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Revision 1.393 by root, Sat Jan 21 12:23:45 2012 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_now_update> 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.	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
		520	not least, it also refuses to work with some file descriptors which work
		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...
445		526
446	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
447	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
448	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
449	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
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		597
517	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,
518	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)).
519		600
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	604	might perform better.
528		605
529	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
532	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.
533		620
534	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
535	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
536		623
537	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
538		625
539	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
540	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
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		629
543	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).
544		639
545	=back	640	=back
546		641
547	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,
548	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
549	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
550	()> will be tried.	645	()> will be tried.
551		646
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
579		648
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	650	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
583		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
584	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
585		659
586	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
587	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
588	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
589	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
590	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
591	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).
592		667
593	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
594	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
595	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
596		671
597	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
598	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.
599	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>
600	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
601		680
602	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
603		682
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	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
610	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
611	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
612	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
613	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
614	functions, and it will only take effect at the next C<ev_loop> iteration.
615		688
616	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
617	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
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	692	during fork.
620		693
621	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
622	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
623	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
624	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).
625		700
626	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
627	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		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	...
630	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		715
639	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
640		717
641	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
642	otherwise.	719	otherwise.
643		720
644	=item unsigned int ev_iteration (loop)	721	=item unsigned int ev_iteration (loop)
645		722
646	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
647	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>
648	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
649		726
650	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
651	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
652	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
653	prepare and check phases.	730	prepare and check phases.
654		731
655	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
656		733
657	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
658	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.
659		736
660	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
661	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),
662	in which case it is higher.	739	in which case it is higher.
663		740
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	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
666	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.
667		745
668	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
669		747
670	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
671	use.	749	use.
…		…
680		758
681	=item ev_now_update (loop)	759	=item ev_now_update (loop)
682		760
683	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
684	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
685	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
686		764
687	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
688	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
689	the current time is a good idea.	767	the current time is a good idea.
690		768
…		…
692		770
693	=item ev_suspend (loop)	771	=item ev_suspend (loop)
694		772
695	=item ev_resume (loop)	773	=item ev_resume (loop)
696		774
697	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
698	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.
699		777
700	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
701	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
702	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
703	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>
…		…
714	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
715		793
716	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
717	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
718		796
719	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
720		798
721	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
722	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
723	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>.
724		804
725	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
726	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.
727		808
728	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
729	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
730	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
731	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
732	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
733	beauty.	814	beauty.
734		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
735	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
736	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
737	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
738	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.
739		826
740	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
741	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
742	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
743	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
744	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
745	iteration of the loop.	832	iteration of the loop.
746		833
747	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
748	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
749	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
750	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
751		838
752	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):
753		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- 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.
757	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	852	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
765	- 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.
766	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
768	- 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.
769	- Queue all expired timers.	863	- Queue all expired timers.
770	- Queue all expired periodics.	864	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	866	- Queue all check watchers.
773	- 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).
774	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
775	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
776	- 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
777	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
778	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.
779		877
780	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
781	anymore.	879	anymore.
782		880
783	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
784	... 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..)
785	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
787		885
788	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
789		887
790	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
791	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
792	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
793	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.
794		892
795	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>.
796		894
797	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.
798		897
799	=item ev_ref (loop)	898	=item ev_ref (loop)
800		899
801	=item ev_unref (loop)	900	=item ev_unref (loop)
802		901
803	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
804	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
805	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.
806		905
807	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
808	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
809	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>
810	before stopping it.	909	before stopping it.
811		910
812	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
813	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
814	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
815	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
816	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
817	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
818	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
819	(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>
820	in the callback).	919	in the callback).
821		920
822	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>
823	running when nothing else is active.	922	running when nothing else is active.
824		923
825	ev_signal exitsig;	924	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	927	ev_unref (loop);
829		928
830	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
831		930
832	ev_ref (loop);	931	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
853	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.
854		953
855	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
856	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,
857	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
858	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
859	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
860	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
861	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
862		962
863	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
864	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
866	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
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		991
892	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
893		993
894	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
896	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).
897		1001
898	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
899		1003
900	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1005	are pending.
902		1006
903	=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))
904		1008
905	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
906	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
907	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
908	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
909		1013
910	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
911	callback.	1015	callback.
…		…
914		1018
915	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
916	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
917	each call to a libev function.	1021	each call to a libev function.
918		1022
919	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
920	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
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
923		1027
924	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
925	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1030	afterwards.
927		1031
…		…
930		1034
931	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
932	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
933	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
934	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
935	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
936	to take note of any changes you made.	1040	to take note of any changes you made.
937		1041
938	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
939	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
940		1044
941	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
942	document.	1046	document.
943		1047
944	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
945		1049
946	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
947		1051
948	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
949	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
950	C<0.>	1054	C<0>.
951		1055
952	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,
953	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
954	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
955	any other purpose as well.	1059	any other purpose as well.
956		1060
957	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
958		1062
959	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
960	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
961	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
962	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
…		…
973		1077
974	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
975	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
976	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
977		1081
978	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
979	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
980	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:
981		1086
982	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)
983	{	1088	{
984	ev_io_stop (w);	1089	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
986	}	1091	}
987		1092
988	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
989		1094
990	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
991		1096
992	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
995		1100
996	ev_loop (loop, 0);	1101	ev_run (loop, 0);
997		1102
998	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
999	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
1000	stack).	1105	stack).
1001		1106
1002	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>
1003	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).
1004		1109
1005	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
1006	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
1007	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
1008	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
1009	is readable and/or writable).	1114	and/or writable).
1010		1115
1011	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 *, ...) >>
1012	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
1013	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<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1170
1066	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1067		1172
1068	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1069		1174
1070	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
1071	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
1072	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
1073	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
1074	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
1075	(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
1076	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1077		1182
1078	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1079		1184
1080	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.
1081		1186
1082	=item C<EV_FORK>	1187	=item C<EV_FORK>
1083		1188
1084	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
1085	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>).
1086		1195
1087	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1088		1197
1089	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>).
1090		1199
…		…
1263	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
1264	functions that do not need a watcher.	1373	functions that do not need a watcher.
1265		1374
1266	=back	1375	=back
1267		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1268		1379
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1270		1381
1271	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1272	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
1273	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
1274	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".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1386
1278	struct my_io	1387	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1388
1286	...	1389	=item initialiased
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1390
1290	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
1291	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.
1292		1394
1293	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
1294	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1296	...	1398	C<ev_TYPE_init> again.
1297	}
1298		1399
1299	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1300	instead have been omitted.
1301		1401
1302	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
1303	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.
1304		1407
1305	struct my_biggy	1408	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1409
1312	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
1313	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
1314	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
1315	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
1316	programmers):	1414	callback.
1317		1415
1318	#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.
1319		1422
1320	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1425	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1426
1327	static void	1427	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1329	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1332	}	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
1333		1441
1334	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1335		1443
1336	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1464	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
1465	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
1466	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
1467	required if you know what you are doing).	1575	required if you know what you are doing).
1468		1576
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarantee any specific behaviour in that case.
1474
1475	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
1476	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1477	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
1478	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
1479	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
1480	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
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1483		1584
1484	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
1485	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
1486	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
1487	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
1488	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
1489	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
1490	indefinitely.	1591	indefinitely.
1491		1592
1492	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1493		1594
…		…
1521		1622
1522	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		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
1526	=head3 The special problem of fork	1660	=head3 The special problem of fork
1527		1661
1528	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
1529	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
1530	it in the child.	1664	it in the child if you want to continue to use it in the child.
1531		1665
1532	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
1533	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
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1669
1537	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1538		1671
1539	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>:
1540	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
…		…
1622	...	1755	...
1623	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1757	ev_io stdin_readable;
1625	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);
1626	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1628		1761
1629		1762
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1764
1632	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
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1640		1773
1641	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
1642	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
1643	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1778	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1779	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1647		1781
1648	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1649		1783
1650	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1860
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1863	within the callback:
1730		1864
		1865	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1732		1868
1733	static void	1869	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1735	{	1871	{
1736	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1874
1739	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1740	if (timeout < now)	1876	if (after < 0.)
