ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC vs.
Revision 1.334 by root, Mon Oct 25 10:30:23 2010 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)) [NOT REENTRANT]
199		247
200	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	250	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	251	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	252	or take some potentially destructive action.
205	function.	253
		254	Since some systems (at least OpenBSD and Darwin) fail to implement
		255	correct C<realloc> semantics, libev will use a wrapper around the system
		256	C<realloc> and C<free> functions by default.
206		257
207	You could override this function in high-availability programs to, say,	258	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	259	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	260	or even to sleep a while and retry until some memory is available.
210		261
211	Example: Replace the libev allocator with one that waits a bit and then	262	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	263	retries (example requires a standards-compliant C<realloc>).
213		264
214	static void *	265	static void *
215	persistent_realloc (void *ptr, size_t size)	266	persistent_realloc (void *ptr, size_t size)
216	{	267	{
217	for (;;)	268	for (;;)
…		…
226	}	277	}
227		278
228	...	279	...
229	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
230		281
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		283
233	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
234	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
235	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
236	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
237	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
238	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
239	(such as abort).	290	(such as abort).
240		291
241	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.
…		…
250	...	301	...
251	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
252		303
253	=back	304	=back
254		305
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
256		307
257	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
258	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
259	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
260		311
261	If you use threads, a common model is to run the default event loop	312	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	313	supports child process events, and dynamically created event loops which
263	create, you also create another event loop. Libev itself does no locking	314	do not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		315
268	=over 4	316	=over 4
269		317
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		319
272	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
273	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
274	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
276		330
277	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
278	function.	332	function (or via the C<EV_DEFAULT> macro).
279		333
		334	Note that this function is I<not> thread-safe, so if you want to use it
		335	from multiple threads, you have to employ some kind of mutex (note also
		336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
		338
280	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
281	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
282	for C<SIGCHLD>. If this is a problem for your app you can either	341	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	342	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	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
285	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
286		363
287	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
289		366
290	The following flags are supported:	367	The following flags are supported:
…		…
296	The default flags value. Use this if you have no clue (it's the right	373	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	374	thing, believe me).
298		375
299	=item C<EVFLAG_NOENV>	376	=item C<EVFLAG_NOENV>
300		377
301	If this flag bit is ored into the flag value (or the program runs setuid	378	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	379	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	381	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	382	useful to try out specific backends to test their performance, or to work
306	around bugs.	383	around bugs.
307		384
308	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
309		386
310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
311	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
312	enabling this flag.
313		389
314	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	394	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	395	C<pthread_atfork> which is even faster).
320		396
321	The big advantage of this flag is that you can forget about fork (and	397	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	398	forget about forgetting to tell libev about forking) when you use this
323	flag.	399	flag.
324		400
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	402	environment variable.
		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
327		423
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		425
330	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	429	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.	430	usually the fastest backend for a low number of (low-numbered :) fds.
335		431
336	To get good performance out of this backend you need a high amount of	432	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	433	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	434	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	435	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	436	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	437	readiness notifications you get per iteration.
		438
		439	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		440	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		441	C<exceptfds> set on that platform).
342		442
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	443	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		444
345	And this is your standard poll(2) backend. It's more complicated	445	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	446	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	447	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,	448	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	449	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	450	performance tips.
351		451
		452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		454
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
353		459
354	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	461	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),	462	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	463	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	464
359	cases and rewiring a syscall per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup and
		469	so on. The biggest issue is fork races, however - if a program forks then
		470	I<both> parent and child process have to recreate the epoll set, which can
		471	take considerable time (one syscall per file descriptor) and is of course
		472	hard to detect.
		473
		474	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		475	of course I<doesn't>, and epoll just loves to report events for totally
		476	I<different> file descriptors (even already closed ones, so one cannot
		477	even remove them from the set) than registered in the set (especially
		478	on SMP systems). Libev tries to counter these spurious notifications by
		479	employing an additional generation counter and comparing that against the
		480	events to filter out spurious ones, recreating the set when required. Last
		481	not least, it also refuses to work with some file descriptors which work
		482	perfectly fine with C<select> (files, many character devices...).
361		483
362	While stopping, setting and starting an I/O watcher in the same iteration	484	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	485	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	486	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	487	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	488	file descriptors might not work very well if you register events for both
367		489	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		490
372	Best performance from this backend is achieved by not unregistering all	491	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.	492	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	493	i.e. keep at least one watcher active per fd at all times. Stopping and
		494	starting a watcher (without re-setting it) also usually doesn't cause
		495	extra overhead. A fork can both result in spurious notifications as well
		496	as in libev having to destroy and recreate the epoll object, which can
		497	take considerable time and thus should be avoided.
375		498
		499	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		500	faster than epoll for maybe up to a hundred file descriptors, depending on
		501	the usage. So sad.
		502
376	While nominally embeddeble in other event loops, this feature is broken in	503	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	504	all kernel versions tested so far.
		505
		506	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		507	C<EVBACKEND_POLL>.
378		508
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	509	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		510
381	Kqueue deserves special mention, as at the time of this writing, it	511	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	512	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	513	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"	514	it's completely useless). Unlike epoll, however, whose brokenness
		515	is by design, these kqueue bugs can (and eventually will) be fixed
		516	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	517	"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)	518	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	519	system like NetBSD.
388		520
389	You still can embed kqueue into a normal poll or select backend and use it	521	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	522	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.	523	the target platform). See C<ev_embed> watchers for more info.
392		524
393	It scales in the same way as the epoll backend, but the interface to the	525	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	526	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	527	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	528	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	529	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	530	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		531	cases
399		532
400	This backend usually performs well under most conditions.	533	This backend usually performs well under most conditions.
401		534
402	While nominally embeddable in other event loops, this doesn't work	535	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	536	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	537	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	538	(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	539	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	540	also broken on OS X)) and, did I mention it, using it only for sockets.
		541
		542	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		543	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		544	C<NOTE_EOF>.
408		545
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	546	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		547
411	This is not implemented yet (and might never be, unless you send me an	548	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	549	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	553	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		554
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	555	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)).	556	it's really slow, but it still scales very well (O(active_fds)).
420		557
421	Please note that solaris event ports can deliver a lot of spurious	558	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	559	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	560	blocking when no data (or space) is available.
424		561
425	While this backend scales well, it requires one system call per active	562	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	563	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	564	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	565	might perform better.
429		566
430	On the positive side, ignoring the spurious readyness notifications, this	567	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	568	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	569	in all tests and is fully embeddable, which is a rare feat among the
		570	OS-specific backends (I vastly prefer correctness over speed hacks).
		571
		572	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		573	C<EVBACKEND_POLL>.
433		574
434	=item C<EVBACKEND_ALL>	575	=item C<EVBACKEND_ALL>
435		576
436	Try all backends (even potentially broken ones that wouldn't be tried	577	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	578	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		580
440	It is definitely not recommended to use this flag.	581	It is definitely not recommended to use this flag.
441		582
442	=back	583	=back
443		584
444	If one or more of these are ored into the flags value, then only these	585	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	586	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.	587	here). If none are specified, all backends in C<ev_recommended_backends
447		588	()> 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		589
471	Example: Try to create a event loop that uses epoll and nothing else.	590	Example: Try to create a event loop that uses epoll and nothing else.
472		591
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	592	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	593	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	594	fatal ("no epoll found here, maybe it hides under your chair");
476		595
		596	Example: Use whatever libev has to offer, but make sure that kqueue is
		597	used if available.
		598
		599	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		600
477	=item ev_default_destroy ()	601	=item ev_loop_destroy (loop)
478		602
479	Destroys the default loop again (frees all memory and kernel state	603	Destroys an event loop object (frees all memory and kernel state
480	etc.). None of the active event watchers will be stopped in the normal	604	etc.). None of the active event watchers will be stopped in the normal
481	sense, so e.g. C<ev_is_active> might still return true. It is your	605	sense, so e.g. C<ev_is_active> might still return true. It is your
482	responsibility to either stop all watchers cleanly yoursef I<before>	606	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	607	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	608	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	609	for example).
486		610
487	Note that certain global state, such as signal state, will not be freed by	611	Note that certain global state, such as signal state (and installed signal
488	this function, and related watchers (such as signal and child watchers)	612	handlers), will not be freed by this function, and related watchers (such
489	would need to be stopped manually.	613	as signal and child watchers) would need to be stopped manually.
490		614
491	In general it is not advisable to call this function except in the	615	This function is normally used on loop objects allocated by
492	rare occasion where you really need to free e.g. the signal handling	616	C<ev_loop_new>, but it can also be used on the default loop returned by
		617	C<ev_default_loop>, in which case it is not thread-safe.
		618
		619	Note that it is not advisable to call this function on the default loop
		620	except in the rare occasion where you really need to free it's resources.
493	pipe fds. If you need dynamically allocated loops it is better to use	621	If you need dynamically allocated loops it is better to use C<ev_loop_new>
494	C<ev_loop_new> and C<ev_loop_destroy>).	622	and C<ev_loop_destroy>.
495		623
496	=item ev_loop_destroy (loop)	624	=item ev_loop_fork (loop)
497		625
498	Like C<ev_default_destroy>, but destroys an event loop created by an
499	earlier call to C<ev_loop_new>.
500
501	=item ev_default_fork ()
502
503	This function sets a flag that causes subsequent C<ev_loop> iterations	626	This function sets a flag that causes subsequent C<ev_run> iterations to
504	to reinitialise the kernel state for backends that have one. Despite the	627	reinitialise the kernel state for backends that have one. Despite the
505	name, you can call it anytime, but it makes most sense after forking, in	628	name, you can call it anytime, but it makes most sense after forking, in
506	the child process (or both child and parent, but that again makes little	629	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
507	sense). You I<must> call it in the child before using any of the libev	630	child before resuming or calling C<ev_run>.
508	functions, and it will only take effect at the next C<ev_loop> iteration.	631
		632	Again, you I<have> to call it on I<any> loop that you want to re-use after
		633	a fork, I<even if you do not plan to use the loop in the parent>. This is
		634	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		635	during fork.
509		636
510	On the other hand, you only need to call this function in the child	637	On the other hand, you only need to call this function in the child
511	process if and only if you want to use the event library in the child. If	638	process if and only if you want to use the event loop in the child. If
512	you just fork+exec, you don't have to call it at all.	639	you just fork+exec or create a new loop in the child, you don't have to
		640	call it at all (in fact, C<epoll> is so badly broken that it makes a
		641	difference, but libev will usually detect this case on its own and do a
		642	costly reset of the backend).
513		643
514	The function itself is quite fast and it's usually not a problem to call	644	The function itself is quite fast and it's usually not a problem to call
515	it just in case after a fork. To make this easy, the function will fit in	645	it just in case after a fork.
516	quite nicely into a call to C<pthread_atfork>:
517		646
		647	Example: Automate calling C<ev_loop_fork> on the default loop when
		648	using pthreads.
		649
		650	static void
		651	post_fork_child (void)
		652	{
		653	ev_loop_fork (EV_DEFAULT);
		654	}
		655
		656	...
518	pthread_atfork (0, 0, ev_default_fork);	657	pthread_atfork (0, 0, post_fork_child);
519
520	=item ev_loop_fork (loop)
521
522	Like C<ev_default_fork>, but acts on an event loop created by
523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
524	after fork, and how you do this is entirely your own problem.
525		658
526	=item int ev_is_default_loop (loop)	659	=item int ev_is_default_loop (loop)
527		660
528	Returns true when the given loop actually is the default loop, false otherwise.	661	Returns true when the given loop is, in fact, the default loop, and false
		662	otherwise.
529		663
530	=item unsigned int ev_loop_count (loop)	664	=item unsigned int ev_iteration (loop)
531		665
532	Returns the count of loop iterations for the loop, which is identical to	666	Returns the current iteration count for the event loop, which is identical
533	the number of times libev did poll for new events. It starts at C<0> and	667	to the number of times libev did poll for new events. It starts at C<0>
534	happily wraps around with enough iterations.	668	and happily wraps around with enough iterations.
535		669
536	This value can sometimes be useful as a generation counter of sorts (it	670	This value can sometimes be useful as a generation counter of sorts (it
537	"ticks" the number of loop iterations), as it roughly corresponds with	671	"ticks" the number of loop iterations), as it roughly corresponds with
538	C<ev_prepare> and C<ev_check> calls.	672	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		673	prepare and check phases.
		674
		675	=item unsigned int ev_depth (loop)
		676
		677	Returns the number of times C<ev_run> was entered minus the number of
		678	times C<ev_run> was exited, in other words, the recursion depth.
		679
		680	Outside C<ev_run>, this number is zero. In a callback, this number is
		681	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		682	in which case it is higher.
		683
		684	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		685	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		686	ungentleman-like behaviour unless it's really convenient.
539		687
540	=item unsigned int ev_backend (loop)	688	=item unsigned int ev_backend (loop)
541		689
542	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	690	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
543	use.	691	use.
…		…
548	received events and started processing them. This timestamp does not	696	received events and started processing them. This timestamp does not
549	change as long as callbacks are being processed, and this is also the base	697	change as long as callbacks are being processed, and this is also the base
550	time used for relative timers. You can treat it as the timestamp of the	698	time used for relative timers. You can treat it as the timestamp of the
551	event occurring (or more correctly, libev finding out about it).	699	event occurring (or more correctly, libev finding out about it).
552		700
		701	=item ev_now_update (loop)
		702
		703	Establishes the current time by querying the kernel, updating the time
		704	returned by C<ev_now ()> in the progress. This is a costly operation and
		705	is usually done automatically within C<ev_run ()>.
		706
		707	This function is rarely useful, but when some event callback runs for a
		708	very long time without entering the event loop, updating libev's idea of
		709	the current time is a good idea.
		710
		711	See also L<The special problem of time updates> in the C<ev_timer> section.
		712
		713	=item ev_suspend (loop)
		714
		715	=item ev_resume (loop)
		716
		717	These two functions suspend and resume an event loop, for use when the
		718	loop is not used for a while and timeouts should not be processed.
		719
		720	A typical use case would be an interactive program such as a game: When
		721	the user presses C<^Z> to suspend the game and resumes it an hour later it
		722	would be best to handle timeouts as if no time had actually passed while
		723	the program was suspended. This can be achieved by calling C<ev_suspend>
		724	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		725	C<ev_resume> directly afterwards to resume timer processing.
		726
		727	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		728	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		729	will be rescheduled (that is, they will lose any events that would have
		730	occurred while suspended).
		731
		732	After calling C<ev_suspend> you B<must not> call I<any> function on the
		733	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		734	without a previous call to C<ev_suspend>.
		735
		736	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		737	event loop time (see C<ev_now_update>).
		738
553	=item ev_loop (loop, int flags)	739	=item ev_run (loop, int flags)
554		740
555	Finally, this is it, the event handler. This function usually is called	741	Finally, this is it, the event handler. This function usually is called
556	after you initialised all your watchers and you want to start handling	742	after you have initialised all your watchers and you want to start
557	events.	743	handling events. It will ask the operating system for any new events, call
		744	the watcher callbacks, an then repeat the whole process indefinitely: This
		745	is why event loops are called I<loops>.
558		746
559	If the flags argument is specified as C<0>, it will not return until	747	If the flags argument is specified as C<0>, it will keep handling events
560	either no event watchers are active anymore or C<ev_unloop> was called.	748	until either no event watchers are active anymore or C<ev_break> was
		749	called.
561		750
562	Please note that an explicit C<ev_unloop> is usually better than	751	Please note that an explicit C<ev_break> is usually better than
563	relying on all watchers to be stopped when deciding when a program has	752	relying on all watchers to be stopped when deciding when a program has
564	finished (especially in interactive programs), but having a program that	753	finished (especially in interactive programs), but having a program
565	automatically loops as long as it has to and no longer by virtue of	754	that automatically loops as long as it has to and no longer by virtue
566	relying on its watchers stopping correctly is a thing of beauty.	755	of relying on its watchers stopping correctly, that is truly a thing of
		756	beauty.
567		757
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	758	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	759	those events and any already outstanding ones, but will not wait and
570	case there are no events and will return after one iteration of the loop.	760	block your process in case there are no events and will return after one
		761	iteration of the loop. This is sometimes useful to poll and handle new
		762	events while doing lengthy calculations, to keep the program responsive.
571		763
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	764	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	765	necessary) and will handle those and any already outstanding ones. It
574	your process until at least one new event arrives, and will return after	766	will block your process until at least one new event arrives (which could
575	one iteration of the loop. This is useful if you are waiting for some	767	be an event internal to libev itself, so there is no guarantee that a
576	external event in conjunction with something not expressible using other	768	user-registered callback will be called), and will return after one
		769	iteration of the loop.
		770
		771	This is useful if you are waiting for some external event in conjunction
		772	with something not expressible using other libev watchers (i.e. "roll your
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	773	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	774	usually a better approach for this kind of thing.
579		775
580	Here are the gory details of what C<ev_loop> does:	776	Here are the gory details of what C<ev_run> does:
581		777
		778	- Increment loop depth.
		779	- Reset the ev_break status.
582	- Before the first iteration, call any pending watchers.	780	- Before the first iteration, call any pending watchers.
		781	LOOP:
583	* If EVFLAG_FORKCHECK was used, check for a fork.	782	- If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	783	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	784	- Queue and call all prepare watchers.
		785	- If ev_break was called, goto FINISH.
586	- If we have been forked, recreate the kernel state.	786	- If we have been forked, detach and recreate the kernel state
		787	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	788	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	789	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	790	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	791	(active idle watchers, EVRUN_NOWAIT or not having
591	any active watchers at all will result in not sleeping).	792	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	793	- Sleep if the I/O and timer collect interval say so.
		794	- Increment loop iteration counter.
593	- Block the process, waiting for any events.	795	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	796	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	797	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	798	- Queue all expired timers.
597	- Queue all outstanding periodics.	799	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	800	- Queue all idle watchers with priority higher than that of pending events.
599	- Queue all check watchers.	801	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	802	- Call all queued watchers in reverse order (i.e. check watchers first).
601	Signals and child watchers are implemented as I/O watchers, and will	803	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	804	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	805	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
604	were used, or there are no active watchers, return, otherwise	806	were used, or there are no active watchers, goto FINISH, otherwise
605	continue with step *.	807	continue with step LOOP.
		808	FINISH:
		809	- Reset the ev_break status iff it was EVBREAK_ONE.
		810	- Decrement the loop depth.
		811	- Return.
606		812
607	Example: Queue some jobs and then loop until no events are outstanding	813	Example: Queue some jobs and then loop until no events are outstanding
608	anymore.	814	anymore.
609		815
610	... queue jobs here, make sure they register event watchers as long	816	... queue jobs here, make sure they register event watchers as long
611	... as they still have work to do (even an idle watcher will do..)	817	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	818	ev_run (my_loop, 0);
613	... jobs done. yeah!	819	... jobs done or somebody called unloop. yeah!
614		820
615	=item ev_unloop (loop, how)	821	=item ev_break (loop, how)
616		822
617	Can be used to make a call to C<ev_loop> return early (but only after it	823	Can be used to make a call to C<ev_run> return early (but only after it
618	has processed all outstanding events). The C<how> argument must be either	824	has processed all outstanding events). The C<how> argument must be either
619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	825	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	826	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
621		827
622	This "unloop state" will be cleared when entering C<ev_loop> again.	828	This "unloop state" will be cleared when entering C<ev_run> again.
		829
		830	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
623		831
624	=item ev_ref (loop)	832	=item ev_ref (loop)
625		833
626	=item ev_unref (loop)	834	=item ev_unref (loop)
627		835
628	Ref/unref can be used to add or remove a reference count on the event	836	Ref/unref can be used to add or remove a reference count on the event
629	loop: Every watcher keeps one reference, and as long as the reference	837	loop: Every watcher keeps one reference, and as long as the reference
630	count is nonzero, C<ev_loop> will not return on its own. If you have	838	count is nonzero, C<ev_run> will not return on its own.
631	a watcher you never unregister that should not keep C<ev_loop> from	839
632	returning, ev_unref() after starting, and ev_ref() before stopping it. For	840	This is useful when you have a watcher that you never intend to
		841	unregister, but that nevertheless should not keep C<ev_run> from
		842	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		843	before stopping it.
		844
633	example, libev itself uses this for its internal signal pipe: It is not	845	As an example, libev itself uses this for its internal signal pipe: It
634	visible to the libev user and should not keep C<ev_loop> from exiting if	846	is not visible to the libev user and should not keep C<ev_run> from
635	no event watchers registered by it are active. It is also an excellent	847	exiting if no event watchers registered by it are active. It is also an
636	way to do this for generic recurring timers or from within third-party	848	excellent way to do this for generic recurring timers or from within
637	libraries. Just remember to I<unref after start> and I<ref before stop>	849	third-party libraries. Just remember to I<unref after start> and I<ref
638	(but only if the watcher wasn't active before, or was active before,	850	before stop> (but only if the watcher wasn't active before, or was active
639	respectively).	851	before, respectively. Note also that libev might stop watchers itself
		852	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		853	in the callback).
640		854
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	855	Example: Create a signal watcher, but keep it from keeping C<ev_run>
642	running when nothing else is active.	856	running when nothing else is active.
643		857
644	struct ev_signal exitsig;	858	ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	859	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	860	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	861	evf_unref (loop);
648		862
649	Example: For some weird reason, unregister the above signal handler again.	863	Example: For some weird reason, unregister the above signal handler again.
650		864
651	ev_ref (loop);	865	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	866	ev_signal_stop (loop, &exitsig);
653		867
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	868	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		869
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	870	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		871
658	These advanced functions influence the time that libev will spend waiting	872	These advanced functions influence the time that libev will spend waiting
659	for events. Both are by default C<0>, meaning that libev will try to	873	for events. Both time intervals are by default C<0>, meaning that libev
660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	874	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		875	latency.
661		876
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	877	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
663	allows libev to delay invocation of I/O and timer/periodic callbacks to	878	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	879	to increase efficiency of loop iterations (or to increase power-saving
		880	opportunities).
665		881
666	The background is that sometimes your program runs just fast enough to	882	The idea is that sometimes your program runs just fast enough to handle
667	handle one (or very few) event(s) per loop iteration. While this makes	883	one (or very few) event(s) per loop iteration. While this makes the
668	the program responsive, it also wastes a lot of CPU time to poll for new	884	program responsive, it also wastes a lot of CPU time to poll for new
669	events, especially with backends like C<select ()> which have a high	885	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	886	overhead for the actual polling but can deliver many events at once.
671		887
672	By setting a higher I<io collect interval> you allow libev to spend more	888	By setting a higher I<io collect interval> you allow libev to spend more
673	time collecting I/O events, so you can handle more events per iteration,	889	time collecting I/O events, so you can handle more events per iteration,
674	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	890	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
675	C<ev_timer>) will be not affected. Setting this to a non-null value will	891	C<ev_timer>) will be not affected. Setting this to a non-null value will
676	introduce an additional C<ev_sleep ()> call into most loop iterations.	892	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		893	sleep time ensures that libev will not poll for I/O events more often then
		894	once per this interval, on average.
677		895
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	896	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	897	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	898	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	899	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	900	value will not introduce any overhead in libev.
683		901
684	Many (busy) programs can usually benefit by setting the io collect	902	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	903	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	904	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	905	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	906	as this approaches the timing granularity of most systems. Note that if
		907	you do transactions with the outside world and you can't increase the
		908	parallelity, then this setting will limit your transaction rate (if you
		909	need to poll once per transaction and the I/O collect interval is 0.01,
		910	then you can't do more than 100 transactions per second).
		911
		912	Setting the I<timeout collect interval> can improve the opportunity for
		913	saving power, as the program will "bundle" timer callback invocations that
		914	are "near" in time together, by delaying some, thus reducing the number of
		915	times the process sleeps and wakes up again. Another useful technique to
		916	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		917	they fire on, say, one-second boundaries only.
		918
		919	Example: we only need 0.1s timeout granularity, and we wish not to poll
		920	more often than 100 times per second:
		921
		922	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		923	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		924
		925	=item ev_invoke_pending (loop)
		926
		927	This call will simply invoke all pending watchers while resetting their
		928	pending state. Normally, C<ev_run> does this automatically when required,
		929	but when overriding the invoke callback this call comes handy. This
		930	function can be invoked from a watcher - this can be useful for example
		931	when you want to do some lengthy calculation and want to pass further
		932	event handling to another thread (you still have to make sure only one
		933	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		934
		935	=item int ev_pending_count (loop)
		936
		937	Returns the number of pending watchers - zero indicates that no watchers
		938	are pending.
		939
		940	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		941
		942	This overrides the invoke pending functionality of the loop: Instead of
		943	invoking all pending watchers when there are any, C<ev_run> will call
		944	this callback instead. This is useful, for example, when you want to
		945	invoke the actual watchers inside another context (another thread etc.).
		946
		947	If you want to reset the callback, use C<ev_invoke_pending> as new
		948	callback.
		949
		950	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		951
		952	Sometimes you want to share the same loop between multiple threads. This
		953	can be done relatively simply by putting mutex_lock/unlock calls around
		954	each call to a libev function.
		955
		956	However, C<ev_run> can run an indefinite time, so it is not feasible
		957	to wait for it to return. One way around this is to wake up the event
		958	loop via C<ev_break> and C<av_async_send>, another way is to set these
		959	I<release> and I<acquire> callbacks on the loop.
		960
		961	When set, then C<release> will be called just before the thread is
		962	suspended waiting for new events, and C<acquire> is called just
		963	afterwards.
		964
		965	Ideally, C<release> will just call your mutex_unlock function, and
		966	C<acquire> will just call the mutex_lock function again.
		967
		968	While event loop modifications are allowed between invocations of
		969	C<release> and C<acquire> (that's their only purpose after all), no
		970	modifications done will affect the event loop, i.e. adding watchers will
		971	have no effect on the set of file descriptors being watched, or the time
		972	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		973	to take note of any changes you made.
		974
		975	In theory, threads executing C<ev_run> will be async-cancel safe between
		976	invocations of C<release> and C<acquire>.
