ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.229 by root, Wed Apr 15 17:49:27 2009 UTC vs.
Revision 1.326 by root, Sun Oct 24 19:44:27 2010 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
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		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
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
72		84
73	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
74	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
75	these event sources and provide your program with events.	87	these event sources and provide your program with events.
76		88
…		…
86	=head2 FEATURES	98	=head2 FEATURES
87		99
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
98		111
99	It also is quite fast (see this	112	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	114	for example).
102		115
…		…
105	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	124	this argument.
112		125
113	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
114		127
115	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
121	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
122	throughout libev.	136	time differences (e.g. delays) throughout libev.
123		137
124	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
125		139
126	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	141	and internal errors (bugs).
…		…
151		165
152	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
153		167
154	Returns the current time as libev would use it. Please note that the	168	Returns the current time as libev would use it. Please note that the
155	C<ev_now> function is usually faster and also often returns the timestamp	169	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
157		172
158	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
159		174
160	Sleep for the given interval: The current thread will be blocked until	175	Sleep for the given interval: The current thread will be blocked until
161	either it is interrupted or the given time interval has passed. Basically	176	either it is interrupted or the given time interval has passed. Basically
…		…
178	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	195	not a problem.
181		196
182	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
184		200
185	assert (("libev version mismatch",	201	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
188		204
…		…
199	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
201		217
202	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
203		219
204	Return the set of all backends compiled into this binary of libev and also	220	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	221	also recommended for this platform, meaning it will work for most file
		222	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	223	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	224	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	225	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	226	probe for if you specify no backends explicitly.
210		227
211	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
212		229
213	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	231	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	232	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
218		235
219	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
220		237
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
222		239
…		…
276	...	293	...
277	ev_set_syserr_cb (fatal_error);	294	ev_set_syserr_cb (fatal_error);
278		295
279	=back	296	=back
280		297
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		299
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	302	libev 3 had an C<ev_loop> function colliding with the struct name).
286		303
287	The library knows two types of such loops, the I<default> loop, which	304	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	305	supports signals and child events, and dynamically created event loops
289	not.	306	which do not.
290		307
291	=over 4	308	=over 4
292		309
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		311
295	This will initialise the default event loop if it hasn't been initialised	312	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	313	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	314	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	315	C<ev_loop_new>.
		316
		317	If the default loop is already initialised then this function simply
		318	returns it (and ignores the flags. If that is troubling you, check
		319	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		320	flags, which should almost always be C<0>, unless the caller is also the
		321	one calling C<ev_run> or otherwise qualifies as "the main program".
299		322
300	If you don't know what event loop to use, use the one returned from this	323	If you don't know what event loop to use, use the one returned from this
301	function.	324	function (or via the C<EV_DEFAULT> macro).
302		325
303	Note that this function is I<not> thread-safe, so if you want to use it	326	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	327	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
306		330
307	The default loop is the only loop that can handle C<ev_signal> and	331	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	332	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	333	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	334	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	336
		337	Example: This is the most typical usage.
		338
		339	if (!ev_default_loop (0))
		340	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		341
		342	Example: Restrict libev to the select and poll backends, and do not allow
		343	environment settings to be taken into account:
		344
		345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		346
		347	=item struct ev_loop *ev_loop_new (unsigned int flags)
		348
		349	This will create and initialise a new event loop object. If the loop
		350	could not be initialised, returns false.
		351
		352	Note that this function I<is> thread-safe, and one common way to use
		353	libev with threads is indeed to create one loop per thread, and using the
		354	default loop in the "main" or "initial" thread.
313		355
314	The flags argument can be used to specify special behaviour or specific	356	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	357	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		358
317	The following flags are supported:	359	The following flags are supported:
…		…
332	useful to try out specific backends to test their performance, or to work	374	useful to try out specific backends to test their performance, or to work
333	around bugs.	375	around bugs.
334		376
335	=item C<EVFLAG_FORKCHECK>	377	=item C<EVFLAG_FORKCHECK>
336		378
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	379	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	380	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		381
341	This works by calling C<getpid ()> on every iteration of the loop,	382	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	383	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	384	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	385	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	391	flag.
351		392
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	393	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	394	environment variable.
354		395
		396	=item C<EVFLAG_NOINOTIFY>
		397
		398	When this flag is specified, then libev will not attempt to use the
		399	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		400	testing, this flag can be useful to conserve inotify file descriptors, as
		401	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		402
		403	=item C<EVFLAG_SIGNALFD>
		404
		405	When this flag is specified, then libev will attempt to use the
		406	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		407	delivers signals synchronously, which makes it both faster and might make
		408	it possible to get the queued signal data. It can also simplify signal
		409	handling with threads, as long as you properly block signals in your
		410	threads that are not interested in handling them.
		411
		412	Signalfd will not be used by default as this changes your signal mask, and
		413	there are a lot of shoddy libraries and programs (glib's threadpool for
		414	example) that can't properly initialise their signal masks.
		415
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		417
357	This is your standard select(2) backend. Not I<completely> standard, as	418	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	419	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	420	but if that fails, expect a fairly low limit on the number of fds when
…		…
382		443
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	444	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	445	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		446
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	447	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		448
		449	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		450	kernels).
387		451
388	For few fds, this backend is a bit little slower than poll and select,	452	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	453	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	454	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	455	epoll scales either O(1) or O(active_fds).
…		…
403	of course I<doesn't>, and epoll just loves to report events for totally	467	of course I<doesn't>, and epoll just loves to report events for totally
404	I<different> file descriptors (even already closed ones, so one cannot	468	I<different> file descriptors (even already closed ones, so one cannot
405	even remove them from the set) than registered in the set (especially	469	even remove them from the set) than registered in the set (especially
406	on SMP systems). Libev tries to counter these spurious notifications by	470	on SMP systems). Libev tries to counter these spurious notifications by
407	employing an additional generation counter and comparing that against the	471	employing an additional generation counter and comparing that against the
408	events to filter out spurious ones, recreating the set when required.	472	events to filter out spurious ones, recreating the set when required. Last
		473	not least, it also refuses to work with some file descriptors which work
		474	perfectly fine with C<select> (files, many character devices...).
409		475
410	While stopping, setting and starting an I/O watcher in the same iteration	476	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	477	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	478	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	479	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
506		572
507	It is definitely not recommended to use this flag.	573	It is definitely not recommended to use this flag.
508		574
509	=back	575	=back
510		576
511	If one or more of these are or'ed into the flags value, then only these	577	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	578	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	579	here). If none are specified, all backends in C<ev_recommended_backends
514		580	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		581
543	Example: Try to create a event loop that uses epoll and nothing else.	582	Example: Try to create a event loop that uses epoll and nothing else.
544		583
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	585	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	586	fatal ("no epoll found here, maybe it hides under your chair");
548		587
		588	Example: Use whatever libev has to offer, but make sure that kqueue is
		589	used if available.
		590
		591	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		592
549	=item ev_default_destroy ()	593	=item ev_loop_destroy (loop)
550		594
551	Destroys the default loop again (frees all memory and kernel state	595	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	596	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	597	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	598	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	599	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	600	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		602
559	Note that certain global state, such as signal state (and installed signal	603	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	604	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	605	as signal and child watchers) would need to be stopped manually.
562		606
563	In general it is not advisable to call this function except in the	607	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	608	C<ev_loop_new>, but it can also be used on the default loop returned by
		609	C<ev_default_loop>, in which case it is not thread-safe.
		610
		611	Note that it is not advisable to call this function on the default loop
		612	except in the rare occasion where you really need to free it's resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	613	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	614	and C<ev_loop_destroy>.
567		615
568	=item ev_loop_destroy (loop)	616	=item ev_loop_fork (loop)
569		617
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	618	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	619	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	620	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	621	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	622	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	623
		624	Again, you I<have> to call it on I<any> loop that you want to re-use after
		625	a fork, I<even if you do not plan to use the loop in the parent>. This is
		626	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		627	during fork.
581		628
582	On the other hand, you only need to call this function in the child	629	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	630	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	631	you just fork+exec or create a new loop in the child, you don't have to
		632	call it at all (in fact, C<epoll> is so badly broken that it makes a
		633	difference, but libev will usually detect this case on its own and do a
		634	costly reset of the backend).
585		635
586	The function itself is quite fast and it's usually not a problem to call	636	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	637	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		638
		639	Example: Automate calling C<ev_loop_fork> on the default loop when
		640	using pthreads.
		641
		642	static void
		643	post_fork_child (void)
		644	{
		645	ev_loop_fork (EV_DEFAULT);
		646	}
		647
		648	...
590	pthread_atfork (0, 0, ev_default_fork);	649	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		650
599	=item int ev_is_default_loop (loop)	651	=item int ev_is_default_loop (loop)
600		652
601	Returns true when the given loop is, in fact, the default loop, and false	653	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	654	otherwise.
603		655
604	=item unsigned int ev_loop_count (loop)	656	=item unsigned int ev_iteration (loop)
605		657
606	Returns the count of loop iterations for the loop, which is identical to	658	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	659	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	660	and happily wraps around with enough iterations.
609		661
610	This value can sometimes be useful as a generation counter of sorts (it	662	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	663	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	664	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		665	prepare and check phases.
		666
		667	=item unsigned int ev_depth (loop)
		668
		669	Returns the number of times C<ev_run> was entered minus the number of
		670	times C<ev_run> was exited, in other words, the recursion depth.
		671
		672	Outside C<ev_run>, this number is zero. In a callback, this number is
		673	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		674	in which case it is higher.
		675
		676	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		677	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		678	ungentleman-like behaviour unless it's really convenient.
613		679
614	=item unsigned int ev_backend (loop)	680	=item unsigned int ev_backend (loop)
615		681
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	682	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	683	use.
…		…
626		692
627	=item ev_now_update (loop)	693	=item ev_now_update (loop)
628		694
629	Establishes the current time by querying the kernel, updating the time	695	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	696	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	697	is usually done automatically within C<ev_run ()>.
632		698
633	This function is rarely useful, but when some event callback runs for a	699	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	700	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	701	the current time is a good idea.
636		702
637	See also "The special problem of time updates" in the C<ev_timer> section.	703	See also L<The special problem of time updates> in the C<ev_timer> section.
638		704
		705	=item ev_suspend (loop)
		706
		707	=item ev_resume (loop)
		708
		709	These two functions suspend and resume an event loop, for use when the
		710	loop is not used for a while and timeouts should not be processed.
		711
		712	A typical use case would be an interactive program such as a game: When
		713	the user presses C<^Z> to suspend the game and resumes it an hour later it
		714	would be best to handle timeouts as if no time had actually passed while
		715	the program was suspended. This can be achieved by calling C<ev_suspend>
		716	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		717	C<ev_resume> directly afterwards to resume timer processing.
		718
		719	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		720	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		721	will be rescheduled (that is, they will lose any events that would have
		722	occurred while suspended).
		723
		724	After calling C<ev_suspend> you B<must not> call I<any> function on the
		725	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		726	without a previous call to C<ev_suspend>.
		727
		728	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		729	event loop time (see C<ev_now_update>).
		730
639	=item ev_loop (loop, int flags)	731	=item ev_run (loop, int flags)
640		732
641	Finally, this is it, the event handler. This function usually is called	733	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	734	after you have initialised all your watchers and you want to start
643	events.	735	handling events. It will ask the operating system for any new events, call
		736	the watcher callbacks, an then repeat the whole process indefinitely: This
		737	is why event loops are called I<loops>.
644		738
645	If the flags argument is specified as C<0>, it will not return until	739	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	740	until either no event watchers are active anymore or C<ev_break> was
		741	called.
647		742
648	Please note that an explicit C<ev_unloop> is usually better than	743	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	744	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	745	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	746	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	747	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	748	beauty.
654		749
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	750	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	751	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	752	block your process in case there are no events and will return after one
658	the loop.	753	iteration of the loop. This is sometimes useful to poll and handle new
		754	events while doing lengthy calculations, to keep the program responsive.
659		755
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	756	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	757	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	758	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	759	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	760	user-registered callback will be called), and will return after one
665	iteration of the loop.	761	iteration of the loop.
666		762
667	This is useful if you are waiting for some external event in conjunction	763	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	764	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	765	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	766	usually a better approach for this kind of thing.
671		767
672	Here are the gory details of what C<ev_loop> does:	768	Here are the gory details of what C<ev_run> does:
673		769
		770	- Increment loop depth.
		771	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	772	- Before the first iteration, call any pending watchers.
		773	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	774	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	775	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	776	- Queue and call all prepare watchers.
		777	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	778	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	779	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	780	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	781	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	782	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	783	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	784	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	785	- Sleep if the I/O and timer collect interval say so.
		786	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	787	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	788	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	789	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	790	- Queue all expired timers.
690	- Queue all expired periodics.	791	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	792	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	793	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	794	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	795	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	796	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	797	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	798	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	799	continue with step LOOP.
		800	FINISH:
		801	- Reset the ev_break status iff it was EVBREAK_ONE.
		802	- Decrement the loop depth.
		803	- Return.
699		804
700	Example: Queue some jobs and then loop until no events are outstanding	805	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	806	anymore.
702		807
703	... queue jobs here, make sure they register event watchers as long	808	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	809	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	810	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	811	... jobs done or somebody called unloop. yeah!
707		812
708	=item ev_unloop (loop, how)	813	=item ev_break (loop, how)
709		814
710	Can be used to make a call to C<ev_loop> return early (but only after it	815	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	816	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	817	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	818	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		819
715	This "unloop state" will be cleared when entering C<ev_loop> again.	820	This "unloop state" will be cleared when entering C<ev_run> again.
716		821
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	822	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
718		823
719	=item ev_ref (loop)	824	=item ev_ref (loop)
720		825
721	=item ev_unref (loop)	826	=item ev_unref (loop)
722		827
723	Ref/unref can be used to add or remove a reference count on the event	828	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	829	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	830	count is nonzero, C<ev_run> will not return on its own.
726		831
727	If you have a watcher you never unregister that should not keep C<ev_loop>	832	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	833	unregister, but that nevertheless should not keep C<ev_run> from
		834	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	835	before stopping it.
