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Revision 1.367 by root, Sun Feb 20 02:56:23 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 it both faster and might make	428	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	429	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
387		451
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		453
390	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
427	epoll scales either O(1) or O(active_fds).	491	epoll scales either O(1) or O(active_fds).
428		492
429	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	502	and is of course hard to detect.
437		503
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
439	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
440	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
442	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
443	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
445		517
446	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		588
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
519		591
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	595	might perform better.
528		596
529	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
533		611
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
536		614
537	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
538		616
539	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		620
543	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		630
545	=back	631	=back
546		632
547	If one or more of the backend flags are or'ed into the flags value,	633	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	634	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	635	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	636	()> will be tried.
551		637
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	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.
581		639
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	641	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
585		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
586	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
587		650
588	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
589	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
590	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
591	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
592	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
593	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
…		…
595		658
596	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
597	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
598	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
599		662
600	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
601	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.
602	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>
603	C<ev_loop_new> and C<ev_loop_destroy>.	670	and C<ev_loop_destroy>.
604		671
605	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
606		673
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	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
613	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
614	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
615	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
616	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
617	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.
618		684
619	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
620	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
621	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).
622		691
623	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
624	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		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	...
627	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		706
636	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
637		708
638	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
639	otherwise.	710	otherwise.
640		711
641	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
642		713
643	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
644	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>
645	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
646		717
647	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
648	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
649	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.
650		722
651	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
652		724
653	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
654	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.
655		727
656	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
657	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),
658	in which case it is higher.	730	in which case it is higher.
659		731
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	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.
662		736
663	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
664		738
665	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
666	use.	740	use.
…		…
675		749
676	=item ev_now_update (loop)	750	=item ev_now_update (loop)
677		751
678	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
679	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
680	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
681		755
682	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
683	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
684	the current time is a good idea.	758	the current time is a good idea.
685		759
…		…
687		761
688	=item ev_suspend (loop)	762	=item ev_suspend (loop)
689		763
690	=item ev_resume (loop)	764	=item ev_resume (loop)
691		765
692	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
693	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.
694		768
695	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
696	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
697	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
698	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>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
701		775
702	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
703	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
704	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
705	occured while suspended).	779	occurred while suspended).
706		780
707	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
708	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>
709	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
710		784
711	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
712	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
713		787
714	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
715		789
716	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
717	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
718	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>.
719		795
720	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
721	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.
722		799
723	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
724	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
725	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
726	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
727	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
728	beauty.	805	beauty.
729		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
730	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
731	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
732	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
733	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.
734		817
735	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
736	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
737	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
738	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
739	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
740	iteration of the loop.	823	iteration of the loop.
741		824
742	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
743	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
744	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
745	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
746		829
747	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
748		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- 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.
752	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	841	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
760	- 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.
761	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
763	- 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.
764	- Queue all expired timers.	852	- Queue all expired timers.
765	- Queue all expired periodics.	853	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	855	- Queue all check watchers.
768	- 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).
769	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
770	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
771	- 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
772	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
773	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.
774		866
775	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
776	anymore.	868	anymore.
777		869
778	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
779	... 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..)
780	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
782		874
783	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
784		876
785	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
786	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
787	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
788	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.
789		881
790	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>.
791		883
792	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.
793		886
794	=item ev_ref (loop)	887	=item ev_ref (loop)
795		888
796	=item ev_unref (loop)	889	=item ev_unref (loop)
797		890
798	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
799	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
800	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.
801		894
802	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
803	unregister, but that nevertheless should not keep C<ev_loop> from	896	unregister, but that nevertheless should not keep C<ev_run> from
804	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>
805	before stopping it.	898	before stopping it.
806		899
807	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
808	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
809	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
810	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
811	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
812	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
813	before, respectively. Note also that libev might stop watchers itself	906	before, respectively. Note also that libev might stop watchers itself
814	(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>
815	in the callback).	908	in the callback).
816		909
817	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>
818	running when nothing else is active.	911	running when nothing else is active.
819		912
820	ev_signal exitsig;	913	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	916	ev_unref (loop);
824		917
825	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
826		919
827	ev_ref (loop);	920	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
867	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>,
868	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
869	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
870	parallelity, then this setting will limit your transaction rate (if you	963	parallelity, then this setting will limit your transaction rate (if you
871	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,
872	then you can't do more than 100 transations per second).	965	then you can't do more than 100 transactions per second).
873		966
874	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
876	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
877	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
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		979
887	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
888		981
889	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
891	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).
892		989
893	=item int ev_pending_count (loop)	990	=item int ev_pending_count (loop)
894		991
895	Returns the number of pending watchers - zero indicates that no watchers	992	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	993	are pending.
897		994
898	=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))
899		996
900	This overrides the invoke pending functionality of the loop: Instead of	997	This overrides the invoke pending functionality of the loop: Instead of
901	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
902	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
903	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
904		1001
905	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
906	callback.	1003	callback.
…		…
909		1006
910	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
911	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
912	each call to a libev function.	1009	each call to a libev function.
913		1010
914	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
915	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
916	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
917	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
918		1015
919	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
920	suspended waiting for new events, and C<acquire> is called just	1017	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1018	afterwards.
922		1019
…		…
925		1022
926	While event loop modifications are allowed between invocations of	1023	While event loop modifications are allowed between invocations of
927	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
928	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
929	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
930	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
931	to take note of any changes you made.	1028	to take note of any changes you made.
932		1029
933	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
934	invocations of C<release> and C<acquire>.	1031	invocations of C<release> and C<acquire>.
935		1032
936	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
937	document.	1034	document.
938		1035
939	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
940		1037
941	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
942		1039
943	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
944	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
945	C<0.>	1042	C<0>.
946		1043
947	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,
948	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
949	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
950	any other purpose as well.	1047	any other purpose as well.
951		1048
952	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
953		1050
954	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
955	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
956	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
957	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
…		…
968		1065
969	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
970	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
971	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
972		1069
973	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
974	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
975	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:
976		1074
977	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)
978	{	1076	{
979	ev_io_stop (w);	1077	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
981	}	1079	}
982		1080
983	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
984		1082
985	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
986		1084
987	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
990		1088
991	ev_loop (loop, 0);	1089	ev_run (loop, 0);
992		1090
993	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
994	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
995	stack).	1093	stack).
996		1094
997	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>
998	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).
999		1097
1000	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
1001	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
1002	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
1003	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
1004	is readable and/or writable).	1102	and/or writable).
1005		1103
1006	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 *, ...) >>
1007	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
1008	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<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
1033		1131
1034	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
1035	writable.	1133	writable.
1036		1134
1037	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
1038		1136
1039	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
1040		1138
1041	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
1042		1140
…		…
1060		1158
1061	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1062		1160
1063	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1064		1162
1065	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
1066	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
1067	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
1068	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
1069	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
1070	(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
1071	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1072		1170
1073	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1074		1172
1075	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.
1076		1174
1077	=item C<EV_FORK>	1175	=item C<EV_FORK>
1078		1176
1079	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
1080	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>).
1081		1183
1082	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1083		1185
1084	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>).
1085		1187
…		…
1258	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
1259	functions that do not need a watcher.	1361	functions that do not need a watcher.
1260		1362
1261	=back	1363	=back
1262		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1263		1367
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1265		1369
1266	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1267	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
1268	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
1269	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".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1374
1273	struct my_io	1375	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1376
1281	...	1377	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1378
1285	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
1286	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.
1287		1382
1288	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
1289	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1291	...	1386	C<ev_TYPE_init> again.
1292	}
1293		1387
1294	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1295	instead have been omitted.
1296		1389
1297	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
1298	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.
1299		1395
1300	struct my_biggy	1396	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1397
1307	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
1308	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
1309	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
1310	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
1311	programmers):	1402	callback.
1312		1403
1313	#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.
1314		1410
1315	static void	1411	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1413	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1414
1322	static void	1415	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1324	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1327	}	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
1328		1429
1329	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1330		1431
1331	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1375		1476
1376	For example, to emulate how many other event libraries handle priorities,	1477	For example, to emulate how many other event libraries handle priorities,
1377	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
1378	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
1379	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
1380	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
1381	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
1382	workable.	1483	workable.
1383		1484
1384	Usually, however, the lock-out model implemented that way will perform	1485	Usually, however, the lock-out model implemented that way will perform
1385	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,
…		…
1399	{	1500	{
1400	// stop the I/O watcher, we received the event, but	1501	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1502	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1503	ev_io_stop (EV_A_ w);
1403		1504
1404	// start the idle watcher to ahndle the actual event.	1505	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1506	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1507	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1508	ev_idle_start (EV_A_ &idle);
1408	}	1509	}
1409		1510
…		…
1459	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
1460	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
1461	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
1462	required if you know what you are doing).	1563	required if you know what you are doing).
1463		1564
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	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
1471	receive "spurious" readiness notifications, that is your callback might	1566	receive "spurious" readiness notifications, that is, your callback might
1472	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
1473	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
1474	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
1475	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
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1571	preferable to a program hanging until some data arrives.
1478		1572
1479	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
1480	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
1481	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
1482	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
1483	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
1484	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
1485	indefinitely.	1579	indefinitely.
1486		1580
1487	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1488		1582
…		…
1516		1610
1517	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		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
1521	=head3 The special problem of fork	1648	=head3 The special problem of fork
1522		1649
1523	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
1524	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
1525	it in the child.	1652	it in the child if you want to continue to use it in the child.
1526		1653
1527	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
1528	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
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1657
1532	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1533		1659
1534	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>:
1535	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
…		…
1538		1664
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1665	So when you encounter spurious, unexplained daemon exits, make sure you
1540	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
1541	somewhere, as that would have given you a big clue).	1667	somewhere, as that would have given you a big clue).
1542		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.
1543		1707
1544	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1545		1709
1546	=over 4	1710	=over 4
1547		1711
…		…
1579	...	1743	...
