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Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC vs.
Revision 1.343 by root, Wed Nov 10 13:39:10 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	#include <ev.h>	12	#include <ev.h>
12		13
		14	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_run's to stop iterating
		32	ev_break (EV_A_ EVBREAK_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_run to stop iterating
		41	ev_break (EV_A_ EVBREAK_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
35	struct ev_loop *loop = ev_default_loop (0);	47	// use the default event loop unless you have special needs
		48	struct ev_loop *loop = EV_DEFAULT;
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	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);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_run (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
52		68
		69	This document documents the libev software package.
		70
53	The newest version of this document is also available as a html-formatted	71	The newest version of this document is also available as an html-formatted
54	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
55	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
56		92
57	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
58	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
59	these event sources and provide your program with events.	95	these event sources and provide your program with events.
60		96
…		…
70	=head2 FEATURES	106	=head2 FEATURES
71		107
72	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
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	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
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
76	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
77	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
78	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
79	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
80	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
81	(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>).
82		119
83	It also is quite fast (see this	120	It also is quite fast (see this
84	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
85	for example).	122	for example).
86		123
87	=head2 CONVENTIONS	124	=head2 CONVENTIONS
88		125
89	Libev is very configurable. In this manual the default configuration will	126	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	127	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	128	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	129	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	130	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		132	this argument.
95		133
96	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
97		135
98	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
100	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
101	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
102	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
103	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
104	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
105	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
106		166
107	=head1 GLOBAL FUNCTIONS	167	=head1 GLOBAL FUNCTIONS
108		168
109	These functions can be called anytime, even before initialising the	169	These functions can be called anytime, even before initialising the
110	library in any way.	170	library in any way.
…		…
113		173
114	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
115		175
116	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
117	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
118	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>.
119		180
120	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
121		182
122	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
123	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
124	this is a subsecond-resolution C<sleep ()>.	185	this is a sub-second-resolution C<sleep ()>.
125		186
126	=item int ev_version_major ()	187	=item int ev_version_major ()
127		188
128	=item int ev_version_minor ()	189	=item int ev_version_minor ()
129		190
…		…
140	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
141	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
142	not a problem.	203	not a problem.
143		204
144	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
145	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
146		208
147	assert (("libev version mismatch",	209	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
150		212
151	=item unsigned int ev_supported_backends ()	213	=item unsigned int ev_supported_backends ()
152		214
153	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_*>
154	value) compiled into this binary of libev (independent of their	216	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	218	a description of the set values.
157		219
158	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
159	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
160		222
161	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
163		225
164	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
165		227
166	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
167	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
168	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
169	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
170	(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
171	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
172		235
173	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
174		237
175	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
176	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
177	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
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
179	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
180		243
181	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
182		245
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		247
185	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
186	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
187	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
188	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
189	potentially destructive action. The default is your system realloc	252	or take some potentially destructive action.
190	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.
191		257
192	You could override this function in high-availability programs to, say,	258	You could override this function in high-availability programs to, say,
193	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,
194	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.
195		261
196	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
197	retries).	263	retries (example requires a standards-compliant C<realloc>).
198		264
199	static void *	265	static void *
200	persistent_realloc (void *ptr, size_t size)	266	persistent_realloc (void *ptr, size_t size)
201	{	267	{
202	for (;;)	268	for (;;)
…		…
211	}	277	}
212		278
213	...	279	...
214	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
215		281
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
217		283
218	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
219	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
220	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
221	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
222	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
223	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
224	(such as abort).	290	(such as abort).
225		291
226	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.
…		…
235	...	301	...
236	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
237		303
238	=back	304	=back
239		305
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
241		307
242	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
243	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
244	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
245		311
246	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
247	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
248	create, you also create another event loop. Libev itself does no locking	314	do not.
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		315
253	=over 4	316	=over 4
254		317
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		319
257	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
258	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
259	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
260	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".
261		330
262	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
263	function.	332	function (or via the C<EV_DEFAULT> macro).
		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
		339	The default loop is the only loop that can handle C<ev_child> watchers,
		340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
		341	a problem for your application you can either create a dynamic loop with
		342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
		343	C<SIGCHLD> signal handler I<after> calling 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	This function is thread-safe, and one common way to use libev with
		361	threads is indeed to create one loop per thread, and using the default
		362	loop in the "main" or "initial" thread.
264		363
265	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
266	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>).
267		366
268	The following flags are supported:	367	The following flags are supported:
…		…
274	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
275	thing, believe me).	374	thing, believe me).
276		375
277	=item C<EVFLAG_NOENV>	376	=item C<EVFLAG_NOENV>
278		377
279	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
280	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
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	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
283	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
284	around bugs.	383	around bugs.
285		384
286	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
287		386
288	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
289	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.
290	enabling this flag.
291		389
292	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,
293	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
294	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
295	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
296	without a syscall and thus I<very> fast, but my Linux system also has	394	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	395	C<pthread_atfork> which is even faster).
298		396
299	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
300	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
301	flag.	399	flag.
302		400
303	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>
304	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 its 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 its 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.
305		423
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		425
308	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
309	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,
310	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
311	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
312	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.
313		431
314	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
315	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
316	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
317	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
318	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
319	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).
320		442
321	=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)
322		444
323	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
324	than select, but handles sparse fds better and has no artificial	446	than select, but handles sparse fds better and has no artificial
325	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
326	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,
327	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
328	performance tips.	450	performance tips.
329		451
		452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		454
330	=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).
331		459
332	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,
333	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
334	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),
335	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).
336	of shortcomings, such as silently dropping events in some hard-to-detect	464
337	cases and rewiring a syscall per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
338	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,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
		471	0.1ms) and so on. The biggest issue is fork races, however - if a program
		472	forks then I<both> parent and child process have to recreate the epoll
		473	set, which can take considerable time (one syscall per file descriptor)
		474	and is of course hard to detect.
		475
		476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		477	of course I<doesn't>, and epoll just loves to report events for totally
		478	I<different> file descriptors (even already closed ones, so one cannot
		479	even remove them from the set) than registered in the set (especially
		480	on SMP systems). Libev tries to counter these spurious notifications by
		481	employing an additional generation counter and comparing that against the
		482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
339		487
340	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	489	will result in some caching, there is still a system call per such
342	(because the fd could point to a different file description now), so its	490	incident (because the same I<file descriptor> could point to a different
343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
344	very well if you register events for both fds.	492	file descriptors might not work very well if you register events for both
345		493	file descriptors.
346	Please note that epoll sometimes generates spurious notifications, so you
347	need to use non-blocking I/O or other means to avoid blocking when no data
348	(or space) is available.
349		494
350	Best performance from this backend is achieved by not unregistering all	495	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	496	watchers for a file descriptor until it has been closed, if possible,
352	keep at least one watcher active per fd at all times.	497	i.e. keep at least one watcher active per fd at all times. Stopping and
		498	starting a watcher (without re-setting it) also usually doesn't cause
		499	extra overhead. A fork can both result in spurious notifications as well
		500	as in libev having to destroy and recreate the epoll object, which can
		501	take considerable time and thus should be avoided.
353		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
		506
354	While nominally embeddeble in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	508	all kernel versions tested so far.
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
356		512
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		514
359	Kqueue deserves special mention, as at the time of this writing, it	515	Kqueue deserves special mention, as at the time of this writing, it
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	516	was broken on all BSDs except NetBSD (usually it doesn't work reliably
361	with anything but sockets and pipes, except on Darwin, where of course	517	with anything but sockets and pipes, except on Darwin, where of course
362	it's completely useless). For this reason it's not being "autodetected"	518	it's completely useless). Unlike epoll, however, whose brokenness
		519	is by design, these kqueue bugs can (and eventually will) be fixed
		520	without API changes to existing programs. For this reason it's not being
363	unless you explicitly specify it explicitly in the flags (i.e. using	521	"auto-detected" unless you explicitly specify it in the flags (i.e. using
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	522	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365	system like NetBSD.	523	system like NetBSD.
366		524
367	You still can embed kqueue into a normal poll or select backend and use it	525	You still can embed kqueue into a normal poll or select backend and use it
368	only for sockets (after having made sure that sockets work with kqueue on	526	only for sockets (after having made sure that sockets work with kqueue on
369	the target platform). See C<ev_embed> watchers for more info.	527	the target platform). See C<ev_embed> watchers for more info.
370		528
371	It scales in the same way as the epoll backend, but the interface to the	529	It scales in the same way as the epoll backend, but the interface to the
372	kernel is more efficient (which says nothing about its actual speed, of	530	kernel is more efficient (which says nothing about its actual speed, of
373	course). While stopping, setting and starting an I/O watcher does never	531	course). While stopping, setting and starting an I/O watcher does never
374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
375	two event changes per incident, support for C<fork ()> is very bad and it	533	two event changes per incident. Support for C<fork ()> is very bad (but
376	drops fds silently in similarly hard-to-detect cases.	534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		535	cases
377		536
378	This backend usually performs well under most conditions.	537	This backend usually performs well under most conditions.
379		538
380	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
381	everywhere, so you might need to test for this. And since it is broken	540	everywhere, so you might need to test for this. And since it is broken
382	almost everywhere, you should only use it when you have a lot of sockets	541	almost everywhere, you should only use it when you have a lot of sockets
383	(for which it usually works), by embedding it into another event loop	542	(for which it usually works), by embedding it into another event loop
384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
385	sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
		545
		546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		548	C<NOTE_EOF>.
386		549
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	550	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		551
389	This is not implemented yet (and might never be, unless you send me an	552	This is not implemented yet (and might never be, unless you send me an
390	implementation). According to reports, C</dev/poll> only supports sockets	553	implementation). According to reports, C</dev/poll> only supports sockets
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	557	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		558
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	559	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
397	it's really slow, but it still scales very well (O(active_fds)).	560	it's really slow, but it still scales very well (O(active_fds)).
398		561
399	Please note that solaris event ports can deliver a lot of spurious	562	Please note that Solaris event ports can deliver a lot of spurious
400	notifications, so you need to use non-blocking I/O or other means to avoid	563	notifications, so you need to use non-blocking I/O or other means to avoid
401	blocking when no data (or space) is available.	564	blocking when no data (or space) is available.
402		565
403	While this backend scales well, it requires one system call per active	566	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	567	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	568	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	569	might perform better.
407		570
		571	On the positive side, with the exception of the spurious readiness
		572	notifications, this backend actually performed fully to specification
		573	in all tests and is fully embeddable, which is a rare feat among the
		574	OS-specific backends (I vastly prefer correctness over speed hacks).
		575
		576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		577	C<EVBACKEND_POLL>.
		578
408	=item C<EVBACKEND_ALL>	579	=item C<EVBACKEND_ALL>
409		580
410	Try all backends (even potentially broken ones that wouldn't be tried	581	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	582	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	583	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		584
414	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
415		586
416	=back	587	=back
417		588
418	If one or more of these are ored into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
419	backends will be tried (in the reverse order as given here). If none are	590	then only these backends will be tried (in the reverse order as listed
420	specified, most compiled-in backend will be tried, usually in reverse	591	here). If none are specified, all backends in C<ev_recommended_backends
421	order of their flag values :)	592	()> will be tried.
422
423	The most typical usage is like this:
424
425	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427
428	Restrict libev to the select and poll backends, and do not allow
429	environment settings to be taken into account:
430
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432
433	Use whatever libev has to offer, but make sure that kqueue is used if
434	available (warning, breaks stuff, best use only with your own private
435	event loop and only if you know the OS supports your types of fds):
436
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438
439	=item struct ev_loop *ev_loop_new (unsigned int flags)
440
441	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).
445		593
446	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
447		595
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	597	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
451		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		604
452	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
453		606
454	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	608	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	609	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
458	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
459	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	613	for example).
461		614
462	Note that certain global state, such as signal state, will not be freed by	615	Note that certain global state, such as signal state (and installed signal
463	this function, and related watchers (such as signal and child watchers)	616	handlers), will not be freed by this function, and related watchers (such
464	would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
465		618
466	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
467	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
468	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
469	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
470		627
471	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
472		629
473	Like C<ev_default_destroy>, but destroys an event loop created by an	630	This function sets a flag that causes subsequent C<ev_run> iterations to
474	earlier call to C<ev_loop_new>.
475
476	=item ev_default_fork ()
477
478	This function reinitialises the kernel state for backends that have	631	reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	632	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
481	again makes little sense).	634	child before resuming or calling C<ev_run>.
482		635
483	You I<must> call this function in the child process after forking if and	636	Again, you I<have> to call it on I<any> loop that you want to re-use after
484	only if you want to use the event library in both processes. If you just	637	a fork, I<even if you do not plan to use the loop in the parent>. This is
485	fork+exec, you don't have to call it.	638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		639	during fork.
		640
		641	On the other hand, you only need to call this function in the child
		642	process if and only if you want to use the event loop in the child. If
		643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
486		647
487	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
489	quite nicely into a call to C<pthread_atfork>:
490		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
491	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
492		662
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use	663	=item int ev_is_default_loop (loop)
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496		664
497	=item ev_loop_fork (loop)	665	Returns true when the given loop is, in fact, the default loop, and false
		666	otherwise.
498		667
499	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.
502
503	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
504		669
505	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
506	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
507	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
508		673
509	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
510	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
511	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited normally, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		689	throwing an exception etc.), doesn't count as "exit" - consider this
		690	as a hint to avoid such ungentleman-like behaviour unless it's really
		691	convenient, in which case it is fully supported.
512		692
513	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
514		694
515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	695	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
516	use.	696	use.
…		…
521	received events and started processing them. This timestamp does not	701	received events and started processing them. This timestamp does not
522	change as long as callbacks are being processed, and this is also the base	702	change as long as callbacks are being processed, and this is also the base
523	time used for relative timers. You can treat it as the timestamp of the	703	time used for relative timers. You can treat it as the timestamp of the
524	event occurring (or more correctly, libev finding out about it).	704	event occurring (or more correctly, libev finding out about it).
525		705
		706	=item ev_now_update (loop)
		707
		708	Establishes the current time by querying the kernel, updating the time
		709	returned by C<ev_now ()> in the progress. This is a costly operation and
		710	is usually done automatically within C<ev_run ()>.
		711
		712	This function is rarely useful, but when some event callback runs for a
		713	very long time without entering the event loop, updating libev's idea of
		714	the current time is a good idea.
		715
		716	See also L<The special problem of time updates> in the C<ev_timer> section.
		717
		718	=item ev_suspend (loop)
		719
		720	=item ev_resume (loop)
		721
		722	These two functions suspend and resume an event loop, for use when the
		723	loop is not used for a while and timeouts should not be processed.
		724
		725	A typical use case would be an interactive program such as a game: When
		726	the user presses C<^Z> to suspend the game and resumes it an hour later it
		727	would be best to handle timeouts as if no time had actually passed while
		728	the program was suspended. This can be achieved by calling C<ev_suspend>
		729	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		730	C<ev_resume> directly afterwards to resume timer processing.
		731
		732	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		733	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		734	will be rescheduled (that is, they will lose any events that would have
		735	occurred while suspended).
		736
		737	After calling C<ev_suspend> you B<must not> call I<any> function on the
		738	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		739	without a previous call to C<ev_suspend>.
		740
		741	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		742	event loop time (see C<ev_now_update>).
		743
526	=item ev_loop (loop, int flags)	744	=item ev_run (loop, int flags)
527		745
528	Finally, this is it, the event handler. This function usually is called	746	Finally, this is it, the event handler. This function usually is called
529	after you initialised all your watchers and you want to start handling	747	after you have initialised all your watchers and you want to start
530	events.	748	handling events. It will ask the operating system for any new events, call
		749	the watcher callbacks, an then repeat the whole process indefinitely: This
		750	is why event loops are called I<loops>.
531		751
532	If the flags argument is specified as C<0>, it will not return until	752	If the flags argument is specified as C<0>, it will keep handling events
533	either no event watchers are active anymore or C<ev_unloop> was called.	753	until either no event watchers are active anymore or C<ev_break> was
		754	called.
534		755
535	Please note that an explicit C<ev_unloop> is usually better than	756	Please note that an explicit C<ev_break> is usually better than
536	relying on all watchers to be stopped when deciding when a program has	757	relying on all watchers to be stopped when deciding when a program has
537	finished (especially in interactive programs), but having a program that	758	finished (especially in interactive programs), but having a program
538	automatically loops as long as it has to and no longer by virtue of	759	that automatically loops as long as it has to and no longer by virtue
539	relying on its watchers stopping correctly is a thing of beauty.	760	of relying on its watchers stopping correctly, that is truly a thing of
		761	beauty.
540		762
		763	This function is also I<mostly> exception-safe - you can break out of
		764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		765	exception and so on. This does not decrement the C<ev_depth> value, nor
		766	will it clear any outstanding C<EVBREAK_ONE> breaks.
		767
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
542	those events and any outstanding ones, but will not block your process in	769	those events and any already outstanding ones, but will not wait and
543	case there are no events and will return after one iteration of the loop.	770	block your process in case there are no events and will return after one
		771	iteration of the loop. This is sometimes useful to poll and handle new
		772	events while doing lengthy calculations, to keep the program responsive.
544		773
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	774	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
546	neccessary) and will handle those and any outstanding ones. It will block	775	necessary) and will handle those and any already outstanding ones. It
547	your process until at least one new event arrives, and will return after	776	will block your process until at least one new event arrives (which could
548	one iteration of the loop. This is useful if you are waiting for some	777	be an event internal to libev itself, so there is no guarantee that a
549	external event in conjunction with something not expressible using other	778	user-registered callback will be called), and will return after one
		779	iteration of the loop.
		780
		781	This is useful if you are waiting for some external event in conjunction
		782	with something not expressible using other libev watchers (i.e. "roll your
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	783	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	784	usually a better approach for this kind of thing.
552		785
553	Here are the gory details of what C<ev_loop> does:	786	Here are the gory details of what C<ev_run> does:
554		787
		788	- Increment loop depth.
		789	- Reset the ev_break status.
555	- Before the first iteration, call any pending watchers.	790	- Before the first iteration, call any pending watchers.
		791	LOOP:
556	* If EVFLAG_FORKCHECK was used, check for a fork.	792	- If EVFLAG_FORKCHECK was used, check for a fork.
557	- If a fork was detected, queue and call all fork watchers.	793	- If a fork was detected (by any means), queue and call all fork watchers.
558	- Queue and call all prepare watchers.	794	- Queue and call all prepare watchers.
		795	- If ev_break was called, goto FINISH.
559	- If we have been forked, recreate the kernel state.	796	- If we have been forked, detach and recreate the kernel state
		797	as to not disturb the other process.
560	- Update the kernel state with all outstanding changes.	798	- Update the kernel state with all outstanding changes.
561	- Update the "event loop time".	799	- Update the "event loop time" (ev_now ()).
562	- Calculate for how long to sleep or block, if at all	800	- Calculate for how long to sleep or block, if at all
563	(active idle watchers, EVLOOP_NONBLOCK or not having	801	(active idle watchers, EVRUN_NOWAIT or not having
564	any active watchers at all will result in not sleeping).	802	any active watchers at all will result in not sleeping).
565	- Sleep if the I/O and timer collect interval say so.	803	- Sleep if the I/O and timer collect interval say so.
		804	- Increment loop iteration counter.
566	- Block the process, waiting for any events.	805	- Block the process, waiting for any events.
567	- Queue all outstanding I/O (fd) events.	806	- Queue all outstanding I/O (fd) events.
568	- Update the "event loop time" and do time jump handling.	807	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
569	- Queue all outstanding timers.	808	- Queue all expired timers.
570	- Queue all outstanding periodics.	809	- Queue all expired periodics.
571	- If no events are pending now, queue all idle watchers.	810	- Queue all idle watchers with priority higher than that of pending events.
572	- Queue all check watchers.	811	- Queue all check watchers.
573	- Call all queued watchers in reverse order (i.e. check watchers first).	812	- Call all queued watchers in reverse order (i.e. check watchers first).
574	Signals and child watchers are implemented as I/O watchers, and will	813	Signals and child watchers are implemented as I/O watchers, and will
575	be handled here by queueing them when their watcher gets executed.	814	be handled here by queueing them when their watcher gets executed.
576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	815	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
577	were used, or there are no active watchers, return, otherwise	816	were used, or there are no active watchers, goto FINISH, otherwise
578	continue with step *.	817	continue with step LOOP.
		818	FINISH:
		819	- Reset the ev_break status iff it was EVBREAK_ONE.
		820	- Decrement the loop depth.
		821	- Return.
579		822
580	Example: Queue some jobs and then loop until no events are outstanding	823	Example: Queue some jobs and then loop until no events are outstanding
581	anymore.	824	anymore.
582		825
583	... queue jobs here, make sure they register event watchers as long	826	... queue jobs here, make sure they register event watchers as long
584	... as they still have work to do (even an idle watcher will do..)	827	... as they still have work to do (even an idle watcher will do..)
585	ev_loop (my_loop, 0);	828	ev_run (my_loop, 0);
586	... jobs done. yeah!	829	... jobs done or somebody called unloop. yeah!
587		830
588	=item ev_unloop (loop, how)	831	=item ev_break (loop, how)
589		832
590	Can be used to make a call to C<ev_loop> return early (but only after it	833	Can be used to make a call to C<ev_run> return early (but only after it
591	has processed all outstanding events). The C<how> argument must be either	834	has processed all outstanding events). The C<how> argument must be either
592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	835	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	836	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
594		837
595	This "unloop state" will be cleared when entering C<ev_loop> again.	838	This "break state" will be cleared on the next call to C<ev_run>.
		839
		840	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		841	which case it will have no effect.
596		842
597	=item ev_ref (loop)	843	=item ev_ref (loop)
598		844
599	=item ev_unref (loop)	845	=item ev_unref (loop)
600		846
601	Ref/unref can be used to add or remove a reference count on the event	847	Ref/unref can be used to add or remove a reference count on the event
602	loop: Every watcher keeps one reference, and as long as the reference	848	loop: Every watcher keeps one reference, and as long as the reference
603	count is nonzero, C<ev_loop> will not return on its own. If you have	849	count is nonzero, C<ev_run> will not return on its own.
604	a watcher you never unregister that should not keep C<ev_loop> from	850
605	returning, ev_unref() after starting, and ev_ref() before stopping it. For	851	This is useful when you have a watcher that you never intend to
		852	unregister, but that nevertheless should not keep C<ev_run> from
		853	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		854	before stopping it.
		855
606	example, libev itself uses this for its internal signal pipe: It is not	856	As an example, libev itself uses this for its internal signal pipe: It
607	visible to the libev user and should not keep C<ev_loop> from exiting if	857	is not visible to the libev user and should not keep C<ev_run> from
608	no event watchers registered by it are active. It is also an excellent	858	exiting if no event watchers registered by it are active. It is also an
609	way to do this for generic recurring timers or from within third-party	859	excellent way to do this for generic recurring timers or from within
610	libraries. Just remember to I<unref after start> and I<ref before stop>	860	third-party libraries. Just remember to I<unref after start> and I<ref
611	(but only if the watcher wasn't active before, or was active before,	861	before stop> (but only if the watcher wasn't active before, or was active
612	respectively).	862	before, respectively. Note also that libev might stop watchers itself
		863	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		864	in the callback).
613		865
614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	866	Example: Create a signal watcher, but keep it from keeping C<ev_run>
615	running when nothing else is active.	867	running when nothing else is active.
616		868
617	struct ev_signal exitsig;	869	ev_signal exitsig;
618	ev_signal_init (&exitsig, sig_cb, SIGINT);	870	ev_signal_init (&exitsig, sig_cb, SIGINT);
619	ev_signal_start (loop, &exitsig);	871	ev_signal_start (loop, &exitsig);
620	evf_unref (loop);	872	evf_unref (loop);
621		873
622	Example: For some weird reason, unregister the above signal handler again.	874	Example: For some weird reason, unregister the above signal handler again.
623		875
624	ev_ref (loop);	876	ev_ref (loop);
625	ev_signal_stop (loop, &exitsig);	877	ev_signal_stop (loop, &exitsig);
626		878
627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	879	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
628		880
629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	881	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
630		882
631	These advanced functions influence the time that libev will spend waiting	883	These advanced functions influence the time that libev will spend waiting
632	for events. Both are by default C<0>, meaning that libev will try to	884	for events. Both time intervals are by default C<0>, meaning that libev
633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	885	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		886	latency.
634		887
635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	888	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
636	allows libev to delay invocation of I/O and timer/periodic callbacks to	889	allows libev to delay invocation of I/O and timer/periodic callbacks
637	increase efficiency of loop iterations.	890	to increase efficiency of loop iterations (or to increase power-saving
		891	opportunities).
638		892
639	The background is that sometimes your program runs just fast enough to	893	The idea is that sometimes your program runs just fast enough to handle
640	handle one (or very few) event(s) per loop iteration. While this makes	894	one (or very few) event(s) per loop iteration. While this makes the
641	the program responsive, it also wastes a lot of CPU time to poll for new	895	program responsive, it also wastes a lot of CPU time to poll for new
642	events, especially with backends like C<select ()> which have a high	896	events, especially with backends like C<select ()> which have a high
643	overhead for the actual polling but can deliver many events at once.	897	overhead for the actual polling but can deliver many events at once.
644		898
645	By setting a higher I<io collect interval> you allow libev to spend more	899	By setting a higher I<io collect interval> you allow libev to spend more
646	time collecting I/O events, so you can handle more events per iteration,	900	time collecting I/O events, so you can handle more events per iteration,
647	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	901	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
648	C<ev_timer>) will be not affected. Setting this to a non-null value will	902	C<ev_timer>) will be not affected. Setting this to a non-null value will
649	introduce an additional C<ev_sleep ()> call into most loop iterations.	903	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		904	sleep time ensures that libev will not poll for I/O events more often then
		905	once per this interval, on average.
650		906
651	Likewise, by setting a higher I<timeout collect interval> you allow libev	907	Likewise, by setting a higher I<timeout collect interval> you allow libev
652	to spend more time collecting timeouts, at the expense of increased	908	to spend more time collecting timeouts, at the expense of increased
653	latency (the watcher callback will be called later). C<ev_io> watchers	909	latency/jitter/inexactness (the watcher callback will be called
654	will not be affected. Setting this to a non-null value will not introduce	910	later). C<ev_io> watchers will not be affected. Setting this to a non-null
655	any overhead in libev.	911	value will not introduce any overhead in libev.
656		912
657	Many (busy) programs can usually benefit by setting the io collect	913	Many (busy) programs can usually benefit by setting the I/O collect
658	interval to a value near C<0.1> or so, which is often enough for	914	interval to a value near C<0.1> or so, which is often enough for
659	interactive servers (of course not for games), likewise for timeouts. It	915	interactive servers (of course not for games), likewise for timeouts. It
660	usually doesn't make much sense to set it to a lower value than C<0.01>,	916	usually doesn't make much sense to set it to a lower value than C<0.01>,
661	as this approsaches the timing granularity of most systems.	917	as this approaches the timing granularity of most systems. Note that if
		918	you do transactions with the outside world and you can't increase the
		919	parallelity, then this setting will limit your transaction rate (if you
		920	need to poll once per transaction and the I/O collect interval is 0.01,
		921	then you can't do more than 100 transactions per second).
