[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.276 by root, Tue Dec 29 13:11:00 2009 UTC vs.
Revision 1.360 by root, Mon Jan 17 12:11:12 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
174	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
191	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	203	not a problem.
194		204
195	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
197		208
198	assert (("libev version mismatch",	209	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
201		212
…		…
212	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
214		225
215	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
216		227
217	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
223		235
224	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
225		237
226	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
231		243
232	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
233		245
234	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void (cb)(void *ptr, long size))
235		247
236	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	277	}
266		278
267	...	279	...
268	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
269		281
270	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (cb)(const char msg))
271		283
272	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	299	}
288		300
289	...	301	...
290	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
291		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
292	=back	317	=back
293		318
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		320
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
299		324
300	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
302	not.	327	do not.
303		328
304	=over 4	329	=over 4
305		330
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		332
308	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
312		343
313	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
314	function.	345	function (or via the C<EV_DEFAULT> macro).
315		346
316	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
319		351
320	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
326		376
327	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		379
330	The following flags are supported:	380	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
346	around bugs.	396	around bugs.
347		397
348	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
349		399
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		402
354	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	415	environment variable.
367		416
368	=item C<EVFLAG_NOINOTIFY>	417	=item C<EVFLAG_NOINOTIFY>
369		418
370	When this flag is specified, then libev will not attempt to use the	419	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	421	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		423
375	=item C<EVFLAG_NOSIGFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will not attempt to use the	426	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	428	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	429	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
382		451
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		453
385	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
386	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
422	epoll scales either O(1) or O(active_fds).	491	epoll scales either O(1) or O(active_fds).
423		492
424	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
425	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
426	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
427	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
428	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
429	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
430	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
431	hard to detect.	502	and is of course hard to detect.
432		503
433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
434	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
435	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
436	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
437	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
438	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
439	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
440		517
441	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
442	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
443	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
511		588
512	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
513	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
514		591
515	Please note that Solaris event ports can deliver a lot of spurious
516	notifications, so you need to use non-blocking I/O or other means to avoid
517	blocking when no data (or space) is available.
518
519	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
520	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
522	might perform better.	595	might perform better.
523		596
524	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
525	notifications, this backend actually performed fully to specification
526	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
527	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
528		611
529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
530	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
531		614
532	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
533		616
534	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
536	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
537		620
538	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
539		630
540	=back	631	=back
541		632
542	If one or more of the backend flags are or'ed into the flags value,	633	If one or more of the backend flags are or'ed into the flags value,
543	then only these backends will be tried (in the reverse order as listed	634	then only these backends will be tried (in the reverse order as listed
544	here). If none are specified, all backends in C<ev_recommended_backends	635	here). If none are specified, all backends in C<ev_recommended_backends
545	()> will be tried.	636	()> will be tried.
546		637
547	Example: This is the most typical usage.
548
549	if (!ev_default_loop (0))
550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
551
552	Example: Restrict libev to the select and poll backends, and do not allow
553	environment settings to be taken into account:
554
555	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
556
557	Example: Use whatever libev has to offer, but make sure that kqueue is
558	used if available (warning, breaks stuff, best use only with your own
559	private event loop and only if you know the OS supports your types of
560	fds):
561
562	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
563
564	=item struct ev_loop *ev_loop_new (unsigned int flags)
565
566	Similar to C<ev_default_loop>, but always creates a new event loop that is
567	always distinct from the default loop. Unlike the default loop, it cannot
568	handle signal and child watchers, and attempts to do so will be greeted by
569	undefined behaviour (or a failed assertion if assertions are enabled).
570
571	Note that this function I<is> thread-safe, and the recommended way to use
572	libev with threads is indeed to create one loop per thread, and using the
573	default loop in the "main" or "initial" thread.
574
575	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
576		639
577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
578	if (!epoller)	641	if (!epoller)
579	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
580		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		648
581	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
582		650
583	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
584	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
585	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
586	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
587	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
588	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
590		658
591	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
592	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
593	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
594		662
595	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
596	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
597	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
598	C<ev_loop_new> and C<ev_loop_destroy>.	670	and C<ev_loop_destroy>.
599		671
600	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
601		673
602	Like C<ev_default_destroy>, but destroys an event loop created by an
603	earlier call to C<ev_loop_new>.
604
605	=item ev_default_fork ()
606
607	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
608	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
609	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
610	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
611	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
612	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces cough I<kqueue> cough do funny things
		683	during fork.
613		684
614	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
615	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
616	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
617		691
618	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
619	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
620	quite nicely into a call to C<pthread_atfork>:
621		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
622	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
623
624	=item ev_loop_fork (loop)
625
626	Like C<ev_default_fork>, but acts on an event loop created by
627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
628	after fork that you want to re-use in the child, and how you do this is
629	entirely your own problem.
630		706
631	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
632		708
633	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
634	otherwise.	710	otherwise.
635		711
636	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
637		713
638	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
639	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
640	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
641		717
642	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
643	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
644	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
645		722
646	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
647		724
648	Returns the number of times C<ev_loop> was entered minus the number of	725	Returns the number of times C<ev_run> was entered minus the number of
649	times C<ev_loop> was exited, in other words, the recursion depth.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
650		727
651	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	Outside C<ev_run>, this number is zero. In a callback, this number is
652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
653	in which case it is higher.	730	in which case it is higher.
654		731
655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
656	etc.), doesn't count as exit.	733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
657		736
658	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
659		738
660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
661	use.	740	use.
…		…
670		749
671	=item ev_now_update (loop)	750	=item ev_now_update (loop)
672		751
673	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
674	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
675	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
676		755
677	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
678	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
679	the current time is a good idea.	758	the current time is a good idea.
680		759
…		…
682		761
683	=item ev_suspend (loop)	762	=item ev_suspend (loop)
684		763
685	=item ev_resume (loop)	764	=item ev_resume (loop)
686		765
687	These two functions suspend and resume a loop, for use when the loop is	766	These two functions suspend and resume an event loop, for use when the
688	not used for a while and timeouts should not be processed.	767	loop is not used for a while and timeouts should not be processed.
689		768
690	A typical use case would be an interactive program such as a game: When	769	A typical use case would be an interactive program such as a game: When
691	the user presses C<^Z> to suspend the game and resumes it an hour later it	770	the user presses C<^Z> to suspend the game and resumes it an hour later it
692	would be best to handle timeouts as if no time had actually passed while	771	would be best to handle timeouts as if no time had actually passed while
693	the program was suspended. This can be achieved by calling C<ev_suspend>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
695	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
696		775
697	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
699	will be rescheduled (that is, they will lose any events that would have	778	will be rescheduled (that is, they will lose any events that would have
700	occured while suspended).	779	occurred while suspended).
701		780
702	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	After calling C<ev_suspend> you B<must not> call I<any> function on the
703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
704	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
705		784
706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
707	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
708		787
709	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
710		789
711	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
712	after you have initialised all your watchers and you want to start	791	after you have initialised all your watchers and you want to start
713	handling events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
714		795
715	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
716	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
717		799
718	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
719	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
720	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
721	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
722	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
723	beauty.	805	beauty.
724		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
726	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
727	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
728	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
729		817
730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
731	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
732	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
733	be an event internal to libev itself, so there is no guarantee that a	821	be an event internal to libev itself, so there is no guarantee that a
734	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
735	iteration of the loop.	823	iteration of the loop.
736		824
737	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
738	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
740	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
741		829
742	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
743		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
747	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	841	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
755	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
756	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
759	- Queue all expired timers.	852	- Queue all expired timers.
760	- Queue all expired periodics.	853	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	855	- Queue all check watchers.
763	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- Call all queued watchers in reverse order (i.e. check watchers first).
764	Signals and child watchers are implemented as I/O watchers, and will	857	Signals and child watchers are implemented as I/O watchers, and will
765	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
767	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
768	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
769		866
770	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
771	anymore.	868	anymore.
772		869
773	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
774	... as they still have work to do (even an idle watcher will do..)	871	... as they still have work to do (even an idle watcher will do..)
775	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called unloop. yeah!
777		874
778	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
779		876
780	Can be used to make a call to C<ev_loop> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
781	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	879	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
784		881
785	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
786		883
787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
788		886
789	=item ev_ref (loop)	887	=item ev_ref (loop)
790		888
791	=item ev_unref (loop)	889	=item ev_unref (loop)
792		890
793	Ref/unref can be used to add or remove a reference count on the event	891	Ref/unref can be used to add or remove a reference count on the event
794	loop: Every watcher keeps one reference, and as long as the reference	892	loop: Every watcher keeps one reference, and as long as the reference
795	count is nonzero, C<ev_loop> will not return on its own.	893	count is nonzero, C<ev_run> will not return on its own.
796		894
797	This is useful when you have a watcher that you never intend to	895	This is useful when you have a watcher that you never intend to
798	unregister, but that nevertheless should not keep C<ev_loop> from	896	unregister, but that nevertheless should not keep C<ev_run> from
799	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
800	before stopping it.	898	before stopping it.
801		899
802	As an example, libev itself uses this for its internal signal pipe: It	900	As an example, libev itself uses this for its internal signal pipe: It
803	is not visible to the libev user and should not keep C<ev_loop> from	901	is not visible to the libev user and should not keep C<ev_run> from
804	exiting if no event watchers registered by it are active. It is also an	902	exiting if no event watchers registered by it are active. It is also an
805	excellent way to do this for generic recurring timers or from within	903	excellent way to do this for generic recurring timers or from within
806	third-party libraries. Just remember to I<unref after start> and I<ref	904	third-party libraries. Just remember to I<unref after start> and I<ref
807	before stop> (but only if the watcher wasn't active before, or was active	905	before stop> (but only if the watcher wasn't active before, or was active
808	before, respectively. Note also that libev might stop watchers itself	906	before, respectively. Note also that libev might stop watchers itself
809	(e.g. non-repeating timers) in which case you have to C<ev_ref>	907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
810	in the callback).	908	in the callback).
811		909
812	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
813	running when nothing else is active.	911	running when nothing else is active.
814		912
815	ev_signal exitsig;	913	ev_signal exitsig;
816	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
817	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
818	evf_unref (loop);	916	ev_unref (loop);
819		917
820	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
821		919
822	ev_ref (loop);	920	ev_ref (loop);
823	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
862	usually doesn't make much sense to set it to a lower value than C<0.01>,	960	usually doesn't make much sense to set it to a lower value than C<0.01>,
863	as this approaches the timing granularity of most systems. Note that if	961	as this approaches the timing granularity of most systems. Note that if
864	you do transactions with the outside world and you can't increase the	962	you do transactions with the outside world and you can't increase the
865	parallelity, then this setting will limit your transaction rate (if you	963	parallelity, then this setting will limit your transaction rate (if you
866	need to poll once per transaction and the I/O collect interval is 0.01,	964	need to poll once per transaction and the I/O collect interval is 0.01,
867	then you can't do more than 100 transations per second).	965	then you can't do more than 100 transactions per second).
868		966
869	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
870	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
871	are "near" in time together, by delaying some, thus reducing the number of	969	are "near" in time together, by delaying some, thus reducing the number of
872	times the process sleeps and wakes up again. Another useful technique to	970	times the process sleeps and wakes up again. Another useful technique to
…		…
880	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
881		979
882	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
883		981
884	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
885	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
886	but when overriding the invoke callback this call comes handy.	984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
887		989
888	=item int ev_pending_count (loop)	990	=item int ev_pending_count (loop)
889		991
890	Returns the number of pending watchers - zero indicates that no watchers	992	Returns the number of pending watchers - zero indicates that no watchers
891	are pending.	993	are pending.
892		994
893	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
894		996
895	This overrides the invoke pending functionality of the loop: Instead of	997	This overrides the invoke pending functionality of the loop: Instead of
896	invoking all pending watchers when there are any, C<ev_loop> will call	998	invoking all pending watchers when there are any, C<ev_run> will call
897	this callback instead. This is useful, for example, when you want to	999	this callback instead. This is useful, for example, when you want to
898	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
899		1001
900	If you want to reset the callback, use C<ev_invoke_pending> as new	1002	If you want to reset the callback, use C<ev_invoke_pending> as new
901	callback.	1003	callback.
…		…
904		1006
905	Sometimes you want to share the same loop between multiple threads. This	1007	Sometimes you want to share the same loop between multiple threads. This
906	can be done relatively simply by putting mutex_lock/unlock calls around	1008	can be done relatively simply by putting mutex_lock/unlock calls around
907	each call to a libev function.	1009	each call to a libev function.
908		1010
909	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1011	However, C<ev_run> can run an indefinite time, so it is not feasible
910	wait for it to return. One way around this is to wake up the loop via	1012	to wait for it to return. One way around this is to wake up the event
911	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
912	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
913		1015
914	When set, then C<release> will be called just before the thread is	1016	When set, then C<release> will be called just before the thread is
915	suspended waiting for new events, and C<acquire> is called just	1017	suspended waiting for new events, and C<acquire> is called just
916	afterwards.	1018	afterwards.
917		1019
…		…
920		1022
921	While event loop modifications are allowed between invocations of	1023	While event loop modifications are allowed between invocations of
922	C<release> and C<acquire> (that's their only purpose after all), no	1024	C<release> and C<acquire> (that's their only purpose after all), no
923	modifications done will affect the event loop, i.e. adding watchers will	1025	modifications done will affect the event loop, i.e. adding watchers will
924	have no effect on the set of file descriptors being watched, or the time	1026	have no effect on the set of file descriptors being watched, or the time
925	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
926	to take note of any changes you made.	1028	to take note of any changes you made.
