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Revision 1.282 by root, Wed Mar 10 08:19:39 2010 UTC vs.
Revision 1.356 by root, Tue Jan 11 01:42:47 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_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	428	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	429	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
387		448
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		450
390	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
427	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
428		489
429	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	499	and is of course hard to detect.
437		500
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
439	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
440	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
442	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
443	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
445		514
446	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	516	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	517	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		585
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
519		588
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	592	might perform better.
528		593
529	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
533		608
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
536		611
537	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
538		613
539	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		617
543	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		627
545	=back	628	=back
546		629
547	If one or more of the backend flags are or'ed into the flags value,	630	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	631	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	632	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	633	()> will be tried.
551		634
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
581		636
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	638	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
585		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
586	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
587		647
588	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		655
596	Note that certain global state, such as signal state (and installed signal	656	Note that certain global state, such as signal state (and installed signal
597	handlers), will not be freed by this function, and related watchers (such	657	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
599		659
600	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
602	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
603	C<ev_loop_new> and C<ev_loop_destroy>.	667	and C<ev_loop_destroy>.
604		668
605	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
606		670
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
613	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
614	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
615	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
616	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
617	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
618		681
619	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
620	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
622		688
623	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
624	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
627	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		703
636	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
637		705
638	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	707	otherwise.
640		708
641	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
642		710
643	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
644	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
646		714
647	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
648	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
650		719
651	=item unsigned int ev_loop_depth (loop)	720	=item unsigned int ev_depth (loop)
652		721
653	Returns the number of times C<ev_loop> was entered minus the number of	722	Returns the number of times C<ev_run> was entered minus the number of
654	times C<ev_loop> was exited, in other words, the recursion depth.	723	times C<ev_run> was exited normally, in other words, the recursion depth.
655		724
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	725	Outside C<ev_run>, this number is zero. In a callback, this number is
657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	727	in which case it is higher.
659		728
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
662		733
663	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
664		735
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	737	use.
…		…
675		746
676	=item ev_now_update (loop)	747	=item ev_now_update (loop)
677		748
678	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
681		752
682	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
683	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	755	the current time is a good idea.
685		756
…		…
687		758
688	=item ev_suspend (loop)	759	=item ev_suspend (loop)
689		760
690	=item ev_resume (loop)	761	=item ev_resume (loop)
691		762
692	These two functions suspend and resume a loop, for use when the loop is	763	These two functions suspend and resume an event loop, for use when the
693	not used for a while and timeouts should not be processed.	764	loop is not used for a while and timeouts should not be processed.
694		765
695	A typical use case would be an interactive program such as a game: When	766	A typical use case would be an interactive program such as a game: When
696	the user presses C<^Z> to suspend the game and resumes it an hour later it	767	the user presses C<^Z> to suspend the game and resumes it an hour later it
697	would be best to handle timeouts as if no time had actually passed while	768	would be best to handle timeouts as if no time had actually passed while
698	the program was suspended. This can be achieved by calling C<ev_suspend>	769	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	771	C<ev_resume> directly afterwards to resume timer processing.
701		772
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	775	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	776	occurred while suspended).
706		777
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	778	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	780	without a previous call to C<ev_suspend>.
710		781
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	783	event loop time (see C<ev_now_update>).
713		784
714	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
715		786
716	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
717	after you have initialised all your watchers and you want to start	788	after you have initialised all your watchers and you want to start
718	handling events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
719		792
720	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
721	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
722		796
723	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
724	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
727	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	802	beauty.
729		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
731	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
732	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
733	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
734		814
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
736	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
740	iteration of the loop.	820	iteration of the loop.
741		821
742	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
743	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
745	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
746		826
747	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
748		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	838	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	849	- Queue all expired timers.
765	- Queue all expired periodics.	850	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	852	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
769	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
770	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
774		863
775	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	865	anymore.
777		866
778	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
782		871
783	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
784		873
785	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
786	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		878
790	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
791		880
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
793		883
794	=item ev_ref (loop)	884	=item ev_ref (loop)
795		885
796	=item ev_unref (loop)	886	=item ev_unref (loop)
797		887
798	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
799	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
800	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
801		891
802	This is useful when you have a watcher that you never intend to	892	This is useful when you have a watcher that you never intend to
803	unregister, but that nevertheless should not keep C<ev_loop> from	893	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	895	before stopping it.
806		896
807	As an example, libev itself uses this for its internal signal pipe: It	897	As an example, libev itself uses this for its internal signal pipe: It
808	is not visible to the libev user and should not keep C<ev_loop> from	898	is not visible to the libev user and should not keep C<ev_run> from
809	exiting if no event watchers registered by it are active. It is also an	899	exiting if no event watchers registered by it are active. It is also an
810	excellent way to do this for generic recurring timers or from within	900	excellent way to do this for generic recurring timers or from within
811	third-party libraries. Just remember to I<unref after start> and I<ref	901	third-party libraries. Just remember to I<unref after start> and I<ref
812	before stop> (but only if the watcher wasn't active before, or was active	902	before stop> (but only if the watcher wasn't active before, or was active
813	before, respectively. Note also that libev might stop watchers itself	903	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	905	in the callback).
816		906
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	908	running when nothing else is active.
819		909
820	ev_signal exitsig;	910	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	913	ev_unref (loop);
824		914
825	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
826		916
827	ev_ref (loop);	917	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	958	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	959	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	960	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	961	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	962	then you can't do more than 100 transactions per second).
873		963
874	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		976
887	=item ev_invoke_pending (loop)	977	=item ev_invoke_pending (loop)
888		978
889	This call will simply invoke all pending watchers while resetting their	979	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	980	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		986
893	=item int ev_pending_count (loop)	987	=item int ev_pending_count (loop)
894		988
895	Returns the number of pending watchers - zero indicates that no watchers	989	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	990	are pending.
897		991
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		993
900	This overrides the invoke pending functionality of the loop: Instead of	994	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	995	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	996	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	997	invoke the actual watchers inside another context (another thread etc.).
904		998
905	If you want to reset the callback, use C<ev_invoke_pending> as new	999	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1000	callback.
…		…
909		1003
910	Sometimes you want to share the same loop between multiple threads. This	1004	Sometimes you want to share the same loop between multiple threads. This
911	can be done relatively simply by putting mutex_lock/unlock calls around	1005	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1006	each call to a libev function.
913		1007
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1008	However, C<ev_run> can run an indefinite time, so it is not feasible
915	wait for it to return. One way around this is to wake up the loop via	1009	to wait for it to return. One way around this is to wake up the event
916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1011	I<release> and I<acquire> callbacks on the loop.
918		1012
919	When set, then C<release> will be called just before the thread is	1013	When set, then C<release> will be called just before the thread is
920	suspended waiting for new events, and C<acquire> is called just	1014	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1015	afterwards.
922		1016
…		…
925		1019
926	While event loop modifications are allowed between invocations of	1020	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1021	C<release> and C<acquire> (that's their only purpose after all), no
928	modifications done will affect the event loop, i.e. adding watchers will	1022	modifications done will affect the event loop, i.e. adding watchers will
929	have no effect on the set of file descriptors being watched, or the time	1023	have no effect on the set of file descriptors being watched, or the time
930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
931	to take note of any changes you made.	1025	to take note of any changes you made.
932		1026
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1027	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1028	invocations of C<release> and C<acquire>.
935		1029
936	See also the locking example in the C<THREADS> section later in this	1030	See also the locking example in the C<THREADS> section later in this
937	document.	1031	document.
938		1032
939	=item ev_set_userdata (loop, void *data)	1033	=item ev_set_userdata (loop, void *data)
940		1034
941	=item ev_userdata (loop)	1035	=item void *ev_userdata (loop)
942		1036
943	Set and retrieve a single C<void *> associated with a loop. When	1037	Set and retrieve a single C<void *> associated with a loop. When
944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1039	C<0>.
946		1040
947	These two functions can be used to associate arbitrary data with a loop,	1041	These two functions can be used to associate arbitrary data with a loop,
948	and are intended solely for the C<invoke_pending_cb>, C<release> and	1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
949	C<acquire> callbacks described above, but of course can be (ab-)used for	1043	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1044	any other purpose as well.