1580	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1745	ev_io stdin_readable;
1582	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);
1583	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1585		1749
1586		1750
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1752
1589	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
…		…
1598	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
1599	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
1600	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
1601	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
1602	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
1603	no longer true when a callback calls C<ev_loop> recursively).	1767	no longer true when a callback calls C<ev_run> recursively).
1604		1768
1605	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1606		1770
1607	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
1608	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,
…		…
1694	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1695		1859
1696	// 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
1697	if (timeout < now)	1861	if (timeout < now)
1698	{	1862	{
1699	// timeout occured, take action	1863	// timeout occurred, take action
1700	}	1864	}
1701	else	1865	else
1702	{	1866	{
1703	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1704	// the watcher to fire in last_activity + 60, which is	1868	// the watcher to fire in last_activity + 60, which is
…		…
1726	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
1727	callback, which will "do the right thing" and start the timer:	1891	callback, which will "do the right thing" and start the timer:
1728		1892
1729	ev_init (timer, callback);	1893	ev_init (timer, callback);
1730	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1731	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1732		1896
1733	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
1734	C<last_activity>, no libev calls at all:	1898	C<last_activity>, no libev calls at all:
1735		1899
1736	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1737		1901
1738	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
1739	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1740		1904
1741	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
…		…
1779		1943
1780	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1781		1945
1782	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
1783	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
1784	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
1785	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
1786	lots of events in one iteration.	1950	lots of events in one iteration.
1787		1951
1788	The relative timeouts are calculated relative to the C<ev_now ()>	1952	The relative timeouts are calculated relative to the C<ev_now ()>
1789	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
…		…
1906	}	2070	}
1907		2071
1908	ev_timer mytimer;	2072	ev_timer mytimer;
1909	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 */
1910	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1912		2076
1913	// 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":
1914	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1916		2080
…		…
1942		2106
1943	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
1944	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
1945	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
1946	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
1947	(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).
1948		2112
1949	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1950		2114
1951	=over 4	2115	=over 4
1952		2116
…		…
1987		2151
1988	Another way to think about it (for the mathematically inclined) is that	2152	Another way to think about it (for the mathematically inclined) is that
1989	C<ev_periodic> will try to run the callback in this mode at the next possible	2153	C<ev_periodic> will try to run the callback in this mode at the next possible
1990	time where C<time = offset (mod interval)>, regardless of any time jumps.	2154	time where C<time = offset (mod interval)>, regardless of any time jumps.
1991		2155
1992	For numerical stability it is preferable that the C<offset> value is near	2156	The C<interval> I<MUST> be positive, and for numerical stability, the
1993	C<ev_now ()> (the current time), but there is no range requirement for	2157	interval value should be higher than C<1/8192> (which is around 100
1994	this value, and in fact is often specified as zero.	2158	microseconds) and C<offset> should be higher than C<0> and should have
		2159	at most a similar magnitude as the current time (say, within a factor of
		2160	ten). Typical values for offset are, in fact, C<0> or something between
		2161	C<0> and C<interval>, which is also the recommended range.
1995		2162
1996	Note also that there is an upper limit to how often a timer can fire (CPU	2163	Note also that there is an upper limit to how often a timer can fire (CPU
1997	speed for example), so if C<interval> is very small then timing stability	2164	speed for example), so if C<interval> is very small then timing stability
1998	will of course deteriorate. Libev itself tries to be exact to be about one	2165	will of course deteriorate. Libev itself tries to be exact to be about one
1999	millisecond (if the OS supports it and the machine is fast enough).	2166	millisecond (if the OS supports it and the machine is fast enough).
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2247	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2248	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2249	potentially a lot of jitter, but good long-term stability.
2083		2250
2084	static void	2251	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2252	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2253	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2254	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2255	}
2089		2256
2090	ev_periodic hourly_tick;	2257	ev_periodic hourly_tick;
…		…
2113		2280
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2281	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2282
2116	Signal watchers will trigger an event when the process receives a specific	2283	Signal watchers will trigger an event when the process receives a specific
2117	signal one or more times. Even though signals are very asynchronous, libev	2284	signal one or more times. Even though signals are very asynchronous, libev
2118	will try it's best to deliver signals synchronously, i.e. as part of the	2285	will try its best to deliver signals synchronously, i.e. as part of the
2119	normal event processing, like any other event.	2286	normal event processing, like any other event.
2120		2287
2121	If you want signals to be delivered truly asynchronously, just use	2288	If you want signals to be delivered truly asynchronously, just use
2122	C<sigaction> as you would do without libev and forget about sharing	2289	C<sigaction> as you would do without libev and forget about sharing
2123	the signal. You can even use C<ev_async> from a signal handler to	2290	the signal. You can even use C<ev_async> from a signal handler to
…		…
2142	=head3 The special problem of inheritance over fork/execve/pthread_create	2309	=head3 The special problem of inheritance over fork/execve/pthread_create
2143		2310
2144	Both the signal mask (C<sigprocmask>) and the signal disposition	2311	Both the signal mask (C<sigprocmask>) and the signal disposition
2145	(C<sigaction>) are unspecified after starting a signal watcher (and after	2312	(C<sigaction>) are unspecified after starting a signal watcher (and after
2146	stopping it again), that is, libev might or might not block the signal,	2313	stopping it again), that is, libev might or might not block the signal,
2147	and might or might not set or restore the installed signal handler.	2314	and might or might not set or restore the installed signal handler (but
		2315	see C<EVFLAG_NOSIGMASK>).
2148		2316
2149	While this does not matter for the signal disposition (libev never	2317	While this does not matter for the signal disposition (libev never
2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2318	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2151	C<execve>), this matters for the signal mask: many programs do not expect	2319	C<execve>), this matters for the signal mask: many programs do not expect
2152	certain signals to be blocked.	2320	certain signals to be blocked.
…		…
2166		2334
2167	So I can't stress this enough: I<If you do not reset your signal mask when	2335	So I can't stress this enough: I<If you do not reset your signal mask when
2168	you expect it to be empty, you have a race condition in your code>. This	2336	you expect it to be empty, you have a race condition in your code>. This
2169	is not a libev-specific thing, this is true for most event libraries.	2337	is not a libev-specific thing, this is true for most event libraries.
2170		2338
		2339	=head3 The special problem of threads signal handling
		2340
		2341	POSIX threads has problematic signal handling semantics, specifically,
		2342	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2343	threads in a process block signals, which is hard to achieve.
		2344
		2345	When you want to use sigwait (or mix libev signal handling with your own
		2346	for the same signals), you can tackle this problem by globally blocking
		2347	all signals before creating any threads (or creating them with a fully set
		2348	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2349	loops. Then designate one thread as "signal receiver thread" which handles
		2350	these signals. You can pass on any signals that libev might be interested
		2351	in by calling C<ev_feed_signal>.
		2352
2171	=head3 Watcher-Specific Functions and Data Members	2353	=head3 Watcher-Specific Functions and Data Members
2172		2354
2173	=over 4	2355	=over 4
2174		2356
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2357	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2372	Example: Try to exit cleanly on SIGINT.
2191		2373
2192	static void	2374	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2375	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2376	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2377	ev_break (loop, EVBREAK_ALL);
2196	}	2378	}
2197		2379
2198	ev_signal signal_watcher;	2380	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2382	ev_signal_start (loop, &signal_watcher);
…		…
2586		2768
2587	Prepare and check watchers are usually (but not always) used in pairs:	2769	Prepare and check watchers are usually (but not always) used in pairs:
2588	prepare watchers get invoked before the process blocks and check watchers	2770	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2771	afterwards.
2590		2772
2591	You I<must not> call C<ev_loop> or similar functions that enter	2773	You I<must not> call C<ev_run> or similar functions that enter
2592	the current event loop from either C<ev_prepare> or C<ev_check>	2774	the current event loop from either C<ev_prepare> or C<ev_check>
2593	watchers. Other loops than the current one are fine, however. The	2775	watchers. Other loops than the current one are fine, however. The
2594	rationale behind this is that you do not need to check for recursion in	2776	rationale behind this is that you do not need to check for recursion in
2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2777	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2596	C<ev_check> so if you have one watcher of each kind they will always be	2778	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2764		2946
2765	if (timeout >= 0)	2947	if (timeout >= 0)
2766	// create/start timer	2948	// create/start timer
2767		2949
2768	// poll	2950	// poll
2769	ev_loop (EV_A_ 0);	2951	ev_run (EV_A_ 0);
2770		2952
2771	// stop timer again	2953	// stop timer again
2772	if (timeout >= 0)	2954	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	2955	ev_timer_stop (EV_A_ &to);
2774		2956
…		…
2852	if you do not want that, you need to temporarily stop the embed watcher).	3034	if you do not want that, you need to temporarily stop the embed watcher).
2853		3035
2854	=item ev_embed_sweep (loop, ev_embed *)	3036	=item ev_embed_sweep (loop, ev_embed *)
2855		3037
2856	Make a single, non-blocking sweep over the embedded loop. This works	3038	Make a single, non-blocking sweep over the embedded loop. This works
2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3039	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2858	appropriate way for embedded loops.	3040	appropriate way for embedded loops.
2859		3041
2860	=item struct ev_loop *other [read-only]	3042	=item struct ev_loop *other [read-only]
2861		3043
2862	The embedded event loop.	3044	The embedded event loop.
…		…
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3104	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923	handlers will be invoked, too, of course.	3105	handlers will be invoked, too, of course.
2924		3106
2925	=head3 The special problem of life after fork - how is it possible?	3107	=head3 The special problem of life after fork - how is it possible?
2926		3108
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3109	Most uses of C<fork()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3110	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3111	sequence should be handled by libev without any problems.
2930		3112
2931	This changes when the application actually wants to do event handling	3113	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3114	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	disadvantage of having to use multiple event loops (which do not support	3130	disadvantage of having to use multiple event loops (which do not support
2949	signal watchers).	3131	signal watchers).