1741	{	1877	{
1742	// timeout occurred, take action	1878	// timeout occurred, take action
1743	}	1879	}
1744	else	1880	else
1745	{	1881	{
1746	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1751	}	1888	}
1752	}	1889	}
1753		1890
1754	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1755	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1756	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1757	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1758	re-schedule the timer to fire at that future time, to see if maybe we have
1759	a timeout then.
1760		1895
1761	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1763		1905
1764	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1908	libev to change the timeout.
1767		1909
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1771		1914
		1915	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		1918
1776	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1778		1921
		1922	if (activity detected)
1779	last_activity = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1780		1932
1781	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1783
1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
1785	callback :) - just change the timeout and invoke the callback, which will
1786	fix things for you.
1787		1935
1788	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1789		1937
1790	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1791	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1819	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1820	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	1969	overkill :)
1822		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1823	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1824		2009
1825	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2014	lots of events in one iteration.
1830		2015
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1838		2023
1839	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2026	()>.
		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
1842		2060
1843	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1844		2062
1845	When you leave the server world it is quite customary to hit machines that	2063	When you leave the server world it is quite customary to hit machines that
1846	can suspend/hibernate - what happens to the clocks during such a suspend?	2064	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1890	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1891	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1892		2110
1893	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1894		2112
1895	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out and restarts it again if it is
1896	repeating. The exact semantics are:	2114	repeating. The exact semantics are:
1897		2115
1898	If the timer is pending, its pending status is cleared.	2116	If the timer is pending, its pending status is cleared.
1899		2117
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2118	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1949	}	2167	}
1950		2168
1951	ev_timer mytimer;	2169	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2170	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2171	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2172	ev_run (loop, 0);
1955		2173
1956	// and in some piece of code that gets executed on any "activity":	2174	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2175	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2176	ev_timer_again (&mytimer);
1959		2177
…		…
1985		2203
1986	As with timers, the callback is guaranteed to be invoked only when the	2204	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2205	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2206	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2207	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2208	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2209
1992	=head3 Watcher-Specific Functions and Data Members	2210	=head3 Watcher-Specific Functions and Data Members
1993		2211
1994	=over 4	2212	=over 4
1995		2213
…		…
2030		2248
2031	Another way to think about it (for the mathematically inclined) is that	2249	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2250	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2251	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2252
2035	For numerical stability it is preferable that the C<offset> value is near	2253	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2254	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2255	microseconds) and C<offset> should be higher than C<0> and should have
		2256	at most a similar magnitude as the current time (say, within a factor of
		2257	ten). Typical values for offset are, in fact, C<0> or something between
		2258	C<0> and C<interval>, which is also the recommended range.
2038		2259
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2260	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2261	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2262	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2263	millisecond (if the OS supports it and the machine is fast enough).
…		…
2156		2377
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2378	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2379
2159	Signal watchers will trigger an event when the process receives a specific	2380	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2381	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2382	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2383	normal event processing, like any other event.
2163		2384
2164	If you want signals to be delivered truly asynchronously, just use	2385	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2386	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2387	the signal. You can even use C<ev_async> from a signal handler to
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2406	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2407
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2408	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2409	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2410	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2411	and might or might not set or restore the installed signal handler (but
		2412	see C<EVFLAG_NOSIGMASK>).
2191		2413
2192	While this does not matter for the signal disposition (libev never	2414	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2415	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2416	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2417	certain signals to be blocked.
…		…
2209		2431
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2432	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2433	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2434	is not a libev-specific thing, this is true for most event libraries.
2213		2435
		2436	=head3 The special problem of threads signal handling
		2437
		2438	POSIX threads has problematic signal handling semantics, specifically,
		2439	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2440	threads in a process block signals, which is hard to achieve.
		2441
		2442	When you want to use sigwait (or mix libev signal handling with your own
		2443	for the same signals), you can tackle this problem by globally blocking
		2444	all signals before creating any threads (or creating them with a fully set
		2445	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2446	loops. Then designate one thread as "signal receiver thread" which handles
		2447	these signals. You can pass on any signals that libev might be interested
		2448	in by calling C<ev_feed_signal>.
		2449
2214	=head3 Watcher-Specific Functions and Data Members	2450	=head3 Watcher-Specific Functions and Data Members
2215		2451
2216	=over 4	2452	=over 4
2217		2453
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2454	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2469	Example: Try to exit cleanly on SIGINT.
2234		2470
2235	static void	2471	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2472	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2473	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2474	ev_break (loop, EVBREAK_ALL);
2239	}	2475	}
2240		2476
2241	ev_signal signal_watcher;	2477	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2478	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2479	ev_signal_start (loop, &signal_watcher);
…		…
2629		2865
2630	Prepare and check watchers are usually (but not always) used in pairs:	2866	Prepare and check watchers are usually (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2867	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2868	afterwards.
2633		2869
2634	You I<must not> call C<ev_loop> or similar functions that enter	2870	You I<must not> call C<ev_run> or similar functions that enter
2635	the current event loop from either C<ev_prepare> or C<ev_check>	2871	the current event loop from either C<ev_prepare> or C<ev_check>
2636	watchers. Other loops than the current one are fine, however. The	2872	watchers. Other loops than the current one are fine, however. The
2637	rationale behind this is that you do not need to check for recursion in	2873	rationale behind this is that you do not need to check for recursion in
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2874	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2639	C<ev_check> so if you have one watcher of each kind they will always be	2875	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2807		3043
2808	if (timeout >= 0)	3044	if (timeout >= 0)
2809	// create/start timer	3045	// create/start timer
2810		3046
2811	// poll	3047	// poll
2812	ev_loop (EV_A_ 0);	3048	ev_run (EV_A_ 0);
2813		3049
2814	// stop timer again	3050	// stop timer again
2815	if (timeout >= 0)	3051	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3052	ev_timer_stop (EV_A_ &to);
2817		3053
…		…
2895	if you do not want that, you need to temporarily stop the embed watcher).	3131	if you do not want that, you need to temporarily stop the embed watcher).
2896		3132
2897	=item ev_embed_sweep (loop, ev_embed *)	3133	=item ev_embed_sweep (loop, ev_embed *)
2898		3134
2899	Make a single, non-blocking sweep over the embedded loop. This works	3135	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3136	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3137	appropriate way for embedded loops.
2902		3138
2903	=item struct ev_loop *other [read-only]	3139	=item struct ev_loop *other [read-only]
2904		3140
2905	The embedded event loop.	3141	The embedded event loop.
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3227	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3228	signal watchers).
2993		3229
2994	When this is not possible, or you want to use the default loop for	3230	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3231	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3232	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3233	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3234	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3235	those watchers. Note also that in that case, you have to re-register any
		3236	signal watchers.
3000		3237
3001	=head3 Watcher-Specific Functions and Data Members	3238	=head3 Watcher-Specific Functions and Data Members
3002		3239
3003	=over 4	3240	=over 4
3004		3241
3005	=item ev_fork_init (ev_signal *, callback)	3242	=item ev_fork_init (ev_fork *, callback)
3006		3243
3007	Initialises and configures the fork watcher - it has no parameters of any	3244	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3245	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3246	really.
3010		3247
3011	=back	3248	=back
		3249
		3250
		3251	=head2 C<ev_cleanup> - even the best things end
		3252
		3253	Cleanup watchers are called just before the event loop is being destroyed
		3254	by a call to C<ev_loop_destroy>.
		3255
		3256	While there is no guarantee that the event loop gets destroyed, cleanup
		3257	watchers provide a convenient method to install cleanup hooks for your
		3258	program, worker threads and so on - you just to make sure to destroy the
		3259	loop when you want them to be invoked.
		3260
		3261	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3262	all other watchers, they do not keep a reference to the event loop (which
		3263	makes a lot of sense if you think about it). Like all other watchers, you
		3264	can call libev functions in the callback, except C<ev_cleanup_start>.
		3265
		3266	=head3 Watcher-Specific Functions and Data Members
		3267
		3268	=over 4
		3269
		3270	=item ev_cleanup_init (ev_cleanup *, callback)
		3271
		3272	Initialises and configures the cleanup watcher - it has no parameters of
		3273	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3274	pointless, I assure you.
		3275
		3276	=back
		3277
		3278	Example: Register an atexit handler to destroy the default loop, so any
		3279	cleanup functions are called.
		3280
		3281	static void
		3282	program_exits (void)
		3283	{
		3284	ev_loop_destroy (EV_DEFAULT_UC);
		3285	}
		3286
		3287	...