951		1045
952	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
953		1047
954	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
955	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
956	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
968		1062
969	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
971	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
972		1066
973	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
974	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
975	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
976		1071
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1073	{
979	ev_io_stop (w);	1074	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
981	}	1076	}
982		1077
983	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
984		1079
985	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
986		1081
987	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
990		1085
991	ev_loop (loop, 0);	1086	ev_run (loop, 0);
992		1087
993	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
994	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1090	stack).
996		1091
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1094
1000	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
1001	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1099	and/or writable).
1005		1100
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1007	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
1008	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
1033		1128
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1130	writable.
1036		1131
1037	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
1038		1133
1039	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
1040		1135
1041	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
1042		1137
…		…
1060		1155
1061	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
1062		1157
1063	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
1064		1159
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1066	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
1067	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
1068	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
1069	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
1070	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1071	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
1072		1167
1073	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
1074		1169
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1171
1077	=item C<EV_FORK>	1172	=item C<EV_FORK>
1078		1173
1079	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1175	C<ev_fork>).
		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1180
1082	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
1083		1182
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1184
…		…
1257		1356
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1358	functions that do not need a watcher.
1260		1359
1261	=back	1360	=back
1262
1263		1361
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1265		1363
1266	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
1267	and read at any time: libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
…		…
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1324	{	1422	{
1325	struct my_biggy big = (struct my_biggy *)	1423	struct my_biggy big = (struct my_biggy *)
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1327	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
1328		1485
1329	=head2 WATCHER PRIORITY MODELS	1486	=head2 WATCHER PRIORITY MODELS
1330		1487
1331	Many event loops support I<watcher priorities>, which are usually small	1488	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1489	integers that influence the ordering of event callback invocation
…		…
1375		1532
1376	For example, to emulate how many other event libraries handle priorities,	1533	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1534	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1535	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1536	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1537	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1538	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1539	workable.
1383		1540
1384	Usually, however, the lock-out model implemented that way will perform	1541	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1542	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1556	{
1400	// stop the I/O watcher, we received the event, but	1557	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1558	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1559	ev_io_stop (EV_A_ w);
1403		1560
1404	// start the idle watcher to ahndle the actual event.	1561	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1562	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1563	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1564	ev_idle_start (EV_A_ &idle);
1408	}	1565	}
1409		1566
…		…
1459	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1460	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1461	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1619	required if you know what you are doing).
1463		1620
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1478		1628
1479	If you cannot run the fd in non-blocking mode (for example you should	1629	If you cannot run the fd in non-blocking mode (for example you should
1480	not play around with an Xlib connection), then you have to separately	1630	not play around with an Xlib connection), then you have to separately
1481	re-test whether a file descriptor is really ready with a known-to-be good	1631	re-test whether a file descriptor is really ready with a known-to-be good
1482	interface such as poll (fortunately in our Xlib example, Xlib already	1632	interface such as poll (fortunately in the case of Xlib, it already does
1483	does this on its own, so its quite safe to use). Some people additionally	1633	this on its own, so its quite safe to use). Some people additionally
1484	use C<SIGALRM> and an interval timer, just to be sure you won't block	1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1635	indefinitely.
1486		1636
1487	But really, best use non-blocking mode.	1637	But really, best use non-blocking mode.
1488		1638
…		…
1516		1666
1517	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1521	=head3 The special problem of fork	1704	=head3 The special problem of fork
1522		1705
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1524	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1525	it in the child.	1708	it in the child if you want to continue to use it in the child.
1526		1709
1527	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1528	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1713
1532	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1533		1715
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1535	when writing to a pipe whose other end has been closed, your program gets	1717	when writing to a pipe whose other end has been closed, your program gets
…		…
1538		1720
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1721	So when you encounter spurious, unexplained daemon exits, make sure you
1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1722	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541	somewhere, as that would have given you a big clue).	1723	somewhere, as that would have given you a big clue).
1542		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1543		1763
1544	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1545		1765
1546	=over 4	1766	=over 4
1547		1767
…		…
1579	...	1799	...
1580	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1801	ev_io stdin_readable;
1582	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1583	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1585		1805
1586		1806
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1808
1589	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
…		…
1598	The callback is guaranteed to be invoked only I<after> its timeout has	1818	The callback is guaranteed to be invoked only I<after> its timeout has
1599	passed (not I<at>, so on systems with very low-resolution clocks this	1819	passed (not I<at>, so on systems with very low-resolution clocks this
1600	might introduce a small delay). If multiple timers become ready during the	1820	might introduce a small delay). If multiple timers become ready during the
1601	same loop iteration then the ones with earlier time-out values are invoked	1821	same loop iteration then the ones with earlier time-out values are invoked
1602	before ones of the same priority with later time-out values (but this is	1822	before ones of the same priority with later time-out values (but this is
1603	no longer true when a callback calls C<ev_loop> recursively).	1823	no longer true when a callback calls C<ev_run> recursively).
1604		1824
1605	=head3 Be smart about timeouts	1825	=head3 Be smart about timeouts
1606		1826
1607	Many real-world problems involve some kind of timeout, usually for error	1827	Many real-world problems involve some kind of timeout, usually for error
1608	recovery. A typical example is an HTTP request - if the other side hangs,	1828	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1694	ev_tstamp timeout = last_activity + 60.;	1914	ev_tstamp timeout = last_activity + 60.;
1695		1915
1696	// if last_activity + 60. is older than now, we did time out	1916	// if last_activity + 60. is older than now, we did time out
1697	if (timeout < now)	1917	if (timeout < now)
1698	{	1918	{
1699	// timeout occured, take action	1919	// timeout occurred, take action
1700	}	1920	}
1701	else	1921	else
1702	{	1922	{
1703	// callback was invoked, but there was some activity, re-arm	1923	// callback was invoked, but there was some activity, re-arm
1704	// the watcher to fire in last_activity + 60, which is	1924	// the watcher to fire in last_activity + 60, which is
…		…
1726	to the current time (meaning we just have some activity :), then call the	1946	to the current time (meaning we just have some activity :), then call the
1727	callback, which will "do the right thing" and start the timer:	1947	callback, which will "do the right thing" and start the timer:
1728		1948
1729	ev_init (timer, callback);	1949	ev_init (timer, callback);
1730	last_activity = ev_now (loop);	1950	last_activity = ev_now (loop);
1731	callback (loop, timer, EV_TIMEOUT);	1951	callback (loop, timer, EV_TIMER);
1732		1952
1733	And when there is some activity, simply store the current time in	1953	And when there is some activity, simply store the current time in
1734	C<last_activity>, no libev calls at all:	1954	C<last_activity>, no libev calls at all:
1735		1955
1736	last_actiivty = ev_now (loop);	1956	last_activity = ev_now (loop);
1737		1957
1738	This technique is slightly more complex, but in most cases where the	1958	This technique is slightly more complex, but in most cases where the
1739	time-out is unlikely to be triggered, much more efficient.	1959	time-out is unlikely to be triggered, much more efficient.
1740		1960
1741	Changing the timeout is trivial as well (if it isn't hard-coded in the	1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1779		1999
1780	=head3 The special problem of time updates	2000	=head3 The special problem of time updates
1781		2001
1782	Establishing the current time is a costly operation (it usually takes at	2002	Establishing the current time is a costly operation (it usually takes at
1783	least two system calls): EV therefore updates its idea of the current	2003	least two system calls): EV therefore updates its idea of the current
1784	time only before and after C<ev_loop> collects new events, which causes a	2004	time only before and after C<ev_run> collects new events, which causes a
1785	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1786	lots of events in one iteration.	2006	lots of events in one iteration.
