ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC vs.
Revision 1.356 by root, Tue Jan 11 01:42:47 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	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	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	This flag's behaviour will become the default in future versions of libev.
327		448
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		450
330	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	453	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	454	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.	455	usually the fastest backend for a low number of (low-numbered :) fds.
335		456
336	To get good performance out of this backend you need a high amount of	457	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	458	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	459	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	460	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	461	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	462	readiness notifications you get per iteration.
		463
		464	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		465	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		466	C<exceptfds> set on that platform).
342		467
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	468	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		469
345	And this is your standard poll(2) backend. It's more complicated	470	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	471	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	472	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,	473	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	474	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	475	performance tips.
351		476
		477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		479
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
353		484
354	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	488	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	489
359	cases and requiring a syscall per fd change, no fork support and bad	490	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
		493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
		496	0.1ms) and so on. The biggest issue is fork races, however - if a program
		497	forks then I<both> parent and child process have to recreate the epoll
		498	set, which can take considerable time (one syscall per file descriptor)
		499	and is of course hard to detect.
		500
		501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		502	of course I<doesn't>, and epoll just loves to report events for totally
		503	I<different> file descriptors (even already closed ones, so one cannot
		504	even remove them from the set) than registered in the set (especially
		505	on SMP systems). Libev tries to counter these spurious notifications by
		506	employing an additional generation counter and comparing that against the
		507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
361		514
362	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	516	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	517	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	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	519	file descriptors might not work very well if you register events for both
367		520	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		521
372	Best performance from this backend is achieved by not unregistering all	522	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.	523	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	524	i.e. keep at least one watcher active per fd at all times. Stopping and
		525	starting a watcher (without re-setting it) also usually doesn't cause
		526	extra overhead. A fork can both result in spurious notifications as well
		527	as in libev having to destroy and recreate the epoll object, which can
		528	take considerable time and thus should be avoided.
375		529
		530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		531	faster than epoll for maybe up to a hundred file descriptors, depending on
		532	the usage. So sad.
		533
376	While nominally embeddeble in other event loops, this feature is broken in	534	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	535	all kernel versions tested so far.
		536
		537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		538	C<EVBACKEND_POLL>.
378		539
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		541
381	Kqueue deserves special mention, as at the time of this writing, it	542	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	543	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	544	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"	545	it's completely useless). Unlike epoll, however, whose brokenness
		546	is by design, these kqueue bugs can (and eventually will) be fixed
		547	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	548	"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)	549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	550	system like NetBSD.
388		551
389	You still can embed kqueue into a normal poll or select backend and use it	552	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	553	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.	554	the target platform). See C<ev_embed> watchers for more info.
392		555
393	It scales in the same way as the epoll backend, but the interface to the	556	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	557	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	558	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	559	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	560	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		562	cases
399		563
400	This backend usually performs well under most conditions.	564	This backend usually performs well under most conditions.
401		565
402	While nominally embeddable in other event loops, this doesn't work	566	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	567	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	568	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	569	(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	570	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	571	also broken on OS X)) and, did I mention it, using it only for sockets.
		572
		573	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		574	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		575	C<NOTE_EOF>.
408		576
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	577	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		578
411	This is not implemented yet (and might never be, unless you send me an	579	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	580	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		585
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
420		588
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	589	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	590	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	592	might perform better.
429		593
430	On the positive side, ignoring the spurious readyness notifications, this	594	On the positive side, this backend actually performed fully to
431	backend actually performed to specification in all tests and is fully	595	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.	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
		608
		609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		610	C<EVBACKEND_POLL>.
433		611
434	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
435		613
436	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
439		617
440	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
441		627
442	=back	628	=back
443		629
444	If one or more of these are ored into the flags value, then only these	630	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	631	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.	632	here). If none are specified, all backends in C<ev_recommended_backends
447		633	()> 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		634
475	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
476		636
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	638	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
480		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
481	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
482		647
483	Destroys the default loop again (frees all memory and kernel state	648	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	649	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	650	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>	651	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	654	for example).
490		655
491	Note that certain global state, such as signal state, will not be freed by	656	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	657	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
494		659
495	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
496	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
497	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
498	C<ev_loop_new> and C<ev_loop_destroy>).	667	and C<ev_loop_destroy>.
499		668
500	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
501		670
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	671	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	672	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	673	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	674	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	675	child before resuming or calling C<ev_run>.
512	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
513		681
514	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
515	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
516	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
517		688
518	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
519	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
520	quite nicely into a call to C<pthread_atfork>:
521		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
522	pthread_atfork (0, 0, ev_default_fork);	702	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		703
530	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
531		705
532	Returns true when the given loop actually is the default loop, false otherwise.	706	Returns true when the given loop is, in fact, the default loop, and false
		707	otherwise.
533		708
534	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
535		710
536	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
537	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
538	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
539		714
540	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
543		733
544	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
545		735
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	737	use.
…		…
552	received events and started processing them. This timestamp does not	742	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	743	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	744	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).	745	event occurring (or more correctly, libev finding out about it).
556		746
		747	=item ev_now_update (loop)
		748
		749	Establishes the current time by querying the kernel, updating the time
		750	returned by C<ev_now ()> in the progress. This is a costly operation and
		751	is usually done automatically within C<ev_run ()>.
		752
		753	This function is rarely useful, but when some event callback runs for a
		754	very long time without entering the event loop, updating libev's idea of
		755	the current time is a good idea.
		756
		757	See also L<The special problem of time updates> in the C<ev_timer> section.
		758
		759	=item ev_suspend (loop)
		760
		761	=item ev_resume (loop)
		762
		763	These two functions suspend and resume an event loop, for use when the
		764	loop is not used for a while and timeouts should not be processed.
		765
		766	A typical use case would be an interactive program such as a game: When
		767	the user presses C<^Z> to suspend the game and resumes it an hour later it
		768	would be best to handle timeouts as if no time had actually passed while
		769	the program was suspended. This can be achieved by calling C<ev_suspend>
		770	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		771	C<ev_resume> directly afterwards to resume timer processing.
		772
		773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		775	will be rescheduled (that is, they will lose any events that would have
		776	occurred while suspended).
		777
		778	After calling C<ev_suspend> you B<must not> call I<any> function on the
		779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		780	without a previous call to C<ev_suspend>.
		781
		782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		783	event loop time (see C<ev_now_update>).
		784
557	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
558		786
559	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
561	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
562		792
563	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
564	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
565		796
566	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	799	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	800	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.	801	of relying on its watchers stopping correctly, that is truly a thing of
		802	beauty.
571		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	810	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.	811	block your process in case there are no events and will return after one
		812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
575		814
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	816	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	817	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	818	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	819	user-registered callback will be called), and will return after one
		820	iteration of the loop.
		821
		822	This is useful if you are waiting for some external event in conjunction
		823	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	824	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.	825	usually a better approach for this kind of thing.
583		826
584	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
585		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
586	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
587	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
590	- If we have been forked, recreate the kernel state.	837	- If we have been forked, detach and recreate the kernel state
		838	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	840	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
595	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
597	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	849	- Queue all expired timers.
601	- Queue all outstanding periodics.	850	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
603	- Queue all check watchers.	852	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
608	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
609	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
610		863
611	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
612	anymore.	865	anymore.
613		866
614	... queue jobs here, make sure they register event watchers as long	867	... 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..)	868	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
617	... jobs done. yeah!	870	... jobs done or somebody called unloop. yeah!
618		871
619	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
620		873
621	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
625		878
626	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
		880
		881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
627		883
628	=item ev_ref (loop)	884	=item ev_ref (loop)
629		885
630	=item ev_unref (loop)	886	=item ev_unref (loop)
631		887
632	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	890	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	891
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	892	This is useful when you have a watcher that you never intend to
		893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		895	before stopping it.
		896
637	example, libev itself uses this for its internal signal pipe: It is not	897	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	898	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	899	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	900	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>	901	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,	902	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	903	before, respectively. Note also that libev might stop watchers itself
		904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		905	in the callback).
644		906
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
646	running when nothing else is active.	908	running when nothing else is active.
647		909
648	struct ev_signal exitsig;	910	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	913	ev_unref (loop);
652		914
653	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
654		916
655	ev_ref (loop);	917	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
657		919
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	920	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		921
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	922	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		923
662	These advanced functions influence the time that libev will spend waiting	924	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	925	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.	926	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		927	latency.
665		928
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	929	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	930	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	931	to increase efficiency of loop iterations (or to increase power-saving
		932	opportunities).
669		933
670	The background is that sometimes your program runs just fast enough to	934	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	935	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	936	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	937	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	938	overhead for the actual polling but can deliver many events at once.
675		939
676	By setting a higher I<io collect interval> you allow libev to spend more	940	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,	941	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	942	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	943	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.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
681		947
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	950	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	952	value will not introduce any overhead in libev.
687		953
688	Many (busy) programs can usually benefit by setting the io collect	954	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	955	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	956	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>,	957	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.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
		963
		964	Setting the I<timeout collect interval> can improve the opportunity for
		965	saving power, as the program will "bundle" timer callback invocations that
		966	are "near" in time together, by delaying some, thus reducing the number of
		967	times the process sleeps and wakes up again. Another useful technique to
		968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		969	they fire on, say, one-second boundaries only.
		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
		1046	=item ev_verify (loop)
		1047
		1048	This function only does something when C<EV_VERIFY> support has been
		1049	compiled in, which is the default for non-minimal builds. It tries to go
		1050	through all internal structures and checks them for validity. If anything
		1051	is found to be inconsistent, it will print an error message to standard
		1052	error and call C<abort ()>.
		1053
		1054	This can be used to catch bugs inside libev itself: under normal
		1055	circumstances, this function will never abort as of course libev keeps its
		1056	data structures consistent.
693		1057
694	=back	1058	=back
695		1059
696		1060
697	=head1 ANATOMY OF A WATCHER	1061	=head1 ANATOMY OF A WATCHER
698		1062
		1063	In the following description, uppercase C<TYPE> in names stands for the
		1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1065	watchers and C<ev_io_start> for I/O watchers.
		1066
699	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
700	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
701	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
702		1071
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	1073	{
705	ev_io_stop (w);	1074	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
707	}	1076	}
708		1077
709	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
		1079
710	struct ev_io stdin_watcher;	1080	ev_io stdin_watcher;
		1081
711	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
		1085
714	ev_loop (loop, 0);	1086	ev_run (loop, 0);
715		1087
716	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	1089	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	1090	stack).
719		1091
		1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1094
720	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
721	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, 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	1097	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	1098	time the event loop detects that the file descriptor given is readable
724	is readable and/or writable).	1099	and/or writable).
725		1100
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1101	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	1102	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	1103	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
730		1105
731	To make the watcher actually watch out for events, you have to start it	1106	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	1107	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	1108	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1109	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1110
736	As long as your watcher is active (has been started but not stopped) you	1111	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	1112	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1113	reinitialise it or call its C<ev_TYPE_set> macro.
739		1114
740	Each and every callback receives the event loop pointer as first, the	1115	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	1116	registered watcher structure as second, and a bitset of received events as
742	third argument.	1117	third argument.
743		1118
…		…
752	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
753		1128
754	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
755	writable.	1130	writable.
756		1131
757	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
758		1133
759	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
760		1135
761	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
762		1137
…		…
780		1155
781	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
782		1157
783	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
784		1159
785	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
786	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
787	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
788	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
789	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
790	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
791	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
792		1167
793	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
794		1169
795	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
796		1171
797	=item C<EV_FORK>	1172	=item C<EV_FORK>
798		1173
799	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
800	C<ev_fork>).	1175	C<ev_fork>).
801		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
802	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
803		1182
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1184
		1185	=item C<EV_CUSTOM>
		1186
		1187	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1188	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1189
806	=item C<EV_ERROR>	1190	=item C<EV_ERROR>
807		1191
808	An unspecified error has occured, the watcher has been stopped. This might	1192	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1193	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	1194	ran out of memory, a file descriptor was found to be closed or any other
		1195	problem. Libev considers these application bugs.
		1196
811	problem. You best act on it by reporting the problem and somehow coping	1197	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1198	watcher being stopped. Note that well-written programs should not receive
		1199	an error ever, so when your watcher receives it, this usually indicates a
		1200	bug in your program.
813		1201
814	Libev will usually signal a few "dummy" events together with an error,	1202	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	1203	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	1204	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	1205	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1206	programs, though, as the fd could already be closed and reused for another
		1207	thing, so beware.
819		1208
820	=back	1209	=back
821		1210
822	=head2 GENERIC WATCHER FUNCTIONS	1211	=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		1212
827	=over 4	1213	=over 4
828		1214
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1215	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1216
…		…
836	which rolls both calls into one.	1222	which rolls both calls into one.
837		1223
838	You can reinitialise a watcher at any time as long as it has been stopped	1224	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.	1225	(or never started) and there are no pending events outstanding.
840		1226
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1227	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1228	int revents)>.
843		1229
		1230	Example: Initialise an C<ev_io> watcher in two steps.
		1231
		1232	ev_io w;
		1233	ev_init (&w, my_cb);
		1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1235
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
845		1237
846	This macro initialises the type-specific parts of a watcher. You need to	1238	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	1239	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	1240	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	1241	macro on a watcher that is active (it can be pending, however, which is a
850	difference to the C<ev_init> macro).	1242	difference to the C<ev_init> macro).
851		1243
852	Although some watcher types do not have type-specific arguments	1244	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.	1245	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1246
		1247	See C<ev_init>, above, for an example.
		1248
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1249	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1250
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1251	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	1252	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1253	a watcher. The same limitations apply, of course.
860		1254
		1255	Example: Initialise and set an C<ev_io> watcher in one step.
		1256
		1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1258
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
862		1260
863	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
865		1263
		1264	Example: Start the C<ev_io> watcher that is being abused as example in this
		1265	whole section.
		1266
		1267	ev_io_start (EV_DEFAULT_UC, &w);
		1268
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
867		1270
868	Stops the given watcher again (if active) and clears the pending	1271	Stops the given watcher if active, and clears the pending status (whether
		1272	the watcher was active or not).
		1273
869	status. It is possible that stopped watchers are pending (for example,	1274	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1275	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	1276	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	1277	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.	1278	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1279
875	=item bool ev_is_active (ev_TYPE *watcher)	1280	=item bool ev_is_active (ev_TYPE *watcher)
876		1281
877	Returns a true value iff the watcher is active (i.e. it has been started	1282	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	1283	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)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
895		1300
896	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
897	(modulo threads).	1302	(modulo threads).
898		1303
899	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
900		1305
901	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
902		1307
903	Set and query the priority of the watcher. The priority is a small	1308	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>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
908		1313
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	1314	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.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1316
917	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1318	pending.
919		1319
		1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1321	fine, as long as you do not mind that the priority value you query might
		1322	or might not have been clamped to the valid range.
		1323
920	The default priority used by watchers when no priority has been set is	1324	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 :).	1325	always C<0>, which is supposed to not be too high and not be too low :).
922		1326
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1327	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	1328	priorities.
925	or might not have been adjusted to be within valid range.
926		1329
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1331
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	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	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1334	can deal with that fact, as both are simply passed through to the
		1335	callback.
932		1336
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1337	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1338
935	If the watcher is pending, this function returns clears its pending status	1339	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	1340	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>.	1341	watcher isn't pending it does nothing and returns C<0>.
938		1342
		1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1344	callback to be invoked, which can be accomplished with this function.
		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
939	=back	1360	=back
940		1361
941
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1363
944	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1366	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1367	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1368	member, you can also "subclass" the watcher type and provide your own
949	data:	1369	data:
950		1370
951	struct my_io	1371	struct my_io
952	{	1372	{
953	struct ev_io io;	1373	ev_io io;
954	int otherfd;	1374	int otherfd;
955	void *somedata;	1375	void *somedata;
956	struct whatever *mostinteresting;	1376	struct whatever *mostinteresting;
957	}	1377	};
		1378
		1379	...
		1380	struct my_io w;
		1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1382
959	And since your callback will be called with a pointer to the watcher, you	1383	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1384	can cast it back to your own type:
961		1385
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1387	{
964	struct my_io *w = (struct my_io *)w_;	1388	struct my_io *w = (struct my_io *)w_;
965	...	1389	...
966	}	1390	}
967		1391
968	More interesting and less C-conformant ways of casting your callback type	1392	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1393	instead have been omitted.
970		1394
971	Another common scenario is having some data structure with multiple	1395	Another common scenario is to use some data structure with multiple
972	watchers:	1396	embedded watchers:
973		1397
974	struct my_biggy	1398	struct my_biggy
975	{	1399	{
976	int some_data;	1400	int some_data;
977	ev_timer t1;	1401	ev_timer t1;
978	ev_timer t2;	1402	ev_timer t2;
979	}	1403	}
980		1404
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1405	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1406	complicated: Either you store the address of your C<my_biggy> struct
		1407	in the C<data> member of the watcher (for woozies), or you need to use
		1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1409	programmers):
983		1410
984	#include <stddef.h>	1411	#include <stddef.h>
985		1412
986	static void	1413	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1415	{
989	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1418	}
992		1419
993	static void	1420	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1422	{
996	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
		1485
		1486	=head2 WATCHER PRIORITY MODELS
		1487
		1488	Many event loops support I<watcher priorities>, which are usually small
		1489	integers that influence the ordering of event callback invocation
		1490	between watchers in some way, all else being equal.
		1491
		1492	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1493	description for the more technical details such as the actual priority
		1494	range.
		1495
		1496	There are two common ways how these these priorities are being interpreted
		1497	by event loops:
		1498
		1499	In the more common lock-out model, higher priorities "lock out" invocation
		1500	of lower priority watchers, which means as long as higher priority
		1501	watchers receive events, lower priority watchers are not being invoked.
		1502
		1503	The less common only-for-ordering model uses priorities solely to order
		1504	callback invocation within a single event loop iteration: Higher priority
		1505	watchers are invoked before lower priority ones, but they all get invoked
		1506	before polling for new events.