		922
		923	Setting the I<timeout collect interval> can improve the opportunity for
		924	saving power, as the program will "bundle" timer callback invocations that
		925	are "near" in time together, by delaying some, thus reducing the number of
		926	times the process sleeps and wakes up again. Another useful technique to
		927	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		928	they fire on, say, one-second boundaries only.
		929
		930	Example: we only need 0.1s timeout granularity, and we wish not to poll
		931	more often than 100 times per second:
		932
		933	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		934	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		935
		936	=item ev_invoke_pending (loop)
		937
		938	This call will simply invoke all pending watchers while resetting their
		939	pending state. Normally, C<ev_run> does this automatically when required,
		940	but when overriding the invoke callback this call comes handy. This
		941	function can be invoked from a watcher - this can be useful for example
		942	when you want to do some lengthy calculation and want to pass further
		943	event handling to another thread (you still have to make sure only one
		944	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		945
		946	=item int ev_pending_count (loop)
		947
		948	Returns the number of pending watchers - zero indicates that no watchers
		949	are pending.
		950
		951	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		952
		953	This overrides the invoke pending functionality of the loop: Instead of
		954	invoking all pending watchers when there are any, C<ev_run> will call
		955	this callback instead. This is useful, for example, when you want to
		956	invoke the actual watchers inside another context (another thread etc.).
		957
		958	If you want to reset the callback, use C<ev_invoke_pending> as new
		959	callback.
		960
		961	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		962
		963	Sometimes you want to share the same loop between multiple threads. This
		964	can be done relatively simply by putting mutex_lock/unlock calls around
		965	each call to a libev function.
		966
		967	However, C<ev_run> can run an indefinite time, so it is not feasible
		968	to wait for it to return. One way around this is to wake up the event
		969	loop via C<ev_break> and C<av_async_send>, another way is to set these
		970	I<release> and I<acquire> callbacks on the loop.
		971
		972	When set, then C<release> will be called just before the thread is
		973	suspended waiting for new events, and C<acquire> is called just
		974	afterwards.
		975
		976	Ideally, C<release> will just call your mutex_unlock function, and
		977	C<acquire> will just call the mutex_lock function again.
		978
		979	While event loop modifications are allowed between invocations of
		980	C<release> and C<acquire> (that's their only purpose after all), no
		981	modifications done will affect the event loop, i.e. adding watchers will
		982	have no effect on the set of file descriptors being watched, or the time
		983	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		984	to take note of any changes you made.
		985
		986	In theory, threads executing C<ev_run> will be async-cancel safe between
		987	invocations of C<release> and C<acquire>.
		988
		989	See also the locking example in the C<THREADS> section later in this
		990	document.
		991
		992	=item ev_set_userdata (loop, void *data)
		993
		994	=item ev_userdata (loop)
		995
		996	Set and retrieve a single C<void *> associated with a loop. When
		997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		998	C<0>.
		999
		1000	These two functions can be used to associate arbitrary data with a loop,
		1001	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1002	C<acquire> callbacks described above, but of course can be (ab-)used for
		1003	any other purpose as well.
		1004
		1005	=item ev_verify (loop)
		1006
		1007	This function only does something when C<EV_VERIFY> support has been
		1008	compiled in, which is the default for non-minimal builds. It tries to go
		1009	through all internal structures and checks them for validity. If anything
		1010	is found to be inconsistent, it will print an error message to standard
		1011	error and call C<abort ()>.
		1012
		1013	This can be used to catch bugs inside libev itself: under normal
		1014	circumstances, this function will never abort as of course libev keeps its
		1015	data structures consistent.
662		1016
663	=back	1017	=back
664		1018
665		1019
666	=head1 ANATOMY OF A WATCHER	1020	=head1 ANATOMY OF A WATCHER
667		1021
		1022	In the following description, uppercase C<TYPE> in names stands for the
		1023	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1024	watchers and C<ev_io_start> for I/O watchers.
		1025
668	A watcher is a structure that you create and register to record your	1026	A watcher is an opaque structure that you allocate and register to record
669	interest in some event. For instance, if you want to wait for STDIN to	1027	your interest in some event. To make a concrete example, imagine you want
670	become readable, you would create an C<ev_io> watcher for that:	1028	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1029	for that:
671		1030
672	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1031	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
673	{	1032	{
674	ev_io_stop (w);	1033	ev_io_stop (w);
675	ev_unloop (loop, EVUNLOOP_ALL);	1034	ev_break (loop, EVBREAK_ALL);
676	}	1035	}
677		1036
678	struct ev_loop *loop = ev_default_loop (0);	1037	struct ev_loop *loop = ev_default_loop (0);
		1038
679	struct ev_io stdin_watcher;	1039	ev_io stdin_watcher;
		1040
680	ev_init (&stdin_watcher, my_cb);	1041	ev_init (&stdin_watcher, my_cb);
681	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1042	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
682	ev_io_start (loop, &stdin_watcher);	1043	ev_io_start (loop, &stdin_watcher);
		1044
683	ev_loop (loop, 0);	1045	ev_run (loop, 0);
684		1046
685	As you can see, you are responsible for allocating the memory for your	1047	As you can see, you are responsible for allocating the memory for your
686	watcher structures (and it is usually a bad idea to do this on the stack,	1048	watcher structures (and it is I<usually> a bad idea to do this on the
687	although this can sometimes be quite valid).	1049	stack).
688		1050
		1051	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1052	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1053
689	Each watcher structure must be initialised by a call to C<ev_init	1054	Each watcher structure must be initialised by a call to C<ev_init (watcher
690	(watcher *, callback)>, which expects a callback to be provided. This	1055	*, callback)>, which expects a callback to be provided. This callback is
691	callback gets invoked each time the event occurs (or, in the case of io	1056	invoked each time the event occurs (or, in the case of I/O watchers, each
692	watchers, each time the event loop detects that the file descriptor given	1057	time the event loop detects that the file descriptor given is readable
693	is readable and/or writable).	1058	and/or writable).
694		1059
695	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1060	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
696	with arguments specific to this watcher type. There is also a macro	1061	macro to configure it, with arguments specific to the watcher type. There
697	to combine initialisation and setting in one call: C<< ev_<type>_init	1062	is also a macro to combine initialisation and setting in one call: C<<
698	(watcher *, callback, ...) >>.	1063	ev_TYPE_init (watcher *, callback, ...) >>.
699		1064
700	To make the watcher actually watch out for events, you have to start it	1065	To make the watcher actually watch out for events, you have to start it
701	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1066	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
702	*) >>), and you can stop watching for events at any time by calling the	1067	*) >>), and you can stop watching for events at any time by calling the
703	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1068	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
704		1069
705	As long as your watcher is active (has been started but not stopped) you	1070	As long as your watcher is active (has been started but not stopped) you
706	must not touch the values stored in it. Most specifically you must never	1071	must not touch the values stored in it. Most specifically you must never
707	reinitialise it or call its C<set> macro.	1072	reinitialise it or call its C<ev_TYPE_set> macro.
708		1073
709	Each and every callback receives the event loop pointer as first, the	1074	Each and every callback receives the event loop pointer as first, the
710	registered watcher structure as second, and a bitset of received events as	1075	registered watcher structure as second, and a bitset of received events as
711	third argument.	1076	third argument.
712		1077
…		…
721	=item C<EV_WRITE>	1086	=item C<EV_WRITE>
722		1087
723	The file descriptor in the C<ev_io> watcher has become readable and/or	1088	The file descriptor in the C<ev_io> watcher has become readable and/or
724	writable.	1089	writable.
725		1090
726	=item C<EV_TIMEOUT>	1091	=item C<EV_TIMER>
727		1092
728	The C<ev_timer> watcher has timed out.	1093	The C<ev_timer> watcher has timed out.
729		1094
730	=item C<EV_PERIODIC>	1095	=item C<EV_PERIODIC>
731		1096
…		…
749		1114
750	=item C<EV_PREPARE>	1115	=item C<EV_PREPARE>
751		1116
752	=item C<EV_CHECK>	1117	=item C<EV_CHECK>
753		1118
754	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1119	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
755	to gather new events, and all C<ev_check> watchers are invoked just after	1120	to gather new events, and all C<ev_check> watchers are invoked just after
756	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1121	C<ev_run> has gathered them, but before it invokes any callbacks for any
757	received events. Callbacks of both watcher types can start and stop as	1122	received events. Callbacks of both watcher types can start and stop as
758	many watchers as they want, and all of them will be taken into account	1123	many watchers as they want, and all of them will be taken into account
759	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1124	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
760	C<ev_loop> from blocking).	1125	C<ev_run> from blocking).
761		1126
762	=item C<EV_EMBED>	1127	=item C<EV_EMBED>
763		1128
764	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1129	The embedded event loop specified in the C<ev_embed> watcher needs attention.
765		1130
766	=item C<EV_FORK>	1131	=item C<EV_FORK>
767		1132
768	The event loop has been resumed in the child process after fork (see	1133	The event loop has been resumed in the child process after fork (see
769	C<ev_fork>).	1134	C<ev_fork>).
770		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
		1140	=item C<EV_ASYNC>
		1141
		1142	The given async watcher has been asynchronously notified (see C<ev_async>).
		1143
		1144	=item C<EV_CUSTOM>
		1145
		1146	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1147	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1148
771	=item C<EV_ERROR>	1149	=item C<EV_ERROR>
772		1150
773	An unspecified error has occured, the watcher has been stopped. This might	1151	An unspecified error has occurred, the watcher has been stopped. This might
774	happen because the watcher could not be properly started because libev	1152	happen because the watcher could not be properly started because libev
775	ran out of memory, a file descriptor was found to be closed or any other	1153	ran out of memory, a file descriptor was found to be closed or any other
		1154	problem. Libev considers these application bugs.
		1155
776	problem. You best act on it by reporting the problem and somehow coping	1156	You best act on it by reporting the problem and somehow coping with the
777	with the watcher being stopped.	1157	watcher being stopped. Note that well-written programs should not receive
		1158	an error ever, so when your watcher receives it, this usually indicates a
		1159	bug in your program.
778		1160
779	Libev will usually signal a few "dummy" events together with an error,	1161	Libev will usually signal a few "dummy" events together with an error, for
780	for example it might indicate that a fd is readable or writable, and if	1162	example it might indicate that a fd is readable or writable, and if your
781	your callbacks is well-written it can just attempt the operation and cope	1163	callbacks is well-written it can just attempt the operation and cope with
782	with the error from read() or write(). This will not work in multithreaded	1164	the error from read() or write(). This will not work in multi-threaded
783	programs, though, so beware.	1165	programs, though, as the fd could already be closed and reused for another
		1166	thing, so beware.
784		1167
785	=back	1168	=back
786		1169
787	=head2 GENERIC WATCHER FUNCTIONS	1170	=head2 GENERIC WATCHER FUNCTIONS
788
789	In the following description, C<TYPE> stands for the watcher type,
790	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
791		1171
792	=over 4	1172	=over 4
793		1173
794	=item C<ev_init> (ev_TYPE *watcher, callback)	1174	=item C<ev_init> (ev_TYPE *watcher, callback)
795		1175
…		…
801	which rolls both calls into one.	1181	which rolls both calls into one.
802		1182
803	You can reinitialise a watcher at any time as long as it has been stopped	1183	You can reinitialise a watcher at any time as long as it has been stopped
804	(or never started) and there are no pending events outstanding.	1184	(or never started) and there are no pending events outstanding.
805		1185
806	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1186	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
807	int revents)>.	1187	int revents)>.
808		1188
		1189	Example: Initialise an C<ev_io> watcher in two steps.
		1190
		1191	ev_io w;
		1192	ev_init (&w, my_cb);
		1193	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1194
809	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1195	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
810		1196
811	This macro initialises the type-specific parts of a watcher. You need to	1197	This macro initialises the type-specific parts of a watcher. You need to
812	call C<ev_init> at least once before you call this macro, but you can	1198	call C<ev_init> at least once before you call this macro, but you can
813	call C<ev_TYPE_set> any number of times. You must not, however, call this	1199	call C<ev_TYPE_set> any number of times. You must not, however, call this
814	macro on a watcher that is active (it can be pending, however, which is a	1200	macro on a watcher that is active (it can be pending, however, which is a
815	difference to the C<ev_init> macro).	1201	difference to the C<ev_init> macro).
816		1202
817	Although some watcher types do not have type-specific arguments	1203	Although some watcher types do not have type-specific arguments
818	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1204	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
819		1205
		1206	See C<ev_init>, above, for an example.
		1207
820	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1208	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
821		1209
822	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1210	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
823	calls into a single call. This is the most convinient method to initialise	1211	calls into a single call. This is the most convenient method to initialise
824	a watcher. The same limitations apply, of course.	1212	a watcher. The same limitations apply, of course.
825		1213
		1214	Example: Initialise and set an C<ev_io> watcher in one step.
		1215
		1216	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1217
826	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
827		1219
828	Starts (activates) the given watcher. Only active watchers will receive	1220	Starts (activates) the given watcher. Only active watchers will receive
829	events. If the watcher is already active nothing will happen.	1221	events. If the watcher is already active nothing will happen.
830		1222
		1223	Example: Start the C<ev_io> watcher that is being abused as example in this
		1224	whole section.
		1225
		1226	ev_io_start (EV_DEFAULT_UC, &w);
		1227
831	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1228	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
832		1229
833	Stops the given watcher again (if active) and clears the pending	1230	Stops the given watcher if active, and clears the pending status (whether
		1231	the watcher was active or not).
		1232
834	status. It is possible that stopped watchers are pending (for example,	1233	It is possible that stopped watchers are pending - for example,
835	non-repeating timers are being stopped when they become pending), but	1234	non-repeating timers are being stopped when they become pending - but
836	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1235	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
837	you want to free or reuse the memory used by the watcher it is therefore a	1236	pending. If you want to free or reuse the memory used by the watcher it is
838	good idea to always call its C<ev_TYPE_stop> function.	1237	therefore a good idea to always call its C<ev_TYPE_stop> function.
839		1238
840	=item bool ev_is_active (ev_TYPE *watcher)	1239	=item bool ev_is_active (ev_TYPE *watcher)
841		1240
842	Returns a true value iff the watcher is active (i.e. it has been started	1241	Returns a true value iff the watcher is active (i.e. it has been started
843	and not yet been stopped). As long as a watcher is active you must not modify	1242	and not yet been stopped). As long as a watcher is active you must not modify
…		…
859	=item ev_cb_set (ev_TYPE *watcher, callback)	1258	=item ev_cb_set (ev_TYPE *watcher, callback)
860		1259
861	Change the callback. You can change the callback at virtually any time	1260	Change the callback. You can change the callback at virtually any time
862	(modulo threads).	1261	(modulo threads).
863		1262
864	=item ev_set_priority (ev_TYPE *watcher, priority)	1263	=item ev_set_priority (ev_TYPE *watcher, int priority)
865		1264
866	=item int ev_priority (ev_TYPE *watcher)	1265	=item int ev_priority (ev_TYPE *watcher)
867		1266
868	Set and query the priority of the watcher. The priority is a small	1267	Set and query the priority of the watcher. The priority is a small
869	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1268	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
870	(default: C<-2>). Pending watchers with higher priority will be invoked	1269	(default: C<-2>). Pending watchers with higher priority will be invoked
871	before watchers with lower priority, but priority will not keep watchers	1270	before watchers with lower priority, but priority will not keep watchers
872	from being executed (except for C<ev_idle> watchers).	1271	from being executed (except for C<ev_idle> watchers).
873		1272
874	This means that priorities are I<only> used for ordering callback
875	invocation after new events have been received. This is useful, for
876	example, to reduce latency after idling, or more often, to bind two
877	watchers on the same event and make sure one is called first.
878
879	If you need to suppress invocation when higher priority events are pending	1273	If you need to suppress invocation when higher priority events are pending
880	you need to look at C<ev_idle> watchers, which provide this functionality.	1274	you need to look at C<ev_idle> watchers, which provide this functionality.
881		1275
882	You I<must not> change the priority of a watcher as long as it is active or	1276	You I<must not> change the priority of a watcher as long as it is active or
883	pending.	1277	pending.
884		1278
		1279	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1280	fine, as long as you do not mind that the priority value you query might
		1281	or might not have been clamped to the valid range.
		1282
885	The default priority used by watchers when no priority has been set is	1283	The default priority used by watchers when no priority has been set is
886	always C<0>, which is supposed to not be too high and not be too low :).	1284	always C<0>, which is supposed to not be too high and not be too low :).
887		1285
888	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1286	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
889	fine, as long as you do not mind that the priority value you query might	1287	priorities.
890	or might not have been adjusted to be within valid range.
891		1288
892	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
893		1290
894	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1291	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
895	C<loop> nor C<revents> need to be valid as long as the watcher callback	1292	C<loop> nor C<revents> need to be valid as long as the watcher callback
896	can deal with that fact.	1293	can deal with that fact, as both are simply passed through to the
		1294	callback.
897		1295
898	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1296	=item int ev_clear_pending (loop, ev_TYPE *watcher)
899		1297
900	If the watcher is pending, this function returns clears its pending status	1298	If the watcher is pending, this function clears its pending status and
901	and returns its C<revents> bitset (as if its callback was invoked). If the	1299	returns its C<revents> bitset (as if its callback was invoked). If the
902	watcher isn't pending it does nothing and returns C<0>.	1300	watcher isn't pending it does nothing and returns C<0>.
903		1301
		1302	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1303	callback to be invoked, which can be accomplished with this function.
		1304
		1305	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1306
		1307	Feeds the given event set into the event loop, as if the specified event
		1308	had happened for the specified watcher (which must be a pointer to an
		1309	initialised but not necessarily started event watcher). Obviously you must
		1310	not free the watcher as long as it has pending events.
		1311
		1312	Stopping the watcher, letting libev invoke it, or calling
		1313	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1314	not started in the first place.
		1315
		1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1317	functions that do not need a watcher.
		1318
904	=back	1319	=back
905		1320
906
907	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
908		1322
909	Each watcher has, by default, a member C<void *data> that you can change	1323	Each watcher has, by default, a member C<void *data> that you can change
910	and read at any time, libev will completely ignore it. This can be used	1324	and read at any time: libev will completely ignore it. This can be used
911	to associate arbitrary data with your watcher. If you need more data and	1325	to associate arbitrary data with your watcher. If you need more data and
912	don't want to allocate memory and store a pointer to it in that data	1326	don't want to allocate memory and store a pointer to it in that data
913	member, you can also "subclass" the watcher type and provide your own	1327	member, you can also "subclass" the watcher type and provide your own
914	data:	1328	data:
915		1329
916	struct my_io	1330	struct my_io
917	{	1331	{
918	struct ev_io io;	1332	ev_io io;
919	int otherfd;	1333	int otherfd;
920	void *somedata;	1334	void *somedata;
921	struct whatever *mostinteresting;	1335	struct whatever *mostinteresting;
922	}	1336	};
		1337
		1338	...
		1339	struct my_io w;
		1340	ev_io_init (&w.io, my_cb, fd, EV_READ);
923		1341
924	And since your callback will be called with a pointer to the watcher, you	1342	And since your callback will be called with a pointer to the watcher, you
925	can cast it back to your own type:	1343	can cast it back to your own type:
926		1344
927	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1345	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
928	{	1346	{
929	struct my_io *w = (struct my_io *)w_;	1347	struct my_io *w = (struct my_io *)w_;
930	...	1348	...
931	}	1349	}
932		1350
933	More interesting and less C-conformant ways of casting your callback type	1351	More interesting and less C-conformant ways of casting your callback type
934	instead have been omitted.	1352	instead have been omitted.
935		1353
936	Another common scenario is having some data structure with multiple	1354	Another common scenario is to use some data structure with multiple
937	watchers:	1355	embedded watchers:
938		1356
939	struct my_biggy	1357	struct my_biggy
940	{	1358	{
941	int some_data;	1359	int some_data;
942	ev_timer t1;	1360	ev_timer t1;
943	ev_timer t2;	1361	ev_timer t2;
944	}	1362	}
945		1363
946	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1364	In this case getting the pointer to C<my_biggy> is a bit more
947	you need to use C<offsetof>:	1365	complicated: Either you store the address of your C<my_biggy> struct
		1366	in the C<data> member of the watcher (for woozies), or you need to use
		1367	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1368	programmers):
948		1369
949	#include <stddef.h>	1370	#include <stddef.h>
950		1371
951	static void	1372	static void
952	t1_cb (EV_P_ struct ev_timer *w, int revents)	1373	t1_cb (EV_P_ ev_timer *w, int revents)
953	{	1374	{
954	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
955	(((char *)w) - offsetof (struct my_biggy, t1));	1376	(((char *)w) - offsetof (struct my_biggy, t1));
956	}	1377	}
957		1378
958	static void	1379	static void
959	t2_cb (EV_P_ struct ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
960	{	1381	{
961	struct my_biggy big = (struct my_biggy *	1382	struct my_biggy big = (struct my_biggy *)
962	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
963	}	1384	}
		1385
		1386	=head2 WATCHER STATES
		1387
		1388	There are various watcher states mentioned throughout this manual -
		1389	active, pending and so on. In this section these states and the rules to
		1390	transition between them will be described in more detail - and while these
		1391	rules might look complicated, they usually do "the right thing".
		1392
		1393	=over 4
		1394
		1395	=item initialiased
		1396
		1397	Before a watcher can be registered with the event looop it has to be
		1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1400
		1401	In this state it is simply some block of memory that is suitable for use
		1402	in an event loop. It can be moved around, freed, reused etc. at will.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is it can be reused, moved, modified in any way
		1441	you wish.
		1442
		1443	=back
		1444
		1445	=head2 WATCHER PRIORITY MODELS
		1446
		1447	Many event loops support I<watcher priorities>, which are usually small
		1448	integers that influence the ordering of event callback invocation
		1449	between watchers in some way, all else being equal.
		1450
		1451	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1452	description for the more technical details such as the actual priority
		1453	range.
		1454
		1455	There are two common ways how these these priorities are being interpreted
		1456	by event loops:
		1457
		1458	In the more common lock-out model, higher priorities "lock out" invocation
		1459	of lower priority watchers, which means as long as higher priority
		1460	watchers receive events, lower priority watchers are not being invoked.
		1461
		1462	The less common only-for-ordering model uses priorities solely to order
		1463	callback invocation within a single event loop iteration: Higher priority
		1464	watchers are invoked before lower priority ones, but they all get invoked
		1465	before polling for new events.
		1466
		1467	Libev uses the second (only-for-ordering) model for all its watchers
		1468	except for idle watchers (which use the lock-out model).
		1469
		1470	The rationale behind this is that implementing the lock-out model for
		1471	watchers is not well supported by most kernel interfaces, and most event
		1472	libraries will just poll for the same events again and again as long as
		1473	their callbacks have not been executed, which is very inefficient in the
		1474	common case of one high-priority watcher locking out a mass of lower
		1475	priority ones.
		1476
		1477	Static (ordering) priorities are most useful when you have two or more
		1478	watchers handling the same resource: a typical usage example is having an
		1479	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1480	timeouts. Under load, data might be received while the program handles
		1481	other jobs, but since timers normally get invoked first, the timeout
		1482	handler will be executed before checking for data. In that case, giving
		1483	the timer a lower priority than the I/O watcher ensures that I/O will be
		1484	handled first even under adverse conditions (which is usually, but not
		1485	always, what you want).
		1486
		1487	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1488	will only be executed when no same or higher priority watchers have
		1489	received events, they can be used to implement the "lock-out" model when
		1490	required.
		1491
		1492	For example, to emulate how many other event libraries handle priorities,
		1493	you can associate an C<ev_idle> watcher to each such watcher, and in
		1494	the normal watcher callback, you just start the idle watcher. The real
		1495	processing is done in the idle watcher callback. This causes libev to
		1496	continuously poll and process kernel event data for the watcher, but when
		1497	the lock-out case is known to be rare (which in turn is rare :), this is
		1498	workable.
		1499
		1500	Usually, however, the lock-out model implemented that way will perform
		1501	miserably under the type of load it was designed to handle. In that case,
		1502	it might be preferable to stop the real watcher before starting the
		1503	idle watcher, so the kernel will not have to process the event in case
		1504	the actual processing will be delayed for considerable time.
		1505
		1506	Here is an example of an I/O watcher that should run at a strictly lower
		1507	priority than the default, and which should only process data when no
		1508	other events are pending:
		1509
		1510	ev_idle idle; // actual processing watcher
		1511	ev_io io; // actual event watcher
		1512
		1513	static void
		1514	io_cb (EV_P_ ev_io *w, int revents)
		1515	{
		1516	// stop the I/O watcher, we received the event, but
		1517	// are not yet ready to handle it.
		1518	ev_io_stop (EV_A_ w);
		1519
		1520	// start the idle watcher to handle the actual event.
		1521	// it will not be executed as long as other watchers
		1522	// with the default priority are receiving events.
		1523	ev_idle_start (EV_A_ &idle);
		1524	}
		1525
		1526	static void
		1527	idle_cb (EV_P_ ev_idle *w, int revents)
		1528	{
		1529	// actual processing
		1530	read (STDIN_FILENO, ...);
		1531
		1532	// have to start the I/O watcher again, as
		1533	// we have handled the event
		1534	ev_io_start (EV_P_ &io);
		1535	}
		1536
		1537	// initialisation
		1538	ev_idle_init (&idle, idle_cb);
		1539	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1540	ev_io_start (EV_DEFAULT_ &io);
		1541
		1542	In the "real" world, it might also be beneficial to start a timer, so that
		1543	low-priority connections can not be locked out forever under load. This
		1544	enables your program to keep a lower latency for important connections
		1545	during short periods of high load, while not completely locking out less
		1546	important ones.
964		1547
965		1548
966	=head1 WATCHER TYPES	1549	=head1 WATCHER TYPES
967		1550
968	This section describes each watcher in detail, but will not repeat	1551	This section describes each watcher in detail, but will not repeat
…		…
992	In general you can register as many read and/or write event watchers per	1575	In general you can register as many read and/or write event watchers per
993	fd as you want (as long as you don't confuse yourself). Setting all file	1576	fd as you want (as long as you don't confuse yourself). Setting all file
994	descriptors to non-blocking mode is also usually a good idea (but not	1577	descriptors to non-blocking mode is also usually a good idea (but not
995	required if you know what you are doing).	1578	required if you know what you are doing).
996		1579
997	If you must do this, then force the use of a known-to-be-good backend	1580	If you cannot use non-blocking mode, then force the use of a
998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1581	known-to-be-good backend (at the time of this writing, this includes only
999	C<EVBACKEND_POLL>).	1582	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1583	descriptors for which non-blocking operation makes no sense (such as
		1584	files) - libev doesn't guarantee any specific behaviour in that case.