1787		2007
1788	The relative timeouts are calculated relative to the C<ev_now ()>	2008	The relative timeouts are calculated relative to the C<ev_now ()>
1789	time. This is usually the right thing as this timestamp refers to the time	2009	time. This is usually the right thing as this timestamp refers to the time
…		…
1906	}	2126	}
1907		2127
1908	ev_timer mytimer;	2128	ev_timer mytimer;
1909	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1910	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1912		2132
1913	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1914	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1916		2136
…		…
1942		2162
1943	As with timers, the callback is guaranteed to be invoked only when the	2163	As with timers, the callback is guaranteed to be invoked only when the
1944	point in time where it is supposed to trigger has passed. If multiple	2164	point in time where it is supposed to trigger has passed. If multiple
1945	timers become ready during the same loop iteration then the ones with	2165	timers become ready during the same loop iteration then the ones with
1946	earlier time-out values are invoked before ones with later time-out values	2166	earlier time-out values are invoked before ones with later time-out values
1947	(but this is no longer true when a callback calls C<ev_loop> recursively).	2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1948		2168
1949	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1950		2170
1951	=over 4	2171	=over 4
1952		2172
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
2083		2303
2084	static void	2304	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2306	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2308	}
2089		2309
2090	ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
…		…
2113		2333
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2335
2116	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
2117	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
2118	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
2119	normal event processing, like any other event.	2339	normal event processing, like any other event.
2120		2340
2121	If you want signals to be delivered truly asynchronously, just use	2341	If you want signals to be delivered truly asynchronously, just use
2122	C<sigaction> as you would do without libev and forget about sharing	2342	C<sigaction> as you would do without libev and forget about sharing
2123	the signal. You can even use C<ev_async> from a signal handler to	2343	the signal. You can even use C<ev_async> from a signal handler to
…		…
2166		2386
2167	So I can't stress this enough: I<If you do not reset your signal mask when	2387	So I can't stress this enough: I<If you do not reset your signal mask when
2168	you expect it to be empty, you have a race condition in your code>. This	2388	you expect it to be empty, you have a race condition in your code>. This
2169	is not a libev-specific thing, this is true for most event libraries.	2389	is not a libev-specific thing, this is true for most event libraries.
2170		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
		2404
2171	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
2172		2406
2173	=over 4	2407	=over 4
2174		2408
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2409	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2424	Example: Try to exit cleanly on SIGINT.
2191		2425
2192	static void	2426	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2428	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
2196	}	2430	}
2197		2431
2198	ev_signal signal_watcher;	2432	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2434	ev_signal_start (loop, &signal_watcher);
…		…
2586		2820
2587	Prepare and check watchers are usually (but not always) used in pairs:	2821	Prepare and check watchers are usually (but not always) used in pairs:
2588	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2823	afterwards.
2590		2824
2591	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
2592	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
2593	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
2594	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2596	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2764		2998
2765	if (timeout >= 0)	2999	if (timeout >= 0)
2766	// create/start timer	3000	// create/start timer
2767		3001
2768	// poll	3002	// poll
2769	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
2770		3004
2771	// stop timer again	3005	// stop timer again
2772	if (timeout >= 0)	3006	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2774		3008
…		…
2852	if you do not want that, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2853		3087
2854	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2855		3089
2856	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2858	appropriate way for embedded loops.	3092	appropriate way for embedded loops.
2859		3093
2860	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2861		3095
2862	The embedded event loop.	3096	The embedded event loop.
…		…
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2924		3158
2925	=head3 The special problem of life after fork - how is it possible?	3159	=head3 The special problem of life after fork - how is it possible?
2926		3160
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3161	Most uses of C<fork()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3162	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3163	sequence should be handled by libev without any problems.
2930		3164
2931	This changes when the application actually wants to do event handling	3165	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3166	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	disadvantage of having to use multiple event loops (which do not support	3182	disadvantage of having to use multiple event loops (which do not support
2949	signal watchers).	3183	signal watchers).
2950		3184
2951	When this is not possible, or you want to use the default loop for	3185	When this is not possible, or you want to use the default loop for
2952	other reasons, then in the process that wants to start "fresh", call	3186	other reasons, then in the process that wants to start "fresh", call
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3188	Destroying the default loop will "orphan" (not stop) all registered
2955	have to be careful not to execute code that modifies those watchers. Note	3189	watchers, so you have to be careful not to execute code that modifies
2956	also that in that case, you have to re-register any signal watchers.	3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
2957		3192
2958	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2959		3194
2960	=over 4	3195	=over 4
2961		3196
2962	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2963		3198
2964	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2965	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2966	believe me.	3201	really.
2967		3202
2968	=back	3203	=back
2969		3204
2970		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2971	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2972		3247
2973	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2976		3251
2977	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3256
2983	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2985	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2986	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2987		3264
2988	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2989	just the default loop.	3266	just the default loop.
2990		3267
2991	=head3 Queueing	3268	=head3 Queueing
…		…
3141		3418
3142	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3421	repeat = 0) will be started. C<0> is a valid timeout.
3145		3422
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3427	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3428	events precedence.
3152		3429
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3431
3155	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
3156	{	3433	{
3157	if (revents & EV_READ)	3434	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3436	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3437	/* doh, nothing entered */;
3161	}	3438	}
3162		3439
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3441
…		…
3167	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
3168	the given events it.	3445	the given events it.
3169		3446
3170	=item ev_feed_signal_event (loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
3171		3448
3172	Feed an event as if the given signal occurred (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3173	loop!).	3450	which is async-safe.
3174		3451
3175	=back	3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
3176		3637
3177		3638
3178	=head1 LIBEVENT EMULATION	3639	=head1 LIBEVENT EMULATION
3179		3640
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3641	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3642	emulate the internals of libevent, so here are some usage hints:
3182		3643
3183	=over 4	3644	=over 4
		3645
		3646	=item * Only the libevent-1.4.1-beta API is being emulated.
		3647
		3648	This was the newest libevent version available when libev was implemented,
		3649	and is still mostly unchanged in 2010.
3184		3650
3185	=item * Use it by including <event.h>, as usual.	3651	=item * Use it by including <event.h>, as usual.
3186		3652
3187	=item * The following members are fully supported: ev_base, ev_callback,	3653	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3654	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3660	=item * Priorities are not currently supported. Initialising priorities
3195	will fail and all watchers will have the same priority, even though there	3661	will fail and all watchers will have the same priority, even though there
3196	is an ev_pri field.	3662	is an ev_pri field.
3197		3663
3198	=item * In libevent, the last base created gets the signals, in libev, the	3664	=item * In libevent, the last base created gets the signals, in libev, the
3199	first base created (== the default loop) gets the signals.	3665	base that registered the signal gets the signals.
3200		3666
3201	=item * Other members are not supported.	3667	=item * Other members are not supported.
3202		3668
3203	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3669	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3204	to use the libev header file and library.	3670	to use the libev header file and library.
…		…
3223	Care has been taken to keep the overhead low. The only data member the C++	3689	Care has been taken to keep the overhead low. The only data member the C++
3224	classes add (compared to plain C-style watchers) is the event loop pointer	3690	classes add (compared to plain C-style watchers) is the event loop pointer
3225	that the watcher is associated with (or no additional members at all if	3691	that the watcher is associated with (or no additional members at all if
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	3692	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		3693
3228	Currently, functions, and static and non-static member functions can be	3694	Currently, functions, static and non-static member functions and classes
3229	used as callbacks. Other types should be easy to add as long as they only	3695	with C<operator ()> can be used as callbacks. Other types should be easy
3230	need one additional pointer for context. If you need support for other	3696	to add as long as they only need one additional pointer for context. If
3231	types of functors please contact the author (preferably after implementing	3697	you need support for other types of functors please contact the author
3232	it).	3698	(preferably after implementing it).
3233		3699
3234	Here is a list of things available in the C<ev> namespace:	3700	Here is a list of things available in the C<ev> namespace:
3235		3701
3236	=over 4	3702	=over 4
3237		3703
…		…
3298	myclass obj;	3764	myclass obj;
3299	ev::io iow;	3765	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	3766	iow.set <myclass, &myclass::io_cb> (&obj);
3301		3767
3302	=item w->set (object *)	3768	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		3769
3306	This is a variation of a method callback - leaving out the method to call	3770	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	3771	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	3772	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	3773	the time. Incidentally, you can then also leave out the template argument
…		…
3349	Associates a different C<struct ev_loop> with this watcher. You can only	3813	Associates a different C<struct ev_loop> with this watcher. You can only
3350	do this when the watcher is inactive (and not pending either).	3814	do this when the watcher is inactive (and not pending either).