730		836
731	As an example, libev itself uses this for its internal signal pipe: It	837	As an example, libev itself uses this for its internal signal pipe: It
732	is not visible to the libev user and should not keep C<ev_loop> from	838	is not visible to the libev user and should not keep C<ev_run> from
733	exiting if no event watchers registered by it are active. It is also an	839	exiting if no event watchers registered by it are active. It is also an
734	excellent way to do this for generic recurring timers or from within	840	excellent way to do this for generic recurring timers or from within
735	third-party libraries. Just remember to I<unref after start> and I<ref	841	third-party libraries. Just remember to I<unref after start> and I<ref
736	before stop> (but only if the watcher wasn't active before, or was active	842	before stop> (but only if the watcher wasn't active before, or was active
737	before, respectively. Note also that libev might stop watchers itself	843	before, respectively. Note also that libev might stop watchers itself
738	(e.g. non-repeating timers) in which case you have to C<ev_ref>	844	(e.g. non-repeating timers) in which case you have to C<ev_ref>
739	in the callback).	845	in the callback).
740		846
741	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	847	Example: Create a signal watcher, but keep it from keeping C<ev_run>
742	running when nothing else is active.	848	running when nothing else is active.
743		849
744	ev_signal exitsig;	850	ev_signal exitsig;
745	ev_signal_init (&exitsig, sig_cb, SIGINT);	851	ev_signal_init (&exitsig, sig_cb, SIGINT);
746	ev_signal_start (loop, &exitsig);	852	ev_signal_start (loop, &exitsig);
…		…
773		879
774	By setting a higher I<io collect interval> you allow libev to spend more	880	By setting a higher I<io collect interval> you allow libev to spend more
775	time collecting I/O events, so you can handle more events per iteration,	881	time collecting I/O events, so you can handle more events per iteration,
776	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	882	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
777	C<ev_timer>) will be not affected. Setting this to a non-null value will	883	C<ev_timer>) will be not affected. Setting this to a non-null value will
778	introduce an additional C<ev_sleep ()> call into most loop iterations.	884	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		885	sleep time ensures that libev will not poll for I/O events more often then
		886	once per this interval, on average.
779		887
780	Likewise, by setting a higher I<timeout collect interval> you allow libev	888	Likewise, by setting a higher I<timeout collect interval> you allow libev
781	to spend more time collecting timeouts, at the expense of increased	889	to spend more time collecting timeouts, at the expense of increased
782	latency/jitter/inexactness (the watcher callback will be called	890	latency/jitter/inexactness (the watcher callback will be called
783	later). C<ev_io> watchers will not be affected. Setting this to a non-null	891	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
785		893
786	Many (busy) programs can usually benefit by setting the I/O collect	894	Many (busy) programs can usually benefit by setting the I/O collect
787	interval to a value near C<0.1> or so, which is often enough for	895	interval to a value near C<0.1> or so, which is often enough for
788	interactive servers (of course not for games), likewise for timeouts. It	896	interactive servers (of course not for games), likewise for timeouts. It
789	usually doesn't make much sense to set it to a lower value than C<0.01>,	897	usually doesn't make much sense to set it to a lower value than C<0.01>,
790	as this approaches the timing granularity of most systems.	898	as this approaches the timing granularity of most systems. Note that if
		899	you do transactions with the outside world and you can't increase the
		900	parallelity, then this setting will limit your transaction rate (if you
		901	need to poll once per transaction and the I/O collect interval is 0.01,
		902	then you can't do more than 100 transactions per second).
791		903
792	Setting the I<timeout collect interval> can improve the opportunity for	904	Setting the I<timeout collect interval> can improve the opportunity for
793	saving power, as the program will "bundle" timer callback invocations that	905	saving power, as the program will "bundle" timer callback invocations that
794	are "near" in time together, by delaying some, thus reducing the number of	906	are "near" in time together, by delaying some, thus reducing the number of
795	times the process sleeps and wakes up again. Another useful technique to	907	times the process sleeps and wakes up again. Another useful technique to
796	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	908	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
797	they fire on, say, one-second boundaries only.	909	they fire on, say, one-second boundaries only.
798		910
		911	Example: we only need 0.1s timeout granularity, and we wish not to poll
		912	more often than 100 times per second:
		913
		914	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		915	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		916
		917	=item ev_invoke_pending (loop)
		918
		919	This call will simply invoke all pending watchers while resetting their
		920	pending state. Normally, C<ev_run> does this automatically when required,
		921	but when overriding the invoke callback this call comes handy. This
		922	function can be invoked from a watcher - this can be useful for example
		923	when you want to do some lengthy calculation and want to pass further
		924	event handling to another thread (you still have to make sure only one
		925	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		926
		927	=item int ev_pending_count (loop)
		928
		929	Returns the number of pending watchers - zero indicates that no watchers
		930	are pending.
		931
		932	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		933
		934	This overrides the invoke pending functionality of the loop: Instead of
		935	invoking all pending watchers when there are any, C<ev_run> will call
		936	this callback instead. This is useful, for example, when you want to
		937	invoke the actual watchers inside another context (another thread etc.).
		938
		939	If you want to reset the callback, use C<ev_invoke_pending> as new
		940	callback.
		941
		942	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		943
		944	Sometimes you want to share the same loop between multiple threads. This
		945	can be done relatively simply by putting mutex_lock/unlock calls around
		946	each call to a libev function.
		947
		948	However, C<ev_run> can run an indefinite time, so it is not feasible
		949	to wait for it to return. One way around this is to wake up the event
		950	loop via C<ev_break> and C<av_async_send>, another way is to set these
		951	I<release> and I<acquire> callbacks on the loop.
		952
		953	When set, then C<release> will be called just before the thread is
		954	suspended waiting for new events, and C<acquire> is called just
		955	afterwards.
		956
		957	Ideally, C<release> will just call your mutex_unlock function, and
		958	C<acquire> will just call the mutex_lock function again.
		959
		960	While event loop modifications are allowed between invocations of
		961	C<release> and C<acquire> (that's their only purpose after all), no
		962	modifications done will affect the event loop, i.e. adding watchers will
		963	have no effect on the set of file descriptors being watched, or the time
		964	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		965	to take note of any changes you made.
		966
		967	In theory, threads executing C<ev_run> will be async-cancel safe between
		968	invocations of C<release> and C<acquire>.
		969
		970	See also the locking example in the C<THREADS> section later in this
		971	document.
		972
		973	=item ev_set_userdata (loop, void *data)
		974
		975	=item ev_userdata (loop)
		976
		977	Set and retrieve a single C<void *> associated with a loop. When
		978	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		979	C<0.>
		980
		981	These two functions can be used to associate arbitrary data with a loop,
		982	and are intended solely for the C<invoke_pending_cb>, C<release> and
		983	C<acquire> callbacks described above, but of course can be (ab-)used for
		984	any other purpose as well.
		985
799	=item ev_loop_verify (loop)	986	=item ev_verify (loop)
800		987
801	This function only does something when C<EV_VERIFY> support has been	988	This function only does something when C<EV_VERIFY> support has been
802	compiled in, which is the default for non-minimal builds. It tries to go	989	compiled in, which is the default for non-minimal builds. It tries to go
803	through all internal structures and checks them for validity. If anything	990	through all internal structures and checks them for validity. If anything
804	is found to be inconsistent, it will print an error message to standard	991	is found to be inconsistent, it will print an error message to standard
…		…
815		1002
816	In the following description, uppercase C<TYPE> in names stands for the	1003	In the following description, uppercase C<TYPE> in names stands for the
817	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1004	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
818	watchers and C<ev_io_start> for I/O watchers.	1005	watchers and C<ev_io_start> for I/O watchers.
819		1006
820	A watcher is a structure that you create and register to record your	1007	A watcher is an opaque structure that you allocate and register to record
821	interest in some event. For instance, if you want to wait for STDIN to	1008	your interest in some event. To make a concrete example, imagine you want
822	become readable, you would create an C<ev_io> watcher for that:	1009	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1010	for that:
823		1011
824	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1012	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
825	{	1013	{
826	ev_io_stop (w);	1014	ev_io_stop (w);
827	ev_unloop (loop, EVUNLOOP_ALL);	1015	ev_break (loop, EVBREAK_ALL);
828	}	1016	}
829		1017
830	struct ev_loop *loop = ev_default_loop (0);	1018	struct ev_loop *loop = ev_default_loop (0);
831		1019
832	ev_io stdin_watcher;	1020	ev_io stdin_watcher;
833		1021
834	ev_init (&stdin_watcher, my_cb);	1022	ev_init (&stdin_watcher, my_cb);
835	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1023	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
836	ev_io_start (loop, &stdin_watcher);	1024	ev_io_start (loop, &stdin_watcher);
837		1025
838	ev_loop (loop, 0);	1026	ev_run (loop, 0);
839		1027
840	As you can see, you are responsible for allocating the memory for your	1028	As you can see, you are responsible for allocating the memory for your
841	watcher structures (and it is I<usually> a bad idea to do this on the	1029	watcher structures (and it is I<usually> a bad idea to do this on the
842	stack).	1030	stack).
843		1031
844	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1032	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
845	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1033	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
846		1034
847	Each watcher structure must be initialised by a call to C<ev_init	1035	Each watcher structure must be initialised by a call to C<ev_init (watcher
848	(watcher *, callback)>, which expects a callback to be provided. This	1036	*, callback)>, which expects a callback to be provided. This callback is
849	callback gets invoked each time the event occurs (or, in the case of I/O	1037	invoked each time the event occurs (or, in the case of I/O watchers, each
850	watchers, each time the event loop detects that the file descriptor given	1038	time the event loop detects that the file descriptor given is readable
851	is readable and/or writable).	1039	and/or writable).
852		1040
853	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1041	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
854	macro to configure it, with arguments specific to the watcher type. There	1042	macro to configure it, with arguments specific to the watcher type. There
855	is also a macro to combine initialisation and setting in one call: C<<	1043	is also a macro to combine initialisation and setting in one call: C<<
856	ev_TYPE_init (watcher *, callback, ...) >>.	1044	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
879	=item C<EV_WRITE>	1067	=item C<EV_WRITE>
880		1068
881	The file descriptor in the C<ev_io> watcher has become readable and/or	1069	The file descriptor in the C<ev_io> watcher has become readable and/or
882	writable.	1070	writable.
883		1071
884	=item C<EV_TIMEOUT>	1072	=item C<EV_TIMER>
885		1073
886	The C<ev_timer> watcher has timed out.	1074	The C<ev_timer> watcher has timed out.
887		1075
888	=item C<EV_PERIODIC>	1076	=item C<EV_PERIODIC>
889		1077
…		…
907		1095
908	=item C<EV_PREPARE>	1096	=item C<EV_PREPARE>
909		1097
910	=item C<EV_CHECK>	1098	=item C<EV_CHECK>
911		1099
912	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1100	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
913	to gather new events, and all C<ev_check> watchers are invoked just after	1101	to gather new events, and all C<ev_check> watchers are invoked just after
914	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1102	C<ev_run> has gathered them, but before it invokes any callbacks for any
915	received events. Callbacks of both watcher types can start and stop as	1103	received events. Callbacks of both watcher types can start and stop as
916	many watchers as they want, and all of them will be taken into account	1104	many watchers as they want, and all of them will be taken into account
917	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1105	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
918	C<ev_loop> from blocking).	1106	C<ev_run> from blocking).
919		1107
920	=item C<EV_EMBED>	1108	=item C<EV_EMBED>
921		1109
922	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1110	The embedded event loop specified in the C<ev_embed> watcher needs attention.
923		1111
924	=item C<EV_FORK>	1112	=item C<EV_FORK>
925		1113
926	The event loop has been resumed in the child process after fork (see	1114	The event loop has been resumed in the child process after fork (see
927	C<ev_fork>).	1115	C<ev_fork>).
		1116
		1117	=item C<EV_CLEANUP>
		1118
		1119	The event loop is abotu to be destroyed (see C<ev_cleanup>).
928		1120
929	=item C<EV_ASYNC>	1121	=item C<EV_ASYNC>
930		1122
931	The given async watcher has been asynchronously notified (see C<ev_async>).	1123	The given async watcher has been asynchronously notified (see C<ev_async>).
932		1124
…		…
954	programs, though, as the fd could already be closed and reused for another	1146	programs, though, as the fd could already be closed and reused for another
955	thing, so beware.	1147	thing, so beware.
956		1148
957	=back	1149	=back
958		1150
		1151	=head2 WATCHER STATES
		1152
		1153	There are various watcher states mentioned throughout this manual -
		1154	active, pending and so on. In this section these states and the rules to
		1155	transition between them will be described in more detail - and while these
		1156	rules might look complicated, they usually do "the right thing".
		1157
		1158	=over 4
		1159
		1160	=item initialiased
		1161
		1162	Before a watcher can be registered with the event looop it has to be
		1163	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1164	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1165
		1166	In this state it is simply some block of memory that is suitable for use
		1167	in an event loop. It can be moved around, freed, reused etc. at will.
		1168
		1169	=item started/running/active
		1170
		1171	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1172	property of the event loop, and is actively waiting for events. While in
		1173	this state it cannot be accessed (except in a few documented ways), moved,
		1174	freed or anything else - the only legal thing is to keep a pointer to it,
		1175	and call libev functions on it that are documented to work on active watchers.
		1176
		1177	=item pending
		1178
		1179	If a watcher is active and libev determines that an event it is interested
		1180	in has occurred (such as a timer expiring), it will become pending. It will
		1181	stay in this pending state until either it is stopped or its callback is
		1182	about to be invoked, so it is not normally pending inside the watcher
		1183	callback.
		1184
		1185	The watcher might or might not be active while it is pending (for example,
		1186	an expired non-repeating timer can be pending but no longer active). If it
		1187	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1188	but it is still property of the event loop at this time, so cannot be
		1189	moved, freed or reused. And if it is active the rules described in the
		1190	previous item still apply.
		1191
		1192	It is also possible to feed an event on a watcher that is not active (e.g.
		1193	via C<ev_feed_event>), in which case it becomes pending without being
		1194	active.
		1195
		1196	=item stopped
		1197
		1198	A watcher can be stopped implicitly by libev (in which case it might still
		1199	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1200	latter will clear any pending state the watcher might be in, regardless
		1201	of whether it was active or not, so stopping a watcher explicitly before
		1202	freeing it is often a good idea.
		1203
		1204	While stopped (and not pending) the watcher is essentially in the
		1205	initialised state, that is it can be reused, moved, modified in any way
		1206	you wish.