		3288	atexit (program_exits);
3012		3289
3013		3290
3014	=head2 C<ev_async> - how to wake up an event loop	3291	=head2 C<ev_async> - how to wake up an event loop
3015		3292
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3293	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3023	it by calling C<ev_async_send>, which is thread- and signal safe.	3300	it by calling C<ev_async_send>, which is thread- and signal safe.
3024		3301
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3302	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3303	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3304	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3305	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3029		3306	of "global async watchers" by using a watcher on an otherwise unused
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3307	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3031	just the default loop.	3308	even without knowing which loop owns the signal.
3032		3309
3033	=head3 Queueing	3310	=head3 Queueing
3034		3311
3035	C<ev_async> does not support queueing of data in any way. The reason	3312	C<ev_async> does not support queueing of data in any way. The reason
3036	is that the author does not know of a simple (or any) algorithm for a	3313	is that the author does not know of a simple (or any) algorithm for a
…		…
3128	trust me.	3405	trust me.
3129		3406
3130	=item ev_async_send (loop, ev_async *)	3407	=item ev_async_send (loop, ev_async *)
3131		3408
3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3409	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3410	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3411	returns.
		3412
3134	C<ev_feed_event>, this call is safe to do from other threads, signal or	3413	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3414	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3136	section below on what exactly this means).	3415	embedding section below on what exactly this means).
3137		3416
3138	Note that, as with other watchers in libev, multiple events might get	3417	Note that, as with other watchers in libev, multiple events might get
3139	compressed into a single callback invocation (another way to look at this	3418	compressed into a single callback invocation (another way to look at
3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3419	this is that C<ev_async> watchers are level-triggered: they are set on
3141	reset when the event loop detects that).	3420	C<ev_async_send>, reset when the event loop detects that).
3142		3421
3143	This call incurs the overhead of a system call only once per event loop	3422	This call incurs the overhead of at most one extra system call per event
3144	iteration, so while the overhead might be noticeable, it doesn't apply to	3423	loop iteration, if the event loop is blocked, and no syscall at all if
3145	repeated calls to C<ev_async_send> for the same event loop.	3424	the event loop (or your program) is processing events. That means that
		3425	repeated calls are basically free (there is no need to avoid calls for
		3426	performance reasons) and that the overhead becomes smaller (typically
		3427	zero) under load.
3146		3428
3147	=item bool = ev_async_pending (ev_async *)	3429	=item bool = ev_async_pending (ev_async *)
3148		3430
3149	Returns a non-zero value when C<ev_async_send> has been called on the	3431	Returns a non-zero value when C<ev_async_send> has been called on the
3150	watcher but the event has not yet been processed (or even noted) by the	3432	watcher but the event has not yet been processed (or even noted) by the
…		…
3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3487	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3206		3488
3207	=item ev_feed_fd_event (loop, int fd, int revents)	3489	=item ev_feed_fd_event (loop, int fd, int revents)
3208		3490
3209	Feed an event on the given fd, as if a file descriptor backend detected	3491	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3492	the given events.
3211		3493
3212	=item ev_feed_signal_event (loop, int signum)	3494	=item ev_feed_signal_event (loop, int signum)
3213		3495
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3496	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3497	which is async-safe.
3216		3498
3217	=back	3499	=back
		3500
		3501
		3502	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3503
		3504	This section explains some common idioms that are not immediately
		3505	obvious. Note that examples are sprinkled over the whole manual, and this
		3506	section only contains stuff that wouldn't fit anywhere else.
		3507
		3508	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3509
		3510	Each watcher has, by default, a C<void *data> member that you can read
		3511	or modify at any time: libev will completely ignore it. This can be used
		3512	to associate arbitrary data with your watcher. If you need more data and
		3513	don't want to allocate memory separately and store a pointer to it in that
		3514	data member, you can also "subclass" the watcher type and provide your own
		3515	data:
		3516
		3517	struct my_io
		3518	{
		3519	ev_io io;
		3520	int otherfd;
		3521	void *somedata;
		3522	struct whatever *mostinteresting;
		3523	};
		3524
		3525	...
		3526	struct my_io w;
		3527	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3528
		3529	And since your callback will be called with a pointer to the watcher, you
		3530	can cast it back to your own type:
		3531
		3532	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3533	{
		3534	struct my_io *w = (struct my_io *)w_;
		3535	...
		3536	}
		3537
		3538	More interesting and less C-conformant ways of casting your callback
		3539	function type instead have been omitted.
		3540
		3541	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3542
		3543	Another common scenario is to use some data structure with multiple
		3544	embedded watchers, in effect creating your own watcher that combines
		3545	multiple libev event sources into one "super-watcher":
		3546
		3547	struct my_biggy
		3548	{
		3549	int some_data;
		3550	ev_timer t1;
		3551	ev_timer t2;
		3552	}
		3553
		3554	In this case getting the pointer to C<my_biggy> is a bit more
		3555	complicated: Either you store the address of your C<my_biggy> struct in
		3556	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3557	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3558	real programmers):
		3559
		3560	#include <stddef.h>
		3561
		3562	static void
		3563	t1_cb (EV_P_ ev_timer *w, int revents)
		3564	{
		3565	struct my_biggy big = (struct my_biggy *)
		3566	(((char *)w) - offsetof (struct my_biggy, t1));
		3567	}
		3568
		3569	static void
		3570	t2_cb (EV_P_ ev_timer *w, int revents)
		3571	{
		3572	struct my_biggy big = (struct my_biggy *)
		3573	(((char *)w) - offsetof (struct my_biggy, t2));
		3574	}
		3575
		3576	=head2 AVOIDING FINISHING BEFORE RETURNING
		3577
		3578	Often you have structures like this in event-based programs:
		3579
		3580	callback ()
		3581	{
		3582	free (request);
		3583	}
		3584
		3585	request = start_new_request (..., callback);
		3586
		3587	The intent is to start some "lengthy" operation. The C<request> could be
		3588	used to cancel the operation, or do other things with it.
		3589
		3590	It's not uncommon to have code paths in C<start_new_request> that
		3591	immediately invoke the callback, for example, to report errors. Or you add
		3592	some caching layer that finds that it can skip the lengthy aspects of the
		3593	operation and simply invoke the callback with the result.
		3594
		3595	The problem here is that this will happen I<before> C<start_new_request>
		3596	has returned, so C<request> is not set.
		3597
		3598	Even if you pass the request by some safer means to the callback, you
		3599	might want to do something to the request after starting it, such as
		3600	canceling it, which probably isn't working so well when the callback has
		3601	already been invoked.
		3602
		3603	A common way around all these issues is to make sure that
		3604	C<start_new_request> I<always> returns before the callback is invoked. If
		3605	C<start_new_request> immediately knows the result, it can artificially
		3606	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3607	for example, or more sneakily, by reusing an existing (stopped) watcher
		3608	and pushing it into the pending queue:
		3609
		3610	ev_set_cb (watcher, callback);
		3611	ev_feed_event (EV_A_ watcher, 0);
		3612
		3613	This way, C<start_new_request> can safely return before the callback is
		3614	invoked, while not delaying callback invocation too much.
		3615
		3616	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3617
		3618	Often (especially in GUI toolkits) there are places where you have
		3619	I<modal> interaction, which is most easily implemented by recursively
		3620	invoking C<ev_run>.
		3621
		3622	This brings the problem of exiting - a callback might want to finish the
		3623	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3624	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3625	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3626	other combination: In these cases, C<ev_break> will not work alone.
		3627
		3628	The solution is to maintain "break this loop" variable for each C<ev_run>
		3629	invocation, and use a loop around C<ev_run> until the condition is
		3630	triggered, using C<EVRUN_ONCE>:
		3631
		3632	// main loop
		3633	int exit_main_loop = 0;
		3634
		3635	while (!exit_main_loop)
		3636	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3637
		3638	// in a modal watcher
		3639	int exit_nested_loop = 0;
		3640
		3641	while (!exit_nested_loop)
		3642	ev_run (EV_A_ EVRUN_ONCE);
		3643
		3644	To exit from any of these loops, just set the corresponding exit variable:
		3645
		3646	// exit modal loop
		3647	exit_nested_loop = 1;
		3648
		3649	// exit main program, after modal loop is finished
		3650	exit_main_loop = 1;
		3651
		3652	// exit both
		3653	exit_main_loop = exit_nested_loop = 1;
		3654
		3655	=head2 THREAD LOCKING EXAMPLE
		3656
		3657	Here is a fictitious example of how to run an event loop in a different
		3658	thread from where callbacks are being invoked and watchers are
		3659	created/added/removed.