3351		3815
3352	=item w->set ([arguments])	3816	=item w->set ([arguments])
3353		3817
3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3818	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3355	called at least once. Unlike the C counterpart, an active watcher gets	3819	method or a suitable start method must be called at least once. Unlike the
3356	automatically stopped and restarted when reconfiguring it with this	3820	C counterpart, an active watcher gets automatically stopped and restarted
3357	method.	3821	when reconfiguring it with this method.
3358		3822
3359	=item w->start ()	3823	=item w->start ()
3360		3824
3361	Starts the watcher. Note that there is no C<loop> argument, as the	3825	Starts the watcher. Note that there is no C<loop> argument, as the
3362	constructor already stores the event loop.	3826	constructor already stores the event loop.
3363		3827
		3828	=item w->start ([arguments])
		3829
		3830	Instead of calling C<set> and C<start> methods separately, it is often
		3831	convenient to wrap them in one call. Uses the same type of arguments as
		3832	the configure C<set> method of the watcher.
		3833
3364	=item w->stop ()	3834	=item w->stop ()
3365		3835
3366	Stops the watcher if it is active. Again, no C<loop> argument.	3836	Stops the watcher if it is active. Again, no C<loop> argument.
3367		3837
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3838	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		3850
3381	=back	3851	=back
3382		3852
3383	=back	3853	=back
3384		3854
3385	Example: Define a class with an IO and idle watcher, start one of them in	3855	Example: Define a class with two I/O and idle watchers, start the I/O
3386	the constructor.	3856	watchers in the constructor.
3387		3857
3388	class myclass	3858	class myclass
3389	{	3859	{
3390	ev::io io ; void io_cb (ev::io &w, int revents);	3860	ev::io io ; void io_cb (ev::io &w, int revents);
		3861	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3862	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		3863
3393	myclass (int fd)	3864	myclass (int fd)
3394	{	3865	{
3395	io .set <myclass, &myclass::io_cb > (this);	3866	io .set <myclass, &myclass::io_cb > (this);
		3867	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	3868	idle.set <myclass, &myclass::idle_cb> (this);
3397		3869
3398	io.start (fd, ev::READ);	3870	io.set (fd, ev::WRITE); // configure the watcher
		3871	io.start (); // start it whenever convenient
		3872
		3873	io2.start (fd, ev::READ); // set + start in one call
3399	}	3874	}
3400	};	3875	};
3401		3876
3402		3877
3403	=head1 OTHER LANGUAGE BINDINGS	3878	=head1 OTHER LANGUAGE BINDINGS
…		…
3477	loop argument"). The C<EV_A> form is used when this is the sole argument,	3952	loop argument"). The C<EV_A> form is used when this is the sole argument,
3478	C<EV_A_> is used when other arguments are following. Example:	3953	C<EV_A_> is used when other arguments are following. Example:
3479		3954
3480	ev_unref (EV_A);	3955	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	3956	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	3957	ev_run (EV_A_ 0);
3483		3958
3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3959	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3485	which is often provided by the following macro.	3960	which is often provided by the following macro.
3486		3961
3487	=item C<EV_P>, C<EV_P_>	3962	=item C<EV_P>, C<EV_P_>
…		…
3527	}	4002	}
3528		4003
3529	ev_check check;	4004	ev_check check;
3530	ev_check_init (&check, check_cb);	4005	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4006	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4007	ev_run (EV_DEFAULT_ 0);
3533		4008
3534	=head1 EMBEDDING	4009	=head1 EMBEDDING
3535		4010
3536	Libev can (and often is) directly embedded into host	4011	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4012	applications. Examples of applications that embed it include the Deliantra
…		…
3622	define before including (or compiling) any of its files. The default in	4097	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4098	the absence of autoconf is documented for every option.
3624		4099
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4100	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4101	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4102	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4103	to a compiled library. All other symbols change the ABI, which means all
3629	users of libev and the libev code itself must be compiled with compatible	4104	users of libev and the libev code itself must be compiled with compatible
3630	settings.	4105	settings.
3631		4106
3632	=over 4	4107	=over 4
		4108
		4109	=item EV_COMPAT3 (h)
		4110
		4111	Backwards compatibility is a major concern for libev. This is why this
		4112	release of libev comes with wrappers for the functions and symbols that
		4113	have been renamed between libev version 3 and 4.
		4114
		4115	You can disable these wrappers (to test compatibility with future
		4116	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4117	sources. This has the additional advantage that you can drop the C<struct>
		4118	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4119	typedef in that case.
		4120
		4121	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4122	and in some even more future version the compatibility code will be
		4123	removed completely.
3633		4124
3634	=item EV_STANDALONE (h)	4125	=item EV_STANDALONE (h)
3635		4126
3636	Must always be C<1> if you do not use autoconf configuration, which	4127	Must always be C<1> if you do not use autoconf configuration, which
3637	keeps libev from including F<config.h>, and it also defines dummy	4128	keeps libev from including F<config.h>, and it also defines dummy
…		…
3838	fine.	4329	fine.
3839		4330
3840	If your embedding application does not need any priorities, defining these	4331	If your embedding application does not need any priorities, defining these
3841	both to C<0> will save some memory and CPU.	4332	both to C<0> will save some memory and CPU.
3842		4333
3843	=item EV_PERIODIC_ENABLE	4334	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4335	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4336	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844		4337
3845	If undefined or defined to be C<1>, then periodic timers are supported. If	4338	If undefined or defined to be C<1> (and the platform supports it), then
3846	defined to be C<0>, then they are not. Disabling them saves a few kB of	4339	the respective watcher type is supported. If defined to be C<0>, then it
3847	code.	4340	is not. Disabling watcher types mainly saves code size.
3848		4341
3849	=item EV_IDLE_ENABLE	4342	=item EV_FEATURES
3850
3851	If undefined or defined to be C<1>, then idle watchers are supported. If
3852	defined to be C<0>, then they are not. Disabling them saves a few kB of
3853	code.
3854
3855	=item EV_EMBED_ENABLE
3856
3857	If undefined or defined to be C<1>, then embed watchers are supported. If
3858	defined to be C<0>, then they are not. Embed watchers rely on most other
3859	watcher types, which therefore must not be disabled.
3860
3861	=item EV_STAT_ENABLE
3862
3863	If undefined or defined to be C<1>, then stat watchers are supported. If
3864	defined to be C<0>, then they are not.
3865
3866	=item EV_FORK_ENABLE
3867
3868	If undefined or defined to be C<1>, then fork watchers are supported. If
3869	defined to be C<0>, then they are not.
3870
3871	=item EV_SIGNAL_ENABLE
3872
3873	If undefined or defined to be C<1>, then signal watchers are supported. If
3874	defined to be C<0>, then they are not.
3875
3876	=item EV_ASYNC_ENABLE
3877
3878	If undefined or defined to be C<1>, then async watchers are supported. If
3879	defined to be C<0>, then they are not.
3880
3881	=item EV_CHILD_ENABLE
3882
3883	If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884	child watchers are supported. If defined to be C<0>, then they are not.
3885
3886	=item EV_MINIMAL
3887		4343
3888	If you need to shave off some kilobytes of code at the expense of some	4344	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), define this symbol to C<1>. Currently this	4345	speed (but with the full API), you can define this symbol to request
3890	is used to override some inlining decisions, saves roughly 30% code size	4346	certain subsets of functionality. The default is to enable all features
3891	on amd64. It also selects a much smaller 2-heap for timer management over	4347	that can be enabled on the platform.
3892	the default 4-heap.
