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Revision 1.306 by root, Mon Oct 18 07:36:05 2010 UTC vs.
Revision 1.378 by sf-exg, Thu Jul 7 16:30:49 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familiarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	138	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	140	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	141	any calculations on it, you should treat it as some floating point value.
134		142
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
171		180
172	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
173		182
174	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
176	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
177		192
178	=item int ev_version_major ()	193	=item int ev_version_major ()
179		194
180	=item int ev_version_minor ()	195	=item int ev_version_minor ()
181		196
…		…
192	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	209	not a problem.
195		210
196	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
198		214
199	assert (("libev version mismatch",	215	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
202		218
…		…
213	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
215		231
216	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
217		233
218	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
224		241
225	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
226		243
227	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
232		249
233	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
234		251
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
236		253
237	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	283	}
267		284
268	...	285	...
269	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
270		287
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
272		289
273	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	305	}
289		306
290	...	307	...
291	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
292		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
293	=back	323	=back
294		324
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		326
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
300		330
301	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
303	not.	333	do not.
304		334
305	=over 4	335	=over 4
306		336
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		338
309	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
313		349
314	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
315	function.	351	function (or via the C<EV_DEFAULT> macro).
316		352
317	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
320		357
321	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
327		382
328	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		385
331	The following flags are supported:	386	The following flags are supported:
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	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	426	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	427	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.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	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	433	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	434	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	435	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	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	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	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	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,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(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	505	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	506	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	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
447		526
448	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		597
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
521		600
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	604	might perform better.
530		605
531	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
535		620
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
538		623
539	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
540		625
541	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		629
545	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		639
547	=back	640	=back
548		641
549	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	645	()> will be tried.
553		646
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common 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.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	661	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	662	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	664	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
594		667
595	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
598		671
599	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
603		680
604	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
605		682
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610
611	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
612	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
613	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
614	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
615	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_loop> iteration.
617		688
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	690	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	692	during fork.
622		693
623	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
624	process if and only if you want to use the event loop in the child. If you	695	process if and only if you want to use the event loop in the child. If
625	just fork+exec or create a new loop in the child, you don't have to call	696	you just fork+exec or create a new loop in the child, you don't have to
626	it at all.	697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
627		700
628	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
629	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
630	quite nicely into a call to C<pthread_atfork>:
631		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
632	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
633
634	=item ev_loop_fork (loop)
635
636	Like C<ev_default_fork>, but acts on an event loop created by
637	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
638	after fork that you want to re-use in the child, and how you keep track of
639	them is entirely your own problem.
640		715
641	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
642		717
643	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
644	otherwise.	719	otherwise.
645		720
646	=item unsigned int ev_iteration (loop)	721	=item unsigned int ev_iteration (loop)
647		722
648	Returns the current iteration count for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
649	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
650	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
651		726
652	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
653	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
654	C<ev_prepare> and C<ev_check> calls - and is incremented between the	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
655	prepare and check phases.	730	prepare and check phases.
656		731
657	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
658		733
659	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
660	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
661		736
662	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
663	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
664	in which case it is higher.	739	in which case it is higher.
665		740
666	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
667	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
668	ungentleman behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
669		745
670	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
671		747
672	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
673	use.	749	use.
…		…
682		758
683	=item ev_now_update (loop)	759	=item ev_now_update (loop)
684		760
685	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
686	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
687	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
688		764
689	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
690	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
691	the current time is a good idea.	767	the current time is a good idea.
692		768
…		…
694		770
695	=item ev_suspend (loop)	771	=item ev_suspend (loop)
696		772
697	=item ev_resume (loop)	773	=item ev_resume (loop)
698		774
699	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
700	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
701		777
702	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
703	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
704	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
705	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
716	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
717		793
718	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
719	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
720		796
721	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
722		798
723	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
724	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
725	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
726		804
727	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
728	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
729		808
730	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
731	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
732	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
733	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
734	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
735	beauty.	814	beauty.
736		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
737	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
738	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
739	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
740	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
741		826
742	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
743	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
744	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
745	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
746	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
747	iteration of the loop.	832	iteration of the loop.
748		833
749	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
750	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
751	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
752	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
753		838
754	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
755		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
756	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
757	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
758	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
759	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
760	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
761	as to not disturb the other process.	852	as to not disturb the other process.
762	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
763	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
764	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
765	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
766	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
767	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
768	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
769	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
770	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
771	- Queue all expired timers.	863	- Queue all expired timers.
772	- Queue all expired periodics.	864	- Queue all expired periodics.
773	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
774	- Queue all check watchers.	866	- Queue all check watchers.
775	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
776	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
777	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
778	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
779	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
780	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
781		877
782	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
783	anymore.	879	anymore.
784		880
785	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
786	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
787	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
788	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
789		885
790	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
791		887
792	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
793	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
794	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
795	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
796		892
797	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
798		894
799	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
800		897
801	=item ev_ref (loop)	898	=item ev_ref (loop)
802		899
803	=item ev_unref (loop)	900	=item ev_unref (loop)
804		901
805	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
806	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
807	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
808		905
809	This is useful when you have a watcher that you never intend to	906	This is useful when you have a watcher that you never intend to
810	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
811	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
812	before stopping it.	909	before stopping it.
813		910
814	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
815	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
816	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
817	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
818	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
819	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
820	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
821	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
822	in the callback).	919	in the callback).
823		920
824	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
825	running when nothing else is active.	922	running when nothing else is active.
826		923
827	ev_signal exitsig;	924	ev_signal exitsig;
828	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
829	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
830	evf_unref (loop);	927	ev_unref (loop);
831		928
832	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
833		930
834	ev_ref (loop);	931	ev_ref (loop);
835	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
855	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
856		953
857	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
858	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
859	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
860	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
861	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
862	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
863	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
864		962
865	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
866	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
867	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
868	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
892	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
893		991
894	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
895		993
896	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
897	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
898	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
899		1001
900	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
901		1003
902	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
903	are pending.	1005	are pending.
904		1006
905	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
906		1008
907	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
908	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
909	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
910	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
911		1013
912	If you want to reset the callback, use C<ev_invoke_pending> as new	1014	If you want to reset the callback, use C<ev_invoke_pending> as new
913	callback.	1015	callback.
…		…
916		1018
917	Sometimes you want to share the same loop between multiple threads. This	1019	Sometimes you want to share the same loop between multiple threads. This
918	can be done relatively simply by putting mutex_lock/unlock calls around	1020	can be done relatively simply by putting mutex_lock/unlock calls around
919	each call to a libev function.	1021	each call to a libev function.
920		1022
921	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1023	However, C<ev_run> can run an indefinite time, so it is not feasible
922	wait for it to return. One way around this is to wake up the loop via	1024	to wait for it to return. One way around this is to wake up the event
923	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<av_async_send>, another way is to set these
924	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
925		1027
926	When set, then C<release> will be called just before the thread is	1028	When set, then C<release> will be called just before the thread is
927	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
928	afterwards.	1030	afterwards.
929		1031
…		…
932		1034
933	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
934	C<release> and C<acquire> (that's their only purpose after all), no	1036	C<release> and C<acquire> (that's their only purpose after all), no
935	modifications done will affect the event loop, i.e. adding watchers will	1037	modifications done will affect the event loop, i.e. adding watchers will
936	have no effect on the set of file descriptors being watched, or the time	1038	have no effect on the set of file descriptors being watched, or the time
937	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
938	to take note of any changes you made.	1040	to take note of any changes you made.
939		1041
940	In theory, threads executing C<ev_loop> will be async-cancel safe between	1042	In theory, threads executing C<ev_run> will be async-cancel safe between
941	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
942		1044
943	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
944	document.	1046	document.
945		1047
946	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
947		1049
948	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
949		1051
950	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
951	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
952	C<0.>	1054	C<0>.
953		1055
954	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
955	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
956	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
957	any other purpose as well.	1059	any other purpose as well.
958		1060
959	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
960		1062
961	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
962	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
963	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
964	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
975		1077
976	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
977	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
978	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
979		1081
980	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
981	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
982	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
983		1086
984	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
985	{	1088	{
986	ev_io_stop (w);	1089	ev_io_stop (w);
987	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
988	}	1091	}
989		1092
990	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
991		1094
992	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
993		1096
994	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
995	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
996	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
997		1100
998	ev_loop (loop, 0);	1101	ev_run (loop, 0);
999		1102
1000	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
1001	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
1002	stack).	1105	stack).
1003		1106
1004	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1005	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1006		1109
1007	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
1008	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
1009	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
1010	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
1011	is readable and/or writable).	1114	and/or writable).
1012		1115
1013	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1014	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
1015	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
1016	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1067		1170
1068	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1069		1172
1070	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1071		1174
1072	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1073	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
1074	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
1075	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
1076	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
1077	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1078	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1079		1182
1080	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1081		1184
1082	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1083		1186
1084	=item C<EV_FORK>	1187	=item C<EV_FORK>
1085		1188
1086	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1087	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
1088		1195
1089	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1090		1197
1091	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1092		1199
…		…
1265	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1266	functions that do not need a watcher.	1373	functions that do not need a watcher.