		1507
		1508	Libev uses the second (only-for-ordering) model for all its watchers
		1509	except for idle watchers (which use the lock-out model).
		1510
		1511	The rationale behind this is that implementing the lock-out model for
		1512	watchers is not well supported by most kernel interfaces, and most event
		1513	libraries will just poll for the same events again and again as long as
		1514	their callbacks have not been executed, which is very inefficient in the
		1515	common case of one high-priority watcher locking out a mass of lower
		1516	priority ones.
		1517
		1518	Static (ordering) priorities are most useful when you have two or more
		1519	watchers handling the same resource: a typical usage example is having an
		1520	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1521	timeouts. Under load, data might be received while the program handles
		1522	other jobs, but since timers normally get invoked first, the timeout
		1523	handler will be executed before checking for data. In that case, giving
		1524	the timer a lower priority than the I/O watcher ensures that I/O will be
		1525	handled first even under adverse conditions (which is usually, but not
		1526	always, what you want).
		1527
		1528	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1529	will only be executed when no same or higher priority watchers have
		1530	received events, they can be used to implement the "lock-out" model when
		1531	required.
		1532
		1533	For example, to emulate how many other event libraries handle priorities,
		1534	you can associate an C<ev_idle> watcher to each such watcher, and in
		1535	the normal watcher callback, you just start the idle watcher. The real
		1536	processing is done in the idle watcher callback. This causes libev to
		1537	continuously poll and process kernel event data for the watcher, but when
		1538	the lock-out case is known to be rare (which in turn is rare :), this is
		1539	workable.
		1540
		1541	Usually, however, the lock-out model implemented that way will perform
		1542	miserably under the type of load it was designed to handle. In that case,
		1543	it might be preferable to stop the real watcher before starting the
		1544	idle watcher, so the kernel will not have to process the event in case
		1545	the actual processing will be delayed for considerable time.
		1546
		1547	Here is an example of an I/O watcher that should run at a strictly lower
		1548	priority than the default, and which should only process data when no
		1549	other events are pending:
		1550
		1551	ev_idle idle; // actual processing watcher
		1552	ev_io io; // actual event watcher
		1553
		1554	static void
		1555	io_cb (EV_P_ ev_io *w, int revents)
		1556	{
		1557	// stop the I/O watcher, we received the event, but
		1558	// are not yet ready to handle it.
		1559	ev_io_stop (EV_A_ w);
		1560
		1561	// start the idle watcher to handle the actual event.
		1562	// it will not be executed as long as other watchers
		1563	// with the default priority are receiving events.
		1564	ev_idle_start (EV_A_ &idle);
		1565	}
		1566
		1567	static void
		1568	idle_cb (EV_P_ ev_idle *w, int revents)
		1569	{
		1570	// actual processing
		1571	read (STDIN_FILENO, ...);
		1572
		1573	// have to start the I/O watcher again, as
		1574	// we have handled the event
		1575	ev_io_start (EV_P_ &io);
		1576	}
		1577
		1578	// initialisation
		1579	ev_idle_init (&idle, idle_cb);
		1580	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1581	ev_io_start (EV_DEFAULT_ &io);
		1582
		1583	In the "real" world, it might also be beneficial to start a timer, so that
		1584	low-priority connections can not be locked out forever under load. This
		1585	enables your program to keep a lower latency for important connections
		1586	during short periods of high load, while not completely locking out less
		1587	important ones.
999		1588
1000		1589
1001	=head1 WATCHER TYPES	1590	=head1 WATCHER TYPES
1002		1591
1003	This section describes each watcher in detail, but will not repeat	1592	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	1616	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	1617	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	1618	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1619	required if you know what you are doing).
1031		1620
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	1621	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1622	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	1623	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	1624	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	1625	with a relatively standard program structure. Thus it is best to always
1041	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
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.	1627	preferable to a program hanging until some data arrives.
1044		1628
1045	If you cannot run the fd in non-blocking mode (for example you should not	1629	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	1630	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	1631	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	1632	interface such as poll (fortunately in the case of Xlib, it already does
1049	its own, so its quite safe to use).	1633	this on its own, so its quite safe to use). Some people additionally
		1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1635	indefinitely.
		1636
		1637	But really, best use non-blocking mode.
1050		1638
1051	=head3 The special problem of disappearing file descriptors	1639	=head3 The special problem of disappearing file descriptors
1052		1640
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1641	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,	1642	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	1643	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	1644	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	1645	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	1646	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1647	fact, a different file descriptor.
1060		1648
…		…
1078		1666
1079	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1080	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1081	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1082		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1083	=head3 The special problem of fork	1704	=head3 The special problem of fork
1084		1705
1085	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1086	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1087	it in the child.	1708	it in the child if you want to continue to use it in the child.
1088		1709
1089	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1092	C<EVBACKEND_POLL>.
1093		1713
1094	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1095		1715
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1716	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	1717	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	1718	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1719	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1720
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1721	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	1722	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).	1723	somewhere, as that would have given you a big clue).
1105		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1106		1763
1107	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1108		1765
1109	=over 4	1766	=over 4
1110		1767
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1768	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1769
1113	=item ev_io_set (ev_io *, int fd, int events)	1770	=item ev_io_set (ev_io *, int fd, int events)
1114		1771
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1772	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	1773	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.	1774	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1775
1119	=item int fd [read-only]	1776	=item int fd [read-only]
1120		1777
1121	The file descriptor being watched.	1778	The file descriptor being watched.
1122		1779
…		…
1130		1787
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1788	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	1789	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1790	attempt to read a whole line in the callback.
1134		1791
1135	static void	1792	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1793	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1794	{
1138	ev_io_stop (loop, w);	1795	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1796	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1797	}
1141		1798
1142	...	1799	...
1143	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1801	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1148		1805
1149		1806
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1808
1152	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1810	given time, and optionally repeating in regular intervals after that.
1154		1811
1155	The timers are based on real time, that is, if you register an event that	1812	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	1813	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	1814	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1816	monotonic clock option helps a lot here).
		1817
		1818	The callback is guaranteed to be invoked only I<after> its timeout has
		1819	passed (not I<at>, so on systems with very low-resolution clocks this
		1820	might introduce a small delay). If multiple timers become ready during the
		1821	same loop iteration then the ones with earlier time-out values are invoked
		1822	before ones of the same priority with later time-out values (but this is
		1823	no longer true when a callback calls C<ev_run> recursively).
		1824
		1825	=head3 Be smart about timeouts
		1826
		1827	Many real-world problems involve some kind of timeout, usually for error
		1828	recovery. A typical example is an HTTP request - if the other side hangs,
		1829	you want to raise some error after a while.
		1830
		1831	What follows are some ways to handle this problem, from obvious and
		1832	inefficient to smart and efficient.
		1833
		1834	In the following, a 60 second activity timeout is assumed - a timeout that
		1835	gets reset to 60 seconds each time there is activity (e.g. each time some
		1836	data or other life sign was received).
		1837
		1838	=over 4
		1839
		1840	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1841
		1842	This is the most obvious, but not the most simple way: In the beginning,
		1843	start the watcher:
		1844
		1845	ev_timer_init (timer, callback, 60., 0.);
		1846	ev_timer_start (loop, timer);
		1847
		1848	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1849	and start it again:
		1850
		1851	ev_timer_stop (loop, timer);
		1852	ev_timer_set (timer, 60., 0.);
		1853	ev_timer_start (loop, timer);
		1854
		1855	This is relatively simple to implement, but means that each time there is
		1856	some activity, libev will first have to remove the timer from its internal
		1857	data structure and then add it again. Libev tries to be fast, but it's
		1858	still not a constant-time operation.
		1859
		1860	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1861
		1862	This is the easiest way, and involves using C<ev_timer_again> instead of
		1863	C<ev_timer_start>.
		1864
		1865	To implement this, configure an C<ev_timer> with a C<repeat> value
		1866	of C<60> and then call C<ev_timer_again> at start and each time you
		1867	successfully read or write some data. If you go into an idle state where
		1868	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1869	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1870
		1871	That means you can ignore both the C<ev_timer_start> function and the
		1872	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1873	member and C<ev_timer_again>.
		1874
		1875	At start:
		1876
		1877	ev_init (timer, callback);
		1878	timer->repeat = 60.;
		1879	ev_timer_again (loop, timer);
		1880
		1881	Each time there is some activity:
		1882
		1883	ev_timer_again (loop, timer);
		1884
		1885	It is even possible to change the time-out on the fly, regardless of
		1886	whether the watcher is active or not:
		1887
		1888	timer->repeat = 30.;
		1889	ev_timer_again (loop, timer);
		1890
		1891	This is slightly more efficient then stopping/starting the timer each time
		1892	you want to modify its timeout value, as libev does not have to completely
		1893	remove and re-insert the timer from/into its internal data structure.
		1894
		1895	It is, however, even simpler than the "obvious" way to do it.
		1896
		1897	=item 3. Let the timer time out, but then re-arm it as required.
		1898
		1899	This method is more tricky, but usually most efficient: Most timeouts are
		1900	relatively long compared to the intervals between other activity - in
		1901	our example, within 60 seconds, there are usually many I/O events with
		1902	associated activity resets.
		1903
		1904	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1905	but remember the time of last activity, and check for a real timeout only
		1906	within the callback:
		1907
		1908	ev_tstamp last_activity; // time of last activity
		1909
		1910	static void
		1911	callback (EV_P_ ev_timer *w, int revents)
		1912	{
		1913	ev_tstamp now = ev_now (EV_A);
		1914	ev_tstamp timeout = last_activity + 60.;
		1915
		1916	// if last_activity + 60. is older than now, we did time out
		1917	if (timeout < now)
		1918	{
		1919	// timeout occurred, take action
		1920	}
		1921	else
		1922	{
		1923	// callback was invoked, but there was some activity, re-arm
		1924	// the watcher to fire in last_activity + 60, which is
		1925	// guaranteed to be in the future, so "again" is positive:
		1926	w->repeat = timeout - now;
		1927	ev_timer_again (EV_A_ w);
		1928	}
		1929	}
		1930
		1931	To summarise the callback: first calculate the real timeout (defined
		1932	as "60 seconds after the last activity"), then check if that time has
		1933	been reached, which means something I<did>, in fact, time out. Otherwise
		1934	the callback was invoked too early (C<timeout> is in the future), so
		1935	re-schedule the timer to fire at that future time, to see if maybe we have
		1936	a timeout then.
		1937
		1938	Note how C<ev_timer_again> is used, taking advantage of the
		1939	C<ev_timer_again> optimisation when the timer is already running.
		1940
		1941	This scheme causes more callback invocations (about one every 60 seconds
		1942	minus half the average time between activity), but virtually no calls to
		1943	libev to change the timeout.
		1944
		1945	To start the timer, simply initialise the watcher and set C<last_activity>
		1946	to the current time (meaning we just have some activity :), then call the
		1947	callback, which will "do the right thing" and start the timer:
		1948
		1949	ev_init (timer, callback);
		1950	last_activity = ev_now (loop);
		1951	callback (loop, timer, EV_TIMER);
		1952
		1953	And when there is some activity, simply store the current time in
		1954	C<last_activity>, no libev calls at all:
		1955
		1956	last_activity = ev_now (loop);
		1957
		1958	This technique is slightly more complex, but in most cases where the
		1959	time-out is unlikely to be triggered, much more efficient.
		1960
		1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1962	callback :) - just change the timeout and invoke the callback, which will
		1963	fix things for you.
		1964
		1965	=item 4. Wee, just use a double-linked list for your timeouts.
		1966
		1967	If there is not one request, but many thousands (millions...), all
		1968	employing some kind of timeout with the same timeout value, then one can
		1969	do even better:
		1970
		1971	When starting the timeout, calculate the timeout value and put the timeout
		1972	at the I<end> of the list.
		1973
		1974	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1975	the list is expected to fire (for example, using the technique #3).
		1976
		1977	When there is some activity, remove the timer from the list, recalculate
		1978	the timeout, append it to the end of the list again, and make sure to
		1979	update the C<ev_timer> if it was taken from the beginning of the list.
		1980
		1981	This way, one can manage an unlimited number of timeouts in O(1) time for
		1982	starting, stopping and updating the timers, at the expense of a major
		1983	complication, and having to use a constant timeout. The constant timeout
		1984	ensures that the list stays sorted.
		1985
		1986	=back
		1987
		1988	So which method the best?
		1989
		1990	Method #2 is a simple no-brain-required solution that is adequate in most
		1991	situations. Method #3 requires a bit more thinking, but handles many cases
		1992	better, and isn't very complicated either. In most case, choosing either
		1993	one is fine, with #3 being better in typical situations.
		1994
		1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1996	rather complicated, but extremely efficient, something that really pays
		1997	off after the first million or so of active timers, i.e. it's usually
		1998	overkill :)
		1999
		2000	=head3 The special problem of time updates
		2001
		2002	Establishing the current time is a costly operation (it usually takes at
		2003	least two system calls): EV therefore updates its idea of the current
		2004	time only before and after C<ev_run> collects new events, which causes a
		2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		2006	lots of events in one iteration.
1160		2007
1161	The relative timeouts are calculated relative to the C<ev_now ()>	2008	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	2009	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	2010	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	2011	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:	2012	timeout on the current time, use something like this to adjust for this:
1166		2013
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		2015
1169	The callback is guarenteed to be invoked only when its timeout has passed,	2016	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	2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	2018	()>.
		2019
		2020	=head3 The special problems of suspended animation
		2021
		2022	When you leave the server world it is quite customary to hit machines that
		2023	can suspend/hibernate - what happens to the clocks during such a suspend?
		2024
		2025	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2026	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2027	to run until the system is suspended, but they will not advance while the
		2028	system is suspended. That means, on resume, it will be as if the program
		2029	was frozen for a few seconds, but the suspend time will not be counted
		2030	towards C<ev_timer> when a monotonic clock source is used. The real time
		2031	clock advanced as expected, but if it is used as sole clocksource, then a
		2032	long suspend would be detected as a time jump by libev, and timers would
		2033	be adjusted accordingly.
		2034
		2035	I would not be surprised to see different behaviour in different between
		2036	operating systems, OS versions or even different hardware.
		2037
		2038	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2039	time jump in the monotonic clocks and the realtime clock. If the program
		2040	is suspended for a very long time, and monotonic clock sources are in use,
		2041	then you can expect C<ev_timer>s to expire as the full suspension time
		2042	will be counted towards the timers. When no monotonic clock source is in
		2043	use, then libev will again assume a timejump and adjust accordingly.
		2044
		2045	It might be beneficial for this latter case to call C<ev_suspend>
		2046	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2047	deterministic behaviour in this case (you can do nothing against
		2048	C<SIGSTOP>).
1172		2049
1173	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1174		2051
1175	=over 4	2052	=over 4
1176		2053
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		2055
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2056	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		2057
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	2058	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	2059	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	2060	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	2061	configured to trigger again C<repeat> seconds later, again, and again,
		2062	until stopped manually.
1185		2063
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	2064	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	2065	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	2066	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	2067	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.	2068	do stuff) the timer will not fire more than once per event loop iteration.
1191		2069
1192	=item ev_timer_again (loop, ev_timer *)	2070	=item ev_timer_again (loop, ev_timer *)
1193		2071
1194	This will act as if the timer timed out and restart it again if it is	2072	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	2073	repeating. The exact semantics are:
1196		2074
1197	If the timer is pending, its pending status is cleared.	2075	If the timer is pending, its pending status is cleared.
1198		2076
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	2077	If the timer is started but non-repeating, stop it (as if it timed out).
1200		2078
1201	If the timer is repeating, either start it if necessary (with the	2079	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.	2080	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		2081
1204	This sounds a bit complicated, but here is a useful and typical	2082	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	2083	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		2084
1214	That means you can ignore the C<after> value and C<ev_timer_start>	2085	=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		2086
1217	ev_timer_init (timer, callback, 0., 5.);	2087	Returns the remaining time until a timer fires. If the timer is active,
1218	ev_timer_again (loop, timer);	2088	then this time is relative to the current event loop time, otherwise it's
1219	...	2089	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		2090
1226	This is more slightly efficient then stopping/starting the timer each time	2091	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1227	you want to modify its timeout value.	2092	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2093	will return C<4>. When the timer expires and is restarted, it will return
		2094	roughly C<7> (likely slightly less as callback invocation takes some time,
		2095	too), and so on.
1228		2096
1229	=item ev_tstamp repeat [read-write]	2097	=item ev_tstamp repeat [read-write]
1230		2098
1231	The current C<repeat> value. Will be used each time the watcher times out	2099	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),	2100	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.	2101	which is also when any modifications are taken into account.
1234		2102
1235	=back	2103	=back
1236		2104
1237	=head3 Examples	2105	=head3 Examples
1238		2106
1239	Example: Create a timer that fires after 60 seconds.	2107	Example: Create a timer that fires after 60 seconds.
1240		2108
1241	static void	2109	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2110	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	2111	{
1244	.. one minute over, w is actually stopped right here	2112	.. one minute over, w is actually stopped right here
1245	}	2113	}
1246		2114
1247	struct ev_timer mytimer;	2115	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2116	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	2117	ev_timer_start (loop, &mytimer);
1250		2118
1251	Example: Create a timeout timer that times out after 10 seconds of	2119	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	2120	inactivity.
1253		2121
1254	static void	2122	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2123	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	2124	{
1257	.. ten seconds without any activity	2125	.. ten seconds without any activity
1258	}	2126	}
1259		2127
1260	struct ev_timer mytimer;	2128	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1264		2132
1265	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1268		2136
1269		2137
1270	=head2 C<ev_periodic> - to cron or not to cron?	2138	=head2 C<ev_periodic> - to cron or not to cron?
1271		2139
1272	Periodic watchers are also timers of a kind, but they are very versatile	2140	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	2141	(and unfortunately a bit complex).
