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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	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
68	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
69	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 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	310	libev 3 had an C<ev_loop> function colliding with the struct name).
284		311
285	The library knows two types of such loops, the I<default> loop, which	312	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	313	supports child process events, and dynamically created event loops which
287	not.	314	do not.
288		315
289	=over 4	316	=over 4
290		317
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		319
293	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
297		330
298	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
299	function.	332	function (or via the C<EV_DEFAULT> macro).
300		333
301	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
304		338
305	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
311		363
312	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		366
315	The following flags are supported:	367	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
331	around bugs.	383	around bugs.
332		384
333	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
334		386
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		389
339	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	399	flag.
349		400
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	402	environment variable.
352		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		425
355	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
380		451
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		454
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
385		459
386	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
…		…
401	of course I<doesn't>, and epoll just loves to report events for totally	475	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	476	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	477	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	478	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	479	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	480	events to filter out spurious ones, recreating the set when required. Last
		481	not least, it also refuses to work with some file descriptors which work
		482	perfectly fine with C<select> (files, many character devices...).
407		483
408	While stopping, setting and starting an I/O watcher in the same iteration	484	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	485	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	486	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	487	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
417	i.e. keep at least one watcher active per fd at all times. Stopping and	493	i.e. keep at least one watcher active per fd at all times. Stopping and
418	starting a watcher (without re-setting it) also usually doesn't cause	494	starting a watcher (without re-setting it) also usually doesn't cause
419	extra overhead. A fork can both result in spurious notifications as well	495	extra overhead. A fork can both result in spurious notifications as well
420	as in libev having to destroy and recreate the epoll object, which can	496	as in libev having to destroy and recreate the epoll object, which can
421	take considerable time and thus should be avoided.	497	take considerable time and thus should be avoided.
		498
		499	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		500	faster than epoll for maybe up to a hundred file descriptors, depending on
		501	the usage. So sad.
422		502
423	While nominally embeddable in other event loops, this feature is broken in	503	While nominally embeddable in other event loops, this feature is broken in
424	all kernel versions tested so far.	504	all kernel versions tested so far.
425		505
426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	506	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
454		534
455	While nominally embeddable in other event loops, this doesn't work	535	While nominally embeddable in other event loops, this doesn't work
456	everywhere, so you might need to test for this. And since it is broken	536	everywhere, so you might need to test for this. And since it is broken
457	almost everywhere, you should only use it when you have a lot of sockets	537	almost everywhere, you should only use it when you have a lot of sockets
458	(for which it usually works), by embedding it into another event loop	538	(for which it usually works), by embedding it into another event loop
459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	539	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
460	using it only for sockets.	540	also broken on OS X)) and, did I mention it, using it only for sockets.
461		541
462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	542	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	543	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
464	C<NOTE_EOF>.	544	C<NOTE_EOF>.
465		545
…		…
500		580
501	It is definitely not recommended to use this flag.	581	It is definitely not recommended to use this flag.
502		582
503	=back	583	=back
504		584
505	If one or more of these are or'ed into the flags value, then only these	585	If one or more of the backend flags are or'ed into the flags value,
506	backends will be tried (in the reverse order as listed here). If none are	586	then only these backends will be tried (in the reverse order as listed
507	specified, all backends in C<ev_recommended_backends ()> will be tried.	587	here). If none are specified, all backends in C<ev_recommended_backends
508		588	()> will be tried.
509	Example: This is the most typical usage.
510
511	if (!ev_default_loop (0))
512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
513
514	Example: Restrict libev to the select and poll backends, and do not allow
515	environment settings to be taken into account:
516
517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
518
519	Example: Use whatever libev has to offer, but make sure that kqueue is
520	used if available (warning, breaks stuff, best use only with your own
521	private event loop and only if you know the OS supports your types of
522	fds):
523
524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
525
526	=item struct ev_loop *ev_loop_new (unsigned int flags)
527
528	Similar to C<ev_default_loop>, but always creates a new event loop that is
529	always distinct from the default loop. Unlike the default loop, it cannot
530	handle signal and child watchers, and attempts to do so will be greeted by
531	undefined behaviour (or a failed assertion if assertions are enabled).
532
533	Note that this function I<is> thread-safe, and the recommended way to use
534	libev with threads is indeed to create one loop per thread, and using the
535	default loop in the "main" or "initial" thread.
536		589
537	Example: Try to create a event loop that uses epoll and nothing else.	590	Example: Try to create a event loop that uses epoll and nothing else.
538		591
539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	592	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
540	if (!epoller)	593	if (!epoller)
541	fatal ("no epoll found here, maybe it hides under your chair");	594	fatal ("no epoll found here, maybe it hides under your chair");
542		595
		596	Example: Use whatever libev has to offer, but make sure that kqueue is
		597	used if available.
		598
		599	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		600
543	=item ev_default_destroy ()	601	=item ev_loop_destroy (loop)
544		602
545	Destroys the default loop again (frees all memory and kernel state	603	Destroys an event loop object (frees all memory and kernel state
546	etc.). None of the active event watchers will be stopped in the normal	604	etc.). None of the active event watchers will be stopped in the normal
547	sense, so e.g. C<ev_is_active> might still return true. It is your	605	sense, so e.g. C<ev_is_active> might still return true. It is your
548	responsibility to either stop all watchers cleanly yourself I<before>	606	responsibility to either stop all watchers cleanly yourself I<before>
549	calling this function, or cope with the fact afterwards (which is usually	607	calling this function, or cope with the fact afterwards (which is usually
550	the easiest thing, you can just ignore the watchers and/or C<free ()> them	608	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
552		610
553	Note that certain global state, such as signal state (and installed signal	611	Note that certain global state, such as signal state (and installed signal
554	handlers), will not be freed by this function, and related watchers (such	612	handlers), will not be freed by this function, and related watchers (such
555	as signal and child watchers) would need to be stopped manually.	613	as signal and child watchers) would need to be stopped manually.
556		614
557	In general it is not advisable to call this function except in the	615	This function is normally used on loop objects allocated by
558	rare occasion where you really need to free e.g. the signal handling	616	C<ev_loop_new>, but it can also be used on the default loop returned by
		617	C<ev_default_loop>, in which case it is not thread-safe.
		618
		619	Note that it is not advisable to call this function on the default loop
		620	except in the rare occasion where you really need to free it's resources.
559	pipe fds. If you need dynamically allocated loops it is better to use	621	If you need dynamically allocated loops it is better to use C<ev_loop_new>
560	C<ev_loop_new> and C<ev_loop_destroy>).	622	and C<ev_loop_destroy>.
561		623
562	=item ev_loop_destroy (loop)	624	=item ev_loop_fork (loop)
563		625
564	Like C<ev_default_destroy>, but destroys an event loop created by an
565	earlier call to C<ev_loop_new>.
566
567	=item ev_default_fork ()
568
569	This function sets a flag that causes subsequent C<ev_loop> iterations	626	This function sets a flag that causes subsequent C<ev_run> iterations to
570	to reinitialise the kernel state for backends that have one. Despite the	627	reinitialise the kernel state for backends that have one. Despite the
571	name, you can call it anytime, but it makes most sense after forking, in	628	name, you can call it anytime, but it makes most sense after forking, in
572	the child process (or both child and parent, but that again makes little	629	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
573	sense). You I<must> call it in the child before using any of the libev	630	child before resuming or calling C<ev_run>.
574	functions, and it will only take effect at the next C<ev_loop> iteration.	631
		632	Again, you I<have> to call it on I<any> loop that you want to re-use after
		633	a fork, I<even if you do not plan to use the loop in the parent>. This is
		634	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		635	during fork.
575		636
576	On the other hand, you only need to call this function in the child	637	On the other hand, you only need to call this function in the child
577	process if and only if you want to use the event library in the child. If	638	process if and only if you want to use the event loop in the child. If
578	you just fork+exec, you don't have to call it at all.	639	you just fork+exec or create a new loop in the child, you don't have to
		640	call it at all (in fact, C<epoll> is so badly broken that it makes a
		641	difference, but libev will usually detect this case on its own and do a
		642	costly reset of the backend).
579		643
580	The function itself is quite fast and it's usually not a problem to call	644	The function itself is quite fast and it's usually not a problem to call
581	it just in case after a fork. To make this easy, the function will fit in	645	it just in case after a fork.
582	quite nicely into a call to C<pthread_atfork>:
583		646
		647	Example: Automate calling C<ev_loop_fork> on the default loop when
		648	using pthreads.
		649
		650	static void
		651	post_fork_child (void)
		652	{
		653	ev_loop_fork (EV_DEFAULT);
		654	}
		655
		656	...
584	pthread_atfork (0, 0, ev_default_fork);	657	pthread_atfork (0, 0, post_fork_child);
585
586	=item ev_loop_fork (loop)
587
588	Like C<ev_default_fork>, but acts on an event loop created by
589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
590	after fork that you want to re-use in the child, and how you do this is
591	entirely your own problem.
592		658
593	=item int ev_is_default_loop (loop)	659	=item int ev_is_default_loop (loop)
594		660
595	Returns true when the given loop is, in fact, the default loop, and false	661	Returns true when the given loop is, in fact, the default loop, and false
596	otherwise.	662	otherwise.
597		663
598	=item unsigned int ev_loop_count (loop)	664	=item unsigned int ev_iteration (loop)
599		665
600	Returns the count of loop iterations for the loop, which is identical to	666	Returns the current iteration count for the event loop, which is identical
601	the number of times libev did poll for new events. It starts at C<0> and	667	to the number of times libev did poll for new events. It starts at C<0>
602	happily wraps around with enough iterations.	668	and happily wraps around with enough iterations.
603		669
604	This value can sometimes be useful as a generation counter of sorts (it	670	This value can sometimes be useful as a generation counter of sorts (it
605	"ticks" the number of loop iterations), as it roughly corresponds with	671	"ticks" the number of loop iterations), as it roughly corresponds with
606	C<ev_prepare> and C<ev_check> calls.	672	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		673	prepare and check phases.
		674
		675	=item unsigned int ev_depth (loop)
		676
		677	Returns the number of times C<ev_run> was entered minus the number of
		678	times C<ev_run> was exited, in other words, the recursion depth.
		679
		680	Outside C<ev_run>, this number is zero. In a callback, this number is
		681	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		682	in which case it is higher.
		683
		684	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		685	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		686	ungentleman-like behaviour unless it's really convenient.
607		687
608	=item unsigned int ev_backend (loop)	688	=item unsigned int ev_backend (loop)
609		689
610	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	690	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
611	use.	691	use.
…		…
620		700
621	=item ev_now_update (loop)	701	=item ev_now_update (loop)
622		702
623	Establishes the current time by querying the kernel, updating the time	703	Establishes the current time by querying the kernel, updating the time
624	returned by C<ev_now ()> in the progress. This is a costly operation and	704	returned by C<ev_now ()> in the progress. This is a costly operation and
625	is usually done automatically within C<ev_loop ()>.	705	is usually done automatically within C<ev_run ()>.
626		706
627	This function is rarely useful, but when some event callback runs for a	707	This function is rarely useful, but when some event callback runs for a
628	very long time without entering the event loop, updating libev's idea of	708	very long time without entering the event loop, updating libev's idea of
629	the current time is a good idea.	709	the current time is a good idea.
630		710
631	See also "The special problem of time updates" in the C<ev_timer> section.	711	See also L<The special problem of time updates> in the C<ev_timer> section.
632		712
		713	=item ev_suspend (loop)
		714
		715	=item ev_resume (loop)
		716
		717	These two functions suspend and resume an event loop, for use when the
		718	loop is not used for a while and timeouts should not be processed.
		719
		720	A typical use case would be an interactive program such as a game: When
		721	the user presses C<^Z> to suspend the game and resumes it an hour later it
		722	would be best to handle timeouts as if no time had actually passed while
		723	the program was suspended. This can be achieved by calling C<ev_suspend>
		724	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		725	C<ev_resume> directly afterwards to resume timer processing.
		726
		727	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		728	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		729	will be rescheduled (that is, they will lose any events that would have
		730	occurred while suspended).
		731
		732	After calling C<ev_suspend> you B<must not> call I<any> function on the
		733	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		734	without a previous call to C<ev_suspend>.
		735
		736	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		737	event loop time (see C<ev_now_update>).
		738
633	=item ev_loop (loop, int flags)	739	=item ev_run (loop, int flags)
634		740
635	Finally, this is it, the event handler. This function usually is called	741	Finally, this is it, the event handler. This function usually is called
636	after you initialised all your watchers and you want to start handling	742	after you have initialised all your watchers and you want to start
637	events.	743	handling events. It will ask the operating system for any new events, call
		744	the watcher callbacks, an then repeat the whole process indefinitely: This
		745	is why event loops are called I<loops>.
638		746
639	If the flags argument is specified as C<0>, it will not return until	747	If the flags argument is specified as C<0>, it will keep handling events
640	either no event watchers are active anymore or C<ev_unloop> was called.	748	until either no event watchers are active anymore or C<ev_break> was
		749	called.
641		750
642	Please note that an explicit C<ev_unloop> is usually better than	751	Please note that an explicit C<ev_break> is usually better than
643	relying on all watchers to be stopped when deciding when a program has	752	relying on all watchers to be stopped when deciding when a program has
644	finished (especially in interactive programs), but having a program	753	finished (especially in interactive programs), but having a program
645	that automatically loops as long as it has to and no longer by virtue	754	that automatically loops as long as it has to and no longer by virtue
646	of relying on its watchers stopping correctly, that is truly a thing of	755	of relying on its watchers stopping correctly, that is truly a thing of
647	beauty.	756	beauty.
648		757
649	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	758	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
650	those events and any already outstanding ones, but will not block your	759	those events and any already outstanding ones, but will not wait and
651	process in case there are no events and will return after one iteration of	760	block your process in case there are no events and will return after one
652	the loop.	761	iteration of the loop. This is sometimes useful to poll and handle new
		762	events while doing lengthy calculations, to keep the program responsive.
653		763
654	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	764	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
655	necessary) and will handle those and any already outstanding ones. It	765	necessary) and will handle those and any already outstanding ones. It
656	will block your process until at least one new event arrives (which could	766	will block your process until at least one new event arrives (which could
657	be an event internal to libev itself, so there is no guarantee that a	767	be an event internal to libev itself, so there is no guarantee that a
658	user-registered callback will be called), and will return after one	768	user-registered callback will be called), and will return after one
659	iteration of the loop.	769	iteration of the loop.
660		770
661	This is useful if you are waiting for some external event in conjunction	771	This is useful if you are waiting for some external event in conjunction
662	with something not expressible using other libev watchers (i.e. "roll your	772	with something not expressible using other libev watchers (i.e. "roll your
663	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	773	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
664	usually a better approach for this kind of thing.	774	usually a better approach for this kind of thing.
665		775
666	Here are the gory details of what C<ev_loop> does:	776	Here are the gory details of what C<ev_run> does:
667		777
		778	- Increment loop depth.
		779	- Reset the ev_break status.
668	- Before the first iteration, call any pending watchers.	780	- Before the first iteration, call any pending watchers.
		781	LOOP:
669	* If EVFLAG_FORKCHECK was used, check for a fork.	782	- If EVFLAG_FORKCHECK was used, check for a fork.
670	- If a fork was detected (by any means), queue and call all fork watchers.	783	- If a fork was detected (by any means), queue and call all fork watchers.
671	- Queue and call all prepare watchers.	784	- Queue and call all prepare watchers.
		785	- If ev_break was called, goto FINISH.
672	- If we have been forked, detach and recreate the kernel state	786	- If we have been forked, detach and recreate the kernel state
673	as to not disturb the other process.	787	as to not disturb the other process.
674	- Update the kernel state with all outstanding changes.	788	- Update the kernel state with all outstanding changes.
675	- Update the "event loop time" (ev_now ()).	789	- Update the "event loop time" (ev_now ()).
676	- Calculate for how long to sleep or block, if at all	790	- Calculate for how long to sleep or block, if at all
677	(active idle watchers, EVLOOP_NONBLOCK or not having	791	(active idle watchers, EVRUN_NOWAIT or not having
678	any active watchers at all will result in not sleeping).	792	any active watchers at all will result in not sleeping).
679	- Sleep if the I/O and timer collect interval say so.	793	- Sleep if the I/O and timer collect interval say so.
		794	- Increment loop iteration counter.
680	- Block the process, waiting for any events.	795	- Block the process, waiting for any events.
681	- Queue all outstanding I/O (fd) events.	796	- Queue all outstanding I/O (fd) events.
682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	797	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
683	- Queue all expired timers.	798	- Queue all expired timers.
684	- Queue all expired periodics.	799	- Queue all expired periodics.
685	- Unless any events are pending now, queue all idle watchers.	800	- Queue all idle watchers with priority higher than that of pending events.
686	- Queue all check watchers.	801	- Queue all check watchers.
687	- Call all queued watchers in reverse order (i.e. check watchers first).	802	- Call all queued watchers in reverse order (i.e. check watchers first).
688	Signals and child watchers are implemented as I/O watchers, and will	803	Signals and child watchers are implemented as I/O watchers, and will
689	be handled here by queueing them when their watcher gets executed.	804	be handled here by queueing them when their watcher gets executed.
690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	805	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
691	were used, or there are no active watchers, return, otherwise	806	were used, or there are no active watchers, goto FINISH, otherwise
692	continue with step *.	807	continue with step LOOP.
		808	FINISH:
		809	- Reset the ev_break status iff it was EVBREAK_ONE.
		810	- Decrement the loop depth.
		811	- Return.
693		812
694	Example: Queue some jobs and then loop until no events are outstanding	813	Example: Queue some jobs and then loop until no events are outstanding
695	anymore.	814	anymore.