1000		1585
1001	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1002	receive "spurious" readyness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is your callback might
1003	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1004	because there is no data. Not only are some backends known to create a	1589	because there is no data. Not only are some backends known to create a
1005	lot of those (for example solaris ports), it is very easy to get into	1590	lot of those (for example Solaris ports), it is very easy to get into
1006	this situation even with a relatively standard program structure. Thus	1591	this situation even with a relatively standard program structure. Thus
1007	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1592	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1008	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1593	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1009		1594
1010	If you cannot run the fd in non-blocking mode (for example you should not	1595	If you cannot run the fd in non-blocking mode (for example you should
1011	play around with an Xlib connection), then you have to seperately re-test	1596	not play around with an Xlib connection), then you have to separately
1012	whether a file descriptor is really ready with a known-to-be good interface	1597	re-test whether a file descriptor is really ready with a known-to-be good
1013	such as poll (fortunately in our Xlib example, Xlib already does this on	1598	interface such as poll (fortunately in our Xlib example, Xlib already
1014	its own, so its quite safe to use).	1599	does this on its own, so its quite safe to use). Some people additionally
		1600	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1601	indefinitely.
		1602
		1603	But really, best use non-blocking mode.
1015		1604
1016	=head3 The special problem of disappearing file descriptors	1605	=head3 The special problem of disappearing file descriptors
1017		1606
1018	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1607	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1019	descriptor (either by calling C<close> explicitly or by any other means,	1608	descriptor (either due to calling C<close> explicitly or any other means,
1020	such as C<dup>). The reason is that you register interest in some file	1609	such as C<dup2>). The reason is that you register interest in some file
1021	descriptor, but when it goes away, the operating system will silently drop	1610	descriptor, but when it goes away, the operating system will silently drop
1022	this interest. If another file descriptor with the same number then is	1611	this interest. If another file descriptor with the same number then is
1023	registered with libev, there is no efficient way to see that this is, in	1612	registered with libev, there is no efficient way to see that this is, in
1024	fact, a different file descriptor.	1613	fact, a different file descriptor.
1025		1614
…		…
1054	To support fork in your programs, you either have to call	1643	To support fork in your programs, you either have to call
1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1644	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1645	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1057	C<EVBACKEND_POLL>.	1646	C<EVBACKEND_POLL>.
1058		1647
		1648	=head3 The special problem of SIGPIPE
		1649
		1650	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1651	when writing to a pipe whose other end has been closed, your program gets
		1652	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1653	this is sensible behaviour, for daemons, this is usually undesirable.
		1654
		1655	So when you encounter spurious, unexplained daemon exits, make sure you
		1656	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1657	somewhere, as that would have given you a big clue).
		1658
		1659	=head3 The special problem of accept()ing when you can't
		1660
		1661	Many implementations of the POSIX C<accept> function (for example,
		1662	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1663	connection from the pending queue in all error cases.
		1664
		1665	For example, larger servers often run out of file descriptors (because
		1666	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1667	rejecting the connection, leading to libev signalling readiness on
		1668	the next iteration again (the connection still exists after all), and
		1669	typically causing the program to loop at 100% CPU usage.
		1670
		1671	Unfortunately, the set of errors that cause this issue differs between
		1672	operating systems, there is usually little the app can do to remedy the
		1673	situation, and no known thread-safe method of removing the connection to
		1674	cope with overload is known (to me).
		1675
		1676	One of the easiest ways to handle this situation is to just ignore it
		1677	- when the program encounters an overload, it will just loop until the
		1678	situation is over. While this is a form of busy waiting, no OS offers an
		1679	event-based way to handle this situation, so it's the best one can do.
		1680
		1681	A better way to handle the situation is to log any errors other than
		1682	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1683	messages, and continue as usual, which at least gives the user an idea of
		1684	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1685	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1686	usage.
		1687
		1688	If your program is single-threaded, then you could also keep a dummy file
		1689	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1690	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1691	close that fd, and create a new dummy fd. This will gracefully refuse
		1692	clients under typical overload conditions.
		1693
		1694	The last way to handle it is to simply log the error and C<exit>, as
		1695	is often done with C<malloc> failures, but this results in an easy
		1696	opportunity for a DoS attack.
1059		1697
1060	=head3 Watcher-Specific Functions	1698	=head3 Watcher-Specific Functions
1061		1699
1062	=over 4	1700	=over 4
1063		1701
1064	=item ev_io_init (ev_io *, callback, int fd, int events)	1702	=item ev_io_init (ev_io *, callback, int fd, int events)
1065		1703
1066	=item ev_io_set (ev_io *, int fd, int events)	1704	=item ev_io_set (ev_io *, int fd, int events)
1067		1705
1068	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1706	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1069	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1707	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1070	C<EV_READ | EV_WRITE> to receive the given events.	1708	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1071		1709
1072	=item int fd [read-only]	1710	=item int fd [read-only]
1073		1711
1074	The file descriptor being watched.	1712	The file descriptor being watched.
1075		1713
…		…
1083		1721
1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1722	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1085	readable, but only once. Since it is likely line-buffered, you could	1723	readable, but only once. Since it is likely line-buffered, you could
1086	attempt to read a whole line in the callback.	1724	attempt to read a whole line in the callback.
1087		1725
1088	static void	1726	static void
1089	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1727	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1090	{	1728	{
1091	ev_io_stop (loop, w);	1729	ev_io_stop (loop, w);
1092	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1730	.. read from stdin here (or from w->fd) and handle any I/O errors
1093	}	1731	}
1094		1732
1095	...	1733	...
1096	struct ev_loop *loop = ev_default_init (0);	1734	struct ev_loop *loop = ev_default_init (0);
1097	struct ev_io stdin_readable;	1735	ev_io stdin_readable;
1098	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1736	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1099	ev_io_start (loop, &stdin_readable);	1737	ev_io_start (loop, &stdin_readable);
1100	ev_loop (loop, 0);	1738	ev_run (loop, 0);
1101		1739
1102		1740
1103	=head2 C<ev_timer> - relative and optionally repeating timeouts	1741	=head2 C<ev_timer> - relative and optionally repeating timeouts
1104		1742
1105	Timer watchers are simple relative timers that generate an event after a	1743	Timer watchers are simple relative timers that generate an event after a
1106	given time, and optionally repeating in regular intervals after that.	1744	given time, and optionally repeating in regular intervals after that.
1107		1745
1108	The timers are based on real time, that is, if you register an event that	1746	The timers are based on real time, that is, if you register an event that
1109	times out after an hour and you reset your system clock to last years	1747	times out after an hour and you reset your system clock to January last
1110	time, it will still time out after (roughly) and hour. "Roughly" because	1748	year, it will still time out after (roughly) one hour. "Roughly" because
1111	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1112	monotonic clock option helps a lot here).	1750	monotonic clock option helps a lot here).
		1751
		1752	The callback is guaranteed to be invoked only I<after> its timeout has
		1753	passed (not I<at>, so on systems with very low-resolution clocks this
		1754	might introduce a small delay). If multiple timers become ready during the
		1755	same loop iteration then the ones with earlier time-out values are invoked
		1756	before ones of the same priority with later time-out values (but this is
		1757	no longer true when a callback calls C<ev_run> recursively).
		1758
		1759	=head3 Be smart about timeouts
		1760
		1761	Many real-world problems involve some kind of timeout, usually for error
		1762	recovery. A typical example is an HTTP request - if the other side hangs,
		1763	you want to raise some error after a while.
		1764
		1765	What follows are some ways to handle this problem, from obvious and
		1766	inefficient to smart and efficient.
		1767
		1768	In the following, a 60 second activity timeout is assumed - a timeout that
		1769	gets reset to 60 seconds each time there is activity (e.g. each time some
		1770	data or other life sign was received).
		1771
		1772	=over 4
		1773
		1774	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1775
		1776	This is the most obvious, but not the most simple way: In the beginning,
		1777	start the watcher:
		1778
		1779	ev_timer_init (timer, callback, 60., 0.);
		1780	ev_timer_start (loop, timer);
		1781
		1782	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1783	and start it again:
		1784
		1785	ev_timer_stop (loop, timer);
		1786	ev_timer_set (timer, 60., 0.);
		1787	ev_timer_start (loop, timer);
		1788
		1789	This is relatively simple to implement, but means that each time there is
		1790	some activity, libev will first have to remove the timer from its internal
		1791	data structure and then add it again. Libev tries to be fast, but it's
		1792	still not a constant-time operation.
		1793
		1794	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1795
		1796	This is the easiest way, and involves using C<ev_timer_again> instead of
		1797	C<ev_timer_start>.
		1798
		1799	To implement this, configure an C<ev_timer> with a C<repeat> value
		1800	of C<60> and then call C<ev_timer_again> at start and each time you
		1801	successfully read or write some data. If you go into an idle state where
		1802	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1803	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1804
		1805	That means you can ignore both the C<ev_timer_start> function and the
		1806	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1807	member and C<ev_timer_again>.
		1808
		1809	At start:
		1810
		1811	ev_init (timer, callback);
		1812	timer->repeat = 60.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	Each time there is some activity:
		1816
		1817	ev_timer_again (loop, timer);
		1818
		1819	It is even possible to change the time-out on the fly, regardless of
		1820	whether the watcher is active or not:
		1821
		1822	timer->repeat = 30.;
		1823	ev_timer_again (loop, timer);
		1824
		1825	This is slightly more efficient then stopping/starting the timer each time
		1826	you want to modify its timeout value, as libev does not have to completely
		1827	remove and re-insert the timer from/into its internal data structure.
		1828
		1829	It is, however, even simpler than the "obvious" way to do it.
		1830
		1831	=item 3. Let the timer time out, but then re-arm it as required.
		1832
		1833	This method is more tricky, but usually most efficient: Most timeouts are
		1834	relatively long compared to the intervals between other activity - in
		1835	our example, within 60 seconds, there are usually many I/O events with
		1836	associated activity resets.
		1837
		1838	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1839	but remember the time of last activity, and check for a real timeout only
		1840	within the callback:
		1841
		1842	ev_tstamp last_activity; // time of last activity
		1843
		1844	static void
		1845	callback (EV_P_ ev_timer *w, int revents)
		1846	{
		1847	ev_tstamp now = ev_now (EV_A);
		1848	ev_tstamp timeout = last_activity + 60.;
		1849
		1850	// if last_activity + 60. is older than now, we did time out
		1851	if (timeout < now)
		1852	{
		1853	// timeout occurred, take action
		1854	}
		1855	else
		1856	{
		1857	// callback was invoked, but there was some activity, re-arm
		1858	// the watcher to fire in last_activity + 60, which is
		1859	// guaranteed to be in the future, so "again" is positive:
		1860	w->repeat = timeout - now;
		1861	ev_timer_again (EV_A_ w);
		1862	}
		1863	}
		1864
		1865	To summarise the callback: first calculate the real timeout (defined
		1866	as "60 seconds after the last activity"), then check if that time has
		1867	been reached, which means something I<did>, in fact, time out. Otherwise
		1868	the callback was invoked too early (C<timeout> is in the future), so
		1869	re-schedule the timer to fire at that future time, to see if maybe we have
		1870	a timeout then.
		1871
		1872	Note how C<ev_timer_again> is used, taking advantage of the
		1873	C<ev_timer_again> optimisation when the timer is already running.
		1874
		1875	This scheme causes more callback invocations (about one every 60 seconds
		1876	minus half the average time between activity), but virtually no calls to
		1877	libev to change the timeout.
		1878
		1879	To start the timer, simply initialise the watcher and set C<last_activity>
		1880	to the current time (meaning we just have some activity :), then call the
		1881	callback, which will "do the right thing" and start the timer:
		1882
		1883	ev_init (timer, callback);
		1884	last_activity = ev_now (loop);
		1885	callback (loop, timer, EV_TIMER);
		1886
		1887	And when there is some activity, simply store the current time in
		1888	C<last_activity>, no libev calls at all:
		1889
		1890	last_activity = ev_now (loop);
		1891
		1892	This technique is slightly more complex, but in most cases where the
		1893	time-out is unlikely to be triggered, much more efficient.
		1894
		1895	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1896	callback :) - just change the timeout and invoke the callback, which will
		1897	fix things for you.
		1898
		1899	=item 4. Wee, just use a double-linked list for your timeouts.
		1900
		1901	If there is not one request, but many thousands (millions...), all
		1902	employing some kind of timeout with the same timeout value, then one can
		1903	do even better:
		1904
		1905	When starting the timeout, calculate the timeout value and put the timeout
		1906	at the I<end> of the list.
		1907
		1908	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1909	the list is expected to fire (for example, using the technique #3).
		1910
		1911	When there is some activity, remove the timer from the list, recalculate
		1912	the timeout, append it to the end of the list again, and make sure to
		1913	update the C<ev_timer> if it was taken from the beginning of the list.
		1914
		1915	This way, one can manage an unlimited number of timeouts in O(1) time for
		1916	starting, stopping and updating the timers, at the expense of a major
		1917	complication, and having to use a constant timeout. The constant timeout
		1918	ensures that the list stays sorted.
		1919
		1920	=back
		1921
		1922	So which method the best?
		1923
		1924	Method #2 is a simple no-brain-required solution that is adequate in most
		1925	situations. Method #3 requires a bit more thinking, but handles many cases
		1926	better, and isn't very complicated either. In most case, choosing either
		1927	one is fine, with #3 being better in typical situations.
		1928
		1929	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1930	rather complicated, but extremely efficient, something that really pays
		1931	off after the first million or so of active timers, i.e. it's usually
		1932	overkill :)
		1933
		1934	=head3 The special problem of time updates
		1935
		1936	Establishing the current time is a costly operation (it usually takes at
		1937	least two system calls): EV therefore updates its idea of the current
		1938	time only before and after C<ev_run> collects new events, which causes a
		1939	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1940	lots of events in one iteration.
1113		1941
1114	The relative timeouts are calculated relative to the C<ev_now ()>	1942	The relative timeouts are calculated relative to the C<ev_now ()>
1115	time. This is usually the right thing as this timestamp refers to the time	1943	time. This is usually the right thing as this timestamp refers to the time
1116	of the event triggering whatever timeout you are modifying/starting. If	1944	of the event triggering whatever timeout you are modifying/starting. If
1117	you suspect event processing to be delayed and you I<need> to base the timeout	1945	you suspect event processing to be delayed and you I<need> to base the
1118	on the current time, use something like this to adjust for this:	1946	timeout on the current time, use something like this to adjust for this:
1119		1947
1120	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1121		1949
1122	The callback is guarenteed to be invoked only when its timeout has passed,	1950	If the event loop is suspended for a long time, you can also force an
1123	but if multiple timers become ready during the same loop iteration then	1951	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1124	order of execution is undefined.	1952	()>.
		1953
		1954	=head3 The special problems of suspended animation
		1955
		1956	When you leave the server world it is quite customary to hit machines that
		1957	can suspend/hibernate - what happens to the clocks during such a suspend?
		1958
		1959	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1960	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1961	to run until the system is suspended, but they will not advance while the
		1962	system is suspended. That means, on resume, it will be as if the program
		1963	was frozen for a few seconds, but the suspend time will not be counted
		1964	towards C<ev_timer> when a monotonic clock source is used. The real time
		1965	clock advanced as expected, but if it is used as sole clocksource, then a
		1966	long suspend would be detected as a time jump by libev, and timers would
		1967	be adjusted accordingly.
		1968
		1969	I would not be surprised to see different behaviour in different between
		1970	operating systems, OS versions or even different hardware.
		1971
		1972	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1973	time jump in the monotonic clocks and the realtime clock. If the program
		1974	is suspended for a very long time, and monotonic clock sources are in use,
		1975	then you can expect C<ev_timer>s to expire as the full suspension time
		1976	will be counted towards the timers. When no monotonic clock source is in
		1977	use, then libev will again assume a timejump and adjust accordingly.
		1978
		1979	It might be beneficial for this latter case to call C<ev_suspend>
		1980	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1981	deterministic behaviour in this case (you can do nothing against
		1982	C<SIGSTOP>).
1125		1983
1126	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1127		1985
1128	=over 4	1986	=over 4
1129		1987
1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1988	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1131		1989
1132	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1990	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1133		1991
1134	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1992	Configure the timer to trigger after C<after> seconds. If C<repeat>
1135	C<0.>, then it will automatically be stopped. If it is positive, then the	1993	is C<0.>, then it will automatically be stopped once the timeout is
1136	timer will automatically be configured to trigger again C<repeat> seconds	1994	reached. If it is positive, then the timer will automatically be
1137	later, again, and again, until stopped manually.	1995	configured to trigger again C<repeat> seconds later, again, and again,
		1996	until stopped manually.
1138		1997
1139	The timer itself will do a best-effort at avoiding drift, that is, if you	1998	The timer itself will do a best-effort at avoiding drift, that is, if
1140	configure a timer to trigger every 10 seconds, then it will trigger at	1999	you configure a timer to trigger every 10 seconds, then it will normally
1141	exactly 10 second intervals. If, however, your program cannot keep up with	2000	trigger at exactly 10 second intervals. If, however, your program cannot
1142	the timer (because it takes longer than those 10 seconds to do stuff) the	2001	keep up with the timer (because it takes longer than those 10 seconds to
1143	timer will not fire more than once per event loop iteration.	2002	do stuff) the timer will not fire more than once per event loop iteration.
1144		2003
1145	=item ev_timer_again (loop)	2004	=item ev_timer_again (loop, ev_timer *)
1146		2005
1147	This will act as if the timer timed out and restart it again if it is	2006	This will act as if the timer timed out and restart it again if it is
1148	repeating. The exact semantics are:	2007	repeating. The exact semantics are:
1149		2008
1150	If the timer is pending, its pending status is cleared.	2009	If the timer is pending, its pending status is cleared.
1151		2010
1152	If the timer is started but nonrepeating, stop it (as if it timed out).	2011	If the timer is started but non-repeating, stop it (as if it timed out).
1153		2012
1154	If the timer is repeating, either start it if necessary (with the	2013	If the timer is repeating, either start it if necessary (with the
1155	C<repeat> value), or reset the running timer to the C<repeat> value.	2014	C<repeat> value), or reset the running timer to the C<repeat> value.
1156		2015
1157	This sounds a bit complicated, but here is a useful and typical	2016	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1158	example: Imagine you have a tcp connection and you want a so-called idle	2017	usage example.
1159	timeout, that is, you want to be called when there have been, say, 60
1160	seconds of inactivity on the socket. The easiest way to do this is to
1161	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1162	C<ev_timer_again> each time you successfully read or write some data. If
1163	you go into an idle state where you do not expect data to travel on the
1164	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1165	automatically restart it if need be.
1166		2018
1167	That means you can ignore the C<after> value and C<ev_timer_start>	2019	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1168	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1169		2020
1170	ev_timer_init (timer, callback, 0., 5.);	2021	Returns the remaining time until a timer fires. If the timer is active,
1171	ev_timer_again (loop, timer);	2022	then this time is relative to the current event loop time, otherwise it's
1172	...	2023	the timeout value currently configured.
1173	timer->again = 17.;
1174	ev_timer_again (loop, timer);
1175	...
1176	timer->again = 10.;
1177	ev_timer_again (loop, timer);
1178		2024
1179	This is more slightly efficient then stopping/starting the timer each time	2025	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1180	you want to modify its timeout value.	2026	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2027	will return C<4>. When the timer expires and is restarted, it will return
		2028	roughly C<7> (likely slightly less as callback invocation takes some time,
		2029	too), and so on.
1181		2030
1182	=item ev_tstamp repeat [read-write]	2031	=item ev_tstamp repeat [read-write]
1183		2032
1184	The current C<repeat> value. Will be used each time the watcher times out	2033	The current C<repeat> value. Will be used each time the watcher times out
1185	or C<ev_timer_again> is called and determines the next timeout (if any),	2034	or C<ev_timer_again> is called, and determines the next timeout (if any),
1186	which is also when any modifications are taken into account.	2035	which is also when any modifications are taken into account.
1187		2036
1188	=back	2037	=back
1189		2038
1190	=head3 Examples	2039	=head3 Examples
1191		2040
1192	Example: Create a timer that fires after 60 seconds.	2041	Example: Create a timer that fires after 60 seconds.
1193		2042
1194	static void	2043	static void
1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2044	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1196	{	2045	{
1197	.. one minute over, w is actually stopped right here	2046	.. one minute over, w is actually stopped right here
1198	}	2047	}
1199		2048
1200	struct ev_timer mytimer;	2049	ev_timer mytimer;
1201	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2050	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1202	ev_timer_start (loop, &mytimer);	2051	ev_timer_start (loop, &mytimer);
1203		2052
1204	Example: Create a timeout timer that times out after 10 seconds of	2053	Example: Create a timeout timer that times out after 10 seconds of
1205	inactivity.	2054	inactivity.
1206		2055
1207	static void	2056	static void
1208	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2057	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1209	{	2058	{
1210	.. ten seconds without any activity	2059	.. ten seconds without any activity
1211	}	2060	}
1212		2061
1213	struct ev_timer mytimer;	2062	ev_timer mytimer;
1214	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2063	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1215	ev_timer_again (&mytimer); /* start timer */	2064	ev_timer_again (&mytimer); /* start timer */
1216	ev_loop (loop, 0);	2065	ev_run (loop, 0);
1217		2066
1218	// and in some piece of code that gets executed on any "activity":	2067	// and in some piece of code that gets executed on any "activity":
1219	// reset the timeout to start ticking again at 10 seconds	2068	// reset the timeout to start ticking again at 10 seconds
1220	ev_timer_again (&mytimer);	2069	ev_timer_again (&mytimer);
1221		2070
1222		2071
1223	=head2 C<ev_periodic> - to cron or not to cron?	2072	=head2 C<ev_periodic> - to cron or not to cron?
1224		2073
1225	Periodic watchers are also timers of a kind, but they are very versatile	2074	Periodic watchers are also timers of a kind, but they are very versatile
1226	(and unfortunately a bit complex).	2075	(and unfortunately a bit complex).
1227		2076
1228	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2077	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1229	but on wallclock time (absolute time). You can tell a periodic watcher	2078	relative time, the physical time that passes) but on wall clock time
1230	to trigger "at" some specific point in time. For example, if you tell a	2079	(absolute time, the thing you can read on your calender or clock). The
1231	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2080	difference is that wall clock time can run faster or slower than real
1232	+ 10.>) and then reset your system clock to the last year, then it will	2081	time, and time jumps are not uncommon (e.g. when you adjust your
1233	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	2082	wrist-watch).
1234	roughly 10 seconds later).
1235		2083
1236	They can also be used to implement vastly more complex timers, such as	2084	You can tell a periodic watcher to trigger after some specific point
1237	triggering an event on each midnight, local time or other, complicated,	2085	in time: for example, if you tell a periodic watcher to trigger "in 10
1238	rules.	2086	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2087	not a delay) and then reset your system clock to January of the previous
		2088	year, then it will take a year or more to trigger the event (unlike an
		2089	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2090	it, as it uses a relative timeout).
1239		2091
		2092	C<ev_periodic> watchers can also be used to implement vastly more complex
		2093	timers, such as triggering an event on each "midnight, local time", or
		2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2095	those cannot react to time jumps.
		2096
1240	As with timers, the callback is guarenteed to be invoked only when the	2097	As with timers, the callback is guaranteed to be invoked only when the
1241	time (C<at>) has been passed, but if multiple periodic timers become ready	2098	point in time where it is supposed to trigger has passed. If multiple
1242	during the same loop iteration then order of execution is undefined.	2099	timers become ready during the same loop iteration then the ones with
		2100	earlier time-out values are invoked before ones with later time-out values
		2101	(but this is no longer true when a callback calls C<ev_run> recursively).
1243		2102
1244	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1245		2104
1246	=over 4	2105	=over 4
1247		2106
1248	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2107	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1249		2108
1250	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2109	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1251		2110
1252	Lots of arguments, lets sort it out... There are basically three modes of	2111	Lots of arguments, let's sort it out... There are basically three modes of
1253	operation, and we will explain them from simplest to complex:	2112	operation, and we will explain them from simplest to most complex:
1254		2113
1255	=over 4	2114	=over 4
1256		2115
1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2116	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1258		2117
1259	In this configuration the watcher triggers an event at the wallclock time	2118	In this configuration the watcher triggers an event after the wall clock
1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	2119	time C<offset> has passed. It will not repeat and will not adjust when a
1261	that is, if it is to be run at January 1st 2011 then it will run when the	2120	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1262	system time reaches or surpasses this time.	2121	will be stopped and invoked when the system clock reaches or surpasses
		2122	this point in time.
1263		2123
1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2124	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1265		2125
1266	In this mode the watcher will always be scheduled to time out at the next	2126	In this mode the watcher will always be scheduled to time out at the next
1267	C<at + N * interval> time (for some integer N, which can also be negative)	2127	C<offset + N * interval> time (for some integer N, which can also be
1268	and then repeat, regardless of any time jumps.	2128	negative) and then repeat, regardless of any time jumps. The C<offset>
		2129	argument is merely an offset into the C<interval> periods.
1269		2130
1270	This can be used to create timers that do not drift with respect to system	2131	This can be used to create timers that do not drift with respect to the
1271	time:	2132	system clock, for example, here is an C<ev_periodic> that triggers each
		2133	hour, on the hour (with respect to UTC):
1272		2134
1273	ev_periodic_set (&periodic, 0., 3600., 0);	2135	ev_periodic_set (&periodic, 0., 3600., 0);
1274		2136
1275	This doesn't mean there will always be 3600 seconds in between triggers,	2137	This doesn't mean there will always be 3600 seconds in between triggers,
1276	but only that the the callback will be called when the system time shows a	2138	but only that the callback will be called when the system time shows a
1277	full hour (UTC), or more correctly, when the system time is evenly divisible	2139	full hour (UTC), or more correctly, when the system time is evenly divisible
1278	by 3600.	2140	by 3600.
1279		2141
1280	Another way to think about it (for the mathematically inclined) is that	2142	Another way to think about it (for the mathematically inclined) is that
1281	C<ev_periodic> will try to run the callback in this mode at the next possible	2143	C<ev_periodic> will try to run the callback in this mode at the next possible
1282	time where C<time = at (mod interval)>, regardless of any time jumps.	2144	time where C<time = offset (mod interval)>, regardless of any time jumps.
1283		2145
1284	For numerical stability it is preferable that the C<at> value is near	2146	For numerical stability it is preferable that the C<offset> value is near
1285	C<ev_now ()> (the current time), but there is no range requirement for	2147	C<ev_now ()> (the current time), but there is no range requirement for
1286	this value.	2148	this value, and in fact is often specified as zero.
1287		2149
		2150	Note also that there is an upper limit to how often a timer can fire (CPU
		2151	speed for example), so if C<interval> is very small then timing stability
		2152	will of course deteriorate. Libev itself tries to be exact to be about one
		2153	millisecond (if the OS supports it and the machine is fast enough).