1267		1374
1268	=back	1375	=back
1269		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1270		1379
1271	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1272		1381
1273	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1274	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1275	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1276	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1277	member, you can also "subclass" the watcher type and provide your own
1278	data:
1279		1386
1280	struct my_io	1387	=over 4
1281	{
1282	ev_io io;
1283	int otherfd;
1284	void *somedata;
1285	struct whatever *mostinteresting;
1286	};
1287		1388
1288	...	1389	=item initialiased
1289	struct my_io w;
1290	ev_io_init (&w.io, my_cb, fd, EV_READ);
1291		1390
1292	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1293	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1294		1394
1295	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1296	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1297	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1298	...	1398	C<ev_TYPE_init> again.
1299	}
1300		1399
1301	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1302	instead have been omitted.
1303		1401
1304	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1305	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1306		1407
1307	struct my_biggy	1408	=item pending
1308	{
1309	int some_data;
1310	ev_timer t1;
1311	ev_timer t2;
1312	}
1313		1409
1314	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1315	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1316	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1317	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1318	programmers):	1414	callback.
1319		1415
1320	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1321		1422
1322	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1323	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1324	{	1425	active.
1325	struct my_biggy big = (struct my_biggy *)
1326	(((char *)w) - offsetof (struct my_biggy, t1));
1327	}
1328		1426
1329	static void	1427	=item stopped
1330	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1331	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1332	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1333	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1334	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1335		1441
1336	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1337		1443
1338	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1339	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1466	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1467	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1468	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1469	required if you know what you are doing).	1575	required if you know what you are doing).
1470		1576
1471	If you cannot use non-blocking mode, then force the use of a
1472	known-to-be-good backend (at the time of this writing, this includes only
1473	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1474	descriptors for which non-blocking operation makes no sense (such as
1475	files) - libev doesn't guarantee any specific behaviour in that case.
1476
1477	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1478	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1479	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1480	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1481	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1482	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1483	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1484	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1485		1584
1486	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1487	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1488	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1489	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1490	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1491	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1492	indefinitely.	1591	indefinitely.
1493		1592
1494	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1495		1594
…		…
1523		1622
1524	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1525	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1526	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1527		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1528	=head3 The special problem of fork	1660	=head3 The special problem of fork
1529		1661
1530	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1531	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1532	it in the child.	1664	it in the child if you want to continue to use it in the child.
1533		1665
1534	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1535	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1536	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1537	C<EVBACKEND_POLL>.
1538		1669
1539	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1540		1671
1541	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1542	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1624	...	1755	...
1625	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1626	ev_io stdin_readable;	1757	ev_io stdin_readable;
1627	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1628	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1629	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1630		1761
1631		1762
1632	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1633		1764
1634	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1643	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1644	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1645	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay). If multiple timers become ready during the
1646	same loop iteration then the ones with earlier time-out values are invoked	1777	same loop iteration then the ones with earlier time-out values are invoked
1647	before ones of the same priority with later time-out values (but this is	1778	before ones of the same priority with later time-out values (but this is
1648	no longer true when a callback calls C<ev_loop> recursively).	1779	no longer true when a callback calls C<ev_run> recursively).
1649		1780
1650	=head3 Be smart about timeouts	1781	=head3 Be smart about timeouts
1651		1782
1652	Many real-world problems involve some kind of timeout, usually for error	1783	Many real-world problems involve some kind of timeout, usually for error
1653	recovery. A typical example is an HTTP request - if the other side hangs,	1784	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1824		1955
1825	=head3 The special problem of time updates	1956	=head3 The special problem of time updates
1826		1957
1827	Establishing the current time is a costly operation (it usually takes at	1958	Establishing the current time is a costly operation (it usually takes at
1828	least two system calls): EV therefore updates its idea of the current	1959	least two system calls): EV therefore updates its idea of the current
1829	time only before and after C<ev_loop> collects new events, which causes a	1960	time only before and after C<ev_run> collects new events, which causes a
1830	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1961	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1831	lots of events in one iteration.	1962	lots of events in one iteration.
1832		1963
1833	The relative timeouts are calculated relative to the C<ev_now ()>	1964	The relative timeouts are calculated relative to the C<ev_now ()>
1834	time. This is usually the right thing as this timestamp refers to the time	1965	time. This is usually the right thing as this timestamp refers to the time
…		…
1892	keep up with the timer (because it takes longer than those 10 seconds to	2023	keep up with the timer (because it takes longer than those 10 seconds to
1893	do stuff) the timer will not fire more than once per event loop iteration.	2024	do stuff) the timer will not fire more than once per event loop iteration.
1894		2025
1895	=item ev_timer_again (loop, ev_timer *)	2026	=item ev_timer_again (loop, ev_timer *)
1896		2027
1897	This will act as if the timer timed out and restart it again if it is	2028	This will act as if the timer timed out and restarts it again if it is
1898	repeating. The exact semantics are:	2029	repeating. The exact semantics are:
1899		2030
1900	If the timer is pending, its pending status is cleared.	2031	If the timer is pending, its pending status is cleared.
1901		2032
1902	If the timer is started but non-repeating, stop it (as if it timed out).	2033	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1951	}	2082	}
1952		2083
1953	ev_timer mytimer;	2084	ev_timer mytimer;
1954	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2085	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1955	ev_timer_again (&mytimer); /* start timer */	2086	ev_timer_again (&mytimer); /* start timer */
1956	ev_loop (loop, 0);	2087	ev_run (loop, 0);
1957		2088
1958	// and in some piece of code that gets executed on any "activity":	2089	// and in some piece of code that gets executed on any "activity":
1959	// reset the timeout to start ticking again at 10 seconds	2090	// reset the timeout to start ticking again at 10 seconds
1960	ev_timer_again (&mytimer);	2091	ev_timer_again (&mytimer);
1961		2092
…		…
1987		2118
1988	As with timers, the callback is guaranteed to be invoked only when the	2119	As with timers, the callback is guaranteed to be invoked only when the
1989	point in time where it is supposed to trigger has passed. If multiple	2120	point in time where it is supposed to trigger has passed. If multiple
1990	timers become ready during the same loop iteration then the ones with	2121	timers become ready during the same loop iteration then the ones with
1991	earlier time-out values are invoked before ones with later time-out values	2122	earlier time-out values are invoked before ones with later time-out values
1992	(but this is no longer true when a callback calls C<ev_loop> recursively).	2123	(but this is no longer true when a callback calls C<ev_run> recursively).
1993		2124
1994	=head3 Watcher-Specific Functions and Data Members	2125	=head3 Watcher-Specific Functions and Data Members
1995		2126
1996	=over 4	2127	=over 4
1997		2128
…		…
2032		2163
2033	Another way to think about it (for the mathematically inclined) is that	2164	Another way to think about it (for the mathematically inclined) is that
2034	C<ev_periodic> will try to run the callback in this mode at the next possible	2165	C<ev_periodic> will try to run the callback in this mode at the next possible
2035	time where C<time = offset (mod interval)>, regardless of any time jumps.	2166	time where C<time = offset (mod interval)>, regardless of any time jumps.
2036		2167
2037	For numerical stability it is preferable that the C<offset> value is near	2168	The C<interval> I<MUST> be positive, and for numerical stability, the
2038	C<ev_now ()> (the current time), but there is no range requirement for	2169	interval value should be higher than C<1/8192> (which is around 100
2039	this value, and in fact is often specified as zero.	2170	microseconds) and C<offset> should be higher than C<0> and should have
		2171	at most a similar magnitude as the current time (say, within a factor of
		2172	ten). Typical values for offset are, in fact, C<0> or something between
		2173	C<0> and C<interval>, which is also the recommended range.
2040		2174
2041	Note also that there is an upper limit to how often a timer can fire (CPU	2175	Note also that there is an upper limit to how often a timer can fire (CPU
2042	speed for example), so if C<interval> is very small then timing stability	2176	speed for example), so if C<interval> is very small then timing stability
2043	will of course deteriorate. Libev itself tries to be exact to be about one	2177	will of course deteriorate. Libev itself tries to be exact to be about one
2044	millisecond (if the OS supports it and the machine is fast enough).	2178	millisecond (if the OS supports it and the machine is fast enough).
…		…
2158		2292
2159	=head2 C<ev_signal> - signal me when a signal gets signalled!	2293	=head2 C<ev_signal> - signal me when a signal gets signalled!