927		1029
928	In theory, threads executing C<ev_loop> will be async-cancel safe between	1030	In theory, threads executing C<ev_run> will be async-cancel safe between
929	invocations of C<release> and C<acquire>.	1031	invocations of C<release> and C<acquire>.
930		1032
931	See also the locking example in the C<THREADS> section later in this	1033	See also the locking example in the C<THREADS> section later in this
932	document.	1034	document.
933		1035
934	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
935		1037
936	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
937		1039
938	Set and retrieve a single C<void *> associated with a loop. When	1040	Set and retrieve a single C<void *> associated with a loop. When
939	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
940	C<0.>	1042	C<0>.
941		1043
942	These two functions can be used to associate arbitrary data with a loop,	1044	These two functions can be used to associate arbitrary data with a loop,
943	and are intended solely for the C<invoke_pending_cb>, C<release> and	1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
944	C<acquire> callbacks described above, but of course can be (ab-)used for	1046	C<acquire> callbacks described above, but of course can be (ab-)used for
945	any other purpose as well.	1047	any other purpose as well.
946		1048
947	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
948		1050
949	This function only does something when C<EV_VERIFY> support has been	1051	This function only does something when C<EV_VERIFY> support has been
950	compiled in, which is the default for non-minimal builds. It tries to go	1052	compiled in, which is the default for non-minimal builds. It tries to go
951	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
952	is found to be inconsistent, it will print an error message to standard	1054	is found to be inconsistent, it will print an error message to standard
…		…
963		1065
964	In the following description, uppercase C<TYPE> in names stands for the	1066	In the following description, uppercase C<TYPE> in names stands for the
965	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
966	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
967		1069
968	A watcher is a structure that you create and register to record your	1070	A watcher is an opaque structure that you allocate and register to record
969	interest in some event. For instance, if you want to wait for STDIN to	1071	your interest in some event. To make a concrete example, imagine you want
970	become readable, you would create an C<ev_io> watcher for that:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
971		1074
972	static void my_cb (struct ev_loop loop, ev_io w, int revents)	1075	static void my_cb (struct ev_loop loop, ev_io w, int revents)
973	{	1076	{
974	ev_io_stop (w);	1077	ev_io_stop (w);
975	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
976	}	1079	}
977		1080
978	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
979		1082
980	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
981		1084
982	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
983	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
984	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
985		1088
986	ev_loop (loop, 0);	1089	ev_run (loop, 0);
987		1090
988	As you can see, you are responsible for allocating the memory for your	1091	As you can see, you are responsible for allocating the memory for your
989	watcher structures (and it is I<usually> a bad idea to do this on the	1092	watcher structures (and it is I<usually> a bad idea to do this on the
990	stack).	1093	stack).
991		1094
992	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
993	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
994		1097
995	Each watcher structure must be initialised by a call to C<ev_init	1098	Each watcher structure must be initialised by a call to C<ev_init (watcher
996	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
997	callback gets invoked each time the event occurs (or, in the case of I/O	1100	invoked each time the event occurs (or, in the case of I/O watchers, each
998	watchers, each time the event loop detects that the file descriptor given	1101	time the event loop detects that the file descriptor given is readable
999	is readable and/or writable).	1102	and/or writable).
1000		1103
1001	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1104	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1002	macro to configure it, with arguments specific to the watcher type. There	1105	macro to configure it, with arguments specific to the watcher type. There
1003	is also a macro to combine initialisation and setting in one call: C<<	1106	is also a macro to combine initialisation and setting in one call: C<<
1004	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1027	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
1028		1131
1029	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
1030	writable.	1133	writable.
1031		1134
1032	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
1033		1136
1034	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
1035		1138
1036	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
1037		1140
…		…
1055		1158
1056	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1057		1160
1058	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1059		1162
1060	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1061	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
1062	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
1063	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
1064	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
1065	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1066	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1067		1170
1068	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1069		1172
1070	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1071		1174
1072	=item C<EV_FORK>	1175	=item C<EV_FORK>
1073		1176
1074	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
1075	C<ev_fork>).	1178	C<ev_fork>).
		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
1076		1183
1077	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1078		1185
1079	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
1080		1187
…		…
1253	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1254	functions that do not need a watcher.	1361	functions that do not need a watcher.
1255		1362
1256	=back	1363	=back
1257		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1258		1367
1259	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1260		1369
1261	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1262	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1263	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1264	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1265	member, you can also "subclass" the watcher type and provide your own
1266	data:
1267		1374
1268	struct my_io	1375	=over 4
1269	{
1270	ev_io io;
1271	int otherfd;
1272	void *somedata;
1273	struct whatever *mostinteresting;
1274	};
1275		1376
1276	...	1377	=item initialiased
1277	struct my_io w;
1278	ev_io_init (&w.io, my_cb, fd, EV_READ);
1279		1378
1280	And since your callback will be called with a pointer to the watcher, you	1379	Before a watcher can be registered with the event looop it has to be
1281	can cast it back to your own type:	1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1282		1382
1283	static void my_cb (struct ev_loop loop, ev_io w_, int revents)	1383	In this state it is simply some block of memory that is suitable for use
1284	{	1384	in an event loop. It can be moved around, freed, reused etc. at will.
1285	struct my_io w = (struct my_io )w_;
1286	...
1287	}
1288		1385
1289	More interesting and less C-conformant ways of casting your callback type	1386	=item started/running/active
1290	instead have been omitted.
1291		1387
1292	Another common scenario is to use some data structure with multiple	1388	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1293	embedded watchers:	1389	property of the event loop, and is actively waiting for events. While in
		1390	this state it cannot be accessed (except in a few documented ways), moved,
		1391	freed or anything else - the only legal thing is to keep a pointer to it,
		1392	and call libev functions on it that are documented to work on active watchers.
1294		1393
1295	struct my_biggy	1394	=item pending
1296	{
1297	int some_data;
1298	ev_timer t1;
1299	ev_timer t2;
1300	}
1301		1395
1302	In this case getting the pointer to C<my_biggy> is a bit more	1396	If a watcher is active and libev determines that an event it is interested
1303	complicated: Either you store the address of your C<my_biggy> struct	1397	in has occurred (such as a timer expiring), it will become pending. It will
1304	in the C<data> member of the watcher (for woozies), or you need to use	1398	stay in this pending state until either it is stopped or its callback is
1305	some pointer arithmetic using C<offsetof> inside your watchers (for real	1399	about to be invoked, so it is not normally pending inside the watcher
1306	programmers):	1400	callback.
1307		1401
1308	#include <stddef.h>	1402	The watcher might or might not be active while it is pending (for example,
		1403	an expired non-repeating timer can be pending but no longer active). If it
		1404	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1405	but it is still property of the event loop at this time, so cannot be
		1406	moved, freed or reused. And if it is active the rules described in the
		1407	previous item still apply.
1309		1408
1310	static void	1409	It is also possible to feed an event on a watcher that is not active (e.g.
1311	t1_cb (EV_P_ ev_timer *w, int revents)	1410	via C<ev_feed_event>), in which case it becomes pending without being
1312	{	1411	active.
1313	struct my_biggy big = (struct my_biggy *)
1314	(((char *)w) - offsetof (struct my_biggy, t1));
1315	}
1316		1412
1317	static void	1413	=item stopped
1318	t2_cb (EV_P_ ev_timer *w, int revents)	1414
1319	{	1415	A watcher can be stopped implicitly by libev (in which case it might still
1320	struct my_biggy big = (struct my_biggy *)	1416	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1321	(((char *)w) - offsetof (struct my_biggy, t2));	1417	latter will clear any pending state the watcher might be in, regardless
1322	}	1418	of whether it was active or not, so stopping a watcher explicitly before
		1419	freeing it is often a good idea.
		1420
		1421	While stopped (and not pending) the watcher is essentially in the
		1422	initialised state, that is it can be reused, moved, modified in any way
		1423	you wish.
		1424
		1425	=back
1323		1426
1324	=head2 WATCHER PRIORITY MODELS	1427	=head2 WATCHER PRIORITY MODELS
1325		1428
1326	Many event loops support I<watcher priorities>, which are usually small	1429	Many event loops support I<watcher priorities>, which are usually small
1327	integers that influence the ordering of event callback invocation	1430	integers that influence the ordering of event callback invocation
…		…
1370		1473
1371	For example, to emulate how many other event libraries handle priorities,	1474	For example, to emulate how many other event libraries handle priorities,
1372	you can associate an C<ev_idle> watcher to each such watcher, and in	1475	you can associate an C<ev_idle> watcher to each such watcher, and in
1373	the normal watcher callback, you just start the idle watcher. The real	1476	the normal watcher callback, you just start the idle watcher. The real
1374	processing is done in the idle watcher callback. This causes libev to	1477	processing is done in the idle watcher callback. This causes libev to
1375	continously poll and process kernel event data for the watcher, but when	1478	continuously poll and process kernel event data for the watcher, but when
1376	the lock-out case is known to be rare (which in turn is rare :), this is	1479	the lock-out case is known to be rare (which in turn is rare :), this is
1377	workable.	1480	workable.
1378		1481
1379	Usually, however, the lock-out model implemented that way will perform	1482	Usually, however, the lock-out model implemented that way will perform
1380	miserably under the type of load it was designed to handle. In that case,	1483	miserably under the type of load it was designed to handle. In that case,
…		…
1394	{	1497	{
1395	// stop the I/O watcher, we received the event, but	1498	// stop the I/O watcher, we received the event, but
1396	// are not yet ready to handle it.	1499	// are not yet ready to handle it.
1397	ev_io_stop (EV_A_ w);	1500	ev_io_stop (EV_A_ w);
1398		1501
1399	// start the idle watcher to ahndle the actual event.	1502	// start the idle watcher to handle the actual event.
1400	// it will not be executed as long as other watchers	1503	// it will not be executed as long as other watchers
1401	// with the default priority are receiving events.	1504	// with the default priority are receiving events.
1402	ev_idle_start (EV_A_ &idle);	1505	ev_idle_start (EV_A_ &idle);
1403	}	1506	}
1404		1507
…		…
1454	In general you can register as many read and/or write event watchers per	1557	In general you can register as many read and/or write event watchers per
1455	fd as you want (as long as you don't confuse yourself). Setting all file	1558	fd as you want (as long as you don't confuse yourself). Setting all file
1456	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1457	required if you know what you are doing).	1560	required if you know what you are doing).
1458		1561
1459	If you cannot use non-blocking mode, then force the use of a
1460	known-to-be-good backend (at the time of this writing, this includes only
1461	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1462	descriptors for which non-blocking operation makes no sense (such as
1463	files) - libev doesn't guarentee any specific behaviour in that case.
1464
1465	Another thing you have to watch out for is that it is quite easy to	1562	Another thing you have to watch out for is that it is quite easy to
1466	receive "spurious" readiness notifications, that is your callback might	1563	receive "spurious" readiness notifications, that is, your callback might
1467	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1564	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1468	because there is no data. Not only are some backends known to create a	1565	because there is no data. It is very easy to get into this situation even
1469	lot of those (for example Solaris ports), it is very easy to get into	1566	with a relatively standard program structure. Thus it is best to always
1470	this situation even with a relatively standard program structure. Thus	1567	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1471	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1472	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1568	preferable to a program hanging until some data arrives.
1473		1569
1474	If you cannot run the fd in non-blocking mode (for example you should	1570	If you cannot run the fd in non-blocking mode (for example you should
1475	not play around with an Xlib connection), then you have to separately	1571	not play around with an Xlib connection), then you have to separately
1476	re-test whether a file descriptor is really ready with a known-to-be good	1572	re-test whether a file descriptor is really ready with a known-to-be good
1477	interface such as poll (fortunately in our Xlib example, Xlib already	1573	interface such as poll (fortunately in the case of Xlib, it already does
1478	does this on its own, so its quite safe to use). Some people additionally	1574	this on its own, so its quite safe to use). Some people additionally
1479	use C<SIGALRM> and an interval timer, just to be sure you won't block	1575	use C<SIGALRM> and an interval timer, just to be sure you won't block
1480	indefinitely.	1576	indefinitely.
1481		1577
1482	But really, best use non-blocking mode.	1578	But really, best use non-blocking mode.
1483		1579
…		…
1511		1607
1512	There is no workaround possible except not registering events	1608	There is no workaround possible except not registering events
1513	for potentially C<dup ()>'ed file descriptors, or to resort to	1609	for potentially C<dup ()>'ed file descriptors, or to resort to
1514	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1610	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1515		1611
		1612	=head3 The special problem of files
		1613
		1614	Many people try to use C<select> (or libev) on file descriptors
		1615	representing files, and expect it to become ready when their program
		1616	doesn't block on disk accesses (which can take a long time on their own).
		1617
		1618	However, this cannot ever work in the "expected" way - you get a readiness
		1619	notification as soon as the kernel knows whether and how much data is
		1620	there, and in the case of open files, that's always the case, so you
		1621	always get a readiness notification instantly, and your read (or possibly
		1622	write) will still block on the disk I/O.
		1623
		1624	Another way to view it is that in the case of sockets, pipes, character
		1625	devices and so on, there is another party (the sender) that delivers data
		1626	on its own, but in the case of files, there is no such thing: the disk
		1627	will not send data on its own, simply because it doesn't know what you
		1628	wish to read - you would first have to request some data.
		1629
		1630	Since files are typically not-so-well supported by advanced notification
		1631	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1632	to files, even though you should not use it. The reason for this is
		1633	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1634	usually a tty, often a pipe, but also sometimes files or special devices
		1635	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1636	F</dev/urandom>), and even though the file might better be served with
		1637	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1638	it "just works" instead of freezing.