		1207
		1208	=back
		1209
959	=head2 GENERIC WATCHER FUNCTIONS	1210	=head2 GENERIC WATCHER FUNCTIONS
960		1211
961	=over 4	1212	=over 4
962		1213
963	=item C<ev_init> (ev_TYPE *watcher, callback)	1214	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
979		1230
980	ev_io w;	1231	ev_io w;
981	ev_init (&w, my_cb);	1232	ev_init (&w, my_cb);
982	ev_io_set (&w, STDIN_FILENO, EV_READ);	1233	ev_io_set (&w, STDIN_FILENO, EV_READ);
983		1234
984	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1235	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
985		1236
986	This macro initialises the type-specific parts of a watcher. You need to	1237	This macro initialises the type-specific parts of a watcher. You need to
987	call C<ev_init> at least once before you call this macro, but you can	1238	call C<ev_init> at least once before you call this macro, but you can
988	call C<ev_TYPE_set> any number of times. You must not, however, call this	1239	call C<ev_TYPE_set> any number of times. You must not, however, call this
989	macro on a watcher that is active (it can be pending, however, which is a	1240	macro on a watcher that is active (it can be pending, however, which is a
…		…
1002		1253
1003	Example: Initialise and set an C<ev_io> watcher in one step.	1254	Example: Initialise and set an C<ev_io> watcher in one step.
1004		1255
1005	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1256	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1006		1257
1007	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1258	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1008		1259
1009	Starts (activates) the given watcher. Only active watchers will receive	1260	Starts (activates) the given watcher. Only active watchers will receive
1010	events. If the watcher is already active nothing will happen.	1261	events. If the watcher is already active nothing will happen.
1011		1262
1012	Example: Start the C<ev_io> watcher that is being abused as example in this	1263	Example: Start the C<ev_io> watcher that is being abused as example in this
1013	whole section.	1264	whole section.
1014		1265
1015	ev_io_start (EV_DEFAULT_UC, &w);	1266	ev_io_start (EV_DEFAULT_UC, &w);
1016		1267
1017	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1268	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1018		1269
1019	Stops the given watcher if active, and clears the pending status (whether	1270	Stops the given watcher if active, and clears the pending status (whether
1020	the watcher was active or not).	1271	the watcher was active or not).
1021		1272
1022	It is possible that stopped watchers are pending - for example,	1273	It is possible that stopped watchers are pending - for example,
…		…
1047	=item ev_cb_set (ev_TYPE *watcher, callback)	1298	=item ev_cb_set (ev_TYPE *watcher, callback)
1048		1299
1049	Change the callback. You can change the callback at virtually any time	1300	Change the callback. You can change the callback at virtually any time
1050	(modulo threads).	1301	(modulo threads).
1051		1302
1052	=item ev_set_priority (ev_TYPE *watcher, priority)	1303	=item ev_set_priority (ev_TYPE *watcher, int priority)
1053		1304
1054	=item int ev_priority (ev_TYPE *watcher)	1305	=item int ev_priority (ev_TYPE *watcher)
1055		1306
1056	Set and query the priority of the watcher. The priority is a small	1307	Set and query the priority of the watcher. The priority is a small
1057	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1308	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1058	(default: C<-2>). Pending watchers with higher priority will be invoked	1309	(default: C<-2>). Pending watchers with higher priority will be invoked
1059	before watchers with lower priority, but priority will not keep watchers	1310	before watchers with lower priority, but priority will not keep watchers
1060	from being executed (except for C<ev_idle> watchers).	1311	from being executed (except for C<ev_idle> watchers).
1061		1312
1062	This means that priorities are I<only> used for ordering callback
1063	invocation after new events have been received. This is useful, for
1064	example, to reduce latency after idling, or more often, to bind two
1065	watchers on the same event and make sure one is called first.
1066
1067	If you need to suppress invocation when higher priority events are pending	1313	If you need to suppress invocation when higher priority events are pending
1068	you need to look at C<ev_idle> watchers, which provide this functionality.	1314	you need to look at C<ev_idle> watchers, which provide this functionality.
1069		1315
1070	You I<must not> change the priority of a watcher as long as it is active or	1316	You I<must not> change the priority of a watcher as long as it is active or
1071	pending.	1317	pending.
1072
1073	The default priority used by watchers when no priority has been set is
1074	always C<0>, which is supposed to not be too high and not be too low :).
1075		1318
1076	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1319	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1077	fine, as long as you do not mind that the priority value you query might	1320	fine, as long as you do not mind that the priority value you query might
1078	or might not have been clamped to the valid range.	1321	or might not have been clamped to the valid range.
		1322
		1323	The default priority used by watchers when no priority has been set is
		1324	always C<0>, which is supposed to not be too high and not be too low :).
		1325
		1326	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1327	priorities.
1079		1328
1080	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1329	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1081		1330
1082	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1331	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1083	C<loop> nor C<revents> need to be valid as long as the watcher callback	1332	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1090	returns its C<revents> bitset (as if its callback was invoked). If the	1339	returns its C<revents> bitset (as if its callback was invoked). If the
1091	watcher isn't pending it does nothing and returns C<0>.	1340	watcher isn't pending it does nothing and returns C<0>.
1092		1341
1093	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1342	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1094	callback to be invoked, which can be accomplished with this function.	1343	callback to be invoked, which can be accomplished with this function.
		1344
		1345	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1346
		1347	Feeds the given event set into the event loop, as if the specified event
		1348	had happened for the specified watcher (which must be a pointer to an
		1349	initialised but not necessarily started event watcher). Obviously you must
		1350	not free the watcher as long as it has pending events.
		1351
		1352	Stopping the watcher, letting libev invoke it, or calling
		1353	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1354	not started in the first place.
		1355
		1356	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1357	functions that do not need a watcher.
1095		1358
1096	=back	1359	=back
1097		1360
1098		1361
1099	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1148	#include <stddef.h>	1411	#include <stddef.h>
1149		1412
1150	static void	1413	static void
1151	t1_cb (EV_P_ ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1152	{	1415	{
1153	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1154	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1155	}	1418	}
1156		1419
1157	static void	1420	static void
1158	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1159	{	1422	{
1160	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1161	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1162	}	1425	}
		1426
		1427	=head2 WATCHER PRIORITY MODELS
		1428
		1429	Many event loops support I<watcher priorities>, which are usually small
		1430	integers that influence the ordering of event callback invocation
		1431	between watchers in some way, all else being equal.
		1432
		1433	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1434	description for the more technical details such as the actual priority
		1435	range.
		1436
		1437	There are two common ways how these these priorities are being interpreted
		1438	by event loops:
		1439
		1440	In the more common lock-out model, higher priorities "lock out" invocation
		1441	of lower priority watchers, which means as long as higher priority
		1442	watchers receive events, lower priority watchers are not being invoked.
		1443
		1444	The less common only-for-ordering model uses priorities solely to order
		1445	callback invocation within a single event loop iteration: Higher priority
		1446	watchers are invoked before lower priority ones, but they all get invoked
		1447	before polling for new events.
		1448
		1449	Libev uses the second (only-for-ordering) model for all its watchers
		1450	except for idle watchers (which use the lock-out model).
		1451
		1452	The rationale behind this is that implementing the lock-out model for
		1453	watchers is not well supported by most kernel interfaces, and most event
		1454	libraries will just poll for the same events again and again as long as
		1455	their callbacks have not been executed, which is very inefficient in the
		1456	common case of one high-priority watcher locking out a mass of lower
		1457	priority ones.
		1458
		1459	Static (ordering) priorities are most useful when you have two or more
		1460	watchers handling the same resource: a typical usage example is having an
		1461	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1462	timeouts. Under load, data might be received while the program handles
		1463	other jobs, but since timers normally get invoked first, the timeout
		1464	handler will be executed before checking for data. In that case, giving
		1465	the timer a lower priority than the I/O watcher ensures that I/O will be
		1466	handled first even under adverse conditions (which is usually, but not
		1467	always, what you want).
		1468
		1469	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1470	will only be executed when no same or higher priority watchers have
		1471	received events, they can be used to implement the "lock-out" model when
		1472	required.
		1473
		1474	For example, to emulate how many other event libraries handle priorities,
		1475	you can associate an C<ev_idle> watcher to each such watcher, and in
		1476	the normal watcher callback, you just start the idle watcher. The real
		1477	processing is done in the idle watcher callback. This causes libev to
		1478	continuously poll and process kernel event data for the watcher, but when
		1479	the lock-out case is known to be rare (which in turn is rare :), this is
		1480	workable.
		1481
		1482	Usually, however, the lock-out model implemented that way will perform
		1483	miserably under the type of load it was designed to handle. In that case,
		1484	it might be preferable to stop the real watcher before starting the
		1485	idle watcher, so the kernel will not have to process the event in case
		1486	the actual processing will be delayed for considerable time.
		1487
		1488	Here is an example of an I/O watcher that should run at a strictly lower
		1489	priority than the default, and which should only process data when no
		1490	other events are pending:
		1491
		1492	ev_idle idle; // actual processing watcher
		1493	ev_io io; // actual event watcher
		1494
		1495	static void
		1496	io_cb (EV_P_ ev_io *w, int revents)
		1497	{
		1498	// stop the I/O watcher, we received the event, but
		1499	// are not yet ready to handle it.
		1500	ev_io_stop (EV_A_ w);
		1501
		1502	// start the idle watcher to handle the actual event.
		1503	// it will not be executed as long as other watchers
		1504	// with the default priority are receiving events.
		1505	ev_idle_start (EV_A_ &idle);
		1506	}
		1507
		1508	static void
		1509	idle_cb (EV_P_ ev_idle *w, int revents)
		1510	{
		1511	// actual processing
		1512	read (STDIN_FILENO, ...);
		1513
		1514	// have to start the I/O watcher again, as
		1515	// we have handled the event
		1516	ev_io_start (EV_P_ &io);
		1517	}
		1518
		1519	// initialisation
		1520	ev_idle_init (&idle, idle_cb);
		1521	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1522	ev_io_start (EV_DEFAULT_ &io);
		1523
		1524	In the "real" world, it might also be beneficial to start a timer, so that
		1525	low-priority connections can not be locked out forever under load. This
		1526	enables your program to keep a lower latency for important connections
		1527	during short periods of high load, while not completely locking out less
		1528	important ones.
1163		1529
1164		1530
1165	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1166		1532
1167	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1193	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1194	required if you know what you are doing).	1560	required if you know what you are doing).
1195		1561
1196	If you cannot use non-blocking mode, then force the use of a	1562	If you cannot use non-blocking mode, then force the use of a
1197	known-to-be-good backend (at the time of this writing, this includes only	1563	known-to-be-good backend (at the time of this writing, this includes only
1198	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1564	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1565	descriptors for which non-blocking operation makes no sense (such as
		1566	files) - libev doesn't guarantee any specific behaviour in that case.
1199		1567
1200	Another thing you have to watch out for is that it is quite easy to	1568	Another thing you have to watch out for is that it is quite easy to
1201	receive "spurious" readiness notifications, that is your callback might	1569	receive "spurious" readiness notifications, that is your callback might
1202	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1570	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1203	because there is no data. Not only are some backends known to create a	1571	because there is no data. Not only are some backends known to create a
…		…
1268		1636
1269	So when you encounter spurious, unexplained daemon exits, make sure you	1637	So when you encounter spurious, unexplained daemon exits, make sure you
1270	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1638	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1271	somewhere, as that would have given you a big clue).	1639	somewhere, as that would have given you a big clue).
1272		1640
		1641	=head3 The special problem of accept()ing when you can't
		1642
		1643	Many implementations of the POSIX C<accept> function (for example,
		1644	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1645	connection from the pending queue in all error cases.
		1646
		1647	For example, larger servers often run out of file descriptors (because
		1648	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1649	rejecting the connection, leading to libev signalling readiness on
		1650	the next iteration again (the connection still exists after all), and
		1651	typically causing the program to loop at 100% CPU usage.
		1652
		1653	Unfortunately, the set of errors that cause this issue differs between
		1654	operating systems, there is usually little the app can do to remedy the
		1655	situation, and no known thread-safe method of removing the connection to
		1656	cope with overload is known (to me).
		1657
		1658	One of the easiest ways to handle this situation is to just ignore it
		1659	- when the program encounters an overload, it will just loop until the
		1660	situation is over. While this is a form of busy waiting, no OS offers an
		1661	event-based way to handle this situation, so it's the best one can do.
		1662
		1663	A better way to handle the situation is to log any errors other than
		1664	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1665	messages, and continue as usual, which at least gives the user an idea of
		1666	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1667	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1668	usage.
		1669
		1670	If your program is single-threaded, then you could also keep a dummy file
		1671	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1672	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1673	close that fd, and create a new dummy fd. This will gracefully refuse
		1674	clients under typical overload conditions.
		1675
		1676	The last way to handle it is to simply log the error and C<exit>, as
		1677	is often done with C<malloc> failures, but this results in an easy
		1678	opportunity for a DoS attack.
1273		1679
1274	=head3 Watcher-Specific Functions	1680	=head3 Watcher-Specific Functions
1275		1681
1276	=over 4	1682	=over 4
1277		1683
…		…
1309	...	1715	...
1310	struct ev_loop *loop = ev_default_init (0);	1716	struct ev_loop *loop = ev_default_init (0);
1311	ev_io stdin_readable;	1717	ev_io stdin_readable;
1312	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1718	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1313	ev_io_start (loop, &stdin_readable);	1719	ev_io_start (loop, &stdin_readable);
1314	ev_loop (loop, 0);	1720	ev_run (loop, 0);
1315		1721
1316		1722
1317	=head2 C<ev_timer> - relative and optionally repeating timeouts	1723	=head2 C<ev_timer> - relative and optionally repeating timeouts
1318		1724
1319	Timer watchers are simple relative timers that generate an event after a	1725	Timer watchers are simple relative timers that generate an event after a
…		…
1324	year, it will still time out after (roughly) one hour. "Roughly" because	1730	year, it will still time out after (roughly) one hour. "Roughly" because
1325	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1731	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1326	monotonic clock option helps a lot here).	1732	monotonic clock option helps a lot here).
1327		1733
1328	The callback is guaranteed to be invoked only I<after> its timeout has	1734	The callback is guaranteed to be invoked only I<after> its timeout has
1329	passed, but if multiple timers become ready during the same loop iteration	1735	passed (not I<at>, so on systems with very low-resolution clocks this
1330	then order of execution is undefined.	1736	might introduce a small delay). If multiple timers become ready during the
		1737	same loop iteration then the ones with earlier time-out values are invoked
		1738	before ones of the same priority with later time-out values (but this is
		1739	no longer true when a callback calls C<ev_run> recursively).