		977
		978	See also the locking example in the C<THREADS> section later in this
		979	document.
		980
		981	=item ev_set_userdata (loop, void *data)
		982
		983	=item ev_userdata (loop)
		984
		985	Set and retrieve a single C<void *> associated with a loop. When
		986	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		987	C<0.>
		988
		989	These two functions can be used to associate arbitrary data with a loop,
		990	and are intended solely for the C<invoke_pending_cb>, C<release> and
		991	C<acquire> callbacks described above, but of course can be (ab-)used for
		992	any other purpose as well.
		993
		994	=item ev_verify (loop)
		995
		996	This function only does something when C<EV_VERIFY> support has been
		997	compiled in, which is the default for non-minimal builds. It tries to go
		998	through all internal structures and checks them for validity. If anything
		999	is found to be inconsistent, it will print an error message to standard
		1000	error and call C<abort ()>.
		1001
		1002	This can be used to catch bugs inside libev itself: under normal
		1003	circumstances, this function will never abort as of course libev keeps its
		1004	data structures consistent.
689		1005
690	=back	1006	=back
691		1007
692		1008
693	=head1 ANATOMY OF A WATCHER	1009	=head1 ANATOMY OF A WATCHER
694		1010
		1011	In the following description, uppercase C<TYPE> in names stands for the
		1012	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1013	watchers and C<ev_io_start> for I/O watchers.
		1014
695	A watcher is a structure that you create and register to record your	1015	A watcher is an opaque structure that you allocate and register to record
696	interest in some event. For instance, if you want to wait for STDIN to	1016	your interest in some event. To make a concrete example, imagine you want
697	become readable, you would create an C<ev_io> watcher for that:	1017	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1018	for that:
698		1019
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1020	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
700	{	1021	{
701	ev_io_stop (w);	1022	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	1023	ev_break (loop, EVBREAK_ALL);
703	}	1024	}
704		1025
705	struct ev_loop *loop = ev_default_loop (0);	1026	struct ev_loop *loop = ev_default_loop (0);
		1027
706	struct ev_io stdin_watcher;	1028	ev_io stdin_watcher;
		1029
707	ev_init (&stdin_watcher, my_cb);	1030	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1031	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	1032	ev_io_start (loop, &stdin_watcher);
		1033
710	ev_loop (loop, 0);	1034	ev_run (loop, 0);
711		1035
712	As you can see, you are responsible for allocating the memory for your	1036	As you can see, you are responsible for allocating the memory for your
713	watcher structures (and it is usually a bad idea to do this on the stack,	1037	watcher structures (and it is I<usually> a bad idea to do this on the
714	although this can sometimes be quite valid).	1038	stack).
715		1039
		1040	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1041	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1042
716	Each watcher structure must be initialised by a call to C<ev_init	1043	Each watcher structure must be initialised by a call to C<ev_init (watcher
717	(watcher *, callback)>, which expects a callback to be provided. This	1044	*, callback)>, which expects a callback to be provided. This callback is
718	callback gets invoked each time the event occurs (or, in the case of io	1045	invoked each time the event occurs (or, in the case of I/O watchers, each
719	watchers, each time the event loop detects that the file descriptor given	1046	time the event loop detects that the file descriptor given is readable
720	is readable and/or writable).	1047	and/or writable).
721		1048
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1049	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
723	with arguments specific to this watcher type. There is also a macro	1050	macro to configure it, with arguments specific to the watcher type. There
724	to combine initialisation and setting in one call: C<< ev_<type>_init	1051	is also a macro to combine initialisation and setting in one call: C<<
725	(watcher *, callback, ...) >>.	1052	ev_TYPE_init (watcher *, callback, ...) >>.
726		1053
727	To make the watcher actually watch out for events, you have to start it	1054	To make the watcher actually watch out for events, you have to start it
728	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1055	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
729	*) >>), and you can stop watching for events at any time by calling the	1056	*) >>), and you can stop watching for events at any time by calling the
730	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1057	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
731		1058
732	As long as your watcher is active (has been started but not stopped) you	1059	As long as your watcher is active (has been started but not stopped) you
733	must not touch the values stored in it. Most specifically you must never	1060	must not touch the values stored in it. Most specifically you must never
734	reinitialise it or call its C<set> macro.	1061	reinitialise it or call its C<ev_TYPE_set> macro.
735		1062
736	Each and every callback receives the event loop pointer as first, the	1063	Each and every callback receives the event loop pointer as first, the
737	registered watcher structure as second, and a bitset of received events as	1064	registered watcher structure as second, and a bitset of received events as
738	third argument.	1065	third argument.
739		1066
…		…
748	=item C<EV_WRITE>	1075	=item C<EV_WRITE>
749		1076
750	The file descriptor in the C<ev_io> watcher has become readable and/or	1077	The file descriptor in the C<ev_io> watcher has become readable and/or
751	writable.	1078	writable.
752		1079
753	=item C<EV_TIMEOUT>	1080	=item C<EV_TIMER>
754		1081
755	The C<ev_timer> watcher has timed out.	1082	The C<ev_timer> watcher has timed out.
756		1083
757	=item C<EV_PERIODIC>	1084	=item C<EV_PERIODIC>
758		1085
…		…
776		1103
777	=item C<EV_PREPARE>	1104	=item C<EV_PREPARE>
778		1105
779	=item C<EV_CHECK>	1106	=item C<EV_CHECK>
780		1107
781	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1108	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
782	to gather new events, and all C<ev_check> watchers are invoked just after	1109	to gather new events, and all C<ev_check> watchers are invoked just after
783	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1110	C<ev_run> has gathered them, but before it invokes any callbacks for any
784	received events. Callbacks of both watcher types can start and stop as	1111	received events. Callbacks of both watcher types can start and stop as
785	many watchers as they want, and all of them will be taken into account	1112	many watchers as they want, and all of them will be taken into account
786	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1113	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
787	C<ev_loop> from blocking).	1114	C<ev_run> from blocking).
788		1115
789	=item C<EV_EMBED>	1116	=item C<EV_EMBED>
790		1117
791	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1118	The embedded event loop specified in the C<ev_embed> watcher needs attention.
792		1119
793	=item C<EV_FORK>	1120	=item C<EV_FORK>
794		1121
795	The event loop has been resumed in the child process after fork (see	1122	The event loop has been resumed in the child process after fork (see
796	C<ev_fork>).	1123	C<ev_fork>).
797		1124
		1125	=item C<EV_CLEANUP>
		1126
		1127	The event loop is about to be destroyed (see C<ev_cleanup>).
		1128
798	=item C<EV_ASYNC>	1129	=item C<EV_ASYNC>
799		1130
800	The given async watcher has been asynchronously notified (see C<ev_async>).	1131	The given async watcher has been asynchronously notified (see C<ev_async>).
801		1132
		1133	=item C<EV_CUSTOM>
		1134
		1135	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1136	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1137
802	=item C<EV_ERROR>	1138	=item C<EV_ERROR>
803		1139
804	An unspecified error has occured, the watcher has been stopped. This might	1140	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	1141	happen because the watcher could not be properly started because libev
806	ran out of memory, a file descriptor was found to be closed or any other	1142	ran out of memory, a file descriptor was found to be closed or any other
		1143	problem. Libev considers these application bugs.
		1144
807	problem. You best act on it by reporting the problem and somehow coping	1145	You best act on it by reporting the problem and somehow coping with the
808	with the watcher being stopped.	1146	watcher being stopped. Note that well-written programs should not receive
		1147	an error ever, so when your watcher receives it, this usually indicates a
		1148	bug in your program.
809		1149
810	Libev will usually signal a few "dummy" events together with an error,	1150	Libev will usually signal a few "dummy" events together with an error, for
811	for example it might indicate that a fd is readable or writable, and if	1151	example it might indicate that a fd is readable or writable, and if your
812	your callbacks is well-written it can just attempt the operation and cope	1152	callbacks is well-written it can just attempt the operation and cope with
813	with the error from read() or write(). This will not work in multithreaded	1153	the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	1154	programs, though, as the fd could already be closed and reused for another
		1155	thing, so beware.
815		1156
816	=back	1157	=back
817		1158
		1159	=head2 WATCHER STATES
		1160
		1161	There are various watcher states mentioned throughout this manual -
		1162	active, pending and so on. In this section these states and the rules to
		1163	transition between them will be described in more detail - and while these
		1164	rules might look complicated, they usually do "the right thing".
		1165
		1166	=over 4
		1167
		1168	=item initialiased
		1169
		1170	Before a watcher can be registered with the event looop it has to be
		1171	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1172	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1173
		1174	In this state it is simply some block of memory that is suitable for use
		1175	in an event loop. It can be moved around, freed, reused etc. at will.
		1176
		1177	=item started/running/active
		1178
		1179	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1180	property of the event loop, and is actively waiting for events. While in
		1181	this state it cannot be accessed (except in a few documented ways), moved,
		1182	freed or anything else - the only legal thing is to keep a pointer to it,
		1183	and call libev functions on it that are documented to work on active watchers.
		1184
		1185	=item pending
		1186
		1187	If a watcher is active and libev determines that an event it is interested
		1188	in has occurred (such as a timer expiring), it will become pending. It will
		1189	stay in this pending state until either it is stopped or its callback is
		1190	about to be invoked, so it is not normally pending inside the watcher
		1191	callback.
		1192
		1193	The watcher might or might not be active while it is pending (for example,
		1194	an expired non-repeating timer can be pending but no longer active). If it
		1195	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1196	but it is still property of the event loop at this time, so cannot be
		1197	moved, freed or reused. And if it is active the rules described in the
		1198	previous item still apply.
		1199
		1200	It is also possible to feed an event on a watcher that is not active (e.g.
		1201	via C<ev_feed_event>), in which case it becomes pending without being
		1202	active.
		1203
		1204	=item stopped
		1205
		1206	A watcher can be stopped implicitly by libev (in which case it might still
		1207	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1208	latter will clear any pending state the watcher might be in, regardless
		1209	of whether it was active or not, so stopping a watcher explicitly before
		1210	freeing it is often a good idea.
		1211
		1212	While stopped (and not pending) the watcher is essentially in the
		1213	initialised state, that is it can be reused, moved, modified in any way
		1214	you wish.
		1215
		1216	=back
		1217
818	=head2 GENERIC WATCHER FUNCTIONS	1218	=head2 GENERIC WATCHER FUNCTIONS
819
820	In the following description, C<TYPE> stands for the watcher type,
821	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
822		1219
823	=over 4	1220	=over 4
824		1221
825	=item C<ev_init> (ev_TYPE *watcher, callback)	1222	=item C<ev_init> (ev_TYPE *watcher, callback)
826		1223
…		…
832	which rolls both calls into one.	1229	which rolls both calls into one.
833		1230
834	You can reinitialise a watcher at any time as long as it has been stopped	1231	You can reinitialise a watcher at any time as long as it has been stopped
835	(or never started) and there are no pending events outstanding.	1232	(or never started) and there are no pending events outstanding.
836		1233
837	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1234	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
838	int revents)>.	1235	int revents)>.
839		1236
		1237	Example: Initialise an C<ev_io> watcher in two steps.
		1238
		1239	ev_io w;
		1240	ev_init (&w, my_cb);
		1241	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1242
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1243	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
841		1244
842	This macro initialises the type-specific parts of a watcher. You need to	1245	This macro initialises the type-specific parts of a watcher. You need to
843	call C<ev_init> at least once before you call this macro, but you can	1246	call C<ev_init> at least once before you call this macro, but you can
844	call C<ev_TYPE_set> any number of times. You must not, however, call this	1247	call C<ev_TYPE_set> any number of times. You must not, however, call this
845	macro on a watcher that is active (it can be pending, however, which is a	1248	macro on a watcher that is active (it can be pending, however, which is a
846	difference to the C<ev_init> macro).	1249	difference to the C<ev_init> macro).
847		1250
848	Although some watcher types do not have type-specific arguments	1251	Although some watcher types do not have type-specific arguments
849	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1252	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		1253
		1254	See C<ev_init>, above, for an example.
		1255
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1256	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		1257
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1258	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	1259	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	1260	a watcher. The same limitations apply, of course.
856		1261
		1262	Example: Initialise and set an C<ev_io> watcher in one step.
		1263
		1264	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1265
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1266	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
858		1267
859	Starts (activates) the given watcher. Only active watchers will receive	1268	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	1269	events. If the watcher is already active nothing will happen.
861		1270
		1271	Example: Start the C<ev_io> watcher that is being abused as example in this
		1272	whole section.
		1273
		1274	ev_io_start (EV_DEFAULT_UC, &w);
		1275
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1276	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
863		1277
864	Stops the given watcher again (if active) and clears the pending	1278	Stops the given watcher if active, and clears the pending status (whether
		1279	the watcher was active or not).
		1280
865	status. It is possible that stopped watchers are pending (for example,	1281	It is possible that stopped watchers are pending - for example,
866	non-repeating timers are being stopped when they become pending), but	1282	non-repeating timers are being stopped when they become pending - but
867	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1283	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
868	you want to free or reuse the memory used by the watcher it is therefore a	1284	pending. If you want to free or reuse the memory used by the watcher it is
869	good idea to always call its C<ev_TYPE_stop> function.	1285	therefore a good idea to always call its C<ev_TYPE_stop> function.
870		1286
871	=item bool ev_is_active (ev_TYPE *watcher)	1287	=item bool ev_is_active (ev_TYPE *watcher)
872		1288
873	Returns a true value iff the watcher is active (i.e. it has been started	1289	Returns a true value iff the watcher is active (i.e. it has been started
874	and not yet been stopped). As long as a watcher is active you must not modify	1290	and not yet been stopped). As long as a watcher is active you must not modify
…		…
890	=item ev_cb_set (ev_TYPE *watcher, callback)	1306	=item ev_cb_set (ev_TYPE *watcher, callback)
891		1307
892	Change the callback. You can change the callback at virtually any time	1308	Change the callback. You can change the callback at virtually any time
893	(modulo threads).	1309	(modulo threads).
894		1310
895	=item ev_set_priority (ev_TYPE *watcher, priority)	1311	=item ev_set_priority (ev_TYPE *watcher, int priority)
896		1312
897	=item int ev_priority (ev_TYPE *watcher)	1313	=item int ev_priority (ev_TYPE *watcher)
898		1314
899	Set and query the priority of the watcher. The priority is a small	1315	Set and query the priority of the watcher. The priority is a small
900	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1316	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
901	(default: C<-2>). Pending watchers with higher priority will be invoked	1317	(default: C<-2>). Pending watchers with higher priority will be invoked
902	before watchers with lower priority, but priority will not keep watchers	1318	before watchers with lower priority, but priority will not keep watchers
903	from being executed (except for C<ev_idle> watchers).	1319	from being executed (except for C<ev_idle> watchers).
904		1320
905	This means that priorities are I<only> used for ordering callback
906	invocation after new events have been received. This is useful, for
907	example, to reduce latency after idling, or more often, to bind two
908	watchers on the same event and make sure one is called first.
909
910	If you need to suppress invocation when higher priority events are pending	1321	If you need to suppress invocation when higher priority events are pending
911	you need to look at C<ev_idle> watchers, which provide this functionality.	1322	you need to look at C<ev_idle> watchers, which provide this functionality.
912		1323
913	You I<must not> change the priority of a watcher as long as it is active or	1324	You I<must not> change the priority of a watcher as long as it is active or
914	pending.	1325	pending.
915		1326
		1327	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1328	fine, as long as you do not mind that the priority value you query might
		1329	or might not have been clamped to the valid range.
		1330
916	The default priority used by watchers when no priority has been set is	1331	The default priority used by watchers when no priority has been set is
917	always C<0>, which is supposed to not be too high and not be too low :).	1332	always C<0>, which is supposed to not be too high and not be too low :).
918		1333
919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1334	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
920	fine, as long as you do not mind that the priority value you query might	1335	priorities.
921	or might not have been adjusted to be within valid range.
922		1336
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1337	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1338
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1339	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
926	C<loop> nor C<revents> need to be valid as long as the watcher callback	1340	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1341	can deal with that fact, as both are simply passed through to the
		1342	callback.
928		1343
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1344	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1345
931	If the watcher is pending, this function returns clears its pending status	1346	If the watcher is pending, this function clears its pending status and
932	and returns its C<revents> bitset (as if its callback was invoked). If the	1347	returns its C<revents> bitset (as if its callback was invoked). If the
933	watcher isn't pending it does nothing and returns C<0>.	1348	watcher isn't pending it does nothing and returns C<0>.
934		1349
		1350	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1351	callback to be invoked, which can be accomplished with this function.
		1352
		1353	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1354
		1355	Feeds the given event set into the event loop, as if the specified event
		1356	had happened for the specified watcher (which must be a pointer to an
		1357	initialised but not necessarily started event watcher). Obviously you must
		1358	not free the watcher as long as it has pending events.
		1359
		1360	Stopping the watcher, letting libev invoke it, or calling
		1361	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1362	not started in the first place.
		1363
		1364	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1365	functions that do not need a watcher.
		1366
935	=back	1367	=back
936		1368
937		1369
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1371
940	Each watcher has, by default, a member C<void *data> that you can change	1372	Each watcher has, by default, a member C<void *data> that you can change
941	and read at any time, libev will completely ignore it. This can be used	1373	and read at any time: libev will completely ignore it. This can be used
942	to associate arbitrary data with your watcher. If you need more data and	1374	to associate arbitrary data with your watcher. If you need more data and
943	don't want to allocate memory and store a pointer to it in that data	1375	don't want to allocate memory and store a pointer to it in that data
944	member, you can also "subclass" the watcher type and provide your own	1376	member, you can also "subclass" the watcher type and provide your own
945	data:	1377	data:
946		1378
947	struct my_io	1379	struct my_io
948	{	1380	{
949	struct ev_io io;	1381	ev_io io;
950	int otherfd;	1382	int otherfd;
951	void *somedata;	1383	void *somedata;
952	struct whatever *mostinteresting;	1384	struct whatever *mostinteresting;
953	}	1385	};
		1386
		1387	...
		1388	struct my_io w;
		1389	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1390
955	And since your callback will be called with a pointer to the watcher, you	1391	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1392	can cast it back to your own type:
957		1393
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1394	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
959	{	1395	{
960	struct my_io *w = (struct my_io *)w_;	1396	struct my_io *w = (struct my_io *)w_;
961	...	1397	...
962	}	1398	}
963		1399
964	More interesting and less C-conformant ways of casting your callback type	1400	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1401	instead have been omitted.
966		1402
967	Another common scenario is having some data structure with multiple	1403	Another common scenario is to use some data structure with multiple
968	watchers:	1404	embedded watchers:
969		1405
970	struct my_biggy	1406	struct my_biggy
971	{	1407	{
972	int some_data;	1408	int some_data;
973	ev_timer t1;	1409	ev_timer t1;
974	ev_timer t2;	1410	ev_timer t2;
975	}	1411	}
976		1412
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1413	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1414	complicated: Either you store the address of your C<my_biggy> struct
		1415	in the C<data> member of the watcher (for woozies), or you need to use
		1416	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1417	programmers):
979		1418
980	#include <stddef.h>	1419	#include <stddef.h>
981		1420
982	static void	1421	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1422	t1_cb (EV_P_ ev_timer *w, int revents)
984	{	1423	{
985	struct my_biggy big = (struct my_biggy *	1424	struct my_biggy big = (struct my_biggy *)
986	(((char *)w) - offsetof (struct my_biggy, t1));	1425	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1426	}
988		1427
989	static void	1428	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1429	t2_cb (EV_P_ ev_timer *w, int revents)
991	{	1430	{
992	struct my_biggy big = (struct my_biggy *	1431	struct my_biggy big = (struct my_biggy *)
993	(((char *)w) - offsetof (struct my_biggy, t2));	1432	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1433	}
		1434
		1435	=head2 WATCHER PRIORITY MODELS
		1436
		1437	Many event loops support I<watcher priorities>, which are usually small
		1438	integers that influence the ordering of event callback invocation
		1439	between watchers in some way, all else being equal.
		1440
		1441	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1442	description for the more technical details such as the actual priority
		1443	range.
		1444
		1445	There are two common ways how these these priorities are being interpreted
		1446	by event loops:
		1447
		1448	In the more common lock-out model, higher priorities "lock out" invocation
		1449	of lower priority watchers, which means as long as higher priority
		1450	watchers receive events, lower priority watchers are not being invoked.
		1451
		1452	The less common only-for-ordering model uses priorities solely to order
		1453	callback invocation within a single event loop iteration: Higher priority
		1454	watchers are invoked before lower priority ones, but they all get invoked
		1455	before polling for new events.
		1456
		1457	Libev uses the second (only-for-ordering) model for all its watchers
		1458	except for idle watchers (which use the lock-out model).
		1459
		1460	The rationale behind this is that implementing the lock-out model for
		1461	watchers is not well supported by most kernel interfaces, and most event
		1462	libraries will just poll for the same events again and again as long as
		1463	their callbacks have not been executed, which is very inefficient in the
		1464	common case of one high-priority watcher locking out a mass of lower
		1465	priority ones.
		1466
		1467	Static (ordering) priorities are most useful when you have two or more
		1468	watchers handling the same resource: a typical usage example is having an
		1469	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1470	timeouts. Under load, data might be received while the program handles
		1471	other jobs, but since timers normally get invoked first, the timeout
		1472	handler will be executed before checking for data. In that case, giving
		1473	the timer a lower priority than the I/O watcher ensures that I/O will be
		1474	handled first even under adverse conditions (which is usually, but not
		1475	always, what you want).
		1476
		1477	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1478	will only be executed when no same or higher priority watchers have
		1479	received events, they can be used to implement the "lock-out" model when
		1480	required.
		1481
		1482	For example, to emulate how many other event libraries handle priorities,
		1483	you can associate an C<ev_idle> watcher to each such watcher, and in
		1484	the normal watcher callback, you just start the idle watcher. The real
		1485	processing is done in the idle watcher callback. This causes libev to
		1486	continuously poll and process kernel event data for the watcher, but when
		1487	the lock-out case is known to be rare (which in turn is rare :), this is
		1488	workable.
		1489
		1490	Usually, however, the lock-out model implemented that way will perform
		1491	miserably under the type of load it was designed to handle. In that case,
		1492	it might be preferable to stop the real watcher before starting the
		1493	idle watcher, so the kernel will not have to process the event in case
		1494	the actual processing will be delayed for considerable time.
		1495
		1496	Here is an example of an I/O watcher that should run at a strictly lower
		1497	priority than the default, and which should only process data when no
		1498	other events are pending:
		1499
		1500	ev_idle idle; // actual processing watcher
		1501	ev_io io; // actual event watcher
		1502
		1503	static void
		1504	io_cb (EV_P_ ev_io *w, int revents)
		1505	{
		1506	// stop the I/O watcher, we received the event, but
		1507	// are not yet ready to handle it.
		1508	ev_io_stop (EV_A_ w);
		1509
		1510	// start the idle watcher to handle the actual event.
		1511	// it will not be executed as long as other watchers
		1512	// with the default priority are receiving events.
		1513	ev_idle_start (EV_A_ &idle);
		1514	}
		1515
		1516	static void
		1517	idle_cb (EV_P_ ev_idle *w, int revents)
		1518	{
		1519	// actual processing
		1520	read (STDIN_FILENO, ...);
		1521
		1522	// have to start the I/O watcher again, as
		1523	// we have handled the event
		1524	ev_io_start (EV_P_ &io);
		1525	}
		1526
		1527	// initialisation
		1528	ev_idle_init (&idle, idle_cb);
		1529	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1530	ev_io_start (EV_DEFAULT_ &io);
		1531
		1532	In the "real" world, it might also be beneficial to start a timer, so that
		1533	low-priority connections can not be locked out forever under load. This
		1534	enables your program to keep a lower latency for important connections
		1535	during short periods of high load, while not completely locking out less
		1536	important ones.
995		1537
996		1538
997	=head1 WATCHER TYPES	1539	=head1 WATCHER TYPES
998		1540
999	This section describes each watcher in detail, but will not repeat	1541	This section describes each watcher in detail, but will not repeat
…		…
1023	In general you can register as many read and/or write event watchers per	1565	In general you can register as many read and/or write event watchers per
1024	fd as you want (as long as you don't confuse yourself). Setting all file	1566	fd as you want (as long as you don't confuse yourself). Setting all file
1025	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1568	required if you know what you are doing).
1027		1569
1028	If you must do this, then force the use of a known-to-be-good backend	1570	If you cannot use non-blocking mode, then force the use of a
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1571	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1573	descriptors for which non-blocking operation makes no sense (such as
		1574	files) - libev doesn't guarantee any specific behaviour in that case.
1031		1575
1032	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is your callback might
1034	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1035	because there is no data. Not only are some backends known to create a	1579	because there is no data. Not only are some backends known to create a
1036	lot of those (for example solaris ports), it is very easy to get into	1580	lot of those (for example Solaris ports), it is very easy to get into
1037	this situation even with a relatively standard program structure. Thus	1581	this situation even with a relatively standard program structure. Thus
1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1582	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1584
1041	If you cannot run the fd in non-blocking mode (for example you should not	1585	If you cannot run the fd in non-blocking mode (for example you should
1042	play around with an Xlib connection), then you have to seperately re-test	1586	not play around with an Xlib connection), then you have to separately
1043	whether a file descriptor is really ready with a known-to-be good interface	1587	re-test whether a file descriptor is really ready with a known-to-be good
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1588	interface such as poll (fortunately in our Xlib example, Xlib already
1045	its own, so its quite safe to use).	1589	does this on its own, so its quite safe to use). Some people additionally
		1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1591	indefinitely.
