ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.156 by root, Tue May 20 20:00:34 2008 UTC vs.
Revision 1.369 by root, Mon May 30 18:34:28 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 until
138	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	185	this is a sub-second-resolution C<sleep ()>.
140		186
141	=item int ev_version_major ()	187	=item int ev_version_major ()
142		188
143	=item int ev_version_minor ()	189	=item int ev_version_minor ()
144		190
…		…
155	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
156	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
157	not a problem.	203	not a problem.
158		204
159	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
161		208
162	assert (("libev version mismatch",	209	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
165		212
166	=item unsigned int ev_supported_backends ()	213	=item unsigned int ev_supported_backends ()
167		214
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	215	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	216	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	218	a description of the set values.
172		219
173	Example: make sure we have the epoll method, because yeah this is cool and	220	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	221	a must have and can we have a torrent of it please!!!11
175		222
176	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
178		225
179	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
180		227
181	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
182	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
184	most BSDs and will not be autodetected unless you explicitly request it	232	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	233	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.	234	probe for if you specify no backends explicitly.
187		235
188	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
189		237
190	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
191	is the theoretical, all-platform, value. To find which backends	239	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	240	current system. To find which embeddable backends might be supported on
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
194	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
195		243
196	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
197		245
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
199		247
…		…
229	}	277	}
230		278
231	...	279	...
232	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
233		281
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
235		283
236	Set the callback function to call on a retryable syscall error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	286	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	287	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	288	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	289	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	290	(such as abort).
243		291
244	Example: This is basically the same thing that libev does internally, too.	292	Example: This is basically the same thing that libev does internally, too.
…		…
251	}	299	}
252		300
253	...	301	...
254	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
255		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
256	=back	317	=back
257		318
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
259		320
260	An event loop is described by a C<struct ev_loop *>. The library knows two	321	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	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
262	events, and dynamically created loops which do not.	323	libev 3 had an C<ev_loop> function colliding with the struct name).
		324
		325	The library knows two types of such loops, the I<default> loop, which
		326	supports child process events, and dynamically created event loops which
		327	do not.
263		328
264	=over 4	329	=over 4
265		330
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		332
268	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
269	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
270	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
271	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
272		343
273	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
274	function.	345	function (or via the C<EV_DEFAULT> macro).
275		346
276	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
278	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
279		351
280	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
281	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
282	for C<SIGCHLD>. If this is a problem for your app you can either	354	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	355	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	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
285	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
286		376
287	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
289		379
290	The following flags are supported:	380	The following flags are supported:
…		…
296	The default flags value. Use this if you have no clue (it's the right	386	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	387	thing, believe me).
298		388
299	=item C<EVFLAG_NOENV>	389	=item C<EVFLAG_NOENV>
300		390
301	If this flag bit is ored into the flag value (or the program runs setuid	391	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	392	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	393	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	394	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	395	useful to try out specific backends to test their performance, or to work
306	around bugs.	396	around bugs.
307		397
308	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
309		399
310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
311	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
312	enabling this flag.
313		402
314	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	407	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	408	C<pthread_atfork> which is even faster).
320		409
321	The big advantage of this flag is that you can forget about fork (and	410	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	411	forget about forgetting to tell libev about forking) when you use this
323	flag.	412	flag.
324		413
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	415	environment variable.
		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
327		451
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		453
330	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	456	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	457	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.	458	usually the fastest backend for a low number of (low-numbered :) fds.
335		459
336	To get good performance out of this backend you need a high amount of	460	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	461	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	462	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	463	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	464	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	465	readiness notifications you get per iteration.
		466
		467	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		468	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		469	C<exceptfds> set on that platform).
342		470
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	471	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		472
345	And this is your standard poll(2) backend. It's more complicated	473	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	474	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	475	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,	476	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	477	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	478	performance tips.
351		479
		480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		482
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
354	For few fds, this backend is a bit little slower than poll and select,	488	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	489	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),	490	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	491	fd), epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	492
359	cases and requiring a syscall per fd change, no fork support and bad	493	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	494	of the more advanced event mechanisms: mere annoyances include silently
		495	dropping file descriptors, requiring a system call per change per file
		496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
		499	0.1ms) and so on. The biggest issue is fork races, however - if a program
		500	forks then I<both> parent and child process have to recreate the epoll
		501	set, which can take considerable time (one syscall per file descriptor)
		502	and is of course hard to detect.
		503
		504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		505	of course I<doesn't>, and epoll just loves to report events for totally
		506	I<different> file descriptors (even already closed ones, so one cannot
		507	even remove them from the set) than registered in the set (especially
		508	on SMP systems). Libev tries to counter these spurious notifications by
		509	employing an additional generation counter and comparing that against the
		510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
361		517
362	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	519	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	520	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	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	522	file descriptors might not work very well if you register events for both
367		523	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		524
372	Best performance from this backend is achieved by not unregistering all	525	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.	526	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	527	i.e. keep at least one watcher active per fd at all times. Stopping and
		528	starting a watcher (without re-setting it) also usually doesn't cause
		529	extra overhead. A fork can both result in spurious notifications as well
		530	as in libev having to destroy and recreate the epoll object, which can
		531	take considerable time and thus should be avoided.
375		532
		533	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		534	faster than epoll for maybe up to a hundred file descriptors, depending on
		535	the usage. So sad.
		536
376	While nominally embeddeble in other event loops, this feature is broken in	537	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	538	all kernel versions tested so far.
		539
		540	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		541	C<EVBACKEND_POLL>.
378		542
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	543	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		544
381	Kqueue deserves special mention, as at the time of this writing, it	545	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	546	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	547	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"	548	it's completely useless). Unlike epoll, however, whose brokenness
		549	is by design, these kqueue bugs can (and eventually will) be fixed
		550	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	551	"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)	552	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	553	system like NetBSD.
388		554
389	You still can embed kqueue into a normal poll or select backend and use it	555	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	556	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.	557	the target platform). See C<ev_embed> watchers for more info.
392		558
393	It scales in the same way as the epoll backend, but the interface to the	559	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	560	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	561	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	562	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	563	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	564	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		565	cases
399		566
400	This backend usually performs well under most conditions.	567	This backend usually performs well under most conditions.
401		568
402	While nominally embeddable in other event loops, this doesn't work	569	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	570	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	571	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	572	(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	573	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	574	also broken on OS X)) and, did I mention it, using it only for sockets.
		575
		576	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		577	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		578	C<NOTE_EOF>.
408		579
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	580	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		581
411	This is not implemented yet (and might never be, unless you send me an	582	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	583	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		588
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
420		591
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	592	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	593	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	595	might perform better.
429		596
430	On the positive side, ignoring the spurious readiness notifications, this	597	On the positive side, this backend actually performed fully to
431	backend actually performed to specification in all tests and is fully	598	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.	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
		611
		612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		613	C<EVBACKEND_POLL>.
433		614
434	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
435		616
436	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
439		620
440	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
441		630
442	=back	631	=back
443		632
444	If one or more of these are ored into the flags value, then only these	633	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	634	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.	635	here). If none are specified, all backends in C<ev_recommended_backends
447		636	()> 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		637
475	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
476		639
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	641	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
480		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
481	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
482		650
483	Destroys the default loop again (frees all memory and kernel state	651	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	652	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	653	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>	654	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	657	for example).
490		658
491	Note that certain global state, such as signal state, will not be freed by	659	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	660	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
494		662
495	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
496	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
497	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
498	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
499		671
500	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
501		673
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	674	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	675	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	676	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	677	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	678	child before resuming or calling C<ev_run>.
512	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
513		684
514	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
515	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
516	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
517		691
518	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
519	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
520	quite nicely into a call to C<pthread_atfork>:
521		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
522	pthread_atfork (0, 0, ev_default_fork);	705	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		706
530	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
531		708
532	Returns true when the given loop actually is the default loop, false otherwise.	709	Returns true when the given loop is, in fact, the default loop, and false
		710	otherwise.
533		711
534	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
535		713
536	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
537	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
538	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
539		717
540	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
		722
		723	=item unsigned int ev_depth (loop)
		724
		725	Returns the number of times C<ev_run> was entered minus the number of
		726	times C<ev_run> was exited normally, in other words, the recursion depth.
		727
		728	Outside C<ev_run>, this number is zero. In a callback, this number is
		729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		730	in which case it is higher.
		731
		732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
543		736
544	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
545		738
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	740	use.
…		…
552	received events and started processing them. This timestamp does not	745	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	746	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	747	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).	748	event occurring (or more correctly, libev finding out about it).
556		749
		750	=item ev_now_update (loop)
		751
		752	Establishes the current time by querying the kernel, updating the time
		753	returned by C<ev_now ()> in the progress. This is a costly operation and
		754	is usually done automatically within C<ev_run ()>.
		755
		756	This function is rarely useful, but when some event callback runs for a
		757	very long time without entering the event loop, updating libev's idea of
		758	the current time is a good idea.
		759
		760	See also L<The special problem of time updates> in the C<ev_timer> section.
		761
		762	=item ev_suspend (loop)
		763
		764	=item ev_resume (loop)
		765
		766	These two functions suspend and resume an event loop, for use when the
		767	loop is not used for a while and timeouts should not be processed.
		768
		769	A typical use case would be an interactive program such as a game: When
		770	the user presses C<^Z> to suspend the game and resumes it an hour later it
		771	would be best to handle timeouts as if no time had actually passed while
		772	the program was suspended. This can be achieved by calling C<ev_suspend>
		773	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		774	C<ev_resume> directly afterwards to resume timer processing.
		775
		776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		778	will be rescheduled (that is, they will lose any events that would have
		779	occurred while suspended).
		780
		781	After calling C<ev_suspend> you B<must not> call I<any> function on the
		782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		783	without a previous call to C<ev_suspend>.
		784
		785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		786	event loop time (see C<ev_now_update>).
		787
557	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
558		789
559	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
561	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
562		795
563	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
564	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
565		799
566	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	802	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	803	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.	804	of relying on its watchers stopping correctly, that is truly a thing of
		805	beauty.
571		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	813	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.	814	block your process in case there are no events and will return after one
		815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
575		817
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	819	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	820	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	821	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	822	user-registered callback will be called), and will return after one
		823	iteration of the loop.
		824
		825	This is useful if you are waiting for some external event in conjunction
		826	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	827	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.	828	usually a better approach for this kind of thing.
583		829
584	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does (this is for your
		831	understanding, not a guarantee that things will work exactly like this in
		832	future versions):
585		833
		834	- Increment loop depth.
		835	- Reset the ev_break status.
586	- Before the first iteration, call any pending watchers.	836	- Before the first iteration, call any pending watchers.
		837	LOOP:
587	* If EVFLAG_FORKCHECK was used, check for a fork.	838	- If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	839	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	840	- Queue and call all prepare watchers.
		841	- If ev_break was called, goto FINISH.
590	- If we have been forked, recreate the kernel state.	842	- If we have been forked, detach and recreate the kernel state
		843	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	844	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	845	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	846	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	847	(active idle watchers, EVRUN_NOWAIT or not having
595	any active watchers at all will result in not sleeping).	848	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	849	- Sleep if the I/O and timer collect interval say so.
		850	- Increment loop iteration counter.
597	- Block the process, waiting for any events.	851	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	852	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	853	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	854	- Queue all expired timers.
601	- Queue all outstanding periodics.	855	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	856	- Queue all idle watchers with priority higher than that of pending events.
603	- Queue all check watchers.	857	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	858	- 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	859	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	860	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	861	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
608	were used, or there are no active watchers, return, otherwise	862	were used, or there are no active watchers, goto FINISH, otherwise
609	continue with step *.	863	continue with step LOOP.
		864	FINISH:
		865	- Reset the ev_break status iff it was EVBREAK_ONE.
		866	- Decrement the loop depth.
		867	- Return.
610		868
611	Example: Queue some jobs and then loop until no events are outstanding	869	Example: Queue some jobs and then loop until no events are outstanding
612	anymore.	870	anymore.
613		871
614	... queue jobs here, make sure they register event watchers as long	872	... 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..)	873	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	874	ev_run (my_loop, 0);
617	... jobs done. yeah!	875	... jobs done or somebody called break. yeah!
618		876
619	=item ev_unloop (loop, how)	877	=item ev_break (loop, how)
620		878
621	Can be used to make a call to C<ev_loop> return early (but only after it	879	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	880	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	881	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.	882	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
625		883
626	This "unloop state" will be cleared when entering C<ev_loop> again.	884	This "break state" will be cleared on the next call to C<ev_run>.
		885
		886	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		887	which case it will have no effect.
627		888
628	=item ev_ref (loop)	889	=item ev_ref (loop)
629		890
630	=item ev_unref (loop)	891	=item ev_unref (loop)
631		892
632	Ref/unref can be used to add or remove a reference count on the event	893	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	894	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	895	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	896
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	897	This is useful when you have a watcher that you never intend to
		898	unregister, but that nevertheless should not keep C<ev_run> from
		899	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		900	before stopping it.
		901
637	example, libev itself uses this for its internal signal pipe: It is not	902	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	903	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	904	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	905	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>	906	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,	907	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	908	before, respectively. Note also that libev might stop watchers itself
		909	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		910	in the callback).
644		911
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	912	Example: Create a signal watcher, but keep it from keeping C<ev_run>
646	running when nothing else is active.	913	running when nothing else is active.
647		914
648	struct ev_signal exitsig;	915	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	916	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	917	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	918	ev_unref (loop);
652		919
653	Example: For some weird reason, unregister the above signal handler again.	920	Example: For some weird reason, unregister the above signal handler again.
654		921
655	ev_ref (loop);	922	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	923	ev_signal_stop (loop, &exitsig);
657		924
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	925	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		926
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	927	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		928
662	These advanced functions influence the time that libev will spend waiting	929	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	930	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.	931	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		932	latency.
665		933
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	934	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	935	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	936	to increase efficiency of loop iterations (or to increase power-saving
		937	opportunities).
669		938
670	The background is that sometimes your program runs just fast enough to	939	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	940	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	941	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	942	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	943	overhead for the actual polling but can deliver many events at once.
675		944
676	By setting a higher I<io collect interval> you allow libev to spend more	945	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,	946	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	947	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	948	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	949	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		950	sleep time ensures that libev will not poll for I/O events more often then
		951	once per this interval, on average.
681		952
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	953	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	954	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	955	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	956	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	957	value will not introduce any overhead in libev.
687		958
688	Many (busy) programs can usually benefit by setting the io collect	959	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	960	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	961	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>,	962	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.	963	as this approaches the timing granularity of most systems. Note that if
		964	you do transactions with the outside world and you can't increase the
		965	parallelity, then this setting will limit your transaction rate (if you
		966	need to poll once per transaction and the I/O collect interval is 0.01,
		967	then you can't do more than 100 transactions per second).
		968
		969	Setting the I<timeout collect interval> can improve the opportunity for
		970	saving power, as the program will "bundle" timer callback invocations that
		971	are "near" in time together, by delaying some, thus reducing the number of
		972	times the process sleeps and wakes up again. Another useful technique to
		973	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		974	they fire on, say, one-second boundaries only.
		975
		976	Example: we only need 0.1s timeout granularity, and we wish not to poll
		977	more often than 100 times per second:
		978
		979	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		980	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		981
		982	=item ev_invoke_pending (loop)
		983
		984	This call will simply invoke all pending watchers while resetting their
		985	pending state. Normally, C<ev_run> does this automatically when required,
		986	but when overriding the invoke callback this call comes handy. This
		987	function can be invoked from a watcher - this can be useful for example
		988	when you want to do some lengthy calculation and want to pass further
		989	event handling to another thread (you still have to make sure only one
		990	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		991
		992	=item int ev_pending_count (loop)
		993
		994	Returns the number of pending watchers - zero indicates that no watchers
		995	are pending.
		996
		997	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		998
		999	This overrides the invoke pending functionality of the loop: Instead of
		1000	invoking all pending watchers when there are any, C<ev_run> will call
		1001	this callback instead. This is useful, for example, when you want to
		1002	invoke the actual watchers inside another context (another thread etc.).
		1003
		1004	If you want to reset the callback, use C<ev_invoke_pending> as new
		1005	callback.
		1006
		1007	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1008
		1009	Sometimes you want to share the same loop between multiple threads. This
		1010	can be done relatively simply by putting mutex_lock/unlock calls around
		1011	each call to a libev function.
		1012
		1013	However, C<ev_run> can run an indefinite time, so it is not feasible
		1014	to wait for it to return. One way around this is to wake up the event
		1015	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1016	I<release> and I<acquire> callbacks on the loop.
		1017
		1018	When set, then C<release> will be called just before the thread is
		1019	suspended waiting for new events, and C<acquire> is called just
		1020	afterwards.
		1021
		1022	Ideally, C<release> will just call your mutex_unlock function, and
		1023	C<acquire> will just call the mutex_lock function again.
		1024
		1025	While event loop modifications are allowed between invocations of
		1026	C<release> and C<acquire> (that's their only purpose after all), no
		1027	modifications done will affect the event loop, i.e. adding watchers will
		1028	have no effect on the set of file descriptors being watched, or the time
		1029	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1030	to take note of any changes you made.
		1031
		1032	In theory, threads executing C<ev_run> will be async-cancel safe between
		1033	invocations of C<release> and C<acquire>.
		1034
		1035	See also the locking example in the C<THREADS> section later in this
		1036	document.
		1037
		1038	=item ev_set_userdata (loop, void *data)
		1039
		1040	=item void *ev_userdata (loop)
		1041
		1042	Set and retrieve a single C<void *> associated with a loop. When
		1043	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1044	C<0>.
		1045
		1046	These two functions can be used to associate arbitrary data with a loop,
		1047	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1048	C<acquire> callbacks described above, but of course can be (ab-)used for
		1049	any other purpose as well.
		1050
		1051	=item ev_verify (loop)
		1052
		1053	This function only does something when C<EV_VERIFY> support has been
		1054	compiled in, which is the default for non-minimal builds. It tries to go
		1055	through all internal structures and checks them for validity. If anything
		1056	is found to be inconsistent, it will print an error message to standard
		1057	error and call C<abort ()>.
		1058
		1059	This can be used to catch bugs inside libev itself: under normal
		1060	circumstances, this function will never abort as of course libev keeps its
		1061	data structures consistent.
693		1062
694	=back	1063	=back
695		1064
696		1065
697	=head1 ANATOMY OF A WATCHER	1066	=head1 ANATOMY OF A WATCHER
698		1067
		1068	In the following description, uppercase C<TYPE> in names stands for the
		1069	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1070	watchers and C<ev_io_start> for I/O watchers.
		1071
699	A watcher is a structure that you create and register to record your	1072	A watcher is an opaque structure that you allocate and register to record
700	interest in some event. For instance, if you want to wait for STDIN to	1073	your interest in some event. To make a concrete example, imagine you want
701	become readable, you would create an C<ev_io> watcher for that:	1074	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1075	for that:
702		1076
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1077	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	1078	{
705	ev_io_stop (w);	1079	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	1080	ev_break (loop, EVBREAK_ALL);
707	}	1081	}
708		1082
709	struct ev_loop *loop = ev_default_loop (0);	1083	struct ev_loop *loop = ev_default_loop (0);
		1084
710	struct ev_io stdin_watcher;	1085	ev_io stdin_watcher;
		1086
711	ev_init (&stdin_watcher, my_cb);	1087	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1088	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	1089	ev_io_start (loop, &stdin_watcher);
		1090
714	ev_loop (loop, 0);	1091	ev_run (loop, 0);
715		1092
716	As you can see, you are responsible for allocating the memory for your	1093	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	1094	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	1095	stack).
719		1096
		1097	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1098	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1099
720	Each watcher structure must be initialised by a call to C<ev_init	1100	Each watcher structure must be initialised by a call to C<ev_init (watcher
721	(watcher *, callback)>, which expects a callback to be provided. This	1101	*, callback)>, which expects a callback to be provided. This callback is
722	callback gets invoked each time the event occurs (or, in the case of io	1102	invoked each time the event occurs (or, in the case of I/O watchers, each
723	watchers, each time the event loop detects that the file descriptor given	1103	time the event loop detects that the file descriptor given is readable
724	is readable and/or writable).	1104	and/or writable).
725		1105
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1106	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	1107	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	1108	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1109	ev_TYPE_init (watcher *, callback, ...) >>.
730		1110
731	To make the watcher actually watch out for events, you have to start it	1111	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1112	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	1113	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1114	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1115
736	As long as your watcher is active (has been started but not stopped) you	1116	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	1117	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1118	reinitialise it or call its C<ev_TYPE_set> macro.
739		1119
740	Each and every callback receives the event loop pointer as first, the	1120	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	1121	registered watcher structure as second, and a bitset of received events as
742	third argument.	1122	third argument.
743		1123
…		…
752	=item C<EV_WRITE>	1132	=item C<EV_WRITE>
753		1133
754	The file descriptor in the C<ev_io> watcher has become readable and/or	1134	The file descriptor in the C<ev_io> watcher has become readable and/or
755	writable.	1135	writable.
756		1136
757	=item C<EV_TIMEOUT>	1137	=item C<EV_TIMER>
758		1138
759	The C<ev_timer> watcher has timed out.	1139	The C<ev_timer> watcher has timed out.
760		1140
761	=item C<EV_PERIODIC>	1141	=item C<EV_PERIODIC>
762		1142
…		…
780		1160
781	=item C<EV_PREPARE>	1161	=item C<EV_PREPARE>
782		1162
783	=item C<EV_CHECK>	1163	=item C<EV_CHECK>
784		1164
785	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1165	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
786	to gather new events, and all C<ev_check> watchers are invoked just after	1166	to gather new events, and all C<ev_check> watchers are invoked just after
787	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1167	C<ev_run> has gathered them, but before it invokes any callbacks for any
788	received events. Callbacks of both watcher types can start and stop as	1168	received events. Callbacks of both watcher types can start and stop as
789	many watchers as they want, and all of them will be taken into account	1169	many watchers as they want, and all of them will be taken into account
790	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1170	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
791	C<ev_loop> from blocking).	1171	C<ev_run> from blocking).
792		1172
793	=item C<EV_EMBED>	1173	=item C<EV_EMBED>
794		1174
795	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1175	The embedded event loop specified in the C<ev_embed> watcher needs attention.
796		1176
797	=item C<EV_FORK>	1177	=item C<EV_FORK>
798		1178
799	The event loop has been resumed in the child process after fork (see	1179	The event loop has been resumed in the child process after fork (see
800	C<ev_fork>).	1180	C<ev_fork>).
801		1181
		1182	=item C<EV_CLEANUP>
		1183
		1184	The event loop is about to be destroyed (see C<ev_cleanup>).
		1185
802	=item C<EV_ASYNC>	1186	=item C<EV_ASYNC>
803		1187
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1188	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1189
		1190	=item C<EV_CUSTOM>
		1191
		1192	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1193	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1194
806	=item C<EV_ERROR>	1195	=item C<EV_ERROR>
807		1196
808	An unspecified error has occured, the watcher has been stopped. This might	1197	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1198	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	1199	ran out of memory, a file descriptor was found to be closed or any other
		1200	problem. Libev considers these application bugs.
		1201
811	problem. You best act on it by reporting the problem and somehow coping	1202	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1203	watcher being stopped. Note that well-written programs should not receive
		1204	an error ever, so when your watcher receives it, this usually indicates a
		1205	bug in your program.