1274		2142
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2143	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	2144	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	2145	(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 ()	2146	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	2147	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	2148	wrist-watch).
1281	roughly 10 seconds later).
1282		2149
1283	They can also be used to implement vastly more complex timers, such as	2150	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	2151	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	2152	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2153	not a delay) and then reset your system clock to January of the previous
		2154	year, then it will take a year or more to trigger the event (unlike an
		2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2156	it, as it uses a relative timeout).
1286		2157
		2158	C<ev_periodic> watchers can also be used to implement vastly more complex
		2159	timers, such as triggering an event on each "midnight, local time", or
		2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2161	those cannot react to time jumps.
		2162
1287	As with timers, the callback is guarenteed to be invoked only when the	2163	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	2164	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.	2165	timers become ready during the same loop iteration then the ones with
		2166	earlier time-out values are invoked before ones with later time-out values
		2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1290		2168
1291	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1292		2170
1293	=over 4	2171	=over 4
1294		2172
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2173	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		2174
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2175	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		2176
1299	Lots of arguments, lets sort it out... There are basically three modes of	2177	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:	2178	operation, and we will explain them from simplest to most complex:
1301		2179
1302	=over 4	2180	=over 4
1303		2181
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2182	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		2183
1306	In this configuration the watcher triggers an event at the wallclock time	2184	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,	2185	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	2186	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.	2187	will be stopped and invoked when the system clock reaches or surpasses
		2188	this point in time.
1310		2189
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2190	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		2191
1313	In this mode the watcher will always be scheduled to time out at the next	2192	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)	2193	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	2194	negative) and then repeat, regardless of any time jumps. The C<offset>
		2195	argument is merely an offset into the C<interval> periods.
1316		2196
1317	This can be used to create timers that do not drift with respect to system	2197	This can be used to create timers that do not drift with respect to the
1318	time:	2198	system clock, for example, here is an C<ev_periodic> that triggers each
		2199	hour, on the hour (with respect to UTC):
1319		2200
1320	ev_periodic_set (&periodic, 0., 3600., 0);	2201	ev_periodic_set (&periodic, 0., 3600., 0);
1321		2202
1322	This doesn't mean there will always be 3600 seconds in between triggers,	2203	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	2204	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	2205	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	2206	by 3600.
1326		2207
1327	Another way to think about it (for the mathematically inclined) is that	2208	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	2209	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.	2210	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		2211
1331	For numerical stability it is preferable that the C<at> value is near	2212	For numerical stability it is preferable that the C<offset> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	2213	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	2214	this value, and in fact is often specified as zero.
1334		2215
		2216	Note also that there is an upper limit to how often a timer can fire (CPU
		2217	speed for example), so if C<interval> is very small then timing stability
		2218	will of course deteriorate. Libev itself tries to be exact to be about one
		2219	millisecond (if the OS supports it and the machine is fast enough).
		2220
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2221	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		2222
1337	In this mode the values for C<interval> and C<at> are both being	2223	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	2224	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	2225	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	2226	current time as second argument.
1341		2227
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2228	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,	2229	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	2230	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		2231
		2232	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2233	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2234	only event loop modification you are allowed to do).
		2235
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2236	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	2237	*w, ev_tstamp now)>, e.g.:
1349		2238
		2239	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2240	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	2241	{
1352	return now + 60.;	2242	return now + 60.;
1353	}	2243	}
1354		2244
1355	It must return the next time to trigger, based on the passed time value	2245	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	2246	(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	2247	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	2248	might be called at other times, too.
1359		2249
1360	NOTE: I<< This callback must always return a time that is later than the	2250	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.	2251	equal to the passed C<now> value >>.
1362		2252
1363	This can be used to create very complex timers, such as a timer that	2253	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	2254	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	2255	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	2256	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).	2257	reason I omitted it as an example).
1368		2258
1369	=back	2259	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	2263	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	2264	when you changed some parameters or the reschedule callback would return
1375	a different time than the last time it was called (e.g. in a crond like	2265	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	2266	program when the crontabs have changed).
1377		2267
		2268	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2269
		2270	When active, returns the absolute time that the watcher is supposed
		2271	to trigger next. This is not the same as the C<offset> argument to
		2272	C<ev_periodic_set>, but indeed works even in interval and manual
		2273	rescheduling modes.
		2274
1378	=item ev_tstamp offset [read-write]	2275	=item ev_tstamp offset [read-write]
1379		2276
1380	When repeating, this contains the offset value, otherwise this is the	2277	When repeating, this contains the offset value, otherwise this is the
1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2278	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2279	although libev might modify this value for better numerical stability).
1382		2280
1383	Can be modified any time, but changes only take effect when the periodic	2281	Can be modified any time, but changes only take effect when the periodic
1384	timer fires or C<ev_periodic_again> is being called.	2282	timer fires or C<ev_periodic_again> is being called.
1385		2283
1386	=item ev_tstamp interval [read-write]	2284	=item ev_tstamp interval [read-write]
1387		2285
1388	The current interval value. Can be modified any time, but changes only	2286	The current interval value. Can be modified any time, but changes only
1389	take effect when the periodic timer fires or C<ev_periodic_again> is being	2287	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	2288	called.
1391		2289
1392	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2290	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1393		2291
1394	The current reschedule callback, or C<0>, if this functionality is	2292	The current reschedule callback, or C<0>, if this functionality is
1395	switched off. Can be changed any time, but changes only take effect when	2293	switched off. Can be changed any time, but changes only take effect when
1396	the periodic timer fires or C<ev_periodic_again> is being called.	2294	the periodic timer fires or C<ev_periodic_again> is being called.
1397		2295
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402
1403	=back	2296	=back
1404		2297
1405	=head3 Examples	2298	=head3 Examples
1406		2299
1407	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
1410		2303
1411	static void	2304	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1413	{	2306	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	2308	}
1416		2309
1417	struct ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2311	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	2312	ev_periodic_start (loop, &hourly_tick);
1420		2313
1421	Example: The same as above, but use a reschedule callback to do it:	2314	Example: The same as above, but use a reschedule callback to do it:
1422		2315
1423	#include <math.h>	2316	#include <math.h>
1424		2317
1425	static ev_tstamp	2318	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2319	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	2320	{
1428	return fmod (now, 3600.) + 3600.;	2321	return now + (3600. - fmod (now, 3600.));
1429	}	2322	}
1430		2323
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2324	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		2325
1433	Example: Call a callback every hour, starting now:	2326	Example: Call a callback every hour, starting now:
1434		2327
1435	struct ev_periodic hourly_tick;	2328	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	2329	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	2330	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	2331	ev_periodic_start (loop, &hourly_tick);
1439		2332
1440		2333
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		2335
1443	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	2339	normal event processing, like any other event.
1447		2340
		2341	If you want signals to be delivered truly asynchronously, just use
		2342	C<sigaction> as you would do without libev and forget about sharing
		2343	the signal. You can even use C<ev_async> from a signal handler to
		2344	synchronously wake up an event loop.
		2345
1448	You can configure as many watchers as you like per signal. Only when the	2346	You can configure as many watchers as you like for the same signal, but
		2347	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2348	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2349	C<SIGINT> in both the default loop and another loop at the same time. At
		2350	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2351
1449	first watcher gets started will libev actually register a signal watcher	2352	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	2353	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	2354	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		2355
1455	If possible and supported, libev will install its handlers with	2356	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1457	interrupted. If you have a problem with syscalls getting interrupted by	2358	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	2359	interrupted by signals you can block all signals in an C<ev_check> watcher
1459	them in an C<ev_prepare> watcher.	2360	and unblock them in an C<ev_prepare> watcher.
		2361
		2362	=head3 The special problem of inheritance over fork/execve/pthread_create
		2363
		2364	Both the signal mask (C<sigprocmask>) and the signal disposition
		2365	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2366	stopping it again), that is, libev might or might not block the signal,
		2367	and might or might not set or restore the installed signal handler.
		2368
		2369	While this does not matter for the signal disposition (libev never
		2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2371	C<execve>), this matters for the signal mask: many programs do not expect
		2372	certain signals to be blocked.
		2373
		2374	This means that before calling C<exec> (from the child) you should reset
		2375	the signal mask to whatever "default" you expect (all clear is a good
		2376	choice usually).
		2377
		2378	The simplest way to ensure that the signal mask is reset in the child is
		2379	to install a fork handler with C<pthread_atfork> that resets it. That will
		2380	catch fork calls done by libraries (such as the libc) as well.
		2381
		2382	In current versions of libev, the signal will not be blocked indefinitely
		2383	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2384	the window of opportunity for problems, it will not go away, as libev
		2385	I<has> to modify the signal mask, at least temporarily.
		2386
		2387	So I can't stress this enough: I<If you do not reset your signal mask when
		2388	you expect it to be empty, you have a race condition in your code>. This
		2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
1460		2404
1461	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
1462		2406
1463	=over 4	2407	=over 4
1464		2408
…		…
1475		2419
1476	=back	2420	=back
1477		2421
1478	=head3 Examples	2422	=head3 Examples
1479		2423
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2424	Example: Try to exit cleanly on SIGINT.
1481		2425
1482	static void	2426	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2428	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
1486	}	2430	}
1487		2431
1488	struct ev_signal signal_watcher;	2432	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2434	ev_signal_start (loop, &signal_watcher);
1491		2435
1492		2436
1493	=head2 C<ev_child> - watch out for process status changes	2437	=head2 C<ev_child> - watch out for process status changes
1494		2438
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2439	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	2440	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	2441	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	2442	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2443	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2444	forking and then immediately registering a watcher for the child is fine,
		2445	but forking and registering a watcher a few event loop iterations later or
		2446	in the next callback invocation is not.
1500		2447
1501	Only the default event loop is capable of handling signals, and therefore	2448	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2449	you can only register child watchers in the default event loop.
		2450
		2451	Due to some design glitches inside libev, child watchers will always be
		2452	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2453	libev)
1503		2454
1504	=head3 Process Interaction	2455	=head3 Process Interaction
1505		2456
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2457	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2458	initialised. This is necessary to guarantee proper behaviour even if the
1508	the first child watcher is started after the child exits. The occurance	2459	first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2460	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2461	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2462	children, even ones not watched.
1512		2463
1513	=head3 Overriding the Built-In Processing	2464	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2468	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2469	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2470	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	2471	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.	2472	that, so other libev users can use C<ev_child> watchers freely.
		2473
		2474	=head3 Stopping the Child Watcher
		2475
		2476	Currently, the child watcher never gets stopped, even when the
		2477	child terminates, so normally one needs to stop the watcher in the
		2478	callback. Future versions of libev might stop the watcher automatically
		2479	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2480	problem).
1522		2481
1523	=head3 Watcher-Specific Functions and Data Members	2482	=head3 Watcher-Specific Functions and Data Members
1524		2483
1525	=over 4	2484	=over 4
1526		2485
…		…
1555	=head3 Examples	2514	=head3 Examples
1556		2515
1557	Example: C<fork()> a new process and install a child handler to wait for	2516	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2517	its completion.
1559		2518
1560	ev_child cw;	2519	ev_child cw;
1561		2520
1562	static void	2521	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2522	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2523	{
1565	ev_child_stop (EV_A_ w);	2524	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2525	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2526	}
1568		2527
1569	pid_t pid = fork ();	2528	pid_t pid = fork ();
1570		2529
1571	if (pid < 0)	2530	if (pid < 0)
1572	// error	2531	// error
1573	else if (pid == 0)	2532	else if (pid == 0)
1574	{	2533	{
1575	// the forked child executes here	2534	// the forked child executes here
1576	exit (1);	2535	exit (1);
1577	}	2536	}
1578	else	2537	else
1579	{	2538	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2539	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2540	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2541	}
1583		2542
1584		2543
1585	=head2 C<ev_stat> - did the file attributes just change?	2544	=head2 C<ev_stat> - did the file attributes just change?
1586		2545
1587	This watches a filesystem path for attribute changes. That is, it calls	2546	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	2547	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.	2548	and sees if it changed compared to the last time, invoking the callback if
		2549	it did.
1590		2550
1591	The path does not need to exist: changing from "path exists" to "path does	2551	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	2552	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	2553	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	2554	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2555	least one) and all the other fields of the stat buffer having unspecified
		2556	contents.
1596		2557
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2558	The path I<must not> end in a slash or contain special components such as
		2559	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.	2560	your working directory changes, then the behaviour is undefined.
1599		2561
1600	Since there is no standard to do this, the portable implementation simply	2562	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	2563	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2564	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,	2565	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	2566	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2567	(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	2568	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2569	currently around C<0.1>, but that's usually overkill.
1608		2570
1609	This watcher type is not meant for massive numbers of stat watchers,	2571	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2572	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2573	resource-intensive.
1612		2574
1613	At the time of this writing, only the Linux inotify interface is	2575	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2576	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader). Inotify will be used to give hints only and should not change the	2577	exercise for the reader. Note, however, that the author sees no way of
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2578	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	to fall back to regular polling again even with inotify, but changes are
1618	usually detected immediately, and if the file exists there will be no
1619	polling.
1620		2579
1621	=head3 ABI Issues (Largefile Support)	2580	=head3 ABI Issues (Largefile Support)
1622		2581
1623	Libev by default (unless the user overrides this) uses the default	2582	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	2583	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	2584	support disabled by default, you get the 32 bit version of the stat
1626	structure. When using the library from programs that change the ABI to	2585	structure. When using the library from programs that change the ABI to
1627	use 64 bit file offsets the programs will fail. In that case you have to	2586	use 64 bit file offsets the programs will fail. In that case you have to
1628	compile libev with the same flags to get binary compatibility. This is	2587	compile libev with the same flags to get binary compatibility. This is
1629	obviously the case with any flags that change the ABI, but the problem is	2588	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	2589	most noticeably displayed with ev_stat and large file support.
1631		2590
1632	=head3 Inotify	2591	The solution for this is to lobby your distribution maker to make large
		2592	file interfaces available by default (as e.g. FreeBSD does) and not
		2593	optional. Libev cannot simply switch on large file support because it has
		2594	to exchange stat structures with application programs compiled using the
		2595	default compilation environment.
1633		2596
		2597	=head3 Inotify and Kqueue
		2598
1634	When C<inotify (7)> support has been compiled into libev (generally only	2599	When C<inotify (7)> support has been compiled into libev and present at
1635	available on Linux) and present at runtime, it will be used to speed up	2600	runtime, it will be used to speed up change detection where possible. The
1636	change detection where possible. The inotify descriptor will be created lazily	2601	inotify descriptor will be created lazily when the first C<ev_stat>
1637	when the first C<ev_stat> watcher is being started.	2602	watcher is being started.
1638		2603
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	2604	Inotify presence does not change the semantics of C<ev_stat> watchers
1640	except that changes might be detected earlier, and in some cases, to avoid	2605	except that changes might be detected earlier, and in some cases, to avoid
1641	making regular C<stat> calls. Even in the presence of inotify support	2606	making regular C<stat> calls. Even in the presence of inotify support
1642	there are many cases where libev has to resort to regular C<stat> polling.	2607	there are many cases where libev has to resort to regular C<stat> polling,
		2608	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2609	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2610	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2611	xfs are fully working) libev usually gets away without polling.
1643		2612
1644	(There is no support for kqueue, as apparently it cannot be used to	2613	There is no support for kqueue, as apparently it cannot be used to
1645	implement this functionality, due to the requirement of having a file	2614	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	2615	descriptor open on the object at all times, and detecting renames, unlinks
		2616	etc. is difficult.
		2617
		2618	=head3 C<stat ()> is a synchronous operation
		2619
		2620	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2621	the process. The exception are C<ev_stat> watchers - those call C<stat
		2622	()>, which is a synchronous operation.
		2623
		2624	For local paths, this usually doesn't matter: unless the system is very
		2625	busy or the intervals between stat's are large, a stat call will be fast,
		2626	as the path data is usually in memory already (except when starting the
		2627	watcher).
		2628
		2629	For networked file systems, calling C<stat ()> can block an indefinite
		2630	time due to network issues, and even under good conditions, a stat call
		2631	often takes multiple milliseconds.
		2632
		2633	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2634	paths, although this is fully supported by libev.
1647		2635
1648	=head3 The special problem of stat time resolution	2636	=head3 The special problem of stat time resolution
1649		2637
1650	The C<stat ()> syscall only supports full-second resolution portably, and	2638	The C<stat ()> system call only supports full-second resolution portably,
1651	even on systems where the resolution is higher, many filesystems still	2639	and even on systems where the resolution is higher, most file systems
1652	only support whole seconds.	2640	still only support whole seconds.
1653		2641
1654	That means that, if the time is the only thing that changes, you might	2642	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	2643	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	2644	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2645	within the same second, C<ev_stat> will be unable to detect unless the
		2646	stat data does change in other ways (e.g. file size).
1658		2647
1659	The solution to this is to delay acting on a change for a second (or till	2648	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	2649	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2650	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	2651	ev_timer_again (loop, w)>).
1663	systems.	2652
		2653	The C<.02> offset is added to work around small timing inconsistencies
		2654	of some operating systems (where the second counter of the current time
		2655	might be be delayed. One such system is the Linux kernel, where a call to
		2656	C<gettimeofday> might return a timestamp with a full second later than
		2657	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2658	update file times then there will be a small window where the kernel uses
		2659	the previous second to update file times but libev might already execute
		2660	the timer callback).
1664		2661
1665	=head3 Watcher-Specific Functions and Data Members	2662	=head3 Watcher-Specific Functions and Data Members
1666		2663
1667	=over 4	2664	=over 4
1668		2665
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2671	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	2672	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	2673	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	2674	path for as long as the watcher is active.
1678		2675
1679	The callback will be receive C<EV_STAT> when a change was detected,	2676	The callback will receive an C<EV_STAT> event when a change was detected,
1680	relative to the attributes at the time the watcher was started (or the	2677	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2678	last change was detected).
