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Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC vs.
Revision 1.366 by sf-exg, Thu Feb 3 16:21:08 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_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes is both faster and might make	428	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data.	429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
381		432
382	Signalfd will not be used by default as this changes your signal mask, and	433	Signalfd will not be used by default as this changes your signal mask, and
383	there are a lot of shoddy libraries and programs (glib's threadpool for	434	there are a lot of shoddy libraries and programs (glib's threadpool for
384	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
385		451
386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
387		453
388	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
389	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,
…		…
425	epoll scales either O(1) or O(active_fds).	491	epoll scales either O(1) or O(active_fds).
426		492
427	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
428	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
429	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
430	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
431	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
432	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
433	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
434	hard to detect.	502	and is of course hard to detect.
435		503
436	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
437	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
438	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
439	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
440	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
441	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
442	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.
443		517
444	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
445	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
446	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
447	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
…		…
513	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
514		588
515	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,
516	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)).
517		591
518	Please note that Solaris event ports can deliver a lot of spurious
519	notifications, so you need to use non-blocking I/O or other means to avoid
520	blocking when no data (or space) is available.
521
522	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
523	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
524	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
525	might perform better.	595	might perform better.
526		596
527	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
528	notifications, this backend actually performed fully to specification
529	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
530	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.
531		611
532	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
533	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
534		614
535	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
536		616
537	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
538	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
539	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
540		620
541	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).
542		630
543	=back	631	=back
544		632
545	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,
546	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
547	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
548	()> will be tried.	636	()> will be tried.
549		637
550	Example: This is the most typical usage.
551
552	if (!ev_default_loop (0))
553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
554
555	Example: Restrict libev to the select and poll backends, and do not allow
556	environment settings to be taken into account:
557
558	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
559
560	Example: Use whatever libev has to offer, but make sure that kqueue is
561	used if available (warning, breaks stuff, best use only with your own
562	private event loop and only if you know the OS supports your types of
563	fds):
564
565	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
566
567	=item struct ev_loop *ev_loop_new (unsigned int flags)
568
569	Similar to C<ev_default_loop>, but always creates a new event loop that is
570	always distinct from the default loop. Unlike the default loop, it cannot
571	handle signal and child watchers, and attempts to do so will be greeted by
572	undefined behaviour (or a failed assertion if assertions are enabled).
573
574	Note that this function I<is> thread-safe, and the recommended way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
579		639
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	641	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
583		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
584	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
585		650
586	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
587	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
588	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
589	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
590	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
591	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
…		…
593		658
594	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
595	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
596	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
597		662
598	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
599	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.
600	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>
601	C<ev_loop_new> and C<ev_loop_destroy>.	670	and C<ev_loop_destroy>.
602		671
603	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
604		673
605	Like C<ev_default_destroy>, but destroys an event loop created by an
606	earlier call to C<ev_loop_new>.
607
608	=item ev_default_fork ()
609
610	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
611	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
612	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
613	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
614	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
615	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.
616		684
617	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
618	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
619	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).
620		691
621	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
622	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
623	quite nicely into a call to C<pthread_atfork>:
624		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	...
625	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
626
627	=item ev_loop_fork (loop)
628
629	Like C<ev_default_fork>, but acts on an event loop created by
630	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
631	after fork that you want to re-use in the child, and how you do this is
632	entirely your own problem.
633		706
634	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
635		708
636	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
637	otherwise.	710	otherwise.
638		711
639	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
640		713
641	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
642	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>
643	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
644		717
645	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
646	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
647	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.
648		722
649	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
650		724
651	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
652	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.
653		727
654	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
655	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),
656	in which case it is higher.	730	in which case it is higher.
657		731
658	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
659	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.
660		736
661	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
662		738
663	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
664	use.	740	use.
…		…
673		749
674	=item ev_now_update (loop)	750	=item ev_now_update (loop)
675		751
676	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
677	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
678	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
679		755
680	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
681	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
682	the current time is a good idea.	758	the current time is a good idea.
683		759
…		…
685		761
686	=item ev_suspend (loop)	762	=item ev_suspend (loop)
687		763
688	=item ev_resume (loop)	764	=item ev_resume (loop)
689		765
690	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
691	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.
692		768
693	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
694	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
695	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
696	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>
…		…
698	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
699		775
700	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
701	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
702	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
703	occured while suspended).	779	occurred while suspended).
704		780
705	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
706	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>
707	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
708		784
709	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
710	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
711		787
712	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
713		789
714	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
715	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
716	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>.
717		795
718	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
719	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.
720		799
721	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
722	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
723	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
724	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
725	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
726	beauty.	805	beauty.
727		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
728	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
729	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
730	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
731	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.
732		817
733	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
734	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
735	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
736	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
737	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
738	iteration of the loop.	823	iteration of the loop.
739		824
740	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
741	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
742	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
743	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
744		829
745	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
746		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
747	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
748	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
749	- 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.
750	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
751	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
752	as to not disturb the other process.	841	as to not disturb the other process.
753	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
754	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
755	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
756	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
757	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
758	- 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.
759	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
760	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
761	- 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.
762	- Queue all expired timers.	852	- Queue all expired timers.
763	- Queue all expired periodics.	853	- Queue all expired periodics.
764	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
765	- Queue all check watchers.	855	- Queue all check watchers.
766	- 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).
767	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
768	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
769	- 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
770	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
771	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.
772		866
773	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
774	anymore.	868	anymore.
775		869
776	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
777	... 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..)
778	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
779	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
780		874
781	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
782		876
783	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
784	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
785	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
786	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.
787		881
788	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>.
789		883
790	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.
791		886
792	=item ev_ref (loop)	887	=item ev_ref (loop)
793		888
794	=item ev_unref (loop)	889	=item ev_unref (loop)
795		890
796	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
797	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
798	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.
799		894
800	This is useful when you have a watcher that you never intend to	895	This is useful when you have a watcher that you never intend to
801	unregister, but that nevertheless should not keep C<ev_loop> from	896	unregister, but that nevertheless should not keep C<ev_run> from
802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
803	before stopping it.	898	before stopping it.
804		899
805	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
806	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
807	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
808	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
809	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
810	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
811	before, respectively. Note also that libev might stop watchers itself	906	before, respectively. Note also that libev might stop watchers itself
812	(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>
813	in the callback).	908	in the callback).
814		909
815	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>
816	running when nothing else is active.	911	running when nothing else is active.
817		912
818	ev_signal exitsig;	913	ev_signal exitsig;
819	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
820	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
821	evf_unref (loop);	916	ev_unref (loop);
822		917
823	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
824		919
825	ev_ref (loop);	920	ev_ref (loop);
826	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
865	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>,
866	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
867	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
868	parallelity, then this setting will limit your transaction rate (if you	963	parallelity, then this setting will limit your transaction rate (if you
869	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,
870	then you can't do more than 100 transations per second).	965	then you can't do more than 100 transactions per second).
871		966
872	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
873	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
874	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
875	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
…		…
883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
884		979
885	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
886		981
887	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
888	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
889	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).
890		989
891	=item int ev_pending_count (loop)	990	=item int ev_pending_count (loop)
892		991
893	Returns the number of pending watchers - zero indicates that no watchers	992	Returns the number of pending watchers - zero indicates that no watchers
894	are pending.	993	are pending.
895		994
896	=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))
897		996
898	This overrides the invoke pending functionality of the loop: Instead of	997	This overrides the invoke pending functionality of the loop: Instead of
899	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
900	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
901	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
902		1001
903	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
904	callback.	1003	callback.
…		…
907		1006
908	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
909	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
910	each call to a libev function.	1009	each call to a libev function.
911		1010
912	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
913	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
914	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
915	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
916		1015
917	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
918	suspended waiting for new events, and C<acquire> is called just	1017	suspended waiting for new events, and C<acquire> is called just
919	afterwards.	1018	afterwards.
920		1019
…		…
923		1022
924	While event loop modifications are allowed between invocations of	1023	While event loop modifications are allowed between invocations of
925	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
926	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
927	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
928	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
929	to take note of any changes you made.	1028	to take note of any changes you made.
930		1029
931	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
932	invocations of C<release> and C<acquire>.	1031	invocations of C<release> and C<acquire>.
933		1032
934	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
935	document.	1034	document.
936		1035
937	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
938		1037
939	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
940		1039
941	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
942	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
943	C<0.>	1042	C<0>.
944		1043
945	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,
946	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
947	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
948	any other purpose as well.	1047	any other purpose as well.
949		1048
950	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
951		1050
952	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
953	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
954	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
955	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
…		…
966		1065
967	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
968	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
969	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
970		1069
971	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
972	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
973	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:
974		1074
975	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)
976	{	1076	{
977	ev_io_stop (w);	1077	ev_io_stop (w);
978	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
979	}	1079	}
980		1080
981	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
982		1082
983	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
984		1084
985	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
986	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
987	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
988		1088
989	ev_loop (loop, 0);	1089	ev_run (loop, 0);
990		1090
991	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
992	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
993	stack).	1093	stack).
994		1094
995	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>
996	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).
997		1097
998	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
999	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
1000	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
1001	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
1002	is readable and/or writable).	1102	and/or writable).
1003		1103
1004	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 *, ...) >>
1005	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
1006	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<<
1007	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1030	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
1031		1131
1032	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
1033	writable.	1133	writable.
1034		1134
1035	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
1036		1136
1037	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
1038		1138
1039	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
1040		1140
…		…
1058		1158
1059	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1060		1160
1061	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1062		1162
1063	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
1064	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
1065	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
1066	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
1067	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
1068	(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
1069	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1070		1170
1071	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1072		1172
1073	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.
1074		1174
1075	=item C<EV_FORK>	1175	=item C<EV_FORK>
1076		1176
1077	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
1078	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>).
1079		1183
1080	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1081		1185
1082	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>).
1083		1187
…		…
1256	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
1257	functions that do not need a watcher.	1361	functions that do not need a watcher.
1258		1362
1259	=back	1363	=back
1260		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1261		1367
1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1263		1369
1264	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1265	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
1266	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
1267	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".