2160		2294
2161	Signal watchers will trigger an event when the process receives a specific	2295	Signal watchers will trigger an event when the process receives a specific
2162	signal one or more times. Even though signals are very asynchronous, libev	2296	signal one or more times. Even though signals are very asynchronous, libev
2163	will try it's best to deliver signals synchronously, i.e. as part of the	2297	will try its best to deliver signals synchronously, i.e. as part of the
2164	normal event processing, like any other event.	2298	normal event processing, like any other event.
2165		2299
2166	If you want signals to be delivered truly asynchronously, just use	2300	If you want signals to be delivered truly asynchronously, just use
2167	C<sigaction> as you would do without libev and forget about sharing	2301	C<sigaction> as you would do without libev and forget about sharing
2168	the signal. You can even use C<ev_async> from a signal handler to	2302	the signal. You can even use C<ev_async> from a signal handler to
…		…
2187	=head3 The special problem of inheritance over fork/execve/pthread_create	2321	=head3 The special problem of inheritance over fork/execve/pthread_create
2188		2322
2189	Both the signal mask (C<sigprocmask>) and the signal disposition	2323	Both the signal mask (C<sigprocmask>) and the signal disposition
2190	(C<sigaction>) are unspecified after starting a signal watcher (and after	2324	(C<sigaction>) are unspecified after starting a signal watcher (and after
2191	stopping it again), that is, libev might or might not block the signal,	2325	stopping it again), that is, libev might or might not block the signal,
2192	and might or might not set or restore the installed signal handler.	2326	and might or might not set or restore the installed signal handler (but
		2327	see C<EVFLAG_NOSIGMASK>).
2193		2328
2194	While this does not matter for the signal disposition (libev never	2329	While this does not matter for the signal disposition (libev never
2195	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2330	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2196	C<execve>), this matters for the signal mask: many programs do not expect	2331	C<execve>), this matters for the signal mask: many programs do not expect
2197	certain signals to be blocked.	2332	certain signals to be blocked.
…		…
2211		2346
2212	So I can't stress this enough: I<If you do not reset your signal mask when	2347	So I can't stress this enough: I<If you do not reset your signal mask when
2213	you expect it to be empty, you have a race condition in your code>. This	2348	you expect it to be empty, you have a race condition in your code>. This
2214	is not a libev-specific thing, this is true for most event libraries.	2349	is not a libev-specific thing, this is true for most event libraries.
2215		2350
		2351	=head3 The special problem of threads signal handling
		2352
		2353	POSIX threads has problematic signal handling semantics, specifically,
		2354	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2355	threads in a process block signals, which is hard to achieve.
		2356
		2357	When you want to use sigwait (or mix libev signal handling with your own
		2358	for the same signals), you can tackle this problem by globally blocking
		2359	all signals before creating any threads (or creating them with a fully set
		2360	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2361	loops. Then designate one thread as "signal receiver thread" which handles
		2362	these signals. You can pass on any signals that libev might be interested
		2363	in by calling C<ev_feed_signal>.
		2364
2216	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2217		2366
2218	=over 4	2367	=over 4
2219		2368
2220	=item ev_signal_init (ev_signal *, callback, int signum)	2369	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2235	Example: Try to exit cleanly on SIGINT.	2384	Example: Try to exit cleanly on SIGINT.
2236		2385
2237	static void	2386	static void
2238	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2387	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2239	{	2388	{
2240	ev_unloop (loop, EVUNLOOP_ALL);	2389	ev_break (loop, EVBREAK_ALL);
2241	}	2390	}
2242		2391
2243	ev_signal signal_watcher;	2392	ev_signal signal_watcher;
2244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2393	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2245	ev_signal_start (loop, &signal_watcher);	2394	ev_signal_start (loop, &signal_watcher);
…		…
2631		2780
2632	Prepare and check watchers are usually (but not always) used in pairs:	2781	Prepare and check watchers are usually (but not always) used in pairs:
2633	prepare watchers get invoked before the process blocks and check watchers	2782	prepare watchers get invoked before the process blocks and check watchers
2634	afterwards.	2783	afterwards.
2635		2784
2636	You I<must not> call C<ev_loop> or similar functions that enter	2785	You I<must not> call C<ev_run> or similar functions that enter
2637	the current event loop from either C<ev_prepare> or C<ev_check>	2786	the current event loop from either C<ev_prepare> or C<ev_check>
2638	watchers. Other loops than the current one are fine, however. The	2787	watchers. Other loops than the current one are fine, however. The
2639	rationale behind this is that you do not need to check for recursion in	2788	rationale behind this is that you do not need to check for recursion in
2640	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2789	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2641	C<ev_check> so if you have one watcher of each kind they will always be	2790	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2809		2958
2810	if (timeout >= 0)	2959	if (timeout >= 0)
2811	// create/start timer	2960	// create/start timer
2812		2961
2813	// poll	2962	// poll
2814	ev_loop (EV_A_ 0);	2963	ev_run (EV_A_ 0);
2815		2964
2816	// stop timer again	2965	// stop timer again
2817	if (timeout >= 0)	2966	if (timeout >= 0)
2818	ev_timer_stop (EV_A_ &to);	2967	ev_timer_stop (EV_A_ &to);
2819		2968
…		…
2897	if you do not want that, you need to temporarily stop the embed watcher).	3046	if you do not want that, you need to temporarily stop the embed watcher).
2898		3047
2899	=item ev_embed_sweep (loop, ev_embed *)	3048	=item ev_embed_sweep (loop, ev_embed *)
2900		3049
2901	Make a single, non-blocking sweep over the embedded loop. This works	3050	Make a single, non-blocking sweep over the embedded loop. This works
2902	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3051	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2903	appropriate way for embedded loops.	3052	appropriate way for embedded loops.
2904		3053
2905	=item struct ev_loop *other [read-only]	3054	=item struct ev_loop *other [read-only]
2906		3055
2907	The embedded event loop.	3056	The embedded event loop.
…		…
2993	disadvantage of having to use multiple event loops (which do not support	3142	disadvantage of having to use multiple event loops (which do not support
2994	signal watchers).	3143	signal watchers).
2995		3144
2996	When this is not possible, or you want to use the default loop for	3145	When this is not possible, or you want to use the default loop for
2997	other reasons, then in the process that wants to start "fresh", call	3146	other reasons, then in the process that wants to start "fresh", call
2998	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3147	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2999	the default loop will "orphan" (not stop) all registered watchers, so you	3148	Destroying the default loop will "orphan" (not stop) all registered
3000	have to be careful not to execute code that modifies those watchers. Note	3149	watchers, so you have to be careful not to execute code that modifies
3001	also that in that case, you have to re-register any signal watchers.	3150	those watchers. Note also that in that case, you have to re-register any
		3151	signal watchers.
3002		3152
3003	=head3 Watcher-Specific Functions and Data Members	3153	=head3 Watcher-Specific Functions and Data Members
3004		3154
3005	=over 4	3155	=over 4
3006		3156
3007	=item ev_fork_init (ev_signal *, callback)	3157	=item ev_fork_init (ev_fork *, callback)
3008		3158
3009	Initialises and configures the fork watcher - it has no parameters of any	3159	Initialises and configures the fork watcher - it has no parameters of any
3010	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3160	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3011	believe me.	3161	really.
3012		3162
3013	=back	3163	=back
		3164
		3165
		3166	=head2 C<ev_cleanup> - even the best things end
		3167
		3168	Cleanup watchers are called just before the event loop is being destroyed
		3169	by a call to C<ev_loop_destroy>.
		3170
		3171	While there is no guarantee that the event loop gets destroyed, cleanup
		3172	watchers provide a convenient method to install cleanup hooks for your
		3173	program, worker threads and so on - you just to make sure to destroy the
		3174	loop when you want them to be invoked.
		3175
		3176	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3177	all other watchers, they do not keep a reference to the event loop (which
		3178	makes a lot of sense if you think about it). Like all other watchers, you
		3179	can call libev functions in the callback, except C<ev_cleanup_start>.
		3180
		3181	=head3 Watcher-Specific Functions and Data Members
		3182
		3183	=over 4
		3184
		3185	=item ev_cleanup_init (ev_cleanup *, callback)
		3186
		3187	Initialises and configures the cleanup watcher - it has no parameters of
		3188	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3189	pointless, I assure you.
		3190
		3191	=back
		3192
		3193	Example: Register an atexit handler to destroy the default loop, so any
		3194	cleanup functions are called.
		3195
		3196	static void
		3197	program_exits (void)
		3198	{
		3199	ev_loop_destroy (EV_DEFAULT_UC);
		3200	}
		3201
		3202	...
		3203	atexit (program_exits);
3014		3204
3015		3205
3016	=head2 C<ev_async> - how to wake up an event loop	3206	=head2 C<ev_async> - how to wake up an event loop
3017		3207
3018	In general, you cannot use an C<ev_loop> from multiple threads or other	3208	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3025	it by calling C<ev_async_send>, which is thread- and signal safe.	3215	it by calling C<ev_async_send>, which is thread- and signal safe.