		3660
		3661	For a real-world example, see the C<EV::Loop::Async> perl module,
		3662	which uses exactly this technique (which is suited for many high-level
		3663	languages).
		3664
		3665	The example uses a pthread mutex to protect the loop data, a condition
		3666	variable to wait for callback invocations, an async watcher to notify the
		3667	event loop thread and an unspecified mechanism to wake up the main thread.
		3668
		3669	First, you need to associate some data with the event loop:
		3670
		3671	typedef struct {
		3672	mutex_t lock; /* global loop lock */
		3673	ev_async async_w;
		3674	thread_t tid;
		3675	cond_t invoke_cv;
		3676	} userdata;
		3677
		3678	void prepare_loop (EV_P)
		3679	{
		3680	// for simplicity, we use a static userdata struct.
		3681	static userdata u;
		3682
		3683	ev_async_init (&u->async_w, async_cb);
		3684	ev_async_start (EV_A_ &u->async_w);
		3685
		3686	pthread_mutex_init (&u->lock, 0);
		3687	pthread_cond_init (&u->invoke_cv, 0);
		3688
		3689	// now associate this with the loop
		3690	ev_set_userdata (EV_A_ u);
		3691	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3692	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3693
		3694	// then create the thread running ev_run
		3695	pthread_create (&u->tid, 0, l_run, EV_A);
		3696	}
		3697
		3698	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3699	solely to wake up the event loop so it takes notice of any new watchers
		3700	that might have been added:
		3701
		3702	static void
		3703	async_cb (EV_P_ ev_async *w, int revents)
		3704	{
		3705	// just used for the side effects
		3706	}
		3707
		3708	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3709	protecting the loop data, respectively.
		3710
		3711	static void
		3712	l_release (EV_P)
		3713	{
		3714	userdata *u = ev_userdata (EV_A);
		3715	pthread_mutex_unlock (&u->lock);
		3716	}
		3717
		3718	static void
		3719	l_acquire (EV_P)
		3720	{
		3721	userdata *u = ev_userdata (EV_A);
		3722	pthread_mutex_lock (&u->lock);
		3723	}
		3724
		3725	The event loop thread first acquires the mutex, and then jumps straight
		3726	into C<ev_run>:
		3727
		3728	void *
		3729	l_run (void *thr_arg)
		3730	{
		3731	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3732
		3733	l_acquire (EV_A);
		3734	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3735	ev_run (EV_A_ 0);
		3736	l_release (EV_A);
		3737
		3738	return 0;
		3739	}
		3740
		3741	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3742	signal the main thread via some unspecified mechanism (signals? pipe
		3743	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3744	have been called (in a while loop because a) spurious wakeups are possible
		3745	and b) skipping inter-thread-communication when there are no pending
		3746	watchers is very beneficial):
		3747
		3748	static void
		3749	l_invoke (EV_P)
		3750	{
		3751	userdata *u = ev_userdata (EV_A);
		3752
		3753	while (ev_pending_count (EV_A))
		3754	{
		3755	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3756	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3757	}
		3758	}
		3759
		3760	Now, whenever the main thread gets told to invoke pending watchers, it
		3761	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3762	thread to continue:
		3763
		3764	static void
		3765	real_invoke_pending (EV_P)
		3766	{
		3767	userdata *u = ev_userdata (EV_A);
		3768
		3769	pthread_mutex_lock (&u->lock);
		3770	ev_invoke_pending (EV_A);
		3771	pthread_cond_signal (&u->invoke_cv);
		3772	pthread_mutex_unlock (&u->lock);
		3773	}
		3774
		3775	Whenever you want to start/stop a watcher or do other modifications to an
		3776	event loop, you will now have to lock:
		3777
		3778	ev_timer timeout_watcher;
		3779	userdata *u = ev_userdata (EV_A);
		3780
		3781	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3782
		3783	pthread_mutex_lock (&u->lock);
		3784	ev_timer_start (EV_A_ &timeout_watcher);
		3785	ev_async_send (EV_A_ &u->async_w);
		3786	pthread_mutex_unlock (&u->lock);
		3787
		3788	Note that sending the C<ev_async> watcher is required because otherwise
		3789	an event loop currently blocking in the kernel will have no knowledge
		3790	about the newly added timer. By waking up the loop it will pick up any new
		3791	watchers in the next event loop iteration.
		3792
		3793	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3794
		3795	While the overhead of a callback that e.g. schedules a thread is small, it
		3796	is still an overhead. If you embed libev, and your main usage is with some
		3797	kind of threads or coroutines, you might want to customise libev so that
		3798	doesn't need callbacks anymore.
		3799
		3800	Imagine you have coroutines that you can switch to using a function
		3801	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3802	and that due to some magic, the currently active coroutine is stored in a
		3803	global called C<current_coro>. Then you can build your own "wait for libev
		3804	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3805	the differing C<;> conventions):
		3806
		3807	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3808	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3809
		3810	That means instead of having a C callback function, you store the
		3811	coroutine to switch to in each watcher, and instead of having libev call
		3812	your callback, you instead have it switch to that coroutine.
		3813
		3814	A coroutine might now wait for an event with a function called
		3815	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3816	matter when, or whether the watcher is active or not when this function is
		3817	called):
		3818
		3819	void
		3820	wait_for_event (ev_watcher *w)
		3821	{
		3822	ev_cb_set (w) = current_coro;
		3823	switch_to (libev_coro);
		3824	}
		3825
		3826	That basically suspends the coroutine inside C<wait_for_event> and
		3827	continues the libev coroutine, which, when appropriate, switches back to
		3828	this or any other coroutine.
		3829
		3830	You can do similar tricks if you have, say, threads with an event queue -
		3831	instead of storing a coroutine, you store the queue object and instead of
		3832	switching to a coroutine, you push the watcher onto the queue and notify
		3833	any waiters.
		3834
		3835	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3836	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3837
		3838	// my_ev.h
		3839	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3840	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3841	#include "../libev/ev.h"
		3842
		3843	// my_ev.c
		3844	#define EV_H "my_ev.h"
		3845	#include "../libev/ev.c"
		3846
		3847	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3848	F<my_ev.c> into your project. When properly specifying include paths, you
		3849	can even use F<ev.h> as header file name directly.
3218		3850
3219		3851
3220	=head1 LIBEVENT EMULATION	3852	=head1 LIBEVENT EMULATION
3221		3853
3222	Libev offers a compatibility emulation layer for libevent. It cannot	3854	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	3855	emulate the internals of libevent, so here are some usage hints:
3224		3856
3225	=over 4	3857	=over 4
		3858
		3859	=item * Only the libevent-1.4.1-beta API is being emulated.
		3860
		3861	This was the newest libevent version available when libev was implemented,
		3862	and is still mostly unchanged in 2010.
3226		3863
3227	=item * Use it by including <event.h>, as usual.	3864	=item * Use it by including <event.h>, as usual.
3228		3865
3229	=item * The following members are fully supported: ev_base, ev_callback,	3866	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	3867	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	3873	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	3874	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	3875	is an ev_pri field.
3239		3876
3240	=item * In libevent, the last base created gets the signals, in libev, the	3877	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	3878	base that registered the signal gets the signals.
3242		3879
3243	=item * Other members are not supported.	3880	=item * Other members are not supported.
3244		3881
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3882	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	3883	to use the libev header file and library.
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	3902	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	3903	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	3904	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	3905	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		3906
3270	Currently, functions, and static and non-static member functions can be	3907	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	3908	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	3909	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	3910	you need support for other types of functors please contact the author
3274	it).	3911	(preferably after implementing it).
3275		3912
3276	Here is a list of things available in the C<ev> namespace:	3913	Here is a list of things available in the C<ev> namespace:
3277		3914
3278	=over 4	3915	=over 4
3279		3916
…		…
3289	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3926	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3290		3927
3291	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3928	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3292	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3929	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3293	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3930	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3294	defines by many implementations.	3931	defined by many implementations.