2950		3132
2951	When this is not possible, or you want to use the default loop for	3133	When this is not possible, or you want to use the default loop for
2952	other reasons, then in the process that wants to start "fresh", call	3134	other reasons, then in the process that wants to start "fresh", call
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3135	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3136	Destroying the default loop will "orphan" (not stop) all registered
2955	have to be careful not to execute code that modifies those watchers. Note	3137	watchers, so you have to be careful not to execute code that modifies
2956	also that in that case, you have to re-register any signal watchers.	3138	those watchers. Note also that in that case, you have to re-register any
		3139	signal watchers.
2957		3140
2958	=head3 Watcher-Specific Functions and Data Members	3141	=head3 Watcher-Specific Functions and Data Members
2959		3142
2960	=over 4	3143	=over 4
2961		3144
2962	=item ev_fork_init (ev_signal *, callback)	3145	=item ev_fork_init (ev_fork *, callback)
2963		3146
2964	Initialises and configures the fork watcher - it has no parameters of any	3147	Initialises and configures the fork watcher - it has no parameters of any
2965	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3148	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2966	believe me.	3149	really.
2967		3150
2968	=back	3151	=back
2969		3152
2970		3153
		3154	=head2 C<ev_cleanup> - even the best things end
		3155
		3156	Cleanup watchers are called just before the event loop is being destroyed
		3157	by a call to C<ev_loop_destroy>.
		3158
		3159	While there is no guarantee that the event loop gets destroyed, cleanup
		3160	watchers provide a convenient method to install cleanup hooks for your
		3161	program, worker threads and so on - you just to make sure to destroy the
		3162	loop when you want them to be invoked.
		3163
		3164	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3165	all other watchers, they do not keep a reference to the event loop (which
		3166	makes a lot of sense if you think about it). Like all other watchers, you
		3167	can call libev functions in the callback, except C<ev_cleanup_start>.
		3168
		3169	=head3 Watcher-Specific Functions and Data Members
		3170
		3171	=over 4
		3172
		3173	=item ev_cleanup_init (ev_cleanup *, callback)
		3174
		3175	Initialises and configures the cleanup watcher - it has no parameters of
		3176	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3177	pointless, I assure you.
		3178
		3179	=back
		3180
		3181	Example: Register an atexit handler to destroy the default loop, so any
		3182	cleanup functions are called.
		3183
		3184	static void
		3185	program_exits (void)
		3186	{
		3187	ev_loop_destroy (EV_DEFAULT_UC);
		3188	}
		3189
		3190	...
		3191	atexit (program_exits);
		3192
		3193
2971	=head2 C<ev_async> - how to wake up another event loop	3194	=head2 C<ev_async> - how to wake up an event loop
2972		3195
2973	In general, you cannot use an C<ev_loop> from multiple threads or other	3196	In general, you cannot use an C<ev_loop> from multiple threads or other
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3197	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3198	loops - those are of course safe to use in different threads).
2976		3199
2977	Sometimes, however, you need to wake up another event loop you do not	3200	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3201	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3202	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3203	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3204
2983	This functionality is very similar to C<ev_signal> watchers, as signals,	3205	This functionality is very similar to C<ev_signal> watchers, as signals,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3206	too, are asynchronous in nature, and signals, too, will be compressed
2985	(i.e. the number of callback invocations may be less than the number of	3207	(i.e. the number of callback invocations may be less than the number of
2986	C<ev_async_sent> calls).	3208	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3209	of "global async watchers" by using a watcher on an otherwise unused
		3210	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3211	even without knowing which loop owns the signal.
2987		3212
2988	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3213	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2989	just the default loop.	3214	just the default loop.
2990		3215
2991	=head3 Queueing	3216	=head3 Queueing
…		…
3086	trust me.	3311	trust me.
3087		3312
3088	=item ev_async_send (loop, ev_async *)	3313	=item ev_async_send (loop, ev_async *)
3089		3314
3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3315	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3316	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3317	returns.
		3318
3092	C<ev_feed_event>, this call is safe to do from other threads, signal or	3319	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3320	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3094	section below on what exactly this means).	3321	embedding section below on what exactly this means).
3095		3322
3096	Note that, as with other watchers in libev, multiple events might get	3323	Note that, as with other watchers in libev, multiple events might get
3097	compressed into a single callback invocation (another way to look at this	3324	compressed into a single callback invocation (another way to look at this
3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3325	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3099	reset when the event loop detects that).	3326	reset when the event loop detects that).
…		…
3141		3368
3142	If C<timeout> is less than 0, then no timeout watcher will be	3369	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3370	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3371	repeat = 0) will be started. C<0> is a valid timeout.
3145		3372
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3373	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3374	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3375	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3376	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3377	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3378	events precedence.
3152		3379
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3380	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3381
3155	static void stdin_ready (int revents, void *arg)	3382	static void stdin_ready (int revents, void *arg)
3156	{	3383	{
3157	if (revents & EV_READ)	3384	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3385	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3386	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3387	/* doh, nothing entered */;
3161	}	3388	}
3162		3389
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3390	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3391
…		…
3167	Feed an event on the given fd, as if a file descriptor backend detected	3394	Feed an event on the given fd, as if a file descriptor backend detected
3168	the given events it.	3395	the given events it.
3169		3396
3170	=item ev_feed_signal_event (loop, int signum)	3397	=item ev_feed_signal_event (loop, int signum)
3171		3398
3172	Feed an event as if the given signal occurred (C<loop> must be the default	3399	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3173	loop!).	3400	which is async-safe.
3174		3401
3175	=back	3402	=back
		3403
		3404
		3405	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3406
		3407	This section explains some common idioms that are not immediately
		3408	obvious. Note that examples are sprinkled over the whole manual, and this
		3409	section only contains stuff that wouldn't fit anywhere else.
		3410
		3411	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3412
		3413	Each watcher has, by default, a C<void *data> member that you can read
		3414	or modify at any time: libev will completely ignore it. This can be used
		3415	to associate arbitrary data with your watcher. If you need more data and
		3416	don't want to allocate memory separately and store a pointer to it in that
		3417	data member, you can also "subclass" the watcher type and provide your own
		3418	data:
		3419
		3420	struct my_io
		3421	{
		3422	ev_io io;
		3423	int otherfd;
		3424	void *somedata;
		3425	struct whatever *mostinteresting;
		3426	};
		3427
		3428	...
		3429	struct my_io w;
		3430	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3431
		3432	And since your callback will be called with a pointer to the watcher, you
		3433	can cast it back to your own type:
		3434
		3435	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3436	{
		3437	struct my_io *w = (struct my_io *)w_;
		3438	...
		3439	}
		3440
		3441	More interesting and less C-conformant ways of casting your callback
		3442	function type instead have been omitted.
		3443
		3444	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3445
		3446	Another common scenario is to use some data structure with multiple
		3447	embedded watchers, in effect creating your own watcher that combines
		3448	multiple libev event sources into one "super-watcher":
		3449
		3450	struct my_biggy
		3451	{
		3452	int some_data;
		3453	ev_timer t1;
		3454	ev_timer t2;
		3455	}
		3456
		3457	In this case getting the pointer to C<my_biggy> is a bit more
		3458	complicated: Either you store the address of your C<my_biggy> struct in
		3459	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3460	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3461	real programmers):
		3462
		3463	#include <stddef.h>
		3464
		3465	static void
		3466	t1_cb (EV_P_ ev_timer *w, int revents)
		3467	{
		3468	struct my_biggy big = (struct my_biggy *)
		3469	(((char *)w) - offsetof (struct my_biggy, t1));
		3470	}
		3471
		3472	static void
		3473	t2_cb (EV_P_ ev_timer *w, int revents)
		3474	{
		3475	struct my_biggy big = (struct my_biggy *)
		3476	(((char *)w) - offsetof (struct my_biggy, t2));
		3477	}
		3478
		3479	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3480
		3481	Often (especially in GUI toolkits) there are places where you have
		3482	I<modal> interaction, which is most easily implemented by recursively
		3483	invoking C<ev_run>.
		3484
		3485	This brings the problem of exiting - a callback might want to finish the
		3486	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3487	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3488	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3489	other combination: In these cases, C<ev_break> will not work alone.
		3490
		3491	The solution is to maintain "break this loop" variable for each C<ev_run>
		3492	invocation, and use a loop around C<ev_run> until the condition is
		3493	triggered, using C<EVRUN_ONCE>:
		3494
		3495	// main loop
		3496	int exit_main_loop = 0;
		3497
		3498	while (!exit_main_loop)
		3499	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3500
		3501	// in a model watcher
		3502	int exit_nested_loop = 0;
		3503
		3504	while (!exit_nested_loop)
		3505	ev_run (EV_A_ EVRUN_ONCE);
		3506
		3507	To exit from any of these loops, just set the corresponding exit variable:
		3508
		3509	// exit modal loop
		3510	exit_nested_loop = 1;
		3511
		3512	// exit main program, after modal loop is finished
		3513	exit_main_loop = 1;
		3514
		3515	// exit both
		3516	exit_main_loop = exit_nested_loop = 1;
		3517
		3518	=head2 THREAD LOCKING EXAMPLE
		3519
		3520	Here is a fictitious example of how to run an event loop in a different
		3521	thread from where callbacks are being invoked and watchers are
		3522	created/added/removed.
		3523
		3524	For a real-world example, see the C<EV::Loop::Async> perl module,
		3525	which uses exactly this technique (which is suited for many high-level
		3526	languages).
		3527
		3528	The example uses a pthread mutex to protect the loop data, a condition
		3529	variable to wait for callback invocations, an async watcher to notify the
		3530	event loop thread and an unspecified mechanism to wake up the main thread.
		3531
		3532	First, you need to associate some data with the event loop:
		3533
		3534	typedef struct {
		3535	mutex_t lock; /* global loop lock */
		3536	ev_async async_w;
		3537	thread_t tid;
		3538	cond_t invoke_cv;
		3539	} userdata;
		3540
		3541	void prepare_loop (EV_P)
		3542	{
		3543	// for simplicity, we use a static userdata struct.