3026		3216
3027	This functionality is very similar to C<ev_signal> watchers, as signals,	3217	This functionality is very similar to C<ev_signal> watchers, as signals,
3028	too, are asynchronous in nature, and signals, too, will be compressed	3218	too, are asynchronous in nature, and signals, too, will be compressed
3029	(i.e. the number of callback invocations may be less than the number of	3219	(i.e. the number of callback invocations may be less than the number of
3030	C<ev_async_sent> calls).	3220	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3031		3221	of "global async watchers" by using a watcher on an otherwise unused
3032	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3222	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3033	just the default loop.	3223	even without knowing which loop owns the signal.
3034		3224
3035	=head3 Queueing	3225	=head3 Queueing
3036		3226
3037	C<ev_async> does not support queueing of data in any way. The reason	3227	C<ev_async> does not support queueing of data in any way. The reason
3038	is that the author does not know of a simple (or any) algorithm for a	3228	is that the author does not know of a simple (or any) algorithm for a
…		…
3130	trust me.	3320	trust me.
3131		3321
3132	=item ev_async_send (loop, ev_async *)	3322	=item ev_async_send (loop, ev_async *)
3133		3323
3134	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3324	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3135	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3325	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3326	returns.
		3327
3136	C<ev_feed_event>, this call is safe to do from other threads, signal or	3328	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3137	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3329	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3138	section below on what exactly this means).	3330	embedding section below on what exactly this means).
3139		3331
3140	Note that, as with other watchers in libev, multiple events might get	3332	Note that, as with other watchers in libev, multiple events might get
3141	compressed into a single callback invocation (another way to look at this	3333	compressed into a single callback invocation (another way to look at
3142	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3334	this is that C<ev_async> watchers are level-triggered: they are set on
3143	reset when the event loop detects that).	3335	C<ev_async_send>, reset when the event loop detects that).
3144		3336
3145	This call incurs the overhead of a system call only once per event loop	3337	This call incurs the overhead of at most one extra system call per event
3146	iteration, so while the overhead might be noticeable, it doesn't apply to	3338	loop iteration, if the event loop is blocked, and no syscall at all if
3147	repeated calls to C<ev_async_send> for the same event loop.	3339	the event loop (or your program) is processing events. That means that
		3340	repeated calls are basically free (there is no need to avoid calls for
		3341	performance reasons) and that the overhead becomes smaller (typically
		3342	zero) under load.
3148		3343
3149	=item bool = ev_async_pending (ev_async *)	3344	=item bool = ev_async_pending (ev_async *)
3150		3345
3151	Returns a non-zero value when C<ev_async_send> has been called on the	3346	Returns a non-zero value when C<ev_async_send> has been called on the
3152	watcher but the event has not yet been processed (or even noted) by the	3347	watcher but the event has not yet been processed (or even noted) by the
…		…
3211	Feed an event on the given fd, as if a file descriptor backend detected	3406	Feed an event on the given fd, as if a file descriptor backend detected
3212	the given events it.	3407	the given events it.
3213		3408
3214	=item ev_feed_signal_event (loop, int signum)	3409	=item ev_feed_signal_event (loop, int signum)
3215		3410
3216	Feed an event as if the given signal occurred (C<loop> must be the default	3411	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3217	loop!).	3412	which is async-safe.
3218		3413
3219	=back	3414	=back
		3415
		3416
		3417	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3418
		3419	This section explains some common idioms that are not immediately
		3420	obvious. Note that examples are sprinkled over the whole manual, and this
		3421	section only contains stuff that wouldn't fit anywhere else.
		3422
		3423	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3424
		3425	Each watcher has, by default, a C<void *data> member that you can read
		3426	or modify at any time: libev will completely ignore it. This can be used
		3427	to associate arbitrary data with your watcher. If you need more data and
		3428	don't want to allocate memory separately and store a pointer to it in that
		3429	data member, you can also "subclass" the watcher type and provide your own
		3430	data:
		3431
		3432	struct my_io
		3433	{
		3434	ev_io io;
		3435	int otherfd;
		3436	void *somedata;
		3437	struct whatever *mostinteresting;
		3438	};
		3439
		3440	...
		3441	struct my_io w;
		3442	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3443
		3444	And since your callback will be called with a pointer to the watcher, you
		3445	can cast it back to your own type:
		3446
		3447	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3448	{
		3449	struct my_io *w = (struct my_io *)w_;
		3450	...
		3451	}
		3452
		3453	More interesting and less C-conformant ways of casting your callback
		3454	function type instead have been omitted.
		3455
		3456	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3457
		3458	Another common scenario is to use some data structure with multiple
		3459	embedded watchers, in effect creating your own watcher that combines
		3460	multiple libev event sources into one "super-watcher":
		3461
		3462	struct my_biggy
		3463	{
		3464	int some_data;
		3465	ev_timer t1;
		3466	ev_timer t2;
		3467	}
		3468
		3469	In this case getting the pointer to C<my_biggy> is a bit more
		3470	complicated: Either you store the address of your C<my_biggy> struct in
		3471	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3472	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3473	real programmers):
		3474
		3475	#include <stddef.h>
		3476
		3477	static void
		3478	t1_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t1));
		3482	}
		3483
		3484	static void
		3485	t2_cb (EV_P_ ev_timer *w, int revents)
		3486	{
		3487	struct my_biggy big = (struct my_biggy *)
		3488	(((char *)w) - offsetof (struct my_biggy, t2));
		3489	}
		3490
		3491	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3492
		3493	Often (especially in GUI toolkits) there are places where you have
		3494	I<modal> interaction, which is most easily implemented by recursively
		3495	invoking C<ev_run>.
		3496
		3497	This brings the problem of exiting - a callback might want to finish the
		3498	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3499	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3500	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3501	other combination: In these cases, C<ev_break> will not work alone.
		3502
		3503	The solution is to maintain "break this loop" variable for each C<ev_run>
		3504	invocation, and use a loop around C<ev_run> until the condition is
		3505	triggered, using C<EVRUN_ONCE>:
		3506
		3507	// main loop
		3508	int exit_main_loop = 0;
		3509
		3510	while (!exit_main_loop)
		3511	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3512
		3513	// in a model watcher
		3514	int exit_nested_loop = 0;
		3515
		3516	while (!exit_nested_loop)
		3517	ev_run (EV_A_ EVRUN_ONCE);
		3518
		3519	To exit from any of these loops, just set the corresponding exit variable:
		3520
		3521	// exit modal loop
		3522	exit_nested_loop = 1;
		3523
		3524	// exit main program, after modal loop is finished
		3525	exit_main_loop = 1;
		3526
		3527	// exit both
		3528	exit_main_loop = exit_nested_loop = 1;
		3529
		3530	=head2 THREAD LOCKING EXAMPLE
		3531
		3532	Here is a fictitious example of how to run an event loop in a different
		3533	thread from where callbacks are being invoked and watchers are
		3534	created/added/removed.
		3535
		3536	For a real-world example, see the C<EV::Loop::Async> perl module,
		3537	which uses exactly this technique (which is suited for many high-level
		3538	languages).
		3539
		3540	The example uses a pthread mutex to protect the loop data, a condition
		3541	variable to wait for callback invocations, an async watcher to notify the
		3542	event loop thread and an unspecified mechanism to wake up the main thread.
		3543
		3544	First, you need to associate some data with the event loop:
		3545
		3546	typedef struct {
		3547	mutex_t lock; /* global loop lock */
		3548	ev_async async_w;
		3549	thread_t tid;
		3550	cond_t invoke_cv;
		3551	} userdata;
		3552
		3553	void prepare_loop (EV_P)
		3554	{
		3555	// for simplicity, we use a static userdata struct.
		3556	static userdata u;
		3557
		3558	ev_async_init (&u->async_w, async_cb);
		3559	ev_async_start (EV_A_ &u->async_w);
		3560
		3561	pthread_mutex_init (&u->lock, 0);
		3562	pthread_cond_init (&u->invoke_cv, 0);
		3563
		3564	// now associate this with the loop
		3565	ev_set_userdata (EV_A_ u);
		3566	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3567	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3568
		3569	// then create the thread running ev_run
		3570	pthread_create (&u->tid, 0, l_run, EV_A);
		3571	}
		3572
		3573	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3574	solely to wake up the event loop so it takes notice of any new watchers
		3575	that might have been added:
		3576
		3577	static void
		3578	async_cb (EV_P_ ev_async *w, int revents)
		3579	{
		3580	// just used for the side effects
		3581	}
		3582
		3583	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3584	protecting the loop data, respectively.