		1639
		1640	So avoid file descriptors pointing to files when you know it (e.g. use
		1641	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1642	when you rarely read from a file instead of from a socket, and want to
		1643	reuse the same code path.
		1644
1516	=head3 The special problem of fork	1645	=head3 The special problem of fork
1517		1646
1518	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1647	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1519	useless behaviour. Libev fully supports fork, but needs to be told about	1648	useless behaviour. Libev fully supports fork, but needs to be told about
1520	it in the child.	1649	it in the child if you want to continue to use it in the child.
1521		1650
1522	To support fork in your programs, you either have to call	1651	To support fork in your child processes, you have to call C<ev_loop_fork
1523	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1652	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1524	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1653	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525	C<EVBACKEND_POLL>.
1526		1654
1527	=head3 The special problem of SIGPIPE	1655	=head3 The special problem of SIGPIPE
1528		1656
1529	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1657	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1530	when writing to a pipe whose other end has been closed, your program gets	1658	when writing to a pipe whose other end has been closed, your program gets
…		…
1533		1661
1534	So when you encounter spurious, unexplained daemon exits, make sure you	1662	So when you encounter spurious, unexplained daemon exits, make sure you
1535	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1663	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1536	somewhere, as that would have given you a big clue).	1664	somewhere, as that would have given you a big clue).
1537		1665
		1666	=head3 The special problem of accept()ing when you can't
		1667
		1668	Many implementations of the POSIX C<accept> function (for example,
		1669	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1670	connection from the pending queue in all error cases.
		1671
		1672	For example, larger servers often run out of file descriptors (because
		1673	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1674	rejecting the connection, leading to libev signalling readiness on
		1675	the next iteration again (the connection still exists after all), and
		1676	typically causing the program to loop at 100% CPU usage.
		1677
		1678	Unfortunately, the set of errors that cause this issue differs between
		1679	operating systems, there is usually little the app can do to remedy the
		1680	situation, and no known thread-safe method of removing the connection to
		1681	cope with overload is known (to me).
		1682
		1683	One of the easiest ways to handle this situation is to just ignore it
		1684	- when the program encounters an overload, it will just loop until the
		1685	situation is over. While this is a form of busy waiting, no OS offers an
		1686	event-based way to handle this situation, so it's the best one can do.
		1687
		1688	A better way to handle the situation is to log any errors other than
		1689	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1690	messages, and continue as usual, which at least gives the user an idea of
		1691	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1692	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1693	usage.
		1694
		1695	If your program is single-threaded, then you could also keep a dummy file
		1696	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1697	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1698	close that fd, and create a new dummy fd. This will gracefully refuse
		1699	clients under typical overload conditions.
		1700
		1701	The last way to handle it is to simply log the error and C<exit>, as
		1702	is often done with C<malloc> failures, but this results in an easy
		1703	opportunity for a DoS attack.
1538		1704
1539	=head3 Watcher-Specific Functions	1705	=head3 Watcher-Specific Functions
1540		1706
1541	=over 4	1707	=over 4
1542		1708
…		…
1574	...	1740	...
1575	struct ev_loop *loop = ev_default_init (0);	1741	struct ev_loop *loop = ev_default_init (0);
1576	ev_io stdin_readable;	1742	ev_io stdin_readable;
1577	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1743	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1578	ev_io_start (loop, &stdin_readable);	1744	ev_io_start (loop, &stdin_readable);
1579	ev_loop (loop, 0);	1745	ev_run (loop, 0);
1580		1746
1581		1747
1582	=head2 C<ev_timer> - relative and optionally repeating timeouts	1748	=head2 C<ev_timer> - relative and optionally repeating timeouts
1583		1749
1584	Timer watchers are simple relative timers that generate an event after a	1750	Timer watchers are simple relative timers that generate an event after a
…		…
1593	The callback is guaranteed to be invoked only I<after> its timeout has	1759	The callback is guaranteed to be invoked only I<after> its timeout has
1594	passed (not I<at>, so on systems with very low-resolution clocks this	1760	passed (not I<at>, so on systems with very low-resolution clocks this
1595	might introduce a small delay). If multiple timers become ready during the	1761	might introduce a small delay). If multiple timers become ready during the
1596	same loop iteration then the ones with earlier time-out values are invoked	1762	same loop iteration then the ones with earlier time-out values are invoked
1597	before ones of the same priority with later time-out values (but this is	1763	before ones of the same priority with later time-out values (but this is
1598	no longer true when a callback calls C<ev_loop> recursively).	1764	no longer true when a callback calls C<ev_run> recursively).
1599		1765
1600	=head3 Be smart about timeouts	1766	=head3 Be smart about timeouts
1601		1767
1602	Many real-world problems involve some kind of timeout, usually for error	1768	Many real-world problems involve some kind of timeout, usually for error
1603	recovery. A typical example is an HTTP request - if the other side hangs,	1769	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1689	ev_tstamp timeout = last_activity + 60.;	1855	ev_tstamp timeout = last_activity + 60.;
1690		1856
1691	// if last_activity + 60. is older than now, we did time out	1857	// if last_activity + 60. is older than now, we did time out
1692	if (timeout < now)	1858	if (timeout < now)
1693	{	1859	{
1694	// timeout occured, take action	1860	// timeout occurred, take action
1695	}	1861	}
1696	else	1862	else
1697	{	1863	{
1698	// callback was invoked, but there was some activity, re-arm	1864	// callback was invoked, but there was some activity, re-arm
1699	// the watcher to fire in last_activity + 60, which is	1865	// the watcher to fire in last_activity + 60, which is
…		…
1721	to the current time (meaning we just have some activity :), then call the	1887	to the current time (meaning we just have some activity :), then call the
1722	callback, which will "do the right thing" and start the timer:	1888	callback, which will "do the right thing" and start the timer:
1723		1889
1724	ev_init (timer, callback);	1890	ev_init (timer, callback);
1725	last_activity = ev_now (loop);	1891	last_activity = ev_now (loop);
1726	callback (loop, timer, EV_TIMEOUT);	1892	callback (loop, timer, EV_TIMER);
1727		1893
1728	And when there is some activity, simply store the current time in	1894	And when there is some activity, simply store the current time in
1729	C<last_activity>, no libev calls at all:	1895	C<last_activity>, no libev calls at all:
1730		1896
1731	last_actiivty = ev_now (loop);	1897	last_activity = ev_now (loop);
1732		1898
1733	This technique is slightly more complex, but in most cases where the	1899	This technique is slightly more complex, but in most cases where the
1734	time-out is unlikely to be triggered, much more efficient.	1900	time-out is unlikely to be triggered, much more efficient.
1735		1901
1736	Changing the timeout is trivial as well (if it isn't hard-coded in the	1902	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1774		1940
1775	=head3 The special problem of time updates	1941	=head3 The special problem of time updates
1776		1942
1777	Establishing the current time is a costly operation (it usually takes at	1943	Establishing the current time is a costly operation (it usually takes at
1778	least two system calls): EV therefore updates its idea of the current	1944	least two system calls): EV therefore updates its idea of the current
1779	time only before and after C<ev_loop> collects new events, which causes a	1945	time only before and after C<ev_run> collects new events, which causes a
1780	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1946	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1781	lots of events in one iteration.	1947	lots of events in one iteration.
1782		1948
1783	The relative timeouts are calculated relative to the C<ev_now ()>	1949	The relative timeouts are calculated relative to the C<ev_now ()>
1784	time. This is usually the right thing as this timestamp refers to the time	1950	time. This is usually the right thing as this timestamp refers to the time
…		…
1862	Returns the remaining time until a timer fires. If the timer is active,	2028	Returns the remaining time until a timer fires. If the timer is active,
1863	then this time is relative to the current event loop time, otherwise it's	2029	then this time is relative to the current event loop time, otherwise it's
1864	the timeout value currently configured.	2030	the timeout value currently configured.
1865		2031
1866	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2032	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1867	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2033	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1868	will return C<4>. When the timer expires and is restarted, it will return	2034	will return C<4>. When the timer expires and is restarted, it will return
1869	roughly C<7> (likely slightly less as callback invocation takes some time,	2035	roughly C<7> (likely slightly less as callback invocation takes some time,
1870	too), and so on.	2036	too), and so on.
1871		2037
1872	=item ev_tstamp repeat [read-write]	2038	=item ev_tstamp repeat [read-write]
…		…
1901	}	2067	}
1902		2068
1903	ev_timer mytimer;	2069	ev_timer mytimer;
1904	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2070	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1905	ev_timer_again (&mytimer); /* start timer */	2071	ev_timer_again (&mytimer); /* start timer */
1906	ev_loop (loop, 0);	2072	ev_run (loop, 0);
1907		2073
1908	// and in some piece of code that gets executed on any "activity":	2074	// and in some piece of code that gets executed on any "activity":
1909	// reset the timeout to start ticking again at 10 seconds	2075	// reset the timeout to start ticking again at 10 seconds
1910	ev_timer_again (&mytimer);	2076	ev_timer_again (&mytimer);
1911		2077
…		…
1937		2103
1938	As with timers, the callback is guaranteed to be invoked only when the	2104	As with timers, the callback is guaranteed to be invoked only when the
1939	point in time where it is supposed to trigger has passed. If multiple	2105	point in time where it is supposed to trigger has passed. If multiple
1940	timers become ready during the same loop iteration then the ones with	2106	timers become ready during the same loop iteration then the ones with
1941	earlier time-out values are invoked before ones with later time-out values	2107	earlier time-out values are invoked before ones with later time-out values
1942	(but this is no longer true when a callback calls C<ev_loop> recursively).	2108	(but this is no longer true when a callback calls C<ev_run> recursively).
1943		2109
1944	=head3 Watcher-Specific Functions and Data Members	2110	=head3 Watcher-Specific Functions and Data Members
1945		2111
1946	=over 4	2112	=over 4
1947		2113
…		…
2075	Example: Call a callback every hour, or, more precisely, whenever the	2241	Example: Call a callback every hour, or, more precisely, whenever the
2076	system time is divisible by 3600. The callback invocation times have	2242	system time is divisible by 3600. The callback invocation times have
2077	potentially a lot of jitter, but good long-term stability.	2243	potentially a lot of jitter, but good long-term stability.
2078		2244
2079	static void	2245	static void
2080	clock_cb (struct ev_loop loop, ev_io w, int revents)	2246	clock_cb (struct ev_loop loop, ev_periodic w, int revents)
2081	{	2247	{
2082	... its now a full hour (UTC, or TAI or whatever your clock follows)	2248	... its now a full hour (UTC, or TAI or whatever your clock follows)
2083	}	2249	}
2084		2250
2085	ev_periodic hourly_tick;	2251	ev_periodic hourly_tick;
…		…
2108		2274
2109	=head2 C<ev_signal> - signal me when a signal gets signalled!	2275	=head2 C<ev_signal> - signal me when a signal gets signalled!
2110		2276
2111	Signal watchers will trigger an event when the process receives a specific	2277	Signal watchers will trigger an event when the process receives a specific
2112	signal one or more times. Even though signals are very asynchronous, libev	2278	signal one or more times. Even though signals are very asynchronous, libev
2113	will try it's best to deliver signals synchronously, i.e. as part of the	2279	will try its best to deliver signals synchronously, i.e. as part of the
2114	normal event processing, like any other event.	2280	normal event processing, like any other event.
2115		2281
2116	If you want signals to be delivered truly asynchronously, just use	2282	If you want signals to be delivered truly asynchronously, just use
2117	C<sigaction> as you would do without libev and forget about sharing	2283	C<sigaction> as you would do without libev and forget about sharing
2118	the signal. You can even use C<ev_async> from a signal handler to	2284	the signal. You can even use C<ev_async> from a signal handler to
…		…
2132	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2298	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2133	not be unduly interrupted. If you have a problem with system calls getting	2299	not be unduly interrupted. If you have a problem with system calls getting
2134	interrupted by signals you can block all signals in an C<ev_check> watcher	2300	interrupted by signals you can block all signals in an C<ev_check> watcher
2135	and unblock them in an C<ev_prepare> watcher.	2301	and unblock them in an C<ev_prepare> watcher.
2136		2302
2137	=head3 The special problem of inheritance over execve	2303	=head3 The special problem of inheritance over fork/execve/pthread_create
2138		2304
2139	Both the signal mask (C<sigprocmask>) and the signal disposition	2305	Both the signal mask (C<sigprocmask>) and the signal disposition
2140	(C<sigaction>) are unspecified after starting a signal watcher (and after	2306	(C<sigaction>) are unspecified after starting a signal watcher (and after
2141	stopping it again), that is, libev might or might not block the signal,	2307	stopping it again), that is, libev might or might not block the signal,
2142	and might or might not set or restore the installed signal handler.	2308	and might or might not set or restore the installed signal handler (but
		2309	see C<EVFLAG_NOSIGMASK>).
2143		2310
2144	While this does not matter for the signal disposition (libev never	2311	While this does not matter for the signal disposition (libev never
2145	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2312	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2146	C<execve>), this matters for the signal mask: many programs do not expect	2313	C<execve>), this matters for the signal mask: many programs do not expect
2147	certain signals to be blocked.	2314	certain signals to be blocked.
…		…
2152		2319
2153	The simplest way to ensure that the signal mask is reset in the child is	2320	The simplest way to ensure that the signal mask is reset in the child is
2154	to install a fork handler with C<pthread_atfork> that resets it. That will	2321	to install a fork handler with C<pthread_atfork> that resets it. That will
2155	catch fork calls done by libraries (such as the libc) as well.	2322	catch fork calls done by libraries (such as the libc) as well.