3893		4348
3894	You can save even more by disabling watcher types you do not need	4349	A typical way to use this symbol is to define it to C<0> (or to a bitset
3895	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4350	with some broad features you want) and then selectively re-enable
3896	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4351	additional parts you want, for example if you want everything minimal,
3897	eventfd and signalfd will further help, and disabling backends one doesn't	4352	but multiple event loop support, async and child watchers and the poll
3898	need (e.g. poll, epoll, kqueue, ports) will help further.	4353	backend, use this:
3899		4354
3900	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4355	#define EV_FEATURES 0
3901	provide a bare-bones event library. See C<ev.h> for details on what parts
3902	of the API are still available, and do not complain if this subset changes
3903	over time.
3904
3905	This example set of settings reduces the compiled size of libev from 24Kb
3906	to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907	an effect on the amount of memory used). With an intelligent-enough linker
3908	further unused functions might be left out as well automatically.
3909
3910	// tuning and API changes
3911	#define EV_MINIMAL 2
3912	#define EV_MULTIPLICITY 0	4356	#define EV_MULTIPLICITY 1
3913	#define EV_MINPRI 0
3914	#define EV_MAXPRI 0
3915
3916	// OS-specific backends
3917	#define EV_USE_INOTIFY 0
3918	#define EV_USE_EVENTFD 0
3919	#define EV_USE_SIGNALFD 0
3920	#define EV_USE_REALTIME 0
3921	#define EV_USE_MONOTONIC 0
3922	#define EV_USE_CLOCK_SYSCALL 0
3923
3924	// disable all backends except select
3925	#define EV_USE_POLL 0	4357	#define EV_USE_POLL 1
3926	#define EV_USE_PORT 0
3927	#define EV_USE_KQUEUE 0
3928	#define EV_USE_EPOLL 0
3929
3930	// disable all watcher types that cna be disabled
3931	#define EV_STAT_ENABLE 0
3932	#define EV_PERIODIC_ENABLE 0
3933	#define EV_IDLE_ENABLE 0
3934	#define EV_FORK_ENABLE 0
3935	#define EV_SIGNAL_ENABLE 0
3936	#define EV_CHILD_ENABLE 0	4358	#define EV_CHILD_ENABLE 1
3937	#define EV_ASYNC_ENABLE 0	4359	#define EV_ASYNC_ENABLE 1
3938	#define EV_EMBED_ENABLE 0	4360
		4361	The actual value is a bitset, it can be a combination of the following
		4362	values:
		4363
		4364	=over 4
		4365
		4366	=item C<1> - faster/larger code
		4367
		4368	Use larger code to speed up some operations.
		4369
		4370	Currently this is used to override some inlining decisions (enlarging the
		4371	code size by roughly 30% on amd64).
		4372
		4373	When optimising for size, use of compiler flags such as C<-Os> with
		4374	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4375	assertions.
		4376
		4377	=item C<2> - faster/larger data structures
		4378
		4379	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4380	hash table sizes and so on. This will usually further increase code size
		4381	and can additionally have an effect on the size of data structures at
		4382	runtime.
		4383
		4384	=item C<4> - full API configuration
		4385
		4386	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4387	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4388
		4389	=item C<8> - full API
		4390
		4391	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4392	details on which parts of the API are still available without this
		4393	feature, and do not complain if this subset changes over time.
		4394
		4395	=item C<16> - enable all optional watcher types
		4396
		4397	Enables all optional watcher types. If you want to selectively enable
		4398	only some watcher types other than I/O and timers (e.g. prepare,
		4399	embed, async, child...) you can enable them manually by defining
		4400	C<EV_watchertype_ENABLE> to C<1> instead.
		4401
		4402	=item C<32> - enable all backends
		4403
		4404	This enables all backends - without this feature, you need to enable at
		4405	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4406
		4407	=item C<64> - enable OS-specific "helper" APIs
		4408
		4409	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4410	default.
		4411
		4412	=back
		4413
		4414	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4415	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4416	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4417	watchers, timers and monotonic clock support.
		4418
		4419	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4420	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4421	your program might be left out as well - a binary starting a timer and an
		4422	I/O watcher then might come out at only 5Kb.
3939		4423
3940	=item EV_AVOID_STDIO	4424	=item EV_AVOID_STDIO
3941		4425
3942	If this is set to C<1> at compiletime, then libev will avoid using stdio	4426	If this is set to C<1> at compiletime, then libev will avoid using stdio
3943	functions (printf, scanf, perror etc.). This will increase the codesize	4427	functions (printf, scanf, perror etc.). This will increase the code size
3944	somewhat, but if your program doesn't otherwise depend on stdio and your	4428	somewhat, but if your program doesn't otherwise depend on stdio and your
3945	libc allows it, this avoids linking in the stdio library which is quite	4429	libc allows it, this avoids linking in the stdio library which is quite
3946	big.	4430	big.
3947		4431
3948	Note that error messages might become less precise when this option is	4432	Note that error messages might become less precise when this option is
…		…
3952		4436
3953	The highest supported signal number, +1 (or, the number of	4437	The highest supported signal number, +1 (or, the number of
3954	signals): Normally, libev tries to deduce the maximum number of signals	4438	signals): Normally, libev tries to deduce the maximum number of signals
3955	automatically, but sometimes this fails, in which case it can be	4439	automatically, but sometimes this fails, in which case it can be
3956	specified. Also, using a lower number than detected (C<32> should be	4440	specified. Also, using a lower number than detected (C<32> should be
3957	good for about any system in existance) can save some memory, as libev	4441	good for about any system in existence) can save some memory, as libev
3958	statically allocates some 12-24 bytes per signal number.	4442	statically allocates some 12-24 bytes per signal number.
3959		4443
3960	=item EV_PID_HASHSIZE	4444	=item EV_PID_HASHSIZE
3961		4445
3962	C<ev_child> watchers use a small hash table to distribute workload by	4446	C<ev_child> watchers use a small hash table to distribute workload by
3963	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4447	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964	than enough. If you need to manage thousands of children you might want to	4448	usually more than enough. If you need to manage thousands of children you
3965	increase this value (I<must> be a power of two).	4449	might want to increase this value (I<must> be a power of two).
3966		4450
3967	=item EV_INOTIFY_HASHSIZE	4451	=item EV_INOTIFY_HASHSIZE
3968		4452
3969	C<ev_stat> watchers use a small hash table to distribute workload by	4453	C<ev_stat> watchers use a small hash table to distribute workload by
3970	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4454	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971	usually more than enough. If you need to manage thousands of C<ev_stat>	4455	disabled), usually more than enough. If you need to manage thousands of
3972	watchers you might want to increase this value (I<must> be a power of	4456	C<ev_stat> watchers you might want to increase this value (I<must> be a
3973	two).	4457	power of two).
3974		4458
3975	=item EV_USE_4HEAP	4459	=item EV_USE_4HEAP
3976		4460
3977	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4461	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4462	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4463	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980	faster performance with many (thousands) of watchers.	4464	faster performance with many (thousands) of watchers.
3981		4465
3982	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4466	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983	(disabled).	4467	will be C<0>.
3984		4468
3985	=item EV_HEAP_CACHE_AT	4469	=item EV_HEAP_CACHE_AT
3986		4470
3987	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4471	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4472	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4473	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4474	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991	but avoids random read accesses on heap changes. This improves performance	4475	but avoids random read accesses on heap changes. This improves performance
3992	noticeably with many (hundreds) of watchers.	4476	noticeably with many (hundreds) of watchers.
3993		4477
3994	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4478	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995	(disabled).	4479	will be C<0>.
3996		4480
3997	=item EV_VERIFY	4481	=item EV_VERIFY
3998		4482
3999	Controls how much internal verification (see C<ev_loop_verify ()>) will	4483	Controls how much internal verification (see C<ev_verify ()>) will
4000	be done: If set to C<0>, no internal verification code will be compiled	4484	be done: If set to C<0>, no internal verification code will be compiled
4001	in. If set to C<1>, then verification code will be compiled in, but not	4485	in. If set to C<1>, then verification code will be compiled in, but not
4002	called. If set to C<2>, then the internal verification code will be	4486	called. If set to C<2>, then the internal verification code will be
4003	called once per loop, which can slow down libev. If set to C<3>, then the	4487	called once per loop, which can slow down libev. If set to C<3>, then the
4004	verification code will be called very frequently, which will slow down	4488	verification code will be called very frequently, which will slow down
4005	libev considerably.	4489	libev considerably.
