries to deduce the maximum number of signals
3880	automatically, but sometimes this fails, in which case it can be	4510	automatically, but sometimes this fails, in which case it can be
3881	specified. Also, using a lower number than detected (C<32> should be	4511	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	4512	good for about any system in existence) can save some memory, as libev
3883	statically allocates some 12-24 bytes per signal number.	4513	statically allocates some 12-24 bytes per signal number.
3884		4514
3885	=item EV_PID_HASHSIZE	4515	=item EV_PID_HASHSIZE
3886		4516
3887	C<ev_child> watchers use a small hash table to distribute workload by	4517	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	4518	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	4519	usually more than enough. If you need to manage thousands of children you
3890	increase this value (I<must> be a power of two).	4520	might want to increase this value (I<must> be a power of two).
3891		4521
3892	=item EV_INOTIFY_HASHSIZE	4522	=item EV_INOTIFY_HASHSIZE
3893		4523
3894	C<ev_stat> watchers use a small hash table to distribute workload by	4524	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>),	4525	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>	4526	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	4527	C<ev_stat> watchers you might want to increase this value (I<must> be a
3898	two).	4528	power of two).
3899		4529
3900	=item EV_USE_4HEAP	4530	=item EV_USE_4HEAP
3901		4531
3902	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4532	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	4533	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	4534	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3905	faster performance with many (thousands) of watchers.	4535	faster performance with many (thousands) of watchers.
3906		4536
3907	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4537	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3908	(disabled).	4538	will be C<0>.
3909		4539
3910	=item EV_HEAP_CACHE_AT	4540	=item EV_HEAP_CACHE_AT
3911		4541
3912	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4542	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	4543	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>),	4544	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,	4545	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	4546	but avoids random read accesses on heap changes. This improves performance
3917	noticeably with many (hundreds) of watchers.	4547	noticeably with many (hundreds) of watchers.
3918		4548
3919	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4549	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3920	(disabled).	4550	will be C<0>.
3921		4551
3922	=item EV_VERIFY	4552	=item EV_VERIFY
3923		4553
3924	Controls how much internal verification (see C<ev_loop_verify ()>) will	4554	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	4555	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	4556	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	4557	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	4558	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	4559	verification code will be called very frequently, which will slow down
3930	libev considerably.	4560	libev considerably.
3931		4561
3932	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3933	C<0>.	4563	will be C<0>.
3934		4564
3935	=item EV_COMMON	4565	=item EV_COMMON
3936		4566
3937	By default, all watchers have a C<void *data> member. By redefining	4567	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	4568	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,	4569	members. You have to define it each time you include one of the files,
3940	though, and it must be identical each time.	4570	though, and it must be identical each time.
3941		4571
3942	For example, the perl EV module uses something like this:	4572	For example, the perl EV module uses something like this:
3943		4573
…		…
3996	file.	4626	file.
3997		4627
3998	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4628	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:	4629	that everybody includes and which overrides some configure choices:
4000		4630
4001	#define EV_MINIMAL 1	4631	#define EV_FEATURES 8
4002	#define EV_USE_POLL 0	4632	#define EV_USE_SELECT 1
4003	#define EV_MULTIPLICITY 0
4004	#define EV_PERIODIC_ENABLE 0	4633	#define EV_PREPARE_ENABLE 1
		4634	#define EV_IDLE_ENABLE 1
4005	#define EV_STAT_ENABLE 0	4635	#define EV_SIGNAL_ENABLE 1
4006	#define EV_FORK_ENABLE 0	4636	#define EV_CHILD_ENABLE 1
		4637	#define EV_USE_STDEXCEPT 0
4007	#define EV_CONFIG_H <config.h>	4638	#define EV_CONFIG_H <config.h>
4008	#define EV_MINPRI 0
4009	#define EV_MAXPRI 0
4010		4639
4011	#include "ev++.h"	4640	#include "ev++.h"
4012		4641
4013	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4642	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4014		4643
4015	#include "ev_cpp.h"	4644	#include "ev_cpp.h"
4016	#include "ev.c"	4645	#include "ev.c"
4017		4646
4018	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4647	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4019		4648
4020	=head2 THREADS AND COROUTINES	4649	=head2 THREADS AND COROUTINES
4021		4650
4022	=head3 THREADS	4651	=head3 THREADS
4023		4652
…		…
4074	default loop and triggering an C<ev_async> watcher from the default loop	4703	default loop and triggering an C<ev_async> watcher from the default loop
4075	watcher callback into the event loop interested in the signal.	4704	watcher callback into the event loop interested in the signal.