2156		2323
2157	In current versions of libev, you can also ensure that the signal mask is	2324	In current versions of libev, the signal will not be blocked indefinitely
2158	not blocking any signals (except temporarily, so thread users watch out)	2325	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2159	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This	2326	the window of opportunity for problems, it will not go away, as libev
2160	is not guaranteed for future versions, however.	2327	I<has> to modify the signal mask, at least temporarily.
		2328
		2329	So I can't stress this enough: I<If you do not reset your signal mask when
		2330	you expect it to be empty, you have a race condition in your code>. This
		2331	is not a libev-specific thing, this is true for most event libraries.
		2332
		2333	=head3 The special problem of threads signal handling
		2334
		2335	POSIX threads has problematic signal handling semantics, specifically,
		2336	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2337	threads in a process block signals, which is hard to achieve.
		2338
		2339	When you want to use sigwait (or mix libev signal handling with your own
		2340	for the same signals), you can tackle this problem by globally blocking
		2341	all signals before creating any threads (or creating them with a fully set
		2342	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2343	loops. Then designate one thread as "signal receiver thread" which handles
		2344	these signals. You can pass on any signals that libev might be interested
		2345	in by calling C<ev_feed_signal>.
2161		2346
2162	=head3 Watcher-Specific Functions and Data Members	2347	=head3 Watcher-Specific Functions and Data Members
2163		2348
2164	=over 4	2349	=over 4
2165		2350
…		…
2181	Example: Try to exit cleanly on SIGINT.	2366	Example: Try to exit cleanly on SIGINT.
2182		2367
2183	static void	2368	static void
2184	sigint_cb (struct ev_loop loop, ev_signal w, int revents)	2369	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
2185	{	2370	{
2186	ev_unloop (loop, EVUNLOOP_ALL);	2371	ev_break (loop, EVBREAK_ALL);
2187	}	2372	}
2188		2373
2189	ev_signal signal_watcher;	2374	ev_signal signal_watcher;
2190	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2375	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2191	ev_signal_start (loop, &signal_watcher);	2376	ev_signal_start (loop, &signal_watcher);
…		…
2577		2762
2578	Prepare and check watchers are usually (but not always) used in pairs:	2763	Prepare and check watchers are usually (but not always) used in pairs:
2579	prepare watchers get invoked before the process blocks and check watchers	2764	prepare watchers get invoked before the process blocks and check watchers
2580	afterwards.	2765	afterwards.
2581		2766
2582	You I<must not> call C<ev_loop> or similar functions that enter	2767	You I<must not> call C<ev_run> or similar functions that enter
2583	the current event loop from either C<ev_prepare> or C<ev_check>	2768	the current event loop from either C<ev_prepare> or C<ev_check>
2584	watchers. Other loops than the current one are fine, however. The	2769	watchers. Other loops than the current one are fine, however. The
2585	rationale behind this is that you do not need to check for recursion in	2770	rationale behind this is that you do not need to check for recursion in
2586	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2771	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2587	C<ev_check> so if you have one watcher of each kind they will always be	2772	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2755		2940
2756	if (timeout >= 0)	2941	if (timeout >= 0)
2757	// create/start timer	2942	// create/start timer
2758		2943
2759	// poll	2944	// poll
2760	ev_loop (EV_A_ 0);	2945	ev_run (EV_A_ 0);
2761		2946
2762	// stop timer again	2947	// stop timer again
2763	if (timeout >= 0)	2948	if (timeout >= 0)
2764	ev_timer_stop (EV_A_ &to);	2949	ev_timer_stop (EV_A_ &to);
2765		2950
…		…
2843	if you do not want that, you need to temporarily stop the embed watcher).	3028	if you do not want that, you need to temporarily stop the embed watcher).
2844		3029
2845	=item ev_embed_sweep (loop, ev_embed *)	3030	=item ev_embed_sweep (loop, ev_embed *)
2846		3031
2847	Make a single, non-blocking sweep over the embedded loop. This works	3032	Make a single, non-blocking sweep over the embedded loop. This works
2848	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3033	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2849	appropriate way for embedded loops.	3034	appropriate way for embedded loops.
2850		3035
2851	=item struct ev_loop *other [read-only]	3036	=item struct ev_loop *other [read-only]
2852		3037
2853	The embedded event loop.	3038	The embedded event loop.
…		…
2913	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3098	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2914	handlers will be invoked, too, of course.	3099	handlers will be invoked, too, of course.
2915		3100
2916	=head3 The special problem of life after fork - how is it possible?	3101	=head3 The special problem of life after fork - how is it possible?
2917		3102
2918	Most uses of C<fork()> consist of forking, then some simple calls to ste	3103	Most uses of C<fork()> consist of forking, then some simple calls to set
2919	up/change the process environment, followed by a call to C<exec()>. This	3104	up/change the process environment, followed by a call to C<exec()>. This
2920	sequence should be handled by libev without any problems.	3105	sequence should be handled by libev without any problems.
2921		3106
2922	This changes when the application actually wants to do event handling	3107	This changes when the application actually wants to do event handling
2923	in the child, or both parent in child, in effect "continuing" after the	3108	in the child, or both parent in child, in effect "continuing" after the
…		…
2939	disadvantage of having to use multiple event loops (which do not support	3124	disadvantage of having to use multiple event loops (which do not support
2940	signal watchers).	3125	signal watchers).
2941		3126
2942	When this is not possible, or you want to use the default loop for	3127	When this is not possible, or you want to use the default loop for
2943	other reasons, then in the process that wants to start "fresh", call	3128	other reasons, then in the process that wants to start "fresh", call
2944	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3129	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2945	the default loop will "orphan" (not stop) all registered watchers, so you	3130	Destroying the default loop will "orphan" (not stop) all registered
2946	have to be careful not to execute code that modifies those watchers. Note	3131	watchers, so you have to be careful not to execute code that modifies
2947	also that in that case, you have to re-register any signal watchers.	3132	those watchers. Note also that in that case, you have to re-register any
		3133	signal watchers.
2948		3134
2949	=head3 Watcher-Specific Functions and Data Members	3135	=head3 Watcher-Specific Functions and Data Members
2950		3136
2951	=over 4	3137	=over 4
2952		3138
2953	=item ev_fork_init (ev_signal *, callback)	3139	=item ev_fork_init (ev_fork *, callback)
2954		3140
2955	Initialises and configures the fork watcher - it has no parameters of any	3141	Initialises and configures the fork watcher - it has no parameters of any
2956	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3142	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2957	believe me.	3143	really.
2958		3144
2959	=back	3145	=back
2960		3146
2961		3147
		3148	=head2 C<ev_cleanup> - even the best things end
		3149
		3150	Cleanup watchers are called just before the event loop is being destroyed
		3151	by a call to C<ev_loop_destroy>.
		3152
		3153	While there is no guarantee that the event loop gets destroyed, cleanup
		3154	watchers provide a convenient method to install cleanup hooks for your
		3155	program, worker threads and so on - you just to make sure to destroy the
		3156	loop when you want them to be invoked.
		3157
		3158	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3159	all other watchers, they do not keep a reference to the event loop (which
		3160	makes a lot of sense if you think about it). Like all other watchers, you
		3161	can call libev functions in the callback, except C<ev_cleanup_start>.
		3162
		3163	=head3 Watcher-Specific Functions and Data Members
		3164
		3165	=over 4
		3166
		3167	=item ev_cleanup_init (ev_cleanup *, callback)
		3168
		3169	Initialises and configures the cleanup watcher - it has no parameters of
		3170	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3171	pointless, I assure you.
		3172
		3173	=back
		3174
		3175	Example: Register an atexit handler to destroy the default loop, so any
		3176	cleanup functions are called.
		3177
		3178	static void
		3179	program_exits (void)
		3180	{
		3181	ev_loop_destroy (EV_DEFAULT_UC);
		3182	}
		3183
		3184	...
		3185	atexit (program_exits);
		3186
		3187
2962	=head2 C<ev_async> - how to wake up another event loop	3188	=head2 C<ev_async> - how to wake up an event loop
2963		3189
2964	In general, you cannot use an C<ev_loop> from multiple threads or other	3190	In general, you cannot use an C<ev_run> from multiple threads or other
2965	asynchronous sources such as signal handlers (as opposed to multiple event	3191	asynchronous sources such as signal handlers (as opposed to multiple event
2966	loops - those are of course safe to use in different threads).	3192	loops - those are of course safe to use in different threads).
2967		3193
2968	Sometimes, however, you need to wake up another event loop you do not	3194	Sometimes, however, you need to wake up an event loop you do not control,
2969	control, for example because it belongs to another thread. This is what	3195	for example because it belongs to another thread. This is what C<ev_async>
2970	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3196	watchers do: as long as the C<ev_async> watcher is active, you can signal
2971	can signal it by calling C<ev_async_send>, which is thread- and signal	3197	it by calling C<ev_async_send>, which is thread- and signal safe.
2972	safe.
2973		3198
2974	This functionality is very similar to C<ev_signal> watchers, as signals,	3199	This functionality is very similar to C<ev_signal> watchers, as signals,
2975	too, are asynchronous in nature, and signals, too, will be compressed	3200	too, are asynchronous in nature, and signals, too, will be compressed
2976	(i.e. the number of callback invocations may be less than the number of	3201	(i.e. the number of callback invocations may be less than the number of
2977	C<ev_async_sent> calls).	3202	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3203	of "global async watchers" by using a watcher on an otherwise unused
		3204	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3205	even without knowing which loop owns the signal.
2978		3206
2979	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3207	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2980	just the default loop.	3208	just the default loop.
2981		3209
2982	=head3 Queueing	3210	=head3 Queueing
…		…
3132		3360
3133	If C<timeout> is less than 0, then no timeout watcher will be	3361	If C<timeout> is less than 0, then no timeout watcher will be
3134	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3362	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3135	repeat = 0) will be started. C<0> is a valid timeout.	3363	repeat = 0) will be started. C<0> is a valid timeout.
3136		3364
3137	The callback has the type C<void (cb)(int revents, void arg)> and gets	3365	The callback has the type C<void (cb)(int revents, void arg)> and is
3138	passed an C<revents> set like normal event callbacks (a combination of	3366	passed an C<revents> set like normal event callbacks (a combination of
3139	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3367	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3140	value passed to C<ev_once>. Note that it is possible to receive I<both>	3368	value passed to C<ev_once>. Note that it is possible to receive I<both>
3141	a timeout and an io event at the same time - you probably should give io	3369	a timeout and an io event at the same time - you probably should give io
3142	events precedence.	3370	events precedence.
3143		3371
3144	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3372	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3145		3373
3146	static void stdin_ready (int revents, void *arg)	3374	static void stdin_ready (int revents, void *arg)
3147	{	3375	{
3148	if (revents & EV_READ)	3376	if (revents & EV_READ)
3149	/* stdin might have data for us, joy! */;	3377	/* stdin might have data for us, joy! */;
3150	else if (revents & EV_TIMEOUT)	3378	else if (revents & EV_TIMER)
3151	/* doh, nothing entered */;	3379	/* doh, nothing entered */;
3152	}	3380	}
3153		3381
3154	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3382	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3155		3383
…		…
3158	Feed an event on the given fd, as if a file descriptor backend detected	3386	Feed an event on the given fd, as if a file descriptor backend detected
3159	the given events it.	3387	the given events it.
3160		3388
3161	=item ev_feed_signal_event (loop, int signum)	3389	=item ev_feed_signal_event (loop, int signum)
3162		3390
3163	Feed an event as if the given signal occurred (C<loop> must be the default	3391	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3164	loop!).	3392	which is async-safe.
3165		3393
3166	=back	3394	=back
		3395
		3396
		3397	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3398
		3399	This section explains some common idioms that are not immediately
		3400	obvious. Note that examples are sprinkled over the whole manual, and this
		3401	section only contains stuff that wouldn't fit anywhere else.
		3402
		3403	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3404
		3405	Each watcher has, by default, a C<void *data> member that you can read
		3406	or modify at any time: libev will completely ignore it. This can be used
		3407	to associate arbitrary data with your watcher. If you need more data and
		3408	don't want to allocate memory separately and store a pointer to it in that
		3409	data member, you can also "subclass" the watcher type and provide your own
		3410	data:
		3411
		3412	struct my_io
		3413	{
		3414	ev_io io;
		3415	int otherfd;
		3416	void *somedata;
		3417	struct whatever *mostinteresting;
		3418	};
		3419
		3420	...
		3421	struct my_io w;
		3422	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3423
		3424	And since your callback will be called with a pointer to the watcher, you
		3425	can cast it back to your own type:
		3426
		3427	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3428	{
		3429	struct my_io w = (struct my_io )w_;
		3430	...
		3431	}
		3432
		3433	More interesting and less C-conformant ways of casting your callback
		3434	function type instead have been omitted.
		3435
		3436	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3437
		3438	Another common scenario is to use some data structure with multiple
		3439	embedded watchers, in effect creating your own watcher that combines
		3440	multiple libev event sources into one "super-watcher":
		3441
		3442	struct my_biggy
		3443	{
		3444	int some_data;
		3445	ev_timer t1;
		3446	ev_timer t2;
		3447	}
		3448
		3449	In this case getting the pointer to C<my_biggy> is a bit more
		3450	complicated: Either you store the address of your C<my_biggy> struct in
		3451	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3452	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3453	real programmers):
		3454
		3455	#include <stddef.h>
		3456
		3457	static void
		3458	t1_cb (EV_P_ ev_timer *w, int revents)
		3459	{
		3460	struct my_biggy big = (struct my_biggy *)
		3461	(((char *)w) - offsetof (struct my_biggy, t1));
		3462	}
		3463
		3464	static void
		3465	t2_cb (EV_P_ ev_timer *w, int revents)
		3466	{
		3467	struct my_biggy big = (struct my_biggy *)
		3468	(((char *)w) - offsetof (struct my_biggy, t2));
		3469	}
		3470
		3471	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3472
		3473	Often (especially in GUI toolkits) there are places where you have
		3474	I<modal> interaction, which is most easily implemented by recursively
		3475	invoking C<ev_run>.