		3585
		3586	static void
		3587	l_release (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_unlock (&u->lock);
		3591	}
		3592
		3593	static void
		3594	l_acquire (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597	pthread_mutex_lock (&u->lock);
		3598	}
		3599
		3600	The event loop thread first acquires the mutex, and then jumps straight
		3601	into C<ev_run>:
		3602
		3603	void *
		3604	l_run (void *thr_arg)
		3605	{
		3606	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3607
		3608	l_acquire (EV_A);
		3609	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3610	ev_run (EV_A_ 0);
		3611	l_release (EV_A);
		3612
		3613	return 0;
		3614	}
		3615
		3616	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3617	signal the main thread via some unspecified mechanism (signals? pipe
		3618	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3619	have been called (in a while loop because a) spurious wakeups are possible
		3620	and b) skipping inter-thread-communication when there are no pending
		3621	watchers is very beneficial):
		3622
		3623	static void
		3624	l_invoke (EV_P)
		3625	{
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	while (ev_pending_count (EV_A))
		3629	{
		3630	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3631	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3632	}
		3633	}
		3634
		3635	Now, whenever the main thread gets told to invoke pending watchers, it
		3636	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3637	thread to continue:
		3638
		3639	static void
		3640	real_invoke_pending (EV_P)
		3641	{
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	pthread_mutex_lock (&u->lock);
		3645	ev_invoke_pending (EV_A);
		3646	pthread_cond_signal (&u->invoke_cv);
		3647	pthread_mutex_unlock (&u->lock);
		3648	}
		3649
		3650	Whenever you want to start/stop a watcher or do other modifications to an
		3651	event loop, you will now have to lock:
		3652
		3653	ev_timer timeout_watcher;
		3654	userdata *u = ev_userdata (EV_A);
		3655
		3656	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3657
		3658	pthread_mutex_lock (&u->lock);
		3659	ev_timer_start (EV_A_ &timeout_watcher);
		3660	ev_async_send (EV_A_ &u->async_w);
		3661	pthread_mutex_unlock (&u->lock);
		3662
		3663	Note that sending the C<ev_async> watcher is required because otherwise
		3664	an event loop currently blocking in the kernel will have no knowledge
		3665	about the newly added timer. By waking up the loop it will pick up any new
		3666	watchers in the next event loop iteration.
		3667
		3668	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3669
		3670	While the overhead of a callback that e.g. schedules a thread is small, it
		3671	is still an overhead. If you embed libev, and your main usage is with some
		3672	kind of threads or coroutines, you might want to customise libev so that
		3673	doesn't need callbacks anymore.
		3674
		3675	Imagine you have coroutines that you can switch to using a function
		3676	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3677	and that due to some magic, the currently active coroutine is stored in a
		3678	global called C<current_coro>. Then you can build your own "wait for libev
		3679	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3680	the differing C<;> conventions):
		3681
		3682	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3683	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3684
		3685	That means instead of having a C callback function, you store the
		3686	coroutine to switch to in each watcher, and instead of having libev call
		3687	your callback, you instead have it switch to that coroutine.
		3688
		3689	A coroutine might now wait for an event with a function called
		3690	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3691	matter when, or whether the watcher is active or not when this function is
		3692	called):
		3693
		3694	void
		3695	wait_for_event (ev_watcher *w)
		3696	{
		3697	ev_cb_set (w) = current_coro;
		3698	switch_to (libev_coro);
		3699	}
		3700
		3701	That basically suspends the coroutine inside C<wait_for_event> and
		3702	continues the libev coroutine, which, when appropriate, switches back to
		3703	this or any other coroutine. I am sure if you sue this your own :)
		3704
		3705	You can do similar tricks if you have, say, threads with an event queue -
		3706	instead of storing a coroutine, you store the queue object and instead of
		3707	switching to a coroutine, you push the watcher onto the queue and notify
		3708	any waiters.
		3709
		3710	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3711	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3712
		3713	// my_ev.h
		3714	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3715	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3716	#include "../libev/ev.h"
		3717
		3718	// my_ev.c
		3719	#define EV_H "my_ev.h"
		3720	#include "../libev/ev.c"
		3721
		3722	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3723	F<my_ev.c> into your project. When properly specifying include paths, you
		3724	can even use F<ev.h> as header file name directly.
3220		3725
3221		3726
3222	=head1 LIBEVENT EMULATION	3727	=head1 LIBEVENT EMULATION
3223		3728
3224	Libev offers a compatibility emulation layer for libevent. It cannot	3729	Libev offers a compatibility emulation layer for libevent. It cannot
3225	emulate the internals of libevent, so here are some usage hints:	3730	emulate the internals of libevent, so here are some usage hints:
3226		3731
3227	=over 4	3732	=over 4
		3733
		3734	=item * Only the libevent-1.4.1-beta API is being emulated.
		3735
		3736	This was the newest libevent version available when libev was implemented,
		3737	and is still mostly unchanged in 2010.
3228		3738
3229	=item * Use it by including <event.h>, as usual.	3739	=item * Use it by including <event.h>, as usual.
3230		3740
3231	=item * The following members are fully supported: ev_base, ev_callback,	3741	=item * The following members are fully supported: ev_base, ev_callback,
3232	ev_arg, ev_fd, ev_res, ev_events.	3742	ev_arg, ev_fd, ev_res, ev_events.
…		…
3238	=item * Priorities are not currently supported. Initialising priorities	3748	=item * Priorities are not currently supported. Initialising priorities
3239	will fail and all watchers will have the same priority, even though there	3749	will fail and all watchers will have the same priority, even though there
3240	is an ev_pri field.	3750	is an ev_pri field.
3241		3751
3242	=item * In libevent, the last base created gets the signals, in libev, the	3752	=item * In libevent, the last base created gets the signals, in libev, the
3243	first base created (== the default loop) gets the signals.	3753	base that registered the signal gets the signals.
3244		3754
3245	=item * Other members are not supported.	3755	=item * Other members are not supported.
3246		3756
3247	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3757	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3248	to use the libev header file and library.	3758	to use the libev header file and library.
…		…
3267	Care has been taken to keep the overhead low. The only data member the C++	3777	Care has been taken to keep the overhead low. The only data member the C++
3268	classes add (compared to plain C-style watchers) is the event loop pointer	3778	classes add (compared to plain C-style watchers) is the event loop pointer
3269	that the watcher is associated with (or no additional members at all if	3779	that the watcher is associated with (or no additional members at all if
3270	you disable C<EV_MULTIPLICITY> when embedding libev).	3780	you disable C<EV_MULTIPLICITY> when embedding libev).
3271		3781
3272	Currently, functions, and static and non-static member functions can be	3782	Currently, functions, static and non-static member functions and classes
3273	used as callbacks. Other types should be easy to add as long as they only	3783	with C<operator ()> can be used as callbacks. Other types should be easy
3274	need one additional pointer for context. If you need support for other	3784	to add as long as they only need one additional pointer for context. If
3275	types of functors please contact the author (preferably after implementing	3785	you need support for other types of functors please contact the author
3276	it).	3786	(preferably after implementing it).
3277		3787
3278	Here is a list of things available in the C<ev> namespace:	3788	Here is a list of things available in the C<ev> namespace:
3279		3789
3280	=over 4	3790	=over 4
3281		3791
…		…
3391	Associates a different C<struct ev_loop> with this watcher. You can only	3901	Associates a different C<struct ev_loop> with this watcher. You can only
3392	do this when the watcher is inactive (and not pending either).	3902	do this when the watcher is inactive (and not pending either).
3393		3903
3394	=item w->set ([arguments])	3904	=item w->set ([arguments])
3395		3905
3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3906	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3397	called at least once. Unlike the C counterpart, an active watcher gets	3907	method or a suitable start method must be called at least once. Unlike the
3398	automatically stopped and restarted when reconfiguring it with this	3908	C counterpart, an active watcher gets automatically stopped and restarted
3399	method.	3909	when reconfiguring it with this method.
3400		3910
3401	=item w->start ()	3911	=item w->start ()
3402		3912
3403	Starts the watcher. Note that there is no C<loop> argument, as the	3913	Starts the watcher. Note that there is no C<loop> argument, as the
3404	constructor already stores the event loop.	3914	constructor already stores the event loop.
3405		3915
		3916	=item w->start ([arguments])
		3917
		3918	Instead of calling C<set> and C<start> methods separately, it is often
		3919	convenient to wrap them in one call. Uses the same type of arguments as
		3920	the configure C<set> method of the watcher.
		3921
3406	=item w->stop ()	3922	=item w->stop ()
3407		3923
3408	Stops the watcher if it is active. Again, no C<loop> argument.	3924	Stops the watcher if it is active. Again, no C<loop> argument.
3409		3925
3410	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3926	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3422		3938
3423	=back	3939	=back
3424		3940
3425	=back	3941	=back
3426		3942
3427	Example: Define a class with an IO and idle watcher, start one of them in	3943	Example: Define a class with two I/O and idle watchers, start the I/O
3428	the constructor.	3944	watchers in the constructor.