1682		2679
1683	=item ev_stat_stat (loop, ev_stat *)	2680	=item ev_stat_stat (loop, ev_stat *)
1684		2681
1685	Updates the stat buffer immediately with new values. If you change the	2682	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	2683	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2684	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2685	the only one changing the path). Can also be useful simply to find out the
		2686	new values.
1689		2687
1690	=item ev_statdata attr [read-only]	2688	=item ev_statdata attr [read-only]
1691		2689
1692	The most-recently detected attributes of the file. Although the type is of	2690	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2691	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	2692	suitable for your system, but you can only rely on the POSIX-standardised
		2693	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	2694	some error while C<stat>ing the file.
1696		2695
1697	=item ev_statdata prev [read-only]	2696	=item ev_statdata prev [read-only]
1698		2697
1699	The previous attributes of the file. The callback gets invoked whenever	2698	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2699	C<prev> != C<attr>, or, more precisely, one or more of these members
		2700	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2701	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2702
1702	=item ev_tstamp interval [read-only]	2703	=item ev_tstamp interval [read-only]
1703		2704
1704	The specified interval.	2705	The specified interval.
1705		2706
1706	=item const char *path [read-only]	2707	=item const char *path [read-only]
1707		2708
1708	The filesystem path that is being watched.	2709	The file system path that is being watched.
1709		2710
1710	=back	2711	=back
1711		2712
1712	=head3 Examples	2713	=head3 Examples
1713		2714
1714	Example: Watch C</etc/passwd> for attribute changes.	2715	Example: Watch C</etc/passwd> for attribute changes.
1715		2716
1716	static void	2717	static void
1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2718	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1718	{	2719	{
1719	/* /etc/passwd changed in some way */	2720	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2721	if (w->attr.st_nlink)
1721	{	2722	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2723	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2724	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2725	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2726	}
1726	else	2727	else
1727	/* you shalt not abuse printf for puts */	2728	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2729	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2730	"if this is windows, they already arrived\n");
1730	}	2731	}
1731		2732
1732	...	2733	...
1733	ev_stat passwd;	2734	ev_stat passwd;
1734		2735
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2736	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2737	ev_stat_start (loop, &passwd);
1737		2738
1738	Example: Like above, but additionally use a one-second delay so we do not	2739	Example: Like above, but additionally use a one-second delay so we do not
1739	miss updates (however, frequent updates will delay processing, too, so	2740	miss updates (however, frequent updates will delay processing, too, so
1740	one might do the work both on C<ev_stat> callback invocation I<and> on	2741	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2742	C<ev_timer> callback invocation).
1742		2743
1743	static ev_stat passwd;	2744	static ev_stat passwd;
1744	static ev_timer timer;	2745	static ev_timer timer;
1745		2746
1746	static void	2747	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2748	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2749	{
1749	ev_timer_stop (EV_A_ w);	2750	ev_timer_stop (EV_A_ w);
1750		2751
1751	/* now it's one second after the most recent passwd change */	2752	/* now it's one second after the most recent passwd change */
1752	}	2753	}
1753		2754
1754	static void	2755	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2756	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2757	{
1757	/* reset the one-second timer */	2758	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2759	ev_timer_again (EV_A_ &timer);
1759	}	2760	}
1760		2761
1761	...	2762	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2763	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2764	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2765	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2766
1766		2767
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2768	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2769
1769	Idle watchers trigger events when no other events of the same or higher	2770	Idle watchers trigger events when no other events of the same or higher
1770	priority are pending (prepare, check and other idle watchers do not	2771	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2772	as receiving "events").
1772		2773
1773	That is, as long as your process is busy handling sockets or timeouts	2774	That is, as long as your process is busy handling sockets or timeouts
1774	(or even signals, imagine) of the same or higher priority it will not be	2775	(or even signals, imagine) of the same or higher priority it will not be
1775	triggered. But when your process is idle (or only lower-priority watchers	2776	triggered. But when your process is idle (or only lower-priority watchers
1776	are pending), the idle watchers are being called once per event loop	2777	are pending), the idle watchers are being called once per event loop
…		…
1787		2788
1788	=head3 Watcher-Specific Functions and Data Members	2789	=head3 Watcher-Specific Functions and Data Members
1789		2790
1790	=over 4	2791	=over 4
1791		2792
1792	=item ev_idle_init (ev_signal *, callback)	2793	=item ev_idle_init (ev_idle *, callback)
1793		2794
1794	Initialises and configures the idle watcher - it has no parameters of any	2795	Initialises and configures the idle watcher - it has no parameters of any
1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2796	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1796	believe me.	2797	believe me.
1797		2798
…		…
1800	=head3 Examples	2801	=head3 Examples
1801		2802
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2803	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2804	callback, free it. Also, use no error checking, as usual.
1804		2805
1805	static void	2806	static void
1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2807	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1807	{	2808	{
1808	free (w);	2809	free (w);
1809	// now do something you wanted to do when the program has	2810	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2811	// no longer anything immediate to do.
1811	}	2812	}
1812		2813
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2815	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2816	ev_idle_start (loop, idle_watcher);
1816		2817
1817		2818
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2820
1820	Prepare and check watchers are usually (but not always) used in tandem:	2821	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2823	afterwards.
1823		2824
1824	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
1825	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
1826	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
1827	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1829	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2831	called in pairs bracketing the blocking call.
1831		2832
1832	Their main purpose is to integrate other event mechanisms into libev and	2833	Their main purpose is to integrate other event mechanisms into libev and
1833	their use is somewhat advanced. This could be used, for example, to track	2834	their use is somewhat advanced. They could be used, for example, to track
1834	variable changes, implement your own watchers, integrate net-snmp or a	2835	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2836	coroutine library and lots more. They are also occasionally useful if
1836	you cache some data and want to flush it before blocking (for example,	2837	you cache some data and want to flush it before blocking (for example,
1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2838	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2839	watcher).
1839		2840
1840	This is done by examining in each prepare call which file descriptors need	2841	This is done by examining in each prepare call which file descriptors
1841	to be watched by the other library, registering C<ev_io> watchers for	2842	need to be watched by the other library, registering C<ev_io> watchers
1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2843	for them and starting an C<ev_timer> watcher for any timeouts (many
1843	provide just this functionality). Then, in the check watcher you check for	2844	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2845	you check for any events that occurred (by checking the pending status
1845	and stopping them) and call back into the library. The I/O and timer	2846	of all watchers and stopping them) and call back into the library. The
1846	callbacks will never actually be called (but must be valid nevertheless,	2847	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2848	nevertheless, because you never know, you know?).
1848		2849
1849	As another example, the Perl Coro module uses these hooks to integrate	2850	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2851	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2852	during each prepare and only letting the process block if no coroutines
1852	are ready to run (it's actually more complicated: it only runs coroutines	2853	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1855	loop from blocking if lower-priority coroutines are active, thus mapping	2856	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2857	low-priority coroutines to idle/background tasks).
1857		2858
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	2860	priority, to ensure that they are being run before any other watchers
		2861	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2862
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1861	too) should not activate ("feed") events into libev. While libev fully	2864	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2865	might get executed before other C<ev_check> watchers did their job. As
1863	did their job. As C<ev_check> watchers are often used to embed other	2866	C<ev_check> watchers are often used to embed other (non-libev) event
1864	(non-libev) event loops those other event loops might be in an unusable	2867	loops those other event loops might be in an unusable state until their
1865	state until their C<ev_check> watcher ran (always remind yourself to	2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2869	others).
1867		2870
1868	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
1869		2872
1870	=over 4	2873	=over 4
1871		2874
…		…
1873		2876
1874	=item ev_check_init (ev_check *, callback)	2877	=item ev_check_init (ev_check *, callback)
1875		2878
1876	Initialises and configures the prepare or check watcher - they have no	2879	Initialises and configures the prepare or check watcher - they have no
1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2880	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1878	macros, but using them is utterly, utterly and completely pointless.	2881	macros, but using them is utterly, utterly, utterly and completely
		2882	pointless.
1879		2883
1880	=back	2884	=back
1881		2885
1882	=head3 Examples	2886	=head3 Examples
1883		2887
1884	There are a number of principal ways to embed other event loops or modules	2888	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	2889	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	2890	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	2891	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2892	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2893	Glib event loop).
1890		2894
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	2896	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	2897	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1895	the callbacks for the IO/timeout watchers might not have been called yet.	2899	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2900
1897	static ev_io iow [nfd];	2901	static ev_io iow [nfd];
1898	static ev_timer tw;	2902	static ev_timer tw;
1899		2903
1900	static void	2904	static void
1901	io_cb (ev_loop *loop, ev_io *w, int revents)	2905	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1902	{	2906	{
1903	}	2907	}
1904		2908
1905	// create io watchers for each fd and a timer before blocking	2909	// create io watchers for each fd and a timer before blocking
1906	static void	2910	static void
1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2911	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1908	{	2912	{
1909	int timeout = 3600000;	2913	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2914	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2915	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2917
1914	/* the callback is illegal, but won't be called as we stop during check */	2918	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2919	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1916	ev_timer_start (loop, &tw);	2920	ev_timer_start (loop, &tw);
1917		2921
1918	// create one ev_io per pollfd	2922	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2923	for (int i = 0; i < nfd; ++i)
1920	{	2924	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2925	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2926	((fds [i].events & POLLIN ? EV_READ : 0)
1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2928
1925	fds [i].revents = 0;	2929	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2930	ev_io_start (loop, iow + i);
1927	}	2931	}
1928	}	2932	}
1929		2933
1930	// stop all watchers after blocking	2934	// stop all watchers after blocking
1931	static void	2935	static void
1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2936	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1933	{	2937	{
1934	ev_timer_stop (loop, &tw);	2938	ev_timer_stop (loop, &tw);
1935		2939
1936	for (int i = 0; i < nfd; ++i)	2940	for (int i = 0; i < nfd; ++i)
1937	{	2941	{
1938	// set the relevant poll flags	2942	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2943	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2944	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2945	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1944		2948
1945	// now stop the watcher	2949	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2950	ev_io_stop (loop, iow + i);
1947	}	2951	}
1948		2952
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2954	}
1951		2955
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1953	in the prepare watcher and would dispose of the check watcher.	2957	in the prepare watcher and would dispose of the check watcher.
1954		2958
1955	Method 3: If the module to be embedded supports explicit event	2959	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2960	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2961	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2962
1959	static void	2963	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2964	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2965	{
1962	adns_state ads = (adns_state)w->data;	2966	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2967	update_now (EV_A);
1964		2968
1965	adns_processtimeouts (ads, &tv_now);	2969	adns_processtimeouts (ads, &tv_now);
1966	}	2970	}
1967		2971
1968	static void	2972	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2973	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2974	{
1971	adns_state ads = (adns_state)w->data;	2975	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2976	update_now (EV_A);
1973		2977
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2980	}
1977		2981
1978	// do not ever call adns_afterpoll	2982	// do not ever call adns_afterpoll
1979		2983
1980	Method 4: Do not use a prepare or check watcher because the module you	2984	Method 4: Do not use a prepare or check watcher because the module you
1981	want to embed is too inflexible to support it. Instead, youc na override	2985	want to embed is not flexible enough to support it. Instead, you can
1982	their poll function. The drawback with this solution is that the main	2986	override their poll function. The drawback with this solution is that the
1983	loop is now no longer controllable by EV. The C<Glib::EV> module does	2987	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2988	this approach, effectively embedding EV as a client into the horrible
		2989	libglib event loop.
1985		2990
1986	static gint	2991	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2992	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2993	{
1989	int got_events = 0;	2994	int got_events = 0;
1990		2995
1991	for (n = 0; n < nfds; ++n)	2996	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2997	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2998
1994	if (timeout >= 0)	2999	if (timeout >= 0)
1995	// create/start timer	3000	// create/start timer
1996		3001
1997	// poll	3002	// poll
1998	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
1999		3004
2000	// stop timer again	3005	// stop timer again
2001	if (timeout >= 0)	3006	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2003		3008
2004	// stop io watchers again - their callbacks should have set	3009	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	3010	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	3011	ev_io_stop (EV_A_ iow [n]);
2007		3012
2008	return got_events;	3013	return got_events;
2009	}	3014	}
2010		3015
2011		3016
2012	=head2 C<ev_embed> - when one backend isn't enough...	3017	=head2 C<ev_embed> - when one backend isn't enough...
2013		3018
2014	This is a rather advanced watcher type that lets you embed one event loop	3019	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	3025	prioritise I/O.
2021		3026
2022	As an example for a bug workaround, the kqueue backend might only support	3027	As an example for a bug workaround, the kqueue backend might only support
2023	sockets on some platform, so it is unusable as generic backend, but you	3028	sockets on some platform, so it is unusable as generic backend, but you
2024	still want to make use of it because you have many sockets and it scales	3029	still want to make use of it because you have many sockets and it scales
2025	so nicely. In this case, you would create a kqueue-based loop and embed it	3030	so nicely. In this case, you would create a kqueue-based loop and embed
2026	into your default loop (which might use e.g. poll). Overall operation will	3031	it into your default loop (which might use e.g. poll). Overall operation
2027	be a bit slower because first libev has to poll and then call kevent, but	3032	will be a bit slower because first libev has to call C<poll> and then
2028	at least you can use both at what they are best.	3033	C<kevent>, but at least you can use both mechanisms for what they are
		3034	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		3035
2030	As for prioritising I/O: rarely you have the case where some fds have	3036	As for prioritising I/O: under rare circumstances you have the case where
2031	to be watched and handled very quickly (with low latency), and even	3037	some fds have to be watched and handled very quickly (with low latency),
2032	priorities and idle watchers might have too much overhead. In this case	3038	and even priorities and idle watchers might have too much overhead. In
2033	you would put all the high priority stuff in one loop and all the rest in	3039	this case you would put all the high priority stuff in one loop and all
2034	a second one, and embed the second one in the first.	3040	the rest in a second one, and embed the second one in the first.
2035		3041
2036	As long as the watcher is active, the callback will be invoked every time	3042	As long as the watcher is active, the callback will be invoked every
2037	there might be events pending in the embedded loop. The callback must then	3043	time there might be events pending in the embedded loop. The callback
2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3044	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2039	their callbacks (you could also start an idle watcher to give the embedded	3045	sweep and invoke their callbacks (the callback doesn't need to invoke the
2040	loop strictly lower priority for example). You can also set the callback	3046	C<ev_embed_sweep> function directly, it could also start an idle watcher
2041	to C<0>, in which case the embed watcher will automatically execute the	3047	to give the embedded loop strictly lower priority for example).
2042	embedded loop sweep.
2043		3048
2044	As long as the watcher is started it will automatically handle events. The	3049	You can also set the callback to C<0>, in which case the embed watcher
2045	callback will be invoked whenever some events have been handled. You can	3050	will automatically execute the embedded loop sweep whenever necessary.
2046	set the callback to C<0> to avoid having to specify one if you are not
2047	interested in that.
2048		3051
2049	Also, there have not currently been made special provisions for forking:	3052	Fork detection will be handled transparently while the C<ev_embed> watcher
2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3053	is active, i.e., the embedded loop will automatically be forked when the
2051	but you will also have to stop and restart any C<ev_embed> watchers	3054	embedding loop forks. In other cases, the user is responsible for calling
2052	yourself.	3055	C<ev_loop_fork> on the embedded loop.
2053		3056
2054	Unfortunately, not all backends are embeddable, only the ones returned by	3057	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3058	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	3059	portable one.
2057		3060
2058	So when you want to use this feature you will always have to be prepared	3061	So when you want to use this feature you will always have to be prepared
2059	that you cannot get an embeddable loop. The recommended way to get around	3062	that you cannot get an embeddable loop. The recommended way to get around
2060	this is to have a separate variables for your embeddable loop, try to	3063	this is to have a separate variables for your embeddable loop, try to
2061	create it, and if that fails, use the normal loop for everything.	3064	create it, and if that fails, use the normal loop for everything.
2062		3065
		3066	=head3 C<ev_embed> and fork
		3067
		3068	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3069	automatically be applied to the embedded loop as well, so no special
		3070	fork handling is required in that case. When the watcher is not running,
		3071	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3072	as applicable.
		3073
2063	=head3 Watcher-Specific Functions and Data Members	3074	=head3 Watcher-Specific Functions and Data Members
2064		3075
2065	=over 4	3076	=over 4
2066		3077
2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3078	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2070		3081
2071	Configures the watcher to embed the given loop, which must be	3082	Configures the watcher to embed the given loop, which must be
2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3083	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2073	invoked automatically, otherwise it is the responsibility of the callback	3084	invoked automatically, otherwise it is the responsibility of the callback
2074	to invoke it (it will continue to be called until the sweep has been done,	3085	to invoke it (it will continue to be called until the sweep has been done,
2075	if you do not want thta, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2076		3087
2077	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2078		3089
2079	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2081	apropriate way for embedded loops.	3092	appropriate way for embedded loops.
2082		3093
2083	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2084		3095
2085	The embedded event loop.	3096	The embedded event loop.
2086		3097
…		…
2088		3099
2089	=head3 Examples	3100	=head3 Examples
2090		3101
2091	Example: Try to get an embeddable event loop and embed it into the default	3102	Example: Try to get an embeddable event loop and embed it into the default
2092	event loop. If that is not possible, use the default loop. The default	3103	event loop. If that is not possible, use the default loop. The default
2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3104	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3105	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	3106	used).