1331		1740
1332	=head3 Be smart about timeouts	1741	=head3 Be smart about timeouts
1333		1742
1334	Many real-world problems involve some kind of timeout, usually for error	1743	Many real-world problems involve some kind of timeout, usually for error
1335	recovery. A typical example is an HTTP request - if the other side hangs,	1744	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1379	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1788	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1380	member and C<ev_timer_again>.	1789	member and C<ev_timer_again>.
1381		1790
1382	At start:	1791	At start:
1383		1792
1384	ev_timer_init (timer, callback);	1793	ev_init (timer, callback);
1385	timer->repeat = 60.;	1794	timer->repeat = 60.;
1386	ev_timer_again (loop, timer);	1795	ev_timer_again (loop, timer);
1387		1796
1388	Each time there is some activity:	1797	Each time there is some activity:
1389		1798
…		…
1421	ev_tstamp timeout = last_activity + 60.;	1830	ev_tstamp timeout = last_activity + 60.;
1422		1831
1423	// if last_activity + 60. is older than now, we did time out	1832	// if last_activity + 60. is older than now, we did time out
1424	if (timeout < now)	1833	if (timeout < now)
1425	{	1834	{
1426	// timeout occured, take action	1835	// timeout occurred, take action
1427	}	1836	}
1428	else	1837	else
1429	{	1838	{
1430	// callback was invoked, but there was some activity, re-arm	1839	// callback was invoked, but there was some activity, re-arm
1431	// the watcher to fire in last_activity + 60, which is	1840	// the watcher to fire in last_activity + 60, which is
…		…
1451		1860
1452	To start the timer, simply initialise the watcher and set C<last_activity>	1861	To start the timer, simply initialise the watcher and set C<last_activity>
1453	to the current time (meaning we just have some activity :), then call the	1862	to the current time (meaning we just have some activity :), then call the
1454	callback, which will "do the right thing" and start the timer:	1863	callback, which will "do the right thing" and start the timer:
1455		1864
1456	ev_timer_init (timer, callback);	1865	ev_init (timer, callback);
1457	last_activity = ev_now (loop);	1866	last_activity = ev_now (loop);
1458	callback (loop, timer, EV_TIMEOUT);	1867	callback (loop, timer, EV_TIMER);
1459		1868
1460	And when there is some activity, simply store the current time in	1869	And when there is some activity, simply store the current time in
1461	C<last_activity>, no libev calls at all:	1870	C<last_activity>, no libev calls at all:
1462		1871
1463	last_actiivty = ev_now (loop);	1872	last_activity = ev_now (loop);
1464		1873
1465	This technique is slightly more complex, but in most cases where the	1874	This technique is slightly more complex, but in most cases where the
1466	time-out is unlikely to be triggered, much more efficient.	1875	time-out is unlikely to be triggered, much more efficient.
1467		1876
1468	Changing the timeout is trivial as well (if it isn't hard-coded in the	1877	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1506		1915
1507	=head3 The special problem of time updates	1916	=head3 The special problem of time updates
1508		1917
1509	Establishing the current time is a costly operation (it usually takes at	1918	Establishing the current time is a costly operation (it usually takes at
1510	least two system calls): EV therefore updates its idea of the current	1919	least two system calls): EV therefore updates its idea of the current
1511	time only before and after C<ev_loop> collects new events, which causes a	1920	time only before and after C<ev_run> collects new events, which causes a
1512	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1921	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1513	lots of events in one iteration.	1922	lots of events in one iteration.
1514		1923
1515	The relative timeouts are calculated relative to the C<ev_now ()>	1924	The relative timeouts are calculated relative to the C<ev_now ()>
1516	time. This is usually the right thing as this timestamp refers to the time	1925	time. This is usually the right thing as this timestamp refers to the time
…		…
1522		1931
1523	If the event loop is suspended for a long time, you can also force an	1932	If the event loop is suspended for a long time, you can also force an
1524	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1933	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1525	()>.	1934	()>.
1526		1935
		1936	=head3 The special problems of suspended animation
		1937
		1938	When you leave the server world it is quite customary to hit machines that
		1939	can suspend/hibernate - what happens to the clocks during such a suspend?
		1940
		1941	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1942	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1943	to run until the system is suspended, but they will not advance while the
		1944	system is suspended. That means, on resume, it will be as if the program
		1945	was frozen for a few seconds, but the suspend time will not be counted
		1946	towards C<ev_timer> when a monotonic clock source is used. The real time
		1947	clock advanced as expected, but if it is used as sole clocksource, then a
		1948	long suspend would be detected as a time jump by libev, and timers would
		1949	be adjusted accordingly.
		1950
		1951	I would not be surprised to see different behaviour in different between
		1952	operating systems, OS versions or even different hardware.
		1953
		1954	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1955	time jump in the monotonic clocks and the realtime clock. If the program
		1956	is suspended for a very long time, and monotonic clock sources are in use,
		1957	then you can expect C<ev_timer>s to expire as the full suspension time
		1958	will be counted towards the timers. When no monotonic clock source is in
		1959	use, then libev will again assume a timejump and adjust accordingly.
		1960
		1961	It might be beneficial for this latter case to call C<ev_suspend>
		1962	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1963	deterministic behaviour in this case (you can do nothing against
		1964	C<SIGSTOP>).
		1965
1527	=head3 Watcher-Specific Functions and Data Members	1966	=head3 Watcher-Specific Functions and Data Members
1528		1967
1529	=over 4	1968	=over 4
1530		1969
1531	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1970	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1554	If the timer is started but non-repeating, stop it (as if it timed out).	1993	If the timer is started but non-repeating, stop it (as if it timed out).
1555		1994
1556	If the timer is repeating, either start it if necessary (with the	1995	If the timer is repeating, either start it if necessary (with the
1557	C<repeat> value), or reset the running timer to the C<repeat> value.	1996	C<repeat> value), or reset the running timer to the C<repeat> value.
1558		1997
1559	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1998	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1560	usage example.	1999	usage example.
		2000
		2001	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2002
		2003	Returns the remaining time until a timer fires. If the timer is active,
		2004	then this time is relative to the current event loop time, otherwise it's
		2005	the timeout value currently configured.
		2006
		2007	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2008	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2009	will return C<4>. When the timer expires and is restarted, it will return
		2010	roughly C<7> (likely slightly less as callback invocation takes some time,
		2011	too), and so on.
1561		2012
1562	=item ev_tstamp repeat [read-write]	2013	=item ev_tstamp repeat [read-write]
1563		2014
1564	The current C<repeat> value. Will be used each time the watcher times out	2015	The current C<repeat> value. Will be used each time the watcher times out
1565	or C<ev_timer_again> is called, and determines the next timeout (if any),	2016	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1591	}	2042	}
1592		2043
1593	ev_timer mytimer;	2044	ev_timer mytimer;
1594	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2045	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1595	ev_timer_again (&mytimer); /* start timer */	2046	ev_timer_again (&mytimer); /* start timer */
1596	ev_loop (loop, 0);	2047	ev_run (loop, 0);
1597		2048
1598	// and in some piece of code that gets executed on any "activity":	2049	// and in some piece of code that gets executed on any "activity":
1599	// reset the timeout to start ticking again at 10 seconds	2050	// reset the timeout to start ticking again at 10 seconds
1600	ev_timer_again (&mytimer);	2051	ev_timer_again (&mytimer);
1601		2052
…		…
1624	timers, such as triggering an event on each "midnight, local time", or	2075	timers, such as triggering an event on each "midnight, local time", or
1625	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2076	other complicated rules. This cannot be done with C<ev_timer> watchers, as
1626	those cannot react to time jumps.	2077	those cannot react to time jumps.
1627		2078
1628	As with timers, the callback is guaranteed to be invoked only when the	2079	As with timers, the callback is guaranteed to be invoked only when the
1629	point in time where it is supposed to trigger has passed, but if multiple	2080	point in time where it is supposed to trigger has passed. If multiple
1630	periodic timers become ready during the same loop iteration, then order of	2081	timers become ready during the same loop iteration then the ones with
1631	execution is undefined.	2082	earlier time-out values are invoked before ones with later time-out values
		2083	(but this is no longer true when a callback calls C<ev_run> recursively).
1632		2084
1633	=head3 Watcher-Specific Functions and Data Members	2085	=head3 Watcher-Specific Functions and Data Members
1634		2086
1635	=over 4	2087	=over 4
1636		2088
…		…
1764	Example: Call a callback every hour, or, more precisely, whenever the	2216	Example: Call a callback every hour, or, more precisely, whenever the
1765	system time is divisible by 3600. The callback invocation times have	2217	system time is divisible by 3600. The callback invocation times have
1766	potentially a lot of jitter, but good long-term stability.	2218	potentially a lot of jitter, but good long-term stability.
1767		2219
1768	static void	2220	static void
1769	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2221	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1770	{	2222	{
1771	... its now a full hour (UTC, or TAI or whatever your clock follows)	2223	... its now a full hour (UTC, or TAI or whatever your clock follows)
1772	}	2224	}
1773		2225
1774	ev_periodic hourly_tick;	2226	ev_periodic hourly_tick;
…		…
1800	Signal watchers will trigger an event when the process receives a specific	2252	Signal watchers will trigger an event when the process receives a specific
1801	signal one or more times. Even though signals are very asynchronous, libev	2253	signal one or more times. Even though signals are very asynchronous, libev
1802	will try it's best to deliver signals synchronously, i.e. as part of the	2254	will try it's best to deliver signals synchronously, i.e. as part of the
1803	normal event processing, like any other event.	2255	normal event processing, like any other event.
1804		2256
1805	If you want signals asynchronously, just use C<sigaction> as you would	2257	If you want signals to be delivered truly asynchronously, just use
1806	do without libev and forget about sharing the signal. You can even use	2258	C<sigaction> as you would do without libev and forget about sharing
1807	C<ev_async> from a signal handler to synchronously wake up an event loop.	2259	the signal. You can even use C<ev_async> from a signal handler to
		2260	synchronously wake up an event loop.
1808		2261
1809	You can configure as many watchers as you like per signal. Only when the	2262	You can configure as many watchers as you like for the same signal, but
		2263	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2264	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2265	C<SIGINT> in both the default loop and another loop at the same time. At
		2266	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2267
1810	first watcher gets started will libev actually register a signal handler	2268	When the first watcher gets started will libev actually register something
1811	with the kernel (thus it coexists with your own signal handlers as long as	2269	with the kernel (thus it coexists with your own signal handlers as long as
1812	you don't register any with libev for the same signal). Similarly, when	2270	you don't register any with libev for the same signal).
1813	the last signal watcher for a signal is stopped, libev will reset the
1814	signal handler to SIG_DFL (regardless of what it was set to before).
1815		2271
1816	If possible and supported, libev will install its handlers with	2272	If possible and supported, libev will install its handlers with
1817	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2273	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1818	interrupted. If you have a problem with system calls getting interrupted by	2274	not be unduly interrupted. If you have a problem with system calls getting
1819	signals you can block all signals in an C<ev_check> watcher and unblock	2275	interrupted by signals you can block all signals in an C<ev_check> watcher
1820	them in an C<ev_prepare> watcher.	2276	and unblock them in an C<ev_prepare> watcher.
		2277
		2278	=head3 The special problem of inheritance over fork/execve/pthread_create
		2279
		2280	Both the signal mask (C<sigprocmask>) and the signal disposition
		2281	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2282	stopping it again), that is, libev might or might not block the signal,
		2283	and might or might not set or restore the installed signal handler.
		2284
		2285	While this does not matter for the signal disposition (libev never
		2286	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2287	C<execve>), this matters for the signal mask: many programs do not expect
		2288	certain signals to be blocked.
		2289
		2290	This means that before calling C<exec> (from the child) you should reset
		2291	the signal mask to whatever "default" you expect (all clear is a good
		2292	choice usually).
		2293
		2294	The simplest way to ensure that the signal mask is reset in the child is
		2295	to install a fork handler with C<pthread_atfork> that resets it. That will
		2296	catch fork calls done by libraries (such as the libc) as well.
		2297
		2298	In current versions of libev, the signal will not be blocked indefinitely
		2299	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2300	the window of opportunity for problems, it will not go away, as libev
		2301	I<has> to modify the signal mask, at least temporarily.
		2302
		2303	So I can't stress this enough: I<If you do not reset your signal mask when
		2304	you expect it to be empty, you have a race condition in your code>. This
		2305	is not a libev-specific thing, this is true for most event libraries.
1821		2306
1822	=head3 Watcher-Specific Functions and Data Members	2307	=head3 Watcher-Specific Functions and Data Members
1823		2308
1824	=over 4	2309	=over 4
1825		2310
…		…
1841	Example: Try to exit cleanly on SIGINT.	2326	Example: Try to exit cleanly on SIGINT.
1842		2327
1843	static void	2328	static void
1844	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2329	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1845	{	2330	{
1846	ev_unloop (loop, EVUNLOOP_ALL);	2331	ev_break (loop, EVBREAK_ALL);
1847	}	2332	}
1848		2333
1849	ev_signal signal_watcher;	2334	ev_signal signal_watcher;
1850	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2335	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1851	ev_signal_start (loop, &signal_watcher);	2336	ev_signal_start (loop, &signal_watcher);
…		…
1857	some child status changes (most typically when a child of yours dies or	2342	some child status changes (most typically when a child of yours dies or
1858	exits). It is permissible to install a child watcher I<after> the child	2343	exits). It is permissible to install a child watcher I<after> the child
1859	has been forked (which implies it might have already exited), as long	2344	has been forked (which implies it might have already exited), as long
1860	as the event loop isn't entered (or is continued from a watcher), i.e.,	2345	as the event loop isn't entered (or is continued from a watcher), i.e.,
1861	forking and then immediately registering a watcher for the child is fine,	2346	forking and then immediately registering a watcher for the child is fine,
1862	but forking and registering a watcher a few event loop iterations later is	2347	but forking and registering a watcher a few event loop iterations later or
1863	not.	2348	in the next callback invocation is not.
1864		2349
1865	Only the default event loop is capable of handling signals, and therefore	2350	Only the default event loop is capable of handling signals, and therefore
1866	you can only register child watchers in the default event loop.	2351	you can only register child watchers in the default event loop.
1867		2352
		2353	Due to some design glitches inside libev, child watchers will always be
		2354	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2355	libev)
		2356
1868	=head3 Process Interaction	2357	=head3 Process Interaction
1869		2358
1870	Libev grabs C<SIGCHLD> as soon as the default event loop is	2359	Libev grabs C<SIGCHLD> as soon as the default event loop is
1871	initialised. This is necessary to guarantee proper behaviour even if	2360	initialised. This is necessary to guarantee proper behaviour even if the
1872	the first child watcher is started after the child exits. The occurrence	2361	first child watcher is started after the child exits. The occurrence
1873	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2362	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1874	synchronously as part of the event loop processing. Libev always reaps all	2363	synchronously as part of the event loop processing. Libev always reaps all
1875	children, even ones not watched.	2364	children, even ones not watched.