1268	member, you can also "subclass" the watcher type and provide your own
1269	data:
1270		1374
1271	struct my_io	1375	=over 4
1272	{
1273	ev_io io;
1274	int otherfd;
1275	void *somedata;
1276	struct whatever *mostinteresting;
1277	};
1278		1376
1279	...	1377	=item initialiased
1280	struct my_io w;
1281	ev_io_init (&w.io, my_cb, fd, EV_READ);
1282		1378
1283	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
1284	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.
1285		1382
1286	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
1287	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1288	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1289	...	1386	C<ev_TYPE_init> again.
1290	}
1291		1387
1292	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1293	instead have been omitted.
1294		1389
1295	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
1296	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.
1297		1395
1298	struct my_biggy	1396	=item pending
1299	{
1300	int some_data;
1301	ev_timer t1;
1302	ev_timer t2;
1303	}
1304		1397
1305	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
1306	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
1307	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
1308	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
1309	programmers):	1402	callback.
1310		1403
1311	#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.
1312		1410
1313	static void	1411	It is also possible to feed an event on a watcher that is not active (e.g.
1314	t1_cb (EV_P_ ev_timer *w, int revents)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1315	{	1413	active.
1316	struct my_biggy big = (struct my_biggy *)
1317	(((char *)w) - offsetof (struct my_biggy, t1));
1318	}
1319		1414
1320	static void	1415	=item stopped
1321	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1322	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1323	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1324	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1325	}	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
1326		1429
1327	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1328		1431
1329	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1330	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1373		1476
1374	For example, to emulate how many other event libraries handle priorities,	1477	For example, to emulate how many other event libraries handle priorities,
1375	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
1376	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
1377	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
1378	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
1379	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
1380	workable.	1483	workable.
1381		1484
1382	Usually, however, the lock-out model implemented that way will perform	1485	Usually, however, the lock-out model implemented that way will perform
1383	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,
…		…
1397	{	1500	{
1398	// stop the I/O watcher, we received the event, but	1501	// stop the I/O watcher, we received the event, but
1399	// are not yet ready to handle it.	1502	// are not yet ready to handle it.
1400	ev_io_stop (EV_A_ w);	1503	ev_io_stop (EV_A_ w);
1401		1504
1402	// start the idle watcher to ahndle the actual event.	1505	// start the idle watcher to handle the actual event.
1403	// it will not be executed as long as other watchers	1506	// it will not be executed as long as other watchers
1404	// with the default priority are receiving events.	1507	// with the default priority are receiving events.
1405	ev_idle_start (EV_A_ &idle);	1508	ev_idle_start (EV_A_ &idle);
1406	}	1509	}
1407		1510
…		…
1457	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
1458	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
1459	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
1460	required if you know what you are doing).	1563	required if you know what you are doing).
1461		1564
1462	If you cannot use non-blocking mode, then force the use of a
1463	known-to-be-good backend (at the time of this writing, this includes only
1464	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1465	descriptors for which non-blocking operation makes no sense (such as
1466	files) - libev doesn't guarentee any specific behaviour in that case.
1467
1468	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
1469	receive "spurious" readiness notifications, that is your callback might	1566	receive "spurious" readiness notifications, that is, your callback might
1470	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
1471	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
1472	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
1473	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
1474	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1475	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1571	preferable to a program hanging until some data arrives.
1476		1572
1477	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
1478	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
1479	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
1480	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
1481	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
1482	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
1483	indefinitely.	1579	indefinitely.
1484		1580
1485	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1486		1582
…		…
1514		1610
1515	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1516	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1517	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1518		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
1519	=head3 The special problem of fork	1648	=head3 The special problem of fork
1520		1649
1521	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
1522	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
1523	it in the child.	1652	it in the child if you want to continue to use it in the child.
1524		1653
1525	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
1526	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
1527	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1528	C<EVBACKEND_POLL>.
1529		1657
1530	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1531		1659
1532	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>:
1533	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
…		…
1536		1664
1537	So when you encounter spurious, unexplained daemon exits, make sure you	1665	So when you encounter spurious, unexplained daemon exits, make sure you
1538	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
1539	somewhere, as that would have given you a big clue).	1667	somewhere, as that would have given you a big clue).
1540		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.
1541		1707
1542	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1543		1709
1544	=over 4	1710	=over 4
1545		1711
…		…
1577	...	1743	...
1578	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1579	ev_io stdin_readable;	1745	ev_io stdin_readable;
1580	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);
1581	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1582	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1583		1749
1584		1750
1585	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1586		1752
1587	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
…		…
1596	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
1597	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
1598	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
1599	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
1600	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
1601	no longer true when a callback calls C<ev_loop> recursively).	1767	no longer true when a callback calls C<ev_run> recursively).
1602		1768
1603	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1604		1770
1605	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
1606	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,
…		…
1692	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1693		1859
1694	// 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
1695	if (timeout < now)	1861	if (timeout < now)
1696	{	1862	{
1697	// timeout occured, take action	1863	// timeout occurred, take action
1698	}	1864	}
1699	else	1865	else
1700	{	1866	{
1701	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1702	// the watcher to fire in last_activity + 60, which is	1868	// the watcher to fire in last_activity + 60, which is
…		…
1724	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
1725	callback, which will "do the right thing" and start the timer:	1891	callback, which will "do the right thing" and start the timer:
1726		1892
1727	ev_init (timer, callback);	1893	ev_init (timer, callback);
1728	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1729	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1730		1896
1731	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
1732	C<last_activity>, no libev calls at all:	1898	C<last_activity>, no libev calls at all:
1733		1899
1734	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1735		1901
1736	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
1737	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1738		1904
1739	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
…		…
1777		1943
1778	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1779		1945
1780	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
1781	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
1782	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
1783	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
1784	lots of events in one iteration.	1950	lots of events in one iteration.
1785		1951
1786	The relative timeouts are calculated relative to the C<ev_now ()>	1952	The relative timeouts are calculated relative to the C<ev_now ()>
1787	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
…		…
1865	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,
1866	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
1867	the timeout value currently configured.	2033	the timeout value currently configured.
1868		2034
1869	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
1870	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>
1871	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
1872	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,
1873	too), and so on.	2039	too), and so on.
1874		2040
1875	=item ev_tstamp repeat [read-write]	2041	=item ev_tstamp repeat [read-write]
…		…
1904	}	2070	}
1905		2071
1906	ev_timer mytimer;	2072	ev_timer mytimer;
1907	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 */
1908	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1909	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1910		2076
1911	// 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":
1912	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1913	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1914		2080
…		…
1940		2106
1941	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
1942	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
1943	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
1944	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
1945	(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).
1946		2112
1947	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1948		2114
1949	=over 4	2115	=over 4
1950		2116
…		…
2078	Example: Call a callback every hour, or, more precisely, whenever the	2244	Example: Call a callback every hour, or, more precisely, whenever the
2079	system time is divisible by 3600. The callback invocation times have	2245	system time is divisible by 3600. The callback invocation times have
2080	potentially a lot of jitter, but good long-term stability.	2246	potentially a lot of jitter, but good long-term stability.
2081		2247
2082	static void	2248	static void
2083	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2249	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2084	{	2250	{
2085	... 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)
2086	}	2252	}
2087		2253
2088	ev_periodic hourly_tick;	2254	ev_periodic hourly_tick;
…		…
2111		2277
2112	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
2113		2279
2114	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
2115	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
2116	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
2117	normal event processing, like any other event.	2283	normal event processing, like any other event.
2118		2284
2119	If you want signals to be delivered truly asynchronously, just use	2285	If you want signals to be delivered truly asynchronously, just use
2120	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
2121	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
…		…
2140	=head3 The special problem of inheritance over fork/execve/pthread_create	2306	=head3 The special problem of inheritance over fork/execve/pthread_create
2141		2307
2142	Both the signal mask (C<sigprocmask>) and the signal disposition	2308	Both the signal mask (C<sigprocmask>) and the signal disposition
2143	(C<sigaction>) are unspecified after starting a signal watcher (and after	2309	(C<sigaction>) are unspecified after starting a signal watcher (and after
2144	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,
2145	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>).
2146		2313
2147	While this does not matter for the signal disposition (libev never	2314	While this does not matter for the signal disposition (libev never
2148	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
2149	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
2150	certain signals to be blocked.	2317	certain signals to be blocked.
…		…
2160	In current versions of libev, the signal will not be blocked indefinitely	2327	In current versions of libev, the signal will not be blocked indefinitely
2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces	2328	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162	the window of opportunity for problems, it will not go away, as libev	2329	the window of opportunity for problems, it will not go away, as libev
2163	I<has> to modify the signal mask, at least temporarily.	2330	I<has> to modify the signal mask, at least temporarily.
2164		2331
2165	So I can't stress this enough I<if you do not reset your signal mask	2332	So I can't stress this enough: I<If you do not reset your signal mask when
2166	when you expect it to be empty, you have a race condition in your	2333	you expect it to be empty, you have a race condition in your code>. This
2167	program>. This is not a libev-specific thing, this is true for most event	2334	is not a libev-specific thing, this is true for most event libraries.
2168	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>.
2169		2349
2170	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
2171		2351
2172	=over 4	2352	=over 4
2173		2353
…		…
2189	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
2190		2370
2191	static void	2371	static void
2192	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2193	{	2373	{
2194	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
2195	}	2375	}
2196		2376
2197	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
2198	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2199	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
2585		2765
2586	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:
2587	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2588	afterwards.	2768	afterwards.
2589		2769
2590	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
2591	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>
2592	watchers. Other loops than the current one are fine, however. The	2772	watchers. Other loops than the current one are fine, however. The
2593	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
2594	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,
2595	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
…		…
2763		2943
2764	if (timeout >= 0)	2944	if (timeout >= 0)
2765	// create/start timer	2945	// create/start timer
2766		2946
2767	// poll	2947	// poll
2768	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2769		2949
2770	// stop timer again	2950	// stop timer again
2771	if (timeout >= 0)	2951	if (timeout >= 0)
2772	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2773		2953
…		…
2851	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).