2096		3107
2097	struct ev_loop *loop_hi = ev_default_init (0);	3108	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	3109	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	3110	ev_embed embed;
2100		3111
2101	// see if there is a chance of getting one that works	3112	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	3113	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	3116	: 0;
2106		3117
2107	// if we got one, then embed it, otherwise default to loop_hi	3118	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	3119	if (loop_lo)
2109	{	3120	{
2110	ev_embed_init (&embed, 0, loop_lo);	3121	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	3122	ev_embed_start (loop_hi, &embed);
2112	}	3123	}
2113	else	3124	else
2114	loop_lo = loop_hi;	3125	loop_lo = loop_hi;
2115		3126
2116	Example: Check if kqueue is available but not recommended and create	3127	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	3128	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	3129	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		3131
2121	struct ev_loop *loop = ev_default_init (0);	3132	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	3133	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	3134	ev_embed embed;
2124		3135
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	3138	{
2128	ev_embed_init (&embed, 0, loop_socket);	3139	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	3140	ev_embed_start (loop, &embed);
2130	}	3141	}
2131		3142
2132	if (!loop_socket)	3143	if (!loop_socket)
2133	loop_socket = loop;	3144	loop_socket = loop;
2134		3145
2135	// now use loop_socket for all sockets, and loop for everything else	3146	// now use loop_socket for all sockets, and loop for everything else
2136		3147
2137		3148
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		3150
2140	Fork watchers are called when a C<fork ()> was detected (usually because	3151	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2143	event loop blocks next and before C<ev_check> watchers are being called,	3154	event loop blocks next and before C<ev_check> watchers are being called,
2144	and only in the child after the fork. If whoever good citizen calling	3155	and only in the child after the fork. If whoever good citizen calling
2145	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2146	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2147		3158
		3159	=head3 The special problem of life after fork - how is it possible?
		3160
		3161	Most uses of C<fork()> consist of forking, then some simple calls to set
		3162	up/change the process environment, followed by a call to C<exec()>. This
		3163	sequence should be handled by libev without any problems.
		3164
		3165	This changes when the application actually wants to do event handling
		3166	in the child, or both parent in child, in effect "continuing" after the
		3167	fork.
		3168
		3169	The default mode of operation (for libev, with application help to detect
		3170	forks) is to duplicate all the state in the child, as would be expected
		3171	when I<either> the parent I<or> the child process continues.
		3172
		3173	When both processes want to continue using libev, then this is usually the
		3174	wrong result. In that case, usually one process (typically the parent) is
		3175	supposed to continue with all watchers in place as before, while the other
		3176	process typically wants to start fresh, i.e. without any active watchers.
		3177
		3178	The cleanest and most efficient way to achieve that with libev is to
		3179	simply create a new event loop, which of course will be "empty", and
		3180	use that for new watchers. This has the advantage of not touching more
		3181	memory than necessary, and thus avoiding the copy-on-write, and the
		3182	disadvantage of having to use multiple event loops (which do not support
		3183	signal watchers).
		3184
		3185	When this is not possible, or you want to use the default loop for
		3186	other reasons, then in the process that wants to start "fresh", call
		3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3188	Destroying the default loop will "orphan" (not stop) all registered
		3189	watchers, so you have to be careful not to execute code that modifies
		3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
		3192
2148	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2149		3194
2150	=over 4	3195	=over 4
2151		3196
2152	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2153		3198
2154	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2155	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2156	believe me.	3201	really.
2157		3202
2158	=back	3203	=back
2159		3204
2160		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2161	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2162		3247
2163	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2164	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2165	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2166		3251
2167	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2168	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2169	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2170	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2171	safe.
2172		3256
2173	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2174	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2175	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2176	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2177		3264
2178	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2179	just the default loop.	3266	just the default loop.
2180		3267
2181	=head3 Queueing	3268	=head3 Queueing
2182		3269
2183	C<ev_async> does not support queueing of data in any way. The reason	3270	C<ev_async> does not support queueing of data in any way. The reason
2184	is that the author does not know of a simple (or any) algorithm for a	3271	is that the author does not know of a simple (or any) algorithm for a
2185	multiple-writer-single-reader queue that works in all cases and doesn't	3272	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	3273	need elaborate support such as pthreads or unportable memory access
		3274	semantics.
2187		3275
2188	That means that if you want to queue data, you have to provide your own	3276	That means that if you want to queue data, you have to provide your own
2189	queue. But at least I can tell you would implement locking around your	3277	queue. But at least I can tell you how to implement locking around your
2190	queue:	3278	queue:
2191		3279
2192	=over 4	3280	=over 4
2193		3281
2194	=item queueing from a signal handler context	3282	=item queueing from a signal handler context
2195		3283
2196	To implement race-free queueing, you simply add to the queue in the signal	3284	To implement race-free queueing, you simply add to the queue in the signal
2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3285	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	3286	an example that does that for some fictitious SIGUSR1 handler:
2199		3287
2200	static ev_async mysig;	3288	static ev_async mysig;
2201		3289
2202	static void	3290	static void
2203	sigusr1_handler (void)	3291	sigusr1_handler (void)
…		…
2269	=over 4	3357	=over 4
2270		3358
2271	=item ev_async_init (ev_async *, callback)	3359	=item ev_async_init (ev_async *, callback)
2272		3360
2273	Initialises and configures the async watcher - it has no parameters of any	3361	Initialises and configures the async watcher - it has no parameters of any
2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3362	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2275	believe me.	3363	trust me.
2276		3364
2277	=item ev_async_send (loop, ev_async *)	3365	=item ev_async_send (loop, ev_async *)
2278		3366
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2281	C<ev_feed_event>, this call is safe to do in other threads, signal or	3369	C<ev_feed_event>, this call is safe to do from other threads, signal or
2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	3371	section below on what exactly this means).
2284		3372
		3373	Note that, as with other watchers in libev, multiple events might get
		3374	compressed into a single callback invocation (another way to look at this
		3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3376	reset when the event loop detects that).
		3377
2285	This call incurs the overhead of a syscall only once per loop iteration,	3378	This call incurs the overhead of a system call only once per event loop
2286	so while the overhead might be noticable, it doesn't apply to repeated	3379	iteration, so while the overhead might be noticeable, it doesn't apply to
2287	calls to C<ev_async_send>.	3380	repeated calls to C<ev_async_send> for the same event loop.
2288		3381
2289	=item bool = ev_async_pending (ev_async *)	3382	=item bool = ev_async_pending (ev_async *)
2290		3383
2291	Returns a non-zero value when C<ev_async_send> has been called on the	3384	Returns a non-zero value when C<ev_async_send> has been called on the
2292	watcher but the event has not yet been processed (or even noted) by the	3385	watcher but the event has not yet been processed (or even noted) by the
2293	event loop.	3386	event loop.
2294		3387
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3388	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2296	the loop iterates next and checks for the watcher to have become active,	3389	the loop iterates next and checks for the watcher to have become active,
2297	it will reset the flag again. C<ev_async_pending> can be used to very	3390	it will reset the flag again. C<ev_async_pending> can be used to very
2298	quickly check wether invoking the loop might be a good idea.	3391	quickly check whether invoking the loop might be a good idea.
2299		3392
2300	Not that this does I<not> check wether the watcher itself is pending, only	3393	Not that this does I<not> check whether the watcher itself is pending,
2301	wether it has been requested to make this watcher pending.	3394	only whether it has been requested to make this watcher pending: there
		3395	is a time window between the event loop checking and resetting the async
		3396	notification, and the callback being invoked.
2302		3397
2303	=back	3398	=back
2304		3399
2305		3400
2306	=head1 OTHER FUNCTIONS	3401	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	3405	=over 4
2311		3406
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3407	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		3408
2314	This function combines a simple timer and an I/O watcher, calls your	3409	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	3410	callback on whichever event happens first and automatically stops both
2316	watchers. This is useful if you want to wait for a single event on an fd	3411	watchers. This is useful if you want to wait for a single event on an fd
2317	or timeout without having to allocate/configure/start/stop/free one or	3412	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	3413	more watchers yourself.
2319		3414
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	3415	If C<fd> is less than 0, then no I/O watcher will be started and the
2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3416	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	3417	the given C<fd> and C<events> set will be created and started.
2323		3418
2324	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3421	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		3422
2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2330	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2332	value passed to C<ev_once>:	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3427	a timeout and an io event at the same time - you probably should give io
		3428	events precedence.
2333		3429
		3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3431
2334	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
2335	{	3433	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	3434	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
		3436	else if (revents & EV_TIMER)
		3437	/* doh, nothing entered */;
2340	}	3438	}
2341		3439
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		3441
2344	=item ev_feed_event (ev_loop *, watcher *, int revents)
2345
2346	Feeds the given event set into the event loop, as if the specified event
2347	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).
2349
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3442	=item ev_feed_fd_event (loop, int fd, int revents)
2351		3443
2352	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	3445	the given events it.
2354		3446
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
2356		3448
2357	Feed an event as if the given signal occured (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2358	loop!).	3450	which is async-safe.
2359		3451
2360	=back	3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
2361		3637
2362		3638
2363	=head1 LIBEVENT EMULATION	3639	=head1 LIBEVENT EMULATION
2364		3640
2365	Libev offers a compatibility emulation layer for libevent. It cannot	3641	Libev offers a compatibility emulation layer for libevent. It cannot
2366	emulate the internals of libevent, so here are some usage hints:	3642	emulate the internals of libevent, so here are some usage hints:
2367		3643
2368	=over 4	3644	=over 4
		3645
		3646	=item * Only the libevent-1.4.1-beta API is being emulated.
		3647
		3648	This was the newest libevent version available when libev was implemented,
		3649	and is still mostly unchanged in 2010.
2369		3650
2370	=item * Use it by including <event.h>, as usual.	3651	=item * Use it by including <event.h>, as usual.
2371		3652
2372	=item * The following members are fully supported: ev_base, ev_callback,	3653	=item * The following members are fully supported: ev_base, ev_callback,
2373	ev_arg, ev_fd, ev_res, ev_events.	3654	ev_arg, ev_fd, ev_res, ev_events.
…		…
2379	=item * Priorities are not currently supported. Initialising priorities	3660	=item * Priorities are not currently supported. Initialising priorities
2380	will fail and all watchers will have the same priority, even though there	3661	will fail and all watchers will have the same priority, even though there
2381	is an ev_pri field.	3662	is an ev_pri field.
2382		3663
2383	=item * In libevent, the last base created gets the signals, in libev, the	3664	=item * In libevent, the last base created gets the signals, in libev, the
2384	first base created (== the default loop) gets the signals.	3665	base that registered the signal gets the signals.
2385		3666
2386	=item * Other members are not supported.	3667	=item * Other members are not supported.
2387		3668
2388	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3669	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2389	to use the libev header file and library.	3670	to use the libev header file and library.
…		…
2391	=back	3672	=back
2392		3673
2393	=head1 C++ SUPPORT	3674	=head1 C++ SUPPORT
2394		3675
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3676	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2396	you to use some convinience methods to start/stop watchers and also change	3677	you to use some convenience methods to start/stop watchers and also change
2397	the callback model to a model using method callbacks on objects.	3678	the callback model to a model using method callbacks on objects.
2398		3679
2399	To use it,	3680	To use it,
2400		3681
2401	#include <ev++.h>	3682	#include <ev++.h>
2402		3683
2403	This automatically includes F<ev.h> and puts all of its definitions (many	3684	This automatically includes F<ev.h> and puts all of its definitions (many
2404	of them macros) into the global namespace. All C++ specific things are	3685	of them macros) into the global namespace. All C++ specific things are
2405	put into the C<ev> namespace. It should support all the same embedding	3686	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3687	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2408	Care has been taken to keep the overhead low. The only data member the C++	3689	Care has been taken to keep the overhead low. The only data member the C++
2409	classes add (compared to plain C-style watchers) is the event loop pointer	3690	classes add (compared to plain C-style watchers) is the event loop pointer
2410	that the watcher is associated with (or no additional members at all if	3691	that the watcher is associated with (or no additional members at all if
2411	you disable C<EV_MULTIPLICITY> when embedding libev).	3692	you disable C<EV_MULTIPLICITY> when embedding libev).
2412		3693
2413	Currently, functions, and static and non-static member functions can be	3694	Currently, functions, static and non-static member functions and classes
2414	used as callbacks. Other types should be easy to add as long as they only	3695	with C<operator ()> can be used as callbacks. Other types should be easy
2415	need one additional pointer for context. If you need support for other	3696	to add as long as they only need one additional pointer for context. If
2416	types of functors please contact the author (preferably after implementing	3697	you need support for other types of functors please contact the author
2417	it).	3698	(preferably after implementing it).
2418		3699
2419	Here is a list of things available in the C<ev> namespace:	3700	Here is a list of things available in the C<ev> namespace:
2420		3701
2421	=over 4	3702	=over 4
2422		3703
…		…
2440		3721
2441	=over 4	3722	=over 4
2442		3723
2443	=item ev::TYPE::TYPE ()	3724	=item ev::TYPE::TYPE ()
2444		3725
2445	=item ev::TYPE::TYPE (struct ev_loop *)	3726	=item ev::TYPE::TYPE (loop)
2446		3727
2447	=item ev::TYPE::~TYPE	3728	=item ev::TYPE::~TYPE
2448		3729
2449	The constructor (optionally) takes an event loop to associate the watcher	3730	The constructor (optionally) takes an event loop to associate the watcher
2450	with. If it is omitted, it will use C<EV_DEFAULT>.	3731	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	3754	your compiler is good :), then the method will be fully inlined into the
2474	thunking function, making it as fast as a direct C callback.	3755	thunking function, making it as fast as a direct C callback.
2475		3756
2476	Example: simple class declaration and watcher initialisation	3757	Example: simple class declaration and watcher initialisation
2477		3758
2478	struct myclass	3759	struct myclass
2479	{	3760	{
2480	void io_cb (ev::io &w, int revents) { }	3761	void io_cb (ev::io &w, int revents) { }
2481	}	3762	}
2482		3763
2483	myclass obj;	3764	myclass obj;
2484	ev::io iow;	3765	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	3766	iow.set <myclass, &myclass::io_cb> (&obj);
		3767
		3768	=item w->set (object *)
		3769
		3770	This is a variation of a method callback - leaving out the method to call
		3771	will default the method to C<operator ()>, which makes it possible to use
		3772	functor objects without having to manually specify the C<operator ()> all
		3773	the time. Incidentally, you can then also leave out the template argument
		3774	list.
		3775
		3776	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3777	int revents)>.
		3778
		3779	See the method-C<set> above for more details.
		3780
		3781	Example: use a functor object as callback.
		3782
		3783	struct myfunctor
		3784	{
		3785	void operator() (ev::io &w, int revents)
		3786	{
		3787	...
		3788	}
		3789	}
		3790
		3791	myfunctor f;
		3792
		3793	ev::io w;
		3794	w.set (&f);
2486		3795
2487	=item w->set<function> (void *data = 0)	3796	=item w->set<function> (void *data = 0)
2488		3797
2489	Also sets a callback, but uses a static method or plain function as	3798	Also sets a callback, but uses a static method or plain function as
2490	callback. The optional C<data> argument will be stored in the watcher's	3799	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		3801
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3802	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		3803
2495	See the method-C<set> above for more details.	3804	See the method-C<set> above for more details.
2496		3805
2497	Example:	3806	Example: Use a plain function as callback.
2498		3807
2499	static void io_cb (ev::io &w, int revents) { }	3808	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	3809	iow.set <io_cb> ();
2501		3810
2502	=item w->set (struct ev_loop *)	3811	=item w->set (loop)
2503		3812
2504	Associates a different C<struct ev_loop> with this watcher. You can only	3813	Associates a different C<struct ev_loop> with this watcher. You can only
2505	do this when the watcher is inactive (and not pending either).	3814	do this when the watcher is inactive (and not pending either).
2506		3815
2507	=item w->set ([args])	3816	=item w->set ([arguments])
2508		3817
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3818	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2510	called at least once. Unlike the C counterpart, an active watcher gets	3819	method or a suitable start method must be called at least once. Unlike the
2511	automatically stopped and restarted when reconfiguring it with this	3820	C counterpart, an active watcher gets automatically stopped and restarted
2512	method.	3821	when reconfiguring it with this method.
2513		3822
2514	=item w->start ()	3823	=item w->start ()
2515		3824
2516	Starts the watcher. Note that there is no C<loop> argument, as the	3825	Starts the watcher. Note that there is no C<loop> argument, as the
2517	constructor already stores the event loop.	3826	constructor already stores the event loop.
2518		3827
		3828	=item w->start ([arguments])
		3829
		3830	Instead of calling C<set> and C<start> methods separately, it is often
		3831	convenient to wrap them in one call. Uses the same type of arguments as
		3832	the configure C<set> method of the watcher.
		3833
2519	=item w->stop ()	3834	=item w->stop ()
2520		3835
2521	Stops the watcher if it is active. Again, no C<loop> argument.	3836	Stops the watcher if it is active. Again, no C<loop> argument.
2522		3837
2523	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3838	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2535		3850
2536	=back	3851	=back
2537		3852
2538	=back	3853	=back
2539		3854
2540	Example: Define a class with an IO and idle watcher, start one of them in	3855	Example: Define a class with two I/O and idle watchers, start the I/O
2541	the constructor.	3856	watchers in the constructor.
2542		3857
2543	class myclass	3858	class myclass
2544	{	3859	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	3860	ev::io io ; void io_cb (ev::io &w, int revents);
		3861	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	3862	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		3863
2548	myclass (int fd)	3864	myclass (int fd)
2549	{	3865	{
2550	io .set <myclass, &myclass::io_cb > (this);	3866	io .set <myclass, &myclass::io_cb > (this);
		3867	io2 .set <myclass, &myclass::io2_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	3868	idle.set <myclass, &myclass::idle_cb> (this);
2552		3869
2553	io.start (fd, ev::READ);	3870	io.set (fd, ev::WRITE); // configure the watcher
		3871	io.start (); // start it whenever convenient
		3872
		3873	io2.start (fd, ev::READ); // set + start in one call
2554	}	3874	}
2555	};	3875	};
2556		3876
2557		3877
2558	=head1 OTHER LANGUAGE BINDINGS	3878	=head1 OTHER LANGUAGE BINDINGS
2559		3879
2560	Libev does not offer other language bindings itself, but bindings for a	3880	Libev does not offer other language bindings itself, but bindings for a
2561	numbe rof languages exist in the form of third-party packages. If you know	3881	number of languages exist in the form of third-party packages. If you know
2562	any interesting language binding in addition to the ones listed here, drop	3882	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	3883	me a note.