		3544	static userdata u;
		3545
		3546	ev_async_init (&u->async_w, async_cb);
		3547	ev_async_start (EV_A_ &u->async_w);
		3548
		3549	pthread_mutex_init (&u->lock, 0);
		3550	pthread_cond_init (&u->invoke_cv, 0);
		3551
		3552	// now associate this with the loop
		3553	ev_set_userdata (EV_A_ u);
		3554	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3555	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3556
		3557	// then create the thread running ev_run
		3558	pthread_create (&u->tid, 0, l_run, EV_A);
		3559	}
		3560
		3561	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3562	solely to wake up the event loop so it takes notice of any new watchers
		3563	that might have been added:
		3564
		3565	static void
		3566	async_cb (EV_P_ ev_async *w, int revents)
		3567	{
		3568	// just used for the side effects
		3569	}
		3570
		3571	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3572	protecting the loop data, respectively.
		3573
		3574	static void
		3575	l_release (EV_P)
		3576	{
		3577	userdata *u = ev_userdata (EV_A);
		3578	pthread_mutex_unlock (&u->lock);
		3579	}
		3580
		3581	static void
		3582	l_acquire (EV_P)
		3583	{
		3584	userdata *u = ev_userdata (EV_A);
		3585	pthread_mutex_lock (&u->lock);
		3586	}
		3587
		3588	The event loop thread first acquires the mutex, and then jumps straight
		3589	into C<ev_run>:
		3590
		3591	void *
		3592	l_run (void *thr_arg)
		3593	{
		3594	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3595
		3596	l_acquire (EV_A);
		3597	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3598	ev_run (EV_A_ 0);
		3599	l_release (EV_A);
		3600
		3601	return 0;
		3602	}
		3603
		3604	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3605	signal the main thread via some unspecified mechanism (signals? pipe
		3606	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3607	have been called (in a while loop because a) spurious wakeups are possible
		3608	and b) skipping inter-thread-communication when there are no pending
		3609	watchers is very beneficial):
		3610
		3611	static void
		3612	l_invoke (EV_P)
		3613	{
		3614	userdata *u = ev_userdata (EV_A);
		3615
		3616	while (ev_pending_count (EV_A))
		3617	{
		3618	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3619	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3620	}
		3621	}
		3622
		3623	Now, whenever the main thread gets told to invoke pending watchers, it
		3624	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3625	thread to continue:
		3626
		3627	static void
		3628	real_invoke_pending (EV_P)
		3629	{
		3630	userdata *u = ev_userdata (EV_A);
		3631
		3632	pthread_mutex_lock (&u->lock);
		3633	ev_invoke_pending (EV_A);
		3634	pthread_cond_signal (&u->invoke_cv);
		3635	pthread_mutex_unlock (&u->lock);
		3636	}
		3637
		3638	Whenever you want to start/stop a watcher or do other modifications to an
		3639	event loop, you will now have to lock:
		3640
		3641	ev_timer timeout_watcher;
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3645
		3646	pthread_mutex_lock (&u->lock);
		3647	ev_timer_start (EV_A_ &timeout_watcher);
		3648	ev_async_send (EV_A_ &u->async_w);
		3649	pthread_mutex_unlock (&u->lock);
		3650
		3651	Note that sending the C<ev_async> watcher is required because otherwise
		3652	an event loop currently blocking in the kernel will have no knowledge
		3653	about the newly added timer. By waking up the loop it will pick up any new
		3654	watchers in the next event loop iteration.
		3655
		3656	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3657
		3658	While the overhead of a callback that e.g. schedules a thread is small, it
		3659	is still an overhead. If you embed libev, and your main usage is with some
		3660	kind of threads or coroutines, you might want to customise libev so that
		3661	doesn't need callbacks anymore.
		3662
		3663	Imagine you have coroutines that you can switch to using a function
		3664	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3665	and that due to some magic, the currently active coroutine is stored in a
		3666	global called C<current_coro>. Then you can build your own "wait for libev
		3667	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3668	the differing C<;> conventions):
		3669
		3670	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3671	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3672
		3673	That means instead of having a C callback function, you store the
		3674	coroutine to switch to in each watcher, and instead of having libev call
		3675	your callback, you instead have it switch to that coroutine.
		3676
		3677	A coroutine might now wait for an event with a function called
		3678	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3679	matter when, or whether the watcher is active or not when this function is
		3680	called):
		3681
		3682	void
		3683	wait_for_event (ev_watcher *w)
		3684	{
		3685	ev_cb_set (w) = current_coro;
		3686	switch_to (libev_coro);
		3687	}
		3688
		3689	That basically suspends the coroutine inside C<wait_for_event> and
		3690	continues the libev coroutine, which, when appropriate, switches back to
		3691	this or any other coroutine. I am sure if you sue this your own :)
		3692
		3693	You can do similar tricks if you have, say, threads with an event queue -
		3694	instead of storing a coroutine, you store the queue object and instead of
		3695	switching to a coroutine, you push the watcher onto the queue and notify
		3696	any waiters.
		3697
		3698	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3699	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3700
		3701	// my_ev.h
		3702	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3703	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3704	#include "../libev/ev.h"
		3705
		3706	// my_ev.c
		3707	#define EV_H "my_ev.h"
		3708	#include "../libev/ev.c"
		3709
		3710	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3711	F<my_ev.c> into your project. When properly specifying include paths, you
		3712	can even use F<ev.h> as header file name directly.
3176		3713
3177		3714
3178	=head1 LIBEVENT EMULATION	3715	=head1 LIBEVENT EMULATION
3179		3716
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3717	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3718	emulate the internals of libevent, so here are some usage hints:
3182		3719
3183	=over 4	3720	=over 4
		3721
		3722	=item * Only the libevent-1.4.1-beta API is being emulated.
		3723
		3724	This was the newest libevent version available when libev was implemented,
		3725	and is still mostly unchanged in 2010.
3184		3726
3185	=item * Use it by including <event.h>, as usual.	3727	=item * Use it by including <event.h>, as usual.
3186		3728
3187	=item * The following members are fully supported: ev_base, ev_callback,	3729	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3730	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3736	=item * Priorities are not currently supported. Initialising priorities
3195	will fail and all watchers will have the same priority, even though there	3737	will fail and all watchers will have the same priority, even though there
3196	is an ev_pri field.	3738	is an ev_pri field.
3197		3739
3198	=item * In libevent, the last base created gets the signals, in libev, the	3740	=item * In libevent, the last base created gets the signals, in libev, the
3199	first base created (== the default loop) gets the signals.	3741	base that registered the signal gets the signals.
3200		3742
3201	=item * Other members are not supported.	3743	=item * Other members are not supported.
3202		3744
3203	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3745	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3204	to use the libev header file and library.	3746	to use the libev header file and library.
…		…
3223	Care has been taken to keep the overhead low. The only data member the C++	3765	Care has been taken to keep the overhead low. The only data member the C++
3224	classes add (compared to plain C-style watchers) is the event loop pointer	3766	classes add (compared to plain C-style watchers) is the event loop pointer
3225	that the watcher is associated with (or no additional members at all if	3767	that the watcher is associated with (or no additional members at all if
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	3768	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		3769
3228	Currently, functions, and static and non-static member functions can be	3770	Currently, functions, static and non-static member functions and classes
3229	used as callbacks. Other types should be easy to add as long as they only	3771	with C<operator ()> can be used as callbacks. Other types should be easy
3230	need one additional pointer for context. If you need support for other	3772	to add as long as they only need one additional pointer for context. If
3231	types of functors please contact the author (preferably after implementing	3773	you need support for other types of functors please contact the author
3232	it).	3774	(preferably after implementing it).
3233		3775
3234	Here is a list of things available in the C<ev> namespace:	3776	Here is a list of things available in the C<ev> namespace:
3235		3777
3236	=over 4	3778	=over 4
3237		3779
…		…
3298	myclass obj;	3840	myclass obj;
3299	ev::io iow;	3841	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	3842	iow.set <myclass, &myclass::io_cb> (&obj);
3301		3843
3302	=item w->set (object *)	3844	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		3845
3306	This is a variation of a method callback - leaving out the method to call	3846	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	3847	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	3848	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	3849	the time. Incidentally, you can then also leave out the template argument
…		…
3349	Associates a different C<struct ev_loop> with this watcher. You can only	3889	Associates a different C<struct ev_loop> with this watcher. You can only
3350	do this when the watcher is inactive (and not pending either).	3890	do this when the watcher is inactive (and not pending either).
3351		3891
3352	=item w->set ([arguments])	3892	=item w->set ([arguments])
3353		3893
3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3894	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3355	called at least once. Unlike the C counterpart, an active watcher gets	3895	method or a suitable start method must be called at least once. Unlike the
3356	automatically stopped and restarted when reconfiguring it with this	3896	C counterpart, an active watcher gets automatically stopped and restarted
3357	method.	3897	when reconfiguring it with this method.
3358		3898
3359	=item w->start ()	3899	=item w->start ()
3360		3900
3361	Starts the watcher. Note that there is no C<loop> argument, as the	3901	Starts the watcher. Note that there is no C<loop> argument, as the
3362	constructor already stores the event loop.	3902	constructor already stores the event loop.
3363		3903
		3904	=item w->start ([arguments])
		3905
		3906	Instead of calling C<set> and C<start> methods separately, it is often
		3907	convenient to wrap them in one call. Uses the same type of arguments as
		3908	the configure C<set> method of the watcher.
		3909
3364	=item w->stop ()	3910	=item w->stop ()
3365		3911
3366	Stops the watcher if it is active. Again, no C<loop> argument.	3912	Stops the watcher if it is active. Again, no C<loop> argument.
3367		3913
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3914	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		3926
3381	=back	3927	=back
3382		3928
3383	=back	3929	=back
3384		3930
3385	Example: Define a class with an IO and idle watcher, start one of them in	3931	Example: Define a class with two I/O and idle watchers, start the I/O
3386	the constructor.	3932	watchers in the constructor.