3429		3945
3430	class myclass	3946	class myclass
3431	{	3947	{
3432	ev::io io ; void io_cb (ev::io &w, int revents);	3948	ev::io io ; void io_cb (ev::io &w, int revents);
		3949	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3950	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3434		3951
3435	myclass (int fd)	3952	myclass (int fd)
3436	{	3953	{
3437	io .set <myclass, &myclass::io_cb > (this);	3954	io .set <myclass, &myclass::io_cb > (this);
		3955	io2 .set <myclass, &myclass::io2_cb > (this);
3438	idle.set <myclass, &myclass::idle_cb> (this);	3956	idle.set <myclass, &myclass::idle_cb> (this);
3439		3957
3440	io.start (fd, ev::READ);	3958	io.set (fd, ev::WRITE); // configure the watcher
		3959	io.start (); // start it whenever convenient
		3960
		3961	io2.start (fd, ev::READ); // set + start in one call
3441	}	3962	}
3442	};	3963	};
3443		3964
3444		3965
3445	=head1 OTHER LANGUAGE BINDINGS	3966	=head1 OTHER LANGUAGE BINDINGS
…		…
3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4005	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3485		4006
3486	=item D	4007	=item D
3487		4008
3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4009	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4010	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3490		4011
3491	=item Ocaml	4012	=item Ocaml
3492		4013
3493	Erkki Seppala has written Ocaml bindings for libev, to be found at	4014	Erkki Seppala has written Ocaml bindings for libev, to be found at
3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3519	loop argument"). The C<EV_A> form is used when this is the sole argument,	4040	loop argument"). The C<EV_A> form is used when this is the sole argument,
3520	C<EV_A_> is used when other arguments are following. Example:	4041	C<EV_A_> is used when other arguments are following. Example:
3521		4042
3522	ev_unref (EV_A);	4043	ev_unref (EV_A);
3523	ev_timer_add (EV_A_ watcher);	4044	ev_timer_add (EV_A_ watcher);
3524	ev_loop (EV_A_ 0);	4045	ev_run (EV_A_ 0);
3525		4046
3526	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4047	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3527	which is often provided by the following macro.	4048	which is often provided by the following macro.
3528		4049
3529	=item C<EV_P>, C<EV_P_>	4050	=item C<EV_P>, C<EV_P_>
…		…
3569	}	4090	}
3570		4091
3571	ev_check check;	4092	ev_check check;
3572	ev_check_init (&check, check_cb);	4093	ev_check_init (&check, check_cb);
3573	ev_check_start (EV_DEFAULT_ &check);	4094	ev_check_start (EV_DEFAULT_ &check);
3574	ev_loop (EV_DEFAULT_ 0);	4095	ev_run (EV_DEFAULT_ 0);
3575		4096
3576	=head1 EMBEDDING	4097	=head1 EMBEDDING
3577		4098
3578	Libev can (and often is) directly embedded into host	4099	Libev can (and often is) directly embedded into host
3579	applications. Examples of applications that embed it include the Deliantra	4100	applications. Examples of applications that embed it include the Deliantra
…		…
3671	users of libev and the libev code itself must be compiled with compatible	4192	users of libev and the libev code itself must be compiled with compatible
3672	settings.	4193	settings.
3673		4194
3674	=over 4	4195	=over 4
3675		4196
		4197	=item EV_COMPAT3 (h)
		4198
		4199	Backwards compatibility is a major concern for libev. This is why this
		4200	release of libev comes with wrappers for the functions and symbols that
		4201	have been renamed between libev version 3 and 4.
		4202
		4203	You can disable these wrappers (to test compatibility with future
		4204	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4205	sources. This has the additional advantage that you can drop the C<struct>
		4206	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4207	typedef in that case.
		4208
		4209	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4210	and in some even more future version the compatibility code will be
		4211	removed completely.
		4212
3676	=item EV_STANDALONE (h)	4213	=item EV_STANDALONE (h)
3677		4214
3678	Must always be C<1> if you do not use autoconf configuration, which	4215	Must always be C<1> if you do not use autoconf configuration, which
3679	keeps libev from including F<config.h>, and it also defines dummy	4216	keeps libev from including F<config.h>, and it also defines dummy
3680	implementations for some libevent functions (such as logging, which is not	4217	implementations for some libevent functions (such as logging, which is not
3681	supported). It will also not define any of the structs usually found in	4218	supported). It will also not define any of the structs usually found in
3682	F<event.h> that are not directly supported by the libev core alone.	4219	F<event.h> that are not directly supported by the libev core alone.
3683		4220
3684	In standalone mode, libev will still try to automatically deduce the	4221	In standalone mode, libev will still try to automatically deduce the
3685	configuration, but has to be more conservative.	4222	configuration, but has to be more conservative.
		4223
		4224	=item EV_USE_FLOOR
		4225
		4226	If defined to be C<1>, libev will use the C<floor ()> function for its
		4227	periodic reschedule calculations, otherwise libev will fall back on a
		4228	portable (slower) implementation. If you enable this, you usually have to
		4229	link against libm or something equivalent. Enabling this when the C<floor>
		4230	function is not available will fail, so the safe default is to not enable
		4231	this.
3686		4232
3687	=item EV_USE_MONOTONIC	4233	=item EV_USE_MONOTONIC
3688		4234
3689	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
3690	monotonic clock option at both compile time and runtime. Otherwise no	4236	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3823	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4369	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3824		4370
3825	=item EV_ATOMIC_T	4371	=item EV_ATOMIC_T
3826		4372
3827	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4373	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3828	access is atomic with respect to other threads or signal contexts. No such	4374	access is atomic and serialised with respect to other threads or signal
3829	type is easily found in the C language, so you can provide your own type	4375	contexts. No such type is easily found in the C language, so you can
3830	that you know is safe for your purposes. It is used both for signal handler "locking"	4376	provide your own type that you know is safe for your purposes. It is used
3831	as well as for signal and thread safety in C<ev_async> watchers.	4377	both for signal handler "locking" as well as for signal and thread safety
		4378	in C<ev_async> watchers.
3832		4379
3833	In the absence of this define, libev will use C<sig_atomic_t volatile>	4380	In the absence of this define, libev will use C<sig_atomic_t volatile>
3834	(from F<signal.h>), which is usually good enough on most platforms.	4381	(from F<signal.h>), which is usually good enough on most platforms.
3835		4382
3836	=item EV_H (h)	4383	=item EV_H (h)
…		…
4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4576	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4030	will be C<0>.	4577	will be C<0>.
4031		4578
4032	=item EV_VERIFY	4579	=item EV_VERIFY
4033		4580
4034	Controls how much internal verification (see C<ev_loop_verify ()>) will	4581	Controls how much internal verification (see C<ev_verify ()>) will
4035	be done: If set to C<0>, no internal verification code will be compiled	4582	be done: If set to C<0>, no internal verification code will be compiled
4036	in. If set to C<1>, then verification code will be compiled in, but not	4583	in. If set to C<1>, then verification code will be compiled in, but not
4037	called. If set to C<2>, then the internal verification code will be	4584	called. If set to C<2>, then the internal verification code will be
4038	called once per loop, which can slow down libev. If set to C<3>, then the	4585	called once per loop, which can slow down libev. If set to C<3>, then the
4039	verification code will be called very frequently, which will slow down	4586	verification code will be called very frequently, which will slow down
…		…
4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4669	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4123		4670
4124	#include "ev_cpp.h"	4671	#include "ev_cpp.h"
4125	#include "ev.c"	4672	#include "ev.c"
4126		4673
4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4674	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4128		4675
4129	=head2 THREADS AND COROUTINES	4676	=head2 THREADS AND COROUTINES
4130		4677
4131	=head3 THREADS	4678	=head3 THREADS
4132		4679
…		…
4183	default loop and triggering an C<ev_async> watcher from the default loop	4730	default loop and triggering an C<ev_async> watcher from the default loop
4184	watcher callback into the event loop interested in the signal.	4731	watcher callback into the event loop interested in the signal.
4185		4732
4186	=back	4733	=back
4187		4734
4188	=head4 THREAD LOCKING EXAMPLE	4735	See also L<THREAD LOCKING EXAMPLE>.
4189
4190	Here is a fictitious example of how to run an event loop in a different
4191	thread than where callbacks are being invoked and watchers are
4192	created/added/removed.
4193
4194	For a real-world example, see the C<EV::Loop::Async> perl module,
4195	which uses exactly this technique (which is suited for many high-level
4196	languages).
4197
4198	The example uses a pthread mutex to protect the loop data, a condition
4199	variable to wait for callback invocations, an async watcher to notify the
4200	event loop thread and an unspecified mechanism to wake up the main thread.
4201
4202	First, you need to associate some data with the event loop:
4203
4204	typedef struct {
4205	mutex_t lock; /* global loop lock */
4206	ev_async async_w;
4207	thread_t tid;
4208	cond_t invoke_cv;
4209	} userdata;
4210
4211	void prepare_loop (EV_P)
4212	{
4213	// for simplicity, we use a static userdata struct.