4006		4490
4007	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4491	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008	C<0>.	4492	will be C<0>.
4009		4493
4010	=item EV_COMMON	4494	=item EV_COMMON
4011		4495
4012	By default, all watchers have a C<void *data> member. By redefining	4496	By default, all watchers have a C<void *data> member. By redefining
4013	this macro to a something else you can include more and other types of	4497	this macro to something else you can include more and other types of
4014	members. You have to define it each time you include one of the files,	4498	members. You have to define it each time you include one of the files,
4015	though, and it must be identical each time.	4499	though, and it must be identical each time.
4016		4500
4017	For example, the perl EV module uses something like this:	4501	For example, the perl EV module uses something like this:
4018		4502
…		…
4071	file.	4555	file.
4072		4556
4073	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4557	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074	that everybody includes and which overrides some configure choices:	4558	that everybody includes and which overrides some configure choices:
4075		4559
4076	#define EV_MINIMAL 1	4560	#define EV_FEATURES 8
4077	#define EV_USE_POLL 0	4561	#define EV_USE_SELECT 1
4078	#define EV_MULTIPLICITY 0
4079	#define EV_PERIODIC_ENABLE 0	4562	#define EV_PREPARE_ENABLE 1
		4563	#define EV_IDLE_ENABLE 1
4080	#define EV_STAT_ENABLE 0	4564	#define EV_SIGNAL_ENABLE 1
4081	#define EV_FORK_ENABLE 0	4565	#define EV_CHILD_ENABLE 1
		4566	#define EV_USE_STDEXCEPT 0
4082	#define EV_CONFIG_H <config.h>	4567	#define EV_CONFIG_H <config.h>
4083	#define EV_MINPRI 0
4084	#define EV_MAXPRI 0
4085		4568
4086	#include "ev++.h"	4569	#include "ev++.h"
4087		4570
4088	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089		4572
4090	#include "ev_cpp.h"	4573	#include "ev_cpp.h"
4091	#include "ev.c"	4574	#include "ev.c"
4092		4575
4093	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4576	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4094		4577
4095	=head2 THREADS AND COROUTINES	4578	=head2 THREADS AND COROUTINES
4096		4579
4097	=head3 THREADS	4580	=head3 THREADS
4098		4581
…		…
4149	default loop and triggering an C<ev_async> watcher from the default loop	4632	default loop and triggering an C<ev_async> watcher from the default loop
4150	watcher callback into the event loop interested in the signal.	4633	watcher callback into the event loop interested in the signal.
4151		4634
4152	=back	4635	=back
4153		4636
4154	=head4 THREAD LOCKING EXAMPLE	4637	See also L<THREAD LOCKING EXAMPLE>.
4155
4156	Here is a fictitious example of how to run an event loop in a different
4157	thread than where callbacks are being invoked and watchers are
4158	created/added/removed.
4159
4160	For a real-world example, see the C<EV::Loop::Async> perl module,
4161	which uses exactly this technique (which is suited for many high-level
4162	languages).
4163
4164	The example uses a pthread mutex to protect the loop data, a condition
4165	variable to wait for callback invocations, an async watcher to notify the
4166	event loop thread and an unspecified mechanism to wake up the main thread.
4167
4168	First, you need to associate some data with the event loop:
4169
4170	typedef struct {
4171	mutex_t lock; /* global loop lock */
4172	ev_async async_w;
4173	thread_t tid;
4174	cond_t invoke_cv;
4175	} userdata;
4176
4177	void prepare_loop (EV_P)
4178	{
4179	// for simplicity, we use a static userdata struct.
4180	static userdata u;
4181
4182	ev_async_init (&u->async_w, async_cb);
4183	ev_async_start (EV_A_ &u->async_w);
4184
4185	pthread_mutex_init (&u->lock, 0);
4186	pthread_cond_init (&u->invoke_cv, 0);
4187
4188	// now associate this with the loop
4189	ev_set_userdata (EV_A_ u);
4190	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4191	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4192
4193	// then create the thread running ev_loop
4194	pthread_create (&u->tid, 0, l_run, EV_A);
4195	}
4196
4197	The callback for the C<ev_async> watcher does nothing: the watcher is used
4198	solely to wake up the event loop so it takes notice of any new watchers
4199	that might have been added:
4200
4201	static void
4202	async_cb (EV_P_ ev_async *w, int revents)
4203	{
4204	// just used for the side effects
4205	}
4206
4207	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4208	protecting the loop data, respectively.
4209
4210	static void
4211	l_release (EV_P)
4212	{
4213	userdata *u = ev_userdata (EV_A);
4214	pthread_mutex_unlock (&u->lock);
4215	}
4216
4217	static void
4218	l_acquire (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221	pthread_mutex_lock (&u->lock);
4222	}
4223
4224	The event loop thread first acquires the mutex, and then jumps straight
4225	into C<ev_loop>:
4226
4227	void *
4228	l_run (void *thr_arg)
4229	{
4230	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4231
4232	l_acquire (EV_A);
4233	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4234	ev_loop (EV_A_ 0);
4235	l_release (EV_A);
4236
4237	return 0;
4238	}
4239
4240	Instead of invoking all pending watchers, the C<l_invoke> callback will
4241	signal the main thread via some unspecified mechanism (signals? pipe
4242	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4243	have been called (in a while loop because a) spurious wakeups are possible
4244	and b) skipping inter-thread-communication when there are no pending
4245	watchers is very beneficial):
4246
4247	static void
4248	l_invoke (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251
4252	while (ev_pending_count (EV_A))
4253	{
4254	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4255	pthread_cond_wait (&u->invoke_cv, &u->lock);
4256	}
4257	}
4258
4259	Now, whenever the main thread gets told to invoke pending watchers, it
4260	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4261	thread to continue:
4262
4263	static void
4264	real_invoke_pending (EV_P)
4265	{
4266	userdata *u = ev_userdata (EV_A);
4267
4268	pthread_mutex_lock (&u->lock);
4269	ev_invoke_pending (EV_A);
4270	pthread_cond_signal (&u->invoke_cv);
4271	pthread_mutex_unlock (&u->lock);
4272	}
4273
4274	Whenever you want to start/stop a watcher or do other modifications to an
4275	event loop, you will now have to lock:
4276
4277	ev_timer timeout_watcher;
4278	userdata *u = ev_userdata (EV_A);
4279
4280	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4281
4282	pthread_mutex_lock (&u->lock);
4283	ev_timer_start (EV_A_ &timeout_watcher);
4284	ev_async_send (EV_A_ &u->async_w);
4285	pthread_mutex_unlock (&u->lock);
4286
4287	Note that sending the C<ev_async> watcher is required because otherwise
4288	an event loop currently blocking in the kernel will have no knowledge
4289	about the newly added timer. By waking up the loop it will pick up any new
4290	watchers in the next event loop iteration.
4291		4638
4292	=head3 COROUTINES	4639	=head3 COROUTINES
4293		4640
4294	Libev is very accommodating to coroutines ("cooperative threads"):	4641	Libev is very accommodating to coroutines ("cooperative threads"):
4295	libev fully supports nesting calls to its functions from different	4642	libev fully supports nesting calls to its functions from different
4296	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4643	coroutines (e.g. you can call C<ev_run> on the same loop from two
4297	different coroutines, and switch freely between both coroutines running	4644	different coroutines, and switch freely between both coroutines running
4298	the loop, as long as you don't confuse yourself). The only exception is	4645	the loop, as long as you don't confuse yourself). The only exception is
4299	that you must not do this from C<ev_periodic> reschedule callbacks.	4646	that you must not do this from C<ev_periodic> reschedule callbacks.
4300		4647
4301	Care has been taken to ensure that libev does not keep local state inside	4648	Care has been taken to ensure that libev does not keep local state inside
4302	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4649	C<ev_run>, and other calls do not usually allow for coroutine switches as
4303	they do not call any callbacks.	4650	they do not call any callbacks.