4076		4705
4077	=back	4706	=back
4078		4707
4079	=head4 THREAD LOCKING EXAMPLE	4708	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		4709
4217	=head3 COROUTINES	4710	=head3 COROUTINES
4218		4711
4219	Libev is very accommodating to coroutines ("cooperative threads"):	4712	Libev is very accommodating to coroutines ("cooperative threads"):
4220	libev fully supports nesting calls to its functions from different	4713	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	4714	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	4715	different coroutines, and switch freely between both coroutines running
4223	the loop, as long as you don't confuse yourself). The only exception is	4716	the loop, as long as you don't confuse yourself). The only exception is
4224	that you must not do this from C<ev_periodic> reschedule callbacks.	4717	that you must not do this from C<ev_periodic> reschedule callbacks.
4225		4718
4226	Care has been taken to ensure that libev does not keep local state inside	4719	Care has been taken to ensure that libev does not keep local state inside
4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4720	C<ev_run>, and other calls do not usually allow for coroutine switches as
4228	they do not call any callbacks.	4721	they do not call any callbacks.
4229		4722
4230	=head2 COMPILER WARNINGS	4723	=head2 COMPILER WARNINGS
4231		4724
4232	Depending on your compiler and compiler settings, you might get no or a	4725	Depending on your compiler and compiler settings, you might get no or a
…		…
4243	maintainable.	4736	maintainable.
4244		4737
4245	And of course, some compiler warnings are just plain stupid, or simply	4738	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	4739	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	4740	seems to warn about). For example, certain older gcc versions had some
4248	warnings that resulted an extreme number of false positives. These have	4741	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	4742	been fixed, but some people still insist on making code warn-free with
4250	such buggy versions.	4743	such buggy versions.
4251		4744
4252	While libev is written to generate as few warnings as possible,	4745	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	4746	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4289	I suggest using suppression lists.	4782	I suggest using suppression lists.
4290		4783
4291		4784
4292	=head1 PORTABILITY NOTES	4785	=head1 PORTABILITY NOTES
4293		4786
		4787	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4788
		4789	GNU/Linux is the only common platform that supports 64 bit file/large file
		4790	interfaces but I<disables> them by default.
		4791
		4792	That means that libev compiled in the default environment doesn't support
		4793	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4794
		4795	Unfortunately, many programs try to work around this GNU/Linux issue
		4796	by enabling the large file API, which makes them incompatible with the
		4797	standard libev compiled for their system.
		4798
		4799	Likewise, libev cannot enable the large file API itself as this would
		4800	suddenly make it incompatible to the default compile time environment,
		4801	i.e. all programs not using special compile switches.
		4802
		4803	=head2 OS/X AND DARWIN BUGS
		4804
		4805	The whole thing is a bug if you ask me - basically any system interface
		4806	you touch is broken, whether it is locales, poll, kqueue or even the
		4807	OpenGL drivers.
		4808
		4809	=head3 C<kqueue> is buggy
		4810
		4811	The kqueue syscall is broken in all known versions - most versions support
		4812	only sockets, many support pipes.
		4813
		4814	Libev tries to work around this by not using C<kqueue> by default on this
		4815	rotten platform, but of course you can still ask for it when creating a
		4816	loop - embedding a socket-only kqueue loop into a select-based one is
		4817	probably going to work well.