3387		3933
3388	class myclass	3934	class myclass
3389	{	3935	{
3390	ev::io io ; void io_cb (ev::io &w, int revents);	3936	ev::io io ; void io_cb (ev::io &w, int revents);
		3937	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3938	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		3939
3393	myclass (int fd)	3940	myclass (int fd)
3394	{	3941	{
3395	io .set <myclass, &myclass::io_cb > (this);	3942	io .set <myclass, &myclass::io_cb > (this);
		3943	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	3944	idle.set <myclass, &myclass::idle_cb> (this);
3397		3945
3398	io.start (fd, ev::READ);	3946	io.set (fd, ev::WRITE); // configure the watcher
		3947	io.start (); // start it whenever convenient
		3948
		3949	io2.start (fd, ev::READ); // set + start in one call
3399	}	3950	}
3400	};	3951	};
3401		3952
3402		3953
3403	=head1 OTHER LANGUAGE BINDINGS	3954	=head1 OTHER LANGUAGE BINDINGS
…		…
3477	loop argument"). The C<EV_A> form is used when this is the sole argument,	4028	loop argument"). The C<EV_A> form is used when this is the sole argument,
3478	C<EV_A_> is used when other arguments are following. Example:	4029	C<EV_A_> is used when other arguments are following. Example:
3479		4030
3480	ev_unref (EV_A);	4031	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	4032	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	4033	ev_run (EV_A_ 0);
3483		4034
3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4035	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3485	which is often provided by the following macro.	4036	which is often provided by the following macro.
3486		4037
3487	=item C<EV_P>, C<EV_P_>	4038	=item C<EV_P>, C<EV_P_>
…		…
3527	}	4078	}
3528		4079
3529	ev_check check;	4080	ev_check check;
3530	ev_check_init (&check, check_cb);	4081	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4082	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4083	ev_run (EV_DEFAULT_ 0);
3533		4084
3534	=head1 EMBEDDING	4085	=head1 EMBEDDING
3535		4086
3536	Libev can (and often is) directly embedded into host	4087	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4088	applications. Examples of applications that embed it include the Deliantra
…		…
3622	define before including (or compiling) any of its files. The default in	4173	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4174	the absence of autoconf is documented for every option.
3624		4175
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4176	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4177	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4178	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4179	to a compiled library. All other symbols change the ABI, which means all
3629	users of libev and the libev code itself must be compiled with compatible	4180	users of libev and the libev code itself must be compiled with compatible
3630	settings.	4181	settings.
3631		4182
3632	=over 4	4183	=over 4
		4184
		4185	=item EV_COMPAT3 (h)
		4186
		4187	Backwards compatibility is a major concern for libev. This is why this
		4188	release of libev comes with wrappers for the functions and symbols that
		4189	have been renamed between libev version 3 and 4.
		4190
		4191	You can disable these wrappers (to test compatibility with future
		4192	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4193	sources. This has the additional advantage that you can drop the C<struct>
		4194	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4195	typedef in that case.
		4196
		4197	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4198	and in some even more future version the compatibility code will be
		4199	removed completely.
3633		4200
3634	=item EV_STANDALONE (h)	4201	=item EV_STANDALONE (h)
3635		4202
3636	Must always be C<1> if you do not use autoconf configuration, which	4203	Must always be C<1> if you do not use autoconf configuration, which
3637	keeps libev from including F<config.h>, and it also defines dummy	4204	keeps libev from including F<config.h>, and it also defines dummy
…		…
3639	supported). It will also not define any of the structs usually found in	4206	supported). It will also not define any of the structs usually found in
3640	F<event.h> that are not directly supported by the libev core alone.	4207	F<event.h> that are not directly supported by the libev core alone.
3641		4208
3642	In standalone mode, libev will still try to automatically deduce the	4209	In standalone mode, libev will still try to automatically deduce the
3643	configuration, but has to be more conservative.	4210	configuration, but has to be more conservative.
		4211
		4212	=item EV_USE_FLOOR
		4213
		4214	If defined to be C<1>, libev will use the C<floor ()> function for its
		4215	periodic reschedule calculations, otherwise libev will fall back on a
		4216	portable (slower) implementation. If you enable this, you usually have to
		4217	link against libm or something equivalent. Enabling this when the C<floor>
		4218	function is not available will fail, so the safe default is to not enable
		4219	this.
3644		4220
3645	=item EV_USE_MONOTONIC	4221	=item EV_USE_MONOTONIC
3646		4222
3647	If defined to be C<1>, libev will try to detect the availability of the	4223	If defined to be C<1>, libev will try to detect the availability of the
3648	monotonic clock option at both compile time and runtime. Otherwise no	4224	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3838	fine.	4414	fine.
3839		4415
3840	If your embedding application does not need any priorities, defining these	4416	If your embedding application does not need any priorities, defining these
3841	both to C<0> will save some memory and CPU.	4417	both to C<0> will save some memory and CPU.
3842		4418
3843	=item EV_PERIODIC_ENABLE	4419	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4420	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4421	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844		4422
3845	If undefined or defined to be C<1>, then periodic timers are supported. If	4423	If undefined or defined to be C<1> (and the platform supports it), then
3846	defined to be C<0>, then they are not. Disabling them saves a few kB of	4424	the respective watcher type is supported. If defined to be C<0>, then it
3847	code.	4425	is not. Disabling watcher types mainly saves code size.
3848		4426
3849	=item EV_IDLE_ENABLE	4427	=item EV_FEATURES
3850
3851	If undefined or defined to be C<1>, then idle watchers are supported. If
3852	defined to be C<0>, then they are not. Disabling them saves a few kB of
3853	code.
3854
3855	=item EV_EMBED_ENABLE
3856
3857	If undefined or defined to be C<1>, then embed watchers are supported. If
3858	defined to be C<0>, then they are not. Embed watchers rely on most other
3859	watcher types, which therefore must not be disabled.
3860
3861	=item EV_STAT_ENABLE
3862
3863	If undefined or defined to be C<1>, then stat watchers are supported. If
3864	defined to be C<0>, then they are not.
3865
3866	=item EV_FORK_ENABLE
3867
3868	If undefined or defined to be C<1>, then fork watchers are supported. If
3869	defined to be C<0>, then they are not.
3870
3871	=item EV_SIGNAL_ENABLE
3872
3873	If undefined or defined to be C<1>, then signal watchers are supported. If
3874	defined to be C<0>, then they are not.
3875
3876	=item EV_ASYNC_ENABLE
3877
3878	If undefined or defined to be C<1>, then async watchers are supported. If
3879	defined to be C<0>, then they are not.
3880
3881	=item EV_CHILD_ENABLE
3882
3883	If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884	child watchers are supported. If defined to be C<0>, then they are not.
3885
3886	=item EV_MINIMAL
3887		4428
3888	If you need to shave off some kilobytes of code at the expense of some	4429	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), define this symbol to C<1>. Currently this	4430	speed (but with the full API), you can define this symbol to request
3890	is used to override some inlining decisions, saves roughly 30% code size	4431	certain subsets of functionality. The default is to enable all features
3891	on amd64. It also selects a much smaller 2-heap for timer management over	4432	that can be enabled on the platform.
3892	the default 4-heap.
3893		4433
3894	You can save even more by disabling watcher types you do not need	4434	A typical way to use this symbol is to define it to C<0> (or to a bitset
3895	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4435	with some broad features you want) and then selectively re-enable
3896	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4436	additional parts you want, for example if you want everything minimal,
3897	eventfd and signalfd will further help, and disabling backends one doesn't	4437	but multiple event loop support, async and child watchers and the poll
3898	need (e.g. poll, epoll, kqueue, ports) will help further.	4438	backend, use this:
3899		4439
3900	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4440	#define EV_FEATURES 0
3901	provide a bare-bones event library. See C<ev.h> for details on what parts
3902	of the API are still available, and do not complain if this subset changes
3903	over time.
3904
3905	This example set of settings reduces the compiled size of libev from 24Kb
3906	to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907	an effect on the amount of memory used). With an intelligent-enough linker
3908	further unused functions might be left out as well automatically.
3909
3910	// tuning and API changes
3911	#define EV_MINIMAL 2
3912	#define EV_MULTIPLICITY 0	4441	#define EV_MULTIPLICITY 1
3913	#define EV_MINPRI 0
3914	#define EV_MAXPRI 0
3915
3916	// OS-specific backends
3917	#define EV_USE_INOTIFY 0
3918	#define EV_USE_EVENTFD 0
3919	#define EV_USE_SIGNALFD 0
3920	#define EV_USE_REALTIME 0
3921	#define EV_USE_MONOTONIC 0
3922	#define EV_USE_CLOCK_SYSCALL 0
3923
3924	// disable all backends except select
3925	#define EV_USE_POLL 0	4442	#define EV_USE_POLL 1
3926	#define EV_USE_PORT 0
3927	#define EV_USE_KQUEUE 0
3928	#define EV_USE_EPOLL 0
3929
3930	// disable all watcher types that cna be disabled
3931	#define EV_STAT_ENABLE 0
3932	#define EV_PERIODIC_ENABLE 0
3933	#define EV_IDLE_ENABLE 0
3934	#define EV_FORK_ENABLE 0
3935	#define EV_SIGNAL_ENABLE 0
3936	#define EV_CHILD_ENABLE 0	4443	#define EV_CHILD_ENABLE 1
3937	#define EV_ASYNC_ENABLE 0	4444	#define EV_ASYNC_ENABLE 1
3938	#define EV_EMBED_ENABLE 0	4445
		4446	The actual value is a bitset, it can be a combination of the following
		4447	values:
		4448
		4449	=over 4
		4450
		4451	=item C<1> - faster/larger code
		4452
		4453	Use larger code to speed up some operations.
		4454
		4455	Currently this is used to override some inlining decisions (enlarging the
		4456	code size by roughly 30% on amd64).
		4457
		4458	When optimising for size, use of compiler flags such as C<-Os> with
		4459	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4460	assertions.