2852		3032
2853	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2854		3034
2855	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
2856	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
2857	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2858		3038
2859	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2860		3040
2861	The embedded event loop.	3041	The embedded event loop.
…		…
2921	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
2922	handlers will be invoked, too, of course.	3102	handlers will be invoked, too, of course.
2923		3103
2924	=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?
2925		3105
2926	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
2927	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
2928	sequence should be handled by libev without any problems.	3108	sequence should be handled by libev without any problems.
2929		3109
2930	This changes when the application actually wants to do event handling	3110	This changes when the application actually wants to do event handling
2931	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
…		…
2947	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
2948	signal watchers).	3128	signal watchers).
2949		3129
2950	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
2951	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
2952	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3132	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2953	the default loop will "orphan" (not stop) all registered watchers, so you	3133	Destroying the default loop will "orphan" (not stop) all registered
2954	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
2955	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.
2956		3137
2957	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
2958		3139
2959	=over 4	3140	=over 4
2960		3141
2961	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
2962		3143
2963	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
2964	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,
2965	believe me.	3146	really.
2966		3147
2967	=back	3148	=back
2968		3149
2969		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
2970	=head2 C<ev_async> - how to wake up another event loop	3191	=head2 C<ev_async> - how to wake up an event loop
2971		3192
2972	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	In general, you cannot use an C<ev_loop> from multiple threads or other
2973	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
2974	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
2975		3196
2976	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,
2977	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>
2978	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
2979	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.
2980	safe.
2981		3201
2982	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,
2983	too, are asynchronous in nature, and signals, too, will be compressed	3203	too, are asynchronous in nature, and signals, too, will be compressed
2984	(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
2985	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.
2986		3209
2987	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
2988	just the default loop.	3211	just the default loop.
2989		3212
2990	=head3 Queueing	3213	=head3 Queueing
…		…
3085	trust me.	3308	trust me.
3086		3309
3087	=item ev_async_send (loop, ev_async *)	3310	=item ev_async_send (loop, ev_async *)
3088		3311
3089	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3312	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3090	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3313	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3314	returns.
		3315
3091	C<ev_feed_event>, this call is safe to do from other threads, signal or	3316	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3092	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3317	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3093	section below on what exactly this means).	3318	embedding section below on what exactly this means).
3094		3319
3095	Note that, as with other watchers in libev, multiple events might get	3320	Note that, as with other watchers in libev, multiple events might get
3096	compressed into a single callback invocation (another way to look at this	3321	compressed into a single callback invocation (another way to look at this
3097	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3322	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3098	reset when the event loop detects that).	3323	reset when the event loop detects that).
…		…
3140		3365
3141	If C<timeout> is less than 0, then no timeout watcher will be	3366	If C<timeout> is less than 0, then no timeout watcher will be
3142	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3367	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3143	repeat = 0) will be started. C<0> is a valid timeout.	3368	repeat = 0) will be started. C<0> is a valid timeout.
3144		3369
3145	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3370	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3146	passed an C<revents> set like normal event callbacks (a combination of	3371	passed an C<revents> set like normal event callbacks (a combination of
3147	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3372	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3148	value passed to C<ev_once>. Note that it is possible to receive I<both>	3373	value passed to C<ev_once>. Note that it is possible to receive I<both>
3149	a timeout and an io event at the same time - you probably should give io	3374	a timeout and an io event at the same time - you probably should give io
3150	events precedence.	3375	events precedence.
3151		3376
3152	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3377	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3153		3378
3154	static void stdin_ready (int revents, void *arg)	3379	static void stdin_ready (int revents, void *arg)
3155	{	3380	{
3156	if (revents & EV_READ)	3381	if (revents & EV_READ)
3157	/* stdin might have data for us, joy! */;	3382	/* stdin might have data for us, joy! */;
3158	else if (revents & EV_TIMEOUT)	3383	else if (revents & EV_TIMER)
3159	/* doh, nothing entered */;	3384	/* doh, nothing entered */;
3160	}	3385	}
3161		3386
3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3387	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3163		3388
…		…
3166	Feed an event on the given fd, as if a file descriptor backend detected	3391	Feed an event on the given fd, as if a file descriptor backend detected
3167	the given events it.	3392	the given events it.
3168		3393
3169	=item ev_feed_signal_event (loop, int signum)	3394	=item ev_feed_signal_event (loop, int signum)
3170		3395
3171	Feed an event as if the given signal occurred (C<loop> must be the default	3396	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3172	loop!).	3397	which is async-safe.
3173		3398
3174	=back	3399	=back
		3400
		3401
		3402	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3403
		3404	This section explains some common idioms that are not immediately
		3405	obvious. Note that examples are sprinkled over the whole manual, and this
		3406	section only contains stuff that wouldn't fit anywhere else.
		3407
		3408	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3409
		3410	Each watcher has, by default, a C<void *data> member that you can read
		3411	or modify at any time: libev will completely ignore it. This can be used
		3412	to associate arbitrary data with your watcher. If you need more data and
		3413	don't want to allocate memory separately and store a pointer to it in that
		3414	data member, you can also "subclass" the watcher type and provide your own
		3415	data:
		3416
		3417	struct my_io
		3418	{
		3419	ev_io io;
		3420	int otherfd;
		3421	void *somedata;
		3422	struct whatever *mostinteresting;
		3423	};
		3424
		3425	...
		3426	struct my_io w;
		3427	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3428
		3429	And since your callback will be called with a pointer to the watcher, you
		3430	can cast it back to your own type:
		3431
		3432	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3433	{
		3434	struct my_io *w = (struct my_io *)w_;
		3435	...
		3436	}
		3437
		3438	More interesting and less C-conformant ways of casting your callback
		3439	function type instead have been omitted.
		3440
		3441	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3442
		3443	Another common scenario is to use some data structure with multiple
		3444	embedded watchers, in effect creating your own watcher that combines
		3445	multiple libev event sources into one "super-watcher":
		3446
		3447	struct my_biggy
		3448	{
		3449	int some_data;
		3450	ev_timer t1;
		3451	ev_timer t2;
		3452	}
		3453
		3454	In this case getting the pointer to C<my_biggy> is a bit more
		3455	complicated: Either you store the address of your C<my_biggy> struct in
		3456	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3457	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3458	real programmers):
		3459
		3460	#include <stddef.h>
		3461
		3462	static void
		3463	t1_cb (EV_P_ ev_timer *w, int revents)
		3464	{
		3465	struct my_biggy big = (struct my_biggy *)
		3466	(((char *)w) - offsetof (struct my_biggy, t1));
		3467	}
		3468
		3469	static void
		3470	t2_cb (EV_P_ ev_timer *w, int revents)
		3471	{
		3472	struct my_biggy big = (struct my_biggy *)
		3473	(((char *)w) - offsetof (struct my_biggy, t2));
		3474	}
		3475
		3476	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3477
		3478	Often (especially in GUI toolkits) there are places where you have
		3479	I<modal> interaction, which is most easily implemented by recursively
		3480	invoking C<ev_run>.
		3481
		3482	This brings the problem of exiting - a callback might want to finish the
		3483	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3484	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3485	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3486	other combination: In these cases, C<ev_break> will not work alone.
		3487
		3488	The solution is to maintain "break this loop" variable for each C<ev_run>
		3489	invocation, and use a loop around C<ev_run> until the condition is
		3490	triggered, using C<EVRUN_ONCE>:
		3491
		3492	// main loop
		3493	int exit_main_loop = 0;
		3494
		3495	while (!exit_main_loop)
		3496	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3497
		3498	// in a model watcher
		3499	int exit_nested_loop = 0;
		3500
		3501	while (!exit_nested_loop)
		3502	ev_run (EV_A_ EVRUN_ONCE);
		3503
		3504	To exit from any of these loops, just set the corresponding exit variable:
		3505
		3506	// exit modal loop
		3507	exit_nested_loop = 1;
		3508
		3509	// exit main program, after modal loop is finished
		3510	exit_main_loop = 1;
		3511
		3512	// exit both
		3513	exit_main_loop = exit_nested_loop = 1;
		3514
		3515	=head2 THREAD LOCKING EXAMPLE
		3516
		3517	Here is a fictitious example of how to run an event loop in a different
		3518	thread from where callbacks are being invoked and watchers are
		3519	created/added/removed.
		3520
		3521	For a real-world example, see the C<EV::Loop::Async> perl module,
		3522	which uses exactly this technique (which is suited for many high-level
		3523	languages).
		3524
		3525	The example uses a pthread mutex to protect the loop data, a condition
		3526	variable to wait for callback invocations, an async watcher to notify the
		3527	event loop thread and an unspecified mechanism to wake up the main thread.
		3528
		3529	First, you need to associate some data with the event loop:
		3530
		3531	typedef struct {
		3532	mutex_t lock; /* global loop lock */
		3533	ev_async async_w;
		3534	thread_t tid;
		3535	cond_t invoke_cv;
		3536	} userdata;
		3537
		3538	void prepare_loop (EV_P)
		3539	{
		3540	// for simplicity, we use a static userdata struct.
		3541	static userdata u;
		3542
		3543	ev_async_init (&u->async_w, async_cb);
		3544	ev_async_start (EV_A_ &u->async_w);
		3545
		3546	pthread_mutex_init (&u->lock, 0);
		3547	pthread_cond_init (&u->invoke_cv, 0);
		3548
		3549	// now associate this with the loop
		3550	ev_set_userdata (EV_A_ u);
		3551	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3552	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3553
		3554	// then create the thread running ev_run
		3555	pthread_create (&u->tid, 0, l_run, EV_A);
		3556	}
		3557
		3558	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3559	solely to wake up the event loop so it takes notice of any new watchers
		3560	that might have been added:
		3561
		3562	static void
		3563	async_cb (EV_P_ ev_async *w, int revents)
		3564	{
		3565	// just used for the side effects
		3566	}
		3567
		3568	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3569	protecting the loop data, respectively.