813		1206
814	Libev will usually signal a few "dummy" events together with an error,	1207	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	1208	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	1209	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	1210	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1211	programs, though, as the fd could already be closed and reused for another
		1212	thing, so beware.
819		1213
820	=back	1214	=back
821		1215
822	=head2 GENERIC WATCHER FUNCTIONS	1216	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		1217
827	=over 4	1218	=over 4
828		1219
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1220	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1221
…		…
836	which rolls both calls into one.	1227	which rolls both calls into one.
837		1228
838	You can reinitialise a watcher at any time as long as it has been stopped	1229	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	1230	(or never started) and there are no pending events outstanding.
840		1231
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1232	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1233	int revents)>.
843		1234
		1235	Example: Initialise an C<ev_io> watcher in two steps.
		1236
		1237	ev_io w;
		1238	ev_init (&w, my_cb);
		1239	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1240
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1241	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
845		1242
846	This macro initialises the type-specific parts of a watcher. You need to	1243	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	1244	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	1245	call C<ev_TYPE_set> any number of times. You must not, however, call this
849	macro on a watcher that is active (it can be pending, however, which is a	1246	macro on a watcher that is active (it can be pending, however, which is a
850	difference to the C<ev_init> macro).	1247	difference to the C<ev_init> macro).
851		1248
852	Although some watcher types do not have type-specific arguments	1249	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1250	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1251
		1252	See C<ev_init>, above, for an example.
		1253
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1254	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1255
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1256	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	1257	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1258	a watcher. The same limitations apply, of course.
860		1259
		1260	Example: Initialise and set an C<ev_io> watcher in one step.
		1261
		1262	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1263
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1264	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
862		1265
863	Starts (activates) the given watcher. Only active watchers will receive	1266	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1267	events. If the watcher is already active nothing will happen.
865		1268
		1269	Example: Start the C<ev_io> watcher that is being abused as example in this
		1270	whole section.
		1271
		1272	ev_io_start (EV_DEFAULT_UC, &w);
		1273
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
867		1275
868	Stops the given watcher again (if active) and clears the pending	1276	Stops the given watcher if active, and clears the pending status (whether
		1277	the watcher was active or not).
		1278
869	status. It is possible that stopped watchers are pending (for example,	1279	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1280	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1281	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1282	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1283	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1284
875	=item bool ev_is_active (ev_TYPE *watcher)	1285	=item bool ev_is_active (ev_TYPE *watcher)
876		1286
877	Returns a true value iff the watcher is active (i.e. it has been started	1287	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1288	and not yet been stopped). As long as a watcher is active you must not modify
…		…
894	=item ev_cb_set (ev_TYPE *watcher, callback)	1304	=item ev_cb_set (ev_TYPE *watcher, callback)
895		1305
896	Change the callback. You can change the callback at virtually any time	1306	Change the callback. You can change the callback at virtually any time
897	(modulo threads).	1307	(modulo threads).
898		1308
899	=item ev_set_priority (ev_TYPE *watcher, priority)	1309	=item ev_set_priority (ev_TYPE *watcher, int priority)
900		1310
901	=item int ev_priority (ev_TYPE *watcher)	1311	=item int ev_priority (ev_TYPE *watcher)
902		1312
903	Set and query the priority of the watcher. The priority is a small	1313	Set and query the priority of the watcher. The priority is a small
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1314	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1315	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1316	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1317	from being executed (except for C<ev_idle> watchers).
908		1318
909	This means that priorities are I<only> used for ordering callback
910	invocation after new events have been received. This is useful, for
911	example, to reduce latency after idling, or more often, to bind two
912	watchers on the same event and make sure one is called first.
913
914	If you need to suppress invocation when higher priority events are pending	1319	If you need to suppress invocation when higher priority events are pending
915	you need to look at C<ev_idle> watchers, which provide this functionality.	1320	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1321
917	You I<must not> change the priority of a watcher as long as it is active or	1322	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1323	pending.
919		1324
		1325	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1326	fine, as long as you do not mind that the priority value you query might
		1327	or might not have been clamped to the valid range.
		1328
920	The default priority used by watchers when no priority has been set is	1329	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1330	always C<0>, which is supposed to not be too high and not be too low :).
922		1331
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1332	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
924	fine, as long as you do not mind that the priority value you query might	1333	priorities.
925	or might not have been adjusted to be within valid range.
926		1334
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1335	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1336
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1337	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1338	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1339	can deal with that fact, as both are simply passed through to the
		1340	callback.
932		1341
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1342	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1343
935	If the watcher is pending, this function returns clears its pending status	1344	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1345	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1346	watcher isn't pending it does nothing and returns C<0>.
938		1347
		1348	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1349	callback to be invoked, which can be accomplished with this function.
		1350
		1351	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1352
		1353	Feeds the given event set into the event loop, as if the specified event
		1354	had happened for the specified watcher (which must be a pointer to an
		1355	initialised but not necessarily started event watcher). Obviously you must
		1356	not free the watcher as long as it has pending events.
		1357
		1358	Stopping the watcher, letting libev invoke it, or calling
		1359	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1360	not started in the first place.
		1361
		1362	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1363	functions that do not need a watcher.
		1364
939	=back	1365	=back
940		1366
		1367	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1368	OWN COMPOSITE WATCHERS> idioms.
941		1369
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 WATCHER STATES
943		1371
944	Each watcher has, by default, a member C<void *data> that you can change	1372	There are various watcher states mentioned throughout this manual -
945	and read at any time, libev will completely ignore it. This can be used	1373	active, pending and so on. In this section these states and the rules to
946	to associate arbitrary data with your watcher. If you need more data and	1374	transition between them will be described in more detail - and while these
947	don't want to allocate memory and store a pointer to it in that data	1375	rules might look complicated, they usually do "the right thing".
948	member, you can also "subclass" the watcher type and provide your own
949	data:
950		1376
951	struct my_io	1377	=over 4
952	{
953	struct ev_io io;
954	int otherfd;
955	void *somedata;
956	struct whatever *mostinteresting;
957	}
958		1378
959	And since your callback will be called with a pointer to the watcher, you	1379	=item initialiased
960	can cast it back to your own type:
961		1380
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1381	Before a watcher can be registered with the event looop it has to be
963	{	1382	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
964	struct my_io *w = (struct my_io *)w_;	1383	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
965	...
966	}
967		1384
968	More interesting and less C-conformant ways of casting your callback type	1385	In this state it is simply some block of memory that is suitable for
969	instead have been omitted.	1386	use in an event loop. It can be moved around, freed, reused etc. at
		1387	will - as long as you either keep the memory contents intact, or call
		1388	C<ev_TYPE_init> again.
970		1389
971	Another common scenario is having some data structure with multiple	1390	=item started/running/active
972	watchers:
973		1391
974	struct my_biggy	1392	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
975	{	1393	property of the event loop, and is actively waiting for events. While in
976	int some_data;	1394	this state it cannot be accessed (except in a few documented ways), moved,
977	ev_timer t1;	1395	freed or anything else - the only legal thing is to keep a pointer to it,
978	ev_timer t2;	1396	and call libev functions on it that are documented to work on active watchers.
979	}
980		1397
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1398	=item pending
982	you need to use C<offsetof>:
983		1399
984	#include <stddef.h>	1400	If a watcher is active and libev determines that an event it is interested
		1401	in has occurred (such as a timer expiring), it will become pending. It will
		1402	stay in this pending state until either it is stopped or its callback is
		1403	about to be invoked, so it is not normally pending inside the watcher
		1404	callback.
985		1405
		1406	The watcher might or might not be active while it is pending (for example,
		1407	an expired non-repeating timer can be pending but no longer active). If it
		1408	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1409	but it is still property of the event loop at this time, so cannot be
		1410	moved, freed or reused. And if it is active the rules described in the
		1411	previous item still apply.
		1412
		1413	It is also possible to feed an event on a watcher that is not active (e.g.
		1414	via C<ev_feed_event>), in which case it becomes pending without being
		1415	active.
		1416
		1417	=item stopped
		1418
		1419	A watcher can be stopped implicitly by libev (in which case it might still
		1420	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1421	latter will clear any pending state the watcher might be in, regardless
		1422	of whether it was active or not, so stopping a watcher explicitly before
		1423	freeing it is often a good idea.
		1424
		1425	While stopped (and not pending) the watcher is essentially in the
		1426	initialised state, that is, it can be reused, moved, modified in any way
		1427	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1428	it again).
		1429
		1430	=back
		1431
		1432	=head2 WATCHER PRIORITY MODELS
		1433
		1434	Many event loops support I<watcher priorities>, which are usually small
		1435	integers that influence the ordering of event callback invocation
		1436	between watchers in some way, all else being equal.
		1437
		1438	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1439	description for the more technical details such as the actual priority
		1440	range.
		1441
		1442	There are two common ways how these these priorities are being interpreted
		1443	by event loops:
		1444
		1445	In the more common lock-out model, higher priorities "lock out" invocation
		1446	of lower priority watchers, which means as long as higher priority
		1447	watchers receive events, lower priority watchers are not being invoked.
		1448
		1449	The less common only-for-ordering model uses priorities solely to order
		1450	callback invocation within a single event loop iteration: Higher priority
		1451	watchers are invoked before lower priority ones, but they all get invoked
		1452	before polling for new events.
		1453
		1454	Libev uses the second (only-for-ordering) model for all its watchers
		1455	except for idle watchers (which use the lock-out model).
		1456
		1457	The rationale behind this is that implementing the lock-out model for
		1458	watchers is not well supported by most kernel interfaces, and most event
		1459	libraries will just poll for the same events again and again as long as
		1460	their callbacks have not been executed, which is very inefficient in the
		1461	common case of one high-priority watcher locking out a mass of lower
		1462	priority ones.
		1463
		1464	Static (ordering) priorities are most useful when you have two or more
		1465	watchers handling the same resource: a typical usage example is having an
		1466	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1467	timeouts. Under load, data might be received while the program handles
		1468	other jobs, but since timers normally get invoked first, the timeout
		1469	handler will be executed before checking for data. In that case, giving
		1470	the timer a lower priority than the I/O watcher ensures that I/O will be
		1471	handled first even under adverse conditions (which is usually, but not
		1472	always, what you want).
		1473
		1474	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1475	will only be executed when no same or higher priority watchers have
		1476	received events, they can be used to implement the "lock-out" model when
		1477	required.
		1478
		1479	For example, to emulate how many other event libraries handle priorities,
		1480	you can associate an C<ev_idle> watcher to each such watcher, and in
		1481	the normal watcher callback, you just start the idle watcher. The real
		1482	processing is done in the idle watcher callback. This causes libev to
		1483	continuously poll and process kernel event data for the watcher, but when
		1484	the lock-out case is known to be rare (which in turn is rare :), this is
		1485	workable.
		1486
		1487	Usually, however, the lock-out model implemented that way will perform
		1488	miserably under the type of load it was designed to handle. In that case,
		1489	it might be preferable to stop the real watcher before starting the
		1490	idle watcher, so the kernel will not have to process the event in case
		1491	the actual processing will be delayed for considerable time.
		1492
		1493	Here is an example of an I/O watcher that should run at a strictly lower
		1494	priority than the default, and which should only process data when no
		1495	other events are pending:
		1496
		1497	ev_idle idle; // actual processing watcher
		1498	ev_io io; // actual event watcher
		1499
986	static void	1500	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1501	io_cb (EV_P_ ev_io *w, int revents)
988	{	1502	{
989	struct my_biggy big = (struct my_biggy *	1503	// stop the I/O watcher, we received the event, but
990	(((char *)w) - offsetof (struct my_biggy, t1));	1504	// are not yet ready to handle it.
		1505	ev_io_stop (EV_A_ w);
		1506
		1507	// start the idle watcher to handle the actual event.
		1508	// it will not be executed as long as other watchers
		1509	// with the default priority are receiving events.
		1510	ev_idle_start (EV_A_ &idle);
991	}	1511	}
992		1512
993	static void	1513	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1514	idle_cb (EV_P_ ev_idle *w, int revents)
995	{	1515	{
996	struct my_biggy big = (struct my_biggy *	1516	// actual processing
997	(((char *)w) - offsetof (struct my_biggy, t2));	1517	read (STDIN_FILENO, ...);
		1518
		1519	// have to start the I/O watcher again, as
		1520	// we have handled the event
		1521	ev_io_start (EV_P_ &io);
998	}	1522	}
		1523
		1524	// initialisation
		1525	ev_idle_init (&idle, idle_cb);
		1526	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1527	ev_io_start (EV_DEFAULT_ &io);
		1528
		1529	In the "real" world, it might also be beneficial to start a timer, so that
		1530	low-priority connections can not be locked out forever under load. This
		1531	enables your program to keep a lower latency for important connections
		1532	during short periods of high load, while not completely locking out less
		1533	important ones.
999		1534
1000		1535
1001	=head1 WATCHER TYPES	1536	=head1 WATCHER TYPES
1002		1537
1003	This section describes each watcher in detail, but will not repeat	1538	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1562	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1563	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1564	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1565	required if you know what you are doing).
1031		1566
1032	If you must do this, then force the use of a known-to-be-good backend
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1034	C<EVBACKEND_POLL>).
1035
1036	Another thing you have to watch out for is that it is quite easy to	1567	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1568	receive "spurious" readiness notifications, that is, your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1569	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1570	because there is no data. It is very easy to get into this situation even
1040	lot of those (for example solaris ports), it is very easy to get into	1571	with a relatively standard program structure. Thus it is best to always
1041	this situation even with a relatively standard program structure. Thus	1572	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1573	preferable to a program hanging until some data arrives.
1044		1574
1045	If you cannot run the fd in non-blocking mode (for example you should not	1575	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1576	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1577	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1578	interface such as poll (fortunately in the case of Xlib, it already does
1049	its own, so its quite safe to use).	1579	this on its own, so its quite safe to use). Some people additionally
		1580	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1581	indefinitely.
		1582
		1583	But really, best use non-blocking mode.
1050		1584
1051	=head3 The special problem of disappearing file descriptors	1585	=head3 The special problem of disappearing file descriptors
1052		1586
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1587	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1588	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1589	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1590	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1591	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1592	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1593	fact, a different file descriptor.
1060		1594
…		…
1078		1612
1079	There is no workaround possible except not registering events	1613	There is no workaround possible except not registering events
1080	for potentially C<dup ()>'ed file descriptors, or to resort to	1614	for potentially C<dup ()>'ed file descriptors, or to resort to
1081	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1082		1616
		1617	=head3 The special problem of files
		1618
		1619	Many people try to use C<select> (or libev) on file descriptors
		1620	representing files, and expect it to become ready when their program
		1621	doesn't block on disk accesses (which can take a long time on their own).
		1622
		1623	However, this cannot ever work in the "expected" way - you get a readiness
		1624	notification as soon as the kernel knows whether and how much data is
		1625	there, and in the case of open files, that's always the case, so you
		1626	always get a readiness notification instantly, and your read (or possibly
		1627	write) will still block on the disk I/O.
		1628
		1629	Another way to view it is that in the case of sockets, pipes, character
		1630	devices and so on, there is another party (the sender) that delivers data
		1631	on its own, but in the case of files, there is no such thing: the disk
		1632	will not send data on its own, simply because it doesn't know what you
		1633	wish to read - you would first have to request some data.
		1634
		1635	Since files are typically not-so-well supported by advanced notification
		1636	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1637	to files, even though you should not use it. The reason for this is
		1638	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1639	usually a tty, often a pipe, but also sometimes files or special devices
		1640	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1641	F</dev/urandom>), and even though the file might better be served with
		1642	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1643	it "just works" instead of freezing.
		1644
		1645	So avoid file descriptors pointing to files when you know it (e.g. use
		1646	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1647	when you rarely read from a file instead of from a socket, and want to
		1648	reuse the same code path.
		1649
1083	=head3 The special problem of fork	1650	=head3 The special problem of fork
1084		1651
1085	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1652	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1086	useless behaviour. Libev fully supports fork, but needs to be told about	1653	useless behaviour. Libev fully supports fork, but needs to be told about
1087	it in the child.	1654	it in the child if you want to continue to use it in the child.
1088		1655
1089	To support fork in your programs, you either have to call	1656	To support fork in your child processes, you have to call C<ev_loop_fork
1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1657	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1658	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1092	C<EVBACKEND_POLL>.
1093		1659
1094	=head3 The special problem of SIGPIPE	1660	=head3 The special problem of SIGPIPE
1095		1661
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1662	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1663	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1664	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1665	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1666
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1667	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1668	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1669	somewhere, as that would have given you a big clue).
1105		1670
		1671	=head3 The special problem of accept()ing when you can't
		1672
		1673	Many implementations of the POSIX C<accept> function (for example,
		1674	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1675	connection from the pending queue in all error cases.
		1676
		1677	For example, larger servers often run out of file descriptors (because
		1678	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1679	rejecting the connection, leading to libev signalling readiness on
		1680	the next iteration again (the connection still exists after all), and
		1681	typically causing the program to loop at 100% CPU usage.
		1682
		1683	Unfortunately, the set of errors that cause this issue differs between
		1684	operating systems, there is usually little the app can do to remedy the
		1685	situation, and no known thread-safe method of removing the connection to
		1686	cope with overload is known (to me).
		1687
		1688	One of the easiest ways to handle this situation is to just ignore it
		1689	- when the program encounters an overload, it will just loop until the
		1690	situation is over. While this is a form of busy waiting, no OS offers an
		1691	event-based way to handle this situation, so it's the best one can do.
		1692
		1693	A better way to handle the situation is to log any errors other than
		1694	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1695	messages, and continue as usual, which at least gives the user an idea of
		1696	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1697	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1698	usage.
		1699
		1700	If your program is single-threaded, then you could also keep a dummy file
		1701	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1702	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1703	close that fd, and create a new dummy fd. This will gracefully refuse
		1704	clients under typical overload conditions.
		1705
		1706	The last way to handle it is to simply log the error and C<exit>, as
		1707	is often done with C<malloc> failures, but this results in an easy
		1708	opportunity for a DoS attack.
1106		1709
1107	=head3 Watcher-Specific Functions	1710	=head3 Watcher-Specific Functions
1108		1711
1109	=over 4	1712	=over 4
1110		1713
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1714	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1715
1113	=item ev_io_set (ev_io *, int fd, int events)	1716	=item ev_io_set (ev_io *, int fd, int events)
1114		1717
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1718	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1719	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1720	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1721
1119	=item int fd [read-only]	1722	=item int fd [read-only]
1120		1723
1121	The file descriptor being watched.	1724	The file descriptor being watched.
1122		1725
…		…
1130		1733
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1734	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1735	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1736	attempt to read a whole line in the callback.
1134		1737
1135	static void	1738	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1739	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1740	{
1138	ev_io_stop (loop, w);	1741	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1742	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1743	}
1141		1744
1142	...	1745	...
1143	struct ev_loop *loop = ev_default_init (0);	1746	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1747	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1748	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1749	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1750	ev_run (loop, 0);
1148		1751
1149		1752
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1753	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1754
1152	Timer watchers are simple relative timers that generate an event after a	1755	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1756	given time, and optionally repeating in regular intervals after that.
1154		1757
1155	The timers are based on real time, that is, if you register an event that	1758	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1759	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1760	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1761	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1762	monotonic clock option helps a lot here).
		1763
		1764	The callback is guaranteed to be invoked only I<after> its timeout has
		1765	passed (not I<at>, so on systems with very low-resolution clocks this
		1766	might introduce a small delay). If multiple timers become ready during the
		1767	same loop iteration then the ones with earlier time-out values are invoked
		1768	before ones of the same priority with later time-out values (but this is
		1769	no longer true when a callback calls C<ev_run> recursively).
		1770
		1771	=head3 Be smart about timeouts
		1772
		1773	Many real-world problems involve some kind of timeout, usually for error
		1774	recovery. A typical example is an HTTP request - if the other side hangs,
		1775	you want to raise some error after a while.
		1776
		1777	What follows are some ways to handle this problem, from obvious and
		1778	inefficient to smart and efficient.
		1779
		1780	In the following, a 60 second activity timeout is assumed - a timeout that
		1781	gets reset to 60 seconds each time there is activity (e.g. each time some
		1782	data or other life sign was received).
		1783
		1784	=over 4
		1785
		1786	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1787
		1788	This is the most obvious, but not the most simple way: In the beginning,
		1789	start the watcher:
		1790
		1791	ev_timer_init (timer, callback, 60., 0.);
		1792	ev_timer_start (loop, timer);
		1793
		1794	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1795	and start it again:
		1796
		1797	ev_timer_stop (loop, timer);
		1798	ev_timer_set (timer, 60., 0.);
		1799	ev_timer_start (loop, timer);
		1800
		1801	This is relatively simple to implement, but means that each time there is
		1802	some activity, libev will first have to remove the timer from its internal
		1803	data structure and then add it again. Libev tries to be fast, but it's
		1804	still not a constant-time operation.
		1805
		1806	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1807
		1808	This is the easiest way, and involves using C<ev_timer_again> instead of
		1809	C<ev_timer_start>.
		1810
		1811	To implement this, configure an C<ev_timer> with a C<repeat> value
		1812	of C<60> and then call C<ev_timer_again> at start and each time you
		1813	successfully read or write some data. If you go into an idle state where
		1814	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1815	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1816
		1817	That means you can ignore both the C<ev_timer_start> function and the
		1818	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1819	member and C<ev_timer_again>.
		1820
		1821	At start:
		1822
		1823	ev_init (timer, callback);
		1824	timer->repeat = 60.;
		1825	ev_timer_again (loop, timer);
		1826
		1827	Each time there is some activity:
		1828
		1829	ev_timer_again (loop, timer);
		1830
		1831	It is even possible to change the time-out on the fly, regardless of
		1832	whether the watcher is active or not:
		1833
		1834	timer->repeat = 30.;
		1835	ev_timer_again (loop, timer);
		1836
		1837	This is slightly more efficient then stopping/starting the timer each time
		1838	you want to modify its timeout value, as libev does not have to completely
		1839	remove and re-insert the timer from/into its internal data structure.
		1840
		1841	It is, however, even simpler than the "obvious" way to do it.
		1842
		1843	=item 3. Let the timer time out, but then re-arm it as required.
		1844
		1845	This method is more tricky, but usually most efficient: Most timeouts are
		1846	relatively long compared to the intervals between other activity - in
		1847	our example, within 60 seconds, there are usually many I/O events with
		1848	associated activity resets.
		1849
		1850	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1851	but remember the time of last activity, and check for a real timeout only
		1852	within the callback:
		1853
		1854	ev_tstamp last_activity; // time of last activity
		1855
		1856	static void
		1857	callback (EV_P_ ev_timer *w, int revents)
		1858	{
		1859	ev_tstamp now = ev_now (EV_A);
		1860	ev_tstamp timeout = last_activity + 60.;
		1861
		1862	// if last_activity + 60. is older than now, we did time out
		1863	if (timeout < now)
		1864	{
		1865	// timeout occurred, take action
		1866	}
		1867	else
		1868	{
		1869	// callback was invoked, but there was some activity, re-arm
		1870	// the watcher to fire in last_activity + 60, which is
		1871	// guaranteed to be in the future, so "again" is positive:
		1872	w->repeat = timeout - now;
		1873	ev_timer_again (EV_A_ w);
		1874	}
		1875	}
		1876
		1877	To summarise the callback: first calculate the real timeout (defined
		1878	as "60 seconds after the last activity"), then check if that time has
		1879	been reached, which means something I<did>, in fact, time out. Otherwise
		1880	the callback was invoked too early (C<timeout> is in the future), so
		1881	re-schedule the timer to fire at that future time, to see if maybe we have
		1882	a timeout then.