4304		4651
4305	=head2 COMPILER WARNINGS	4652	=head2 COMPILER WARNINGS
4306		4653
4307	Depending on your compiler and compiler settings, you might get no or a	4654	Depending on your compiler and compiler settings, you might get no or a
…		…
4318	maintainable.	4665	maintainable.
4319		4666
4320	And of course, some compiler warnings are just plain stupid, or simply	4667	And of course, some compiler warnings are just plain stupid, or simply
4321	wrong (because they don't actually warn about the condition their message	4668	wrong (because they don't actually warn about the condition their message
4322	seems to warn about). For example, certain older gcc versions had some	4669	seems to warn about). For example, certain older gcc versions had some
4323	warnings that resulted an extreme number of false positives. These have	4670	warnings that resulted in an extreme number of false positives. These have
4324	been fixed, but some people still insist on making code warn-free with	4671	been fixed, but some people still insist on making code warn-free with
4325	such buggy versions.	4672	such buggy versions.
4326		4673
4327	While libev is written to generate as few warnings as possible,	4674	While libev is written to generate as few warnings as possible,
4328	"warn-free" code is not a goal, and it is recommended not to build libev	4675	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4364	I suggest using suppression lists.	4711	I suggest using suppression lists.
4365		4712
4366		4713
4367	=head1 PORTABILITY NOTES	4714	=head1 PORTABILITY NOTES
4368		4715
		4716	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4717
		4718	GNU/Linux is the only common platform that supports 64 bit file/large file
		4719	interfaces but I<disables> them by default.
		4720
		4721	That means that libev compiled in the default environment doesn't support
		4722	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4723
		4724	Unfortunately, many programs try to work around this GNU/Linux issue
		4725	by enabling the large file API, which makes them incompatible with the
		4726	standard libev compiled for their system.
		4727
		4728	Likewise, libev cannot enable the large file API itself as this would
		4729	suddenly make it incompatible to the default compile time environment,
		4730	i.e. all programs not using special compile switches.
		4731
		4732	=head2 OS/X AND DARWIN BUGS
		4733
		4734	The whole thing is a bug if you ask me - basically any system interface
		4735	you touch is broken, whether it is locales, poll, kqueue or even the
		4736	OpenGL drivers.
		4737
		4738	=head3 C<kqueue> is buggy
		4739
		4740	The kqueue syscall is broken in all known versions - most versions support
		4741	only sockets, many support pipes.
		4742
		4743	Libev tries to work around this by not using C<kqueue> by default on this
		4744	rotten platform, but of course you can still ask for it when creating a
		4745	loop - embedding a socket-only kqueue loop into a select-based one is
		4746	probably going to work well.
		4747
		4748	=head3 C<poll> is buggy
		4749
		4750	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4751	implementation by something calling C<kqueue> internally around the 10.5.6
		4752	release, so now C<kqueue> I<and> C<poll> are broken.
		4753
		4754	Libev tries to work around this by not using C<poll> by default on
		4755	this rotten platform, but of course you can still ask for it when creating
		4756	a loop.
		4757
		4758	=head3 C<select> is buggy
		4759
		4760	All that's left is C<select>, and of course Apple found a way to fuck this
		4761	one up as well: On OS/X, C<select> actively limits the number of file
		4762	descriptors you can pass in to 1024 - your program suddenly crashes when
		4763	you use more.
		4764
		4765	There is an undocumented "workaround" for this - defining
		4766	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4767	work on OS/X.
		4768
		4769	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4770
		4771	=head3 C<errno> reentrancy
		4772
		4773	The default compile environment on Solaris is unfortunately so
		4774	thread-unsafe that you can't even use components/libraries compiled
		4775	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4776	defined by default. A valid, if stupid, implementation choice.
		4777
		4778	If you want to use libev in threaded environments you have to make sure
		4779	it's compiled with C<_REENTRANT> defined.
		4780
		4781	=head3 Event port backend
		4782
		4783	The scalable event interface for Solaris is called "event
		4784	ports". Unfortunately, this mechanism is very buggy in all major
		4785	releases. If you run into high CPU usage, your program freezes or you get
		4786	a large number of spurious wakeups, make sure you have all the relevant
		4787	and latest kernel patches applied. No, I don't know which ones, but there
		4788	are multiple ones to apply, and afterwards, event ports actually work
		4789	great.
		4790
		4791	If you can't get it to work, you can try running the program by setting
		4792	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4793	C<select> backends.
		4794
		4795	=head2 AIX POLL BUG
		4796
		4797	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4798	this by trying to avoid the poll backend altogether (i.e. it's not even
		4799	compiled in), which normally isn't a big problem as C<select> works fine
		4800	with large bitsets on AIX, and AIX is dead anyway.
		4801
4369	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4802	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4803
		4804	=head3 General issues
4370		4805
4371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4806	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372	requires, and its I/O model is fundamentally incompatible with the POSIX	4807	requires, and its I/O model is fundamentally incompatible with the POSIX
4373	model. Libev still offers limited functionality on this platform in	4808	model. Libev still offers limited functionality on this platform in
4374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4809	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375	descriptors. This only applies when using Win32 natively, not when using	4810	descriptors. This only applies when using Win32 natively, not when using
4376	e.g. cygwin.	4811	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4812	as every compielr comes with a slightly differently broken/incompatible
		4813	environment.
4377		4814
4378	Lifting these limitations would basically require the full	4815	Lifting these limitations would basically require the full
4379	re-implementation of the I/O system. If you are into these kinds of	4816	re-implementation of the I/O system. If you are into this kind of thing,
4380	things, then note that glib does exactly that for you in a very portable	4817	then note that glib does exactly that for you in a very portable way (note
4381	way (note also that glib is the slowest event library known to man).	4818	also that glib is the slowest event library known to man).
4382		4819
4383	There is no supported compilation method available on windows except	4820	There is no supported compilation method available on windows except
4384	embedding it into other applications.	4821	embedding it into other applications.
4385		4822
4386	Sensible signal handling is officially unsupported by Microsoft - libev	4823	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4414	you do I<not> compile the F<ev.c> or any other embedded source files!):	4851	you do I<not> compile the F<ev.c> or any other embedded source files!):
4415		4852
4416	#include "evwrap.h"	4853	#include "evwrap.h"
4417	#include "ev.c"	4854	#include "ev.c"
4418		4855
4419	=over 4
4420
4421	=item The winsocket select function	4856	=head3 The winsocket C<select> function
4422		4857
4423	The winsocket C<select> function doesn't follow POSIX in that it	4858	The winsocket C<select> function doesn't follow POSIX in that it
4424	requires socket I<handles> and not socket I<file descriptors> (it is	4859	requires socket I<handles> and not socket I<file descriptors> (it is
4425	also extremely buggy). This makes select very inefficient, and also	4860	also extremely buggy). This makes select very inefficient, and also
4426	requires a mapping from file descriptors to socket handles (the Microsoft	4861	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4435	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4870	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436		4871
4437	Note that winsockets handling of fd sets is O(n), so you can easily get a	4872	Note that winsockets handling of fd sets is O(n), so you can easily get a
4438	complexity in the O(n²) range when using win32.	4873	complexity in the O(n²) range when using win32.
4439		4874
4440	=item Limited number of file descriptors	4875	=head3 Limited number of file descriptors
4441		4876
4442	Windows has numerous arbitrary (and low) limits on things.	4877	Windows has numerous arbitrary (and low) limits on things.
4443		4878
4444	Early versions of winsocket's select only supported waiting for a maximum	4879	Early versions of winsocket's select only supported waiting for a maximum
4445	of C<64> handles (probably owning to the fact that all windows kernels	4880	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4460	runtime libraries. This might get you to about C<512> or C<2048> sockets	4895	runtime libraries. This might get you to about C<512> or C<2048> sockets
4461	(depending on windows version and/or the phase of the moon). To get more,	4896	(depending on windows version and/or the phase of the moon). To get more,
4462	you need to wrap all I/O functions and provide your own fd management, but	4897	you need to wrap all I/O functions and provide your own fd management, but
4463	the cost of calling select (O(n²)) will likely make this unworkable.	4898	the cost of calling select (O(n²)) will likely make this unworkable.