2564		3884
2565	=over 4	3885	=over 4
2566		3886
2567	=item Perl	3887	=item Perl
2568		3888
2569	The EV module implements the full libev API and is actually used to test	3889	The EV module implements the full libev API and is actually used to test
2570	libev. EV is developed together with libev. Apart from the EV core module,	3890	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	3891	there are additional modules that implement libev-compatible interfaces
2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3892	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3893	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3894	and C<EV::Glib>).
2574		3895
2575	It can be found and installed via CPAN, its homepage is found at	3896	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	3897	L<http://software.schmorp.de/pkg/EV>.
2577		3898
		3899	=item Python
		3900
		3901	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3902	seems to be quite complete and well-documented.
		3903
2578	=item Ruby	3904	=item Ruby
2579		3905
2580	Tony Arcieri has written a ruby extension that offers access to a subset	3906	Tony Arcieri has written a ruby extension that offers access to a subset
2581	of the libev API and adds filehandle abstractions, asynchronous DNS and	3907	of the libev API and adds file handle abstractions, asynchronous DNS and
2582	more on top of it. It can be found via gem servers. Its homepage is at	3908	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	3909	L<http://rev.rubyforge.org/>.
2584		3910
		3911	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3912	makes rev work even on mingw.
		3913
		3914	=item Haskell
		3915
		3916	A haskell binding to libev is available at
		3917	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3918
2585	=item D	3919	=item D
2586		3920
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3921	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3922	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3923
		3924	=item Ocaml
		3925
		3926	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3927	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3928
		3929	=item Lua
		3930
		3931	Brian Maher has written a partial interface to libev for lua (at the
		3932	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3933	L<http://github.com/brimworks/lua-ev>.
2589		3934
2590	=back	3935	=back
2591		3936
2592		3937
2593	=head1 MACRO MAGIC	3938	=head1 MACRO MAGIC
2594		3939
2595	Libev can be compiled with a variety of options, the most fundamantal	3940	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3941	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	3942	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		3943
2599	To make it easier to write programs that cope with either variant, the	3944	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	3945	following macros are defined:
…		…
2605		3950
2606	This provides the loop I<argument> for functions, if one is required ("ev	3951	This provides the loop I<argument> for functions, if one is required ("ev
2607	loop argument"). The C<EV_A> form is used when this is the sole argument,	3952	loop argument"). The C<EV_A> form is used when this is the sole argument,
2608	C<EV_A_> is used when other arguments are following. Example:	3953	C<EV_A_> is used when other arguments are following. Example:
2609		3954
2610	ev_unref (EV_A);	3955	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3956	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3957	ev_run (EV_A_ 0);
2613		3958
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3959	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3960	which is often provided by the following macro.
2616		3961
2617	=item C<EV_P>, C<EV_P_>	3962	=item C<EV_P>, C<EV_P_>
2618		3963
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3964	This provides the loop I<parameter> for functions, if one is required ("ev
2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3965	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2621	C<EV_P_> is used when other parameters are following. Example:	3966	C<EV_P_> is used when other parameters are following. Example:
2622		3967
2623	// this is how ev_unref is being declared	3968	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3969	static void ev_unref (EV_P);
2625		3970
2626	// this is how you can declare your typical callback	3971	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3972	static void cb (EV_P_ ev_timer *w, int revents)
2628		3973
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3974	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3975	suitable for use with C<EV_A>.
2631		3976
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3977	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3993
2649	Example: Declare and initialise a check watcher, utilising the above	3994	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3995	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3996	or not.
2652		3997
2653	static void	3998	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3999	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	4000	{
2656	ev_check_stop (EV_A_ w);	4001	ev_check_stop (EV_A_ w);
2657	}	4002	}
2658		4003
2659	ev_check check;	4004	ev_check check;
2660	ev_check_init (&check, check_cb);	4005	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	4006	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	4007	ev_run (EV_DEFAULT_ 0);
2663		4008
2664	=head1 EMBEDDING	4009	=head1 EMBEDDING
2665		4010
2666	Libev can (and often is) directly embedded into host	4011	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	4012	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	4019	libev somewhere in your source tree).
2675		4020
2676	=head2 FILESETS	4021	=head2 FILESETS
2677		4022
2678	Depending on what features you need you need to include one or more sets of files	4023	Depending on what features you need you need to include one or more sets of files
2679	in your app.	4024	in your application.
2680		4025
2681	=head3 CORE EVENT LOOP	4026	=head3 CORE EVENT LOOP
2682		4027
2683	To include only the libev core (all the C<ev_*> functions), with manual	4028	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	4029	configuration (no autoconf):
2685		4030
2686	#define EV_STANDALONE 1	4031	#define EV_STANDALONE 1
2687	#include "ev.c"	4032	#include "ev.c"
2688		4033
2689	This will automatically include F<ev.h>, too, and should be done in a	4034	This will automatically include F<ev.h>, too, and should be done in a
2690	single C source file only to provide the function implementations. To use	4035	single C source file only to provide the function implementations. To use
2691	it, do the same for F<ev.h> in all files wishing to use this API (best	4036	it, do the same for F<ev.h> in all files wishing to use this API (best
2692	done by writing a wrapper around F<ev.h> that you can include instead and	4037	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	4038	where you can put other configuration options):
2694		4039
2695	#define EV_STANDALONE 1	4040	#define EV_STANDALONE 1
2696	#include "ev.h"	4041	#include "ev.h"
2697		4042
2698	Both header files and implementation files can be compiled with a C++	4043	Both header files and implementation files can be compiled with a C++
2699	compiler (at least, thats a stated goal, and breakage will be treated	4044	compiler (at least, that's a stated goal, and breakage will be treated
2700	as a bug).	4045	as a bug).
2701		4046
2702	You need the following files in your source tree, or in a directory	4047	You need the following files in your source tree, or in a directory
2703	in your include path (e.g. in libev/ when using -Ilibev):	4048	in your include path (e.g. in libev/ when using -Ilibev):
2704		4049
2705	ev.h	4050	ev.h
2706	ev.c	4051	ev.c
2707	ev_vars.h	4052	ev_vars.h
2708	ev_wrap.h	4053	ev_wrap.h
2709		4054
2710	ev_win32.c required on win32 platforms only	4055	ev_win32.c required on win32 platforms only
2711		4056
2712	ev_select.c only when select backend is enabled (which is enabled by default)	4057	ev_select.c only when select backend is enabled (which is enabled by default)
2713	ev_poll.c only when poll backend is enabled (disabled by default)	4058	ev_poll.c only when poll backend is enabled (disabled by default)
2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4059	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4060	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2716	ev_port.c only when the solaris port backend is enabled (disabled by default)	4061	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		4062
2718	F<ev.c> includes the backend files directly when enabled, so you only need	4063	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	4064	to compile this single file.
2720		4065
2721	=head3 LIBEVENT COMPATIBILITY API	4066	=head3 LIBEVENT COMPATIBILITY API
2722		4067
2723	To include the libevent compatibility API, also include:	4068	To include the libevent compatibility API, also include:
2724		4069
2725	#include "event.c"	4070	#include "event.c"
2726		4071
2727	in the file including F<ev.c>, and:	4072	in the file including F<ev.c>, and:
2728		4073
2729	#include "event.h"	4074	#include "event.h"
2730		4075
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	4076	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		4077
2733	You need the following additional files for this:	4078	You need the following additional files for this:
2734		4079
2735	event.h	4080	event.h
2736	event.c	4081	event.c
2737		4082
2738	=head3 AUTOCONF SUPPORT	4083	=head3 AUTOCONF SUPPORT
2739		4084
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	4085	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2741	whatever way you want, you can also C<m4_include([libev.m4])> in your	4086	whatever way you want, you can also C<m4_include([libev.m4])> in your
2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	4087	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	4088	include F<config.h> and configure itself accordingly.
2744		4089
2745	For this of course you need the m4 file:	4090	For this of course you need the m4 file:
2746		4091
2747	libev.m4	4092	libev.m4
2748		4093
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	4094	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		4095
2751	Libev can be configured via a variety of preprocessor symbols you have to	4096	Libev can be configured via a variety of preprocessor symbols you have to
2752	define before including any of its files. The default in the absense of	4097	define before including (or compiling) any of its files. The default in
2753	autoconf is noted for every option.	4098	the absence of autoconf is documented for every option.
		4099
		4100	Symbols marked with "(h)" do not change the ABI, and can have different
		4101	values when compiling libev vs. including F<ev.h>, so it is permissible
		4102	to redefine them before including F<ev.h> without breaking compatibility
		4103	to a compiled library. All other symbols change the ABI, which means all
		4104	users of libev and the libev code itself must be compiled with compatible
		4105	settings.
2754		4106
2755	=over 4	4107	=over 4
2756		4108
		4109	=item EV_COMPAT3 (h)
		4110
		4111	Backwards compatibility is a major concern for libev. This is why this
		4112	release of libev comes with wrappers for the functions and symbols that
		4113	have been renamed between libev version 3 and 4.
		4114
		4115	You can disable these wrappers (to test compatibility with future
		4116	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4117	sources. This has the additional advantage that you can drop the C<struct>
		4118	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4119	typedef in that case.
		4120
		4121	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4122	and in some even more future version the compatibility code will be
		4123	removed completely.
		4124
2757	=item EV_STANDALONE	4125	=item EV_STANDALONE (h)
2758		4126
2759	Must always be C<1> if you do not use autoconf configuration, which	4127	Must always be C<1> if you do not use autoconf configuration, which
2760	keeps libev from including F<config.h>, and it also defines dummy	4128	keeps libev from including F<config.h>, and it also defines dummy
2761	implementations for some libevent functions (such as logging, which is not	4129	implementations for some libevent functions (such as logging, which is not
2762	supported). It will also not define any of the structs usually found in	4130	supported). It will also not define any of the structs usually found in
2763	F<event.h> that are not directly supported by the libev core alone.	4131	F<event.h> that are not directly supported by the libev core alone.
2764		4132
		4133	In standalone mode, libev will still try to automatically deduce the
		4134	configuration, but has to be more conservative.
		4135
2765	=item EV_USE_MONOTONIC	4136	=item EV_USE_MONOTONIC
2766		4137
2767	If defined to be C<1>, libev will try to detect the availability of the	4138	If defined to be C<1>, libev will try to detect the availability of the
2768	monotonic clock option at both compiletime and runtime. Otherwise no use	4139	monotonic clock option at both compile time and runtime. Otherwise no
2769	of the monotonic clock option will be attempted. If you enable this, you	4140	use of the monotonic clock option will be attempted. If you enable this,
2770	usually have to link against librt or something similar. Enabling it when	4141	you usually have to link against librt or something similar. Enabling it
2771	the functionality isn't available is safe, though, although you have	4142	when the functionality isn't available is safe, though, although you have
2772	to make sure you link against any libraries where the C<clock_gettime>	4143	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	4144	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2774		4145
2775	=item EV_USE_REALTIME	4146	=item EV_USE_REALTIME
2776		4147
2777	If defined to be C<1>, libev will try to detect the availability of the	4148	If defined to be C<1>, libev will try to detect the availability of the
2778	realtime clock option at compiletime (and assume its availability at	4149	real-time clock option at compile time (and assume its availability
2779	runtime if successful). Otherwise no use of the realtime clock option will	4150	at runtime if successful). Otherwise no use of the real-time clock
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4151	option will be attempted. This effectively replaces C<gettimeofday>
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4152	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4153	correctness. See the note about libraries in the description of
		4154	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4155	C<EV_USE_CLOCK_SYSCALL>.
		4156
		4157	=item EV_USE_CLOCK_SYSCALL
		4158
		4159	If defined to be C<1>, libev will try to use a direct syscall instead
		4160	of calling the system-provided C<clock_gettime> function. This option
		4161	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4162	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4163	programs needlessly. Using a direct syscall is slightly slower (in
		4164	theory), because no optimised vdso implementation can be used, but avoids
		4165	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4166	higher, as it simplifies linking (no need for C<-lrt>).
2783		4167
2784	=item EV_USE_NANOSLEEP	4168	=item EV_USE_NANOSLEEP
2785		4169
2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4170	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2787	and will use it for delays. Otherwise it will use C<select ()>.	4171	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2795	2.7 or newer, otherwise disabled.	4179	2.7 or newer, otherwise disabled.
2796		4180
2797	=item EV_USE_SELECT	4181	=item EV_USE_SELECT
2798		4182
2799	If undefined or defined to be C<1>, libev will compile in support for the	4183	If undefined or defined to be C<1>, libev will compile in support for the
2800	C<select>(2) backend. No attempt at autodetection will be done: if no	4184	C<select>(2) backend. No attempt at auto-detection will be done: if no
2801	other method takes over, select will be it. Otherwise the select backend	4185	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	4186	will not be compiled in.
2803		4187
2804	=item EV_SELECT_USE_FD_SET	4188	=item EV_SELECT_USE_FD_SET
2805		4189
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	4190	If defined to C<1>, then the select backend will use the system C<fd_set>
2807	structure. This is useful if libev doesn't compile due to a missing	4191	structure. This is useful if libev doesn't compile due to a missing
2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	4192	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2809	exotic systems. This usually limits the range of file descriptors to some	4193	on exotic systems. This usually limits the range of file descriptors to
2810	low limit such as 1024 or might have other limitations (winsocket only	4194	some low limit such as 1024 or might have other limitations (winsocket
2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4195	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2812	influence the size of the C<fd_set> used.	4196	configures the maximum size of the C<fd_set>.
2813		4197
2814	=item EV_SELECT_IS_WINSOCKET	4198	=item EV_SELECT_IS_WINSOCKET
2815		4199
2816	When defined to C<1>, the select backend will assume that	4200	When defined to C<1>, the select backend will assume that
2817	select/socket/connect etc. don't understand file descriptors but	4201	select/socket/connect etc. don't understand file descriptors but
…		…
2819	be used is the winsock select). This means that it will call	4203	be used is the winsock select). This means that it will call
2820	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4204	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2821	it is assumed that all these functions actually work on fds, even	4205	it is assumed that all these functions actually work on fds, even
2822	on win32. Should not be defined on non-win32 platforms.	4206	on win32. Should not be defined on non-win32 platforms.
2823		4207
2824	=item EV_FD_TO_WIN32_HANDLE	4208	=item EV_FD_TO_WIN32_HANDLE(fd)
2825		4209
2826	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4210	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2827	file descriptors to socket handles. When not defining this symbol (the	4211	file descriptors to socket handles. When not defining this symbol (the
2828	default), then libev will call C<_get_osfhandle>, which is usually	4212	default), then libev will call C<_get_osfhandle>, which is usually
2829	correct. In some cases, programs use their own file descriptor management,	4213	correct. In some cases, programs use their own file descriptor management,
2830	in which case they can provide this function to map fds to socket handles.	4214	in which case they can provide this function to map fds to socket handles.
		4215
		4216	=item EV_WIN32_HANDLE_TO_FD(handle)
		4217
		4218	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4219	using the standard C<_open_osfhandle> function. For programs implementing
		4220	their own fd to handle mapping, overwriting this function makes it easier
		4221	to do so. This can be done by defining this macro to an appropriate value.
		4222
		4223	=item EV_WIN32_CLOSE_FD(fd)
		4224
		4225	If programs implement their own fd to handle mapping on win32, then this
		4226	macro can be used to override the C<close> function, useful to unregister
		4227	file descriptors again. Note that the replacement function has to close
		4228	the underlying OS handle.
2831		4229
2832	=item EV_USE_POLL	4230	=item EV_USE_POLL
2833		4231
2834	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4232	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2835	backend. Otherwise it will be enabled on non-win32 platforms. It	4233	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2862	otherwise another method will be used as fallback. This is the preferred	4260	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	4261	backend for Solaris 10 systems.
2864		4262
2865	=item EV_USE_DEVPOLL	4263	=item EV_USE_DEVPOLL
2866		4264
2867	reserved for future expansion, works like the USE symbols above.	4265	Reserved for future expansion, works like the USE symbols above.
2868		4266
2869	=item EV_USE_INOTIFY	4267	=item EV_USE_INOTIFY
2870		4268
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	4269	If defined to be C<1>, libev will compile in support for the Linux inotify
2872	interface to speed up C<ev_stat> watchers. Its actual availability will	4270	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2879	access is atomic with respect to other threads or signal contexts. No such	4277	access is atomic with respect to other threads or signal contexts. No such
2880	type is easily found in the C language, so you can provide your own type	4278	type is easily found in the C language, so you can provide your own type
2881	that you know is safe for your purposes. It is used both for signal handler "locking"	4279	that you know is safe for your purposes. It is used both for signal handler "locking"
2882	as well as for signal and thread safety in C<ev_async> watchers.	4280	as well as for signal and thread safety in C<ev_async> watchers.
2883		4281
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	4282	In the absence of this define, libev will use C<sig_atomic_t volatile>
2885	(from F<signal.h>), which is usually good enough on most platforms.	4283	(from F<signal.h>), which is usually good enough on most platforms.
2886		4284
2887	=item EV_H	4285	=item EV_H (h)
2888		4286
2889	The name of the F<ev.h> header file used to include it. The default if	4287	The name of the F<ev.h> header file used to include it. The default if
2890	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4288	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2891	used to virtually rename the F<ev.h> header file in case of conflicts.	4289	used to virtually rename the F<ev.h> header file in case of conflicts.
2892		4290
2893	=item EV_CONFIG_H	4291	=item EV_CONFIG_H (h)
2894		4292
2895	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4293	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2896	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4294	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2897	C<EV_H>, above.	4295	C<EV_H>, above.