		4461
		4462	=item C<2> - faster/larger data structures
		4463
		4464	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4465	hash table sizes and so on. This will usually further increase code size
		4466	and can additionally have an effect on the size of data structures at
		4467	runtime.
		4468
		4469	=item C<4> - full API configuration
		4470
		4471	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4472	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4473
		4474	=item C<8> - full API
		4475
		4476	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4477	details on which parts of the API are still available without this
		4478	feature, and do not complain if this subset changes over time.
		4479
		4480	=item C<16> - enable all optional watcher types
		4481
		4482	Enables all optional watcher types. If you want to selectively enable
		4483	only some watcher types other than I/O and timers (e.g. prepare,
		4484	embed, async, child...) you can enable them manually by defining
		4485	C<EV_watchertype_ENABLE> to C<1> instead.
		4486
		4487	=item C<32> - enable all backends
		4488
		4489	This enables all backends - without this feature, you need to enable at
		4490	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4491
		4492	=item C<64> - enable OS-specific "helper" APIs
		4493
		4494	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4495	default.
		4496
		4497	=back
		4498
		4499	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4500	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4501	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4502	watchers, timers and monotonic clock support.
		4503
		4504	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4505	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4506	your program might be left out as well - a binary starting a timer and an
		4507	I/O watcher then might come out at only 5Kb.
3939		4508
3940	=item EV_AVOID_STDIO	4509	=item EV_AVOID_STDIO
3941		4510
3942	If this is set to C<1> at compiletime, then libev will avoid using stdio	4511	If this is set to C<1> at compiletime, then libev will avoid using stdio
3943	functions (printf, scanf, perror etc.). This will increase the codesize	4512	functions (printf, scanf, perror etc.). This will increase the code size
3944	somewhat, but if your program doesn't otherwise depend on stdio and your	4513	somewhat, but if your program doesn't otherwise depend on stdio and your
3945	libc allows it, this avoids linking in the stdio library which is quite	4514	libc allows it, this avoids linking in the stdio library which is quite
3946	big.	4515	big.
3947		4516
3948	Note that error messages might become less precise when this option is	4517	Note that error messages might become less precise when this option is
…		…
3952		4521
3953	The highest supported signal number, +1 (or, the number of	4522	The highest supported signal number, +1 (or, the number of
3954	signals): Normally, libev tries to deduce the maximum number of signals	4523	signals): Normally, libev tries to deduce the maximum number of signals
3955	automatically, but sometimes this fails, in which case it can be	4524	automatically, but sometimes this fails, in which case it can be
3956	specified. Also, using a lower number than detected (C<32> should be	4525	specified. Also, using a lower number than detected (C<32> should be
3957	good for about any system in existance) can save some memory, as libev	4526	good for about any system in existence) can save some memory, as libev
3958	statically allocates some 12-24 bytes per signal number.	4527	statically allocates some 12-24 bytes per signal number.
3959		4528
3960	=item EV_PID_HASHSIZE	4529	=item EV_PID_HASHSIZE
3961		4530
3962	C<ev_child> watchers use a small hash table to distribute workload by	4531	C<ev_child> watchers use a small hash table to distribute workload by
3963	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4532	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964	than enough. If you need to manage thousands of children you might want to	4533	usually more than enough. If you need to manage thousands of children you
3965	increase this value (I<must> be a power of two).	4534	might want to increase this value (I<must> be a power of two).
3966		4535
3967	=item EV_INOTIFY_HASHSIZE	4536	=item EV_INOTIFY_HASHSIZE
3968		4537
3969	C<ev_stat> watchers use a small hash table to distribute workload by	4538	C<ev_stat> watchers use a small hash table to distribute workload by
3970	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4539	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971	usually more than enough. If you need to manage thousands of C<ev_stat>	4540	disabled), usually more than enough. If you need to manage thousands of
3972	watchers you might want to increase this value (I<must> be a power of	4541	C<ev_stat> watchers you might want to increase this value (I<must> be a
3973	two).	4542	power of two).
3974		4543
3975	=item EV_USE_4HEAP	4544	=item EV_USE_4HEAP
3976		4545
3977	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4546	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4547	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4548	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980	faster performance with many (thousands) of watchers.	4549	faster performance with many (thousands) of watchers.
3981		4550
3982	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
3983	(disabled).	4552	will be C<0>.
3984		4553
3985	=item EV_HEAP_CACHE_AT	4554	=item EV_HEAP_CACHE_AT
3986		4555
3987	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4556	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4557	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4558	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4559	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991	but avoids random read accesses on heap changes. This improves performance	4560	but avoids random read accesses on heap changes. This improves performance
3992	noticeably with many (hundreds) of watchers.	4561	noticeably with many (hundreds) of watchers.
3993		4562
3994	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4563	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995	(disabled).	4564	will be C<0>.
3996		4565
3997	=item EV_VERIFY	4566	=item EV_VERIFY
3998		4567
3999	Controls how much internal verification (see C<ev_loop_verify ()>) will	4568	Controls how much internal verification (see C<ev_verify ()>) will
4000	be done: If set to C<0>, no internal verification code will be compiled	4569	be done: If set to C<0>, no internal verification code will be compiled
4001	in. If set to C<1>, then verification code will be compiled in, but not	4570	in. If set to C<1>, then verification code will be compiled in, but not
4002	called. If set to C<2>, then the internal verification code will be	4571	called. If set to C<2>, then the internal verification code will be
4003	called once per loop, which can slow down libev. If set to C<3>, then the	4572	called once per loop, which can slow down libev. If set to C<3>, then the
4004	verification code will be called very frequently, which will slow down	4573	verification code will be called very frequently, which will slow down
4005	libev considerably.	4574	libev considerably.
4006		4575
4007	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4576	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008	C<0>.	4577	will be C<0>.
4009		4578
4010	=item EV_COMMON	4579	=item EV_COMMON
4011		4580
4012	By default, all watchers have a C<void *data> member. By redefining	4581	By default, all watchers have a C<void *data> member. By redefining
4013	this macro to a something else you can include more and other types of	4582	this macro to something else you can include more and other types of
4014	members. You have to define it each time you include one of the files,	4583	members. You have to define it each time you include one of the files,
4015	though, and it must be identical each time.	4584	though, and it must be identical each time.
4016		4585
4017	For example, the perl EV module uses something like this:	4586	For example, the perl EV module uses something like this:
4018		4587
…		…
4071	file.	4640	file.
4072		4641
4073	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4642	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074	that everybody includes and which overrides some configure choices:	4643	that everybody includes and which overrides some configure choices:
4075		4644
4076	#define EV_MINIMAL 1	4645	#define EV_FEATURES 8
4077	#define EV_USE_POLL 0	4646	#define EV_USE_SELECT 1
4078	#define EV_MULTIPLICITY 0
4079	#define EV_PERIODIC_ENABLE 0	4647	#define EV_PREPARE_ENABLE 1
		4648	#define EV_IDLE_ENABLE 1
4080	#define EV_STAT_ENABLE 0	4649	#define EV_SIGNAL_ENABLE 1
4081	#define EV_FORK_ENABLE 0	4650	#define EV_CHILD_ENABLE 1
		4651	#define EV_USE_STDEXCEPT 0
4082	#define EV_CONFIG_H <config.h>	4652	#define EV_CONFIG_H <config.h>
4083	#define EV_MINPRI 0
4084	#define EV_MAXPRI 0
4085		4653
4086	#include "ev++.h"	4654	#include "ev++.h"
4087		4655
4088	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4656	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089		4657
4090	#include "ev_cpp.h"	4658	#include "ev_cpp.h"
4091	#include "ev.c"	4659	#include "ev.c"
4092		4660
4093	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4661	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4094		4662
4095	=head2 THREADS AND COROUTINES	4663	=head2 THREADS AND COROUTINES
4096		4664
4097	=head3 THREADS	4665	=head3 THREADS
4098		4666
…		…
4149	default loop and triggering an C<ev_async> watcher from the default loop	4717	default loop and triggering an C<ev_async> watcher from the default loop
4150	watcher callback into the event loop interested in the signal.	4718	watcher callback into the event loop interested in the signal.
4151		4719
4152	=back	4720	=back
4153		4721
4154	=head4 THREAD LOCKING EXAMPLE	4722	See also L<THREAD LOCKING EXAMPLE>.
4155
4156	Here is a fictitious example of how to run an event loop in a different
4157	thread than where callbacks are being invoked and watchers are
4158	created/added/removed.
4159
4160	For a real-world example, see the C<EV::Loop::Async> perl module,
4161	which uses exactly this technique (which is suited for many high-level
4162	languages).
4163
4164	The example uses a pthread mutex to protect the loop data, a condition
4165	variable to wait for callback invocations, an async watcher to notify the
4166	event loop thread and an unspecified mechanism to wake up the main thread.
4167
4168	First, you need to associate some data with the event loop:
4169
4170	typedef struct {
4171	mutex_t lock; /* global loop lock */
4172	ev_async async_w;
4173	thread_t tid;
4174	cond_t invoke_cv;
4175	} userdata;
4176
4177	void prepare_loop (EV_P)
4178	{
4179	// for simplicity, we use a static userdata struct.
4180	static userdata u;
4181
4182	ev_async_init (&u->async_w, async_cb);
4183	ev_async_start (EV_A_ &u->async_w);
4184
4185	pthread_mutex_init (&u->lock, 0);
4186	pthread_cond_init (&u->invoke_cv, 0);
4187
4188	// now associate this with the loop
4189	ev_set_userdata (EV_A_ u);
4190	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4191	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4192
4193	// then create the thread running ev_loop
4194	pthread_create (&u->tid, 0, l_run, EV_A);
4195	}
4196
4197	The callback for the C<ev_async> watcher does nothing: the watcher is used
4198	solely to wake up the event loop so it takes notice of any new watchers
4199	that might have been added:
4200
4201	static void
4202	async_cb (EV_P_ ev_async *w, int revents)
4203	{
4204	// just used for the side effects
4205	}
4206
4207	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4208	protecting the loop data, respectively.