3295		3932
3296	All of those classes have these methods:	3933	All of those classes have these methods:
3297		3934
3298	=over 4	3935	=over 4
3299		3936
…		…
3389	Associates a different C<struct ev_loop> with this watcher. You can only	4026	Associates a different C<struct ev_loop> with this watcher. You can only
3390	do this when the watcher is inactive (and not pending either).	4027	do this when the watcher is inactive (and not pending either).
3391		4028
3392	=item w->set ([arguments])	4029	=item w->set ([arguments])
3393		4030
3394	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4031	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3395	called at least once. Unlike the C counterpart, an active watcher gets	4032	method or a suitable start method must be called at least once. Unlike the
3396	automatically stopped and restarted when reconfiguring it with this	4033	C counterpart, an active watcher gets automatically stopped and restarted
3397	method.	4034	when reconfiguring it with this method.
3398		4035
3399	=item w->start ()	4036	=item w->start ()
3400		4037
3401	Starts the watcher. Note that there is no C<loop> argument, as the	4038	Starts the watcher. Note that there is no C<loop> argument, as the
3402	constructor already stores the event loop.	4039	constructor already stores the event loop.
3403		4040
		4041	=item w->start ([arguments])
		4042
		4043	Instead of calling C<set> and C<start> methods separately, it is often
		4044	convenient to wrap them in one call. Uses the same type of arguments as
		4045	the configure C<set> method of the watcher.
		4046
3404	=item w->stop ()	4047	=item w->stop ()
3405		4048
3406	Stops the watcher if it is active. Again, no C<loop> argument.	4049	Stops the watcher if it is active. Again, no C<loop> argument.
3407		4050
3408	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4051	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3420		4063
3421	=back	4064	=back
3422		4065
3423	=back	4066	=back
3424		4067
3425	Example: Define a class with an IO and idle watcher, start one of them in	4068	Example: Define a class with two I/O and idle watchers, start the I/O
3426	the constructor.	4069	watchers in the constructor.
3427		4070
3428	class myclass	4071	class myclass
3429	{	4072	{
3430	ev::io io ; void io_cb (ev::io &w, int revents);	4073	ev::io io ; void io_cb (ev::io &w, int revents);
		4074	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3431	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4075	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3432		4076
3433	myclass (int fd)	4077	myclass (int fd)
3434	{	4078	{
3435	io .set <myclass, &myclass::io_cb > (this);	4079	io .set <myclass, &myclass::io_cb > (this);
		4080	io2 .set <myclass, &myclass::io2_cb > (this);
3436	idle.set <myclass, &myclass::idle_cb> (this);	4081	idle.set <myclass, &myclass::idle_cb> (this);
3437		4082
3438	io.start (fd, ev::READ);	4083	io.set (fd, ev::WRITE); // configure the watcher
		4084	io.start (); // start it whenever convenient
		4085
		4086	io2.start (fd, ev::READ); // set + start in one call
3439	}	4087	}
3440	};	4088	};
3441		4089
3442		4090
3443	=head1 OTHER LANGUAGE BINDINGS	4091	=head1 OTHER LANGUAGE BINDINGS
…		…
3482	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4130	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3483		4131
3484	=item D	4132	=item D
3485		4133
3486	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4134	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3487	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4135	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3488		4136
3489	=item Ocaml	4137	=item Ocaml
3490		4138
3491	Erkki Seppala has written Ocaml bindings for libev, to be found at	4139	Erkki Seppala has written Ocaml bindings for libev, to be found at
3492	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4140	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3517	loop argument"). The C<EV_A> form is used when this is the sole argument,	4165	loop argument"). The C<EV_A> form is used when this is the sole argument,
3518	C<EV_A_> is used when other arguments are following. Example:	4166	C<EV_A_> is used when other arguments are following. Example:
3519		4167
3520	ev_unref (EV_A);	4168	ev_unref (EV_A);
3521	ev_timer_add (EV_A_ watcher);	4169	ev_timer_add (EV_A_ watcher);
3522	ev_loop (EV_A_ 0);	4170	ev_run (EV_A_ 0);
3523		4171
3524	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4172	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3525	which is often provided by the following macro.	4173	which is often provided by the following macro.
3526		4174
3527	=item C<EV_P>, C<EV_P_>	4175	=item C<EV_P>, C<EV_P_>
…		…
3540	suitable for use with C<EV_A>.	4188	suitable for use with C<EV_A>.
3541		4189
3542	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4190	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3543		4191
3544	Similar to the other two macros, this gives you the value of the default	4192	Similar to the other two macros, this gives you the value of the default
3545	loop, if multiple loops are supported ("ev loop default").	4193	loop, if multiple loops are supported ("ev loop default"). The default loop
		4194	will be initialised if it isn't already initialised.
		4195
		4196	For non-multiplicity builds, these macros do nothing, so you always have
		4197	to initialise the loop somewhere.
3546		4198
3547	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4199	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3548		4200
3549	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4201	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3550	default loop has been initialised (C<UC> == unchecked). Their behaviour	4202	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3567	}	4219	}
3568		4220
3569	ev_check check;	4221	ev_check check;
3570	ev_check_init (&check, check_cb);	4222	ev_check_init (&check, check_cb);
3571	ev_check_start (EV_DEFAULT_ &check);	4223	ev_check_start (EV_DEFAULT_ &check);
3572	ev_loop (EV_DEFAULT_ 0);	4224	ev_run (EV_DEFAULT_ 0);
3573		4225
3574	=head1 EMBEDDING	4226	=head1 EMBEDDING
3575		4227
3576	Libev can (and often is) directly embedded into host	4228	Libev can (and often is) directly embedded into host
3577	applications. Examples of applications that embed it include the Deliantra	4229	applications. Examples of applications that embed it include the Deliantra
…		…
3669	users of libev and the libev code itself must be compiled with compatible	4321	users of libev and the libev code itself must be compiled with compatible
3670	settings.	4322	settings.
3671		4323
3672	=over 4	4324	=over 4
3673		4325
		4326	=item EV_COMPAT3 (h)
		4327
		4328	Backwards compatibility is a major concern for libev. This is why this
		4329	release of libev comes with wrappers for the functions and symbols that
		4330	have been renamed between libev version 3 and 4.
		4331
		4332	You can disable these wrappers (to test compatibility with future
		4333	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4334	sources. This has the additional advantage that you can drop the C<struct>
		4335	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4336	typedef in that case.
		4337
		4338	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4339	and in some even more future version the compatibility code will be
		4340	removed completely.
		4341
3674	=item EV_STANDALONE (h)	4342	=item EV_STANDALONE (h)
3675		4343
3676	Must always be C<1> if you do not use autoconf configuration, which	4344	Must always be C<1> if you do not use autoconf configuration, which
3677	keeps libev from including F<config.h>, and it also defines dummy	4345	keeps libev from including F<config.h>, and it also defines dummy
3678	implementations for some libevent functions (such as logging, which is not	4346	implementations for some libevent functions (such as logging, which is not
3679	supported). It will also not define any of the structs usually found in	4347	supported). It will also not define any of the structs usually found in
3680	F<event.h> that are not directly supported by the libev core alone.	4348	F<event.h> that are not directly supported by the libev core alone.
3681		4349
3682	In standalone mode, libev will still try to automatically deduce the	4350	In standalone mode, libev will still try to automatically deduce the
3683	configuration, but has to be more conservative.	4351	configuration, but has to be more conservative.
		4352
		4353	=item EV_USE_FLOOR
		4354
		4355	If defined to be C<1>, libev will use the C<floor ()> function for its
		4356	periodic reschedule calculations, otherwise libev will fall back on a
		4357	portable (slower) implementation. If you enable this, you usually have to
		4358	link against libm or something equivalent. Enabling this when the C<floor>
		4359	function is not available will fail, so the safe default is to not enable
		4360	this.