1876		2365
1877	=head3 Overriding the Built-In Processing	2366	=head3 Overriding the Built-In Processing
…		…
1887	=head3 Stopping the Child Watcher	2376	=head3 Stopping the Child Watcher
1888		2377
1889	Currently, the child watcher never gets stopped, even when the	2378	Currently, the child watcher never gets stopped, even when the
1890	child terminates, so normally one needs to stop the watcher in the	2379	child terminates, so normally one needs to stop the watcher in the
1891	callback. Future versions of libev might stop the watcher automatically	2380	callback. Future versions of libev might stop the watcher automatically
1892	when a child exit is detected.	2381	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2382	problem).
1893		2383
1894	=head3 Watcher-Specific Functions and Data Members	2384	=head3 Watcher-Specific Functions and Data Members
1895		2385
1896	=over 4	2386	=over 4
1897		2387
…		…
2223	// no longer anything immediate to do.	2713	// no longer anything immediate to do.
2224	}	2714	}
2225		2715
2226	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2716	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2227	ev_idle_init (idle_watcher, idle_cb);	2717	ev_idle_init (idle_watcher, idle_cb);
2228	ev_idle_start (loop, idle_cb);	2718	ev_idle_start (loop, idle_watcher);
2229		2719
2230		2720
2231	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2721	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2232		2722
2233	Prepare and check watchers are usually (but not always) used in pairs:	2723	Prepare and check watchers are usually (but not always) used in pairs:
2234	prepare watchers get invoked before the process blocks and check watchers	2724	prepare watchers get invoked before the process blocks and check watchers
2235	afterwards.	2725	afterwards.
2236		2726
2237	You I<must not> call C<ev_loop> or similar functions that enter	2727	You I<must not> call C<ev_run> or similar functions that enter
2238	the current event loop from either C<ev_prepare> or C<ev_check>	2728	the current event loop from either C<ev_prepare> or C<ev_check>
2239	watchers. Other loops than the current one are fine, however. The	2729	watchers. Other loops than the current one are fine, however. The
2240	rationale behind this is that you do not need to check for recursion in	2730	rationale behind this is that you do not need to check for recursion in
2241	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2731	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2242	C<ev_check> so if you have one watcher of each kind they will always be	2732	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2326	struct pollfd fds [nfd];	2816	struct pollfd fds [nfd];
2327	// actual code will need to loop here and realloc etc.	2817	// actual code will need to loop here and realloc etc.
2328	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2818	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2329		2819
2330	/* the callback is illegal, but won't be called as we stop during check */	2820	/* the callback is illegal, but won't be called as we stop during check */
2331	ev_timer_init (&tw, 0, timeout * 1e-3);	2821	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2332	ev_timer_start (loop, &tw);	2822	ev_timer_start (loop, &tw);
2333		2823
2334	// create one ev_io per pollfd	2824	// create one ev_io per pollfd
2335	for (int i = 0; i < nfd; ++i)	2825	for (int i = 0; i < nfd; ++i)
2336	{	2826	{
…		…
2410		2900
2411	if (timeout >= 0)	2901	if (timeout >= 0)
2412	// create/start timer	2902	// create/start timer
2413		2903
2414	// poll	2904	// poll
2415	ev_loop (EV_A_ 0);	2905	ev_run (EV_A_ 0);
2416		2906
2417	// stop timer again	2907	// stop timer again
2418	if (timeout >= 0)	2908	if (timeout >= 0)
2419	ev_timer_stop (EV_A_ &to);	2909	ev_timer_stop (EV_A_ &to);
2420		2910
…		…
2498	if you do not want that, you need to temporarily stop the embed watcher).	2988	if you do not want that, you need to temporarily stop the embed watcher).
2499		2989
2500	=item ev_embed_sweep (loop, ev_embed *)	2990	=item ev_embed_sweep (loop, ev_embed *)
2501		2991
2502	Make a single, non-blocking sweep over the embedded loop. This works	2992	Make a single, non-blocking sweep over the embedded loop. This works
2503	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2993	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2504	appropriate way for embedded loops.	2994	appropriate way for embedded loops.
2505		2995
2506	=item struct ev_loop *other [read-only]	2996	=item struct ev_loop *other [read-only]
2507		2997
2508	The embedded event loop.	2998	The embedded event loop.
…		…
2566	event loop blocks next and before C<ev_check> watchers are being called,	3056	event loop blocks next and before C<ev_check> watchers are being called,
2567	and only in the child after the fork. If whoever good citizen calling	3057	and only in the child after the fork. If whoever good citizen calling
2568	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3058	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2569	handlers will be invoked, too, of course.	3059	handlers will be invoked, too, of course.
2570		3060
		3061	=head3 The special problem of life after fork - how is it possible?
		3062
		3063	Most uses of C<fork()> consist of forking, then some simple calls to set
		3064	up/change the process environment, followed by a call to C<exec()>. This
		3065	sequence should be handled by libev without any problems.
		3066
		3067	This changes when the application actually wants to do event handling
		3068	in the child, or both parent in child, in effect "continuing" after the
		3069	fork.
		3070
		3071	The default mode of operation (for libev, with application help to detect
		3072	forks) is to duplicate all the state in the child, as would be expected
		3073	when I<either> the parent I<or> the child process continues.
		3074
		3075	When both processes want to continue using libev, then this is usually the
		3076	wrong result. In that case, usually one process (typically the parent) is
		3077	supposed to continue with all watchers in place as before, while the other
		3078	process typically wants to start fresh, i.e. without any active watchers.
		3079
		3080	The cleanest and most efficient way to achieve that with libev is to
		3081	simply create a new event loop, which of course will be "empty", and
		3082	use that for new watchers. This has the advantage of not touching more
		3083	memory than necessary, and thus avoiding the copy-on-write, and the
		3084	disadvantage of having to use multiple event loops (which do not support
		3085	signal watchers).
		3086
		3087	When this is not possible, or you want to use the default loop for
		3088	other reasons, then in the process that wants to start "fresh", call
		3089	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3090	Destroying the default loop will "orphan" (not stop) all registered
		3091	watchers, so you have to be careful not to execute code that modifies
		3092	those watchers. Note also that in that case, you have to re-register any
		3093	signal watchers.
		3094
2571	=head3 Watcher-Specific Functions and Data Members	3095	=head3 Watcher-Specific Functions and Data Members
2572		3096
2573	=over 4	3097	=over 4
2574		3098
2575	=item ev_fork_init (ev_signal *, callback)	3099	=item ev_fork_init (ev_fork *, callback)
2576		3100
2577	Initialises and configures the fork watcher - it has no parameters of any	3101	Initialises and configures the fork watcher - it has no parameters of any
2578	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3102	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2579	believe me.	3103	believe me.
2580		3104
2581	=back	3105	=back
2582		3106
2583		3107
		3108	=head2 C<ev_cleanup> - even the best things end
		3109
		3110	Cleanup watchers are called just before the event loop they are registered
		3111	with is being destroyed.
		3112
		3113	While there is no guarantee that the event loop gets destroyed, cleanup
		3114	watchers provide a convenient method to install cleanup hooks for your
		3115	program, worker threads and so on - you just to make sure to destroy the
		3116	loop when you want them to be invoked.
		3117
		3118	=head3 Watcher-Specific Functions and Data Members
		3119
		3120	=over 4
		3121
		3122	=item ev_cleanup_init (ev_cleanup *, callback)
		3123
		3124	Initialises and configures the cleanup watcher - it has no parameters of
		3125	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3126	pointless, believe me.
		3127
		3128	=back
		3129
		3130	Example: Register an atexit handler to destroy the default loop, so any
		3131	cleanup functions are called.
		3132
		3133	static void
		3134	program_exits (void)
		3135	{
		3136	ev_loop_destroy (EV_DEFAULT_UC);
		3137	}
		3138
		3139	...
		3140	atexit (program_exits);
		3141
		3142
2584	=head2 C<ev_async> - how to wake up another event loop	3143	=head2 C<ev_async> - how to wake up an event loop
2585		3144
2586	In general, you cannot use an C<ev_loop> from multiple threads or other	3145	In general, you cannot use an C<ev_run> from multiple threads or other
2587	asynchronous sources such as signal handlers (as opposed to multiple event	3146	asynchronous sources such as signal handlers (as opposed to multiple event
2588	loops - those are of course safe to use in different threads).	3147	loops - those are of course safe to use in different threads).
2589		3148
2590	Sometimes, however, you need to wake up another event loop you do not	3149	Sometimes, however, you need to wake up an event loop you do not control,
2591	control, for example because it belongs to another thread. This is what	3150	for example because it belongs to another thread. This is what C<ev_async>
2592	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3151	watchers do: as long as the C<ev_async> watcher is active, you can signal
2593	can signal it by calling C<ev_async_send>, which is thread- and signal	3152	it by calling C<ev_async_send>, which is thread- and signal safe.
2594	safe.
2595		3153
2596	This functionality is very similar to C<ev_signal> watchers, as signals,	3154	This functionality is very similar to C<ev_signal> watchers, as signals,
2597	too, are asynchronous in nature, and signals, too, will be compressed	3155	too, are asynchronous in nature, and signals, too, will be compressed
2598	(i.e. the number of callback invocations may be less than the number of	3156	(i.e. the number of callback invocations may be less than the number of
2599	C<ev_async_sent> calls).	3157	C<ev_async_sent> calls).
…		…
2604	=head3 Queueing	3162	=head3 Queueing
2605		3163
2606	C<ev_async> does not support queueing of data in any way. The reason	3164	C<ev_async> does not support queueing of data in any way. The reason
2607	is that the author does not know of a simple (or any) algorithm for a	3165	is that the author does not know of a simple (or any) algorithm for a
2608	multiple-writer-single-reader queue that works in all cases and doesn't	3166	multiple-writer-single-reader queue that works in all cases and doesn't
2609	need elaborate support such as pthreads.	3167	need elaborate support such as pthreads or unportable memory access
		3168	semantics.
2610		3169
2611	That means that if you want to queue data, you have to provide your own	3170	That means that if you want to queue data, you have to provide your own
2612	queue. But at least I can tell you how to implement locking around your	3171	queue. But at least I can tell you how to implement locking around your
2613	queue:	3172	queue:
2614		3173
…		…
2753		3312
2754	If C<timeout> is less than 0, then no timeout watcher will be	3313	If C<timeout> is less than 0, then no timeout watcher will be
2755	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3314	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2756	repeat = 0) will be started. C<0> is a valid timeout.	3315	repeat = 0) will be started. C<0> is a valid timeout.
2757		3316
2758	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3317	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2759	passed an C<revents> set like normal event callbacks (a combination of	3318	passed an C<revents> set like normal event callbacks (a combination of
2760	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3319	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2761	value passed to C<ev_once>. Note that it is possible to receive I<both>	3320	value passed to C<ev_once>. Note that it is possible to receive I<both>
2762	a timeout and an io event at the same time - you probably should give io	3321	a timeout and an io event at the same time - you probably should give io
2763	events precedence.	3322	events precedence.
2764		3323
2765	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3324	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2766		3325
2767	static void stdin_ready (int revents, void *arg)	3326	static void stdin_ready (int revents, void *arg)
2768	{	3327	{
2769	if (revents & EV_READ)	3328	if (revents & EV_READ)
2770	/* stdin might have data for us, joy! */;	3329	/* stdin might have data for us, joy! */;
2771	else if (revents & EV_TIMEOUT)	3330	else if (revents & EV_TIMER)
2772	/* doh, nothing entered */;	3331	/* doh, nothing entered */;
2773	}	3332	}
2774		3333
2775	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3334	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2776		3335
2777	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2778
2779	Feeds the given event set into the event loop, as if the specified event
2780	had happened for the specified watcher (which must be a pointer to an
2781	initialised but not necessarily started event watcher).
2782
2783	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3336	=item ev_feed_fd_event (loop, int fd, int revents)
2784		3337
2785	Feed an event on the given fd, as if a file descriptor backend detected	3338	Feed an event on the given fd, as if a file descriptor backend detected
2786	the given events it.	3339	the given events it.
2787		3340
2788	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3341	=item ev_feed_signal_event (loop, int signum)
2789		3342
2790	Feed an event as if the given signal occurred (C<loop> must be the default	3343	Feed an event as if the given signal occurred (C<loop> must be the default
2791	loop!).	3344	loop!).
2792		3345
2793	=back	3346	=back
…		…
2873		3426
2874	=over 4	3427	=over 4
2875		3428
2876	=item ev::TYPE::TYPE ()	3429	=item ev::TYPE::TYPE ()
2877		3430
2878	=item ev::TYPE::TYPE (struct ev_loop *)	3431	=item ev::TYPE::TYPE (loop)
2879		3432
2880	=item ev::TYPE::~TYPE	3433	=item ev::TYPE::~TYPE
2881		3434
2882	The constructor (optionally) takes an event loop to associate the watcher	3435	The constructor (optionally) takes an event loop to associate the watcher
2883	with. If it is omitted, it will use C<EV_DEFAULT>.	3436	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2916	myclass obj;	3469	myclass obj;
2917	ev::io iow;	3470	ev::io iow;
2918	iow.set <myclass, &myclass::io_cb> (&obj);	3471	iow.set <myclass, &myclass::io_cb> (&obj);
2919		3472
2920	=item w->set (object *)	3473	=item w->set (object *)
2921
2922	This is an B<experimental> feature that might go away in a future version.
2923		3474
2924	This is a variation of a method callback - leaving out the method to call	3475	This is a variation of a method callback - leaving out the method to call
2925	will default the method to C<operator ()>, which makes it possible to use	3476	will default the method to C<operator ()>, which makes it possible to use
2926	functor objects without having to manually specify the C<operator ()> all	3477	functor objects without having to manually specify the C<operator ()> all
2927	the time. Incidentally, you can then also leave out the template argument	3478	the time. Incidentally, you can then also leave out the template argument
…		…
2960	Example: Use a plain function as callback.	3511	Example: Use a plain function as callback.
2961		3512
2962	static void io_cb (ev::io &w, int revents) { }	3513	static void io_cb (ev::io &w, int revents) { }
2963	iow.set <io_cb> ();	3514	iow.set <io_cb> ();
2964		3515
2965	=item w->set (struct ev_loop *)	3516	=item w->set (loop)
2966		3517
2967	Associates a different C<struct ev_loop> with this watcher. You can only	3518	Associates a different C<struct ev_loop> with this watcher. You can only
2968	do this when the watcher is inactive (and not pending either).	3519	do this when the watcher is inactive (and not pending either).