		2154
1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2155	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1289		2156
1290	In this mode the values for C<interval> and C<at> are both being	2157	In this mode the values for C<interval> and C<offset> are both being
1291	ignored. Instead, each time the periodic watcher gets scheduled, the	2158	ignored. Instead, each time the periodic watcher gets scheduled, the
1292	reschedule callback will be called with the watcher as first, and the	2159	reschedule callback will be called with the watcher as first, and the
1293	current time as second argument.	2160	current time as second argument.
1294		2161
1295	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2162	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1296	ever, or make any event loop modifications>. If you need to stop it,	2163	or make ANY other event loop modifications whatsoever, unless explicitly
1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	2164	allowed by documentation here>.
1298	starting an C<ev_prepare> watcher, which is legal).
1299		2165
		2166	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2167	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2168	only event loop modification you are allowed to do).
		2169
1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2170	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1301	ev_tstamp now)>, e.g.:	2171	*w, ev_tstamp now)>, e.g.:
1302		2172
		2173	static ev_tstamp
1303	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2174	my_rescheduler (ev_periodic *w, ev_tstamp now)
1304	{	2175	{
1305	return now + 60.;	2176	return now + 60.;
1306	}	2177	}
1307		2178
1308	It must return the next time to trigger, based on the passed time value	2179	It must return the next time to trigger, based on the passed time value
1309	(that is, the lowest time value larger than to the second argument). It	2180	(that is, the lowest time value larger than to the second argument). It
1310	will usually be called just before the callback will be triggered, but	2181	will usually be called just before the callback will be triggered, but
1311	might be called at other times, too.	2182	might be called at other times, too.
1312		2183
1313	NOTE: I<< This callback must always return a time that is later than the	2184	NOTE: I<< This callback must always return a time that is higher than or
1314	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2185	equal to the passed C<now> value >>.
1315		2186
1316	This can be used to create very complex timers, such as a timer that	2187	This can be used to create very complex timers, such as a timer that
1317	triggers on each midnight, local time. To do this, you would calculate the	2188	triggers on "next midnight, local time". To do this, you would calculate the
1318	next midnight after C<now> and return the timestamp value for this. How	2189	next midnight after C<now> and return the timestamp value for this. How
1319	you do this is, again, up to you (but it is not trivial, which is the main	2190	you do this is, again, up to you (but it is not trivial, which is the main
1320	reason I omitted it as an example).	2191	reason I omitted it as an example).
1321		2192
1322	=back	2193	=back
…		…
1326	Simply stops and restarts the periodic watcher again. This is only useful	2197	Simply stops and restarts the periodic watcher again. This is only useful
1327	when you changed some parameters or the reschedule callback would return	2198	when you changed some parameters or the reschedule callback would return
1328	a different time than the last time it was called (e.g. in a crond like	2199	a different time than the last time it was called (e.g. in a crond like
1329	program when the crontabs have changed).	2200	program when the crontabs have changed).
1330		2201
		2202	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2203
		2204	When active, returns the absolute time that the watcher is supposed
		2205	to trigger next. This is not the same as the C<offset> argument to
		2206	C<ev_periodic_set>, but indeed works even in interval and manual
		2207	rescheduling modes.
		2208
1331	=item ev_tstamp offset [read-write]	2209	=item ev_tstamp offset [read-write]
1332		2210
1333	When repeating, this contains the offset value, otherwise this is the	2211	When repeating, this contains the offset value, otherwise this is the
1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2212	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2213	although libev might modify this value for better numerical stability).
1335		2214
1336	Can be modified any time, but changes only take effect when the periodic	2215	Can be modified any time, but changes only take effect when the periodic
1337	timer fires or C<ev_periodic_again> is being called.	2216	timer fires or C<ev_periodic_again> is being called.
1338		2217
1339	=item ev_tstamp interval [read-write]	2218	=item ev_tstamp interval [read-write]
1340		2219
1341	The current interval value. Can be modified any time, but changes only	2220	The current interval value. Can be modified any time, but changes only
1342	take effect when the periodic timer fires or C<ev_periodic_again> is being	2221	take effect when the periodic timer fires or C<ev_periodic_again> is being
1343	called.	2222	called.
1344		2223
1345	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2224	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1346		2225
1347	The current reschedule callback, or C<0>, if this functionality is	2226	The current reschedule callback, or C<0>, if this functionality is
1348	switched off. Can be changed any time, but changes only take effect when	2227	switched off. Can be changed any time, but changes only take effect when
1349	the periodic timer fires or C<ev_periodic_again> is being called.	2228	the periodic timer fires or C<ev_periodic_again> is being called.
1350		2229
1351	=item ev_tstamp at [read-only]
1352
1353	When active, contains the absolute time that the watcher is supposed to
1354	trigger next.
1355
1356	=back	2230	=back
1357		2231
1358	=head3 Examples	2232	=head3 Examples
1359		2233
1360	Example: Call a callback every hour, or, more precisely, whenever the	2234	Example: Call a callback every hour, or, more precisely, whenever the
1361	system clock is divisible by 3600. The callback invocation times have	2235	system time is divisible by 3600. The callback invocation times have
1362	potentially a lot of jittering, but good long-term stability.	2236	potentially a lot of jitter, but good long-term stability.
1363		2237
1364	static void	2238	static void
1365	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2239	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1366	{	2240	{
1367	... its now a full hour (UTC, or TAI or whatever your clock follows)	2241	... its now a full hour (UTC, or TAI or whatever your clock follows)
1368	}	2242	}
1369		2243
1370	struct ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
1371	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2245	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1372	ev_periodic_start (loop, &hourly_tick);	2246	ev_periodic_start (loop, &hourly_tick);
1373		2247
1374	Example: The same as above, but use a reschedule callback to do it:	2248	Example: The same as above, but use a reschedule callback to do it:
1375		2249
1376	#include <math.h>	2250	#include <math.h>
1377		2251
1378	static ev_tstamp	2252	static ev_tstamp
1379	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2253	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1380	{	2254	{
1381	return fmod (now, 3600.) + 3600.;	2255	return now + (3600. - fmod (now, 3600.));
1382	}	2256	}
1383		2257
1384	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2258	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1385		2259
1386	Example: Call a callback every hour, starting now:	2260	Example: Call a callback every hour, starting now:
1387		2261
1388	struct ev_periodic hourly_tick;	2262	ev_periodic hourly_tick;
1389	ev_periodic_init (&hourly_tick, clock_cb,	2263	ev_periodic_init (&hourly_tick, clock_cb,
1390	fmod (ev_now (loop), 3600.), 3600., 0);	2264	fmod (ev_now (loop), 3600.), 3600., 0);
1391	ev_periodic_start (loop, &hourly_tick);	2265	ev_periodic_start (loop, &hourly_tick);
1392		2266
1393		2267
1394	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
1395		2269
1396	Signal watchers will trigger an event when the process receives a specific	2270	Signal watchers will trigger an event when the process receives a specific
1397	signal one or more times. Even though signals are very asynchronous, libev	2271	signal one or more times. Even though signals are very asynchronous, libev
1398	will try it's best to deliver signals synchronously, i.e. as part of the	2272	will try its best to deliver signals synchronously, i.e. as part of the
1399	normal event processing, like any other event.	2273	normal event processing, like any other event.
1400		2274
		2275	If you want signals to be delivered truly asynchronously, just use
		2276	C<sigaction> as you would do without libev and forget about sharing
		2277	the signal. You can even use C<ev_async> from a signal handler to
		2278	synchronously wake up an event loop.
		2279
1401	You can configure as many watchers as you like per signal. Only when the	2280	You can configure as many watchers as you like for the same signal, but
		2281	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2282	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2283	C<SIGINT> in both the default loop and another loop at the same time. At
		2284	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2285
1402	first watcher gets started will libev actually register a signal watcher	2286	When the first watcher gets started will libev actually register something
1403	with the kernel (thus it coexists with your own signal handlers as long	2287	with the kernel (thus it coexists with your own signal handlers as long as
1404	as you don't register any with libev). Similarly, when the last signal	2288	you don't register any with libev for the same signal).
1405	watcher for a signal is stopped libev will reset the signal handler to	2289
1406	SIG_DFL (regardless of what it was set to before).	2290	If possible and supported, libev will install its handlers with
		2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
		2292	not be unduly interrupted. If you have a problem with system calls getting
		2293	interrupted by signals you can block all signals in an C<ev_check> watcher
		2294	and unblock them in an C<ev_prepare> watcher.
		2295
		2296	=head3 The special problem of inheritance over fork/execve/pthread_create
		2297
		2298	Both the signal mask (C<sigprocmask>) and the signal disposition
		2299	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2300	stopping it again), that is, libev might or might not block the signal,
		2301	and might or might not set or restore the installed signal handler.
		2302
		2303	While this does not matter for the signal disposition (libev never
		2304	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2305	C<execve>), this matters for the signal mask: many programs do not expect
		2306	certain signals to be blocked.
		2307
		2308	This means that before calling C<exec> (from the child) you should reset
		2309	the signal mask to whatever "default" you expect (all clear is a good
		2310	choice usually).
		2311
		2312	The simplest way to ensure that the signal mask is reset in the child is
		2313	to install a fork handler with C<pthread_atfork> that resets it. That will
		2314	catch fork calls done by libraries (such as the libc) as well.
		2315
		2316	In current versions of libev, the signal will not be blocked indefinitely
		2317	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2318	the window of opportunity for problems, it will not go away, as libev
		2319	I<has> to modify the signal mask, at least temporarily.
		2320
		2321	So I can't stress this enough: I<If you do not reset your signal mask when
		2322	you expect it to be empty, you have a race condition in your code>. This
		2323	is not a libev-specific thing, this is true for most event libraries.
1407		2324
1408	=head3 Watcher-Specific Functions and Data Members	2325	=head3 Watcher-Specific Functions and Data Members
1409		2326
1410	=over 4	2327	=over 4
1411		2328
…		…
1420		2337
1421	The signal the watcher watches out for.	2338	The signal the watcher watches out for.
1422		2339
1423	=back	2340	=back
1424		2341
		2342	=head3 Examples
		2343
		2344	Example: Try to exit cleanly on SIGINT.
		2345
		2346	static void
		2347	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		2348	{
		2349	ev_break (loop, EVBREAK_ALL);
		2350	}
		2351
		2352	ev_signal signal_watcher;
		2353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2354	ev_signal_start (loop, &signal_watcher);
		2355
1425		2356
1426	=head2 C<ev_child> - watch out for process status changes	2357	=head2 C<ev_child> - watch out for process status changes
1427		2358
1428	Child watchers trigger when your process receives a SIGCHLD in response to	2359	Child watchers trigger when your process receives a SIGCHLD in response to
1429	some child status changes (most typically when a child of yours dies).	2360	some child status changes (most typically when a child of yours dies or
		2361	exits). It is permissible to install a child watcher I<after> the child
		2362	has been forked (which implies it might have already exited), as long
		2363	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2364	forking and then immediately registering a watcher for the child is fine,
		2365	but forking and registering a watcher a few event loop iterations later or
		2366	in the next callback invocation is not.
		2367
		2368	Only the default event loop is capable of handling signals, and therefore
		2369	you can only register child watchers in the default event loop.
		2370
		2371	Due to some design glitches inside libev, child watchers will always be
		2372	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2373	libev)
		2374
		2375	=head3 Process Interaction
		2376
		2377	Libev grabs C<SIGCHLD> as soon as the default event loop is
		2378	initialised. This is necessary to guarantee proper behaviour even if the
		2379	first child watcher is started after the child exits. The occurrence
		2380	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		2381	synchronously as part of the event loop processing. Libev always reaps all
		2382	children, even ones not watched.
		2383
		2384	=head3 Overriding the Built-In Processing
		2385
		2386	Libev offers no special support for overriding the built-in child
		2387	processing, but if your application collides with libev's default child
		2388	handler, you can override it easily by installing your own handler for
		2389	C<SIGCHLD> after initialising the default loop, and making sure the
		2390	default loop never gets destroyed. You are encouraged, however, to use an
		2391	event-based approach to child reaping and thus use libev's support for
		2392	that, so other libev users can use C<ev_child> watchers freely.
		2393
		2394	=head3 Stopping the Child Watcher
		2395
		2396	Currently, the child watcher never gets stopped, even when the
		2397	child terminates, so normally one needs to stop the watcher in the
		2398	callback. Future versions of libev might stop the watcher automatically
		2399	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2400	problem).
1430		2401
1431	=head3 Watcher-Specific Functions and Data Members	2402	=head3 Watcher-Specific Functions and Data Members
1432		2403
1433	=over 4	2404	=over 4
1434		2405
1435	=item ev_child_init (ev_child *, callback, int pid)	2406	=item ev_child_init (ev_child *, callback, int pid, int trace)
1436		2407
1437	=item ev_child_set (ev_child *, int pid)	2408	=item ev_child_set (ev_child *, int pid, int trace)
1438		2409
1439	Configures the watcher to wait for status changes of process C<pid> (or	2410	Configures the watcher to wait for status changes of process C<pid> (or
1440	I<any> process if C<pid> is specified as C<0>). The callback can look	2411	I<any> process if C<pid> is specified as C<0>). The callback can look
1441	at the C<rstatus> member of the C<ev_child> watcher structure to see	2412	at the C<rstatus> member of the C<ev_child> watcher structure to see
1442	the status word (use the macros from C<sys/wait.h> and see your systems	2413	the status word (use the macros from C<sys/wait.h> and see your systems
1443	C<waitpid> documentation). The C<rpid> member contains the pid of the	2414	C<waitpid> documentation). The C<rpid> member contains the pid of the
1444	process causing the status change.	2415	process causing the status change. C<trace> must be either C<0> (only
		2416	activate the watcher when the process terminates) or C<1> (additionally
		2417	activate the watcher when the process is stopped or continued).
1445		2418
1446	=item int pid [read-only]	2419	=item int pid [read-only]
1447		2420
1448	The process id this watcher watches out for, or C<0>, meaning any process id.	2421	The process id this watcher watches out for, or C<0>, meaning any process id.
1449		2422
…		…
1458		2431
1459	=back	2432	=back
1460		2433
1461	=head3 Examples	2434	=head3 Examples
1462		2435
1463	Example: Try to exit cleanly on SIGINT and SIGTERM.	2436	Example: C<fork()> a new process and install a child handler to wait for
		2437	its completion.
1464		2438
		2439	ev_child cw;
		2440
1465	static void	2441	static void
1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2442	child_cb (EV_P_ ev_child *w, int revents)
1467	{	2443	{
1468	ev_unloop (loop, EVUNLOOP_ALL);	2444	ev_child_stop (EV_A_ w);
		2445	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1469	}	2446	}
1470		2447
1471	struct ev_signal signal_watcher;	2448	pid_t pid = fork ();
1472	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2449
1473	ev_signal_start (loop, &sigint_cb);	2450	if (pid < 0)
		2451	// error
		2452	else if (pid == 0)
		2453	{
		2454	// the forked child executes here
		2455	exit (1);
		2456	}
		2457	else
		2458	{
		2459	ev_child_init (&cw, child_cb, pid, 0);
		2460	ev_child_start (EV_DEFAULT_ &cw);
		2461	}
1474		2462
1475		2463
1476	=head2 C<ev_stat> - did the file attributes just change?	2464	=head2 C<ev_stat> - did the file attributes just change?
1477		2465
1478	This watches a filesystem path for attribute changes. That is, it calls	2466	This watches a file system path for attribute changes. That is, it calls
1479	C<stat> regularly (or when the OS says it changed) and sees if it changed	2467	C<stat> on that path in regular intervals (or when the OS says it changed)
1480	compared to the last time, invoking the callback if it did.	2468	and sees if it changed compared to the last time, invoking the callback if
		2469	it did.
1481		2470
1482	The path does not need to exist: changing from "path exists" to "path does	2471	The path does not need to exist: changing from "path exists" to "path does
1483	not exist" is a status change like any other. The condition "path does	2472	not exist" is a status change like any other. The condition "path does not
1484	not exist" is signified by the C<st_nlink> field being zero (which is	2473	exist" (or more correctly "path cannot be stat'ed") is signified by the
1485	otherwise always forced to be at least one) and all the other fields of	2474	C<st_nlink> field being zero (which is otherwise always forced to be at
1486	the stat buffer having unspecified contents.	2475	least one) and all the other fields of the stat buffer having unspecified
		2476	contents.
1487		2477
1488	The path I<should> be absolute and I<must not> end in a slash. If it is	2478	The path I<must not> end in a slash or contain special components such as
		2479	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1489	relative and your working directory changes, the behaviour is undefined.	2480	your working directory changes, then the behaviour is undefined.
1490		2481
1491	Since there is no standard to do this, the portable implementation simply	2482	Since there is no portable change notification interface available, the
1492	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2483	portable implementation simply calls C<stat(2)> regularly on the path
1493	can specify a recommended polling interval for this case. If you specify	2484	to see if it changed somehow. You can specify a recommended polling
1494	a polling interval of C<0> (highly recommended!) then a I<suitable,	2485	interval for this case. If you specify a polling interval of C<0> (highly
1495	unspecified default> value will be used (which you can expect to be around	2486	recommended!) then a I<suitable, unspecified default> value will be used
1496	five seconds, although this might change dynamically). Libev will also	2487	(which you can expect to be around five seconds, although this might
1497	impose a minimum interval which is currently around C<0.1>, but thats	2488	change dynamically). Libev will also impose a minimum interval which is
1498	usually overkill.	2489	currently around C<0.1>, but that's usually overkill.
1499		2490
1500	This watcher type is not meant for massive numbers of stat watchers,	2491	This watcher type is not meant for massive numbers of stat watchers,
1501	as even with OS-supported change notifications, this can be	2492	as even with OS-supported change notifications, this can be
1502	resource-intensive.	2493	resource-intensive.
1503		2494
1504	At the time of this writing, only the Linux inotify interface is	2495	At the time of this writing, the only OS-specific interface implemented
1505	implemented (implementing kqueue support is left as an exercise for the	2496	is the Linux inotify interface (implementing kqueue support is left as an
1506	reader). Inotify will be used to give hints only and should not change the	2497	exercise for the reader. Note, however, that the author sees no way of
1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2498	implementing C<ev_stat> semantics with kqueue, except as a hint).
1508	to fall back to regular polling again even with inotify, but changes are
1509	usually detected immediately, and if the file exists there will be no
1510	polling.
1511		2499
1512	=head3 Inotify	2500	=head3 ABI Issues (Largefile Support)
1513		2501
		2502	Libev by default (unless the user overrides this) uses the default
		2503	compilation environment, which means that on systems with large file
		2504	support disabled by default, you get the 32 bit version of the stat
		2505	structure. When using the library from programs that change the ABI to
		2506	use 64 bit file offsets the programs will fail. In that case you have to
		2507	compile libev with the same flags to get binary compatibility. This is
		2508	obviously the case with any flags that change the ABI, but the problem is
		2509	most noticeably displayed with ev_stat and large file support.
		2510
		2511	The solution for this is to lobby your distribution maker to make large
		2512	file interfaces available by default (as e.g. FreeBSD does) and not
		2513	optional. Libev cannot simply switch on large file support because it has
		2514	to exchange stat structures with application programs compiled using the
		2515	default compilation environment.
		2516
		2517	=head3 Inotify and Kqueue
		2518
1514	When C<inotify (7)> support has been compiled into libev (generally only	2519	When C<inotify (7)> support has been compiled into libev and present at
1515	available on Linux) and present at runtime, it will be used to speed up	2520	runtime, it will be used to speed up change detection where possible. The
1516	change detection where possible. The inotify descriptor will be created lazily	2521	inotify descriptor will be created lazily when the first C<ev_stat>
1517	when the first C<ev_stat> watcher is being started.	2522	watcher is being started.
1518		2523
1519	Inotify presense does not change the semantics of C<ev_stat> watchers	2524	Inotify presence does not change the semantics of C<ev_stat> watchers
1520	except that changes might be detected earlier, and in some cases, to avoid	2525	except that changes might be detected earlier, and in some cases, to avoid
1521	making regular C<stat> calls. Even in the presense of inotify support	2526	making regular C<stat> calls. Even in the presence of inotify support
1522	there are many cases where libev has to resort to regular C<stat> polling.	2527	there are many cases where libev has to resort to regular C<stat> polling,
		2528	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2529	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2530	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2531	xfs are fully working) libev usually gets away without polling.
1523		2532
1524	(There is no support for kqueue, as apparently it cannot be used to	2533	There is no support for kqueue, as apparently it cannot be used to
1525	implement this functionality, due to the requirement of having a file	2534	implement this functionality, due to the requirement of having a file
1526	descriptor open on the object at all times).	2535	descriptor open on the object at all times, and detecting renames, unlinks
		2536	etc. is difficult.
		2537
		2538	=head3 C<stat ()> is a synchronous operation
		2539
		2540	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2541	the process. The exception are C<ev_stat> watchers - those call C<stat
		2542	()>, which is a synchronous operation.
		2543
		2544	For local paths, this usually doesn't matter: unless the system is very
		2545	busy or the intervals between stat's are large, a stat call will be fast,
		2546	as the path data is usually in memory already (except when starting the
		2547	watcher).
		2548
		2549	For networked file systems, calling C<stat ()> can block an indefinite
		2550	time due to network issues, and even under good conditions, a stat call
		2551	often takes multiple milliseconds.
		2552
		2553	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2554	paths, although this is fully supported by libev.
1527		2555
1528	=head3 The special problem of stat time resolution	2556	=head3 The special problem of stat time resolution
1529		2557
1530	The C<stat ()> syscall only supports full-second resolution portably, and	2558	The C<stat ()> system call only supports full-second resolution portably,
1531	even on systems where the resolution is higher, many filesystems still	2559	and even on systems where the resolution is higher, most file systems
1532	only support whole seconds.	2560	still only support whole seconds.
1533		2561
1534	That means that, if the time is the only thing that changes, you might	2562	That means that, if the time is the only thing that changes, you can
1535	miss updates: on the first update, C<ev_stat> detects a change and calls	2563	easily miss updates: on the first update, C<ev_stat> detects a change and
1536	your callback, which does something. When there is another update within	2564	calls your callback, which does something. When there is another update
1537	the same second, C<ev_stat> will be unable to detect it.	2565	within the same second, C<ev_stat> will be unable to detect unless the
		2566	stat data does change in other ways (e.g. file size).
1538		2567
1539	The solution to this is to delay acting on a change for a second (or till	2568	The solution to this is to delay acting on a change for slightly more
1540	the next second boundary), using a roughly one-second delay C<ev_timer>	2569	than a second (or till slightly after the next full second boundary), using
1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2570	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1542	is added to work around small timing inconsistencies of some operating	2571	ev_timer_again (loop, w)>).
1543	systems.	2572
		2573	The C<.02> offset is added to work around small timing inconsistencies
		2574	of some operating systems (where the second counter of the current time
		2575	might be be delayed. One such system is the Linux kernel, where a call to
		2576	C<gettimeofday> might return a timestamp with a full second later than
		2577	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2578	update file times then there will be a small window where the kernel uses
		2579	the previous second to update file times but libev might already execute
		2580	the timer callback).
1544		2581
1545	=head3 Watcher-Specific Functions and Data Members	2582	=head3 Watcher-Specific Functions and Data Members
1546		2583
1547	=over 4	2584	=over 4
1548		2585
…		…
1554	C<path>. The C<interval> is a hint on how quickly a change is expected to	2591	C<path>. The C<interval> is a hint on how quickly a change is expected to
1555	be detected and should normally be specified as C<0> to let libev choose	2592	be detected and should normally be specified as C<0> to let libev choose
1556	a suitable value. The memory pointed to by C<path> must point to the same	2593	a suitable value. The memory pointed to by C<path> must point to the same
1557	path for as long as the watcher is active.	2594	path for as long as the watcher is active.
1558		2595
1559	The callback will be receive C<EV_STAT> when a change was detected,	2596	The callback will receive an C<EV_STAT> event when a change was detected,
1560	relative to the attributes at the time the watcher was started (or the	2597	relative to the attributes at the time the watcher was started (or the
1561	last change was detected).	2598	last change was detected).
1562		2599
1563	=item ev_stat_stat (ev_stat *)	2600	=item ev_stat_stat (loop, ev_stat *)
1564		2601
1565	Updates the stat buffer immediately with new values. If you change the	2602	Updates the stat buffer immediately with new values. If you change the
1566	watched path in your callback, you could call this fucntion to avoid	2603	watched path in your callback, you could call this function to avoid
1567	detecting this change (while introducing a race condition). Can also be	2604	detecting this change (while introducing a race condition if you are not
1568	useful simply to find out the new values.	2605	the only one changing the path). Can also be useful simply to find out the
		2606	new values.
1569		2607
1570	=item ev_statdata attr [read-only]	2608	=item ev_statdata attr [read-only]
1571		2609
1572	The most-recently detected attributes of the file. Although the type is of	2610	The most-recently detected attributes of the file. Although the type is
1573	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2611	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1574	suitable for your system. If the C<st_nlink> member is C<0>, then there	2612	suitable for your system, but you can only rely on the POSIX-standardised
		2613	members to be present. If the C<st_nlink> member is C<0>, then there was
1575	was some error while C<stat>ing the file.	2614	some error while C<stat>ing the file.
1576		2615
1577	=item ev_statdata prev [read-only]	2616	=item ev_statdata prev [read-only]
1578		2617
1579	The previous attributes of the file. The callback gets invoked whenever	2618	The previous attributes of the file. The callback gets invoked whenever
1580	C<prev> != C<attr>.	2619	C<prev> != C<attr>, or, more precisely, one or more of these members
		2620	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2621	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1581		2622
1582	=item ev_tstamp interval [read-only]	2623	=item ev_tstamp interval [read-only]
1583		2624
1584	The specified interval.	2625	The specified interval.
1585		2626
1586	=item const char *path [read-only]	2627	=item const char *path [read-only]
1587		2628
1588	The filesystem path that is being watched.	2629	The file system path that is being watched.
1589		2630
1590	=back	2631	=back
1591		2632
1592	=head3 Examples	2633	=head3 Examples
1593		2634
1594	Example: Watch C</etc/passwd> for attribute changes.	2635	Example: Watch C</etc/passwd> for attribute changes.
1595		2636
1596	static void	2637	static void
1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2638	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1598	{	2639	{
1599	/* /etc/passwd changed in some way */	2640	/* /etc/passwd changed in some way */
1600	if (w->attr.st_nlink)	2641	if (w->attr.st_nlink)
1601	{	2642	{
1602	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2643	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1603	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2644	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1604	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2645	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1605	}	2646	}
1606	else	2647	else
1607	/* you shalt not abuse printf for puts */	2648	/* you shalt not abuse printf for puts */
1608	puts ("wow, /etc/passwd is not there, expect problems. "	2649	puts ("wow, /etc/passwd is not there, expect problems. "
1609	"if this is windows, they already arrived\n");	2650	"if this is windows, they already arrived\n");
1610	}	2651	}
1611		2652
1612	...	2653	...