3684		4361
3685	=item EV_USE_MONOTONIC	4362	=item EV_USE_MONOTONIC
3686		4363
3687	If defined to be C<1>, libev will try to detect the availability of the	4364	If defined to be C<1>, libev will try to detect the availability of the
3688	monotonic clock option at both compile time and runtime. Otherwise no	4365	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3821	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4498	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3822		4499
3823	=item EV_ATOMIC_T	4500	=item EV_ATOMIC_T
3824		4501
3825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4502	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3826	access is atomic with respect to other threads or signal contexts. No such	4503	access is atomic and serialised with respect to other threads or signal
3827	type is easily found in the C language, so you can provide your own type	4504	contexts. No such type is easily found in the C language, so you can
3828	that you know is safe for your purposes. It is used both for signal handler "locking"	4505	provide your own type that you know is safe for your purposes. It is used
3829	as well as for signal and thread safety in C<ev_async> watchers.	4506	both for signal handler "locking" as well as for signal and thread safety
		4507	in C<ev_async> watchers.
3830		4508
3831	In the absence of this define, libev will use C<sig_atomic_t volatile>	4509	In the absence of this define, libev will use C<sig_atomic_t volatile>
3832	(from F<signal.h>), which is usually good enough on most platforms.	4510	(from F<signal.h>), which is usually good enough on most platforms,
		4511	although strictly speaking using a type that also implies a memory fence
		4512	is required.
3833		4513
3834	=item EV_H (h)	4514	=item EV_H (h)
3835		4515
3836	The name of the F<ev.h> header file used to include it. The default if	4516	The name of the F<ev.h> header file used to include it. The default if
3837	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4517	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3861	will have the C<struct ev_loop *> as first argument, and you can create	4541	will have the C<struct ev_loop *> as first argument, and you can create
3862	additional independent event loops. Otherwise there will be no support	4542	additional independent event loops. Otherwise there will be no support
3863	for multiple event loops and there is no first event loop pointer	4543	for multiple event loops and there is no first event loop pointer
3864	argument. Instead, all functions act on the single default loop.	4544	argument. Instead, all functions act on the single default loop.
3865		4545
		4546	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4547	default loop when multiplicity is switched off - you always have to
		4548	initialise the loop manually in this case.
		4549
3866	=item EV_MINPRI	4550	=item EV_MINPRI
3867		4551
3868	=item EV_MAXPRI	4552	=item EV_MAXPRI
3869		4553
3870	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4554	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3967		4651
3968	With an intelligent-enough linker (gcc+binutils are intelligent enough	4652	With an intelligent-enough linker (gcc+binutils are intelligent enough
3969	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4653	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3970	your program might be left out as well - a binary starting a timer and an	4654	your program might be left out as well - a binary starting a timer and an
3971	I/O watcher then might come out at only 5Kb.	4655	I/O watcher then might come out at only 5Kb.
		4656
		4657	=item EV_API_STATIC
		4658
		4659	If this symbol is defined (by default it is not), then all identifiers
		4660	will have static linkage. This means that libev will not export any
		4661	identifiers, and you cannot link against libev anymore. This can be useful
		4662	when you embed libev, only want to use libev functions in a single file,
		4663	and do not want its identifiers to be visible.
		4664
		4665	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4666	wants to use libev.
		4667
		4668	This option only works when libev is compiled with a C compiler, as C++
		4669	doesn't support the required declaration syntax.
3972		4670
3973	=item EV_AVOID_STDIO	4671	=item EV_AVOID_STDIO
3974		4672
3975	If this is set to C<1> at compiletime, then libev will avoid using stdio	4673	If this is set to C<1> at compiletime, then libev will avoid using stdio
3976	functions (printf, scanf, perror etc.). This will increase the code size	4674	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4725	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4028	will be C<0>.	4726	will be C<0>.
4029		4727
4030	=item EV_VERIFY	4728	=item EV_VERIFY
4031		4729
4032	Controls how much internal verification (see C<ev_loop_verify ()>) will	4730	Controls how much internal verification (see C<ev_verify ()>) will
4033	be done: If set to C<0>, no internal verification code will be compiled	4731	be done: If set to C<0>, no internal verification code will be compiled
4034	in. If set to C<1>, then verification code will be compiled in, but not	4732	in. If set to C<1>, then verification code will be compiled in, but not
4035	called. If set to C<2>, then the internal verification code will be	4733	called. If set to C<2>, then the internal verification code will be
4036	called once per loop, which can slow down libev. If set to C<3>, then the	4734	called once per loop, which can slow down libev. If set to C<3>, then the
4037	verification code will be called very frequently, which will slow down	4735	verification code will be called very frequently, which will slow down
…		…
4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4818	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4121		4819
4122	#include "ev_cpp.h"	4820	#include "ev_cpp.h"
4123	#include "ev.c"	4821	#include "ev.c"
4124		4822
4125	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4823	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4126		4824
4127	=head2 THREADS AND COROUTINES	4825	=head2 THREADS AND COROUTINES
4128		4826
4129	=head3 THREADS	4827	=head3 THREADS
4130		4828
…		…
4181	default loop and triggering an C<ev_async> watcher from the default loop	4879	default loop and triggering an C<ev_async> watcher from the default loop
4182	watcher callback into the event loop interested in the signal.	4880	watcher callback into the event loop interested in the signal.
4183		4881
4184	=back	4882	=back
4185		4883
4186	=head4 THREAD LOCKING EXAMPLE	4884	See also L<THREAD LOCKING EXAMPLE>.
4187
4188	Here is a fictitious example of how to run an event loop in a different
4189	thread than where callbacks are being invoked and watchers are
4190	created/added/removed.
4191
4192	For a real-world example, see the C<EV::Loop::Async> perl module,
4193	which uses exactly this technique (which is suited for many high-level
4194	languages).
4195
4196	The example uses a pthread mutex to protect the loop data, a condition
4197	variable to wait for callback invocations, an async watcher to notify the
4198	event loop thread and an unspecified mechanism to wake up the main thread.
4199
4200	First, you need to associate some data with the event loop:
4201
4202	typedef struct {
4203	mutex_t lock; /* global loop lock */
4204	ev_async async_w;
4205	thread_t tid;
4206	cond_t invoke_cv;
4207	} userdata;
4208
4209	void prepare_loop (EV_P)
4210	{
4211	// for simplicity, we use a static userdata struct.
4212	static userdata u;
4213
4214	ev_async_init (&u->async_w, async_cb);
4215	ev_async_start (EV_A_ &u->async_w);
4216
4217	pthread_mutex_init (&u->lock, 0);
4218	pthread_cond_init (&u->invoke_cv, 0);
4219
4220	// now associate this with the loop
4221	ev_set_userdata (EV_A_ u);
4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4224
4225	// then create the thread running ev_loop
4226	pthread_create (&u->tid, 0, l_run, EV_A);
4227	}
4228
4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
4230	solely to wake up the event loop so it takes notice of any new watchers
4231	that might have been added:
4232
4233	static void
4234	async_cb (EV_P_ ev_async *w, int revents)
4235	{
4236	// just used for the side effects
4237	}
4238
4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4240	protecting the loop data, respectively.
4241
4242	static void
4243	l_release (EV_P)
4244	{
4245	userdata *u = ev_userdata (EV_A);
4246	pthread_mutex_unlock (&u->lock);
4247	}
4248
4249	static void
4250	l_acquire (EV_P)
4251	{
4252	userdata *u = ev_userdata (EV_A);
4253	pthread_mutex_lock (&u->lock);
4254	}
4255
4256	The event loop thread first acquires the mutex, and then jumps straight
4257	into C<ev_loop>:
4258
4259	void *
4260	l_run (void *thr_arg)
4261	{
4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4263
4264	l_acquire (EV_A);
4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4266	ev_loop (EV_A_ 0);
4267	l_release (EV_A);
4268
4269	return 0;
4270	}
4271
4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
4273	signal the main thread via some unspecified mechanism (signals? pipe
4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4275	have been called (in a while loop because a) spurious wakeups are possible
4276	and b) skipping inter-thread-communication when there are no pending
4277	watchers is very beneficial):
4278
4279	static void
4280	l_invoke (EV_P)
4281	{
4282	userdata *u = ev_userdata (EV_A);
4283
4284	while (ev_pending_count (EV_A))
4285	{
4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
4288	}
4289	}
4290
4291	Now, whenever the main thread gets told to invoke pending watchers, it
4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4293	thread to continue:
4294
4295	static void
4296	real_invoke_pending (EV_P)
4297	{
4298	userdata *u = ev_userdata (EV_A);
4299
4300	pthread_mutex_lock (&u->lock);
4301	ev_invoke_pending (EV_A);
4302	pthread_cond_signal (&u->invoke_cv);
4303	pthread_mutex_unlock (&u->lock);
4304	}
4305
4306	Whenever you want to start/stop a watcher or do other modifications to an
4307	event loop, you will now have to lock:
4308
4309	ev_timer timeout_watcher;
4310	userdata *u = ev_userdata (EV_A);
4311
4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4313
4314	pthread_mutex_lock (&u->lock);
4315	ev_timer_start (EV_A_ &timeout_watcher);
4316	ev_async_send (EV_A_ &u->async_w);
4317	pthread_mutex_unlock (&u->lock);
4318
4319	Note that sending the C<ev_async> watcher is required because otherwise
4320	an event loop currently blocking in the kernel will have no knowledge
4321	about the newly added timer. By waking up the loop it will pick up any new
4322	watchers in the next event loop iteration.