		3570
		3571	static void
		3572	l_release (EV_P)
		3573	{
		3574	userdata *u = ev_userdata (EV_A);
		3575	pthread_mutex_unlock (&u->lock);
		3576	}
		3577
		3578	static void
		3579	l_acquire (EV_P)
		3580	{
		3581	userdata *u = ev_userdata (EV_A);
		3582	pthread_mutex_lock (&u->lock);
		3583	}
		3584
		3585	The event loop thread first acquires the mutex, and then jumps straight
		3586	into C<ev_run>:
		3587
		3588	void *
		3589	l_run (void *thr_arg)
		3590	{
		3591	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3592
		3593	l_acquire (EV_A);
		3594	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3595	ev_run (EV_A_ 0);
		3596	l_release (EV_A);
		3597
		3598	return 0;
		3599	}
		3600
		3601	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3602	signal the main thread via some unspecified mechanism (signals? pipe
		3603	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3604	have been called (in a while loop because a) spurious wakeups are possible
		3605	and b) skipping inter-thread-communication when there are no pending
		3606	watchers is very beneficial):
		3607
		3608	static void
		3609	l_invoke (EV_P)
		3610	{
		3611	userdata *u = ev_userdata (EV_A);
		3612
		3613	while (ev_pending_count (EV_A))
		3614	{
		3615	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3616	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3617	}
		3618	}
		3619
		3620	Now, whenever the main thread gets told to invoke pending watchers, it
		3621	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3622	thread to continue:
		3623
		3624	static void
		3625	real_invoke_pending (EV_P)
		3626	{
		3627	userdata *u = ev_userdata (EV_A);
		3628
		3629	pthread_mutex_lock (&u->lock);
		3630	ev_invoke_pending (EV_A);
		3631	pthread_cond_signal (&u->invoke_cv);
		3632	pthread_mutex_unlock (&u->lock);
		3633	}
		3634
		3635	Whenever you want to start/stop a watcher or do other modifications to an
		3636	event loop, you will now have to lock:
		3637
		3638	ev_timer timeout_watcher;
		3639	userdata *u = ev_userdata (EV_A);
		3640
		3641	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_timer_start (EV_A_ &timeout_watcher);
		3645	ev_async_send (EV_A_ &u->async_w);
		3646	pthread_mutex_unlock (&u->lock);
		3647
		3648	Note that sending the C<ev_async> watcher is required because otherwise
		3649	an event loop currently blocking in the kernel will have no knowledge
		3650	about the newly added timer. By waking up the loop it will pick up any new
		3651	watchers in the next event loop iteration.
		3652
		3653	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3654
		3655	While the overhead of a callback that e.g. schedules a thread is small, it
		3656	is still an overhead. If you embed libev, and your main usage is with some
		3657	kind of threads or coroutines, you might want to customise libev so that
		3658	doesn't need callbacks anymore.
		3659
		3660	Imagine you have coroutines that you can switch to using a function
		3661	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3662	and that due to some magic, the currently active coroutine is stored in a
		3663	global called C<current_coro>. Then you can build your own "wait for libev
		3664	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3665	the differing C<;> conventions):
		3666
		3667	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3668	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3669
		3670	That means instead of having a C callback function, you store the
		3671	coroutine to switch to in each watcher, and instead of having libev call
		3672	your callback, you instead have it switch to that coroutine.
		3673
		3674	A coroutine might now wait for an event with a function called
		3675	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3676	matter when, or whether the watcher is active or not when this function is
		3677	called):
		3678
		3679	void
		3680	wait_for_event (ev_watcher *w)
		3681	{
		3682	ev_cb_set (w) = current_coro;
		3683	switch_to (libev_coro);
		3684	}
		3685
		3686	That basically suspends the coroutine inside C<wait_for_event> and
		3687	continues the libev coroutine, which, when appropriate, switches back to
		3688	this or any other coroutine. I am sure if you sue this your own :)
		3689
		3690	You can do similar tricks if you have, say, threads with an event queue -
		3691	instead of storing a coroutine, you store the queue object and instead of
		3692	switching to a coroutine, you push the watcher onto the queue and notify
		3693	any waiters.
		3694
		3695	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3696	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3697
		3698	// my_ev.h
		3699	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3700	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3701	#include "../libev/ev.h"
		3702
		3703	// my_ev.c
		3704	#define EV_H "my_ev.h"
		3705	#include "../libev/ev.c"
		3706
		3707	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3708	F<my_ev.c> into your project. When properly specifying include paths, you
		3709	can even use F<ev.h> as header file name directly.
3175		3710
3176		3711
3177	=head1 LIBEVENT EMULATION	3712	=head1 LIBEVENT EMULATION
3178		3713
3179	Libev offers a compatibility emulation layer for libevent. It cannot	3714	Libev offers a compatibility emulation layer for libevent. It cannot
3180	emulate the internals of libevent, so here are some usage hints:	3715	emulate the internals of libevent, so here are some usage hints:
3181		3716
3182	=over 4	3717	=over 4
		3718
		3719	=item * Only the libevent-1.4.1-beta API is being emulated.
		3720
		3721	This was the newest libevent version available when libev was implemented,
		3722	and is still mostly unchanged in 2010.
3183		3723
3184	=item * Use it by including <event.h>, as usual.	3724	=item * Use it by including <event.h>, as usual.
3185		3725
3186	=item * The following members are fully supported: ev_base, ev_callback,	3726	=item * The following members are fully supported: ev_base, ev_callback,
3187	ev_arg, ev_fd, ev_res, ev_events.	3727	ev_arg, ev_fd, ev_res, ev_events.
…		…
3193	=item * Priorities are not currently supported. Initialising priorities	3733	=item * Priorities are not currently supported. Initialising priorities
3194	will fail and all watchers will have the same priority, even though there	3734	will fail and all watchers will have the same priority, even though there
3195	is an ev_pri field.	3735	is an ev_pri field.
3196		3736
3197	=item * In libevent, the last base created gets the signals, in libev, the	3737	=item * In libevent, the last base created gets the signals, in libev, the
3198	first base created (== the default loop) gets the signals.	3738	base that registered the signal gets the signals.
3199		3739
3200	=item * Other members are not supported.	3740	=item * Other members are not supported.
3201		3741
3202	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3742	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3203	to use the libev header file and library.	3743	to use the libev header file and library.
…		…
3222	Care has been taken to keep the overhead low. The only data member the C++	3762	Care has been taken to keep the overhead low. The only data member the C++
3223	classes add (compared to plain C-style watchers) is the event loop pointer	3763	classes add (compared to plain C-style watchers) is the event loop pointer
3224	that the watcher is associated with (or no additional members at all if	3764	that the watcher is associated with (or no additional members at all if
3225	you disable C<EV_MULTIPLICITY> when embedding libev).	3765	you disable C<EV_MULTIPLICITY> when embedding libev).
3226		3766
3227	Currently, functions, and static and non-static member functions can be	3767	Currently, functions, static and non-static member functions and classes
3228	used as callbacks. Other types should be easy to add as long as they only	3768	with C<operator ()> can be used as callbacks. Other types should be easy
3229	need one additional pointer for context. If you need support for other	3769	to add as long as they only need one additional pointer for context. If
3230	types of functors please contact the author (preferably after implementing	3770	you need support for other types of functors please contact the author
3231	it).	3771	(preferably after implementing it).
3232		3772
3233	Here is a list of things available in the C<ev> namespace:	3773	Here is a list of things available in the C<ev> namespace:
3234		3774
3235	=over 4	3775	=over 4
3236		3776
…		…
3297	myclass obj;	3837	myclass obj;
3298	ev::io iow;	3838	ev::io iow;
3299	iow.set <myclass, &myclass::io_cb> (&obj);	3839	iow.set <myclass, &myclass::io_cb> (&obj);
3300		3840
3301	=item w->set (object *)	3841	=item w->set (object *)
3302
3303	This is an B<experimental> feature that might go away in a future version.
3304		3842
3305	This is a variation of a method callback - leaving out the method to call	3843	This is a variation of a method callback - leaving out the method to call
3306	will default the method to C<operator ()>, which makes it possible to use	3844	will default the method to C<operator ()>, which makes it possible to use
3307	functor objects without having to manually specify the C<operator ()> all	3845	functor objects without having to manually specify the C<operator ()> all
3308	the time. Incidentally, you can then also leave out the template argument	3846	the time. Incidentally, you can then also leave out the template argument
…		…
3348	Associates a different C<struct ev_loop> with this watcher. You can only	3886	Associates a different C<struct ev_loop> with this watcher. You can only
3349	do this when the watcher is inactive (and not pending either).	3887	do this when the watcher is inactive (and not pending either).
3350		3888
3351	=item w->set ([arguments])	3889	=item w->set ([arguments])
3352		3890
3353	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3891	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3354	called at least once. Unlike the C counterpart, an active watcher gets	3892	method or a suitable start method must be called at least once. Unlike the
3355	automatically stopped and restarted when reconfiguring it with this	3893	C counterpart, an active watcher gets automatically stopped and restarted
3356	method.	3894	when reconfiguring it with this method.
3357		3895
3358	=item w->start ()	3896	=item w->start ()
3359		3897
3360	Starts the watcher. Note that there is no C<loop> argument, as the	3898	Starts the watcher. Note that there is no C<loop> argument, as the
3361	constructor already stores the event loop.	3899	constructor already stores the event loop.
3362		3900
		3901	=item w->start ([arguments])
		3902
		3903	Instead of calling C<set> and C<start> methods separately, it is often
		3904	convenient to wrap them in one call. Uses the same type of arguments as
		3905	the configure C<set> method of the watcher.
		3906
3363	=item w->stop ()	3907	=item w->stop ()
3364		3908
3365	Stops the watcher if it is active. Again, no C<loop> argument.	3909	Stops the watcher if it is active. Again, no C<loop> argument.
3366		3910
3367	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3911	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3379		3923
3380	=back	3924	=back
3381		3925
3382	=back	3926	=back
3383		3927
3384	Example: Define a class with an IO and idle watcher, start one of them in	3928	Example: Define a class with two I/O and idle watchers, start the I/O
3385	the constructor.	3929	watchers in the constructor.