4464		4899
4465	=back
4466
4467	=head2 PORTABILITY REQUIREMENTS	4900	=head2 PORTABILITY REQUIREMENTS
4468		4901
4469	In addition to a working ISO-C implementation and of course the	4902	In addition to a working ISO-C implementation and of course the
4470	backend-specific APIs, libev relies on a few additional extensions:	4903	backend-specific APIs, libev relies on a few additional extensions:
4471		4904
…		…
4477	Libev assumes not only that all watcher pointers have the same internal	4910	Libev assumes not only that all watcher pointers have the same internal
4478	structure (guaranteed by POSIX but not by ISO C for example), but it also	4911	structure (guaranteed by POSIX but not by ISO C for example), but it also
4479	assumes that the same (machine) code can be used to call any watcher	4912	assumes that the same (machine) code can be used to call any watcher
4480	callback: The watcher callbacks have different type signatures, but libev	4913	callback: The watcher callbacks have different type signatures, but libev
4481	calls them using an C<ev_watcher *> internally.	4914	calls them using an C<ev_watcher *> internally.
		4915
		4916	=item pointer accesses must be thread-atomic
		4917
		4918	Accessing a pointer value must be atomic, it must both be readable and
		4919	writable in one piece - this is the case on all current architectures.
4482		4920
4483	=item C<sig_atomic_t volatile> must be thread-atomic as well	4921	=item C<sig_atomic_t volatile> must be thread-atomic as well
4484		4922
4485	The type C<sig_atomic_t volatile> (or whatever is defined as	4923	The type C<sig_atomic_t volatile> (or whatever is defined as
4486	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4924	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4509	watchers.	4947	watchers.
4510		4948
4511	=item C<double> must hold a time value in seconds with enough accuracy	4949	=item C<double> must hold a time value in seconds with enough accuracy
4512		4950
4513	The type C<double> is used to represent timestamps. It is required to	4951	The type C<double> is used to represent timestamps. It is required to
4514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4952	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4515	enough for at least into the year 4000. This requirement is fulfilled by	4953	good enough for at least into the year 4000 with millisecond accuracy
		4954	(the design goal for libev). This requirement is overfulfilled by
4516	implementations implementing IEEE 754, which is basically all existing	4955	implementations using IEEE 754, which is basically all existing ones. With
4517	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	4956	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4518	2200.
4519		4957
4520	=back	4958	=back
4521		4959
4522	If you know of other additional requirements drop me a note.	4960	If you know of other additional requirements drop me a note.
4523		4961
…		…
4591	involves iterating over all running async watchers or all signal numbers.	5029	involves iterating over all running async watchers or all signal numbers.
4592		5030
4593	=back	5031	=back
4594		5032
4595		5033
		5034	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5035
		5036	The major version 4 introduced some incompatible changes to the API.
		5037
		5038	At the moment, the C<ev.h> header file provides compatibility definitions
		5039	for all changes, so most programs should still compile. The compatibility
		5040	layer might be removed in later versions of libev, so better update to the
		5041	new API early than late.
		5042
		5043	=over 4
		5044
		5045	=item C<EV_COMPAT3> backwards compatibility mechanism
		5046
		5047	The backward compatibility mechanism can be controlled by
		5048	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5049	section.
		5050
		5051	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5052
		5053	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5054
		5055	ev_loop_destroy (EV_DEFAULT_UC);
		5056	ev_loop_fork (EV_DEFAULT);
		5057
		5058	=item function/symbol renames
		5059
		5060	A number of functions and symbols have been renamed:
		5061
		5062	ev_loop => ev_run
		5063	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5064	EVLOOP_ONESHOT => EVRUN_ONCE
		5065
		5066	ev_unloop => ev_break
		5067	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5068	EVUNLOOP_ONE => EVBREAK_ONE
		5069	EVUNLOOP_ALL => EVBREAK_ALL
		5070
		5071	EV_TIMEOUT => EV_TIMER
		5072
		5073	ev_loop_count => ev_iteration
		5074	ev_loop_depth => ev_depth
		5075	ev_loop_verify => ev_verify
		5076
		5077	Most functions working on C<struct ev_loop> objects don't have an
		5078	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5079	associated constants have been renamed to not collide with the C<struct
		5080	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5081	as all other watcher types. Note that C<ev_loop_fork> is still called
		5082	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5083	typedef.
		5084
		5085	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5086
		5087	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5088	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5089	and work, but the library code will of course be larger.
		5090
		5091	=back
		5092
		5093
4596	=head1 GLOSSARY	5094	=head1 GLOSSARY
4597		5095
4598	=over 4	5096	=over 4
4599		5097
4600	=item active	5098	=item active
4601		5099
4602	A watcher is active as long as it has been started (has been attached to	5100	A watcher is active as long as it has been started and not yet stopped.
4603	an event loop) but not yet stopped (disassociated from the event loop).	5101	See L<WATCHER STATES> for details.
4604		5102
4605	=item application	5103	=item application
4606		5104
4607	In this document, an application is whatever is using libev.	5105	In this document, an application is whatever is using libev.
		5106
		5107	=item backend
		5108
		5109	The part of the code dealing with the operating system interfaces.
4608		5110
4609	=item callback	5111	=item callback
4610		5112
4611	The address of a function that is called when some event has been	5113	The address of a function that is called when some event has been
4612	detected. Callbacks are being passed the event loop, the watcher that	5114	detected. Callbacks are being passed the event loop, the watcher that
4613	received the event, and the actual event bitset.	5115	received the event, and the actual event bitset.
4614		5116
4615	=item callback invocation	5117	=item callback/watcher invocation
4616		5118
4617	The act of calling the callback associated with a watcher.	5119	The act of calling the callback associated with a watcher.
4618		5120
4619	=item event	5121	=item event
4620		5122
4621	A change of state of some external event, such as data now being available	5123	A change of state of some external event, such as data now being available
4622	for reading on a file descriptor, time having passed or simply not having	5124	for reading on a file descriptor, time having passed or simply not having
4623	any other events happening anymore.	5125	any other events happening anymore.
4624		5126
4625	In libev, events are represented as single bits (such as C<EV_READ> or	5127	In libev, events are represented as single bits (such as C<EV_READ> or
4626	C<EV_TIMEOUT>).	5128	C<EV_TIMER>).
4627		5129
4628	=item event library	5130	=item event library
4629		5131
4630	A software package implementing an event model and loop.	5132	A software package implementing an event model and loop.
4631		5133
…		…
4639	The model used to describe how an event loop handles and processes	5141	The model used to describe how an event loop handles and processes
4640	watchers and events.	5142	watchers and events.
4641		5143
4642	=item pending	5144	=item pending
4643		5145
4644	A watcher is pending as soon as the corresponding event has been detected,	5146	A watcher is pending as soon as the corresponding event has been
4645	and stops being pending as soon as the watcher will be invoked or its	5147	detected. See L<WATCHER STATES> for details.
4646	pending status is explicitly cleared by the application.
4647
4648	A watcher can be pending, but not active. Stopping a watcher also clears
4649	its pending status.
4650		5148
4651	=item real time	5149	=item real time
4652		5150
4653	The physical time that is observed. It is apparently strictly monotonic :)	5151	The physical time that is observed. It is apparently strictly monotonic :)
4654		5152
…		…
4661	=item watcher	5159	=item watcher
4662		5160
4663	A data structure that describes interest in certain events. Watchers need	5161	A data structure that describes interest in certain events. Watchers need
4664	to be started (attached to an event loop) before they can receive events.	5162	to be started (attached to an event loop) before they can receive events.
4665		5163
4666	=item watcher invocation
4667
4668	The act of calling the callback associated with a watcher.
4669
4670	=back	5164	=back
4671		5165
4672	=head1 AUTHOR	5166	=head1 AUTHOR
4673		5167
4674	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5168	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5169	Magnusson and Emanuele Giaquinta.
4675		5170

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