		4818
		4819	=head3 C<poll> is buggy
		4820
		4821	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4822	implementation by something calling C<kqueue> internally around the 10.5.6
		4823	release, so now C<kqueue> I<and> C<poll> are broken.
		4824
		4825	Libev tries to work around this by not using C<poll> by default on
		4826	this rotten platform, but of course you can still ask for it when creating
		4827	a loop.
		4828
		4829	=head3 C<select> is buggy
		4830
		4831	All that's left is C<select>, and of course Apple found a way to fuck this
		4832	one up as well: On OS/X, C<select> actively limits the number of file
		4833	descriptors you can pass in to 1024 - your program suddenly crashes when
		4834	you use more.
		4835
		4836	There is an undocumented "workaround" for this - defining
		4837	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4838	work on OS/X.
		4839
		4840	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4841
		4842	=head3 C<errno> reentrancy
		4843
		4844	The default compile environment on Solaris is unfortunately so
		4845	thread-unsafe that you can't even use components/libraries compiled
		4846	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4847	defined by default. A valid, if stupid, implementation choice.
		4848
		4849	If you want to use libev in threaded environments you have to make sure
		4850	it's compiled with C<_REENTRANT> defined.
		4851
		4852	=head3 Event port backend
		4853
		4854	The scalable event interface for Solaris is called "event
		4855	ports". Unfortunately, this mechanism is very buggy in all major
		4856	releases. If you run into high CPU usage, your program freezes or you get
		4857	a large number of spurious wakeups, make sure you have all the relevant
		4858	and latest kernel patches applied. No, I don't know which ones, but there
		4859	are multiple ones to apply, and afterwards, event ports actually work
		4860	great.
		4861
		4862	If you can't get it to work, you can try running the program by setting
		4863	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4864	C<select> backends.
		4865
		4866	=head2 AIX POLL BUG
		4867
		4868	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4869	this by trying to avoid the poll backend altogether (i.e. it's not even
		4870	compiled in), which normally isn't a big problem as C<select> works fine
		4871	with large bitsets on AIX, and AIX is dead anyway.
		4872
4294	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4873	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4874
		4875	=head3 General issues
4295		4876
4296	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4877	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	4878	requires, and its I/O model is fundamentally incompatible with the POSIX
4298	model. Libev still offers limited functionality on this platform in	4879	model. Libev still offers limited functionality on this platform in
4299	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4300	descriptors. This only applies when using Win32 natively, not when using	4881	descriptors. This only applies when using Win32 natively, not when using
4301	e.g. cygwin.	4882	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4883	as every compielr comes with a slightly differently broken/incompatible
		4884	environment.
4302		4885
4303	Lifting these limitations would basically require the full	4886	Lifting these limitations would basically require the full
4304	re-implementation of the I/O system. If you are into these kinds of	4887	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	4888	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).	4889	also that glib is the slowest event library known to man).
4307		4890
4308	There is no supported compilation method available on windows except	4891	There is no supported compilation method available on windows except
4309	embedding it into other applications.	4892	embedding it into other applications.
4310		4893
4311	Sensible signal handling is officially unsupported by Microsoft - libev	4894	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!):	4922	you do I<not> compile the F<ev.c> or any other embedded source files!):
4340		4923
4341	#include "evwrap.h"	4924	#include "evwrap.h"
4342	#include "ev.c"	4925	#include "ev.c"
4343		4926
4344	=over 4
4345
4346	=item The winsocket select function	4927	=head3 The winsocket C<select> function
4347		4928
4348	The winsocket C<select> function doesn't follow POSIX in that it	4929	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	4930	requires socket I<handles> and not socket I<file descriptors> (it is
4350	also extremely buggy). This makes select very inefficient, and also	4931	also extremely buggy). This makes select very inefficient, and also
4351	requires a mapping from file descriptors to socket handles (the Microsoft	4932	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 */	4941	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4361		4942
4362	Note that winsockets handling of fd sets is O(n), so you can easily get a	4943	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.	4944	complexity in the O(n²) range when using win32.