		1883
		1884	Note how C<ev_timer_again> is used, taking advantage of the
		1885	C<ev_timer_again> optimisation when the timer is already running.
		1886
		1887	This scheme causes more callback invocations (about one every 60 seconds
		1888	minus half the average time between activity), but virtually no calls to
		1889	libev to change the timeout.
		1890
		1891	To start the timer, simply initialise the watcher and set C<last_activity>
		1892	to the current time (meaning we just have some activity :), then call the
		1893	callback, which will "do the right thing" and start the timer:
		1894
		1895	ev_init (timer, callback);
		1896	last_activity = ev_now (loop);
		1897	callback (loop, timer, EV_TIMER);
		1898
		1899	And when there is some activity, simply store the current time in
		1900	C<last_activity>, no libev calls at all:
		1901
		1902	last_activity = ev_now (loop);
		1903
		1904	This technique is slightly more complex, but in most cases where the
		1905	time-out is unlikely to be triggered, much more efficient.
		1906
		1907	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1908	callback :) - just change the timeout and invoke the callback, which will
		1909	fix things for you.
		1910
		1911	=item 4. Wee, just use a double-linked list for your timeouts.
		1912
		1913	If there is not one request, but many thousands (millions...), all
		1914	employing some kind of timeout with the same timeout value, then one can
		1915	do even better:
		1916
		1917	When starting the timeout, calculate the timeout value and put the timeout
		1918	at the I<end> of the list.
		1919
		1920	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1921	the list is expected to fire (for example, using the technique #3).
		1922
		1923	When there is some activity, remove the timer from the list, recalculate
		1924	the timeout, append it to the end of the list again, and make sure to
		1925	update the C<ev_timer> if it was taken from the beginning of the list.
		1926
		1927	This way, one can manage an unlimited number of timeouts in O(1) time for
		1928	starting, stopping and updating the timers, at the expense of a major
		1929	complication, and having to use a constant timeout. The constant timeout
		1930	ensures that the list stays sorted.
		1931
		1932	=back
		1933
		1934	So which method the best?
		1935
		1936	Method #2 is a simple no-brain-required solution that is adequate in most
		1937	situations. Method #3 requires a bit more thinking, but handles many cases
		1938	better, and isn't very complicated either. In most case, choosing either
		1939	one is fine, with #3 being better in typical situations.
		1940
		1941	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1942	rather complicated, but extremely efficient, something that really pays
		1943	off after the first million or so of active timers, i.e. it's usually
		1944	overkill :)
		1945
		1946	=head3 The special problem of time updates
		1947
		1948	Establishing the current time is a costly operation (it usually takes at
		1949	least two system calls): EV therefore updates its idea of the current
		1950	time only before and after C<ev_run> collects new events, which causes a
		1951	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1952	lots of events in one iteration.
1160		1953
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1954	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1955	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1956	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1957	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1958	timeout on the current time, use something like this to adjust for this:
1166		1959
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1960	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1961
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1962	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1963	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1964	()>.
		1965
		1966	=head3 The special problems of suspended animation
		1967
		1968	When you leave the server world it is quite customary to hit machines that
		1969	can suspend/hibernate - what happens to the clocks during such a suspend?
		1970
		1971	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1972	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1973	to run until the system is suspended, but they will not advance while the
		1974	system is suspended. That means, on resume, it will be as if the program
		1975	was frozen for a few seconds, but the suspend time will not be counted
		1976	towards C<ev_timer> when a monotonic clock source is used. The real time
		1977	clock advanced as expected, but if it is used as sole clocksource, then a
		1978	long suspend would be detected as a time jump by libev, and timers would
		1979	be adjusted accordingly.
		1980
		1981	I would not be surprised to see different behaviour in different between
		1982	operating systems, OS versions or even different hardware.
		1983
		1984	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1985	time jump in the monotonic clocks and the realtime clock. If the program
		1986	is suspended for a very long time, and monotonic clock sources are in use,
		1987	then you can expect C<ev_timer>s to expire as the full suspension time
		1988	will be counted towards the timers. When no monotonic clock source is in
		1989	use, then libev will again assume a timejump and adjust accordingly.
		1990
		1991	It might be beneficial for this latter case to call C<ev_suspend>
		1992	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1993	deterministic behaviour in this case (you can do nothing against
		1994	C<SIGSTOP>).
1172		1995
1173	=head3 Watcher-Specific Functions and Data Members	1996	=head3 Watcher-Specific Functions and Data Members
1174		1997
1175	=over 4	1998	=over 4
1176		1999
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2000	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		2001
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2002	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		2003
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	2004	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	2005	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	2006	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	2007	configured to trigger again C<repeat> seconds later, again, and again,
		2008	until stopped manually.
1185		2009
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	2010	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	2011	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	2012	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	2013	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	2014	do stuff) the timer will not fire more than once per event loop iteration.
1191		2015
1192	=item ev_timer_again (loop, ev_timer *)	2016	=item ev_timer_again (loop, ev_timer *)
1193		2017
1194	This will act as if the timer timed out and restart it again if it is	2018	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	2019	repeating. The exact semantics are:
1196		2020
1197	If the timer is pending, its pending status is cleared.	2021	If the timer is pending, its pending status is cleared.
1198		2022
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	2023	If the timer is started but non-repeating, stop it (as if it timed out).
1200		2024
1201	If the timer is repeating, either start it if necessary (with the	2025	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	2026	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		2027
1204	This sounds a bit complicated, but here is a useful and typical	2028	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	2029	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213		2030
1214	That means you can ignore the C<after> value and C<ev_timer_start>	2031	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216		2032
1217	ev_timer_init (timer, callback, 0., 5.);	2033	Returns the remaining time until a timer fires. If the timer is active,
1218	ev_timer_again (loop, timer);	2034	then this time is relative to the current event loop time, otherwise it's
1219	...	2035	the timeout value currently configured.
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225		2036
1226	This is more slightly efficient then stopping/starting the timer each time	2037	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1227	you want to modify its timeout value.	2038	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2039	will return C<4>. When the timer expires and is restarted, it will return
		2040	roughly C<7> (likely slightly less as callback invocation takes some time,
		2041	too), and so on.
1228		2042
1229	=item ev_tstamp repeat [read-write]	2043	=item ev_tstamp repeat [read-write]
1230		2044
1231	The current C<repeat> value. Will be used each time the watcher times out	2045	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	2046	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	2047	which is also when any modifications are taken into account.
1234		2048
1235	=back	2049	=back
1236		2050
1237	=head3 Examples	2051	=head3 Examples
1238		2052
1239	Example: Create a timer that fires after 60 seconds.	2053	Example: Create a timer that fires after 60 seconds.
1240		2054
1241	static void	2055	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2056	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	2057	{
1244	.. one minute over, w is actually stopped right here	2058	.. one minute over, w is actually stopped right here
1245	}	2059	}
1246		2060
1247	struct ev_timer mytimer;	2061	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2062	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	2063	ev_timer_start (loop, &mytimer);
1250		2064
1251	Example: Create a timeout timer that times out after 10 seconds of	2065	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	2066	inactivity.
1253		2067
1254	static void	2068	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2069	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	2070	{
1257	.. ten seconds without any activity	2071	.. ten seconds without any activity
1258	}	2072	}
1259		2073
1260	struct ev_timer mytimer;	2074	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2075	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	2076	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	2077	ev_run (loop, 0);
1264		2078
1265	// and in some piece of code that gets executed on any "activity":	2079	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	2080	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	2081	ev_timer_again (&mytimer);
1268		2082
1269		2083
1270	=head2 C<ev_periodic> - to cron or not to cron?	2084	=head2 C<ev_periodic> - to cron or not to cron?
1271		2085
1272	Periodic watchers are also timers of a kind, but they are very versatile	2086	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	2087	(and unfortunately a bit complex).
1274		2088
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2089	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1276	but on wallclock time (absolute time). You can tell a periodic watcher	2090	relative time, the physical time that passes) but on wall clock time
1277	to trigger "at" some specific point in time. For example, if you tell a	2091	(absolute time, the thing you can read on your calender or clock). The
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2092	difference is that wall clock time can run faster or slower than real
1279	+ 10.>) and then reset your system clock to the last year, then it will	2093	time, and time jumps are not uncommon (e.g. when you adjust your
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	2094	wrist-watch).
1281	roughly 10 seconds later).
1282		2095
1283	They can also be used to implement vastly more complex timers, such as	2096	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	2097	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	2098	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2099	not a delay) and then reset your system clock to January of the previous
		2100	year, then it will take a year or more to trigger the event (unlike an
		2101	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2102	it, as it uses a relative timeout).
1286		2103
		2104	C<ev_periodic> watchers can also be used to implement vastly more complex
		2105	timers, such as triggering an event on each "midnight, local time", or
		2106	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2107	those cannot react to time jumps.
		2108
1287	As with timers, the callback is guarenteed to be invoked only when the	2109	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	2110	point in time where it is supposed to trigger has passed. If multiple
1289	during the same loop iteration then order of execution is undefined.	2111	timers become ready during the same loop iteration then the ones with
		2112	earlier time-out values are invoked before ones with later time-out values
		2113	(but this is no longer true when a callback calls C<ev_run> recursively).
1290		2114
1291	=head3 Watcher-Specific Functions and Data Members	2115	=head3 Watcher-Specific Functions and Data Members
1292		2116
1293	=over 4	2117	=over 4
1294		2118
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2119	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		2120
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2121	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		2122
1299	Lots of arguments, lets sort it out... There are basically three modes of	2123	Lots of arguments, let's sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	2124	operation, and we will explain them from simplest to most complex:
1301		2125
1302	=over 4	2126	=over 4
1303		2127
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2128	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		2129
1306	In this configuration the watcher triggers an event at the wallclock time	2130	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	2131	time C<offset> has passed. It will not repeat and will not adjust when a
1308	that is, if it is to be run at January 1st 2011 then it will run when the	2132	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1309	system time reaches or surpasses this time.	2133	will be stopped and invoked when the system clock reaches or surpasses
		2134	this point in time.
1310		2135
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2136	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		2137
1313	In this mode the watcher will always be scheduled to time out at the next	2138	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	2139	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	2140	negative) and then repeat, regardless of any time jumps. The C<offset>
		2141	argument is merely an offset into the C<interval> periods.
1316		2142
1317	This can be used to create timers that do not drift with respect to system	2143	This can be used to create timers that do not drift with respect to the
1318	time:	2144	system clock, for example, here is an C<ev_periodic> that triggers each
		2145	hour, on the hour (with respect to UTC):
1319		2146
1320	ev_periodic_set (&periodic, 0., 3600., 0);	2147	ev_periodic_set (&periodic, 0., 3600., 0);
1321		2148
1322	This doesn't mean there will always be 3600 seconds in between triggers,	2149	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	2150	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	2151	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	2152	by 3600.
1326		2153
1327	Another way to think about it (for the mathematically inclined) is that	2154	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	2155	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	2156	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		2157
1331	For numerical stability it is preferable that the C<at> value is near	2158	The C<interval> I<MUST> be positive, and for numerical stability, the
1332	C<ev_now ()> (the current time), but there is no range requirement for	2159	interval value should be higher than C<1/8192> (which is around 100
1333	this value.	2160	microseconds) and C<offset> should be higher than C<0> and should have
		2161	at most a similar magnitude as the current time (say, within a factor of
		2162	ten). Typical values for offset are, in fact, C<0> or something between
		2163	C<0> and C<interval>, which is also the recommended range.
1334		2164
		2165	Note also that there is an upper limit to how often a timer can fire (CPU
		2166	speed for example), so if C<interval> is very small then timing stability
		2167	will of course deteriorate. Libev itself tries to be exact to be about one
		2168	millisecond (if the OS supports it and the machine is fast enough).
		2169
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2170	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		2171
1337	In this mode the values for C<interval> and C<at> are both being	2172	In this mode the values for C<interval> and C<offset> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	2173	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	2174	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	2175	current time as second argument.
1341		2176
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2177	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1343	ever, or make any event loop modifications>. If you need to stop it,	2178	or make ANY other event loop modifications whatsoever, unless explicitly
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	2179	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		2180
		2181	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2182	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2183	only event loop modification you are allowed to do).
		2184
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2185	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	2186	*w, ev_tstamp now)>, e.g.:
1349		2187
		2188	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2189	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	2190	{
1352	return now + 60.;	2191	return now + 60.;
1353	}	2192	}
1354		2193
1355	It must return the next time to trigger, based on the passed time value	2194	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	2195	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	2196	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	2197	might be called at other times, too.
1359		2198
1360	NOTE: I<< This callback must always return a time that is later than the	2199	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2200	equal to the passed C<now> value >>.
1362		2201
1363	This can be used to create very complex timers, such as a timer that	2202	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	2203	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	2204	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	2205	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	2206	reason I omitted it as an example).
1368		2207
1369	=back	2208	=back
…		…
1375	a different time than the last time it was called (e.g. in a crond like	2214	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	2215	program when the crontabs have changed).
1377		2216
1378	=item ev_tstamp ev_periodic_at (ev_periodic *)	2217	=item ev_tstamp ev_periodic_at (ev_periodic *)
1379		2218
1380	When active, returns the absolute time that the watcher is supposed to	2219	When active, returns the absolute time that the watcher is supposed
1381	trigger next.	2220	to trigger next. This is not the same as the C<offset> argument to
		2221	C<ev_periodic_set>, but indeed works even in interval and manual
		2222	rescheduling modes.
1382		2223
1383	=item ev_tstamp offset [read-write]	2224	=item ev_tstamp offset [read-write]
1384		2225
1385	When repeating, this contains the offset value, otherwise this is the	2226	When repeating, this contains the offset value, otherwise this is the
1386	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2227	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2228	although libev might modify this value for better numerical stability).
1387		2229
1388	Can be modified any time, but changes only take effect when the periodic	2230	Can be modified any time, but changes only take effect when the periodic
1389	timer fires or C<ev_periodic_again> is being called.	2231	timer fires or C<ev_periodic_again> is being called.
1390		2232
1391	=item ev_tstamp interval [read-write]	2233	=item ev_tstamp interval [read-write]
1392		2234
1393	The current interval value. Can be modified any time, but changes only	2235	The current interval value. Can be modified any time, but changes only
1394	take effect when the periodic timer fires or C<ev_periodic_again> is being	2236	take effect when the periodic timer fires or C<ev_periodic_again> is being
1395	called.	2237	called.
1396		2238
1397	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2239	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1398		2240
1399	The current reschedule callback, or C<0>, if this functionality is	2241	The current reschedule callback, or C<0>, if this functionality is
1400	switched off. Can be changed any time, but changes only take effect when	2242	switched off. Can be changed any time, but changes only take effect when
1401	the periodic timer fires or C<ev_periodic_again> is being called.	2243	the periodic timer fires or C<ev_periodic_again> is being called.
1402		2244
1403	=back	2245	=back
1404		2246
1405	=head3 Examples	2247	=head3 Examples
1406		2248
1407	Example: Call a callback every hour, or, more precisely, whenever the	2249	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	2250	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	2251	potentially a lot of jitter, but good long-term stability.
1410		2252
1411	static void	2253	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2254	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1413	{	2255	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	2256	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	2257	}
1416		2258
1417	struct ev_periodic hourly_tick;	2259	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2260	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	2261	ev_periodic_start (loop, &hourly_tick);
1420		2262
1421	Example: The same as above, but use a reschedule callback to do it:	2263	Example: The same as above, but use a reschedule callback to do it:
1422		2264
1423	#include <math.h>	2265	#include <math.h>
1424		2266
1425	static ev_tstamp	2267	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2268	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	2269	{
1428	return fmod (now, 3600.) + 3600.;	2270	return now + (3600. - fmod (now, 3600.));
1429	}	2271	}
1430		2272
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2273	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		2274
1433	Example: Call a callback every hour, starting now:	2275	Example: Call a callback every hour, starting now:
1434		2276
1435	struct ev_periodic hourly_tick;	2277	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	2278	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	2279	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	2280	ev_periodic_start (loop, &hourly_tick);
1439		2281
1440		2282
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	2283	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		2284
1443	Signal watchers will trigger an event when the process receives a specific	2285	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	2286	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	2287	will try its best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	2288	normal event processing, like any other event.
1447		2289
		2290	If you want signals to be delivered truly asynchronously, just use
		2291	C<sigaction> as you would do without libev and forget about sharing
		2292	the signal. You can even use C<ev_async> from a signal handler to
		2293	synchronously wake up an event loop.
		2294
1448	You can configure as many watchers as you like per signal. Only when the	2295	You can configure as many watchers as you like for the same signal, but
		2296	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2297	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2298	C<SIGINT> in both the default loop and another loop at the same time. At
		2299	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2300
1449	first watcher gets started will libev actually register a signal watcher	2301	When the first watcher gets started will libev actually register something
1450	with the kernel (thus it coexists with your own signal handlers as long	2302	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	2303	you don't register any with libev for the same signal).
1452	watcher for a signal is stopped libev will reset the signal handler to
1453	SIG_DFL (regardless of what it was set to before).
1454		2304
1455	If possible and supported, libev will install its handlers with	2305	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2306	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1457	interrupted. If you have a problem with syscalls getting interrupted by	2307	not be unduly interrupted. If you have a problem with system calls getting
1458	signals you can block all signals in an C<ev_check> watcher and unblock	2308	interrupted by signals you can block all signals in an C<ev_check> watcher
1459	them in an C<ev_prepare> watcher.	2309	and unblock them in an C<ev_prepare> watcher.
		2310
		2311	=head3 The special problem of inheritance over fork/execve/pthread_create
		2312
		2313	Both the signal mask (C<sigprocmask>) and the signal disposition
		2314	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2315	stopping it again), that is, libev might or might not block the signal,
		2316	and might or might not set or restore the installed signal handler (but
		2317	see C<EVFLAG_NOSIGMASK>).
		2318
		2319	While this does not matter for the signal disposition (libev never
		2320	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2321	C<execve>), this matters for the signal mask: many programs do not expect
		2322	certain signals to be blocked.
		2323
		2324	This means that before calling C<exec> (from the child) you should reset
		2325	the signal mask to whatever "default" you expect (all clear is a good
		2326	choice usually).
		2327
		2328	The simplest way to ensure that the signal mask is reset in the child is
		2329	to install a fork handler with C<pthread_atfork> that resets it. That will
		2330	catch fork calls done by libraries (such as the libc) as well.
		2331
		2332	In current versions of libev, the signal will not be blocked indefinitely
		2333	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2334	the window of opportunity for problems, it will not go away, as libev
		2335	I<has> to modify the signal mask, at least temporarily.
		2336
		2337	So I can't stress this enough: I<If you do not reset your signal mask when
		2338	you expect it to be empty, you have a race condition in your code>. This
		2339	is not a libev-specific thing, this is true for most event libraries.
		2340
		2341	=head3 The special problem of threads signal handling
		2342
		2343	POSIX threads has problematic signal handling semantics, specifically,
		2344	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2345	threads in a process block signals, which is hard to achieve.
		2346
		2347	When you want to use sigwait (or mix libev signal handling with your own
		2348	for the same signals), you can tackle this problem by globally blocking
		2349	all signals before creating any threads (or creating them with a fully set
		2350	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2351	loops. Then designate one thread as "signal receiver thread" which handles
		2352	these signals. You can pass on any signals that libev might be interested
		2353	in by calling C<ev_feed_signal>.
1460		2354
1461	=head3 Watcher-Specific Functions and Data Members	2355	=head3 Watcher-Specific Functions and Data Members
1462		2356
1463	=over 4	2357	=over 4
1464		2358
…		…
1475		2369
1476	=back	2370	=back
1477		2371
1478	=head3 Examples	2372	=head3 Examples
1479		2373
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2374	Example: Try to exit cleanly on SIGINT.
1481		2375
1482	static void	2376	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2377	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2378	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2379	ev_break (loop, EVBREAK_ALL);
1486	}	2380	}
1487		2381
1488	struct ev_signal signal_watcher;	2382	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2383	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2384	ev_signal_start (loop, &signal_watcher);
1491		2385
1492		2386
1493	=head2 C<ev_child> - watch out for process status changes	2387	=head2 C<ev_child> - watch out for process status changes
1494		2388
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2389	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	2390	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	2391	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	2392	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2393	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2394	forking and then immediately registering a watcher for the child is fine,
		2395	but forking and registering a watcher a few event loop iterations later or
		2396	in the next callback invocation is not.
1500		2397
1501	Only the default event loop is capable of handling signals, and therefore	2398	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2399	you can only register child watchers in the default event loop.
		2400
		2401	Due to some design glitches inside libev, child watchers will always be
		2402	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2403	libev)
1503		2404
1504	=head3 Process Interaction	2405	=head3 Process Interaction
1505		2406
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2407	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2408	initialised. This is necessary to guarantee proper behaviour even if the
1508	the first child watcher is started after the child exits. The occurance	2409	first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2410	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2411	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2412	children, even ones not watched.
1512		2413
1513	=head3 Overriding the Built-In Processing	2414	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2418	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2419	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2420	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	2421	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	2422	that, so other libev users can use C<ev_child> watchers freely.
		2423
		2424	=head3 Stopping the Child Watcher
		2425
		2426	Currently, the child watcher never gets stopped, even when the
		2427	child terminates, so normally one needs to stop the watcher in the
		2428	callback. Future versions of libev might stop the watcher automatically
		2429	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2430	problem).
1522		2431
1523	=head3 Watcher-Specific Functions and Data Members	2432	=head3 Watcher-Specific Functions and Data Members
1524		2433
1525	=over 4	2434	=over 4
1526		2435
…		…
1555	=head3 Examples	2464	=head3 Examples
1556		2465
1557	Example: C<fork()> a new process and install a child handler to wait for	2466	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2467	its completion.
1559		2468
1560	ev_child cw;	2469	ev_child cw;
1561		2470
1562	static void	2471	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2472	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2473	{
1565	ev_child_stop (EV_A_ w);	2474	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2475	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2476	}
1568		2477
1569	pid_t pid = fork ();	2478	pid_t pid = fork ();
1570		2479
1571	if (pid < 0)	2480	if (pid < 0)
1572	// error	2481	// error
1573	else if (pid == 0)	2482	else if (pid == 0)
1574	{	2483	{
1575	// the forked child executes here	2484	// the forked child executes here
1576	exit (1);	2485	exit (1);
1577	}	2486	}
1578	else	2487	else
1579	{	2488	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2489	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2490	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2491	}
1583		2492
1584		2493
1585	=head2 C<ev_stat> - did the file attributes just change?	2494	=head2 C<ev_stat> - did the file attributes just change?
1586		2495
1587	This watches a filesystem path for attribute changes. That is, it calls	2496	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	2497	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	2498	and sees if it changed compared to the last time, invoking the callback if
		2499	it did.
1590		2500
1591	The path does not need to exist: changing from "path exists" to "path does	2501	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	2502	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	2503	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	2504	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2505	least one) and all the other fields of the stat buffer having unspecified
		2506	contents.
1596		2507
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2508	The path I<must not> end in a slash or contain special components such as
		2509	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	2510	your working directory changes, then the behaviour is undefined.