1613	ev_stat passwd;	2654	ev_stat passwd;
1614		2655
1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2656	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1616	ev_stat_start (loop, &passwd);	2657	ev_stat_start (loop, &passwd);
1617		2658
1618	Example: Like above, but additionally use a one-second delay so we do not	2659	Example: Like above, but additionally use a one-second delay so we do not
1619	miss updates (however, frequent updates will delay processing, too, so	2660	miss updates (however, frequent updates will delay processing, too, so
1620	one might do the work both on C<ev_stat> callback invocation I<and> on	2661	one might do the work both on C<ev_stat> callback invocation I<and> on
1621	C<ev_timer> callback invocation).	2662	C<ev_timer> callback invocation).
1622		2663
1623	static ev_stat passwd;	2664	static ev_stat passwd;
1624	static ev_timer timer;	2665	static ev_timer timer;
1625		2666
1626	static void	2667	static void
1627	timer_cb (EV_P_ ev_timer *w, int revents)	2668	timer_cb (EV_P_ ev_timer *w, int revents)
1628	{	2669	{
1629	ev_timer_stop (EV_A_ w);	2670	ev_timer_stop (EV_A_ w);
1630		2671
1631	/* now it's one second after the most recent passwd change */	2672	/* now it's one second after the most recent passwd change */
1632	}	2673	}
1633		2674
1634	static void	2675	static void
1635	stat_cb (EV_P_ ev_stat *w, int revents)	2676	stat_cb (EV_P_ ev_stat *w, int revents)
1636	{	2677	{
1637	/* reset the one-second timer */	2678	/* reset the one-second timer */
1638	ev_timer_again (EV_A_ &timer);	2679	ev_timer_again (EV_A_ &timer);
1639	}	2680	}
1640		2681
1641	...	2682	...
1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2683	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1643	ev_stat_start (loop, &passwd);	2684	ev_stat_start (loop, &passwd);
1644	ev_timer_init (&timer, timer_cb, 0., 1.01);	2685	ev_timer_init (&timer, timer_cb, 0., 1.02);
1645		2686
1646		2687
1647	=head2 C<ev_idle> - when you've got nothing better to do...	2688	=head2 C<ev_idle> - when you've got nothing better to do...
1648		2689
1649	Idle watchers trigger events when no other events of the same or higher	2690	Idle watchers trigger events when no other events of the same or higher
1650	priority are pending (prepare, check and other idle watchers do not	2691	priority are pending (prepare, check and other idle watchers do not count
1651	count).	2692	as receiving "events").
1652		2693
1653	That is, as long as your process is busy handling sockets or timeouts	2694	That is, as long as your process is busy handling sockets or timeouts
1654	(or even signals, imagine) of the same or higher priority it will not be	2695	(or even signals, imagine) of the same or higher priority it will not be
1655	triggered. But when your process is idle (or only lower-priority watchers	2696	triggered. But when your process is idle (or only lower-priority watchers
1656	are pending), the idle watchers are being called once per event loop	2697	are pending), the idle watchers are being called once per event loop
…		…
1667		2708
1668	=head3 Watcher-Specific Functions and Data Members	2709	=head3 Watcher-Specific Functions and Data Members
1669		2710
1670	=over 4	2711	=over 4
1671		2712
1672	=item ev_idle_init (ev_signal *, callback)	2713	=item ev_idle_init (ev_idle *, callback)
1673		2714
1674	Initialises and configures the idle watcher - it has no parameters of any	2715	Initialises and configures the idle watcher - it has no parameters of any
1675	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2716	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1676	believe me.	2717	believe me.
1677		2718
…		…
1680	=head3 Examples	2721	=head3 Examples
1681		2722
1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2723	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1683	callback, free it. Also, use no error checking, as usual.	2724	callback, free it. Also, use no error checking, as usual.
1684		2725
1685	static void	2726	static void
1686	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2727	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1687	{	2728	{
1688	free (w);	2729	free (w);
1689	// now do something you wanted to do when the program has	2730	// now do something you wanted to do when the program has
1690	// no longer asnything immediate to do.	2731	// no longer anything immediate to do.
1691	}	2732	}
1692		2733
1693	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1694	ev_idle_init (idle_watcher, idle_cb);	2735	ev_idle_init (idle_watcher, idle_cb);
1695	ev_idle_start (loop, idle_cb);	2736	ev_idle_start (loop, idle_watcher);
1696		2737
1697		2738
1698	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2739	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1699		2740
1700	Prepare and check watchers are usually (but not always) used in tandem:	2741	Prepare and check watchers are usually (but not always) used in pairs:
1701	prepare watchers get invoked before the process blocks and check watchers	2742	prepare watchers get invoked before the process blocks and check watchers
1702	afterwards.	2743	afterwards.
1703		2744
1704	You I<must not> call C<ev_loop> or similar functions that enter	2745	You I<must not> call C<ev_run> or similar functions that enter
1705	the current event loop from either C<ev_prepare> or C<ev_check>	2746	the current event loop from either C<ev_prepare> or C<ev_check>
1706	watchers. Other loops than the current one are fine, however. The	2747	watchers. Other loops than the current one are fine, however. The
1707	rationale behind this is that you do not need to check for recursion in	2748	rationale behind this is that you do not need to check for recursion in
1708	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2749	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1709	C<ev_check> so if you have one watcher of each kind they will always be	2750	C<ev_check> so if you have one watcher of each kind they will always be
1710	called in pairs bracketing the blocking call.	2751	called in pairs bracketing the blocking call.
1711		2752
1712	Their main purpose is to integrate other event mechanisms into libev and	2753	Their main purpose is to integrate other event mechanisms into libev and
1713	their use is somewhat advanced. This could be used, for example, to track	2754	their use is somewhat advanced. They could be used, for example, to track
1714	variable changes, implement your own watchers, integrate net-snmp or a	2755	variable changes, implement your own watchers, integrate net-snmp or a
1715	coroutine library and lots more. They are also occasionally useful if	2756	coroutine library and lots more. They are also occasionally useful if
1716	you cache some data and want to flush it before blocking (for example,	2757	you cache some data and want to flush it before blocking (for example,
1717	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2758	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1718	watcher).	2759	watcher).
1719		2760
1720	This is done by examining in each prepare call which file descriptors need	2761	This is done by examining in each prepare call which file descriptors
1721	to be watched by the other library, registering C<ev_io> watchers for	2762	need to be watched by the other library, registering C<ev_io> watchers
1722	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2763	for them and starting an C<ev_timer> watcher for any timeouts (many
1723	provide just this functionality). Then, in the check watcher you check for	2764	libraries provide exactly this functionality). Then, in the check watcher,
1724	any events that occured (by checking the pending status of all watchers	2765	you check for any events that occurred (by checking the pending status
1725	and stopping them) and call back into the library. The I/O and timer	2766	of all watchers and stopping them) and call back into the library. The
1726	callbacks will never actually be called (but must be valid nevertheless,	2767	I/O and timer callbacks will never actually be called (but must be valid
1727	because you never know, you know?).	2768	nevertheless, because you never know, you know?).
1728		2769
1729	As another example, the Perl Coro module uses these hooks to integrate	2770	As another example, the Perl Coro module uses these hooks to integrate
1730	coroutines into libev programs, by yielding to other active coroutines	2771	coroutines into libev programs, by yielding to other active coroutines
1731	during each prepare and only letting the process block if no coroutines	2772	during each prepare and only letting the process block if no coroutines
1732	are ready to run (it's actually more complicated: it only runs coroutines	2773	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1735	loop from blocking if lower-priority coroutines are active, thus mapping	2776	loop from blocking if lower-priority coroutines are active, thus mapping
1736	low-priority coroutines to idle/background tasks).	2777	low-priority coroutines to idle/background tasks).
1737		2778
1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2779	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1739	priority, to ensure that they are being run before any other watchers	2780	priority, to ensure that they are being run before any other watchers
		2781	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2782
1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2783	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1741	too) should not activate ("feed") events into libev. While libev fully	2784	activate ("feed") events into libev. While libev fully supports this, they
1742	supports this, they will be called before other C<ev_check> watchers	2785	might get executed before other C<ev_check> watchers did their job. As
1743	did their job. As C<ev_check> watchers are often used to embed other	2786	C<ev_check> watchers are often used to embed other (non-libev) event
1744	(non-libev) event loops those other event loops might be in an unusable	2787	loops those other event loops might be in an unusable state until their
1745	state until their C<ev_check> watcher ran (always remind yourself to	2788	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1746	coexist peacefully with others).	2789	others).
1747		2790
1748	=head3 Watcher-Specific Functions and Data Members	2791	=head3 Watcher-Specific Functions and Data Members
1749		2792
1750	=over 4	2793	=over 4
1751		2794
…		…
1753		2796
1754	=item ev_check_init (ev_check *, callback)	2797	=item ev_check_init (ev_check *, callback)
1755		2798
1756	Initialises and configures the prepare or check watcher - they have no	2799	Initialises and configures the prepare or check watcher - they have no
1757	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2800	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1758	macros, but using them is utterly, utterly and completely pointless.	2801	macros, but using them is utterly, utterly, utterly and completely
		2802	pointless.
1759		2803
1760	=back	2804	=back
1761		2805
1762	=head3 Examples	2806	=head3 Examples
1763		2807
1764	There are a number of principal ways to embed other event loops or modules	2808	There are a number of principal ways to embed other event loops or modules
1765	into libev. Here are some ideas on how to include libadns into libev	2809	into libev. Here are some ideas on how to include libadns into libev
1766	(there is a Perl module named C<EV::ADNS> that does this, which you could	2810	(there is a Perl module named C<EV::ADNS> that does this, which you could
1767	use for an actually working example. Another Perl module named C<EV::Glib>	2811	use as a working example. Another Perl module named C<EV::Glib> embeds a
1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2812	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1769	into the Glib event loop).	2813	Glib event loop).
1770		2814
1771	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2815	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1772	and in a check watcher, destroy them and call into libadns. What follows	2816	and in a check watcher, destroy them and call into libadns. What follows
1773	is pseudo-code only of course. This requires you to either use a low	2817	is pseudo-code only of course. This requires you to either use a low
1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2818	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1775	the callbacks for the IO/timeout watchers might not have been called yet.	2819	the callbacks for the IO/timeout watchers might not have been called yet.
1776		2820
1777	static ev_io iow [nfd];	2821	static ev_io iow [nfd];
1778	static ev_timer tw;	2822	static ev_timer tw;
1779		2823
1780	static void	2824	static void
1781	io_cb (ev_loop *loop, ev_io *w, int revents)	2825	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1782	{	2826	{
1783	}	2827	}
1784		2828
1785	// create io watchers for each fd and a timer before blocking	2829	// create io watchers for each fd and a timer before blocking
1786	static void	2830	static void
1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2831	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1788	{	2832	{
1789	int timeout = 3600000;	2833	int timeout = 3600000;
1790	struct pollfd fds [nfd];	2834	struct pollfd fds [nfd];
1791	// actual code will need to loop here and realloc etc.	2835	// actual code will need to loop here and realloc etc.
1792	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2836	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1793		2837
1794	/* the callback is illegal, but won't be called as we stop during check */	2838	/* the callback is illegal, but won't be called as we stop during check */
1795	ev_timer_init (&tw, 0, timeout * 1e-3);	2839	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1796	ev_timer_start (loop, &tw);	2840	ev_timer_start (loop, &tw);
1797		2841
1798	// create one ev_io per pollfd	2842	// create one ev_io per pollfd
1799	for (int i = 0; i < nfd; ++i)	2843	for (int i = 0; i < nfd; ++i)
1800	{	2844	{
1801	ev_io_init (iow + i, io_cb, fds [i].fd,	2845	ev_io_init (iow + i, io_cb, fds [i].fd,
1802	((fds [i].events & POLLIN ? EV_READ : 0)	2846	((fds [i].events & POLLIN ? EV_READ : 0)
1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2847	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1804		2848
1805	fds [i].revents = 0;	2849	fds [i].revents = 0;
1806	ev_io_start (loop, iow + i);	2850	ev_io_start (loop, iow + i);
1807	}	2851	}
1808	}	2852	}
1809		2853
1810	// stop all watchers after blocking	2854	// stop all watchers after blocking
1811	static void	2855	static void
1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2856	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1813	{	2857	{
1814	ev_timer_stop (loop, &tw);	2858	ev_timer_stop (loop, &tw);
1815		2859
1816	for (int i = 0; i < nfd; ++i)	2860	for (int i = 0; i < nfd; ++i)
1817	{	2861	{
1818	// set the relevant poll flags	2862	// set the relevant poll flags
1819	// could also call adns_processreadable etc. here	2863	// could also call adns_processreadable etc. here
1820	struct pollfd *fd = fds + i;	2864	struct pollfd *fd = fds + i;
1821	int revents = ev_clear_pending (iow + i);	2865	int revents = ev_clear_pending (iow + i);
1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2866	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2867	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1824		2868
1825	// now stop the watcher	2869	// now stop the watcher
1826	ev_io_stop (loop, iow + i);	2870	ev_io_stop (loop, iow + i);
1827	}	2871	}
1828		2872
1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2873	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1830	}	2874	}
1831		2875
1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2876	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1833	in the prepare watcher and would dispose of the check watcher.	2877	in the prepare watcher and would dispose of the check watcher.
1834		2878
1835	Method 3: If the module to be embedded supports explicit event	2879	Method 3: If the module to be embedded supports explicit event
1836	notification (adns does), you can also make use of the actual watcher	2880	notification (libadns does), you can also make use of the actual watcher
1837	callbacks, and only destroy/create the watchers in the prepare watcher.	2881	callbacks, and only destroy/create the watchers in the prepare watcher.
1838		2882
1839	static void	2883	static void
1840	timer_cb (EV_P_ ev_timer *w, int revents)	2884	timer_cb (EV_P_ ev_timer *w, int revents)
1841	{	2885	{
1842	adns_state ads = (adns_state)w->data;	2886	adns_state ads = (adns_state)w->data;
1843	update_now (EV_A);	2887	update_now (EV_A);
1844		2888
1845	adns_processtimeouts (ads, &tv_now);	2889	adns_processtimeouts (ads, &tv_now);
1846	}	2890	}
1847		2891
1848	static void	2892	static void
1849	io_cb (EV_P_ ev_io *w, int revents)	2893	io_cb (EV_P_ ev_io *w, int revents)
1850	{	2894	{
1851	adns_state ads = (adns_state)w->data;	2895	adns_state ads = (adns_state)w->data;
1852	update_now (EV_A);	2896	update_now (EV_A);
1853		2897
1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2898	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2899	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1856	}	2900	}
1857		2901
1858	// do not ever call adns_afterpoll	2902	// do not ever call adns_afterpoll
1859		2903
1860	Method 4: Do not use a prepare or check watcher because the module you	2904	Method 4: Do not use a prepare or check watcher because the module you
1861	want to embed is too inflexible to support it. Instead, youc na override	2905	want to embed is not flexible enough to support it. Instead, you can
1862	their poll function. The drawback with this solution is that the main	2906	override their poll function. The drawback with this solution is that the
1863	loop is now no longer controllable by EV. The C<Glib::EV> module does	2907	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1864	this.	2908	this approach, effectively embedding EV as a client into the horrible
		2909	libglib event loop.
1865		2910
1866	static gint	2911	static gint
1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2912	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1868	{	2913	{
1869	int got_events = 0;	2914	int got_events = 0;
1870		2915
1871	for (n = 0; n < nfds; ++n)	2916	for (n = 0; n < nfds; ++n)
1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2917	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1873		2918
1874	if (timeout >= 0)	2919	if (timeout >= 0)
1875	// create/start timer	2920	// create/start timer
1876		2921
1877	// poll	2922	// poll
1878	ev_loop (EV_A_ 0);	2923	ev_run (EV_A_ 0);
1879		2924
1880	// stop timer again	2925	// stop timer again
1881	if (timeout >= 0)	2926	if (timeout >= 0)
1882	ev_timer_stop (EV_A_ &to);	2927	ev_timer_stop (EV_A_ &to);
1883		2928
1884	// stop io watchers again - their callbacks should have set	2929	// stop io watchers again - their callbacks should have set
1885	for (n = 0; n < nfds; ++n)	2930	for (n = 0; n < nfds; ++n)
1886	ev_io_stop (EV_A_ iow [n]);	2931	ev_io_stop (EV_A_ iow [n]);
1887		2932
1888	return got_events;	2933	return got_events;
1889	}	2934	}
1890		2935
1891		2936
1892	=head2 C<ev_embed> - when one backend isn't enough...	2937	=head2 C<ev_embed> - when one backend isn't enough...
1893		2938
1894	This is a rather advanced watcher type that lets you embed one event loop	2939	This is a rather advanced watcher type that lets you embed one event loop
…		…
1900	prioritise I/O.	2945	prioritise I/O.
1901		2946
1902	As an example for a bug workaround, the kqueue backend might only support	2947	As an example for a bug workaround, the kqueue backend might only support
1903	sockets on some platform, so it is unusable as generic backend, but you	2948	sockets on some platform, so it is unusable as generic backend, but you
1904	still want to make use of it because you have many sockets and it scales	2949	still want to make use of it because you have many sockets and it scales
1905	so nicely. In this case, you would create a kqueue-based loop and embed it	2950	so nicely. In this case, you would create a kqueue-based loop and embed
1906	into your default loop (which might use e.g. poll). Overall operation will	2951	it into your default loop (which might use e.g. poll). Overall operation
1907	be a bit slower because first libev has to poll and then call kevent, but	2952	will be a bit slower because first libev has to call C<poll> and then
1908	at least you can use both at what they are best.	2953	C<kevent>, but at least you can use both mechanisms for what they are
		2954	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1909		2955
1910	As for prioritising I/O: rarely you have the case where some fds have	2956	As for prioritising I/O: under rare circumstances you have the case where
1911	to be watched and handled very quickly (with low latency), and even	2957	some fds have to be watched and handled very quickly (with low latency),
1912	priorities and idle watchers might have too much overhead. In this case	2958	and even priorities and idle watchers might have too much overhead. In
1913	you would put all the high priority stuff in one loop and all the rest in	2959	this case you would put all the high priority stuff in one loop and all
1914	a second one, and embed the second one in the first.	2960	the rest in a second one, and embed the second one in the first.
1915		2961
1916	As long as the watcher is active, the callback will be invoked every time	2962	As long as the watcher is active, the callback will be invoked every
1917	there might be events pending in the embedded loop. The callback must then	2963	time there might be events pending in the embedded loop. The callback
1918	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2964	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1919	their callbacks (you could also start an idle watcher to give the embedded	2965	sweep and invoke their callbacks (the callback doesn't need to invoke the
1920	loop strictly lower priority for example). You can also set the callback	2966	C<ev_embed_sweep> function directly, it could also start an idle watcher
1921	to C<0>, in which case the embed watcher will automatically execute the	2967	to give the embedded loop strictly lower priority for example).
1922	embedded loop sweep.
1923		2968
1924	As long as the watcher is started it will automatically handle events. The	2969	You can also set the callback to C<0>, in which case the embed watcher
1925	callback will be invoked whenever some events have been handled. You can	2970	will automatically execute the embedded loop sweep whenever necessary.
1926	set the callback to C<0> to avoid having to specify one if you are not
1927	interested in that.
1928		2971
1929	Also, there have not currently been made special provisions for forking:	2972	Fork detection will be handled transparently while the C<ev_embed> watcher
1930	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2973	is active, i.e., the embedded loop will automatically be forked when the
1931	but you will also have to stop and restart any C<ev_embed> watchers	2974	embedding loop forks. In other cases, the user is responsible for calling
1932	yourself.	2975	C<ev_loop_fork> on the embedded loop.
1933		2976
1934	Unfortunately, not all backends are embeddable, only the ones returned by	2977	Unfortunately, not all backends are embeddable: only the ones returned by
1935	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2978	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1936	portable one.	2979	portable one.
1937		2980
1938	So when you want to use this feature you will always have to be prepared	2981	So when you want to use this feature you will always have to be prepared
1939	that you cannot get an embeddable loop. The recommended way to get around	2982	that you cannot get an embeddable loop. The recommended way to get around
1940	this is to have a separate variables for your embeddable loop, try to	2983	this is to have a separate variables for your embeddable loop, try to
1941	create it, and if that fails, use the normal loop for everything.	2984	create it, and if that fails, use the normal loop for everything.
1942		2985
		2986	=head3 C<ev_embed> and fork
		2987
		2988	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2989	automatically be applied to the embedded loop as well, so no special
		2990	fork handling is required in that case. When the watcher is not running,
		2991	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2992	as applicable.
		2993
1943	=head3 Watcher-Specific Functions and Data Members	2994	=head3 Watcher-Specific Functions and Data Members
1944		2995
1945	=over 4	2996	=over 4
1946		2997
1947	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2998	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1950		3001
1951	Configures the watcher to embed the given loop, which must be	3002	Configures the watcher to embed the given loop, which must be
1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3003	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1953	invoked automatically, otherwise it is the responsibility of the callback	3004	invoked automatically, otherwise it is the responsibility of the callback
1954	to invoke it (it will continue to be called until the sweep has been done,	3005	to invoke it (it will continue to be called until the sweep has been done,
1955	if you do not want thta, you need to temporarily stop the embed watcher).	3006	if you do not want that, you need to temporarily stop the embed watcher).
1956		3007
1957	=item ev_embed_sweep (loop, ev_embed *)	3008	=item ev_embed_sweep (loop, ev_embed *)
1958		3009
1959	Make a single, non-blocking sweep over the embedded loop. This works	3010	Make a single, non-blocking sweep over the embedded loop. This works
1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3011	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
1961	apropriate way for embedded loops.	3012	appropriate way for embedded loops.
1962		3013
1963	=item struct ev_loop *other [read-only]	3014	=item struct ev_loop *other [read-only]
1964		3015
1965	The embedded event loop.	3016	The embedded event loop.
1966		3017
…		…
1968		3019
1969	=head3 Examples	3020	=head3 Examples
1970		3021
1971	Example: Try to get an embeddable event loop and embed it into the default	3022	Example: Try to get an embeddable event loop and embed it into the default
1972	event loop. If that is not possible, use the default loop. The default	3023	event loop. If that is not possible, use the default loop. The default
1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3024	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3025	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1975	used).	3026	used).
1976		3027
1977	struct ev_loop *loop_hi = ev_default_init (0);	3028	struct ev_loop *loop_hi = ev_default_init (0);
1978	struct ev_loop *loop_lo = 0;	3029	struct ev_loop *loop_lo = 0;
1979	struct ev_embed embed;	3030	ev_embed embed;
1980		3031
1981	// see if there is a chance of getting one that works	3032	// see if there is a chance of getting one that works
1982	// (remember that a flags value of 0 means autodetection)	3033	// (remember that a flags value of 0 means autodetection)
1983	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3034	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1984	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3035	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1985	: 0;	3036	: 0;
1986		3037
1987	// if we got one, then embed it, otherwise default to loop_hi	3038	// if we got one, then embed it, otherwise default to loop_hi
1988	if (loop_lo)	3039	if (loop_lo)
1989	{	3040	{
1990	ev_embed_init (&embed, 0, loop_lo);	3041	ev_embed_init (&embed, 0, loop_lo);
1991	ev_embed_start (loop_hi, &embed);	3042	ev_embed_start (loop_hi, &embed);
1992	}	3043	}
1993	else	3044	else
1994	loop_lo = loop_hi;	3045	loop_lo = loop_hi;
1995		3046
1996	Example: Check if kqueue is available but not recommended and create	3047	Example: Check if kqueue is available but not recommended and create
1997	a kqueue backend for use with sockets (which usually work with any	3048	a kqueue backend for use with sockets (which usually work with any
1998	kqueue implementation). Store the kqueue/socket-only event loop in	3049	kqueue implementation). Store the kqueue/socket-only event loop in
1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3050	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2000		3051
2001	struct ev_loop *loop = ev_default_init (0);	3052	struct ev_loop *loop = ev_default_init (0);
2002	struct ev_loop *loop_socket = 0;	3053	struct ev_loop *loop_socket = 0;
2003	struct ev_embed embed;	3054	ev_embed embed;
2004		3055
2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3056	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3057	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2007	{	3058	{
2008	ev_embed_init (&embed, 0, loop_socket);	3059	ev_embed_init (&embed, 0, loop_socket);
2009	ev_embed_start (loop, &embed);	3060	ev_embed_start (loop, &embed);
2010	}	3061	}
2011		3062
2012	if (!loop_socket)	3063	if (!loop_socket)
2013	loop_socket = loop;	3064	loop_socket = loop;
2014		3065
2015	// now use loop_socket for all sockets, and loop for everything else	3066	// now use loop_socket for all sockets, and loop for everything else
2016		3067
2017		3068
2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3069	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2019		3070
2020	Fork watchers are called when a C<fork ()> was detected (usually because	3071	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2023	event loop blocks next and before C<ev_check> watchers are being called,	3074	event loop blocks next and before C<ev_check> watchers are being called,
2024	and only in the child after the fork. If whoever good citizen calling	3075	and only in the child after the fork. If whoever good citizen calling
2025	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3076	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2026	handlers will be invoked, too, of course.	3077	handlers will be invoked, too, of course.
2027		3078
		3079	=head3 The special problem of life after fork - how is it possible?
		3080
		3081	Most uses of C<fork()> consist of forking, then some simple calls to set
		3082	up/change the process environment, followed by a call to C<exec()>. This
		3083	sequence should be handled by libev without any problems.
		3084
		3085	This changes when the application actually wants to do event handling
		3086	in the child, or both parent in child, in effect "continuing" after the
		3087	fork.
		3088
		3089	The default mode of operation (for libev, with application help to detect
		3090	forks) is to duplicate all the state in the child, as would be expected
		3091	when I<either> the parent I<or> the child process continues.
		3092
		3093	When both processes want to continue using libev, then this is usually the
		3094	wrong result. In that case, usually one process (typically the parent) is
		3095	supposed to continue with all watchers in place as before, while the other
		3096	process typically wants to start fresh, i.e. without any active watchers.
		3097
		3098	The cleanest and most efficient way to achieve that with libev is to
		3099	simply create a new event loop, which of course will be "empty", and
		3100	use that for new watchers. This has the advantage of not touching more
		3101	memory than necessary, and thus avoiding the copy-on-write, and the
		3102	disadvantage of having to use multiple event loops (which do not support
		3103	signal watchers).
		3104
		3105	When this is not possible, or you want to use the default loop for
		3106	other reasons, then in the process that wants to start "fresh", call
		3107	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3108	Destroying the default loop will "orphan" (not stop) all registered
		3109	watchers, so you have to be careful not to execute code that modifies
		3110	those watchers. Note also that in that case, you have to re-register any
		3111	signal watchers.
		3112
2028	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
2029		3114
2030	=over 4	3115	=over 4
2031		3116
2032	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
2033		3118
2034	Initialises and configures the fork watcher - it has no parameters of any	3119	Initialises and configures the fork watcher - it has no parameters of any
2035	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2036	believe me.	3121	really.