4214	static userdata u;
4215
4216	ev_async_init (&u->async_w, async_cb);
4217	ev_async_start (EV_A_ &u->async_w);
4218
4219	pthread_mutex_init (&u->lock, 0);
4220	pthread_cond_init (&u->invoke_cv, 0);
4221
4222	// now associate this with the loop
4223	ev_set_userdata (EV_A_ u);
4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4226
4227	// then create the thread running ev_loop
4228	pthread_create (&u->tid, 0, l_run, EV_A);
4229	}
4230
4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
4232	solely to wake up the event loop so it takes notice of any new watchers
4233	that might have been added:
4234
4235	static void
4236	async_cb (EV_P_ ev_async *w, int revents)
4237	{
4238	// just used for the side effects
4239	}
4240
4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4242	protecting the loop data, respectively.
4243
4244	static void
4245	l_release (EV_P)
4246	{
4247	userdata *u = ev_userdata (EV_A);
4248	pthread_mutex_unlock (&u->lock);
4249	}
4250
4251	static void
4252	l_acquire (EV_P)
4253	{
4254	userdata *u = ev_userdata (EV_A);
4255	pthread_mutex_lock (&u->lock);
4256	}
4257
4258	The event loop thread first acquires the mutex, and then jumps straight
4259	into C<ev_loop>:
4260
4261	void *
4262	l_run (void *thr_arg)
4263	{
4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4265
4266	l_acquire (EV_A);
4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4268	ev_loop (EV_A_ 0);
4269	l_release (EV_A);
4270
4271	return 0;
4272	}
4273
4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
4275	signal the main thread via some unspecified mechanism (signals? pipe
4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4277	have been called (in a while loop because a) spurious wakeups are possible
4278	and b) skipping inter-thread-communication when there are no pending
4279	watchers is very beneficial):
4280
4281	static void
4282	l_invoke (EV_P)
4283	{
4284	userdata *u = ev_userdata (EV_A);
4285
4286	while (ev_pending_count (EV_A))
4287	{
4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
4290	}
4291	}
4292
4293	Now, whenever the main thread gets told to invoke pending watchers, it
4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4295	thread to continue:
4296
4297	static void
4298	real_invoke_pending (EV_P)
4299	{
4300	userdata *u = ev_userdata (EV_A);
4301
4302	pthread_mutex_lock (&u->lock);
4303	ev_invoke_pending (EV_A);
4304	pthread_cond_signal (&u->invoke_cv);
4305	pthread_mutex_unlock (&u->lock);
4306	}
4307
4308	Whenever you want to start/stop a watcher or do other modifications to an
4309	event loop, you will now have to lock:
4310
4311	ev_timer timeout_watcher;
4312	userdata *u = ev_userdata (EV_A);
4313
4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4315
4316	pthread_mutex_lock (&u->lock);
4317	ev_timer_start (EV_A_ &timeout_watcher);
4318	ev_async_send (EV_A_ &u->async_w);
4319	pthread_mutex_unlock (&u->lock);
4320
4321	Note that sending the C<ev_async> watcher is required because otherwise
4322	an event loop currently blocking in the kernel will have no knowledge
4323	about the newly added timer. By waking up the loop it will pick up any new
4324	watchers in the next event loop iteration.
4325		4736
4326	=head3 COROUTINES	4737	=head3 COROUTINES
4327		4738
4328	Libev is very accommodating to coroutines ("cooperative threads"):	4739	Libev is very accommodating to coroutines ("cooperative threads"):
4329	libev fully supports nesting calls to its functions from different	4740	libev fully supports nesting calls to its functions from different
4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4741	coroutines (e.g. you can call C<ev_run> on the same loop from two
4331	different coroutines, and switch freely between both coroutines running	4742	different coroutines, and switch freely between both coroutines running
4332	the loop, as long as you don't confuse yourself). The only exception is	4743	the loop, as long as you don't confuse yourself). The only exception is
4333	that you must not do this from C<ev_periodic> reschedule callbacks.	4744	that you must not do this from C<ev_periodic> reschedule callbacks.
4334		4745
4335	Care has been taken to ensure that libev does not keep local state inside	4746	Care has been taken to ensure that libev does not keep local state inside
4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4747	C<ev_run>, and other calls do not usually allow for coroutine switches as
4337	they do not call any callbacks.	4748	they do not call any callbacks.
4338		4749
4339	=head2 COMPILER WARNINGS	4750	=head2 COMPILER WARNINGS
4340		4751
4341	Depending on your compiler and compiler settings, you might get no or a	4752	Depending on your compiler and compiler settings, you might get no or a
…		…
4425	=head3 C<kqueue> is buggy	4836	=head3 C<kqueue> is buggy
4426		4837
4427	The kqueue syscall is broken in all known versions - most versions support	4838	The kqueue syscall is broken in all known versions - most versions support
4428	only sockets, many support pipes.	4839	only sockets, many support pipes.
4429		4840
4430	Libev tries to work around this by not using C<kqueue> by default on	4841	Libev tries to work around this by not using C<kqueue> by default on this
4431	this rotten platform, but of course you can still ask for it when creating	4842	rotten platform, but of course you can still ask for it when creating a
4432	a loop.	4843	loop - embedding a socket-only kqueue loop into a select-based one is
		4844	probably going to work well.
4433		4845
4434	=head3 C<poll> is buggy	4846	=head3 C<poll> is buggy
4435		4847
4436	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4848	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4437	implementation by something calling C<kqueue> internally around the 10.5.6	4849	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4456		4868
4457	=head3 C<errno> reentrancy	4869	=head3 C<errno> reentrancy
4458		4870
4459	The default compile environment on Solaris is unfortunately so	4871	The default compile environment on Solaris is unfortunately so
4460	thread-unsafe that you can't even use components/libraries compiled	4872	thread-unsafe that you can't even use components/libraries compiled
4461	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4873	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4462	isn't defined by default.	4874	defined by default. A valid, if stupid, implementation choice.
4463		4875
4464	If you want to use libev in threaded environments you have to make sure	4876	If you want to use libev in threaded environments you have to make sure
4465	it's compiled with C<_REENTRANT> defined.	4877	it's compiled with C<_REENTRANT> defined.
4466		4878
4467	=head3 Event port backend	4879	=head3 Event port backend
4468		4880
4469	The scalable event interface for Solaris is called "event ports". Unfortunately,	4881	The scalable event interface for Solaris is called "event
4470	this mechanism is very buggy. If you run into high CPU usage, your program	4882	ports". Unfortunately, this mechanism is very buggy in all major
		4883	releases. If you run into high CPU usage, your program freezes or you get
4471	freezes or you get a large number of spurious wakeups, make sure you have	4884	a large number of spurious wakeups, make sure you have all the relevant
4472	all the relevant and latest kernel patches applied. No, I don't know which	4885	and latest kernel patches applied. No, I don't know which ones, but there
4473	ones, but there are multiple ones.	4886	are multiple ones to apply, and afterwards, event ports actually work
		4887	great.
4474		4888
4475	If you can't get it to work, you can try running the program by setting	4889	If you can't get it to work, you can try running the program by setting
4476	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	4890	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4477	C<select> backends.	4891	C<select> backends.
4478		4892
4479	=head2 AIX POLL BUG	4893	=head2 AIX POLL BUG
4480		4894
4481	AIX unfortunately has a broken C<poll.h> header. Libev works around	4895	AIX unfortunately has a broken C<poll.h> header. Libev works around
4482	this by trying to avoid the poll backend altogether (i.e. it's not even	4896	this by trying to avoid the poll backend altogether (i.e. it's not even
4483	compiled in), which normally isn't a big problem as C<select> works fine	4897	compiled in), which normally isn't a big problem as C<select> works fine
4484	with large bitsets, and AIX is dead anyway.	4898	with large bitsets on AIX, and AIX is dead anyway.
4485		4899
4486	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4900	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4487		4901
4488	=head3 General issues	4902	=head3 General issues
4489		4903
…		…
4491	requires, and its I/O model is fundamentally incompatible with the POSIX	4905	requires, and its I/O model is fundamentally incompatible with the POSIX
4492	model. Libev still offers limited functionality on this platform in	4906	model. Libev still offers limited functionality on this platform in
4493	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4907	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4494	descriptors. This only applies when using Win32 natively, not when using	4908	descriptors. This only applies when using Win32 natively, not when using
4495	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	4909	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4496	as every compielr comes with a slightly differently broken/incompatible	4910	as every compiler comes with a slightly differently broken/incompatible
4497	environment.	4911	environment.