2969		3520
2970	=item w->set ([arguments])	3521	=item w->set ([arguments])
2971		3522
2972	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3523	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2973	called at least once. Unlike the C counterpart, an active watcher gets	3524	method or a suitable start method must be called at least once. Unlike the
2974	automatically stopped and restarted when reconfiguring it with this	3525	C counterpart, an active watcher gets automatically stopped and restarted
2975	method.	3526	when reconfiguring it with this method.
2976		3527
2977	=item w->start ()	3528	=item w->start ()
2978		3529
2979	Starts the watcher. Note that there is no C<loop> argument, as the	3530	Starts the watcher. Note that there is no C<loop> argument, as the
2980	constructor already stores the event loop.	3531	constructor already stores the event loop.
2981		3532
		3533	=item w->start ([arguments])
		3534
		3535	Instead of calling C<set> and C<start> methods separately, it is often
		3536	convenient to wrap them in one call. Uses the same type of arguments as
		3537	the configure C<set> method of the watcher.
		3538
2982	=item w->stop ()	3539	=item w->stop ()
2983		3540
2984	Stops the watcher if it is active. Again, no C<loop> argument.	3541	Stops the watcher if it is active. Again, no C<loop> argument.
2985		3542
2986	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3543	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2998		3555
2999	=back	3556	=back
3000		3557
3001	=back	3558	=back
3002		3559
3003	Example: Define a class with an IO and idle watcher, start one of them in	3560	Example: Define a class with two I/O and idle watchers, start the I/O
3004	the constructor.	3561	watchers in the constructor.
3005		3562
3006	class myclass	3563	class myclass
3007	{	3564	{
3008	ev::io io ; void io_cb (ev::io &w, int revents);	3565	ev::io io ; void io_cb (ev::io &w, int revents);
		3566	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3009	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3567	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3010		3568
3011	myclass (int fd)	3569	myclass (int fd)
3012	{	3570	{
3013	io .set <myclass, &myclass::io_cb > (this);	3571	io .set <myclass, &myclass::io_cb > (this);
		3572	io2 .set <myclass, &myclass::io2_cb > (this);
3014	idle.set <myclass, &myclass::idle_cb> (this);	3573	idle.set <myclass, &myclass::idle_cb> (this);
3015		3574
3016	io.start (fd, ev::READ);	3575	io.set (fd, ev::WRITE); // configure the watcher
		3576	io.start (); // start it whenever convenient
		3577
		3578	io2.start (fd, ev::READ); // set + start in one call
3017	}	3579	}
3018	};	3580	};
3019		3581
3020		3582
3021	=head1 OTHER LANGUAGE BINDINGS	3583	=head1 OTHER LANGUAGE BINDINGS
…		…
3067	=item Ocaml	3629	=item Ocaml
3068		3630
3069	Erkki Seppala has written Ocaml bindings for libev, to be found at	3631	Erkki Seppala has written Ocaml bindings for libev, to be found at
3070	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3632	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3071		3633
		3634	=item Lua
		3635
		3636	Brian Maher has written a partial interface to libev for lua (at the
		3637	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3638	L<http://github.com/brimworks/lua-ev>.
		3639
3072	=back	3640	=back
3073		3641
3074		3642
3075	=head1 MACRO MAGIC	3643	=head1 MACRO MAGIC
3076		3644
…		…
3089	loop argument"). The C<EV_A> form is used when this is the sole argument,	3657	loop argument"). The C<EV_A> form is used when this is the sole argument,
3090	C<EV_A_> is used when other arguments are following. Example:	3658	C<EV_A_> is used when other arguments are following. Example:
3091		3659
3092	ev_unref (EV_A);	3660	ev_unref (EV_A);
3093	ev_timer_add (EV_A_ watcher);	3661	ev_timer_add (EV_A_ watcher);
3094	ev_loop (EV_A_ 0);	3662	ev_run (EV_A_ 0);
3095		3663
3096	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3664	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3097	which is often provided by the following macro.	3665	which is often provided by the following macro.
3098		3666
3099	=item C<EV_P>, C<EV_P_>	3667	=item C<EV_P>, C<EV_P_>
…		…
3139	}	3707	}
3140		3708
3141	ev_check check;	3709	ev_check check;
3142	ev_check_init (&check, check_cb);	3710	ev_check_init (&check, check_cb);
3143	ev_check_start (EV_DEFAULT_ &check);	3711	ev_check_start (EV_DEFAULT_ &check);
3144	ev_loop (EV_DEFAULT_ 0);	3712	ev_run (EV_DEFAULT_ 0);
3145		3713
3146	=head1 EMBEDDING	3714	=head1 EMBEDDING
3147		3715
3148	Libev can (and often is) directly embedded into host	3716	Libev can (and often is) directly embedded into host
3149	applications. Examples of applications that embed it include the Deliantra	3717	applications. Examples of applications that embed it include the Deliantra
…		…
3229	libev.m4	3797	libev.m4
3230		3798
3231	=head2 PREPROCESSOR SYMBOLS/MACROS	3799	=head2 PREPROCESSOR SYMBOLS/MACROS
3232		3800
3233	Libev can be configured via a variety of preprocessor symbols you have to	3801	Libev can be configured via a variety of preprocessor symbols you have to
3234	define before including any of its files. The default in the absence of	3802	define before including (or compiling) any of its files. The default in
3235	autoconf is documented for every option.	3803	the absence of autoconf is documented for every option.
		3804
		3805	Symbols marked with "(h)" do not change the ABI, and can have different
		3806	values when compiling libev vs. including F<ev.h>, so it is permissible
		3807	to redefine them before including F<ev.h> without breaking compatibility
		3808	to a compiled library. All other symbols change the ABI, which means all
		3809	users of libev and the libev code itself must be compiled with compatible
		3810	settings.
3236		3811
3237	=over 4	3812	=over 4
3238		3813
		3814	=item EV_COMPAT3 (h)
		3815
		3816	Backwards compatibility is a major concern for libev. This is why this
		3817	release of libev comes with wrappers for the functions and symbols that
		3818	have been renamed between libev version 3 and 4.
		3819
		3820	You can disable these wrappers (to test compatibility with future
		3821	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3822	sources. This has the additional advantage that you can drop the C<struct>
		3823	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3824	typedef in that case.
		3825
		3826	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3827	and in some even more future version the compatibility code will be
		3828	removed completely.
		3829
3239	=item EV_STANDALONE	3830	=item EV_STANDALONE (h)
3240		3831
3241	Must always be C<1> if you do not use autoconf configuration, which	3832	Must always be C<1> if you do not use autoconf configuration, which
3242	keeps libev from including F<config.h>, and it also defines dummy	3833	keeps libev from including F<config.h>, and it also defines dummy
3243	implementations for some libevent functions (such as logging, which is not	3834	implementations for some libevent functions (such as logging, which is not
3244	supported). It will also not define any of the structs usually found in	3835	supported). It will also not define any of the structs usually found in
3245	F<event.h> that are not directly supported by the libev core alone.	3836	F<event.h> that are not directly supported by the libev core alone.
3246		3837
3247	In stanbdalone mode, libev will still try to automatically deduce the	3838	In standalone mode, libev will still try to automatically deduce the
3248	configuration, but has to be more conservative.	3839	configuration, but has to be more conservative.
3249		3840
3250	=item EV_USE_MONOTONIC	3841	=item EV_USE_MONOTONIC
3251		3842
3252	If defined to be C<1>, libev will try to detect the availability of the	3843	If defined to be C<1>, libev will try to detect the availability of the
…		…
3317	be used is the winsock select). This means that it will call	3908	be used is the winsock select). This means that it will call
3318	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3909	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3319	it is assumed that all these functions actually work on fds, even	3910	it is assumed that all these functions actually work on fds, even
3320	on win32. Should not be defined on non-win32 platforms.	3911	on win32. Should not be defined on non-win32 platforms.
3321		3912
3322	=item EV_FD_TO_WIN32_HANDLE	3913	=item EV_FD_TO_WIN32_HANDLE(fd)
3323		3914
3324	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3915	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3325	file descriptors to socket handles. When not defining this symbol (the	3916	file descriptors to socket handles. When not defining this symbol (the
3326	default), then libev will call C<_get_osfhandle>, which is usually	3917	default), then libev will call C<_get_osfhandle>, which is usually
3327	correct. In some cases, programs use their own file descriptor management,	3918	correct. In some cases, programs use their own file descriptor management,
3328	in which case they can provide this function to map fds to socket handles.	3919	in which case they can provide this function to map fds to socket handles.
		3920
		3921	=item EV_WIN32_HANDLE_TO_FD(handle)
		3922
		3923	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3924	using the standard C<_open_osfhandle> function. For programs implementing
		3925	their own fd to handle mapping, overwriting this function makes it easier
		3926	to do so. This can be done by defining this macro to an appropriate value.
		3927
		3928	=item EV_WIN32_CLOSE_FD(fd)
		3929
		3930	If programs implement their own fd to handle mapping on win32, then this
		3931	macro can be used to override the C<close> function, useful to unregister
		3932	file descriptors again. Note that the replacement function has to close
		3933	the underlying OS handle.
3329		3934
3330	=item EV_USE_POLL	3935	=item EV_USE_POLL
3331		3936
3332	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3937	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3333	backend. Otherwise it will be enabled on non-win32 platforms. It	3938	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3380	as well as for signal and thread safety in C<ev_async> watchers.	3985	as well as for signal and thread safety in C<ev_async> watchers.
3381		3986
3382	In the absence of this define, libev will use C<sig_atomic_t volatile>	3987	In the absence of this define, libev will use C<sig_atomic_t volatile>
3383	(from F<signal.h>), which is usually good enough on most platforms.	3988	(from F<signal.h>), which is usually good enough on most platforms.
3384		3989
3385	=item EV_H	3990	=item EV_H (h)
3386		3991
3387	The name of the F<ev.h> header file used to include it. The default if	3992	The name of the F<ev.h> header file used to include it. The default if
3388	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3993	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3389	used to virtually rename the F<ev.h> header file in case of conflicts.	3994	used to virtually rename the F<ev.h> header file in case of conflicts.
3390		3995
3391	=item EV_CONFIG_H	3996	=item EV_CONFIG_H (h)
3392		3997
3393	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3998	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3394	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3999	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3395	C<EV_H>, above.	4000	C<EV_H>, above.
3396		4001
3397	=item EV_EVENT_H	4002	=item EV_EVENT_H (h)
3398		4003
3399	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4004	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3400	of how the F<event.h> header can be found, the default is C<"event.h">.	4005	of how the F<event.h> header can be found, the default is C<"event.h">.
3401		4006
3402	=item EV_PROTOTYPES	4007	=item EV_PROTOTYPES (h)
3403		4008
3404	If defined to be C<0>, then F<ev.h> will not define any function	4009	If defined to be C<0>, then F<ev.h> will not define any function
3405	prototypes, but still define all the structs and other symbols. This is	4010	prototypes, but still define all the structs and other symbols. This is
3406	occasionally useful if you want to provide your own wrapper functions	4011	occasionally useful if you want to provide your own wrapper functions
3407	around libev functions.	4012	around libev functions.
…		…
3429	fine.	4034	fine.
3430		4035
3431	If your embedding application does not need any priorities, defining these	4036	If your embedding application does not need any priorities, defining these
3432	both to C<0> will save some memory and CPU.	4037	both to C<0> will save some memory and CPU.
3433		4038
3434	=item EV_PERIODIC_ENABLE	4039	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4040	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4041	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3435		4042
3436	If undefined or defined to be C<1>, then periodic timers are supported. If	4043	If undefined or defined to be C<1> (and the platform supports it), then
3437	defined to be C<0>, then they are not. Disabling them saves a few kB of	4044	the respective watcher type is supported. If defined to be C<0>, then it
3438	code.	4045	is not. Disabling watcher types mainly saves code size.
3439		4046
3440	=item EV_IDLE_ENABLE	4047	=item EV_FEATURES
3441
3442	If undefined or defined to be C<1>, then idle watchers are supported. If
3443	defined to be C<0>, then they are not. Disabling them saves a few kB of
3444	code.
3445
3446	=item EV_EMBED_ENABLE
3447
3448	If undefined or defined to be C<1>, then embed watchers are supported. If
3449	defined to be C<0>, then they are not. Embed watchers rely on most other
3450	watcher types, which therefore must not be disabled.
3451
3452	=item EV_STAT_ENABLE
3453
3454	If undefined or defined to be C<1>, then stat watchers are supported. If
3455	defined to be C<0>, then they are not.
3456
3457	=item EV_FORK_ENABLE
3458
3459	If undefined or defined to be C<1>, then fork watchers are supported. If
3460	defined to be C<0>, then they are not.
3461
3462	=item EV_ASYNC_ENABLE
3463
3464	If undefined or defined to be C<1>, then async watchers are supported. If
3465	defined to be C<0>, then they are not.
3466
3467	=item EV_MINIMAL
3468		4048
3469	If you need to shave off some kilobytes of code at the expense of some	4049	If you need to shave off some kilobytes of code at the expense of some
3470	speed, define this symbol to C<1>. Currently this is used to override some	4050	speed (but with the full API), you can define this symbol to request
3471	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4051	certain subsets of functionality. The default is to enable all features
3472	much smaller 2-heap for timer management over the default 4-heap.	4052	that can be enabled on the platform.
		4053
		4054	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4055	with some broad features you want) and then selectively re-enable
		4056	additional parts you want, for example if you want everything minimal,
		4057	but multiple event loop support, async and child watchers and the poll
		4058	backend, use this:
		4059
		4060	#define EV_FEATURES 0
		4061	#define EV_MULTIPLICITY 1
		4062	#define EV_USE_POLL 1
		4063	#define EV_CHILD_ENABLE 1
		4064	#define EV_ASYNC_ENABLE 1
		4065
		4066	The actual value is a bitset, it can be a combination of the following
		4067	values:
		4068
		4069	=over 4
		4070
		4071	=item C<1> - faster/larger code
		4072
		4073	Use larger code to speed up some operations.
		4074
		4075	Currently this is used to override some inlining decisions (enlarging the
		4076	code size by roughly 30% on amd64).