4323		4885
4324	=head3 COROUTINES	4886	=head3 COROUTINES
4325		4887
4326	Libev is very accommodating to coroutines ("cooperative threads"):	4888	Libev is very accommodating to coroutines ("cooperative threads"):
4327	libev fully supports nesting calls to its functions from different	4889	libev fully supports nesting calls to its functions from different
4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4890	coroutines (e.g. you can call C<ev_run> on the same loop from two
4329	different coroutines, and switch freely between both coroutines running	4891	different coroutines, and switch freely between both coroutines running
4330	the loop, as long as you don't confuse yourself). The only exception is	4892	the loop, as long as you don't confuse yourself). The only exception is
4331	that you must not do this from C<ev_periodic> reschedule callbacks.	4893	that you must not do this from C<ev_periodic> reschedule callbacks.
4332		4894
4333	Care has been taken to ensure that libev does not keep local state inside	4895	Care has been taken to ensure that libev does not keep local state inside
4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4896	C<ev_run>, and other calls do not usually allow for coroutine switches as
4335	they do not call any callbacks.	4897	they do not call any callbacks.
4336		4898
4337	=head2 COMPILER WARNINGS	4899	=head2 COMPILER WARNINGS
4338		4900
4339	Depending on your compiler and compiler settings, you might get no or a	4901	Depending on your compiler and compiler settings, you might get no or a
…		…
4423	=head3 C<kqueue> is buggy	4985	=head3 C<kqueue> is buggy
4424		4986
4425	The kqueue syscall is broken in all known versions - most versions support	4987	The kqueue syscall is broken in all known versions - most versions support
4426	only sockets, many support pipes.	4988	only sockets, many support pipes.
4427		4989
		4990	Libev tries to work around this by not using C<kqueue> by default on this
		4991	rotten platform, but of course you can still ask for it when creating a
		4992	loop - embedding a socket-only kqueue loop into a select-based one is
		4993	probably going to work well.
		4994
4428	=head3 C<poll> is buggy	4995	=head3 C<poll> is buggy
4429		4996
4430	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4997	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4431	implementation by something calling C<kqueue> internally around the 10.5.6	4998	implementation by something calling C<kqueue> internally around the 10.5.6
4432	release, so now C<kqueue> I<and> C<poll> are broken.	4999	release, so now C<kqueue> I<and> C<poll> are broken.
4433		5000
4434	Libev tries to work around this by neither using C<kqueue> nor C<poll> by	5001	Libev tries to work around this by not using C<poll> by default on
4435	default on this rotten platform, but of course you cna still ask for them	5002	this rotten platform, but of course you can still ask for it when creating
4436	when creating a loop.	5003	a loop.
4437		5004
4438	=head3 C<select> is buggy	5005	=head3 C<select> is buggy
4439		5006
4440	All that's left is C<select>, and of course Apple found a way to fuck this	5007	All that's left is C<select>, and of course Apple found a way to fuck this
4441	one up as well: On OS/X, C<select> actively limits the number of file	5008	one up as well: On OS/X, C<select> actively limits the number of file
4442	descriptors you can pass in to 1024 - your program suddenyl crashes when	5009	descriptors you can pass in to 1024 - your program suddenly crashes when
4443	you use more.	5010	you use more.
4444		5011
4445	There is an undocumented "workaround" for this - defining	5012	There is an undocumented "workaround" for this - defining
4446	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>	5013	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4447	work on OS/X.	5014	work on OS/X.
…		…
4450		5017
4451	=head3 C<errno> reentrancy	5018	=head3 C<errno> reentrancy
4452		5019
4453	The default compile environment on Solaris is unfortunately so	5020	The default compile environment on Solaris is unfortunately so
4454	thread-unsafe that you can't even use components/libraries compiled	5021	thread-unsafe that you can't even use components/libraries compiled
4455	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5022	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4456	isn't defined by default.	5023	defined by default. A valid, if stupid, implementation choice.
4457		5024
4458	If you want to use libev in threaded environments you have to make sure	5025	If you want to use libev in threaded environments you have to make sure
4459	it's compiled with C<_REENTRANT> defined.	5026	it's compiled with C<_REENTRANT> defined.
4460		5027
4461	=head3 Event port backend	5028	=head3 Event port backend
4462		5029
4463	The scalable event interface for Solaris is called "event ports". Unfortunately,	5030	The scalable event interface for Solaris is called "event
4464	this mechanism is very buggy. If you run into high CPU usage, your program	5031	ports". Unfortunately, this mechanism is very buggy in all major
		5032	releases. If you run into high CPU usage, your program freezes or you get
4465	freezes or you get a large number of spurious wakeups, make sure you have	5033	a large number of spurious wakeups, make sure you have all the relevant
4466	all the relevant and latest kernel patches applied. No, I don't know which	5034	and latest kernel patches applied. No, I don't know which ones, but there
4467	ones, but there are multiple ones.	5035	are multiple ones to apply, and afterwards, event ports actually work
		5036	great.
4468		5037
4469	If you can't get it to work, you can try running the program with	5038	If you can't get it to work, you can try running the program by setting
4470	C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends.	5039	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5040	C<select> backends.
4471		5041
4472	=head2 AIX POLL BUG	5042	=head2 AIX POLL BUG
4473		5043
4474	AIX unfortunately has a broken C<poll.h> header. Libev works around	5044	AIX unfortunately has a broken C<poll.h> header. Libev works around
4475	this by trying to avoid the poll backend altogether (i.e. it's not even	5045	this by trying to avoid the poll backend altogether (i.e. it's not even
4476	compiled in), which normally isn't a big problem as C<select> works fine	5046	compiled in), which normally isn't a big problem as C<select> works fine
4477	with large bitsets, and AIX is dead anyway.	5047	with large bitsets on AIX, and AIX is dead anyway.
4478		5048
4479	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5049	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4480		5050
4481	=head3 General issues	5051	=head3 General issues
4482		5052
…		…
4484	requires, and its I/O model is fundamentally incompatible with the POSIX	5054	requires, and its I/O model is fundamentally incompatible with the POSIX
4485	model. Libev still offers limited functionality on this platform in	5055	model. Libev still offers limited functionality on this platform in
4486	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5056	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4487	descriptors. This only applies when using Win32 natively, not when using	5057	descriptors. This only applies when using Win32 natively, not when using
4488	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5058	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4489	as every compielr comes with a slightly differently broken/incompatible	5059	as every compiler comes with a slightly differently broken/incompatible
4490	environment.	5060	environment.
4491		5061
4492	Lifting these limitations would basically require the full	5062	Lifting these limitations would basically require the full
4493	re-implementation of the I/O system. If you are into this kind of thing,	5063	re-implementation of the I/O system. If you are into this kind of thing,
4494	then note that glib does exactly that for you in a very portable way (note	5064	then note that glib does exactly that for you in a very portable way (note
…		…
4588	structure (guaranteed by POSIX but not by ISO C for example), but it also	5158	structure (guaranteed by POSIX but not by ISO C for example), but it also
4589	assumes that the same (machine) code can be used to call any watcher	5159	assumes that the same (machine) code can be used to call any watcher
4590	callback: The watcher callbacks have different type signatures, but libev	5160	callback: The watcher callbacks have different type signatures, but libev
4591	calls them using an C<ev_watcher *> internally.	5161	calls them using an C<ev_watcher *> internally.