		1592
		1593	But really, best use non-blocking mode.
1046		1594
1047	=head3 The special problem of disappearing file descriptors	1595	=head3 The special problem of disappearing file descriptors
1048		1596
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1597	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1050	descriptor (either by calling C<close> explicitly or by any other means,	1598	descriptor (either due to calling C<close> explicitly or any other means,
1051	such as C<dup>). The reason is that you register interest in some file	1599	such as C<dup2>). The reason is that you register interest in some file
1052	descriptor, but when it goes away, the operating system will silently drop	1600	descriptor, but when it goes away, the operating system will silently drop
1053	this interest. If another file descriptor with the same number then is	1601	this interest. If another file descriptor with the same number then is
1054	registered with libev, there is no efficient way to see that this is, in	1602	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1603	fact, a different file descriptor.
1056		1604
…		…
1085	To support fork in your programs, you either have to call	1633	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1634	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1635	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1636	C<EVBACKEND_POLL>.
1089		1637
		1638	=head3 The special problem of SIGPIPE
		1639
		1640	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1641	when writing to a pipe whose other end has been closed, your program gets
		1642	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1643	this is sensible behaviour, for daemons, this is usually undesirable.
		1644
		1645	So when you encounter spurious, unexplained daemon exits, make sure you
		1646	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1647	somewhere, as that would have given you a big clue).
		1648
		1649	=head3 The special problem of accept()ing when you can't
		1650
		1651	Many implementations of the POSIX C<accept> function (for example,
		1652	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1653	connection from the pending queue in all error cases.
		1654
		1655	For example, larger servers often run out of file descriptors (because
		1656	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1657	rejecting the connection, leading to libev signalling readiness on
		1658	the next iteration again (the connection still exists after all), and
		1659	typically causing the program to loop at 100% CPU usage.
		1660
		1661	Unfortunately, the set of errors that cause this issue differs between
		1662	operating systems, there is usually little the app can do to remedy the
		1663	situation, and no known thread-safe method of removing the connection to
		1664	cope with overload is known (to me).
		1665
		1666	One of the easiest ways to handle this situation is to just ignore it
		1667	- when the program encounters an overload, it will just loop until the
		1668	situation is over. While this is a form of busy waiting, no OS offers an
		1669	event-based way to handle this situation, so it's the best one can do.
		1670
		1671	A better way to handle the situation is to log any errors other than
		1672	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1673	messages, and continue as usual, which at least gives the user an idea of
		1674	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1675	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1676	usage.
		1677
		1678	If your program is single-threaded, then you could also keep a dummy file
		1679	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1680	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1681	close that fd, and create a new dummy fd. This will gracefully refuse
		1682	clients under typical overload conditions.
		1683
		1684	The last way to handle it is to simply log the error and C<exit>, as
		1685	is often done with C<malloc> failures, but this results in an easy
		1686	opportunity for a DoS attack.
1090		1687
1091	=head3 Watcher-Specific Functions	1688	=head3 Watcher-Specific Functions
1092		1689
1093	=over 4	1690	=over 4
1094		1691
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1692	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1693
1097	=item ev_io_set (ev_io *, int fd, int events)	1694	=item ev_io_set (ev_io *, int fd, int events)
1098		1695
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1696	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1697	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1101	C<EV_READ | EV_WRITE> to receive the given events.	1698	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1102		1699
1103	=item int fd [read-only]	1700	=item int fd [read-only]
1104		1701
1105	The file descriptor being watched.	1702	The file descriptor being watched.
1106		1703
…		…
1114		1711
1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1712	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1116	readable, but only once. Since it is likely line-buffered, you could	1713	readable, but only once. Since it is likely line-buffered, you could
1117	attempt to read a whole line in the callback.	1714	attempt to read a whole line in the callback.
1118		1715
1119	static void	1716	static void
1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1717	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1121	{	1718	{
1122	ev_io_stop (loop, w);	1719	ev_io_stop (loop, w);
1123	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1720	.. read from stdin here (or from w->fd) and handle any I/O errors
1124	}	1721	}
1125		1722
1126	...	1723	...
1127	struct ev_loop *loop = ev_default_init (0);	1724	struct ev_loop *loop = ev_default_init (0);
1128	struct ev_io stdin_readable;	1725	ev_io stdin_readable;
1129	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1726	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1130	ev_io_start (loop, &stdin_readable);	1727	ev_io_start (loop, &stdin_readable);
1131	ev_loop (loop, 0);	1728	ev_run (loop, 0);
1132		1729
1133		1730
1134	=head2 C<ev_timer> - relative and optionally repeating timeouts	1731	=head2 C<ev_timer> - relative and optionally repeating timeouts
1135		1732
1136	Timer watchers are simple relative timers that generate an event after a	1733	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1734	given time, and optionally repeating in regular intervals after that.
1138		1735
1139	The timers are based on real time, that is, if you register an event that	1736	The timers are based on real time, that is, if you register an event that
1140	times out after an hour and you reset your system clock to last years	1737	times out after an hour and you reset your system clock to January last
1141	time, it will still time out after (roughly) and hour. "Roughly" because	1738	year, it will still time out after (roughly) one hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1740	monotonic clock option helps a lot here).
		1741
		1742	The callback is guaranteed to be invoked only I<after> its timeout has
		1743	passed (not I<at>, so on systems with very low-resolution clocks this
		1744	might introduce a small delay). If multiple timers become ready during the
		1745	same loop iteration then the ones with earlier time-out values are invoked
		1746	before ones of the same priority with later time-out values (but this is
		1747	no longer true when a callback calls C<ev_run> recursively).
		1748
		1749	=head3 Be smart about timeouts
		1750
		1751	Many real-world problems involve some kind of timeout, usually for error
		1752	recovery. A typical example is an HTTP request - if the other side hangs,
		1753	you want to raise some error after a while.
		1754
		1755	What follows are some ways to handle this problem, from obvious and
		1756	inefficient to smart and efficient.
		1757
		1758	In the following, a 60 second activity timeout is assumed - a timeout that
		1759	gets reset to 60 seconds each time there is activity (e.g. each time some
		1760	data or other life sign was received).
		1761
		1762	=over 4
		1763
		1764	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1765
		1766	This is the most obvious, but not the most simple way: In the beginning,
		1767	start the watcher:
		1768
		1769	ev_timer_init (timer, callback, 60., 0.);
		1770	ev_timer_start (loop, timer);
		1771
		1772	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1773	and start it again:
		1774
		1775	ev_timer_stop (loop, timer);
		1776	ev_timer_set (timer, 60., 0.);
		1777	ev_timer_start (loop, timer);
		1778
		1779	This is relatively simple to implement, but means that each time there is
		1780	some activity, libev will first have to remove the timer from its internal
		1781	data structure and then add it again. Libev tries to be fast, but it's
		1782	still not a constant-time operation.
		1783
		1784	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1785
		1786	This is the easiest way, and involves using C<ev_timer_again> instead of
		1787	C<ev_timer_start>.
		1788
		1789	To implement this, configure an C<ev_timer> with a C<repeat> value
		1790	of C<60> and then call C<ev_timer_again> at start and each time you
		1791	successfully read or write some data. If you go into an idle state where
		1792	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1793	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1794
		1795	That means you can ignore both the C<ev_timer_start> function and the
		1796	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1797	member and C<ev_timer_again>.
		1798
		1799	At start:
		1800
		1801	ev_init (timer, callback);
		1802	timer->repeat = 60.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	Each time there is some activity:
		1806
		1807	ev_timer_again (loop, timer);
		1808
		1809	It is even possible to change the time-out on the fly, regardless of
		1810	whether the watcher is active or not:
		1811
		1812	timer->repeat = 30.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	This is slightly more efficient then stopping/starting the timer each time
		1816	you want to modify its timeout value, as libev does not have to completely
		1817	remove and re-insert the timer from/into its internal data structure.
		1818
		1819	It is, however, even simpler than the "obvious" way to do it.
		1820
		1821	=item 3. Let the timer time out, but then re-arm it as required.
		1822
		1823	This method is more tricky, but usually most efficient: Most timeouts are
		1824	relatively long compared to the intervals between other activity - in
		1825	our example, within 60 seconds, there are usually many I/O events with
		1826	associated activity resets.
		1827
		1828	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1829	but remember the time of last activity, and check for a real timeout only
		1830	within the callback:
		1831
		1832	ev_tstamp last_activity; // time of last activity
		1833
		1834	static void
		1835	callback (EV_P_ ev_timer *w, int revents)
		1836	{
		1837	ev_tstamp now = ev_now (EV_A);
		1838	ev_tstamp timeout = last_activity + 60.;
		1839
		1840	// if last_activity + 60. is older than now, we did time out
		1841	if (timeout < now)
		1842	{
		1843	// timeout occurred, take action
		1844	}
		1845	else
		1846	{
		1847	// callback was invoked, but there was some activity, re-arm
		1848	// the watcher to fire in last_activity + 60, which is
		1849	// guaranteed to be in the future, so "again" is positive:
		1850	w->repeat = timeout - now;
		1851	ev_timer_again (EV_A_ w);
		1852	}
		1853	}
		1854
		1855	To summarise the callback: first calculate the real timeout (defined
		1856	as "60 seconds after the last activity"), then check if that time has
		1857	been reached, which means something I<did>, in fact, time out. Otherwise
		1858	the callback was invoked too early (C<timeout> is in the future), so
		1859	re-schedule the timer to fire at that future time, to see if maybe we have
		1860	a timeout then.
		1861
		1862	Note how C<ev_timer_again> is used, taking advantage of the
		1863	C<ev_timer_again> optimisation when the timer is already running.
		1864
		1865	This scheme causes more callback invocations (about one every 60 seconds
		1866	minus half the average time between activity), but virtually no calls to
		1867	libev to change the timeout.
		1868
		1869	To start the timer, simply initialise the watcher and set C<last_activity>
		1870	to the current time (meaning we just have some activity :), then call the
		1871	callback, which will "do the right thing" and start the timer:
		1872
		1873	ev_init (timer, callback);
		1874	last_activity = ev_now (loop);
		1875	callback (loop, timer, EV_TIMER);
		1876
		1877	And when there is some activity, simply store the current time in
		1878	C<last_activity>, no libev calls at all:
		1879
		1880	last_activity = ev_now (loop);
		1881
		1882	This technique is slightly more complex, but in most cases where the
		1883	time-out is unlikely to be triggered, much more efficient.
		1884
		1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1886	callback :) - just change the timeout and invoke the callback, which will
		1887	fix things for you.
		1888
		1889	=item 4. Wee, just use a double-linked list for your timeouts.
		1890
		1891	If there is not one request, but many thousands (millions...), all
		1892	employing some kind of timeout with the same timeout value, then one can
		1893	do even better:
		1894
		1895	When starting the timeout, calculate the timeout value and put the timeout
		1896	at the I<end> of the list.
		1897
		1898	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1899	the list is expected to fire (for example, using the technique #3).
		1900
		1901	When there is some activity, remove the timer from the list, recalculate
		1902	the timeout, append it to the end of the list again, and make sure to
		1903	update the C<ev_timer> if it was taken from the beginning of the list.
		1904
		1905	This way, one can manage an unlimited number of timeouts in O(1) time for
		1906	starting, stopping and updating the timers, at the expense of a major
		1907	complication, and having to use a constant timeout. The constant timeout
		1908	ensures that the list stays sorted.
		1909
		1910	=back
		1911
		1912	So which method the best?
		1913
		1914	Method #2 is a simple no-brain-required solution that is adequate in most
		1915	situations. Method #3 requires a bit more thinking, but handles many cases
		1916	better, and isn't very complicated either. In most case, choosing either
		1917	one is fine, with #3 being better in typical situations.
		1918
		1919	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1920	rather complicated, but extremely efficient, something that really pays
		1921	off after the first million or so of active timers, i.e. it's usually
		1922	overkill :)
		1923
		1924	=head3 The special problem of time updates
		1925
		1926	Establishing the current time is a costly operation (it usually takes at
		1927	least two system calls): EV therefore updates its idea of the current
		1928	time only before and after C<ev_run> collects new events, which causes a
		1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1930	lots of events in one iteration.
1144		1931
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1932	The relative timeouts are calculated relative to the C<ev_now ()>
1146	time. This is usually the right thing as this timestamp refers to the time	1933	time. This is usually the right thing as this timestamp refers to the time
1147	of the event triggering whatever timeout you are modifying/starting. If	1934	of the event triggering whatever timeout you are modifying/starting. If
1148	you suspect event processing to be delayed and you I<need> to base the timeout	1935	you suspect event processing to be delayed and you I<need> to base the
1149	on the current time, use something like this to adjust for this:	1936	timeout on the current time, use something like this to adjust for this:
1150		1937
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1938	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1939
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1940	If the event loop is suspended for a long time, you can also force an
1154	but if multiple timers become ready during the same loop iteration then	1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1155	order of execution is undefined.	1942	()>.
		1943
		1944	=head3 The special problems of suspended animation
		1945
		1946	When you leave the server world it is quite customary to hit machines that
		1947	can suspend/hibernate - what happens to the clocks during such a suspend?
		1948
		1949	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1950	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1951	to run until the system is suspended, but they will not advance while the
		1952	system is suspended. That means, on resume, it will be as if the program
		1953	was frozen for a few seconds, but the suspend time will not be counted
		1954	towards C<ev_timer> when a monotonic clock source is used. The real time
		1955	clock advanced as expected, but if it is used as sole clocksource, then a
		1956	long suspend would be detected as a time jump by libev, and timers would
		1957	be adjusted accordingly.
		1958
		1959	I would not be surprised to see different behaviour in different between
		1960	operating systems, OS versions or even different hardware.
		1961
		1962	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1963	time jump in the monotonic clocks and the realtime clock. If the program
		1964	is suspended for a very long time, and monotonic clock sources are in use,
		1965	then you can expect C<ev_timer>s to expire as the full suspension time
		1966	will be counted towards the timers. When no monotonic clock source is in
		1967	use, then libev will again assume a timejump and adjust accordingly.
		1968
		1969	It might be beneficial for this latter case to call C<ev_suspend>
		1970	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1971	deterministic behaviour in this case (you can do nothing against
		1972	C<SIGSTOP>).
1156		1973
1157	=head3 Watcher-Specific Functions and Data Members	1974	=head3 Watcher-Specific Functions and Data Members
1158		1975
1159	=over 4	1976	=over 4
1160		1977
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1978	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1979
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1980	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1981
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1982	Configure the timer to trigger after C<after> seconds. If C<repeat>
1166	C<0.>, then it will automatically be stopped. If it is positive, then the	1983	is C<0.>, then it will automatically be stopped once the timeout is
1167	timer will automatically be configured to trigger again C<repeat> seconds	1984	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1985	configured to trigger again C<repeat> seconds later, again, and again,
		1986	until stopped manually.
1169		1987
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1988	The timer itself will do a best-effort at avoiding drift, that is, if
1171	configure a timer to trigger every 10 seconds, then it will trigger at	1989	you configure a timer to trigger every 10 seconds, then it will normally
1172	exactly 10 second intervals. If, however, your program cannot keep up with	1990	trigger at exactly 10 second intervals. If, however, your program cannot
1173	the timer (because it takes longer than those 10 seconds to do stuff) the	1991	keep up with the timer (because it takes longer than those 10 seconds to
1174	timer will not fire more than once per event loop iteration.	1992	do stuff) the timer will not fire more than once per event loop iteration.
1175		1993
1176	=item ev_timer_again (loop, ev_timer *)	1994	=item ev_timer_again (loop, ev_timer *)
1177		1995
1178	This will act as if the timer timed out and restart it again if it is	1996	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1997	repeating. The exact semantics are:
1180		1998
1181	If the timer is pending, its pending status is cleared.	1999	If the timer is pending, its pending status is cleared.
1182		2000
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	2001	If the timer is started but non-repeating, stop it (as if it timed out).
1184		2002
1185	If the timer is repeating, either start it if necessary (with the	2003	If the timer is repeating, either start it if necessary (with the
1186	C<repeat> value), or reset the running timer to the C<repeat> value.	2004	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		2005
1188	This sounds a bit complicated, but here is a useful and typical	2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1189	example: Imagine you have a tcp connection and you want a so-called idle	2007	usage example.
1190	timeout, that is, you want to be called when there have been, say, 60
1191	seconds of inactivity on the socket. The easiest way to do this is to
1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1193	C<ev_timer_again> each time you successfully read or write some data. If
1194	you go into an idle state where you do not expect data to travel on the
1195	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1196	automatically restart it if need be.
1197		2008
1198	That means you can ignore the C<after> value and C<ev_timer_start>	2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1199	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1200		2010
1201	ev_timer_init (timer, callback, 0., 5.);	2011	Returns the remaining time until a timer fires. If the timer is active,
1202	ev_timer_again (loop, timer);	2012	then this time is relative to the current event loop time, otherwise it's
1203	...	2013	the timeout value currently configured.
1204	timer->again = 17.;
1205	ev_timer_again (loop, timer);
1206	...
1207	timer->again = 10.;
1208	ev_timer_again (loop, timer);
1209		2014
1210	This is more slightly efficient then stopping/starting the timer each time	2015	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1211	you want to modify its timeout value.	2016	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2017	will return C<4>. When the timer expires and is restarted, it will return
		2018	roughly C<7> (likely slightly less as callback invocation takes some time,
		2019	too), and so on.
1212		2020
1213	=item ev_tstamp repeat [read-write]	2021	=item ev_tstamp repeat [read-write]
1214		2022
1215	The current C<repeat> value. Will be used each time the watcher times out	2023	The current C<repeat> value. Will be used each time the watcher times out
1216	or C<ev_timer_again> is called and determines the next timeout (if any),	2024	or C<ev_timer_again> is called, and determines the next timeout (if any),
1217	which is also when any modifications are taken into account.	2025	which is also when any modifications are taken into account.
1218		2026
1219	=back	2027	=back
1220		2028
1221	=head3 Examples	2029	=head3 Examples
1222		2030
1223	Example: Create a timer that fires after 60 seconds.	2031	Example: Create a timer that fires after 60 seconds.
1224		2032
1225	static void	2033	static void
1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2034	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1227	{	2035	{
1228	.. one minute over, w is actually stopped right here	2036	.. one minute over, w is actually stopped right here
1229	}	2037	}
1230		2038
1231	struct ev_timer mytimer;	2039	ev_timer mytimer;
1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2040	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233	ev_timer_start (loop, &mytimer);	2041	ev_timer_start (loop, &mytimer);
1234		2042
1235	Example: Create a timeout timer that times out after 10 seconds of	2043	Example: Create a timeout timer that times out after 10 seconds of
1236	inactivity.	2044	inactivity.
1237		2045
1238	static void	2046	static void
1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2047	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	2048	{
1241	.. ten seconds without any activity	2049	.. ten seconds without any activity
1242	}	2050	}
1243		2051
1244	struct ev_timer mytimer;	2052	ev_timer mytimer;
1245	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2053	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1246	ev_timer_again (&mytimer); /* start timer */	2054	ev_timer_again (&mytimer); /* start timer */
1247	ev_loop (loop, 0);	2055	ev_run (loop, 0);
1248		2056
1249	// and in some piece of code that gets executed on any "activity":	2057	// and in some piece of code that gets executed on any "activity":
1250	// reset the timeout to start ticking again at 10 seconds	2058	// reset the timeout to start ticking again at 10 seconds
1251	ev_timer_again (&mytimer);	2059	ev_timer_again (&mytimer);
1252		2060
1253		2061
1254	=head2 C<ev_periodic> - to cron or not to cron?	2062	=head2 C<ev_periodic> - to cron or not to cron?
1255		2063
1256	Periodic watchers are also timers of a kind, but they are very versatile	2064	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	2065	(and unfortunately a bit complex).
1258		2066
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2067	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1260	but on wallclock time (absolute time). You can tell a periodic watcher	2068	relative time, the physical time that passes) but on wall clock time
1261	to trigger "at" some specific point in time. For example, if you tell a	2069	(absolute time, the thing you can read on your calender or clock). The
1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2070	difference is that wall clock time can run faster or slower than real
1263	+ 10.>) and then reset your system clock to the last year, then it will	2071	time, and time jumps are not uncommon (e.g. when you adjust your
1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	2072	wrist-watch).
1265	roughly 10 seconds later).
1266		2073
1267	They can also be used to implement vastly more complex timers, such as	2074	You can tell a periodic watcher to trigger after some specific point
1268	triggering an event on each midnight, local time or other, complicated,	2075	in time: for example, if you tell a periodic watcher to trigger "in 10
1269	rules.	2076	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2077	not a delay) and then reset your system clock to January of the previous
		2078	year, then it will take a year or more to trigger the event (unlike an
		2079	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2080	it, as it uses a relative timeout).
1270		2081
		2082	C<ev_periodic> watchers can also be used to implement vastly more complex
		2083	timers, such as triggering an event on each "midnight, local time", or
		2084	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2085	those cannot react to time jumps.
		2086
1271	As with timers, the callback is guarenteed to be invoked only when the	2087	As with timers, the callback is guaranteed to be invoked only when the
1272	time (C<at>) has been passed, but if multiple periodic timers become ready	2088	point in time where it is supposed to trigger has passed. If multiple
1273	during the same loop iteration then order of execution is undefined.	2089	timers become ready during the same loop iteration then the ones with
		2090	earlier time-out values are invoked before ones with later time-out values
		2091	(but this is no longer true when a callback calls C<ev_run> recursively).
1274		2092
1275	=head3 Watcher-Specific Functions and Data Members	2093	=head3 Watcher-Specific Functions and Data Members
1276		2094
1277	=over 4	2095	=over 4
1278		2096
1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2097	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1280		2098
1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2099	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1282		2100
1283	Lots of arguments, lets sort it out... There are basically three modes of	2101	Lots of arguments, let's sort it out... There are basically three modes of
1284	operation, and we will explain them from simplest to complex:	2102	operation, and we will explain them from simplest to most complex:
1285		2103
1286	=over 4	2104	=over 4
1287		2105
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2106	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1289		2107
1290	In this configuration the watcher triggers an event at the wallclock time	2108	In this configuration the watcher triggers an event after the wall clock
1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	2109	time C<offset> has passed. It will not repeat and will not adjust when a
1292	that is, if it is to be run at January 1st 2011 then it will run when the	2110	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1293	system time reaches or surpasses this time.	2111	will be stopped and invoked when the system clock reaches or surpasses
		2112	this point in time.
1294		2113
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2114	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1296		2115
1297	In this mode the watcher will always be scheduled to time out at the next	2116	In this mode the watcher will always be scheduled to time out at the next
1298	C<at + N * interval> time (for some integer N, which can also be negative)	2117	C<offset + N * interval> time (for some integer N, which can also be
1299	and then repeat, regardless of any time jumps.	2118	negative) and then repeat, regardless of any time jumps. The C<offset>
		2119	argument is merely an offset into the C<interval> periods.
1300		2120
1301	This can be used to create timers that do not drift with respect to system	2121	This can be used to create timers that do not drift with respect to the
1302	time:	2122	system clock, for example, here is an C<ev_periodic> that triggers each
		2123	hour, on the hour (with respect to UTC):
1303		2124
1304	ev_periodic_set (&periodic, 0., 3600., 0);	2125	ev_periodic_set (&periodic, 0., 3600., 0);
1305		2126
1306	This doesn't mean there will always be 3600 seconds in between triggers,	2127	This doesn't mean there will always be 3600 seconds in between triggers,
1307	but only that the the callback will be called when the system time shows a	2128	but only that the callback will be called when the system time shows a
1308	full hour (UTC), or more correctly, when the system time is evenly divisible	2129	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	2130	by 3600.
1310		2131
1311	Another way to think about it (for the mathematically inclined) is that	2132	Another way to think about it (for the mathematically inclined) is that
1312	C<ev_periodic> will try to run the callback in this mode at the next possible	2133	C<ev_periodic> will try to run the callback in this mode at the next possible
1313	time where C<time = at (mod interval)>, regardless of any time jumps.	2134	time where C<time = offset (mod interval)>, regardless of any time jumps.
1314		2135
1315	For numerical stability it is preferable that the C<at> value is near	2136	For numerical stability it is preferable that the C<offset> value is near
1316	C<ev_now ()> (the current time), but there is no range requirement for	2137	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	2138	this value, and in fact is often specified as zero.
1318		2139
		2140	Note also that there is an upper limit to how often a timer can fire (CPU
		2141	speed for example), so if C<interval> is very small then timing stability
		2142	will of course deteriorate. Libev itself tries to be exact to be about one
		2143	millisecond (if the OS supports it and the machine is fast enough).
		2144
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2145	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1320		2146
1321	In this mode the values for C<interval> and C<at> are both being	2147	In this mode the values for C<interval> and C<offset> are both being
1322	ignored. Instead, each time the periodic watcher gets scheduled, the	2148	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	2149	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	2150	current time as second argument.
1325		2151
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2152	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1327	ever, or make any event loop modifications>. If you need to stop it,	2153	or make ANY other event loop modifications whatsoever, unless explicitly
1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	2154	allowed by documentation here>.
1329	starting an C<ev_prepare> watcher, which is legal).
1330		2155
		2156	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2157	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2158	only event loop modification you are allowed to do).
		2159
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2160	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1332	ev_tstamp now)>, e.g.:	2161	*w, ev_tstamp now)>, e.g.:
1333		2162
		2163	static ev_tstamp
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2164	my_rescheduler (ev_periodic *w, ev_tstamp now)
1335	{	2165	{
1336	return now + 60.;	2166	return now + 60.;
1337	}	2167	}
1338		2168
1339	It must return the next time to trigger, based on the passed time value	2169	It must return the next time to trigger, based on the passed time value
1340	(that is, the lowest time value larger than to the second argument). It	2170	(that is, the lowest time value larger than to the second argument). It
1341	will usually be called just before the callback will be triggered, but	2171	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	2172	might be called at other times, too.
1343		2173
1344	NOTE: I<< This callback must always return a time that is later than the	2174	NOTE: I<< This callback must always return a time that is higher than or
1345	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2175	equal to the passed C<now> value >>.
1346		2176
1347	This can be used to create very complex timers, such as a timer that	2177	This can be used to create very complex timers, such as a timer that
1348	triggers on each midnight, local time. To do this, you would calculate the	2178	triggers on "next midnight, local time". To do this, you would calculate the
1349	next midnight after C<now> and return the timestamp value for this. How	2179	next midnight after C<now> and return the timestamp value for this. How
1350	you do this is, again, up to you (but it is not trivial, which is the main	2180	you do this is, again, up to you (but it is not trivial, which is the main
1351	reason I omitted it as an example).	2181	reason I omitted it as an example).