4498		4912
4499	Lifting these limitations would basically require the full	4913	Lifting these limitations would basically require the full
4500	re-implementation of the I/O system. If you are into this kind of thing,	4914	re-implementation of the I/O system. If you are into this kind of thing,
4501	then note that glib does exactly that for you in a very portable way (note	4915	then note that glib does exactly that for you in a very portable way (note
…		…
4595	structure (guaranteed by POSIX but not by ISO C for example), but it also	5009	structure (guaranteed by POSIX but not by ISO C for example), but it also
4596	assumes that the same (machine) code can be used to call any watcher	5010	assumes that the same (machine) code can be used to call any watcher
4597	callback: The watcher callbacks have different type signatures, but libev	5011	callback: The watcher callbacks have different type signatures, but libev
4598	calls them using an C<ev_watcher *> internally.	5012	calls them using an C<ev_watcher *> internally.
4599		5013
		5014	=item pointer accesses must be thread-atomic
		5015
		5016	Accessing a pointer value must be atomic, it must both be readable and
		5017	writable in one piece - this is the case on all current architectures.
		5018
4600	=item C<sig_atomic_t volatile> must be thread-atomic as well	5019	=item C<sig_atomic_t volatile> must be thread-atomic as well
4601		5020
4602	The type C<sig_atomic_t volatile> (or whatever is defined as	5021	The type C<sig_atomic_t volatile> (or whatever is defined as
4603	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5022	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4604	threads. This is not part of the specification for C<sig_atomic_t>, but is	5023	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4626	watchers.	5045	watchers.
4627		5046
4628	=item C<double> must hold a time value in seconds with enough accuracy	5047	=item C<double> must hold a time value in seconds with enough accuracy
4629		5048
4630	The type C<double> is used to represent timestamps. It is required to	5049	The type C<double> is used to represent timestamps. It is required to
4631	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5050	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4632	enough for at least into the year 4000. This requirement is fulfilled by	5051	good enough for at least into the year 4000 with millisecond accuracy
		5052	(the design goal for libev). This requirement is overfulfilled by
4633	implementations implementing IEEE 754, which is basically all existing	5053	implementations using IEEE 754, which is basically all existing ones.
		5054
4634	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5055	With IEEE 754 doubles, you get microsecond accuracy until at least the
4635	2200.	5056	year 2255 (and millisecond accuray till the year 287396 - by then, libev
		5057	is either obsolete or somebody patched it to use C<long double> or
		5058	something like that, just kidding).
4636		5059
4637	=back	5060	=back
4638		5061
4639	If you know of other additional requirements drop me a note.	5062	If you know of other additional requirements drop me a note.
4640		5063
…		…
4702	=item Processing ev_async_send: O(number_of_async_watchers)	5125	=item Processing ev_async_send: O(number_of_async_watchers)
4703		5126
4704	=item Processing signals: O(max_signal_number)	5127	=item Processing signals: O(max_signal_number)
4705		5128
4706	Sending involves a system call I<iff> there were no other C<ev_async_send>	5129	Sending involves a system call I<iff> there were no other C<ev_async_send>
4707	calls in the current loop iteration. Checking for async and signal events	5130	calls in the current loop iteration and the loop is currently
		5131	blocked. Checking for async and signal events involves iterating over all
4708	involves iterating over all running async watchers or all signal numbers.	5132	running async watchers or all signal numbers.
4709		5133
4710	=back	5134	=back
4711		5135
4712		5136
4713	=head1 PORTING FROM LIBEV 3.X TO 4.X	5137	=head1 PORTING FROM LIBEV 3.X TO 4.X
4714		5138
4715	The major version 4 introduced some minor incompatible changes to the API.	5139	The major version 4 introduced some incompatible changes to the API.
4716		5140
4717	At the moment, the C<ev.h> header file tries to implement superficial	5141	At the moment, the C<ev.h> header file provides compatibility definitions
4718	compatibility, so most programs should still compile. Those might be	5142	for all changes, so most programs should still compile. The compatibility
4719	removed in later versions of libev, so better update early than late.	5143	layer might be removed in later versions of libev, so better update to the
		5144	new API early than late.
4720		5145
4721	=over 4	5146	=over 4
4722		5147
4723	=item C<ev_loop_count> renamed to C<ev_iteration>	5148	=item C<EV_COMPAT3> backwards compatibility mechanism
4724		5149
4725	=item C<ev_loop_depth> renamed to C<ev_depth>	5150	The backward compatibility mechanism can be controlled by
		5151	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5152	section.
4726		5153
4727	=item C<ev_loop_verify> renamed to C<ev_verify>	5154	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5155
		5156	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5157
		5158	ev_loop_destroy (EV_DEFAULT_UC);
		5159	ev_loop_fork (EV_DEFAULT);
		5160
		5161	=item function/symbol renames
		5162
		5163	A number of functions and symbols have been renamed:
		5164
		5165	ev_loop => ev_run
		5166	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5167	EVLOOP_ONESHOT => EVRUN_ONCE
		5168
		5169	ev_unloop => ev_break
		5170	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5171	EVUNLOOP_ONE => EVBREAK_ONE
		5172	EVUNLOOP_ALL => EVBREAK_ALL
		5173
		5174	EV_TIMEOUT => EV_TIMER
		5175
		5176	ev_loop_count => ev_iteration
		5177	ev_loop_depth => ev_depth
		5178	ev_loop_verify => ev_verify
4728		5179
4729	Most functions working on C<struct ev_loop> objects don't have an	5180	Most functions working on C<struct ev_loop> objects don't have an
4730	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5181	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5182	associated constants have been renamed to not collide with the C<struct
		5183	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5184	as all other watcher types. Note that C<ev_loop_fork> is still called
4731	still called C<ev_loop_fork> because it would otherwise clash with the	5185	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4732	C<ev_fork> typedef.	5186	typedef.
4733
4734	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4735
4736	This is a simple rename - all other watcher types use their name
4737	as revents flag, and now C<ev_timer> does, too.
4738
4739	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4740	and continue to be present for the foreseeable future, so this is mostly a
4741	documentation change.
4742		5187
4743	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5188	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4744		5189
4745	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5190	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4746	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5191	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4753		5198
4754	=over 4	5199	=over 4
4755		5200
4756	=item active	5201	=item active
4757		5202
4758	A watcher is active as long as it has been started (has been attached to	5203	A watcher is active as long as it has been started and not yet stopped.
4759	an event loop) but not yet stopped (disassociated from the event loop).	5204	See L<WATCHER STATES> for details.
4760		5205
4761	=item application	5206	=item application
4762		5207
4763	In this document, an application is whatever is using libev.	5208	In this document, an application is whatever is using libev.
		5209
		5210	=item backend
		5211
		5212	The part of the code dealing with the operating system interfaces.
4764		5213
4765	=item callback	5214	=item callback
4766		5215
4767	The address of a function that is called when some event has been	5216	The address of a function that is called when some event has been
4768	detected. Callbacks are being passed the event loop, the watcher that	5217	detected. Callbacks are being passed the event loop, the watcher that
4769	received the event, and the actual event bitset.	5218	received the event, and the actual event bitset.
4770		5219
4771	=item callback invocation	5220	=item callback/watcher invocation
4772		5221
4773	The act of calling the callback associated with a watcher.	5222	The act of calling the callback associated with a watcher.
4774		5223
4775	=item event	5224	=item event
4776		5225
…		…
4795	The model used to describe how an event loop handles and processes	5244	The model used to describe how an event loop handles and processes
4796	watchers and events.	5245	watchers and events.
4797		5246
4798	=item pending	5247	=item pending
4799		5248
4800	A watcher is pending as soon as the corresponding event has been detected,	5249	A watcher is pending as soon as the corresponding event has been
4801	and stops being pending as soon as the watcher will be invoked or its	5250	detected. See L<WATCHER STATES> for details.
4802	pending status is explicitly cleared by the application.
4803
4804	A watcher can be pending, but not active. Stopping a watcher also clears
4805	its pending status.
4806		5251
4807	=item real time	5252	=item real time
4808		5253
4809	The physical time that is observed. It is apparently strictly monotonic :)	5254	The physical time that is observed. It is apparently strictly monotonic :)
4810		5255
4811	=item wall-clock time	5256	=item wall-clock time
4812		5257
4813	The time and date as shown on clocks. Unlike real time, it can actually	5258	The time and date as shown on clocks. Unlike real time, it can actually
4814	be wrong and jump forwards and backwards, e.g. when the you adjust your	5259	be wrong and jump forwards and backwards, e.g. when you adjust your
4815	clock.	5260	clock.
4816		5261
4817	=item watcher	5262	=item watcher
4818		5263
4819	A data structure that describes interest in certain events. Watchers need	5264	A data structure that describes interest in certain events. Watchers need
4820	to be started (attached to an event loop) before they can receive events.	5265	to be started (attached to an event loop) before they can receive events.
4821		5266
4822	=item watcher invocation
4823
4824	The act of calling the callback associated with a watcher.
4825
4826	=back	5267	=back
4827		5268
4828	=head1 AUTHOR	5269	=head1 AUTHOR
4829		5270
4830	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5271	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5272	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4831		5273

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