1599		2511
1600	Since there is no standard to do this, the portable implementation simply	2512	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2513	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2514	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	2515	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	2516	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2517	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	2518	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2519	currently around C<0.1>, but that's usually overkill.
1608		2520
1609	This watcher type is not meant for massive numbers of stat watchers,	2521	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2522	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2523	resource-intensive.
1612		2524
1613	At the time of this writing, only the Linux inotify interface is	2525	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2526	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader, note, however, that the author sees no way of implementing ev_stat	2527	exercise for the reader. Note, however, that the author sees no way of
1616	semantics with kqueue). Inotify will be used to give hints only and should	2528	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	not change the semantics of C<ev_stat> watchers, which means that libev
1618	sometimes needs to fall back to regular polling again even with inotify,
1619	but changes are usually detected immediately, and if the file exists there
1620	will be no polling.
1621		2529
1622	=head3 ABI Issues (Largefile Support)	2530	=head3 ABI Issues (Largefile Support)
1623		2531
1624	Libev by default (unless the user overrides this) uses the default	2532	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	2533	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	2534	support disabled by default, you get the 32 bit version of the stat
1627	structure. When using the library from programs that change the ABI to	2535	structure. When using the library from programs that change the ABI to
1628	use 64 bit file offsets the programs will fail. In that case you have to	2536	use 64 bit file offsets the programs will fail. In that case you have to
1629	compile libev with the same flags to get binary compatibility. This is	2537	compile libev with the same flags to get binary compatibility. This is
1630	obviously the case with any flags that change the ABI, but the problem is	2538	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	2539	most noticeably displayed with ev_stat and large file support.
1632		2540
1633	=head3 Inotify	2541	The solution for this is to lobby your distribution maker to make large
		2542	file interfaces available by default (as e.g. FreeBSD does) and not
		2543	optional. Libev cannot simply switch on large file support because it has
		2544	to exchange stat structures with application programs compiled using the
		2545	default compilation environment.
1634		2546
		2547	=head3 Inotify and Kqueue
		2548
1635	When C<inotify (7)> support has been compiled into libev (generally only	2549	When C<inotify (7)> support has been compiled into libev and present at
1636	available on Linux) and present at runtime, it will be used to speed up	2550	runtime, it will be used to speed up change detection where possible. The
1637	change detection where possible. The inotify descriptor will be created lazily	2551	inotify descriptor will be created lazily when the first C<ev_stat>
1638	when the first C<ev_stat> watcher is being started.	2552	watcher is being started.
1639		2553
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	2554	Inotify presence does not change the semantics of C<ev_stat> watchers
1641	except that changes might be detected earlier, and in some cases, to avoid	2555	except that changes might be detected earlier, and in some cases, to avoid
1642	making regular C<stat> calls. Even in the presence of inotify support	2556	making regular C<stat> calls. Even in the presence of inotify support
1643	there are many cases where libev has to resort to regular C<stat> polling.	2557	there are many cases where libev has to resort to regular C<stat> polling,
		2558	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2559	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2560	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2561	xfs are fully working) libev usually gets away without polling.
1644		2562
1645	(There is no support for kqueue, as apparently it cannot be used to	2563	There is no support for kqueue, as apparently it cannot be used to
1646	implement this functionality, due to the requirement of having a file	2564	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	2565	descriptor open on the object at all times, and detecting renames, unlinks
		2566	etc. is difficult.
		2567
		2568	=head3 C<stat ()> is a synchronous operation
		2569
		2570	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2571	the process. The exception are C<ev_stat> watchers - those call C<stat
		2572	()>, which is a synchronous operation.
		2573
		2574	For local paths, this usually doesn't matter: unless the system is very
		2575	busy or the intervals between stat's are large, a stat call will be fast,
		2576	as the path data is usually in memory already (except when starting the
		2577	watcher).
		2578
		2579	For networked file systems, calling C<stat ()> can block an indefinite
		2580	time due to network issues, and even under good conditions, a stat call
		2581	often takes multiple milliseconds.
		2582
		2583	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2584	paths, although this is fully supported by libev.
1648		2585
1649	=head3 The special problem of stat time resolution	2586	=head3 The special problem of stat time resolution
1650		2587
1651	The C<stat ()> syscall only supports full-second resolution portably, and	2588	The C<stat ()> system call only supports full-second resolution portably,
1652	even on systems where the resolution is higher, many filesystems still	2589	and even on systems where the resolution is higher, most file systems
1653	only support whole seconds.	2590	still only support whole seconds.
1654		2591
1655	That means that, if the time is the only thing that changes, you can	2592	That means that, if the time is the only thing that changes, you can
1656	easily miss updates: on the first update, C<ev_stat> detects a change and	2593	easily miss updates: on the first update, C<ev_stat> detects a change and
1657	calls your callback, which does something. When there is another update	2594	calls your callback, which does something. When there is another update
1658	within the same second, C<ev_stat> will be unable to detect it as the stat	2595	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	2596	stat data does change in other ways (e.g. file size).
1660		2597
1661	The solution to this is to delay acting on a change for slightly more	2598	The solution to this is to delay acting on a change for slightly more
1662	than a second (or till slightly after the next full second boundary), using	2599	than a second (or till slightly after the next full second boundary), using
1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2600	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	2601	ev_timer_again (loop, w)>).
…		…
1684	C<path>. The C<interval> is a hint on how quickly a change is expected to	2621	C<path>. The C<interval> is a hint on how quickly a change is expected to
1685	be detected and should normally be specified as C<0> to let libev choose	2622	be detected and should normally be specified as C<0> to let libev choose
1686	a suitable value. The memory pointed to by C<path> must point to the same	2623	a suitable value. The memory pointed to by C<path> must point to the same
1687	path for as long as the watcher is active.	2624	path for as long as the watcher is active.
1688		2625
1689	The callback will receive C<EV_STAT> when a change was detected, relative	2626	The callback will receive an C<EV_STAT> event when a change was detected,
1690	to the attributes at the time the watcher was started (or the last change	2627	relative to the attributes at the time the watcher was started (or the
1691	was detected).	2628	last change was detected).
1692		2629
1693	=item ev_stat_stat (loop, ev_stat *)	2630	=item ev_stat_stat (loop, ev_stat *)
1694		2631
1695	Updates the stat buffer immediately with new values. If you change the	2632	Updates the stat buffer immediately with new values. If you change the
1696	watched path in your callback, you could call this function to avoid	2633	watched path in your callback, you could call this function to avoid
…		…
1717		2654
1718	The specified interval.	2655	The specified interval.
1719		2656
1720	=item const char *path [read-only]	2657	=item const char *path [read-only]
1721		2658
1722	The filesystem path that is being watched.	2659	The file system path that is being watched.
1723		2660
1724	=back	2661	=back
1725		2662
1726	=head3 Examples	2663	=head3 Examples
1727		2664
1728	Example: Watch C</etc/passwd> for attribute changes.	2665	Example: Watch C</etc/passwd> for attribute changes.
1729		2666
1730	static void	2667	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2668	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	2669	{
1733	/* /etc/passwd changed in some way */	2670	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	2671	if (w->attr.st_nlink)
1735	{	2672	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2673	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2674	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2675	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	2676	}
1740	else	2677	else
1741	/* you shalt not abuse printf for puts */	2678	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	2679	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	2680	"if this is windows, they already arrived\n");
1744	}	2681	}
1745		2682
1746	...	2683	...
1747	ev_stat passwd;	2684	ev_stat passwd;
1748		2685
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2686	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	2687	ev_stat_start (loop, &passwd);
1751		2688
1752	Example: Like above, but additionally use a one-second delay so we do not	2689	Example: Like above, but additionally use a one-second delay so we do not
1753	miss updates (however, frequent updates will delay processing, too, so	2690	miss updates (however, frequent updates will delay processing, too, so
1754	one might do the work both on C<ev_stat> callback invocation I<and> on	2691	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	2692	C<ev_timer> callback invocation).
1756		2693
1757	static ev_stat passwd;	2694	static ev_stat passwd;
1758	static ev_timer timer;	2695	static ev_timer timer;
1759		2696
1760	static void	2697	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	2698	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	2699	{
1763	ev_timer_stop (EV_A_ w);	2700	ev_timer_stop (EV_A_ w);
1764		2701
1765	/* now it's one second after the most recent passwd change */	2702	/* now it's one second after the most recent passwd change */
1766	}	2703	}
1767		2704
1768	static void	2705	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	2706	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	2707	{
1771	/* reset the one-second timer */	2708	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	2709	ev_timer_again (EV_A_ &timer);
1773	}	2710	}
1774		2711
1775	...	2712	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2713	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	2714	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	2715	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		2716
1780		2717
1781	=head2 C<ev_idle> - when you've got nothing better to do...	2718	=head2 C<ev_idle> - when you've got nothing better to do...
1782		2719
1783	Idle watchers trigger events when no other events of the same or higher	2720	Idle watchers trigger events when no other events of the same or higher
1784	priority are pending (prepare, check and other idle watchers do not	2721	priority are pending (prepare, check and other idle watchers do not count
1785	count).	2722	as receiving "events").
1786		2723
1787	That is, as long as your process is busy handling sockets or timeouts	2724	That is, as long as your process is busy handling sockets or timeouts
1788	(or even signals, imagine) of the same or higher priority it will not be	2725	(or even signals, imagine) of the same or higher priority it will not be
1789	triggered. But when your process is idle (or only lower-priority watchers	2726	triggered. But when your process is idle (or only lower-priority watchers
1790	are pending), the idle watchers are being called once per event loop	2727	are pending), the idle watchers are being called once per event loop
…		…
1801		2738
1802	=head3 Watcher-Specific Functions and Data Members	2739	=head3 Watcher-Specific Functions and Data Members
1803		2740
1804	=over 4	2741	=over 4
1805		2742
1806	=item ev_idle_init (ev_signal *, callback)	2743	=item ev_idle_init (ev_idle *, callback)
1807		2744
1808	Initialises and configures the idle watcher - it has no parameters of any	2745	Initialises and configures the idle watcher - it has no parameters of any
1809	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2746	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1810	believe me.	2747	believe me.
1811		2748
…		…
1814	=head3 Examples	2751	=head3 Examples
1815		2752
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2753	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	2754	callback, free it. Also, use no error checking, as usual.
1818		2755
1819	static void	2756	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2757	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1821	{	2758	{
1822	free (w);	2759	free (w);
1823	// now do something you wanted to do when the program has	2760	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	2761	// no longer anything immediate to do.
1825	}	2762	}
1826		2763
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2764	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2765	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2766	ev_idle_start (loop, idle_watcher);
1830		2767
1831		2768
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2769	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2770
1834	Prepare and check watchers are usually (but not always) used in tandem:	2771	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2772	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2773	afterwards.
1837		2774
1838	You I<must not> call C<ev_loop> or similar functions that enter	2775	You I<must not> call C<ev_run> or similar functions that enter
1839	the current event loop from either C<ev_prepare> or C<ev_check>	2776	the current event loop from either C<ev_prepare> or C<ev_check>
1840	watchers. Other loops than the current one are fine, however. The	2777	watchers. Other loops than the current one are fine, however. The
1841	rationale behind this is that you do not need to check for recursion in	2778	rationale behind this is that you do not need to check for recursion in
1842	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2779	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1843	C<ev_check> so if you have one watcher of each kind they will always be	2780	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2781	called in pairs bracketing the blocking call.
1845		2782
1846	Their main purpose is to integrate other event mechanisms into libev and	2783	Their main purpose is to integrate other event mechanisms into libev and
1847	their use is somewhat advanced. This could be used, for example, to track	2784	their use is somewhat advanced. They could be used, for example, to track
1848	variable changes, implement your own watchers, integrate net-snmp or a	2785	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2786	coroutine library and lots more. They are also occasionally useful if
1850	you cache some data and want to flush it before blocking (for example,	2787	you cache some data and want to flush it before blocking (for example,
1851	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2788	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2789	watcher).
1853		2790
1854	This is done by examining in each prepare call which file descriptors need	2791	This is done by examining in each prepare call which file descriptors
1855	to be watched by the other library, registering C<ev_io> watchers for	2792	need to be watched by the other library, registering C<ev_io> watchers
1856	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2793	for them and starting an C<ev_timer> watcher for any timeouts (many
1857	provide just this functionality). Then, in the check watcher you check for	2794	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2795	you check for any events that occurred (by checking the pending status
1859	and stopping them) and call back into the library. The I/O and timer	2796	of all watchers and stopping them) and call back into the library. The
1860	callbacks will never actually be called (but must be valid nevertheless,	2797	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2798	nevertheless, because you never know, you know?).
1862		2799
1863	As another example, the Perl Coro module uses these hooks to integrate	2800	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2801	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2802	during each prepare and only letting the process block if no coroutines
1866	are ready to run (it's actually more complicated: it only runs coroutines	2803	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1869	loop from blocking if lower-priority coroutines are active, thus mapping	2806	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2807	low-priority coroutines to idle/background tasks).
1871		2808
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2809	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1873	priority, to ensure that they are being run before any other watchers	2810	priority, to ensure that they are being run before any other watchers
		2811	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2812
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2813	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1875	too) should not activate ("feed") events into libev. While libev fully	2814	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2815	might get executed before other C<ev_check> watchers did their job. As
1877	did their job. As C<ev_check> watchers are often used to embed other	2816	C<ev_check> watchers are often used to embed other (non-libev) event
1878	(non-libev) event loops those other event loops might be in an unusable	2817	loops those other event loops might be in an unusable state until their
1879	state until their C<ev_check> watcher ran (always remind yourself to	2818	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2819	others).
1881		2820
1882	=head3 Watcher-Specific Functions and Data Members	2821	=head3 Watcher-Specific Functions and Data Members
1883		2822
1884	=over 4	2823	=over 4
1885		2824
…		…
1887		2826
1888	=item ev_check_init (ev_check *, callback)	2827	=item ev_check_init (ev_check *, callback)
1889		2828
1890	Initialises and configures the prepare or check watcher - they have no	2829	Initialises and configures the prepare or check watcher - they have no
1891	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2830	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1892	macros, but using them is utterly, utterly and completely pointless.	2831	macros, but using them is utterly, utterly, utterly and completely
		2832	pointless.
1893		2833
1894	=back	2834	=back
1895		2835
1896	=head3 Examples	2836	=head3 Examples
1897		2837
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2846	and in a check watcher, destroy them and call into libadns. What follows
1907	is pseudo-code only of course. This requires you to either use a low	2847	is pseudo-code only of course. This requires you to either use a low
1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2848	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909	the callbacks for the IO/timeout watchers might not have been called yet.	2849	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2850
1911	static ev_io iow [nfd];	2851	static ev_io iow [nfd];
1912	static ev_timer tw;	2852	static ev_timer tw;
1913		2853
1914	static void	2854	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2855	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1916	{	2856	{
1917	}	2857	}
1918		2858
1919	// create io watchers for each fd and a timer before blocking	2859	// create io watchers for each fd and a timer before blocking
1920	static void	2860	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2861	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1922	{	2862	{
1923	int timeout = 3600000;	2863	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2864	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2865	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2866	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2867
1928	/* the callback is illegal, but won't be called as we stop during check */	2868	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2869	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1930	ev_timer_start (loop, &tw);	2870	ev_timer_start (loop, &tw);
1931		2871
1932	// create one ev_io per pollfd	2872	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2873	for (int i = 0; i < nfd; ++i)
1934	{	2874	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2875	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2876	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2877	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2878
1939	fds [i].revents = 0;	2879	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2880	ev_io_start (loop, iow + i);
1941	}	2881	}
1942	}	2882	}
1943		2883
1944	// stop all watchers after blocking	2884	// stop all watchers after blocking
1945	static void	2885	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2886	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1947	{	2887	{
1948	ev_timer_stop (loop, &tw);	2888	ev_timer_stop (loop, &tw);
1949		2889
1950	for (int i = 0; i < nfd; ++i)	2890	for (int i = 0; i < nfd; ++i)
1951	{	2891	{
1952	// set the relevant poll flags	2892	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2893	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2894	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2895	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2896	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2897	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2898
1959	// now stop the watcher	2899	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2900	ev_io_stop (loop, iow + i);
1961	}	2901	}
1962		2902
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2903	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2904	}
1965		2905
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2906	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967	in the prepare watcher and would dispose of the check watcher.	2907	in the prepare watcher and would dispose of the check watcher.
1968		2908
1969	Method 3: If the module to be embedded supports explicit event	2909	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2910	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2911	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2912
1973	static void	2913	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2914	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2915	{
1976	adns_state ads = (adns_state)w->data;	2916	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2917	update_now (EV_A);
1978		2918
1979	adns_processtimeouts (ads, &tv_now);	2919	adns_processtimeouts (ads, &tv_now);
1980	}	2920	}
1981		2921
1982	static void	2922	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2923	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2924	{
1985	adns_state ads = (adns_state)w->data;	2925	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2926	update_now (EV_A);
1987		2927
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2928	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2929	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2930	}
1991		2931
1992	// do not ever call adns_afterpoll	2932	// do not ever call adns_afterpoll
1993		2933
1994	Method 4: Do not use a prepare or check watcher because the module you	2934	Method 4: Do not use a prepare or check watcher because the module you
1995	want to embed is too inflexible to support it. Instead, youc na override	2935	want to embed is not flexible enough to support it. Instead, you can
1996	their poll function. The drawback with this solution is that the main	2936	override their poll function. The drawback with this solution is that the
1997	loop is now no longer controllable by EV. The C<Glib::EV> module does	2937	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2938	this approach, effectively embedding EV as a client into the horrible
		2939	libglib event loop.
1999		2940
2000	static gint	2941	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2942	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2943	{
2003	int got_events = 0;	2944	int got_events = 0;
2004		2945
2005	for (n = 0; n < nfds; ++n)	2946	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2947	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2948
2008	if (timeout >= 0)	2949	if (timeout >= 0)
2009	// create/start timer	2950	// create/start timer
2010		2951
2011	// poll	2952	// poll
2012	ev_loop (EV_A_ 0);	2953	ev_run (EV_A_ 0);
2013		2954
2014	// stop timer again	2955	// stop timer again
2015	if (timeout >= 0)	2956	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2957	ev_timer_stop (EV_A_ &to);
2017		2958
2018	// stop io watchers again - their callbacks should have set	2959	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2960	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2961	ev_io_stop (EV_A_ iow [n]);
2021		2962
2022	return got_events;	2963	return got_events;
2023	}	2964	}
2024		2965
2025		2966
2026	=head2 C<ev_embed> - when one backend isn't enough...	2967	=head2 C<ev_embed> - when one backend isn't enough...
2027		2968
2028	This is a rather advanced watcher type that lets you embed one event loop	2969	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2975	prioritise I/O.
2035		2976
2036	As an example for a bug workaround, the kqueue backend might only support	2977	As an example for a bug workaround, the kqueue backend might only support
2037	sockets on some platform, so it is unusable as generic backend, but you	2978	sockets on some platform, so it is unusable as generic backend, but you
2038	still want to make use of it because you have many sockets and it scales	2979	still want to make use of it because you have many sockets and it scales
2039	so nicely. In this case, you would create a kqueue-based loop and embed it	2980	so nicely. In this case, you would create a kqueue-based loop and embed
2040	into your default loop (which might use e.g. poll). Overall operation will	2981	it into your default loop (which might use e.g. poll). Overall operation
2041	be a bit slower because first libev has to poll and then call kevent, but	2982	will be a bit slower because first libev has to call C<poll> and then
2042	at least you can use both at what they are best.	2983	C<kevent>, but at least you can use both mechanisms for what they are
		2984	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2985
2044	As for prioritising I/O: rarely you have the case where some fds have	2986	As for prioritising I/O: under rare circumstances you have the case where
2045	to be watched and handled very quickly (with low latency), and even	2987	some fds have to be watched and handled very quickly (with low latency),
2046	priorities and idle watchers might have too much overhead. In this case	2988	and even priorities and idle watchers might have too much overhead. In
2047	you would put all the high priority stuff in one loop and all the rest in	2989	this case you would put all the high priority stuff in one loop and all
2048	a second one, and embed the second one in the first.	2990	the rest in a second one, and embed the second one in the first.
2049		2991
2050	As long as the watcher is active, the callback will be invoked every time	2992	As long as the watcher is active, the callback will be invoked every
2051	there might be events pending in the embedded loop. The callback must then	2993	time there might be events pending in the embedded loop. The callback
2052	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2994	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2053	their callbacks (you could also start an idle watcher to give the embedded	2995	sweep and invoke their callbacks (the callback doesn't need to invoke the
2054	loop strictly lower priority for example). You can also set the callback	2996	C<ev_embed_sweep> function directly, it could also start an idle watcher
2055	to C<0>, in which case the embed watcher will automatically execute the	2997	to give the embedded loop strictly lower priority for example).
2056	embedded loop sweep.
2057		2998
2058	As long as the watcher is started it will automatically handle events. The	2999	You can also set the callback to C<0>, in which case the embed watcher
2059	callback will be invoked whenever some events have been handled. You can	3000	will automatically execute the embedded loop sweep whenever necessary.
2060	set the callback to C<0> to avoid having to specify one if you are not
2061	interested in that.
2062		3001
2063	Also, there have not currently been made special provisions for forking:	3002	Fork detection will be handled transparently while the C<ev_embed> watcher
2064	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3003	is active, i.e., the embedded loop will automatically be forked when the
2065	but you will also have to stop and restart any C<ev_embed> watchers	3004	embedding loop forks. In other cases, the user is responsible for calling
2066	yourself.	3005	C<ev_loop_fork> on the embedded loop.
2067		3006
2068	Unfortunately, not all backends are embeddable, only the ones returned by	3007	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3008	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	3009	portable one.
2071		3010
2072	So when you want to use this feature you will always have to be prepared	3011	So when you want to use this feature you will always have to be prepared
2073	that you cannot get an embeddable loop. The recommended way to get around	3012	that you cannot get an embeddable loop. The recommended way to get around
2074	this is to have a separate variables for your embeddable loop, try to	3013	this is to have a separate variables for your embeddable loop, try to
2075	create it, and if that fails, use the normal loop for everything.	3014	create it, and if that fails, use the normal loop for everything.
2076		3015
		3016	=head3 C<ev_embed> and fork
		3017
		3018	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3019	automatically be applied to the embedded loop as well, so no special
		3020	fork handling is required in that case. When the watcher is not running,
		3021	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3022	as applicable.
		3023
2077	=head3 Watcher-Specific Functions and Data Members	3024	=head3 Watcher-Specific Functions and Data Members
2078		3025
2079	=over 4	3026	=over 4
2080		3027
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3028	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		3031
2085	Configures the watcher to embed the given loop, which must be	3032	Configures the watcher to embed the given loop, which must be
2086	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3033	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087	invoked automatically, otherwise it is the responsibility of the callback	3034	invoked automatically, otherwise it is the responsibility of the callback
2088	to invoke it (it will continue to be called until the sweep has been done,	3035	to invoke it (it will continue to be called until the sweep has been done,
2089	if you do not want thta, you need to temporarily stop the embed watcher).	3036	if you do not want that, you need to temporarily stop the embed watcher).
2090		3037
2091	=item ev_embed_sweep (loop, ev_embed *)	3038	=item ev_embed_sweep (loop, ev_embed *)
2092		3039
2093	Make a single, non-blocking sweep over the embedded loop. This works	3040	Make a single, non-blocking sweep over the embedded loop. This works
2094	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3041	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2095	apropriate way for embedded loops.	3042	appropriate way for embedded loops.