		3476
		3477	This brings the problem of exiting - a callback might want to finish the
		3478	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3479	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3480	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3481	other combination: In these cases, C<ev_break> will not work alone.
		3482
		3483	The solution is to maintain "break this loop" variable for each C<ev_run>
		3484	invocation, and use a loop around C<ev_run> until the condition is
		3485	triggered, using C<EVRUN_ONCE>:
		3486
		3487	// main loop
		3488	int exit_main_loop = 0;
		3489
		3490	while (!exit_main_loop)
		3491	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3492
		3493	// in a model watcher
		3494	int exit_nested_loop = 0;
		3495
		3496	while (!exit_nested_loop)
		3497	ev_run (EV_A_ EVRUN_ONCE);
		3498
		3499	To exit from any of these loops, just set the corresponding exit variable:
		3500
		3501	// exit modal loop
		3502	exit_nested_loop = 1;
		3503
		3504	// exit main program, after modal loop is finished
		3505	exit_main_loop = 1;
		3506
		3507	// exit both
		3508	exit_main_loop = exit_nested_loop = 1;
		3509
		3510	=head2 THREAD LOCKING EXAMPLE
		3511
		3512	Here is a fictitious example of how to run an event loop in a different
		3513	thread from where callbacks are being invoked and watchers are
		3514	created/added/removed.
		3515
		3516	For a real-world example, see the C<EV::Loop::Async> perl module,
		3517	which uses exactly this technique (which is suited for many high-level
		3518	languages).
		3519
		3520	The example uses a pthread mutex to protect the loop data, a condition
		3521	variable to wait for callback invocations, an async watcher to notify the
		3522	event loop thread and an unspecified mechanism to wake up the main thread.
		3523
		3524	First, you need to associate some data with the event loop:
		3525
		3526	typedef struct {
		3527	mutex_t lock; /* global loop lock */
		3528	ev_async async_w;
		3529	thread_t tid;
		3530	cond_t invoke_cv;
		3531	} userdata;
		3532
		3533	void prepare_loop (EV_P)
		3534	{
		3535	// for simplicity, we use a static userdata struct.
		3536	static userdata u;
		3537
		3538	ev_async_init (&u->async_w, async_cb);
		3539	ev_async_start (EV_A_ &u->async_w);
		3540
		3541	pthread_mutex_init (&u->lock, 0);
		3542	pthread_cond_init (&u->invoke_cv, 0);
		3543
		3544	// now associate this with the loop
		3545	ev_set_userdata (EV_A_ u);
		3546	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3547	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3548
		3549	// then create the thread running ev_loop
		3550	pthread_create (&u->tid, 0, l_run, EV_A);
		3551	}
		3552
		3553	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3554	solely to wake up the event loop so it takes notice of any new watchers
		3555	that might have been added:
		3556
		3557	static void
		3558	async_cb (EV_P_ ev_async *w, int revents)
		3559	{
		3560	// just used for the side effects
		3561	}
		3562
		3563	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3564	protecting the loop data, respectively.
		3565
		3566	static void
		3567	l_release (EV_P)
		3568	{
		3569	userdata *u = ev_userdata (EV_A);
		3570	pthread_mutex_unlock (&u->lock);
		3571	}
		3572
		3573	static void
		3574	l_acquire (EV_P)
		3575	{
		3576	userdata *u = ev_userdata (EV_A);
		3577	pthread_mutex_lock (&u->lock);
		3578	}
		3579
		3580	The event loop thread first acquires the mutex, and then jumps straight
		3581	into C<ev_run>:
		3582
		3583	void *
		3584	l_run (void *thr_arg)
		3585	{
		3586	struct ev_loop loop = (struct ev_loop )thr_arg;
		3587
		3588	l_acquire (EV_A);
		3589	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3590	ev_run (EV_A_ 0);
		3591	l_release (EV_A);
		3592
		3593	return 0;
		3594	}
		3595
		3596	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3597	signal the main thread via some unspecified mechanism (signals? pipe
		3598	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3599	have been called (in a while loop because a) spurious wakeups are possible
		3600	and b) skipping inter-thread-communication when there are no pending
		3601	watchers is very beneficial):
		3602
		3603	static void
		3604	l_invoke (EV_P)
		3605	{
		3606	userdata *u = ev_userdata (EV_A);
		3607
		3608	while (ev_pending_count (EV_A))
		3609	{
		3610	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3611	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3612	}
		3613	}
		3614
		3615	Now, whenever the main thread gets told to invoke pending watchers, it
		3616	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3617	thread to continue:
		3618
		3619	static void
		3620	real_invoke_pending (EV_P)
		3621	{
		3622	userdata *u = ev_userdata (EV_A);
		3623
		3624	pthread_mutex_lock (&u->lock);
		3625	ev_invoke_pending (EV_A);
		3626	pthread_cond_signal (&u->invoke_cv);
		3627	pthread_mutex_unlock (&u->lock);
		3628	}
		3629
		3630	Whenever you want to start/stop a watcher or do other modifications to an
		3631	event loop, you will now have to lock:
		3632
		3633	ev_timer timeout_watcher;
		3634	userdata *u = ev_userdata (EV_A);
		3635
		3636	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3637
		3638	pthread_mutex_lock (&u->lock);
		3639	ev_timer_start (EV_A_ &timeout_watcher);
		3640	ev_async_send (EV_A_ &u->async_w);
		3641	pthread_mutex_unlock (&u->lock);
		3642
		3643	Note that sending the C<ev_async> watcher is required because otherwise
		3644	an event loop currently blocking in the kernel will have no knowledge
		3645	about the newly added timer. By waking up the loop it will pick up any new
		3646	watchers in the next event loop iteration.
		3647
		3648	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3649
		3650	While the overhead of a callback that e.g. schedules a thread is small, it
		3651	is still an overhead. If you embed libev, and your main usage is with some
		3652	kind of threads or coroutines, you might want to customise libev so that
		3653	doesn't need callbacks anymore.
		3654
		3655	Imagine you have coroutines that you can switch to using a function
		3656	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3657	and that due to some magic, the currently active coroutine is stored in a
		3658	global called C<current_coro>. Then you can build your own "wait for libev
		3659	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3660	the differing C<;> conventions):
		3661
		3662	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3663	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3664
		3665	That means instead of having a C callback function, you store the
		3666	coroutine to switch to in each watcher, and instead of having libev call
		3667	your callback, you instead have it switch to that coroutine.
		3668
		3669	A coroutine might now wait for an event with a function called
		3670	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3671	matter when, or whether the watcher is active or not when this function is
		3672	called):
		3673
		3674	void
		3675	wait_for_event (ev_watcher *w)
		3676	{
		3677	ev_cb_set (w) = current_coro;
		3678	switch_to (libev_coro);
		3679	}
		3680
		3681	That basically suspends the coroutine inside C<wait_for_event> and
		3682	continues the libev coroutine, which, when appropriate, switches back to
		3683	this or any other coroutine. I am sure if you sue this your own :)
		3684
		3685	You can do similar tricks if you have, say, threads with an event queue -
		3686	instead of storing a coroutine, you store the queue object and instead of
		3687	switching to a coroutine, you push the watcher onto the queue and notify
		3688	any waiters.
		3689
		3690	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3691	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3692
		3693	// my_ev.h
		3694	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3695	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3696	#include "../libev/ev.h"
		3697
		3698	// my_ev.c
		3699	#define EV_H "my_ev.h"
		3700	#include "../libev/ev.c"
		3701
		3702	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3703	F<my_ev.c> into your project. When properly specifying include paths, you
		3704	can even use F<ev.h> as header file name directly.
3167		3705
3168		3706
3169	=head1 LIBEVENT EMULATION	3707	=head1 LIBEVENT EMULATION
3170		3708
3171	Libev offers a compatibility emulation layer for libevent. It cannot	3709	Libev offers a compatibility emulation layer for libevent. It cannot
3172	emulate the internals of libevent, so here are some usage hints:	3710	emulate the internals of libevent, so here are some usage hints:
3173		3711
3174	=over 4	3712	=over 4
		3713
		3714	=item * Only the libevent-1.4.1-beta API is being emulated.
		3715
		3716	This was the newest libevent version available when libev was implemented,
		3717	and is still mostly unchanged in 2010.
3175		3718
3176	=item * Use it by including <event.h>, as usual.	3719	=item * Use it by including <event.h>, as usual.
3177		3720
3178	=item * The following members are fully supported: ev_base, ev_callback,	3721	=item * The following members are fully supported: ev_base, ev_callback,
3179	ev_arg, ev_fd, ev_res, ev_events.	3722	ev_arg, ev_fd, ev_res, ev_events.
…		…
3185	=item * Priorities are not currently supported. Initialising priorities	3728	=item * Priorities are not currently supported. Initialising priorities
3186	will fail and all watchers will have the same priority, even though there	3729	will fail and all watchers will have the same priority, even though there
3187	is an ev_pri field.	3730	is an ev_pri field.
3188		3731
3189	=item * In libevent, the last base created gets the signals, in libev, the	3732	=item * In libevent, the last base created gets the signals, in libev, the
3190	first base created (== the default loop) gets the signals.	3733	base that registered the signal gets the signals.
3191		3734
3192	=item * Other members are not supported.	3735	=item * Other members are not supported.
3193		3736
3194	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3737	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3195	to use the libev header file and library.	3738	to use the libev header file and library.
…		…
3214	Care has been taken to keep the overhead low. The only data member the C++	3757	Care has been taken to keep the overhead low. The only data member the C++
3215	classes add (compared to plain C-style watchers) is the event loop pointer	3758	classes add (compared to plain C-style watchers) is the event loop pointer
3216	that the watcher is associated with (or no additional members at all if	3759	that the watcher is associated with (or no additional members at all if
3217	you disable C<EV_MULTIPLICITY> when embedding libev).	3760	you disable C<EV_MULTIPLICITY> when embedding libev).
3218		3761
3219	Currently, functions, and static and non-static member functions can be	3762	Currently, functions, static and non-static member functions and classes
3220	used as callbacks. Other types should be easy to add as long as they only	3763	with C<operator ()> can be used as callbacks. Other types should be easy
3221	need one additional pointer for context. If you need support for other	3764	to add as long as they only need one additional pointer for context. If
3222	types of functors please contact the author (preferably after implementing	3765	you need support for other types of functors please contact the author
3223	it).	3766	(preferably after implementing it).
3224		3767
3225	Here is a list of things available in the C<ev> namespace:	3768	Here is a list of things available in the C<ev> namespace:
3226		3769
3227	=over 4	3770	=over 4
3228		3771
…		…
3289	myclass obj;	3832	myclass obj;
3290	ev::io iow;	3833	ev::io iow;
3291	iow.set <myclass, &myclass::io_cb> (&obj);	3834	iow.set <myclass, &myclass::io_cb> (&obj);
3292		3835
3293	=item w->set (object *)	3836	=item w->set (object *)
3294
3295	This is an B<experimental> feature that might go away in a future version.
3296		3837
3297	This is a variation of a method callback - leaving out the method to call	3838	This is a variation of a method callback - leaving out the method to call
3298	will default the method to C<operator ()>, which makes it possible to use	3839	will default the method to C<operator ()>, which makes it possible to use
3299	functor objects without having to manually specify the C<operator ()> all	3840	functor objects without having to manually specify the C<operator ()> all
3300	the time. Incidentally, you can then also leave out the template argument	3841	the time. Incidentally, you can then also leave out the template argument
…		…
3340	Associates a different C<struct ev_loop> with this watcher. You can only	3881	Associates a different C<struct ev_loop> with this watcher. You can only
3341	do this when the watcher is inactive (and not pending either).	3882	do this when the watcher is inactive (and not pending either).
3342		3883
3343	=item w->set ([arguments])	3884	=item w->set ([arguments])
3344		3885
3345	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3886	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3346	called at least once. Unlike the C counterpart, an active watcher gets	3887	method or a suitable start method must be called at least once. Unlike the
3347	automatically stopped and restarted when reconfiguring it with this	3888	C counterpart, an active watcher gets automatically stopped and restarted
3348	method.	3889	when reconfiguring it with this method.
3349		3890
3350	=item w->start ()	3891	=item w->start ()
3351		3892
3352	Starts the watcher. Note that there is no C<loop> argument, as the	3893	Starts the watcher. Note that there is no C<loop> argument, as the
3353	constructor already stores the event loop.	3894	constructor already stores the event loop.
3354		3895
		3896	=item w->start ([arguments])
		3897
		3898	Instead of calling C<set> and C<start> methods separately, it is often
		3899	convenient to wrap them in one call. Uses the same type of arguments as
		3900	the configure C<set> method of the watcher.
		3901
3355	=item w->stop ()	3902	=item w->stop ()
3356		3903
3357	Stops the watcher if it is active. Again, no C<loop> argument.	3904	Stops the watcher if it is active. Again, no C<loop> argument.