696		815
697	... queue jobs here, make sure they register event watchers as long	816	... queue jobs here, make sure they register event watchers as long
698	... as they still have work to do (even an idle watcher will do..)	817	... as they still have work to do (even an idle watcher will do..)
699	ev_loop (my_loop, 0);	818	ev_run (my_loop, 0);
700	... jobs done or somebody called unloop. yeah!	819	... jobs done or somebody called unloop. yeah!
701		820
702	=item ev_unloop (loop, how)	821	=item ev_break (loop, how)
703		822
704	Can be used to make a call to C<ev_loop> return early (but only after it	823	Can be used to make a call to C<ev_run> return early (but only after it
705	has processed all outstanding events). The C<how> argument must be either	824	has processed all outstanding events). The C<how> argument must be either
706	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	825	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	826	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
708		827
709	This "unloop state" will be cleared when entering C<ev_loop> again.	828	This "unloop state" will be cleared when entering C<ev_run> again.
710		829
711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	830	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
712		831
713	=item ev_ref (loop)	832	=item ev_ref (loop)
714		833
715	=item ev_unref (loop)	834	=item ev_unref (loop)
716		835
717	Ref/unref can be used to add or remove a reference count on the event	836	Ref/unref can be used to add or remove a reference count on the event
718	loop: Every watcher keeps one reference, and as long as the reference	837	loop: Every watcher keeps one reference, and as long as the reference
719	count is nonzero, C<ev_loop> will not return on its own.	838	count is nonzero, C<ev_run> will not return on its own.
720		839
721	If you have a watcher you never unregister that should not keep C<ev_loop>	840	This is useful when you have a watcher that you never intend to
722	from returning, call ev_unref() after starting, and ev_ref() before	841	unregister, but that nevertheless should not keep C<ev_run> from
		842	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
723	stopping it.	843	before stopping it.
724		844
725	As an example, libev itself uses this for its internal signal pipe: It is	845	As an example, libev itself uses this for its internal signal pipe: It
726	not visible to the libev user and should not keep C<ev_loop> from exiting	846	is not visible to the libev user and should not keep C<ev_run> from
727	if no event watchers registered by it are active. It is also an excellent	847	exiting if no event watchers registered by it are active. It is also an
728	way to do this for generic recurring timers or from within third-party	848	excellent way to do this for generic recurring timers or from within
729	libraries. Just remember to I<unref after start> and I<ref before stop>	849	third-party libraries. Just remember to I<unref after start> and I<ref
730	(but only if the watcher wasn't active before, or was active before,	850	before stop> (but only if the watcher wasn't active before, or was active
731	respectively).	851	before, respectively. Note also that libev might stop watchers itself
		852	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		853	in the callback).
732		854
733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	855	Example: Create a signal watcher, but keep it from keeping C<ev_run>
734	running when nothing else is active.	856	running when nothing else is active.
735		857
736	ev_signal exitsig;	858	ev_signal exitsig;
737	ev_signal_init (&exitsig, sig_cb, SIGINT);	859	ev_signal_init (&exitsig, sig_cb, SIGINT);
738	ev_signal_start (loop, &exitsig);	860	ev_signal_start (loop, &exitsig);
…		…
765		887
766	By setting a higher I<io collect interval> you allow libev to spend more	888	By setting a higher I<io collect interval> you allow libev to spend more
767	time collecting I/O events, so you can handle more events per iteration,	889	time collecting I/O events, so you can handle more events per iteration,
768	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	890	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
769	C<ev_timer>) will be not affected. Setting this to a non-null value will	891	C<ev_timer>) will be not affected. Setting this to a non-null value will
770	introduce an additional C<ev_sleep ()> call into most loop iterations.	892	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		893	sleep time ensures that libev will not poll for I/O events more often then
		894	once per this interval, on average.
771		895
772	Likewise, by setting a higher I<timeout collect interval> you allow libev	896	Likewise, by setting a higher I<timeout collect interval> you allow libev
773	to spend more time collecting timeouts, at the expense of increased	897	to spend more time collecting timeouts, at the expense of increased
774	latency/jitter/inexactness (the watcher callback will be called	898	latency/jitter/inexactness (the watcher callback will be called
775	later). C<ev_io> watchers will not be affected. Setting this to a non-null	899	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
777		901
778	Many (busy) programs can usually benefit by setting the I/O collect	902	Many (busy) programs can usually benefit by setting the I/O collect
779	interval to a value near C<0.1> or so, which is often enough for	903	interval to a value near C<0.1> or so, which is often enough for
780	interactive servers (of course not for games), likewise for timeouts. It	904	interactive servers (of course not for games), likewise for timeouts. It
781	usually doesn't make much sense to set it to a lower value than C<0.01>,	905	usually doesn't make much sense to set it to a lower value than C<0.01>,
782	as this approaches the timing granularity of most systems.	906	as this approaches the timing granularity of most systems. Note that if
		907	you do transactions with the outside world and you can't increase the
		908	parallelity, then this setting will limit your transaction rate (if you
		909	need to poll once per transaction and the I/O collect interval is 0.01,
		910	then you can't do more than 100 transactions per second).
783		911
784	Setting the I<timeout collect interval> can improve the opportunity for	912	Setting the I<timeout collect interval> can improve the opportunity for
785	saving power, as the program will "bundle" timer callback invocations that	913	saving power, as the program will "bundle" timer callback invocations that
786	are "near" in time together, by delaying some, thus reducing the number of	914	are "near" in time together, by delaying some, thus reducing the number of
787	times the process sleeps and wakes up again. Another useful technique to	915	times the process sleeps and wakes up again. Another useful technique to
788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	916	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
789	they fire on, say, one-second boundaries only.	917	they fire on, say, one-second boundaries only.
790		918
		919	Example: we only need 0.1s timeout granularity, and we wish not to poll
		920	more often than 100 times per second:
		921
		922	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		923	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		924
		925	=item ev_invoke_pending (loop)
		926
		927	This call will simply invoke all pending watchers while resetting their
		928	pending state. Normally, C<ev_run> does this automatically when required,
		929	but when overriding the invoke callback this call comes handy. This
		930	function can be invoked from a watcher - this can be useful for example
		931	when you want to do some lengthy calculation and want to pass further
		932	event handling to another thread (you still have to make sure only one
		933	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		934
		935	=item int ev_pending_count (loop)
		936
		937	Returns the number of pending watchers - zero indicates that no watchers
		938	are pending.
		939
		940	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		941
		942	This overrides the invoke pending functionality of the loop: Instead of
		943	invoking all pending watchers when there are any, C<ev_run> will call
		944	this callback instead. This is useful, for example, when you want to
		945	invoke the actual watchers inside another context (another thread etc.).
		946
		947	If you want to reset the callback, use C<ev_invoke_pending> as new
		948	callback.
		949
		950	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		951
		952	Sometimes you want to share the same loop between multiple threads. This
		953	can be done relatively simply by putting mutex_lock/unlock calls around
		954	each call to a libev function.
		955
		956	However, C<ev_run> can run an indefinite time, so it is not feasible
		957	to wait for it to return. One way around this is to wake up the event
		958	loop via C<ev_break> and C<av_async_send>, another way is to set these
		959	I<release> and I<acquire> callbacks on the loop.
		960
		961	When set, then C<release> will be called just before the thread is
		962	suspended waiting for new events, and C<acquire> is called just
		963	afterwards.
		964
		965	Ideally, C<release> will just call your mutex_unlock function, and
		966	C<acquire> will just call the mutex_lock function again.
		967
		968	While event loop modifications are allowed between invocations of
		969	C<release> and C<acquire> (that's their only purpose after all), no
		970	modifications done will affect the event loop, i.e. adding watchers will
		971	have no effect on the set of file descriptors being watched, or the time
		972	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		973	to take note of any changes you made.
		974
		975	In theory, threads executing C<ev_run> will be async-cancel safe between
		976	invocations of C<release> and C<acquire>.
		977
		978	See also the locking example in the C<THREADS> section later in this
		979	document.
		980
		981	=item ev_set_userdata (loop, void *data)
		982
		983	=item ev_userdata (loop)
		984
		985	Set and retrieve a single C<void *> associated with a loop. When
		986	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		987	C<0.>
		988
		989	These two functions can be used to associate arbitrary data with a loop,
		990	and are intended solely for the C<invoke_pending_cb>, C<release> and
		991	C<acquire> callbacks described above, but of course can be (ab-)used for
		992	any other purpose as well.
		993
791	=item ev_loop_verify (loop)	994	=item ev_verify (loop)
792		995
793	This function only does something when C<EV_VERIFY> support has been	996	This function only does something when C<EV_VERIFY> support has been
794	compiled in, which is the default for non-minimal builds. It tries to go	997	compiled in, which is the default for non-minimal builds. It tries to go
795	through all internal structures and checks them for validity. If anything	998	through all internal structures and checks them for validity. If anything
796	is found to be inconsistent, it will print an error message to standard	999	is found to be inconsistent, it will print an error message to standard
…		…
807		1010
808	In the following description, uppercase C<TYPE> in names stands for the	1011	In the following description, uppercase C<TYPE> in names stands for the
809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1012	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
810	watchers and C<ev_io_start> for I/O watchers.	1013	watchers and C<ev_io_start> for I/O watchers.
811		1014
812	A watcher is a structure that you create and register to record your	1015	A watcher is an opaque structure that you allocate and register to record
813	interest in some event. For instance, if you want to wait for STDIN to	1016	your interest in some event. To make a concrete example, imagine you want
814	become readable, you would create an C<ev_io> watcher for that:	1017	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1018	for that:
815		1019
816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1020	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
817	{	1021	{
818	ev_io_stop (w);	1022	ev_io_stop (w);
819	ev_unloop (loop, EVUNLOOP_ALL);	1023	ev_break (loop, EVBREAK_ALL);
820	}	1024	}
821		1025
822	struct ev_loop *loop = ev_default_loop (0);	1026	struct ev_loop *loop = ev_default_loop (0);
823		1027
824	ev_io stdin_watcher;	1028	ev_io stdin_watcher;
825		1029
826	ev_init (&stdin_watcher, my_cb);	1030	ev_init (&stdin_watcher, my_cb);
827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1031	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
828	ev_io_start (loop, &stdin_watcher);	1032	ev_io_start (loop, &stdin_watcher);
829		1033
830	ev_loop (loop, 0);	1034	ev_run (loop, 0);
831		1035
832	As you can see, you are responsible for allocating the memory for your	1036	As you can see, you are responsible for allocating the memory for your
833	watcher structures (and it is I<usually> a bad idea to do this on the	1037	watcher structures (and it is I<usually> a bad idea to do this on the
834	stack).	1038	stack).
835		1039
836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1040	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1041	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
838		1042
839	Each watcher structure must be initialised by a call to C<ev_init	1043	Each watcher structure must be initialised by a call to C<ev_init (watcher
840	(watcher *, callback)>, which expects a callback to be provided. This	1044	*, callback)>, which expects a callback to be provided. This callback is
841	callback gets invoked each time the event occurs (or, in the case of I/O	1045	invoked each time the event occurs (or, in the case of I/O watchers, each
842	watchers, each time the event loop detects that the file descriptor given	1046	time the event loop detects that the file descriptor given is readable
843	is readable and/or writable).	1047	and/or writable).
844		1048
845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1049	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
846	macro to configure it, with arguments specific to the watcher type. There	1050	macro to configure it, with arguments specific to the watcher type. There
847	is also a macro to combine initialisation and setting in one call: C<<	1051	is also a macro to combine initialisation and setting in one call: C<<
848	ev_TYPE_init (watcher *, callback, ...) >>.	1052	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
871	=item C<EV_WRITE>	1075	=item C<EV_WRITE>
872		1076
873	The file descriptor in the C<ev_io> watcher has become readable and/or	1077	The file descriptor in the C<ev_io> watcher has become readable and/or
874	writable.	1078	writable.
875		1079
876	=item C<EV_TIMEOUT>	1080	=item C<EV_TIMER>
877		1081
878	The C<ev_timer> watcher has timed out.	1082	The C<ev_timer> watcher has timed out.
879		1083
880	=item C<EV_PERIODIC>	1084	=item C<EV_PERIODIC>
881		1085
…		…
899		1103
900	=item C<EV_PREPARE>	1104	=item C<EV_PREPARE>
901		1105
902	=item C<EV_CHECK>	1106	=item C<EV_CHECK>
903		1107
904	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1108	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
905	to gather new events, and all C<ev_check> watchers are invoked just after	1109	to gather new events, and all C<ev_check> watchers are invoked just after
906	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1110	C<ev_run> has gathered them, but before it invokes any callbacks for any
907	received events. Callbacks of both watcher types can start and stop as	1111	received events. Callbacks of both watcher types can start and stop as
908	many watchers as they want, and all of them will be taken into account	1112	many watchers as they want, and all of them will be taken into account
909	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1113	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
910	C<ev_loop> from blocking).	1114	C<ev_run> from blocking).
911		1115
912	=item C<EV_EMBED>	1116	=item C<EV_EMBED>
913		1117
914	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1118	The embedded event loop specified in the C<ev_embed> watcher needs attention.
915		1119
916	=item C<EV_FORK>	1120	=item C<EV_FORK>
917		1121
918	The event loop has been resumed in the child process after fork (see	1122	The event loop has been resumed in the child process after fork (see
919	C<ev_fork>).	1123	C<ev_fork>).
920		1124
		1125	=item C<EV_CLEANUP>
		1126
		1127	The event loop is about to be destroyed (see C<ev_cleanup>).
		1128
921	=item C<EV_ASYNC>	1129	=item C<EV_ASYNC>
922		1130
923	The given async watcher has been asynchronously notified (see C<ev_async>).	1131	The given async watcher has been asynchronously notified (see C<ev_async>).
		1132
		1133	=item C<EV_CUSTOM>
		1134
		1135	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1136	by libev users to signal watchers (e.g. via C<ev_feed_event>).
924		1137
925	=item C<EV_ERROR>	1138	=item C<EV_ERROR>
926		1139
927	An unspecified error has occurred, the watcher has been stopped. This might	1140	An unspecified error has occurred, the watcher has been stopped. This might
928	happen because the watcher could not be properly started because libev	1141	happen because the watcher could not be properly started because libev
…		…
966		1179
967	ev_io w;	1180	ev_io w;
968	ev_init (&w, my_cb);	1181	ev_init (&w, my_cb);
969	ev_io_set (&w, STDIN_FILENO, EV_READ);	1182	ev_io_set (&w, STDIN_FILENO, EV_READ);
970		1183
971	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1184	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
972		1185
973	This macro initialises the type-specific parts of a watcher. You need to	1186	This macro initialises the type-specific parts of a watcher. You need to
974	call C<ev_init> at least once before you call this macro, but you can	1187	call C<ev_init> at least once before you call this macro, but you can
975	call C<ev_TYPE_set> any number of times. You must not, however, call this	1188	call C<ev_TYPE_set> any number of times. You must not, however, call this
976	macro on a watcher that is active (it can be pending, however, which is a	1189	macro on a watcher that is active (it can be pending, however, which is a
…		…
989		1202
990	Example: Initialise and set an C<ev_io> watcher in one step.	1203	Example: Initialise and set an C<ev_io> watcher in one step.
991		1204
992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1205	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
993		1206
994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1207	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
995		1208
996	Starts (activates) the given watcher. Only active watchers will receive	1209	Starts (activates) the given watcher. Only active watchers will receive
997	events. If the watcher is already active nothing will happen.	1210	events. If the watcher is already active nothing will happen.
998		1211
999	Example: Start the C<ev_io> watcher that is being abused as example in this	1212	Example: Start the C<ev_io> watcher that is being abused as example in this
1000	whole section.	1213	whole section.
1001		1214
1002	ev_io_start (EV_DEFAULT_UC, &w);	1215	ev_io_start (EV_DEFAULT_UC, &w);
1003		1216
1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1217	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1005		1218
1006	Stops the given watcher if active, and clears the pending status (whether	1219	Stops the given watcher if active, and clears the pending status (whether
1007	the watcher was active or not).	1220	the watcher was active or not).
1008		1221
1009	It is possible that stopped watchers are pending - for example,	1222	It is possible that stopped watchers are pending - for example,
…		…
1034	=item ev_cb_set (ev_TYPE *watcher, callback)	1247	=item ev_cb_set (ev_TYPE *watcher, callback)
1035		1248
1036	Change the callback. You can change the callback at virtually any time	1249	Change the callback. You can change the callback at virtually any time
1037	(modulo threads).	1250	(modulo threads).
1038		1251
1039	=item ev_set_priority (ev_TYPE *watcher, priority)	1252	=item ev_set_priority (ev_TYPE *watcher, int priority)
1040		1253
1041	=item int ev_priority (ev_TYPE *watcher)	1254	=item int ev_priority (ev_TYPE *watcher)
1042		1255
1043	Set and query the priority of the watcher. The priority is a small	1256	Set and query the priority of the watcher. The priority is a small
1044	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1257	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1045	(default: C<-2>). Pending watchers with higher priority will be invoked	1258	(default: C<-2>). Pending watchers with higher priority will be invoked
1046	before watchers with lower priority, but priority will not keep watchers	1259	before watchers with lower priority, but priority will not keep watchers
1047	from being executed (except for C<ev_idle> watchers).	1260	from being executed (except for C<ev_idle> watchers).
1048		1261
1049	This means that priorities are I<only> used for ordering callback
1050	invocation after new events have been received. This is useful, for
1051	example, to reduce latency after idling, or more often, to bind two
1052	watchers on the same event and make sure one is called first.
1053
1054	If you need to suppress invocation when higher priority events are pending	1262	If you need to suppress invocation when higher priority events are pending
1055	you need to look at C<ev_idle> watchers, which provide this functionality.	1263	you need to look at C<ev_idle> watchers, which provide this functionality.
1056		1264
1057	You I<must not> change the priority of a watcher as long as it is active or	1265	You I<must not> change the priority of a watcher as long as it is active or
1058	pending.	1266	pending.
1059
1060	The default priority used by watchers when no priority has been set is
1061	always C<0>, which is supposed to not be too high and not be too low :).
1062		1267
1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1268	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1064	fine, as long as you do not mind that the priority value you query might	1269	fine, as long as you do not mind that the priority value you query might
1065	or might not have been clamped to the valid range.	1270	or might not have been clamped to the valid range.
		1271
		1272	The default priority used by watchers when no priority has been set is
		1273	always C<0>, which is supposed to not be too high and not be too low :).
		1274
		1275	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1276	priorities.
1066		1277
1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1278	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1068		1279
1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1280	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1070	C<loop> nor C<revents> need to be valid as long as the watcher callback	1281	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1078	watcher isn't pending it does nothing and returns C<0>.	1289	watcher isn't pending it does nothing and returns C<0>.
1079		1290
1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1291	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1081	callback to be invoked, which can be accomplished with this function.	1292	callback to be invoked, which can be accomplished with this function.
1082		1293
		1294	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1295
		1296	Feeds the given event set into the event loop, as if the specified event
		1297	had happened for the specified watcher (which must be a pointer to an
		1298	initialised but not necessarily started event watcher). Obviously you must
		1299	not free the watcher as long as it has pending events.
		1300
		1301	Stopping the watcher, letting libev invoke it, or calling
		1302	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1303	not started in the first place.
		1304
		1305	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1306	functions that do not need a watcher.
		1307
1083	=back	1308	=back
1084
1085		1309
1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1310	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1087		1311
1088	Each watcher has, by default, a member C<void *data> that you can change	1312	Each watcher has, by default, a member C<void *data> that you can change
1089	and read at any time: libev will completely ignore it. This can be used	1313	and read at any time: libev will completely ignore it. This can be used
…		…
1135	#include <stddef.h>	1359	#include <stddef.h>
1136		1360
1137	static void	1361	static void
1138	t1_cb (EV_P_ ev_timer *w, int revents)	1362	t1_cb (EV_P_ ev_timer *w, int revents)
1139	{	1363	{
1140	struct my_biggy big = (struct my_biggy *	1364	struct my_biggy big = (struct my_biggy *)
1141	(((char *)w) - offsetof (struct my_biggy, t1));	1365	(((char *)w) - offsetof (struct my_biggy, t1));
1142	}	1366	}
1143		1367
1144	static void	1368	static void
1145	t2_cb (EV_P_ ev_timer *w, int revents)	1369	t2_cb (EV_P_ ev_timer *w, int revents)
1146	{	1370	{
1147	struct my_biggy big = (struct my_biggy *	1371	struct my_biggy big = (struct my_biggy *)
1148	(((char *)w) - offsetof (struct my_biggy, t2));	1372	(((char *)w) - offsetof (struct my_biggy, t2));
1149	}	1373	}
		1374
		1375	=head2 WATCHER STATES
		1376
		1377	There are various watcher states mentioned throughout this manual -
		1378	active, pending and so on. In this section these states and the rules to
		1379	transition between them will be described in more detail - and while these
		1380	rules might look complicated, they usually do "the right thing".
		1381
		1382	=over 4
		1383
		1384	=item initialiased
		1385
		1386	Before a watcher can be registered with the event looop it has to be
		1387	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1388	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1389
		1390	In this state it is simply some block of memory that is suitable for use
		1391	in an event loop. It can be moved around, freed, reused etc. at will.
		1392
		1393	=item started/running/active
		1394
		1395	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1396	property of the event loop, and is actively waiting for events. While in
		1397	this state it cannot be accessed (except in a few documented ways), moved,
		1398	freed or anything else - the only legal thing is to keep a pointer to it,
		1399	and call libev functions on it that are documented to work on active watchers.
		1400
		1401	=item pending
		1402
		1403	If a watcher is active and libev determines that an event it is interested
		1404	in has occurred (such as a timer expiring), it will become pending. It will
		1405	stay in this pending state until either it is stopped or its callback is
		1406	about to be invoked, so it is not normally pending inside the watcher
		1407	callback.
		1408
		1409	The watcher might or might not be active while it is pending (for example,
		1410	an expired non-repeating timer can be pending but no longer active). If it
		1411	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1412	but it is still property of the event loop at this time, so cannot be
		1413	moved, freed or reused. And if it is active the rules described in the
		1414	previous item still apply.
		1415
		1416	It is also possible to feed an event on a watcher that is not active (e.g.
		1417	via C<ev_feed_event>), in which case it becomes pending without being
		1418	active.
		1419
		1420	=item stopped
		1421
		1422	A watcher can be stopped implicitly by libev (in which case it might still
		1423	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1424	latter will clear any pending state the watcher might be in, regardless
		1425	of whether it was active or not, so stopping a watcher explicitly before
		1426	freeing it is often a good idea.
		1427
		1428	While stopped (and not pending) the watcher is essentially in the
		1429	initialised state, that is it can be reused, moved, modified in any way
		1430	you wish.
		1431
		1432	=back
		1433
		1434	=head2 WATCHER PRIORITY MODELS
		1435
		1436	Many event loops support I<watcher priorities>, which are usually small
		1437	integers that influence the ordering of event callback invocation
		1438	between watchers in some way, all else being equal.
		1439
		1440	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1441	description for the more technical details such as the actual priority
		1442	range.
		1443
		1444	There are two common ways how these these priorities are being interpreted
		1445	by event loops:
		1446
		1447	In the more common lock-out model, higher priorities "lock out" invocation
		1448	of lower priority watchers, which means as long as higher priority
		1449	watchers receive events, lower priority watchers are not being invoked.
		1450
		1451	The less common only-for-ordering model uses priorities solely to order
		1452	callback invocation within a single event loop iteration: Higher priority
		1453	watchers are invoked before lower priority ones, but they all get invoked
		1454	before polling for new events.
		1455
		1456	Libev uses the second (only-for-ordering) model for all its watchers
		1457	except for idle watchers (which use the lock-out model).
		1458
		1459	The rationale behind this is that implementing the lock-out model for
		1460	watchers is not well supported by most kernel interfaces, and most event
		1461	libraries will just poll for the same events again and again as long as
		1462	their callbacks have not been executed, which is very inefficient in the
		1463	common case of one high-priority watcher locking out a mass of lower
		1464	priority ones.
		1465
		1466	Static (ordering) priorities are most useful when you have two or more
		1467	watchers handling the same resource: a typical usage example is having an
		1468	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1469	timeouts. Under load, data might be received while the program handles
		1470	other jobs, but since timers normally get invoked first, the timeout
		1471	handler will be executed before checking for data. In that case, giving
		1472	the timer a lower priority than the I/O watcher ensures that I/O will be
		1473	handled first even under adverse conditions (which is usually, but not
		1474	always, what you want).
		1475
		1476	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1477	will only be executed when no same or higher priority watchers have
		1478	received events, they can be used to implement the "lock-out" model when
		1479	required.
		1480
		1481	For example, to emulate how many other event libraries handle priorities,
		1482	you can associate an C<ev_idle> watcher to each such watcher, and in
		1483	the normal watcher callback, you just start the idle watcher. The real
		1484	processing is done in the idle watcher callback. This causes libev to
		1485	continuously poll and process kernel event data for the watcher, but when
		1486	the lock-out case is known to be rare (which in turn is rare :), this is
		1487	workable.
		1488
		1489	Usually, however, the lock-out model implemented that way will perform
		1490	miserably under the type of load it was designed to handle. In that case,
		1491	it might be preferable to stop the real watcher before starting the
		1492	idle watcher, so the kernel will not have to process the event in case
		1493	the actual processing will be delayed for considerable time.
		1494
		1495	Here is an example of an I/O watcher that should run at a strictly lower
		1496	priority than the default, and which should only process data when no
		1497	other events are pending:
		1498
		1499	ev_idle idle; // actual processing watcher
		1500	ev_io io; // actual event watcher
		1501
		1502	static void
		1503	io_cb (EV_P_ ev_io *w, int revents)
		1504	{
		1505	// stop the I/O watcher, we received the event, but
		1506	// are not yet ready to handle it.
		1507	ev_io_stop (EV_A_ w);
		1508
		1509	// start the idle watcher to handle the actual event.
		1510	// it will not be executed as long as other watchers
		1511	// with the default priority are receiving events.
		1512	ev_idle_start (EV_A_ &idle);
		1513	}
		1514
		1515	static void
		1516	idle_cb (EV_P_ ev_idle *w, int revents)
		1517	{
		1518	// actual processing
		1519	read (STDIN_FILENO, ...);
		1520
		1521	// have to start the I/O watcher again, as
		1522	// we have handled the event
		1523	ev_io_start (EV_P_ &io);
		1524	}
		1525
		1526	// initialisation
		1527	ev_idle_init (&idle, idle_cb);
		1528	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1529	ev_io_start (EV_DEFAULT_ &io);
		1530
		1531	In the "real" world, it might also be beneficial to start a timer, so that
		1532	low-priority connections can not be locked out forever under load. This
		1533	enables your program to keep a lower latency for important connections
		1534	during short periods of high load, while not completely locking out less
		1535	important ones.
1150		1536
1151		1537
1152	=head1 WATCHER TYPES	1538	=head1 WATCHER TYPES
1153		1539
1154	This section describes each watcher in detail, but will not repeat	1540	This section describes each watcher in detail, but will not repeat
…		…
1180	descriptors to non-blocking mode is also usually a good idea (but not	1566	descriptors to non-blocking mode is also usually a good idea (but not
1181	required if you know what you are doing).	1567	required if you know what you are doing).
1182		1568
1183	If you cannot use non-blocking mode, then force the use of a	1569	If you cannot use non-blocking mode, then force the use of a
1184	known-to-be-good backend (at the time of this writing, this includes only	1570	known-to-be-good backend (at the time of this writing, this includes only
1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1571	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1572	descriptors for which non-blocking operation makes no sense (such as
		1573	files) - libev doesn't guarantee any specific behaviour in that case.
1186		1574
1187	Another thing you have to watch out for is that it is quite easy to	1575	Another thing you have to watch out for is that it is quite easy to
1188	receive "spurious" readiness notifications, that is your callback might	1576	receive "spurious" readiness notifications, that is your callback might
1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1577	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1190	because there is no data. Not only are some backends known to create a	1578	because there is no data. Not only are some backends known to create a
…		…
1255		1643
1256	So when you encounter spurious, unexplained daemon exits, make sure you	1644	So when you encounter spurious, unexplained daemon exits, make sure you
1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1645	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1258	somewhere, as that would have given you a big clue).	1646	somewhere, as that would have given you a big clue).
1259		1647
		1648	=head3 The special problem of accept()ing when you can't
		1649
		1650	Many implementations of the POSIX C<accept> function (for example,
		1651	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1652	connection from the pending queue in all error cases.
		1653
		1654	For example, larger servers often run out of file descriptors (because
		1655	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1656	rejecting the connection, leading to libev signalling readiness on
		1657	the next iteration again (the connection still exists after all), and
		1658	typically causing the program to loop at 100% CPU usage.
		1659
		1660	Unfortunately, the set of errors that cause this issue differs between
		1661	operating systems, there is usually little the app can do to remedy the
		1662	situation, and no known thread-safe method of removing the connection to
		1663	cope with overload is known (to me).
		1664
		1665	One of the easiest ways to handle this situation is to just ignore it
		1666	- when the program encounters an overload, it will just loop until the
		1667	situation is over. While this is a form of busy waiting, no OS offers an
		1668	event-based way to handle this situation, so it's the best one can do.
		1669
		1670	A better way to handle the situation is to log any errors other than
		1671	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1672	messages, and continue as usual, which at least gives the user an idea of
		1673	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1674	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1675	usage.
		1676
		1677	If your program is single-threaded, then you could also keep a dummy file
		1678	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1679	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1680	close that fd, and create a new dummy fd. This will gracefully refuse
		1681	clients under typical overload conditions.
		1682
		1683	The last way to handle it is to simply log the error and C<exit>, as
		1684	is often done with C<malloc> failures, but this results in an easy
		1685	opportunity for a DoS attack.
1260		1686
1261	=head3 Watcher-Specific Functions	1687	=head3 Watcher-Specific Functions
1262		1688
1263	=over 4	1689	=over 4
1264		1690
…		…
1296	...	1722	...
1297	struct ev_loop *loop = ev_default_init (0);	1723	struct ev_loop *loop = ev_default_init (0);
1298	ev_io stdin_readable;	1724	ev_io stdin_readable;
1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1725	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1300	ev_io_start (loop, &stdin_readable);	1726	ev_io_start (loop, &stdin_readable);
1301	ev_loop (loop, 0);	1727	ev_run (loop, 0);
1302		1728
1303		1729
1304	=head2 C<ev_timer> - relative and optionally repeating timeouts	1730	=head2 C<ev_timer> - relative and optionally repeating timeouts
1305		1731
1306	Timer watchers are simple relative timers that generate an event after a	1732	Timer watchers are simple relative timers that generate an event after a
…		…
1311	year, it will still time out after (roughly) one hour. "Roughly" because	1737	year, it will still time out after (roughly) one hour. "Roughly" because
1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1738	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1313	monotonic clock option helps a lot here).	1739	monotonic clock option helps a lot here).
1314		1740
1315	The callback is guaranteed to be invoked only I<after> its timeout has	1741	The callback is guaranteed to be invoked only I<after> its timeout has
1316	passed, but if multiple timers become ready during the same loop iteration	1742	passed (not I<at>, so on systems with very low-resolution clocks this
1317	then order of execution is undefined.	1743	might introduce a small delay). If multiple timers become ready during the
		1744	same loop iteration then the ones with earlier time-out values are invoked
		1745	before ones of the same priority with later time-out values (but this is
		1746	no longer true when a callback calls C<ev_run> recursively).
1318		1747
1319	=head3 Be smart about timeouts	1748	=head3 Be smart about timeouts
1320		1749
1321	Many real-world problems involve some kind of timeout, usually for error	1750	Many real-world problems involve some kind of timeout, usually for error
1322	recovery. A typical example is an HTTP request - if the other side hangs,	1751	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1795	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1367	member and C<ev_timer_again>.	1796	member and C<ev_timer_again>.
1368		1797
1369	At start:	1798	At start:
1370		1799
1371	ev_timer_init (timer, callback);	1800	ev_init (timer, callback);
1372	timer->repeat = 60.;	1801	timer->repeat = 60.;
1373	ev_timer_again (loop, timer);	1802	ev_timer_again (loop, timer);
1374		1803
1375	Each time there is some activity:	1804	Each time there is some activity:
1376		1805
…		…
1408	ev_tstamp timeout = last_activity + 60.;	1837	ev_tstamp timeout = last_activity + 60.;
1409		1838
1410	// if last_activity + 60. is older than now, we did time out	1839	// if last_activity + 60. is older than now, we did time out
1411	if (timeout < now)	1840	if (timeout < now)
1412	{	1841	{
1413	// timeout occured, take action	1842	// timeout occurred, take action
1414	}	1843	}
1415	else	1844	else
1416	{	1845	{
1417	// callback was invoked, but there was some activity, re-arm	1846	// callback was invoked, but there was some activity, re-arm
1418	// the watcher to fire in last_activity + 60, which is	1847	// the watcher to fire in last_activity + 60, which is
1419	// guaranteed to be in the future, so "again" is positive:	1848	// guaranteed to be in the future, so "again" is positive:
1420	w->again = timeout - now;	1849	w->repeat = timeout - now;
1421	ev_timer_again (EV_A_ w);	1850	ev_timer_again (EV_A_ w);
1422	}	1851	}
1423	}	1852	}
1424		1853
1425	To summarise the callback: first calculate the real timeout (defined	1854	To summarise the callback: first calculate the real timeout (defined
…		…
1438		1867
1439	To start the timer, simply initialise the watcher and set C<last_activity>	1868	To start the timer, simply initialise the watcher and set C<last_activity>
1440	to the current time (meaning we just have some activity :), then call the	1869	to the current time (meaning we just have some activity :), then call the
1441	callback, which will "do the right thing" and start the timer:	1870	callback, which will "do the right thing" and start the timer:
1442		1871
1443	ev_timer_init (timer, callback);	1872	ev_init (timer, callback);
1444	last_activity = ev_now (loop);	1873	last_activity = ev_now (loop);
1445	callback (loop, timer, EV_TIMEOUT);	1874	callback (loop, timer, EV_TIMER);
1446		1875
1447	And when there is some activity, simply store the current time in	1876	And when there is some activity, simply store the current time in
1448	C<last_activity>, no libev calls at all:	1877	C<last_activity>, no libev calls at all:
1449		1878
1450	last_actiivty = ev_now (loop);	1879	last_activity = ev_now (loop);
1451		1880
1452	This technique is slightly more complex, but in most cases where the	1881	This technique is slightly more complex, but in most cases where the
1453	time-out is unlikely to be triggered, much more efficient.	1882	time-out is unlikely to be triggered, much more efficient.
1454		1883
1455	Changing the timeout is trivial as well (if it isn't hard-coded in the	1884	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1493		1922
1494	=head3 The special problem of time updates	1923	=head3 The special problem of time updates
1495		1924
1496	Establishing the current time is a costly operation (it usually takes at	1925	Establishing the current time is a costly operation (it usually takes at
1497	least two system calls): EV therefore updates its idea of the current	1926	least two system calls): EV therefore updates its idea of the current
1498	time only before and after C<ev_loop> collects new events, which causes a	1927	time only before and after C<ev_run> collects new events, which causes a
1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1928	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1500	lots of events in one iteration.	1929	lots of events in one iteration.
1501		1930
1502	The relative timeouts are calculated relative to the C<ev_now ()>	1931	The relative timeouts are calculated relative to the C<ev_now ()>
1503	time. This is usually the right thing as this timestamp refers to the time	1932	time. This is usually the right thing as this timestamp refers to the time
…		…
1509		1938
1510	If the event loop is suspended for a long time, you can also force an	1939	If the event loop is suspended for a long time, you can also force an
1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1940	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1512	()>.	1941	()>.
1513		1942
		1943	=head3 The special problems of suspended animation
		1944
		1945	When you leave the server world it is quite customary to hit machines that
		1946	can suspend/hibernate - what happens to the clocks during such a suspend?
		1947
		1948	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1949	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1950	to run until the system is suspended, but they will not advance while the
		1951	system is suspended. That means, on resume, it will be as if the program
		1952	was frozen for a few seconds, but the suspend time will not be counted
		1953	towards C<ev_timer> when a monotonic clock source is used. The real time
		1954	clock advanced as expected, but if it is used as sole clocksource, then a
		1955	long suspend would be detected as a time jump by libev, and timers would
		1956	be adjusted accordingly.
		1957
		1958	I would not be surprised to see different behaviour in different between
		1959	operating systems, OS versions or even different hardware.
		1960
		1961	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1962	time jump in the monotonic clocks and the realtime clock. If the program
		1963	is suspended for a very long time, and monotonic clock sources are in use,
		1964	then you can expect C<ev_timer>s to expire as the full suspension time
		1965	will be counted towards the timers. When no monotonic clock source is in
		1966	use, then libev will again assume a timejump and adjust accordingly.
		1967
		1968	It might be beneficial for this latter case to call C<ev_suspend>
		1969	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1970	deterministic behaviour in this case (you can do nothing against
		1971	C<SIGSTOP>).
		1972
1514	=head3 Watcher-Specific Functions and Data Members	1973	=head3 Watcher-Specific Functions and Data Members
1515		1974
1516	=over 4	1975	=over 4
1517		1976
1518	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1541	If the timer is started but non-repeating, stop it (as if it timed out).	2000	If the timer is started but non-repeating, stop it (as if it timed out).
1542		2001
1543	If the timer is repeating, either start it if necessary (with the	2002	If the timer is repeating, either start it if necessary (with the
1544	C<repeat> value), or reset the running timer to the C<repeat> value.	2003	C<repeat> value), or reset the running timer to the C<repeat> value.
1545		2004
1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2005	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1547	usage example.	2006	usage example.
		2007
		2008	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2009
		2010	Returns the remaining time until a timer fires. If the timer is active,
		2011	then this time is relative to the current event loop time, otherwise it's
		2012	the timeout value currently configured.
		2013
		2014	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2015	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2016	will return C<4>. When the timer expires and is restarted, it will return
		2017	roughly C<7> (likely slightly less as callback invocation takes some time,
		2018	too), and so on.
1548		2019
1549	=item ev_tstamp repeat [read-write]	2020	=item ev_tstamp repeat [read-write]
1550		2021
1551	The current C<repeat> value. Will be used each time the watcher times out	2022	The current C<repeat> value. Will be used each time the watcher times out
1552	or C<ev_timer_again> is called, and determines the next timeout (if any),	2023	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1578	}	2049	}
1579		2050
1580	ev_timer mytimer;	2051	ev_timer mytimer;
1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2052	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1582	ev_timer_again (&mytimer); /* start timer */	2053	ev_timer_again (&mytimer); /* start timer */
1583	ev_loop (loop, 0);	2054	ev_run (loop, 0);
1584		2055
1585	// and in some piece of code that gets executed on any "activity":	2056	// and in some piece of code that gets executed on any "activity":
1586	// reset the timeout to start ticking again at 10 seconds	2057	// reset the timeout to start ticking again at 10 seconds
1587	ev_timer_again (&mytimer);	2058	ev_timer_again (&mytimer);
1588		2059
…		…
1590	=head2 C<ev_periodic> - to cron or not to cron?	2061	=head2 C<ev_periodic> - to cron or not to cron?
1591		2062
1592	Periodic watchers are also timers of a kind, but they are very versatile	2063	Periodic watchers are also timers of a kind, but they are very versatile
1593	(and unfortunately a bit complex).	2064	(and unfortunately a bit complex).
1594		2065
1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2066	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1596	but on wall clock time (absolute time). You can tell a periodic watcher	2067	relative time, the physical time that passes) but on wall clock time
1597	to trigger after some specific point in time. For example, if you tell a	2068	(absolute time, the thing you can read on your calender or clock). The
1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2069	difference is that wall clock time can run faster or slower than real
1599	+ 10.>, that is, an absolute time not a delay) and then reset your system	2070	time, and time jumps are not uncommon (e.g. when you adjust your
1600	clock to January of the previous year, then it will take more than year	2071	wrist-watch).
1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1602	roughly 10 seconds later as it uses a relative timeout).
1603		2072
		2073	You can tell a periodic watcher to trigger after some specific point
		2074	in time: for example, if you tell a periodic watcher to trigger "in 10
		2075	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2076	not a delay) and then reset your system clock to January of the previous
		2077	year, then it will take a year or more to trigger the event (unlike an
		2078	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2079	it, as it uses a relative timeout).
		2080
1604	C<ev_periodic>s can also be used to implement vastly more complex timers,	2081	C<ev_periodic> watchers can also be used to implement vastly more complex
1605	such as triggering an event on each "midnight, local time", or other	2082	timers, such as triggering an event on each "midnight, local time", or
1606	complicated rules.	2083	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2084	those cannot react to time jumps.
1607		2085
1608	As with timers, the callback is guaranteed to be invoked only when the	2086	As with timers, the callback is guaranteed to be invoked only when the
1609	time (C<at>) has passed, but if multiple periodic timers become ready	2087	point in time where it is supposed to trigger has passed. If multiple
1610	during the same loop iteration, then order of execution is undefined.	2088	timers become ready during the same loop iteration then the ones with
		2089	earlier time-out values are invoked before ones with later time-out values
		2090	(but this is no longer true when a callback calls C<ev_run> recursively).
1611		2091
1612	=head3 Watcher-Specific Functions and Data Members	2092	=head3 Watcher-Specific Functions and Data Members
1613		2093
1614	=over 4	2094	=over 4
1615		2095
1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2096	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1617		2097
1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2098	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1619		2099
1620	Lots of arguments, lets sort it out... There are basically three modes of	2100	Lots of arguments, let's sort it out... There are basically three modes of
1621	operation, and we will explain them from simplest to most complex:	2101	operation, and we will explain them from simplest to most complex:
1622		2102
1623	=over 4	2103	=over 4
1624		2104
1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2105	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1626		2106
1627	In this configuration the watcher triggers an event after the wall clock	2107	In this configuration the watcher triggers an event after the wall clock
1628	time C<at> has passed. It will not repeat and will not adjust when a time	2108	time C<offset> has passed. It will not repeat and will not adjust when a
1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2109	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1630	only run when the system clock reaches or surpasses this time.	2110	will be stopped and invoked when the system clock reaches or surpasses
		2111	this point in time.
1631		2112
1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2113	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1633		2114
1634	In this mode the watcher will always be scheduled to time out at the next	2115	In this mode the watcher will always be scheduled to time out at the next
1635	C<at + N * interval> time (for some integer N, which can also be negative)	2116	C<offset + N * interval> time (for some integer N, which can also be
1636	and then repeat, regardless of any time jumps.	2117	negative) and then repeat, regardless of any time jumps. The C<offset>
		2118	argument is merely an offset into the C<interval> periods.
1637		2119
1638	This can be used to create timers that do not drift with respect to the	2120	This can be used to create timers that do not drift with respect to the
1639	system clock, for example, here is a C<ev_periodic> that triggers each	2121	system clock, for example, here is an C<ev_periodic> that triggers each
1640	hour, on the hour:	2122	hour, on the hour (with respect to UTC):
1641		2123
1642	ev_periodic_set (&periodic, 0., 3600., 0);	2124	ev_periodic_set (&periodic, 0., 3600., 0);
1643		2125
1644	This doesn't mean there will always be 3600 seconds in between triggers,	2126	This doesn't mean there will always be 3600 seconds in between triggers,
1645	but only that the callback will be called when the system time shows a	2127	but only that the callback will be called when the system time shows a
1646	full hour (UTC), or more correctly, when the system time is evenly divisible	2128	full hour (UTC), or more correctly, when the system time is evenly divisible
1647	by 3600.	2129	by 3600.
1648		2130
1649	Another way to think about it (for the mathematically inclined) is that	2131	Another way to think about it (for the mathematically inclined) is that
1650	C<ev_periodic> will try to run the callback in this mode at the next possible	2132	C<ev_periodic> will try to run the callback in this mode at the next possible
1651	time where C<time = at (mod interval)>, regardless of any time jumps.	2133	time where C<time = offset (mod interval)>, regardless of any time jumps.
1652		2134
1653	For numerical stability it is preferable that the C<at> value is near	2135	For numerical stability it is preferable that the C<offset> value is near
1654	C<ev_now ()> (the current time), but there is no range requirement for	2136	C<ev_now ()> (the current time), but there is no range requirement for
1655	this value, and in fact is often specified as zero.	2137	this value, and in fact is often specified as zero.
1656		2138
1657	Note also that there is an upper limit to how often a timer can fire (CPU	2139	Note also that there is an upper limit to how often a timer can fire (CPU
1658	speed for example), so if C<interval> is very small then timing stability	2140	speed for example), so if C<interval> is very small then timing stability
1659	will of course deteriorate. Libev itself tries to be exact to be about one	2141	will of course deteriorate. Libev itself tries to be exact to be about one
1660	millisecond (if the OS supports it and the machine is fast enough).	2142	millisecond (if the OS supports it and the machine is fast enough).
1661		2143
1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2144	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1663		2145
1664	In this mode the values for C<interval> and C<at> are both being	2146	In this mode the values for C<interval> and C<offset> are both being
1665	ignored. Instead, each time the periodic watcher gets scheduled, the	2147	ignored. Instead, each time the periodic watcher gets scheduled, the
1666	reschedule callback will be called with the watcher as first, and the	2148	reschedule callback will be called with the watcher as first, and the
1667	current time as second argument.	2149	current time as second argument.
1668		2150
1669	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2151	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1670	ever, or make ANY event loop modifications whatsoever>.	2152	or make ANY other event loop modifications whatsoever, unless explicitly
		2153	allowed by documentation here>.
1671		2154
1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2155	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2156	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1674	only event loop modification you are allowed to do).	2157	only event loop modification you are allowed to do).
1675		2158
…		…
1705	a different time than the last time it was called (e.g. in a crond like	2188	a different time than the last time it was called (e.g. in a crond like
1706	program when the crontabs have changed).	2189	program when the crontabs have changed).
1707		2190
1708	=item ev_tstamp ev_periodic_at (ev_periodic *)	2191	=item ev_tstamp ev_periodic_at (ev_periodic *)
1709		2192
1710	When active, returns the absolute time that the watcher is supposed to	2193	When active, returns the absolute time that the watcher is supposed
1711	trigger next.	2194	to trigger next. This is not the same as the C<offset> argument to
		2195	C<ev_periodic_set>, but indeed works even in interval and manual
		2196	rescheduling modes.
1712		2197
1713	=item ev_tstamp offset [read-write]	2198	=item ev_tstamp offset [read-write]
1714		2199
1715	When repeating, this contains the offset value, otherwise this is the	2200	When repeating, this contains the offset value, otherwise this is the
1716	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2201	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2202	although libev might modify this value for better numerical stability).
1717		2203
1718	Can be modified any time, but changes only take effect when the periodic	2204	Can be modified any time, but changes only take effect when the periodic
1719	timer fires or C<ev_periodic_again> is being called.	2205	timer fires or C<ev_periodic_again> is being called.
1720		2206
1721	=item ev_tstamp interval [read-write]	2207	=item ev_tstamp interval [read-write]
…		…
1737	Example: Call a callback every hour, or, more precisely, whenever the	2223	Example: Call a callback every hour, or, more precisely, whenever the
1738	system time is divisible by 3600. The callback invocation times have	2224	system time is divisible by 3600. The callback invocation times have
1739	potentially a lot of jitter, but good long-term stability.	2225	potentially a lot of jitter, but good long-term stability.
1740		2226
1741	static void	2227	static void
1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2228	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1743	{	2229	{
1744	... its now a full hour (UTC, or TAI or whatever your clock follows)	2230	... its now a full hour (UTC, or TAI or whatever your clock follows)
1745	}	2231	}
1746		2232
1747	ev_periodic hourly_tick;	2233	ev_periodic hourly_tick;
…		…
1773	Signal watchers will trigger an event when the process receives a specific	2259	Signal watchers will trigger an event when the process receives a specific
1774	signal one or more times. Even though signals are very asynchronous, libev	2260	signal one or more times. Even though signals are very asynchronous, libev
1775	will try it's best to deliver signals synchronously, i.e. as part of the	2261	will try it's best to deliver signals synchronously, i.e. as part of the
1776	normal event processing, like any other event.	2262	normal event processing, like any other event.
1777		2263
1778	If you want signals asynchronously, just use C<sigaction> as you would	2264	If you want signals to be delivered truly asynchronously, just use
1779	do without libev and forget about sharing the signal. You can even use	2265	C<sigaction> as you would do without libev and forget about sharing
1780	C<ev_async> from a signal handler to synchronously wake up an event loop.	2266	the signal. You can even use C<ev_async> from a signal handler to
		2267	synchronously wake up an event loop.
1781		2268
1782	You can configure as many watchers as you like per signal. Only when the	2269	You can configure as many watchers as you like for the same signal, but
		2270	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2271	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2272	C<SIGINT> in both the default loop and another loop at the same time. At
		2273	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2274
1783	first watcher gets started will libev actually register a signal handler	2275	When the first watcher gets started will libev actually register something
1784	with the kernel (thus it coexists with your own signal handlers as long as	2276	with the kernel (thus it coexists with your own signal handlers as long as
1785	you don't register any with libev for the same signal). Similarly, when	2277	you don't register any with libev for the same signal).
1786	the last signal watcher for a signal is stopped, libev will reset the
1787	signal handler to SIG_DFL (regardless of what it was set to before).
1788		2278
1789	If possible and supported, libev will install its handlers with	2279	If possible and supported, libev will install its handlers with
1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2280	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1791	interrupted. If you have a problem with system calls getting interrupted by	2281	not be unduly interrupted. If you have a problem with system calls getting
1792	signals you can block all signals in an C<ev_check> watcher and unblock	2282	interrupted by signals you can block all signals in an C<ev_check> watcher
1793	them in an C<ev_prepare> watcher.	2283	and unblock them in an C<ev_prepare> watcher.
		2284
		2285	=head3 The special problem of inheritance over fork/execve/pthread_create
		2286
		2287	Both the signal mask (C<sigprocmask>) and the signal disposition
		2288	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2289	stopping it again), that is, libev might or might not block the signal,
		2290	and might or might not set or restore the installed signal handler.
		2291
		2292	While this does not matter for the signal disposition (libev never
		2293	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2294	C<execve>), this matters for the signal mask: many programs do not expect
		2295	certain signals to be blocked.
		2296
		2297	This means that before calling C<exec> (from the child) you should reset
		2298	the signal mask to whatever "default" you expect (all clear is a good
		2299	choice usually).
		2300
		2301	The simplest way to ensure that the signal mask is reset in the child is
		2302	to install a fork handler with C<pthread_atfork> that resets it. That will
		2303	catch fork calls done by libraries (such as the libc) as well.
		2304
		2305	In current versions of libev, the signal will not be blocked indefinitely
		2306	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2307	the window of opportunity for problems, it will not go away, as libev
		2308	I<has> to modify the signal mask, at least temporarily.
		2309
		2310	So I can't stress this enough: I<If you do not reset your signal mask when
		2311	you expect it to be empty, you have a race condition in your code>. This
		2312	is not a libev-specific thing, this is true for most event libraries.
1794		2313
1795	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1796		2315
1797	=over 4	2316	=over 4
1798		2317
…		…
1814	Example: Try to exit cleanly on SIGINT.	2333	Example: Try to exit cleanly on SIGINT.
1815		2334
1816	static void	2335	static void
1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2336	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1818	{	2337	{
1819	ev_unloop (loop, EVUNLOOP_ALL);	2338	ev_break (loop, EVBREAK_ALL);
1820	}	2339	}
1821		2340
1822	ev_signal signal_watcher;	2341	ev_signal signal_watcher;
1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2342	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1824	ev_signal_start (loop, &signal_watcher);	2343	ev_signal_start (loop, &signal_watcher);
…		…
1830	some child status changes (most typically when a child of yours dies or	2349	some child status changes (most typically when a child of yours dies or
1831	exits). It is permissible to install a child watcher I<after> the child	2350	exits). It is permissible to install a child watcher I<after> the child
1832	has been forked (which implies it might have already exited), as long	2351	has been forked (which implies it might have already exited), as long
1833	as the event loop isn't entered (or is continued from a watcher), i.e.,	2352	as the event loop isn't entered (or is continued from a watcher), i.e.,
1834	forking and then immediately registering a watcher for the child is fine,	2353	forking and then immediately registering a watcher for the child is fine,
1835	but forking and registering a watcher a few event loop iterations later is	2354	but forking and registering a watcher a few event loop iterations later or
1836	not.	2355	in the next callback invocation is not.
1837		2356
1838	Only the default event loop is capable of handling signals, and therefore	2357	Only the default event loop is capable of handling signals, and therefore
1839	you can only register child watchers in the default event loop.	2358	you can only register child watchers in the default event loop.
1840		2359
		2360	Due to some design glitches inside libev, child watchers will always be
		2361	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2362	libev)
		2363
1841	=head3 Process Interaction	2364	=head3 Process Interaction
1842		2365
1843	Libev grabs C<SIGCHLD> as soon as the default event loop is	2366	Libev grabs C<SIGCHLD> as soon as the default event loop is
1844	initialised. This is necessary to guarantee proper behaviour even if	2367	initialised. This is necessary to guarantee proper behaviour even if the
1845	the first child watcher is started after the child exits. The occurrence	2368	first child watcher is started after the child exits. The occurrence
1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2369	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1847	synchronously as part of the event loop processing. Libev always reaps all	2370	synchronously as part of the event loop processing. Libev always reaps all
1848	children, even ones not watched.	2371	children, even ones not watched.
1849		2372
1850	=head3 Overriding the Built-In Processing	2373	=head3 Overriding the Built-In Processing
…		…
1860	=head3 Stopping the Child Watcher	2383	=head3 Stopping the Child Watcher
1861		2384
1862	Currently, the child watcher never gets stopped, even when the	2385	Currently, the child watcher never gets stopped, even when the
1863	child terminates, so normally one needs to stop the watcher in the	2386	child terminates, so normally one needs to stop the watcher in the
1864	callback. Future versions of libev might stop the watcher automatically	2387	callback. Future versions of libev might stop the watcher automatically
1865	when a child exit is detected.	2388	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2389	problem).
1866		2390
1867	=head3 Watcher-Specific Functions and Data Members	2391	=head3 Watcher-Specific Functions and Data Members
1868		2392
1869	=over 4	2393	=over 4
1870		2394
…		…
1997		2521
1998	There is no support for kqueue, as apparently it cannot be used to	2522	There is no support for kqueue, as apparently it cannot be used to
1999	implement this functionality, due to the requirement of having a file	2523	implement this functionality, due to the requirement of having a file
2000	descriptor open on the object at all times, and detecting renames, unlinks	2524	descriptor open on the object at all times, and detecting renames, unlinks
2001	etc. is difficult.	2525	etc. is difficult.
		2526
		2527	=head3 C<stat ()> is a synchronous operation
		2528
		2529	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2530	the process. The exception are C<ev_stat> watchers - those call C<stat
		2531	()>, which is a synchronous operation.
		2532
		2533	For local paths, this usually doesn't matter: unless the system is very
		2534	busy or the intervals between stat's are large, a stat call will be fast,
		2535	as the path data is usually in memory already (except when starting the
		2536	watcher).
		2537
		2538	For networked file systems, calling C<stat ()> can block an indefinite
		2539	time due to network issues, and even under good conditions, a stat call
		2540	often takes multiple milliseconds.
		2541
		2542	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2543	paths, although this is fully supported by libev.
2002		2544
2003	=head3 The special problem of stat time resolution	2545	=head3 The special problem of stat time resolution
2004		2546
2005	The C<stat ()> system call only supports full-second resolution portably,	2547	The C<stat ()> system call only supports full-second resolution portably,
2006	and even on systems where the resolution is higher, most file systems	2548	and even on systems where the resolution is higher, most file systems
…		…
2155		2697
2156	=head3 Watcher-Specific Functions and Data Members	2698	=head3 Watcher-Specific Functions and Data Members
2157		2699
2158	=over 4	2700	=over 4
2159		2701
2160	=item ev_idle_init (ev_signal *, callback)	2702	=item ev_idle_init (ev_idle *, callback)
2161		2703
2162	Initialises and configures the idle watcher - it has no parameters of any	2704	Initialises and configures the idle watcher - it has no parameters of any
2163	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2705	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2164	believe me.	2706	believe me.
2165		2707
…		…
2178	// no longer anything immediate to do.	2720	// no longer anything immediate to do.
2179	}	2721	}
2180		2722
2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2723	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2182	ev_idle_init (idle_watcher, idle_cb);	2724	ev_idle_init (idle_watcher, idle_cb);
2183	ev_idle_start (loop, idle_cb);	2725	ev_idle_start (loop, idle_watcher);
2184		2726
2185		2727
2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2728	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2187		2729
2188	Prepare and check watchers are usually (but not always) used in pairs:	2730	Prepare and check watchers are usually (but not always) used in pairs:
2189	prepare watchers get invoked before the process blocks and check watchers	2731	prepare watchers get invoked before the process blocks and check watchers
2190	afterwards.	2732	afterwards.
2191		2733
2192	You I<must not> call C<ev_loop> or similar functions that enter	2734	You I<must not> call C<ev_run> or similar functions that enter
2193	the current event loop from either C<ev_prepare> or C<ev_check>	2735	the current event loop from either C<ev_prepare> or C<ev_check>
2194	watchers. Other loops than the current one are fine, however. The	2736	watchers. Other loops than the current one are fine, however. The
2195	rationale behind this is that you do not need to check for recursion in	2737	rationale behind this is that you do not need to check for recursion in
2196	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2738	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2197	C<ev_check> so if you have one watcher of each kind they will always be	2739	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2281	struct pollfd fds [nfd];	2823	struct pollfd fds [nfd];
2282	// actual code will need to loop here and realloc etc.	2824	// actual code will need to loop here and realloc etc.
2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2825	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2284		2826
2285	/* the callback is illegal, but won't be called as we stop during check */	2827	/* the callback is illegal, but won't be called as we stop during check */
2286	ev_timer_init (&tw, 0, timeout * 1e-3);	2828	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2287	ev_timer_start (loop, &tw);	2829	ev_timer_start (loop, &tw);
2288		2830
2289	// create one ev_io per pollfd	2831	// create one ev_io per pollfd
2290	for (int i = 0; i < nfd; ++i)	2832	for (int i = 0; i < nfd; ++i)
2291	{	2833	{
…		…
2365		2907
2366	if (timeout >= 0)	2908	if (timeout >= 0)
2367	// create/start timer	2909	// create/start timer
2368		2910
2369	// poll	2911	// poll
2370	ev_loop (EV_A_ 0);	2912	ev_run (EV_A_ 0);
2371		2913
2372	// stop timer again	2914	// stop timer again
2373	if (timeout >= 0)	2915	if (timeout >= 0)
2374	ev_timer_stop (EV_A_ &to);	2916	ev_timer_stop (EV_A_ &to);
2375		2917
…		…
2404	some fds have to be watched and handled very quickly (with low latency),	2946	some fds have to be watched and handled very quickly (with low latency),
2405	and even priorities and idle watchers might have too much overhead. In	2947	and even priorities and idle watchers might have too much overhead. In
2406	this case you would put all the high priority stuff in one loop and all	2948	this case you would put all the high priority stuff in one loop and all
2407	the rest in a second one, and embed the second one in the first.	2949	the rest in a second one, and embed the second one in the first.
2408		2950
2409	As long as the watcher is active, the callback will be invoked every time	2951	As long as the watcher is active, the callback will be invoked every
2410	there might be events pending in the embedded loop. The callback must then	2952	time there might be events pending in the embedded loop. The callback
2411	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2953	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2412	their callbacks (you could also start an idle watcher to give the embedded	2954	sweep and invoke their callbacks (the callback doesn't need to invoke the
2413	loop strictly lower priority for example). You can also set the callback	2955	C<ev_embed_sweep> function directly, it could also start an idle watcher
2414	to C<0>, in which case the embed watcher will automatically execute the	2956	to give the embedded loop strictly lower priority for example).
2415	embedded loop sweep.
2416		2957
2417	As long as the watcher is started it will automatically handle events. The	2958	You can also set the callback to C<0>, in which case the embed watcher
2418	callback will be invoked whenever some events have been handled. You can	2959	will automatically execute the embedded loop sweep whenever necessary.
2419	set the callback to C<0> to avoid having to specify one if you are not
2420	interested in that.
2421		2960
2422	Also, there have not currently been made special provisions for forking:	2961	Fork detection will be handled transparently while the C<ev_embed> watcher
2423	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2962	is active, i.e., the embedded loop will automatically be forked when the
2424	but you will also have to stop and restart any C<ev_embed> watchers	2963	embedding loop forks. In other cases, the user is responsible for calling
2425	yourself - but you can use a fork watcher to handle this automatically,	2964	C<ev_loop_fork> on the embedded loop.
2426	and future versions of libev might do just that.
2427		2965
2428	Unfortunately, not all backends are embeddable: only the ones returned by	2966	Unfortunately, not all backends are embeddable: only the ones returned by
2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2967	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2430	portable one.	2968	portable one.
2431		2969
…		…
2457	if you do not want that, you need to temporarily stop the embed watcher).	2995	if you do not want that, you need to temporarily stop the embed watcher).
2458		2996
2459	=item ev_embed_sweep (loop, ev_embed *)	2997	=item ev_embed_sweep (loop, ev_embed *)
2460		2998
2461	Make a single, non-blocking sweep over the embedded loop. This works	2999	Make a single, non-blocking sweep over the embedded loop. This works
2462	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3000	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2463	appropriate way for embedded loops.	3001	appropriate way for embedded loops.
2464		3002
2465	=item struct ev_loop *other [read-only]	3003	=item struct ev_loop *other [read-only]
2466		3004
2467	The embedded event loop.	3005	The embedded event loop.
…		…
2525	event loop blocks next and before C<ev_check> watchers are being called,	3063	event loop blocks next and before C<ev_check> watchers are being called,
2526	and only in the child after the fork. If whoever good citizen calling	3064	and only in the child after the fork. If whoever good citizen calling
2527	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3065	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2528	handlers will be invoked, too, of course.	3066	handlers will be invoked, too, of course.
2529		3067
		3068	=head3 The special problem of life after fork - how is it possible?
		3069
		3070	Most uses of C<fork()> consist of forking, then some simple calls to set
		3071	up/change the process environment, followed by a call to C<exec()>. This
		3072	sequence should be handled by libev without any problems.
		3073
		3074	This changes when the application actually wants to do event handling
		3075	in the child, or both parent in child, in effect "continuing" after the
		3076	fork.
		3077
		3078	The default mode of operation (for libev, with application help to detect
		3079	forks) is to duplicate all the state in the child, as would be expected
		3080	when I<either> the parent I<or> the child process continues.
		3081
		3082	When both processes want to continue using libev, then this is usually the
		3083	wrong result. In that case, usually one process (typically the parent) is
		3084	supposed to continue with all watchers in place as before, while the other
		3085	process typically wants to start fresh, i.e. without any active watchers.
		3086
		3087	The cleanest and most efficient way to achieve that with libev is to
		3088	simply create a new event loop, which of course will be "empty", and
		3089	use that for new watchers. This has the advantage of not touching more
		3090	memory than necessary, and thus avoiding the copy-on-write, and the
		3091	disadvantage of having to use multiple event loops (which do not support
		3092	signal watchers).
		3093
		3094	When this is not possible, or you want to use the default loop for
		3095	other reasons, then in the process that wants to start "fresh", call
		3096	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3097	Destroying the default loop will "orphan" (not stop) all registered
		3098	watchers, so you have to be careful not to execute code that modifies
		3099	those watchers. Note also that in that case, you have to re-register any
		3100	signal watchers.
		3101
2530	=head3 Watcher-Specific Functions and Data Members	3102	=head3 Watcher-Specific Functions and Data Members
2531		3103
2532	=over 4	3104	=over 4
2533		3105
2534	=item ev_fork_init (ev_signal *, callback)	3106	=item ev_fork_init (ev_fork *, callback)
2535		3107
2536	Initialises and configures the fork watcher - it has no parameters of any	3108	Initialises and configures the fork watcher - it has no parameters of any
2537	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3109	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2538	believe me.	3110	really.
2539		3111
2540	=back	3112	=back
2541		3113
2542		3114
		3115	=head2 C<ev_cleanup> - even the best things end
		3116
		3117	Cleanup watchers are called just before the event loop is being destroyed
		3118	by a call to C<ev_loop_destroy>.
		3119
		3120	While there is no guarantee that the event loop gets destroyed, cleanup
		3121	watchers provide a convenient method to install cleanup hooks for your
		3122	program, worker threads and so on - you just to make sure to destroy the
		3123	loop when you want them to be invoked.
		3124
		3125	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3126	all other watchers, they do not keep a reference to the event loop (which
		3127	makes a lot of sense if you think about it). Like all other watchers, you
		3128	can call libev functions in the callback, except C<ev_cleanup_start>.
		3129
		3130	=head3 Watcher-Specific Functions and Data Members
		3131
		3132	=over 4
		3133
		3134	=item ev_cleanup_init (ev_cleanup *, callback)
		3135
		3136	Initialises and configures the cleanup watcher - it has no parameters of
		3137	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3138	pointless, I assure you.
		3139
		3140	=back
		3141
		3142	Example: Register an atexit handler to destroy the default loop, so any
		3143	cleanup functions are called.
		3144
		3145	static void
		3146	program_exits (void)
		3147	{
		3148	ev_loop_destroy (EV_DEFAULT_UC);
		3149	}
		3150
		3151	...
		3152	atexit (program_exits);
		3153
		3154
2543	=head2 C<ev_async> - how to wake up another event loop	3155	=head2 C<ev_async> - how to wake up an event loop
2544		3156
2545	In general, you cannot use an C<ev_loop> from multiple threads or other	3157	In general, you cannot use an C<ev_run> from multiple threads or other
2546	asynchronous sources such as signal handlers (as opposed to multiple event	3158	asynchronous sources such as signal handlers (as opposed to multiple event
2547	loops - those are of course safe to use in different threads).	3159	loops - those are of course safe to use in different threads).
2548		3160
2549	Sometimes, however, you need to wake up another event loop you do not	3161	Sometimes, however, you need to wake up an event loop you do not control,
2550	control, for example because it belongs to another thread. This is what	3162	for example because it belongs to another thread. This is what C<ev_async>
2551	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3163	watchers do: as long as the C<ev_async> watcher is active, you can signal
2552	can signal it by calling C<ev_async_send>, which is thread- and signal	3164	it by calling C<ev_async_send>, which is thread- and signal safe.
2553	safe.
2554		3165
2555	This functionality is very similar to C<ev_signal> watchers, as signals,	3166	This functionality is very similar to C<ev_signal> watchers, as signals,
2556	too, are asynchronous in nature, and signals, too, will be compressed	3167	too, are asynchronous in nature, and signals, too, will be compressed
2557	(i.e. the number of callback invocations may be less than the number of	3168	(i.e. the number of callback invocations may be less than the number of
2558	C<ev_async_sent> calls).	3169	C<ev_async_sent> calls).
…		…
2563	=head3 Queueing	3174	=head3 Queueing
2564		3175
2565	C<ev_async> does not support queueing of data in any way. The reason	3176	C<ev_async> does not support queueing of data in any way. The reason
2566	is that the author does not know of a simple (or any) algorithm for a	3177	is that the author does not know of a simple (or any) algorithm for a
2567	multiple-writer-single-reader queue that works in all cases and doesn't	3178	multiple-writer-single-reader queue that works in all cases and doesn't
2568	need elaborate support such as pthreads.	3179	need elaborate support such as pthreads or unportable memory access
		3180	semantics.
2569		3181
2570	That means that if you want to queue data, you have to provide your own	3182	That means that if you want to queue data, you have to provide your own
2571	queue. But at least I can tell you how to implement locking around your	3183	queue. But at least I can tell you how to implement locking around your
2572	queue:	3184	queue:
2573		3185
…		…
2662	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3274	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2663	C<ev_feed_event>, this call is safe to do from other threads, signal or	3275	C<ev_feed_event>, this call is safe to do from other threads, signal or
2664	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3276	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2665	section below on what exactly this means).	3277	section below on what exactly this means).
2666		3278
		3279	Note that, as with other watchers in libev, multiple events might get
		3280	compressed into a single callback invocation (another way to look at this
		3281	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3282	reset when the event loop detects that).
		3283
2667	This call incurs the overhead of a system call only once per loop iteration,	3284	This call incurs the overhead of a system call only once per event loop
2668	so while the overhead might be noticeable, it doesn't apply to repeated	3285	iteration, so while the overhead might be noticeable, it doesn't apply to
2669	calls to C<ev_async_send>.	3286	repeated calls to C<ev_async_send> for the same event loop.
2670		3287
2671	=item bool = ev_async_pending (ev_async *)	3288	=item bool = ev_async_pending (ev_async *)
2672		3289
2673	Returns a non-zero value when C<ev_async_send> has been called on the	3290	Returns a non-zero value when C<ev_async_send> has been called on the
2674	watcher but the event has not yet been processed (or even noted) by the	3291	watcher but the event has not yet been processed (or even noted) by the
…		…
2677	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3294	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2678	the loop iterates next and checks for the watcher to have become active,	3295	the loop iterates next and checks for the watcher to have become active,
2679	it will reset the flag again. C<ev_async_pending> can be used to very	3296	it will reset the flag again. C<ev_async_pending> can be used to very
2680	quickly check whether invoking the loop might be a good idea.	3297	quickly check whether invoking the loop might be a good idea.
2681		3298
2682	Not that this does I<not> check whether the watcher itself is pending, only	3299	Not that this does I<not> check whether the watcher itself is pending,
2683	whether it has been requested to make this watcher pending.	3300	only whether it has been requested to make this watcher pending: there
		3301	is a time window between the event loop checking and resetting the async
		3302	notification, and the callback being invoked.
2684		3303
2685	=back	3304	=back
2686		3305
2687		3306
2688	=head1 OTHER FUNCTIONS	3307	=head1 OTHER FUNCTIONS
…		…
2705		3324
2706	If C<timeout> is less than 0, then no timeout watcher will be	3325	If C<timeout> is less than 0, then no timeout watcher will be
2707	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3326	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2708	repeat = 0) will be started. C<0> is a valid timeout.	3327	repeat = 0) will be started. C<0> is a valid timeout.
2709		3328
2710	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3329	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2711	passed an C<revents> set like normal event callbacks (a combination of	3330	passed an C<revents> set like normal event callbacks (a combination of
2712	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2713	value passed to C<ev_once>. Note that it is possible to receive I<both>	3332	value passed to C<ev_once>. Note that it is possible to receive I<both>
2714	a timeout and an io event at the same time - you probably should give io	3333	a timeout and an io event at the same time - you probably should give io
2715	events precedence.	3334	events precedence.
2716		3335
2717	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3336	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2718		3337
2719	static void stdin_ready (int revents, void *arg)	3338	static void stdin_ready (int revents, void *arg)
2720	{	3339	{
2721	if (revents & EV_READ)	3340	if (revents & EV_READ)
2722	/* stdin might have data for us, joy! */;	3341	/* stdin might have data for us, joy! */;
2723	else if (revents & EV_TIMEOUT)	3342	else if (revents & EV_TIMER)
2724	/* doh, nothing entered */;	3343	/* doh, nothing entered */;
2725	}	3344	}
2726		3345
2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2728		3347
2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2730
2731	Feeds the given event set into the event loop, as if the specified event
2732	had happened for the specified watcher (which must be a pointer to an
2733	initialised but not necessarily started event watcher).
2734
2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3348	=item ev_feed_fd_event (loop, int fd, int revents)
2736		3349
2737	Feed an event on the given fd, as if a file descriptor backend detected	3350	Feed an event on the given fd, as if a file descriptor backend detected
2738	the given events it.	3351	the given events it.
2739		3352
2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3353	=item ev_feed_signal_event (loop, int signum)
2741		3354
2742	Feed an event as if the given signal occurred (C<loop> must be the default	3355	Feed an event as if the given signal occurred (C<loop> must be the default
2743	loop!).	3356	loop!).
2744		3357
2745	=back	3358	=back
…		…
2825		3438
2826	=over 4	3439	=over 4
2827		3440
2828	=item ev::TYPE::TYPE ()	3441	=item ev::TYPE::TYPE ()
2829		3442
2830	=item ev::TYPE::TYPE (struct ev_loop *)	3443	=item ev::TYPE::TYPE (loop)
2831		3444
2832	=item ev::TYPE::~TYPE	3445	=item ev::TYPE::~TYPE
2833		3446
2834	The constructor (optionally) takes an event loop to associate the watcher	3447	The constructor (optionally) takes an event loop to associate the watcher
2835	with. If it is omitted, it will use C<EV_DEFAULT>.	3448	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2867		3480
2868	myclass obj;	3481	myclass obj;
2869	ev::io iow;	3482	ev::io iow;
2870	iow.set <myclass, &myclass::io_cb> (&obj);	3483	iow.set <myclass, &myclass::io_cb> (&obj);
2871		3484
		3485	=item w->set (object *)
		3486
		3487	This is a variation of a method callback - leaving out the method to call
		3488	will default the method to C<operator ()>, which makes it possible to use
		3489	functor objects without having to manually specify the C<operator ()> all
		3490	the time. Incidentally, you can then also leave out the template argument
		3491	list.
		3492
		3493	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3494	int revents)>.
		3495
		3496	See the method-C<set> above for more details.
		3497
		3498	Example: use a functor object as callback.
		3499
		3500	struct myfunctor
		3501	{
		3502	void operator() (ev::io &w, int revents)
		3503	{
		3504	...
		3505	}
		3506	}
		3507
		3508	myfunctor f;
		3509
		3510	ev::io w;
		3511	w.set (&f);
		3512
2872	=item w->set<function> (void *data = 0)	3513	=item w->set<function> (void *data = 0)
2873		3514
2874	Also sets a callback, but uses a static method or plain function as	3515	Also sets a callback, but uses a static method or plain function as
2875	callback. The optional C<data> argument will be stored in the watcher's	3516	callback. The optional C<data> argument will be stored in the watcher's
2876	C<data> member and is free for you to use.	3517	C<data> member and is free for you to use.
…		…
2882	Example: Use a plain function as callback.	3523	Example: Use a plain function as callback.
2883		3524
2884	static void io_cb (ev::io &w, int revents) { }	3525	static void io_cb (ev::io &w, int revents) { }
2885	iow.set <io_cb> ();	3526	iow.set <io_cb> ();
2886		3527
2887	=item w->set (struct ev_loop *)	3528	=item w->set (loop)
2888		3529
2889	Associates a different C<struct ev_loop> with this watcher. You can only	3530	Associates a different C<struct ev_loop> with this watcher. You can only
2890	do this when the watcher is inactive (and not pending either).	3531	do this when the watcher is inactive (and not pending either).
2891		3532
2892	=item w->set ([arguments])	3533	=item w->set ([arguments])
2893		3534
2894	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3535	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2895	called at least once. Unlike the C counterpart, an active watcher gets	3536	method or a suitable start method must be called at least once. Unlike the
2896	automatically stopped and restarted when reconfiguring it with this	3537	C counterpart, an active watcher gets automatically stopped and restarted
2897	method.	3538	when reconfiguring it with this method.
2898		3539
2899	=item w->start ()	3540	=item w->start ()
2900		3541
2901	Starts the watcher. Note that there is no C<loop> argument, as the	3542	Starts the watcher. Note that there is no C<loop> argument, as the
2902	constructor already stores the event loop.	3543	constructor already stores the event loop.
2903		3544
		3545	=item w->start ([arguments])
		3546
		3547	Instead of calling C<set> and C<start> methods separately, it is often
		3548	convenient to wrap them in one call. Uses the same type of arguments as
		3549	the configure C<set> method of the watcher.
		3550
2904	=item w->stop ()	3551	=item w->stop ()
2905		3552
2906	Stops the watcher if it is active. Again, no C<loop> argument.	3553	Stops the watcher if it is active. Again, no C<loop> argument.
2907		3554
2908	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3555	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2920		3567
2921	=back	3568	=back
2922		3569
2923	=back	3570	=back
2924		3571
2925	Example: Define a class with an IO and idle watcher, start one of them in	3572	Example: Define a class with two I/O and idle watchers, start the I/O
2926	the constructor.	3573	watchers in the constructor.
2927		3574
2928	class myclass	3575	class myclass
2929	{	3576	{
2930	ev::io io ; void io_cb (ev::io &w, int revents);	3577	ev::io io ; void io_cb (ev::io &w, int revents);
		3578	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3579	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2932		3580
2933	myclass (int fd)	3581	myclass (int fd)
2934	{	3582	{
2935	io .set <myclass, &myclass::io_cb > (this);	3583	io .set <myclass, &myclass::io_cb > (this);
		3584	io2 .set <myclass, &myclass::io2_cb > (this);
2936	idle.set <myclass, &myclass::idle_cb> (this);	3585	idle.set <myclass, &myclass::idle_cb> (this);
2937		3586
2938	io.start (fd, ev::READ);	3587	io.set (fd, ev::WRITE); // configure the watcher
		3588	io.start (); // start it whenever convenient
		3589
		3590	io2.start (fd, ev::READ); // set + start in one call
2939	}	3591	}
2940	};	3592	};
2941		3593
2942		3594
2943	=head1 OTHER LANGUAGE BINDINGS	3595	=head1 OTHER LANGUAGE BINDINGS
…		…
2962	L<http://software.schmorp.de/pkg/EV>.	3614	L<http://software.schmorp.de/pkg/EV>.
2963		3615
2964	=item Python	3616	=item Python
2965		3617
2966	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3618	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2967	seems to be quite complete and well-documented. Note, however, that the	3619	seems to be quite complete and well-documented.
2968	patch they require for libev is outright dangerous as it breaks the ABI
2969	for everybody else, and therefore, should never be applied in an installed
2970	libev (if python requires an incompatible ABI then it needs to embed
2971	libev).
2972		3620
2973	=item Ruby	3621	=item Ruby
2974		3622
2975	Tony Arcieri has written a ruby extension that offers access to a subset	3623	Tony Arcieri has written a ruby extension that offers access to a subset
2976	of the libev API and adds file handle abstractions, asynchronous DNS and	3624	of the libev API and adds file handle abstractions, asynchronous DNS and
2977	more on top of it. It can be found via gem servers. Its homepage is at	3625	more on top of it. It can be found via gem servers. Its homepage is at
2978	L<http://rev.rubyforge.org/>.	3626	L<http://rev.rubyforge.org/>.
2979		3627
		3628	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3629	makes rev work even on mingw.
		3630
		3631	=item Haskell
		3632
		3633	A haskell binding to libev is available at
		3634	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3635
2980	=item D	3636	=item D
2981		3637
2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3638	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3639	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2984		3640
2985	=item Ocaml	3641	=item Ocaml
2986		3642
2987	Erkki Seppala has written Ocaml bindings for libev, to be found at	3643	Erkki Seppala has written Ocaml bindings for libev, to be found at
2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3644	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3645
		3646	=item Lua
		3647
		3648	Brian Maher has written a partial interface to libev for lua (at the
		3649	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3650	L<http://github.com/brimworks/lua-ev>.
2989		3651
2990	=back	3652	=back
2991		3653
2992		3654
2993	=head1 MACRO MAGIC	3655	=head1 MACRO MAGIC
…		…
3007	loop argument"). The C<EV_A> form is used when this is the sole argument,	3669	loop argument"). The C<EV_A> form is used when this is the sole argument,
3008	C<EV_A_> is used when other arguments are following. Example:	3670	C<EV_A_> is used when other arguments are following. Example:
3009		3671
3010	ev_unref (EV_A);	3672	ev_unref (EV_A);
3011	ev_timer_add (EV_A_ watcher);	3673	ev_timer_add (EV_A_ watcher);
3012	ev_loop (EV_A_ 0);	3674	ev_run (EV_A_ 0);
3013		3675
3014	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3676	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3015	which is often provided by the following macro.	3677	which is often provided by the following macro.
3016		3678
3017	=item C<EV_P>, C<EV_P_>	3679	=item C<EV_P>, C<EV_P_>
…		…
3057	}	3719	}
3058		3720
3059	ev_check check;	3721	ev_check check;
3060	ev_check_init (&check, check_cb);	3722	ev_check_init (&check, check_cb);
3061	ev_check_start (EV_DEFAULT_ &check);	3723	ev_check_start (EV_DEFAULT_ &check);
3062	ev_loop (EV_DEFAULT_ 0);	3724	ev_run (EV_DEFAULT_ 0);
3063		3725
3064	=head1 EMBEDDING	3726	=head1 EMBEDDING
3065		3727
3066	Libev can (and often is) directly embedded into host	3728	Libev can (and often is) directly embedded into host
3067	applications. Examples of applications that embed it include the Deliantra	3729	applications. Examples of applications that embed it include the Deliantra
…		…
3147	libev.m4	3809	libev.m4
3148		3810
3149	=head2 PREPROCESSOR SYMBOLS/MACROS	3811	=head2 PREPROCESSOR SYMBOLS/MACROS
3150		3812
3151	Libev can be configured via a variety of preprocessor symbols you have to	3813	Libev can be configured via a variety of preprocessor symbols you have to
3152	define before including any of its files. The default in the absence of	3814	define before including (or compiling) any of its files. The default in
3153	autoconf is documented for every option.	3815	the absence of autoconf is documented for every option.
		3816
		3817	Symbols marked with "(h)" do not change the ABI, and can have different
		3818	values when compiling libev vs. including F<ev.h>, so it is permissible
		3819	to redefine them before including F<ev.h> without breaking compatibility
		3820	to a compiled library. All other symbols change the ABI, which means all
		3821	users of libev and the libev code itself must be compiled with compatible
		3822	settings.
3154		3823
3155	=over 4	3824	=over 4
3156		3825
		3826	=item EV_COMPAT3 (h)
		3827
		3828	Backwards compatibility is a major concern for libev. This is why this
		3829	release of libev comes with wrappers for the functions and symbols that
		3830	have been renamed between libev version 3 and 4.
		3831
		3832	You can disable these wrappers (to test compatibility with future
		3833	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3834	sources. This has the additional advantage that you can drop the C<struct>
		3835	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3836	typedef in that case.
		3837
		3838	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3839	and in some even more future version the compatibility code will be
		3840	removed completely.
		3841
3157	=item EV_STANDALONE	3842	=item EV_STANDALONE (h)
3158		3843
3159	Must always be C<1> if you do not use autoconf configuration, which	3844	Must always be C<1> if you do not use autoconf configuration, which
3160	keeps libev from including F<config.h>, and it also defines dummy	3845	keeps libev from including F<config.h>, and it also defines dummy
3161	implementations for some libevent functions (such as logging, which is not	3846	implementations for some libevent functions (such as logging, which is not
3162	supported). It will also not define any of the structs usually found in	3847	supported). It will also not define any of the structs usually found in
3163	F<event.h> that are not directly supported by the libev core alone.	3848	F<event.h> that are not directly supported by the libev core alone.
3164		3849
		3850	In standalone mode, libev will still try to automatically deduce the
		3851	configuration, but has to be more conservative.
		3852
3165	=item EV_USE_MONOTONIC	3853	=item EV_USE_MONOTONIC
3166		3854
3167	If defined to be C<1>, libev will try to detect the availability of the	3855	If defined to be C<1>, libev will try to detect the availability of the
3168	monotonic clock option at both compile time and runtime. Otherwise no use	3856	monotonic clock option at both compile time and runtime. Otherwise no
3169	of the monotonic clock option will be attempted. If you enable this, you	3857	use of the monotonic clock option will be attempted. If you enable this,
3170	usually have to link against librt or something similar. Enabling it when	3858	you usually have to link against librt or something similar. Enabling it
3171	the functionality isn't available is safe, though, although you have	3859	when the functionality isn't available is safe, though, although you have
3172	to make sure you link against any libraries where the C<clock_gettime>	3860	to make sure you link against any libraries where the C<clock_gettime>
3173	function is hiding in (often F<-lrt>).	3861	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3174		3862
3175	=item EV_USE_REALTIME	3863	=item EV_USE_REALTIME
3176		3864
3177	If defined to be C<1>, libev will try to detect the availability of the	3865	If defined to be C<1>, libev will try to detect the availability of the
3178	real-time clock option at compile time (and assume its availability at	3866	real-time clock option at compile time (and assume its availability
3179	runtime if successful). Otherwise no use of the real-time clock option will	3867	at runtime if successful). Otherwise no use of the real-time clock
3180	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3868	option will be attempted. This effectively replaces C<gettimeofday>
3181	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3869	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3182	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3870	correctness. See the note about libraries in the description of
		3871	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3872	C<EV_USE_CLOCK_SYSCALL>.
		3873
		3874	=item EV_USE_CLOCK_SYSCALL
		3875
		3876	If defined to be C<1>, libev will try to use a direct syscall instead
		3877	of calling the system-provided C<clock_gettime> function. This option
		3878	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3879	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3880	programs needlessly. Using a direct syscall is slightly slower (in
		3881	theory), because no optimised vdso implementation can be used, but avoids
		3882	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3883	higher, as it simplifies linking (no need for C<-lrt>).
3183		3884
3184	=item EV_USE_NANOSLEEP	3885	=item EV_USE_NANOSLEEP
3185		3886
3186	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3887	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3187	and will use it for delays. Otherwise it will use C<select ()>.	3888	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3203		3904
3204	=item EV_SELECT_USE_FD_SET	3905	=item EV_SELECT_USE_FD_SET
3205		3906
3206	If defined to C<1>, then the select backend will use the system C<fd_set>	3907	If defined to C<1>, then the select backend will use the system C<fd_set>
3207	structure. This is useful if libev doesn't compile due to a missing	3908	structure. This is useful if libev doesn't compile due to a missing
3208	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3909	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3209	exotic systems. This usually limits the range of file descriptors to some	3910	on exotic systems. This usually limits the range of file descriptors to
3210	low limit such as 1024 or might have other limitations (winsocket only	3911	some low limit such as 1024 or might have other limitations (winsocket
3211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3912	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3212	influence the size of the C<fd_set> used.	3913	configures the maximum size of the C<fd_set>.
3213		3914
3214	=item EV_SELECT_IS_WINSOCKET	3915	=item EV_SELECT_IS_WINSOCKET
3215		3916
3216	When defined to C<1>, the select backend will assume that	3917	When defined to C<1>, the select backend will assume that
3217	select/socket/connect etc. don't understand file descriptors but	3918	select/socket/connect etc. don't understand file descriptors but
…		…
3219	be used is the winsock select). This means that it will call	3920	be used is the winsock select). This means that it will call
3220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3921	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3221	it is assumed that all these functions actually work on fds, even	3922	it is assumed that all these functions actually work on fds, even
3222	on win32. Should not be defined on non-win32 platforms.	3923	on win32. Should not be defined on non-win32 platforms.
3223		3924
3224	=item EV_FD_TO_WIN32_HANDLE	3925	=item EV_FD_TO_WIN32_HANDLE(fd)
3225		3926
3226	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3927	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3227	file descriptors to socket handles. When not defining this symbol (the	3928	file descriptors to socket handles. When not defining this symbol (the
3228	default), then libev will call C<_get_osfhandle>, which is usually	3929	default), then libev will call C<_get_osfhandle>, which is usually
3229	correct. In some cases, programs use their own file descriptor management,	3930	correct. In some cases, programs use their own file descriptor management,
3230	in which case they can provide this function to map fds to socket handles.	3931	in which case they can provide this function to map fds to socket handles.
		3932
		3933	=item EV_WIN32_HANDLE_TO_FD(handle)
		3934
		3935	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3936	using the standard C<_open_osfhandle> function. For programs implementing
		3937	their own fd to handle mapping, overwriting this function makes it easier
		3938	to do so. This can be done by defining this macro to an appropriate value.
		3939
		3940	=item EV_WIN32_CLOSE_FD(fd)
		3941
		3942	If programs implement their own fd to handle mapping on win32, then this
		3943	macro can be used to override the C<close> function, useful to unregister
		3944	file descriptors again. Note that the replacement function has to close
		3945	the underlying OS handle.
3231		3946
3232	=item EV_USE_POLL	3947	=item EV_USE_POLL
3233		3948
3234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3949	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3235	backend. Otherwise it will be enabled on non-win32 platforms. It	3950	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3282	as well as for signal and thread safety in C<ev_async> watchers.	3997	as well as for signal and thread safety in C<ev_async> watchers.
3283		3998
3284	In the absence of this define, libev will use C<sig_atomic_t volatile>	3999	In the absence of this define, libev will use C<sig_atomic_t volatile>
3285	(from F<signal.h>), which is usually good enough on most platforms.	4000	(from F<signal.h>), which is usually good enough on most platforms.
3286		4001
3287	=item EV_H	4002	=item EV_H (h)
3288		4003
3289	The name of the F<ev.h> header file used to include it. The default if	4004	The name of the F<ev.h> header file used to include it. The default if
3290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4005	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3291	used to virtually rename the F<ev.h> header file in case of conflicts.	4006	used to virtually rename the F<ev.h> header file in case of conflicts.
3292		4007
3293	=item EV_CONFIG_H	4008	=item EV_CONFIG_H (h)
3294		4009
3295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4010	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4011	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3297	C<EV_H>, above.	4012	C<EV_H>, above.
3298		4013
3299	=item EV_EVENT_H	4014	=item EV_EVENT_H (h)
3300		4015
3301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4016	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3302	of how the F<event.h> header can be found, the default is C<"event.h">.	4017	of how the F<event.h> header can be found, the default is C<"event.h">.
3303		4018
3304	=item EV_PROTOTYPES	4019	=item EV_PROTOTYPES (h)
3305		4020
3306	If defined to be C<0>, then F<ev.h> will not define any function	4021	If defined to be C<0>, then F<ev.h> will not define any function
3307	prototypes, but still define all the structs and other symbols. This is	4022	prototypes, but still define all the structs and other symbols. This is
3308	occasionally useful if you want to provide your own wrapper functions	4023	occasionally useful if you want to provide your own wrapper functions
3309	around libev functions.	4024	around libev functions.
…		…
3331	fine.	4046	fine.
3332		4047
3333	If your embedding application does not need any priorities, defining these	4048	If your embedding application does not need any priorities, defining these
3334	both to C<0> will save some memory and CPU.	4049	both to C<0> will save some memory and CPU.
3335		4050
3336	=item EV_PERIODIC_ENABLE	4051	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4052	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4053	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3337		4054
3338	If undefined or defined to be C<1>, then periodic timers are supported. If	4055	If undefined or defined to be C<1> (and the platform supports it), then
3339	defined to be C<0>, then they are not. Disabling them saves a few kB of	4056	the respective watcher type is supported. If defined to be C<0>, then it
3340	code.	4057	is not. Disabling watcher types mainly saves code size.
3341		4058
3342	=item EV_IDLE_ENABLE	4059	=item EV_FEATURES
3343
3344	If undefined or defined to be C<1>, then idle watchers are supported. If
3345	defined to be C<0>, then they are not. Disabling them saves a few kB of
3346	code.
3347
3348	=item EV_EMBED_ENABLE
3349
3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3351	defined to be C<0>, then they are not. Embed watchers rely on most other
3352	watcher types, which therefore must not be disabled.
3353
3354	=item EV_STAT_ENABLE
3355
3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3357	defined to be C<0>, then they are not.
3358
3359	=item EV_FORK_ENABLE
3360
3361	If undefined or defined to be C<1>, then fork watchers are supported. If
3362	defined to be C<0>, then they are not.
3363
3364	=item EV_ASYNC_ENABLE
3365
3366	If undefined or defined to be C<1>, then async watchers are supported. If
3367	defined to be C<0>, then they are not.
3368
3369	=item EV_MINIMAL
3370		4060
3371	If you need to shave off some kilobytes of code at the expense of some	4061	If you need to shave off some kilobytes of code at the expense of some
3372	speed, define this symbol to C<1>. Currently this is used to override some	4062	speed (but with the full API), you can define this symbol to request
3373	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4063	certain subsets of functionality. The default is to enable all features
3374	much smaller 2-heap for timer management over the default 4-heap.	4064	that can be enabled on the platform.
		4065
		4066	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4067	with some broad features you want) and then selectively re-enable
		4068	additional parts you want, for example if you want everything minimal,
		4069	but multiple event loop support, async and child watchers and the poll
		4070	backend, use this:
		4071
		4072	#define EV_FEATURES 0
		4073	#define EV_MULTIPLICITY 1
		4074	#define EV_USE_POLL 1
		4075	#define EV_CHILD_ENABLE 1
		4076	#define EV_ASYNC_ENABLE 1
		4077
		4078	The actual value is a bitset, it can be a combination of the following
		4079	values:
		4080
		4081	=over 4
		4082
		4083	=item C<1> - faster/larger code
		4084
		4085	Use larger code to speed up some operations.
		4086
		4087	Currently this is used to override some inlining decisions (enlarging the
		4088	code size by roughly 30% on amd64).
		4089
		4090	When optimising for size, use of compiler flags such as C<-Os> with
		4091	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4092	assertions.
		4093
		4094	=item C<2> - faster/larger data structures
		4095
		4096	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4097	hash table sizes and so on. This will usually further increase code size
		4098	and can additionally have an effect on the size of data structures at
		4099	runtime.
		4100
		4101	=item C<4> - full API configuration
		4102
		4103	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4104	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4105
		4106	=item C<8> - full API
		4107
		4108	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4109	details on which parts of the API are still available without this
		4110	feature, and do not complain if this subset changes over time.
		4111
		4112	=item C<16> - enable all optional watcher types
		4113
		4114	Enables all optional watcher types. If you want to selectively enable
		4115	only some watcher types other than I/O and timers (e.g. prepare,
		4116	embed, async, child...) you can enable them manually by defining
		4117	C<EV_watchertype_ENABLE> to C<1> instead.
		4118
		4119	=item C<32> - enable all backends
		4120
		4121	This enables all backends - without this feature, you need to enable at
		4122	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4123
		4124	=item C<64> - enable OS-specific "helper" APIs
		4125
		4126	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4127	default.
		4128
		4129	=back
		4130
		4131	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4132	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4133	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4134	watchers, timers and monotonic clock support.
		4135
		4136	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4137	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4138	your program might be left out as well - a binary starting a timer and an
		4139	I/O watcher then might come out at only 5Kb.
		4140
		4141	=item EV_AVOID_STDIO
		4142
		4143	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4144	functions (printf, scanf, perror etc.). This will increase the code size
		4145	somewhat, but if your program doesn't otherwise depend on stdio and your
		4146	libc allows it, this avoids linking in the stdio library which is quite
		4147	big.
		4148
		4149	Note that error messages might become less precise when this option is
		4150	enabled.
		4151
		4152	=item EV_NSIG
		4153
		4154	The highest supported signal number, +1 (or, the number of
		4155	signals): Normally, libev tries to deduce the maximum number of signals
		4156	automatically, but sometimes this fails, in which case it can be
		4157	specified. Also, using a lower number than detected (C<32> should be
		4158	good for about any system in existence) can save some memory, as libev
		4159	statically allocates some 12-24 bytes per signal number.
3375		4160
3376	=item EV_PID_HASHSIZE	4161	=item EV_PID_HASHSIZE
3377		4162
3378	C<ev_child> watchers use a small hash table to distribute workload by	4163	C<ev_child> watchers use a small hash table to distribute workload by
3379	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4164	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3380	than enough. If you need to manage thousands of children you might want to	4165	usually more than enough. If you need to manage thousands of children you
3381	increase this value (I<must> be a power of two).	4166	might want to increase this value (I<must> be a power of two).
3382		4167
3383	=item EV_INOTIFY_HASHSIZE	4168	=item EV_INOTIFY_HASHSIZE
3384		4169
3385	C<ev_stat> watchers use a small hash table to distribute workload by	4170	C<ev_stat> watchers use a small hash table to distribute workload by
3386	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4171	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3387	usually more than enough. If you need to manage thousands of C<ev_stat>	4172	disabled), usually more than enough. If you need to manage thousands of
3388	watchers you might want to increase this value (I<must> be a power of	4173	C<ev_stat> watchers you might want to increase this value (I<must> be a
3389	two).	4174	power of two).
3390		4175
3391	=item EV_USE_4HEAP	4176	=item EV_USE_4HEAP
3392		4177
3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4178	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4179	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4180	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3396	faster performance with many (thousands) of watchers.	4181	faster performance with many (thousands) of watchers.
3397		4182
3398	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
3399	(disabled).	4184	will be C<0>.
3400		4185
3401	=item EV_HEAP_CACHE_AT	4186	=item EV_HEAP_CACHE_AT
3402		4187
3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4188	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4189	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4190	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4191	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3407	but avoids random read accesses on heap changes. This improves performance	4192	but avoids random read accesses on heap changes. This improves performance
3408	noticeably with many (hundreds) of watchers.	4193	noticeably with many (hundreds) of watchers.
3409		4194
3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4195	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3411	(disabled).	4196	will be C<0>.
3412		4197
3413	=item EV_VERIFY	4198	=item EV_VERIFY
3414		4199
3415	Controls how much internal verification (see C<ev_loop_verify ()>) will	4200	Controls how much internal verification (see C<ev_verify ()>) will
3416	be done: If set to C<0>, no internal verification code will be compiled	4201	be done: If set to C<0>, no internal verification code will be compiled
3417	in. If set to C<1>, then verification code will be compiled in, but not	4202	in. If set to C<1>, then verification code will be compiled in, but not
3418	called. If set to C<2>, then the internal verification code will be	4203	called. If set to C<2>, then the internal verification code will be
3419	called once per loop, which can slow down libev. If set to C<3>, then the	4204	called once per loop, which can slow down libev. If set to C<3>, then the
3420	verification code will be called very frequently, which will slow down	4205	verification code will be called very frequently, which will slow down
3421	libev considerably.	4206	libev considerably.
3422		4207
3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4208	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3424	C<0>.	4209	will be C<0>.
3425		4210
3426	=item EV_COMMON	4211	=item EV_COMMON
3427		4212
3428	By default, all watchers have a C<void *data> member. By redefining	4213	By default, all watchers have a C<void *data> member. By redefining
3429	this macro to a something else you can include more and other types of	4214	this macro to something else you can include more and other types of
3430	members. You have to define it each time you include one of the files,	4215	members. You have to define it each time you include one of the files,
3431	though, and it must be identical each time.	4216	though, and it must be identical each time.
3432		4217
3433	For example, the perl EV module uses something like this:	4218	For example, the perl EV module uses something like this:
3434		4219
…		…
3487	file.	4272	file.
3488		4273
3489	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4274	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3490	that everybody includes and which overrides some configure choices:	4275	that everybody includes and which overrides some configure choices:
3491		4276
3492	#define EV_MINIMAL 1	4277	#define EV_FEATURES 8
3493	#define EV_USE_POLL 0	4278	#define EV_USE_SELECT 1
3494	#define EV_MULTIPLICITY 0
3495	#define EV_PERIODIC_ENABLE 0	4279	#define EV_PREPARE_ENABLE 1
		4280	#define EV_IDLE_ENABLE 1
3496	#define EV_STAT_ENABLE 0	4281	#define EV_SIGNAL_ENABLE 1
3497	#define EV_FORK_ENABLE 0	4282	#define EV_CHILD_ENABLE 1
		4283	#define EV_USE_STDEXCEPT 0
3498	#define EV_CONFIG_H <config.h>	4284	#define EV_CONFIG_H <config.h>
3499	#define EV_MINPRI 0
3500	#define EV_MAXPRI 0
3501		4285
3502	#include "ev++.h"	4286	#include "ev++.h"
3503		4287
3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4288	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3505		4289
…		…
3565	default loop and triggering an C<ev_async> watcher from the default loop	4349	default loop and triggering an C<ev_async> watcher from the default loop
3566	watcher callback into the event loop interested in the signal.	4350	watcher callback into the event loop interested in the signal.
3567		4351
3568	=back	4352	=back
3569		4353
		4354	=head4 THREAD LOCKING EXAMPLE
		4355
		4356	Here is a fictitious example of how to run an event loop in a different
		4357	thread than where callbacks are being invoked and watchers are
		4358	created/added/removed.
		4359
		4360	For a real-world example, see the C<EV::Loop::Async> perl module,
		4361	which uses exactly this technique (which is suited for many high-level
		4362	languages).
		4363
		4364	The example uses a pthread mutex to protect the loop data, a condition
		4365	variable to wait for callback invocations, an async watcher to notify the
		4366	event loop thread and an unspecified mechanism to wake up the main thread.
		4367
		4368	First, you need to associate some data with the event loop:
		4369
		4370	typedef struct {
		4371	mutex_t lock; /* global loop lock */
		4372	ev_async async_w;
		4373	thread_t tid;
		4374	cond_t invoke_cv;
		4375	} userdata;
		4376
		4377	void prepare_loop (EV_P)
		4378	{
		4379	// for simplicity, we use a static userdata struct.
		4380	static userdata u;
		4381
		4382	ev_async_init (&u->async_w, async_cb);
		4383	ev_async_start (EV_A_ &u->async_w);
		4384
		4385	pthread_mutex_init (&u->lock, 0);
		4386	pthread_cond_init (&u->invoke_cv, 0);
		4387
		4388	// now associate this with the loop
		4389	ev_set_userdata (EV_A_ u);
		4390	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4391	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4392
		4393	// then create the thread running ev_loop
		4394	pthread_create (&u->tid, 0, l_run, EV_A);
		4395	}
		4396
		4397	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4398	solely to wake up the event loop so it takes notice of any new watchers
		4399	that might have been added:
		4400
		4401	static void
		4402	async_cb (EV_P_ ev_async *w, int revents)
		4403	{
		4404	// just used for the side effects
		4405	}
		4406
		4407	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4408	protecting the loop data, respectively.
		4409
		4410	static void
		4411	l_release (EV_P)
		4412	{
		4413	userdata *u = ev_userdata (EV_A);
		4414	pthread_mutex_unlock (&u->lock);
		4415	}
		4416
		4417	static void
		4418	l_acquire (EV_P)
		4419	{
		4420	userdata *u = ev_userdata (EV_A);
		4421	pthread_mutex_lock (&u->lock);
		4422	}
		4423
		4424	The event loop thread first acquires the mutex, and then jumps straight
		4425	into C<ev_run>:
		4426
		4427	void *
		4428	l_run (void *thr_arg)
		4429	{
		4430	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4431
		4432	l_acquire (EV_A);
		4433	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4434	ev_run (EV_A_ 0);
		4435	l_release (EV_A);
		4436
		4437	return 0;
		4438	}
		4439
		4440	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4441	signal the main thread via some unspecified mechanism (signals? pipe
		4442	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4443	have been called (in a while loop because a) spurious wakeups are possible
		4444	and b) skipping inter-thread-communication when there are no pending
		4445	watchers is very beneficial):
		4446
		4447	static void
		4448	l_invoke (EV_P)
		4449	{
		4450	userdata *u = ev_userdata (EV_A);
		4451
		4452	while (ev_pending_count (EV_A))
		4453	{
		4454	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4455	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4456	}
		4457	}
		4458
		4459	Now, whenever the main thread gets told to invoke pending watchers, it
		4460	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4461	thread to continue:
		4462
		4463	static void
		4464	real_invoke_pending (EV_P)
		4465	{
		4466	userdata *u = ev_userdata (EV_A);
		4467
		4468	pthread_mutex_lock (&u->lock);
		4469	ev_invoke_pending (EV_A);
		4470	pthread_cond_signal (&u->invoke_cv);
		4471	pthread_mutex_unlock (&u->lock);
		4472	}
		4473
		4474	Whenever you want to start/stop a watcher or do other modifications to an
		4475	event loop, you will now have to lock:
		4476
		4477	ev_timer timeout_watcher;
		4478	userdata *u = ev_userdata (EV_A);
		4479
		4480	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4481
		4482	pthread_mutex_lock (&u->lock);
		4483	ev_timer_start (EV_A_ &timeout_watcher);
		4484	ev_async_send (EV_A_ &u->async_w);
		4485	pthread_mutex_unlock (&u->lock);
		4486
		4487	Note that sending the C<ev_async> watcher is required because otherwise
		4488	an event loop currently blocking in the kernel will have no knowledge
		4489	about the newly added timer. By waking up the loop it will pick up any new
		4490	watchers in the next event loop iteration.
		4491
3570	=head3 COROUTINES	4492	=head3 COROUTINES
3571		4493
3572	Libev is very accommodating to coroutines ("cooperative threads"):	4494	Libev is very accommodating to coroutines ("cooperative threads"):
3573	libev fully supports nesting calls to its functions from different	4495	libev fully supports nesting calls to its functions from different
3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4496	coroutines (e.g. you can call C<ev_run> on the same loop from two
3575	different coroutines, and switch freely between both coroutines running the	4497	different coroutines, and switch freely between both coroutines running
3576	loop, as long as you don't confuse yourself). The only exception is that	4498	the loop, as long as you don't confuse yourself). The only exception is
3577	you must not do this from C<ev_periodic> reschedule callbacks.	4499	that you must not do this from C<ev_periodic> reschedule callbacks.
3578		4500
3579	Care has been taken to ensure that libev does not keep local state inside	4501	Care has been taken to ensure that libev does not keep local state inside
3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4502	C<ev_run>, and other calls do not usually allow for coroutine switches as
3581	they do not call any callbacks.	4503	they do not call any callbacks.
3582		4504
3583	=head2 COMPILER WARNINGS	4505	=head2 COMPILER WARNINGS
3584		4506
3585	Depending on your compiler and compiler settings, you might get no or a	4507	Depending on your compiler and compiler settings, you might get no or a
…		…
3596	maintainable.	4518	maintainable.
3597		4519
3598	And of course, some compiler warnings are just plain stupid, or simply	4520	And of course, some compiler warnings are just plain stupid, or simply
3599	wrong (because they don't actually warn about the condition their message	4521	wrong (because they don't actually warn about the condition their message
3600	seems to warn about). For example, certain older gcc versions had some	4522	seems to warn about). For example, certain older gcc versions had some
3601	warnings that resulted an extreme number of false positives. These have	4523	warnings that resulted in an extreme number of false positives. These have
3602	been fixed, but some people still insist on making code warn-free with	4524	been fixed, but some people still insist on making code warn-free with
3603	such buggy versions.	4525	such buggy versions.
3604		4526
3605	While libev is written to generate as few warnings as possible,	4527	While libev is written to generate as few warnings as possible,
3606	"warn-free" code is not a goal, and it is recommended not to build libev	4528	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3642	I suggest using suppression lists.	4564	I suggest using suppression lists.
3643		4565
3644		4566
3645	=head1 PORTABILITY NOTES	4567	=head1 PORTABILITY NOTES
3646		4568
		4569	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4570
		4571	GNU/Linux is the only common platform that supports 64 bit file/large file
		4572	interfaces but I<disables> them by default.
		4573
		4574	That means that libev compiled in the default environment doesn't support
		4575	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4576
		4577	Unfortunately, many programs try to work around this GNU/Linux issue
		4578	by enabling the large file API, which makes them incompatible with the
		4579	standard libev compiled for their system.
		4580
		4581	Likewise, libev cannot enable the large file API itself as this would
		4582	suddenly make it incompatible to the default compile time environment,
		4583	i.e. all programs not using special compile switches.
		4584
		4585	=head2 OS/X AND DARWIN BUGS
		4586
		4587	The whole thing is a bug if you ask me - basically any system interface
		4588	you touch is broken, whether it is locales, poll, kqueue or even the
		4589	OpenGL drivers.
		4590
		4591	=head3 C<kqueue> is buggy
		4592
		4593	The kqueue syscall is broken in all known versions - most versions support
		4594	only sockets, many support pipes.
		4595
		4596	Libev tries to work around this by not using C<kqueue> by default on this
		4597	rotten platform, but of course you can still ask for it when creating a
		4598	loop - embedding a socket-only kqueue loop into a select-based one is
		4599	probably going to work well.
		4600
		4601	=head3 C<poll> is buggy
		4602
		4603	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4604	implementation by something calling C<kqueue> internally around the 10.5.6
		4605	release, so now C<kqueue> I<and> C<poll> are broken.
		4606
		4607	Libev tries to work around this by not using C<poll> by default on
		4608	this rotten platform, but of course you can still ask for it when creating
		4609	a loop.
		4610
		4611	=head3 C<select> is buggy
		4612
		4613	All that's left is C<select>, and of course Apple found a way to fuck this
		4614	one up as well: On OS/X, C<select> actively limits the number of file
		4615	descriptors you can pass in to 1024 - your program suddenly crashes when
		4616	you use more.
		4617
		4618	There is an undocumented "workaround" for this - defining
		4619	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4620	work on OS/X.
		4621
		4622	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4623
		4624	=head3 C<errno> reentrancy
		4625
		4626	The default compile environment on Solaris is unfortunately so
		4627	thread-unsafe that you can't even use components/libraries compiled
		4628	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4629	defined by default. A valid, if stupid, implementation choice.
		4630
		4631	If you want to use libev in threaded environments you have to make sure
		4632	it's compiled with C<_REENTRANT> defined.
		4633
		4634	=head3 Event port backend
		4635
		4636	The scalable event interface for Solaris is called "event
		4637	ports". Unfortunately, this mechanism is very buggy in all major
		4638	releases. If you run into high CPU usage, your program freezes or you get
		4639	a large number of spurious wakeups, make sure you have all the relevant
		4640	and latest kernel patches applied. No, I don't know which ones, but there
		4641	are multiple ones to apply, and afterwards, event ports actually work
		4642	great.
		4643
		4644	If you can't get it to work, you can try running the program by setting
		4645	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4646	C<select> backends.
		4647
		4648	=head2 AIX POLL BUG
		4649
		4650	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4651	this by trying to avoid the poll backend altogether (i.e. it's not even
		4652	compiled in), which normally isn't a big problem as C<select> works fine
		4653	with large bitsets on AIX, and AIX is dead anyway.
		4654
3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4655	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4656
		4657	=head3 General issues
3648		4658
3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4659	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3650	requires, and its I/O model is fundamentally incompatible with the POSIX	4660	requires, and its I/O model is fundamentally incompatible with the POSIX
3651	model. Libev still offers limited functionality on this platform in	4661	model. Libev still offers limited functionality on this platform in
3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4662	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3653	descriptors. This only applies when using Win32 natively, not when using	4663	descriptors. This only applies when using Win32 natively, not when using
3654	e.g. cygwin.	4664	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4665	as every compielr comes with a slightly differently broken/incompatible
		4666	environment.
3655		4667
3656	Lifting these limitations would basically require the full	4668	Lifting these limitations would basically require the full
3657	re-implementation of the I/O system. If you are into these kinds of	4669	re-implementation of the I/O system. If you are into this kind of thing,
3658	things, then note that glib does exactly that for you in a very portable	4670	then note that glib does exactly that for you in a very portable way (note
3659	way (note also that glib is the slowest event library known to man).	4671	also that glib is the slowest event library known to man).
3660		4672
3661	There is no supported compilation method available on windows except	4673	There is no supported compilation method available on windows except
3662	embedding it into other applications.	4674	embedding it into other applications.
		4675
		4676	Sensible signal handling is officially unsupported by Microsoft - libev
		4677	tries its best, but under most conditions, signals will simply not work.
3663		4678
3664	Not a libev limitation but worth mentioning: windows apparently doesn't	4679	Not a libev limitation but worth mentioning: windows apparently doesn't
3665	accept large writes: instead of resulting in a partial write, windows will	4680	accept large writes: instead of resulting in a partial write, windows will
3666	either accept everything or return C<ENOBUFS> if the buffer is too large,	4681	either accept everything or return C<ENOBUFS> if the buffer is too large,
3667	so make sure you only write small amounts into your sockets (less than a	4682	so make sure you only write small amounts into your sockets (less than a
…		…
3672	the abysmal performance of winsockets, using a large number of sockets	4687	the abysmal performance of winsockets, using a large number of sockets
3673	is not recommended (and not reasonable). If your program needs to use	4688	is not recommended (and not reasonable). If your program needs to use
3674	more than a hundred or so sockets, then likely it needs to use a totally	4689	more than a hundred or so sockets, then likely it needs to use a totally
3675	different implementation for windows, as libev offers the POSIX readiness	4690	different implementation for windows, as libev offers the POSIX readiness
3676	notification model, which cannot be implemented efficiently on windows	4691	notification model, which cannot be implemented efficiently on windows
3677	(Microsoft monopoly games).	4692	(due to Microsoft monopoly games).
3678		4693
3679	A typical way to use libev under windows is to embed it (see the embedding	4694	A typical way to use libev under windows is to embed it (see the embedding
3680	section for details) and use the following F<evwrap.h> header file instead	4695	section for details) and use the following F<evwrap.h> header file instead
3681	of F<ev.h>:	4696	of F<ev.h>:
3682		4697
…		…
3689	you do I<not> compile the F<ev.c> or any other embedded source files!):	4704	you do I<not> compile the F<ev.c> or any other embedded source files!):
3690		4705
3691	#include "evwrap.h"	4706	#include "evwrap.h"
3692	#include "ev.c"	4707	#include "ev.c"
3693		4708
3694	=over 4
3695
3696	=item The winsocket select function	4709	=head3 The winsocket C<select> function
3697		4710
3698	The winsocket C<select> function doesn't follow POSIX in that it	4711	The winsocket C<select> function doesn't follow POSIX in that it
3699	requires socket I<handles> and not socket I<file descriptors> (it is	4712	requires socket I<handles> and not socket I<file descriptors> (it is
3700	also extremely buggy). This makes select very inefficient, and also	4713	also extremely buggy). This makes select very inefficient, and also
3701	requires a mapping from file descriptors to socket handles (the Microsoft	4714	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3710	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4723	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3711		4724
3712	Note that winsockets handling of fd sets is O(n), so you can easily get a	4725	Note that winsockets handling of fd sets is O(n), so you can easily get a
3713	complexity in the O(n²) range when using win32.	4726	complexity in the O(n²) range when using win32.
3714		4727
3715	=item Limited number of file descriptors	4728	=head3 Limited number of file descriptors
3716		4729
3717	Windows has numerous arbitrary (and low) limits on things.	4730	Windows has numerous arbitrary (and low) limits on things.
3718		4731
3719	Early versions of winsocket's select only supported waiting for a maximum	4732	Early versions of winsocket's select only supported waiting for a maximum
3720	of C<64> handles (probably owning to the fact that all windows kernels	4733	of C<64> handles (probably owning to the fact that all windows kernels
3721	can only wait for C<64> things at the same time internally; Microsoft	4734	can only wait for C<64> things at the same time internally; Microsoft
3722	recommends spawning a chain of threads and wait for 63 handles and the	4735	recommends spawning a chain of threads and wait for 63 handles and the
3723	previous thread in each. Great).	4736	previous thread in each. Sounds great!).
3724		4737
3725	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4738	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3726	to some high number (e.g. C<2048>) before compiling the winsocket select	4739	to some high number (e.g. C<2048>) before compiling the winsocket select
3727	call (which might be in libev or elsewhere, for example, perl does its own	4740	call (which might be in libev or elsewhere, for example, perl and many
3728	select emulation on windows).	4741	other interpreters do their own select emulation on windows).
3729		4742
3730	Another limit is the number of file descriptors in the Microsoft runtime	4743	Another limit is the number of file descriptors in the Microsoft runtime
3731	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4744	libraries, which by default is C<64> (there must be a hidden I<64>
3732	or something like this inside Microsoft). You can increase this by calling	4745	fetish or something like this inside Microsoft). You can increase this
3733	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4746	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3734	arbitrary limit), but is broken in many versions of the Microsoft runtime	4747	(another arbitrary limit), but is broken in many versions of the Microsoft
3735	libraries.
3736
3737	This might get you to about C<512> or C<2048> sockets (depending on	4748	runtime libraries. This might get you to about C<512> or C<2048> sockets
3738	windows version and/or the phase of the moon). To get more, you need to	4749	(depending on windows version and/or the phase of the moon). To get more,
3739	wrap all I/O functions and provide your own fd management, but the cost of	4750	you need to wrap all I/O functions and provide your own fd management, but
3740	calling select (O(n²)) will likely make this unworkable.	4751	the cost of calling select (O(n²)) will likely make this unworkable.
3741
3742	=back
3743		4752
3744	=head2 PORTABILITY REQUIREMENTS	4753	=head2 PORTABILITY REQUIREMENTS
3745		4754
3746	In addition to a working ISO-C implementation and of course the	4755	In addition to a working ISO-C implementation and of course the
3747	backend-specific APIs, libev relies on a few additional extensions:	4756	backend-specific APIs, libev relies on a few additional extensions:
…		…
3754	Libev assumes not only that all watcher pointers have the same internal	4763	Libev assumes not only that all watcher pointers have the same internal
3755	structure (guaranteed by POSIX but not by ISO C for example), but it also	4764	structure (guaranteed by POSIX but not by ISO C for example), but it also
3756	assumes that the same (machine) code can be used to call any watcher	4765	assumes that the same (machine) code can be used to call any watcher
3757	callback: The watcher callbacks have different type signatures, but libev	4766	callback: The watcher callbacks have different type signatures, but libev
3758	calls them using an C<ev_watcher *> internally.	4767	calls them using an C<ev_watcher *> internally.
		4768
		4769	=item pointer accesses must be thread-atomic
		4770
		4771	Accessing a pointer value must be atomic, it must both be readable and
		4772	writable in one piece - this is the case on all current architectures.
3759		4773
3760	=item C<sig_atomic_t volatile> must be thread-atomic as well	4774	=item C<sig_atomic_t volatile> must be thread-atomic as well
3761		4775
3762	The type C<sig_atomic_t volatile> (or whatever is defined as	4776	The type C<sig_atomic_t volatile> (or whatever is defined as
3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4777	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3786	watchers.	4800	watchers.
3787		4801
3788	=item C<double> must hold a time value in seconds with enough accuracy	4802	=item C<double> must hold a time value in seconds with enough accuracy
3789		4803
3790	The type C<double> is used to represent timestamps. It is required to	4804	The type C<double> is used to represent timestamps. It is required to
3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4805	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3792	enough for at least into the year 4000. This requirement is fulfilled by	4806	good enough for at least into the year 4000 with millisecond accuracy
		4807	(the design goal for libev). This requirement is overfulfilled by
3793	implementations implementing IEEE 754 (basically all existing ones).	4808	implementations using IEEE 754, which is basically all existing ones. With
		4809	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3794		4810
3795	=back	4811	=back
3796		4812
3797	If you know of other additional requirements drop me a note.	4813	If you know of other additional requirements drop me a note.
3798		4814
…		…
3866	involves iterating over all running async watchers or all signal numbers.	4882	involves iterating over all running async watchers or all signal numbers.
3867		4883
3868	=back	4884	=back
3869		4885
3870		4886
		4887	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4888
		4889	The major version 4 introduced some incompatible changes to the API.
		4890
		4891	At the moment, the C<ev.h> header file provides compatibility definitions
		4892	for all changes, so most programs should still compile. The compatibility
		4893	layer might be removed in later versions of libev, so better update to the
		4894	new API early than late.
		4895
		4896	=over 4
		4897
		4898	=item C<EV_COMPAT3> backwards compatibility mechanism
		4899
		4900	The backward compatibility mechanism can be controlled by
		4901	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4902	section.
		4903
		4904	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4905
		4906	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4907
		4908	ev_loop_destroy (EV_DEFAULT_UC);
		4909	ev_loop_fork (EV_DEFAULT);
		4910
		4911	=item function/symbol renames
		4912
		4913	A number of functions and symbols have been renamed:
		4914
		4915	ev_loop => ev_run
		4916	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4917	EVLOOP_ONESHOT => EVRUN_ONCE
		4918
		4919	ev_unloop => ev_break
		4920	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4921	EVUNLOOP_ONE => EVBREAK_ONE
		4922	EVUNLOOP_ALL => EVBREAK_ALL
		4923
		4924	EV_TIMEOUT => EV_TIMER
		4925
		4926	ev_loop_count => ev_iteration
		4927	ev_loop_depth => ev_depth
		4928	ev_loop_verify => ev_verify
		4929
		4930	Most functions working on C<struct ev_loop> objects don't have an
		4931	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4932	associated constants have been renamed to not collide with the C<struct
		4933	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4934	as all other watcher types. Note that C<ev_loop_fork> is still called
		4935	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4936	typedef.
		4937
		4938	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4939
		4940	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4941	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4942	and work, but the library code will of course be larger.
		4943
		4944	=back
		4945
		4946
		4947	=head1 GLOSSARY
		4948
		4949	=over 4
		4950
		4951	=item active
		4952
		4953	A watcher is active as long as it has been started and not yet stopped.
		4954	See L<WATCHER STATES> for details.
		4955
		4956	=item application
		4957
		4958	In this document, an application is whatever is using libev.
		4959
		4960	=item backend
		4961
		4962	The part of the code dealing with the operating system interfaces.
		4963
		4964	=item callback
		4965
		4966	The address of a function that is called when some event has been
		4967	detected. Callbacks are being passed the event loop, the watcher that
		4968	received the event, and the actual event bitset.
		4969
		4970	=item callback/watcher invocation
		4971
		4972	The act of calling the callback associated with a watcher.
		4973
		4974	=item event
		4975
		4976	A change of state of some external event, such as data now being available
		4977	for reading on a file descriptor, time having passed or simply not having
		4978	any other events happening anymore.
		4979
		4980	In libev, events are represented as single bits (such as C<EV_READ> or
		4981	C<EV_TIMER>).
		4982
		4983	=item event library
		4984
		4985	A software package implementing an event model and loop.
		4986
		4987	=item event loop
		4988
		4989	An entity that handles and processes external events and converts them
		4990	into callback invocations.
		4991
		4992	=item event model
		4993
		4994	The model used to describe how an event loop handles and processes
		4995	watchers and events.
		4996
		4997	=item pending
		4998
		4999	A watcher is pending as soon as the corresponding event has been
		5000	detected. See L<WATCHER STATES> for details.
		5001
		5002	=item real time
		5003
		5004	The physical time that is observed. It is apparently strictly monotonic :)
		5005
		5006	=item wall-clock time
		5007
		5008	The time and date as shown on clocks. Unlike real time, it can actually
		5009	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5010	clock.
		5011
		5012	=item watcher
		5013
		5014	A data structure that describes interest in certain events. Watchers need
		5015	to be started (attached to an event loop) before they can receive events.
		5016
		5017	=back
		5018
3871	=head1 AUTHOR	5019	=head1 AUTHOR
3872		5020
3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5021	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5022	Magnusson and Emanuele Giaquinta.
3874		5023

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