2096		3043
2097	=item struct ev_loop *other [read-only]	3044	=item struct ev_loop *other [read-only]
2098		3045
2099	The embedded event loop.	3046	The embedded event loop.
2100		3047
…		…
2102		3049
2103	=head3 Examples	3050	=head3 Examples
2104		3051
2105	Example: Try to get an embeddable event loop and embed it into the default	3052	Example: Try to get an embeddable event loop and embed it into the default
2106	event loop. If that is not possible, use the default loop. The default	3053	event loop. If that is not possible, use the default loop. The default
2107	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3054	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3055	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	3056	used).
2110		3057
2111	struct ev_loop *loop_hi = ev_default_init (0);	3058	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	3059	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	3060	ev_embed embed;
2114		3061
2115	// see if there is a chance of getting one that works	3062	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	3063	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3064	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3065	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	3066	: 0;
2120		3067
2121	// if we got one, then embed it, otherwise default to loop_hi	3068	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	3069	if (loop_lo)
2123	{	3070	{
2124	ev_embed_init (&embed, 0, loop_lo);	3071	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	3072	ev_embed_start (loop_hi, &embed);
2126	}	3073	}
2127	else	3074	else
2128	loop_lo = loop_hi;	3075	loop_lo = loop_hi;
2129		3076
2130	Example: Check if kqueue is available but not recommended and create	3077	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	3078	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	3079	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3080	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		3081
2135	struct ev_loop *loop = ev_default_init (0);	3082	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	3083	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	3084	ev_embed embed;
2138		3085
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3086	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3087	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	3088	{
2142	ev_embed_init (&embed, 0, loop_socket);	3089	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	3090	ev_embed_start (loop, &embed);
2144	}	3091	}
2145		3092
2146	if (!loop_socket)	3093	if (!loop_socket)
2147	loop_socket = loop;	3094	loop_socket = loop;
2148		3095
2149	// now use loop_socket for all sockets, and loop for everything else	3096	// now use loop_socket for all sockets, and loop for everything else
2150		3097
2151		3098
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3099	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		3100
2154	Fork watchers are called when a C<fork ()> was detected (usually because	3101	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2157	event loop blocks next and before C<ev_check> watchers are being called,	3104	event loop blocks next and before C<ev_check> watchers are being called,
2158	and only in the child after the fork. If whoever good citizen calling	3105	and only in the child after the fork. If whoever good citizen calling
2159	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3106	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2160	handlers will be invoked, too, of course.	3107	handlers will be invoked, too, of course.
2161		3108
		3109	=head3 The special problem of life after fork - how is it possible?
		3110
		3111	Most uses of C<fork()> consist of forking, then some simple calls to set
		3112	up/change the process environment, followed by a call to C<exec()>. This
		3113	sequence should be handled by libev without any problems.
		3114
		3115	This changes when the application actually wants to do event handling
		3116	in the child, or both parent in child, in effect "continuing" after the
		3117	fork.
		3118
		3119	The default mode of operation (for libev, with application help to detect
		3120	forks) is to duplicate all the state in the child, as would be expected
		3121	when I<either> the parent I<or> the child process continues.
		3122
		3123	When both processes want to continue using libev, then this is usually the
		3124	wrong result. In that case, usually one process (typically the parent) is
		3125	supposed to continue with all watchers in place as before, while the other
		3126	process typically wants to start fresh, i.e. without any active watchers.
		3127
		3128	The cleanest and most efficient way to achieve that with libev is to
		3129	simply create a new event loop, which of course will be "empty", and
		3130	use that for new watchers. This has the advantage of not touching more
		3131	memory than necessary, and thus avoiding the copy-on-write, and the
		3132	disadvantage of having to use multiple event loops (which do not support
		3133	signal watchers).
		3134
		3135	When this is not possible, or you want to use the default loop for
		3136	other reasons, then in the process that wants to start "fresh", call
		3137	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3138	Destroying the default loop will "orphan" (not stop) all registered
		3139	watchers, so you have to be careful not to execute code that modifies
		3140	those watchers. Note also that in that case, you have to re-register any
		3141	signal watchers.
		3142
2162	=head3 Watcher-Specific Functions and Data Members	3143	=head3 Watcher-Specific Functions and Data Members
2163		3144
2164	=over 4	3145	=over 4
2165		3146
2166	=item ev_fork_init (ev_signal *, callback)	3147	=item ev_fork_init (ev_fork *, callback)
2167		3148
2168	Initialises and configures the fork watcher - it has no parameters of any	3149	Initialises and configures the fork watcher - it has no parameters of any
2169	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3150	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2170	believe me.	3151	really.
2171		3152
2172	=back	3153	=back
2173		3154
2174		3155
		3156	=head2 C<ev_cleanup> - even the best things end
		3157
		3158	Cleanup watchers are called just before the event loop is being destroyed
		3159	by a call to C<ev_loop_destroy>.
		3160
		3161	While there is no guarantee that the event loop gets destroyed, cleanup
		3162	watchers provide a convenient method to install cleanup hooks for your
		3163	program, worker threads and so on - you just to make sure to destroy the
		3164	loop when you want them to be invoked.
		3165
		3166	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3167	all other watchers, they do not keep a reference to the event loop (which
		3168	makes a lot of sense if you think about it). Like all other watchers, you
		3169	can call libev functions in the callback, except C<ev_cleanup_start>.
		3170
		3171	=head3 Watcher-Specific Functions and Data Members
		3172
		3173	=over 4
		3174
		3175	=item ev_cleanup_init (ev_cleanup *, callback)
		3176
		3177	Initialises and configures the cleanup watcher - it has no parameters of
		3178	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3179	pointless, I assure you.
		3180
		3181	=back
		3182
		3183	Example: Register an atexit handler to destroy the default loop, so any
		3184	cleanup functions are called.
		3185
		3186	static void
		3187	program_exits (void)
		3188	{
		3189	ev_loop_destroy (EV_DEFAULT_UC);
		3190	}
		3191
		3192	...
		3193	atexit (program_exits);
		3194
		3195
2175	=head2 C<ev_async> - how to wake up another event loop	3196	=head2 C<ev_async> - how to wake up an event loop
2176		3197
2177	In general, you cannot use an C<ev_loop> from multiple threads or other	3198	In general, you cannot use an C<ev_loop> from multiple threads or other
2178	asynchronous sources such as signal handlers (as opposed to multiple event	3199	asynchronous sources such as signal handlers (as opposed to multiple event
2179	loops - those are of course safe to use in different threads).	3200	loops - those are of course safe to use in different threads).
2180		3201
2181	Sometimes, however, you need to wake up another event loop you do not	3202	Sometimes, however, you need to wake up an event loop you do not control,
2182	control, for example because it belongs to another thread. This is what	3203	for example because it belongs to another thread. This is what C<ev_async>
2183	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3204	watchers do: as long as the C<ev_async> watcher is active, you can signal
2184	can signal it by calling C<ev_async_send>, which is thread- and signal	3205	it by calling C<ev_async_send>, which is thread- and signal safe.
2185	safe.
2186		3206
2187	This functionality is very similar to C<ev_signal> watchers, as signals,	3207	This functionality is very similar to C<ev_signal> watchers, as signals,
2188	too, are asynchronous in nature, and signals, too, will be compressed	3208	too, are asynchronous in nature, and signals, too, will be compressed
2189	(i.e. the number of callback invocations may be less than the number of	3209	(i.e. the number of callback invocations may be less than the number of
2190	C<ev_async_sent> calls).	3210	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3211	of "global async watchers" by using a watcher on an otherwise unused
		3212	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3213	even without knowing which loop owns the signal.
2191		3214
2192	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3215	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2193	just the default loop.	3216	just the default loop.
2194		3217
2195	=head3 Queueing	3218	=head3 Queueing
2196		3219
2197	C<ev_async> does not support queueing of data in any way. The reason	3220	C<ev_async> does not support queueing of data in any way. The reason
2198	is that the author does not know of a simple (or any) algorithm for a	3221	is that the author does not know of a simple (or any) algorithm for a
2199	multiple-writer-single-reader queue that works in all cases and doesn't	3222	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	3223	need elaborate support such as pthreads or unportable memory access
		3224	semantics.
2201		3225
2202	That means that if you want to queue data, you have to provide your own	3226	That means that if you want to queue data, you have to provide your own
2203	queue. But at least I can tell you would implement locking around your	3227	queue. But at least I can tell you how to implement locking around your
2204	queue:	3228	queue:
2205		3229
2206	=over 4	3230	=over 4
2207		3231
2208	=item queueing from a signal handler context	3232	=item queueing from a signal handler context
2209		3233
2210	To implement race-free queueing, you simply add to the queue in the signal	3234	To implement race-free queueing, you simply add to the queue in the signal
2211	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3235	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	3236	an example that does that for some fictitious SIGUSR1 handler:
2213		3237
2214	static ev_async mysig;	3238	static ev_async mysig;
2215		3239
2216	static void	3240	static void
2217	sigusr1_handler (void)	3241	sigusr1_handler (void)
…		…
2283	=over 4	3307	=over 4
2284		3308
2285	=item ev_async_init (ev_async *, callback)	3309	=item ev_async_init (ev_async *, callback)
2286		3310
2287	Initialises and configures the async watcher - it has no parameters of any	3311	Initialises and configures the async watcher - it has no parameters of any
2288	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3312	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2289	believe me.	3313	trust me.
2290		3314
2291	=item ev_async_send (loop, ev_async *)	3315	=item ev_async_send (loop, ev_async *)
2292		3316
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3317	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3318	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3319	returns.
		3320
2295	C<ev_feed_event>, this call is safe to do in other threads, signal or	3321	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2296	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3322	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2297	section below on what exactly this means).	3323	embedding section below on what exactly this means).
2298		3324
		3325	Note that, as with other watchers in libev, multiple events might get
		3326	compressed into a single callback invocation (another way to look at this
		3327	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3328	reset when the event loop detects that).
		3329
2299	This call incurs the overhead of a syscall only once per loop iteration,	3330	This call incurs the overhead of a system call only once per event loop
2300	so while the overhead might be noticable, it doesn't apply to repeated	3331	iteration, so while the overhead might be noticeable, it doesn't apply to
2301	calls to C<ev_async_send>.	3332	repeated calls to C<ev_async_send> for the same event loop.
2302		3333
2303	=item bool = ev_async_pending (ev_async *)	3334	=item bool = ev_async_pending (ev_async *)
2304		3335
2305	Returns a non-zero value when C<ev_async_send> has been called on the	3336	Returns a non-zero value when C<ev_async_send> has been called on the
2306	watcher but the event has not yet been processed (or even noted) by the	3337	watcher but the event has not yet been processed (or even noted) by the
2307	event loop.	3338	event loop.
2308		3339
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3340	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310	the loop iterates next and checks for the watcher to have become active,	3341	the loop iterates next and checks for the watcher to have become active,
2311	it will reset the flag again. C<ev_async_pending> can be used to very	3342	it will reset the flag again. C<ev_async_pending> can be used to very
2312	quickly check wether invoking the loop might be a good idea.	3343	quickly check whether invoking the loop might be a good idea.
2313		3344
2314	Not that this does I<not> check wether the watcher itself is pending, only	3345	Not that this does I<not> check whether the watcher itself is pending,
2315	wether it has been requested to make this watcher pending.	3346	only whether it has been requested to make this watcher pending: there
		3347	is a time window between the event loop checking and resetting the async
		3348	notification, and the callback being invoked.
2316		3349
2317	=back	3350	=back
2318		3351
2319		3352
2320	=head1 OTHER FUNCTIONS	3353	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	3357	=over 4
2325		3358
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3359	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		3360
2328	This function combines a simple timer and an I/O watcher, calls your	3361	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	3362	callback on whichever event happens first and automatically stops both
2330	watchers. This is useful if you want to wait for a single event on an fd	3363	watchers. This is useful if you want to wait for a single event on an fd
2331	or timeout without having to allocate/configure/start/stop/free one or	3364	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	3365	more watchers yourself.
2333		3366
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	3367	If C<fd> is less than 0, then no I/O watcher will be started and the
2335	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3368	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	3369	the given C<fd> and C<events> set will be created and started.
2337		3370
2338	If C<timeout> is less than 0, then no timeout watcher will be	3371	If C<timeout> is less than 0, then no timeout watcher will be
2339	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3372	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3373	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		3374
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3375	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2344	passed an C<revents> set like normal event callbacks (a combination of	3376	passed an C<revents> set like normal event callbacks (a combination of
2345	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3377	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2346	value passed to C<ev_once>:	3378	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3379	a timeout and an io event at the same time - you probably should give io
		3380	events precedence.
2347		3381
		3382	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3383
2348	static void stdin_ready (int revents, void *arg)	3384	static void stdin_ready (int revents, void *arg)
2349	{	3385	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	3386	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	3387	/* stdin might have data for us, joy! */;
		3388	else if (revents & EV_TIMER)
		3389	/* doh, nothing entered */;
2354	}	3390	}
2355		3391
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3392	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		3393
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)
2359
2360	Feeds the given event set into the event loop, as if the specified event
2361	had happened for the specified watcher (which must be a pointer to an
2362	initialised but not necessarily started event watcher).
2363
2364	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3394	=item ev_feed_fd_event (loop, int fd, int revents)
2365		3395
2366	Feed an event on the given fd, as if a file descriptor backend detected	3396	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	3397	the given events it.
2368		3398
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	3399	=item ev_feed_signal_event (loop, int signum)
2370		3400
2371	Feed an event as if the given signal occured (C<loop> must be the default	3401	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2372	loop!).	3402	which is async-safe.
2373		3403
2374	=back	3404	=back
		3405
		3406
		3407	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3408
		3409	This section explains some common idioms that are not immediately
		3410	obvious. Note that examples are sprinkled over the whole manual, and this
		3411	section only contains stuff that wouldn't fit anywhere else.
		3412
		3413	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3414
		3415	Each watcher has, by default, a C<void *data> member that you can read
		3416	or modify at any time: libev will completely ignore it. This can be used
		3417	to associate arbitrary data with your watcher. If you need more data and
		3418	don't want to allocate memory separately and store a pointer to it in that
		3419	data member, you can also "subclass" the watcher type and provide your own
		3420	data:
		3421
		3422	struct my_io
		3423	{
		3424	ev_io io;
		3425	int otherfd;
		3426	void *somedata;
		3427	struct whatever *mostinteresting;
		3428	};
		3429
		3430	...
		3431	struct my_io w;
		3432	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3433
		3434	And since your callback will be called with a pointer to the watcher, you
		3435	can cast it back to your own type:
		3436
		3437	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3438	{
		3439	struct my_io *w = (struct my_io *)w_;
		3440	...
		3441	}
		3442
		3443	More interesting and less C-conformant ways of casting your callback
		3444	function type instead have been omitted.
		3445
		3446	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3447
		3448	Another common scenario is to use some data structure with multiple
		3449	embedded watchers, in effect creating your own watcher that combines
		3450	multiple libev event sources into one "super-watcher":
		3451
		3452	struct my_biggy
		3453	{
		3454	int some_data;
		3455	ev_timer t1;
		3456	ev_timer t2;
		3457	}
		3458
		3459	In this case getting the pointer to C<my_biggy> is a bit more
		3460	complicated: Either you store the address of your C<my_biggy> struct in
		3461	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3462	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3463	real programmers):
		3464
		3465	#include <stddef.h>
		3466
		3467	static void
		3468	t1_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t1));
		3472	}
		3473
		3474	static void
		3475	t2_cb (EV_P_ ev_timer *w, int revents)
		3476	{
		3477	struct my_biggy big = (struct my_biggy *)
		3478	(((char *)w) - offsetof (struct my_biggy, t2));
		3479	}
		3480
		3481	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3482
		3483	Often (especially in GUI toolkits) there are places where you have
		3484	I<modal> interaction, which is most easily implemented by recursively
		3485	invoking C<ev_run>.
		3486
		3487	This brings the problem of exiting - a callback might want to finish the
		3488	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3489	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3490	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3491	other combination: In these cases, C<ev_break> will not work alone.
		3492
		3493	The solution is to maintain "break this loop" variable for each C<ev_run>
		3494	invocation, and use a loop around C<ev_run> until the condition is
		3495	triggered, using C<EVRUN_ONCE>:
		3496
		3497	// main loop
		3498	int exit_main_loop = 0;
		3499
		3500	while (!exit_main_loop)
		3501	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3502
		3503	// in a model watcher
		3504	int exit_nested_loop = 0;
		3505
		3506	while (!exit_nested_loop)
		3507	ev_run (EV_A_ EVRUN_ONCE);
		3508
		3509	To exit from any of these loops, just set the corresponding exit variable:
		3510
		3511	// exit modal loop
		3512	exit_nested_loop = 1;
		3513
		3514	// exit main program, after modal loop is finished
		3515	exit_main_loop = 1;
		3516
		3517	// exit both
		3518	exit_main_loop = exit_nested_loop = 1;
		3519
		3520	=head2 THREAD LOCKING EXAMPLE
		3521
		3522	Here is a fictitious example of how to run an event loop in a different
		3523	thread from where callbacks are being invoked and watchers are
		3524	created/added/removed.
		3525
		3526	For a real-world example, see the C<EV::Loop::Async> perl module,
		3527	which uses exactly this technique (which is suited for many high-level
		3528	languages).
		3529
		3530	The example uses a pthread mutex to protect the loop data, a condition
		3531	variable to wait for callback invocations, an async watcher to notify the
		3532	event loop thread and an unspecified mechanism to wake up the main thread.
		3533
		3534	First, you need to associate some data with the event loop:
		3535
		3536	typedef struct {
		3537	mutex_t lock; /* global loop lock */
		3538	ev_async async_w;
		3539	thread_t tid;
		3540	cond_t invoke_cv;
		3541	} userdata;
		3542
		3543	void prepare_loop (EV_P)
		3544	{
		3545	// for simplicity, we use a static userdata struct.
		3546	static userdata u;
		3547
		3548	ev_async_init (&u->async_w, async_cb);
		3549	ev_async_start (EV_A_ &u->async_w);
		3550
		3551	pthread_mutex_init (&u->lock, 0);
		3552	pthread_cond_init (&u->invoke_cv, 0);
		3553
		3554	// now associate this with the loop
		3555	ev_set_userdata (EV_A_ u);
		3556	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3557	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3558
		3559	// then create the thread running ev_run
		3560	pthread_create (&u->tid, 0, l_run, EV_A);
		3561	}
		3562
		3563	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3564	solely to wake up the event loop so it takes notice of any new watchers
		3565	that might have been added:
		3566
		3567	static void
		3568	async_cb (EV_P_ ev_async *w, int revents)
		3569	{
		3570	// just used for the side effects
		3571	}
		3572
		3573	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3574	protecting the loop data, respectively.
		3575
		3576	static void
		3577	l_release (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_unlock (&u->lock);
		3581	}
		3582
		3583	static void
		3584	l_acquire (EV_P)
		3585	{
		3586	userdata *u = ev_userdata (EV_A);
		3587	pthread_mutex_lock (&u->lock);
		3588	}
		3589
		3590	The event loop thread first acquires the mutex, and then jumps straight
		3591	into C<ev_run>:
		3592
		3593	void *
		3594	l_run (void *thr_arg)
		3595	{
		3596	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3597
		3598	l_acquire (EV_A);
		3599	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3600	ev_run (EV_A_ 0);
		3601	l_release (EV_A);
		3602
		3603	return 0;
		3604	}
		3605
		3606	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3607	signal the main thread via some unspecified mechanism (signals? pipe
		3608	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3609	have been called (in a while loop because a) spurious wakeups are possible
		3610	and b) skipping inter-thread-communication when there are no pending
		3611	watchers is very beneficial):
		3612
		3613	static void
		3614	l_invoke (EV_P)
		3615	{
		3616	userdata *u = ev_userdata (EV_A);
		3617
		3618	while (ev_pending_count (EV_A))
		3619	{
		3620	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3621	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3622	}
		3623	}
		3624
		3625	Now, whenever the main thread gets told to invoke pending watchers, it
		3626	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3627	thread to continue:
		3628
		3629	static void
		3630	real_invoke_pending (EV_P)
		3631	{
		3632	userdata *u = ev_userdata (EV_A);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_invoke_pending (EV_A);
		3636	pthread_cond_signal (&u->invoke_cv);
		3637	pthread_mutex_unlock (&u->lock);
		3638	}
		3639
		3640	Whenever you want to start/stop a watcher or do other modifications to an
		3641	event loop, you will now have to lock:
		3642
		3643	ev_timer timeout_watcher;
		3644	userdata *u = ev_userdata (EV_A);
		3645
		3646	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3647
		3648	pthread_mutex_lock (&u->lock);
		3649	ev_timer_start (EV_A_ &timeout_watcher);
		3650	ev_async_send (EV_A_ &u->async_w);
		3651	pthread_mutex_unlock (&u->lock);
		3652
		3653	Note that sending the C<ev_async> watcher is required because otherwise
		3654	an event loop currently blocking in the kernel will have no knowledge
		3655	about the newly added timer. By waking up the loop it will pick up any new
		3656	watchers in the next event loop iteration.
		3657
		3658	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3659
		3660	While the overhead of a callback that e.g. schedules a thread is small, it
		3661	is still an overhead. If you embed libev, and your main usage is with some
		3662	kind of threads or coroutines, you might want to customise libev so that
		3663	doesn't need callbacks anymore.
		3664
		3665	Imagine you have coroutines that you can switch to using a function
		3666	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3667	and that due to some magic, the currently active coroutine is stored in a
		3668	global called C<current_coro>. Then you can build your own "wait for libev
		3669	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3670	the differing C<;> conventions):
		3671
		3672	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3673	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3674
		3675	That means instead of having a C callback function, you store the
		3676	coroutine to switch to in each watcher, and instead of having libev call
		3677	your callback, you instead have it switch to that coroutine.
		3678
		3679	A coroutine might now wait for an event with a function called
		3680	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3681	matter when, or whether the watcher is active or not when this function is
		3682	called):
		3683
		3684	void
		3685	wait_for_event (ev_watcher *w)
		3686	{
		3687	ev_cb_set (w) = current_coro;
		3688	switch_to (libev_coro);
		3689	}
		3690
		3691	That basically suspends the coroutine inside C<wait_for_event> and
		3692	continues the libev coroutine, which, when appropriate, switches back to
		3693	this or any other coroutine. I am sure if you sue this your own :)
		3694
		3695	You can do similar tricks if you have, say, threads with an event queue -
		3696	instead of storing a coroutine, you store the queue object and instead of
		3697	switching to a coroutine, you push the watcher onto the queue and notify
		3698	any waiters.
		3699
		3700	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3701	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3702
		3703	// my_ev.h
		3704	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3705	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3706	#include "../libev/ev.h"
		3707
		3708	// my_ev.c
		3709	#define EV_H "my_ev.h"
		3710	#include "../libev/ev.c"
		3711
		3712	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3713	F<my_ev.c> into your project. When properly specifying include paths, you
		3714	can even use F<ev.h> as header file name directly.