3358		3905
3359	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3906	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3371		3918
3372	=back	3919	=back
3373		3920
3374	=back	3921	=back
3375		3922
3376	Example: Define a class with an IO and idle watcher, start one of them in	3923	Example: Define a class with two I/O and idle watchers, start the I/O
3377	the constructor.	3924	watchers in the constructor.
3378		3925
3379	class myclass	3926	class myclass
3380	{	3927	{
3381	ev::io io ; void io_cb (ev::io &w, int revents);	3928	ev::io io ; void io_cb (ev::io &w, int revents);
		3929	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3382	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3930	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3383		3931
3384	myclass (int fd)	3932	myclass (int fd)
3385	{	3933	{
3386	io .set <myclass, &myclass::io_cb > (this);	3934	io .set <myclass, &myclass::io_cb > (this);
		3935	io2 .set <myclass, &myclass::io2_cb > (this);
3387	idle.set <myclass, &myclass::idle_cb> (this);	3936	idle.set <myclass, &myclass::idle_cb> (this);
3388		3937
3389	io.start (fd, ev::READ);	3938	io.set (fd, ev::WRITE); // configure the watcher
		3939	io.start (); // start it whenever convenient
		3940
		3941	io2.start (fd, ev::READ); // set + start in one call
3390	}	3942	}
3391	};	3943	};
3392		3944
3393		3945
3394	=head1 OTHER LANGUAGE BINDINGS	3946	=head1 OTHER LANGUAGE BINDINGS
…		…
3442	Erkki Seppala has written Ocaml bindings for libev, to be found at	3994	Erkki Seppala has written Ocaml bindings for libev, to be found at
3443	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3995	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3444		3996
3445	=item Lua	3997	=item Lua
3446		3998
3447	Brian Maher has written a partial interface to libev	3999	Brian Maher has written a partial interface to libev for lua (at the
3448	for lua (only C<ev_io> and C<ev_timer>), to be found at	4000	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3449	L<http://github.com/brimworks/lua-ev>.	4001	L<http://github.com/brimworks/lua-ev>.
3450		4002
3451	=back	4003	=back
3452		4004
3453		4005
…		…
3468	loop argument"). The C<EV_A> form is used when this is the sole argument,	4020	loop argument"). The C<EV_A> form is used when this is the sole argument,
3469	C<EV_A_> is used when other arguments are following. Example:	4021	C<EV_A_> is used when other arguments are following. Example:
3470		4022
3471	ev_unref (EV_A);	4023	ev_unref (EV_A);
3472	ev_timer_add (EV_A_ watcher);	4024	ev_timer_add (EV_A_ watcher);
3473	ev_loop (EV_A_ 0);	4025	ev_run (EV_A_ 0);
3474		4026
3475	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4027	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3476	which is often provided by the following macro.	4028	which is often provided by the following macro.
3477		4029
3478	=item C<EV_P>, C<EV_P_>	4030	=item C<EV_P>, C<EV_P_>
…		…
3518	}	4070	}
3519		4071
3520	ev_check check;	4072	ev_check check;
3521	ev_check_init (&check, check_cb);	4073	ev_check_init (&check, check_cb);
3522	ev_check_start (EV_DEFAULT_ &check);	4074	ev_check_start (EV_DEFAULT_ &check);
3523	ev_loop (EV_DEFAULT_ 0);	4075	ev_run (EV_DEFAULT_ 0);
3524		4076
3525	=head1 EMBEDDING	4077	=head1 EMBEDDING
3526		4078
3527	Libev can (and often is) directly embedded into host	4079	Libev can (and often is) directly embedded into host
3528	applications. Examples of applications that embed it include the Deliantra	4080	applications. Examples of applications that embed it include the Deliantra
…		…
3608	libev.m4	4160	libev.m4
3609		4161
3610	=head2 PREPROCESSOR SYMBOLS/MACROS	4162	=head2 PREPROCESSOR SYMBOLS/MACROS
3611		4163
3612	Libev can be configured via a variety of preprocessor symbols you have to	4164	Libev can be configured via a variety of preprocessor symbols you have to
3613	define before including any of its files. The default in the absence of	4165	define before including (or compiling) any of its files. The default in
3614	autoconf is documented for every option.	4166	the absence of autoconf is documented for every option.
		4167
		4168	Symbols marked with "(h)" do not change the ABI, and can have different
		4169	values when compiling libev vs. including F<ev.h>, so it is permissible
		4170	to redefine them before including F<ev.h> without breaking compatibility
		4171	to a compiled library. All other symbols change the ABI, which means all
		4172	users of libev and the libev code itself must be compiled with compatible
		4173	settings.
3615		4174
3616	=over 4	4175	=over 4
3617		4176
		4177	=item EV_COMPAT3 (h)
		4178
		4179	Backwards compatibility is a major concern for libev. This is why this
		4180	release of libev comes with wrappers for the functions and symbols that
		4181	have been renamed between libev version 3 and 4.
		4182
		4183	You can disable these wrappers (to test compatibility with future
		4184	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4185	sources. This has the additional advantage that you can drop the C<struct>
		4186	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4187	typedef in that case.
		4188
		4189	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4190	and in some even more future version the compatibility code will be
		4191	removed completely.
		4192
3618	=item EV_STANDALONE	4193	=item EV_STANDALONE (h)
3619		4194
3620	Must always be C<1> if you do not use autoconf configuration, which	4195	Must always be C<1> if you do not use autoconf configuration, which
3621	keeps libev from including F<config.h>, and it also defines dummy	4196	keeps libev from including F<config.h>, and it also defines dummy
3622	implementations for some libevent functions (such as logging, which is not	4197	implementations for some libevent functions (such as logging, which is not
3623	supported). It will also not define any of the structs usually found in	4198	supported). It will also not define any of the structs usually found in
…		…
3773	as well as for signal and thread safety in C<ev_async> watchers.	4348	as well as for signal and thread safety in C<ev_async> watchers.
3774		4349
3775	In the absence of this define, libev will use C<sig_atomic_t volatile>	4350	In the absence of this define, libev will use C<sig_atomic_t volatile>
3776	(from F<signal.h>), which is usually good enough on most platforms.	4351	(from F<signal.h>), which is usually good enough on most platforms.
3777		4352
3778	=item EV_H	4353	=item EV_H (h)
3779		4354
3780	The name of the F<ev.h> header file used to include it. The default if	4355	The name of the F<ev.h> header file used to include it. The default if
3781	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4356	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3782	used to virtually rename the F<ev.h> header file in case of conflicts.	4357	used to virtually rename the F<ev.h> header file in case of conflicts.
3783		4358
3784	=item EV_CONFIG_H	4359	=item EV_CONFIG_H (h)
3785		4360
3786	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4361	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3787	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4362	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3788	C<EV_H>, above.	4363	C<EV_H>, above.
3789		4364
3790	=item EV_EVENT_H	4365	=item EV_EVENT_H (h)
3791		4366
3792	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4367	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3793	of how the F<event.h> header can be found, the default is C<"event.h">.	4368	of how the F<event.h> header can be found, the default is C<"event.h">.
3794		4369
3795	=item EV_PROTOTYPES	4370	=item EV_PROTOTYPES (h)
3796		4371
3797	If defined to be C<0>, then F<ev.h> will not define any function	4372	If defined to be C<0>, then F<ev.h> will not define any function
3798	prototypes, but still define all the structs and other symbols. This is	4373	prototypes, but still define all the structs and other symbols. This is
3799	occasionally useful if you want to provide your own wrapper functions	4374	occasionally useful if you want to provide your own wrapper functions
3800	around libev functions.	4375	around libev functions.
…		…
3822	fine.	4397	fine.
3823		4398
3824	If your embedding application does not need any priorities, defining these	4399	If your embedding application does not need any priorities, defining these
3825	both to C<0> will save some memory and CPU.	4400	both to C<0> will save some memory and CPU.
3826		4401
3827	=item EV_PERIODIC_ENABLE	4402	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4403	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4404	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3828		4405
3829	If undefined or defined to be C<1>, then periodic timers are supported. If	4406	If undefined or defined to be C<1> (and the platform supports it), then
3830	defined to be C<0>, then they are not. Disabling them saves a few kB of	4407	the respective watcher type is supported. If defined to be C<0>, then it
3831	code.	4408	is not. Disabling watcher types mainly saves code size.
3832		4409
3833	=item EV_IDLE_ENABLE	4410	=item EV_FEATURES
3834
3835	If undefined or defined to be C<1>, then idle watchers are supported. If
3836	defined to be C<0>, then they are not. Disabling them saves a few kB of
3837	code.
3838
3839	=item EV_EMBED_ENABLE
3840
3841	If undefined or defined to be C<1>, then embed watchers are supported. If
3842	defined to be C<0>, then they are not. Embed watchers rely on most other
3843	watcher types, which therefore must not be disabled.
3844
3845	=item EV_STAT_ENABLE
3846
3847	If undefined or defined to be C<1>, then stat watchers are supported. If
3848	defined to be C<0>, then they are not.
3849
3850	=item EV_FORK_ENABLE
3851
3852	If undefined or defined to be C<1>, then fork watchers are supported. If
3853	defined to be C<0>, then they are not.
3854
3855	=item EV_ASYNC_ENABLE
3856
3857	If undefined or defined to be C<1>, then async watchers are supported. If
3858	defined to be C<0>, then they are not.
3859
3860	=item EV_MINIMAL
3861		4411
3862	If you need to shave off some kilobytes of code at the expense of some	4412	If you need to shave off some kilobytes of code at the expense of some
3863	speed (but with the full API), define this symbol to C<1>. Currently this	4413	speed (but with the full API), you can define this symbol to request
3864	is used to override some inlining decisions, saves roughly 30% code size	4414	certain subsets of functionality. The default is to enable all features
3865	on amd64. It also selects a much smaller 2-heap for timer management over	4415	that can be enabled on the platform.
3866	the default 4-heap.
3867		4416
3868	You can save even more by disabling watcher types you do not need	4417	A typical way to use this symbol is to define it to C<0> (or to a bitset
3869	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4418	with some broad features you want) and then selectively re-enable
3870	(C<-DNDEBUG>) will usually reduce code size a lot.	4419	additional parts you want, for example if you want everything minimal,
		4420	but multiple event loop support, async and child watchers and the poll
		4421	backend, use this:
3871		4422
3872	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4423	#define EV_FEATURES 0
3873	provide a bare-bones event library. See C<ev.h> for details on what parts	4424	#define EV_MULTIPLICITY 1
3874	of the API are still available, and do not complain if this subset changes	4425	#define EV_USE_POLL 1
3875	over time.	4426	#define EV_CHILD_ENABLE 1
		4427	#define EV_ASYNC_ENABLE 1
		4428
		4429	The actual value is a bitset, it can be a combination of the following
		4430	values:
		4431
		4432	=over 4
		4433
		4434	=item C<1> - faster/larger code
		4435
		4436	Use larger code to speed up some operations.
		4437
		4438	Currently this is used to override some inlining decisions (enlarging the
		4439	code size by roughly 30% on amd64).
		4440
		4441	When optimising for size, use of compiler flags such as C<-Os> with
		4442	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4443	assertions.
		4444
		4445	=item C<2> - faster/larger data structures
		4446
		4447	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4448	hash table sizes and so on. This will usually further increase code size
		4449	and can additionally have an effect on the size of data structures at
		4450	runtime.
		4451
		4452	=item C<4> - full API configuration
		4453
		4454	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4455	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4456
		4457	=item C<8> - full API
		4458
		4459	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4460	details on which parts of the API are still available without this
		4461	feature, and do not complain if this subset changes over time.
		4462
		4463	=item C<16> - enable all optional watcher types
		4464
		4465	Enables all optional watcher types. If you want to selectively enable
		4466	only some watcher types other than I/O and timers (e.g. prepare,
		4467	embed, async, child...) you can enable them manually by defining
		4468	C<EV_watchertype_ENABLE> to C<1> instead.
		4469
		4470	=item C<32> - enable all backends
		4471
		4472	This enables all backends - without this feature, you need to enable at
		4473	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4474
		4475	=item C<64> - enable OS-specific "helper" APIs
		4476
		4477	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4478	default.
		4479
		4480	=back
		4481
		4482	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4483	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4484	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4485	watchers, timers and monotonic clock support.
		4486
		4487	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4488	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4489	your program might be left out as well - a binary starting a timer and an
		4490	I/O watcher then might come out at only 5Kb.
		4491
		4492	=item EV_AVOID_STDIO
		4493
		4494	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4495	functions (printf, scanf, perror etc.). This will increase the code size
		4496	somewhat, but if your program doesn't otherwise depend on stdio and your
		4497	libc allows it, this avoids linking in the stdio library which is quite
		4498	big.
		4499
		4500	Note that error messages might become less precise when this option is
		4501	enabled.
3876		4502
3877	=item EV_NSIG	4503	=item EV_NSIG
3878		4504
3879	The highest supported signal number, +1 (or, the number of	4505	The highest supported signal number, +1 (or, the number of
3880	signals): Normally, libev tries to deduce the maximum number of signals	4506	signals): Normally, libev tries to deduce the maximum number of signals
3881	automatically, but sometimes this fails, in which case it can be	4507	automatically, but sometimes this fails, in which case it can be
3882	specified. Also, using a lower number than detected (C<32> should be	4508	specified. Also, using a lower number than detected (C<32> should be
3883	good for about any system in existance) can save some memory, as libev	4509	good for about any system in existence) can save some memory, as libev
3884	statically allocates some 12-24 bytes per signal number.	4510	statically allocates some 12-24 bytes per signal number.