2037		3122
2038	=back	3123	=back
2039		3124
2040		3125
		3126	=head2 C<ev_cleanup> - even the best things end
		3127
		3128	Cleanup watchers are called just before the event loop is being destroyed
		3129	by a call to C<ev_loop_destroy>.
		3130
		3131	While there is no guarantee that the event loop gets destroyed, cleanup
		3132	watchers provide a convenient method to install cleanup hooks for your
		3133	program, worker threads and so on - you just to make sure to destroy the
		3134	loop when you want them to be invoked.
		3135
		3136	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3137	all other watchers, they do not keep a reference to the event loop (which
		3138	makes a lot of sense if you think about it). Like all other watchers, you
		3139	can call libev functions in the callback, except C<ev_cleanup_start>.
		3140
		3141	=head3 Watcher-Specific Functions and Data Members
		3142
		3143	=over 4
		3144
		3145	=item ev_cleanup_init (ev_cleanup *, callback)
		3146
		3147	Initialises and configures the cleanup watcher - it has no parameters of
		3148	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3149	pointless, I assure you.
		3150
		3151	=back
		3152
		3153	Example: Register an atexit handler to destroy the default loop, so any
		3154	cleanup functions are called.
		3155
		3156	static void
		3157	program_exits (void)
		3158	{
		3159	ev_loop_destroy (EV_DEFAULT_UC);
		3160	}
		3161
		3162	...
		3163	atexit (program_exits);
		3164
		3165
		3166	=head2 C<ev_async> - how to wake up an event loop
		3167
		3168	In general, you cannot use an C<ev_run> from multiple threads or other
		3169	asynchronous sources such as signal handlers (as opposed to multiple event
		3170	loops - those are of course safe to use in different threads).
		3171
		3172	Sometimes, however, you need to wake up an event loop you do not control,
		3173	for example because it belongs to another thread. This is what C<ev_async>
		3174	watchers do: as long as the C<ev_async> watcher is active, you can signal
		3175	it by calling C<ev_async_send>, which is thread- and signal safe.
		3176
		3177	This functionality is very similar to C<ev_signal> watchers, as signals,
		3178	too, are asynchronous in nature, and signals, too, will be compressed
		3179	(i.e. the number of callback invocations may be less than the number of
		3180	C<ev_async_sent> calls).
		3181
		3182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		3183	just the default loop.
		3184
		3185	=head3 Queueing
		3186
		3187	C<ev_async> does not support queueing of data in any way. The reason
		3188	is that the author does not know of a simple (or any) algorithm for a
		3189	multiple-writer-single-reader queue that works in all cases and doesn't
		3190	need elaborate support such as pthreads or unportable memory access
		3191	semantics.
		3192
		3193	That means that if you want to queue data, you have to provide your own
		3194	queue. But at least I can tell you how to implement locking around your
		3195	queue:
		3196
		3197	=over 4
		3198
		3199	=item queueing from a signal handler context
		3200
		3201	To implement race-free queueing, you simply add to the queue in the signal
		3202	handler but you block the signal handler in the watcher callback. Here is
		3203	an example that does that for some fictitious SIGUSR1 handler:
		3204
		3205	static ev_async mysig;
		3206
		3207	static void
		3208	sigusr1_handler (void)
		3209	{
		3210	sometype data;
		3211
		3212	// no locking etc.
		3213	queue_put (data);
		3214	ev_async_send (EV_DEFAULT_ &mysig);
		3215	}
		3216
		3217	static void
		3218	mysig_cb (EV_P_ ev_async *w, int revents)
		3219	{
		3220	sometype data;
		3221	sigset_t block, prev;
		3222
		3223	sigemptyset (&block);
		3224	sigaddset (&block, SIGUSR1);
		3225	sigprocmask (SIG_BLOCK, &block, &prev);
		3226
		3227	while (queue_get (&data))
		3228	process (data);
		3229
		3230	if (sigismember (&prev, SIGUSR1)
		3231	sigprocmask (SIG_UNBLOCK, &block, 0);
		3232	}
		3233
		3234	(Note: pthreads in theory requires you to use C<pthread_setmask>
		3235	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		3236	either...).
		3237
		3238	=item queueing from a thread context
		3239
		3240	The strategy for threads is different, as you cannot (easily) block
		3241	threads but you can easily preempt them, so to queue safely you need to
		3242	employ a traditional mutex lock, such as in this pthread example:
		3243
		3244	static ev_async mysig;
		3245	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		3246
		3247	static void
		3248	otherthread (void)
		3249	{
		3250	// only need to lock the actual queueing operation
		3251	pthread_mutex_lock (&mymutex);
		3252	queue_put (data);
		3253	pthread_mutex_unlock (&mymutex);
		3254
		3255	ev_async_send (EV_DEFAULT_ &mysig);
		3256	}
		3257
		3258	static void
		3259	mysig_cb (EV_P_ ev_async *w, int revents)
		3260	{
		3261	pthread_mutex_lock (&mymutex);
		3262
		3263	while (queue_get (&data))
		3264	process (data);
		3265
		3266	pthread_mutex_unlock (&mymutex);
		3267	}
		3268
		3269	=back
		3270
		3271
		3272	=head3 Watcher-Specific Functions and Data Members
		3273
		3274	=over 4
		3275
		3276	=item ev_async_init (ev_async *, callback)
		3277
		3278	Initialises and configures the async watcher - it has no parameters of any
		3279	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		3280	trust me.
		3281
		3282	=item ev_async_send (loop, ev_async *)
		3283
		3284	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		3285	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		3286	C<ev_feed_event>, this call is safe to do from other threads, signal or
		3287	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		3288	section below on what exactly this means).
		3289
		3290	Note that, as with other watchers in libev, multiple events might get
		3291	compressed into a single callback invocation (another way to look at this
		3292	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3293	reset when the event loop detects that).
		3294
		3295	This call incurs the overhead of a system call only once per event loop
		3296	iteration, so while the overhead might be noticeable, it doesn't apply to
		3297	repeated calls to C<ev_async_send> for the same event loop.
		3298
		3299	=item bool = ev_async_pending (ev_async *)
		3300
		3301	Returns a non-zero value when C<ev_async_send> has been called on the
		3302	watcher but the event has not yet been processed (or even noted) by the
		3303	event loop.
		3304
		3305	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		3306	the loop iterates next and checks for the watcher to have become active,
		3307	it will reset the flag again. C<ev_async_pending> can be used to very
		3308	quickly check whether invoking the loop might be a good idea.
		3309
		3310	Not that this does I<not> check whether the watcher itself is pending,
		3311	only whether it has been requested to make this watcher pending: there
		3312	is a time window between the event loop checking and resetting the async
		3313	notification, and the callback being invoked.
		3314
		3315	=back
		3316
		3317
2041	=head1 OTHER FUNCTIONS	3318	=head1 OTHER FUNCTIONS
2042		3319
2043	There are some other functions of possible interest. Described. Here. Now.	3320	There are some other functions of possible interest. Described. Here. Now.
2044		3321
2045	=over 4	3322	=over 4
2046		3323
2047	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3324	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2048		3325
2049	This function combines a simple timer and an I/O watcher, calls your	3326	This function combines a simple timer and an I/O watcher, calls your
2050	callback on whichever event happens first and automatically stop both	3327	callback on whichever event happens first and automatically stops both
2051	watchers. This is useful if you want to wait for a single event on an fd	3328	watchers. This is useful if you want to wait for a single event on an fd
2052	or timeout without having to allocate/configure/start/stop/free one or	3329	or timeout without having to allocate/configure/start/stop/free one or
2053	more watchers yourself.	3330	more watchers yourself.
2054		3331
2055	If C<fd> is less than 0, then no I/O watcher will be started and events	3332	If C<fd> is less than 0, then no I/O watcher will be started and the
2056	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3333	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2057	C<events> set will be craeted and started.	3334	the given C<fd> and C<events> set will be created and started.
2058		3335
2059	If C<timeout> is less than 0, then no timeout watcher will be	3336	If C<timeout> is less than 0, then no timeout watcher will be
2060	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3337	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2061	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3338	repeat = 0) will be started. C<0> is a valid timeout.
2062	dubious value.
2063		3339
2064	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3340	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2065	passed an C<revents> set like normal event callbacks (a combination of	3341	passed an C<revents> set like normal event callbacks (a combination of
2066	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3342	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2067	value passed to C<ev_once>:	3343	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3344	a timeout and an io event at the same time - you probably should give io
		3345	events precedence.
2068		3346
		3347	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3348
2069	static void stdin_ready (int revents, void *arg)	3349	static void stdin_ready (int revents, void *arg)
2070	{	3350	{
2071	if (revents & EV_TIMEOUT)
2072	/* doh, nothing entered */;
2073	else if (revents & EV_READ)	3351	if (revents & EV_READ)
2074	/* stdin might have data for us, joy! */;	3352	/* stdin might have data for us, joy! */;
		3353	else if (revents & EV_TIMER)
		3354	/* doh, nothing entered */;
2075	}	3355	}
2076		3356
2077	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2078		3358
2079	=item ev_feed_event (ev_loop *, watcher *, int revents)
2080
2081	Feeds the given event set into the event loop, as if the specified event
2082	had happened for the specified watcher (which must be a pointer to an
2083	initialised but not necessarily started event watcher).
2084
2085	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3359	=item ev_feed_fd_event (loop, int fd, int revents)
2086		3360
2087	Feed an event on the given fd, as if a file descriptor backend detected	3361	Feed an event on the given fd, as if a file descriptor backend detected
2088	the given events it.	3362	the given events it.
2089		3363
2090	=item ev_feed_signal_event (ev_loop *loop, int signum)	3364	=item ev_feed_signal_event (loop, int signum)
2091		3365
2092	Feed an event as if the given signal occured (C<loop> must be the default	3366	Feed an event as if the given signal occurred (C<loop> must be the default
2093	loop!).	3367	loop!).
2094		3368
2095	=back	3369	=back
2096		3370
2097		3371
…		…
2113		3387
2114	=item * Priorities are not currently supported. Initialising priorities	3388	=item * Priorities are not currently supported. Initialising priorities
2115	will fail and all watchers will have the same priority, even though there	3389	will fail and all watchers will have the same priority, even though there
2116	is an ev_pri field.	3390	is an ev_pri field.
2117		3391
		3392	=item * In libevent, the last base created gets the signals, in libev, the
		3393	base that registered the signal gets the signals.
		3394
2118	=item * Other members are not supported.	3395	=item * Other members are not supported.
2119		3396
2120	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3397	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2121	to use the libev header file and library.	3398	to use the libev header file and library.
2122		3399
2123	=back	3400	=back
2124		3401
2125	=head1 C++ SUPPORT	3402	=head1 C++ SUPPORT
2126		3403
2127	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3404	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2128	you to use some convinience methods to start/stop watchers and also change	3405	you to use some convenience methods to start/stop watchers and also change
2129	the callback model to a model using method callbacks on objects.	3406	the callback model to a model using method callbacks on objects.
2130		3407
2131	To use it,	3408	To use it,
2132		3409
2133	#include <ev++.h>	3410	#include <ev++.h>
2134		3411
2135	This automatically includes F<ev.h> and puts all of its definitions (many	3412	This automatically includes F<ev.h> and puts all of its definitions (many
2136	of them macros) into the global namespace. All C++ specific things are	3413	of them macros) into the global namespace. All C++ specific things are
2137	put into the C<ev> namespace. It should support all the same embedding	3414	put into the C<ev> namespace. It should support all the same embedding
2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3415	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2172		3449
2173	=over 4	3450	=over 4
2174		3451
2175	=item ev::TYPE::TYPE ()	3452	=item ev::TYPE::TYPE ()
2176		3453
2177	=item ev::TYPE::TYPE (struct ev_loop *)	3454	=item ev::TYPE::TYPE (loop)
2178		3455
2179	=item ev::TYPE::~TYPE	3456	=item ev::TYPE::~TYPE
2180		3457
2181	The constructor (optionally) takes an event loop to associate the watcher	3458	The constructor (optionally) takes an event loop to associate the watcher
2182	with. If it is omitted, it will use C<EV_DEFAULT>.	3459	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2205	your compiler is good :), then the method will be fully inlined into the	3482	your compiler is good :), then the method will be fully inlined into the
2206	thunking function, making it as fast as a direct C callback.	3483	thunking function, making it as fast as a direct C callback.
2207		3484
2208	Example: simple class declaration and watcher initialisation	3485	Example: simple class declaration and watcher initialisation
2209		3486
2210	struct myclass	3487	struct myclass
2211	{	3488	{
2212	void io_cb (ev::io &w, int revents) { }	3489	void io_cb (ev::io &w, int revents) { }
2213	}	3490	}
2214		3491
2215	myclass obj;	3492	myclass obj;
2216	ev::io iow;	3493	ev::io iow;
2217	iow.set <myclass, &myclass::io_cb> (&obj);	3494	iow.set <myclass, &myclass::io_cb> (&obj);
		3495
		3496	=item w->set (object *)
		3497
		3498	This is a variation of a method callback - leaving out the method to call
		3499	will default the method to C<operator ()>, which makes it possible to use
		3500	functor objects without having to manually specify the C<operator ()> all
		3501	the time. Incidentally, you can then also leave out the template argument
		3502	list.
		3503
		3504	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3505	int revents)>.
		3506
		3507	See the method-C<set> above for more details.
		3508
		3509	Example: use a functor object as callback.
		3510
		3511	struct myfunctor
		3512	{
		3513	void operator() (ev::io &w, int revents)
		3514	{
		3515	...
		3516	}
		3517	}
		3518
		3519	myfunctor f;
		3520
		3521	ev::io w;
		3522	w.set (&f);
2218		3523
2219	=item w->set<function> (void *data = 0)	3524	=item w->set<function> (void *data = 0)
2220		3525
2221	Also sets a callback, but uses a static method or plain function as	3526	Also sets a callback, but uses a static method or plain function as
2222	callback. The optional C<data> argument will be stored in the watcher's	3527	callback. The optional C<data> argument will be stored in the watcher's
…		…
2224		3529
2225	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3530	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2226		3531
2227	See the method-C<set> above for more details.	3532	See the method-C<set> above for more details.
2228		3533
2229	Example:	3534	Example: Use a plain function as callback.
2230		3535
2231	static void io_cb (ev::io &w, int revents) { }	3536	static void io_cb (ev::io &w, int revents) { }
2232	iow.set <io_cb> ();	3537	iow.set <io_cb> ();
2233		3538
2234	=item w->set (struct ev_loop *)	3539	=item w->set (loop)
2235		3540
2236	Associates a different C<struct ev_loop> with this watcher. You can only	3541	Associates a different C<struct ev_loop> with this watcher. You can only
2237	do this when the watcher is inactive (and not pending either).	3542	do this when the watcher is inactive (and not pending either).
2238		3543
2239	=item w->set ([args])	3544	=item w->set ([arguments])
2240		3545
2241	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3546	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2242	called at least once. Unlike the C counterpart, an active watcher gets	3547	method or a suitable start method must be called at least once. Unlike the
2243	automatically stopped and restarted when reconfiguring it with this	3548	C counterpart, an active watcher gets automatically stopped and restarted
2244	method.	3549	when reconfiguring it with this method.
2245		3550
2246	=item w->start ()	3551	=item w->start ()
2247		3552
2248	Starts the watcher. Note that there is no C<loop> argument, as the	3553	Starts the watcher. Note that there is no C<loop> argument, as the
2249	constructor already stores the event loop.	3554	constructor already stores the event loop.
2250		3555
		3556	=item w->start ([arguments])
		3557
		3558	Instead of calling C<set> and C<start> methods separately, it is often
		3559	convenient to wrap them in one call. Uses the same type of arguments as
		3560	the configure C<set> method of the watcher.
		3561
2251	=item w->stop ()	3562	=item w->stop ()
2252		3563
2253	Stops the watcher if it is active. Again, no C<loop> argument.	3564	Stops the watcher if it is active. Again, no C<loop> argument.
2254		3565
2255	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3566	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2267		3578
2268	=back	3579	=back
2269		3580
2270	=back	3581	=back
2271		3582
2272	Example: Define a class with an IO and idle watcher, start one of them in	3583	Example: Define a class with two I/O and idle watchers, start the I/O
2273	the constructor.	3584	watchers in the constructor.
2274		3585
2275	class myclass	3586	class myclass
2276	{	3587	{
2277	ev_io io; void io_cb (ev::io &w, int revents);	3588	ev::io io ; void io_cb (ev::io &w, int revents);
		3589	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2278	ev_idle idle void idle_cb (ev::idle &w, int revents);	3590	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2279		3591
2280	myclass ();	3592	myclass (int fd)
2281	}	3593	{
2282
2283	myclass::myclass (int fd)
2284	{
2285	io .set <myclass, &myclass::io_cb > (this);	3594	io .set <myclass, &myclass::io_cb > (this);
		3595	io2 .set <myclass, &myclass::io2_cb > (this);
2286	idle.set <myclass, &myclass::idle_cb> (this);	3596	idle.set <myclass, &myclass::idle_cb> (this);
2287		3597
2288	io.start (fd, ev::READ);	3598	io.set (fd, ev::WRITE); // configure the watcher
		3599	io.start (); // start it whenever convenient
		3600
		3601	io2.start (fd, ev::READ); // set + start in one call
		3602	}
2289	}	3603	};
		3604
		3605
		3606	=head1 OTHER LANGUAGE BINDINGS
		3607
		3608	Libev does not offer other language bindings itself, but bindings for a
		3609	number of languages exist in the form of third-party packages. If you know
		3610	any interesting language binding in addition to the ones listed here, drop
		3611	me a note.
		3612
		3613	=over 4
		3614
		3615	=item Perl
		3616
		3617	The EV module implements the full libev API and is actually used to test
		3618	libev. EV is developed together with libev. Apart from the EV core module,
		3619	there are additional modules that implement libev-compatible interfaces
		3620	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3621	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3622	and C<EV::Glib>).
		3623
		3624	It can be found and installed via CPAN, its homepage is at
		3625	L<http://software.schmorp.de/pkg/EV>.
		3626
		3627	=item Python
		3628
		3629	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3630	seems to be quite complete and well-documented.
		3631
		3632	=item Ruby
		3633
		3634	Tony Arcieri has written a ruby extension that offers access to a subset
		3635	of the libev API and adds file handle abstractions, asynchronous DNS and
		3636	more on top of it. It can be found via gem servers. Its homepage is at
		3637	L<http://rev.rubyforge.org/>.
		3638
		3639	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3640	makes rev work even on mingw.
		3641
		3642	=item Haskell
		3643
		3644	A haskell binding to libev is available at
		3645	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3646
		3647	=item D
		3648
		3649	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3650	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3651
		3652	=item Ocaml
		3653
		3654	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3655	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3656
		3657	=item Lua
		3658
		3659	Brian Maher has written a partial interface to libev for lua (at the
		3660	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3661	L<http://github.com/brimworks/lua-ev>.
		3662
		3663	=back
2290		3664
2291		3665
2292	=head1 MACRO MAGIC	3666	=head1 MACRO MAGIC
2293		3667
2294	Libev can be compiled with a variety of options, the most fundamantal	3668	Libev can be compiled with a variety of options, the most fundamental
2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3669	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2296	functions and callbacks have an initial C<struct ev_loop *> argument.	3670	functions and callbacks have an initial C<struct ev_loop *> argument.
2297		3671
2298	To make it easier to write programs that cope with either variant, the	3672	To make it easier to write programs that cope with either variant, the
2299	following macros are defined:	3673	following macros are defined:
…		…
2304		3678
2305	This provides the loop I<argument> for functions, if one is required ("ev	3679	This provides the loop I<argument> for functions, if one is required ("ev
2306	loop argument"). The C<EV_A> form is used when this is the sole argument,	3680	loop argument"). The C<EV_A> form is used when this is the sole argument,
2307	C<EV_A_> is used when other arguments are following. Example:	3681	C<EV_A_> is used when other arguments are following. Example:
2308		3682
2309	ev_unref (EV_A);	3683	ev_unref (EV_A);
2310	ev_timer_add (EV_A_ watcher);	3684	ev_timer_add (EV_A_ watcher);
2311	ev_loop (EV_A_ 0);	3685	ev_run (EV_A_ 0);
2312		3686
2313	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3687	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2314	which is often provided by the following macro.	3688	which is often provided by the following macro.
2315		3689
2316	=item C<EV_P>, C<EV_P_>	3690	=item C<EV_P>, C<EV_P_>
2317		3691
2318	This provides the loop I<parameter> for functions, if one is required ("ev	3692	This provides the loop I<parameter> for functions, if one is required ("ev
2319	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3693	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2320	C<EV_P_> is used when other parameters are following. Example:	3694	C<EV_P_> is used when other parameters are following. Example:
2321		3695
2322	// this is how ev_unref is being declared	3696	// this is how ev_unref is being declared
2323	static void ev_unref (EV_P);	3697	static void ev_unref (EV_P);
2324		3698
2325	// this is how you can declare your typical callback	3699	// this is how you can declare your typical callback
2326	static void cb (EV_P_ ev_timer *w, int revents)	3700	static void cb (EV_P_ ev_timer *w, int revents)
2327		3701
2328	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3702	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2329	suitable for use with C<EV_A>.	3703	suitable for use with C<EV_A>.
2330		3704
2331	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3705	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2332		3706
2333	Similar to the other two macros, this gives you the value of the default	3707	Similar to the other two macros, this gives you the value of the default
2334	loop, if multiple loops are supported ("ev loop default").	3708	loop, if multiple loops are supported ("ev loop default").
		3709
		3710	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3711
		3712	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3713	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3714	is undefined when the default loop has not been initialised by a previous
		3715	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3716
		3717	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3718	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2335		3719
2336	=back	3720	=back
2337		3721
2338	Example: Declare and initialise a check watcher, utilising the above	3722	Example: Declare and initialise a check watcher, utilising the above
2339	macros so it will work regardless of whether multiple loops are supported	3723	macros so it will work regardless of whether multiple loops are supported
2340	or not.	3724	or not.
2341		3725
2342	static void	3726	static void
2343	check_cb (EV_P_ ev_timer *w, int revents)	3727	check_cb (EV_P_ ev_timer *w, int revents)
2344	{	3728	{
2345	ev_check_stop (EV_A_ w);	3729	ev_check_stop (EV_A_ w);
2346	}	3730	}
2347		3731
2348	ev_check check;	3732	ev_check check;
2349	ev_check_init (&check, check_cb);	3733	ev_check_init (&check, check_cb);
2350	ev_check_start (EV_DEFAULT_ &check);	3734	ev_check_start (EV_DEFAULT_ &check);
2351	ev_loop (EV_DEFAULT_ 0);	3735	ev_run (EV_DEFAULT_ 0);
2352		3736
2353	=head1 EMBEDDING	3737	=head1 EMBEDDING
2354		3738
2355	Libev can (and often is) directly embedded into host	3739	Libev can (and often is) directly embedded into host
2356	applications. Examples of applications that embed it include the Deliantra	3740	applications. Examples of applications that embed it include the Deliantra
…		…
2363	libev somewhere in your source tree).	3747	libev somewhere in your source tree).
2364		3748
2365	=head2 FILESETS	3749	=head2 FILESETS
2366		3750
2367	Depending on what features you need you need to include one or more sets of files	3751	Depending on what features you need you need to include one or more sets of files
2368	in your app.	3752	in your application.
2369		3753
2370	=head3 CORE EVENT LOOP	3754	=head3 CORE EVENT LOOP
2371		3755
2372	To include only the libev core (all the C<ev_*> functions), with manual	3756	To include only the libev core (all the C<ev_*> functions), with manual
2373	configuration (no autoconf):	3757	configuration (no autoconf):
2374		3758
2375	#define EV_STANDALONE 1	3759	#define EV_STANDALONE 1
2376	#include "ev.c"	3760	#include "ev.c"
2377		3761
2378	This will automatically include F<ev.h>, too, and should be done in a	3762	This will automatically include F<ev.h>, too, and should be done in a
2379	single C source file only to provide the function implementations. To use	3763	single C source file only to provide the function implementations. To use
2380	it, do the same for F<ev.h> in all files wishing to use this API (best	3764	it, do the same for F<ev.h> in all files wishing to use this API (best
2381	done by writing a wrapper around F<ev.h> that you can include instead and	3765	done by writing a wrapper around F<ev.h> that you can include instead and
2382	where you can put other configuration options):	3766	where you can put other configuration options):
2383		3767
2384	#define EV_STANDALONE 1	3768	#define EV_STANDALONE 1
2385	#include "ev.h"	3769	#include "ev.h"
2386		3770
2387	Both header files and implementation files can be compiled with a C++	3771	Both header files and implementation files can be compiled with a C++
2388	compiler (at least, thats a stated goal, and breakage will be treated	3772	compiler (at least, that's a stated goal, and breakage will be treated
2389	as a bug).	3773	as a bug).
2390		3774
2391	You need the following files in your source tree, or in a directory	3775	You need the following files in your source tree, or in a directory
2392	in your include path (e.g. in libev/ when using -Ilibev):	3776	in your include path (e.g. in libev/ when using -Ilibev):
2393		3777
2394	ev.h	3778	ev.h
2395	ev.c	3779	ev.c
2396	ev_vars.h	3780	ev_vars.h
2397	ev_wrap.h	3781	ev_wrap.h
2398		3782
2399	ev_win32.c required on win32 platforms only	3783	ev_win32.c required on win32 platforms only
2400		3784
2401	ev_select.c only when select backend is enabled (which is enabled by default)	3785	ev_select.c only when select backend is enabled (which is enabled by default)
2402	ev_poll.c only when poll backend is enabled (disabled by default)	3786	ev_poll.c only when poll backend is enabled (disabled by default)
2403	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3787	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2404	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3788	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2405	ev_port.c only when the solaris port backend is enabled (disabled by default)	3789	ev_port.c only when the solaris port backend is enabled (disabled by default)
2406		3790
2407	F<ev.c> includes the backend files directly when enabled, so you only need	3791	F<ev.c> includes the backend files directly when enabled, so you only need
2408	to compile this single file.	3792	to compile this single file.
2409		3793
2410	=head3 LIBEVENT COMPATIBILITY API	3794	=head3 LIBEVENT COMPATIBILITY API
2411		3795
2412	To include the libevent compatibility API, also include:	3796	To include the libevent compatibility API, also include:
2413		3797
2414	#include "event.c"	3798	#include "event.c"
2415		3799
2416	in the file including F<ev.c>, and:	3800	in the file including F<ev.c>, and:
2417		3801
2418	#include "event.h"	3802	#include "event.h"
2419		3803
2420	in the files that want to use the libevent API. This also includes F<ev.h>.	3804	in the files that want to use the libevent API. This also includes F<ev.h>.