1352		2182
1353	=back	2183	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	2187	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	2188	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	2189	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	2190	program when the crontabs have changed).
1361		2191
		2192	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2193
		2194	When active, returns the absolute time that the watcher is supposed
		2195	to trigger next. This is not the same as the C<offset> argument to
		2196	C<ev_periodic_set>, but indeed works even in interval and manual
		2197	rescheduling modes.
		2198
1362	=item ev_tstamp offset [read-write]	2199	=item ev_tstamp offset [read-write]
1363		2200
1364	When repeating, this contains the offset value, otherwise this is the	2201	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2202	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2203	although libev might modify this value for better numerical stability).
1366		2204
1367	Can be modified any time, but changes only take effect when the periodic	2205	Can be modified any time, but changes only take effect when the periodic
1368	timer fires or C<ev_periodic_again> is being called.	2206	timer fires or C<ev_periodic_again> is being called.
1369		2207
1370	=item ev_tstamp interval [read-write]	2208	=item ev_tstamp interval [read-write]
1371		2209
1372	The current interval value. Can be modified any time, but changes only	2210	The current interval value. Can be modified any time, but changes only
1373	take effect when the periodic timer fires or C<ev_periodic_again> is being	2211	take effect when the periodic timer fires or C<ev_periodic_again> is being
1374	called.	2212	called.
1375		2213
1376	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2214	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1377		2215
1378	The current reschedule callback, or C<0>, if this functionality is	2216	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	2217	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	2218	the periodic timer fires or C<ev_periodic_again> is being called.
1381		2219
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386
1387	=back	2220	=back
1388		2221
1389	=head3 Examples	2222	=head3 Examples
1390		2223
1391	Example: Call a callback every hour, or, more precisely, whenever the	2224	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	2225	system time is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	2226	potentially a lot of jitter, but good long-term stability.
1394		2227
1395	static void	2228	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2229	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1397	{	2230	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	2231	... its now a full hour (UTC, or TAI or whatever your clock follows)
1399	}	2232	}
1400		2233
1401	struct ev_periodic hourly_tick;	2234	ev_periodic hourly_tick;
1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2235	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	2236	ev_periodic_start (loop, &hourly_tick);
1404		2237
1405	Example: The same as above, but use a reschedule callback to do it:	2238	Example: The same as above, but use a reschedule callback to do it:
1406		2239
1407	#include <math.h>	2240	#include <math.h>
1408		2241
1409	static ev_tstamp	2242	static ev_tstamp
1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2243	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1411	{	2244	{
1412	return fmod (now, 3600.) + 3600.;	2245	return now + (3600. - fmod (now, 3600.));
1413	}	2246	}
1414		2247
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2248	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1416		2249
1417	Example: Call a callback every hour, starting now:	2250	Example: Call a callback every hour, starting now:
1418		2251
1419	struct ev_periodic hourly_tick;	2252	ev_periodic hourly_tick;
1420	ev_periodic_init (&hourly_tick, clock_cb,	2253	ev_periodic_init (&hourly_tick, clock_cb,
1421	fmod (ev_now (loop), 3600.), 3600., 0);	2254	fmod (ev_now (loop), 3600.), 3600., 0);
1422	ev_periodic_start (loop, &hourly_tick);	2255	ev_periodic_start (loop, &hourly_tick);
1423		2256
1424		2257
1425	=head2 C<ev_signal> - signal me when a signal gets signalled!	2258	=head2 C<ev_signal> - signal me when a signal gets signalled!
1426		2259
1427	Signal watchers will trigger an event when the process receives a specific	2260	Signal watchers will trigger an event when the process receives a specific
1428	signal one or more times. Even though signals are very asynchronous, libev	2261	signal one or more times. Even though signals are very asynchronous, libev
1429	will try it's best to deliver signals synchronously, i.e. as part of the	2262	will try it's best to deliver signals synchronously, i.e. as part of the
1430	normal event processing, like any other event.	2263	normal event processing, like any other event.
1431		2264
		2265	If you want signals to be delivered truly asynchronously, just use
		2266	C<sigaction> as you would do without libev and forget about sharing
		2267	the signal. You can even use C<ev_async> from a signal handler to
		2268	synchronously wake up an event loop.
		2269
1432	You can configure as many watchers as you like per signal. Only when the	2270	You can configure as many watchers as you like for the same signal, but
		2271	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2272	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2273	C<SIGINT> in both the default loop and another loop at the same time. At
		2274	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2275
1433	first watcher gets started will libev actually register a signal watcher	2276	When the first watcher gets started will libev actually register something
1434	with the kernel (thus it coexists with your own signal handlers as long	2277	with the kernel (thus it coexists with your own signal handlers as long as
1435	as you don't register any with libev). Similarly, when the last signal	2278	you don't register any with libev for the same signal).
1436	watcher for a signal is stopped libev will reset the signal handler to
1437	SIG_DFL (regardless of what it was set to before).
1438		2279
1439	If possible and supported, libev will install its handlers with	2280	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1441	interrupted. If you have a problem with syscalls getting interrupted by	2282	not be unduly interrupted. If you have a problem with system calls getting
1442	signals you can block all signals in an C<ev_check> watcher and unblock	2283	interrupted by signals you can block all signals in an C<ev_check> watcher
1443	them in an C<ev_prepare> watcher.	2284	and unblock them in an C<ev_prepare> watcher.
		2285
		2286	=head3 The special problem of inheritance over fork/execve/pthread_create
		2287
		2288	Both the signal mask (C<sigprocmask>) and the signal disposition
		2289	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2290	stopping it again), that is, libev might or might not block the signal,
		2291	and might or might not set or restore the installed signal handler.
		2292
		2293	While this does not matter for the signal disposition (libev never
		2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2295	C<execve>), this matters for the signal mask: many programs do not expect
		2296	certain signals to be blocked.
		2297
		2298	This means that before calling C<exec> (from the child) you should reset
		2299	the signal mask to whatever "default" you expect (all clear is a good
		2300	choice usually).
		2301
		2302	The simplest way to ensure that the signal mask is reset in the child is
		2303	to install a fork handler with C<pthread_atfork> that resets it. That will
		2304	catch fork calls done by libraries (such as the libc) as well.
		2305
		2306	In current versions of libev, the signal will not be blocked indefinitely
		2307	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2308	the window of opportunity for problems, it will not go away, as libev
		2309	I<has> to modify the signal mask, at least temporarily.
		2310
		2311	So I can't stress this enough: I<If you do not reset your signal mask when
		2312	you expect it to be empty, you have a race condition in your code>. This
		2313	is not a libev-specific thing, this is true for most event libraries.
1444		2314
1445	=head3 Watcher-Specific Functions and Data Members	2315	=head3 Watcher-Specific Functions and Data Members
1446		2316
1447	=over 4	2317	=over 4
1448		2318
…		…
1459		2329
1460	=back	2330	=back
1461		2331
1462	=head3 Examples	2332	=head3 Examples
1463		2333
1464	Example: Try to exit cleanly on SIGINT and SIGTERM.	2334	Example: Try to exit cleanly on SIGINT.
1465		2335
1466	static void	2336	static void
1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2337	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1468	{	2338	{
1469	ev_unloop (loop, EVUNLOOP_ALL);	2339	ev_break (loop, EVBREAK_ALL);
1470	}	2340	}
1471		2341
1472	struct ev_signal signal_watcher;	2342	ev_signal signal_watcher;
1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2343	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474	ev_signal_start (loop, &sigint_cb);	2344	ev_signal_start (loop, &signal_watcher);
1475		2345
1476		2346
1477	=head2 C<ev_child> - watch out for process status changes	2347	=head2 C<ev_child> - watch out for process status changes
1478		2348
1479	Child watchers trigger when your process receives a SIGCHLD in response to	2349	Child watchers trigger when your process receives a SIGCHLD in response to
1480	some child status changes (most typically when a child of yours dies). It	2350	some child status changes (most typically when a child of yours dies or
1481	is permissible to install a child watcher I<after> the child has been	2351	exits). It is permissible to install a child watcher I<after> the child
1482	forked (which implies it might have already exited), as long as the event	2352	has been forked (which implies it might have already exited), as long
1483	loop isn't entered (or is continued from a watcher).	2353	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2354	forking and then immediately registering a watcher for the child is fine,
		2355	but forking and registering a watcher a few event loop iterations later or
		2356	in the next callback invocation is not.
1484		2357
1485	Only the default event loop is capable of handling signals, and therefore	2358	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	2359	you can only register child watchers in the default event loop.
		2360
		2361	Due to some design glitches inside libev, child watchers will always be
		2362	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2363	libev)
1487		2364
1488	=head3 Process Interaction	2365	=head3 Process Interaction
1489		2366
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	2367	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	2368	initialised. This is necessary to guarantee proper behaviour even if the
1492	the first child watcher is started after the child exits. The occurance	2369	first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2370	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	2371	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	2372	children, even ones not watched.
1496		2373
1497	=head3 Overriding the Built-In Processing	2374	=head3 Overriding the Built-In Processing
…		…
1501	handler, you can override it easily by installing your own handler for	2378	handler, you can override it easily by installing your own handler for
1502	C<SIGCHLD> after initialising the default loop, and making sure the	2379	C<SIGCHLD> after initialising the default loop, and making sure the
1503	default loop never gets destroyed. You are encouraged, however, to use an	2380	default loop never gets destroyed. You are encouraged, however, to use an
1504	event-based approach to child reaping and thus use libev's support for	2381	event-based approach to child reaping and thus use libev's support for
1505	that, so other libev users can use C<ev_child> watchers freely.	2382	that, so other libev users can use C<ev_child> watchers freely.
		2383
		2384	=head3 Stopping the Child Watcher
		2385
		2386	Currently, the child watcher never gets stopped, even when the
		2387	child terminates, so normally one needs to stop the watcher in the
		2388	callback. Future versions of libev might stop the watcher automatically
		2389	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2390	problem).
1506		2391
1507	=head3 Watcher-Specific Functions and Data Members	2392	=head3 Watcher-Specific Functions and Data Members
1508		2393
1509	=over 4	2394	=over 4
1510		2395
…		…
1539	=head3 Examples	2424	=head3 Examples
1540		2425
1541	Example: C<fork()> a new process and install a child handler to wait for	2426	Example: C<fork()> a new process and install a child handler to wait for
1542	its completion.	2427	its completion.
1543		2428
1544	ev_child cw;	2429	ev_child cw;
1545		2430
1546	static void	2431	static void
1547	child_cb (EV_P_ struct ev_child *w, int revents)	2432	child_cb (EV_P_ ev_child *w, int revents)
1548	{	2433	{
1549	ev_child_stop (EV_A_ w);	2434	ev_child_stop (EV_A_ w);
1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2435	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1551	}	2436	}
1552		2437
1553	pid_t pid = fork ();	2438	pid_t pid = fork ();
1554		2439
1555	if (pid < 0)	2440	if (pid < 0)
1556	// error	2441	// error
1557	else if (pid == 0)	2442	else if (pid == 0)
1558	{	2443	{
1559	// the forked child executes here	2444	// the forked child executes here
1560	exit (1);	2445	exit (1);
1561	}	2446	}
1562	else	2447	else
1563	{	2448	{
1564	ev_child_init (&cw, child_cb, pid, 0);	2449	ev_child_init (&cw, child_cb, pid, 0);
1565	ev_child_start (EV_DEFAULT_ &cw);	2450	ev_child_start (EV_DEFAULT_ &cw);
1566	}	2451	}
1567		2452
1568		2453
1569	=head2 C<ev_stat> - did the file attributes just change?	2454	=head2 C<ev_stat> - did the file attributes just change?
1570		2455
1571	This watches a filesystem path for attribute changes. That is, it calls	2456	This watches a file system path for attribute changes. That is, it calls
1572	C<stat> regularly (or when the OS says it changed) and sees if it changed	2457	C<stat> on that path in regular intervals (or when the OS says it changed)
1573	compared to the last time, invoking the callback if it did.	2458	and sees if it changed compared to the last time, invoking the callback if
		2459	it did.
1574		2460
1575	The path does not need to exist: changing from "path exists" to "path does	2461	The path does not need to exist: changing from "path exists" to "path does
1576	not exist" is a status change like any other. The condition "path does	2462	not exist" is a status change like any other. The condition "path does not
1577	not exist" is signified by the C<st_nlink> field being zero (which is	2463	exist" (or more correctly "path cannot be stat'ed") is signified by the
1578	otherwise always forced to be at least one) and all the other fields of	2464	C<st_nlink> field being zero (which is otherwise always forced to be at
1579	the stat buffer having unspecified contents.	2465	least one) and all the other fields of the stat buffer having unspecified
		2466	contents.
1580		2467
1581	The path I<should> be absolute and I<must not> end in a slash. If it is	2468	The path I<must not> end in a slash or contain special components such as
		2469	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1582	relative and your working directory changes, the behaviour is undefined.	2470	your working directory changes, then the behaviour is undefined.
1583		2471
1584	Since there is no standard to do this, the portable implementation simply	2472	Since there is no portable change notification interface available, the
1585	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2473	portable implementation simply calls C<stat(2)> regularly on the path
1586	can specify a recommended polling interval for this case. If you specify	2474	to see if it changed somehow. You can specify a recommended polling
1587	a polling interval of C<0> (highly recommended!) then a I<suitable,	2475	interval for this case. If you specify a polling interval of C<0> (highly
1588	unspecified default> value will be used (which you can expect to be around	2476	recommended!) then a I<suitable, unspecified default> value will be used
1589	five seconds, although this might change dynamically). Libev will also	2477	(which you can expect to be around five seconds, although this might
1590	impose a minimum interval which is currently around C<0.1>, but thats	2478	change dynamically). Libev will also impose a minimum interval which is
1591	usually overkill.	2479	currently around C<0.1>, but that's usually overkill.
1592		2480
1593	This watcher type is not meant for massive numbers of stat watchers,	2481	This watcher type is not meant for massive numbers of stat watchers,
1594	as even with OS-supported change notifications, this can be	2482	as even with OS-supported change notifications, this can be
1595	resource-intensive.	2483	resource-intensive.
1596		2484
1597	At the time of this writing, only the Linux inotify interface is	2485	At the time of this writing, the only OS-specific interface implemented
1598	implemented (implementing kqueue support is left as an exercise for the	2486	is the Linux inotify interface (implementing kqueue support is left as an
1599	reader). Inotify will be used to give hints only and should not change the	2487	exercise for the reader. Note, however, that the author sees no way of
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2488	implementing C<ev_stat> semantics with kqueue, except as a hint).
1601	to fall back to regular polling again even with inotify, but changes are
1602	usually detected immediately, and if the file exists there will be no
1603	polling.
1604		2489
1605	=head3 Inotify	2490	=head3 ABI Issues (Largefile Support)
1606		2491
		2492	Libev by default (unless the user overrides this) uses the default
		2493	compilation environment, which means that on systems with large file
		2494	support disabled by default, you get the 32 bit version of the stat
		2495	structure. When using the library from programs that change the ABI to
		2496	use 64 bit file offsets the programs will fail. In that case you have to
		2497	compile libev with the same flags to get binary compatibility. This is
		2498	obviously the case with any flags that change the ABI, but the problem is
		2499	most noticeably displayed with ev_stat and large file support.
		2500
		2501	The solution for this is to lobby your distribution maker to make large
		2502	file interfaces available by default (as e.g. FreeBSD does) and not
		2503	optional. Libev cannot simply switch on large file support because it has
		2504	to exchange stat structures with application programs compiled using the
		2505	default compilation environment.
		2506
		2507	=head3 Inotify and Kqueue
		2508
1607	When C<inotify (7)> support has been compiled into libev (generally only	2509	When C<inotify (7)> support has been compiled into libev and present at
1608	available on Linux) and present at runtime, it will be used to speed up	2510	runtime, it will be used to speed up change detection where possible. The
1609	change detection where possible. The inotify descriptor will be created lazily	2511	inotify descriptor will be created lazily when the first C<ev_stat>
1610	when the first C<ev_stat> watcher is being started.	2512	watcher is being started.
1611		2513
1612	Inotify presense does not change the semantics of C<ev_stat> watchers	2514	Inotify presence does not change the semantics of C<ev_stat> watchers
1613	except that changes might be detected earlier, and in some cases, to avoid	2515	except that changes might be detected earlier, and in some cases, to avoid
1614	making regular C<stat> calls. Even in the presense of inotify support	2516	making regular C<stat> calls. Even in the presence of inotify support
1615	there are many cases where libev has to resort to regular C<stat> polling.	2517	there are many cases where libev has to resort to regular C<stat> polling,
		2518	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2519	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2520	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2521	xfs are fully working) libev usually gets away without polling.
1616		2522
1617	(There is no support for kqueue, as apparently it cannot be used to	2523	There is no support for kqueue, as apparently it cannot be used to
1618	implement this functionality, due to the requirement of having a file	2524	implement this functionality, due to the requirement of having a file
1619	descriptor open on the object at all times).	2525	descriptor open on the object at all times, and detecting renames, unlinks
		2526	etc. is difficult.
		2527
		2528	=head3 C<stat ()> is a synchronous operation
		2529
		2530	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2531	the process. The exception are C<ev_stat> watchers - those call C<stat
		2532	()>, which is a synchronous operation.
		2533
		2534	For local paths, this usually doesn't matter: unless the system is very
		2535	busy or the intervals between stat's are large, a stat call will be fast,
		2536	as the path data is usually in memory already (except when starting the
		2537	watcher).
		2538
		2539	For networked file systems, calling C<stat ()> can block an indefinite
		2540	time due to network issues, and even under good conditions, a stat call
		2541	often takes multiple milliseconds.
		2542
		2543	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2544	paths, although this is fully supported by libev.
1620		2545
1621	=head3 The special problem of stat time resolution	2546	=head3 The special problem of stat time resolution
1622		2547
1623	The C<stat ()> syscall only supports full-second resolution portably, and	2548	The C<stat ()> system call only supports full-second resolution portably,
1624	even on systems where the resolution is higher, many filesystems still	2549	and even on systems where the resolution is higher, most file systems
1625	only support whole seconds.	2550	still only support whole seconds.
1626		2551
1627	That means that, if the time is the only thing that changes, you might	2552	That means that, if the time is the only thing that changes, you can
1628	miss updates: on the first update, C<ev_stat> detects a change and calls	2553	easily miss updates: on the first update, C<ev_stat> detects a change and
1629	your callback, which does something. When there is another update within	2554	calls your callback, which does something. When there is another update
1630	the same second, C<ev_stat> will be unable to detect it.	2555	within the same second, C<ev_stat> will be unable to detect unless the
		2556	stat data does change in other ways (e.g. file size).
1631		2557
1632	The solution to this is to delay acting on a change for a second (or till	2558	The solution to this is to delay acting on a change for slightly more
1633	the next second boundary), using a roughly one-second delay C<ev_timer>	2559	than a second (or till slightly after the next full second boundary), using
1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2560	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1635	is added to work around small timing inconsistencies of some operating	2561	ev_timer_again (loop, w)>).
1636	systems.	2562
		2563	The C<.02> offset is added to work around small timing inconsistencies
		2564	of some operating systems (where the second counter of the current time
		2565	might be be delayed. One such system is the Linux kernel, where a call to
		2566	C<gettimeofday> might return a timestamp with a full second later than
		2567	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2568	update file times then there will be a small window where the kernel uses
		2569	the previous second to update file times but libev might already execute
		2570	the timer callback).
1637		2571
1638	=head3 Watcher-Specific Functions and Data Members	2572	=head3 Watcher-Specific Functions and Data Members
1639		2573
1640	=over 4	2574	=over 4
1641		2575
…		…
1647	C<path>. The C<interval> is a hint on how quickly a change is expected to	2581	C<path>. The C<interval> is a hint on how quickly a change is expected to
1648	be detected and should normally be specified as C<0> to let libev choose	2582	be detected and should normally be specified as C<0> to let libev choose
1649	a suitable value. The memory pointed to by C<path> must point to the same	2583	a suitable value. The memory pointed to by C<path> must point to the same
1650	path for as long as the watcher is active.	2584	path for as long as the watcher is active.
1651		2585
1652	The callback will be receive C<EV_STAT> when a change was detected,	2586	The callback will receive an C<EV_STAT> event when a change was detected,
1653	relative to the attributes at the time the watcher was started (or the	2587	relative to the attributes at the time the watcher was started (or the
1654	last change was detected).	2588	last change was detected).
1655		2589
1656	=item ev_stat_stat (loop, ev_stat *)	2590	=item ev_stat_stat (loop, ev_stat *)
1657		2591
1658	Updates the stat buffer immediately with new values. If you change the	2592	Updates the stat buffer immediately with new values. If you change the
1659	watched path in your callback, you could call this fucntion to avoid	2593	watched path in your callback, you could call this function to avoid
1660	detecting this change (while introducing a race condition). Can also be	2594	detecting this change (while introducing a race condition if you are not
1661	useful simply to find out the new values.	2595	the only one changing the path). Can also be useful simply to find out the
		2596	new values.
1662		2597
1663	=item ev_statdata attr [read-only]	2598	=item ev_statdata attr [read-only]
1664		2599
1665	The most-recently detected attributes of the file. Although the type is of	2600	The most-recently detected attributes of the file. Although the type is
1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2601	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1667	suitable for your system. If the C<st_nlink> member is C<0>, then there	2602	suitable for your system, but you can only rely on the POSIX-standardised
		2603	members to be present. If the C<st_nlink> member is C<0>, then there was
1668	was some error while C<stat>ing the file.	2604	some error while C<stat>ing the file.
1669		2605
1670	=item ev_statdata prev [read-only]	2606	=item ev_statdata prev [read-only]
1671		2607
1672	The previous attributes of the file. The callback gets invoked whenever	2608	The previous attributes of the file. The callback gets invoked whenever
1673	C<prev> != C<attr>.	2609	C<prev> != C<attr>, or, more precisely, one or more of these members
		2610	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2611	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1674		2612
1675	=item ev_tstamp interval [read-only]	2613	=item ev_tstamp interval [read-only]
1676		2614
1677	The specified interval.	2615	The specified interval.
1678		2616
1679	=item const char *path [read-only]	2617	=item const char *path [read-only]
1680		2618
1681	The filesystem path that is being watched.	2619	The file system path that is being watched.
1682		2620
1683	=back	2621	=back
1684		2622
1685	=head3 Examples	2623	=head3 Examples
1686		2624
1687	Example: Watch C</etc/passwd> for attribute changes.	2625	Example: Watch C</etc/passwd> for attribute changes.
1688		2626
1689	static void	2627	static void
1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2628	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1691	{	2629	{
1692	/* /etc/passwd changed in some way */	2630	/* /etc/passwd changed in some way */
1693	if (w->attr.st_nlink)	2631	if (w->attr.st_nlink)
1694	{	2632	{
1695	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2633	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1696	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2634	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1697	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2635	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1698	}	2636	}
1699	else	2637	else
1700	/* you shalt not abuse printf for puts */	2638	/* you shalt not abuse printf for puts */
1701	puts ("wow, /etc/passwd is not there, expect problems. "	2639	puts ("wow, /etc/passwd is not there, expect problems. "
1702	"if this is windows, they already arrived\n");	2640	"if this is windows, they already arrived\n");
1703	}	2641	}
1704		2642
1705	...	2643	...
1706	ev_stat passwd;	2644	ev_stat passwd;
1707		2645
1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2646	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1709	ev_stat_start (loop, &passwd);	2647	ev_stat_start (loop, &passwd);
1710		2648
1711	Example: Like above, but additionally use a one-second delay so we do not	2649	Example: Like above, but additionally use a one-second delay so we do not
1712	miss updates (however, frequent updates will delay processing, too, so	2650	miss updates (however, frequent updates will delay processing, too, so
1713	one might do the work both on C<ev_stat> callback invocation I<and> on	2651	one might do the work both on C<ev_stat> callback invocation I<and> on
1714	C<ev_timer> callback invocation).	2652	C<ev_timer> callback invocation).
1715		2653
1716	static ev_stat passwd;	2654	static ev_stat passwd;
1717	static ev_timer timer;	2655	static ev_timer timer;
1718		2656
1719	static void	2657	static void
1720	timer_cb (EV_P_ ev_timer *w, int revents)	2658	timer_cb (EV_P_ ev_timer *w, int revents)
1721	{	2659	{
1722	ev_timer_stop (EV_A_ w);	2660	ev_timer_stop (EV_A_ w);
1723		2661
1724	/* now it's one second after the most recent passwd change */	2662	/* now it's one second after the most recent passwd change */
1725	}	2663	}
1726		2664
1727	static void	2665	static void
1728	stat_cb (EV_P_ ev_stat *w, int revents)	2666	stat_cb (EV_P_ ev_stat *w, int revents)
1729	{	2667	{
1730	/* reset the one-second timer */	2668	/* reset the one-second timer */
1731	ev_timer_again (EV_A_ &timer);	2669	ev_timer_again (EV_A_ &timer);
1732	}	2670	}
1733		2671
1734	...	2672	...
1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2673	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2674	ev_stat_start (loop, &passwd);
1737	ev_timer_init (&timer, timer_cb, 0., 1.01);	2675	ev_timer_init (&timer, timer_cb, 0., 1.02);
1738		2676
1739		2677
1740	=head2 C<ev_idle> - when you've got nothing better to do...	2678	=head2 C<ev_idle> - when you've got nothing better to do...
1741		2679
1742	Idle watchers trigger events when no other events of the same or higher	2680	Idle watchers trigger events when no other events of the same or higher
1743	priority are pending (prepare, check and other idle watchers do not	2681	priority are pending (prepare, check and other idle watchers do not count
1744	count).	2682	as receiving "events").