4209
4210	static void
4211	l_release (EV_P)
4212	{
4213	userdata *u = ev_userdata (EV_A);
4214	pthread_mutex_unlock (&u->lock);
4215	}
4216
4217	static void
4218	l_acquire (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221	pthread_mutex_lock (&u->lock);
4222	}
4223
4224	The event loop thread first acquires the mutex, and then jumps straight
4225	into C<ev_loop>:
4226
4227	void *
4228	l_run (void *thr_arg)
4229	{
4230	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4231
4232	l_acquire (EV_A);
4233	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4234	ev_loop (EV_A_ 0);
4235	l_release (EV_A);
4236
4237	return 0;
4238	}
4239
4240	Instead of invoking all pending watchers, the C<l_invoke> callback will
4241	signal the main thread via some unspecified mechanism (signals? pipe
4242	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4243	have been called (in a while loop because a) spurious wakeups are possible
4244	and b) skipping inter-thread-communication when there are no pending
4245	watchers is very beneficial):
4246
4247	static void
4248	l_invoke (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251
4252	while (ev_pending_count (EV_A))
4253	{
4254	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4255	pthread_cond_wait (&u->invoke_cv, &u->lock);
4256	}
4257	}
4258
4259	Now, whenever the main thread gets told to invoke pending watchers, it
4260	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4261	thread to continue:
4262
4263	static void
4264	real_invoke_pending (EV_P)
4265	{
4266	userdata *u = ev_userdata (EV_A);
4267
4268	pthread_mutex_lock (&u->lock);
4269	ev_invoke_pending (EV_A);
4270	pthread_cond_signal (&u->invoke_cv);
4271	pthread_mutex_unlock (&u->lock);
4272	}
4273
4274	Whenever you want to start/stop a watcher or do other modifications to an
4275	event loop, you will now have to lock:
4276
4277	ev_timer timeout_watcher;
4278	userdata *u = ev_userdata (EV_A);
4279
4280	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4281
4282	pthread_mutex_lock (&u->lock);
4283	ev_timer_start (EV_A_ &timeout_watcher);
4284	ev_async_send (EV_A_ &u->async_w);
4285	pthread_mutex_unlock (&u->lock);
4286
4287	Note that sending the C<ev_async> watcher is required because otherwise
4288	an event loop currently blocking in the kernel will have no knowledge
4289	about the newly added timer. By waking up the loop it will pick up any new
4290	watchers in the next event loop iteration.
4291		4723
4292	=head3 COROUTINES	4724	=head3 COROUTINES
4293		4725
4294	Libev is very accommodating to coroutines ("cooperative threads"):	4726	Libev is very accommodating to coroutines ("cooperative threads"):
4295	libev fully supports nesting calls to its functions from different	4727	libev fully supports nesting calls to its functions from different
4296	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4728	coroutines (e.g. you can call C<ev_run> on the same loop from two
4297	different coroutines, and switch freely between both coroutines running	4729	different coroutines, and switch freely between both coroutines running
4298	the loop, as long as you don't confuse yourself). The only exception is	4730	the loop, as long as you don't confuse yourself). The only exception is
4299	that you must not do this from C<ev_periodic> reschedule callbacks.	4731	that you must not do this from C<ev_periodic> reschedule callbacks.
4300		4732
4301	Care has been taken to ensure that libev does not keep local state inside	4733	Care has been taken to ensure that libev does not keep local state inside
4302	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4734	C<ev_run>, and other calls do not usually allow for coroutine switches as
4303	they do not call any callbacks.	4735	they do not call any callbacks.
4304		4736
4305	=head2 COMPILER WARNINGS	4737	=head2 COMPILER WARNINGS
4306		4738
4307	Depending on your compiler and compiler settings, you might get no or a	4739	Depending on your compiler and compiler settings, you might get no or a
…		…
4318	maintainable.	4750	maintainable.
4319		4751
4320	And of course, some compiler warnings are just plain stupid, or simply	4752	And of course, some compiler warnings are just plain stupid, or simply
4321	wrong (because they don't actually warn about the condition their message	4753	wrong (because they don't actually warn about the condition their message
4322	seems to warn about). For example, certain older gcc versions had some	4754	seems to warn about). For example, certain older gcc versions had some
4323	warnings that resulted an extreme number of false positives. These have	4755	warnings that resulted in an extreme number of false positives. These have
4324	been fixed, but some people still insist on making code warn-free with	4756	been fixed, but some people still insist on making code warn-free with
4325	such buggy versions.	4757	such buggy versions.
4326		4758
4327	While libev is written to generate as few warnings as possible,	4759	While libev is written to generate as few warnings as possible,
4328	"warn-free" code is not a goal, and it is recommended not to build libev	4760	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4364	I suggest using suppression lists.	4796	I suggest using suppression lists.
4365		4797
4366		4798
4367	=head1 PORTABILITY NOTES	4799	=head1 PORTABILITY NOTES
4368		4800
		4801	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4802
		4803	GNU/Linux is the only common platform that supports 64 bit file/large file
		4804	interfaces but I<disables> them by default.
		4805
		4806	That means that libev compiled in the default environment doesn't support
		4807	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4808
		4809	Unfortunately, many programs try to work around this GNU/Linux issue
		4810	by enabling the large file API, which makes them incompatible with the
		4811	standard libev compiled for their system.
		4812
		4813	Likewise, libev cannot enable the large file API itself as this would
		4814	suddenly make it incompatible to the default compile time environment,
		4815	i.e. all programs not using special compile switches.
		4816
		4817	=head2 OS/X AND DARWIN BUGS
		4818
		4819	The whole thing is a bug if you ask me - basically any system interface
		4820	you touch is broken, whether it is locales, poll, kqueue or even the
		4821	OpenGL drivers.
		4822
		4823	=head3 C<kqueue> is buggy
		4824
		4825	The kqueue syscall is broken in all known versions - most versions support
		4826	only sockets, many support pipes.
		4827
		4828	Libev tries to work around this by not using C<kqueue> by default on this
		4829	rotten platform, but of course you can still ask for it when creating a
		4830	loop - embedding a socket-only kqueue loop into a select-based one is
		4831	probably going to work well.
		4832
		4833	=head3 C<poll> is buggy
		4834
		4835	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4836	implementation by something calling C<kqueue> internally around the 10.5.6
		4837	release, so now C<kqueue> I<and> C<poll> are broken.
		4838
		4839	Libev tries to work around this by not using C<poll> by default on
		4840	this rotten platform, but of course you can still ask for it when creating
		4841	a loop.
		4842
		4843	=head3 C<select> is buggy
		4844
		4845	All that's left is C<select>, and of course Apple found a way to fuck this
		4846	one up as well: On OS/X, C<select> actively limits the number of file
		4847	descriptors you can pass in to 1024 - your program suddenly crashes when
		4848	you use more.
		4849
		4850	There is an undocumented "workaround" for this - defining
		4851	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4852	work on OS/X.
		4853
		4854	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4855
		4856	=head3 C<errno> reentrancy
		4857
		4858	The default compile environment on Solaris is unfortunately so
		4859	thread-unsafe that you can't even use components/libraries compiled
		4860	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4861	defined by default. A valid, if stupid, implementation choice.
		4862
		4863	If you want to use libev in threaded environments you have to make sure
		4864	it's compiled with C<_REENTRANT> defined.
		4865
		4866	=head3 Event port backend
		4867
		4868	The scalable event interface for Solaris is called "event
		4869	ports". Unfortunately, this mechanism is very buggy in all major
		4870	releases. If you run into high CPU usage, your program freezes or you get
		4871	a large number of spurious wakeups, make sure you have all the relevant
		4872	and latest kernel patches applied. No, I don't know which ones, but there
		4873	are multiple ones to apply, and afterwards, event ports actually work
		4874	great.
		4875
		4876	If you can't get it to work, you can try running the program by setting
		4877	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4878	C<select> backends.
		4879
		4880	=head2 AIX POLL BUG
		4881
		4882	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4883	this by trying to avoid the poll backend altogether (i.e. it's not even
		4884	compiled in), which normally isn't a big problem as C<select> works fine
		4885	with large bitsets on AIX, and AIX is dead anyway.
		4886
4369	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4887	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4888
		4889	=head3 General issues
4370		4890
4371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4891	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372	requires, and its I/O model is fundamentally incompatible with the POSIX	4892	requires, and its I/O model is fundamentally incompatible with the POSIX
4373	model. Libev still offers limited functionality on this platform in	4893	model. Libev still offers limited functionality on this platform in
4374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4894	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375	descriptors. This only applies when using Win32 natively, not when using	4895	descriptors. This only applies when using Win32 natively, not when using
4376	e.g. cygwin.	4896	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4897	as every compielr comes with a slightly differently broken/incompatible
		4898	environment.
4377		4899
4378	Lifting these limitations would basically require the full	4900	Lifting these limitations would basically require the full
4379	re-implementation of the I/O system. If you are into these kinds of	4901	re-implementation of the I/O system. If you are into this kind of thing,
4380	things, then note that glib does exactly that for you in a very portable	4902	then note that glib does exactly that for you in a very portable way (note
4381	way (note also that glib is the slowest event library known to man).	4903	also that glib is the slowest event library known to man).
4382		4904
4383	There is no supported compilation method available on windows except	4905	There is no supported compilation method available on windows except
4384	embedding it into other applications.	4906	embedding it into other applications.