		4077
		4078	When optimising for size, use of compiler flags such as C<-Os> with
		4079	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4080	assertions.
		4081
		4082	=item C<2> - faster/larger data structures
		4083
		4084	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4085	hash table sizes and so on. This will usually further increase code size
		4086	and can additionally have an effect on the size of data structures at
		4087	runtime.
		4088
		4089	=item C<4> - full API configuration
		4090
		4091	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4092	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4093
		4094	=item C<8> - full API
		4095
		4096	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4097	details on which parts of the API are still available without this
		4098	feature, and do not complain if this subset changes over time.
		4099
		4100	=item C<16> - enable all optional watcher types
		4101
		4102	Enables all optional watcher types. If you want to selectively enable
		4103	only some watcher types other than I/O and timers (e.g. prepare,
		4104	embed, async, child...) you can enable them manually by defining
		4105	C<EV_watchertype_ENABLE> to C<1> instead.
		4106
		4107	=item C<32> - enable all backends
		4108
		4109	This enables all backends - without this feature, you need to enable at
		4110	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4111
		4112	=item C<64> - enable OS-specific "helper" APIs
		4113
		4114	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4115	default.
		4116
		4117	=back
		4118
		4119	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4120	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4121	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4122	watchers, timers and monotonic clock support.
		4123
		4124	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4125	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4126	your program might be left out as well - a binary starting a timer and an
		4127	I/O watcher then might come out at only 5Kb.
		4128
		4129	=item EV_AVOID_STDIO
		4130
		4131	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4132	functions (printf, scanf, perror etc.). This will increase the code size
		4133	somewhat, but if your program doesn't otherwise depend on stdio and your
		4134	libc allows it, this avoids linking in the stdio library which is quite
		4135	big.
		4136
		4137	Note that error messages might become less precise when this option is
		4138	enabled.
		4139
		4140	=item EV_NSIG
		4141
		4142	The highest supported signal number, +1 (or, the number of
		4143	signals): Normally, libev tries to deduce the maximum number of signals
		4144	automatically, but sometimes this fails, in which case it can be
		4145	specified. Also, using a lower number than detected (C<32> should be
		4146	good for about any system in existence) can save some memory, as libev
		4147	statically allocates some 12-24 bytes per signal number.
3473		4148
3474	=item EV_PID_HASHSIZE	4149	=item EV_PID_HASHSIZE
3475		4150
3476	C<ev_child> watchers use a small hash table to distribute workload by	4151	C<ev_child> watchers use a small hash table to distribute workload by
3477	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4152	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3478	than enough. If you need to manage thousands of children you might want to	4153	usually more than enough. If you need to manage thousands of children you
3479	increase this value (I<must> be a power of two).	4154	might want to increase this value (I<must> be a power of two).
3480		4155
3481	=item EV_INOTIFY_HASHSIZE	4156	=item EV_INOTIFY_HASHSIZE
3482		4157
3483	C<ev_stat> watchers use a small hash table to distribute workload by	4158	C<ev_stat> watchers use a small hash table to distribute workload by
3484	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4159	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3485	usually more than enough. If you need to manage thousands of C<ev_stat>	4160	disabled), usually more than enough. If you need to manage thousands of
3486	watchers you might want to increase this value (I<must> be a power of	4161	C<ev_stat> watchers you might want to increase this value (I<must> be a
3487	two).	4162	power of two).
3488		4163
3489	=item EV_USE_4HEAP	4164	=item EV_USE_4HEAP
3490		4165
3491	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4166	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3492	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4167	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3493	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4168	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3494	faster performance with many (thousands) of watchers.	4169	faster performance with many (thousands) of watchers.
3495		4170
3496	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4171	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3497	(disabled).	4172	will be C<0>.
3498		4173
3499	=item EV_HEAP_CACHE_AT	4174	=item EV_HEAP_CACHE_AT
3500		4175
3501	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4176	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3502	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4177	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3503	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4178	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3504	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4179	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3505	but avoids random read accesses on heap changes. This improves performance	4180	but avoids random read accesses on heap changes. This improves performance
3506	noticeably with many (hundreds) of watchers.	4181	noticeably with many (hundreds) of watchers.
3507		4182
3508	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4183	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3509	(disabled).	4184	will be C<0>.
3510		4185
3511	=item EV_VERIFY	4186	=item EV_VERIFY
3512		4187
3513	Controls how much internal verification (see C<ev_loop_verify ()>) will	4188	Controls how much internal verification (see C<ev_verify ()>) will
3514	be done: If set to C<0>, no internal verification code will be compiled	4189	be done: If set to C<0>, no internal verification code will be compiled
3515	in. If set to C<1>, then verification code will be compiled in, but not	4190	in. If set to C<1>, then verification code will be compiled in, but not
3516	called. If set to C<2>, then the internal verification code will be	4191	called. If set to C<2>, then the internal verification code will be
3517	called once per loop, which can slow down libev. If set to C<3>, then the	4192	called once per loop, which can slow down libev. If set to C<3>, then the
3518	verification code will be called very frequently, which will slow down	4193	verification code will be called very frequently, which will slow down
3519	libev considerably.	4194	libev considerably.
3520		4195
3521	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3522	C<0>.	4197	will be C<0>.
3523		4198
3524	=item EV_COMMON	4199	=item EV_COMMON
3525		4200
3526	By default, all watchers have a C<void *data> member. By redefining	4201	By default, all watchers have a C<void *data> member. By redefining
3527	this macro to a something else you can include more and other types of	4202	this macro to something else you can include more and other types of
3528	members. You have to define it each time you include one of the files,	4203	members. You have to define it each time you include one of the files,
3529	though, and it must be identical each time.	4204	though, and it must be identical each time.
3530		4205
3531	For example, the perl EV module uses something like this:	4206	For example, the perl EV module uses something like this:
3532		4207
…		…
3585	file.	4260	file.
3586		4261
3587	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4262	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3588	that everybody includes and which overrides some configure choices:	4263	that everybody includes and which overrides some configure choices:
3589		4264
3590	#define EV_MINIMAL 1	4265	#define EV_FEATURES 8
3591	#define EV_USE_POLL 0	4266	#define EV_USE_SELECT 1
3592	#define EV_MULTIPLICITY 0
3593	#define EV_PERIODIC_ENABLE 0	4267	#define EV_PREPARE_ENABLE 1
		4268	#define EV_IDLE_ENABLE 1
3594	#define EV_STAT_ENABLE 0	4269	#define EV_SIGNAL_ENABLE 1
3595	#define EV_FORK_ENABLE 0	4270	#define EV_CHILD_ENABLE 1
		4271	#define EV_USE_STDEXCEPT 0
3596	#define EV_CONFIG_H <config.h>	4272	#define EV_CONFIG_H <config.h>
3597	#define EV_MINPRI 0
3598	#define EV_MAXPRI 0
3599		4273
3600	#include "ev++.h"	4274	#include "ev++.h"
3601		4275
3602	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4276	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3603		4277
…		…
3663	default loop and triggering an C<ev_async> watcher from the default loop	4337	default loop and triggering an C<ev_async> watcher from the default loop
3664	watcher callback into the event loop interested in the signal.	4338	watcher callback into the event loop interested in the signal.
3665		4339
3666	=back	4340	=back
3667		4341
		4342	=head4 THREAD LOCKING EXAMPLE
		4343
		4344	Here is a fictitious example of how to run an event loop in a different
		4345	thread than where callbacks are being invoked and watchers are
		4346	created/added/removed.
		4347
		4348	For a real-world example, see the C<EV::Loop::Async> perl module,
		4349	which uses exactly this technique (which is suited for many high-level
		4350	languages).
		4351
		4352	The example uses a pthread mutex to protect the loop data, a condition
		4353	variable to wait for callback invocations, an async watcher to notify the
		4354	event loop thread and an unspecified mechanism to wake up the main thread.
		4355
		4356	First, you need to associate some data with the event loop:
		4357
		4358	typedef struct {
		4359	mutex_t lock; /* global loop lock */
		4360	ev_async async_w;
		4361	thread_t tid;
		4362	cond_t invoke_cv;
		4363	} userdata;
		4364
		4365	void prepare_loop (EV_P)
		4366	{
		4367	// for simplicity, we use a static userdata struct.
		4368	static userdata u;
		4369
		4370	ev_async_init (&u->async_w, async_cb);
		4371	ev_async_start (EV_A_ &u->async_w);
		4372
		4373	pthread_mutex_init (&u->lock, 0);
		4374	pthread_cond_init (&u->invoke_cv, 0);
		4375
		4376	// now associate this with the loop
		4377	ev_set_userdata (EV_A_ u);
		4378	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4379	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4380
		4381	// then create the thread running ev_loop
		4382	pthread_create (&u->tid, 0, l_run, EV_A);
		4383	}
		4384
		4385	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4386	solely to wake up the event loop so it takes notice of any new watchers
		4387	that might have been added:
		4388
		4389	static void
		4390	async_cb (EV_P_ ev_async *w, int revents)
		4391	{
		4392	// just used for the side effects
		4393	}
		4394
		4395	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4396	protecting the loop data, respectively.
		4397
		4398	static void
		4399	l_release (EV_P)
		4400	{
		4401	userdata *u = ev_userdata (EV_A);
		4402	pthread_mutex_unlock (&u->lock);
		4403	}
		4404
		4405	static void
		4406	l_acquire (EV_P)
		4407	{
		4408	userdata *u = ev_userdata (EV_A);
		4409	pthread_mutex_lock (&u->lock);
		4410	}
		4411
		4412	The event loop thread first acquires the mutex, and then jumps straight
		4413	into C<ev_run>:
		4414
		4415	void *
		4416	l_run (void *thr_arg)
		4417	{
		4418	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4419
		4420	l_acquire (EV_A);
		4421	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4422	ev_run (EV_A_ 0);
		4423	l_release (EV_A);
		4424
		4425	return 0;
		4426	}
		4427
		4428	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4429	signal the main thread via some unspecified mechanism (signals? pipe
		4430	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4431	have been called (in a while loop because a) spurious wakeups are possible
		4432	and b) skipping inter-thread-communication when there are no pending
		4433	watchers is very beneficial):
		4434
		4435	static void
		4436	l_invoke (EV_P)
		4437	{
		4438	userdata *u = ev_userdata (EV_A);
		4439
		4440	while (ev_pending_count (EV_A))
		4441	{
		4442	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4443	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4444	}
		4445	}
		4446
		4447	Now, whenever the main thread gets told to invoke pending watchers, it
		4448	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4449	thread to continue:
		4450
		4451	static void
		4452	real_invoke_pending (EV_P)
		4453	{
		4454	userdata *u = ev_userdata (EV_A);
		4455
		4456	pthread_mutex_lock (&u->lock);
		4457	ev_invoke_pending (EV_A);
		4458	pthread_cond_signal (&u->invoke_cv);
		4459	pthread_mutex_unlock (&u->lock);
		4460	}
		4461
		4462	Whenever you want to start/stop a watcher or do other modifications to an
		4463	event loop, you will now have to lock:
		4464
		4465	ev_timer timeout_watcher;
		4466	userdata *u = ev_userdata (EV_A);
		4467
		4468	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4469
		4470	pthread_mutex_lock (&u->lock);
		4471	ev_timer_start (EV_A_ &timeout_watcher);
		4472	ev_async_send (EV_A_ &u->async_w);
		4473	pthread_mutex_unlock (&u->lock);
		4474
		4475	Note that sending the C<ev_async> watcher is required because otherwise
		4476	an event loop currently blocking in the kernel will have no knowledge
		4477	about the newly added timer. By waking up the loop it will pick up any new
		4478	watchers in the next event loop iteration.
		4479
3668	=head3 COROUTINES	4480	=head3 COROUTINES
3669		4481
3670	Libev is very accommodating to coroutines ("cooperative threads"):	4482	Libev is very accommodating to coroutines ("cooperative threads"):
3671	libev fully supports nesting calls to its functions from different	4483	libev fully supports nesting calls to its functions from different
3672	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4484	coroutines (e.g. you can call C<ev_run> on the same loop from two
3673	different coroutines, and switch freely between both coroutines running the	4485	different coroutines, and switch freely between both coroutines running
3674	loop, as long as you don't confuse yourself). The only exception is that	4486	the loop, as long as you don't confuse yourself). The only exception is
3675	you must not do this from C<ev_periodic> reschedule callbacks.	4487	that you must not do this from C<ev_periodic> reschedule callbacks.
3676		4488
3677	Care has been taken to ensure that libev does not keep local state inside	4489	Care has been taken to ensure that libev does not keep local state inside
3678	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4490	C<ev_run>, and other calls do not usually allow for coroutine switches as
3679	they do not call any callbacks.	4491	they do not call any callbacks.
3680		4492
3681	=head2 COMPILER WARNINGS	4493	=head2 COMPILER WARNINGS
3682		4494
3683	Depending on your compiler and compiler settings, you might get no or a	4495	Depending on your compiler and compiler settings, you might get no or a
…		…
3694	maintainable.	4506	maintainable.
3695		4507
3696	And of course, some compiler warnings are just plain stupid, or simply	4508	And of course, some compiler warnings are just plain stupid, or simply
3697	wrong (because they don't actually warn about the condition their message	4509	wrong (because they don't actually warn about the condition their message
3698	seems to warn about). For example, certain older gcc versions had some	4510	seems to warn about). For example, certain older gcc versions had some
3699	warnings that resulted an extreme number of false positives. These have	4511	warnings that resulted in an extreme number of false positives. These have
3700	been fixed, but some people still insist on making code warn-free with	4512	been fixed, but some people still insist on making code warn-free with
3701	such buggy versions.	4513	such buggy versions.
3702		4514
3703	While libev is written to generate as few warnings as possible,	4515	While libev is written to generate as few warnings as possible,
3704	"warn-free" code is not a goal, and it is recommended not to build libev	4516	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3740	I suggest using suppression lists.	4552	I suggest using suppression lists.
3741		4553
3742		4554
3743	=head1 PORTABILITY NOTES	4555	=head1 PORTABILITY NOTES
3744		4556
		4557	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4558
		4559	GNU/Linux is the only common platform that supports 64 bit file/large file
		4560	interfaces but I<disables> them by default.
		4561
		4562	That means that libev compiled in the default environment doesn't support
		4563	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4564
		4565	Unfortunately, many programs try to work around this GNU/Linux issue
		4566	by enabling the large file API, which makes them incompatible with the
		4567	standard libev compiled for their system.