3386		3930
3387	class myclass	3931	class myclass
3388	{	3932	{
3389	ev::io io ; void io_cb (ev::io &w, int revents);	3933	ev::io io ; void io_cb (ev::io &w, int revents);
		3934	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3390	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3935	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3391		3936
3392	myclass (int fd)	3937	myclass (int fd)
3393	{	3938	{
3394	io .set <myclass, &myclass::io_cb > (this);	3939	io .set <myclass, &myclass::io_cb > (this);
		3940	io2 .set <myclass, &myclass::io2_cb > (this);
3395	idle.set <myclass, &myclass::idle_cb> (this);	3941	idle.set <myclass, &myclass::idle_cb> (this);
3396		3942
3397	io.start (fd, ev::READ);	3943	io.set (fd, ev::WRITE); // configure the watcher
		3944	io.start (); // start it whenever convenient
		3945
		3946	io2.start (fd, ev::READ); // set + start in one call
3398	}	3947	}
3399	};	3948	};
3400		3949
3401		3950
3402	=head1 OTHER LANGUAGE BINDINGS	3951	=head1 OTHER LANGUAGE BINDINGS
…		…
3450	Erkki Seppala has written Ocaml bindings for libev, to be found at	3999	Erkki Seppala has written Ocaml bindings for libev, to be found at
3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4000	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3452		4001
3453	=item Lua	4002	=item Lua
3454		4003
3455	Brian Maher has written a partial interface to libev	4004	Brian Maher has written a partial interface to libev for lua (at the
3456	for lua (only C<ev_io> and C<ev_timer>), to be found at	4005	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3457	L<http://github.com/brimworks/lua-ev>.	4006	L<http://github.com/brimworks/lua-ev>.
3458		4007
3459	=back	4008	=back
3460		4009
3461		4010
…		…
3476	loop argument"). The C<EV_A> form is used when this is the sole argument,	4025	loop argument"). The C<EV_A> form is used when this is the sole argument,
3477	C<EV_A_> is used when other arguments are following. Example:	4026	C<EV_A_> is used when other arguments are following. Example:
3478		4027
3479	ev_unref (EV_A);	4028	ev_unref (EV_A);
3480	ev_timer_add (EV_A_ watcher);	4029	ev_timer_add (EV_A_ watcher);
3481	ev_loop (EV_A_ 0);	4030	ev_run (EV_A_ 0);
3482		4031
3483	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4032	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3484	which is often provided by the following macro.	4033	which is often provided by the following macro.
3485		4034
3486	=item C<EV_P>, C<EV_P_>	4035	=item C<EV_P>, C<EV_P_>
…		…
3526	}	4075	}
3527		4076
3528	ev_check check;	4077	ev_check check;
3529	ev_check_init (&check, check_cb);	4078	ev_check_init (&check, check_cb);
3530	ev_check_start (EV_DEFAULT_ &check);	4079	ev_check_start (EV_DEFAULT_ &check);
3531	ev_loop (EV_DEFAULT_ 0);	4080	ev_run (EV_DEFAULT_ 0);
3532		4081
3533	=head1 EMBEDDING	4082	=head1 EMBEDDING
3534		4083
3535	Libev can (and often is) directly embedded into host	4084	Libev can (and often is) directly embedded into host
3536	applications. Examples of applications that embed it include the Deliantra	4085	applications. Examples of applications that embed it include the Deliantra
…		…
3616	libev.m4	4165	libev.m4
3617		4166
3618	=head2 PREPROCESSOR SYMBOLS/MACROS	4167	=head2 PREPROCESSOR SYMBOLS/MACROS
3619		4168
3620	Libev can be configured via a variety of preprocessor symbols you have to	4169	Libev can be configured via a variety of preprocessor symbols you have to
3621	define before including any of its files. The default in the absence of	4170	define before including (or compiling) any of its files. The default in
3622	autoconf is documented for every option.	4171	the absence of autoconf is documented for every option.
		4172
		4173	Symbols marked with "(h)" do not change the ABI, and can have different
		4174	values when compiling libev vs. including F<ev.h>, so it is permissible
		4175	to redefine them before including F<ev.h> without breaking compatibility
		4176	to a compiled library. All other symbols change the ABI, which means all
		4177	users of libev and the libev code itself must be compiled with compatible
		4178	settings.
3623		4179
3624	=over 4	4180	=over 4
3625		4181
		4182	=item EV_COMPAT3 (h)
		4183
		4184	Backwards compatibility is a major concern for libev. This is why this
		4185	release of libev comes with wrappers for the functions and symbols that
		4186	have been renamed between libev version 3 and 4.
		4187
		4188	You can disable these wrappers (to test compatibility with future
		4189	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4190	sources. This has the additional advantage that you can drop the C<struct>
		4191	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4192	typedef in that case.
		4193
		4194	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4195	and in some even more future version the compatibility code will be
		4196	removed completely.
		4197
3626	=item EV_STANDALONE	4198	=item EV_STANDALONE (h)
3627		4199
3628	Must always be C<1> if you do not use autoconf configuration, which	4200	Must always be C<1> if you do not use autoconf configuration, which
3629	keeps libev from including F<config.h>, and it also defines dummy	4201	keeps libev from including F<config.h>, and it also defines dummy
3630	implementations for some libevent functions (such as logging, which is not	4202	implementations for some libevent functions (such as logging, which is not
3631	supported). It will also not define any of the structs usually found in	4203	supported). It will also not define any of the structs usually found in
…		…
3781	as well as for signal and thread safety in C<ev_async> watchers.	4353	as well as for signal and thread safety in C<ev_async> watchers.
3782		4354
3783	In the absence of this define, libev will use C<sig_atomic_t volatile>	4355	In the absence of this define, libev will use C<sig_atomic_t volatile>
3784	(from F<signal.h>), which is usually good enough on most platforms.	4356	(from F<signal.h>), which is usually good enough on most platforms.
3785		4357
3786	=item EV_H	4358	=item EV_H (h)
3787		4359
3788	The name of the F<ev.h> header file used to include it. The default if	4360	The name of the F<ev.h> header file used to include it. The default if
3789	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4361	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3790	used to virtually rename the F<ev.h> header file in case of conflicts.	4362	used to virtually rename the F<ev.h> header file in case of conflicts.
3791		4363
3792	=item EV_CONFIG_H	4364	=item EV_CONFIG_H (h)
3793		4365
3794	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4366	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3795	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4367	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3796	C<EV_H>, above.	4368	C<EV_H>, above.
3797		4369
3798	=item EV_EVENT_H	4370	=item EV_EVENT_H (h)
3799		4371
3800	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4372	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3801	of how the F<event.h> header can be found, the default is C<"event.h">.	4373	of how the F<event.h> header can be found, the default is C<"event.h">.
3802		4374
3803	=item EV_PROTOTYPES	4375	=item EV_PROTOTYPES (h)
3804		4376
3805	If defined to be C<0>, then F<ev.h> will not define any function	4377	If defined to be C<0>, then F<ev.h> will not define any function
3806	prototypes, but still define all the structs and other symbols. This is	4378	prototypes, but still define all the structs and other symbols. This is
3807	occasionally useful if you want to provide your own wrapper functions	4379	occasionally useful if you want to provide your own wrapper functions
3808	around libev functions.	4380	around libev functions.
…		…
3830	fine.	4402	fine.
3831		4403
3832	If your embedding application does not need any priorities, defining these	4404	If your embedding application does not need any priorities, defining these
3833	both to C<0> will save some memory and CPU.	4405	both to C<0> will save some memory and CPU.
3834		4406
3835	=item EV_PERIODIC_ENABLE	4407	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4408	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4409	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3836		4410
3837	If undefined or defined to be C<1>, then periodic timers are supported. If	4411	If undefined or defined to be C<1> (and the platform supports it), then
3838	defined to be C<0>, then they are not. Disabling them saves a few kB of	4412	the respective watcher type is supported. If defined to be C<0>, then it
3839	code.	4413	is not. Disabling watcher types mainly saves code size.
3840		4414
3841	=item EV_IDLE_ENABLE	4415	=item EV_FEATURES
3842
3843	If undefined or defined to be C<1>, then idle watchers are supported. If
3844	defined to be C<0>, then they are not. Disabling them saves a few kB of
3845	code.
3846
3847	=item EV_EMBED_ENABLE
3848
3849	If undefined or defined to be C<1>, then embed watchers are supported. If
3850	defined to be C<0>, then they are not. Embed watchers rely on most other
3851	watcher types, which therefore must not be disabled.
3852
3853	=item EV_STAT_ENABLE
3854
3855	If undefined or defined to be C<1>, then stat watchers are supported. If
3856	defined to be C<0>, then they are not.
3857
3858	=item EV_FORK_ENABLE
3859
3860	If undefined or defined to be C<1>, then fork watchers are supported. If
3861	defined to be C<0>, then they are not.
3862
3863	=item EV_ASYNC_ENABLE
3864
3865	If undefined or defined to be C<1>, then async watchers are supported. If
3866	defined to be C<0>, then they are not.
3867
3868	=item EV_MINIMAL
3869		4416
3870	If you need to shave off some kilobytes of code at the expense of some	4417	If you need to shave off some kilobytes of code at the expense of some
3871	speed (but with the full API), define this symbol to C<1>. Currently this	4418	speed (but with the full API), you can define this symbol to request
3872	is used to override some inlining decisions, saves roughly 30% code size	4419	certain subsets of functionality. The default is to enable all features
3873	on amd64. It also selects a much smaller 2-heap for timer management over	4420	that can be enabled on the platform.
3874	the default 4-heap.
3875		4421
3876	You can save even more by disabling watcher types you do not need	4422	A typical way to use this symbol is to define it to C<0> (or to a bitset
3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4423	with some broad features you want) and then selectively re-enable
3878	(C<-DNDEBUG>) will usually reduce code size a lot.	4424	additional parts you want, for example if you want everything minimal,
		4425	but multiple event loop support, async and child watchers and the poll
		4426	backend, use this:
3879		4427
3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4428	#define EV_FEATURES 0
3881	provide a bare-bones event library. See C<ev.h> for details on what parts	4429	#define EV_MULTIPLICITY 1
3882	of the API are still available, and do not complain if this subset changes	4430	#define EV_USE_POLL 1
3883	over time.	4431	#define EV_CHILD_ENABLE 1
		4432	#define EV_ASYNC_ENABLE 1
		4433
		4434	The actual value is a bitset, it can be a combination of the following
		4435	values:
		4436
		4437	=over 4
		4438
		4439	=item C<1> - faster/larger code
		4440
		4441	Use larger code to speed up some operations.
		4442
		4443	Currently this is used to override some inlining decisions (enlarging the
		4444	code size by roughly 30% on amd64).
		4445
		4446	When optimising for size, use of compiler flags such as C<-Os> with
		4447	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4448	assertions.
		4449
		4450	=item C<2> - faster/larger data structures
		4451
		4452	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4453	hash table sizes and so on. This will usually further increase code size
		4454	and can additionally have an effect on the size of data structures at
		4455	runtime.
		4456
		4457	=item C<4> - full API configuration
		4458
		4459	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4460	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4461
		4462	=item C<8> - full API
		4463
		4464	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4465	details on which parts of the API are still available without this
		4466	feature, and do not complain if this subset changes over time.
		4467
		4468	=item C<16> - enable all optional watcher types
		4469
		4470	Enables all optional watcher types. If you want to selectively enable
		4471	only some watcher types other than I/O and timers (e.g. prepare,
		4472	embed, async, child...) you can enable them manually by defining
		4473	C<EV_watchertype_ENABLE> to C<1> instead.
		4474
		4475	=item C<32> - enable all backends
		4476
		4477	This enables all backends - without this feature, you need to enable at
		4478	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4479
		4480	=item C<64> - enable OS-specific "helper" APIs
		4481
		4482	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4483	default.
		4484
		4485	=back
		4486
		4487	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4488	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4489	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4490	watchers, timers and monotonic clock support.
		4491
		4492	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4493	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4494	your program might be left out as well - a binary starting a timer and an
		4495	I/O watcher then might come out at only 5Kb.
		4496
		4497	=item EV_AVOID_STDIO
		4498
		4499	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4500	functions (printf, scanf, perror etc.). This will increase the code size
		4501	somewhat, but if your program doesn't otherwise depend on stdio and your
		4502	libc allows it, this avoids linking in the stdio library which is quite
		4503	big.
		4504
		4505	Note that error messages might become less precise when this option is
		4506	enabled.
3884		4507
3885	=item EV_NSIG	4508	=item EV_NSIG
3886		4509
3887	The highest supported signal number, +1 (or, the number of	4510	The highest supported signal number, +1 (or, the number of
3888	signals): Normally, libev tries to deduce the maximum number of signals	4511	signals): Normally, libev tries to deduce the maximum number of signals
3889	automatically, but sometimes this fails, in which case it can be	4512	automatically, but sometimes this fails, in which case it can be
3890	specified. Also, using a lower number than detected (C<32> should be	4513	specified. Also, using a lower number than detected (C<32> should be
3891	good for about any system in existance) can save some memory, as libev	4514	good for about any system in existence) can save some memory, as libev
3892	statically allocates some 12-24 bytes per signal number.	4515	statically allocates some 12-24 bytes per signal number.
3893		4516
3894	=item EV_PID_HASHSIZE	4517	=item EV_PID_HASHSIZE
3895		4518
3896	C<ev_child> watchers use a small hash table to distribute workload by	4519	C<ev_child> watchers use a small hash table to distribute workload by
3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4520	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3898	than enough. If you need to manage thousands of children you might want to	4521	usually more than enough. If you need to manage thousands of children you
3899	increase this value (I<must> be a power of two).	4522	might want to increase this value (I<must> be a power of two).
3900		4523
3901	=item EV_INOTIFY_HASHSIZE	4524	=item EV_INOTIFY_HASHSIZE
3902		4525
3903	C<ev_stat> watchers use a small hash table to distribute workload by	4526	C<ev_stat> watchers use a small hash table to distribute workload by
3904	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4527	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3905	usually more than enough. If you need to manage thousands of C<ev_stat>	4528	disabled), usually more than enough. If you need to manage thousands of
3906	watchers you might want to increase this value (I<must> be a power of	4529	C<ev_stat> watchers you might want to increase this value (I<must> be a
3907	two).	4530	power of two).
3908		4531
3909	=item EV_USE_4HEAP	4532	=item EV_USE_4HEAP
3910		4533
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4534	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4535	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3913	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4536	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3914	faster performance with many (thousands) of watchers.	4537	faster performance with many (thousands) of watchers.
3915		4538
3916	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4539	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3917	(disabled).	4540	will be C<0>.
3918		4541
3919	=item EV_HEAP_CACHE_AT	4542	=item EV_HEAP_CACHE_AT
3920		4543
3921	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4544	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3922	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4545	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3923	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4546	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3924	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4547	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3925	but avoids random read accesses on heap changes. This improves performance	4548	but avoids random read accesses on heap changes. This improves performance
3926	noticeably with many (hundreds) of watchers.	4549	noticeably with many (hundreds) of watchers.
3927		4550
3928	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4551	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3929	(disabled).	4552	will be C<0>.
3930		4553
3931	=item EV_VERIFY	4554	=item EV_VERIFY
3932		4555
3933	Controls how much internal verification (see C<ev_loop_verify ()>) will	4556	Controls how much internal verification (see C<ev_verify ()>) will
3934	be done: If set to C<0>, no internal verification code will be compiled	4557	be done: If set to C<0>, no internal verification code will be compiled
3935	in. If set to C<1>, then verification code will be compiled in, but not	4558	in. If set to C<1>, then verification code will be compiled in, but not
3936	called. If set to C<2>, then the internal verification code will be	4559	called. If set to C<2>, then the internal verification code will be
3937	called once per loop, which can slow down libev. If set to C<3>, then the	4560	called once per loop, which can slow down libev. If set to C<3>, then the
3938	verification code will be called very frequently, which will slow down	4561	verification code will be called very frequently, which will slow down
3939	libev considerably.	4562	libev considerably.
3940		4563
3941	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4564	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3942	C<0>.	4565	will be C<0>.
3943		4566
3944	=item EV_COMMON	4567	=item EV_COMMON
3945		4568
3946	By default, all watchers have a C<void *data> member. By redefining	4569	By default, all watchers have a C<void *data> member. By redefining
3947	this macro to a something else you can include more and other types of	4570	this macro to something else you can include more and other types of
3948	members. You have to define it each time you include one of the files,	4571	members. You have to define it each time you include one of the files,
3949	though, and it must be identical each time.	4572	though, and it must be identical each time.
3950		4573
3951	For example, the perl EV module uses something like this:	4574	For example, the perl EV module uses something like this:
3952		4575
…		…
4005	file.	4628	file.
4006		4629
4007	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4630	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4008	that everybody includes and which overrides some configure choices:	4631	that everybody includes and which overrides some configure choices:
4009		4632
4010	#define EV_MINIMAL 1	4633	#define EV_FEATURES 8
4011	#define EV_USE_POLL 0	4634	#define EV_USE_SELECT 1
4012	#define EV_MULTIPLICITY 0
4013	#define EV_PERIODIC_ENABLE 0	4635	#define EV_PREPARE_ENABLE 1
		4636	#define EV_IDLE_ENABLE 1
4014	#define EV_STAT_ENABLE 0	4637	#define EV_SIGNAL_ENABLE 1
4015	#define EV_FORK_ENABLE 0	4638	#define EV_CHILD_ENABLE 1
		4639	#define EV_USE_STDEXCEPT 0
4016	#define EV_CONFIG_H <config.h>	4640	#define EV_CONFIG_H <config.h>
4017	#define EV_MINPRI 0
4018	#define EV_MAXPRI 0
4019		4641
4020	#include "ev++.h"	4642	#include "ev++.h"
4021		4643
4022	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4644	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4023		4645
4024	#include "ev_cpp.h"	4646	#include "ev_cpp.h"
4025	#include "ev.c"	4647	#include "ev.c"
4026		4648
4027	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4649	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4028		4650
4029	=head2 THREADS AND COROUTINES	4651	=head2 THREADS AND COROUTINES
4030		4652
4031	=head3 THREADS	4653	=head3 THREADS
4032		4654
…		…
4083	default loop and triggering an C<ev_async> watcher from the default loop	4705	default loop and triggering an C<ev_async> watcher from the default loop
4084	watcher callback into the event loop interested in the signal.	4706	watcher callback into the event loop interested in the signal.
4085		4707
4086	=back	4708	=back
4087		4709
4088	=head4 THREAD LOCKING EXAMPLE	4710	See also L<THREAD LOCKING EXAMPLE>.
4089
4090	Here is a fictitious example of how to run an event loop in a different
4091	thread than where callbacks are being invoked and watchers are
4092	created/added/removed.
4093
4094	For a real-world example, see the C<EV::Loop::Async> perl module,
4095	which uses exactly this technique (which is suited for many high-level
4096	languages).
4097
4098	The example uses a pthread mutex to protect the loop data, a condition
4099	variable to wait for callback invocations, an async watcher to notify the
4100	event loop thread and an unspecified mechanism to wake up the main thread.
4101
4102	First, you need to associate some data with the event loop:
4103
4104	typedef struct {
4105	mutex_t lock; /* global loop lock */
4106	ev_async async_w;
4107	thread_t tid;
4108	cond_t invoke_cv;
4109	} userdata;
4110
4111	void prepare_loop (EV_P)
4112	{
4113	// for simplicity, we use a static userdata struct.
4114	static userdata u;
4115
4116	ev_async_init (&u->async_w, async_cb);
4117	ev_async_start (EV_A_ &u->async_w);
4118
4119	pthread_mutex_init (&u->lock, 0);
4120	pthread_cond_init (&u->invoke_cv, 0);
4121
4122	// now associate this with the loop
4123	ev_set_userdata (EV_A_ u);
4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4126
4127	// then create the thread running ev_loop
4128	pthread_create (&u->tid, 0, l_run, EV_A);
4129	}
4130
4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
4132	solely to wake up the event loop so it takes notice of any new watchers
4133	that might have been added:
4134
4135	static void
4136	async_cb (EV_P_ ev_async *w, int revents)
4137	{
4138	// just used for the side effects
4139	}
4140
4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4142	protecting the loop data, respectively.