4364		4945
4365	=item Limited number of file descriptors	4946	=head3 Limited number of file descriptors
4366		4947
4367	Windows has numerous arbitrary (and low) limits on things.	4948	Windows has numerous arbitrary (and low) limits on things.
4368		4949
4369	Early versions of winsocket's select only supported waiting for a maximum	4950	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	4951	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	4966	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,	4967	(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	4968	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.	4969	the cost of calling select (O(n²)) will likely make this unworkable.
4389		4970
4390	=back
4391
4392	=head2 PORTABILITY REQUIREMENTS	4971	=head2 PORTABILITY REQUIREMENTS
4393		4972
4394	In addition to a working ISO-C implementation and of course the	4973	In addition to a working ISO-C implementation and of course the
4395	backend-specific APIs, libev relies on a few additional extensions:	4974	backend-specific APIs, libev relies on a few additional extensions:
4396		4975
…		…
4402	Libev assumes not only that all watcher pointers have the same internal	4981	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	4982	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	4983	assumes that the same (machine) code can be used to call any watcher
4405	callback: The watcher callbacks have different type signatures, but libev	4984	callback: The watcher callbacks have different type signatures, but libev
4406	calls them using an C<ev_watcher *> internally.	4985	calls them using an C<ev_watcher *> internally.
		4986
		4987	=item pointer accesses must be thread-atomic
		4988
		4989	Accessing a pointer value must be atomic, it must both be readable and
		4990	writable in one piece - this is the case on all current architectures.
4407		4991
4408	=item C<sig_atomic_t volatile> must be thread-atomic as well	4992	=item C<sig_atomic_t volatile> must be thread-atomic as well
4409		4993
4410	The type C<sig_atomic_t volatile> (or whatever is defined as	4994	The type C<sig_atomic_t volatile> (or whatever is defined as
4411	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4995	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4434	watchers.	5018	watchers.
4435		5019
4436	=item C<double> must hold a time value in seconds with enough accuracy	5020	=item C<double> must hold a time value in seconds with enough accuracy
4437		5021
4438	The type C<double> is used to represent timestamps. It is required to	5022	The type C<double> is used to represent timestamps. It is required to
4439	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5023	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4440	enough for at least into the year 4000. This requirement is fulfilled by	5024	good enough for at least into the year 4000 with millisecond accuracy
		5025	(the design goal for libev). This requirement is overfulfilled by
4441	implementations implementing IEEE 754, which is basically all existing	5026	implementations using IEEE 754, which is basically all existing ones. With
4442	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5027	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4443	2200.
4444		5028
4445	=back	5029	=back
4446		5030
4447	If you know of other additional requirements drop me a note.	5031	If you know of other additional requirements drop me a note.
4448		5032
…		…
4516	involves iterating over all running async watchers or all signal numbers.	5100	involves iterating over all running async watchers or all signal numbers.
4517		5101
4518	=back	5102	=back
4519		5103
4520		5104
		5105	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5106
		5107	The major version 4 introduced some incompatible changes to the API.
		5108
		5109	At the moment, the C<ev.h> header file provides compatibility definitions
		5110	for all changes, so most programs should still compile. The compatibility
		5111	layer might be removed in later versions of libev, so better update to the
		5112	new API early than late.
		5113
		5114	=over 4
		5115
		5116	=item C<EV_COMPAT3> backwards compatibility mechanism
		5117
		5118	The backward compatibility mechanism can be controlled by
		5119	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5120	section.