2375		3715
2376		3716
2377	=head1 LIBEVENT EMULATION	3717	=head1 LIBEVENT EMULATION
2378		3718
2379	Libev offers a compatibility emulation layer for libevent. It cannot	3719	Libev offers a compatibility emulation layer for libevent. It cannot
2380	emulate the internals of libevent, so here are some usage hints:	3720	emulate the internals of libevent, so here are some usage hints:
2381		3721
2382	=over 4	3722	=over 4
		3723
		3724	=item * Only the libevent-1.4.1-beta API is being emulated.
		3725
		3726	This was the newest libevent version available when libev was implemented,
		3727	and is still mostly unchanged in 2010.
2383		3728
2384	=item * Use it by including <event.h>, as usual.	3729	=item * Use it by including <event.h>, as usual.
2385		3730
2386	=item * The following members are fully supported: ev_base, ev_callback,	3731	=item * The following members are fully supported: ev_base, ev_callback,
2387	ev_arg, ev_fd, ev_res, ev_events.	3732	ev_arg, ev_fd, ev_res, ev_events.
…		…
2393	=item * Priorities are not currently supported. Initialising priorities	3738	=item * Priorities are not currently supported. Initialising priorities
2394	will fail and all watchers will have the same priority, even though there	3739	will fail and all watchers will have the same priority, even though there
2395	is an ev_pri field.	3740	is an ev_pri field.
2396		3741
2397	=item * In libevent, the last base created gets the signals, in libev, the	3742	=item * In libevent, the last base created gets the signals, in libev, the
2398	first base created (== the default loop) gets the signals.	3743	base that registered the signal gets the signals.
2399		3744
2400	=item * Other members are not supported.	3745	=item * Other members are not supported.
2401		3746
2402	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3747	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2403	to use the libev header file and library.	3748	to use the libev header file and library.
…		…
2405	=back	3750	=back
2406		3751
2407	=head1 C++ SUPPORT	3752	=head1 C++ SUPPORT
2408		3753
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3754	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410	you to use some convinience methods to start/stop watchers and also change	3755	you to use some convenience methods to start/stop watchers and also change
2411	the callback model to a model using method callbacks on objects.	3756	the callback model to a model using method callbacks on objects.
2412		3757
2413	To use it,	3758	To use it,
2414		3759
2415	#include <ev++.h>	3760	#include <ev++.h>
2416		3761
2417	This automatically includes F<ev.h> and puts all of its definitions (many	3762	This automatically includes F<ev.h> and puts all of its definitions (many
2418	of them macros) into the global namespace. All C++ specific things are	3763	of them macros) into the global namespace. All C++ specific things are
2419	put into the C<ev> namespace. It should support all the same embedding	3764	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3765	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2422	Care has been taken to keep the overhead low. The only data member the C++	3767	Care has been taken to keep the overhead low. The only data member the C++
2423	classes add (compared to plain C-style watchers) is the event loop pointer	3768	classes add (compared to plain C-style watchers) is the event loop pointer
2424	that the watcher is associated with (or no additional members at all if	3769	that the watcher is associated with (or no additional members at all if
2425	you disable C<EV_MULTIPLICITY> when embedding libev).	3770	you disable C<EV_MULTIPLICITY> when embedding libev).
2426		3771
2427	Currently, functions, and static and non-static member functions can be	3772	Currently, functions, static and non-static member functions and classes
2428	used as callbacks. Other types should be easy to add as long as they only	3773	with C<operator ()> can be used as callbacks. Other types should be easy
2429	need one additional pointer for context. If you need support for other	3774	to add as long as they only need one additional pointer for context. If
2430	types of functors please contact the author (preferably after implementing	3775	you need support for other types of functors please contact the author
2431	it).	3776	(preferably after implementing it).
2432		3777
2433	Here is a list of things available in the C<ev> namespace:	3778	Here is a list of things available in the C<ev> namespace:
2434		3779
2435	=over 4	3780	=over 4
2436		3781
…		…
2454		3799
2455	=over 4	3800	=over 4
2456		3801
2457	=item ev::TYPE::TYPE ()	3802	=item ev::TYPE::TYPE ()
2458		3803
2459	=item ev::TYPE::TYPE (struct ev_loop *)	3804	=item ev::TYPE::TYPE (loop)
2460		3805
2461	=item ev::TYPE::~TYPE	3806	=item ev::TYPE::~TYPE
2462		3807
2463	The constructor (optionally) takes an event loop to associate the watcher	3808	The constructor (optionally) takes an event loop to associate the watcher
2464	with. If it is omitted, it will use C<EV_DEFAULT>.	3809	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	3832	your compiler is good :), then the method will be fully inlined into the
2488	thunking function, making it as fast as a direct C callback.	3833	thunking function, making it as fast as a direct C callback.
2489		3834
2490	Example: simple class declaration and watcher initialisation	3835	Example: simple class declaration and watcher initialisation
2491		3836
2492	struct myclass	3837	struct myclass
2493	{	3838	{
2494	void io_cb (ev::io &w, int revents) { }	3839	void io_cb (ev::io &w, int revents) { }
2495	}	3840	}
2496		3841
2497	myclass obj;	3842	myclass obj;
2498	ev::io iow;	3843	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	3844	iow.set <myclass, &myclass::io_cb> (&obj);
		3845
		3846	=item w->set (object *)
		3847
		3848	This is a variation of a method callback - leaving out the method to call
		3849	will default the method to C<operator ()>, which makes it possible to use
		3850	functor objects without having to manually specify the C<operator ()> all
		3851	the time. Incidentally, you can then also leave out the template argument
		3852	list.
		3853
		3854	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3855	int revents)>.
		3856
		3857	See the method-C<set> above for more details.
		3858
		3859	Example: use a functor object as callback.
		3860
		3861	struct myfunctor
		3862	{
		3863	void operator() (ev::io &w, int revents)
		3864	{
		3865	...
		3866	}
		3867	}
		3868
		3869	myfunctor f;
		3870
		3871	ev::io w;
		3872	w.set (&f);
2500		3873
2501	=item w->set<function> (void *data = 0)	3874	=item w->set<function> (void *data = 0)
2502		3875
2503	Also sets a callback, but uses a static method or plain function as	3876	Also sets a callback, but uses a static method or plain function as
2504	callback. The optional C<data> argument will be stored in the watcher's	3877	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		3879
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3880	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		3881
2509	See the method-C<set> above for more details.	3882	See the method-C<set> above for more details.
2510		3883
2511	Example:	3884	Example: Use a plain function as callback.
2512		3885
2513	static void io_cb (ev::io &w, int revents) { }	3886	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	3887	iow.set <io_cb> ();
2515		3888
2516	=item w->set (struct ev_loop *)	3889	=item w->set (loop)
2517		3890
2518	Associates a different C<struct ev_loop> with this watcher. You can only	3891	Associates a different C<struct ev_loop> with this watcher. You can only
2519	do this when the watcher is inactive (and not pending either).	3892	do this when the watcher is inactive (and not pending either).
2520		3893
2521	=item w->set ([args])	3894	=item w->set ([arguments])
2522		3895
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3896	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2524	called at least once. Unlike the C counterpart, an active watcher gets	3897	method or a suitable start method must be called at least once. Unlike the
2525	automatically stopped and restarted when reconfiguring it with this	3898	C counterpart, an active watcher gets automatically stopped and restarted
2526	method.	3899	when reconfiguring it with this method.
2527		3900
2528	=item w->start ()	3901	=item w->start ()
2529		3902
2530	Starts the watcher. Note that there is no C<loop> argument, as the	3903	Starts the watcher. Note that there is no C<loop> argument, as the
2531	constructor already stores the event loop.	3904	constructor already stores the event loop.
2532		3905
		3906	=item w->start ([arguments])
		3907
		3908	Instead of calling C<set> and C<start> methods separately, it is often
		3909	convenient to wrap them in one call. Uses the same type of arguments as
		3910	the configure C<set> method of the watcher.
		3911
2533	=item w->stop ()	3912	=item w->stop ()
2534		3913
2535	Stops the watcher if it is active. Again, no C<loop> argument.	3914	Stops the watcher if it is active. Again, no C<loop> argument.
2536		3915
2537	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3916	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2549		3928
2550	=back	3929	=back
2551		3930
2552	=back	3931	=back
2553		3932
2554	Example: Define a class with an IO and idle watcher, start one of them in	3933	Example: Define a class with two I/O and idle watchers, start the I/O
2555	the constructor.	3934	watchers in the constructor.
2556		3935
2557	class myclass	3936	class myclass
2558	{	3937	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	3938	ev::io io ; void io_cb (ev::io &w, int revents);
		3939	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	3940	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		3941
2562	myclass (int fd)	3942	myclass (int fd)
2563	{	3943	{
2564	io .set <myclass, &myclass::io_cb > (this);	3944	io .set <myclass, &myclass::io_cb > (this);
		3945	io2 .set <myclass, &myclass::io2_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	3946	idle.set <myclass, &myclass::idle_cb> (this);
2566		3947
2567	io.start (fd, ev::READ);	3948	io.set (fd, ev::WRITE); // configure the watcher
		3949	io.start (); // start it whenever convenient
		3950
		3951	io2.start (fd, ev::READ); // set + start in one call
2568	}	3952	}
2569	};	3953	};
2570		3954
2571		3955
2572	=head1 OTHER LANGUAGE BINDINGS	3956	=head1 OTHER LANGUAGE BINDINGS
2573		3957
2574	Libev does not offer other language bindings itself, but bindings for a	3958	Libev does not offer other language bindings itself, but bindings for a
2575	numbe rof languages exist in the form of third-party packages. If you know	3959	number of languages exist in the form of third-party packages. If you know
2576	any interesting language binding in addition to the ones listed here, drop	3960	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	3961	me a note.
2578		3962
2579	=over 4	3963	=over 4
2580		3964
2581	=item Perl	3965	=item Perl
2582		3966
2583	The EV module implements the full libev API and is actually used to test	3967	The EV module implements the full libev API and is actually used to test
2584	libev. EV is developed together with libev. Apart from the EV core module,	3968	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	3969	there are additional modules that implement libev-compatible interfaces
2586	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3970	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2587	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3971	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3972	and C<EV::Glib>).
2588		3973
2589	It can be found and installed via CPAN, its homepage is found at	3974	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	3975	L<http://software.schmorp.de/pkg/EV>.
2591		3976
		3977	=item Python
		3978
		3979	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3980	seems to be quite complete and well-documented.
		3981
2592	=item Ruby	3982	=item Ruby
2593		3983
2594	Tony Arcieri has written a ruby extension that offers access to a subset	3984	Tony Arcieri has written a ruby extension that offers access to a subset
2595	of the libev API and adds filehandle abstractions, asynchronous DNS and	3985	of the libev API and adds file handle abstractions, asynchronous DNS and
2596	more on top of it. It can be found via gem servers. Its homepage is at	3986	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	3987	L<http://rev.rubyforge.org/>.
2598		3988
		3989	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3990	makes rev work even on mingw.
		3991
		3992	=item Haskell
		3993
		3994	A haskell binding to libev is available at
		3995	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3996
2599	=item D	3997	=item D
2600		3998
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3999	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	4000	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		4001
		4002	=item Ocaml
		4003
		4004	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4005	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4006
		4007	=item Lua
		4008
		4009	Brian Maher has written a partial interface to libev for lua (at the
		4010	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4011	L<http://github.com/brimworks/lua-ev>.
2603		4012
2604	=back	4013	=back
2605		4014
2606		4015
2607	=head1 MACRO MAGIC	4016	=head1 MACRO MAGIC
2608		4017
2609	Libev can be compiled with a variety of options, the most fundamantal	4018	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	4019	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	4020	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		4021
2613	To make it easier to write programs that cope with either variant, the	4022	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	4023	following macros are defined:
…		…
2619		4028
2620	This provides the loop I<argument> for functions, if one is required ("ev	4029	This provides the loop I<argument> for functions, if one is required ("ev
2621	loop argument"). The C<EV_A> form is used when this is the sole argument,	4030	loop argument"). The C<EV_A> form is used when this is the sole argument,
2622	C<EV_A_> is used when other arguments are following. Example:	4031	C<EV_A_> is used when other arguments are following. Example:
2623		4032
2624	ev_unref (EV_A);	4033	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	4034	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	4035	ev_run (EV_A_ 0);
2627		4036
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	4038	which is often provided by the following macro.
2630		4039
2631	=item C<EV_P>, C<EV_P_>	4040	=item C<EV_P>, C<EV_P_>
2632		4041
2633	This provides the loop I<parameter> for functions, if one is required ("ev	4042	This provides the loop I<parameter> for functions, if one is required ("ev
2634	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	4043	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635	C<EV_P_> is used when other parameters are following. Example:	4044	C<EV_P_> is used when other parameters are following. Example:
2636		4045
2637	// this is how ev_unref is being declared	4046	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	4047	static void ev_unref (EV_P);
2639		4048
2640	// this is how you can declare your typical callback	4049	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	4050	static void cb (EV_P_ ev_timer *w, int revents)
2642		4051
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	4052	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	4053	suitable for use with C<EV_A>.
2645		4054
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4055	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		4071
2663	Example: Declare and initialise a check watcher, utilising the above	4072	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	4073	macros so it will work regardless of whether multiple loops are supported
2665	or not.	4074	or not.
2666		4075
2667	static void	4076	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	4077	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	4078	{
2670	ev_check_stop (EV_A_ w);	4079	ev_check_stop (EV_A_ w);
2671	}	4080	}
2672		4081
2673	ev_check check;	4082	ev_check check;
2674	ev_check_init (&check, check_cb);	4083	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	4084	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	4085	ev_run (EV_DEFAULT_ 0);
2677		4086
2678	=head1 EMBEDDING	4087	=head1 EMBEDDING
2679		4088
2680	Libev can (and often is) directly embedded into host	4089	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	4090	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	4097	libev somewhere in your source tree).
2689		4098
2690	=head2 FILESETS	4099	=head2 FILESETS
2691		4100
2692	Depending on what features you need you need to include one or more sets of files	4101	Depending on what features you need you need to include one or more sets of files
2693	in your app.	4102	in your application.
2694		4103
2695	=head3 CORE EVENT LOOP	4104	=head3 CORE EVENT LOOP
2696		4105
2697	To include only the libev core (all the C<ev_*> functions), with manual	4106	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	4107	configuration (no autoconf):
2699		4108
2700	#define EV_STANDALONE 1	4109	#define EV_STANDALONE 1
2701	#include "ev.c"	4110	#include "ev.c"
2702		4111
2703	This will automatically include F<ev.h>, too, and should be done in a	4112	This will automatically include F<ev.h>, too, and should be done in a
2704	single C source file only to provide the function implementations. To use	4113	single C source file only to provide the function implementations. To use
2705	it, do the same for F<ev.h> in all files wishing to use this API (best	4114	it, do the same for F<ev.h> in all files wishing to use this API (best
2706	done by writing a wrapper around F<ev.h> that you can include instead and	4115	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	4116	where you can put other configuration options):
2708		4117
2709	#define EV_STANDALONE 1	4118	#define EV_STANDALONE 1
2710	#include "ev.h"	4119	#include "ev.h"
2711		4120
2712	Both header files and implementation files can be compiled with a C++	4121	Both header files and implementation files can be compiled with a C++
2713	compiler (at least, thats a stated goal, and breakage will be treated	4122	compiler (at least, that's a stated goal, and breakage will be treated
2714	as a bug).	4123	as a bug).
2715		4124
2716	You need the following files in your source tree, or in a directory	4125	You need the following files in your source tree, or in a directory
2717	in your include path (e.g. in libev/ when using -Ilibev):	4126	in your include path (e.g. in libev/ when using -Ilibev):
2718		4127
2719	ev.h	4128	ev.h
2720	ev.c	4129	ev.c
2721	ev_vars.h	4130	ev_vars.h
2722	ev_wrap.h	4131	ev_wrap.h
2723		4132
2724	ev_win32.c required on win32 platforms only	4133	ev_win32.c required on win32 platforms only
2725		4134
2726	ev_select.c only when select backend is enabled (which is enabled by default)	4135	ev_select.c only when select backend is enabled (which is enabled by default)
2727	ev_poll.c only when poll backend is enabled (disabled by default)	4136	ev_poll.c only when poll backend is enabled (disabled by default)
2728	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4137	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4138	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730	ev_port.c only when the solaris port backend is enabled (disabled by default)	4139	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		4140
2732	F<ev.c> includes the backend files directly when enabled, so you only need	4141	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	4142	to compile this single file.
2734		4143
2735	=head3 LIBEVENT COMPATIBILITY API	4144	=head3 LIBEVENT COMPATIBILITY API
2736		4145
2737	To include the libevent compatibility API, also include:	4146	To include the libevent compatibility API, also include:
2738		4147
2739	#include "event.c"	4148	#include "event.c"
2740		4149
2741	in the file including F<ev.c>, and:	4150	in the file including F<ev.c>, and:
2742		4151
2743	#include "event.h"	4152	#include "event.h"
2744		4153
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	4154	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		4155
2747	You need the following additional files for this:	4156	You need the following additional files for this:
2748		4157
2749	event.h	4158	event.h
2750	event.c	4159	event.c
2751		4160
2752	=head3 AUTOCONF SUPPORT	4161	=head3 AUTOCONF SUPPORT
2753		4162
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	4163	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755	whatever way you want, you can also C<m4_include([libev.m4])> in your	4164	whatever way you want, you can also C<m4_include([libev.m4])> in your
2756	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	4165	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	4166	include F<config.h> and configure itself accordingly.
2758		4167
2759	For this of course you need the m4 file:	4168	For this of course you need the m4 file:
2760		4169
2761	libev.m4	4170	libev.m4
2762		4171
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	4172	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		4173
2765	Libev can be configured via a variety of preprocessor symbols you have to	4174	Libev can be configured via a variety of preprocessor symbols you have to
2766	define before including any of its files. The default in the absense of	4175	define before including (or compiling) any of its files. The default in
2767	autoconf is noted for every option.	4176	the absence of autoconf is documented for every option.
		4177
		4178	Symbols marked with "(h)" do not change the ABI, and can have different
		4179	values when compiling libev vs. including F<ev.h>, so it is permissible
		4180	to redefine them before including F<ev.h> without breaking compatibility
		4181	to a compiled library. All other symbols change the ABI, which means all
		4182	users of libev and the libev code itself must be compiled with compatible
		4183	settings.
2768		4184
2769	=over 4	4185	=over 4
2770		4186
		4187	=item EV_COMPAT3 (h)
		4188
		4189	Backwards compatibility is a major concern for libev. This is why this
		4190	release of libev comes with wrappers for the functions and symbols that
		4191	have been renamed between libev version 3 and 4.
		4192
		4193	You can disable these wrappers (to test compatibility with future
		4194	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4195	sources. This has the additional advantage that you can drop the C<struct>
		4196	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4197	typedef in that case.
		4198
		4199	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4200	and in some even more future version the compatibility code will be
		4201	removed completely.
		4202
2771	=item EV_STANDALONE	4203	=item EV_STANDALONE (h)
2772		4204
2773	Must always be C<1> if you do not use autoconf configuration, which	4205	Must always be C<1> if you do not use autoconf configuration, which
2774	keeps libev from including F<config.h>, and it also defines dummy	4206	keeps libev from including F<config.h>, and it also defines dummy
2775	implementations for some libevent functions (such as logging, which is not	4207	implementations for some libevent functions (such as logging, which is not
2776	supported). It will also not define any of the structs usually found in	4208	supported). It will also not define any of the structs usually found in
2777	F<event.h> that are not directly supported by the libev core alone.	4209	F<event.h> that are not directly supported by the libev core alone.
2778		4210
		4211	In standalone mode, libev will still try to automatically deduce the
		4212	configuration, but has to be more conservative.
		4213
		4214	=item EV_USE_FLOOR
		4215
		4216	If defined to be C<1>, libev will use the C<floor ()> function for its
		4217	periodic reschedule calculations, otherwise libev will fall back on a
		4218	portable (slower) implementation. If you enable this, you usually have to
		4219	link against libm or something equivalent. Enabling this when the C<floor>
		4220	function is not available will fail, so the safe default is to not enable
		4221	this.
		4222
2779	=item EV_USE_MONOTONIC	4223	=item EV_USE_MONOTONIC
2780		4224
2781	If defined to be C<1>, libev will try to detect the availability of the	4225	If defined to be C<1>, libev will try to detect the availability of the
2782	monotonic clock option at both compiletime and runtime. Otherwise no use	4226	monotonic clock option at both compile time and runtime. Otherwise no
2783	of the monotonic clock option will be attempted. If you enable this, you	4227	use of the monotonic clock option will be attempted. If you enable this,
2784	usually have to link against librt or something similar. Enabling it when	4228	you usually have to link against librt or something similar. Enabling it
2785	the functionality isn't available is safe, though, although you have	4229	when the functionality isn't available is safe, though, although you have
2786	to make sure you link against any libraries where the C<clock_gettime>	4230	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	4231	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2788		4232
2789	=item EV_USE_REALTIME	4233	=item EV_USE_REALTIME
2790		4234
2791	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
2792	realtime clock option at compiletime (and assume its availability at	4236	real-time clock option at compile time (and assume its availability
2793	runtime if successful). Otherwise no use of the realtime clock option will	4237	at runtime if successful). Otherwise no use of the real-time clock
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4238	option will be attempted. This effectively replaces C<gettimeofday>
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4239	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4240	correctness. See the note about libraries in the description of
		4241	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4242	C<EV_USE_CLOCK_SYSCALL>.
		4243
		4244	=item EV_USE_CLOCK_SYSCALL
		4245
		4246	If defined to be C<1>, libev will try to use a direct syscall instead
		4247	of calling the system-provided C<clock_gettime> function. This option
		4248	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4249	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4250	programs needlessly. Using a direct syscall is slightly slower (in
		4251	theory), because no optimised vdso implementation can be used, but avoids
		4252	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4253	higher, as it simplifies linking (no need for C<-lrt>).
2797		4254
2798	=item EV_USE_NANOSLEEP	4255	=item EV_USE_NANOSLEEP
2799		4256
2800	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4257	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2801	and will use it for delays. Otherwise it will use C<select ()>.	4258	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2809	2.7 or newer, otherwise disabled.	4266	2.7 or newer, otherwise disabled.
2810		4267
2811	=item EV_USE_SELECT	4268	=item EV_USE_SELECT
2812		4269
2813	If undefined or defined to be C<1>, libev will compile in support for the	4270	If undefined or defined to be C<1>, libev will compile in support for the
2814	C<select>(2) backend. No attempt at autodetection will be done: if no	4271	C<select>(2) backend. No attempt at auto-detection will be done: if no
2815	other method takes over, select will be it. Otherwise the select backend	4272	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	4273	will not be compiled in.
2817		4274
2818	=item EV_SELECT_USE_FD_SET	4275	=item EV_SELECT_USE_FD_SET
2819		4276
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	4277	If defined to C<1>, then the select backend will use the system C<fd_set>
2821	structure. This is useful if libev doesn't compile due to a missing	4278	structure. This is useful if libev doesn't compile due to a missing
2822	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	4279	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2823	exotic systems. This usually limits the range of file descriptors to some	4280	on exotic systems. This usually limits the range of file descriptors to
2824	low limit such as 1024 or might have other limitations (winsocket only	4281	some low limit such as 1024 or might have other limitations (winsocket
2825	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4282	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2826	influence the size of the C<fd_set> used.	4283	configures the maximum size of the C<fd_set>.