4143
4144	static void
4145	l_release (EV_P)
4146	{
4147	userdata *u = ev_userdata (EV_A);
4148	pthread_mutex_unlock (&u->lock);
4149	}
4150
4151	static void
4152	l_acquire (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155	pthread_mutex_lock (&u->lock);
4156	}
4157
4158	The event loop thread first acquires the mutex, and then jumps straight
4159	into C<ev_loop>:
4160
4161	void *
4162	l_run (void *thr_arg)
4163	{
4164	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4165
4166	l_acquire (EV_A);
4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4168	ev_loop (EV_A_ 0);
4169	l_release (EV_A);
4170
4171	return 0;
4172	}
4173
4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
4175	signal the main thread via some unspecified mechanism (signals? pipe
4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4177	have been called (in a while loop because a) spurious wakeups are possible
4178	and b) skipping inter-thread-communication when there are no pending
4179	watchers is very beneficial):
4180
4181	static void
4182	l_invoke (EV_P)
4183	{
4184	userdata *u = ev_userdata (EV_A);
4185
4186	while (ev_pending_count (EV_A))
4187	{
4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
4190	}
4191	}
4192
4193	Now, whenever the main thread gets told to invoke pending watchers, it
4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4195	thread to continue:
4196
4197	static void
4198	real_invoke_pending (EV_P)
4199	{
4200	userdata *u = ev_userdata (EV_A);
4201
4202	pthread_mutex_lock (&u->lock);
4203	ev_invoke_pending (EV_A);
4204	pthread_cond_signal (&u->invoke_cv);
4205	pthread_mutex_unlock (&u->lock);
4206	}
4207
4208	Whenever you want to start/stop a watcher or do other modifications to an
4209	event loop, you will now have to lock:
4210
4211	ev_timer timeout_watcher;
4212	userdata *u = ev_userdata (EV_A);
4213
4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4215
4216	pthread_mutex_lock (&u->lock);
4217	ev_timer_start (EV_A_ &timeout_watcher);
4218	ev_async_send (EV_A_ &u->async_w);
4219	pthread_mutex_unlock (&u->lock);
4220
4221	Note that sending the C<ev_async> watcher is required because otherwise
4222	an event loop currently blocking in the kernel will have no knowledge
4223	about the newly added timer. By waking up the loop it will pick up any new
4224	watchers in the next event loop iteration.
4225		4711
4226	=head3 COROUTINES	4712	=head3 COROUTINES
4227		4713
4228	Libev is very accommodating to coroutines ("cooperative threads"):	4714	Libev is very accommodating to coroutines ("cooperative threads"):
4229	libev fully supports nesting calls to its functions from different	4715	libev fully supports nesting calls to its functions from different
4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4716	coroutines (e.g. you can call C<ev_run> on the same loop from two
4231	different coroutines, and switch freely between both coroutines running	4717	different coroutines, and switch freely between both coroutines running
4232	the loop, as long as you don't confuse yourself). The only exception is	4718	the loop, as long as you don't confuse yourself). The only exception is
4233	that you must not do this from C<ev_periodic> reschedule callbacks.	4719	that you must not do this from C<ev_periodic> reschedule callbacks.
4234		4720
4235	Care has been taken to ensure that libev does not keep local state inside	4721	Care has been taken to ensure that libev does not keep local state inside
4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4722	C<ev_run>, and other calls do not usually allow for coroutine switches as
4237	they do not call any callbacks.	4723	they do not call any callbacks.
4238		4724
4239	=head2 COMPILER WARNINGS	4725	=head2 COMPILER WARNINGS
4240		4726
4241	Depending on your compiler and compiler settings, you might get no or a	4727	Depending on your compiler and compiler settings, you might get no or a
…		…
4252	maintainable.	4738	maintainable.
4253		4739
4254	And of course, some compiler warnings are just plain stupid, or simply	4740	And of course, some compiler warnings are just plain stupid, or simply
4255	wrong (because they don't actually warn about the condition their message	4741	wrong (because they don't actually warn about the condition their message
4256	seems to warn about). For example, certain older gcc versions had some	4742	seems to warn about). For example, certain older gcc versions had some
4257	warnings that resulted an extreme number of false positives. These have	4743	warnings that resulted in an extreme number of false positives. These have
4258	been fixed, but some people still insist on making code warn-free with	4744	been fixed, but some people still insist on making code warn-free with
4259	such buggy versions.	4745	such buggy versions.
4260		4746
4261	While libev is written to generate as few warnings as possible,	4747	While libev is written to generate as few warnings as possible,
4262	"warn-free" code is not a goal, and it is recommended not to build libev	4748	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4298	I suggest using suppression lists.	4784	I suggest using suppression lists.
4299		4785
4300		4786
4301	=head1 PORTABILITY NOTES	4787	=head1 PORTABILITY NOTES
4302		4788
		4789	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4790
		4791	GNU/Linux is the only common platform that supports 64 bit file/large file
		4792	interfaces but I<disables> them by default.
		4793
		4794	That means that libev compiled in the default environment doesn't support
		4795	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4796
		4797	Unfortunately, many programs try to work around this GNU/Linux issue
		4798	by enabling the large file API, which makes them incompatible with the
		4799	standard libev compiled for their system.
		4800
		4801	Likewise, libev cannot enable the large file API itself as this would
		4802	suddenly make it incompatible to the default compile time environment,
		4803	i.e. all programs not using special compile switches.
		4804
		4805	=head2 OS/X AND DARWIN BUGS
		4806
		4807	The whole thing is a bug if you ask me - basically any system interface
		4808	you touch is broken, whether it is locales, poll, kqueue or even the
		4809	OpenGL drivers.
		4810
		4811	=head3 C<kqueue> is buggy
		4812
		4813	The kqueue syscall is broken in all known versions - most versions support
		4814	only sockets, many support pipes.
		4815
		4816	Libev tries to work around this by not using C<kqueue> by default on this
		4817	rotten platform, but of course you can still ask for it when creating a
		4818	loop - embedding a socket-only kqueue loop into a select-based one is
		4819	probably going to work well.
		4820
		4821	=head3 C<poll> is buggy
		4822
		4823	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4824	implementation by something calling C<kqueue> internally around the 10.5.6
		4825	release, so now C<kqueue> I<and> C<poll> are broken.
		4826
		4827	Libev tries to work around this by not using C<poll> by default on
		4828	this rotten platform, but of course you can still ask for it when creating
		4829	a loop.
		4830
		4831	=head3 C<select> is buggy
		4832
		4833	All that's left is C<select>, and of course Apple found a way to fuck this
		4834	one up as well: On OS/X, C<select> actively limits the number of file
		4835	descriptors you can pass in to 1024 - your program suddenly crashes when
		4836	you use more.
		4837
		4838	There is an undocumented "workaround" for this - defining
		4839	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4840	work on OS/X.
		4841
		4842	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4843
		4844	=head3 C<errno> reentrancy
		4845
		4846	The default compile environment on Solaris is unfortunately so
		4847	thread-unsafe that you can't even use components/libraries compiled
		4848	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4849	defined by default. A valid, if stupid, implementation choice.
		4850
		4851	If you want to use libev in threaded environments you have to make sure
		4852	it's compiled with C<_REENTRANT> defined.
		4853
		4854	=head3 Event port backend
		4855
		4856	The scalable event interface for Solaris is called "event
		4857	ports". Unfortunately, this mechanism is very buggy in all major
		4858	releases. If you run into high CPU usage, your program freezes or you get
		4859	a large number of spurious wakeups, make sure you have all the relevant
		4860	and latest kernel patches applied. No, I don't know which ones, but there
		4861	are multiple ones to apply, and afterwards, event ports actually work
		4862	great.
		4863
		4864	If you can't get it to work, you can try running the program by setting
		4865	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4866	C<select> backends.
		4867
		4868	=head2 AIX POLL BUG
		4869
		4870	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4871	this by trying to avoid the poll backend altogether (i.e. it's not even
		4872	compiled in), which normally isn't a big problem as C<select> works fine
		4873	with large bitsets on AIX, and AIX is dead anyway.
		4874
4303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4876
		4877	=head3 General issues
4304		4878
4305	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4879	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4306	requires, and its I/O model is fundamentally incompatible with the POSIX	4880	requires, and its I/O model is fundamentally incompatible with the POSIX
4307	model. Libev still offers limited functionality on this platform in	4881	model. Libev still offers limited functionality on this platform in
4308	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4882	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4309	descriptors. This only applies when using Win32 natively, not when using	4883	descriptors. This only applies when using Win32 natively, not when using
4310	e.g. cygwin.	4884	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4885	as every compielr comes with a slightly differently broken/incompatible
		4886	environment.
4311		4887
4312	Lifting these limitations would basically require the full	4888	Lifting these limitations would basically require the full
4313	re-implementation of the I/O system. If you are into these kinds of	4889	re-implementation of the I/O system. If you are into this kind of thing,
4314	things, then note that glib does exactly that for you in a very portable	4890	then note that glib does exactly that for you in a very portable way (note
4315	way (note also that glib is the slowest event library known to man).	4891	also that glib is the slowest event library known to man).
4316		4892
4317	There is no supported compilation method available on windows except	4893	There is no supported compilation method available on windows except
4318	embedding it into other applications.	4894	embedding it into other applications.