2898		4296
2899	=item EV_EVENT_H	4297	=item EV_EVENT_H (h)
2900		4298
2901	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4299	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2902	of how the F<event.h> header can be found, the default is C<"event.h">.	4300	of how the F<event.h> header can be found, the default is C<"event.h">.
2903		4301
2904	=item EV_PROTOTYPES	4302	=item EV_PROTOTYPES (h)
2905		4303
2906	If defined to be C<0>, then F<ev.h> will not define any function	4304	If defined to be C<0>, then F<ev.h> will not define any function
2907	prototypes, but still define all the structs and other symbols. This is	4305	prototypes, but still define all the structs and other symbols. This is
2908	occasionally useful if you want to provide your own wrapper functions	4306	occasionally useful if you want to provide your own wrapper functions
2909	around libev functions.	4307	around libev functions.
…		…
2928	When doing priority-based operations, libev usually has to linearly search	4326	When doing priority-based operations, libev usually has to linearly search
2929	all the priorities, so having many of them (hundreds) uses a lot of space	4327	all the priorities, so having many of them (hundreds) uses a lot of space
2930	and time, so using the defaults of five priorities (-2 .. +2) is usually	4328	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	4329	fine.
2932		4330
2933	If your embedding app does not need any priorities, defining these both to	4331	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	4332	both to C<0> will save some memory and CPU.
2935		4333
2936	=item EV_PERIODIC_ENABLE	4334	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4335	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4336	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2937		4337
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	4338	If undefined or defined to be C<1> (and the platform supports it), then
2939	defined to be C<0>, then they are not. Disabling them saves a few kB of	4339	the respective watcher type is supported. If defined to be C<0>, then it
2940	code.	4340	is not. Disabling watcher types mainly saves code size.
2941		4341
2942	=item EV_IDLE_ENABLE	4342	=item EV_FEATURES
2943
2944	If undefined or defined to be C<1>, then idle watchers are supported. If
2945	defined to be C<0>, then they are not. Disabling them saves a few kB of
2946	code.
2947
2948	=item EV_EMBED_ENABLE
2949
2950	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.
2952
2953	=item EV_STAT_ENABLE
2954
2955	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.
2957
2958	=item EV_FORK_ENABLE
2959
2960	If undefined or defined to be C<1>, then fork watchers are supported. If
2961	defined to be C<0>, then they are not.
2962
2963	=item EV_ASYNC_ENABLE
2964
2965	If undefined or defined to be C<1>, then async watchers are supported. If
2966	defined to be C<0>, then they are not.
2967
2968	=item EV_MINIMAL
2969		4343
2970	If you need to shave off some kilobytes of code at the expense of some	4344	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	4345	speed (but with the full API), you can define this symbol to request
2972	some inlining decisions, saves roughly 30% codesize of amd64.	4346	certain subsets of functionality. The default is to enable all features
		4347	that can be enabled on the platform.
		4348
		4349	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4350	with some broad features you want) and then selectively re-enable
		4351	additional parts you want, for example if you want everything minimal,
		4352	but multiple event loop support, async and child watchers and the poll
		4353	backend, use this:
		4354
		4355	#define EV_FEATURES 0
		4356	#define EV_MULTIPLICITY 1
		4357	#define EV_USE_POLL 1
		4358	#define EV_CHILD_ENABLE 1
		4359	#define EV_ASYNC_ENABLE 1
		4360
		4361	The actual value is a bitset, it can be a combination of the following
		4362	values:
		4363
		4364	=over 4
		4365
		4366	=item C<1> - faster/larger code
		4367
		4368	Use larger code to speed up some operations.
		4369
		4370	Currently this is used to override some inlining decisions (enlarging the
		4371	code size by roughly 30% on amd64).
		4372
		4373	When optimising for size, use of compiler flags such as C<-Os> with
		4374	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4375	assertions.
		4376
		4377	=item C<2> - faster/larger data structures
		4378
		4379	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4380	hash table sizes and so on. This will usually further increase code size
		4381	and can additionally have an effect on the size of data structures at
		4382	runtime.
		4383
		4384	=item C<4> - full API configuration
		4385
		4386	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4387	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4388
		4389	=item C<8> - full API
		4390
		4391	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4392	details on which parts of the API are still available without this
		4393	feature, and do not complain if this subset changes over time.
		4394
		4395	=item C<16> - enable all optional watcher types
		4396
		4397	Enables all optional watcher types. If you want to selectively enable
		4398	only some watcher types other than I/O and timers (e.g. prepare,
		4399	embed, async, child...) you can enable them manually by defining
		4400	C<EV_watchertype_ENABLE> to C<1> instead.
		4401
		4402	=item C<32> - enable all backends
		4403
		4404	This enables all backends - without this feature, you need to enable at
		4405	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4406
		4407	=item C<64> - enable OS-specific "helper" APIs
		4408
		4409	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4410	default.
		4411
		4412	=back
		4413
		4414	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4415	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4416	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4417	watchers, timers and monotonic clock support.
		4418
		4419	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4420	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4421	your program might be left out as well - a binary starting a timer and an
		4422	I/O watcher then might come out at only 5Kb.
		4423
		4424	=item EV_AVOID_STDIO
		4425
		4426	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4427	functions (printf, scanf, perror etc.). This will increase the code size
		4428	somewhat, but if your program doesn't otherwise depend on stdio and your
		4429	libc allows it, this avoids linking in the stdio library which is quite
		4430	big.
		4431
		4432	Note that error messages might become less precise when this option is
		4433	enabled.
		4434
		4435	=item EV_NSIG
		4436
		4437	The highest supported signal number, +1 (or, the number of
		4438	signals): Normally, libev tries to deduce the maximum number of signals
		4439	automatically, but sometimes this fails, in which case it can be
		4440	specified. Also, using a lower number than detected (C<32> should be
		4441	good for about any system in existence) can save some memory, as libev
		4442	statically allocates some 12-24 bytes per signal number.
2973		4443
2974	=item EV_PID_HASHSIZE	4444	=item EV_PID_HASHSIZE
2975		4445
2976	C<ev_child> watchers use a small hash table to distribute workload by	4446	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4447	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2978	than enough. If you need to manage thousands of children you might want to	4448	usually more than enough. If you need to manage thousands of children you
2979	increase this value (I<must> be a power of two).	4449	might want to increase this value (I<must> be a power of two).
2980		4450
2981	=item EV_INOTIFY_HASHSIZE	4451	=item EV_INOTIFY_HASHSIZE
2982		4452
2983	C<ev_stat> watchers use a small hash table to distribute workload by	4453	C<ev_stat> watchers use a small hash table to distribute workload by
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4454	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	4455	disabled), usually more than enough. If you need to manage thousands of
2986	watchers you might want to increase this value (I<must> be a power of	4456	C<ev_stat> watchers you might want to increase this value (I<must> be a
2987	two).	4457	power of two).
		4458
		4459	=item EV_USE_4HEAP
		4460
		4461	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4462	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		4463	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		4464	faster performance with many (thousands) of watchers.
		4465
		4466	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4467	will be C<0>.
		4468
		4469	=item EV_HEAP_CACHE_AT
		4470
		4471	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4472	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		4473	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		4474	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		4475	but avoids random read accesses on heap changes. This improves performance
		4476	noticeably with many (hundreds) of watchers.
		4477
		4478	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4479	will be C<0>.
		4480
		4481	=item EV_VERIFY
		4482
		4483	Controls how much internal verification (see C<ev_verify ()>) will
		4484	be done: If set to C<0>, no internal verification code will be compiled
		4485	in. If set to C<1>, then verification code will be compiled in, but not
		4486	called. If set to C<2>, then the internal verification code will be
		4487	called once per loop, which can slow down libev. If set to C<3>, then the
		4488	verification code will be called very frequently, which will slow down
		4489	libev considerably.
		4490
		4491	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4492	will be C<0>.
2988		4493
2989	=item EV_COMMON	4494	=item EV_COMMON
2990		4495
2991	By default, all watchers have a C<void *data> member. By redefining	4496	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	4497	this macro to something else you can include more and other types of
2993	members. You have to define it each time you include one of the files,	4498	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	4499	though, and it must be identical each time.
2995		4500
2996	For example, the perl EV module uses something like this:	4501	For example, the perl EV module uses something like this:
2997		4502
2998	#define EV_COMMON \	4503	#define EV_COMMON \
2999	SV *self; /* contains this struct */ \	4504	SV *self; /* contains this struct */ \
3000	SV *cb_sv, *fh /* note no trailing ";" */	4505	SV *cb_sv, *fh /* note no trailing ";" */
3001		4506
3002	=item EV_CB_DECLARE (type)	4507	=item EV_CB_DECLARE (type)
3003		4508
3004	=item EV_CB_INVOKE (watcher, revents)	4509	=item EV_CB_INVOKE (watcher, revents)
3005		4510
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	4515	definition and a statement, respectively. See the F<ev.h> header file for
3011	their default definitions. One possible use for overriding these is to	4516	their default definitions. One possible use for overriding these is to
3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4517	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3013	method calls instead of plain function calls in C++.	4518	method calls instead of plain function calls in C++.
3014		4519
		4520	=back
		4521
3015	=head2 EXPORTED API SYMBOLS	4522	=head2 EXPORTED API SYMBOLS
3016		4523
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	4524	If you need to re-export the API (e.g. via a DLL) and you need a list of
3018	exported symbols, you can use the provided F<Symbol.*> files which list	4525	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	4526	all public symbols, one per line:
3020		4527
3021	Symbols.ev for libev proper	4528	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	4529	Symbols.event for the libevent emulation
3023		4530
3024	This can also be used to rename all public symbols to avoid clashes with	4531	This can also be used to rename all public symbols to avoid clashes with
3025	multiple versions of libev linked together (which is obviously bad in	4532	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	4533	itself, but sometimes it is inconvenient to avoid this).
3027		4534
3028	A sed command like this will create wrapper C<#define>'s that you need to	4535	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	4536	include before including F<ev.h>:
3030		4537
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4538	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	4555	file.
3049		4556
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4557	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3051	that everybody includes and which overrides some configure choices:	4558	that everybody includes and which overrides some configure choices:
3052		4559
3053	#define EV_MINIMAL 1	4560	#define EV_FEATURES 8
3054	#define EV_USE_POLL 0	4561	#define EV_USE_SELECT 1
3055	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	4562	#define EV_PREPARE_ENABLE 1
		4563	#define EV_IDLE_ENABLE 1
3057	#define EV_STAT_ENABLE 0	4564	#define EV_SIGNAL_ENABLE 1
3058	#define EV_FORK_ENABLE 0	4565	#define EV_CHILD_ENABLE 1
		4566	#define EV_USE_STDEXCEPT 0
3059	#define EV_CONFIG_H <config.h>	4567	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0
3062		4568
3063	#include "ev++.h"	4569	#include "ev++.h"
3064		4570
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		4572
3067	#include "ev_cpp.h"	4573	#include "ev_cpp.h"
3068	#include "ev.c"	4574	#include "ev.c"
3069		4575
		4576	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3070		4577
3071	=head1 THREADS AND COROUTINES	4578	=head2 THREADS AND COROUTINES
3072		4579
3073	=head2 THREADS	4580	=head3 THREADS
3074		4581
3075	Libev itself is completely threadsafe, but it uses no locking. This	4582	All libev functions are reentrant and thread-safe unless explicitly
		4583	documented otherwise, but libev implements no locking itself. This means
3076	means that you can use as many loops as you want in parallel, as long as	4584	that you can use as many loops as you want in parallel, as long as there
3077	only one thread ever calls into one libev function with the same loop	4585	are no concurrent calls into any libev function with the same loop
3078	parameter.	4586	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4587	of course): libev guarantees that different event loops share no data
		4588	structures that need any locking.
3079		4589
3080	Or put differently: calls with different loop parameters can be done in	4590	Or to put it differently: calls with different loop parameters can be done
3081	parallel from multiple threads, calls with the same loop parameter must be	4591	concurrently from multiple threads, calls with the same loop parameter
3082	done serially (but can be done from different threads, as long as only one	4592	must be done serially (but can be done from different threads, as long as
3083	thread ever is inside a call at any point in time, e.g. by using a mutex	4593	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	4594	a mutex per loop).
3085		4595
3086	If you want to know which design is best for your problem, then I cannot	4596	Specifically to support threads (and signal handlers), libev implements
		4597	so-called C<ev_async> watchers, which allow some limited form of
		4598	concurrency on the same event loop, namely waking it up "from the
		4599	outside".
		4600
		4601	If you want to know which design (one loop, locking, or multiple loops
		4602	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	4603	help you, but here is some generic advice:
3088		4604
3089	=over 4	4605	=over 4
3090		4606
3091	=item * most applications have a main thread: use the default libev loop	4607	=item * most applications have a main thread: use the default libev loop
3092	in that thread, or create a seperate thread running only the default loop.	4608	in that thread, or create a separate thread running only the default loop.
3093		4609
3094	This helps integrating other libraries or software modules that use libev	4610	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	4611	themselves and don't care/know about threading.
3096		4612
3097	=item * one loop per thread is usually a good model.	4613	=item * one loop per thread is usually a good model.
3098		4614
3099	Doing this is almost never wrong, sometimes a better-performance model	4615	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	4616	exists, but it is always a good start.
3101		4617
3102	=item * other models exist, such as the leader/follower pattern, where one	4618	=item * other models exist, such as the leader/follower pattern, where one
3103	loop is handed through multiple threads in a kind of round-robbin fashion.	4619	loop is handed through multiple threads in a kind of round-robin fashion.
3104		4620
3105	Chosing a model is hard - look around, learn, know that usually you cna do	4621	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	4622	better than you currently do :-)
3107		4623
3108	=item * often you need to talk to some other thread which blocks in the	4624	=item * often you need to talk to some other thread which blocks in the
		4625	event loop.
		4626
3109	event loop - C<ev_async> watchers can be used to wake them up from other	4627	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	4628	(or from signal contexts...).
		4629
		4630	An example use would be to communicate signals or other events that only
		4631	work in the default loop by registering the signal watcher with the
		4632	default loop and triggering an C<ev_async> watcher from the default loop
		4633	watcher callback into the event loop interested in the signal.
3111		4634
3112	=back	4635	=back
3113		4636
		4637	See also L<THREAD LOCKING EXAMPLE>.
		4638
3114	=head2 COROUTINES	4639	=head3 COROUTINES
3115		4640
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	4641	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	4642	libev fully supports nesting calls to its functions from different
3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4643	coroutines (e.g. you can call C<ev_run> on the same loop from two
3119	different coroutines and switch freely between both coroutines running the	4644	different coroutines, and switch freely between both coroutines running
3120	loop, as long as you don't confuse yourself). The only exception is that	4645	the loop, as long as you don't confuse yourself). The only exception is
3121	you must not do this from C<ev_periodic> reschedule callbacks.	4646	that you must not do this from C<ev_periodic> reschedule callbacks.
3122		4647
3123	Care has been invested into making sure that libev does not keep local	4648	Care has been taken to ensure that libev does not keep local state inside
3124	state inside C<ev_loop>, and other calls do not usually allow coroutine	4649	C<ev_run>, and other calls do not usually allow for coroutine switches as
3125	switches.	4650	they do not call any callbacks.
3126		4651
		4652	=head2 COMPILER WARNINGS
3127		4653
3128	=head1 COMPLEXITIES	4654	Depending on your compiler and compiler settings, you might get no or a
		4655	lot of warnings when compiling libev code. Some people are apparently
		4656	scared by this.
3129		4657
3130	In this section the complexities of (many of) the algorithms used inside	4658	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	4659	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	4660	warning options. "Warn-free" code therefore cannot be a goal except when
		4661	targeting a specific compiler and compiler-version.
3133		4662
3134	All of the following are about amortised time: If an array needs to be	4663	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	4664	workarounds, or other changes to the code that make it less clear and less
3136	happens asymptotically never with higher number of elements, so O(1) might	4665	maintainable.
3137	mean it might do a lengthy realloc operation in rare cases, but on average
3138	it is much faster and asymptotically approaches constant time.
3139		4666
3140	=over 4	4667	And of course, some compiler warnings are just plain stupid, or simply
		4668	wrong (because they don't actually warn about the condition their message
		4669	seems to warn about). For example, certain older gcc versions had some
		4670	warnings that resulted in an extreme number of false positives. These have
		4671	been fixed, but some people still insist on making code warn-free with
		4672	such buggy versions.
3141		4673
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4674	While libev is written to generate as few warnings as possible,
		4675	"warn-free" code is not a goal, and it is recommended not to build libev
		4676	with any compiler warnings enabled unless you are prepared to cope with
		4677	them (e.g. by ignoring them). Remember that warnings are just that:
		4678	warnings, not errors, or proof of bugs.
3143		4679
3144	This means that, when you have a watcher that triggers in one hour and
3145	there are 100 watchers that would trigger before that then inserting will
3146	have to skip roughly seven (C<ld 100>) of these watchers.
3147		4680
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4681	=head2 VALGRIND
3149		4682
3150	That means that changing a timer costs less than removing/adding them	4683	Valgrind has a special section here because it is a popular tool that is
3151	as only the relative motion in the event queue has to be paid for.	4684	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		4685
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4686	If you think you found a bug (memory leak, uninitialised data access etc.)
		4687	in libev, then check twice: If valgrind reports something like:
3154		4688
3155	These just add the watcher into an array or at the head of a list.	4689	==2274== definitely lost: 0 bytes in 0 blocks.
		4690	==2274== possibly lost: 0 bytes in 0 blocks.
		4691	==2274== still reachable: 256 bytes in 1 blocks.
3156		4692
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4693	Then there is no memory leak, just as memory accounted to global variables
		4694	is not a memleak - the memory is still being referenced, and didn't leak.