4385		4907
4386	Sensible signal handling is officially unsupported by Microsoft - libev	4908	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4414	you do I<not> compile the F<ev.c> or any other embedded source files!):	4936	you do I<not> compile the F<ev.c> or any other embedded source files!):
4415		4937
4416	#include "evwrap.h"	4938	#include "evwrap.h"
4417	#include "ev.c"	4939	#include "ev.c"
4418		4940
4419	=over 4
4420
4421	=item The winsocket select function	4941	=head3 The winsocket C<select> function
4422		4942
4423	The winsocket C<select> function doesn't follow POSIX in that it	4943	The winsocket C<select> function doesn't follow POSIX in that it
4424	requires socket I<handles> and not socket I<file descriptors> (it is	4944	requires socket I<handles> and not socket I<file descriptors> (it is
4425	also extremely buggy). This makes select very inefficient, and also	4945	also extremely buggy). This makes select very inefficient, and also
4426	requires a mapping from file descriptors to socket handles (the Microsoft	4946	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4435	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4955	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436		4956
4437	Note that winsockets handling of fd sets is O(n), so you can easily get a	4957	Note that winsockets handling of fd sets is O(n), so you can easily get a
4438	complexity in the O(n²) range when using win32.	4958	complexity in the O(n²) range when using win32.
4439		4959
4440	=item Limited number of file descriptors	4960	=head3 Limited number of file descriptors
4441		4961
4442	Windows has numerous arbitrary (and low) limits on things.	4962	Windows has numerous arbitrary (and low) limits on things.
4443		4963
4444	Early versions of winsocket's select only supported waiting for a maximum	4964	Early versions of winsocket's select only supported waiting for a maximum
4445	of C<64> handles (probably owning to the fact that all windows kernels	4965	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4460	runtime libraries. This might get you to about C<512> or C<2048> sockets	4980	runtime libraries. This might get you to about C<512> or C<2048> sockets
4461	(depending on windows version and/or the phase of the moon). To get more,	4981	(depending on windows version and/or the phase of the moon). To get more,
4462	you need to wrap all I/O functions and provide your own fd management, but	4982	you need to wrap all I/O functions and provide your own fd management, but
4463	the cost of calling select (O(n²)) will likely make this unworkable.	4983	the cost of calling select (O(n²)) will likely make this unworkable.
4464		4984
4465	=back
4466
4467	=head2 PORTABILITY REQUIREMENTS	4985	=head2 PORTABILITY REQUIREMENTS
4468		4986
4469	In addition to a working ISO-C implementation and of course the	4987	In addition to a working ISO-C implementation and of course the
4470	backend-specific APIs, libev relies on a few additional extensions:	4988	backend-specific APIs, libev relies on a few additional extensions:
4471		4989
…		…
4477	Libev assumes not only that all watcher pointers have the same internal	4995	Libev assumes not only that all watcher pointers have the same internal
4478	structure (guaranteed by POSIX but not by ISO C for example), but it also	4996	structure (guaranteed by POSIX but not by ISO C for example), but it also
4479	assumes that the same (machine) code can be used to call any watcher	4997	assumes that the same (machine) code can be used to call any watcher
4480	callback: The watcher callbacks have different type signatures, but libev	4998	callback: The watcher callbacks have different type signatures, but libev
4481	calls them using an C<ev_watcher *> internally.	4999	calls them using an C<ev_watcher *> internally.
		5000
		5001	=item pointer accesses must be thread-atomic
		5002
		5003	Accessing a pointer value must be atomic, it must both be readable and
		5004	writable in one piece - this is the case on all current architectures.
4482		5005
4483	=item C<sig_atomic_t volatile> must be thread-atomic as well	5006	=item C<sig_atomic_t volatile> must be thread-atomic as well
4484		5007
4485	The type C<sig_atomic_t volatile> (or whatever is defined as	5008	The type C<sig_atomic_t volatile> (or whatever is defined as
4486	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5009	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4509	watchers.	5032	watchers.
4510		5033
4511	=item C<double> must hold a time value in seconds with enough accuracy	5034	=item C<double> must hold a time value in seconds with enough accuracy
4512		5035
4513	The type C<double> is used to represent timestamps. It is required to	5036	The type C<double> is used to represent timestamps. It is required to
4514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5037	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4515	enough for at least into the year 4000. This requirement is fulfilled by	5038	good enough for at least into the year 4000 with millisecond accuracy
		5039	(the design goal for libev). This requirement is overfulfilled by
4516	implementations implementing IEEE 754, which is basically all existing	5040	implementations using IEEE 754, which is basically all existing ones. With
4517	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5041	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4518	2200.
4519		5042
4520	=back	5043	=back
4521		5044
4522	If you know of other additional requirements drop me a note.	5045	If you know of other additional requirements drop me a note.
4523		5046
…		…
4591	involves iterating over all running async watchers or all signal numbers.	5114	involves iterating over all running async watchers or all signal numbers.
4592		5115
4593	=back	5116	=back
4594		5117
4595		5118
		5119	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5120
		5121	The major version 4 introduced some incompatible changes to the API.
		5122
		5123	At the moment, the C<ev.h> header file provides compatibility definitions
		5124	for all changes, so most programs should still compile. The compatibility
		5125	layer might be removed in later versions of libev, so better update to the
		5126	new API early than late.
		5127
		5128	=over 4
		5129
		5130	=item C<EV_COMPAT3> backwards compatibility mechanism
		5131
		5132	The backward compatibility mechanism can be controlled by
		5133	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5134	section.
		5135
		5136	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5137
		5138	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5139
		5140	ev_loop_destroy (EV_DEFAULT_UC);
		5141	ev_loop_fork (EV_DEFAULT);
		5142
		5143	=item function/symbol renames
		5144
		5145	A number of functions and symbols have been renamed:
		5146
		5147	ev_loop => ev_run
		5148	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5149	EVLOOP_ONESHOT => EVRUN_ONCE
		5150
		5151	ev_unloop => ev_break
		5152	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5153	EVUNLOOP_ONE => EVBREAK_ONE
		5154	EVUNLOOP_ALL => EVBREAK_ALL
		5155
		5156	EV_TIMEOUT => EV_TIMER
		5157
		5158	ev_loop_count => ev_iteration
		5159	ev_loop_depth => ev_depth
		5160	ev_loop_verify => ev_verify
		5161
		5162	Most functions working on C<struct ev_loop> objects don't have an
		5163	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5164	associated constants have been renamed to not collide with the C<struct
		5165	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5166	as all other watcher types. Note that C<ev_loop_fork> is still called
		5167	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5168	typedef.
		5169
		5170	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5171
		5172	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5173	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5174	and work, but the library code will of course be larger.
		5175
		5176	=back
		5177
		5178
4596	=head1 GLOSSARY	5179	=head1 GLOSSARY
4597		5180
4598	=over 4	5181	=over 4
4599		5182
4600	=item active	5183	=item active
4601		5184
4602	A watcher is active as long as it has been started (has been attached to	5185	A watcher is active as long as it has been started and not yet stopped.
4603	an event loop) but not yet stopped (disassociated from the event loop).	5186	See L<WATCHER STATES> for details.
4604		5187
4605	=item application	5188	=item application
4606		5189
4607	In this document, an application is whatever is using libev.	5190	In this document, an application is whatever is using libev.
		5191
		5192	=item backend
		5193
		5194	The part of the code dealing with the operating system interfaces.
4608		5195
4609	=item callback	5196	=item callback
4610		5197
4611	The address of a function that is called when some event has been	5198	The address of a function that is called when some event has been
4612	detected. Callbacks are being passed the event loop, the watcher that	5199	detected. Callbacks are being passed the event loop, the watcher that
4613	received the event, and the actual event bitset.	5200	received the event, and the actual event bitset.
4614		5201
4615	=item callback invocation	5202	=item callback/watcher invocation
4616		5203
4617	The act of calling the callback associated with a watcher.	5204	The act of calling the callback associated with a watcher.
4618		5205
4619	=item event	5206	=item event
4620		5207
4621	A change of state of some external event, such as data now being available	5208	A change of state of some external event, such as data now being available
4622	for reading on a file descriptor, time having passed or simply not having	5209	for reading on a file descriptor, time having passed or simply not having
4623	any other events happening anymore.	5210	any other events happening anymore.
4624		5211
4625	In libev, events are represented as single bits (such as C<EV_READ> or	5212	In libev, events are represented as single bits (such as C<EV_READ> or
4626	C<EV_TIMEOUT>).	5213	C<EV_TIMER>).
4627		5214
4628	=item event library	5215	=item event library
4629		5216
4630	A software package implementing an event model and loop.	5217	A software package implementing an event model and loop.
4631		5218
…		…
4639	The model used to describe how an event loop handles and processes	5226	The model used to describe how an event loop handles and processes
4640	watchers and events.	5227	watchers and events.
4641		5228
4642	=item pending	5229	=item pending
4643		5230
4644	A watcher is pending as soon as the corresponding event has been detected,	5231	A watcher is pending as soon as the corresponding event has been
4645	and stops being pending as soon as the watcher will be invoked or its	5232	detected. See L<WATCHER STATES> for details.
4646	pending status is explicitly cleared by the application.
4647
4648	A watcher can be pending, but not active. Stopping a watcher also clears
4649	its pending status.
4650		5233
4651	=item real time	5234	=item real time
4652		5235
4653	The physical time that is observed. It is apparently strictly monotonic :)	5236	The physical time that is observed. It is apparently strictly monotonic :)
4654		5237
4655	=item wall-clock time	5238	=item wall-clock time
4656		5239
4657	The time and date as shown on clocks. Unlike real time, it can actually	5240	The time and date as shown on clocks. Unlike real time, it can actually
4658	be wrong and jump forwards and backwards, e.g. when the you adjust your	5241	be wrong and jump forwards and backwards, e.g. when you adjust your
4659	clock.	5242	clock.
4660		5243
4661	=item watcher	5244	=item watcher
4662		5245
4663	A data structure that describes interest in certain events. Watchers need	5246	A data structure that describes interest in certain events. Watchers need
4664	to be started (attached to an event loop) before they can receive events.	5247	to be started (attached to an event loop) before they can receive events.
4665		5248
4666	=item watcher invocation
4667
4668	The act of calling the callback associated with a watcher.
4669
4670	=back	5249	=back
4671		5250
4672	=head1 AUTHOR	5251	=head1 AUTHOR
4673		5252
4674	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5253	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5254	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4675		5255

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