3885		4511
3886	=item EV_PID_HASHSIZE	4512	=item EV_PID_HASHSIZE
3887		4513
3888	C<ev_child> watchers use a small hash table to distribute workload by	4514	C<ev_child> watchers use a small hash table to distribute workload by
3889	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4515	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3890	than enough. If you need to manage thousands of children you might want to	4516	usually more than enough. If you need to manage thousands of children you
3891	increase this value (I<must> be a power of two).	4517	might want to increase this value (I<must> be a power of two).
3892		4518
3893	=item EV_INOTIFY_HASHSIZE	4519	=item EV_INOTIFY_HASHSIZE
3894		4520
3895	C<ev_stat> watchers use a small hash table to distribute workload by	4521	C<ev_stat> watchers use a small hash table to distribute workload by
3896	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4522	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3897	usually more than enough. If you need to manage thousands of C<ev_stat>	4523	disabled), usually more than enough. If you need to manage thousands of
3898	watchers you might want to increase this value (I<must> be a power of	4524	C<ev_stat> watchers you might want to increase this value (I<must> be a
3899	two).	4525	power of two).
3900		4526
3901	=item EV_USE_4HEAP	4527	=item EV_USE_4HEAP
3902		4528
3903	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4529	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3904	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4530	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3905	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4531	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3906	faster performance with many (thousands) of watchers.	4532	faster performance with many (thousands) of watchers.
3907		4533
3908	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4534	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3909	(disabled).	4535	will be C<0>.
3910		4536
3911	=item EV_HEAP_CACHE_AT	4537	=item EV_HEAP_CACHE_AT
3912		4538
3913	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4539	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3914	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4540	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3915	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4541	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3916	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4542	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3917	but avoids random read accesses on heap changes. This improves performance	4543	but avoids random read accesses on heap changes. This improves performance
3918	noticeably with many (hundreds) of watchers.	4544	noticeably with many (hundreds) of watchers.
3919		4545
3920	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4546	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3921	(disabled).	4547	will be C<0>.
3922		4548
3923	=item EV_VERIFY	4549	=item EV_VERIFY
3924		4550
3925	Controls how much internal verification (see C<ev_loop_verify ()>) will	4551	Controls how much internal verification (see C<ev_verify ()>) will
3926	be done: If set to C<0>, no internal verification code will be compiled	4552	be done: If set to C<0>, no internal verification code will be compiled
3927	in. If set to C<1>, then verification code will be compiled in, but not	4553	in. If set to C<1>, then verification code will be compiled in, but not
3928	called. If set to C<2>, then the internal verification code will be	4554	called. If set to C<2>, then the internal verification code will be
3929	called once per loop, which can slow down libev. If set to C<3>, then the	4555	called once per loop, which can slow down libev. If set to C<3>, then the
3930	verification code will be called very frequently, which will slow down	4556	verification code will be called very frequently, which will slow down
3931	libev considerably.	4557	libev considerably.
3932		4558
3933	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4559	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3934	C<0>.	4560	will be C<0>.
3935		4561
3936	=item EV_COMMON	4562	=item EV_COMMON
3937		4563
3938	By default, all watchers have a C<void *data> member. By redefining	4564	By default, all watchers have a C<void *data> member. By redefining
3939	this macro to a something else you can include more and other types of	4565	this macro to something else you can include more and other types of
3940	members. You have to define it each time you include one of the files,	4566	members. You have to define it each time you include one of the files,
3941	though, and it must be identical each time.	4567	though, and it must be identical each time.
3942		4568
3943	For example, the perl EV module uses something like this:	4569	For example, the perl EV module uses something like this:
3944		4570
…		…
3997	file.	4623	file.
3998		4624
3999	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4625	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4000	that everybody includes and which overrides some configure choices:	4626	that everybody includes and which overrides some configure choices:
4001		4627
4002	#define EV_MINIMAL 1	4628	#define EV_FEATURES 8
4003	#define EV_USE_POLL 0	4629	#define EV_USE_SELECT 1
4004	#define EV_MULTIPLICITY 0
4005	#define EV_PERIODIC_ENABLE 0	4630	#define EV_PREPARE_ENABLE 1
		4631	#define EV_IDLE_ENABLE 1
4006	#define EV_STAT_ENABLE 0	4632	#define EV_SIGNAL_ENABLE 1
4007	#define EV_FORK_ENABLE 0	4633	#define EV_CHILD_ENABLE 1
		4634	#define EV_USE_STDEXCEPT 0
4008	#define EV_CONFIG_H <config.h>	4635	#define EV_CONFIG_H <config.h>
4009	#define EV_MINPRI 0
4010	#define EV_MAXPRI 0
4011		4636
4012	#include "ev++.h"	4637	#include "ev++.h"
4013		4638
4014	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4639	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4015		4640
4016	#include "ev_cpp.h"	4641	#include "ev_cpp.h"
4017	#include "ev.c"	4642	#include "ev.c"
4018		4643
4019	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4644	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4020		4645
4021	=head2 THREADS AND COROUTINES	4646	=head2 THREADS AND COROUTINES
4022		4647
4023	=head3 THREADS	4648	=head3 THREADS
4024		4649
…		…
4075	default loop and triggering an C<ev_async> watcher from the default loop	4700	default loop and triggering an C<ev_async> watcher from the default loop
4076	watcher callback into the event loop interested in the signal.	4701	watcher callback into the event loop interested in the signal.
4077		4702
4078	=back	4703	=back
4079		4704
4080	=head4 THREAD LOCKING EXAMPLE	4705	See also L<THREAD LOCKING EXAMPLE>.
4081
4082	Here is a fictitious example of how to run an event loop in a different
4083	thread than where callbacks are being invoked and watchers are
4084	created/added/removed.
4085
4086	For a real-world example, see the C<EV::Loop::Async> perl module,
4087	which uses exactly this technique (which is suited for many high-level
4088	languages).
4089
4090	The example uses a pthread mutex to protect the loop data, a condition
4091	variable to wait for callback invocations, an async watcher to notify the
4092	event loop thread and an unspecified mechanism to wake up the main thread.
4093
4094	First, you need to associate some data with the event loop:
4095
4096	typedef struct {
4097	mutex_t lock; /* global loop lock */
4098	ev_async async_w;
4099	thread_t tid;
4100	cond_t invoke_cv;
4101	} userdata;
4102
4103	void prepare_loop (EV_P)
4104	{
4105	// for simplicity, we use a static userdata struct.
4106	static userdata u;
4107
4108	ev_async_init (&u->async_w, async_cb);
4109	ev_async_start (EV_A_ &u->async_w);
4110
4111	pthread_mutex_init (&u->lock, 0);
4112	pthread_cond_init (&u->invoke_cv, 0);
4113
4114	// now associate this with the loop
4115	ev_set_userdata (EV_A_ u);
4116	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4117	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4118
4119	// then create the thread running ev_loop
4120	pthread_create (&u->tid, 0, l_run, EV_A);
4121	}
4122
4123	The callback for the C<ev_async> watcher does nothing: the watcher is used
4124	solely to wake up the event loop so it takes notice of any new watchers
4125	that might have been added:
4126
4127	static void
4128	async_cb (EV_P_ ev_async *w, int revents)
4129	{
4130	// just used for the side effects
4131	}
4132
4133	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4134	protecting the loop data, respectively.
4135
4136	static void
4137	l_release (EV_P)
4138	{
4139	userdata *u = ev_userdata (EV_A);
4140	pthread_mutex_unlock (&u->lock);
4141	}
4142
4143	static void
4144	l_acquire (EV_P)
4145	{
4146	userdata *u = ev_userdata (EV_A);
4147	pthread_mutex_lock (&u->lock);
4148	}
4149
4150	The event loop thread first acquires the mutex, and then jumps straight
4151	into C<ev_loop>:
4152
4153	void *
4154	l_run (void *thr_arg)
4155	{
4156	struct ev_loop loop = (struct ev_loop )thr_arg;
4157
4158	l_acquire (EV_A);
4159	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4160	ev_loop (EV_A_ 0);
4161	l_release (EV_A);
4162
4163	return 0;
4164	}
4165
4166	Instead of invoking all pending watchers, the C<l_invoke> callback will
4167	signal the main thread via some unspecified mechanism (signals? pipe
4168	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4169	have been called (in a while loop because a) spurious wakeups are possible
4170	and b) skipping inter-thread-communication when there are no pending
4171	watchers is very beneficial):
4172
4173	static void
4174	l_invoke (EV_P)
4175	{
4176	userdata *u = ev_userdata (EV_A);
4177
4178	while (ev_pending_count (EV_A))
4179	{
4180	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4181	pthread_cond_wait (&u->invoke_cv, &u->lock);
4182	}
4183	}
4184
4185	Now, whenever the main thread gets told to invoke pending watchers, it
4186	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4187	thread to continue:
4188
4189	static void
4190	real_invoke_pending (EV_P)
4191	{
4192	userdata *u = ev_userdata (EV_A);
4193
4194	pthread_mutex_lock (&u->lock);
4195	ev_invoke_pending (EV_A);
4196	pthread_cond_signal (&u->invoke_cv);
4197	pthread_mutex_unlock (&u->lock);
4198	}
4199
4200	Whenever you want to start/stop a watcher or do other modifications to an
4201	event loop, you will now have to lock:
4202
4203	ev_timer timeout_watcher;
4204	userdata *u = ev_userdata (EV_A);
4205
4206	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4207
4208	pthread_mutex_lock (&u->lock);
4209	ev_timer_start (EV_A_ &timeout_watcher);
4210	ev_async_send (EV_A_ &u->async_w);
4211	pthread_mutex_unlock (&u->lock);
4212
4213	Note that sending the C<ev_async> watcher is required because otherwise
4214	an event loop currently blocking in the kernel will have no knowledge
4215	about the newly added timer. By waking up the loop it will pick up any new
4216	watchers in the next event loop iteration.
4217		4706
4218	=head3 COROUTINES	4707	=head3 COROUTINES
4219		4708
4220	Libev is very accommodating to coroutines ("cooperative threads"):	4709	Libev is very accommodating to coroutines ("cooperative threads"):
4221	libev fully supports nesting calls to its functions from different	4710	libev fully supports nesting calls to its functions from different
4222	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4711	coroutines (e.g. you can call C<ev_run> on the same loop from two
4223	different coroutines, and switch freely between both coroutines running	4712	different coroutines, and switch freely between both coroutines running
4224	the loop, as long as you don't confuse yourself). The only exception is	4713	the loop, as long as you don't confuse yourself). The only exception is
4225	that you must not do this from C<ev_periodic> reschedule callbacks.	4714	that you must not do this from C<ev_periodic> reschedule callbacks.
4226		4715
4227	Care has been taken to ensure that libev does not keep local state inside	4716	Care has been taken to ensure that libev does not keep local state inside
4228	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4717	C<ev_run>, and other calls do not usually allow for coroutine switches as
4229	they do not call any callbacks.	4718	they do not call any callbacks.
4230		4719
4231	=head2 COMPILER WARNINGS	4720	=head2 COMPILER WARNINGS
4232		4721
4233	Depending on your compiler and compiler settings, you might get no or a	4722	Depending on your compiler and compiler settings, you might get no or a
…		…
4244	maintainable.	4733	maintainable.
4245		4734
4246	And of course, some compiler warnings are just plain stupid, or simply	4735	And of course, some compiler warnings are just plain stupid, or simply
4247	wrong (because they don't actually warn about the condition their message	4736	wrong (because they don't actually warn about the condition their message
4248	seems to warn about). For example, certain older gcc versions had some	4737	seems to warn about). For example, certain older gcc versions had some
4249	warnings that resulted an extreme number of false positives. These have	4738	warnings that resulted in an extreme number of false positives. These have
4250	been fixed, but some people still insist on making code warn-free with	4739	been fixed, but some people still insist on making code warn-free with
4251	such buggy versions.	4740	such buggy versions.
4252		4741
4253	While libev is written to generate as few warnings as possible,	4742	While libev is written to generate as few warnings as possible,
4254	"warn-free" code is not a goal, and it is recommended not to build libev	4743	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4290	I suggest using suppression lists.	4779	I suggest using suppression lists.
4291		4780
4292		4781
4293	=head1 PORTABILITY NOTES	4782	=head1 PORTABILITY NOTES
4294		4783
		4784	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4785
		4786	GNU/Linux is the only common platform that supports 64 bit file/large file
		4787	interfaces but I<disables> them by default.
		4788
		4789	That means that libev compiled in the default environment doesn't support
		4790	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4791
		4792	Unfortunately, many programs try to work around this GNU/Linux issue
		4793	by enabling the large file API, which makes them incompatible with the
		4794	standard libev compiled for their system.
		4795
		4796	Likewise, libev cannot enable the large file API itself as this would
		4797	suddenly make it incompatible to the default compile time environment,
		4798	i.e. all programs not using special compile switches.
		4799
		4800	=head2 OS/X AND DARWIN BUGS
		4801
		4802	The whole thing is a bug if you ask me - basically any system interface
		4803	you touch is broken, whether it is locales, poll, kqueue or even the
		4804	OpenGL drivers.
		4805
		4806	=head3 C<kqueue> is buggy
		4807
		4808	The kqueue syscall is broken in all known versions - most versions support
		4809	only sockets, many support pipes.
		4810
		4811	Libev tries to work around this by not using C<kqueue> by default on this
		4812	rotten platform, but of course you can still ask for it when creating a
		4813	loop - embedding a socket-only kqueue loop into a select-based one is
		4814	probably going to work well.
		4815
		4816	=head3 C<poll> is buggy
		4817
		4818	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4819	implementation by something calling C<kqueue> internally around the 10.5.6
		4820	release, so now C<kqueue> I<and> C<poll> are broken.