1745		2683
1746	That is, as long as your process is busy handling sockets or timeouts	2684	That is, as long as your process is busy handling sockets or timeouts
1747	(or even signals, imagine) of the same or higher priority it will not be	2685	(or even signals, imagine) of the same or higher priority it will not be
1748	triggered. But when your process is idle (or only lower-priority watchers	2686	triggered. But when your process is idle (or only lower-priority watchers
1749	are pending), the idle watchers are being called once per event loop	2687	are pending), the idle watchers are being called once per event loop
…		…
1760		2698
1761	=head3 Watcher-Specific Functions and Data Members	2699	=head3 Watcher-Specific Functions and Data Members
1762		2700
1763	=over 4	2701	=over 4
1764		2702
1765	=item ev_idle_init (ev_signal *, callback)	2703	=item ev_idle_init (ev_idle *, callback)
1766		2704
1767	Initialises and configures the idle watcher - it has no parameters of any	2705	Initialises and configures the idle watcher - it has no parameters of any
1768	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2706	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1769	believe me.	2707	believe me.
1770		2708
…		…
1773	=head3 Examples	2711	=head3 Examples
1774		2712
1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2713	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1776	callback, free it. Also, use no error checking, as usual.	2714	callback, free it. Also, use no error checking, as usual.
1777		2715
1778	static void	2716	static void
1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1780	{	2718	{
1781	free (w);	2719	free (w);
1782	// now do something you wanted to do when the program has	2720	// now do something you wanted to do when the program has
1783	// no longer anything immediate to do.	2721	// no longer anything immediate to do.
1784	}	2722	}
1785		2723
1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1787	ev_idle_init (idle_watcher, idle_cb);	2725	ev_idle_init (idle_watcher, idle_cb);
1788	ev_idle_start (loop, idle_cb);	2726	ev_idle_start (loop, idle_watcher);
1789		2727
1790		2728
1791	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1792		2730
1793	Prepare and check watchers are usually (but not always) used in tandem:	2731	Prepare and check watchers are usually (but not always) used in pairs:
1794	prepare watchers get invoked before the process blocks and check watchers	2732	prepare watchers get invoked before the process blocks and check watchers
1795	afterwards.	2733	afterwards.
1796		2734
1797	You I<must not> call C<ev_loop> or similar functions that enter	2735	You I<must not> call C<ev_run> or similar functions that enter
1798	the current event loop from either C<ev_prepare> or C<ev_check>	2736	the current event loop from either C<ev_prepare> or C<ev_check>
1799	watchers. Other loops than the current one are fine, however. The	2737	watchers. Other loops than the current one are fine, however. The
1800	rationale behind this is that you do not need to check for recursion in	2738	rationale behind this is that you do not need to check for recursion in
1801	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2739	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1802	C<ev_check> so if you have one watcher of each kind they will always be	2740	C<ev_check> so if you have one watcher of each kind they will always be
1803	called in pairs bracketing the blocking call.	2741	called in pairs bracketing the blocking call.
1804		2742
1805	Their main purpose is to integrate other event mechanisms into libev and	2743	Their main purpose is to integrate other event mechanisms into libev and
1806	their use is somewhat advanced. This could be used, for example, to track	2744	their use is somewhat advanced. They could be used, for example, to track
1807	variable changes, implement your own watchers, integrate net-snmp or a	2745	variable changes, implement your own watchers, integrate net-snmp or a
1808	coroutine library and lots more. They are also occasionally useful if	2746	coroutine library and lots more. They are also occasionally useful if
1809	you cache some data and want to flush it before blocking (for example,	2747	you cache some data and want to flush it before blocking (for example,
1810	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2748	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1811	watcher).	2749	watcher).
1812		2750
1813	This is done by examining in each prepare call which file descriptors need	2751	This is done by examining in each prepare call which file descriptors
1814	to be watched by the other library, registering C<ev_io> watchers for	2752	need to be watched by the other library, registering C<ev_io> watchers
1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2753	for them and starting an C<ev_timer> watcher for any timeouts (many
1816	provide just this functionality). Then, in the check watcher you check for	2754	libraries provide exactly this functionality). Then, in the check watcher,
1817	any events that occured (by checking the pending status of all watchers	2755	you check for any events that occurred (by checking the pending status
1818	and stopping them) and call back into the library. The I/O and timer	2756	of all watchers and stopping them) and call back into the library. The
1819	callbacks will never actually be called (but must be valid nevertheless,	2757	I/O and timer callbacks will never actually be called (but must be valid
1820	because you never know, you know?).	2758	nevertheless, because you never know, you know?).
1821		2759
1822	As another example, the Perl Coro module uses these hooks to integrate	2760	As another example, the Perl Coro module uses these hooks to integrate
1823	coroutines into libev programs, by yielding to other active coroutines	2761	coroutines into libev programs, by yielding to other active coroutines
1824	during each prepare and only letting the process block if no coroutines	2762	during each prepare and only letting the process block if no coroutines
1825	are ready to run (it's actually more complicated: it only runs coroutines	2763	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1828	loop from blocking if lower-priority coroutines are active, thus mapping	2766	loop from blocking if lower-priority coroutines are active, thus mapping
1829	low-priority coroutines to idle/background tasks).	2767	low-priority coroutines to idle/background tasks).
1830		2768
1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2769	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1832	priority, to ensure that they are being run before any other watchers	2770	priority, to ensure that they are being run before any other watchers
		2771	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2772
1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2773	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1834	too) should not activate ("feed") events into libev. While libev fully	2774	activate ("feed") events into libev. While libev fully supports this, they
1835	supports this, they will be called before other C<ev_check> watchers	2775	might get executed before other C<ev_check> watchers did their job. As
1836	did their job. As C<ev_check> watchers are often used to embed other	2776	C<ev_check> watchers are often used to embed other (non-libev) event
1837	(non-libev) event loops those other event loops might be in an unusable	2777	loops those other event loops might be in an unusable state until their
1838	state until their C<ev_check> watcher ran (always remind yourself to	2778	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1839	coexist peacefully with others).	2779	others).
1840		2780
1841	=head3 Watcher-Specific Functions and Data Members	2781	=head3 Watcher-Specific Functions and Data Members
1842		2782
1843	=over 4	2783	=over 4
1844		2784
…		…
1846		2786
1847	=item ev_check_init (ev_check *, callback)	2787	=item ev_check_init (ev_check *, callback)
1848		2788
1849	Initialises and configures the prepare or check watcher - they have no	2789	Initialises and configures the prepare or check watcher - they have no
1850	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2790	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1851	macros, but using them is utterly, utterly and completely pointless.	2791	macros, but using them is utterly, utterly, utterly and completely
		2792	pointless.
1852		2793
1853	=back	2794	=back
1854		2795
1855	=head3 Examples	2796	=head3 Examples
1856		2797
1857	There are a number of principal ways to embed other event loops or modules	2798	There are a number of principal ways to embed other event loops or modules
1858	into libev. Here are some ideas on how to include libadns into libev	2799	into libev. Here are some ideas on how to include libadns into libev
1859	(there is a Perl module named C<EV::ADNS> that does this, which you could	2800	(there is a Perl module named C<EV::ADNS> that does this, which you could
1860	use for an actually working example. Another Perl module named C<EV::Glib>	2801	use as a working example. Another Perl module named C<EV::Glib> embeds a
1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2802	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1862	into the Glib event loop).	2803	Glib event loop).
1863		2804
1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2805	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1865	and in a check watcher, destroy them and call into libadns. What follows	2806	and in a check watcher, destroy them and call into libadns. What follows
1866	is pseudo-code only of course. This requires you to either use a low	2807	is pseudo-code only of course. This requires you to either use a low
1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2808	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1868	the callbacks for the IO/timeout watchers might not have been called yet.	2809	the callbacks for the IO/timeout watchers might not have been called yet.
1869		2810
1870	static ev_io iow [nfd];	2811	static ev_io iow [nfd];
1871	static ev_timer tw;	2812	static ev_timer tw;
1872		2813
1873	static void	2814	static void
1874	io_cb (ev_loop *loop, ev_io *w, int revents)	2815	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1875	{	2816	{
1876	}	2817	}
1877		2818
1878	// create io watchers for each fd and a timer before blocking	2819	// create io watchers for each fd and a timer before blocking
1879	static void	2820	static void
1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2821	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1881	{	2822	{
1882	int timeout = 3600000;	2823	int timeout = 3600000;
1883	struct pollfd fds [nfd];	2824	struct pollfd fds [nfd];
1884	// actual code will need to loop here and realloc etc.	2825	// actual code will need to loop here and realloc etc.
1885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2826	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1886		2827
1887	/* the callback is illegal, but won't be called as we stop during check */	2828	/* the callback is illegal, but won't be called as we stop during check */
1888	ev_timer_init (&tw, 0, timeout * 1e-3);	2829	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1889	ev_timer_start (loop, &tw);	2830	ev_timer_start (loop, &tw);
1890		2831
1891	// create one ev_io per pollfd	2832	// create one ev_io per pollfd
1892	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
1893	{	2834	{
1894	ev_io_init (iow + i, io_cb, fds [i].fd,	2835	ev_io_init (iow + i, io_cb, fds [i].fd,
1895	((fds [i].events & POLLIN ? EV_READ : 0)	2836	((fds [i].events & POLLIN ? EV_READ : 0)
1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2837	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1897		2838
1898	fds [i].revents = 0;	2839	fds [i].revents = 0;
1899	ev_io_start (loop, iow + i);	2840	ev_io_start (loop, iow + i);
1900	}	2841	}
1901	}	2842	}
1902		2843
1903	// stop all watchers after blocking	2844	// stop all watchers after blocking
1904	static void	2845	static void
1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2846	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1906	{	2847	{
1907	ev_timer_stop (loop, &tw);	2848	ev_timer_stop (loop, &tw);
1908		2849
1909	for (int i = 0; i < nfd; ++i)	2850	for (int i = 0; i < nfd; ++i)
1910	{	2851	{
1911	// set the relevant poll flags	2852	// set the relevant poll flags
1912	// could also call adns_processreadable etc. here	2853	// could also call adns_processreadable etc. here
1913	struct pollfd *fd = fds + i;	2854	struct pollfd *fd = fds + i;
1914	int revents = ev_clear_pending (iow + i);	2855	int revents = ev_clear_pending (iow + i);
1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2856	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2857	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1917		2858
1918	// now stop the watcher	2859	// now stop the watcher
1919	ev_io_stop (loop, iow + i);	2860	ev_io_stop (loop, iow + i);
1920	}	2861	}
1921		2862
1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2863	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1923	}	2864	}
1924		2865
1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2866	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1926	in the prepare watcher and would dispose of the check watcher.	2867	in the prepare watcher and would dispose of the check watcher.
1927		2868
1928	Method 3: If the module to be embedded supports explicit event	2869	Method 3: If the module to be embedded supports explicit event
1929	notification (adns does), you can also make use of the actual watcher	2870	notification (libadns does), you can also make use of the actual watcher
1930	callbacks, and only destroy/create the watchers in the prepare watcher.	2871	callbacks, and only destroy/create the watchers in the prepare watcher.
1931		2872
1932	static void	2873	static void
1933	timer_cb (EV_P_ ev_timer *w, int revents)	2874	timer_cb (EV_P_ ev_timer *w, int revents)
1934	{	2875	{
1935	adns_state ads = (adns_state)w->data;	2876	adns_state ads = (adns_state)w->data;
1936	update_now (EV_A);	2877	update_now (EV_A);
1937		2878
1938	adns_processtimeouts (ads, &tv_now);	2879	adns_processtimeouts (ads, &tv_now);
1939	}	2880	}
1940		2881
1941	static void	2882	static void
1942	io_cb (EV_P_ ev_io *w, int revents)	2883	io_cb (EV_P_ ev_io *w, int revents)
1943	{	2884	{
1944	adns_state ads = (adns_state)w->data;	2885	adns_state ads = (adns_state)w->data;
1945	update_now (EV_A);	2886	update_now (EV_A);
1946		2887
1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2888	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2889	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1949	}	2890	}
1950		2891
1951	// do not ever call adns_afterpoll	2892	// do not ever call adns_afterpoll
1952		2893
1953	Method 4: Do not use a prepare or check watcher because the module you	2894	Method 4: Do not use a prepare or check watcher because the module you
1954	want to embed is too inflexible to support it. Instead, youc na override	2895	want to embed is not flexible enough to support it. Instead, you can
1955	their poll function. The drawback with this solution is that the main	2896	override their poll function. The drawback with this solution is that the
1956	loop is now no longer controllable by EV. The C<Glib::EV> module does	2897	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1957	this.	2898	this approach, effectively embedding EV as a client into the horrible
		2899	libglib event loop.
1958		2900
1959	static gint	2901	static gint
1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2902	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1961	{	2903	{
1962	int got_events = 0;	2904	int got_events = 0;
1963		2905
1964	for (n = 0; n < nfds; ++n)	2906	for (n = 0; n < nfds; ++n)
1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2907	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1966		2908
1967	if (timeout >= 0)	2909	if (timeout >= 0)
1968	// create/start timer	2910	// create/start timer
1969		2911
1970	// poll	2912	// poll
1971	ev_loop (EV_A_ 0);	2913	ev_run (EV_A_ 0);
1972		2914
1973	// stop timer again	2915	// stop timer again
1974	if (timeout >= 0)	2916	if (timeout >= 0)
1975	ev_timer_stop (EV_A_ &to);	2917	ev_timer_stop (EV_A_ &to);
1976		2918
1977	// stop io watchers again - their callbacks should have set	2919	// stop io watchers again - their callbacks should have set
1978	for (n = 0; n < nfds; ++n)	2920	for (n = 0; n < nfds; ++n)
1979	ev_io_stop (EV_A_ iow [n]);	2921	ev_io_stop (EV_A_ iow [n]);
1980		2922
1981	return got_events;	2923	return got_events;
1982	}	2924	}
1983		2925
1984		2926
1985	=head2 C<ev_embed> - when one backend isn't enough...	2927	=head2 C<ev_embed> - when one backend isn't enough...
1986		2928
1987	This is a rather advanced watcher type that lets you embed one event loop	2929	This is a rather advanced watcher type that lets you embed one event loop
…		…
1993	prioritise I/O.	2935	prioritise I/O.
1994		2936
1995	As an example for a bug workaround, the kqueue backend might only support	2937	As an example for a bug workaround, the kqueue backend might only support
1996	sockets on some platform, so it is unusable as generic backend, but you	2938	sockets on some platform, so it is unusable as generic backend, but you
1997	still want to make use of it because you have many sockets and it scales	2939	still want to make use of it because you have many sockets and it scales
1998	so nicely. In this case, you would create a kqueue-based loop and embed it	2940	so nicely. In this case, you would create a kqueue-based loop and embed
1999	into your default loop (which might use e.g. poll). Overall operation will	2941	it into your default loop (which might use e.g. poll). Overall operation
2000	be a bit slower because first libev has to poll and then call kevent, but	2942	will be a bit slower because first libev has to call C<poll> and then
2001	at least you can use both at what they are best.	2943	C<kevent>, but at least you can use both mechanisms for what they are
		2944	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2002		2945
2003	As for prioritising I/O: rarely you have the case where some fds have	2946	As for prioritising I/O: under rare circumstances you have the case where
2004	to be watched and handled very quickly (with low latency), and even	2947	some fds have to be watched and handled very quickly (with low latency),
2005	priorities and idle watchers might have too much overhead. In this case	2948	and even priorities and idle watchers might have too much overhead. In
2006	you would put all the high priority stuff in one loop and all the rest in	2949	this case you would put all the high priority stuff in one loop and all
2007	a second one, and embed the second one in the first.	2950	the rest in a second one, and embed the second one in the first.
2008		2951
2009	As long as the watcher is active, the callback will be invoked every time	2952	As long as the watcher is active, the callback will be invoked every
2010	there might be events pending in the embedded loop. The callback must then	2953	time there might be events pending in the embedded loop. The callback
2011	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2954	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2012	their callbacks (you could also start an idle watcher to give the embedded	2955	sweep and invoke their callbacks (the callback doesn't need to invoke the
2013	loop strictly lower priority for example). You can also set the callback	2956	C<ev_embed_sweep> function directly, it could also start an idle watcher
2014	to C<0>, in which case the embed watcher will automatically execute the	2957	to give the embedded loop strictly lower priority for example).
2015	embedded loop sweep.
2016		2958
2017	As long as the watcher is started it will automatically handle events. The	2959	You can also set the callback to C<0>, in which case the embed watcher
2018	callback will be invoked whenever some events have been handled. You can	2960	will automatically execute the embedded loop sweep whenever necessary.
2019	set the callback to C<0> to avoid having to specify one if you are not
2020	interested in that.
2021		2961
2022	Also, there have not currently been made special provisions for forking:	2962	Fork detection will be handled transparently while the C<ev_embed> watcher
2023	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2963	is active, i.e., the embedded loop will automatically be forked when the
2024	but you will also have to stop and restart any C<ev_embed> watchers	2964	embedding loop forks. In other cases, the user is responsible for calling
2025	yourself.	2965	C<ev_loop_fork> on the embedded loop.
2026		2966
2027	Unfortunately, not all backends are embeddable, only the ones returned by	2967	Unfortunately, not all backends are embeddable: only the ones returned by
2028	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2968	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2029	portable one.	2969	portable one.
2030		2970
2031	So when you want to use this feature you will always have to be prepared	2971	So when you want to use this feature you will always have to be prepared
2032	that you cannot get an embeddable loop. The recommended way to get around	2972	that you cannot get an embeddable loop. The recommended way to get around
2033	this is to have a separate variables for your embeddable loop, try to	2973	this is to have a separate variables for your embeddable loop, try to
2034	create it, and if that fails, use the normal loop for everything.	2974	create it, and if that fails, use the normal loop for everything.
2035		2975
		2976	=head3 C<ev_embed> and fork
		2977
		2978	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2979	automatically be applied to the embedded loop as well, so no special
		2980	fork handling is required in that case. When the watcher is not running,
		2981	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2982	as applicable.
		2983
2036	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2037		2985
2038	=over 4	2986	=over 4
2039		2987
2040	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2988	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2043		2991
2044	Configures the watcher to embed the given loop, which must be	2992	Configures the watcher to embed the given loop, which must be
2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2993	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2046	invoked automatically, otherwise it is the responsibility of the callback	2994	invoked automatically, otherwise it is the responsibility of the callback
2047	to invoke it (it will continue to be called until the sweep has been done,	2995	to invoke it (it will continue to be called until the sweep has been done,
2048	if you do not want thta, you need to temporarily stop the embed watcher).	2996	if you do not want that, you need to temporarily stop the embed watcher).
2049		2997
2050	=item ev_embed_sweep (loop, ev_embed *)	2998	=item ev_embed_sweep (loop, ev_embed *)
2051		2999
2052	Make a single, non-blocking sweep over the embedded loop. This works	3000	Make a single, non-blocking sweep over the embedded loop. This works
2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3001	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2054	apropriate way for embedded loops.	3002	appropriate way for embedded loops.
2055		3003
2056	=item struct ev_loop *other [read-only]	3004	=item struct ev_loop *other [read-only]
2057		3005
2058	The embedded event loop.	3006	The embedded event loop.
2059		3007
…		…
2061		3009
2062	=head3 Examples	3010	=head3 Examples
2063		3011
2064	Example: Try to get an embeddable event loop and embed it into the default	3012	Example: Try to get an embeddable event loop and embed it into the default
2065	event loop. If that is not possible, use the default loop. The default	3013	event loop. If that is not possible, use the default loop. The default
2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3014	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3015	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2068	used).	3016	used).
2069		3017
2070	struct ev_loop *loop_hi = ev_default_init (0);	3018	struct ev_loop *loop_hi = ev_default_init (0);
2071	struct ev_loop *loop_lo = 0;	3019	struct ev_loop *loop_lo = 0;
2072	struct ev_embed embed;	3020	ev_embed embed;
2073		3021
2074	// see if there is a chance of getting one that works	3022	// see if there is a chance of getting one that works
2075	// (remember that a flags value of 0 means autodetection)	3023	// (remember that a flags value of 0 means autodetection)
2076	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3024	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2077	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3025	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2078	: 0;	3026	: 0;
2079		3027
2080	// if we got one, then embed it, otherwise default to loop_hi	3028	// if we got one, then embed it, otherwise default to loop_hi
2081	if (loop_lo)	3029	if (loop_lo)
2082	{	3030	{
2083	ev_embed_init (&embed, 0, loop_lo);	3031	ev_embed_init (&embed, 0, loop_lo);
2084	ev_embed_start (loop_hi, &embed);	3032	ev_embed_start (loop_hi, &embed);
2085	}	3033	}
2086	else	3034	else
2087	loop_lo = loop_hi;	3035	loop_lo = loop_hi;
2088		3036
2089	Example: Check if kqueue is available but not recommended and create	3037	Example: Check if kqueue is available but not recommended and create
2090	a kqueue backend for use with sockets (which usually work with any	3038	a kqueue backend for use with sockets (which usually work with any
2091	kqueue implementation). Store the kqueue/socket-only event loop in	3039	kqueue implementation). Store the kqueue/socket-only event loop in
2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3040	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2093		3041
2094	struct ev_loop *loop = ev_default_init (0);	3042	struct ev_loop *loop = ev_default_init (0);
2095	struct ev_loop *loop_socket = 0;	3043	struct ev_loop *loop_socket = 0;
2096	struct ev_embed embed;	3044	ev_embed embed;
2097		3045
2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3046	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3047	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2100	{	3048	{
2101	ev_embed_init (&embed, 0, loop_socket);	3049	ev_embed_init (&embed, 0, loop_socket);
2102	ev_embed_start (loop, &embed);	3050	ev_embed_start (loop, &embed);
2103	}	3051	}
2104		3052
2105	if (!loop_socket)	3053	if (!loop_socket)
2106	loop_socket = loop;	3054	loop_socket = loop;
2107		3055
2108	// now use loop_socket for all sockets, and loop for everything else	3056	// now use loop_socket for all sockets, and loop for everything else
2109		3057
2110		3058
2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3059	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2112		3060
2113	Fork watchers are called when a C<fork ()> was detected (usually because	3061	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2116	event loop blocks next and before C<ev_check> watchers are being called,	3064	event loop blocks next and before C<ev_check> watchers are being called,
2117	and only in the child after the fork. If whoever good citizen calling	3065	and only in the child after the fork. If whoever good citizen calling
2118	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2119	handlers will be invoked, too, of course.	3067	handlers will be invoked, too, of course.
2120		3068
		3069	=head3 The special problem of life after fork - how is it possible?
		3070
		3071	Most uses of C<fork()> consist of forking, then some simple calls to set
		3072	up/change the process environment, followed by a call to C<exec()>. This
		3073	sequence should be handled by libev without any problems.
		3074
		3075	This changes when the application actually wants to do event handling
		3076	in the child, or both parent in child, in effect "continuing" after the
		3077	fork.
		3078
		3079	The default mode of operation (for libev, with application help to detect
		3080	forks) is to duplicate all the state in the child, as would be expected
		3081	when I<either> the parent I<or> the child process continues.
		3082
		3083	When both processes want to continue using libev, then this is usually the
		3084	wrong result. In that case, usually one process (typically the parent) is
		3085	supposed to continue with all watchers in place as before, while the other
		3086	process typically wants to start fresh, i.e. without any active watchers.
		3087
		3088	The cleanest and most efficient way to achieve that with libev is to
		3089	simply create a new event loop, which of course will be "empty", and
		3090	use that for new watchers. This has the advantage of not touching more
		3091	memory than necessary, and thus avoiding the copy-on-write, and the
		3092	disadvantage of having to use multiple event loops (which do not support
		3093	signal watchers).
		3094
		3095	When this is not possible, or you want to use the default loop for
		3096	other reasons, then in the process that wants to start "fresh", call
		3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3098	Destroying the default loop will "orphan" (not stop) all registered
		3099	watchers, so you have to be careful not to execute code that modifies
		3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
		3102
2121	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
2122		3104
2123	=over 4	3105	=over 4
2124		3106
2125	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
2126		3108
2127	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
2128	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2129	believe me.	3111	really.
2130		3112
2131	=back	3113	=back
2132		3114
2133		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
		3154
		3155
2134	=head2 C<ev_async> - how to wake up another event loop	3156	=head2 C<ev_async> - how to wake up an event loop
2135		3157
2136	In general, you cannot use an C<ev_loop> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
2137	asynchronous sources such as signal handlers (as opposed to multiple event	3159	asynchronous sources such as signal handlers (as opposed to multiple event
2138	loops - those are of course safe to use in different threads).	3160	loops - those are of course safe to use in different threads).
2139		3161
2140	Sometimes, however, you need to wake up another event loop you do not	3162	Sometimes, however, you need to wake up an event loop you do not control,
2141	control, for example because it belongs to another thread. This is what	3163	for example because it belongs to another thread. This is what C<ev_async>
2142	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3164	watchers do: as long as the C<ev_async> watcher is active, you can signal
2143	can signal it by calling C<ev_async_send>, which is thread- and signal	3165	it by calling C<ev_async_send>, which is thread- and signal safe.
2144	safe.
2145		3166
2146	This functionality is very similar to C<ev_signal> watchers, as signals,	3167	This functionality is very similar to C<ev_signal> watchers, as signals,
2147	too, are asynchronous in nature, and signals, too, will be compressed	3168	too, are asynchronous in nature, and signals, too, will be compressed
2148	(i.e. the number of callback invocations may be less than the number of	3169	(i.e. the number of callback invocations may be less than the number of
2149	C<ev_async_sent> calls).	3170	C<ev_async_sent> calls).
…		…
2154	=head3 Queueing	3175	=head3 Queueing
2155		3176
2156	C<ev_async> does not support queueing of data in any way. The reason	3177	C<ev_async> does not support queueing of data in any way. The reason
2157	is that the author does not know of a simple (or any) algorithm for a	3178	is that the author does not know of a simple (or any) algorithm for a
2158	multiple-writer-single-reader queue that works in all cases and doesn't	3179	multiple-writer-single-reader queue that works in all cases and doesn't
2159	need elaborate support such as pthreads.	3180	need elaborate support such as pthreads or unportable memory access
		3181	semantics.
2160		3182
2161	That means that if you want to queue data, you have to provide your own	3183	That means that if you want to queue data, you have to provide your own
2162	queue. But at least I can tell you would implement locking around your	3184	queue. But at least I can tell you how to implement locking around your
2163	queue:	3185	queue:
2164		3186
2165	=over 4	3187	=over 4
2166		3188
2167	=item queueing from a signal handler context	3189	=item queueing from a signal handler context
2168		3190
2169	To implement race-free queueing, you simply add to the queue in the signal	3191	To implement race-free queueing, you simply add to the queue in the signal
2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3192	handler but you block the signal handler in the watcher callback. Here is
2171	some fictitiuous SIGUSR1 handler:	3193	an example that does that for some fictitious SIGUSR1 handler:
2172		3194
2173	static ev_async mysig;	3195	static ev_async mysig;
2174		3196
2175	static void	3197	static void
2176	sigusr1_handler (void)	3198	sigusr1_handler (void)
…		…
2242	=over 4	3264	=over 4
2243		3265
2244	=item ev_async_init (ev_async *, callback)	3266	=item ev_async_init (ev_async *, callback)
2245		3267
2246	Initialises and configures the async watcher - it has no parameters of any	3268	Initialises and configures the async watcher - it has no parameters of any
2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3269	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2248	believe me.	3270	trust me.
2249		3271
2250	=item ev_async_send (loop, ev_async *)	3272	=item ev_async_send (loop, ev_async *)
2251		3273
2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2254	C<ev_feed_event>, this call is safe to do in other threads, signal or	3276	C<ev_feed_event>, this call is safe to do from other threads, signal or
2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2256	section below on what exactly this means).	3278	section below on what exactly this means).
2257		3279
		3280	Note that, as with other watchers in libev, multiple events might get
		3281	compressed into a single callback invocation (another way to look at this
		3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3283	reset when the event loop detects that).
		3284
2258	This call incurs the overhead of a syscall only once per loop iteration,	3285	This call incurs the overhead of a system call only once per event loop
2259	so while the overhead might be noticable, it doesn't apply to repeated	3286	iteration, so while the overhead might be noticeable, it doesn't apply to
2260	calls to C<ev_async_send>.	3287	repeated calls to C<ev_async_send> for the same event loop.
		3288
		3289	=item bool = ev_async_pending (ev_async *)
		3290
		3291	Returns a non-zero value when C<ev_async_send> has been called on the
		3292	watcher but the event has not yet been processed (or even noted) by the
		3293	event loop.
		3294
		3295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		3296	the loop iterates next and checks for the watcher to have become active,
		3297	it will reset the flag again. C<ev_async_pending> can be used to very
		3298	quickly check whether invoking the loop might be a good idea.
		3299
		3300	Not that this does I<not> check whether the watcher itself is pending,
		3301	only whether it has been requested to make this watcher pending: there
		3302	is a time window between the event loop checking and resetting the async
		3303	notification, and the callback being invoked.
2261		3304
2262	=back	3305	=back
2263		3306
2264		3307
2265	=head1 OTHER FUNCTIONS	3308	=head1 OTHER FUNCTIONS
…		…
2269	=over 4	3312	=over 4
2270		3313
2271	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3314	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2272		3315
2273	This function combines a simple timer and an I/O watcher, calls your	3316	This function combines a simple timer and an I/O watcher, calls your
2274	callback on whichever event happens first and automatically stop both	3317	callback on whichever event happens first and automatically stops both
2275	watchers. This is useful if you want to wait for a single event on an fd	3318	watchers. This is useful if you want to wait for a single event on an fd
2276	or timeout without having to allocate/configure/start/stop/free one or	3319	or timeout without having to allocate/configure/start/stop/free one or
2277	more watchers yourself.	3320	more watchers yourself.
2278		3321
2279	If C<fd> is less than 0, then no I/O watcher will be started and events	3322	If C<fd> is less than 0, then no I/O watcher will be started and the
2280	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3323	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2281	C<events> set will be craeted and started.	3324	the given C<fd> and C<events> set will be created and started.
2282		3325
2283	If C<timeout> is less than 0, then no timeout watcher will be	3326	If C<timeout> is less than 0, then no timeout watcher will be
2284	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3327	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2285	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3328	repeat = 0) will be started. C<0> is a valid timeout.
2286	dubious value.
2287		3329
2288	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3330	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2289	passed an C<revents> set like normal event callbacks (a combination of	3331	passed an C<revents> set like normal event callbacks (a combination of
2290	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3332	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2291	value passed to C<ev_once>:	3333	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3334	a timeout and an io event at the same time - you probably should give io
		3335	events precedence.
2292		3336
		3337	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3338
2293	static void stdin_ready (int revents, void *arg)	3339	static void stdin_ready (int revents, void *arg)
2294	{	3340	{
2295	if (revents & EV_TIMEOUT)
2296	/* doh, nothing entered */;
2297	else if (revents & EV_READ)	3341	if (revents & EV_READ)
2298	/* stdin might have data for us, joy! */;	3342	/* stdin might have data for us, joy! */;
		3343	else if (revents & EV_TIMER)
		3344	/* doh, nothing entered */;
2299	}	3345	}
2300		3346
2301	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2302		3348
2303	=item ev_feed_event (ev_loop *, watcher *, int revents)
2304
2305	Feeds the given event set into the event loop, as if the specified event
2306	had happened for the specified watcher (which must be a pointer to an
2307	initialised but not necessarily started event watcher).
2308
2309	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3349	=item ev_feed_fd_event (loop, int fd, int revents)
2310		3350
2311	Feed an event on the given fd, as if a file descriptor backend detected	3351	Feed an event on the given fd, as if a file descriptor backend detected
2312	the given events it.	3352	the given events it.
2313		3353
2314	=item ev_feed_signal_event (ev_loop *loop, int signum)	3354	=item ev_feed_signal_event (loop, int signum)
2315		3355
2316	Feed an event as if the given signal occured (C<loop> must be the default	3356	Feed an event as if the given signal occurred (C<loop> must be the default
2317	loop!).	3357	loop!).
2318		3358
2319	=back	3359	=back
2320		3360
2321		3361
…		…
2337		3377
2338	=item * Priorities are not currently supported. Initialising priorities	3378	=item * Priorities are not currently supported. Initialising priorities
2339	will fail and all watchers will have the same priority, even though there	3379	will fail and all watchers will have the same priority, even though there
2340	is an ev_pri field.	3380	is an ev_pri field.
2341		3381
		3382	=item * In libevent, the last base created gets the signals, in libev, the
		3383	first base created (== the default loop) gets the signals.
		3384
2342	=item * Other members are not supported.	3385	=item * Other members are not supported.
2343		3386
2344	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3387	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2345	to use the libev header file and library.	3388	to use the libev header file and library.
2346		3389
2347	=back	3390	=back
2348		3391
2349	=head1 C++ SUPPORT	3392	=head1 C++ SUPPORT
2350		3393
2351	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3394	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2352	you to use some convinience methods to start/stop watchers and also change	3395	you to use some convenience methods to start/stop watchers and also change
2353	the callback model to a model using method callbacks on objects.	3396	the callback model to a model using method callbacks on objects.
2354		3397
2355	To use it,	3398	To use it,
2356		3399
2357	#include <ev++.h>	3400	#include <ev++.h>
2358		3401
2359	This automatically includes F<ev.h> and puts all of its definitions (many	3402	This automatically includes F<ev.h> and puts all of its definitions (many
2360	of them macros) into the global namespace. All C++ specific things are	3403	of them macros) into the global namespace. All C++ specific things are
2361	put into the C<ev> namespace. It should support all the same embedding	3404	put into the C<ev> namespace. It should support all the same embedding
2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3405	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2396		3439
2397	=over 4	3440	=over 4
2398		3441
2399	=item ev::TYPE::TYPE ()	3442	=item ev::TYPE::TYPE ()
2400		3443
2401	=item ev::TYPE::TYPE (struct ev_loop *)	3444	=item ev::TYPE::TYPE (loop)
2402		3445
2403	=item ev::TYPE::~TYPE	3446	=item ev::TYPE::~TYPE
2404		3447
2405	The constructor (optionally) takes an event loop to associate the watcher	3448	The constructor (optionally) takes an event loop to associate the watcher
2406	with. If it is omitted, it will use C<EV_DEFAULT>.	3449	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2429	your compiler is good :), then the method will be fully inlined into the	3472	your compiler is good :), then the method will be fully inlined into the
2430	thunking function, making it as fast as a direct C callback.	3473	thunking function, making it as fast as a direct C callback.
2431		3474
2432	Example: simple class declaration and watcher initialisation	3475	Example: simple class declaration and watcher initialisation
2433		3476
2434	struct myclass	3477	struct myclass
2435	{	3478	{
2436	void io_cb (ev::io &w, int revents) { }	3479	void io_cb (ev::io &w, int revents) { }
2437	}	3480	}
2438		3481
2439	myclass obj;	3482	myclass obj;
2440	ev::io iow;	3483	ev::io iow;
2441	iow.set <myclass, &myclass::io_cb> (&obj);	3484	iow.set <myclass, &myclass::io_cb> (&obj);
		3485
		3486	=item w->set (object *)
		3487
		3488	This is a variation of a method callback - leaving out the method to call
		3489	will default the method to C<operator ()>, which makes it possible to use
		3490	functor objects without having to manually specify the C<operator ()> all
		3491	the time. Incidentally, you can then also leave out the template argument
		3492	list.
		3493
		3494	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3495	int revents)>.
		3496
		3497	See the method-C<set> above for more details.
		3498
		3499	Example: use a functor object as callback.
		3500
		3501	struct myfunctor
		3502	{
		3503	void operator() (ev::io &w, int revents)
		3504	{
		3505	...
		3506	}
		3507	}
		3508
		3509	myfunctor f;
		3510
		3511	ev::io w;
		3512	w.set (&f);
2442		3513
2443	=item w->set<function> (void *data = 0)	3514	=item w->set<function> (void *data = 0)
2444		3515
2445	Also sets a callback, but uses a static method or plain function as	3516	Also sets a callback, but uses a static method or plain function as
2446	callback. The optional C<data> argument will be stored in the watcher's	3517	callback. The optional C<data> argument will be stored in the watcher's
…		…
2448		3519
2449	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3520	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2450		3521
2451	See the method-C<set> above for more details.	3522	See the method-C<set> above for more details.
2452		3523
2453	Example:	3524	Example: Use a plain function as callback.
2454		3525
2455	static void io_cb (ev::io &w, int revents) { }	3526	static void io_cb (ev::io &w, int revents) { }
2456	iow.set <io_cb> ();	3527	iow.set <io_cb> ();
2457		3528
2458	=item w->set (struct ev_loop *)	3529	=item w->set (loop)
2459		3530
2460	Associates a different C<struct ev_loop> with this watcher. You can only	3531	Associates a different C<struct ev_loop> with this watcher. You can only
2461	do this when the watcher is inactive (and not pending either).	3532	do this when the watcher is inactive (and not pending either).
2462		3533
2463	=item w->set ([args])	3534	=item w->set ([arguments])
2464		3535
2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2466	called at least once. Unlike the C counterpart, an active watcher gets	3537	method or a suitable start method must be called at least once. Unlike the
2467	automatically stopped and restarted when reconfiguring it with this	3538	C counterpart, an active watcher gets automatically stopped and restarted
2468	method.	3539	when reconfiguring it with this method.
2469		3540
2470	=item w->start ()	3541	=item w->start ()
2471		3542
2472	Starts the watcher. Note that there is no C<loop> argument, as the	3543	Starts the watcher. Note that there is no C<loop> argument, as the
2473	constructor already stores the event loop.	3544	constructor already stores the event loop.
2474		3545
		3546	=item w->start ([arguments])
		3547
		3548	Instead of calling C<set> and C<start> methods separately, it is often
		3549	convenient to wrap them in one call. Uses the same type of arguments as
		3550	the configure C<set> method of the watcher.
		3551
2475	=item w->stop ()	3552	=item w->stop ()
2476		3553
2477	Stops the watcher if it is active. Again, no C<loop> argument.	3554	Stops the watcher if it is active. Again, no C<loop> argument.
2478		3555
2479	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3556	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2491		3568
2492	=back	3569	=back
2493		3570
2494	=back	3571	=back
2495		3572
2496	Example: Define a class with an IO and idle watcher, start one of them in	3573	Example: Define a class with two I/O and idle watchers, start the I/O
2497	the constructor.	3574	watchers in the constructor.
2498		3575
2499	class myclass	3576	class myclass
2500	{	3577	{
2501	ev::io io; void io_cb (ev::io &w, int revents);	3578	ev::io io ; void io_cb (ev::io &w, int revents);
		3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2502	ev:idle idle void idle_cb (ev::idle &w, int revents);	3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2503		3581
2504	myclass (int fd)	3582	myclass (int fd)
2505	{	3583	{
2506	io .set <myclass, &myclass::io_cb > (this);	3584	io .set <myclass, &myclass::io_cb > (this);
		3585	io2 .set <myclass, &myclass::io2_cb > (this);
2507	idle.set <myclass, &myclass::idle_cb> (this);	3586	idle.set <myclass, &myclass::idle_cb> (this);
2508		3587
2509	io.start (fd, ev::READ);	3588	io.set (fd, ev::WRITE); // configure the watcher
		3589	io.start (); // start it whenever convenient
		3590
		3591	io2.start (fd, ev::READ); // set + start in one call
2510	}	3592	}
2511	};	3593	};
2512		3594
2513		3595
2514	=head1 OTHER LANGUAGE BINDINGS	3596	=head1 OTHER LANGUAGE BINDINGS
2515		3597
2516	Libev does not offer other language bindings itself, but bindings for a	3598	Libev does not offer other language bindings itself, but bindings for a
2517	numbe rof languages exist in the form of third-party packages. If you know	3599	number of languages exist in the form of third-party packages. If you know
2518	any interesting language binding in addition to the ones listed here, drop	3600	any interesting language binding in addition to the ones listed here, drop
2519	me a note.	3601	me a note.
2520		3602
2521	=over 4	3603	=over 4
2522		3604
2523	=item Perl	3605	=item Perl
2524		3606
2525	The EV module implements the full libev API and is actually used to test	3607	The EV module implements the full libev API and is actually used to test
2526	libev. EV is developed together with libev. Apart from the EV core module,	3608	libev. EV is developed together with libev. Apart from the EV core module,
2527	there are additional modules that implement libev-compatible interfaces	3609	there are additional modules that implement libev-compatible interfaces
2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3610	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3611	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3612	and C<EV::Glib>).
2530		3613
2531	It can be found and installed via CPAN, its homepage is found at	3614	It can be found and installed via CPAN, its homepage is at
2532	L<http://software.schmorp.de/pkg/EV>.	3615	L<http://software.schmorp.de/pkg/EV>.
2533		3616
		3617	=item Python
		3618
		3619	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3620	seems to be quite complete and well-documented.
		3621
2534	=item Ruby	3622	=item Ruby
2535		3623
2536	Tony Arcieri has written a ruby extension that offers access to a subset	3624	Tony Arcieri has written a ruby extension that offers access to a subset
2537	of the libev API and adds filehandle abstractions, asynchronous DNS and	3625	of the libev API and adds file handle abstractions, asynchronous DNS and
2538	more on top of it. It can be found via gem servers. Its homepage is at	3626	more on top of it. It can be found via gem servers. Its homepage is at
2539	L<http://rev.rubyforge.org/>.	3627	L<http://rev.rubyforge.org/>.
2540		3628
		3629	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3630	makes rev work even on mingw.
		3631
		3632	=item Haskell
		3633
		3634	A haskell binding to libev is available at
		3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3636
2541	=item D	3637	=item D
2542		3638
2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3641
		3642	=item Ocaml
		3643
		3644	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3646
		3647	=item Lua
		3648
		3649	Brian Maher has written a partial interface to libev for lua (at the
		3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3651	L<http://github.com/brimworks/lua-ev>.
2545		3652
2546	=back	3653	=back
2547		3654
2548		3655
2549	=head1 MACRO MAGIC	3656	=head1 MACRO MAGIC
2550		3657
2551	Libev can be compiled with a variety of options, the most fundamantal	3658	Libev can be compiled with a variety of options, the most fundamental
2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3659	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2553	functions and callbacks have an initial C<struct ev_loop *> argument.	3660	functions and callbacks have an initial C<struct ev_loop *> argument.
2554		3661
2555	To make it easier to write programs that cope with either variant, the	3662	To make it easier to write programs that cope with either variant, the
2556	following macros are defined:	3663	following macros are defined:
…		…
2561		3668
2562	This provides the loop I<argument> for functions, if one is required ("ev	3669	This provides the loop I<argument> for functions, if one is required ("ev
2563	loop argument"). The C<EV_A> form is used when this is the sole argument,	3670	loop argument"). The C<EV_A> form is used when this is the sole argument,
2564	C<EV_A_> is used when other arguments are following. Example:	3671	C<EV_A_> is used when other arguments are following. Example:
2565		3672
2566	ev_unref (EV_A);	3673	ev_unref (EV_A);
2567	ev_timer_add (EV_A_ watcher);	3674	ev_timer_add (EV_A_ watcher);
2568	ev_loop (EV_A_ 0);	3675	ev_run (EV_A_ 0);
2569		3676
2570	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3677	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2571	which is often provided by the following macro.	3678	which is often provided by the following macro.
2572		3679
2573	=item C<EV_P>, C<EV_P_>	3680	=item C<EV_P>, C<EV_P_>
2574		3681
2575	This provides the loop I<parameter> for functions, if one is required ("ev	3682	This provides the loop I<parameter> for functions, if one is required ("ev
2576	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3683	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2577	C<EV_P_> is used when other parameters are following. Example:	3684	C<EV_P_> is used when other parameters are following. Example:
2578		3685
2579	// this is how ev_unref is being declared	3686	// this is how ev_unref is being declared
2580	static void ev_unref (EV_P);	3687	static void ev_unref (EV_P);
2581		3688
2582	// this is how you can declare your typical callback	3689	// this is how you can declare your typical callback
2583	static void cb (EV_P_ ev_timer *w, int revents)	3690	static void cb (EV_P_ ev_timer *w, int revents)
2584		3691
2585	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3692	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2586	suitable for use with C<EV_A>.	3693	suitable for use with C<EV_A>.
2587		3694
2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3695	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2589		3696
2590	Similar to the other two macros, this gives you the value of the default	3697	Similar to the other two macros, this gives you the value of the default
2591	loop, if multiple loops are supported ("ev loop default").	3698	loop, if multiple loops are supported ("ev loop default").
		3699
		3700	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3701
		3702	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3703	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3704	is undefined when the default loop has not been initialised by a previous
		3705	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3706
		3707	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3708	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2592		3709
2593	=back	3710	=back
2594		3711
2595	Example: Declare and initialise a check watcher, utilising the above	3712	Example: Declare and initialise a check watcher, utilising the above
2596	macros so it will work regardless of whether multiple loops are supported	3713	macros so it will work regardless of whether multiple loops are supported
2597	or not.	3714	or not.
2598		3715
2599	static void	3716	static void
2600	check_cb (EV_P_ ev_timer *w, int revents)	3717	check_cb (EV_P_ ev_timer *w, int revents)
2601	{	3718	{
2602	ev_check_stop (EV_A_ w);	3719	ev_check_stop (EV_A_ w);
2603	}	3720	}
2604		3721
2605	ev_check check;	3722	ev_check check;
2606	ev_check_init (&check, check_cb);	3723	ev_check_init (&check, check_cb);
2607	ev_check_start (EV_DEFAULT_ &check);	3724	ev_check_start (EV_DEFAULT_ &check);
2608	ev_loop (EV_DEFAULT_ 0);	3725	ev_run (EV_DEFAULT_ 0);
2609		3726
2610	=head1 EMBEDDING	3727	=head1 EMBEDDING
2611		3728
2612	Libev can (and often is) directly embedded into host	3729	Libev can (and often is) directly embedded into host
2613	applications. Examples of applications that embed it include the Deliantra	3730	applications. Examples of applications that embed it include the Deliantra
…		…
2620	libev somewhere in your source tree).	3737	libev somewhere in your source tree).
2621		3738
2622	=head2 FILESETS	3739	=head2 FILESETS
2623		3740
2624	Depending on what features you need you need to include one or more sets of files	3741	Depending on what features you need you need to include one or more sets of files
2625	in your app.	3742	in your application.
2626		3743
2627	=head3 CORE EVENT LOOP	3744	=head3 CORE EVENT LOOP
2628		3745
2629	To include only the libev core (all the C<ev_*> functions), with manual	3746	To include only the libev core (all the C<ev_*> functions), with manual
2630	configuration (no autoconf):	3747	configuration (no autoconf):
2631		3748
2632	#define EV_STANDALONE 1	3749	#define EV_STANDALONE 1
2633	#include "ev.c"	3750	#include "ev.c"
2634		3751
2635	This will automatically include F<ev.h>, too, and should be done in a	3752	This will automatically include F<ev.h>, too, and should be done in a
2636	single C source file only to provide the function implementations. To use	3753	single C source file only to provide the function implementations. To use
2637	it, do the same for F<ev.h> in all files wishing to use this API (best	3754	it, do the same for F<ev.h> in all files wishing to use this API (best
2638	done by writing a wrapper around F<ev.h> that you can include instead and	3755	done by writing a wrapper around F<ev.h> that you can include instead and
2639	where you can put other configuration options):	3756	where you can put other configuration options):
2640		3757
2641	#define EV_STANDALONE 1	3758	#define EV_STANDALONE 1
2642	#include "ev.h"	3759	#include "ev.h"
2643		3760
2644	Both header files and implementation files can be compiled with a C++	3761	Both header files and implementation files can be compiled with a C++
2645	compiler (at least, thats a stated goal, and breakage will be treated	3762	compiler (at least, that's a stated goal, and breakage will be treated
2646	as a bug).	3763	as a bug).
2647		3764
2648	You need the following files in your source tree, or in a directory	3765	You need the following files in your source tree, or in a directory
2649	in your include path (e.g. in libev/ when using -Ilibev):	3766	in your include path (e.g. in libev/ when using -Ilibev):
2650		3767
2651	ev.h	3768	ev.h
2652	ev.c	3769	ev.c
2653	ev_vars.h	3770	ev_vars.h
2654	ev_wrap.h	3771	ev_wrap.h
2655		3772
2656	ev_win32.c required on win32 platforms only	3773	ev_win32.c required on win32 platforms only
2657		3774
2658	ev_select.c only when select backend is enabled (which is enabled by default)	3775	ev_select.c only when select backend is enabled (which is enabled by default)
2659	ev_poll.c only when poll backend is enabled (disabled by default)	3776	ev_poll.c only when poll backend is enabled (disabled by default)
2660	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3777	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2661	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3778	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2662	ev_port.c only when the solaris port backend is enabled (disabled by default)	3779	ev_port.c only when the solaris port backend is enabled (disabled by default)
2663		3780
2664	F<ev.c> includes the backend files directly when enabled, so you only need	3781	F<ev.c> includes the backend files directly when enabled, so you only need
2665	to compile this single file.	3782	to compile this single file.
2666		3783
2667	=head3 LIBEVENT COMPATIBILITY API	3784	=head3 LIBEVENT COMPATIBILITY API
2668		3785
2669	To include the libevent compatibility API, also include:	3786	To include the libevent compatibility API, also include:
2670		3787
2671	#include "event.c"	3788	#include "event.c"
2672		3789
2673	in the file including F<ev.c>, and:	3790	in the file including F<ev.c>, and:
2674		3791
2675	#include "event.h"	3792	#include "event.h"
2676		3793
2677	in the files that want to use the libevent API. This also includes F<ev.h>.	3794	in the files that want to use the libevent API. This also includes F<ev.h>.
2678		3795
2679	You need the following additional files for this:	3796	You need the following additional files for this:
2680		3797
2681	event.h	3798	event.h
2682	event.c	3799	event.c
2683		3800
2684	=head3 AUTOCONF SUPPORT	3801	=head3 AUTOCONF SUPPORT
2685		3802
2686	Instead of using C<EV_STANDALONE=1> and providing your config in	3803	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2687	whatever way you want, you can also C<m4_include([libev.m4])> in your	3804	whatever way you want, you can also C<m4_include([libev.m4])> in your
2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3805	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2689	include F<config.h> and configure itself accordingly.	3806	include F<config.h> and configure itself accordingly.
2690		3807
2691	For this of course you need the m4 file:	3808	For this of course you need the m4 file:
2692		3809
2693	libev.m4	3810	libev.m4
2694		3811
2695	=head2 PREPROCESSOR SYMBOLS/MACROS	3812	=head2 PREPROCESSOR SYMBOLS/MACROS
2696		3813
2697	Libev can be configured via a variety of preprocessor symbols you have to define	3814	Libev can be configured via a variety of preprocessor symbols you have to
2698	before including any of its files. The default is not to build for multiplicity	3815	define before including (or compiling) any of its files. The default in
2699	and only include the select backend.	3816	the absence of autoconf is documented for every option.
		3817
		3818	Symbols marked with "(h)" do not change the ABI, and can have different
		3819	values when compiling libev vs. including F<ev.h>, so it is permissible
		3820	to redefine them before including F<ev.h> without breaking compatibility
		3821	to a compiled library. All other symbols change the ABI, which means all
		3822	users of libev and the libev code itself must be compiled with compatible
		3823	settings.
2700		3824
2701	=over 4	3825	=over 4
2702		3826
		3827	=item EV_COMPAT3 (h)
		3828
		3829	Backwards compatibility is a major concern for libev. This is why this
		3830	release of libev comes with wrappers for the functions and symbols that
		3831	have been renamed between libev version 3 and 4.
		3832
		3833	You can disable these wrappers (to test compatibility with future
		3834	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3835	sources. This has the additional advantage that you can drop the C<struct>
		3836	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3837	typedef in that case.
		3838
		3839	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3840	and in some even more future version the compatibility code will be
		3841	removed completely.
		3842
2703	=item EV_STANDALONE	3843	=item EV_STANDALONE (h)
2704		3844
2705	Must always be C<1> if you do not use autoconf configuration, which	3845	Must always be C<1> if you do not use autoconf configuration, which
2706	keeps libev from including F<config.h>, and it also defines dummy	3846	keeps libev from including F<config.h>, and it also defines dummy
2707	implementations for some libevent functions (such as logging, which is not	3847	implementations for some libevent functions (such as logging, which is not
2708	supported). It will also not define any of the structs usually found in	3848	supported). It will also not define any of the structs usually found in
2709	F<event.h> that are not directly supported by the libev core alone.	3849	F<event.h> that are not directly supported by the libev core alone.
2710		3850
		3851	In standalone mode, libev will still try to automatically deduce the
		3852	configuration, but has to be more conservative.
		3853
2711	=item EV_USE_MONOTONIC	3854	=item EV_USE_MONOTONIC
2712		3855
2713	If defined to be C<1>, libev will try to detect the availability of the	3856	If defined to be C<1>, libev will try to detect the availability of the
2714	monotonic clock option at both compiletime and runtime. Otherwise no use	3857	monotonic clock option at both compile time and runtime. Otherwise no
2715	of the monotonic clock option will be attempted. If you enable this, you	3858	use of the monotonic clock option will be attempted. If you enable this,
2716	usually have to link against librt or something similar. Enabling it when	3859	you usually have to link against librt or something similar. Enabling it
2717	the functionality isn't available is safe, though, although you have	3860	when the functionality isn't available is safe, though, although you have
2718	to make sure you link against any libraries where the C<clock_gettime>	3861	to make sure you link against any libraries where the C<clock_gettime>
2719	function is hiding in (often F<-lrt>).	3862	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2720		3863
2721	=item EV_USE_REALTIME	3864	=item EV_USE_REALTIME
2722		3865
2723	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
2724	realtime clock option at compiletime (and assume its availability at	3867	real-time clock option at compile time (and assume its availability
2725	runtime if successful). Otherwise no use of the realtime clock option will	3868	at runtime if successful). Otherwise no use of the real-time clock
2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3869	option will be attempted. This effectively replaces C<gettimeofday>
2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3870	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3871	correctness. See the note about libraries in the description of
		3872	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3873	C<EV_USE_CLOCK_SYSCALL>.
		3874
		3875	=item EV_USE_CLOCK_SYSCALL
		3876
		3877	If defined to be C<1>, libev will try to use a direct syscall instead
		3878	of calling the system-provided C<clock_gettime> function. This option
		3879	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3880	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3881	programs needlessly. Using a direct syscall is slightly slower (in
		3882	theory), because no optimised vdso implementation can be used, but avoids
		3883	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3884	higher, as it simplifies linking (no need for C<-lrt>).
2729		3885
2730	=item EV_USE_NANOSLEEP	3886	=item EV_USE_NANOSLEEP
2731		3887
2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3888	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2733	and will use it for delays. Otherwise it will use C<select ()>.	3889	and will use it for delays. Otherwise it will use C<select ()>.
2734		3890
		3891	=item EV_USE_EVENTFD
		3892
		3893	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3894	available and will probe for kernel support at runtime. This will improve
		3895	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3896	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3897	2.7 or newer, otherwise disabled.
		3898
2735	=item EV_USE_SELECT	3899	=item EV_USE_SELECT
2736		3900
2737	If undefined or defined to be C<1>, libev will compile in support for the	3901	If undefined or defined to be C<1>, libev will compile in support for the
2738	C<select>(2) backend. No attempt at autodetection will be done: if no	3902	C<select>(2) backend. No attempt at auto-detection will be done: if no
2739	other method takes over, select will be it. Otherwise the select backend	3903	other method takes over, select will be it. Otherwise the select backend
2740	will not be compiled in.	3904	will not be compiled in.
2741		3905
2742	=item EV_SELECT_USE_FD_SET	3906	=item EV_SELECT_USE_FD_SET
2743		3907
2744	If defined to C<1>, then the select backend will use the system C<fd_set>	3908	If defined to C<1>, then the select backend will use the system C<fd_set>
2745	structure. This is useful if libev doesn't compile due to a missing	3909	structure. This is useful if libev doesn't compile due to a missing
2746	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3910	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2747	exotic systems. This usually limits the range of file descriptors to some	3911	on exotic systems. This usually limits the range of file descriptors to
2748	low limit such as 1024 or might have other limitations (winsocket only	3912	some low limit such as 1024 or might have other limitations (winsocket
2749	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3913	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2750	influence the size of the C<fd_set> used.	3914	configures the maximum size of the C<fd_set>.
2751		3915
2752	=item EV_SELECT_IS_WINSOCKET	3916	=item EV_SELECT_IS_WINSOCKET
2753		3917
2754	When defined to C<1>, the select backend will assume that	3918	When defined to C<1>, the select backend will assume that
2755	select/socket/connect etc. don't understand file descriptors but	3919	select/socket/connect etc. don't understand file descriptors but
…		…
2757	be used is the winsock select). This means that it will call	3921	be used is the winsock select). This means that it will call
2758	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3922	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2759	it is assumed that all these functions actually work on fds, even	3923	it is assumed that all these functions actually work on fds, even
2760	on win32. Should not be defined on non-win32 platforms.	3924	on win32. Should not be defined on non-win32 platforms.
2761		3925
2762	=item EV_FD_TO_WIN32_HANDLE	3926	=item EV_FD_TO_WIN32_HANDLE(fd)
2763		3927
2764	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3928	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2765	file descriptors to socket handles. When not defining this symbol (the	3929	file descriptors to socket handles. When not defining this symbol (the
2766	default), then libev will call C<_get_osfhandle>, which is usually	3930	default), then libev will call C<_get_osfhandle>, which is usually
2767	correct. In some cases, programs use their own file descriptor management,	3931	correct. In some cases, programs use their own file descriptor management,
2768	in which case they can provide this function to map fds to socket handles.	3932	in which case they can provide this function to map fds to socket handles.
2769		3933
		3934	=item EV_WIN32_HANDLE_TO_FD(handle)
		3935
		3936	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3937	using the standard C<_open_osfhandle> function. For programs implementing
		3938	their own fd to handle mapping, overwriting this function makes it easier
		3939	to do so. This can be done by defining this macro to an appropriate value.
		3940
		3941	=item EV_WIN32_CLOSE_FD(fd)
		3942
		3943	If programs implement their own fd to handle mapping on win32, then this
		3944	macro can be used to override the C<close> function, useful to unregister
		3945	file descriptors again. Note that the replacement function has to close
		3946	the underlying OS handle.
		3947
2770	=item EV_USE_POLL	3948	=item EV_USE_POLL
2771		3949
2772	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2773	backend. Otherwise it will be enabled on non-win32 platforms. It	3951	backend. Otherwise it will be enabled on non-win32 platforms. It
2774	takes precedence over select.	3952	takes precedence over select.
2775		3953
2776	=item EV_USE_EPOLL	3954	=item EV_USE_EPOLL
2777		3955
2778	If defined to be C<1>, libev will compile in support for the Linux	3956	If defined to be C<1>, libev will compile in support for the Linux
2779	C<epoll>(7) backend. Its availability will be detected at runtime,	3957	C<epoll>(7) backend. Its availability will be detected at runtime,
2780	otherwise another method will be used as fallback. This is the	3958	otherwise another method will be used as fallback. This is the preferred
2781	preferred backend for GNU/Linux systems.	3959	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3960	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2782		3961
2783	=item EV_USE_KQUEUE	3962	=item EV_USE_KQUEUE
2784		3963
2785	If defined to be C<1>, libev will compile in support for the BSD style	3964	If defined to be C<1>, libev will compile in support for the BSD style
2786	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3965	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2799	otherwise another method will be used as fallback. This is the preferred	3978	otherwise another method will be used as fallback. This is the preferred
2800	backend for Solaris 10 systems.	3979	backend for Solaris 10 systems.
2801		3980
2802	=item EV_USE_DEVPOLL	3981	=item EV_USE_DEVPOLL
2803		3982
2804	reserved for future expansion, works like the USE symbols above.	3983	Reserved for future expansion, works like the USE symbols above.
2805		3984
2806	=item EV_USE_INOTIFY	3985	=item EV_USE_INOTIFY
2807		3986
2808	If defined to be C<1>, libev will compile in support for the Linux inotify	3987	If defined to be C<1>, libev will compile in support for the Linux inotify
2809	interface to speed up C<ev_stat> watchers. Its actual availability will	3988	interface to speed up C<ev_stat> watchers. Its actual availability will
2810	be detected at runtime.	3989	be detected at runtime. If undefined, it will be enabled if the headers
		3990	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2811		3991
2812	=item EV_ATOMIC_T	3992	=item EV_ATOMIC_T
2813		3993
2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3994	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815	access is atomic with respect to other threads or signal contexts. No such	3995	access is atomic with respect to other threads or signal contexts. No such
2816	type is easily found in the C language, so you can provide your own type	3996	type is easily found in the C language, so you can provide your own type
2817	that you know is safe for your purposes. It is used both for signal handler "locking"	3997	that you know is safe for your purposes. It is used both for signal handler "locking"
2818	as well as for signal and thread safety in C<ev_async> watchers.	3998	as well as for signal and thread safety in C<ev_async> watchers.
2819		3999
2820	In the absense of this define, libev will use C<sig_atomic_t volatile>	4000	In the absence of this define, libev will use C<sig_atomic_t volatile>
2821	(from F<signal.h>), which is usually good enough on most platforms.	4001	(from F<signal.h>), which is usually good enough on most platforms.
2822		4002
2823	=item EV_H	4003	=item EV_H (h)
2824		4004
2825	The name of the F<ev.h> header file used to include it. The default if	4005	The name of the F<ev.h> header file used to include it. The default if
2826	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4006	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2827	used to virtually rename the F<ev.h> header file in case of conflicts.	4007	used to virtually rename the F<ev.h> header file in case of conflicts.
2828		4008
2829	=item EV_CONFIG_H	4009	=item EV_CONFIG_H (h)
2830		4010
2831	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4011	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2832	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4012	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2833	C<EV_H>, above.	4013	C<EV_H>, above.
2834		4014
2835	=item EV_EVENT_H	4015	=item EV_EVENT_H (h)
2836		4016
2837	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4017	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2838	of how the F<event.h> header can be found, the default is C<"event.h">.	4018	of how the F<event.h> header can be found, the default is C<"event.h">.
2839		4019
2840	=item EV_PROTOTYPES	4020	=item EV_PROTOTYPES (h)
2841		4021
2842	If defined to be C<0>, then F<ev.h> will not define any function	4022	If defined to be C<0>, then F<ev.h> will not define any function
2843	prototypes, but still define all the structs and other symbols. This is	4023	prototypes, but still define all the structs and other symbols. This is
2844	occasionally useful if you want to provide your own wrapper functions	4024	occasionally useful if you want to provide your own wrapper functions
2845	around libev functions.	4025	around libev functions.
…		…
2864	When doing priority-based operations, libev usually has to linearly search	4044	When doing priority-based operations, libev usually has to linearly search
2865	all the priorities, so having many of them (hundreds) uses a lot of space	4045	all the priorities, so having many of them (hundreds) uses a lot of space
2866	and time, so using the defaults of five priorities (-2 .. +2) is usually	4046	and time, so using the defaults of five priorities (-2 .. +2) is usually
2867	fine.	4047	fine.
2868		4048
2869	If your embedding app does not need any priorities, defining these both to	4049	If your embedding application does not need any priorities, defining these
2870	C<0> will save some memory and cpu.	4050	both to C<0> will save some memory and CPU.
2871		4051
2872	=item EV_PERIODIC_ENABLE	4052	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4053	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4054	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2873		4055
2874	If undefined or defined to be C<1>, then periodic timers are supported. If	4056	If undefined or defined to be C<1> (and the platform supports it), then
2875	defined to be C<0>, then they are not. Disabling them saves a few kB of	4057	the respective watcher type is supported. If defined to be C<0>, then it
2876	code.	4058	is not. Disabling watcher types mainly saves code size.
2877		4059
2878	=item EV_IDLE_ENABLE	4060	=item EV_FEATURES
2879
2880	If undefined or defined to be C<1>, then idle watchers are supported. If
2881	defined to be C<0>, then they are not. Disabling them saves a few kB of
2882	code.
2883
2884	=item EV_EMBED_ENABLE
2885
2886	If undefined or defined to be C<1>, then embed watchers are supported. If
2887	defined to be C<0>, then they are not.
2888
2889	=item EV_STAT_ENABLE
2890
2891	If undefined or defined to be C<1>, then stat watchers are supported. If
2892	defined to be C<0>, then they are not.
2893
2894	=item EV_FORK_ENABLE
2895
2896	If undefined or defined to be C<1>, then fork watchers are supported. If
2897	defined to be C<0>, then they are not.
2898
2899	=item EV_ASYNC_ENABLE
2900
2901	If undefined or defined to be C<1>, then async watchers are supported. If
2902	defined to be C<0>, then they are not.
2903
2904	=item EV_MINIMAL
2905		4061
2906	If you need to shave off some kilobytes of code at the expense of some	4062	If you need to shave off some kilobytes of code at the expense of some
2907	speed, define this symbol to C<1>. Currently only used for gcc to override	4063	speed (but with the full API), you can define this symbol to request
2908	some inlining decisions, saves roughly 30% codesize of amd64.	4064	certain subsets of functionality. The default is to enable all features
		4065	that can be enabled on the platform.
		4066
		4067	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4068	with some broad features you want) and then selectively re-enable
		4069	additional parts you want, for example if you want everything minimal,
		4070	but multiple event loop support, async and child watchers and the poll
		4071	backend, use this:
		4072
		4073	#define EV_FEATURES 0
		4074	#define EV_MULTIPLICITY 1
		4075	#define EV_USE_POLL 1
		4076	#define EV_CHILD_ENABLE 1
		4077	#define EV_ASYNC_ENABLE 1
		4078
		4079	The actual value is a bitset, it can be a combination of the following
		4080	values:
		4081
		4082	=over 4
		4083
		4084	=item C<1> - faster/larger code
		4085
		4086	Use larger code to speed up some operations.
		4087
		4088	Currently this is used to override some inlining decisions (enlarging the
		4089	code size by roughly 30% on amd64).
		4090
		4091	When optimising for size, use of compiler flags such as C<-Os> with
		4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4093	assertions.
		4094
		4095	=item C<2> - faster/larger data structures
		4096
		4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4098	hash table sizes and so on. This will usually further increase code size
		4099	and can additionally have an effect on the size of data structures at
		4100	runtime.
		4101
		4102	=item C<4> - full API configuration
		4103
		4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4105	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4106
		4107	=item C<8> - full API
		4108
		4109	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4110	details on which parts of the API are still available without this
		4111	feature, and do not complain if this subset changes over time.
		4112
		4113	=item C<16> - enable all optional watcher types
		4114
		4115	Enables all optional watcher types. If you want to selectively enable
		4116	only some watcher types other than I/O and timers (e.g. prepare,
		4117	embed, async, child...) you can enable them manually by defining
		4118	C<EV_watchertype_ENABLE> to C<1> instead.
		4119
		4120	=item C<32> - enable all backends
		4121
		4122	This enables all backends - without this feature, you need to enable at
		4123	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4124
		4125	=item C<64> - enable OS-specific "helper" APIs
		4126
		4127	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4128	default.
		4129
		4130	=back
		4131
		4132	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4133	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4134	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4135	watchers, timers and monotonic clock support.
		4136
		4137	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4139	your program might be left out as well - a binary starting a timer and an
		4140	I/O watcher then might come out at only 5Kb.
		4141
		4142	=item EV_AVOID_STDIO
		4143
		4144	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4145	functions (printf, scanf, perror etc.). This will increase the code size
		4146	somewhat, but if your program doesn't otherwise depend on stdio and your
		4147	libc allows it, this avoids linking in the stdio library which is quite
		4148	big.
		4149
		4150	Note that error messages might become less precise when this option is
		4151	enabled.
		4152
		4153	=item EV_NSIG
		4154
		4155	The highest supported signal number, +1 (or, the number of
		4156	signals): Normally, libev tries to deduce the maximum number of signals
		4157	automatically, but sometimes this fails, in which case it can be
		4158	specified. Also, using a lower number than detected (C<32> should be
		4159	good for about any system in existence) can save some memory, as libev
		4160	statically allocates some 12-24 bytes per signal number.
2909		4161
2910	=item EV_PID_HASHSIZE	4162	=item EV_PID_HASHSIZE
2911		4163
2912	C<ev_child> watchers use a small hash table to distribute workload by	4164	C<ev_child> watchers use a small hash table to distribute workload by
2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4165	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2914	than enough. If you need to manage thousands of children you might want to	4166	usually more than enough. If you need to manage thousands of children you
2915	increase this value (I<must> be a power of two).	4167	might want to increase this value (I<must> be a power of two).
2916		4168
2917	=item EV_INOTIFY_HASHSIZE	4169	=item EV_INOTIFY_HASHSIZE
2918		4170
2919	C<ev_stat> watchers use a small hash table to distribute workload by	4171	C<ev_stat> watchers use a small hash table to distribute workload by
2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4172	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
2921	usually more than enough. If you need to manage thousands of C<ev_stat>	4173	disabled), usually more than enough. If you need to manage thousands of
2922	watchers you might want to increase this value (I<must> be a power of	4174	C<ev_stat> watchers you might want to increase this value (I<must> be a
2923	two).	4175	power of two).
		4176
		4177	=item EV_USE_4HEAP
		4178
		4179	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4180	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		4181	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		4182	faster performance with many (thousands) of watchers.
		4183
		4184	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4185	will be C<0>.
		4186
		4187	=item EV_HEAP_CACHE_AT
		4188
		4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4190	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		4191	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		4192	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		4193	but avoids random read accesses on heap changes. This improves performance
		4194	noticeably with many (hundreds) of watchers.
		4195
		4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4197	will be C<0>.
		4198
		4199	=item EV_VERIFY
		4200
		4201	Controls how much internal verification (see C<ev_verify ()>) will
		4202	be done: If set to C<0>, no internal verification code will be compiled
		4203	in. If set to C<1>, then verification code will be compiled in, but not
		4204	called. If set to C<2>, then the internal verification code will be
		4205	called once per loop, which can slow down libev. If set to C<3>, then the
		4206	verification code will be called very frequently, which will slow down
		4207	libev considerably.
		4208
		4209	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4210	will be C<0>.
2924		4211
2925	=item EV_COMMON	4212	=item EV_COMMON
2926		4213
2927	By default, all watchers have a C<void *data> member. By redefining	4214	By default, all watchers have a C<void *data> member. By redefining
2928	this macro to a something else you can include more and other types of	4215	this macro to something else you can include more and other types of
2929	members. You have to define it each time you include one of the files,	4216	members. You have to define it each time you include one of the files,
2930	though, and it must be identical each time.	4217	though, and it must be identical each time.
2931		4218
2932	For example, the perl EV module uses something like this:	4219	For example, the perl EV module uses something like this:
2933		4220
2934	#define EV_COMMON \	4221	#define EV_COMMON \
2935	SV *self; /* contains this struct */ \	4222	SV *self; /* contains this struct */ \
2936	SV *cb_sv, *fh /* note no trailing ";" */	4223	SV *cb_sv, *fh /* note no trailing ";" */
2937		4224
2938	=item EV_CB_DECLARE (type)	4225	=item EV_CB_DECLARE (type)
2939		4226
2940	=item EV_CB_INVOKE (watcher, revents)	4227	=item EV_CB_INVOKE (watcher, revents)
2941		4228
…		…
2946	definition and a statement, respectively. See the F<ev.h> header file for	4233	definition and a statement, respectively. See the F<ev.h> header file for
2947	their default definitions. One possible use for overriding these is to	4234	their default definitions. One possible use for overriding these is to
2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4235	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2949	method calls instead of plain function calls in C++.	4236	method calls instead of plain function calls in C++.
2950		4237
		4238	=back
		4239
2951	=head2 EXPORTED API SYMBOLS	4240	=head2 EXPORTED API SYMBOLS
2952		4241
2953	If you need to re-export the API (e.g. via a dll) and you need a list of	4242	If you need to re-export the API (e.g. via a DLL) and you need a list of
2954	exported symbols, you can use the provided F<Symbol.*> files which list	4243	exported symbols, you can use the provided F<Symbol.*> files which list
2955	all public symbols, one per line:	4244	all public symbols, one per line:
2956		4245
2957	Symbols.ev for libev proper	4246	Symbols.ev for libev proper
2958	Symbols.event for the libevent emulation	4247	Symbols.event for the libevent emulation
2959		4248
2960	This can also be used to rename all public symbols to avoid clashes with	4249	This can also be used to rename all public symbols to avoid clashes with
2961	multiple versions of libev linked together (which is obviously bad in	4250	multiple versions of libev linked together (which is obviously bad in
2962	itself, but sometimes it is inconvinient to avoid this).	4251	itself, but sometimes it is inconvenient to avoid this).
2963		4252
2964	A sed command like this will create wrapper C<#define>'s that you need to	4253	A sed command like this will create wrapper C<#define>'s that you need to
2965	include before including F<ev.h>:	4254	include before including F<ev.h>:
2966		4255
2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4256	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2984	file.	4273	file.
2985		4274
2986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4275	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2987	that everybody includes and which overrides some configure choices:	4276	that everybody includes and which overrides some configure choices:
2988		4277
2989	#define EV_MINIMAL 1	4278	#define EV_FEATURES 8
2990	#define EV_USE_POLL 0	4279	#define EV_USE_SELECT 1
2991	#define EV_MULTIPLICITY 0
2992	#define EV_PERIODIC_ENABLE 0	4280	#define EV_PREPARE_ENABLE 1
		4281	#define EV_IDLE_ENABLE 1
2993	#define EV_STAT_ENABLE 0	4282	#define EV_SIGNAL_ENABLE 1
2994	#define EV_FORK_ENABLE 0	4283	#define EV_CHILD_ENABLE 1
		4284	#define EV_USE_STDEXCEPT 0
2995	#define EV_CONFIG_H <config.h>	4285	#define EV_CONFIG_H <config.h>
2996	#define EV_MINPRI 0
2997	#define EV_MAXPRI 0
2998		4286
2999	#include "ev++.h"	4287	#include "ev++.h"
3000		4288
3001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3002		4290
3003	#include "ev_cpp.h"	4291	#include "ev_cpp.h"
3004	#include "ev.c"	4292	#include "ev.c"
3005		4293
		4294	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3006		4295
3007	=head1 COMPLEXITIES	4296	=head2 THREADS AND COROUTINES
3008		4297
3009	In this section the complexities of (many of) the algorithms used inside	4298	=head3 THREADS
3010	libev will be explained. For complexity discussions about backends see the
3011	documentation for C<ev_default_init>.
3012		4299
3013	All of the following are about amortised time: If an array needs to be	4300	All libev functions are reentrant and thread-safe unless explicitly
3014	extended, libev needs to realloc and move the whole array, but this	4301	documented otherwise, but libev implements no locking itself. This means
3015	happens asymptotically never with higher number of elements, so O(1) might	4302	that you can use as many loops as you want in parallel, as long as there
3016	mean it might do a lengthy realloc operation in rare cases, but on average	4303	are no concurrent calls into any libev function with the same loop
3017	it is much faster and asymptotically approaches constant time.	4304	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4305	of course): libev guarantees that different event loops share no data
		4306	structures that need any locking.
		4307
		4308	Or to put it differently: calls with different loop parameters can be done
		4309	concurrently from multiple threads, calls with the same loop parameter
		4310	must be done serially (but can be done from different threads, as long as
		4311	only one thread ever is inside a call at any point in time, e.g. by using
		4312	a mutex per loop).
		4313
		4314	Specifically to support threads (and signal handlers), libev implements
		4315	so-called C<ev_async> watchers, which allow some limited form of
		4316	concurrency on the same event loop, namely waking it up "from the
		4317	outside".
		4318
		4319	If you want to know which design (one loop, locking, or multiple loops
		4320	without or something else still) is best for your problem, then I cannot
		4321	help you, but here is some generic advice:
3018		4322
3019	=over 4	4323	=over 4
3020		4324
3021	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4325	=item * most applications have a main thread: use the default libev loop
		4326	in that thread, or create a separate thread running only the default loop.
3022		4327
3023	This means that, when you have a watcher that triggers in one hour and	4328	This helps integrating other libraries or software modules that use libev
3024	there are 100 watchers that would trigger before that then inserting will	4329	themselves and don't care/know about threading.
3025	have to skip roughly seven (C<ld 100>) of these watchers.
3026		4330
3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4331	=item * one loop per thread is usually a good model.
3028		4332
3029	That means that changing a timer costs less than removing/adding them	4333	Doing this is almost never wrong, sometimes a better-performance model
3030	as only the relative motion in the event queue has to be paid for.	4334	exists, but it is always a good start.
3031		4335
3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4336	=item * other models exist, such as the leader/follower pattern, where one
		4337	loop is handed through multiple threads in a kind of round-robin fashion.
3033		4338
3034	These just add the watcher into an array or at the head of a list.	4339	Choosing a model is hard - look around, learn, know that usually you can do
		4340	better than you currently do :-)
3035		4341
3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4342	=item * often you need to talk to some other thread which blocks in the
		4343	event loop.
3037		4344
3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4345	C<ev_async> watchers can be used to wake them up from other threads safely
		4346	(or from signal contexts...).
3039		4347
3040	These watchers are stored in lists then need to be walked to find the	4348	An example use would be to communicate signals or other events that only
3041	correct watcher to remove. The lists are usually short (you don't usually	4349	work in the default loop by registering the signal watcher with the
3042	have many watchers waiting for the same fd or signal).	4350	default loop and triggering an C<ev_async> watcher from the default loop
3043		4351	watcher callback into the event loop interested in the signal.