		4568
		4569	Likewise, libev cannot enable the large file API itself as this would
		4570	suddenly make it incompatible to the default compile time environment,
		4571	i.e. all programs not using special compile switches.
		4572
		4573	=head2 OS/X AND DARWIN BUGS
		4574
		4575	The whole thing is a bug if you ask me - basically any system interface
		4576	you touch is broken, whether it is locales, poll, kqueue or even the
		4577	OpenGL drivers.
		4578
		4579	=head3 C<kqueue> is buggy
		4580
		4581	The kqueue syscall is broken in all known versions - most versions support
		4582	only sockets, many support pipes.
		4583
		4584	Libev tries to work around this by not using C<kqueue> by default on this
		4585	rotten platform, but of course you can still ask for it when creating a
		4586	loop - embedding a socket-only kqueue loop into a select-based one is
		4587	probably going to work well.
		4588
		4589	=head3 C<poll> is buggy
		4590
		4591	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4592	implementation by something calling C<kqueue> internally around the 10.5.6
		4593	release, so now C<kqueue> I<and> C<poll> are broken.
		4594
		4595	Libev tries to work around this by not using C<poll> by default on
		4596	this rotten platform, but of course you can still ask for it when creating
		4597	a loop.
		4598
		4599	=head3 C<select> is buggy
		4600
		4601	All that's left is C<select>, and of course Apple found a way to fuck this
		4602	one up as well: On OS/X, C<select> actively limits the number of file
		4603	descriptors you can pass in to 1024 - your program suddenly crashes when
		4604	you use more.
		4605
		4606	There is an undocumented "workaround" for this - defining
		4607	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4608	work on OS/X.
		4609
		4610	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4611
		4612	=head3 C<errno> reentrancy
		4613
		4614	The default compile environment on Solaris is unfortunately so
		4615	thread-unsafe that you can't even use components/libraries compiled
		4616	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4617	defined by default. A valid, if stupid, implementation choice.
		4618
		4619	If you want to use libev in threaded environments you have to make sure
		4620	it's compiled with C<_REENTRANT> defined.
		4621
		4622	=head3 Event port backend
		4623
		4624	The scalable event interface for Solaris is called "event
		4625	ports". Unfortunately, this mechanism is very buggy in all major
		4626	releases. If you run into high CPU usage, your program freezes or you get
		4627	a large number of spurious wakeups, make sure you have all the relevant
		4628	and latest kernel patches applied. No, I don't know which ones, but there
		4629	are multiple ones to apply, and afterwards, event ports actually work
		4630	great.
		4631
		4632	If you can't get it to work, you can try running the program by setting
		4633	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4634	C<select> backends.
		4635
		4636	=head2 AIX POLL BUG
		4637
		4638	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4639	this by trying to avoid the poll backend altogether (i.e. it's not even
		4640	compiled in), which normally isn't a big problem as C<select> works fine
		4641	with large bitsets on AIX, and AIX is dead anyway.
		4642
3745	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4643	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4644
		4645	=head3 General issues
3746		4646
3747	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4647	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3748	requires, and its I/O model is fundamentally incompatible with the POSIX	4648	requires, and its I/O model is fundamentally incompatible with the POSIX
3749	model. Libev still offers limited functionality on this platform in	4649	model. Libev still offers limited functionality on this platform in
3750	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4650	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3751	descriptors. This only applies when using Win32 natively, not when using	4651	descriptors. This only applies when using Win32 natively, not when using
3752	e.g. cygwin.	4652	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4653	as every compielr comes with a slightly differently broken/incompatible
		4654	environment.
3753		4655
3754	Lifting these limitations would basically require the full	4656	Lifting these limitations would basically require the full
3755	re-implementation of the I/O system. If you are into these kinds of	4657	re-implementation of the I/O system. If you are into this kind of thing,
3756	things, then note that glib does exactly that for you in a very portable	4658	then note that glib does exactly that for you in a very portable way (note
3757	way (note also that glib is the slowest event library known to man).	4659	also that glib is the slowest event library known to man).
3758		4660
3759	There is no supported compilation method available on windows except	4661	There is no supported compilation method available on windows except
3760	embedding it into other applications.	4662	embedding it into other applications.
		4663
		4664	Sensible signal handling is officially unsupported by Microsoft - libev
		4665	tries its best, but under most conditions, signals will simply not work.
3761		4666
3762	Not a libev limitation but worth mentioning: windows apparently doesn't	4667	Not a libev limitation but worth mentioning: windows apparently doesn't
3763	accept large writes: instead of resulting in a partial write, windows will	4668	accept large writes: instead of resulting in a partial write, windows will
3764	either accept everything or return C<ENOBUFS> if the buffer is too large,	4669	either accept everything or return C<ENOBUFS> if the buffer is too large,
3765	so make sure you only write small amounts into your sockets (less than a	4670	so make sure you only write small amounts into your sockets (less than a
…		…
3770	the abysmal performance of winsockets, using a large number of sockets	4675	the abysmal performance of winsockets, using a large number of sockets
3771	is not recommended (and not reasonable). If your program needs to use	4676	is not recommended (and not reasonable). If your program needs to use
3772	more than a hundred or so sockets, then likely it needs to use a totally	4677	more than a hundred or so sockets, then likely it needs to use a totally
3773	different implementation for windows, as libev offers the POSIX readiness	4678	different implementation for windows, as libev offers the POSIX readiness
3774	notification model, which cannot be implemented efficiently on windows	4679	notification model, which cannot be implemented efficiently on windows
3775	(Microsoft monopoly games).	4680	(due to Microsoft monopoly games).
3776		4681
3777	A typical way to use libev under windows is to embed it (see the embedding	4682	A typical way to use libev under windows is to embed it (see the embedding
3778	section for details) and use the following F<evwrap.h> header file instead	4683	section for details) and use the following F<evwrap.h> header file instead
3779	of F<ev.h>:	4684	of F<ev.h>:
3780		4685
…		…
3787	you do I<not> compile the F<ev.c> or any other embedded source files!):	4692	you do I<not> compile the F<ev.c> or any other embedded source files!):
3788		4693
3789	#include "evwrap.h"	4694	#include "evwrap.h"
3790	#include "ev.c"	4695	#include "ev.c"
3791		4696
3792	=over 4
3793
3794	=item The winsocket select function	4697	=head3 The winsocket C<select> function
3795		4698
3796	The winsocket C<select> function doesn't follow POSIX in that it	4699	The winsocket C<select> function doesn't follow POSIX in that it
3797	requires socket I<handles> and not socket I<file descriptors> (it is	4700	requires socket I<handles> and not socket I<file descriptors> (it is
3798	also extremely buggy). This makes select very inefficient, and also	4701	also extremely buggy). This makes select very inefficient, and also
3799	requires a mapping from file descriptors to socket handles (the Microsoft	4702	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3808	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4711	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3809		4712
3810	Note that winsockets handling of fd sets is O(n), so you can easily get a	4713	Note that winsockets handling of fd sets is O(n), so you can easily get a
3811	complexity in the O(n²) range when using win32.	4714	complexity in the O(n²) range when using win32.
3812		4715
3813	=item Limited number of file descriptors	4716	=head3 Limited number of file descriptors
3814		4717
3815	Windows has numerous arbitrary (and low) limits on things.	4718	Windows has numerous arbitrary (and low) limits on things.
3816		4719
3817	Early versions of winsocket's select only supported waiting for a maximum	4720	Early versions of winsocket's select only supported waiting for a maximum
3818	of C<64> handles (probably owning to the fact that all windows kernels	4721	of C<64> handles (probably owning to the fact that all windows kernels
3819	can only wait for C<64> things at the same time internally; Microsoft	4722	can only wait for C<64> things at the same time internally; Microsoft
3820	recommends spawning a chain of threads and wait for 63 handles and the	4723	recommends spawning a chain of threads and wait for 63 handles and the
3821	previous thread in each. Great).	4724	previous thread in each. Sounds great!).
3822		4725
3823	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4726	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3824	to some high number (e.g. C<2048>) before compiling the winsocket select	4727	to some high number (e.g. C<2048>) before compiling the winsocket select
3825	call (which might be in libev or elsewhere, for example, perl does its own	4728	call (which might be in libev or elsewhere, for example, perl and many
3826	select emulation on windows).	4729	other interpreters do their own select emulation on windows).
3827		4730
3828	Another limit is the number of file descriptors in the Microsoft runtime	4731	Another limit is the number of file descriptors in the Microsoft runtime
3829	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4732	libraries, which by default is C<64> (there must be a hidden I<64>
3830	or something like this inside Microsoft). You can increase this by calling	4733	fetish or something like this inside Microsoft). You can increase this
3831	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4734	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3832	arbitrary limit), but is broken in many versions of the Microsoft runtime	4735	(another arbitrary limit), but is broken in many versions of the Microsoft
3833	libraries.
3834
3835	This might get you to about C<512> or C<2048> sockets (depending on	4736	runtime libraries. This might get you to about C<512> or C<2048> sockets
3836	windows version and/or the phase of the moon). To get more, you need to	4737	(depending on windows version and/or the phase of the moon). To get more,
3837	wrap all I/O functions and provide your own fd management, but the cost of	4738	you need to wrap all I/O functions and provide your own fd management, but
3838	calling select (O(n²)) will likely make this unworkable.	4739	the cost of calling select (O(n²)) will likely make this unworkable.
3839
3840	=back
3841		4740
3842	=head2 PORTABILITY REQUIREMENTS	4741	=head2 PORTABILITY REQUIREMENTS
3843		4742
3844	In addition to a working ISO-C implementation and of course the	4743	In addition to a working ISO-C implementation and of course the
3845	backend-specific APIs, libev relies on a few additional extensions:	4744	backend-specific APIs, libev relies on a few additional extensions:
…		…
3884	watchers.	4783	watchers.
3885		4784
3886	=item C<double> must hold a time value in seconds with enough accuracy	4785	=item C<double> must hold a time value in seconds with enough accuracy
3887		4786
3888	The type C<double> is used to represent timestamps. It is required to	4787	The type C<double> is used to represent timestamps. It is required to
3889	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4788	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3890	enough for at least into the year 4000. This requirement is fulfilled by	4789	good enough for at least into the year 4000 with millisecond accuracy
		4790	(the design goal for libev). This requirement is overfulfilled by
3891	implementations implementing IEEE 754 (basically all existing ones).	4791	implementations using IEEE 754, which is basically all existing ones. With
		4792	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3892		4793
3893	=back	4794	=back
3894		4795
3895	If you know of other additional requirements drop me a note.	4796	If you know of other additional requirements drop me a note.
3896		4797
…		…
3964	involves iterating over all running async watchers or all signal numbers.	4865	involves iterating over all running async watchers or all signal numbers.
3965		4866
3966	=back	4867	=back
3967		4868
3968		4869
		4870	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4871
		4872	The major version 4 introduced some minor incompatible changes to the API.
		4873
		4874	At the moment, the C<ev.h> header file tries to implement superficial
		4875	compatibility, so most programs should still compile. Those might be
		4876	removed in later versions of libev, so better update early than late.
		4877
		4878	=over 4
		4879
		4880	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4881
		4882	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4883
		4884	ev_loop_destroy (EV_DEFAULT_UC);
		4885	ev_loop_fork (EV_DEFAULT);
		4886
		4887	=item function/symbol renames
		4888
		4889	A number of functions and symbols have been renamed:
		4890
		4891	ev_loop => ev_run
		4892	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4893	EVLOOP_ONESHOT => EVRUN_ONCE
		4894
		4895	ev_unloop => ev_break
		4896	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4897	EVUNLOOP_ONE => EVBREAK_ONE
		4898	EVUNLOOP_ALL => EVBREAK_ALL
		4899
		4900	EV_TIMEOUT => EV_TIMER
		4901
		4902	ev_loop_count => ev_iteration
		4903	ev_loop_depth => ev_depth
		4904	ev_loop_verify => ev_verify
		4905
		4906	Most functions working on C<struct ev_loop> objects don't have an
		4907	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4908	associated constants have been renamed to not collide with the C<struct
		4909	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4910	as all other watcher types. Note that C<ev_loop_fork> is still called
		4911	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4912	typedef.
		4913
		4914	=item C<EV_COMPAT3> backwards compatibility mechanism
		4915
		4916	The backward compatibility mechanism can be controlled by
		4917	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4918	section.
		4919
		4920	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4921
		4922	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4923	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4924	and work, but the library code will of course be larger.
		4925
		4926	=back
		4927
		4928
		4929	=head1 GLOSSARY
		4930
		4931	=over 4
		4932
		4933	=item active
		4934
		4935	A watcher is active as long as it has been started and not yet stopped.
		4936	See L<WATCHER STATES> for details.
		4937
		4938	=item application
		4939
		4940	In this document, an application is whatever is using libev.
		4941
		4942	=item backend
		4943
		4944	The part of the code dealing with the operating system interfaces.
		4945
		4946	=item callback
		4947
		4948	The address of a function that is called when some event has been
		4949	detected. Callbacks are being passed the event loop, the watcher that
		4950	received the event, and the actual event bitset.
		4951
		4952	=item callback/watcher invocation
		4953
		4954	The act of calling the callback associated with a watcher.
		4955
		4956	=item event
		4957
		4958	A change of state of some external event, such as data now being available
		4959	for reading on a file descriptor, time having passed or simply not having
		4960	any other events happening anymore.
		4961
		4962	In libev, events are represented as single bits (such as C<EV_READ> or
		4963	C<EV_TIMER>).
		4964
		4965	=item event library
		4966
		4967	A software package implementing an event model and loop.
		4968
		4969	=item event loop
		4970
		4971	An entity that handles and processes external events and converts them
		4972	into callback invocations.
		4973
		4974	=item event model
		4975
		4976	The model used to describe how an event loop handles and processes
		4977	watchers and events.
		4978
		4979	=item pending
		4980
		4981	A watcher is pending as soon as the corresponding event has been
		4982	detected. See L<WATCHER STATES> for details.
		4983
		4984	=item real time
		4985
		4986	The physical time that is observed. It is apparently strictly monotonic :)
		4987
		4988	=item wall-clock time
		4989
		4990	The time and date as shown on clocks. Unlike real time, it can actually
		4991	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4992	clock.
		4993
		4994	=item watcher
		4995
		4996	A data structure that describes interest in certain events. Watchers need
		4997	to be started (attached to an event loop) before they can receive events.
		4998
		4999	=back
		5000
3969	=head1 AUTHOR	5001	=head1 AUTHOR
3970		5002
3971	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5003	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3972		5004

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines