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Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.372 by root, Sat Jun 4 05:44:16 2011 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
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		13
		14	#include <stdio.h> // for puts
		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;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
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_ struct 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	struct 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);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
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	// break 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
…		…
108	name C<loop> (which is always of type C<struct 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 floatingpoint 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.
		145
		146	=head1 ERROR HANDLING
		147
		148	Libev knows three classes of errors: operating system errors, usage errors
		149	and internal errors (bugs).
		150
		151	When libev catches an operating system error it cannot handle (for example
		152	a system call indicating a condition libev cannot fix), it calls the callback
		153	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		154	abort. The default is to print a diagnostic message and to call C<abort
		155	()>.
		156
		157	When libev detects a usage error such as a negative timer interval, then
		158	it will print a diagnostic message and abort (via the C<assert> mechanism,
		159	so C<NDEBUG> will disable this checking): these are programming errors in
		160	the libev caller and need to be fixed there.
		161
		162	Libev also has a few internal error-checking C<assert>ions, and also has
		163	extensive consistency checking code. These do not trigger under normal
		164	circumstances, as they indicate either a bug in libev or worse.
		165
121		166
122	=head1 GLOBAL FUNCTIONS	167	=head1 GLOBAL FUNCTIONS
123		168
124	These functions can be called anytime, even before initialising the	169	These functions can be called anytime, even before initialising the
125	library in any way.	170	library in any way.
…		…
128		173
129	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
130		175
131	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
132	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
133	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>.
134		180
135	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
136		182
137	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
138	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
139	this is a subsecond-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
140		192
141	=item int ev_version_major ()	193	=item int ev_version_major ()
142		194
143	=item int ev_version_minor ()	195	=item int ev_version_minor ()
144		196
…		…
155	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
156	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
157	not a problem.	209	not a problem.
158		210
159	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
161		214
162	assert (("libev version mismatch",	215	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
165		218
166	=item unsigned int ev_supported_backends ()	219	=item unsigned int ev_supported_backends ()
167		220
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	221	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	222	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	224	a description of the set values.
172		225
173	Example: make sure we have the epoll method, because yeah this is cool and	226	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	227	a must have and can we have a torrent of it please!!!11
175		228
176	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
178		231
179	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
180		233
181	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
182	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
184	most BSDs and will not be autodetected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
185	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
186	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
187		241
188	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
189		243
190	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
191	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
192	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
194	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
195		249
196	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
197		251
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
199		253
…		…
229	}	283	}
230		284
231	...	285	...
232	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
233		287
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
235		289
236	Set the callback function to call on a retryable syscall error (such	290	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	293	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	294	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	295	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	296	(such as abort).
243		297
244	Example: This is basically the same thing that libev does internally, too.	298	Example: This is basically the same thing that libev does internally, too.
…		…
251	}	305	}
252		306
253	...	307	...
254	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
255		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
256	=back	323	=back
257		324
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
259		326
260	An event loop is described by a C<struct ev_loop *>. The library knows two	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
261	types of such loops, the I<default> loop, which supports signals and child	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
262	events, and dynamically created loops which do not.	329	libev 3 had an C<ev_loop> function colliding with the struct name).
		330
		331	The library knows two types of such loops, the I<default> loop, which
		332	supports child process events, and dynamically created event loops which
		333	do not.
263		334
264	=over 4	335	=over 4
265		336
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		338
268	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
269	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
270	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
271	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
272		349
273	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
274	function.	351	function (or via the C<EV_DEFAULT> macro).
275		352
276	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
278	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
279		357
280	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
281	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
282	for C<SIGCHLD>. If this is a problem for your app you can either	360	a problem for your application you can either create a dynamic loop with
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
285	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
286		382
287	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
289		385
290	The following flags are supported:	386	The following flags are supported:
…		…
296	The default flags value. Use this if you have no clue (it's the right	392	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	393	thing, believe me).
298		394
299	=item C<EVFLAG_NOENV>	395	=item C<EVFLAG_NOENV>
300		396
301	If this flag bit is ored into the flag value (or the program runs setuid	397	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	398	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	399	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	400	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
306	around bugs.	402	around bugs.
307		403
308	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
309		405
310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
311	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
312	enabling this flag.
313		408
314	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	413	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	414	C<pthread_atfork> which is even faster).
320		415
321	The big advantage of this flag is that you can forget about fork (and	416	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	417	forget about forgetting to tell libev about forking) when you use this
323	flag.	418	flag.
324		419
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	421	environment variable.
		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you ahve to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
327		457
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		459
330	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	463	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	464	usually the fastest backend for a low number of (low-numbered :) fds.
335		465
336	To get good performance out of this backend you need a high amount of	466	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	467	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	468	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	469	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	470	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	471	readiness notifications you get per iteration.
		472
		473	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		474	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		475	C<exceptfds> set on that platform).
342		476
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	477	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		478
345	And this is your standard poll(2) backend. It's more complicated	479	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	480	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	481	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	482	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	483	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	484	performance tips.
351		485
		486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		488
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
354	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
355	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
356	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	497	fd), epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	498
359	cases and requiring a syscall per fd change, no fork support and bad	499	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	500	of the more advanced event mechanisms: mere annoyances include silently
		501	dropping file descriptors, requiring a system call per change per file
		502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
		505	0.1ms) and so on. The biggest issue is fork races, however - if a program
		506	forks then I<both> parent and child process have to recreate the epoll
		507	set, which can take considerable time (one syscall per file descriptor)
		508	and is of course hard to detect.
		509
		510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		511	but of course I<doesn't>, and epoll just loves to report events for
		512	totally I<different> file descriptors (even already closed ones, so
		513	one cannot even remove them from the set) than registered in the set
		514	(especially on SMP systems). Libev tries to counter these spurious
		515	notifications by employing an additional generation counter and comparing
		516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also errornously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
361		526
362	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	528	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	529	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	531	file descriptors might not work very well if you register events for both
367		532	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		533
372	Best performance from this backend is achieved by not unregistering all	534	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	535	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	536	i.e. keep at least one watcher active per fd at all times. Stopping and
		537	starting a watcher (without re-setting it) also usually doesn't cause
		538	extra overhead. A fork can both result in spurious notifications as well
		539	as in libev having to destroy and recreate the epoll object, which can
		540	take considerable time and thus should be avoided.
375		541
		542	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		543	faster than epoll for maybe up to a hundred file descriptors, depending on
		544	the usage. So sad.
		545
376	While nominally embeddeble in other event loops, this feature is broken in	546	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	547	all kernel versions tested so far.
		548
		549	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		550	C<EVBACKEND_POLL>.
378		551
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	552	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		553
381	Kqueue deserves special mention, as at the time of this writing, it	554	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	555	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	556	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	557	it's completely useless). Unlike epoll, however, whose brokenness
		558	is by design, these kqueue bugs can (and eventually will) be fixed
		559	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	560	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	561	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	562	system like NetBSD.
388		563
389	You still can embed kqueue into a normal poll or select backend and use it	564	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	565	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	566	the target platform). See C<ev_embed> watchers for more info.
392		567
393	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	572	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	573	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		574	cases
399		575
400	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
401		577
402	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	580	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	581	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	582	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	583	also broken on OS X)) and, did I mention it, using it only for sockets.
		584
		585	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		586	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		587	C<NOTE_EOF>.
408		588
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	589	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		590
411	This is not implemented yet (and might never be, unless you send me an	591	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	592	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		597
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
420		600
421	Please note that solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.
424
425	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	604	might perform better.
429		605
430	On the positive side, ignoring the spurious readiness notifications, this	606	On the positive side, this backend actually performed fully to
431	backend actually performed to specification in all tests and is fully	607	specification in all tests and is fully embeddable, which is a rare feat
432	embeddable, which is a rare feat among the OS-specific backends.	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returning events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where
		616	you absolutely have to know whether an event occurred or not because you
		617	have to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
		620
		621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		622	C<EVBACKEND_POLL>.
433		623
434	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
435		625
436	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
439		629
440	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
441		639
442	=back	640	=back
443		641
444	If one or more of these are ored into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
445	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
447		645	()> will be tried.
448	The most typical usage is like this:
449
450	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452
453	Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:
455
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457
458	Use whatever libev has to offer, but make sure that kqueue is used if
459	available (warning, breaks stuff, best use only with your own private
460	event loop and only if you know the OS supports your types of fds):
461
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463
464	=item struct ev_loop *ev_loop_new (unsigned int flags)
465
466	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).
470
471	Note that this function I<is> thread-safe, and the recommended way to use
472	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.
474		646
475	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
476		648
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	650	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
480		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
481	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
482		659
483	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	666	for example).
490		667
491	Note that certain global state, such as signal state, will not be freed by	668	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	669	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
494		671
495	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
496	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
497	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
498	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
499		680
500	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
501		682
502	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.
504
505	=item ev_default_fork ()
506
507	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
508	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
509	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
510	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
511	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
512	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
513		693
514	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
515	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
516	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
517		700
518	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
519	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
520	quite nicely into a call to C<pthread_atfork>:
521		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
522	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
523
524	=item ev_loop_fork (loop)
525
526	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.
529		715
530	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
531		717
532	Returns true when the given loop actually is the default loop, false otherwise.	718	Returns true when the given loop is, in fact, the default loop, and false
		719	otherwise.
533		720
534	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
535		722
536	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
537	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
538	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
539		726
540	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
543		745
544	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
545		747
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	749	use.
…		…
552	received events and started processing them. This timestamp does not	754	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	755	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	756	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	757	event occurring (or more correctly, libev finding out about it).
556		758
		759	=item ev_now_update (loop)
		760
		761	Establishes the current time by querying the kernel, updating the time
		762	returned by C<ev_now ()> in the progress. This is a costly operation and
		763	is usually done automatically within C<ev_run ()>.
		764
		765	This function is rarely useful, but when some event callback runs for a
		766	very long time without entering the event loop, updating libev's idea of
		767	the current time is a good idea.
		768
		769	See also L<The special problem of time updates> in the C<ev_timer> section.
		770
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
557	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
558		798
559	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
561	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
562		804
563	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
564	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
565		808
566	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	811	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	812	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	813	of relying on its watchers stopping correctly, that is truly a thing of
		814	beauty.
571		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	822	those events and any already outstanding ones, but will not wait and
574	case there are no events and will return after one iteration of the loop.	823	block your process in case there are no events and will return after one
		824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
575		826
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	828	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	829	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	830	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	831	user-registered callback will be called), and will return after one
		832	iteration of the loop.
		833
		834	This is useful if you are waiting for some external event in conjunction
		835	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
583		838
584	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
585		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
586	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
587	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
590	- If we have been forked, recreate the kernel state.	851	- If we have been forked, detach and recreate the kernel state
		852	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	854	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
595	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
597	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	863	- Queue all expired timers.
601	- Queue all outstanding periodics.	864	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
603	- Queue all check watchers.	866	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
608	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
609	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
610		877
611	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
612	anymore.	879	anymore.
613		880
614	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
617	... jobs done. yeah!	884	... jobs done or somebody called break. yeah!
618		885
619	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
620		887
621	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
625		892
626	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
		894
		895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
627		897
628	=item ev_ref (loop)	898	=item ev_ref (loop)
629		899
630	=item ev_unref (loop)	900	=item ev_unref (loop)
631		901
632	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	904	count is nonzero, C<ev_run> will not return on its own.
635	a watcher you never unregister that should not keep C<ev_loop> from	905
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	906	This is useful when you have a watcher that you never intend to
		907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		909	before stopping it.
		910
637	example, libev itself uses this for its internal signal pipe: It is not	911	As an example, libev itself uses this for its internal signal pipe: It
638	visible to the libev user and should not keep C<ev_loop> from exiting if	912	is not visible to the libev user and should not keep C<ev_run> from
639	no event watchers registered by it are active. It is also an excellent	913	exiting if no event watchers registered by it are active. It is also an
640	way to do this for generic recurring timers or from within third-party	914	excellent way to do this for generic recurring timers or from within
641	libraries. Just remember to I<unref after start> and I<ref before stop>	915	third-party libraries. Just remember to I<unref after start> and I<ref
642	(but only if the watcher wasn't active before, or was active before,	916	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	917	before, respectively. Note also that libev might stop watchers itself
		918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		919	in the callback).
644		920
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
646	running when nothing else is active.	922	running when nothing else is active.
647		923
648	struct ev_signal exitsig;	924	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	927	ev_unref (loop);
652		928
653	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
654		930
655	ev_ref (loop);	931	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
657		933
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	934	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		935
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	936	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		937
662	These advanced functions influence the time that libev will spend waiting	938	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	939	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	940	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		941	latency.
665		942
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	943	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	944	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	945	to increase efficiency of loop iterations (or to increase power-saving
		946	opportunities).
669		947
670	The background is that sometimes your program runs just fast enough to	948	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	949	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	950	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	951	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
675		953
676	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		959	sleep time ensures that libev will not poll for I/O events more often then
		960	once per this interval, on average.
681		961
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	962	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	963	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	964	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	965	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	966	value will not introduce any overhead in libev.
687		967
688	Many (busy) programs can usually benefit by setting the io collect	968	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	969	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	970	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	971	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	972	as this approaches the timing granularity of most systems. Note that if
		973	you do transactions with the outside world and you can't increase the
		974	parallelity, then this setting will limit your transaction rate (if you
		975	need to poll once per transaction and the I/O collect interval is 0.01,
		976	then you can't do more than 100 transactions per second).
693		977
		978	Setting the I<timeout collect interval> can improve the opportunity for
		979	saving power, as the program will "bundle" timer callback invocations that
		980	are "near" in time together, by delaying some, thus reducing the number of
		981	times the process sleeps and wakes up again. Another useful technique to
		982	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		983	they fire on, say, one-second boundaries only.
		984
		985	Example: we only need 0.1s timeout granularity, and we wish not to poll
		986	more often than 100 times per second:
		987
		988	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		989	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		990
		991	=item ev_invoke_pending (loop)
		992
		993	This call will simply invoke all pending watchers while resetting their
		994	pending state. Normally, C<ev_run> does this automatically when required,
		995	but when overriding the invoke callback this call comes handy. This
		996	function can be invoked from a watcher - this can be useful for example
		997	when you want to do some lengthy calculation and want to pass further
		998	event handling to another thread (you still have to make sure only one
		999	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1000
		1001	=item int ev_pending_count (loop)
		1002
		1003	Returns the number of pending watchers - zero indicates that no watchers
		1004	are pending.
		1005
		1006	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1007
		1008	This overrides the invoke pending functionality of the loop: Instead of
		1009	invoking all pending watchers when there are any, C<ev_run> will call
		1010	this callback instead. This is useful, for example, when you want to
		1011	invoke the actual watchers inside another context (another thread etc.).
		1012
		1013	If you want to reset the callback, use C<ev_invoke_pending> as new
		1014	callback.
		1015
		1016	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1017
		1018	Sometimes you want to share the same loop between multiple threads. This
		1019	can be done relatively simply by putting mutex_lock/unlock calls around
		1020	each call to a libev function.
		1021
		1022	However, C<ev_run> can run an indefinite time, so it is not feasible
		1023	to wait for it to return. One way around this is to wake up the event
		1024	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1025	I<release> and I<acquire> callbacks on the loop.
		1026
		1027	When set, then C<release> will be called just before the thread is
		1028	suspended waiting for new events, and C<acquire> is called just
		1029	afterwards.
		1030
		1031	Ideally, C<release> will just call your mutex_unlock function, and
		1032	C<acquire> will just call the mutex_lock function again.
		1033
		1034	While event loop modifications are allowed between invocations of
		1035	C<release> and C<acquire> (that's their only purpose after all), no
		1036	modifications done will affect the event loop, i.e. adding watchers will
		1037	have no effect on the set of file descriptors being watched, or the time
		1038	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1039	to take note of any changes you made.
		1040
		1041	In theory, threads executing C<ev_run> will be async-cancel safe between
		1042	invocations of C<release> and C<acquire>.
		1043
		1044	See also the locking example in the C<THREADS> section later in this
		1045	document.
		1046
		1047	=item ev_set_userdata (loop, void *data)
		1048
		1049	=item void *ev_userdata (loop)
		1050
		1051	Set and retrieve a single C<void *> associated with a loop. When
		1052	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1053	C<0>.
		1054
		1055	These two functions can be used to associate arbitrary data with a loop,
		1056	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1057	C<acquire> callbacks described above, but of course can be (ab-)used for
		1058	any other purpose as well.
		1059
694	=item ev_loop_verify (loop)	1060	=item ev_verify (loop)
695		1061
696	This function only does something when C<EV_VERIFY> support has been	1062	This function only does something when C<EV_VERIFY> support has been
697	compiled in. It tries to go through all internal structures and checks	1063	compiled in, which is the default for non-minimal builds. It tries to go
698	them for validity. If anything is found to be inconsistent, it will print	1064	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	1065	is found to be inconsistent, it will print an error message to standard
		1066	error and call C<abort ()>.
700		1067
701	This can be used to catch bugs inside libev itself: under normal	1068	This can be used to catch bugs inside libev itself: under normal
702	circumstances, this function will never abort as of course libev keeps its	1069	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	1070	data structures consistent.
704		1071
705	=back	1072	=back
706		1073
707		1074
708	=head1 ANATOMY OF A WATCHER	1075	=head1 ANATOMY OF A WATCHER
709		1076
		1077	In the following description, uppercase C<TYPE> in names stands for the
		1078	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1079	watchers and C<ev_io_start> for I/O watchers.
		1080
710	A watcher is a structure that you create and register to record your	1081	A watcher is an opaque structure that you allocate and register to record
711	interest in some event. For instance, if you want to wait for STDIN to	1082	your interest in some event. To make a concrete example, imagine you want
712	become readable, you would create an C<ev_io> watcher for that:	1083	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1084	for that:
713		1085
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1086	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	1087	{
716	ev_io_stop (w);	1088	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	1089	ev_break (loop, EVBREAK_ALL);
718	}	1090	}
719		1091
720	struct ev_loop *loop = ev_default_loop (0);	1092	struct ev_loop *loop = ev_default_loop (0);
		1093
721	struct ev_io stdin_watcher;	1094	ev_io stdin_watcher;
		1095
722	ev_init (&stdin_watcher, my_cb);	1096	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1097	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	1098	ev_io_start (loop, &stdin_watcher);
		1099
725	ev_loop (loop, 0);	1100	ev_run (loop, 0);
726		1101
727	As you can see, you are responsible for allocating the memory for your	1102	As you can see, you are responsible for allocating the memory for your
728	watcher structures (and it is usually a bad idea to do this on the stack,	1103	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	1104	stack).
730		1105
		1106	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1107	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1108
731	Each watcher structure must be initialised by a call to C<ev_init	1109	Each watcher structure must be initialised by a call to C<ev_init (watcher
732	(watcher *, callback)>, which expects a callback to be provided. This	1110	*, callback)>, which expects a callback to be provided. This callback is
733	callback gets invoked each time the event occurs (or, in the case of io	1111	invoked each time the event occurs (or, in the case of I/O watchers, each
734	watchers, each time the event loop detects that the file descriptor given	1112	time the event loop detects that the file descriptor given is readable
735	is readable and/or writable).	1113	and/or writable).
736		1114
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1115	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
738	with arguments specific to this watcher type. There is also a macro	1116	macro to configure it, with arguments specific to the watcher type. There
739	to combine initialisation and setting in one call: C<< ev_<type>_init	1117	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	1118	ev_TYPE_init (watcher *, callback, ...) >>.
741		1119
742	To make the watcher actually watch out for events, you have to start it	1120	To make the watcher actually watch out for events, you have to start it
743	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1121	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
744	*) >>), and you can stop watching for events at any time by calling the	1122	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1123	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		1124
747	As long as your watcher is active (has been started but not stopped) you	1125	As long as your watcher is active (has been started but not stopped) you
748	must not touch the values stored in it. Most specifically you must never	1126	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	1127	reinitialise it or call its C<ev_TYPE_set> macro.
750		1128
751	Each and every callback receives the event loop pointer as first, the	1129	Each and every callback receives the event loop pointer as first, the
752	registered watcher structure as second, and a bitset of received events as	1130	registered watcher structure as second, and a bitset of received events as
753	third argument.	1131	third argument.
754		1132
…		…
763	=item C<EV_WRITE>	1141	=item C<EV_WRITE>
764		1142
765	The file descriptor in the C<ev_io> watcher has become readable and/or	1143	The file descriptor in the C<ev_io> watcher has become readable and/or
766	writable.	1144	writable.
767		1145
768	=item C<EV_TIMEOUT>	1146	=item C<EV_TIMER>
769		1147
770	The C<ev_timer> watcher has timed out.	1148	The C<ev_timer> watcher has timed out.
771		1149
772	=item C<EV_PERIODIC>	1150	=item C<EV_PERIODIC>
773		1151
…		…
791		1169
792	=item C<EV_PREPARE>	1170	=item C<EV_PREPARE>
793		1171
794	=item C<EV_CHECK>	1172	=item C<EV_CHECK>
795		1173
796	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1174	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
797	to gather new events, and all C<ev_check> watchers are invoked just after	1175	to gather new events, and all C<ev_check> watchers are invoked just after
798	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1176	C<ev_run> has gathered them, but before it invokes any callbacks for any
799	received events. Callbacks of both watcher types can start and stop as	1177	received events. Callbacks of both watcher types can start and stop as
800	many watchers as they want, and all of them will be taken into account	1178	many watchers as they want, and all of them will be taken into account
801	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1179	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
802	C<ev_loop> from blocking).	1180	C<ev_run> from blocking).
803		1181
804	=item C<EV_EMBED>	1182	=item C<EV_EMBED>
805		1183
806	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1184	The embedded event loop specified in the C<ev_embed> watcher needs attention.
807		1185
808	=item C<EV_FORK>	1186	=item C<EV_FORK>
809		1187
810	The event loop has been resumed in the child process after fork (see	1188	The event loop has been resumed in the child process after fork (see
811	C<ev_fork>).	1189	C<ev_fork>).
812		1190
		1191	=item C<EV_CLEANUP>
		1192
		1193	The event loop is about to be destroyed (see C<ev_cleanup>).
		1194
813	=item C<EV_ASYNC>	1195	=item C<EV_ASYNC>
814		1196
815	The given async watcher has been asynchronously notified (see C<ev_async>).	1197	The given async watcher has been asynchronously notified (see C<ev_async>).
816		1198
		1199	=item C<EV_CUSTOM>
		1200
		1201	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1202	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1203
817	=item C<EV_ERROR>	1204	=item C<EV_ERROR>
818		1205
819	An unspecified error has occured, the watcher has been stopped. This might	1206	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	1207	happen because the watcher could not be properly started because libev
821	ran out of memory, a file descriptor was found to be closed or any other	1208	ran out of memory, a file descriptor was found to be closed or any other
		1209	problem. Libev considers these application bugs.
		1210
822	problem. You best act on it by reporting the problem and somehow coping	1211	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	1212	watcher being stopped. Note that well-written programs should not receive
		1213	an error ever, so when your watcher receives it, this usually indicates a
		1214	bug in your program.
824		1215
825	Libev will usually signal a few "dummy" events together with an error,	1216	Libev will usually signal a few "dummy" events together with an error, for
826	for example it might indicate that a fd is readable or writable, and if	1217	example it might indicate that a fd is readable or writable, and if your
827	your callbacks is well-written it can just attempt the operation and cope	1218	callbacks is well-written it can just attempt the operation and cope with
828	with the error from read() or write(). This will not work in multithreaded	1219	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	1220	programs, though, as the fd could already be closed and reused for another
		1221	thing, so beware.
830		1222
831	=back	1223	=back
832		1224
833	=head2 GENERIC WATCHER FUNCTIONS	1225	=head2 GENERIC WATCHER FUNCTIONS
834
835	In the following description, C<TYPE> stands for the watcher type,
836	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
837		1226
838	=over 4	1227	=over 4
839		1228
840	=item C<ev_init> (ev_TYPE *watcher, callback)	1229	=item C<ev_init> (ev_TYPE *watcher, callback)
841		1230
…		…
847	which rolls both calls into one.	1236	which rolls both calls into one.
848		1237
849	You can reinitialise a watcher at any time as long as it has been stopped	1238	You can reinitialise a watcher at any time as long as it has been stopped
850	(or never started) and there are no pending events outstanding.	1239	(or never started) and there are no pending events outstanding.
851		1240
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1241	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	1242	int revents)>.
854		1243
		1244	Example: Initialise an C<ev_io> watcher in two steps.
		1245
		1246	ev_io w;
		1247	ev_init (&w, my_cb);
		1248	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1249
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1250	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
856		1251
857	This macro initialises the type-specific parts of a watcher. You need to	1252	This macro initialises the type-specific parts of a watcher. You need to
858	call C<ev_init> at least once before you call this macro, but you can	1253	call C<ev_init> at least once before you call this macro, but you can
859	call C<ev_TYPE_set> any number of times. You must not, however, call this	1254	call C<ev_TYPE_set> any number of times. You must not, however, call this
860	macro on a watcher that is active (it can be pending, however, which is a	1255	macro on a watcher that is active (it can be pending, however, which is a
861	difference to the C<ev_init> macro).	1256	difference to the C<ev_init> macro).
862		1257
863	Although some watcher types do not have type-specific arguments	1258	Although some watcher types do not have type-specific arguments
864	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1259	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		1260
		1261	See C<ev_init>, above, for an example.
		1262
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1263	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		1264
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1265	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
869	calls into a single call. This is the most convinient method to initialise	1266	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	1267	a watcher. The same limitations apply, of course.
871		1268
		1269	Example: Initialise and set an C<ev_io> watcher in one step.
		1270
		1271	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1272
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1273	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
873		1274
874	Starts (activates) the given watcher. Only active watchers will receive	1275	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	1276	events. If the watcher is already active nothing will happen.
876		1277
		1278	Example: Start the C<ev_io> watcher that is being abused as example in this
		1279	whole section.
		1280
		1281	ev_io_start (EV_DEFAULT_UC, &w);
		1282
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
878		1284
879	Stops the given watcher again (if active) and clears the pending	1285	Stops the given watcher if active, and clears the pending status (whether
		1286	the watcher was active or not).
		1287
880	status. It is possible that stopped watchers are pending (for example,	1288	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1289	non-repeating timers are being stopped when they become pending - but
882	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1290	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
883	you want to free or reuse the memory used by the watcher it is therefore a	1291	pending. If you want to free or reuse the memory used by the watcher it is
884	good idea to always call its C<ev_TYPE_stop> function.	1292	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1293
886	=item bool ev_is_active (ev_TYPE *watcher)	1294	=item bool ev_is_active (ev_TYPE *watcher)
887		1295
888	Returns a true value iff the watcher is active (i.e. it has been started	1296	Returns a true value iff the watcher is active (i.e. it has been started
889	and not yet been stopped). As long as a watcher is active you must not modify	1297	and not yet been stopped). As long as a watcher is active you must not modify
…		…
905	=item ev_cb_set (ev_TYPE *watcher, callback)	1313	=item ev_cb_set (ev_TYPE *watcher, callback)
906		1314
907	Change the callback. You can change the callback at virtually any time	1315	Change the callback. You can change the callback at virtually any time
908	(modulo threads).	1316	(modulo threads).
909		1317
910	=item ev_set_priority (ev_TYPE *watcher, priority)	1318	=item ev_set_priority (ev_TYPE *watcher, int priority)
911		1319
912	=item int ev_priority (ev_TYPE *watcher)	1320	=item int ev_priority (ev_TYPE *watcher)
913		1321
914	Set and query the priority of the watcher. The priority is a small	1322	Set and query the priority of the watcher. The priority is a small
915	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1323	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
916	(default: C<-2>). Pending watchers with higher priority will be invoked	1324	(default: C<-2>). Pending watchers with higher priority will be invoked
917	before watchers with lower priority, but priority will not keep watchers	1325	before watchers with lower priority, but priority will not keep watchers
918	from being executed (except for C<ev_idle> watchers).	1326	from being executed (except for C<ev_idle> watchers).
919		1327
920	This means that priorities are I<only> used for ordering callback
921	invocation after new events have been received. This is useful, for
922	example, to reduce latency after idling, or more often, to bind two
923	watchers on the same event and make sure one is called first.
924
925	If you need to suppress invocation when higher priority events are pending	1328	If you need to suppress invocation when higher priority events are pending
926	you need to look at C<ev_idle> watchers, which provide this functionality.	1329	you need to look at C<ev_idle> watchers, which provide this functionality.
927		1330
928	You I<must not> change the priority of a watcher as long as it is active or	1331	You I<must not> change the priority of a watcher as long as it is active or
929	pending.	1332	pending.
930		1333
		1334	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1335	fine, as long as you do not mind that the priority value you query might
		1336	or might not have been clamped to the valid range.
		1337
931	The default priority used by watchers when no priority has been set is	1338	The default priority used by watchers when no priority has been set is
932	always C<0>, which is supposed to not be too high and not be too low :).	1339	always C<0>, which is supposed to not be too high and not be too low :).
933		1340
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1341	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
935	fine, as long as you do not mind that the priority value you query might	1342	priorities.
936	or might not have been adjusted to be within valid range.
937		1343
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1344	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1345
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1346	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
941	C<loop> nor C<revents> need to be valid as long as the watcher callback	1347	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1348	can deal with that fact, as both are simply passed through to the
		1349	callback.
943		1350
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1351	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1352
946	If the watcher is pending, this function returns clears its pending status	1353	If the watcher is pending, this function clears its pending status and
947	and returns its C<revents> bitset (as if its callback was invoked). If the	1354	returns its C<revents> bitset (as if its callback was invoked). If the
948	watcher isn't pending it does nothing and returns C<0>.	1355	watcher isn't pending it does nothing and returns C<0>.
949		1356
		1357	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1358	callback to be invoked, which can be accomplished with this function.
		1359
		1360	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1361
		1362	Feeds the given event set into the event loop, as if the specified event
		1363	had happened for the specified watcher (which must be a pointer to an
		1364	initialised but not necessarily started event watcher). Obviously you must
		1365	not free the watcher as long as it has pending events.
		1366
		1367	Stopping the watcher, letting libev invoke it, or calling
		1368	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1369	not started in the first place.
		1370
		1371	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1372	functions that do not need a watcher.
		1373
950	=back	1374	=back
951		1375
		1376	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1377	OWN COMPOSITE WATCHERS> idioms.
952		1378
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1379	=head2 WATCHER STATES
954		1380
955	Each watcher has, by default, a member C<void *data> that you can change	1381	There are various watcher states mentioned throughout this manual -
956	and read at any time, libev will completely ignore it. This can be used	1382	active, pending and so on. In this section these states and the rules to
957	to associate arbitrary data with your watcher. If you need more data and	1383	transition between them will be described in more detail - and while these
958	don't want to allocate memory and store a pointer to it in that data	1384	rules might look complicated, they usually do "the right thing".
959	member, you can also "subclass" the watcher type and provide your own
960	data:
961		1385
962	struct my_io	1386	=over 4
963	{
964	struct ev_io io;
965	int otherfd;
966	void *somedata;
967	struct whatever *mostinteresting;
968	}
969		1387
970	And since your callback will be called with a pointer to the watcher, you	1388	=item initialiased
971	can cast it back to your own type:
972		1389
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1390	Before a watcher can be registered with the event looop it has to be
974	{	1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
975	struct my_io *w = (struct my_io *)w_;	1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
976	...
977	}
978		1393
979	More interesting and less C-conformant ways of casting your callback type	1394	In this state it is simply some block of memory that is suitable for
980	instead have been omitted.	1395	use in an event loop. It can be moved around, freed, reused etc. at
		1396	will - as long as you either keep the memory contents intact, or call
		1397	C<ev_TYPE_init> again.
981		1398
982	Another common scenario is having some data structure with multiple	1399	=item started/running/active
983	watchers:
984		1400
985	struct my_biggy	1401	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
986	{	1402	property of the event loop, and is actively waiting for events. While in
987	int some_data;	1403	this state it cannot be accessed (except in a few documented ways), moved,
988	ev_timer t1;	1404	freed or anything else - the only legal thing is to keep a pointer to it,
989	ev_timer t2;	1405	and call libev functions on it that are documented to work on active watchers.
990	}
991		1406
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1407	=item pending
993	you need to use C<offsetof>:
994		1408
995	#include <stddef.h>	1409	If a watcher is active and libev determines that an event it is interested
		1410	in has occurred (such as a timer expiring), it will become pending. It will
		1411	stay in this pending state until either it is stopped or its callback is
		1412	about to be invoked, so it is not normally pending inside the watcher
		1413	callback.
996		1414
		1415	The watcher might or might not be active while it is pending (for example,
		1416	an expired non-repeating timer can be pending but no longer active). If it
		1417	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1418	but it is still property of the event loop at this time, so cannot be
		1419	moved, freed or reused. And if it is active the rules described in the
		1420	previous item still apply.
		1421
		1422	It is also possible to feed an event on a watcher that is not active (e.g.
		1423	via C<ev_feed_event>), in which case it becomes pending without being
		1424	active.
		1425
		1426	=item stopped
		1427
		1428	A watcher can be stopped implicitly by libev (in which case it might still
		1429	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1430	latter will clear any pending state the watcher might be in, regardless
		1431	of whether it was active or not, so stopping a watcher explicitly before
		1432	freeing it is often a good idea.
		1433
		1434	While stopped (and not pending) the watcher is essentially in the
		1435	initialised state, that is, it can be reused, moved, modified in any way
		1436	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1437	it again).
		1438
		1439	=back
		1440
		1441	=head2 WATCHER PRIORITY MODELS
		1442
		1443	Many event loops support I<watcher priorities>, which are usually small
		1444	integers that influence the ordering of event callback invocation
		1445	between watchers in some way, all else being equal.
		1446
		1447	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1448	description for the more technical details such as the actual priority
		1449	range.
		1450
		1451	There are two common ways how these these priorities are being interpreted
		1452	by event loops:
		1453
		1454	In the more common lock-out model, higher priorities "lock out" invocation
		1455	of lower priority watchers, which means as long as higher priority
		1456	watchers receive events, lower priority watchers are not being invoked.
		1457
		1458	The less common only-for-ordering model uses priorities solely to order
		1459	callback invocation within a single event loop iteration: Higher priority
		1460	watchers are invoked before lower priority ones, but they all get invoked
		1461	before polling for new events.
		1462
		1463	Libev uses the second (only-for-ordering) model for all its watchers
		1464	except for idle watchers (which use the lock-out model).
		1465
		1466	The rationale behind this is that implementing the lock-out model for
		1467	watchers is not well supported by most kernel interfaces, and most event
		1468	libraries will just poll for the same events again and again as long as
		1469	their callbacks have not been executed, which is very inefficient in the
		1470	common case of one high-priority watcher locking out a mass of lower
		1471	priority ones.
		1472
		1473	Static (ordering) priorities are most useful when you have two or more
		1474	watchers handling the same resource: a typical usage example is having an
		1475	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1476	timeouts. Under load, data might be received while the program handles
		1477	other jobs, but since timers normally get invoked first, the timeout
		1478	handler will be executed before checking for data. In that case, giving
		1479	the timer a lower priority than the I/O watcher ensures that I/O will be
		1480	handled first even under adverse conditions (which is usually, but not
		1481	always, what you want).
		1482
		1483	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1484	will only be executed when no same or higher priority watchers have
		1485	received events, they can be used to implement the "lock-out" model when
		1486	required.
		1487
		1488	For example, to emulate how many other event libraries handle priorities,
		1489	you can associate an C<ev_idle> watcher to each such watcher, and in
		1490	the normal watcher callback, you just start the idle watcher. The real
		1491	processing is done in the idle watcher callback. This causes libev to
		1492	continuously poll and process kernel event data for the watcher, but when
		1493	the lock-out case is known to be rare (which in turn is rare :), this is
		1494	workable.
		1495
		1496	Usually, however, the lock-out model implemented that way will perform
		1497	miserably under the type of load it was designed to handle. In that case,
		1498	it might be preferable to stop the real watcher before starting the
		1499	idle watcher, so the kernel will not have to process the event in case
		1500	the actual processing will be delayed for considerable time.
		1501
		1502	Here is an example of an I/O watcher that should run at a strictly lower
		1503	priority than the default, and which should only process data when no
		1504	other events are pending:
		1505
		1506	ev_idle idle; // actual processing watcher
		1507	ev_io io; // actual event watcher
		1508
997	static void	1509	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1510	io_cb (EV_P_ ev_io *w, int revents)
999	{	1511	{
1000	struct my_biggy big = (struct my_biggy *	1512	// stop the I/O watcher, we received the event, but
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1513	// are not yet ready to handle it.
		1514	ev_io_stop (EV_A_ w);
		1515
		1516	// start the idle watcher to handle the actual event.
		1517	// it will not be executed as long as other watchers
		1518	// with the default priority are receiving events.
		1519	ev_idle_start (EV_A_ &idle);
1002	}	1520	}
1003		1521
1004	static void	1522	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1523	idle_cb (EV_P_ ev_idle *w, int revents)
1006	{	1524	{
1007	struct my_biggy big = (struct my_biggy *	1525	// actual processing
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1526	read (STDIN_FILENO, ...);
		1527
		1528	// have to start the I/O watcher again, as
		1529	// we have handled the event
		1530	ev_io_start (EV_P_ &io);
1009	}	1531	}
		1532
		1533	// initialisation
		1534	ev_idle_init (&idle, idle_cb);
		1535	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1536	ev_io_start (EV_DEFAULT_ &io);
		1537
		1538	In the "real" world, it might also be beneficial to start a timer, so that
		1539	low-priority connections can not be locked out forever under load. This
		1540	enables your program to keep a lower latency for important connections
		1541	during short periods of high load, while not completely locking out less
		1542	important ones.
1010		1543
1011		1544
1012	=head1 WATCHER TYPES	1545	=head1 WATCHER TYPES
1013		1546
1014	This section describes each watcher in detail, but will not repeat	1547	This section describes each watcher in detail, but will not repeat
…		…
1038	In general you can register as many read and/or write event watchers per	1571	In general you can register as many read and/or write event watchers per
1039	fd as you want (as long as you don't confuse yourself). Setting all file	1572	fd as you want (as long as you don't confuse yourself). Setting all file
1040	descriptors to non-blocking mode is also usually a good idea (but not	1573	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1574	required if you know what you are doing).
1042		1575
1043	If you must do this, then force the use of a known-to-be-good backend
1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1045	C<EVBACKEND_POLL>).
1046
1047	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1048	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is, your callback might
1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1050	because there is no data. Not only are some backends known to create a	1579	because there is no data. It is very easy to get into this situation even
1051	lot of those (for example solaris ports), it is very easy to get into	1580	with a relatively standard program structure. Thus it is best to always
1052	this situation even with a relatively standard program structure. Thus	1581	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1054	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	preferable to a program hanging until some data arrives.
1055		1583
1056	If you cannot run the fd in non-blocking mode (for example you should not	1584	If you cannot run the fd in non-blocking mode (for example you should
1057	play around with an Xlib connection), then you have to seperately re-test	1585	not play around with an Xlib connection), then you have to separately
1058	whether a file descriptor is really ready with a known-to-be good interface	1586	re-test whether a file descriptor is really ready with a known-to-be good
1059	such as poll (fortunately in our Xlib example, Xlib already does this on	1587	interface such as poll (fortunately in the case of Xlib, it already does
1060	its own, so its quite safe to use).	1588	this on its own, so its quite safe to use). Some people additionally
		1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1590	indefinitely.
		1591
		1592	But really, best use non-blocking mode.
1061		1593
1062	=head3 The special problem of disappearing file descriptors	1594	=head3 The special problem of disappearing file descriptors
1063		1595
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1596	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1065	descriptor (either by calling C<close> explicitly or by any other means,	1597	descriptor (either due to calling C<close> explicitly or any other means,
1066	such as C<dup>). The reason is that you register interest in some file	1598	such as C<dup2>). The reason is that you register interest in some file
1067	descriptor, but when it goes away, the operating system will silently drop	1599	descriptor, but when it goes away, the operating system will silently drop
1068	this interest. If another file descriptor with the same number then is	1600	this interest. If another file descriptor with the same number then is
1069	registered with libev, there is no efficient way to see that this is, in	1601	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1602	fact, a different file descriptor.
1071		1603
…		…
1089		1621
1090	There is no workaround possible except not registering events	1622	There is no workaround possible except not registering events
1091	for potentially C<dup ()>'ed file descriptors, or to resort to	1623	for potentially C<dup ()>'ed file descriptors, or to resort to
1092	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1624	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1093		1625
		1626	=head3 The special problem of files
		1627
		1628	Many people try to use C<select> (or libev) on file descriptors
		1629	representing files, and expect it to become ready when their program
		1630	doesn't block on disk accesses (which can take a long time on their own).
		1631
		1632	However, this cannot ever work in the "expected" way - you get a readiness
		1633	notification as soon as the kernel knows whether and how much data is
		1634	there, and in the case of open files, that's always the case, so you
		1635	always get a readiness notification instantly, and your read (or possibly
		1636	write) will still block on the disk I/O.
		1637
		1638	Another way to view it is that in the case of sockets, pipes, character
		1639	devices and so on, there is another party (the sender) that delivers data
		1640	on its own, but in the case of files, there is no such thing: the disk
		1641	will not send data on its own, simply because it doesn't know what you
		1642	wish to read - you would first have to request some data.
		1643
		1644	Since files are typically not-so-well supported by advanced notification
		1645	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1646	to files, even though you should not use it. The reason for this is
		1647	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1648	usually a tty, often a pipe, but also sometimes files or special devices
		1649	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1650	F</dev/urandom>), and even though the file might better be served with
		1651	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1652	it "just works" instead of freezing.
		1653
		1654	So avoid file descriptors pointing to files when you know it (e.g. use
		1655	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1656	when you rarely read from a file instead of from a socket, and want to
		1657	reuse the same code path.
		1658
1094	=head3 The special problem of fork	1659	=head3 The special problem of fork
1095		1660
1096	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1661	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1097	useless behaviour. Libev fully supports fork, but needs to be told about	1662	useless behaviour. Libev fully supports fork, but needs to be told about
1098	it in the child.	1663	it in the child if you want to continue to use it in the child.
1099		1664
1100	To support fork in your programs, you either have to call	1665	To support fork in your child processes, you have to call C<ev_loop_fork
1101	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1666	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1667	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1103	C<EVBACKEND_POLL>.
1104		1668
1105	=head3 The special problem of SIGPIPE	1669	=head3 The special problem of SIGPIPE
1106		1670
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1671	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1108	when reading from a pipe whose other end has been closed, your program	1672	when writing to a pipe whose other end has been closed, your program gets
1109	gets send a SIGPIPE, which, by default, aborts your program. For most	1673	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1674	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1675
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1676	So when you encounter spurious, unexplained daemon exits, make sure you
1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1677	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1115	somewhere, as that would have given you a big clue).	1678	somewhere, as that would have given you a big clue).
1116		1679
		1680	=head3 The special problem of accept()ing when you can't
		1681
		1682	Many implementations of the POSIX C<accept> function (for example,
		1683	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1684	connection from the pending queue in all error cases.
		1685
		1686	For example, larger servers often run out of file descriptors (because
		1687	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1688	rejecting the connection, leading to libev signalling readiness on
		1689	the next iteration again (the connection still exists after all), and
		1690	typically causing the program to loop at 100% CPU usage.
		1691
		1692	Unfortunately, the set of errors that cause this issue differs between
		1693	operating systems, there is usually little the app can do to remedy the
		1694	situation, and no known thread-safe method of removing the connection to
		1695	cope with overload is known (to me).
		1696
		1697	One of the easiest ways to handle this situation is to just ignore it
		1698	- when the program encounters an overload, it will just loop until the
		1699	situation is over. While this is a form of busy waiting, no OS offers an
		1700	event-based way to handle this situation, so it's the best one can do.
		1701
		1702	A better way to handle the situation is to log any errors other than
		1703	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1704	messages, and continue as usual, which at least gives the user an idea of
		1705	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1706	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1707	usage.
		1708
		1709	If your program is single-threaded, then you could also keep a dummy file
		1710	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1711	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1712	close that fd, and create a new dummy fd. This will gracefully refuse
		1713	clients under typical overload conditions.
		1714
		1715	The last way to handle it is to simply log the error and C<exit>, as
		1716	is often done with C<malloc> failures, but this results in an easy
		1717	opportunity for a DoS attack.
1117		1718
1118	=head3 Watcher-Specific Functions	1719	=head3 Watcher-Specific Functions
1119		1720
1120	=over 4	1721	=over 4
1121		1722
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1723	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1724
1124	=item ev_io_set (ev_io *, int fd, int events)	1725	=item ev_io_set (ev_io *, int fd, int events)
1125		1726
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1727	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1127	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1728	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1128	C<EV_READ | EV_WRITE> to receive the given events.	1729	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1730
1130	=item int fd [read-only]	1731	=item int fd [read-only]
1131		1732
1132	The file descriptor being watched.	1733	The file descriptor being watched.
1133		1734
…		…
1141		1742
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1743	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1143	readable, but only once. Since it is likely line-buffered, you could	1744	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1745	attempt to read a whole line in the callback.
1145		1746
1146	static void	1747	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1749	{
1149	ev_io_stop (loop, w);	1750	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1751	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1752	}
1152		1753
1153	...	1754	...
1154	struct ev_loop *loop = ev_default_init (0);	1755	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1756	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1757	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1758	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1759	ev_run (loop, 0);
1159		1760
1160		1761
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1762	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1763
1163	Timer watchers are simple relative timers that generate an event after a	1764	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1765	given time, and optionally repeating in regular intervals after that.
1165		1766
1166	The timers are based on real time, that is, if you register an event that	1767	The timers are based on real time, that is, if you register an event that
1167	times out after an hour and you reset your system clock to january last	1768	times out after an hour and you reset your system clock to January last
1168	year, it will still time out after (roughly) and hour. "Roughly" because	1769	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1770	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1771	monotonic clock option helps a lot here).
		1772
		1773	The callback is guaranteed to be invoked only I<after> its timeout has
		1774	passed (not I<at>, so on systems with very low-resolution clocks this
		1775	might introduce a small delay). If multiple timers become ready during the
		1776	same loop iteration then the ones with earlier time-out values are invoked
		1777	before ones of the same priority with later time-out values (but this is
		1778	no longer true when a callback calls C<ev_run> recursively).
		1779
		1780	=head3 Be smart about timeouts
		1781
		1782	Many real-world problems involve some kind of timeout, usually for error
		1783	recovery. A typical example is an HTTP request - if the other side hangs,
		1784	you want to raise some error after a while.
		1785
		1786	What follows are some ways to handle this problem, from obvious and
		1787	inefficient to smart and efficient.
		1788
		1789	In the following, a 60 second activity timeout is assumed - a timeout that
		1790	gets reset to 60 seconds each time there is activity (e.g. each time some
		1791	data or other life sign was received).
		1792
		1793	=over 4
		1794
		1795	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1796
		1797	This is the most obvious, but not the most simple way: In the beginning,
		1798	start the watcher:
		1799
		1800	ev_timer_init (timer, callback, 60., 0.);
		1801	ev_timer_start (loop, timer);
		1802
		1803	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1804	and start it again:
		1805
		1806	ev_timer_stop (loop, timer);
		1807	ev_timer_set (timer, 60., 0.);
		1808	ev_timer_start (loop, timer);
		1809
		1810	This is relatively simple to implement, but means that each time there is
		1811	some activity, libev will first have to remove the timer from its internal
		1812	data structure and then add it again. Libev tries to be fast, but it's
		1813	still not a constant-time operation.
		1814
		1815	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1816
		1817	This is the easiest way, and involves using C<ev_timer_again> instead of
		1818	C<ev_timer_start>.
		1819
		1820	To implement this, configure an C<ev_timer> with a C<repeat> value
		1821	of C<60> and then call C<ev_timer_again> at start and each time you
		1822	successfully read or write some data. If you go into an idle state where
		1823	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1824	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1825
		1826	That means you can ignore both the C<ev_timer_start> function and the
		1827	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1828	member and C<ev_timer_again>.
		1829
		1830	At start:
		1831
		1832	ev_init (timer, callback);
		1833	timer->repeat = 60.;
		1834	ev_timer_again (loop, timer);
		1835
		1836	Each time there is some activity:
		1837
		1838	ev_timer_again (loop, timer);
		1839
		1840	It is even possible to change the time-out on the fly, regardless of
		1841	whether the watcher is active or not:
		1842
		1843	timer->repeat = 30.;
		1844	ev_timer_again (loop, timer);
		1845
		1846	This is slightly more efficient then stopping/starting the timer each time
		1847	you want to modify its timeout value, as libev does not have to completely
		1848	remove and re-insert the timer from/into its internal data structure.
		1849
		1850	It is, however, even simpler than the "obvious" way to do it.
		1851
		1852	=item 3. Let the timer time out, but then re-arm it as required.
		1853
		1854	This method is more tricky, but usually most efficient: Most timeouts are
		1855	relatively long compared to the intervals between other activity - in
		1856	our example, within 60 seconds, there are usually many I/O events with
		1857	associated activity resets.
		1858
		1859	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1860	but remember the time of last activity, and check for a real timeout only
		1861	within the callback:
		1862
		1863	ev_tstamp last_activity; // time of last activity
		1864
		1865	static void
		1866	callback (EV_P_ ev_timer *w, int revents)
		1867	{
		1868	ev_tstamp now = ev_now (EV_A);
		1869	ev_tstamp timeout = last_activity + 60.;
		1870
		1871	// if last_activity + 60. is older than now, we did time out
		1872	if (timeout < now)
		1873	{
		1874	// timeout occurred, take action
		1875	}
		1876	else
		1877	{
		1878	// callback was invoked, but there was some activity, re-arm
		1879	// the watcher to fire in last_activity + 60, which is
		1880	// guaranteed to be in the future, so "again" is positive:
		1881	w->repeat = timeout - now;
		1882	ev_timer_again (EV_A_ w);
		1883	}
		1884	}
		1885
		1886	To summarise the callback: first calculate the real timeout (defined
		1887	as "60 seconds after the last activity"), then check if that time has
		1888	been reached, which means something I<did>, in fact, time out. Otherwise
		1889	the callback was invoked too early (C<timeout> is in the future), so
		1890	re-schedule the timer to fire at that future time, to see if maybe we have
		1891	a timeout then.
		1892
		1893	Note how C<ev_timer_again> is used, taking advantage of the
		1894	C<ev_timer_again> optimisation when the timer is already running.
		1895
		1896	This scheme causes more callback invocations (about one every 60 seconds
		1897	minus half the average time between activity), but virtually no calls to
		1898	libev to change the timeout.
		1899
		1900	To start the timer, simply initialise the watcher and set C<last_activity>
		1901	to the current time (meaning we just have some activity :), then call the
		1902	callback, which will "do the right thing" and start the timer:
		1903
		1904	ev_init (timer, callback);
		1905	last_activity = ev_now (loop);
		1906	callback (loop, timer, EV_TIMER);
		1907
		1908	And when there is some activity, simply store the current time in
		1909	C<last_activity>, no libev calls at all:
		1910
		1911	last_activity = ev_now (loop);
		1912
		1913	This technique is slightly more complex, but in most cases where the
		1914	time-out is unlikely to be triggered, much more efficient.
		1915
		1916	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1917	callback :) - just change the timeout and invoke the callback, which will
		1918	fix things for you.
		1919
		1920	=item 4. Wee, just use a double-linked list for your timeouts.
		1921
		1922	If there is not one request, but many thousands (millions...), all
		1923	employing some kind of timeout with the same timeout value, then one can
		1924	do even better:
		1925
		1926	When starting the timeout, calculate the timeout value and put the timeout
		1927	at the I<end> of the list.
		1928
		1929	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1930	the list is expected to fire (for example, using the technique #3).
		1931
		1932	When there is some activity, remove the timer from the list, recalculate
		1933	the timeout, append it to the end of the list again, and make sure to
		1934	update the C<ev_timer> if it was taken from the beginning of the list.
		1935
		1936	This way, one can manage an unlimited number of timeouts in O(1) time for
		1937	starting, stopping and updating the timers, at the expense of a major
		1938	complication, and having to use a constant timeout. The constant timeout
		1939	ensures that the list stays sorted.
		1940
		1941	=back
		1942
		1943	So which method the best?
		1944
		1945	Method #2 is a simple no-brain-required solution that is adequate in most
		1946	situations. Method #3 requires a bit more thinking, but handles many cases
		1947	better, and isn't very complicated either. In most case, choosing either
		1948	one is fine, with #3 being better in typical situations.
		1949
		1950	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1951	rather complicated, but extremely efficient, something that really pays
		1952	off after the first million or so of active timers, i.e. it's usually
		1953	overkill :)
		1954
		1955	=head3 The special problem of time updates
		1956
		1957	Establishing the current time is a costly operation (it usually takes at
		1958	least two system calls): EV therefore updates its idea of the current
		1959	time only before and after C<ev_run> collects new events, which causes a
		1960	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1961	lots of events in one iteration.
1171		1962
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1963	The relative timeouts are calculated relative to the C<ev_now ()>
1173	time. This is usually the right thing as this timestamp refers to the time	1964	time. This is usually the right thing as this timestamp refers to the time
1174	of the event triggering whatever timeout you are modifying/starting. If	1965	of the event triggering whatever timeout you are modifying/starting. If
1175	you suspect event processing to be delayed and you I<need> to base the timeout	1966	you suspect event processing to be delayed and you I<need> to base the
1176	on the current time, use something like this to adjust for this:	1967	timeout on the current time, use something like this to adjust for this:
1177		1968
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1969	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1970
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1971	If the event loop is suspended for a long time, you can also force an
1181	but if multiple timers become ready during the same loop iteration then	1972	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1973	()>.
		1974
		1975	=head3 The special problems of suspended animation
		1976
		1977	When you leave the server world it is quite customary to hit machines that
		1978	can suspend/hibernate - what happens to the clocks during such a suspend?
		1979
		1980	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1981	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1982	to run until the system is suspended, but they will not advance while the
		1983	system is suspended. That means, on resume, it will be as if the program
		1984	was frozen for a few seconds, but the suspend time will not be counted
		1985	towards C<ev_timer> when a monotonic clock source is used. The real time
		1986	clock advanced as expected, but if it is used as sole clocksource, then a
		1987	long suspend would be detected as a time jump by libev, and timers would
		1988	be adjusted accordingly.
		1989
		1990	I would not be surprised to see different behaviour in different between
		1991	operating systems, OS versions or even different hardware.
		1992
		1993	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1994	time jump in the monotonic clocks and the realtime clock. If the program
		1995	is suspended for a very long time, and monotonic clock sources are in use,
		1996	then you can expect C<ev_timer>s to expire as the full suspension time
		1997	will be counted towards the timers. When no monotonic clock source is in
		1998	use, then libev will again assume a timejump and adjust accordingly.
		1999
		2000	It might be beneficial for this latter case to call C<ev_suspend>
		2001	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2002	deterministic behaviour in this case (you can do nothing against
		2003	C<SIGSTOP>).
1183		2004
1184	=head3 Watcher-Specific Functions and Data Members	2005	=head3 Watcher-Specific Functions and Data Members
1185		2006
1186	=over 4	2007	=over 4
1187		2008
…		…
1206	This will act as if the timer timed out and restart it again if it is	2027	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	2028	repeating. The exact semantics are:
1208		2029
1209	If the timer is pending, its pending status is cleared.	2030	If the timer is pending, its pending status is cleared.
1210		2031
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	2032	If the timer is started but non-repeating, stop it (as if it timed out).
1212		2033
1213	If the timer is repeating, either start it if necessary (with the	2034	If the timer is repeating, either start it if necessary (with the
1214	C<repeat> value), or reset the running timer to the C<repeat> value.	2035	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		2036
1216	This sounds a bit complicated, but here is a useful and typical	2037	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1217	example: Imagine you have a tcp connection and you want a so-called idle	2038	usage example.
1218	timeout, that is, you want to be called when there have been, say, 60
1219	seconds of inactivity on the socket. The easiest way to do this is to
1220	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1221	C<ev_timer_again> each time you successfully read or write some data. If
1222	you go into an idle state where you do not expect data to travel on the
1223	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1224	automatically restart it if need be.
1225		2039
1226	That means you can ignore the C<after> value and C<ev_timer_start>	2040	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1227	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1228		2041
1229	ev_timer_init (timer, callback, 0., 5.);	2042	Returns the remaining time until a timer fires. If the timer is active,
1230	ev_timer_again (loop, timer);	2043	then this time is relative to the current event loop time, otherwise it's
1231	...	2044	the timeout value currently configured.
1232	timer->again = 17.;
1233	ev_timer_again (loop, timer);
1234	...
1235	timer->again = 10.;
1236	ev_timer_again (loop, timer);
1237		2045
1238	This is more slightly efficient then stopping/starting the timer each time	2046	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1239	you want to modify its timeout value.	2047	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2048	will return C<4>. When the timer expires and is restarted, it will return
		2049	roughly C<7> (likely slightly less as callback invocation takes some time,
		2050	too), and so on.
1240		2051
1241	=item ev_tstamp repeat [read-write]	2052	=item ev_tstamp repeat [read-write]
1242		2053
1243	The current C<repeat> value. Will be used each time the watcher times out	2054	The current C<repeat> value. Will be used each time the watcher times out
1244	or C<ev_timer_again> is called and determines the next timeout (if any),	2055	or C<ev_timer_again> is called, and determines the next timeout (if any),
1245	which is also when any modifications are taken into account.	2056	which is also when any modifications are taken into account.
1246		2057
1247	=back	2058	=back
1248		2059
1249	=head3 Examples	2060	=head3 Examples
1250		2061
1251	Example: Create a timer that fires after 60 seconds.	2062	Example: Create a timer that fires after 60 seconds.
1252		2063
1253	static void	2064	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2065	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	2066	{
1256	.. one minute over, w is actually stopped right here	2067	.. one minute over, w is actually stopped right here
1257	}	2068	}
1258		2069
1259	struct ev_timer mytimer;	2070	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2071	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	2072	ev_timer_start (loop, &mytimer);
1262		2073
1263	Example: Create a timeout timer that times out after 10 seconds of	2074	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	2075	inactivity.
1265		2076
1266	static void	2077	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2078	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	2079	{
1269	.. ten seconds without any activity	2080	.. ten seconds without any activity
1270	}	2081	}
1271		2082
1272	struct ev_timer mytimer;	2083	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2084	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	2085	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	2086	ev_run (loop, 0);
1276		2087
1277	// and in some piece of code that gets executed on any "activity":	2088	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	2089	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	2090	ev_timer_again (&mytimer);
1280		2091
1281		2092
1282	=head2 C<ev_periodic> - to cron or not to cron?	2093	=head2 C<ev_periodic> - to cron or not to cron?
1283		2094
1284	Periodic watchers are also timers of a kind, but they are very versatile	2095	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	2096	(and unfortunately a bit complex).
1286		2097
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2098	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1288	but on wallclock time (absolute time). You can tell a periodic watcher	2099	relative time, the physical time that passes) but on wall clock time
1289	to trigger after some specific point in time. For example, if you tell a	2100	(absolute time, the thing you can read on your calender or clock). The
1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2101	difference is that wall clock time can run faster or slower than real
1291	+ 10.>, that is, an absolute time not a delay) and then reset your system	2102	time, and time jumps are not uncommon (e.g. when you adjust your
1292	clock to january of the previous year, then it will take more than year	2103	wrist-watch).
1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1294	roughly 10 seconds later as it uses a relative timeout).
1295		2104
		2105	You can tell a periodic watcher to trigger after some specific point
		2106	in time: for example, if you tell a periodic watcher to trigger "in 10
		2107	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2108	not a delay) and then reset your system clock to January of the previous
		2109	year, then it will take a year or more to trigger the event (unlike an
		2110	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2111	it, as it uses a relative timeout).
		2112
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	2113	C<ev_periodic> watchers can also be used to implement vastly more complex
1297	such as triggering an event on each "midnight, local time", or other	2114	timers, such as triggering an event on each "midnight, local time", or
1298	complicated, rules.	2115	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2116	those cannot react to time jumps.
1299		2117
1300	As with timers, the callback is guarenteed to be invoked only when the	2118	As with timers, the callback is guaranteed to be invoked only when the
1301	time (C<at>) has passed, but if multiple periodic timers become ready	2119	point in time where it is supposed to trigger has passed. If multiple
1302	during the same loop iteration then order of execution is undefined.	2120	timers become ready during the same loop iteration then the ones with
		2121	earlier time-out values are invoked before ones with later time-out values
		2122	(but this is no longer true when a callback calls C<ev_run> recursively).
1303		2123
1304	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1305		2125
1306	=over 4	2126	=over 4
1307		2127
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2128	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1309		2129
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2130	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1311		2131
1312	Lots of arguments, lets sort it out... There are basically three modes of	2132	Lots of arguments, let's sort it out... There are basically three modes of
1313	operation, and we will explain them from simplest to complex:	2133	operation, and we will explain them from simplest to most complex:
1314		2134
1315	=over 4	2135	=over 4
1316		2136
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2137	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1318		2138
1319	In this configuration the watcher triggers an event after the wallclock	2139	In this configuration the watcher triggers an event after the wall clock
1320	time C<at> has passed and doesn't repeat. It will not adjust when a time	2140	time C<offset> has passed. It will not repeat and will not adjust when a
1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2141	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1322	run when the system time reaches or surpasses this time.	2142	will be stopped and invoked when the system clock reaches or surpasses
		2143	this point in time.
1323		2144
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2145	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1325		2146
1326	In this mode the watcher will always be scheduled to time out at the next	2147	In this mode the watcher will always be scheduled to time out at the next
1327	C<at + N * interval> time (for some integer N, which can also be negative)	2148	C<offset + N * interval> time (for some integer N, which can also be
1328	and then repeat, regardless of any time jumps.	2149	negative) and then repeat, regardless of any time jumps. The C<offset>
		2150	argument is merely an offset into the C<interval> periods.
1329		2151
1330	This can be used to create timers that do not drift with respect to system	2152	This can be used to create timers that do not drift with respect to the
1331	time, for example, here is a C<ev_periodic> that triggers each hour, on	2153	system clock, for example, here is an C<ev_periodic> that triggers each
1332	the hour:	2154	hour, on the hour (with respect to UTC):
1333		2155
1334	ev_periodic_set (&periodic, 0., 3600., 0);	2156	ev_periodic_set (&periodic, 0., 3600., 0);
1335		2157
1336	This doesn't mean there will always be 3600 seconds in between triggers,	2158	This doesn't mean there will always be 3600 seconds in between triggers,
1337	but only that the the callback will be called when the system time shows a	2159	but only that the callback will be called when the system time shows a
1338	full hour (UTC), or more correctly, when the system time is evenly divisible	2160	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	2161	by 3600.
1340		2162
1341	Another way to think about it (for the mathematically inclined) is that	2163	Another way to think about it (for the mathematically inclined) is that
1342	C<ev_periodic> will try to run the callback in this mode at the next possible	2164	C<ev_periodic> will try to run the callback in this mode at the next possible
1343	time where C<time = at (mod interval)>, regardless of any time jumps.	2165	time where C<time = offset (mod interval)>, regardless of any time jumps.
1344		2166
1345	For numerical stability it is preferable that the C<at> value is near	2167	The C<interval> I<MUST> be positive, and for numerical stability, the
1346	C<ev_now ()> (the current time), but there is no range requirement for	2168	interval value should be higher than C<1/8192> (which is around 100
1347	this value, and in fact is often specified as zero.	2169	microseconds) and C<offset> should be higher than C<0> and should have
		2170	at most a similar magnitude as the current time (say, within a factor of
		2171	ten). Typical values for offset are, in fact, C<0> or something between
		2172	C<0> and C<interval>, which is also the recommended range.
1348		2173
1349	Note also that there is an upper limit to how often a timer can fire (cpu	2174	Note also that there is an upper limit to how often a timer can fire (CPU
1350	speed for example), so if C<interval> is very small then timing stability	2175	speed for example), so if C<interval> is very small then timing stability
1351	will of course detoriate. Libev itself tries to be exact to be about one	2176	will of course deteriorate. Libev itself tries to be exact to be about one
1352	millisecond (if the OS supports it and the machine is fast enough).	2177	millisecond (if the OS supports it and the machine is fast enough).
1353		2178
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2179	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1355		2180
1356	In this mode the values for C<interval> and C<at> are both being	2181	In this mode the values for C<interval> and C<offset> are both being
1357	ignored. Instead, each time the periodic watcher gets scheduled, the	2182	ignored. Instead, each time the periodic watcher gets scheduled, the
1358	reschedule callback will be called with the watcher as first, and the	2183	reschedule callback will be called with the watcher as first, and the
1359	current time as second argument.	2184	current time as second argument.
1360		2185
1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2186	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1362	ever, or make ANY event loop modifications whatsoever>.	2187	or make ANY other event loop modifications whatsoever, unless explicitly
		2188	allowed by documentation here>.
1363		2189
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2190	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2191	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	2192	only event loop modification you are allowed to do).
1367		2193
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2194	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	2195	*w, ev_tstamp now)>, e.g.:
1370		2196
		2197	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2198	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	2199	{
1373	return now + 60.;	2200	return now + 60.;
1374	}	2201	}
1375		2202
1376	It must return the next time to trigger, based on the passed time value	2203	It must return the next time to trigger, based on the passed time value
…		…
1396	a different time than the last time it was called (e.g. in a crond like	2223	a different time than the last time it was called (e.g. in a crond like
1397	program when the crontabs have changed).	2224	program when the crontabs have changed).
1398		2225
1399	=item ev_tstamp ev_periodic_at (ev_periodic *)	2226	=item ev_tstamp ev_periodic_at (ev_periodic *)
1400		2227
1401	When active, returns the absolute time that the watcher is supposed to	2228	When active, returns the absolute time that the watcher is supposed
1402	trigger next.	2229	to trigger next. This is not the same as the C<offset> argument to
		2230	C<ev_periodic_set>, but indeed works even in interval and manual
		2231	rescheduling modes.
1403		2232
1404	=item ev_tstamp offset [read-write]	2233	=item ev_tstamp offset [read-write]
1405		2234
1406	When repeating, this contains the offset value, otherwise this is the	2235	When repeating, this contains the offset value, otherwise this is the
1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2236	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2237	although libev might modify this value for better numerical stability).
1408		2238
1409	Can be modified any time, but changes only take effect when the periodic	2239	Can be modified any time, but changes only take effect when the periodic
1410	timer fires or C<ev_periodic_again> is being called.	2240	timer fires or C<ev_periodic_again> is being called.
1411		2241
1412	=item ev_tstamp interval [read-write]	2242	=item ev_tstamp interval [read-write]
1413		2243
1414	The current interval value. Can be modified any time, but changes only	2244	The current interval value. Can be modified any time, but changes only
1415	take effect when the periodic timer fires or C<ev_periodic_again> is being	2245	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	2246	called.
1417		2247
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2248	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		2249
1420	The current reschedule callback, or C<0>, if this functionality is	2250	The current reschedule callback, or C<0>, if this functionality is
1421	switched off. Can be changed any time, but changes only take effect when	2251	switched off. Can be changed any time, but changes only take effect when
1422	the periodic timer fires or C<ev_periodic_again> is being called.	2252	the periodic timer fires or C<ev_periodic_again> is being called.
1423		2253
1424	=back	2254	=back
1425		2255
1426	=head3 Examples	2256	=head3 Examples
1427		2257
1428	Example: Call a callback every hour, or, more precisely, whenever the	2258	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	2259	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	2260	potentially a lot of jitter, but good long-term stability.
1431		2261
1432	static void	2262	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2263	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1434	{	2264	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	2265	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	2266	}
1437		2267
1438	struct ev_periodic hourly_tick;	2268	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2269	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	2270	ev_periodic_start (loop, &hourly_tick);
1441		2271
1442	Example: The same as above, but use a reschedule callback to do it:	2272	Example: The same as above, but use a reschedule callback to do it:
1443		2273
1444	#include <math.h>	2274	#include <math.h>
1445		2275
1446	static ev_tstamp	2276	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2277	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	2278	{
1449	return fmod (now, 3600.) + 3600.;	2279	return now + (3600. - fmod (now, 3600.));
1450	}	2280	}
1451		2281
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2282	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		2283
1454	Example: Call a callback every hour, starting now:	2284	Example: Call a callback every hour, starting now:
1455		2285
1456	struct ev_periodic hourly_tick;	2286	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	2287	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	2288	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	2289	ev_periodic_start (loop, &hourly_tick);
1460		2290
1461		2291
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	2292	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		2293
1464	Signal watchers will trigger an event when the process receives a specific	2294	Signal watchers will trigger an event when the process receives a specific
1465	signal one or more times. Even though signals are very asynchronous, libev	2295	signal one or more times. Even though signals are very asynchronous, libev
1466	will try it's best to deliver signals synchronously, i.e. as part of the	2296	will try its best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	2297	normal event processing, like any other event.
1468		2298
		2299	If you want signals to be delivered truly asynchronously, just use
		2300	C<sigaction> as you would do without libev and forget about sharing
		2301	the signal. You can even use C<ev_async> from a signal handler to
		2302	synchronously wake up an event loop.
		2303
1469	You can configure as many watchers as you like per signal. Only when the	2304	You can configure as many watchers as you like for the same signal, but
		2305	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2306	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2307	C<SIGINT> in both the default loop and another loop at the same time. At
		2308	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2309
1470	first watcher gets started will libev actually register a signal watcher	2310	When the first watcher gets started will libev actually register something
1471	with the kernel (thus it coexists with your own signal handlers as long	2311	with the kernel (thus it coexists with your own signal handlers as long as
1472	as you don't register any with libev). Similarly, when the last signal	2312	you don't register any with libev for the same signal).
1473	watcher for a signal is stopped libev will reset the signal handler to
1474	SIG_DFL (regardless of what it was set to before).
1475		2313
1476	If possible and supported, libev will install its handlers with	2314	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2315	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1478	interrupted. If you have a problem with syscalls getting interrupted by	2316	not be unduly interrupted. If you have a problem with system calls getting
1479	signals you can block all signals in an C<ev_check> watcher and unblock	2317	interrupted by signals you can block all signals in an C<ev_check> watcher
1480	them in an C<ev_prepare> watcher.	2318	and unblock them in an C<ev_prepare> watcher.
		2319
		2320	=head3 The special problem of inheritance over fork/execve/pthread_create
		2321
		2322	Both the signal mask (C<sigprocmask>) and the signal disposition
		2323	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2324	stopping it again), that is, libev might or might not block the signal,
		2325	and might or might not set or restore the installed signal handler (but
		2326	see C<EVFLAG_NOSIGMASK>).
		2327
		2328	While this does not matter for the signal disposition (libev never
		2329	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2330	C<execve>), this matters for the signal mask: many programs do not expect
		2331	certain signals to be blocked.
		2332
		2333	This means that before calling C<exec> (from the child) you should reset
		2334	the signal mask to whatever "default" you expect (all clear is a good
		2335	choice usually).
		2336
		2337	The simplest way to ensure that the signal mask is reset in the child is
		2338	to install a fork handler with C<pthread_atfork> that resets it. That will
		2339	catch fork calls done by libraries (such as the libc) as well.
		2340
		2341	In current versions of libev, the signal will not be blocked indefinitely
		2342	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2343	the window of opportunity for problems, it will not go away, as libev
		2344	I<has> to modify the signal mask, at least temporarily.
		2345
		2346	So I can't stress this enough: I<If you do not reset your signal mask when
		2347	you expect it to be empty, you have a race condition in your code>. This
		2348	is not a libev-specific thing, this is true for most event libraries.
		2349
		2350	=head3 The special problem of threads signal handling
		2351
		2352	POSIX threads has problematic signal handling semantics, specifically,
		2353	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2354	threads in a process block signals, which is hard to achieve.
		2355
		2356	When you want to use sigwait (or mix libev signal handling with your own
		2357	for the same signals), you can tackle this problem by globally blocking
		2358	all signals before creating any threads (or creating them with a fully set
		2359	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2360	loops. Then designate one thread as "signal receiver thread" which handles
		2361	these signals. You can pass on any signals that libev might be interested
		2362	in by calling C<ev_feed_signal>.
1481		2363
1482	=head3 Watcher-Specific Functions and Data Members	2364	=head3 Watcher-Specific Functions and Data Members
1483		2365
1484	=over 4	2366	=over 4
1485		2367
…		…
1496		2378
1497	=back	2379	=back
1498		2380
1499	=head3 Examples	2381	=head3 Examples
1500		2382
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	2383	Example: Try to exit cleanly on SIGINT.
1502		2384
1503	static void	2385	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2386	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	2387	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	2388	ev_break (loop, EVBREAK_ALL);
1507	}	2389	}
1508		2390
1509	struct ev_signal signal_watcher;	2391	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2392	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	2393	ev_signal_start (loop, &signal_watcher);
1512		2394
1513		2395
1514	=head2 C<ev_child> - watch out for process status changes	2396	=head2 C<ev_child> - watch out for process status changes
1515		2397
1516	Child watchers trigger when your process receives a SIGCHLD in response to	2398	Child watchers trigger when your process receives a SIGCHLD in response to
1517	some child status changes (most typically when a child of yours dies). It	2399	some child status changes (most typically when a child of yours dies or
1518	is permissible to install a child watcher I<after> the child has been	2400	exits). It is permissible to install a child watcher I<after> the child
1519	forked (which implies it might have already exited), as long as the event	2401	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	2402	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2403	forking and then immediately registering a watcher for the child is fine,
		2404	but forking and registering a watcher a few event loop iterations later or
		2405	in the next callback invocation is not.
1521		2406
1522	Only the default event loop is capable of handling signals, and therefore	2407	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	2408	you can only register child watchers in the default event loop.
		2409
		2410	Due to some design glitches inside libev, child watchers will always be
		2411	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2412	libev)
1524		2413
1525	=head3 Process Interaction	2414	=head3 Process Interaction
1526		2415
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	2416	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	2417	initialised. This is necessary to guarantee proper behaviour even if the
1529	the first child watcher is started after the child exits. The occurance	2418	first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2419	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	2420	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	2421	children, even ones not watched.
1533		2422
1534	=head3 Overriding the Built-In Processing	2423	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	2427	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	2428	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	2429	default loop never gets destroyed. You are encouraged, however, to use an
1541	event-based approach to child reaping and thus use libev's support for	2430	event-based approach to child reaping and thus use libev's support for
1542	that, so other libev users can use C<ev_child> watchers freely.	2431	that, so other libev users can use C<ev_child> watchers freely.
		2432
		2433	=head3 Stopping the Child Watcher
		2434
		2435	Currently, the child watcher never gets stopped, even when the
		2436	child terminates, so normally one needs to stop the watcher in the
		2437	callback. Future versions of libev might stop the watcher automatically
		2438	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2439	problem).
1543		2440
1544	=head3 Watcher-Specific Functions and Data Members	2441	=head3 Watcher-Specific Functions and Data Members
1545		2442
1546	=over 4	2443	=over 4
1547		2444
…		…
1576	=head3 Examples	2473	=head3 Examples
1577		2474
1578	Example: C<fork()> a new process and install a child handler to wait for	2475	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	2476	its completion.
1580		2477
1581	ev_child cw;	2478	ev_child cw;
1582		2479
1583	static void	2480	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	2481	child_cb (EV_P_ ev_child *w, int revents)
1585	{	2482	{
1586	ev_child_stop (EV_A_ w);	2483	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2484	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	2485	}
1589		2486
1590	pid_t pid = fork ();	2487	pid_t pid = fork ();
1591		2488
1592	if (pid < 0)	2489	if (pid < 0)
1593	// error	2490	// error
1594	else if (pid == 0)	2491	else if (pid == 0)
1595	{	2492	{
1596	// the forked child executes here	2493	// the forked child executes here
1597	exit (1);	2494	exit (1);
1598	}	2495	}
1599	else	2496	else
1600	{	2497	{
1601	ev_child_init (&cw, child_cb, pid, 0);	2498	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	2499	ev_child_start (EV_DEFAULT_ &cw);
1603	}	2500	}
1604		2501
1605		2502
1606	=head2 C<ev_stat> - did the file attributes just change?	2503	=head2 C<ev_stat> - did the file attributes just change?
1607		2504
1608	This watches a filesystem path for attribute changes. That is, it calls	2505	This watches a file system path for attribute changes. That is, it calls
1609	C<stat> regularly (or when the OS says it changed) and sees if it changed	2506	C<stat> on that path in regular intervals (or when the OS says it changed)
1610	compared to the last time, invoking the callback if it did.	2507	and sees if it changed compared to the last time, invoking the callback if
		2508	it did.
1611		2509
1612	The path does not need to exist: changing from "path exists" to "path does	2510	The path does not need to exist: changing from "path exists" to "path does
1613	not exist" is a status change like any other. The condition "path does	2511	not exist" is a status change like any other. The condition "path does not
1614	not exist" is signified by the C<st_nlink> field being zero (which is	2512	exist" (or more correctly "path cannot be stat'ed") is signified by the
1615	otherwise always forced to be at least one) and all the other fields of	2513	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	2514	least one) and all the other fields of the stat buffer having unspecified
		2515	contents.
1617		2516
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	2517	The path I<must not> end in a slash or contain special components such as
		2518	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1619	relative and your working directory changes, the behaviour is undefined.	2519	your working directory changes, then the behaviour is undefined.
1620		2520
1621	Since there is no standard to do this, the portable implementation simply	2521	Since there is no portable change notification interface available, the
1622	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2522	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	2523	to see if it changed somehow. You can specify a recommended polling
1624	a polling interval of C<0> (highly recommended!) then a I<suitable,	2524	interval for this case. If you specify a polling interval of C<0> (highly
1625	unspecified default> value will be used (which you can expect to be around	2525	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	2526	(which you can expect to be around five seconds, although this might
1627	impose a minimum interval which is currently around C<0.1>, but thats	2527	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	2528	currently around C<0.1>, but that's usually overkill.
1629		2529
1630	This watcher type is not meant for massive numbers of stat watchers,	2530	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	2531	as even with OS-supported change notifications, this can be
1632	resource-intensive.	2532	resource-intensive.
1633		2533
1634	At the time of this writing, only the Linux inotify interface is	2534	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	2535	is the Linux inotify interface (implementing kqueue support is left as an
1636	reader, note, however, that the author sees no way of implementing ev_stat	2536	exercise for the reader. Note, however, that the author sees no way of
1637	semantics with kqueue). Inotify will be used to give hints only and should	2537	implementing C<ev_stat> semantics with kqueue, except as a hint).
1638	not change the semantics of C<ev_stat> watchers, which means that libev
1639	sometimes needs to fall back to regular polling again even with inotify,
1640	but changes are usually detected immediately, and if the file exists there
1641	will be no polling.
1642		2538
1643	=head3 ABI Issues (Largefile Support)	2539	=head3 ABI Issues (Largefile Support)
1644		2540
1645	Libev by default (unless the user overrides this) uses the default	2541	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	2542	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	2543	support disabled by default, you get the 32 bit version of the stat
1648	structure. When using the library from programs that change the ABI to	2544	structure. When using the library from programs that change the ABI to
1649	use 64 bit file offsets the programs will fail. In that case you have to	2545	use 64 bit file offsets the programs will fail. In that case you have to
1650	compile libev with the same flags to get binary compatibility. This is	2546	compile libev with the same flags to get binary compatibility. This is
1651	obviously the case with any flags that change the ABI, but the problem is	2547	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	2548	most noticeably displayed with ev_stat and large file support.
1653		2549
1654	=head3 Inotify	2550	The solution for this is to lobby your distribution maker to make large
		2551	file interfaces available by default (as e.g. FreeBSD does) and not
		2552	optional. Libev cannot simply switch on large file support because it has
		2553	to exchange stat structures with application programs compiled using the
		2554	default compilation environment.
1655		2555
		2556	=head3 Inotify and Kqueue
		2557
1656	When C<inotify (7)> support has been compiled into libev (generally only	2558	When C<inotify (7)> support has been compiled into libev and present at
1657	available on Linux) and present at runtime, it will be used to speed up	2559	runtime, it will be used to speed up change detection where possible. The
1658	change detection where possible. The inotify descriptor will be created lazily	2560	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	2561	watcher is being started.
1660		2562
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	2563	Inotify presence does not change the semantics of C<ev_stat> watchers
1662	except that changes might be detected earlier, and in some cases, to avoid	2564	except that changes might be detected earlier, and in some cases, to avoid
1663	making regular C<stat> calls. Even in the presence of inotify support	2565	making regular C<stat> calls. Even in the presence of inotify support
1664	there are many cases where libev has to resort to regular C<stat> polling.	2566	there are many cases where libev has to resort to regular C<stat> polling,
		2567	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2568	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2569	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2570	xfs are fully working) libev usually gets away without polling.
1665		2571
1666	(There is no support for kqueue, as apparently it cannot be used to	2572	There is no support for kqueue, as apparently it cannot be used to
1667	implement this functionality, due to the requirement of having a file	2573	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2574	descriptor open on the object at all times, and detecting renames, unlinks
		2575	etc. is difficult.
		2576
		2577	=head3 C<stat ()> is a synchronous operation
		2578
		2579	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2580	the process. The exception are C<ev_stat> watchers - those call C<stat
		2581	()>, which is a synchronous operation.
		2582
		2583	For local paths, this usually doesn't matter: unless the system is very
		2584	busy or the intervals between stat's are large, a stat call will be fast,
		2585	as the path data is usually in memory already (except when starting the
		2586	watcher).
		2587
		2588	For networked file systems, calling C<stat ()> can block an indefinite
		2589	time due to network issues, and even under good conditions, a stat call
		2590	often takes multiple milliseconds.
		2591
		2592	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2593	paths, although this is fully supported by libev.
1669		2594
1670	=head3 The special problem of stat time resolution	2595	=head3 The special problem of stat time resolution
1671		2596
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2597	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2598	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2599	still only support whole seconds.
1675		2600
1676	That means that, if the time is the only thing that changes, you can	2601	That means that, if the time is the only thing that changes, you can
1677	easily miss updates: on the first update, C<ev_stat> detects a change and	2602	easily miss updates: on the first update, C<ev_stat> detects a change and
1678	calls your callback, which does something. When there is another update	2603	calls your callback, which does something. When there is another update
1679	within the same second, C<ev_stat> will be unable to detect it as the stat	2604	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2605	stat data does change in other ways (e.g. file size).
1681		2606
1682	The solution to this is to delay acting on a change for slightly more	2607	The solution to this is to delay acting on a change for slightly more
1683	than a second (or till slightly after the next full second boundary), using	2608	than a second (or till slightly after the next full second boundary), using
1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2609	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2610	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2630	C<path>. The C<interval> is a hint on how quickly a change is expected to
1706	be detected and should normally be specified as C<0> to let libev choose	2631	be detected and should normally be specified as C<0> to let libev choose
1707	a suitable value. The memory pointed to by C<path> must point to the same	2632	a suitable value. The memory pointed to by C<path> must point to the same
1708	path for as long as the watcher is active.	2633	path for as long as the watcher is active.
1709		2634
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2635	The callback will receive an C<EV_STAT> event when a change was detected,
1711	to the attributes at the time the watcher was started (or the last change	2636	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2637	last change was detected).
1713		2638
1714	=item ev_stat_stat (loop, ev_stat *)	2639	=item ev_stat_stat (loop, ev_stat *)
1715		2640
1716	Updates the stat buffer immediately with new values. If you change the	2641	Updates the stat buffer immediately with new values. If you change the
1717	watched path in your callback, you could call this function to avoid	2642	watched path in your callback, you could call this function to avoid
…		…
1738		2663
1739	The specified interval.	2664	The specified interval.
1740		2665
1741	=item const char *path [read-only]	2666	=item const char *path [read-only]
1742		2667
1743	The filesystem path that is being watched.	2668	The file system path that is being watched.
1744		2669
1745	=back	2670	=back
1746		2671
1747	=head3 Examples	2672	=head3 Examples
1748		2673
1749	Example: Watch C</etc/passwd> for attribute changes.	2674	Example: Watch C</etc/passwd> for attribute changes.
1750		2675
1751	static void	2676	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2677	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2678	{
1754	/* /etc/passwd changed in some way */	2679	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2680	if (w->attr.st_nlink)
1756	{	2681	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2682	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2683	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2684	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2685	}
1761	else	2686	else
1762	/* you shalt not abuse printf for puts */	2687	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2688	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2689	"if this is windows, they already arrived\n");
1765	}	2690	}
1766		2691
1767	...	2692	...
1768	ev_stat passwd;	2693	ev_stat passwd;
1769		2694
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2695	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2696	ev_stat_start (loop, &passwd);
1772		2697
1773	Example: Like above, but additionally use a one-second delay so we do not	2698	Example: Like above, but additionally use a one-second delay so we do not
1774	miss updates (however, frequent updates will delay processing, too, so	2699	miss updates (however, frequent updates will delay processing, too, so
1775	one might do the work both on C<ev_stat> callback invocation I<and> on	2700	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2701	C<ev_timer> callback invocation).
1777		2702
1778	static ev_stat passwd;	2703	static ev_stat passwd;
1779	static ev_timer timer;	2704	static ev_timer timer;
1780		2705
1781	static void	2706	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2707	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2708	{
1784	ev_timer_stop (EV_A_ w);	2709	ev_timer_stop (EV_A_ w);
1785		2710
1786	/* now it's one second after the most recent passwd change */	2711	/* now it's one second after the most recent passwd change */
1787	}	2712	}
1788		2713
1789	static void	2714	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2715	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2716	{
1792	/* reset the one-second timer */	2717	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2718	ev_timer_again (EV_A_ &timer);
1794	}	2719	}
1795		2720
1796	...	2721	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2722	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2723	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2724	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2725
1801		2726
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2727	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2728
1804	Idle watchers trigger events when no other events of the same or higher	2729	Idle watchers trigger events when no other events of the same or higher
1805	priority are pending (prepare, check and other idle watchers do not	2730	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2731	as receiving "events").
1807		2732
1808	That is, as long as your process is busy handling sockets or timeouts	2733	That is, as long as your process is busy handling sockets or timeouts
1809	(or even signals, imagine) of the same or higher priority it will not be	2734	(or even signals, imagine) of the same or higher priority it will not be
1810	triggered. But when your process is idle (or only lower-priority watchers	2735	triggered. But when your process is idle (or only lower-priority watchers
1811	are pending), the idle watchers are being called once per event loop	2736	are pending), the idle watchers are being called once per event loop
…		…
1822		2747
1823	=head3 Watcher-Specific Functions and Data Members	2748	=head3 Watcher-Specific Functions and Data Members
1824		2749
1825	=over 4	2750	=over 4
1826		2751
1827	=item ev_idle_init (ev_signal *, callback)	2752	=item ev_idle_init (ev_idle *, callback)
1828		2753
1829	Initialises and configures the idle watcher - it has no parameters of any	2754	Initialises and configures the idle watcher - it has no parameters of any
1830	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2755	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1831	believe me.	2756	believe me.
1832		2757
…		…
1835	=head3 Examples	2760	=head3 Examples
1836		2761
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2762	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2763	callback, free it. Also, use no error checking, as usual.
1839		2764
1840	static void	2765	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2766	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2767	{
1843	free (w);	2768	free (w);
1844	// now do something you wanted to do when the program has	2769	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2770	// no longer anything immediate to do.
1846	}	2771	}
1847		2772
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2773	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2774	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2775	ev_idle_start (loop, idle_watcher);
1851		2776
1852		2777
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2778	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2779
1855	Prepare and check watchers are usually (but not always) used in tandem:	2780	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2781	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2782	afterwards.
1858		2783
1859	You I<must not> call C<ev_loop> or similar functions that enter	2784	You I<must not> call C<ev_run> or similar functions that enter
1860	the current event loop from either C<ev_prepare> or C<ev_check>	2785	the current event loop from either C<ev_prepare> or C<ev_check>
1861	watchers. Other loops than the current one are fine, however. The	2786	watchers. Other loops than the current one are fine, however. The
1862	rationale behind this is that you do not need to check for recursion in	2787	rationale behind this is that you do not need to check for recursion in
1863	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2788	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1864	C<ev_check> so if you have one watcher of each kind they will always be	2789	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2790	called in pairs bracketing the blocking call.
1866		2791
1867	Their main purpose is to integrate other event mechanisms into libev and	2792	Their main purpose is to integrate other event mechanisms into libev and
1868	their use is somewhat advanced. This could be used, for example, to track	2793	their use is somewhat advanced. They could be used, for example, to track
1869	variable changes, implement your own watchers, integrate net-snmp or a	2794	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2795	coroutine library and lots more. They are also occasionally useful if
1871	you cache some data and want to flush it before blocking (for example,	2796	you cache some data and want to flush it before blocking (for example,
1872	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2797	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2798	watcher).
1874		2799
1875	This is done by examining in each prepare call which file descriptors need	2800	This is done by examining in each prepare call which file descriptors
1876	to be watched by the other library, registering C<ev_io> watchers for	2801	need to be watched by the other library, registering C<ev_io> watchers
1877	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2802	for them and starting an C<ev_timer> watcher for any timeouts (many
1878	provide just this functionality). Then, in the check watcher you check for	2803	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2804	you check for any events that occurred (by checking the pending status
1880	and stopping them) and call back into the library. The I/O and timer	2805	of all watchers and stopping them) and call back into the library. The
1881	callbacks will never actually be called (but must be valid nevertheless,	2806	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2807	nevertheless, because you never know, you know?).
1883		2808
1884	As another example, the Perl Coro module uses these hooks to integrate	2809	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2810	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2811	during each prepare and only letting the process block if no coroutines
1887	are ready to run (it's actually more complicated: it only runs coroutines	2812	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1890	loop from blocking if lower-priority coroutines are active, thus mapping	2815	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2816	low-priority coroutines to idle/background tasks).
1892		2817
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2818	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1894	priority, to ensure that they are being run before any other watchers	2819	priority, to ensure that they are being run before any other watchers
		2820	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2821
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2822	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1896	too) should not activate ("feed") events into libev. While libev fully	2823	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2824	might get executed before other C<ev_check> watchers did their job. As
1898	did their job. As C<ev_check> watchers are often used to embed other	2825	C<ev_check> watchers are often used to embed other (non-libev) event
1899	(non-libev) event loops those other event loops might be in an unusable	2826	loops those other event loops might be in an unusable state until their
1900	state until their C<ev_check> watcher ran (always remind yourself to	2827	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2828	others).
1902		2829
1903	=head3 Watcher-Specific Functions and Data Members	2830	=head3 Watcher-Specific Functions and Data Members
1904		2831
1905	=over 4	2832	=over 4
1906		2833
…		…
1908		2835
1909	=item ev_check_init (ev_check *, callback)	2836	=item ev_check_init (ev_check *, callback)
1910		2837
1911	Initialises and configures the prepare or check watcher - they have no	2838	Initialises and configures the prepare or check watcher - they have no
1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2839	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1913	macros, but using them is utterly, utterly and completely pointless.	2840	macros, but using them is utterly, utterly, utterly and completely
		2841	pointless.
1914		2842
1915	=back	2843	=back
1916		2844
1917	=head3 Examples	2845	=head3 Examples
1918		2846
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2855	and in a check watcher, destroy them and call into libadns. What follows
1928	is pseudo-code only of course. This requires you to either use a low	2856	is pseudo-code only of course. This requires you to either use a low
1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2857	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1930	the callbacks for the IO/timeout watchers might not have been called yet.	2858	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2859
1932	static ev_io iow [nfd];	2860	static ev_io iow [nfd];
1933	static ev_timer tw;	2861	static ev_timer tw;
1934		2862
1935	static void	2863	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2864	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2865	{
1938	}	2866	}
1939		2867
1940	// create io watchers for each fd and a timer before blocking	2868	// create io watchers for each fd and a timer before blocking
1941	static void	2869	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2870	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2871	{
1944	int timeout = 3600000;	2872	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2873	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2874	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2875	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2876
1949	/* the callback is illegal, but won't be called as we stop during check */	2877	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2878	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1951	ev_timer_start (loop, &tw);	2879	ev_timer_start (loop, &tw);
1952		2880
1953	// create one ev_io per pollfd	2881	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2882	for (int i = 0; i < nfd; ++i)
1955	{	2883	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2884	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2885	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2886	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2887
1960	fds [i].revents = 0;	2888	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2889	ev_io_start (loop, iow + i);
1962	}	2890	}
1963	}	2891	}
1964		2892
1965	// stop all watchers after blocking	2893	// stop all watchers after blocking
1966	static void	2894	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2895	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2896	{
1969	ev_timer_stop (loop, &tw);	2897	ev_timer_stop (loop, &tw);
1970		2898
1971	for (int i = 0; i < nfd; ++i)	2899	for (int i = 0; i < nfd; ++i)
1972	{	2900	{
1973	// set the relevant poll flags	2901	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2902	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2903	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2904	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2905	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2906	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2907
1980	// now stop the watcher	2908	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2909	ev_io_stop (loop, iow + i);
1982	}	2910	}
1983		2911
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2912	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2913	}
1986		2914
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2915	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1988	in the prepare watcher and would dispose of the check watcher.	2916	in the prepare watcher and would dispose of the check watcher.
1989		2917
1990	Method 3: If the module to be embedded supports explicit event	2918	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2919	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2920	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2921
1994	static void	2922	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2923	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2924	{
1997	adns_state ads = (adns_state)w->data;	2925	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2926	update_now (EV_A);
1999		2927
2000	adns_processtimeouts (ads, &tv_now);	2928	adns_processtimeouts (ads, &tv_now);
2001	}	2929	}
2002		2930
2003	static void	2931	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2932	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2933	{
2006	adns_state ads = (adns_state)w->data;	2934	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2935	update_now (EV_A);
2008		2936
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2937	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2938	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2939	}
2012		2940
2013	// do not ever call adns_afterpoll	2941	// do not ever call adns_afterpoll
2014		2942
2015	Method 4: Do not use a prepare or check watcher because the module you	2943	Method 4: Do not use a prepare or check watcher because the module you
2016	want to embed is too inflexible to support it. Instead, youc na override	2944	want to embed is not flexible enough to support it. Instead, you can
2017	their poll function. The drawback with this solution is that the main	2945	override their poll function. The drawback with this solution is that the
2018	loop is now no longer controllable by EV. The C<Glib::EV> module does	2946	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2947	this approach, effectively embedding EV as a client into the horrible
		2948	libglib event loop.
2020		2949
2021	static gint	2950	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2951	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2952	{
2024	int got_events = 0;	2953	int got_events = 0;
2025		2954
2026	for (n = 0; n < nfds; ++n)	2955	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2956	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2957
2029	if (timeout >= 0)	2958	if (timeout >= 0)
2030	// create/start timer	2959	// create/start timer
2031		2960
2032	// poll	2961	// poll
2033	ev_loop (EV_A_ 0);	2962	ev_run (EV_A_ 0);
2034		2963
2035	// stop timer again	2964	// stop timer again
2036	if (timeout >= 0)	2965	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2966	ev_timer_stop (EV_A_ &to);
2038		2967
2039	// stop io watchers again - their callbacks should have set	2968	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2969	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2970	ev_io_stop (EV_A_ iow [n]);
2042		2971
2043	return got_events;	2972	return got_events;
2044	}	2973	}
2045		2974
2046		2975
2047	=head2 C<ev_embed> - when one backend isn't enough...	2976	=head2 C<ev_embed> - when one backend isn't enough...
2048		2977
2049	This is a rather advanced watcher type that lets you embed one event loop	2978	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2984	prioritise I/O.
2056		2985
2057	As an example for a bug workaround, the kqueue backend might only support	2986	As an example for a bug workaround, the kqueue backend might only support
2058	sockets on some platform, so it is unusable as generic backend, but you	2987	sockets on some platform, so it is unusable as generic backend, but you
2059	still want to make use of it because you have many sockets and it scales	2988	still want to make use of it because you have many sockets and it scales
2060	so nicely. In this case, you would create a kqueue-based loop and embed it	2989	so nicely. In this case, you would create a kqueue-based loop and embed
2061	into your default loop (which might use e.g. poll). Overall operation will	2990	it into your default loop (which might use e.g. poll). Overall operation
2062	be a bit slower because first libev has to poll and then call kevent, but	2991	will be a bit slower because first libev has to call C<poll> and then
2063	at least you can use both at what they are best.	2992	C<kevent>, but at least you can use both mechanisms for what they are
		2993	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2994
2065	As for prioritising I/O: rarely you have the case where some fds have	2995	As for prioritising I/O: under rare circumstances you have the case where
2066	to be watched and handled very quickly (with low latency), and even	2996	some fds have to be watched and handled very quickly (with low latency),
2067	priorities and idle watchers might have too much overhead. In this case	2997	and even priorities and idle watchers might have too much overhead. In
2068	you would put all the high priority stuff in one loop and all the rest in	2998	this case you would put all the high priority stuff in one loop and all
2069	a second one, and embed the second one in the first.	2999	the rest in a second one, and embed the second one in the first.
2070		3000
2071	As long as the watcher is active, the callback will be invoked every time	3001	As long as the watcher is active, the callback will be invoked every
2072	there might be events pending in the embedded loop. The callback must then	3002	time there might be events pending in the embedded loop. The callback
2073	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3003	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2074	their callbacks (you could also start an idle watcher to give the embedded	3004	sweep and invoke their callbacks (the callback doesn't need to invoke the
2075	loop strictly lower priority for example). You can also set the callback	3005	C<ev_embed_sweep> function directly, it could also start an idle watcher
2076	to C<0>, in which case the embed watcher will automatically execute the	3006	to give the embedded loop strictly lower priority for example).
2077	embedded loop sweep.
2078		3007
2079	As long as the watcher is started it will automatically handle events. The	3008	You can also set the callback to C<0>, in which case the embed watcher
2080	callback will be invoked whenever some events have been handled. You can	3009	will automatically execute the embedded loop sweep whenever necessary.
2081	set the callback to C<0> to avoid having to specify one if you are not
2082	interested in that.
2083		3010
2084	Also, there have not currently been made special provisions for forking:	3011	Fork detection will be handled transparently while the C<ev_embed> watcher
2085	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3012	is active, i.e., the embedded loop will automatically be forked when the
2086	but you will also have to stop and restart any C<ev_embed> watchers	3013	embedding loop forks. In other cases, the user is responsible for calling
2087	yourself.	3014	C<ev_loop_fork> on the embedded loop.
2088		3015
2089	Unfortunately, not all backends are embeddable, only the ones returned by	3016	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3017	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	3018	portable one.
2092		3019
2093	So when you want to use this feature you will always have to be prepared	3020	So when you want to use this feature you will always have to be prepared
2094	that you cannot get an embeddable loop. The recommended way to get around	3021	that you cannot get an embeddable loop. The recommended way to get around
2095	this is to have a separate variables for your embeddable loop, try to	3022	this is to have a separate variables for your embeddable loop, try to
2096	create it, and if that fails, use the normal loop for everything.	3023	create it, and if that fails, use the normal loop for everything.
2097		3024
		3025	=head3 C<ev_embed> and fork
		3026
		3027	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3028	automatically be applied to the embedded loop as well, so no special
		3029	fork handling is required in that case. When the watcher is not running,
		3030	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3031	as applicable.
		3032
2098	=head3 Watcher-Specific Functions and Data Members	3033	=head3 Watcher-Specific Functions and Data Members
2099		3034
2100	=over 4	3035	=over 4
2101		3036
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3037	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		3040
2106	Configures the watcher to embed the given loop, which must be	3041	Configures the watcher to embed the given loop, which must be
2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3042	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2108	invoked automatically, otherwise it is the responsibility of the callback	3043	invoked automatically, otherwise it is the responsibility of the callback
2109	to invoke it (it will continue to be called until the sweep has been done,	3044	to invoke it (it will continue to be called until the sweep has been done,
2110	if you do not want thta, you need to temporarily stop the embed watcher).	3045	if you do not want that, you need to temporarily stop the embed watcher).
2111		3046
2112	=item ev_embed_sweep (loop, ev_embed *)	3047	=item ev_embed_sweep (loop, ev_embed *)
2113		3048
2114	Make a single, non-blocking sweep over the embedded loop. This works	3049	Make a single, non-blocking sweep over the embedded loop. This works
2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3050	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2116	apropriate way for embedded loops.	3051	appropriate way for embedded loops.
2117		3052
2118	=item struct ev_loop *other [read-only]	3053	=item struct ev_loop *other [read-only]
2119		3054
2120	The embedded event loop.	3055	The embedded event loop.
2121		3056
…		…
2123		3058
2124	=head3 Examples	3059	=head3 Examples
2125		3060
2126	Example: Try to get an embeddable event loop and embed it into the default	3061	Example: Try to get an embeddable event loop and embed it into the default
2127	event loop. If that is not possible, use the default loop. The default	3062	event loop. If that is not possible, use the default loop. The default
2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3063	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3064	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	3065	used).
2131		3066
2132	struct ev_loop *loop_hi = ev_default_init (0);	3067	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	3068	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	3069	ev_embed embed;
2135		3070
2136	// see if there is a chance of getting one that works	3071	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	3072	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3073	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3074	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	3075	: 0;
2141		3076
2142	// if we got one, then embed it, otherwise default to loop_hi	3077	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	3078	if (loop_lo)
2144	{	3079	{
2145	ev_embed_init (&embed, 0, loop_lo);	3080	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	3081	ev_embed_start (loop_hi, &embed);
2147	}	3082	}
2148	else	3083	else
2149	loop_lo = loop_hi;	3084	loop_lo = loop_hi;
2150		3085
2151	Example: Check if kqueue is available but not recommended and create	3086	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	3087	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	3088	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3089	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		3090
2156	struct ev_loop *loop = ev_default_init (0);	3091	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	3092	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	3093	ev_embed embed;
2159		3094
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3095	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3096	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	3097	{
2163	ev_embed_init (&embed, 0, loop_socket);	3098	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	3099	ev_embed_start (loop, &embed);
2165	}	3100	}
2166		3101
2167	if (!loop_socket)	3102	if (!loop_socket)
2168	loop_socket = loop;	3103	loop_socket = loop;
2169		3104
2170	// now use loop_socket for all sockets, and loop for everything else	3105	// now use loop_socket for all sockets, and loop for everything else
2171		3106
2172		3107
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3108	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		3109
2175	Fork watchers are called when a C<fork ()> was detected (usually because	3110	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2178	event loop blocks next and before C<ev_check> watchers are being called,	3113	event loop blocks next and before C<ev_check> watchers are being called,
2179	and only in the child after the fork. If whoever good citizen calling	3114	and only in the child after the fork. If whoever good citizen calling
2180	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3115	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2181	handlers will be invoked, too, of course.	3116	handlers will be invoked, too, of course.
2182		3117
		3118	=head3 The special problem of life after fork - how is it possible?
		3119
		3120	Most uses of C<fork()> consist of forking, then some simple calls to set
		3121	up/change the process environment, followed by a call to C<exec()>. This
		3122	sequence should be handled by libev without any problems.
		3123
		3124	This changes when the application actually wants to do event handling
		3125	in the child, or both parent in child, in effect "continuing" after the
		3126	fork.
		3127
		3128	The default mode of operation (for libev, with application help to detect
		3129	forks) is to duplicate all the state in the child, as would be expected
		3130	when I<either> the parent I<or> the child process continues.
		3131
		3132	When both processes want to continue using libev, then this is usually the
		3133	wrong result. In that case, usually one process (typically the parent) is
		3134	supposed to continue with all watchers in place as before, while the other
		3135	process typically wants to start fresh, i.e. without any active watchers.
		3136
		3137	The cleanest and most efficient way to achieve that with libev is to
		3138	simply create a new event loop, which of course will be "empty", and
		3139	use that for new watchers. This has the advantage of not touching more
		3140	memory than necessary, and thus avoiding the copy-on-write, and the
		3141	disadvantage of having to use multiple event loops (which do not support
		3142	signal watchers).
		3143
		3144	When this is not possible, or you want to use the default loop for
		3145	other reasons, then in the process that wants to start "fresh", call
		3146	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3147	Destroying the default loop will "orphan" (not stop) all registered
		3148	watchers, so you have to be careful not to execute code that modifies
		3149	those watchers. Note also that in that case, you have to re-register any
		3150	signal watchers.
		3151
2183	=head3 Watcher-Specific Functions and Data Members	3152	=head3 Watcher-Specific Functions and Data Members
2184		3153
2185	=over 4	3154	=over 4
2186		3155
2187	=item ev_fork_init (ev_signal *, callback)	3156	=item ev_fork_init (ev_fork *, callback)
2188		3157
2189	Initialises and configures the fork watcher - it has no parameters of any	3158	Initialises and configures the fork watcher - it has no parameters of any
2190	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2191	believe me.	3160	really.
2192		3161
2193	=back	3162	=back
2194		3163
2195		3164
		3165	=head2 C<ev_cleanup> - even the best things end
		3166
		3167	Cleanup watchers are called just before the event loop is being destroyed
		3168	by a call to C<ev_loop_destroy>.
		3169
		3170	While there is no guarantee that the event loop gets destroyed, cleanup
		3171	watchers provide a convenient method to install cleanup hooks for your
		3172	program, worker threads and so on - you just to make sure to destroy the
		3173	loop when you want them to be invoked.
		3174
		3175	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3176	all other watchers, they do not keep a reference to the event loop (which
		3177	makes a lot of sense if you think about it). Like all other watchers, you
		3178	can call libev functions in the callback, except C<ev_cleanup_start>.
		3179
		3180	=head3 Watcher-Specific Functions and Data Members
		3181
		3182	=over 4
		3183
		3184	=item ev_cleanup_init (ev_cleanup *, callback)
		3185
		3186	Initialises and configures the cleanup watcher - it has no parameters of
		3187	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3188	pointless, I assure you.
		3189
		3190	=back
		3191
		3192	Example: Register an atexit handler to destroy the default loop, so any
		3193	cleanup functions are called.
		3194
		3195	static void
		3196	program_exits (void)
		3197	{
		3198	ev_loop_destroy (EV_DEFAULT_UC);
		3199	}
		3200
		3201	...
		3202	atexit (program_exits);
		3203
		3204
2196	=head2 C<ev_async> - how to wake up another event loop	3205	=head2 C<ev_async> - how to wake up an event loop
2197		3206
2198	In general, you cannot use an C<ev_loop> from multiple threads or other	3207	In general, you cannot use an C<ev_loop> from multiple threads or other
2199	asynchronous sources such as signal handlers (as opposed to multiple event	3208	asynchronous sources such as signal handlers (as opposed to multiple event
2200	loops - those are of course safe to use in different threads).	3209	loops - those are of course safe to use in different threads).
2201		3210
2202	Sometimes, however, you need to wake up another event loop you do not	3211	Sometimes, however, you need to wake up an event loop you do not control,
2203	control, for example because it belongs to another thread. This is what	3212	for example because it belongs to another thread. This is what C<ev_async>
2204	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3213	watchers do: as long as the C<ev_async> watcher is active, you can signal
2205	can signal it by calling C<ev_async_send>, which is thread- and signal	3214	it by calling C<ev_async_send>, which is thread- and signal safe.
2206	safe.
2207		3215
2208	This functionality is very similar to C<ev_signal> watchers, as signals,	3216	This functionality is very similar to C<ev_signal> watchers, as signals,
2209	too, are asynchronous in nature, and signals, too, will be compressed	3217	too, are asynchronous in nature, and signals, too, will be compressed
2210	(i.e. the number of callback invocations may be less than the number of	3218	(i.e. the number of callback invocations may be less than the number of
2211	C<ev_async_sent> calls).	3219	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3220	of "global async watchers" by using a watcher on an otherwise unused
		3221	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3222	even without knowing which loop owns the signal.
2212		3223
2213	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3224	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2214	just the default loop.	3225	just the default loop.
2215		3226
2216	=head3 Queueing	3227	=head3 Queueing
2217		3228
2218	C<ev_async> does not support queueing of data in any way. The reason	3229	C<ev_async> does not support queueing of data in any way. The reason
2219	is that the author does not know of a simple (or any) algorithm for a	3230	is that the author does not know of a simple (or any) algorithm for a
2220	multiple-writer-single-reader queue that works in all cases and doesn't	3231	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	3232	need elaborate support such as pthreads or unportable memory access
		3233	semantics.
2222		3234
2223	That means that if you want to queue data, you have to provide your own	3235	That means that if you want to queue data, you have to provide your own
2224	queue. But at least I can tell you would implement locking around your	3236	queue. But at least I can tell you how to implement locking around your
2225	queue:	3237	queue:
2226		3238
2227	=over 4	3239	=over 4
2228		3240
2229	=item queueing from a signal handler context	3241	=item queueing from a signal handler context
2230		3242
2231	To implement race-free queueing, you simply add to the queue in the signal	3243	To implement race-free queueing, you simply add to the queue in the signal
2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3244	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	3245	an example that does that for some fictitious SIGUSR1 handler:
2234		3246
2235	static ev_async mysig;	3247	static ev_async mysig;
2236		3248
2237	static void	3249	static void
2238	sigusr1_handler (void)	3250	sigusr1_handler (void)
…		…
2304	=over 4	3316	=over 4
2305		3317
2306	=item ev_async_init (ev_async *, callback)	3318	=item ev_async_init (ev_async *, callback)
2307		3319
2308	Initialises and configures the async watcher - it has no parameters of any	3320	Initialises and configures the async watcher - it has no parameters of any
2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3321	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	3322	trust me.
2311		3323
2312	=item ev_async_send (loop, ev_async *)	3324	=item ev_async_send (loop, ev_async *)
2313		3325
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3326	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3327	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3328	returns.
		3329
2316	C<ev_feed_event>, this call is safe to do in other threads, signal or	3330	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3331	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2318	section below on what exactly this means).	3332	embedding section below on what exactly this means).
2319		3333
		3334	Note that, as with other watchers in libev, multiple events might get
		3335	compressed into a single callback invocation (another way to look at this
		3336	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3337	reset when the event loop detects that).
		3338
2320	This call incurs the overhead of a syscall only once per loop iteration,	3339	This call incurs the overhead of a system call only once per event loop
2321	so while the overhead might be noticable, it doesn't apply to repeated	3340	iteration, so while the overhead might be noticeable, it doesn't apply to
2322	calls to C<ev_async_send>.	3341	repeated calls to C<ev_async_send> for the same event loop.
2323		3342
2324	=item bool = ev_async_pending (ev_async *)	3343	=item bool = ev_async_pending (ev_async *)
2325		3344
2326	Returns a non-zero value when C<ev_async_send> has been called on the	3345	Returns a non-zero value when C<ev_async_send> has been called on the
2327	watcher but the event has not yet been processed (or even noted) by the	3346	watcher but the event has not yet been processed (or even noted) by the
2328	event loop.	3347	event loop.
2329		3348
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3349	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2331	the loop iterates next and checks for the watcher to have become active,	3350	the loop iterates next and checks for the watcher to have become active,
2332	it will reset the flag again. C<ev_async_pending> can be used to very	3351	it will reset the flag again. C<ev_async_pending> can be used to very
2333	quickly check wether invoking the loop might be a good idea.	3352	quickly check whether invoking the loop might be a good idea.
2334		3353
2335	Not that this does I<not> check wether the watcher itself is pending, only	3354	Not that this does I<not> check whether the watcher itself is pending,
2336	wether it has been requested to make this watcher pending.	3355	only whether it has been requested to make this watcher pending: there
		3356	is a time window between the event loop checking and resetting the async
		3357	notification, and the callback being invoked.
2337		3358
2338	=back	3359	=back
2339		3360
2340		3361
2341	=head1 OTHER FUNCTIONS	3362	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	3366	=over 4
2346		3367
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		3369
2349	This function combines a simple timer and an I/O watcher, calls your	3370	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	3371	callback on whichever event happens first and automatically stops both
2351	watchers. This is useful if you want to wait for a single event on an fd	3372	watchers. This is useful if you want to wait for a single event on an fd
2352	or timeout without having to allocate/configure/start/stop/free one or	3373	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	3374	more watchers yourself.
2354		3375
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	3376	If C<fd> is less than 0, then no I/O watcher will be started and the
2356	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3377	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	3378	the given C<fd> and C<events> set will be created and started.
2358		3379
2359	If C<timeout> is less than 0, then no timeout watcher will be	3380	If C<timeout> is less than 0, then no timeout watcher will be
2360	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2361	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3382	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		3383
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3384	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2365	passed an C<revents> set like normal event callbacks (a combination of	3385	passed an C<revents> set like normal event callbacks (a combination of
2366	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3386	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2367	value passed to C<ev_once>:	3387	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3388	a timeout and an io event at the same time - you probably should give io
		3389	events precedence.
2368		3390
		3391	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3392
2369	static void stdin_ready (int revents, void *arg)	3393	static void stdin_ready (int revents, void *arg)
2370	{	3394	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	3395	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	3396	/* stdin might have data for us, joy! */;
		3397	else if (revents & EV_TIMER)
		3398	/* doh, nothing entered */;
2375	}	3399	}
2376		3400
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3401	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		3402
2379	=item ev_feed_event (ev_loop *, watcher *, int revents)
2380
2381	Feeds the given event set into the event loop, as if the specified event
2382	had happened for the specified watcher (which must be a pointer to an
2383	initialised but not necessarily started event watcher).
2384
2385	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3403	=item ev_feed_fd_event (loop, int fd, int revents)
2386		3404
2387	Feed an event on the given fd, as if a file descriptor backend detected	3405	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	3406	the given events it.
2389		3407
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	3408	=item ev_feed_signal_event (loop, int signum)
2391		3409
2392	Feed an event as if the given signal occured (C<loop> must be the default	3410	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2393	loop!).	3411	which is async-safe.
2394		3412
2395	=back	3413	=back
		3414
		3415
		3416	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3417
		3418	This section explains some common idioms that are not immediately
		3419	obvious. Note that examples are sprinkled over the whole manual, and this
		3420	section only contains stuff that wouldn't fit anywhere else.
		3421
		3422	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3423
		3424	Each watcher has, by default, a C<void *data> member that you can read
		3425	or modify at any time: libev will completely ignore it. This can be used
		3426	to associate arbitrary data with your watcher. If you need more data and
		3427	don't want to allocate memory separately and store a pointer to it in that
		3428	data member, you can also "subclass" the watcher type and provide your own
		3429	data:
		3430
		3431	struct my_io
		3432	{
		3433	ev_io io;
		3434	int otherfd;
		3435	void *somedata;
		3436	struct whatever *mostinteresting;
		3437	};
		3438
		3439	...
		3440	struct my_io w;
		3441	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3442
		3443	And since your callback will be called with a pointer to the watcher, you
		3444	can cast it back to your own type:
		3445
		3446	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3447	{
		3448	struct my_io *w = (struct my_io *)w_;
		3449	...
		3450	}
		3451
		3452	More interesting and less C-conformant ways of casting your callback
		3453	function type instead have been omitted.
		3454
		3455	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3456
		3457	Another common scenario is to use some data structure with multiple
		3458	embedded watchers, in effect creating your own watcher that combines
		3459	multiple libev event sources into one "super-watcher":
		3460
		3461	struct my_biggy
		3462	{
		3463	int some_data;
		3464	ev_timer t1;
		3465	ev_timer t2;
		3466	}
		3467
		3468	In this case getting the pointer to C<my_biggy> is a bit more
		3469	complicated: Either you store the address of your C<my_biggy> struct in
		3470	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3471	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3472	real programmers):
		3473
		3474	#include <stddef.h>
		3475
		3476	static void
		3477	t1_cb (EV_P_ ev_timer *w, int revents)
		3478	{
		3479	struct my_biggy big = (struct my_biggy *)
		3480	(((char *)w) - offsetof (struct my_biggy, t1));
		3481	}
		3482
		3483	static void
		3484	t2_cb (EV_P_ ev_timer *w, int revents)
		3485	{
		3486	struct my_biggy big = (struct my_biggy *)
		3487	(((char *)w) - offsetof (struct my_biggy, t2));
		3488	}
		3489
		3490	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3491
		3492	Often (especially in GUI toolkits) there are places where you have
		3493	I<modal> interaction, which is most easily implemented by recursively
		3494	invoking C<ev_run>.
		3495
		3496	This brings the problem of exiting - a callback might want to finish the
		3497	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3498	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3499	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3500	other combination: In these cases, C<ev_break> will not work alone.
		3501
		3502	The solution is to maintain "break this loop" variable for each C<ev_run>
		3503	invocation, and use a loop around C<ev_run> until the condition is
		3504	triggered, using C<EVRUN_ONCE>:
		3505
		3506	// main loop
		3507	int exit_main_loop = 0;
		3508
		3509	while (!exit_main_loop)
		3510	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3511
		3512	// in a model watcher
		3513	int exit_nested_loop = 0;
		3514
		3515	while (!exit_nested_loop)
		3516	ev_run (EV_A_ EVRUN_ONCE);
		3517
		3518	To exit from any of these loops, just set the corresponding exit variable:
		3519
		3520	// exit modal loop
		3521	exit_nested_loop = 1;
		3522
		3523	// exit main program, after modal loop is finished
		3524	exit_main_loop = 1;
		3525
		3526	// exit both
		3527	exit_main_loop = exit_nested_loop = 1;
		3528
		3529	=head2 THREAD LOCKING EXAMPLE
		3530
		3531	Here is a fictitious example of how to run an event loop in a different
		3532	thread from where callbacks are being invoked and watchers are
		3533	created/added/removed.
		3534
		3535	For a real-world example, see the C<EV::Loop::Async> perl module,
		3536	which uses exactly this technique (which is suited for many high-level
		3537	languages).
		3538
		3539	The example uses a pthread mutex to protect the loop data, a condition
		3540	variable to wait for callback invocations, an async watcher to notify the
		3541	event loop thread and an unspecified mechanism to wake up the main thread.
		3542
		3543	First, you need to associate some data with the event loop:
		3544
		3545	typedef struct {
		3546	mutex_t lock; /* global loop lock */
		3547	ev_async async_w;
		3548	thread_t tid;
		3549	cond_t invoke_cv;
		3550	} userdata;
		3551
		3552	void prepare_loop (EV_P)
		3553	{
		3554	// for simplicity, we use a static userdata struct.
		3555	static userdata u;
		3556
		3557	ev_async_init (&u->async_w, async_cb);
		3558	ev_async_start (EV_A_ &u->async_w);
		3559
		3560	pthread_mutex_init (&u->lock, 0);
		3561	pthread_cond_init (&u->invoke_cv, 0);
		3562
		3563	// now associate this with the loop
		3564	ev_set_userdata (EV_A_ u);
		3565	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3566	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3567
		3568	// then create the thread running ev_run
		3569	pthread_create (&u->tid, 0, l_run, EV_A);
		3570	}
		3571
		3572	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3573	solely to wake up the event loop so it takes notice of any new watchers
		3574	that might have been added:
		3575
		3576	static void
		3577	async_cb (EV_P_ ev_async *w, int revents)
		3578	{
		3579	// just used for the side effects
		3580	}
		3581
		3582	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3583	protecting the loop data, respectively.
		3584
		3585	static void
		3586	l_release (EV_P)
		3587	{
		3588	userdata *u = ev_userdata (EV_A);
		3589	pthread_mutex_unlock (&u->lock);
		3590	}
		3591
		3592	static void
		3593	l_acquire (EV_P)
		3594	{
		3595	userdata *u = ev_userdata (EV_A);
		3596	pthread_mutex_lock (&u->lock);
		3597	}
		3598
		3599	The event loop thread first acquires the mutex, and then jumps straight
		3600	into C<ev_run>:
		3601
		3602	void *
		3603	l_run (void *thr_arg)
		3604	{
		3605	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3606
		3607	l_acquire (EV_A);
		3608	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3609	ev_run (EV_A_ 0);
		3610	l_release (EV_A);
		3611
		3612	return 0;
		3613	}
		3614
		3615	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3616	signal the main thread via some unspecified mechanism (signals? pipe
		3617	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3618	have been called (in a while loop because a) spurious wakeups are possible
		3619	and b) skipping inter-thread-communication when there are no pending
		3620	watchers is very beneficial):
		3621
		3622	static void
		3623	l_invoke (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	while (ev_pending_count (EV_A))
		3628	{
		3629	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3630	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3631	}
		3632	}
		3633
		3634	Now, whenever the main thread gets told to invoke pending watchers, it
		3635	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3636	thread to continue:
		3637
		3638	static void
		3639	real_invoke_pending (EV_P)
		3640	{
		3641	userdata *u = ev_userdata (EV_A);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_invoke_pending (EV_A);
		3645	pthread_cond_signal (&u->invoke_cv);
		3646	pthread_mutex_unlock (&u->lock);
		3647	}
		3648
		3649	Whenever you want to start/stop a watcher or do other modifications to an
		3650	event loop, you will now have to lock:
		3651
		3652	ev_timer timeout_watcher;
		3653	userdata *u = ev_userdata (EV_A);
		3654
		3655	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3656
		3657	pthread_mutex_lock (&u->lock);
		3658	ev_timer_start (EV_A_ &timeout_watcher);
		3659	ev_async_send (EV_A_ &u->async_w);
		3660	pthread_mutex_unlock (&u->lock);
		3661
		3662	Note that sending the C<ev_async> watcher is required because otherwise
		3663	an event loop currently blocking in the kernel will have no knowledge
		3664	about the newly added timer. By waking up the loop it will pick up any new
		3665	watchers in the next event loop iteration.
		3666
		3667	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3668
		3669	While the overhead of a callback that e.g. schedules a thread is small, it
		3670	is still an overhead. If you embed libev, and your main usage is with some
		3671	kind of threads or coroutines, you might want to customise libev so that
		3672	doesn't need callbacks anymore.
		3673
		3674	Imagine you have coroutines that you can switch to using a function
		3675	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3676	and that due to some magic, the currently active coroutine is stored in a
		3677	global called C<current_coro>. Then you can build your own "wait for libev
		3678	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3679	the differing C<;> conventions):
		3680
		3681	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3682	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3683
		3684	That means instead of having a C callback function, you store the
		3685	coroutine to switch to in each watcher, and instead of having libev call
		3686	your callback, you instead have it switch to that coroutine.
		3687
		3688	A coroutine might now wait for an event with a function called
		3689	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3690	matter when, or whether the watcher is active or not when this function is
		3691	called):
		3692
		3693	void
		3694	wait_for_event (ev_watcher *w)
		3695	{
		3696	ev_cb_set (w) = current_coro;
		3697	switch_to (libev_coro);
		3698	}
		3699
		3700	That basically suspends the coroutine inside C<wait_for_event> and
		3701	continues the libev coroutine, which, when appropriate, switches back to
		3702	this or any other coroutine. I am sure if you sue this your own :)
		3703
		3704	You can do similar tricks if you have, say, threads with an event queue -
		3705	instead of storing a coroutine, you store the queue object and instead of
		3706	switching to a coroutine, you push the watcher onto the queue and notify
		3707	any waiters.
		3708
		3709	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3710	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3711
		3712	// my_ev.h
		3713	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3714	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3715	#include "../libev/ev.h"
		3716
		3717	// my_ev.c
		3718	#define EV_H "my_ev.h"
		3719	#include "../libev/ev.c"
		3720
		3721	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3722	F<my_ev.c> into your project. When properly specifying include paths, you
		3723	can even use F<ev.h> as header file name directly.
2396		3724
2397		3725
2398	=head1 LIBEVENT EMULATION	3726	=head1 LIBEVENT EMULATION
2399		3727
2400	Libev offers a compatibility emulation layer for libevent. It cannot	3728	Libev offers a compatibility emulation layer for libevent. It cannot
2401	emulate the internals of libevent, so here are some usage hints:	3729	emulate the internals of libevent, so here are some usage hints:
2402		3730
2403	=over 4	3731	=over 4
		3732
		3733	=item * Only the libevent-1.4.1-beta API is being emulated.
		3734
		3735	This was the newest libevent version available when libev was implemented,
		3736	and is still mostly unchanged in 2010.
2404		3737
2405	=item * Use it by including <event.h>, as usual.	3738	=item * Use it by including <event.h>, as usual.
2406		3739
2407	=item * The following members are fully supported: ev_base, ev_callback,	3740	=item * The following members are fully supported: ev_base, ev_callback,
2408	ev_arg, ev_fd, ev_res, ev_events.	3741	ev_arg, ev_fd, ev_res, ev_events.
…		…
2414	=item * Priorities are not currently supported. Initialising priorities	3747	=item * Priorities are not currently supported. Initialising priorities
2415	will fail and all watchers will have the same priority, even though there	3748	will fail and all watchers will have the same priority, even though there
2416	is an ev_pri field.	3749	is an ev_pri field.
2417		3750
2418	=item * In libevent, the last base created gets the signals, in libev, the	3751	=item * In libevent, the last base created gets the signals, in libev, the
2419	first base created (== the default loop) gets the signals.	3752	base that registered the signal gets the signals.
2420		3753
2421	=item * Other members are not supported.	3754	=item * Other members are not supported.
2422		3755
2423	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3756	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2424	to use the libev header file and library.	3757	to use the libev header file and library.
…		…
2426	=back	3759	=back
2427		3760
2428	=head1 C++ SUPPORT	3761	=head1 C++ SUPPORT
2429		3762
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3763	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2431	you to use some convinience methods to start/stop watchers and also change	3764	you to use some convenience methods to start/stop watchers and also change
2432	the callback model to a model using method callbacks on objects.	3765	the callback model to a model using method callbacks on objects.
2433		3766
2434	To use it,	3767	To use it,
2435		3768
2436	#include <ev++.h>	3769	#include <ev++.h>
2437		3770
2438	This automatically includes F<ev.h> and puts all of its definitions (many	3771	This automatically includes F<ev.h> and puts all of its definitions (many
2439	of them macros) into the global namespace. All C++ specific things are	3772	of them macros) into the global namespace. All C++ specific things are
2440	put into the C<ev> namespace. It should support all the same embedding	3773	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3774	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2443	Care has been taken to keep the overhead low. The only data member the C++	3776	Care has been taken to keep the overhead low. The only data member the C++
2444	classes add (compared to plain C-style watchers) is the event loop pointer	3777	classes add (compared to plain C-style watchers) is the event loop pointer
2445	that the watcher is associated with (or no additional members at all if	3778	that the watcher is associated with (or no additional members at all if
2446	you disable C<EV_MULTIPLICITY> when embedding libev).	3779	you disable C<EV_MULTIPLICITY> when embedding libev).
2447		3780
2448	Currently, functions, and static and non-static member functions can be	3781	Currently, functions, static and non-static member functions and classes
2449	used as callbacks. Other types should be easy to add as long as they only	3782	with C<operator ()> can be used as callbacks. Other types should be easy
2450	need one additional pointer for context. If you need support for other	3783	to add as long as they only need one additional pointer for context. If
2451	types of functors please contact the author (preferably after implementing	3784	you need support for other types of functors please contact the author
2452	it).	3785	(preferably after implementing it).
2453		3786
2454	Here is a list of things available in the C<ev> namespace:	3787	Here is a list of things available in the C<ev> namespace:
2455		3788
2456	=over 4	3789	=over 4
2457		3790
…		…
2475		3808
2476	=over 4	3809	=over 4
2477		3810
2478	=item ev::TYPE::TYPE ()	3811	=item ev::TYPE::TYPE ()
2479		3812
2480	=item ev::TYPE::TYPE (struct ev_loop *)	3813	=item ev::TYPE::TYPE (loop)
2481		3814
2482	=item ev::TYPE::~TYPE	3815	=item ev::TYPE::~TYPE
2483		3816
2484	The constructor (optionally) takes an event loop to associate the watcher	3817	The constructor (optionally) takes an event loop to associate the watcher
2485	with. If it is omitted, it will use C<EV_DEFAULT>.	3818	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2508	your compiler is good :), then the method will be fully inlined into the	3841	your compiler is good :), then the method will be fully inlined into the
2509	thunking function, making it as fast as a direct C callback.	3842	thunking function, making it as fast as a direct C callback.
2510		3843
2511	Example: simple class declaration and watcher initialisation	3844	Example: simple class declaration and watcher initialisation
2512		3845
2513	struct myclass	3846	struct myclass
2514	{	3847	{
2515	void io_cb (ev::io &w, int revents) { }	3848	void io_cb (ev::io &w, int revents) { }
2516	}	3849	}
2517		3850
2518	myclass obj;	3851	myclass obj;
2519	ev::io iow;	3852	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	3853	iow.set <myclass, &myclass::io_cb> (&obj);
		3854
		3855	=item w->set (object *)
		3856
		3857	This is a variation of a method callback - leaving out the method to call
		3858	will default the method to C<operator ()>, which makes it possible to use
		3859	functor objects without having to manually specify the C<operator ()> all
		3860	the time. Incidentally, you can then also leave out the template argument
		3861	list.
		3862
		3863	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3864	int revents)>.
		3865
		3866	See the method-C<set> above for more details.
		3867
		3868	Example: use a functor object as callback.
		3869
		3870	struct myfunctor
		3871	{
		3872	void operator() (ev::io &w, int revents)
		3873	{
		3874	...
		3875	}
		3876	}
		3877
		3878	myfunctor f;
		3879
		3880	ev::io w;
		3881	w.set (&f);
2521		3882
2522	=item w->set<function> (void *data = 0)	3883	=item w->set<function> (void *data = 0)
2523		3884
2524	Also sets a callback, but uses a static method or plain function as	3885	Also sets a callback, but uses a static method or plain function as
2525	callback. The optional C<data> argument will be stored in the watcher's	3886	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		3888
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3889	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		3890
2530	See the method-C<set> above for more details.	3891	See the method-C<set> above for more details.
2531		3892
2532	Example:	3893	Example: Use a plain function as callback.
2533		3894
2534	static void io_cb (ev::io &w, int revents) { }	3895	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	3896	iow.set <io_cb> ();
2536		3897
2537	=item w->set (struct ev_loop *)	3898	=item w->set (loop)
2538		3899
2539	Associates a different C<struct ev_loop> with this watcher. You can only	3900	Associates a different C<struct ev_loop> with this watcher. You can only
2540	do this when the watcher is inactive (and not pending either).	3901	do this when the watcher is inactive (and not pending either).
2541		3902
2542	=item w->set ([args])	3903	=item w->set ([arguments])
2543		3904
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3905	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2545	called at least once. Unlike the C counterpart, an active watcher gets	3906	method or a suitable start method must be called at least once. Unlike the
2546	automatically stopped and restarted when reconfiguring it with this	3907	C counterpart, an active watcher gets automatically stopped and restarted
2547	method.	3908	when reconfiguring it with this method.
2548		3909
2549	=item w->start ()	3910	=item w->start ()
2550		3911
2551	Starts the watcher. Note that there is no C<loop> argument, as the	3912	Starts the watcher. Note that there is no C<loop> argument, as the
2552	constructor already stores the event loop.	3913	constructor already stores the event loop.
2553		3914
		3915	=item w->start ([arguments])
		3916
		3917	Instead of calling C<set> and C<start> methods separately, it is often
		3918	convenient to wrap them in one call. Uses the same type of arguments as
		3919	the configure C<set> method of the watcher.
		3920
2554	=item w->stop ()	3921	=item w->stop ()
2555		3922
2556	Stops the watcher if it is active. Again, no C<loop> argument.	3923	Stops the watcher if it is active. Again, no C<loop> argument.
2557		3924
2558	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3925	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2570		3937
2571	=back	3938	=back
2572		3939
2573	=back	3940	=back
2574		3941
2575	Example: Define a class with an IO and idle watcher, start one of them in	3942	Example: Define a class with two I/O and idle watchers, start the I/O
2576	the constructor.	3943	watchers in the constructor.
2577		3944
2578	class myclass	3945	class myclass
2579	{	3946	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	3947	ev::io io ; void io_cb (ev::io &w, int revents);
		3948	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	3949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		3950
2583	myclass (int fd)	3951	myclass (int fd)
2584	{	3952	{
2585	io .set <myclass, &myclass::io_cb > (this);	3953	io .set <myclass, &myclass::io_cb > (this);
		3954	io2 .set <myclass, &myclass::io2_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	3955	idle.set <myclass, &myclass::idle_cb> (this);
2587		3956
2588	io.start (fd, ev::READ);	3957	io.set (fd, ev::WRITE); // configure the watcher
		3958	io.start (); // start it whenever convenient
		3959
		3960	io2.start (fd, ev::READ); // set + start in one call
2589	}	3961	}
2590	};	3962	};
2591		3963
2592		3964
2593	=head1 OTHER LANGUAGE BINDINGS	3965	=head1 OTHER LANGUAGE BINDINGS
2594		3966
2595	Libev does not offer other language bindings itself, but bindings for a	3967	Libev does not offer other language bindings itself, but bindings for a
2596	numbe rof languages exist in the form of third-party packages. If you know	3968	number of languages exist in the form of third-party packages. If you know
2597	any interesting language binding in addition to the ones listed here, drop	3969	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	3970	me a note.
2599		3971
2600	=over 4	3972	=over 4
2601		3973
2602	=item Perl	3974	=item Perl
2603		3975
2604	The EV module implements the full libev API and is actually used to test	3976	The EV module implements the full libev API and is actually used to test
2605	libev. EV is developed together with libev. Apart from the EV core module,	3977	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	3978	there are additional modules that implement libev-compatible interfaces
2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3979	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3980	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3981	and C<EV::Glib>).
2609		3982
2610	It can be found and installed via CPAN, its homepage is found at	3983	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	3984	L<http://software.schmorp.de/pkg/EV>.
2612		3985
		3986	=item Python
		3987
		3988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3989	seems to be quite complete and well-documented.
		3990
2613	=item Ruby	3991	=item Ruby
2614		3992
2615	Tony Arcieri has written a ruby extension that offers access to a subset	3993	Tony Arcieri has written a ruby extension that offers access to a subset
2616	of the libev API and adds filehandle abstractions, asynchronous DNS and	3994	of the libev API and adds file handle abstractions, asynchronous DNS and
2617	more on top of it. It can be found via gem servers. Its homepage is at	3995	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	3996	L<http://rev.rubyforge.org/>.
2619		3997
		3998	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3999	makes rev work even on mingw.
		4000
		4001	=item Haskell
		4002
		4003	A haskell binding to libev is available at
		4004	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4005
2620	=item D	4006	=item D
2621		4007
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4008	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	4009	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		4010
		4011	=item Ocaml
		4012
		4013	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4014	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4015
		4016	=item Lua
		4017
		4018	Brian Maher has written a partial interface to libev for lua (at the
		4019	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4020	L<http://github.com/brimworks/lua-ev>.
2624		4021
2625	=back	4022	=back
2626		4023
2627		4024
2628	=head1 MACRO MAGIC	4025	=head1 MACRO MAGIC
2629		4026
2630	Libev can be compiled with a variety of options, the most fundamantal	4027	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	4028	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	4029	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		4030
2634	To make it easier to write programs that cope with either variant, the	4031	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	4032	following macros are defined:
…		…
2640		4037
2641	This provides the loop I<argument> for functions, if one is required ("ev	4038	This provides the loop I<argument> for functions, if one is required ("ev
2642	loop argument"). The C<EV_A> form is used when this is the sole argument,	4039	loop argument"). The C<EV_A> form is used when this is the sole argument,
2643	C<EV_A_> is used when other arguments are following. Example:	4040	C<EV_A_> is used when other arguments are following. Example:
2644		4041
2645	ev_unref (EV_A);	4042	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	4043	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	4044	ev_run (EV_A_ 0);
2648		4045
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4046	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	4047	which is often provided by the following macro.
2651		4048
2652	=item C<EV_P>, C<EV_P_>	4049	=item C<EV_P>, C<EV_P_>
2653		4050
2654	This provides the loop I<parameter> for functions, if one is required ("ev	4051	This provides the loop I<parameter> for functions, if one is required ("ev
2655	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	4052	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2656	C<EV_P_> is used when other parameters are following. Example:	4053	C<EV_P_> is used when other parameters are following. Example:
2657		4054
2658	// this is how ev_unref is being declared	4055	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	4056	static void ev_unref (EV_P);
2660		4057
2661	// this is how you can declare your typical callback	4058	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	4059	static void cb (EV_P_ ev_timer *w, int revents)
2663		4060
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	4061	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	4062	suitable for use with C<EV_A>.
2666		4063
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4064	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		4080
2684	Example: Declare and initialise a check watcher, utilising the above	4081	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	4082	macros so it will work regardless of whether multiple loops are supported
2686	or not.	4083	or not.
2687		4084
2688	static void	4085	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	4086	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	4087	{
2691	ev_check_stop (EV_A_ w);	4088	ev_check_stop (EV_A_ w);
2692	}	4089	}
2693		4090
2694	ev_check check;	4091	ev_check check;
2695	ev_check_init (&check, check_cb);	4092	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	4093	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	4094	ev_run (EV_DEFAULT_ 0);
2698		4095
2699	=head1 EMBEDDING	4096	=head1 EMBEDDING
2700		4097
2701	Libev can (and often is) directly embedded into host	4098	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	4099	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	4106	libev somewhere in your source tree).
2710		4107
2711	=head2 FILESETS	4108	=head2 FILESETS
2712		4109
2713	Depending on what features you need you need to include one or more sets of files	4110	Depending on what features you need you need to include one or more sets of files
2714	in your app.	4111	in your application.
2715		4112
2716	=head3 CORE EVENT LOOP	4113	=head3 CORE EVENT LOOP
2717		4114
2718	To include only the libev core (all the C<ev_*> functions), with manual	4115	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	4116	configuration (no autoconf):
2720		4117
2721	#define EV_STANDALONE 1	4118	#define EV_STANDALONE 1
2722	#include "ev.c"	4119	#include "ev.c"
2723		4120
2724	This will automatically include F<ev.h>, too, and should be done in a	4121	This will automatically include F<ev.h>, too, and should be done in a
2725	single C source file only to provide the function implementations. To use	4122	single C source file only to provide the function implementations. To use
2726	it, do the same for F<ev.h> in all files wishing to use this API (best	4123	it, do the same for F<ev.h> in all files wishing to use this API (best
2727	done by writing a wrapper around F<ev.h> that you can include instead and	4124	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	4125	where you can put other configuration options):
2729		4126
2730	#define EV_STANDALONE 1	4127	#define EV_STANDALONE 1
2731	#include "ev.h"	4128	#include "ev.h"
2732		4129
2733	Both header files and implementation files can be compiled with a C++	4130	Both header files and implementation files can be compiled with a C++
2734	compiler (at least, thats a stated goal, and breakage will be treated	4131	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	4132	as a bug).
2736		4133
2737	You need the following files in your source tree, or in a directory	4134	You need the following files in your source tree, or in a directory
2738	in your include path (e.g. in libev/ when using -Ilibev):	4135	in your include path (e.g. in libev/ when using -Ilibev):
2739		4136
2740	ev.h	4137	ev.h
2741	ev.c	4138	ev.c
2742	ev_vars.h	4139	ev_vars.h
2743	ev_wrap.h	4140	ev_wrap.h
2744		4141
2745	ev_win32.c required on win32 platforms only	4142	ev_win32.c required on win32 platforms only
2746		4143
2747	ev_select.c only when select backend is enabled (which is enabled by default)	4144	ev_select.c only when select backend is enabled (which is enabled by default)
2748	ev_poll.c only when poll backend is enabled (disabled by default)	4145	ev_poll.c only when poll backend is enabled (disabled by default)
2749	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4146	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2750	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4147	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2751	ev_port.c only when the solaris port backend is enabled (disabled by default)	4148	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		4149
2753	F<ev.c> includes the backend files directly when enabled, so you only need	4150	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	4151	to compile this single file.
2755		4152
2756	=head3 LIBEVENT COMPATIBILITY API	4153	=head3 LIBEVENT COMPATIBILITY API
2757		4154
2758	To include the libevent compatibility API, also include:	4155	To include the libevent compatibility API, also include:
2759		4156
2760	#include "event.c"	4157	#include "event.c"
2761		4158
2762	in the file including F<ev.c>, and:	4159	in the file including F<ev.c>, and:
2763		4160
2764	#include "event.h"	4161	#include "event.h"
2765		4162
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	4163	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		4164
2768	You need the following additional files for this:	4165	You need the following additional files for this:
2769		4166
2770	event.h	4167	event.h
2771	event.c	4168	event.c
2772		4169
2773	=head3 AUTOCONF SUPPORT	4170	=head3 AUTOCONF SUPPORT
2774		4171
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	4172	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2776	whatever way you want, you can also C<m4_include([libev.m4])> in your	4173	whatever way you want, you can also C<m4_include([libev.m4])> in your
2777	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	4174	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	4175	include F<config.h> and configure itself accordingly.
2779		4176
2780	For this of course you need the m4 file:	4177	For this of course you need the m4 file:
2781		4178
2782	libev.m4	4179	libev.m4
2783		4180
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	4181	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		4182
2786	Libev can be configured via a variety of preprocessor symbols you have to	4183	Libev can be configured via a variety of preprocessor symbols you have to
2787	define before including any of its files. The default in the absense of	4184	define before including (or compiling) any of its files. The default in
2788	autoconf is noted for every option.	4185	the absence of autoconf is documented for every option.
		4186
		4187	Symbols marked with "(h)" do not change the ABI, and can have different
		4188	values when compiling libev vs. including F<ev.h>, so it is permissible
		4189	to redefine them before including F<ev.h> without breaking compatibility
		4190	to a compiled library. All other symbols change the ABI, which means all
		4191	users of libev and the libev code itself must be compiled with compatible
		4192	settings.
2789		4193
2790	=over 4	4194	=over 4
2791		4195
		4196	=item EV_COMPAT3 (h)
		4197
		4198	Backwards compatibility is a major concern for libev. This is why this
		4199	release of libev comes with wrappers for the functions and symbols that
		4200	have been renamed between libev version 3 and 4.
		4201
		4202	You can disable these wrappers (to test compatibility with future
		4203	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4204	sources. This has the additional advantage that you can drop the C<struct>
		4205	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4206	typedef in that case.
		4207
		4208	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4209	and in some even more future version the compatibility code will be
		4210	removed completely.
		4211
2792	=item EV_STANDALONE	4212	=item EV_STANDALONE (h)
2793		4213
2794	Must always be C<1> if you do not use autoconf configuration, which	4214	Must always be C<1> if you do not use autoconf configuration, which
2795	keeps libev from including F<config.h>, and it also defines dummy	4215	keeps libev from including F<config.h>, and it also defines dummy
2796	implementations for some libevent functions (such as logging, which is not	4216	implementations for some libevent functions (such as logging, which is not
2797	supported). It will also not define any of the structs usually found in	4217	supported). It will also not define any of the structs usually found in
2798	F<event.h> that are not directly supported by the libev core alone.	4218	F<event.h> that are not directly supported by the libev core alone.
2799		4219
		4220	In standalone mode, libev will still try to automatically deduce the
		4221	configuration, but has to be more conservative.
		4222
		4223	=item EV_USE_FLOOR
		4224
		4225	If defined to be C<1>, libev will use the C<floor ()> function for its
		4226	periodic reschedule calculations, otherwise libev will fall back on a
		4227	portable (slower) implementation. If you enable this, you usually have to
		4228	link against libm or something equivalent. Enabling this when the C<floor>
		4229	function is not available will fail, so the safe default is to not enable
		4230	this.
		4231
2800	=item EV_USE_MONOTONIC	4232	=item EV_USE_MONOTONIC
2801		4233
2802	If defined to be C<1>, libev will try to detect the availability of the	4234	If defined to be C<1>, libev will try to detect the availability of the
2803	monotonic clock option at both compiletime and runtime. Otherwise no use	4235	monotonic clock option at both compile time and runtime. Otherwise no
2804	of the monotonic clock option will be attempted. If you enable this, you	4236	use of the monotonic clock option will be attempted. If you enable this,
2805	usually have to link against librt or something similar. Enabling it when	4237	you usually have to link against librt or something similar. Enabling it
2806	the functionality isn't available is safe, though, although you have	4238	when the functionality isn't available is safe, though, although you have
2807	to make sure you link against any libraries where the C<clock_gettime>	4239	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	4240	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2809		4241
2810	=item EV_USE_REALTIME	4242	=item EV_USE_REALTIME
2811		4243
2812	If defined to be C<1>, libev will try to detect the availability of the	4244	If defined to be C<1>, libev will try to detect the availability of the
2813	realtime clock option at compiletime (and assume its availability at	4245	real-time clock option at compile time (and assume its availability
2814	runtime if successful). Otherwise no use of the realtime clock option will	4246	at runtime if successful). Otherwise no use of the real-time clock
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4247	option will be attempted. This effectively replaces C<gettimeofday>
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4248	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4249	correctness. See the note about libraries in the description of
		4250	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4251	C<EV_USE_CLOCK_SYSCALL>.
		4252
		4253	=item EV_USE_CLOCK_SYSCALL
		4254
		4255	If defined to be C<1>, libev will try to use a direct syscall instead
		4256	of calling the system-provided C<clock_gettime> function. This option
		4257	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4258	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4259	programs needlessly. Using a direct syscall is slightly slower (in
		4260	theory), because no optimised vdso implementation can be used, but avoids
		4261	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4262	higher, as it simplifies linking (no need for C<-lrt>).
2818		4263
2819	=item EV_USE_NANOSLEEP	4264	=item EV_USE_NANOSLEEP
2820		4265
2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4266	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2822	and will use it for delays. Otherwise it will use C<select ()>.	4267	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2830	2.7 or newer, otherwise disabled.	4275	2.7 or newer, otherwise disabled.
2831		4276
2832	=item EV_USE_SELECT	4277	=item EV_USE_SELECT
2833		4278
2834	If undefined or defined to be C<1>, libev will compile in support for the	4279	If undefined or defined to be C<1>, libev will compile in support for the
2835	C<select>(2) backend. No attempt at autodetection will be done: if no	4280	C<select>(2) backend. No attempt at auto-detection will be done: if no
2836	other method takes over, select will be it. Otherwise the select backend	4281	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	4282	will not be compiled in.
2838		4283
2839	=item EV_SELECT_USE_FD_SET	4284	=item EV_SELECT_USE_FD_SET
2840		4285
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	4286	If defined to C<1>, then the select backend will use the system C<fd_set>
2842	structure. This is useful if libev doesn't compile due to a missing	4287	structure. This is useful if libev doesn't compile due to a missing
2843	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	4288	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2844	exotic systems. This usually limits the range of file descriptors to some	4289	on exotic systems. This usually limits the range of file descriptors to
2845	low limit such as 1024 or might have other limitations (winsocket only	4290	some low limit such as 1024 or might have other limitations (winsocket
2846	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4291	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2847	influence the size of the C<fd_set> used.	4292	configures the maximum size of the C<fd_set>.
2848		4293
2849	=item EV_SELECT_IS_WINSOCKET	4294	=item EV_SELECT_IS_WINSOCKET
2850		4295
2851	When defined to C<1>, the select backend will assume that	4296	When defined to C<1>, the select backend will assume that
2852	select/socket/connect etc. don't understand file descriptors but	4297	select/socket/connect etc. don't understand file descriptors but
…		…
2854	be used is the winsock select). This means that it will call	4299	be used is the winsock select). This means that it will call
2855	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4300	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2856	it is assumed that all these functions actually work on fds, even	4301	it is assumed that all these functions actually work on fds, even
2857	on win32. Should not be defined on non-win32 platforms.	4302	on win32. Should not be defined on non-win32 platforms.
2858		4303
2859	=item EV_FD_TO_WIN32_HANDLE	4304	=item EV_FD_TO_WIN32_HANDLE(fd)
2860		4305
2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4306	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2862	file descriptors to socket handles. When not defining this symbol (the	4307	file descriptors to socket handles. When not defining this symbol (the
2863	default), then libev will call C<_get_osfhandle>, which is usually	4308	default), then libev will call C<_get_osfhandle>, which is usually
2864	correct. In some cases, programs use their own file descriptor management,	4309	correct. In some cases, programs use their own file descriptor management,
2865	in which case they can provide this function to map fds to socket handles.	4310	in which case they can provide this function to map fds to socket handles.
		4311
		4312	=item EV_WIN32_HANDLE_TO_FD(handle)
		4313
		4314	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4315	using the standard C<_open_osfhandle> function. For programs implementing
		4316	their own fd to handle mapping, overwriting this function makes it easier
		4317	to do so. This can be done by defining this macro to an appropriate value.
		4318
		4319	=item EV_WIN32_CLOSE_FD(fd)
		4320
		4321	If programs implement their own fd to handle mapping on win32, then this
		4322	macro can be used to override the C<close> function, useful to unregister
		4323	file descriptors again. Note that the replacement function has to close
		4324	the underlying OS handle.
2866		4325
2867	=item EV_USE_POLL	4326	=item EV_USE_POLL
2868		4327
2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4328	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2870	backend. Otherwise it will be enabled on non-win32 platforms. It	4329	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2897	otherwise another method will be used as fallback. This is the preferred	4356	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	4357	backend for Solaris 10 systems.
2899		4358
2900	=item EV_USE_DEVPOLL	4359	=item EV_USE_DEVPOLL
2901		4360
2902	reserved for future expansion, works like the USE symbols above.	4361	Reserved for future expansion, works like the USE symbols above.
2903		4362
2904	=item EV_USE_INOTIFY	4363	=item EV_USE_INOTIFY
2905		4364
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	4365	If defined to be C<1>, libev will compile in support for the Linux inotify
2907	interface to speed up C<ev_stat> watchers. Its actual availability will	4366	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2914	access is atomic with respect to other threads or signal contexts. No such	4373	access is atomic with respect to other threads or signal contexts. No such
2915	type is easily found in the C language, so you can provide your own type	4374	type is easily found in the C language, so you can provide your own type
2916	that you know is safe for your purposes. It is used both for signal handler "locking"	4375	that you know is safe for your purposes. It is used both for signal handler "locking"
2917	as well as for signal and thread safety in C<ev_async> watchers.	4376	as well as for signal and thread safety in C<ev_async> watchers.
2918		4377
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	4378	In the absence of this define, libev will use C<sig_atomic_t volatile>
2920	(from F<signal.h>), which is usually good enough on most platforms.	4379	(from F<signal.h>), which is usually good enough on most platforms.
2921		4380
2922	=item EV_H	4381	=item EV_H (h)
2923		4382
2924	The name of the F<ev.h> header file used to include it. The default if	4383	The name of the F<ev.h> header file used to include it. The default if
2925	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4384	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2926	used to virtually rename the F<ev.h> header file in case of conflicts.	4385	used to virtually rename the F<ev.h> header file in case of conflicts.
2927		4386
2928	=item EV_CONFIG_H	4387	=item EV_CONFIG_H (h)
2929		4388
2930	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4389	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2931	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4390	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2932	C<EV_H>, above.	4391	C<EV_H>, above.
2933		4392
2934	=item EV_EVENT_H	4393	=item EV_EVENT_H (h)
2935		4394
2936	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4395	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2937	of how the F<event.h> header can be found, the default is C<"event.h">.	4396	of how the F<event.h> header can be found, the default is C<"event.h">.
2938		4397
2939	=item EV_PROTOTYPES	4398	=item EV_PROTOTYPES (h)
2940		4399
2941	If defined to be C<0>, then F<ev.h> will not define any function	4400	If defined to be C<0>, then F<ev.h> will not define any function
2942	prototypes, but still define all the structs and other symbols. This is	4401	prototypes, but still define all the structs and other symbols. This is
2943	occasionally useful if you want to provide your own wrapper functions	4402	occasionally useful if you want to provide your own wrapper functions
2944	around libev functions.	4403	around libev functions.
…		…
2963	When doing priority-based operations, libev usually has to linearly search	4422	When doing priority-based operations, libev usually has to linearly search
2964	all the priorities, so having many of them (hundreds) uses a lot of space	4423	all the priorities, so having many of them (hundreds) uses a lot of space
2965	and time, so using the defaults of five priorities (-2 .. +2) is usually	4424	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	4425	fine.
2967		4426
2968	If your embedding app does not need any priorities, defining these both to	4427	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	4428	both to C<0> will save some memory and CPU.
2970		4429
2971	=item EV_PERIODIC_ENABLE	4430	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4431	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4432	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2972		4433
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	4434	If undefined or defined to be C<1> (and the platform supports it), then
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	4435	the respective watcher type is supported. If defined to be C<0>, then it
2975	code.	4436	is not. Disabling watcher types mainly saves code size.
2976		4437
2977	=item EV_IDLE_ENABLE	4438	=item EV_FEATURES
2978
2979	If undefined or defined to be C<1>, then idle watchers are supported. If
2980	defined to be C<0>, then they are not. Disabling them saves a few kB of
2981	code.
2982
2983	=item EV_EMBED_ENABLE
2984
2985	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.
2987
2988	=item EV_STAT_ENABLE
2989
2990	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.
2992
2993	=item EV_FORK_ENABLE
2994
2995	If undefined or defined to be C<1>, then fork watchers are supported. If
2996	defined to be C<0>, then they are not.
2997
2998	=item EV_ASYNC_ENABLE
2999
3000	If undefined or defined to be C<1>, then async watchers are supported. If
3001	defined to be C<0>, then they are not.
3002
3003	=item EV_MINIMAL
3004		4439
3005	If you need to shave off some kilobytes of code at the expense of some	4440	If you need to shave off some kilobytes of code at the expense of some
3006	speed, define this symbol to C<1>. Currently this is used to override some	4441	speed (but with the full API), you can define this symbol to request
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	4442	certain subsets of functionality. The default is to enable all features
3008	much smaller 2-heap for timer management over the default 4-heap.	4443	that can be enabled on the platform.
		4444
		4445	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4446	with some broad features you want) and then selectively re-enable
		4447	additional parts you want, for example if you want everything minimal,
		4448	but multiple event loop support, async and child watchers and the poll
		4449	backend, use this:
		4450
		4451	#define EV_FEATURES 0
		4452	#define EV_MULTIPLICITY 1
		4453	#define EV_USE_POLL 1
		4454	#define EV_CHILD_ENABLE 1
		4455	#define EV_ASYNC_ENABLE 1
		4456
		4457	The actual value is a bitset, it can be a combination of the following
		4458	values:
		4459
		4460	=over 4
		4461
		4462	=item C<1> - faster/larger code
		4463
		4464	Use larger code to speed up some operations.
		4465
		4466	Currently this is used to override some inlining decisions (enlarging the
		4467	code size by roughly 30% on amd64).
		4468
		4469	When optimising for size, use of compiler flags such as C<-Os> with
		4470	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4471	assertions.
		4472
		4473	=item C<2> - faster/larger data structures
		4474
		4475	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4476	hash table sizes and so on. This will usually further increase code size
		4477	and can additionally have an effect on the size of data structures at
		4478	runtime.
		4479
		4480	=item C<4> - full API configuration
		4481
		4482	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4483	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4484
		4485	=item C<8> - full API
		4486
		4487	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4488	details on which parts of the API are still available without this
		4489	feature, and do not complain if this subset changes over time.
		4490
		4491	=item C<16> - enable all optional watcher types
		4492
		4493	Enables all optional watcher types. If you want to selectively enable
		4494	only some watcher types other than I/O and timers (e.g. prepare,
		4495	embed, async, child...) you can enable them manually by defining
		4496	C<EV_watchertype_ENABLE> to C<1> instead.
		4497
		4498	=item C<32> - enable all backends
		4499
		4500	This enables all backends - without this feature, you need to enable at
		4501	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4502
		4503	=item C<64> - enable OS-specific "helper" APIs
		4504
		4505	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4506	default.
		4507
		4508	=back
		4509
		4510	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4511	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4512	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4513	watchers, timers and monotonic clock support.
		4514
		4515	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4516	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4517	your program might be left out as well - a binary starting a timer and an
		4518	I/O watcher then might come out at only 5Kb.
		4519
		4520	=item EV_AVOID_STDIO
		4521
		4522	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4523	functions (printf, scanf, perror etc.). This will increase the code size
		4524	somewhat, but if your program doesn't otherwise depend on stdio and your
		4525	libc allows it, this avoids linking in the stdio library which is quite
		4526	big.
		4527
		4528	Note that error messages might become less precise when this option is
		4529	enabled.
		4530
		4531	=item EV_NSIG
		4532
		4533	The highest supported signal number, +1 (or, the number of
		4534	signals): Normally, libev tries to deduce the maximum number of signals
		4535	automatically, but sometimes this fails, in which case it can be
		4536	specified. Also, using a lower number than detected (C<32> should be
		4537	good for about any system in existence) can save some memory, as libev
		4538	statically allocates some 12-24 bytes per signal number.
3009		4539
3010	=item EV_PID_HASHSIZE	4540	=item EV_PID_HASHSIZE
3011		4541
3012	C<ev_child> watchers use a small hash table to distribute workload by	4542	C<ev_child> watchers use a small hash table to distribute workload by
3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4543	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3014	than enough. If you need to manage thousands of children you might want to	4544	usually more than enough. If you need to manage thousands of children you
3015	increase this value (I<must> be a power of two).	4545	might want to increase this value (I<must> be a power of two).
3016		4546
3017	=item EV_INOTIFY_HASHSIZE	4547	=item EV_INOTIFY_HASHSIZE
3018		4548
3019	C<ev_stat> watchers use a small hash table to distribute workload by	4549	C<ev_stat> watchers use a small hash table to distribute workload by
3020	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4550	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3021	usually more than enough. If you need to manage thousands of C<ev_stat>	4551	disabled), usually more than enough. If you need to manage thousands of
3022	watchers you might want to increase this value (I<must> be a power of	4552	C<ev_stat> watchers you might want to increase this value (I<must> be a
3023	two).	4553	power of two).
3024		4554
3025	=item EV_USE_4HEAP	4555	=item EV_USE_4HEAP
3026		4556
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4557	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4558	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3029	to C<1>. The 4-heap uses more complicated (longer) code but has	4559	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	4560	faster performance with many (thousands) of watchers.
3031		4561
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3033	(disabled).	4563	will be C<0>.
3034		4564
3035	=item EV_HEAP_CACHE_AT	4565	=item EV_HEAP_CACHE_AT
3036		4566
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4567	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3038	timer and periodics heap, libev can cache the timestamp (I<at>) within	4568	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4569	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4570	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3041	but avoids random read accesses on heap changes. This improves performance	4571	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	4572	noticeably with many (hundreds) of watchers.
3043		4573
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4574	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3045	(disabled).	4575	will be C<0>.
3046		4576
3047	=item EV_VERIFY	4577	=item EV_VERIFY
3048		4578
3049	Controls how much internal verification (see C<ev_loop_verify ()>) will	4579	Controls how much internal verification (see C<ev_verify ()>) will
3050	be done: If set to C<0>, no internal verification code will be compiled	4580	be done: If set to C<0>, no internal verification code will be compiled
3051	in. If set to C<1>, then verification code will be compiled in, but not	4581	in. If set to C<1>, then verification code will be compiled in, but not
3052	called. If set to C<2>, then the internal verification code will be	4582	called. If set to C<2>, then the internal verification code will be
3053	called once per loop, which can slow down libev. If set to C<3>, then the	4583	called once per loop, which can slow down libev. If set to C<3>, then the
3054	verification code will be called very frequently, which will slow down	4584	verification code will be called very frequently, which will slow down
3055	libev considerably.	4585	libev considerably.
3056		4586
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4587	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3058	C<0.>	4588	will be C<0>.
3059		4589
3060	=item EV_COMMON	4590	=item EV_COMMON
3061		4591
3062	By default, all watchers have a C<void *data> member. By redefining	4592	By default, all watchers have a C<void *data> member. By redefining
3063	this macro to a something else you can include more and other types of	4593	this macro to something else you can include more and other types of
3064	members. You have to define it each time you include one of the files,	4594	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	4595	though, and it must be identical each time.
3066		4596
3067	For example, the perl EV module uses something like this:	4597	For example, the perl EV module uses something like this:
3068		4598
3069	#define EV_COMMON \	4599	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	4600	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	4601	SV *cb_sv, *fh /* note no trailing ";" */
3072		4602
3073	=item EV_CB_DECLARE (type)	4603	=item EV_CB_DECLARE (type)
3074		4604
3075	=item EV_CB_INVOKE (watcher, revents)	4605	=item EV_CB_INVOKE (watcher, revents)
3076		4606
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	4611	definition and a statement, respectively. See the F<ev.h> header file for
3082	their default definitions. One possible use for overriding these is to	4612	their default definitions. One possible use for overriding these is to
3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4613	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3084	method calls instead of plain function calls in C++.	4614	method calls instead of plain function calls in C++.
3085		4615
		4616	=back
		4617
3086	=head2 EXPORTED API SYMBOLS	4618	=head2 EXPORTED API SYMBOLS
3087		4619
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	4620	If you need to re-export the API (e.g. via a DLL) and you need a list of
3089	exported symbols, you can use the provided F<Symbol.*> files which list	4621	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	4622	all public symbols, one per line:
3091		4623
3092	Symbols.ev for libev proper	4624	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	4625	Symbols.event for the libevent emulation
3094		4626
3095	This can also be used to rename all public symbols to avoid clashes with	4627	This can also be used to rename all public symbols to avoid clashes with
3096	multiple versions of libev linked together (which is obviously bad in	4628	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	4629	itself, but sometimes it is inconvenient to avoid this).
3098		4630
3099	A sed command like this will create wrapper C<#define>'s that you need to	4631	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	4632	include before including F<ev.h>:
3101		4633
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4634	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	4651	file.
3120		4652
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4653	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3122	that everybody includes and which overrides some configure choices:	4654	that everybody includes and which overrides some configure choices:
3123		4655
3124	#define EV_MINIMAL 1	4656	#define EV_FEATURES 8
3125	#define EV_USE_POLL 0	4657	#define EV_USE_SELECT 1
3126	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	4658	#define EV_PREPARE_ENABLE 1
		4659	#define EV_IDLE_ENABLE 1
3128	#define EV_STAT_ENABLE 0	4660	#define EV_SIGNAL_ENABLE 1
3129	#define EV_FORK_ENABLE 0	4661	#define EV_CHILD_ENABLE 1
		4662	#define EV_USE_STDEXCEPT 0
3130	#define EV_CONFIG_H <config.h>	4663	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0
3133		4664
3134	#include "ev++.h"	4665	#include "ev++.h"
3135		4666
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4667	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		4668
3138	#include "ev_cpp.h"	4669	#include "ev_cpp.h"
3139	#include "ev.c"	4670	#include "ev.c"
3140		4671
		4672	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3141		4673
3142	=head1 THREADS AND COROUTINES	4674	=head2 THREADS AND COROUTINES
3143		4675
3144	=head2 THREADS	4676	=head3 THREADS
3145		4677
3146	Libev itself is completely threadsafe, but it uses no locking. This	4678	All libev functions are reentrant and thread-safe unless explicitly
		4679	documented otherwise, but libev implements no locking itself. This means
3147	means that you can use as many loops as you want in parallel, as long as	4680	that you can use as many loops as you want in parallel, as long as there
3148	only one thread ever calls into one libev function with the same loop	4681	are no concurrent calls into any libev function with the same loop
3149	parameter.	4682	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4683	of course): libev guarantees that different event loops share no data
		4684	structures that need any locking.
3150		4685
3151	Or put differently: calls with different loop parameters can be done in	4686	Or to put it differently: calls with different loop parameters can be done
3152	parallel from multiple threads, calls with the same loop parameter must be	4687	concurrently from multiple threads, calls with the same loop parameter
3153	done serially (but can be done from different threads, as long as only one	4688	must be done serially (but can be done from different threads, as long as
3154	thread ever is inside a call at any point in time, e.g. by using a mutex	4689	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	4690	a mutex per loop).
3156		4691
3157	If you want to know which design is best for your problem, then I cannot	4692	Specifically to support threads (and signal handlers), libev implements
		4693	so-called C<ev_async> watchers, which allow some limited form of
		4694	concurrency on the same event loop, namely waking it up "from the
		4695	outside".
		4696
		4697	If you want to know which design (one loop, locking, or multiple loops
		4698	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	4699	help you, but here is some generic advice:
3159		4700
3160	=over 4	4701	=over 4
3161		4702
3162	=item * most applications have a main thread: use the default libev loop	4703	=item * most applications have a main thread: use the default libev loop
3163	in that thread, or create a seperate thread running only the default loop.	4704	in that thread, or create a separate thread running only the default loop.
3164		4705
3165	This helps integrating other libraries or software modules that use libev	4706	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	4707	themselves and don't care/know about threading.
3167		4708
3168	=item * one loop per thread is usually a good model.	4709	=item * one loop per thread is usually a good model.
3169		4710
3170	Doing this is almost never wrong, sometimes a better-performance model	4711	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	4712	exists, but it is always a good start.
3172		4713
3173	=item * other models exist, such as the leader/follower pattern, where one	4714	=item * other models exist, such as the leader/follower pattern, where one
3174	loop is handed through multiple threads in a kind of round-robbin fashion.	4715	loop is handed through multiple threads in a kind of round-robin fashion.
3175		4716
3176	Chosing a model is hard - look around, learn, know that usually you cna do	4717	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	4718	better than you currently do :-)
3178		4719
3179	=item * often you need to talk to some other thread which blocks in the	4720	=item * often you need to talk to some other thread which blocks in the
		4721	event loop.
		4722
3180	event loop - C<ev_async> watchers can be used to wake them up from other	4723	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	4724	(or from signal contexts...).
		4725
		4726	An example use would be to communicate signals or other events that only
		4727	work in the default loop by registering the signal watcher with the
		4728	default loop and triggering an C<ev_async> watcher from the default loop
		4729	watcher callback into the event loop interested in the signal.
3182		4730
3183	=back	4731	=back
3184		4732
		4733	See also L<THREAD LOCKING EXAMPLE>.
		4734
3185	=head2 COROUTINES	4735	=head3 COROUTINES
3186		4736
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	4737	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	4738	libev fully supports nesting calls to its functions from different
3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4739	coroutines (e.g. you can call C<ev_run> on the same loop from two
3190	different coroutines and switch freely between both coroutines running the	4740	different coroutines, and switch freely between both coroutines running
3191	loop, as long as you don't confuse yourself). The only exception is that	4741	the loop, as long as you don't confuse yourself). The only exception is
3192	you must not do this from C<ev_periodic> reschedule callbacks.	4742	that you must not do this from C<ev_periodic> reschedule callbacks.
3193		4743
3194	Care has been invested into making sure that libev does not keep local	4744	Care has been taken to ensure that libev does not keep local state inside
3195	state inside C<ev_loop>, and other calls do not usually allow coroutine	4745	C<ev_run>, and other calls do not usually allow for coroutine switches as
3196	switches.	4746	they do not call any callbacks.
3197		4747
		4748	=head2 COMPILER WARNINGS
3198		4749
3199	=head1 COMPLEXITIES	4750	Depending on your compiler and compiler settings, you might get no or a
		4751	lot of warnings when compiling libev code. Some people are apparently
		4752	scared by this.
3200		4753
3201	In this section the complexities of (many of) the algorithms used inside	4754	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	4755	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	4756	warning options. "Warn-free" code therefore cannot be a goal except when
		4757	targeting a specific compiler and compiler-version.
3204		4758
3205	All of the following are about amortised time: If an array needs to be	4759	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	4760	workarounds, or other changes to the code that make it less clear and less
3207	happens asymptotically never with higher number of elements, so O(1) might	4761	maintainable.
3208	mean it might do a lengthy realloc operation in rare cases, but on average
3209	it is much faster and asymptotically approaches constant time.
3210		4762
3211	=over 4	4763	And of course, some compiler warnings are just plain stupid, or simply
		4764	wrong (because they don't actually warn about the condition their message
		4765	seems to warn about). For example, certain older gcc versions had some
		4766	warnings that resulted in an extreme number of false positives. These have
		4767	been fixed, but some people still insist on making code warn-free with
		4768	such buggy versions.
3212		4769
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4770	While libev is written to generate as few warnings as possible,
		4771	"warn-free" code is not a goal, and it is recommended not to build libev
		4772	with any compiler warnings enabled unless you are prepared to cope with
		4773	them (e.g. by ignoring them). Remember that warnings are just that:
		4774	warnings, not errors, or proof of bugs.
3214		4775
3215	This means that, when you have a watcher that triggers in one hour and
3216	there are 100 watchers that would trigger before that then inserting will
3217	have to skip roughly seven (C<ld 100>) of these watchers.
3218		4776
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4777	=head2 VALGRIND
3220		4778
3221	That means that changing a timer costs less than removing/adding them	4779	Valgrind has a special section here because it is a popular tool that is
3222	as only the relative motion in the event queue has to be paid for.	4780	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		4781
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4782	If you think you found a bug (memory leak, uninitialised data access etc.)
		4783	in libev, then check twice: If valgrind reports something like:
3225		4784
3226	These just add the watcher into an array or at the head of a list.	4785	==2274== definitely lost: 0 bytes in 0 blocks.
		4786	==2274== possibly lost: 0 bytes in 0 blocks.
		4787	==2274== still reachable: 256 bytes in 1 blocks.
3227		4788
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4789	Then there is no memory leak, just as memory accounted to global variables
		4790	is not a memleak - the memory is still being referenced, and didn't leak.
3229		4791
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4792	Similarly, under some circumstances, valgrind might report kernel bugs
		4793	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4794	although an acceptable workaround has been found here), or it might be
		4795	confused.
3231		4796
3232	These watchers are stored in lists then need to be walked to find the	4797	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3233	correct watcher to remove. The lists are usually short (you don't usually	4798	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		4799
3236	=item Finding the next timer in each loop iteration: O(1)	4800	If you are unsure about something, feel free to contact the mailing list
		4801	with the full valgrind report and an explanation on why you think this
		4802	is a bug in libev (best check the archives, too :). However, don't be
		4803	annoyed when you get a brisk "this is no bug" answer and take the chance
		4804	of learning how to interpret valgrind properly.
3237		4805
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	4806	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	4807	I suggest using suppression lists.
3240		4808
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		4809
3243	A change means an I/O watcher gets started or stopped, which requires	4810	=head1 PORTABILITY NOTES
3244	libev to recalculate its status (and possibly tell the kernel, depending
3245	on backend and wether C<ev_io_set> was used).
3246		4811
3247	=item Activating one watcher (putting it into the pending state): O(1)	4812	=head2 GNU/LINUX 32 BIT LIMITATIONS
3248		4813
3249	=item Priority handling: O(number_of_priorities)	4814	GNU/Linux is the only common platform that supports 64 bit file/large file
		4815	interfaces but I<disables> them by default.
3250		4816
3251	Priorities are implemented by allocating some space for each	4817	That means that libev compiled in the default environment doesn't support
3252	priority. When doing priority-based operations, libev usually has to	4818	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3253	linearly search all the priorities, but starting/stopping and activating
3254	watchers becomes O(1) w.r.t. priority handling.
3255		4819
3256	=item Sending an ev_async: O(1)	4820	Unfortunately, many programs try to work around this GNU/Linux issue
		4821	by enabling the large file API, which makes them incompatible with the
		4822	standard libev compiled for their system.
3257		4823
3258	=item Processing ev_async_send: O(number_of_async_watchers)	4824	Likewise, libev cannot enable the large file API itself as this would
		4825	suddenly make it incompatible to the default compile time environment,
		4826	i.e. all programs not using special compile switches.
3259		4827
3260	=item Processing signals: O(max_signal_number)	4828	=head2 OS/X AND DARWIN BUGS
3261		4829
3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4830	The whole thing is a bug if you ask me - basically any system interface
3263	calls in the current loop iteration. Checking for async and signal events	4831	you touch is broken, whether it is locales, poll, kqueue or even the
3264	involves iterating over all running async watchers or all signal numbers.	4832	OpenGL drivers.
3265		4833
3266	=back	4834	=head3 C<kqueue> is buggy
3267		4835
		4836	The kqueue syscall is broken in all known versions - most versions support
		4837	only sockets, many support pipes.
3268		4838
3269	=head1 Win32 platform limitations and workarounds	4839	Libev tries to work around this by not using C<kqueue> by default on this
		4840	rotten platform, but of course you can still ask for it when creating a
		4841	loop - embedding a socket-only kqueue loop into a select-based one is
		4842	probably going to work well.
		4843
		4844	=head3 C<poll> is buggy
		4845
		4846	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4847	implementation by something calling C<kqueue> internally around the 10.5.6
		4848	release, so now C<kqueue> I<and> C<poll> are broken.
		4849
		4850	Libev tries to work around this by not using C<poll> by default on
		4851	this rotten platform, but of course you can still ask for it when creating
		4852	a loop.
		4853
		4854	=head3 C<select> is buggy
		4855
		4856	All that's left is C<select>, and of course Apple found a way to fuck this
		4857	one up as well: On OS/X, C<select> actively limits the number of file
		4858	descriptors you can pass in to 1024 - your program suddenly crashes when
		4859	you use more.
		4860
		4861	There is an undocumented "workaround" for this - defining
		4862	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4863	work on OS/X.
		4864
		4865	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4866
		4867	=head3 C<errno> reentrancy
		4868
		4869	The default compile environment on Solaris is unfortunately so
		4870	thread-unsafe that you can't even use components/libraries compiled
		4871	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4872	defined by default. A valid, if stupid, implementation choice.
		4873
		4874	If you want to use libev in threaded environments you have to make sure
		4875	it's compiled with C<_REENTRANT> defined.
		4876
		4877	=head3 Event port backend
		4878
		4879	The scalable event interface for Solaris is called "event
		4880	ports". Unfortunately, this mechanism is very buggy in all major
		4881	releases. If you run into high CPU usage, your program freezes or you get
		4882	a large number of spurious wakeups, make sure you have all the relevant
		4883	and latest kernel patches applied. No, I don't know which ones, but there
		4884	are multiple ones to apply, and afterwards, event ports actually work
		4885	great.
		4886
		4887	If you can't get it to work, you can try running the program by setting
		4888	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4889	C<select> backends.
		4890
		4891	=head2 AIX POLL BUG
		4892
		4893	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4894	this by trying to avoid the poll backend altogether (i.e. it's not even
		4895	compiled in), which normally isn't a big problem as C<select> works fine
		4896	with large bitsets on AIX, and AIX is dead anyway.
		4897
		4898	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4899
		4900	=head3 General issues
3270		4901
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4902	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3272	requires, and its I/O model is fundamentally incompatible with the POSIX	4903	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	4904	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4905	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3275	descriptors. This only applies when using Win32 natively, not when using	4906	descriptors. This only applies when using Win32 natively, not when using
3276	e.g. cygwin.	4907	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4908	as every compielr comes with a slightly differently broken/incompatible
		4909	environment.
3277		4910
3278	Lifting these limitations would basically require the full	4911	Lifting these limitations would basically require the full
3279	re-implementation of the I/O system. If you are into these kinds of	4912	re-implementation of the I/O system. If you are into this kind of thing,
3280	things, then note that glib does exactly that for you in a very portable	4913	then note that glib does exactly that for you in a very portable way (note
3281	way (note also that glib is the slowest event library known to man).	4914	also that glib is the slowest event library known to man).
3282		4915
3283	There is no supported compilation method available on windows except	4916	There is no supported compilation method available on windows except
3284	embedding it into other applications.	4917	embedding it into other applications.
		4918
		4919	Sensible signal handling is officially unsupported by Microsoft - libev
		4920	tries its best, but under most conditions, signals will simply not work.
		4921
		4922	Not a libev limitation but worth mentioning: windows apparently doesn't
		4923	accept large writes: instead of resulting in a partial write, windows will
		4924	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4925	so make sure you only write small amounts into your sockets (less than a
		4926	megabyte seems safe, but this apparently depends on the amount of memory
		4927	available).
3285		4928
3286	Due to the many, low, and arbitrary limits on the win32 platform and	4929	Due to the many, low, and arbitrary limits on the win32 platform and
3287	the abysmal performance of winsockets, using a large number of sockets	4930	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	4931	is not recommended (and not reasonable). If your program needs to use
3289	more than a hundred or so sockets, then likely it needs to use a totally	4932	more than a hundred or so sockets, then likely it needs to use a totally
3290	different implementation for windows, as libev offers the POSIX readiness	4933	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	4934	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	4935	(due to Microsoft monopoly games).
3293		4936
3294	=over 4	4937	A typical way to use libev under windows is to embed it (see the embedding
		4938	section for details) and use the following F<evwrap.h> header file instead
		4939	of F<ev.h>:
3295		4940
		4941	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4942	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4943
		4944	#include "ev.h"
		4945
		4946	And compile the following F<evwrap.c> file into your project (make sure
		4947	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4948
		4949	#include "evwrap.h"
		4950	#include "ev.c"
		4951
3296	=item The winsocket select function	4952	=head3 The winsocket C<select> function
3297		4953
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	4954	The winsocket C<select> function doesn't follow POSIX in that it
3299	socket I<handles> and not socket I<file descriptors>. This makes select	4955	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	4956	also extremely buggy). This makes select very inefficient, and also
3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4957	requires a mapping from file descriptors to socket handles (the Microsoft
3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4958	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	4959	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4960	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		4961
3305	The configuration for a "naked" win32 using the microsoft runtime	4962	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	4963	libraries and raw winsocket select is:
3307		4964
3308	#define EV_USE_SELECT 1	4965	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4966	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		4967
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	4968	Note that winsockets handling of fd sets is O(n), so you can easily get a
3312	complexity in the O(n²) range when using win32.	4969	complexity in the O(n²) range when using win32.
3313		4970
3314	=item Limited number of file descriptors	4971	=head3 Limited number of file descriptors
3315		4972
3316	Windows has numerous arbitrary (and low) limits on things.	4973	Windows has numerous arbitrary (and low) limits on things.
3317		4974
3318	Early versions of winsocket's select only supported waiting for a maximum	4975	Early versions of winsocket's select only supported waiting for a maximum
3319	of C<64> handles (probably owning to the fact that all windows kernels	4976	of C<64> handles (probably owning to the fact that all windows kernels
3320	can only wait for C<64> things at the same time internally; microsoft	4977	can only wait for C<64> things at the same time internally; Microsoft
3321	recommends spawning a chain of threads and wait for 63 handles and the	4978	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	4979	previous thread in each. Sounds great!).
3323		4980
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4981	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3325	to some high number (e.g. C<2048>) before compiling the winsocket select	4982	to some high number (e.g. C<2048>) before compiling the winsocket select
3326	call (which might be in libev or elsewhere, for example, perl does its own	4983	call (which might be in libev or elsewhere, for example, perl and many
3327	select emulation on windows).	4984	other interpreters do their own select emulation on windows).
3328		4985
3329	Another limit is the number of file descriptors in the microsoft runtime	4986	Another limit is the number of file descriptors in the Microsoft runtime
3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4987	libraries, which by default is C<64> (there must be a hidden I<64>
3331	or something like this inside microsoft). You can increase this by calling	4988	fetish or something like this inside Microsoft). You can increase this
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4989	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3333	arbitrary limit), but is broken in many versions of the microsoft runtime	4990	(another arbitrary limit), but is broken in many versions of the Microsoft
3334	libraries.
3335
3336	This might get you to about C<512> or C<2048> sockets (depending on	4991	runtime libraries. This might get you to about C<512> or C<2048> sockets
3337	windows version and/or the phase of the moon). To get more, you need to	4992	(depending on windows version and/or the phase of the moon). To get more,
3338	wrap all I/O functions and provide your own fd management, but the cost of	4993	you need to wrap all I/O functions and provide your own fd management, but
3339	calling select (O(n²)) will likely make this unworkable.	4994	the cost of calling select (O(n²)) will likely make this unworkable.
3340		4995
3341	=back
3342
3343
3344	=head1 PORTABILITY REQUIREMENTS	4996	=head2 PORTABILITY REQUIREMENTS
3345		4997
3346	In addition to a working ISO-C implementation, libev relies on a few	4998	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	4999	backend-specific APIs, libev relies on a few additional extensions:
3348		5000
3349	=over 4	5001	=over 4
3350		5002
		5003	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		5004	calling conventions regardless of C<ev_watcher_type *>.
		5005
		5006	Libev assumes not only that all watcher pointers have the same internal
		5007	structure (guaranteed by POSIX but not by ISO C for example), but it also
		5008	assumes that the same (machine) code can be used to call any watcher
		5009	callback: The watcher callbacks have different type signatures, but libev
		5010	calls them using an C<ev_watcher *> internally.
		5011
		5012	=item pointer accesses must be thread-atomic
		5013
		5014	Accessing a pointer value must be atomic, it must both be readable and
		5015	writable in one piece - this is the case on all current architectures.
		5016
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	5017	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		5018
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	5019	The type C<sig_atomic_t volatile> (or whatever is defined as
3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	5020	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3355	threads. This is not part of the specification for C<sig_atomic_t>, but is	5021	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	5022	believed to be sufficiently portable.
3357		5023
3358	=item C<sigprocmask> must work in a threaded environment	5024	=item C<sigprocmask> must work in a threaded environment
3359		5025
…		…
3368	except the initial one, and run the default loop in the initial thread as	5034	except the initial one, and run the default loop in the initial thread as
3369	well.	5035	well.
3370		5036
3371	=item C<long> must be large enough for common memory allocation sizes	5037	=item C<long> must be large enough for common memory allocation sizes
3372		5038
3373	To improve portability and simplify using libev, libev uses C<long>	5039	To improve portability and simplify its API, libev uses C<long> internally
3374	internally instead of C<size_t> when allocating its data structures. On	5040	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	5041	systems (Microsoft...) this might be unexpectedly low, but is still at
3376	is still at least 31 bits everywhere, which is enough for hundreds of	5042	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	5043	watchers.
3378		5044
3379	=item C<double> must hold a time value in seconds with enough accuracy	5045	=item C<double> must hold a time value in seconds with enough accuracy
3380		5046
3381	The type C<double> is used to represent timestamps. It is required to	5047	The type C<double> is used to represent timestamps. It is required to
3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5048	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3383	enough for at least into the year 4000. This requirement is fulfilled by	5049	good enough for at least into the year 4000 with millisecond accuracy
		5050	(the design goal for libev). This requirement is overfulfilled by
3384	implementations implementing IEEE 754 (basically all existing ones).	5051	implementations using IEEE 754, which is basically all existing ones. With
		5052	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3385		5053
3386	=back	5054	=back
3387		5055
3388	If you know of other additional requirements drop me a note.	5056	If you know of other additional requirements drop me a note.
3389		5057
3390		5058
3391	=head1 VALGRIND	5059	=head1 ALGORITHMIC COMPLEXITIES
3392		5060
3393	Valgrind has a special section here because it is a popular tool that is	5061	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	5062	libev will be documented. For complexity discussions about backends see
		5063	the documentation for C<ev_default_init>.
3395		5064
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	5065	All of the following are about amortised time: If an array needs to be
3397	in libev, then check twice: If valgrind reports something like:	5066	extended, libev needs to realloc and move the whole array, but this
		5067	happens asymptotically rarer with higher number of elements, so O(1) might
		5068	mean that libev does a lengthy realloc operation in rare cases, but on
		5069	average it is much faster and asymptotically approaches constant time.
3398		5070
3399	==2274== definitely lost: 0 bytes in 0 blocks.	5071	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		5072
3403	then there is no memory leak. Similarly, under some circumstances,	5073	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3404	valgrind might report kernel bugs as if it were a bug in libev, or it
3405	might be confused (it is a very good tool, but only a tool).
3406		5074
3407	If you are unsure about something, feel free to contact the mailing list	5075	This means that, when you have a watcher that triggers in one hour and
3408	with the full valgrind report and an explanation on why you think this is	5076	there are 100 watchers that would trigger before that, then inserting will
3409	a bug in libev. However, don't be annoyed when you get a brisk "this is	5077	have to skip roughly seven (C<ld 100>) of these watchers.
3410	no bug" answer and take the chance of learning how to interpret valgrind
3411	properly.
3412		5078
3413	If you need, for some reason, empty reports from valgrind for your project	5079	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.
3415		5080
		5081	That means that changing a timer costs less than removing/adding them,
		5082	as only the relative motion in the event queue has to be paid for.
		5083
		5084	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		5085
		5086	These just add the watcher into an array or at the head of a list.
		5087
		5088	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		5089
		5090	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		5091
		5092	These watchers are stored in lists, so they need to be walked to find the
		5093	correct watcher to remove. The lists are usually short (you don't usually
		5094	have many watchers waiting for the same fd or signal: one is typical, two
		5095	is rare).
		5096
		5097	=item Finding the next timer in each loop iteration: O(1)
		5098
		5099	By virtue of using a binary or 4-heap, the next timer is always found at a
		5100	fixed position in the storage array.
		5101
		5102	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		5103
		5104	A change means an I/O watcher gets started or stopped, which requires
		5105	libev to recalculate its status (and possibly tell the kernel, depending
		5106	on backend and whether C<ev_io_set> was used).
		5107
		5108	=item Activating one watcher (putting it into the pending state): O(1)
		5109
		5110	=item Priority handling: O(number_of_priorities)
		5111
		5112	Priorities are implemented by allocating some space for each
		5113	priority. When doing priority-based operations, libev usually has to
		5114	linearly search all the priorities, but starting/stopping and activating
		5115	watchers becomes O(1) with respect to priority handling.
		5116
		5117	=item Sending an ev_async: O(1)
		5118
		5119	=item Processing ev_async_send: O(number_of_async_watchers)
		5120
		5121	=item Processing signals: O(max_signal_number)
		5122
		5123	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5124	calls in the current loop iteration. Checking for async and signal events
		5125	involves iterating over all running async watchers or all signal numbers.
		5126
		5127	=back
		5128
		5129
		5130	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5131
		5132	The major version 4 introduced some incompatible changes to the API.
		5133
		5134	At the moment, the C<ev.h> header file provides compatibility definitions
		5135	for all changes, so most programs should still compile. The compatibility
		5136	layer might be removed in later versions of libev, so better update to the
		5137	new API early than late.
		5138
		5139	=over 4
		5140
		5141	=item C<EV_COMPAT3> backwards compatibility mechanism
		5142
		5143	The backward compatibility mechanism can be controlled by
		5144	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5145	section.
		5146
		5147	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5148
		5149	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5150
		5151	ev_loop_destroy (EV_DEFAULT_UC);
		5152	ev_loop_fork (EV_DEFAULT);
		5153
		5154	=item function/symbol renames
		5155
		5156	A number of functions and symbols have been renamed:
		5157
		5158	ev_loop => ev_run
		5159	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5160	EVLOOP_ONESHOT => EVRUN_ONCE
		5161
		5162	ev_unloop => ev_break
		5163	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5164	EVUNLOOP_ONE => EVBREAK_ONE
		5165	EVUNLOOP_ALL => EVBREAK_ALL
		5166
		5167	EV_TIMEOUT => EV_TIMER
		5168
		5169	ev_loop_count => ev_iteration
		5170	ev_loop_depth => ev_depth
		5171	ev_loop_verify => ev_verify
		5172
		5173	Most functions working on C<struct ev_loop> objects don't have an
		5174	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5175	associated constants have been renamed to not collide with the C<struct
		5176	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5177	as all other watcher types. Note that C<ev_loop_fork> is still called
		5178	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5179	typedef.
		5180
		5181	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5182
		5183	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5184	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5185	and work, but the library code will of course be larger.
		5186
		5187	=back
		5188
		5189
		5190	=head1 GLOSSARY
		5191
		5192	=over 4
		5193
		5194	=item active
		5195
		5196	A watcher is active as long as it has been started and not yet stopped.
		5197	See L<WATCHER STATES> for details.
		5198
		5199	=item application
		5200
		5201	In this document, an application is whatever is using libev.
		5202
		5203	=item backend
		5204
		5205	The part of the code dealing with the operating system interfaces.
		5206
		5207	=item callback
		5208
		5209	The address of a function that is called when some event has been
		5210	detected. Callbacks are being passed the event loop, the watcher that
		5211	received the event, and the actual event bitset.
		5212
		5213	=item callback/watcher invocation
		5214
		5215	The act of calling the callback associated with a watcher.
		5216
		5217	=item event
		5218
		5219	A change of state of some external event, such as data now being available
		5220	for reading on a file descriptor, time having passed or simply not having
		5221	any other events happening anymore.
		5222
		5223	In libev, events are represented as single bits (such as C<EV_READ> or
		5224	C<EV_TIMER>).
		5225
		5226	=item event library
		5227
		5228	A software package implementing an event model and loop.
		5229
		5230	=item event loop
		5231
		5232	An entity that handles and processes external events and converts them
		5233	into callback invocations.
		5234
		5235	=item event model
		5236
		5237	The model used to describe how an event loop handles and processes
		5238	watchers and events.
		5239
		5240	=item pending
		5241
		5242	A watcher is pending as soon as the corresponding event has been
		5243	detected. See L<WATCHER STATES> for details.
		5244
		5245	=item real time
		5246
		5247	The physical time that is observed. It is apparently strictly monotonic :)
		5248
		5249	=item wall-clock time
		5250
		5251	The time and date as shown on clocks. Unlike real time, it can actually
		5252	be wrong and jump forwards and backwards, e.g. when you adjust your
		5253	clock.
		5254
		5255	=item watcher
		5256
		5257	A data structure that describes interest in certain events. Watchers need
		5258	to be started (attached to an event loop) before they can receive events.
		5259
		5260	=back
3416		5261
3417	=head1 AUTHOR	5262	=head1 AUTHOR
3418		5263
3419	Marc Lehmann <libev@schmorp.de>.	5264	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5265	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3420		5266

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