2827		4284
2828	=item EV_SELECT_IS_WINSOCKET	4285	=item EV_SELECT_IS_WINSOCKET
2829		4286
2830	When defined to C<1>, the select backend will assume that	4287	When defined to C<1>, the select backend will assume that
2831	select/socket/connect etc. don't understand file descriptors but	4288	select/socket/connect etc. don't understand file descriptors but
…		…
2833	be used is the winsock select). This means that it will call	4290	be used is the winsock select). This means that it will call
2834	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4291	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2835	it is assumed that all these functions actually work on fds, even	4292	it is assumed that all these functions actually work on fds, even
2836	on win32. Should not be defined on non-win32 platforms.	4293	on win32. Should not be defined on non-win32 platforms.
2837		4294
2838	=item EV_FD_TO_WIN32_HANDLE	4295	=item EV_FD_TO_WIN32_HANDLE(fd)
2839		4296
2840	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4297	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2841	file descriptors to socket handles. When not defining this symbol (the	4298	file descriptors to socket handles. When not defining this symbol (the
2842	default), then libev will call C<_get_osfhandle>, which is usually	4299	default), then libev will call C<_get_osfhandle>, which is usually
2843	correct. In some cases, programs use their own file descriptor management,	4300	correct. In some cases, programs use their own file descriptor management,
2844	in which case they can provide this function to map fds to socket handles.	4301	in which case they can provide this function to map fds to socket handles.
		4302
		4303	=item EV_WIN32_HANDLE_TO_FD(handle)
		4304
		4305	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4306	using the standard C<_open_osfhandle> function. For programs implementing
		4307	their own fd to handle mapping, overwriting this function makes it easier
		4308	to do so. This can be done by defining this macro to an appropriate value.
		4309
		4310	=item EV_WIN32_CLOSE_FD(fd)
		4311
		4312	If programs implement their own fd to handle mapping on win32, then this
		4313	macro can be used to override the C<close> function, useful to unregister
		4314	file descriptors again. Note that the replacement function has to close
		4315	the underlying OS handle.
2845		4316
2846	=item EV_USE_POLL	4317	=item EV_USE_POLL
2847		4318
2848	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4319	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2849	backend. Otherwise it will be enabled on non-win32 platforms. It	4320	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2876	otherwise another method will be used as fallback. This is the preferred	4347	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	4348	backend for Solaris 10 systems.
2878		4349
2879	=item EV_USE_DEVPOLL	4350	=item EV_USE_DEVPOLL
2880		4351
2881	reserved for future expansion, works like the USE symbols above.	4352	Reserved for future expansion, works like the USE symbols above.
2882		4353
2883	=item EV_USE_INOTIFY	4354	=item EV_USE_INOTIFY
2884		4355
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	4356	If defined to be C<1>, libev will compile in support for the Linux inotify
2886	interface to speed up C<ev_stat> watchers. Its actual availability will	4357	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2893	access is atomic with respect to other threads or signal contexts. No such	4364	access is atomic with respect to other threads or signal contexts. No such
2894	type is easily found in the C language, so you can provide your own type	4365	type is easily found in the C language, so you can provide your own type
2895	that you know is safe for your purposes. It is used both for signal handler "locking"	4366	that you know is safe for your purposes. It is used both for signal handler "locking"
2896	as well as for signal and thread safety in C<ev_async> watchers.	4367	as well as for signal and thread safety in C<ev_async> watchers.
2897		4368
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	4369	In the absence of this define, libev will use C<sig_atomic_t volatile>
2899	(from F<signal.h>), which is usually good enough on most platforms.	4370	(from F<signal.h>), which is usually good enough on most platforms.
2900		4371
2901	=item EV_H	4372	=item EV_H (h)
2902		4373
2903	The name of the F<ev.h> header file used to include it. The default if	4374	The name of the F<ev.h> header file used to include it. The default if
2904	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4375	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2905	used to virtually rename the F<ev.h> header file in case of conflicts.	4376	used to virtually rename the F<ev.h> header file in case of conflicts.
2906		4377
2907	=item EV_CONFIG_H	4378	=item EV_CONFIG_H (h)
2908		4379
2909	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4380	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2910	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4381	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2911	C<EV_H>, above.	4382	C<EV_H>, above.
2912		4383
2913	=item EV_EVENT_H	4384	=item EV_EVENT_H (h)
2914		4385
2915	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4386	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2916	of how the F<event.h> header can be found, the default is C<"event.h">.	4387	of how the F<event.h> header can be found, the default is C<"event.h">.
2917		4388
2918	=item EV_PROTOTYPES	4389	=item EV_PROTOTYPES (h)
2919		4390
2920	If defined to be C<0>, then F<ev.h> will not define any function	4391	If defined to be C<0>, then F<ev.h> will not define any function
2921	prototypes, but still define all the structs and other symbols. This is	4392	prototypes, but still define all the structs and other symbols. This is
2922	occasionally useful if you want to provide your own wrapper functions	4393	occasionally useful if you want to provide your own wrapper functions
2923	around libev functions.	4394	around libev functions.
…		…
2942	When doing priority-based operations, libev usually has to linearly search	4413	When doing priority-based operations, libev usually has to linearly search
2943	all the priorities, so having many of them (hundreds) uses a lot of space	4414	all the priorities, so having many of them (hundreds) uses a lot of space
2944	and time, so using the defaults of five priorities (-2 .. +2) is usually	4415	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	4416	fine.
2946		4417
2947	If your embedding app does not need any priorities, defining these both to	4418	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	4419	both to C<0> will save some memory and CPU.
2949		4420
2950	=item EV_PERIODIC_ENABLE	4421	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4422	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4423	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2951		4424
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	4425	If undefined or defined to be C<1> (and the platform supports it), then
2953	defined to be C<0>, then they are not. Disabling them saves a few kB of	4426	the respective watcher type is supported. If defined to be C<0>, then it
2954	code.	4427	is not. Disabling watcher types mainly saves code size.
2955		4428
2956	=item EV_IDLE_ENABLE	4429	=item EV_FEATURES
2957
2958	If undefined or defined to be C<1>, then idle watchers are supported. If
2959	defined to be C<0>, then they are not. Disabling them saves a few kB of
2960	code.
2961
2962	=item EV_EMBED_ENABLE
2963
2964	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.
2966
2967	=item EV_STAT_ENABLE
2968
2969	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.
2971
2972	=item EV_FORK_ENABLE
2973
2974	If undefined or defined to be C<1>, then fork watchers are supported. If
2975	defined to be C<0>, then they are not.
2976
2977	=item EV_ASYNC_ENABLE
2978
2979	If undefined or defined to be C<1>, then async watchers are supported. If
2980	defined to be C<0>, then they are not.
2981
2982	=item EV_MINIMAL
2983		4430
2984	If you need to shave off some kilobytes of code at the expense of some	4431	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently this is used to override some	4432	speed (but with the full API), you can define this symbol to request
2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	4433	certain subsets of functionality. The default is to enable all features
2987	much smaller 2-heap for timer management over the default 4-heap.	4434	that can be enabled on the platform.
		4435
		4436	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4437	with some broad features you want) and then selectively re-enable
		4438	additional parts you want, for example if you want everything minimal,
		4439	but multiple event loop support, async and child watchers and the poll
		4440	backend, use this:
		4441
		4442	#define EV_FEATURES 0
		4443	#define EV_MULTIPLICITY 1
		4444	#define EV_USE_POLL 1
		4445	#define EV_CHILD_ENABLE 1
		4446	#define EV_ASYNC_ENABLE 1
		4447
		4448	The actual value is a bitset, it can be a combination of the following
		4449	values:
		4450
		4451	=over 4
		4452
		4453	=item C<1> - faster/larger code
		4454
		4455	Use larger code to speed up some operations.
		4456
		4457	Currently this is used to override some inlining decisions (enlarging the
		4458	code size by roughly 30% on amd64).
		4459
		4460	When optimising for size, use of compiler flags such as C<-Os> with
		4461	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4462	assertions.
		4463
		4464	=item C<2> - faster/larger data structures
		4465
		4466	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4467	hash table sizes and so on. This will usually further increase code size
		4468	and can additionally have an effect on the size of data structures at
		4469	runtime.
		4470
		4471	=item C<4> - full API configuration
		4472
		4473	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4474	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4475
		4476	=item C<8> - full API
		4477
		4478	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4479	details on which parts of the API are still available without this
		4480	feature, and do not complain if this subset changes over time.
		4481
		4482	=item C<16> - enable all optional watcher types
		4483
		4484	Enables all optional watcher types. If you want to selectively enable
		4485	only some watcher types other than I/O and timers (e.g. prepare,
		4486	embed, async, child...) you can enable them manually by defining
		4487	C<EV_watchertype_ENABLE> to C<1> instead.
		4488
		4489	=item C<32> - enable all backends
		4490
		4491	This enables all backends - without this feature, you need to enable at
		4492	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4493
		4494	=item C<64> - enable OS-specific "helper" APIs
		4495
		4496	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4497	default.
		4498
		4499	=back
		4500
		4501	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4502	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4503	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4504	watchers, timers and monotonic clock support.
		4505
		4506	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4507	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4508	your program might be left out as well - a binary starting a timer and an
		4509	I/O watcher then might come out at only 5Kb.
		4510
		4511	=item EV_AVOID_STDIO
		4512
		4513	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4514	functions (printf, scanf, perror etc.). This will increase the code size
		4515	somewhat, but if your program doesn't otherwise depend on stdio and your
		4516	libc allows it, this avoids linking in the stdio library which is quite
		4517	big.
		4518
		4519	Note that error messages might become less precise when this option is
		4520	enabled.
		4521
		4522	=item EV_NSIG
		4523
		4524	The highest supported signal number, +1 (or, the number of
		4525	signals): Normally, libev tries to deduce the maximum number of signals
		4526	automatically, but sometimes this fails, in which case it can be
		4527	specified. Also, using a lower number than detected (C<32> should be
		4528	good for about any system in existence) can save some memory, as libev
		4529	statically allocates some 12-24 bytes per signal number.
2988		4530
2989	=item EV_PID_HASHSIZE	4531	=item EV_PID_HASHSIZE
2990		4532
2991	C<ev_child> watchers use a small hash table to distribute workload by	4533	C<ev_child> watchers use a small hash table to distribute workload by
2992	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4534	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2993	than enough. If you need to manage thousands of children you might want to	4535	usually more than enough. If you need to manage thousands of children you
2994	increase this value (I<must> be a power of two).	4536	might want to increase this value (I<must> be a power of two).
2995		4537
2996	=item EV_INOTIFY_HASHSIZE	4538	=item EV_INOTIFY_HASHSIZE
2997		4539
2998	C<ev_stat> watchers use a small hash table to distribute workload by	4540	C<ev_stat> watchers use a small hash table to distribute workload by
2999	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4541	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3000	usually more than enough. If you need to manage thousands of C<ev_stat>	4542	disabled), usually more than enough. If you need to manage thousands of
3001	watchers you might want to increase this value (I<must> be a power of	4543	C<ev_stat> watchers you might want to increase this value (I<must> be a
3002	two).	4544	power of two).
3003		4545
3004	=item EV_USE_4HEAP	4546	=item EV_USE_4HEAP
3005		4547
3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4548	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4549	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3008	to C<1>. The 4-heap uses more complicated (longer) code but has	4550	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3009	noticably faster performance with many (thousands) of watchers.	4551	faster performance with many (thousands) of watchers.
3010		4552
3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4553	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3012	(disabled).	4554	will be C<0>.
3013		4555
3014	=item EV_HEAP_CACHE_AT	4556	=item EV_HEAP_CACHE_AT
3015		4557
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4558	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev can cache the timestamp (I<at>) within	4559	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4560	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4561	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020	but avoids random read accesses on heap changes. This improves performance	4562	but avoids random read accesses on heap changes. This improves performance
3021	noticably with with many (hundreds) of watchers.	4563	noticeably with many (hundreds) of watchers.
3022		4564
3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4565	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3024	(disabled).	4566	will be C<0>.
		4567
		4568	=item EV_VERIFY
		4569
		4570	Controls how much internal verification (see C<ev_verify ()>) will
		4571	be done: If set to C<0>, no internal verification code will be compiled
		4572	in. If set to C<1>, then verification code will be compiled in, but not
		4573	called. If set to C<2>, then the internal verification code will be
		4574	called once per loop, which can slow down libev. If set to C<3>, then the
		4575	verification code will be called very frequently, which will slow down
		4576	libev considerably.
		4577
		4578	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4579	will be C<0>.
3025		4580
3026	=item EV_COMMON	4581	=item EV_COMMON
3027		4582
3028	By default, all watchers have a C<void *data> member. By redefining	4583	By default, all watchers have a C<void *data> member. By redefining
3029	this macro to a something else you can include more and other types of	4584	this macro to something else you can include more and other types of
3030	members. You have to define it each time you include one of the files,	4585	members. You have to define it each time you include one of the files,
3031	though, and it must be identical each time.	4586	though, and it must be identical each time.
3032		4587
3033	For example, the perl EV module uses something like this:	4588	For example, the perl EV module uses something like this:
3034		4589
3035	#define EV_COMMON \	4590	#define EV_COMMON \
3036	SV *self; /* contains this struct */ \	4591	SV *self; /* contains this struct */ \
3037	SV *cb_sv, *fh /* note no trailing ";" */	4592	SV *cb_sv, *fh /* note no trailing ";" */
3038		4593
3039	=item EV_CB_DECLARE (type)	4594	=item EV_CB_DECLARE (type)
3040		4595
3041	=item EV_CB_INVOKE (watcher, revents)	4596	=item EV_CB_INVOKE (watcher, revents)
3042		4597
…		…
3047	definition and a statement, respectively. See the F<ev.h> header file for	4602	definition and a statement, respectively. See the F<ev.h> header file for
3048	their default definitions. One possible use for overriding these is to	4603	their default definitions. One possible use for overriding these is to
3049	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4604	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050	method calls instead of plain function calls in C++.	4605	method calls instead of plain function calls in C++.
3051		4606
		4607	=back
		4608
3052	=head2 EXPORTED API SYMBOLS	4609	=head2 EXPORTED API SYMBOLS
3053		4610
3054	If you need to re-export the API (e.g. via a dll) and you need a list of	4611	If you need to re-export the API (e.g. via a DLL) and you need a list of
3055	exported symbols, you can use the provided F<Symbol.*> files which list	4612	exported symbols, you can use the provided F<Symbol.*> files which list
3056	all public symbols, one per line:	4613	all public symbols, one per line:
3057		4614
3058	Symbols.ev for libev proper	4615	Symbols.ev for libev proper
3059	Symbols.event for the libevent emulation	4616	Symbols.event for the libevent emulation
3060		4617
3061	This can also be used to rename all public symbols to avoid clashes with	4618	This can also be used to rename all public symbols to avoid clashes with
3062	multiple versions of libev linked together (which is obviously bad in	4619	multiple versions of libev linked together (which is obviously bad in
3063	itself, but sometimes it is inconvinient to avoid this).	4620	itself, but sometimes it is inconvenient to avoid this).
3064		4621
3065	A sed command like this will create wrapper C<#define>'s that you need to	4622	A sed command like this will create wrapper C<#define>'s that you need to
3066	include before including F<ev.h>:	4623	include before including F<ev.h>:
3067		4624
3068	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4625	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3085	file.	4642	file.
3086		4643
3087	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4644	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088	that everybody includes and which overrides some configure choices:	4645	that everybody includes and which overrides some configure choices:
3089		4646
3090	#define EV_MINIMAL 1	4647	#define EV_FEATURES 8
3091	#define EV_USE_POLL 0	4648	#define EV_USE_SELECT 1
3092	#define EV_MULTIPLICITY 0
3093	#define EV_PERIODIC_ENABLE 0	4649	#define EV_PREPARE_ENABLE 1
		4650	#define EV_IDLE_ENABLE 1
3094	#define EV_STAT_ENABLE 0	4651	#define EV_SIGNAL_ENABLE 1
3095	#define EV_FORK_ENABLE 0	4652	#define EV_CHILD_ENABLE 1
		4653	#define EV_USE_STDEXCEPT 0
3096	#define EV_CONFIG_H <config.h>	4654	#define EV_CONFIG_H <config.h>
3097	#define EV_MINPRI 0
3098	#define EV_MAXPRI 0
3099		4655
3100	#include "ev++.h"	4656	#include "ev++.h"
3101		4657
3102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103		4659
3104	#include "ev_cpp.h"	4660	#include "ev_cpp.h"
3105	#include "ev.c"	4661	#include "ev.c"
3106		4662
		4663	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3107		4664
3108	=head1 THREADS AND COROUTINES	4665	=head2 THREADS AND COROUTINES
3109		4666
3110	=head2 THREADS	4667	=head3 THREADS
3111		4668
3112	Libev itself is completely threadsafe, but it uses no locking. This	4669	All libev functions are reentrant and thread-safe unless explicitly
		4670	documented otherwise, but libev implements no locking itself. This means
3113	means that you can use as many loops as you want in parallel, as long as	4671	that you can use as many loops as you want in parallel, as long as there
3114	only one thread ever calls into one libev function with the same loop	4672	are no concurrent calls into any libev function with the same loop
3115	parameter.	4673	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4674	of course): libev guarantees that different event loops share no data
		4675	structures that need any locking.
3116		4676
3117	Or put differently: calls with different loop parameters can be done in	4677	Or to put it differently: calls with different loop parameters can be done
3118	parallel from multiple threads, calls with the same loop parameter must be	4678	concurrently from multiple threads, calls with the same loop parameter
3119	done serially (but can be done from different threads, as long as only one	4679	must be done serially (but can be done from different threads, as long as
3120	thread ever is inside a call at any point in time, e.g. by using a mutex	4680	only one thread ever is inside a call at any point in time, e.g. by using
3121	per loop).	4681	a mutex per loop).
3122		4682
3123	If you want to know which design is best for your problem, then I cannot	4683	Specifically to support threads (and signal handlers), libev implements
		4684	so-called C<ev_async> watchers, which allow some limited form of
		4685	concurrency on the same event loop, namely waking it up "from the
		4686	outside".
		4687
		4688	If you want to know which design (one loop, locking, or multiple loops
		4689	without or something else still) is best for your problem, then I cannot
3124	help you but by giving some generic advice:	4690	help you, but here is some generic advice:
3125		4691
3126	=over 4	4692	=over 4
3127		4693
3128	=item * most applications have a main thread: use the default libev loop	4694	=item * most applications have a main thread: use the default libev loop
3129	in that thread, or create a seperate thread running only the default loop.	4695	in that thread, or create a separate thread running only the default loop.
3130		4696
3131	This helps integrating other libraries or software modules that use libev	4697	This helps integrating other libraries or software modules that use libev
3132	themselves and don't care/know about threading.	4698	themselves and don't care/know about threading.
3133		4699
3134	=item * one loop per thread is usually a good model.	4700	=item * one loop per thread is usually a good model.
3135		4701
3136	Doing this is almost never wrong, sometimes a better-performance model	4702	Doing this is almost never wrong, sometimes a better-performance model
3137	exists, but it is always a good start.	4703	exists, but it is always a good start.
3138		4704
3139	=item * other models exist, such as the leader/follower pattern, where one	4705	=item * other models exist, such as the leader/follower pattern, where one
3140	loop is handed through multiple threads in a kind of round-robbin fashion.	4706	loop is handed through multiple threads in a kind of round-robin fashion.
3141		4707
3142	Chosing a model is hard - look around, learn, know that usually you cna do	4708	Choosing a model is hard - look around, learn, know that usually you can do
3143	better than you currently do :-)	4709	better than you currently do :-)
3144		4710
3145	=item * often you need to talk to some other thread which blocks in the	4711	=item * often you need to talk to some other thread which blocks in the
		4712	event loop.
		4713
3146	event loop - C<ev_async> watchers can be used to wake them up from other	4714	C<ev_async> watchers can be used to wake them up from other threads safely
3147	threads safely (or from signal contexts...).	4715	(or from signal contexts...).
		4716
		4717	An example use would be to communicate signals or other events that only
		4718	work in the default loop by registering the signal watcher with the
		4719	default loop and triggering an C<ev_async> watcher from the default loop
		4720	watcher callback into the event loop interested in the signal.
3148		4721
3149	=back	4722	=back
3150		4723
		4724	See also L<THREAD LOCKING EXAMPLE>.
		4725
3151	=head2 COROUTINES	4726	=head3 COROUTINES
3152		4727
3153	Libev is much more accomodating to coroutines ("cooperative threads"):	4728	Libev is very accommodating to coroutines ("cooperative threads"):
3154	libev fully supports nesting calls to it's functions from different	4729	libev fully supports nesting calls to its functions from different
3155	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4730	coroutines (e.g. you can call C<ev_run> on the same loop from two
3156	different coroutines and switch freely between both coroutines running the	4731	different coroutines, and switch freely between both coroutines running
3157	loop, as long as you don't confuse yourself). The only exception is that	4732	the loop, as long as you don't confuse yourself). The only exception is
3158	you must not do this from C<ev_periodic> reschedule callbacks.	4733	that you must not do this from C<ev_periodic> reschedule callbacks.
3159		4734
3160	Care has been invested into making sure that libev does not keep local	4735	Care has been taken to ensure that libev does not keep local state inside
3161	state inside C<ev_loop>, and other calls do not usually allow coroutine	4736	C<ev_run>, and other calls do not usually allow for coroutine switches as
3162	switches.	4737	they do not call any callbacks.
3163		4738
		4739	=head2 COMPILER WARNINGS
3164		4740
3165	=head1 COMPLEXITIES	4741	Depending on your compiler and compiler settings, you might get no or a
		4742	lot of warnings when compiling libev code. Some people are apparently
		4743	scared by this.
3166		4744
3167	In this section the complexities of (many of) the algorithms used inside	4745	However, these are unavoidable for many reasons. For one, each compiler
3168	libev will be explained. For complexity discussions about backends see the	4746	has different warnings, and each user has different tastes regarding
3169	documentation for C<ev_default_init>.	4747	warning options. "Warn-free" code therefore cannot be a goal except when
		4748	targeting a specific compiler and compiler-version.
3170		4749
3171	All of the following are about amortised time: If an array needs to be	4750	Another reason is that some compiler warnings require elaborate
3172	extended, libev needs to realloc and move the whole array, but this	4751	workarounds, or other changes to the code that make it less clear and less
3173	happens asymptotically never with higher number of elements, so O(1) might	4752	maintainable.
3174	mean it might do a lengthy realloc operation in rare cases, but on average
3175	it is much faster and asymptotically approaches constant time.
3176		4753
3177	=over 4	4754	And of course, some compiler warnings are just plain stupid, or simply
		4755	wrong (because they don't actually warn about the condition their message
		4756	seems to warn about). For example, certain older gcc versions had some
		4757	warnings that resulted in an extreme number of false positives. These have
		4758	been fixed, but some people still insist on making code warn-free with
		4759	such buggy versions.
3178		4760
3179	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4761	While libev is written to generate as few warnings as possible,
		4762	"warn-free" code is not a goal, and it is recommended not to build libev
		4763	with any compiler warnings enabled unless you are prepared to cope with
		4764	them (e.g. by ignoring them). Remember that warnings are just that:
		4765	warnings, not errors, or proof of bugs.
3180		4766
3181	This means that, when you have a watcher that triggers in one hour and
3182	there are 100 watchers that would trigger before that then inserting will
3183	have to skip roughly seven (C<ld 100>) of these watchers.