4592		5162
		5163	=item pointer accesses must be thread-atomic
		5164
		5165	Accessing a pointer value must be atomic, it must both be readable and
		5166	writable in one piece - this is the case on all current architectures.
		5167
4593	=item C<sig_atomic_t volatile> must be thread-atomic as well	5168	=item C<sig_atomic_t volatile> must be thread-atomic as well
4594		5169
4595	The type C<sig_atomic_t volatile> (or whatever is defined as	5170	The type C<sig_atomic_t volatile> (or whatever is defined as
4596	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5171	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4597	threads. This is not part of the specification for C<sig_atomic_t>, but is	5172	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4619	watchers.	5194	watchers.
4620		5195
4621	=item C<double> must hold a time value in seconds with enough accuracy	5196	=item C<double> must hold a time value in seconds with enough accuracy
4622		5197
4623	The type C<double> is used to represent timestamps. It is required to	5198	The type C<double> is used to represent timestamps. It is required to
4624	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5199	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4625	enough for at least into the year 4000. This requirement is fulfilled by	5200	good enough for at least into the year 4000 with millisecond accuracy
		5201	(the design goal for libev). This requirement is overfulfilled by
4626	implementations implementing IEEE 754, which is basically all existing	5202	implementations using IEEE 754, which is basically all existing ones.
		5203
4627	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5204	With IEEE 754 doubles, you get microsecond accuracy until at least the
4628	2200.	5205	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5206	is either obsolete or somebody patched it to use C<long double> or
		5207	something like that, just kidding).
4629		5208
4630	=back	5209	=back
4631		5210
4632	If you know of other additional requirements drop me a note.	5211	If you know of other additional requirements drop me a note.
4633		5212
…		…
4695	=item Processing ev_async_send: O(number_of_async_watchers)	5274	=item Processing ev_async_send: O(number_of_async_watchers)
4696		5275
4697	=item Processing signals: O(max_signal_number)	5276	=item Processing signals: O(max_signal_number)
4698		5277
4699	Sending involves a system call I<iff> there were no other C<ev_async_send>	5278	Sending involves a system call I<iff> there were no other C<ev_async_send>
4700	calls in the current loop iteration. Checking for async and signal events	5279	calls in the current loop iteration and the loop is currently
		5280	blocked. Checking for async and signal events involves iterating over all
4701	involves iterating over all running async watchers or all signal numbers.	5281	running async watchers or all signal numbers.
4702		5282
4703	=back	5283	=back
4704		5284
4705		5285
4706	=head1 PORTING FROM LIBEV 3.X TO 4.X	5286	=head1 PORTING FROM LIBEV 3.X TO 4.X
4707		5287
4708	The major version 4 introduced some minor incompatible changes to the API.	5288	The major version 4 introduced some incompatible changes to the API.
4709		5289
4710	At the moment, the C<ev.h> header file tries to implement superficial	5290	At the moment, the C<ev.h> header file provides compatibility definitions
4711	compatibility, so most programs should still compile. Those might be	5291	for all changes, so most programs should still compile. The compatibility
4712	removed in later versions of libev, so better update early than late.	5292	layer might be removed in later versions of libev, so better update to the
		5293	new API early than late.
4713		5294
4714	=over 4	5295	=over 4
4715		5296
4716	=item C<ev_loop_count> renamed to C<ev_iteration>	5297	=item C<EV_COMPAT3> backwards compatibility mechanism
4717		5298
4718	=item C<ev_loop_depth> renamed to C<ev_depth>	5299	The backward compatibility mechanism can be controlled by
		5300	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5301	section.
4719		5302
4720	=item C<ev_loop_verify> renamed to C<ev_verify>	5303	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5304
		5305	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5306
		5307	ev_loop_destroy (EV_DEFAULT_UC);
		5308	ev_loop_fork (EV_DEFAULT);
		5309
		5310	=item function/symbol renames
		5311
		5312	A number of functions and symbols have been renamed:
		5313
		5314	ev_loop => ev_run
		5315	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5316	EVLOOP_ONESHOT => EVRUN_ONCE
		5317
		5318	ev_unloop => ev_break
		5319	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5320	EVUNLOOP_ONE => EVBREAK_ONE
		5321	EVUNLOOP_ALL => EVBREAK_ALL
		5322
		5323	EV_TIMEOUT => EV_TIMER
		5324
		5325	ev_loop_count => ev_iteration
		5326	ev_loop_depth => ev_depth
		5327	ev_loop_verify => ev_verify
4721		5328
4722	Most functions working on C<struct ev_loop> objects don't have an	5329	Most functions working on C<struct ev_loop> objects don't have an
4723	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5330	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5331	associated constants have been renamed to not collide with the C<struct
		5332	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5333	as all other watcher types. Note that C<ev_loop_fork> is still called
4724	still called C<ev_loop_fork> because it would otherwise clash with the	5334	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4725	C<ev_fork> typedef.	5335	typedef.
4726
4727	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4728
4729	This is a simple rename - all other watcher types use their name
4730	as revents flag, and now C<ev_timer> does, too.
4731
4732	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4733	and continue to be present for the foreseeable future, so this is mostly a
4734	documentation change.
4735		5336
4736	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5337	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4737		5338
4738	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5339	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4739	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5340	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4746		5347
4747	=over 4	5348	=over 4
4748		5349
4749	=item active	5350	=item active
4750		5351
4751	A watcher is active as long as it has been started (has been attached to	5352	A watcher is active as long as it has been started and not yet stopped.
4752	an event loop) but not yet stopped (disassociated from the event loop).	5353	See L<WATCHER STATES> for details.
4753		5354
4754	=item application	5355	=item application
4755		5356
4756	In this document, an application is whatever is using libev.	5357	In this document, an application is whatever is using libev.
		5358
		5359	=item backend
		5360
		5361	The part of the code dealing with the operating system interfaces.
4757		5362
4758	=item callback	5363	=item callback
4759		5364
4760	The address of a function that is called when some event has been	5365	The address of a function that is called when some event has been
4761	detected. Callbacks are being passed the event loop, the watcher that	5366	detected. Callbacks are being passed the event loop, the watcher that
4762	received the event, and the actual event bitset.	5367	received the event, and the actual event bitset.
4763		5368
4764	=item callback invocation	5369	=item callback/watcher invocation
4765		5370
4766	The act of calling the callback associated with a watcher.	5371	The act of calling the callback associated with a watcher.
4767		5372
4768	=item event	5373	=item event
4769		5374
…		…
4788	The model used to describe how an event loop handles and processes	5393	The model used to describe how an event loop handles and processes
4789	watchers and events.	5394	watchers and events.
4790		5395
4791	=item pending	5396	=item pending
4792		5397
4793	A watcher is pending as soon as the corresponding event has been detected,	5398	A watcher is pending as soon as the corresponding event has been
4794	and stops being pending as soon as the watcher will be invoked or its	5399	detected. See L<WATCHER STATES> for details.
4795	pending status is explicitly cleared by the application.
4796
4797	A watcher can be pending, but not active. Stopping a watcher also clears
4798	its pending status.
4799		5400
4800	=item real time	5401	=item real time
4801		5402
4802	The physical time that is observed. It is apparently strictly monotonic :)	5403	The physical time that is observed. It is apparently strictly monotonic :)
4803		5404
4804	=item wall-clock time	5405	=item wall-clock time
4805		5406
4806	The time and date as shown on clocks. Unlike real time, it can actually	5407	The time and date as shown on clocks. Unlike real time, it can actually
4807	be wrong and jump forwards and backwards, e.g. when the you adjust your	5408	be wrong and jump forwards and backwards, e.g. when you adjust your
4808	clock.	5409	clock.
4809		5410
4810	=item watcher	5411	=item watcher
4811		5412
4812	A data structure that describes interest in certain events. Watchers need	5413	A data structure that describes interest in certain events. Watchers need
4813	to be started (attached to an event loop) before they can receive events.	5414	to be started (attached to an event loop) before they can receive events.
4814		5415
4815	=item watcher invocation
4816
4817	The act of calling the callback associated with a watcher.
4818
4819	=back	5416	=back
4820		5417
4821	=head1 AUTHOR	5418	=head1 AUTHOR
4822		5419
4823	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5420	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5421	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4824		5422

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