4319		4895
4320	Sensible signal handling is officially unsupported by Microsoft - libev	4896	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4348	you do I<not> compile the F<ev.c> or any other embedded source files!):	4924	you do I<not> compile the F<ev.c> or any other embedded source files!):
4349		4925
4350	#include "evwrap.h"	4926	#include "evwrap.h"
4351	#include "ev.c"	4927	#include "ev.c"
4352		4928
4353	=over 4
4354
4355	=item The winsocket select function	4929	=head3 The winsocket C<select> function
4356		4930
4357	The winsocket C<select> function doesn't follow POSIX in that it	4931	The winsocket C<select> function doesn't follow POSIX in that it
4358	requires socket I<handles> and not socket I<file descriptors> (it is	4932	requires socket I<handles> and not socket I<file descriptors> (it is
4359	also extremely buggy). This makes select very inefficient, and also	4933	also extremely buggy). This makes select very inefficient, and also
4360	requires a mapping from file descriptors to socket handles (the Microsoft	4934	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4369	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4943	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4370		4944
4371	Note that winsockets handling of fd sets is O(n), so you can easily get a	4945	Note that winsockets handling of fd sets is O(n), so you can easily get a
4372	complexity in the O(n²) range when using win32.	4946	complexity in the O(n²) range when using win32.
4373		4947
4374	=item Limited number of file descriptors	4948	=head3 Limited number of file descriptors
4375		4949
4376	Windows has numerous arbitrary (and low) limits on things.	4950	Windows has numerous arbitrary (and low) limits on things.
4377		4951
4378	Early versions of winsocket's select only supported waiting for a maximum	4952	Early versions of winsocket's select only supported waiting for a maximum
4379	of C<64> handles (probably owning to the fact that all windows kernels	4953	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4394	runtime libraries. This might get you to about C<512> or C<2048> sockets	4968	runtime libraries. This might get you to about C<512> or C<2048> sockets
4395	(depending on windows version and/or the phase of the moon). To get more,	4969	(depending on windows version and/or the phase of the moon). To get more,
4396	you need to wrap all I/O functions and provide your own fd management, but	4970	you need to wrap all I/O functions and provide your own fd management, but
4397	the cost of calling select (O(n²)) will likely make this unworkable.	4971	the cost of calling select (O(n²)) will likely make this unworkable.
4398		4972
4399	=back
4400
4401	=head2 PORTABILITY REQUIREMENTS	4973	=head2 PORTABILITY REQUIREMENTS
4402		4974
4403	In addition to a working ISO-C implementation and of course the	4975	In addition to a working ISO-C implementation and of course the
4404	backend-specific APIs, libev relies on a few additional extensions:	4976	backend-specific APIs, libev relies on a few additional extensions:
4405		4977
…		…
4411	Libev assumes not only that all watcher pointers have the same internal	4983	Libev assumes not only that all watcher pointers have the same internal
4412	structure (guaranteed by POSIX but not by ISO C for example), but it also	4984	structure (guaranteed by POSIX but not by ISO C for example), but it also
4413	assumes that the same (machine) code can be used to call any watcher	4985	assumes that the same (machine) code can be used to call any watcher
4414	callback: The watcher callbacks have different type signatures, but libev	4986	callback: The watcher callbacks have different type signatures, but libev
4415	calls them using an C<ev_watcher *> internally.	4987	calls them using an C<ev_watcher *> internally.
		4988
		4989	=item pointer accesses must be thread-atomic
		4990
		4991	Accessing a pointer value must be atomic, it must both be readable and
		4992	writable in one piece - this is the case on all current architectures.
4416		4993
4417	=item C<sig_atomic_t volatile> must be thread-atomic as well	4994	=item C<sig_atomic_t volatile> must be thread-atomic as well
4418		4995
4419	The type C<sig_atomic_t volatile> (or whatever is defined as	4996	The type C<sig_atomic_t volatile> (or whatever is defined as
4420	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4997	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4443	watchers.	5020	watchers.
4444		5021
4445	=item C<double> must hold a time value in seconds with enough accuracy	5022	=item C<double> must hold a time value in seconds with enough accuracy
4446		5023
4447	The type C<double> is used to represent timestamps. It is required to	5024	The type C<double> is used to represent timestamps. It is required to
4448	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5025	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4449	enough for at least into the year 4000. This requirement is fulfilled by	5026	good enough for at least into the year 4000 with millisecond accuracy
		5027	(the design goal for libev). This requirement is overfulfilled by
4450	implementations implementing IEEE 754, which is basically all existing	5028	implementations using IEEE 754, which is basically all existing ones. With
4451	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5029	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4452	2200.
4453		5030
4454	=back	5031	=back
4455		5032
4456	If you know of other additional requirements drop me a note.	5033	If you know of other additional requirements drop me a note.
4457		5034
…		…
4525	involves iterating over all running async watchers or all signal numbers.	5102	involves iterating over all running async watchers or all signal numbers.
4526		5103
4527	=back	5104	=back
4528		5105
4529		5106
		5107	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5108
		5109	The major version 4 introduced some incompatible changes to the API.
		5110
		5111	At the moment, the C<ev.h> header file provides compatibility definitions
		5112	for all changes, so most programs should still compile. The compatibility
		5113	layer might be removed in later versions of libev, so better update to the
		5114	new API early than late.
		5115
		5116	=over 4
		5117
		5118	=item C<EV_COMPAT3> backwards compatibility mechanism
		5119
		5120	The backward compatibility mechanism can be controlled by
		5121	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5122	section.
		5123
		5124	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5125
		5126	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5127
		5128	ev_loop_destroy (EV_DEFAULT_UC);
		5129	ev_loop_fork (EV_DEFAULT);
		5130
		5131	=item function/symbol renames
		5132
		5133	A number of functions and symbols have been renamed:
		5134
		5135	ev_loop => ev_run
		5136	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5137	EVLOOP_ONESHOT => EVRUN_ONCE
		5138
		5139	ev_unloop => ev_break
		5140	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5141	EVUNLOOP_ONE => EVBREAK_ONE
		5142	EVUNLOOP_ALL => EVBREAK_ALL
		5143
		5144	EV_TIMEOUT => EV_TIMER
		5145
		5146	ev_loop_count => ev_iteration
		5147	ev_loop_depth => ev_depth
		5148	ev_loop_verify => ev_verify
		5149
		5150	Most functions working on C<struct ev_loop> objects don't have an
		5151	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5152	associated constants have been renamed to not collide with the C<struct
		5153	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5154	as all other watcher types. Note that C<ev_loop_fork> is still called
		5155	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5156	typedef.
		5157
		5158	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5159
		5160	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5161	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5162	and work, but the library code will of course be larger.
		5163
		5164	=back
		5165
		5166
4530	=head1 GLOSSARY	5167	=head1 GLOSSARY
4531		5168
4532	=over 4	5169	=over 4
4533		5170
4534	=item active	5171	=item active
4535		5172
4536	A watcher is active as long as it has been started (has been attached to	5173	A watcher is active as long as it has been started and not yet stopped.
4537	an event loop) but not yet stopped (disassociated from the event loop).	5174	See L<WATCHER STATES> for details.
4538		5175
4539	=item application	5176	=item application
4540		5177
4541	In this document, an application is whatever is using libev.	5178	In this document, an application is whatever is using libev.
		5179
		5180	=item backend
		5181
		5182	The part of the code dealing with the operating system interfaces.
4542		5183
4543	=item callback	5184	=item callback
4544		5185
4545	The address of a function that is called when some event has been	5186	The address of a function that is called when some event has been
4546	detected. Callbacks are being passed the event loop, the watcher that	5187	detected. Callbacks are being passed the event loop, the watcher that
4547	received the event, and the actual event bitset.	5188	received the event, and the actual event bitset.
4548		5189
4549	=item callback invocation	5190	=item callback/watcher invocation
4550		5191
4551	The act of calling the callback associated with a watcher.	5192	The act of calling the callback associated with a watcher.
4552		5193
4553	=item event	5194	=item event
4554		5195
4555	A change of state of some external event, such as data now being available	5196	A change of state of some external event, such as data now being available
4556	for reading on a file descriptor, time having passed or simply not having	5197	for reading on a file descriptor, time having passed or simply not having
4557	any other events happening anymore.	5198	any other events happening anymore.
4558		5199
4559	In libev, events are represented as single bits (such as C<EV_READ> or	5200	In libev, events are represented as single bits (such as C<EV_READ> or
4560	C<EV_TIMEOUT>).	5201	C<EV_TIMER>).
4561		5202
4562	=item event library	5203	=item event library
4563		5204
4564	A software package implementing an event model and loop.	5205	A software package implementing an event model and loop.
4565		5206
…		…
4573	The model used to describe how an event loop handles and processes	5214	The model used to describe how an event loop handles and processes
4574	watchers and events.	5215	watchers and events.
4575		5216
4576	=item pending	5217	=item pending
4577		5218
4578	A watcher is pending as soon as the corresponding event has been detected,	5219	A watcher is pending as soon as the corresponding event has been
4579	and stops being pending as soon as the watcher will be invoked or its	5220	detected. See L<WATCHER STATES> for details.
4580	pending status is explicitly cleared by the application.
4581
4582	A watcher can be pending, but not active. Stopping a watcher also clears
4583	its pending status.
4584		5221
4585	=item real time	5222	=item real time
4586		5223
4587	The physical time that is observed. It is apparently strictly monotonic :)	5224	The physical time that is observed. It is apparently strictly monotonic :)
4588		5225
4589	=item wall-clock time	5226	=item wall-clock time
4590		5227
4591	The time and date as shown on clocks. Unlike real time, it can actually	5228	The time and date as shown on clocks. Unlike real time, it can actually
4592	be wrong and jump forwards and backwards, e.g. when the you adjust your	5229	be wrong and jump forwards and backwards, e.g. when you adjust your
4593	clock.	5230	clock.
4594		5231
4595	=item watcher	5232	=item watcher
4596		5233
4597	A data structure that describes interest in certain events. Watchers need	5234	A data structure that describes interest in certain events. Watchers need
4598	to be started (attached to an event loop) before they can receive events.	5235	to be started (attached to an event loop) before they can receive events.
4599		5236
4600	=item watcher invocation
4601
4602	The act of calling the callback associated with a watcher.
4603
4604	=back	5237	=back
4605		5238
4606	=head1 AUTHOR	5239	=head1 AUTHOR
4607		5240
4608	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5241	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5242	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4609		5243

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