		5121
		5122	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5123
		5124	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5125
		5126	ev_loop_destroy (EV_DEFAULT_UC);
		5127	ev_loop_fork (EV_DEFAULT);
		5128
		5129	=item function/symbol renames
		5130
		5131	A number of functions and symbols have been renamed:
		5132
		5133	ev_loop => ev_run
		5134	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5135	EVLOOP_ONESHOT => EVRUN_ONCE
		5136
		5137	ev_unloop => ev_break
		5138	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5139	EVUNLOOP_ONE => EVBREAK_ONE
		5140	EVUNLOOP_ALL => EVBREAK_ALL
		5141
		5142	EV_TIMEOUT => EV_TIMER
		5143
		5144	ev_loop_count => ev_iteration
		5145	ev_loop_depth => ev_depth
		5146	ev_loop_verify => ev_verify
		5147
		5148	Most functions working on C<struct ev_loop> objects don't have an
		5149	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5150	associated constants have been renamed to not collide with the C<struct
		5151	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5152	as all other watcher types. Note that C<ev_loop_fork> is still called
		5153	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5154	typedef.
		5155
		5156	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5157
		5158	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5159	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5160	and work, but the library code will of course be larger.
		5161
		5162	=back
		5163
		5164
4521	=head1 GLOSSARY	5165	=head1 GLOSSARY
4522		5166
4523	=over 4	5167	=over 4
4524		5168
4525	=item active	5169	=item active
4526		5170
4527	A watcher is active as long as it has been started (has been attached to	5171	A watcher is active as long as it has been started and not yet stopped.
4528	an event loop) but not yet stopped (disassociated from the event loop).	5172	See L<WATCHER STATES> for details.
4529		5173
4530	=item application	5174	=item application
4531		5175
4532	In this document, an application is whatever is using libev.	5176	In this document, an application is whatever is using libev.
		5177
		5178	=item backend
		5179
		5180	The part of the code dealing with the operating system interfaces.
4533		5181
4534	=item callback	5182	=item callback
4535		5183
4536	The address of a function that is called when some event has been	5184	The address of a function that is called when some event has been
4537	detected. Callbacks are being passed the event loop, the watcher that	5185	detected. Callbacks are being passed the event loop, the watcher that
4538	received the event, and the actual event bitset.	5186	received the event, and the actual event bitset.
4539		5187
4540	=item callback invocation	5188	=item callback/watcher invocation
4541		5189
4542	The act of calling the callback associated with a watcher.	5190	The act of calling the callback associated with a watcher.
4543		5191
4544	=item event	5192	=item event
4545		5193
4546	A change of state of some external event, such as data now being available	5194	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	5195	for reading on a file descriptor, time having passed or simply not having
4548	any other events happening anymore.	5196	any other events happening anymore.
4549		5197
4550	In libev, events are represented as single bits (such as C<EV_READ> or	5198	In libev, events are represented as single bits (such as C<EV_READ> or
4551	C<EV_TIMEOUT>).	5199	C<EV_TIMER>).
4552		5200
4553	=item event library	5201	=item event library
4554		5202
4555	A software package implementing an event model and loop.	5203	A software package implementing an event model and loop.
4556		5204
…		…
4564	The model used to describe how an event loop handles and processes	5212	The model used to describe how an event loop handles and processes
4565	watchers and events.	5213	watchers and events.
4566		5214
4567	=item pending	5215	=item pending
4568		5216
4569	A watcher is pending as soon as the corresponding event has been detected,	5217	A watcher is pending as soon as the corresponding event has been
4570	and stops being pending as soon as the watcher will be invoked or its	5218	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		5219
4576	=item real time	5220	=item real time
4577		5221
4578	The physical time that is observed. It is apparently strictly monotonic :)	5222	The physical time that is observed. It is apparently strictly monotonic :)
4579		5223
…		…
4586	=item watcher	5230	=item watcher
4587		5231
4588	A data structure that describes interest in certain events. Watchers need	5232	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.	5233	to be started (attached to an event loop) before they can receive events.
4590		5234
4591	=item watcher invocation
4592
4593	The act of calling the callback associated with a watcher.
4594
4595	=back	5235	=back
4596		5236
4597	=head1 AUTHOR	5237	=head1 AUTHOR
4598		5238
4599	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5239	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5240	Magnusson and Emanuele Giaquinta.
4600		5241

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