3184		4767
3185	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4768	=head2 VALGRIND
3186		4769
3187	That means that changing a timer costs less than removing/adding them	4770	Valgrind has a special section here because it is a popular tool that is
3188	as only the relative motion in the event queue has to be paid for.	4771	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3189		4772
3190	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4773	If you think you found a bug (memory leak, uninitialised data access etc.)
		4774	in libev, then check twice: If valgrind reports something like:
3191		4775
3192	These just add the watcher into an array or at the head of a list.	4776	==2274== definitely lost: 0 bytes in 0 blocks.
		4777	==2274== possibly lost: 0 bytes in 0 blocks.
		4778	==2274== still reachable: 256 bytes in 1 blocks.
3193		4779
3194	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4780	Then there is no memory leak, just as memory accounted to global variables
		4781	is not a memleak - the memory is still being referenced, and didn't leak.
3195		4782
3196	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4783	Similarly, under some circumstances, valgrind might report kernel bugs
		4784	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4785	although an acceptable workaround has been found here), or it might be
		4786	confused.
3197		4787
3198	These watchers are stored in lists then need to be walked to find the	4788	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3199	correct watcher to remove. The lists are usually short (you don't usually	4789	make it into some kind of religion.
3200	have many watchers waiting for the same fd or signal).
3201		4790
3202	=item Finding the next timer in each loop iteration: O(1)	4791	If you are unsure about something, feel free to contact the mailing list
		4792	with the full valgrind report and an explanation on why you think this
		4793	is a bug in libev (best check the archives, too :). However, don't be
		4794	annoyed when you get a brisk "this is no bug" answer and take the chance
		4795	of learning how to interpret valgrind properly.
3203		4796
3204	By virtue of using a binary or 4-heap, the next timer is always found at a	4797	If you need, for some reason, empty reports from valgrind for your project
3205	fixed position in the storage array.	4798	I suggest using suppression lists.
3206		4799
3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208		4800
3209	A change means an I/O watcher gets started or stopped, which requires	4801	=head1 PORTABILITY NOTES
3210	libev to recalculate its status (and possibly tell the kernel, depending
3211	on backend and wether C<ev_io_set> was used).
3212		4802
3213	=item Activating one watcher (putting it into the pending state): O(1)	4803	=head2 GNU/LINUX 32 BIT LIMITATIONS
3214		4804
3215	=item Priority handling: O(number_of_priorities)	4805	GNU/Linux is the only common platform that supports 64 bit file/large file
		4806	interfaces but I<disables> them by default.
3216		4807
3217	Priorities are implemented by allocating some space for each	4808	That means that libev compiled in the default environment doesn't support
3218	priority. When doing priority-based operations, libev usually has to	4809	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3219	linearly search all the priorities, but starting/stopping and activating
3220	watchers becomes O(1) w.r.t. priority handling.
3221		4810
3222	=item Sending an ev_async: O(1)	4811	Unfortunately, many programs try to work around this GNU/Linux issue
		4812	by enabling the large file API, which makes them incompatible with the
		4813	standard libev compiled for their system.
3223		4814
3224	=item Processing ev_async_send: O(number_of_async_watchers)	4815	Likewise, libev cannot enable the large file API itself as this would
		4816	suddenly make it incompatible to the default compile time environment,
		4817	i.e. all programs not using special compile switches.
3225		4818
3226	=item Processing signals: O(max_signal_number)	4819	=head2 OS/X AND DARWIN BUGS
3227		4820
3228	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4821	The whole thing is a bug if you ask me - basically any system interface
3229	calls in the current loop iteration. Checking for async and signal events	4822	you touch is broken, whether it is locales, poll, kqueue or even the
3230	involves iterating over all running async watchers or all signal numbers.	4823	OpenGL drivers.
3231		4824
3232	=back	4825	=head3 C<kqueue> is buggy
3233		4826
		4827	The kqueue syscall is broken in all known versions - most versions support
		4828	only sockets, many support pipes.
3234		4829
3235	=head1 Win32 platform limitations and workarounds	4830	Libev tries to work around this by not using C<kqueue> by default on this
		4831	rotten platform, but of course you can still ask for it when creating a
		4832	loop - embedding a socket-only kqueue loop into a select-based one is
		4833	probably going to work well.
		4834
		4835	=head3 C<poll> is buggy
		4836
		4837	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4838	implementation by something calling C<kqueue> internally around the 10.5.6
		4839	release, so now C<kqueue> I<and> C<poll> are broken.
		4840
		4841	Libev tries to work around this by not using C<poll> by default on
		4842	this rotten platform, but of course you can still ask for it when creating
		4843	a loop.
		4844
		4845	=head3 C<select> is buggy
		4846
		4847	All that's left is C<select>, and of course Apple found a way to fuck this
		4848	one up as well: On OS/X, C<select> actively limits the number of file
		4849	descriptors you can pass in to 1024 - your program suddenly crashes when
		4850	you use more.
		4851
		4852	There is an undocumented "workaround" for this - defining
		4853	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4854	work on OS/X.
		4855
		4856	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4857
		4858	=head3 C<errno> reentrancy
		4859
		4860	The default compile environment on Solaris is unfortunately so
		4861	thread-unsafe that you can't even use components/libraries compiled
		4862	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4863	defined by default. A valid, if stupid, implementation choice.
		4864
		4865	If you want to use libev in threaded environments you have to make sure
		4866	it's compiled with C<_REENTRANT> defined.
		4867
		4868	=head3 Event port backend
		4869
		4870	The scalable event interface for Solaris is called "event
		4871	ports". Unfortunately, this mechanism is very buggy in all major
		4872	releases. If you run into high CPU usage, your program freezes or you get
		4873	a large number of spurious wakeups, make sure you have all the relevant
		4874	and latest kernel patches applied. No, I don't know which ones, but there
		4875	are multiple ones to apply, and afterwards, event ports actually work
		4876	great.
		4877
		4878	If you can't get it to work, you can try running the program by setting
		4879	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4880	C<select> backends.
		4881
		4882	=head2 AIX POLL BUG
		4883
		4884	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4885	this by trying to avoid the poll backend altogether (i.e. it's not even
		4886	compiled in), which normally isn't a big problem as C<select> works fine
		4887	with large bitsets on AIX, and AIX is dead anyway.
		4888
		4889	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4890
		4891	=head3 General issues
3236		4892
3237	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4893	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238	requires, and its I/O model is fundamentally incompatible with the POSIX	4894	requires, and its I/O model is fundamentally incompatible with the POSIX
3239	model. Libev still offers limited functionality on this platform in	4895	model. Libev still offers limited functionality on this platform in
3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4896	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3241	descriptors. This only applies when using Win32 natively, not when using	4897	descriptors. This only applies when using Win32 natively, not when using
3242	e.g. cygwin.	4898	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4899	as every compielr comes with a slightly differently broken/incompatible
		4900	environment.
3243		4901
3244	Lifting these limitations would basically require the full	4902	Lifting these limitations would basically require the full
3245	re-implementation of the I/O system. If you are into these kinds of	4903	re-implementation of the I/O system. If you are into this kind of thing,
3246	things, then note that glib does exactly that for you in a very portable	4904	then note that glib does exactly that for you in a very portable way (note
3247	way (note also that glib is the slowest event library known to man).	4905	also that glib is the slowest event library known to man).
3248		4906
3249	There is no supported compilation method available on windows except	4907	There is no supported compilation method available on windows except
3250	embedding it into other applications.	4908	embedding it into other applications.
		4909
		4910	Sensible signal handling is officially unsupported by Microsoft - libev
		4911	tries its best, but under most conditions, signals will simply not work.
		4912
		4913	Not a libev limitation but worth mentioning: windows apparently doesn't
		4914	accept large writes: instead of resulting in a partial write, windows will
		4915	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4916	so make sure you only write small amounts into your sockets (less than a
		4917	megabyte seems safe, but this apparently depends on the amount of memory
		4918	available).
3251		4919
3252	Due to the many, low, and arbitrary limits on the win32 platform and	4920	Due to the many, low, and arbitrary limits on the win32 platform and
3253	the abysmal performance of winsockets, using a large number of sockets	4921	the abysmal performance of winsockets, using a large number of sockets
3254	is not recommended (and not reasonable). If your program needs to use	4922	is not recommended (and not reasonable). If your program needs to use
3255	more than a hundred or so sockets, then likely it needs to use a totally	4923	more than a hundred or so sockets, then likely it needs to use a totally
3256	different implementation for windows, as libev offers the POSIX readiness	4924	different implementation for windows, as libev offers the POSIX readiness
3257	notification model, which cannot be implemented efficiently on windows	4925	notification model, which cannot be implemented efficiently on windows
3258	(microsoft monopoly games).	4926	(due to Microsoft monopoly games).
3259		4927
3260	=over 4	4928	A typical way to use libev under windows is to embed it (see the embedding
		4929	section for details) and use the following F<evwrap.h> header file instead
		4930	of F<ev.h>:
3261		4931
		4932	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4933	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4934
		4935	#include "ev.h"
		4936
		4937	And compile the following F<evwrap.c> file into your project (make sure
		4938	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4939
		4940	#include "evwrap.h"
		4941	#include "ev.c"
		4942
3262	=item The winsocket select function	4943	=head3 The winsocket C<select> function
3263		4944
3264	The winsocket C<select> function doesn't follow POSIX in that it requires	4945	The winsocket C<select> function doesn't follow POSIX in that it
3265	socket I<handles> and not socket I<file descriptors>. This makes select	4946	requires socket I<handles> and not socket I<file descriptors> (it is
3266	very inefficient, and also requires a mapping from file descriptors	4947	also extremely buggy). This makes select very inefficient, and also
3267	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4948	requires a mapping from file descriptors to socket handles (the Microsoft
3268	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4949	C runtime provides the function C<_open_osfhandle> for this). See the
3269	symbols for more info.	4950	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4951	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270		4952
3271	The configuration for a "naked" win32 using the microsoft runtime	4953	The configuration for a "naked" win32 using the Microsoft runtime
3272	libraries and raw winsocket select is:	4954	libraries and raw winsocket select is:
3273		4955
3274	#define EV_USE_SELECT 1	4956	#define EV_USE_SELECT 1
3275	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4957	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276		4958
3277	Note that winsockets handling of fd sets is O(n), so you can easily get a	4959	Note that winsockets handling of fd sets is O(n), so you can easily get a
3278	complexity in the O(n²) range when using win32.	4960	complexity in the O(n²) range when using win32.
3279		4961
3280	=item Limited number of file descriptors	4962	=head3 Limited number of file descriptors
3281		4963
3282	Windows has numerous arbitrary (and low) limits on things.	4964	Windows has numerous arbitrary (and low) limits on things.
3283		4965
3284	Early versions of winsocket's select only supported waiting for a maximum	4966	Early versions of winsocket's select only supported waiting for a maximum
3285	of C<64> handles (probably owning to the fact that all windows kernels	4967	of C<64> handles (probably owning to the fact that all windows kernels
3286	can only wait for C<64> things at the same time internally; microsoft	4968	can only wait for C<64> things at the same time internally; Microsoft
3287	recommends spawning a chain of threads and wait for 63 handles and the	4969	recommends spawning a chain of threads and wait for 63 handles and the
3288	previous thread in each. Great).	4970	previous thread in each. Sounds great!).
3289		4971
3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4972	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291	to some high number (e.g. C<2048>) before compiling the winsocket select	4973	to some high number (e.g. C<2048>) before compiling the winsocket select
3292	call (which might be in libev or elsewhere, for example, perl does its own	4974	call (which might be in libev or elsewhere, for example, perl and many
3293	select emulation on windows).	4975	other interpreters do their own select emulation on windows).
3294		4976
3295	Another limit is the number of file descriptors in the microsoft runtime	4977	Another limit is the number of file descriptors in the Microsoft runtime
3296	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4978	libraries, which by default is C<64> (there must be a hidden I<64>
3297	or something like this inside microsoft). You can increase this by calling	4979	fetish or something like this inside Microsoft). You can increase this
3298	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4980	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3299	arbitrary limit), but is broken in many versions of the microsoft runtime	4981	(another arbitrary limit), but is broken in many versions of the Microsoft
3300	libraries.
3301
3302	This might get you to about C<512> or C<2048> sockets (depending on	4982	runtime libraries. This might get you to about C<512> or C<2048> sockets
3303	windows version and/or the phase of the moon). To get more, you need to	4983	(depending on windows version and/or the phase of the moon). To get more,
3304	wrap all I/O functions and provide your own fd management, but the cost of	4984	you need to wrap all I/O functions and provide your own fd management, but
3305	calling select (O(n²)) will likely make this unworkable.	4985	the cost of calling select (O(n²)) will likely make this unworkable.
3306		4986
3307	=back
3308
3309
3310	=head1 PORTABILITY REQUIREMENTS	4987	=head2 PORTABILITY REQUIREMENTS
3311		4988
3312	In addition to a working ISO-C implementation, libev relies on a few	4989	In addition to a working ISO-C implementation and of course the
3313	additional extensions:	4990	backend-specific APIs, libev relies on a few additional extensions:
3314		4991
3315	=over 4	4992	=over 4
3316		4993
		4994	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4995	calling conventions regardless of C<ev_watcher_type *>.
		4996
		4997	Libev assumes not only that all watcher pointers have the same internal
		4998	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4999	assumes that the same (machine) code can be used to call any watcher
		5000	callback: The watcher callbacks have different type signatures, but libev
		5001	calls them using an C<ev_watcher *> internally.
		5002
		5003	=item pointer accesses must be thread-atomic
		5004
		5005	Accessing a pointer value must be atomic, it must both be readable and
		5006	writable in one piece - this is the case on all current architectures.
		5007
3317	=item C<sig_atomic_t volatile> must be thread-atomic as well	5008	=item C<sig_atomic_t volatile> must be thread-atomic as well
3318		5009
3319	The type C<sig_atomic_t volatile> (or whatever is defined as	5010	The type C<sig_atomic_t volatile> (or whatever is defined as
3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	5011	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3321	threads. This is not part of the specification for C<sig_atomic_t>, but is	5012	threads. This is not part of the specification for C<sig_atomic_t>, but is
3322	believed to be sufficiently portable.	5013	believed to be sufficiently portable.
3323		5014
3324	=item C<sigprocmask> must work in a threaded environment	5015	=item C<sigprocmask> must work in a threaded environment
3325		5016
…		…
3334	except the initial one, and run the default loop in the initial thread as	5025	except the initial one, and run the default loop in the initial thread as
3335	well.	5026	well.
3336		5027
3337	=item C<long> must be large enough for common memory allocation sizes	5028	=item C<long> must be large enough for common memory allocation sizes
3338		5029
3339	To improve portability and simplify using libev, libev uses C<long>	5030	To improve portability and simplify its API, libev uses C<long> internally
3340	internally instead of C<size_t> when allocating its data structures. On	5031	instead of C<size_t> when allocating its data structures. On non-POSIX
3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	5032	systems (Microsoft...) this might be unexpectedly low, but is still at
3342	is still at least 31 bits everywhere, which is enough for hundreds of	5033	least 31 bits everywhere, which is enough for hundreds of millions of
3343	millions of watchers.	5034	watchers.
3344		5035
3345	=item C<double> must hold a time value in seconds with enough accuracy	5036	=item C<double> must hold a time value in seconds with enough accuracy
3346		5037
3347	The type C<double> is used to represent timestamps. It is required to	5038	The type C<double> is used to represent timestamps. It is required to
3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5039	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3349	enough for at least into the year 4000. This requirement is fulfilled by	5040	good enough for at least into the year 4000 with millisecond accuracy
		5041	(the design goal for libev). This requirement is overfulfilled by
3350	implementations implementing IEEE 754 (basically all existing ones).	5042	implementations using IEEE 754, which is basically all existing ones. With
		5043	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3351		5044
3352	=back	5045	=back
3353		5046
3354	If you know of other additional requirements drop me a note.	5047	If you know of other additional requirements drop me a note.
3355		5048
3356		5049
3357	=head1 VALGRIND	5050	=head1 ALGORITHMIC COMPLEXITIES
3358		5051
3359	Valgrind has a special section here because it is a popular tool that is	5052	In this section the complexities of (many of) the algorithms used inside
3360	highly useful, but valgrind reports are very hard to interpret.	5053	libev will be documented. For complexity discussions about backends see
		5054	the documentation for C<ev_default_init>.
3361		5055
3362	If you think you found a bug (memory leak, uninitialised data access etc.)	5056	All of the following are about amortised time: If an array needs to be
3363	in libev, then check twice: If valgrind reports something like:	5057	extended, libev needs to realloc and move the whole array, but this
		5058	happens asymptotically rarer with higher number of elements, so O(1) might
		5059	mean that libev does a lengthy realloc operation in rare cases, but on
		5060	average it is much faster and asymptotically approaches constant time.
3364		5061
3365	==2274== definitely lost: 0 bytes in 0 blocks.	5062	=over 4
3366	==2274== possibly lost: 0 bytes in 0 blocks.
3367	==2274== still reachable: 256 bytes in 1 blocks.
3368		5063
3369	then there is no memory leak. Similarly, under some circumstances,	5064	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3370	valgrind might report kernel bugs as if it were a bug in libev, or it
3371	might be confused (it is a very good tool, but only a tool).
3372		5065
3373	If you are unsure about something, feel free to contact the mailing list	5066	This means that, when you have a watcher that triggers in one hour and
3374	with the full valgrind report and an explanation on why you think this is	5067	there are 100 watchers that would trigger before that, then inserting will
3375	a bug in libev. However, don't be annoyed when you get a brisk "this is	5068	have to skip roughly seven (C<ld 100>) of these watchers.
3376	no bug" answer and take the chance of learning how to interpret valgrind
3377	properly.
3378		5069
3379	If you need, for some reason, empty reports from valgrind for your project	5070	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3380	I suggest using suppression lists.
3381		5071
		5072	That means that changing a timer costs less than removing/adding them,
		5073	as only the relative motion in the event queue has to be paid for.
		5074
		5075	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		5076
		5077	These just add the watcher into an array or at the head of a list.
		5078
		5079	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		5080
		5081	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		5082
		5083	These watchers are stored in lists, so they need to be walked to find the
		5084	correct watcher to remove. The lists are usually short (you don't usually
		5085	have many watchers waiting for the same fd or signal: one is typical, two
		5086	is rare).
		5087
		5088	=item Finding the next timer in each loop iteration: O(1)
		5089
		5090	By virtue of using a binary or 4-heap, the next timer is always found at a
		5091	fixed position in the storage array.
		5092
		5093	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		5094
		5095	A change means an I/O watcher gets started or stopped, which requires
		5096	libev to recalculate its status (and possibly tell the kernel, depending
		5097	on backend and whether C<ev_io_set> was used).
		5098
		5099	=item Activating one watcher (putting it into the pending state): O(1)
		5100
		5101	=item Priority handling: O(number_of_priorities)
		5102
		5103	Priorities are implemented by allocating some space for each
		5104	priority. When doing priority-based operations, libev usually has to
		5105	linearly search all the priorities, but starting/stopping and activating
		5106	watchers becomes O(1) with respect to priority handling.
		5107
		5108	=item Sending an ev_async: O(1)
		5109
		5110	=item Processing ev_async_send: O(number_of_async_watchers)
		5111
		5112	=item Processing signals: O(max_signal_number)
		5113
		5114	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5115	calls in the current loop iteration. Checking for async and signal events
		5116	involves iterating over all running async watchers or all signal numbers.
		5117
		5118	=back
		5119
		5120
		5121	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5122
		5123	The major version 4 introduced some incompatible changes to the API.
		5124
		5125	At the moment, the C<ev.h> header file provides compatibility definitions
		5126	for all changes, so most programs should still compile. The compatibility
		5127	layer might be removed in later versions of libev, so better update to the
		5128	new API early than late.
		5129
		5130	=over 4
		5131
		5132	=item C<EV_COMPAT3> backwards compatibility mechanism
		5133
		5134	The backward compatibility mechanism can be controlled by
		5135	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5136	section.
		5137
		5138	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5139
		5140	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5141
		5142	ev_loop_destroy (EV_DEFAULT_UC);
		5143	ev_loop_fork (EV_DEFAULT);
		5144
		5145	=item function/symbol renames
		5146
		5147	A number of functions and symbols have been renamed:
		5148
		5149	ev_loop => ev_run
		5150	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5151	EVLOOP_ONESHOT => EVRUN_ONCE
		5152
		5153	ev_unloop => ev_break
		5154	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5155	EVUNLOOP_ONE => EVBREAK_ONE
		5156	EVUNLOOP_ALL => EVBREAK_ALL
		5157
		5158	EV_TIMEOUT => EV_TIMER
		5159
		5160	ev_loop_count => ev_iteration
		5161	ev_loop_depth => ev_depth
		5162	ev_loop_verify => ev_verify
		5163
		5164	Most functions working on C<struct ev_loop> objects don't have an
		5165	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5166	associated constants have been renamed to not collide with the C<struct
		5167	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5168	as all other watcher types. Note that C<ev_loop_fork> is still called
		5169	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5170	typedef.
		5171
		5172	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5173
		5174	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5175	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5176	and work, but the library code will of course be larger.
		5177
		5178	=back
		5179
		5180
		5181	=head1 GLOSSARY
		5182
		5183	=over 4
		5184
		5185	=item active
		5186
		5187	A watcher is active as long as it has been started and not yet stopped.
		5188	See L<WATCHER STATES> for details.
		5189
		5190	=item application
		5191
		5192	In this document, an application is whatever is using libev.
		5193
		5194	=item backend
		5195
		5196	The part of the code dealing with the operating system interfaces.
		5197
		5198	=item callback
		5199
		5200	The address of a function that is called when some event has been
		5201	detected. Callbacks are being passed the event loop, the watcher that
		5202	received the event, and the actual event bitset.
		5203
		5204	=item callback/watcher invocation
		5205
		5206	The act of calling the callback associated with a watcher.
		5207
		5208	=item event
		5209
		5210	A change of state of some external event, such as data now being available
		5211	for reading on a file descriptor, time having passed or simply not having
		5212	any other events happening anymore.
		5213
		5214	In libev, events are represented as single bits (such as C<EV_READ> or
		5215	C<EV_TIMER>).
		5216
		5217	=item event library
		5218
		5219	A software package implementing an event model and loop.
		5220
		5221	=item event loop
		5222
		5223	An entity that handles and processes external events and converts them
		5224	into callback invocations.
		5225
		5226	=item event model
		5227
		5228	The model used to describe how an event loop handles and processes
		5229	watchers and events.
		5230
		5231	=item pending
		5232
		5233	A watcher is pending as soon as the corresponding event has been
		5234	detected. See L<WATCHER STATES> for details.
		5235
		5236	=item real time
		5237
		5238	The physical time that is observed. It is apparently strictly monotonic :)
		5239
		5240	=item wall-clock time
		5241
		5242	The time and date as shown on clocks. Unlike real time, it can actually
		5243	be wrong and jump forwards and backwards, e.g. when you adjust your
		5244	clock.
		5245
		5246	=item watcher
		5247
		5248	A data structure that describes interest in certain events. Watchers need
		5249	to be started (attached to an event loop) before they can receive events.
		5250
		5251	=back
3382		5252
3383	=head1 AUTHOR	5253	=head1 AUTHOR
3384		5254
3385	Marc Lehmann <libev@schmorp.de>.	5255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5256	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3386		5257

Diff Legend

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