2421		3805
2422	You need the following additional files for this:	3806	You need the following additional files for this:
2423		3807
2424	event.h	3808	event.h
2425	event.c	3809	event.c
2426		3810
2427	=head3 AUTOCONF SUPPORT	3811	=head3 AUTOCONF SUPPORT
2428		3812
2429	Instead of using C<EV_STANDALONE=1> and providing your config in	3813	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2430	whatever way you want, you can also C<m4_include([libev.m4])> in your	3814	whatever way you want, you can also C<m4_include([libev.m4])> in your
2431	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3815	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2432	include F<config.h> and configure itself accordingly.	3816	include F<config.h> and configure itself accordingly.
2433		3817
2434	For this of course you need the m4 file:	3818	For this of course you need the m4 file:
2435		3819
2436	libev.m4	3820	libev.m4
2437		3821
2438	=head2 PREPROCESSOR SYMBOLS/MACROS	3822	=head2 PREPROCESSOR SYMBOLS/MACROS
2439		3823
2440	Libev can be configured via a variety of preprocessor symbols you have to define	3824	Libev can be configured via a variety of preprocessor symbols you have to
2441	before including any of its files. The default is not to build for multiplicity	3825	define before including (or compiling) any of its files. The default in
2442	and only include the select backend.	3826	the absence of autoconf is documented for every option.
		3827
		3828	Symbols marked with "(h)" do not change the ABI, and can have different
		3829	values when compiling libev vs. including F<ev.h>, so it is permissible
		3830	to redefine them before including F<ev.h> without breaking compatibility
		3831	to a compiled library. All other symbols change the ABI, which means all
		3832	users of libev and the libev code itself must be compiled with compatible
		3833	settings.
2443		3834
2444	=over 4	3835	=over 4
2445		3836
		3837	=item EV_COMPAT3 (h)
		3838
		3839	Backwards compatibility is a major concern for libev. This is why this
		3840	release of libev comes with wrappers for the functions and symbols that
		3841	have been renamed between libev version 3 and 4.
		3842
		3843	You can disable these wrappers (to test compatibility with future
		3844	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3845	sources. This has the additional advantage that you can drop the C<struct>
		3846	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3847	typedef in that case.
		3848
		3849	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3850	and in some even more future version the compatibility code will be
		3851	removed completely.
		3852
2446	=item EV_STANDALONE	3853	=item EV_STANDALONE (h)
2447		3854
2448	Must always be C<1> if you do not use autoconf configuration, which	3855	Must always be C<1> if you do not use autoconf configuration, which
2449	keeps libev from including F<config.h>, and it also defines dummy	3856	keeps libev from including F<config.h>, and it also defines dummy
2450	implementations for some libevent functions (such as logging, which is not	3857	implementations for some libevent functions (such as logging, which is not
2451	supported). It will also not define any of the structs usually found in	3858	supported). It will also not define any of the structs usually found in
2452	F<event.h> that are not directly supported by the libev core alone.	3859	F<event.h> that are not directly supported by the libev core alone.
2453		3860
		3861	In standalone mode, libev will still try to automatically deduce the
		3862	configuration, but has to be more conservative.
		3863
2454	=item EV_USE_MONOTONIC	3864	=item EV_USE_MONOTONIC
2455		3865
2456	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
2457	monotonic clock option at both compiletime and runtime. Otherwise no use	3867	monotonic clock option at both compile time and runtime. Otherwise no
2458	of the monotonic clock option will be attempted. If you enable this, you	3868	use of the monotonic clock option will be attempted. If you enable this,
2459	usually have to link against librt or something similar. Enabling it when	3869	you usually have to link against librt or something similar. Enabling it
2460	the functionality isn't available is safe, though, although you have	3870	when the functionality isn't available is safe, though, although you have
2461	to make sure you link against any libraries where the C<clock_gettime>	3871	to make sure you link against any libraries where the C<clock_gettime>
2462	function is hiding in (often F<-lrt>).	3872	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2463		3873
2464	=item EV_USE_REALTIME	3874	=item EV_USE_REALTIME
2465		3875
2466	If defined to be C<1>, libev will try to detect the availability of the	3876	If defined to be C<1>, libev will try to detect the availability of the
2467	realtime clock option at compiletime (and assume its availability at	3877	real-time clock option at compile time (and assume its availability
2468	runtime if successful). Otherwise no use of the realtime clock option will	3878	at runtime if successful). Otherwise no use of the real-time clock
2469	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3879	option will be attempted. This effectively replaces C<gettimeofday>
2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3880	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3881	correctness. See the note about libraries in the description of
		3882	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3883	C<EV_USE_CLOCK_SYSCALL>.
		3884
		3885	=item EV_USE_CLOCK_SYSCALL
		3886
		3887	If defined to be C<1>, libev will try to use a direct syscall instead
		3888	of calling the system-provided C<clock_gettime> function. This option
		3889	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3890	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3891	programs needlessly. Using a direct syscall is slightly slower (in
		3892	theory), because no optimised vdso implementation can be used, but avoids
		3893	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3894	higher, as it simplifies linking (no need for C<-lrt>).
2472		3895
2473	=item EV_USE_NANOSLEEP	3896	=item EV_USE_NANOSLEEP
2474		3897
2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3898	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2476	and will use it for delays. Otherwise it will use C<select ()>.	3899	and will use it for delays. Otherwise it will use C<select ()>.
2477		3900
		3901	=item EV_USE_EVENTFD
		3902
		3903	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3904	available and will probe for kernel support at runtime. This will improve
		3905	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3906	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3907	2.7 or newer, otherwise disabled.
		3908
2478	=item EV_USE_SELECT	3909	=item EV_USE_SELECT
2479		3910
2480	If undefined or defined to be C<1>, libev will compile in support for the	3911	If undefined or defined to be C<1>, libev will compile in support for the
2481	C<select>(2) backend. No attempt at autodetection will be done: if no	3912	C<select>(2) backend. No attempt at auto-detection will be done: if no
2482	other method takes over, select will be it. Otherwise the select backend	3913	other method takes over, select will be it. Otherwise the select backend
2483	will not be compiled in.	3914	will not be compiled in.
2484		3915
2485	=item EV_SELECT_USE_FD_SET	3916	=item EV_SELECT_USE_FD_SET
2486		3917
2487	If defined to C<1>, then the select backend will use the system C<fd_set>	3918	If defined to C<1>, then the select backend will use the system C<fd_set>
2488	structure. This is useful if libev doesn't compile due to a missing	3919	structure. This is useful if libev doesn't compile due to a missing
2489	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3920	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2490	exotic systems. This usually limits the range of file descriptors to some	3921	on exotic systems. This usually limits the range of file descriptors to
2491	low limit such as 1024 or might have other limitations (winsocket only	3922	some low limit such as 1024 or might have other limitations (winsocket
2492	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3923	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2493	influence the size of the C<fd_set> used.	3924	configures the maximum size of the C<fd_set>.
2494		3925
2495	=item EV_SELECT_IS_WINSOCKET	3926	=item EV_SELECT_IS_WINSOCKET
2496		3927
2497	When defined to C<1>, the select backend will assume that	3928	When defined to C<1>, the select backend will assume that
2498	select/socket/connect etc. don't understand file descriptors but	3929	select/socket/connect etc. don't understand file descriptors but
…		…
2500	be used is the winsock select). This means that it will call	3931	be used is the winsock select). This means that it will call
2501	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3932	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2502	it is assumed that all these functions actually work on fds, even	3933	it is assumed that all these functions actually work on fds, even
2503	on win32. Should not be defined on non-win32 platforms.	3934	on win32. Should not be defined on non-win32 platforms.
2504		3935
2505	=item EV_FD_TO_WIN32_HANDLE	3936	=item EV_FD_TO_WIN32_HANDLE(fd)
2506		3937
2507	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3938	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2508	file descriptors to socket handles. When not defining this symbol (the	3939	file descriptors to socket handles. When not defining this symbol (the
2509	default), then libev will call C<_get_osfhandle>, which is usually	3940	default), then libev will call C<_get_osfhandle>, which is usually
2510	correct. In some cases, programs use their own file descriptor management,	3941	correct. In some cases, programs use their own file descriptor management,
2511	in which case they can provide this function to map fds to socket handles.	3942	in which case they can provide this function to map fds to socket handles.
2512		3943
		3944	=item EV_WIN32_HANDLE_TO_FD(handle)
		3945
		3946	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3947	using the standard C<_open_osfhandle> function. For programs implementing
		3948	their own fd to handle mapping, overwriting this function makes it easier
		3949	to do so. This can be done by defining this macro to an appropriate value.
		3950
		3951	=item EV_WIN32_CLOSE_FD(fd)
		3952
		3953	If programs implement their own fd to handle mapping on win32, then this
		3954	macro can be used to override the C<close> function, useful to unregister
		3955	file descriptors again. Note that the replacement function has to close
		3956	the underlying OS handle.
		3957
2513	=item EV_USE_POLL	3958	=item EV_USE_POLL
2514		3959
2515	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3960	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2516	backend. Otherwise it will be enabled on non-win32 platforms. It	3961	backend. Otherwise it will be enabled on non-win32 platforms. It
2517	takes precedence over select.	3962	takes precedence over select.
2518		3963
2519	=item EV_USE_EPOLL	3964	=item EV_USE_EPOLL
2520		3965
2521	If defined to be C<1>, libev will compile in support for the Linux	3966	If defined to be C<1>, libev will compile in support for the Linux
2522	C<epoll>(7) backend. Its availability will be detected at runtime,	3967	C<epoll>(7) backend. Its availability will be detected at runtime,
2523	otherwise another method will be used as fallback. This is the	3968	otherwise another method will be used as fallback. This is the preferred
2524	preferred backend for GNU/Linux systems.	3969	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3970	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2525		3971
2526	=item EV_USE_KQUEUE	3972	=item EV_USE_KQUEUE
2527		3973
2528	If defined to be C<1>, libev will compile in support for the BSD style	3974	If defined to be C<1>, libev will compile in support for the BSD style
2529	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3975	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2542	otherwise another method will be used as fallback. This is the preferred	3988	otherwise another method will be used as fallback. This is the preferred
2543	backend for Solaris 10 systems.	3989	backend for Solaris 10 systems.
2544		3990
2545	=item EV_USE_DEVPOLL	3991	=item EV_USE_DEVPOLL
2546		3992
2547	reserved for future expansion, works like the USE symbols above.	3993	Reserved for future expansion, works like the USE symbols above.
2548		3994
2549	=item EV_USE_INOTIFY	3995	=item EV_USE_INOTIFY
2550		3996
2551	If defined to be C<1>, libev will compile in support for the Linux inotify	3997	If defined to be C<1>, libev will compile in support for the Linux inotify
2552	interface to speed up C<ev_stat> watchers. Its actual availability will	3998	interface to speed up C<ev_stat> watchers. Its actual availability will
2553	be detected at runtime.	3999	be detected at runtime. If undefined, it will be enabled if the headers
		4000	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2554		4001
		4002	=item EV_ATOMIC_T
		4003
		4004	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		4005	access is atomic with respect to other threads or signal contexts. No such
		4006	type is easily found in the C language, so you can provide your own type
		4007	that you know is safe for your purposes. It is used both for signal handler "locking"
		4008	as well as for signal and thread safety in C<ev_async> watchers.
		4009
		4010	In the absence of this define, libev will use C<sig_atomic_t volatile>
		4011	(from F<signal.h>), which is usually good enough on most platforms.
		4012
2555	=item EV_H	4013	=item EV_H (h)
2556		4014
2557	The name of the F<ev.h> header file used to include it. The default if	4015	The name of the F<ev.h> header file used to include it. The default if
2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	4016	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2559	virtually rename the F<ev.h> header file in case of conflicts.	4017	used to virtually rename the F<ev.h> header file in case of conflicts.
2560		4018
2561	=item EV_CONFIG_H	4019	=item EV_CONFIG_H (h)
2562		4020
2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4021	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4022	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2565	C<EV_H>, above.	4023	C<EV_H>, above.
2566		4024
2567	=item EV_EVENT_H	4025	=item EV_EVENT_H (h)
2568		4026
2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4027	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	4028	of how the F<event.h> header can be found, the default is C<"event.h">.
2571		4029
2572	=item EV_PROTOTYPES	4030	=item EV_PROTOTYPES (h)
2573		4031
2574	If defined to be C<0>, then F<ev.h> will not define any function	4032	If defined to be C<0>, then F<ev.h> will not define any function
2575	prototypes, but still define all the structs and other symbols. This is	4033	prototypes, but still define all the structs and other symbols. This is
2576	occasionally useful if you want to provide your own wrapper functions	4034	occasionally useful if you want to provide your own wrapper functions
2577	around libev functions.	4035	around libev functions.
…		…
2596	When doing priority-based operations, libev usually has to linearly search	4054	When doing priority-based operations, libev usually has to linearly search
2597	all the priorities, so having many of them (hundreds) uses a lot of space	4055	all the priorities, so having many of them (hundreds) uses a lot of space
2598	and time, so using the defaults of five priorities (-2 .. +2) is usually	4056	and time, so using the defaults of five priorities (-2 .. +2) is usually
2599	fine.	4057	fine.
2600		4058
2601	If your embedding app does not need any priorities, defining these both to	4059	If your embedding application does not need any priorities, defining these
2602	C<0> will save some memory and cpu.	4060	both to C<0> will save some memory and CPU.
2603		4061
2604	=item EV_PERIODIC_ENABLE	4062	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4063	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4064	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2605		4065
2606	If undefined or defined to be C<1>, then periodic timers are supported. If	4066	If undefined or defined to be C<1> (and the platform supports it), then
2607	defined to be C<0>, then they are not. Disabling them saves a few kB of	4067	the respective watcher type is supported. If defined to be C<0>, then it
2608	code.	4068	is not. Disabling watcher types mainly saves code size.
2609		4069
2610	=item EV_IDLE_ENABLE	4070	=item EV_FEATURES
2611
2612	If undefined or defined to be C<1>, then idle watchers are supported. If
2613	defined to be C<0>, then they are not. Disabling them saves a few kB of
2614	code.
2615
2616	=item EV_EMBED_ENABLE
2617
2618	If undefined or defined to be C<1>, then embed watchers are supported. If
2619	defined to be C<0>, then they are not.
2620
2621	=item EV_STAT_ENABLE
2622
2623	If undefined or defined to be C<1>, then stat watchers are supported. If
2624	defined to be C<0>, then they are not.
2625
2626	=item EV_FORK_ENABLE
2627
2628	If undefined or defined to be C<1>, then fork watchers are supported. If
2629	defined to be C<0>, then they are not.
2630
2631	=item EV_MINIMAL
2632		4071
2633	If you need to shave off some kilobytes of code at the expense of some	4072	If you need to shave off some kilobytes of code at the expense of some
2634	speed, define this symbol to C<1>. Currently only used for gcc to override	4073	speed (but with the full API), you can define this symbol to request
2635	some inlining decisions, saves roughly 30% codesize of amd64.	4074	certain subsets of functionality. The default is to enable all features
		4075	that can be enabled on the platform.
		4076
		4077	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4078	with some broad features you want) and then selectively re-enable
		4079	additional parts you want, for example if you want everything minimal,
		4080	but multiple event loop support, async and child watchers and the poll
		4081	backend, use this:
		4082
		4083	#define EV_FEATURES 0
		4084	#define EV_MULTIPLICITY 1
		4085	#define EV_USE_POLL 1
		4086	#define EV_CHILD_ENABLE 1
		4087	#define EV_ASYNC_ENABLE 1
		4088
		4089	The actual value is a bitset, it can be a combination of the following
		4090	values:
		4091
		4092	=over 4
		4093
		4094	=item C<1> - faster/larger code
		4095
		4096	Use larger code to speed up some operations.
		4097
		4098	Currently this is used to override some inlining decisions (enlarging the
		4099	code size by roughly 30% on amd64).
		4100
		4101	When optimising for size, use of compiler flags such as C<-Os> with
		4102	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4103	assertions.
		4104
		4105	=item C<2> - faster/larger data structures
		4106
		4107	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4108	hash table sizes and so on. This will usually further increase code size
		4109	and can additionally have an effect on the size of data structures at
		4110	runtime.
		4111
		4112	=item C<4> - full API configuration
		4113
		4114	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4115	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4116
		4117	=item C<8> - full API
		4118
		4119	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4120	details on which parts of the API are still available without this
		4121	feature, and do not complain if this subset changes over time.
		4122
		4123	=item C<16> - enable all optional watcher types
		4124
		4125	Enables all optional watcher types. If you want to selectively enable
		4126	only some watcher types other than I/O and timers (e.g. prepare,
		4127	embed, async, child...) you can enable them manually by defining
		4128	C<EV_watchertype_ENABLE> to C<1> instead.
		4129
		4130	=item C<32> - enable all backends
		4131
		4132	This enables all backends - without this feature, you need to enable at
		4133	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4134
		4135	=item C<64> - enable OS-specific "helper" APIs
		4136
		4137	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4138	default.
		4139
		4140	=back
		4141
		4142	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4143	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4144	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4145	watchers, timers and monotonic clock support.
		4146
		4147	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4148	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4149	your program might be left out as well - a binary starting a timer and an
		4150	I/O watcher then might come out at only 5Kb.
		4151
		4152	=item EV_AVOID_STDIO
		4153
		4154	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4155	functions (printf, scanf, perror etc.). This will increase the code size
		4156	somewhat, but if your program doesn't otherwise depend on stdio and your
		4157	libc allows it, this avoids linking in the stdio library which is quite
		4158	big.
		4159
		4160	Note that error messages might become less precise when this option is
		4161	enabled.
		4162
		4163	=item EV_NSIG
		4164
		4165	The highest supported signal number, +1 (or, the number of
		4166	signals): Normally, libev tries to deduce the maximum number of signals
		4167	automatically, but sometimes this fails, in which case it can be
		4168	specified. Also, using a lower number than detected (C<32> should be
		4169	good for about any system in existence) can save some memory, as libev
		4170	statically allocates some 12-24 bytes per signal number.
2636		4171
2637	=item EV_PID_HASHSIZE	4172	=item EV_PID_HASHSIZE
2638		4173
2639	C<ev_child> watchers use a small hash table to distribute workload by	4174	C<ev_child> watchers use a small hash table to distribute workload by
2640	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4175	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2641	than enough. If you need to manage thousands of children you might want to	4176	usually more than enough. If you need to manage thousands of children you
2642	increase this value (I<must> be a power of two).	4177	might want to increase this value (I<must> be a power of two).
2643		4178
2644	=item EV_INOTIFY_HASHSIZE	4179	=item EV_INOTIFY_HASHSIZE
2645		4180
2646	C<ev_stat> watchers use a small hash table to distribute workload by	4181	C<ev_stat> watchers use a small hash table to distribute workload by
2647	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4182	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
2648	usually more than enough. If you need to manage thousands of C<ev_stat>	4183	disabled), usually more than enough. If you need to manage thousands of
2649	watchers you might want to increase this value (I<must> be a power of	4184	C<ev_stat> watchers you might want to increase this value (I<must> be a
2650	two).	4185	power of two).
		4186
		4187	=item EV_USE_4HEAP
		4188
		4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4190	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		4191	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		4192	faster performance with many (thousands) of watchers.
		4193
		4194	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4195	will be C<0>.
		4196
		4197	=item EV_HEAP_CACHE_AT
		4198
		4199	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4200	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		4201	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		4202	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		4203	but avoids random read accesses on heap changes. This improves performance
		4204	noticeably with many (hundreds) of watchers.
		4205
		4206	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4207	will be C<0>.
		4208
		4209	=item EV_VERIFY
		4210
		4211	Controls how much internal verification (see C<ev_verify ()>) will
		4212	be done: If set to C<0>, no internal verification code will be compiled
		4213	in. If set to C<1>, then verification code will be compiled in, but not
		4214	called. If set to C<2>, then the internal verification code will be
		4215	called once per loop, which can slow down libev. If set to C<3>, then the
		4216	verification code will be called very frequently, which will slow down
		4217	libev considerably.
		4218
		4219	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4220	will be C<0>.
2651		4221
2652	=item EV_COMMON	4222	=item EV_COMMON
2653		4223
2654	By default, all watchers have a C<void *data> member. By redefining	4224	By default, all watchers have a C<void *data> member. By redefining
2655	this macro to a something else you can include more and other types of	4225	this macro to something else you can include more and other types of
2656	members. You have to define it each time you include one of the files,	4226	members. You have to define it each time you include one of the files,
2657	though, and it must be identical each time.	4227	though, and it must be identical each time.
2658		4228
2659	For example, the perl EV module uses something like this:	4229	For example, the perl EV module uses something like this:
2660		4230
2661	#define EV_COMMON \	4231	#define EV_COMMON \
2662	SV *self; /* contains this struct */ \	4232	SV *self; /* contains this struct */ \
2663	SV *cb_sv, *fh /* note no trailing ";" */	4233	SV *cb_sv, *fh /* note no trailing ";" */
2664		4234
2665	=item EV_CB_DECLARE (type)	4235	=item EV_CB_DECLARE (type)
2666		4236
2667	=item EV_CB_INVOKE (watcher, revents)	4237	=item EV_CB_INVOKE (watcher, revents)
2668		4238
…		…
2673	definition and a statement, respectively. See the F<ev.h> header file for	4243	definition and a statement, respectively. See the F<ev.h> header file for
2674	their default definitions. One possible use for overriding these is to	4244	their default definitions. One possible use for overriding these is to
2675	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4245	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2676	method calls instead of plain function calls in C++.	4246	method calls instead of plain function calls in C++.
2677		4247
		4248	=back
		4249
2678	=head2 EXPORTED API SYMBOLS	4250	=head2 EXPORTED API SYMBOLS
2679		4251
2680	If you need to re-export the API (e.g. via a dll) and you need a list of	4252	If you need to re-export the API (e.g. via a DLL) and you need a list of
2681	exported symbols, you can use the provided F<Symbol.*> files which list	4253	exported symbols, you can use the provided F<Symbol.*> files which list
2682	all public symbols, one per line:	4254	all public symbols, one per line:
2683		4255
2684	Symbols.ev for libev proper	4256	Symbols.ev for libev proper
2685	Symbols.event for the libevent emulation	4257	Symbols.event for the libevent emulation
2686		4258
2687	This can also be used to rename all public symbols to avoid clashes with	4259	This can also be used to rename all public symbols to avoid clashes with
2688	multiple versions of libev linked together (which is obviously bad in	4260	multiple versions of libev linked together (which is obviously bad in
2689	itself, but sometimes it is inconvinient to avoid this).	4261	itself, but sometimes it is inconvenient to avoid this).
2690		4262
2691	A sed command like this will create wrapper C<#define>'s that you need to	4263	A sed command like this will create wrapper C<#define>'s that you need to
2692	include before including F<ev.h>:	4264	include before including F<ev.h>:
2693		4265
2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4266	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2711	file.	4283	file.
2712		4284
2713	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4285	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2714	that everybody includes and which overrides some configure choices:	4286	that everybody includes and which overrides some configure choices:
2715		4287
2716	#define EV_MINIMAL 1	4288	#define EV_FEATURES 8
2717	#define EV_USE_POLL 0	4289	#define EV_USE_SELECT 1
2718	#define EV_MULTIPLICITY 0
2719	#define EV_PERIODIC_ENABLE 0	4290	#define EV_PREPARE_ENABLE 1
		4291	#define EV_IDLE_ENABLE 1
2720	#define EV_STAT_ENABLE 0	4292	#define EV_SIGNAL_ENABLE 1
2721	#define EV_FORK_ENABLE 0	4293	#define EV_CHILD_ENABLE 1
		4294	#define EV_USE_STDEXCEPT 0
2722	#define EV_CONFIG_H <config.h>	4295	#define EV_CONFIG_H <config.h>
2723	#define EV_MINPRI 0
2724	#define EV_MAXPRI 0
2725		4296
2726	#include "ev++.h"	4297	#include "ev++.h"
2727		4298
2728	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4299	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2729		4300
2730	#include "ev_cpp.h"	4301	#include "ev_cpp.h"
2731	#include "ev.c"	4302	#include "ev.c"
2732		4303
		4304	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2733		4305
2734	=head1 COMPLEXITIES	4306	=head2 THREADS AND COROUTINES
2735		4307
2736	In this section the complexities of (many of) the algorithms used inside	4308	=head3 THREADS
2737	libev will be explained. For complexity discussions about backends see the
2738	documentation for C<ev_default_init>.
2739		4309
2740	All of the following are about amortised time: If an array needs to be	4310	All libev functions are reentrant and thread-safe unless explicitly
2741	extended, libev needs to realloc and move the whole array, but this	4311	documented otherwise, but libev implements no locking itself. This means
2742	happens asymptotically never with higher number of elements, so O(1) might	4312	that you can use as many loops as you want in parallel, as long as there
2743	mean it might do a lengthy realloc operation in rare cases, but on average	4313	are no concurrent calls into any libev function with the same loop
2744	it is much faster and asymptotically approaches constant time.	4314	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4315	of course): libev guarantees that different event loops share no data
		4316	structures that need any locking.
		4317
		4318	Or to put it differently: calls with different loop parameters can be done
		4319	concurrently from multiple threads, calls with the same loop parameter
		4320	must be done serially (but can be done from different threads, as long as
		4321	only one thread ever is inside a call at any point in time, e.g. by using
		4322	a mutex per loop).
		4323
		4324	Specifically to support threads (and signal handlers), libev implements
		4325	so-called C<ev_async> watchers, which allow some limited form of
		4326	concurrency on the same event loop, namely waking it up "from the
		4327	outside".
		4328
		4329	If you want to know which design (one loop, locking, or multiple loops
		4330	without or something else still) is best for your problem, then I cannot
		4331	help you, but here is some generic advice:
2745		4332
2746	=over 4	4333	=over 4
2747		4334
2748	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4335	=item * most applications have a main thread: use the default libev loop
		4336	in that thread, or create a separate thread running only the default loop.
2749		4337
2750	This means that, when you have a watcher that triggers in one hour and	4338	This helps integrating other libraries or software modules that use libev
2751	there are 100 watchers that would trigger before that then inserting will	4339	themselves and don't care/know about threading.
2752	have to skip roughly seven (C<ld 100>) of these watchers.
2753		4340
2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4341	=item * one loop per thread is usually a good model.
2755		4342
2756	That means that changing a timer costs less than removing/adding them	4343	Doing this is almost never wrong, sometimes a better-performance model
2757	as only the relative motion in the event queue has to be paid for.	4344	exists, but it is always a good start.
2758		4345
2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	4346	=item * other models exist, such as the leader/follower pattern, where one
		4347	loop is handed through multiple threads in a kind of round-robin fashion.
2760		4348
2761	These just add the watcher into an array or at the head of a list.	4349	Choosing a model is hard - look around, learn, know that usually you can do
		4350	better than you currently do :-)
2762		4351
2763	=item Stopping check/prepare/idle watchers: O(1)	4352	=item * often you need to talk to some other thread which blocks in the
		4353	event loop.
2764		4354
2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4355	C<ev_async> watchers can be used to wake them up from other threads safely
		4356	(or from signal contexts...).