		4821
		4822	Libev tries to work around this by not using C<poll> by default on
		4823	this rotten platform, but of course you can still ask for it when creating
		4824	a loop.
		4825
		4826	=head3 C<select> is buggy
		4827
		4828	All that's left is C<select>, and of course Apple found a way to fuck this
		4829	one up as well: On OS/X, C<select> actively limits the number of file
		4830	descriptors you can pass in to 1024 - your program suddenly crashes when
		4831	you use more.
		4832
		4833	There is an undocumented "workaround" for this - defining
		4834	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4835	work on OS/X.
		4836
		4837	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4838
		4839	=head3 C<errno> reentrancy
		4840
		4841	The default compile environment on Solaris is unfortunately so
		4842	thread-unsafe that you can't even use components/libraries compiled
		4843	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4844	defined by default. A valid, if stupid, implementation choice.
		4845
		4846	If you want to use libev in threaded environments you have to make sure
		4847	it's compiled with C<_REENTRANT> defined.
		4848
		4849	=head3 Event port backend
		4850
		4851	The scalable event interface for Solaris is called "event
		4852	ports". Unfortunately, this mechanism is very buggy in all major
		4853	releases. If you run into high CPU usage, your program freezes or you get
		4854	a large number of spurious wakeups, make sure you have all the relevant
		4855	and latest kernel patches applied. No, I don't know which ones, but there
		4856	are multiple ones to apply, and afterwards, event ports actually work
		4857	great.
		4858
		4859	If you can't get it to work, you can try running the program by setting
		4860	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4861	C<select> backends.
		4862
		4863	=head2 AIX POLL BUG
		4864
		4865	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4866	this by trying to avoid the poll backend altogether (i.e. it's not even
		4867	compiled in), which normally isn't a big problem as C<select> works fine
		4868	with large bitsets on AIX, and AIX is dead anyway.
		4869
4295	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4870	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4871
		4872	=head3 General issues
4296		4873
4297	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4874	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4298	requires, and its I/O model is fundamentally incompatible with the POSIX	4875	requires, and its I/O model is fundamentally incompatible with the POSIX
4299	model. Libev still offers limited functionality on this platform in	4876	model. Libev still offers limited functionality on this platform in
4300	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4877	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4301	descriptors. This only applies when using Win32 natively, not when using	4878	descriptors. This only applies when using Win32 natively, not when using
4302	e.g. cygwin.	4879	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4880	as every compielr comes with a slightly differently broken/incompatible
		4881	environment.
4303		4882
4304	Lifting these limitations would basically require the full	4883	Lifting these limitations would basically require the full
4305	re-implementation of the I/O system. If you are into these kinds of	4884	re-implementation of the I/O system. If you are into this kind of thing,
4306	things, then note that glib does exactly that for you in a very portable	4885	then note that glib does exactly that for you in a very portable way (note
4307	way (note also that glib is the slowest event library known to man).	4886	also that glib is the slowest event library known to man).
4308		4887
4309	There is no supported compilation method available on windows except	4888	There is no supported compilation method available on windows except
4310	embedding it into other applications.	4889	embedding it into other applications.
4311		4890
4312	Sensible signal handling is officially unsupported by Microsoft - libev	4891	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4340	you do I<not> compile the F<ev.c> or any other embedded source files!):	4919	you do I<not> compile the F<ev.c> or any other embedded source files!):
4341		4920
4342	#include "evwrap.h"	4921	#include "evwrap.h"
4343	#include "ev.c"	4922	#include "ev.c"
4344		4923
4345	=over 4
4346
4347	=item The winsocket select function	4924	=head3 The winsocket C<select> function
4348		4925
4349	The winsocket C<select> function doesn't follow POSIX in that it	4926	The winsocket C<select> function doesn't follow POSIX in that it
4350	requires socket I<handles> and not socket I<file descriptors> (it is	4927	requires socket I<handles> and not socket I<file descriptors> (it is
4351	also extremely buggy). This makes select very inefficient, and also	4928	also extremely buggy). This makes select very inefficient, and also
4352	requires a mapping from file descriptors to socket handles (the Microsoft	4929	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4361	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4938	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4362		4939
4363	Note that winsockets handling of fd sets is O(n), so you can easily get a	4940	Note that winsockets handling of fd sets is O(n), so you can easily get a
4364	complexity in the O(n²) range when using win32.	4941	complexity in the O(n²) range when using win32.
4365		4942
4366	=item Limited number of file descriptors	4943	=head3 Limited number of file descriptors
4367		4944
4368	Windows has numerous arbitrary (and low) limits on things.	4945	Windows has numerous arbitrary (and low) limits on things.
4369		4946
4370	Early versions of winsocket's select only supported waiting for a maximum	4947	Early versions of winsocket's select only supported waiting for a maximum
4371	of C<64> handles (probably owning to the fact that all windows kernels	4948	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4386	runtime libraries. This might get you to about C<512> or C<2048> sockets	4963	runtime libraries. This might get you to about C<512> or C<2048> sockets
4387	(depending on windows version and/or the phase of the moon). To get more,	4964	(depending on windows version and/or the phase of the moon). To get more,
4388	you need to wrap all I/O functions and provide your own fd management, but	4965	you need to wrap all I/O functions and provide your own fd management, but
4389	the cost of calling select (O(n²)) will likely make this unworkable.	4966	the cost of calling select (O(n²)) will likely make this unworkable.
4390		4967
4391	=back
4392
4393	=head2 PORTABILITY REQUIREMENTS	4968	=head2 PORTABILITY REQUIREMENTS
4394		4969
4395	In addition to a working ISO-C implementation and of course the	4970	In addition to a working ISO-C implementation and of course the
4396	backend-specific APIs, libev relies on a few additional extensions:	4971	backend-specific APIs, libev relies on a few additional extensions:
4397		4972
…		…
4403	Libev assumes not only that all watcher pointers have the same internal	4978	Libev assumes not only that all watcher pointers have the same internal
4404	structure (guaranteed by POSIX but not by ISO C for example), but it also	4979	structure (guaranteed by POSIX but not by ISO C for example), but it also
4405	assumes that the same (machine) code can be used to call any watcher	4980	assumes that the same (machine) code can be used to call any watcher
4406	callback: The watcher callbacks have different type signatures, but libev	4981	callback: The watcher callbacks have different type signatures, but libev
4407	calls them using an C<ev_watcher *> internally.	4982	calls them using an C<ev_watcher *> internally.
		4983
		4984	=item pointer accesses must be thread-atomic
		4985
		4986	Accessing a pointer value must be atomic, it must both be readable and
		4987	writable in one piece - this is the case on all current architectures.
4408		4988
4409	=item C<sig_atomic_t volatile> must be thread-atomic as well	4989	=item C<sig_atomic_t volatile> must be thread-atomic as well
4410		4990
4411	The type C<sig_atomic_t volatile> (or whatever is defined as	4991	The type C<sig_atomic_t volatile> (or whatever is defined as
4412	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4992	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4435	watchers.	5015	watchers.
4436		5016
4437	=item C<double> must hold a time value in seconds with enough accuracy	5017	=item C<double> must hold a time value in seconds with enough accuracy
4438		5018
4439	The type C<double> is used to represent timestamps. It is required to	5019	The type C<double> is used to represent timestamps. It is required to
4440	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5020	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4441	enough for at least into the year 4000. This requirement is fulfilled by	5021	good enough for at least into the year 4000 with millisecond accuracy
		5022	(the design goal for libev). This requirement is overfulfilled by
4442	implementations implementing IEEE 754, which is basically all existing	5023	implementations using IEEE 754, which is basically all existing ones. With
4443	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5024	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4444	2200.
4445		5025
4446	=back	5026	=back
4447		5027
4448	If you know of other additional requirements drop me a note.	5028	If you know of other additional requirements drop me a note.
4449		5029
…		…
4517	involves iterating over all running async watchers or all signal numbers.	5097	involves iterating over all running async watchers or all signal numbers.
4518		5098
4519	=back	5099	=back
4520		5100
4521		5101
		5102	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5103
		5104	The major version 4 introduced some incompatible changes to the API.
		5105
		5106	At the moment, the C<ev.h> header file provides compatibility definitions
		5107	for all changes, so most programs should still compile. The compatibility
		5108	layer might be removed in later versions of libev, so better update to the
		5109	new API early than late.
		5110
		5111	=over 4
		5112
		5113	=item C<EV_COMPAT3> backwards compatibility mechanism
		5114
		5115	The backward compatibility mechanism can be controlled by
		5116	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5117	section.
		5118
		5119	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5120
		5121	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5122
		5123	ev_loop_destroy (EV_DEFAULT_UC);
		5124	ev_loop_fork (EV_DEFAULT);
		5125
		5126	=item function/symbol renames
		5127
		5128	A number of functions and symbols have been renamed:
		5129
		5130	ev_loop => ev_run
		5131	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5132	EVLOOP_ONESHOT => EVRUN_ONCE
		5133
		5134	ev_unloop => ev_break
		5135	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5136	EVUNLOOP_ONE => EVBREAK_ONE
		5137	EVUNLOOP_ALL => EVBREAK_ALL
		5138
		5139	EV_TIMEOUT => EV_TIMER
		5140
		5141	ev_loop_count => ev_iteration
		5142	ev_loop_depth => ev_depth
		5143	ev_loop_verify => ev_verify
		5144
		5145	Most functions working on C<struct ev_loop> objects don't have an
		5146	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5147	associated constants have been renamed to not collide with the C<struct
		5148	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5149	as all other watcher types. Note that C<ev_loop_fork> is still called
		5150	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5151	typedef.
		5152
		5153	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5154
		5155	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5156	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5157	and work, but the library code will of course be larger.
		5158
		5159	=back
		5160
		5161
4522	=head1 GLOSSARY	5162	=head1 GLOSSARY
4523		5163
4524	=over 4	5164	=over 4
4525		5165
4526	=item active	5166	=item active
4527		5167
4528	A watcher is active as long as it has been started (has been attached to	5168	A watcher is active as long as it has been started and not yet stopped.
4529	an event loop) but not yet stopped (disassociated from the event loop).	5169	See L<WATCHER STATES> for details.
4530		5170
4531	=item application	5171	=item application
4532		5172
4533	In this document, an application is whatever is using libev.	5173	In this document, an application is whatever is using libev.
		5174
		5175	=item backend
		5176
		5177	The part of the code dealing with the operating system interfaces.
4534		5178
4535	=item callback	5179	=item callback
4536		5180
4537	The address of a function that is called when some event has been	5181	The address of a function that is called when some event has been
4538	detected. Callbacks are being passed the event loop, the watcher that	5182	detected. Callbacks are being passed the event loop, the watcher that
4539	received the event, and the actual event bitset.	5183	received the event, and the actual event bitset.
4540		5184
4541	=item callback invocation	5185	=item callback/watcher invocation
4542		5186
4543	The act of calling the callback associated with a watcher.	5187	The act of calling the callback associated with a watcher.
4544		5188
4545	=item event	5189	=item event
4546		5190
4547	A change of state of some external event, such as data now being available	5191	A change of state of some external event, such as data now being available
4548	for reading on a file descriptor, time having passed or simply not having	5192	for reading on a file descriptor, time having passed or simply not having
4549	any other events happening anymore.	5193	any other events happening anymore.
4550		5194
4551	In libev, events are represented as single bits (such as C<EV_READ> or	5195	In libev, events are represented as single bits (such as C<EV_READ> or
4552	C<EV_TIMEOUT>).	5196	C<EV_TIMER>).
4553		5197
4554	=item event library	5198	=item event library
4555		5199
4556	A software package implementing an event model and loop.	5200	A software package implementing an event model and loop.
4557		5201
…		…
4565	The model used to describe how an event loop handles and processes	5209	The model used to describe how an event loop handles and processes
4566	watchers and events.	5210	watchers and events.
4567		5211
4568	=item pending	5212	=item pending
4569		5213
4570	A watcher is pending as soon as the corresponding event has been detected,	5214	A watcher is pending as soon as the corresponding event has been
4571	and stops being pending as soon as the watcher will be invoked or its	5215	detected. See L<WATCHER STATES> for details.
4572	pending status is explicitly cleared by the application.
4573
4574	A watcher can be pending, but not active. Stopping a watcher also clears
4575	its pending status.
4576		5216
4577	=item real time	5217	=item real time
4578		5218
4579	The physical time that is observed. It is apparently strictly monotonic :)	5219	The physical time that is observed. It is apparently strictly monotonic :)
4580		5220
…		…
4587	=item watcher	5227	=item watcher
4588		5228
4589	A data structure that describes interest in certain events. Watchers need	5229	A data structure that describes interest in certain events. Watchers need
4590	to be started (attached to an event loop) before they can receive events.	5230	to be started (attached to an event loop) before they can receive events.
4591		5231
4592	=item watcher invocation
4593
4594	The act of calling the callback associated with a watcher.
4595
4596	=back	5232	=back
4597		5233
4598	=head1 AUTHOR	5234	=head1 AUTHOR
4599		5235
4600	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5236	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5237	Magnusson and Emanuele Giaquinta.
4601		5238

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Comparing libev/ev.pod (file contents): Revision 1.276 by root, Tue Dec 29 13:11:00 2009 UTC vs. Revision 1.360 by root, Mon Jan 17 12:11:12 2011 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.276 by root, Tue Dec 29 13:11:00 2009 UTC vs.
Revision 1.360 by root, Mon Jan 17 12:11:12 2011 UTC