3158		4695
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4696	Similarly, under some circumstances, valgrind might report kernel bugs
		4697	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4698	although an acceptable workaround has been found here), or it might be
		4699	confused.
3160		4700
3161	These watchers are stored in lists then need to be walked to find the	4701	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3162	correct watcher to remove. The lists are usually short (you don't usually	4702	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		4703
3165	=item Finding the next timer in each loop iteration: O(1)	4704	If you are unsure about something, feel free to contact the mailing list
		4705	with the full valgrind report and an explanation on why you think this
		4706	is a bug in libev (best check the archives, too :). However, don't be
		4707	annoyed when you get a brisk "this is no bug" answer and take the chance
		4708	of learning how to interpret valgrind properly.
3166		4709
3167	By virtue of using a binary heap, the next timer is always found at the	4710	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	4711	I suggest using suppression lists.
3169		4712
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		4713
3172	A change means an I/O watcher gets started or stopped, which requires	4714	=head1 PORTABILITY NOTES
3173	libev to recalculate its status (and possibly tell the kernel, depending
3174	on backend and wether C<ev_io_set> was used).
3175		4715
3176	=item Activating one watcher (putting it into the pending state): O(1)	4716	=head2 GNU/LINUX 32 BIT LIMITATIONS
3177		4717
3178	=item Priority handling: O(number_of_priorities)	4718	GNU/Linux is the only common platform that supports 64 bit file/large file
		4719	interfaces but I<disables> them by default.
3179		4720
3180	Priorities are implemented by allocating some space for each	4721	That means that libev compiled in the default environment doesn't support
3181	priority. When doing priority-based operations, libev usually has to	4722	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3182	linearly search all the priorities, but starting/stopping and activating
3183	watchers becomes O(1) w.r.t. priority handling.
3184		4723
3185	=item Sending an ev_async: O(1)	4724	Unfortunately, many programs try to work around this GNU/Linux issue
		4725	by enabling the large file API, which makes them incompatible with the
		4726	standard libev compiled for their system.
3186		4727
3187	=item Processing ev_async_send: O(number_of_async_watchers)	4728	Likewise, libev cannot enable the large file API itself as this would
		4729	suddenly make it incompatible to the default compile time environment,
		4730	i.e. all programs not using special compile switches.
3188		4731
3189	=item Processing signals: O(max_signal_number)	4732	=head2 OS/X AND DARWIN BUGS
3190		4733
3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4734	The whole thing is a bug if you ask me - basically any system interface
3192	calls in the current loop iteration. Checking for async and signal events	4735	you touch is broken, whether it is locales, poll, kqueue or even the
3193	involves iterating over all running async watchers or all signal numbers.	4736	OpenGL drivers.
3194		4737
3195	=back	4738	=head3 C<kqueue> is buggy
3196		4739
		4740	The kqueue syscall is broken in all known versions - most versions support
		4741	only sockets, many support pipes.
3197		4742
3198	=head1 Win32 platform limitations and workarounds	4743	Libev tries to work around this by not using C<kqueue> by default on this
		4744	rotten platform, but of course you can still ask for it when creating a
		4745	loop - embedding a socket-only kqueue loop into a select-based one is
		4746	probably going to work well.
		4747
		4748	=head3 C<poll> is buggy
		4749
		4750	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4751	implementation by something calling C<kqueue> internally around the 10.5.6
		4752	release, so now C<kqueue> I<and> C<poll> are broken.
		4753
		4754	Libev tries to work around this by not using C<poll> by default on
		4755	this rotten platform, but of course you can still ask for it when creating
		4756	a loop.
		4757
		4758	=head3 C<select> is buggy
		4759
		4760	All that's left is C<select>, and of course Apple found a way to fuck this
		4761	one up as well: On OS/X, C<select> actively limits the number of file
		4762	descriptors you can pass in to 1024 - your program suddenly crashes when
		4763	you use more.
		4764
		4765	There is an undocumented "workaround" for this - defining
		4766	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4767	work on OS/X.
		4768
		4769	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4770
		4771	=head3 C<errno> reentrancy
		4772
		4773	The default compile environment on Solaris is unfortunately so
		4774	thread-unsafe that you can't even use components/libraries compiled
		4775	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4776	defined by default. A valid, if stupid, implementation choice.
		4777
		4778	If you want to use libev in threaded environments you have to make sure
		4779	it's compiled with C<_REENTRANT> defined.
		4780
		4781	=head3 Event port backend
		4782
		4783	The scalable event interface for Solaris is called "event
		4784	ports". Unfortunately, this mechanism is very buggy in all major
		4785	releases. If you run into high CPU usage, your program freezes or you get
		4786	a large number of spurious wakeups, make sure you have all the relevant
		4787	and latest kernel patches applied. No, I don't know which ones, but there
		4788	are multiple ones to apply, and afterwards, event ports actually work
		4789	great.
		4790
		4791	If you can't get it to work, you can try running the program by setting
		4792	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4793	C<select> backends.
		4794
		4795	=head2 AIX POLL BUG
		4796
		4797	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4798	this by trying to avoid the poll backend altogether (i.e. it's not even
		4799	compiled in), which normally isn't a big problem as C<select> works fine
		4800	with large bitsets on AIX, and AIX is dead anyway.
		4801
		4802	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4803
		4804	=head3 General issues
3199		4805
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4806	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3201	requires, and its I/O model is fundamentally incompatible with the POSIX	4807	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	4808	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4809	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	4810	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	4811	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4812	as every compielr comes with a slightly differently broken/incompatible
		4813	environment.
		4814
		4815	Lifting these limitations would basically require the full
		4816	re-implementation of the I/O system. If you are into this kind of thing,
		4817	then note that glib does exactly that for you in a very portable way (note
		4818	also that glib is the slowest event library known to man).
3206		4819
3207	There is no supported compilation method available on windows except	4820	There is no supported compilation method available on windows except
3208	embedding it into other applications.	4821	embedding it into other applications.
3209		4822
		4823	Sensible signal handling is officially unsupported by Microsoft - libev
		4824	tries its best, but under most conditions, signals will simply not work.
		4825
		4826	Not a libev limitation but worth mentioning: windows apparently doesn't
		4827	accept large writes: instead of resulting in a partial write, windows will
		4828	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4829	so make sure you only write small amounts into your sockets (less than a
		4830	megabyte seems safe, but this apparently depends on the amount of memory
		4831	available).
		4832
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	4833	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	4834	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	4835	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	4836	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	4837	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	4838	notification model, which cannot be implemented efficiently on windows
		4839	(due to Microsoft monopoly games).
3216		4840
3217	=over 4	4841	A typical way to use libev under windows is to embed it (see the embedding
		4842	section for details) and use the following F<evwrap.h> header file instead
		4843	of F<ev.h>:
3218		4844
		4845	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4846	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4847
		4848	#include "ev.h"
		4849
		4850	And compile the following F<evwrap.c> file into your project (make sure
		4851	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4852
		4853	#include "evwrap.h"
		4854	#include "ev.c"
		4855
3219	=item The winsocket select function	4856	=head3 The winsocket C<select> function
3220		4857
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	4858	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	4859	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	4860	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4861	requires a mapping from file descriptors to socket handles (the Microsoft
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4862	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	4863	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4864	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		4865
3228	The configuration for a "naked" win32 using the microsoft runtime	4866	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	4867	libraries and raw winsocket select is:
3230		4868
3231	#define EV_USE_SELECT 1	4869	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4870	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		4871
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	4872	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	4873	complexity in the O(n²) range when using win32.
3236		4874
3237	=item Limited number of file descriptors	4875	=head3 Limited number of file descriptors
3238		4876
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	4877	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	4878
		4879	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	4880	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	4881	can only wait for C<64> things at the same time internally; Microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	4882	recommends spawning a chain of threads and wait for 63 handles and the
		4883	previous thread in each. Sounds great!).
3244		4884
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4885	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	4886	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	4887	call (which might be in libev or elsewhere, for example, perl and many
3248	select emulation on windows).	4888	other interpreters do their own select emulation on windows).
3249		4889
3250	Another limit is the number of file descriptors in the microsoft runtime	4890	Another limit is the number of file descriptors in the Microsoft runtime
3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4891	libraries, which by default is C<64> (there must be a hidden I<64>
3252	or something like this inside microsoft). You can increase this by calling	4892	fetish or something like this inside Microsoft). You can increase this
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4893	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	4894	(another arbitrary limit), but is broken in many versions of the Microsoft
3255	libraries.
3256
3257	This might get you to about C<512> or C<2048> sockets (depending on	4895	runtime libraries. This might get you to about C<512> or C<2048> sockets
3258	windows version and/or the phase of the moon). To get more, you need to	4896	(depending on windows version and/or the phase of the moon). To get more,
3259	wrap all I/O functions and provide your own fd management, but the cost of	4897	you need to wrap all I/O functions and provide your own fd management, but
3260	calling select (O(n²)) will likely make this unworkable.	4898	the cost of calling select (O(n²)) will likely make this unworkable.
3261		4899
3262	=back
3263
3264
3265	=head1 PORTABILITY REQUIREMENTS	4900	=head2 PORTABILITY REQUIREMENTS
3266		4901
3267	In addition to a working ISO-C implementation, libev relies on a few	4902	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	4903	backend-specific APIs, libev relies on a few additional extensions:
3269		4904
3270	=over 4	4905	=over 4
3271		4906
		4907	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4908	calling conventions regardless of C<ev_watcher_type *>.
		4909
		4910	Libev assumes not only that all watcher pointers have the same internal
		4911	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4912	assumes that the same (machine) code can be used to call any watcher
		4913	callback: The watcher callbacks have different type signatures, but libev
		4914	calls them using an C<ev_watcher *> internally.
		4915
		4916	=item pointer accesses must be thread-atomic
		4917
		4918	Accessing a pointer value must be atomic, it must both be readable and
		4919	writable in one piece - this is the case on all current architectures.
		4920
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	4921	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		4922
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	4923	The type C<sig_atomic_t volatile> (or whatever is defined as
3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4924	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3276	threads. This is not part of the specification for C<sig_atomic_t>, but is	4925	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	4926	believed to be sufficiently portable.
3278		4927
3279	=item C<sigprocmask> must work in a threaded environment	4928	=item C<sigprocmask> must work in a threaded environment
3280		4929
…		…
3287		4936
3288	The most portable way to handle signals is to block signals in all threads	4937	The most portable way to handle signals is to block signals in all threads
3289	except the initial one, and run the default loop in the initial thread as	4938	except the initial one, and run the default loop in the initial thread as
3290	well.	4939	well.
3291		4940
		4941	=item C<long> must be large enough for common memory allocation sizes
		4942
		4943	To improve portability and simplify its API, libev uses C<long> internally
		4944	instead of C<size_t> when allocating its data structures. On non-POSIX
		4945	systems (Microsoft...) this might be unexpectedly low, but is still at
		4946	least 31 bits everywhere, which is enough for hundreds of millions of
		4947	watchers.
		4948
		4949	=item C<double> must hold a time value in seconds with enough accuracy
		4950
		4951	The type C<double> is used to represent timestamps. It is required to
		4952	have at least 51 bits of mantissa (and 9 bits of exponent), which is
		4953	good enough for at least into the year 4000 with millisecond accuracy
		4954	(the design goal for libev). This requirement is overfulfilled by
		4955	implementations using IEEE 754, which is basically all existing ones. With
		4956	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
		4957
3292	=back	4958	=back
3293		4959
3294	If you know of other additional requirements drop me a note.	4960	If you know of other additional requirements drop me a note.
3295		4961
3296		4962
		4963	=head1 ALGORITHMIC COMPLEXITIES
		4964
		4965	In this section the complexities of (many of) the algorithms used inside
		4966	libev will be documented. For complexity discussions about backends see
		4967	the documentation for C<ev_default_init>.
		4968
		4969	All of the following are about amortised time: If an array needs to be
		4970	extended, libev needs to realloc and move the whole array, but this
		4971	happens asymptotically rarer with higher number of elements, so O(1) might
		4972	mean that libev does a lengthy realloc operation in rare cases, but on
		4973	average it is much faster and asymptotically approaches constant time.
		4974
		4975	=over 4
		4976
		4977	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4978
		4979	This means that, when you have a watcher that triggers in one hour and
		4980	there are 100 watchers that would trigger before that, then inserting will
		4981	have to skip roughly seven (C<ld 100>) of these watchers.
		4982
		4983	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4984
		4985	That means that changing a timer costs less than removing/adding them,
		4986	as only the relative motion in the event queue has to be paid for.
		4987
		4988	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4989
		4990	These just add the watcher into an array or at the head of a list.
		4991
		4992	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4993
		4994	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4995
		4996	These watchers are stored in lists, so they need to be walked to find the
		4997	correct watcher to remove. The lists are usually short (you don't usually
		4998	have many watchers waiting for the same fd or signal: one is typical, two
		4999	is rare).
		5000
		5001	=item Finding the next timer in each loop iteration: O(1)
		5002
		5003	By virtue of using a binary or 4-heap, the next timer is always found at a
		5004	fixed position in the storage array.
		5005
		5006	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		5007
		5008	A change means an I/O watcher gets started or stopped, which requires
		5009	libev to recalculate its status (and possibly tell the kernel, depending
		5010	on backend and whether C<ev_io_set> was used).
		5011
		5012	=item Activating one watcher (putting it into the pending state): O(1)
		5013
		5014	=item Priority handling: O(number_of_priorities)
		5015
		5016	Priorities are implemented by allocating some space for each
		5017	priority. When doing priority-based operations, libev usually has to
		5018	linearly search all the priorities, but starting/stopping and activating
		5019	watchers becomes O(1) with respect to priority handling.
		5020
		5021	=item Sending an ev_async: O(1)
		5022
		5023	=item Processing ev_async_send: O(number_of_async_watchers)
		5024
		5025	=item Processing signals: O(max_signal_number)
		5026
		5027	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5028	calls in the current loop iteration. Checking for async and signal events
		5029	involves iterating over all running async watchers or all signal numbers.
		5030
		5031	=back
		5032
		5033
		5034	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5035
		5036	The major version 4 introduced some incompatible changes to the API.
		5037
		5038	At the moment, the C<ev.h> header file provides compatibility definitions
		5039	for all changes, so most programs should still compile. The compatibility
		5040	layer might be removed in later versions of libev, so better update to the
		5041	new API early than late.
		5042
		5043	=over 4
		5044
		5045	=item C<EV_COMPAT3> backwards compatibility mechanism
		5046
		5047	The backward compatibility mechanism can be controlled by
		5048	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5049	section.
		5050
		5051	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5052
		5053	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5054
		5055	ev_loop_destroy (EV_DEFAULT_UC);
		5056	ev_loop_fork (EV_DEFAULT);
		5057
		5058	=item function/symbol renames
		5059
		5060	A number of functions and symbols have been renamed:
		5061
		5062	ev_loop => ev_run
		5063	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5064	EVLOOP_ONESHOT => EVRUN_ONCE
		5065
		5066	ev_unloop => ev_break
		5067	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5068	EVUNLOOP_ONE => EVBREAK_ONE
		5069	EVUNLOOP_ALL => EVBREAK_ALL
		5070
		5071	EV_TIMEOUT => EV_TIMER
		5072
		5073	ev_loop_count => ev_iteration
		5074	ev_loop_depth => ev_depth
		5075	ev_loop_verify => ev_verify
		5076
		5077	Most functions working on C<struct ev_loop> objects don't have an
		5078	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5079	associated constants have been renamed to not collide with the C<struct
		5080	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5081	as all other watcher types. Note that C<ev_loop_fork> is still called
		5082	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5083	typedef.
		5084
		5085	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5086
		5087	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5088	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5089	and work, but the library code will of course be larger.
		5090
		5091	=back
		5092
		5093
		5094	=head1 GLOSSARY
		5095
		5096	=over 4
		5097
		5098	=item active
		5099
		5100	A watcher is active as long as it has been started and not yet stopped.
		5101	See L<WATCHER STATES> for details.
		5102
		5103	=item application
		5104
		5105	In this document, an application is whatever is using libev.
		5106
		5107	=item backend
		5108
		5109	The part of the code dealing with the operating system interfaces.
		5110
		5111	=item callback
		5112
		5113	The address of a function that is called when some event has been
		5114	detected. Callbacks are being passed the event loop, the watcher that
		5115	received the event, and the actual event bitset.
		5116
		5117	=item callback/watcher invocation
		5118
		5119	The act of calling the callback associated with a watcher.
		5120
		5121	=item event
		5122
		5123	A change of state of some external event, such as data now being available
		5124	for reading on a file descriptor, time having passed or simply not having
		5125	any other events happening anymore.
		5126
		5127	In libev, events are represented as single bits (such as C<EV_READ> or
		5128	C<EV_TIMER>).
		5129
		5130	=item event library
		5131
		5132	A software package implementing an event model and loop.
		5133
		5134	=item event loop
		5135
		5136	An entity that handles and processes external events and converts them
		5137	into callback invocations.
		5138
		5139	=item event model
		5140
		5141	The model used to describe how an event loop handles and processes
		5142	watchers and events.
		5143
		5144	=item pending
		5145
		5146	A watcher is pending as soon as the corresponding event has been
		5147	detected. See L<WATCHER STATES> for details.
		5148
		5149	=item real time
		5150
		5151	The physical time that is observed. It is apparently strictly monotonic :)
		5152
		5153	=item wall-clock time
		5154
		5155	The time and date as shown on clocks. Unlike real time, it can actually
		5156	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5157	clock.
		5158
		5159	=item watcher
		5160
		5161	A data structure that describes interest in certain events. Watchers need
		5162	to be started (attached to an event loop) before they can receive events.
		5163
		5164	=back
		5165
3297	=head1 AUTHOR	5166	=head1 AUTHOR
3298		5167
3299	Marc Lehmann <libev@schmorp.de>.	5168	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5169	Magnusson and Emanuele Giaquinta.
3300		5170

Diff Legend

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