3044	=item Finding the next timer in each loop iteration: O(1)
3045
3046	By virtue of using a binary heap, the next timer is always found at the
3047	beginning of the storage array.
3048
3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3050
3051	A change means an I/O watcher gets started or stopped, which requires
3052	libev to recalculate its status (and possibly tell the kernel, depending
3053	on backend and wether C<ev_io_set> was used).
3054
3055	=item Activating one watcher (putting it into the pending state): O(1)
3056
3057	=item Priority handling: O(number_of_priorities)
3058
3059	Priorities are implemented by allocating some space for each
3060	priority. When doing priority-based operations, libev usually has to
3061	linearly search all the priorities, but starting/stopping and activating
3062	watchers becomes O(1) w.r.t. priority handling.
3063
3064	=item Sending an ev_async: O(1)
3065
3066	=item Processing ev_async_send: O(number_of_async_watchers)
3067
3068	=item Processing signals: O(max_signal_number)
3069
3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3071	calls in the current loop iteration. Checking for async and signal events
3072	involves iterating over all running async watchers or all signal numbers.
3073		4352
3074	=back	4353	=back
3075		4354
		4355	=head4 THREAD LOCKING EXAMPLE
3076		4356
3077	=head1 Win32 platform limitations and workarounds	4357	Here is a fictitious example of how to run an event loop in a different
		4358	thread than where callbacks are being invoked and watchers are
		4359	created/added/removed.
		4360
		4361	For a real-world example, see the C<EV::Loop::Async> perl module,
		4362	which uses exactly this technique (which is suited for many high-level
		4363	languages).
		4364
		4365	The example uses a pthread mutex to protect the loop data, a condition
		4366	variable to wait for callback invocations, an async watcher to notify the
		4367	event loop thread and an unspecified mechanism to wake up the main thread.
		4368
		4369	First, you need to associate some data with the event loop:
		4370
		4371	typedef struct {
		4372	mutex_t lock; /* global loop lock */
		4373	ev_async async_w;
		4374	thread_t tid;
		4375	cond_t invoke_cv;
		4376	} userdata;
		4377
		4378	void prepare_loop (EV_P)
		4379	{
		4380	// for simplicity, we use a static userdata struct.
		4381	static userdata u;
		4382
		4383	ev_async_init (&u->async_w, async_cb);
		4384	ev_async_start (EV_A_ &u->async_w);
		4385
		4386	pthread_mutex_init (&u->lock, 0);
		4387	pthread_cond_init (&u->invoke_cv, 0);
		4388
		4389	// now associate this with the loop
		4390	ev_set_userdata (EV_A_ u);
		4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4393
		4394	// then create the thread running ev_loop
		4395	pthread_create (&u->tid, 0, l_run, EV_A);
		4396	}
		4397
		4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4399	solely to wake up the event loop so it takes notice of any new watchers
		4400	that might have been added:
		4401
		4402	static void
		4403	async_cb (EV_P_ ev_async *w, int revents)
		4404	{
		4405	// just used for the side effects
		4406	}
		4407
		4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4409	protecting the loop data, respectively.
		4410
		4411	static void
		4412	l_release (EV_P)
		4413	{
		4414	userdata *u = ev_userdata (EV_A);
		4415	pthread_mutex_unlock (&u->lock);
		4416	}
		4417
		4418	static void
		4419	l_acquire (EV_P)
		4420	{
		4421	userdata *u = ev_userdata (EV_A);
		4422	pthread_mutex_lock (&u->lock);
		4423	}
		4424
		4425	The event loop thread first acquires the mutex, and then jumps straight
		4426	into C<ev_run>:
		4427
		4428	void *
		4429	l_run (void *thr_arg)
		4430	{
		4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4432
		4433	l_acquire (EV_A);
		4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4435	ev_run (EV_A_ 0);
		4436	l_release (EV_A);
		4437
		4438	return 0;
		4439	}
		4440
		4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4442	signal the main thread via some unspecified mechanism (signals? pipe
		4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4444	have been called (in a while loop because a) spurious wakeups are possible
		4445	and b) skipping inter-thread-communication when there are no pending
		4446	watchers is very beneficial):
		4447
		4448	static void
		4449	l_invoke (EV_P)
		4450	{
		4451	userdata *u = ev_userdata (EV_A);
		4452
		4453	while (ev_pending_count (EV_A))
		4454	{
		4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4457	}
		4458	}
		4459
		4460	Now, whenever the main thread gets told to invoke pending watchers, it
		4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4462	thread to continue:
		4463
		4464	static void
		4465	real_invoke_pending (EV_P)
		4466	{
		4467	userdata *u = ev_userdata (EV_A);
		4468
		4469	pthread_mutex_lock (&u->lock);
		4470	ev_invoke_pending (EV_A);
		4471	pthread_cond_signal (&u->invoke_cv);
		4472	pthread_mutex_unlock (&u->lock);
		4473	}
		4474
		4475	Whenever you want to start/stop a watcher or do other modifications to an
		4476	event loop, you will now have to lock:
		4477
		4478	ev_timer timeout_watcher;
		4479	userdata *u = ev_userdata (EV_A);
		4480
		4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4482
		4483	pthread_mutex_lock (&u->lock);
		4484	ev_timer_start (EV_A_ &timeout_watcher);
		4485	ev_async_send (EV_A_ &u->async_w);
		4486	pthread_mutex_unlock (&u->lock);
		4487
		4488	Note that sending the C<ev_async> watcher is required because otherwise
		4489	an event loop currently blocking in the kernel will have no knowledge
		4490	about the newly added timer. By waking up the loop it will pick up any new
		4491	watchers in the next event loop iteration.
		4492
		4493	=head3 COROUTINES
		4494
		4495	Libev is very accommodating to coroutines ("cooperative threads"):
		4496	libev fully supports nesting calls to its functions from different
		4497	coroutines (e.g. you can call C<ev_run> on the same loop from two
		4498	different coroutines, and switch freely between both coroutines running
		4499	the loop, as long as you don't confuse yourself). The only exception is
		4500	that you must not do this from C<ev_periodic> reschedule callbacks.
		4501
		4502	Care has been taken to ensure that libev does not keep local state inside
		4503	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4504	they do not call any callbacks.
		4505
		4506	=head2 COMPILER WARNINGS
		4507
		4508	Depending on your compiler and compiler settings, you might get no or a
		4509	lot of warnings when compiling libev code. Some people are apparently
		4510	scared by this.
		4511
		4512	However, these are unavoidable for many reasons. For one, each compiler
		4513	has different warnings, and each user has different tastes regarding
		4514	warning options. "Warn-free" code therefore cannot be a goal except when
		4515	targeting a specific compiler and compiler-version.
		4516
		4517	Another reason is that some compiler warnings require elaborate
		4518	workarounds, or other changes to the code that make it less clear and less
		4519	maintainable.
		4520
		4521	And of course, some compiler warnings are just plain stupid, or simply
		4522	wrong (because they don't actually warn about the condition their message
		4523	seems to warn about). For example, certain older gcc versions had some
		4524	warnings that resulted in an extreme number of false positives. These have
		4525	been fixed, but some people still insist on making code warn-free with
		4526	such buggy versions.
		4527
		4528	While libev is written to generate as few warnings as possible,
		4529	"warn-free" code is not a goal, and it is recommended not to build libev
		4530	with any compiler warnings enabled unless you are prepared to cope with
		4531	them (e.g. by ignoring them). Remember that warnings are just that:
		4532	warnings, not errors, or proof of bugs.
		4533
		4534
		4535	=head2 VALGRIND
		4536
		4537	Valgrind has a special section here because it is a popular tool that is
		4538	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4539
		4540	If you think you found a bug (memory leak, uninitialised data access etc.)
		4541	in libev, then check twice: If valgrind reports something like:
		4542
		4543	==2274== definitely lost: 0 bytes in 0 blocks.
		4544	==2274== possibly lost: 0 bytes in 0 blocks.
		4545	==2274== still reachable: 256 bytes in 1 blocks.
		4546
		4547	Then there is no memory leak, just as memory accounted to global variables
		4548	is not a memleak - the memory is still being referenced, and didn't leak.
		4549
		4550	Similarly, under some circumstances, valgrind might report kernel bugs
		4551	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4552	although an acceptable workaround has been found here), or it might be
		4553	confused.
		4554
		4555	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4556	make it into some kind of religion.
		4557
		4558	If you are unsure about something, feel free to contact the mailing list
		4559	with the full valgrind report and an explanation on why you think this
		4560	is a bug in libev (best check the archives, too :). However, don't be
		4561	annoyed when you get a brisk "this is no bug" answer and take the chance
		4562	of learning how to interpret valgrind properly.
		4563
		4564	If you need, for some reason, empty reports from valgrind for your project
		4565	I suggest using suppression lists.
		4566
		4567
		4568	=head1 PORTABILITY NOTES
		4569
		4570	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4571
		4572	GNU/Linux is the only common platform that supports 64 bit file/large file
		4573	interfaces but I<disables> them by default.
		4574
		4575	That means that libev compiled in the default environment doesn't support
		4576	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4577
		4578	Unfortunately, many programs try to work around this GNU/Linux issue
		4579	by enabling the large file API, which makes them incompatible with the
		4580	standard libev compiled for their system.
		4581
		4582	Likewise, libev cannot enable the large file API itself as this would
		4583	suddenly make it incompatible to the default compile time environment,
		4584	i.e. all programs not using special compile switches.
		4585
		4586	=head2 OS/X AND DARWIN BUGS
		4587
		4588	The whole thing is a bug if you ask me - basically any system interface
		4589	you touch is broken, whether it is locales, poll, kqueue or even the
		4590	OpenGL drivers.
		4591
		4592	=head3 C<kqueue> is buggy
		4593
		4594	The kqueue syscall is broken in all known versions - most versions support
		4595	only sockets, many support pipes.
		4596
		4597	Libev tries to work around this by not using C<kqueue> by default on this
		4598	rotten platform, but of course you can still ask for it when creating a
		4599	loop - embedding a socket-only kqueue loop into a select-based one is
		4600	probably going to work well.
		4601
		4602	=head3 C<poll> is buggy
		4603
		4604	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4605	implementation by something calling C<kqueue> internally around the 10.5.6
		4606	release, so now C<kqueue> I<and> C<poll> are broken.
		4607
		4608	Libev tries to work around this by not using C<poll> by default on
		4609	this rotten platform, but of course you can still ask for it when creating
		4610	a loop.
		4611
		4612	=head3 C<select> is buggy
		4613
		4614	All that's left is C<select>, and of course Apple found a way to fuck this
		4615	one up as well: On OS/X, C<select> actively limits the number of file
		4616	descriptors you can pass in to 1024 - your program suddenly crashes when
		4617	you use more.
		4618
		4619	There is an undocumented "workaround" for this - defining
		4620	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4621	work on OS/X.
		4622
		4623	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4624
		4625	=head3 C<errno> reentrancy
		4626
		4627	The default compile environment on Solaris is unfortunately so
		4628	thread-unsafe that you can't even use components/libraries compiled
		4629	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4630	defined by default. A valid, if stupid, implementation choice.
		4631
		4632	If you want to use libev in threaded environments you have to make sure
		4633	it's compiled with C<_REENTRANT> defined.
		4634
		4635	=head3 Event port backend
		4636
		4637	The scalable event interface for Solaris is called "event
		4638	ports". Unfortunately, this mechanism is very buggy in all major
		4639	releases. If you run into high CPU usage, your program freezes or you get
		4640	a large number of spurious wakeups, make sure you have all the relevant
		4641	and latest kernel patches applied. No, I don't know which ones, but there
		4642	are multiple ones to apply, and afterwards, event ports actually work
		4643	great.
		4644
		4645	If you can't get it to work, you can try running the program by setting
		4646	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4647	C<select> backends.
		4648
		4649	=head2 AIX POLL BUG
		4650
		4651	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4652	this by trying to avoid the poll backend altogether (i.e. it's not even
		4653	compiled in), which normally isn't a big problem as C<select> works fine
		4654	with large bitsets on AIX, and AIX is dead anyway.
		4655
		4656	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4657
		4658	=head3 General issues
3078		4659
3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4660	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3080	requires, and its I/O model is fundamentally incompatible with the POSIX	4661	requires, and its I/O model is fundamentally incompatible with the POSIX
3081	model. Libev still offers limited functionality on this platform in	4662	model. Libev still offers limited functionality on this platform in
3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3083	descriptors. This only applies when using Win32 natively, not when using	4664	descriptors. This only applies when using Win32 natively, not when using
3084	e.g. cygwin.	4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4666	as every compielr comes with a slightly differently broken/incompatible
		4667	environment.
		4668
		4669	Lifting these limitations would basically require the full
		4670	re-implementation of the I/O system. If you are into this kind of thing,
		4671	then note that glib does exactly that for you in a very portable way (note
		4672	also that glib is the slowest event library known to man).
3085		4673
3086	There is no supported compilation method available on windows except	4674	There is no supported compilation method available on windows except
3087	embedding it into other applications.	4675	embedding it into other applications.
3088		4676
		4677	Sensible signal handling is officially unsupported by Microsoft - libev
		4678	tries its best, but under most conditions, signals will simply not work.
		4679
		4680	Not a libev limitation but worth mentioning: windows apparently doesn't
		4681	accept large writes: instead of resulting in a partial write, windows will
		4682	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4683	so make sure you only write small amounts into your sockets (less than a
		4684	megabyte seems safe, but this apparently depends on the amount of memory
		4685	available).
		4686
3089	Due to the many, low, and arbitrary limits on the win32 platform and the	4687	Due to the many, low, and arbitrary limits on the win32 platform and
3090	abysmal performance of winsockets, using a large number of sockets is not	4688	the abysmal performance of winsockets, using a large number of sockets
3091	recommended (and not reasonable). If your program needs to use more than	4689	is not recommended (and not reasonable). If your program needs to use
3092	a hundred or so sockets, then likely it needs to use a totally different	4690	more than a hundred or so sockets, then likely it needs to use a totally
3093	implementation for windows, as libev offers the POSIX model, which cannot	4691	different implementation for windows, as libev offers the POSIX readiness
3094	be implemented efficiently on windows (microsoft monopoly games).	4692	notification model, which cannot be implemented efficiently on windows
		4693	(due to Microsoft monopoly games).
3095		4694
3096	=over 4	4695	A typical way to use libev under windows is to embed it (see the embedding
		4696	section for details) and use the following F<evwrap.h> header file instead
		4697	of F<ev.h>:
3097		4698
		4699	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4700	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4701
		4702	#include "ev.h"
		4703
		4704	And compile the following F<evwrap.c> file into your project (make sure
		4705	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4706
		4707	#include "evwrap.h"
		4708	#include "ev.c"
		4709
3098	=item The winsocket select function	4710	=head3 The winsocket C<select> function
3099		4711
3100	The winsocket C<select> function doesn't follow POSIX in that it requires	4712	The winsocket C<select> function doesn't follow POSIX in that it
3101	socket I<handles> and not socket I<file descriptors>. This makes select	4713	requires socket I<handles> and not socket I<file descriptors> (it is
3102	very inefficient, and also requires a mapping from file descriptors	4714	also extremely buggy). This makes select very inefficient, and also
3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4715	requires a mapping from file descriptors to socket handles (the Microsoft
3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4716	C runtime provides the function C<_open_osfhandle> for this). See the
3105	symbols for more info.	4717	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4718	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3106		4719
3107	The configuration for a "naked" win32 using the microsoft runtime	4720	The configuration for a "naked" win32 using the Microsoft runtime
3108	libraries and raw winsocket select is:	4721	libraries and raw winsocket select is:
3109		4722
3110	#define EV_USE_SELECT 1	4723	#define EV_USE_SELECT 1
3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4724	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3112		4725
3113	Note that winsockets handling of fd sets is O(n), so you can easily get a	4726	Note that winsockets handling of fd sets is O(n), so you can easily get a
3114	complexity in the O(n²) range when using win32.	4727	complexity in the O(n²) range when using win32.
3115		4728
3116	=item Limited number of file descriptors	4729	=head3 Limited number of file descriptors
3117		4730
3118	Windows has numerous arbitrary (and low) limits on things. Early versions	4731	Windows has numerous arbitrary (and low) limits on things.
3119	of winsocket's select only supported waiting for a max. of C<64> handles	4732
		4733	Early versions of winsocket's select only supported waiting for a maximum
3120	(probably owning to the fact that all windows kernels can only wait for	4734	of C<64> handles (probably owning to the fact that all windows kernels
3121	C<64> things at the same time internally; microsoft recommends spawning a	4735	can only wait for C<64> things at the same time internally; Microsoft
3122	chain of threads and wait for 63 handles and the previous thread in each).	4736	recommends spawning a chain of threads and wait for 63 handles and the
		4737	previous thread in each. Sounds great!).
3123		4738
3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4739	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3125	to some high number (e.g. C<2048>) before compiling the winsocket select	4740	to some high number (e.g. C<2048>) before compiling the winsocket select
3126	call (which might be in libev or elsewhere, for example, perl does its own	4741	call (which might be in libev or elsewhere, for example, perl and many
3127	select emulation on windows).	4742	other interpreters do their own select emulation on windows).
3128		4743
3129	Another limit is the number of file descriptors in the microsoft runtime	4744	Another limit is the number of file descriptors in the Microsoft runtime
3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4745	libraries, which by default is C<64> (there must be a hidden I<64>
3131	or something like this inside microsoft). You can increase this by calling	4746	fetish or something like this inside Microsoft). You can increase this
3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4747	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3133	arbitrary limit), but is broken in many versions of the microsoft runtime	4748	(another arbitrary limit), but is broken in many versions of the Microsoft
3134	libraries.
3135
3136	This might get you to about C<512> or C<2048> sockets (depending on	4749	runtime libraries. This might get you to about C<512> or C<2048> sockets
3137	windows version and/or the phase of the moon). To get more, you need to	4750	(depending on windows version and/or the phase of the moon). To get more,
3138	wrap all I/O functions and provide your own fd management, but the cost of	4751	you need to wrap all I/O functions and provide your own fd management, but
3139	calling select (O(n²)) will likely make this unworkable.	4752	the cost of calling select (O(n²)) will likely make this unworkable.
		4753
		4754	=head2 PORTABILITY REQUIREMENTS
		4755
		4756	In addition to a working ISO-C implementation and of course the
		4757	backend-specific APIs, libev relies on a few additional extensions:
		4758
		4759	=over 4
		4760
		4761	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4762	calling conventions regardless of C<ev_watcher_type *>.
		4763
		4764	Libev assumes not only that all watcher pointers have the same internal
		4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4766	assumes that the same (machine) code can be used to call any watcher
		4767	callback: The watcher callbacks have different type signatures, but libev
		4768	calls them using an C<ev_watcher *> internally.
		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
		4774
		4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4776
		4777	The type C<sig_atomic_t volatile> (or whatever is defined as
		4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4779	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4780	believed to be sufficiently portable.
		4781
		4782	=item C<sigprocmask> must work in a threaded environment
		4783
		4784	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4785	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4786	pthread implementations will either allow C<sigprocmask> in the "main
		4787	thread" or will block signals process-wide, both behaviours would
		4788	be compatible with libev. Interaction between C<sigprocmask> and
		4789	C<pthread_sigmask> could complicate things, however.
		4790
		4791	The most portable way to handle signals is to block signals in all threads
		4792	except the initial one, and run the default loop in the initial thread as
		4793	well.
		4794
		4795	=item C<long> must be large enough for common memory allocation sizes
		4796
		4797	To improve portability and simplify its API, libev uses C<long> internally
		4798	instead of C<size_t> when allocating its data structures. On non-POSIX
		4799	systems (Microsoft...) this might be unexpectedly low, but is still at
		4800	least 31 bits everywhere, which is enough for hundreds of millions of
		4801	watchers.
		4802
		4803	=item C<double> must hold a time value in seconds with enough accuracy
		4804
		4805	The type C<double> is used to represent timestamps. It is required to
		4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is
		4807	good enough for at least into the year 4000 with millisecond accuracy
		4808	(the design goal for libev). This requirement is overfulfilled by
		4809	implementations using IEEE 754, which is basically all existing ones. With
		4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3140		4811
3141	=back	4812	=back
3142		4813
		4814	If you know of other additional requirements drop me a note.
		4815
		4816
		4817	=head1 ALGORITHMIC COMPLEXITIES
		4818
		4819	In this section the complexities of (many of) the algorithms used inside
		4820	libev will be documented. For complexity discussions about backends see
		4821	the documentation for C<ev_default_init>.
		4822
		4823	All of the following are about amortised time: If an array needs to be
		4824	extended, libev needs to realloc and move the whole array, but this
		4825	happens asymptotically rarer with higher number of elements, so O(1) might
		4826	mean that libev does a lengthy realloc operation in rare cases, but on
		4827	average it is much faster and asymptotically approaches constant time.
		4828
		4829	=over 4
		4830
		4831	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4832
		4833	This means that, when you have a watcher that triggers in one hour and
		4834	there are 100 watchers that would trigger before that, then inserting will
		4835	have to skip roughly seven (C<ld 100>) of these watchers.
		4836
		4837	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4838
		4839	That means that changing a timer costs less than removing/adding them,
		4840	as only the relative motion in the event queue has to be paid for.
		4841
		4842	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4843
		4844	These just add the watcher into an array or at the head of a list.
		4845
		4846	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4847
		4848	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4849
		4850	These watchers are stored in lists, so they need to be walked to find the
		4851	correct watcher to remove. The lists are usually short (you don't usually
		4852	have many watchers waiting for the same fd or signal: one is typical, two
		4853	is rare).
		4854
		4855	=item Finding the next timer in each loop iteration: O(1)
		4856
		4857	By virtue of using a binary or 4-heap, the next timer is always found at a
		4858	fixed position in the storage array.
		4859
		4860	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4861
		4862	A change means an I/O watcher gets started or stopped, which requires
		4863	libev to recalculate its status (and possibly tell the kernel, depending
		4864	on backend and whether C<ev_io_set> was used).
		4865
		4866	=item Activating one watcher (putting it into the pending state): O(1)
		4867
		4868	=item Priority handling: O(number_of_priorities)
		4869
		4870	Priorities are implemented by allocating some space for each
		4871	priority. When doing priority-based operations, libev usually has to
		4872	linearly search all the priorities, but starting/stopping and activating
		4873	watchers becomes O(1) with respect to priority handling.
		4874
		4875	=item Sending an ev_async: O(1)
		4876
		4877	=item Processing ev_async_send: O(number_of_async_watchers)
		4878
		4879	=item Processing signals: O(max_signal_number)
		4880
		4881	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4882	calls in the current loop iteration. Checking for async and signal events
		4883	involves iterating over all running async watchers or all signal numbers.
		4884
		4885	=back
		4886
		4887
		4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4889
		4890	The major version 4 introduced some incompatible changes to the API.
		4891
		4892	At the moment, the C<ev.h> header file provides compatibility definitions
		4893	for all changes, so most programs should still compile. The compatibility
		4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
		4896
		4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
		4911
		4912	=item function/symbol renames
		4913
		4914	A number of functions and symbols have been renamed:
		4915
		4916	ev_loop => ev_run
		4917	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4918	EVLOOP_ONESHOT => EVRUN_ONCE
		4919
		4920	ev_unloop => ev_break
		4921	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4922	EVUNLOOP_ONE => EVBREAK_ONE
		4923	EVUNLOOP_ALL => EVBREAK_ALL
		4924
		4925	EV_TIMEOUT => EV_TIMER
		4926
		4927	ev_loop_count => ev_iteration
		4928	ev_loop_depth => ev_depth
		4929	ev_loop_verify => ev_verify
		4930
		4931	Most functions working on C<struct ev_loop> objects don't have an
		4932	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4933	associated constants have been renamed to not collide with the C<struct
		4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4935	as all other watcher types. Note that C<ev_loop_fork> is still called
		4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4937	typedef.
		4938
		4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4940
		4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4943	and work, but the library code will of course be larger.
		4944
		4945	=back
		4946
		4947
		4948	=head1 GLOSSARY
		4949
		4950	=over 4
		4951
		4952	=item active
		4953
		4954	A watcher is active as long as it has been started and not yet stopped.
		4955	See L<WATCHER STATES> for details.
		4956
		4957	=item application
		4958
		4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
		4964
		4965	=item callback
		4966
		4967	The address of a function that is called when some event has been
		4968	detected. Callbacks are being passed the event loop, the watcher that
		4969	received the event, and the actual event bitset.
		4970
		4971	=item callback/watcher invocation
		4972
		4973	The act of calling the callback associated with a watcher.
		4974
		4975	=item event
		4976
		4977	A change of state of some external event, such as data now being available
		4978	for reading on a file descriptor, time having passed or simply not having
		4979	any other events happening anymore.
		4980
		4981	In libev, events are represented as single bits (such as C<EV_READ> or
		4982	C<EV_TIMER>).
		4983
		4984	=item event library
		4985
		4986	A software package implementing an event model and loop.
		4987
		4988	=item event loop
		4989
		4990	An entity that handles and processes external events and converts them
		4991	into callback invocations.
		4992
		4993	=item event model
		4994
		4995	The model used to describe how an event loop handles and processes
		4996	watchers and events.
		4997
		4998	=item pending
		4999
		5000	A watcher is pending as soon as the corresponding event has been
		5001	detected. See L<WATCHER STATES> for details.
		5002
		5003	=item real time
		5004
		5005	The physical time that is observed. It is apparently strictly monotonic :)
		5006
		5007	=item wall-clock time
		5008
		5009	The time and date as shown on clocks. Unlike real time, it can actually
		5010	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5011	clock.
		5012
		5013	=item watcher
		5014
		5015	A data structure that describes interest in certain events. Watchers need
		5016	to be started (attached to an event loop) before they can receive events.
		5017
		5018	=back
3143		5019
3144	=head1 AUTHOR	5020	=head1 AUTHOR
3145		5021
3146	Marc Lehmann <libev@schmorp.de>.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
3147		5024

Diff Legend

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