2766		4357
2767	These watchers are stored in lists then need to be walked to find the	4358	An example use would be to communicate signals or other events that only
2768	correct watcher to remove. The lists are usually short (you don't usually	4359	work in the default loop by registering the signal watcher with the
2769	have many watchers waiting for the same fd or signal).	4360	default loop and triggering an C<ev_async> watcher from the default loop
2770		4361	watcher callback into the event loop interested in the signal.
2771	=item Finding the next timer in each loop iteration: O(1)
2772
2773	By virtue of using a binary heap, the next timer is always found at the
2774	beginning of the storage array.
2775
2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2777
2778	A change means an I/O watcher gets started or stopped, which requires
2779	libev to recalculate its status (and possibly tell the kernel, depending
2780	on backend and wether C<ev_io_set> was used).
2781
2782	=item Activating one watcher (putting it into the pending state): O(1)
2783
2784	=item Priority handling: O(number_of_priorities)
2785
2786	Priorities are implemented by allocating some space for each
2787	priority. When doing priority-based operations, libev usually has to
2788	linearly search all the priorities, but starting/stopping and activating
2789	watchers becomes O(1) w.r.t. prioritiy handling.
2790		4362
2791	=back	4363	=back
2792		4364
		4365	=head4 THREAD LOCKING EXAMPLE
2793		4366
2794	=head1 Win32 platform limitations and workarounds	4367	Here is a fictitious example of how to run an event loop in a different
		4368	thread than where callbacks are being invoked and watchers are
		4369	created/added/removed.
		4370
		4371	For a real-world example, see the C<EV::Loop::Async> perl module,
		4372	which uses exactly this technique (which is suited for many high-level
		4373	languages).
		4374
		4375	The example uses a pthread mutex to protect the loop data, a condition
		4376	variable to wait for callback invocations, an async watcher to notify the
		4377	event loop thread and an unspecified mechanism to wake up the main thread.
		4378
		4379	First, you need to associate some data with the event loop:
		4380
		4381	typedef struct {
		4382	mutex_t lock; /* global loop lock */
		4383	ev_async async_w;
		4384	thread_t tid;
		4385	cond_t invoke_cv;
		4386	} userdata;
		4387
		4388	void prepare_loop (EV_P)
		4389	{
		4390	// for simplicity, we use a static userdata struct.
		4391	static userdata u;
		4392
		4393	ev_async_init (&u->async_w, async_cb);
		4394	ev_async_start (EV_A_ &u->async_w);
		4395
		4396	pthread_mutex_init (&u->lock, 0);
		4397	pthread_cond_init (&u->invoke_cv, 0);
		4398
		4399	// now associate this with the loop
		4400	ev_set_userdata (EV_A_ u);
		4401	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4402	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4403
		4404	// then create the thread running ev_loop
		4405	pthread_create (&u->tid, 0, l_run, EV_A);
		4406	}
		4407
		4408	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4409	solely to wake up the event loop so it takes notice of any new watchers
		4410	that might have been added:
		4411
		4412	static void
		4413	async_cb (EV_P_ ev_async *w, int revents)
		4414	{
		4415	// just used for the side effects
		4416	}
		4417
		4418	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4419	protecting the loop data, respectively.
		4420
		4421	static void
		4422	l_release (EV_P)
		4423	{
		4424	userdata *u = ev_userdata (EV_A);
		4425	pthread_mutex_unlock (&u->lock);
		4426	}
		4427
		4428	static void
		4429	l_acquire (EV_P)
		4430	{
		4431	userdata *u = ev_userdata (EV_A);
		4432	pthread_mutex_lock (&u->lock);
		4433	}
		4434
		4435	The event loop thread first acquires the mutex, and then jumps straight
		4436	into C<ev_run>:
		4437
		4438	void *
		4439	l_run (void *thr_arg)
		4440	{
		4441	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4442
		4443	l_acquire (EV_A);
		4444	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4445	ev_run (EV_A_ 0);
		4446	l_release (EV_A);
		4447
		4448	return 0;
		4449	}
		4450
		4451	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4452	signal the main thread via some unspecified mechanism (signals? pipe
		4453	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4454	have been called (in a while loop because a) spurious wakeups are possible
		4455	and b) skipping inter-thread-communication when there are no pending
		4456	watchers is very beneficial):
		4457
		4458	static void
		4459	l_invoke (EV_P)
		4460	{
		4461	userdata *u = ev_userdata (EV_A);
		4462
		4463	while (ev_pending_count (EV_A))
		4464	{
		4465	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4466	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4467	}
		4468	}
		4469
		4470	Now, whenever the main thread gets told to invoke pending watchers, it
		4471	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4472	thread to continue:
		4473
		4474	static void
		4475	real_invoke_pending (EV_P)
		4476	{
		4477	userdata *u = ev_userdata (EV_A);
		4478
		4479	pthread_mutex_lock (&u->lock);
		4480	ev_invoke_pending (EV_A);
		4481	pthread_cond_signal (&u->invoke_cv);
		4482	pthread_mutex_unlock (&u->lock);
		4483	}
		4484
		4485	Whenever you want to start/stop a watcher or do other modifications to an
		4486	event loop, you will now have to lock:
		4487
		4488	ev_timer timeout_watcher;
		4489	userdata *u = ev_userdata (EV_A);
		4490
		4491	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4492
		4493	pthread_mutex_lock (&u->lock);
		4494	ev_timer_start (EV_A_ &timeout_watcher);
		4495	ev_async_send (EV_A_ &u->async_w);
		4496	pthread_mutex_unlock (&u->lock);
		4497
		4498	Note that sending the C<ev_async> watcher is required because otherwise
		4499	an event loop currently blocking in the kernel will have no knowledge
		4500	about the newly added timer. By waking up the loop it will pick up any new
		4501	watchers in the next event loop iteration.
		4502
		4503	=head3 COROUTINES
		4504
		4505	Libev is very accommodating to coroutines ("cooperative threads"):
		4506	libev fully supports nesting calls to its functions from different
		4507	coroutines (e.g. you can call C<ev_run> on the same loop from two
		4508	different coroutines, and switch freely between both coroutines running
		4509	the loop, as long as you don't confuse yourself). The only exception is
		4510	that you must not do this from C<ev_periodic> reschedule callbacks.
		4511
		4512	Care has been taken to ensure that libev does not keep local state inside
		4513	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4514	they do not call any callbacks.
		4515
		4516	=head2 COMPILER WARNINGS
		4517
		4518	Depending on your compiler and compiler settings, you might get no or a
		4519	lot of warnings when compiling libev code. Some people are apparently
		4520	scared by this.
		4521
		4522	However, these are unavoidable for many reasons. For one, each compiler
		4523	has different warnings, and each user has different tastes regarding
		4524	warning options. "Warn-free" code therefore cannot be a goal except when
		4525	targeting a specific compiler and compiler-version.
		4526
		4527	Another reason is that some compiler warnings require elaborate
		4528	workarounds, or other changes to the code that make it less clear and less
		4529	maintainable.
		4530
		4531	And of course, some compiler warnings are just plain stupid, or simply
		4532	wrong (because they don't actually warn about the condition their message
		4533	seems to warn about). For example, certain older gcc versions had some
		4534	warnings that resulted in an extreme number of false positives. These have
		4535	been fixed, but some people still insist on making code warn-free with
		4536	such buggy versions.
		4537
		4538	While libev is written to generate as few warnings as possible,
		4539	"warn-free" code is not a goal, and it is recommended not to build libev
		4540	with any compiler warnings enabled unless you are prepared to cope with
		4541	them (e.g. by ignoring them). Remember that warnings are just that:
		4542	warnings, not errors, or proof of bugs.
		4543
		4544
		4545	=head2 VALGRIND
		4546
		4547	Valgrind has a special section here because it is a popular tool that is
		4548	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4549
		4550	If you think you found a bug (memory leak, uninitialised data access etc.)
		4551	in libev, then check twice: If valgrind reports something like:
		4552
		4553	==2274== definitely lost: 0 bytes in 0 blocks.
		4554	==2274== possibly lost: 0 bytes in 0 blocks.
		4555	==2274== still reachable: 256 bytes in 1 blocks.
		4556
		4557	Then there is no memory leak, just as memory accounted to global variables
		4558	is not a memleak - the memory is still being referenced, and didn't leak.
		4559
		4560	Similarly, under some circumstances, valgrind might report kernel bugs
		4561	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4562	although an acceptable workaround has been found here), or it might be
		4563	confused.
		4564
		4565	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4566	make it into some kind of religion.
		4567
		4568	If you are unsure about something, feel free to contact the mailing list
		4569	with the full valgrind report and an explanation on why you think this
		4570	is a bug in libev (best check the archives, too :). However, don't be
		4571	annoyed when you get a brisk "this is no bug" answer and take the chance
		4572	of learning how to interpret valgrind properly.
		4573
		4574	If you need, for some reason, empty reports from valgrind for your project
		4575	I suggest using suppression lists.
		4576
		4577
		4578	=head1 PORTABILITY NOTES
		4579
		4580	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4581
		4582	GNU/Linux is the only common platform that supports 64 bit file/large file
		4583	interfaces but I<disables> them by default.
		4584
		4585	That means that libev compiled in the default environment doesn't support
		4586	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4587
		4588	Unfortunately, many programs try to work around this GNU/Linux issue
		4589	by enabling the large file API, which makes them incompatible with the
		4590	standard libev compiled for their system.
		4591
		4592	Likewise, libev cannot enable the large file API itself as this would
		4593	suddenly make it incompatible to the default compile time environment,
		4594	i.e. all programs not using special compile switches.
		4595
		4596	=head2 OS/X AND DARWIN BUGS
		4597
		4598	The whole thing is a bug if you ask me - basically any system interface
		4599	you touch is broken, whether it is locales, poll, kqueue or even the
		4600	OpenGL drivers.
		4601
		4602	=head3 C<kqueue> is buggy
		4603
		4604	The kqueue syscall is broken in all known versions - most versions support
		4605	only sockets, many support pipes.
		4606
		4607	Libev tries to work around this by not using C<kqueue> by default on this
		4608	rotten platform, but of course you can still ask for it when creating a
		4609	loop - embedding a socket-only kqueue loop into a select-based one is
		4610	probably going to work well.
		4611
		4612	=head3 C<poll> is buggy
		4613
		4614	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4615	implementation by something calling C<kqueue> internally around the 10.5.6
		4616	release, so now C<kqueue> I<and> C<poll> are broken.
		4617
		4618	Libev tries to work around this by not using C<poll> by default on
		4619	this rotten platform, but of course you can still ask for it when creating
		4620	a loop.
		4621
		4622	=head3 C<select> is buggy
		4623
		4624	All that's left is C<select>, and of course Apple found a way to fuck this
		4625	one up as well: On OS/X, C<select> actively limits the number of file
		4626	descriptors you can pass in to 1024 - your program suddenly crashes when
		4627	you use more.
		4628
		4629	There is an undocumented "workaround" for this - defining
		4630	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4631	work on OS/X.
		4632
		4633	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4634
		4635	=head3 C<errno> reentrancy
		4636
		4637	The default compile environment on Solaris is unfortunately so
		4638	thread-unsafe that you can't even use components/libraries compiled
		4639	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4640	defined by default. A valid, if stupid, implementation choice.
		4641
		4642	If you want to use libev in threaded environments you have to make sure
		4643	it's compiled with C<_REENTRANT> defined.
		4644
		4645	=head3 Event port backend
		4646
		4647	The scalable event interface for Solaris is called "event
		4648	ports". Unfortunately, this mechanism is very buggy in all major
		4649	releases. If you run into high CPU usage, your program freezes or you get
		4650	a large number of spurious wakeups, make sure you have all the relevant
		4651	and latest kernel patches applied. No, I don't know which ones, but there
		4652	are multiple ones to apply, and afterwards, event ports actually work
		4653	great.
		4654
		4655	If you can't get it to work, you can try running the program by setting
		4656	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4657	C<select> backends.
		4658
		4659	=head2 AIX POLL BUG
		4660
		4661	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4662	this by trying to avoid the poll backend altogether (i.e. it's not even
		4663	compiled in), which normally isn't a big problem as C<select> works fine
		4664	with large bitsets on AIX, and AIX is dead anyway.
		4665
		4666	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4667
		4668	=head3 General issues
2795		4669
2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2797	requires, and its I/O model is fundamentally incompatible with the POSIX	4671	requires, and its I/O model is fundamentally incompatible with the POSIX
2798	model. Libev still offers limited functionality on this platform in	4672	model. Libev still offers limited functionality on this platform in
2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2800	descriptors. This only applies when using Win32 natively, not when using	4674	descriptors. This only applies when using Win32 natively, not when using
2801	e.g. cygwin.	4675	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4676	as every compielr comes with a slightly differently broken/incompatible
		4677	environment.
		4678
		4679	Lifting these limitations would basically require the full
		4680	re-implementation of the I/O system. If you are into this kind of thing,
		4681	then note that glib does exactly that for you in a very portable way (note
		4682	also that glib is the slowest event library known to man).
2802		4683
2803	There is no supported compilation method available on windows except	4684	There is no supported compilation method available on windows except
2804	embedding it into other applications.	4685	embedding it into other applications.
2805		4686
		4687	Sensible signal handling is officially unsupported by Microsoft - libev
		4688	tries its best, but under most conditions, signals will simply not work.
		4689
		4690	Not a libev limitation but worth mentioning: windows apparently doesn't
		4691	accept large writes: instead of resulting in a partial write, windows will
		4692	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4693	so make sure you only write small amounts into your sockets (less than a
		4694	megabyte seems safe, but this apparently depends on the amount of memory
		4695	available).
		4696
2806	Due to the many, low, and arbitrary limits on the win32 platform and the	4697	Due to the many, low, and arbitrary limits on the win32 platform and
2807	abysmal performance of winsockets, using a large number of sockets is not	4698	the abysmal performance of winsockets, using a large number of sockets
2808	recommended (and not reasonable). If your program needs to use more than	4699	is not recommended (and not reasonable). If your program needs to use
2809	a hundred or so sockets, then likely it needs to use a totally different	4700	more than a hundred or so sockets, then likely it needs to use a totally
2810	implementation for windows, as libev offers the POSIX model, which cannot	4701	different implementation for windows, as libev offers the POSIX readiness
2811	be implemented efficiently on windows (microsoft monopoly games).	4702	notification model, which cannot be implemented efficiently on windows
		4703	(due to Microsoft monopoly games).
2812		4704
2813	=over 4	4705	A typical way to use libev under windows is to embed it (see the embedding
		4706	section for details) and use the following F<evwrap.h> header file instead
		4707	of F<ev.h>:
2814		4708
		4709	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4710	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4711
		4712	#include "ev.h"
		4713
		4714	And compile the following F<evwrap.c> file into your project (make sure
		4715	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4716
		4717	#include "evwrap.h"
		4718	#include "ev.c"
		4719
2815	=item The winsocket select function	4720	=head3 The winsocket C<select> function
2816		4721
2817	The winsocket C<select> function doesn't follow POSIX in that it requires	4722	The winsocket C<select> function doesn't follow POSIX in that it
2818	socket I<handles> and not socket I<file descriptors>. This makes select	4723	requires socket I<handles> and not socket I<file descriptors> (it is
2819	very inefficient, and also requires a mapping from file descriptors	4724	also extremely buggy). This makes select very inefficient, and also
2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4725	requires a mapping from file descriptors to socket handles (the Microsoft
2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4726	C runtime provides the function C<_open_osfhandle> for this). See the
2822	symbols for more info.	4727	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4728	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2823		4729
2824	The configuration for a "naked" win32 using the microsoft runtime	4730	The configuration for a "naked" win32 using the Microsoft runtime
2825	libraries and raw winsocket select is:	4731	libraries and raw winsocket select is:
2826		4732
2827	#define EV_USE_SELECT 1	4733	#define EV_USE_SELECT 1
2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4734	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2829		4735
2830	Note that winsockets handling of fd sets is O(n), so you can easily get a	4736	Note that winsockets handling of fd sets is O(n), so you can easily get a
2831	complexity in the O(n²) range when using win32.	4737	complexity in the O(n²) range when using win32.
2832		4738
2833	=item Limited number of file descriptors	4739	=head3 Limited number of file descriptors
2834		4740
2835	Windows has numerous arbitrary (and low) limits on things. Early versions	4741	Windows has numerous arbitrary (and low) limits on things.
2836	of winsocket's select only supported waiting for a max. of C<64> handles	4742
		4743	Early versions of winsocket's select only supported waiting for a maximum
2837	(probably owning to the fact that all windows kernels can only wait for	4744	of C<64> handles (probably owning to the fact that all windows kernels
2838	C<64> things at the same time internally; microsoft recommends spawning a	4745	can only wait for C<64> things at the same time internally; Microsoft
2839	chain of threads and wait for 63 handles and the previous thread in each).	4746	recommends spawning a chain of threads and wait for 63 handles and the
		4747	previous thread in each. Sounds great!).
2840		4748
2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4749	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2842	to some high number (e.g. C<2048>) before compiling the winsocket select	4750	to some high number (e.g. C<2048>) before compiling the winsocket select
2843	call (which might be in libev or elsewhere, for example, perl does its own	4751	call (which might be in libev or elsewhere, for example, perl and many
2844	select emulation on windows).	4752	other interpreters do their own select emulation on windows).
2845		4753
2846	Another limit is the number of file descriptors in the microsoft runtime	4754	Another limit is the number of file descriptors in the Microsoft runtime
2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4755	libraries, which by default is C<64> (there must be a hidden I<64>
2848	or something like this inside microsoft). You can increase this by calling	4756	fetish or something like this inside Microsoft). You can increase this
2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4757	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
2850	arbitrary limit), but is broken in many versions of the microsoft runtime	4758	(another arbitrary limit), but is broken in many versions of the Microsoft
2851	libraries.
2852
2853	This might get you to about C<512> or C<2048> sockets (depending on	4759	runtime libraries. This might get you to about C<512> or C<2048> sockets
2854	windows version and/or the phase of the moon). To get more, you need to	4760	(depending on windows version and/or the phase of the moon). To get more,
2855	wrap all I/O functions and provide your own fd management, but the cost of	4761	you need to wrap all I/O functions and provide your own fd management, but
2856	calling select (O(n²)) will likely make this unworkable.	4762	the cost of calling select (O(n²)) will likely make this unworkable.
		4763
		4764	=head2 PORTABILITY REQUIREMENTS
		4765
		4766	In addition to a working ISO-C implementation and of course the
		4767	backend-specific APIs, libev relies on a few additional extensions:
		4768
		4769	=over 4
		4770
		4771	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4772	calling conventions regardless of C<ev_watcher_type *>.
		4773
		4774	Libev assumes not only that all watcher pointers have the same internal
		4775	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4776	assumes that the same (machine) code can be used to call any watcher
		4777	callback: The watcher callbacks have different type signatures, but libev
		4778	calls them using an C<ev_watcher *> internally.
		4779
		4780	=item pointer accesses must be thread-atomic
		4781
		4782	Accessing a pointer value must be atomic, it must both be readable and
		4783	writable in one piece - this is the case on all current architectures.
		4784
		4785	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4786
		4787	The type C<sig_atomic_t volatile> (or whatever is defined as
		4788	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4789	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4790	believed to be sufficiently portable.
		4791
		4792	=item C<sigprocmask> must work in a threaded environment
		4793
		4794	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4795	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4796	pthread implementations will either allow C<sigprocmask> in the "main
		4797	thread" or will block signals process-wide, both behaviours would
		4798	be compatible with libev. Interaction between C<sigprocmask> and
		4799	C<pthread_sigmask> could complicate things, however.
		4800
		4801	The most portable way to handle signals is to block signals in all threads
		4802	except the initial one, and run the default loop in the initial thread as
		4803	well.
		4804
		4805	=item C<long> must be large enough for common memory allocation sizes
		4806
		4807	To improve portability and simplify its API, libev uses C<long> internally
		4808	instead of C<size_t> when allocating its data structures. On non-POSIX
		4809	systems (Microsoft...) this might be unexpectedly low, but is still at
		4810	least 31 bits everywhere, which is enough for hundreds of millions of
		4811	watchers.
		4812
		4813	=item C<double> must hold a time value in seconds with enough accuracy
		4814
		4815	The type C<double> is used to represent timestamps. It is required to
		4816	have at least 51 bits of mantissa (and 9 bits of exponent), which is
		4817	good enough for at least into the year 4000 with millisecond accuracy
		4818	(the design goal for libev). This requirement is overfulfilled by
		4819	implementations using IEEE 754, which is basically all existing ones. With
		4820	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
2857		4821
2858	=back	4822	=back
2859		4823
		4824	If you know of other additional requirements drop me a note.
		4825
		4826
		4827	=head1 ALGORITHMIC COMPLEXITIES
		4828
		4829	In this section the complexities of (many of) the algorithms used inside
		4830	libev will be documented. For complexity discussions about backends see
		4831	the documentation for C<ev_default_init>.
		4832
		4833	All of the following are about amortised time: If an array needs to be
		4834	extended, libev needs to realloc and move the whole array, but this
		4835	happens asymptotically rarer with higher number of elements, so O(1) might
		4836	mean that libev does a lengthy realloc operation in rare cases, but on
		4837	average it is much faster and asymptotically approaches constant time.
		4838
		4839	=over 4
		4840
		4841	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4842
		4843	This means that, when you have a watcher that triggers in one hour and
		4844	there are 100 watchers that would trigger before that, then inserting will
		4845	have to skip roughly seven (C<ld 100>) of these watchers.
		4846
		4847	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4848
		4849	That means that changing a timer costs less than removing/adding them,
		4850	as only the relative motion in the event queue has to be paid for.
		4851
		4852	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4853
		4854	These just add the watcher into an array or at the head of a list.
		4855
		4856	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4857
		4858	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4859
		4860	These watchers are stored in lists, so they need to be walked to find the
		4861	correct watcher to remove. The lists are usually short (you don't usually
		4862	have many watchers waiting for the same fd or signal: one is typical, two
		4863	is rare).
		4864
		4865	=item Finding the next timer in each loop iteration: O(1)
		4866
		4867	By virtue of using a binary or 4-heap, the next timer is always found at a
		4868	fixed position in the storage array.
		4869
		4870	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4871
		4872	A change means an I/O watcher gets started or stopped, which requires
		4873	libev to recalculate its status (and possibly tell the kernel, depending
		4874	on backend and whether C<ev_io_set> was used).
		4875
		4876	=item Activating one watcher (putting it into the pending state): O(1)
		4877
		4878	=item Priority handling: O(number_of_priorities)
		4879
		4880	Priorities are implemented by allocating some space for each
		4881	priority. When doing priority-based operations, libev usually has to
		4882	linearly search all the priorities, but starting/stopping and activating
		4883	watchers becomes O(1) with respect to priority handling.
		4884
		4885	=item Sending an ev_async: O(1)
		4886
		4887	=item Processing ev_async_send: O(number_of_async_watchers)
		4888
		4889	=item Processing signals: O(max_signal_number)
		4890
		4891	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4892	calls in the current loop iteration. Checking for async and signal events
		4893	involves iterating over all running async watchers or all signal numbers.
		4894
		4895	=back
		4896
		4897
		4898	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4899
		4900	The major version 4 introduced some incompatible changes to the API.
		4901
		4902	At the moment, the C<ev.h> header file provides compatibility definitions
		4903	for all changes, so most programs should still compile. The compatibility
		4904	layer might be removed in later versions of libev, so better update to the
		4905	new API early than late.
		4906
		4907	=over 4
		4908
		4909	=item C<EV_COMPAT3> backwards compatibility mechanism
		4910
		4911	The backward compatibility mechanism can be controlled by
		4912	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4913	section.
		4914
		4915	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4916
		4917	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4918
		4919	ev_loop_destroy (EV_DEFAULT_UC);
		4920	ev_loop_fork (EV_DEFAULT);
		4921
		4922	=item function/symbol renames
		4923
		4924	A number of functions and symbols have been renamed:
		4925
		4926	ev_loop => ev_run
		4927	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4928	EVLOOP_ONESHOT => EVRUN_ONCE
		4929
		4930	ev_unloop => ev_break
		4931	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4932	EVUNLOOP_ONE => EVBREAK_ONE
		4933	EVUNLOOP_ALL => EVBREAK_ALL
		4934
		4935	EV_TIMEOUT => EV_TIMER
		4936
		4937	ev_loop_count => ev_iteration
		4938	ev_loop_depth => ev_depth
		4939	ev_loop_verify => ev_verify
		4940
		4941	Most functions working on C<struct ev_loop> objects don't have an
		4942	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4943	associated constants have been renamed to not collide with the C<struct
		4944	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4945	as all other watcher types. Note that C<ev_loop_fork> is still called
		4946	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4947	typedef.
		4948
		4949	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4950
		4951	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4952	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4953	and work, but the library code will of course be larger.
		4954
		4955	=back
		4956
		4957
		4958	=head1 GLOSSARY
		4959
		4960	=over 4
		4961
		4962	=item active
		4963
		4964	A watcher is active as long as it has been started and not yet stopped.
		4965	See L<WATCHER STATES> for details.
		4966
		4967	=item application
		4968
		4969	In this document, an application is whatever is using libev.
		4970
		4971	=item backend
		4972
		4973	The part of the code dealing with the operating system interfaces.
		4974
		4975	=item callback
		4976
		4977	The address of a function that is called when some event has been
		4978	detected. Callbacks are being passed the event loop, the watcher that
		4979	received the event, and the actual event bitset.
		4980
		4981	=item callback/watcher invocation
		4982
		4983	The act of calling the callback associated with a watcher.
		4984
		4985	=item event
		4986
		4987	A change of state of some external event, such as data now being available
		4988	for reading on a file descriptor, time having passed or simply not having
		4989	any other events happening anymore.
		4990
		4991	In libev, events are represented as single bits (such as C<EV_READ> or
		4992	C<EV_TIMER>).
		4993
		4994	=item event library
		4995
		4996	A software package implementing an event model and loop.
		4997
		4998	=item event loop
		4999
		5000	An entity that handles and processes external events and converts them
		5001	into callback invocations.
		5002
		5003	=item event model
		5004
		5005	The model used to describe how an event loop handles and processes
		5006	watchers and events.
		5007
		5008	=item pending
		5009
		5010	A watcher is pending as soon as the corresponding event has been
		5011	detected. See L<WATCHER STATES> for details.
		5012
		5013	=item real time
		5014
		5015	The physical time that is observed. It is apparently strictly monotonic :)
		5016
		5017	=item wall-clock time
		5018
		5019	The time and date as shown on clocks. Unlike real time, it can actually
		5020	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5021	clock.
		5022
		5023	=item watcher
		5024
		5025	A data structure that describes interest in certain events. Watchers need
		5026	to be started (attached to an event loop) before they can receive events.
		5027
		5028	=back
2860		5029
2861	=head1 AUTHOR	5030	=head1 AUTHOR
2862		5031
2863	Marc Lehmann <libev@schmorp.de>.	5032	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5033	Magnusson and Emanuele Giaquinta.
2864		5034

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