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Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.174 by root, Mon Aug 18 23:23:45 2008 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
		9	=head2 EXAMPLE PROGRAM
		10
		11	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
8		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		66
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		70
11	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
21	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	117	to the C<double> type in C, and when you need to do any calculations on
		118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
		142
		143	=head1 GLOBAL FUNCTIONS
		144
		145	These functions can be called anytime, even before initialising the
		146	library in any way.
51		147
52	=over 4	148	=over 4
53		149
54	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
55		151
56	Returns the current time as libev would use it.	152	Returns the current time as libev would use it. Please note that the
		153	C<ev_now> function is usually faster and also often returns the timestamp
		154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
57		161
58	=item int ev_version_major ()	162	=item int ev_version_major ()
59		163
60	=item int ev_version_minor ()	164	=item int ev_version_minor ()
61		165
62	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
63	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
64	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
65	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	170	version of the library your program was compiled against.
67		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
68	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	178	not a problem.
72		179
		180	Example: Make sure we haven't accidentally been linked against the wrong
		181	version.
		182
		183	assert (("libev version mismatch",
		184	ev_version_major () == EV_VERSION_MAJOR
		185	&& ev_version_minor () >= EV_VERSION_MINOR));
		186
		187	=item unsigned int ev_supported_backends ()
		188
		189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		190	value) compiled into this binary of libev (independent of their
		191	availability on the system you are running on). See C<ev_default_loop> for
		192	a description of the set values.
		193
		194	Example: make sure we have the epoll method, because yeah this is cool and
		195	a must have and can we have a torrent of it please!!!11
		196
		197	assert (("sorry, no epoll, no sex",
		198	ev_supported_backends () & EVBACKEND_EPOLL));
		199
		200	=item unsigned int ev_recommended_backends ()
		201
		202	Return the set of all backends compiled into this binary of libev and also
		203	recommended for this platform. This set is often smaller than the one
		204	returned by C<ev_supported_backends>, as for example kqueue is broken on
		205	most BSDs and will not be auto-detected unless you explicitly request it
		206	(assuming you know what you are doing). This is the set of backends that
		207	libev will probe for if you specify no backends explicitly.
		208
		209	=item unsigned int ev_embeddable_backends ()
		210
		211	Returns the set of backends that are embeddable in other event loops. This
		212	is the theoretical, all-platform, value. To find which backends
		213	might be supported on the current system, you would need to look at
		214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		215	recommended ones.
		216
		217	See the description of C<ev_embed> watchers for more info.
		218
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		220
75	Sets the allocation function to use (the prototype is similar to the	221	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
77	and free memory (no surprises here). If it returns zero when memory	223	used to allocate and free memory (no surprises here). If it returns zero
78	needs to be allocated, the library might abort or take some potentially	224	when memory needs to be allocated (C<size != 0>), the library might abort
79	destructive action. The default is your system realloc function.	225	or take some potentially destructive action.
		226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
80		230
81	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
82	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
83	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
84		234
		235	Example: Replace the libev allocator with one that waits a bit and then
		236	retries (example requires a standards-compliant C<realloc>).
		237
		238	static void *
		239	persistent_realloc (void *ptr, size_t size)
		240	{
		241	for (;;)
		242	{
		243	void *newptr = realloc (ptr, size);
		244
		245	if (newptr)
		246	return newptr;
		247
		248	sleep (60);
		249	}
		250	}
		251
		252	...
		253	ev_set_allocator (persistent_realloc);
		254
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		256
87	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
88	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
89	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
90	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
91	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
92	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	263	(such as abort).
94		264
		265	Example: This is basically the same thing that libev does internally, too.
		266
		267	static void
		268	fatal_error (const char *msg)
		269	{
		270	perror (msg);
		271	abort ();
		272	}
		273
		274	...
		275	ev_set_syserr_cb (fatal_error);
		276
95	=back	277	=back
96		278
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		280
99	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
102		284
103	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you
105	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).
109
110	=over 4	285	=over 4
111		286
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		288
114	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
115	yet and return it. If the default loop could not be initialised, returns	290	yet and return it. If the default loop could not be initialised, returns
116	false. If it already was initialised it simply returns it (and ignores the	291	false. If it already was initialised it simply returns it (and ignores the
117	flags).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		293
119	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
120	function.	295	function.
121		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
122	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
123	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		310
125	It supports the following flags:	311	The following flags are supported:
126		312
127	=over 4	313	=over 4
128		314
129	=item C<EVFLAG_AUTO>	315	=item C<EVFLAG_AUTO>
130		316
131	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	318	thing, believe me).
133		319
134	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
135		321
136	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
137	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
141	around bugs.	327	around bugs.
142		328
		329	=item C<EVFLAG_FORKCHECK>
		330
		331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		332	a fork, you can also make libev check for a fork in each iteration by
		333	enabling this flag.
		334
		335	This works by calling C<getpid ()> on every iteration of the loop,
		336	and thus this might slow down your event loop if you do a lot of loop
		337	iterations and little real work, but is usually not noticeable (on my
		338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		339	without a system call and thus I<very> fast, but my GNU/Linux system also has
		340	C<pthread_atfork> which is even faster).
		341
		342	The big advantage of this flag is that you can forget about fork (and
		343	forget about forgetting to tell libev about forking) when you use this
		344	flag.
		345
		346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
		347	environment variable.
		348
143	=item C<EVMETHOD_SELECT> (portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		350
		351	This is your standard select(2) backend. Not I<completely> standard, as
		352	libev tries to roll its own fd_set with no limits on the number of fds,
		353	but if that fails, expect a fairly low limit on the number of fds when
		354	using this backend. It doesn't scale too well (O(highest_fd)), but its
		355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		363
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		365
147	=item C<EVMETHOD_EPOLL> (linux only)	366	And this is your standard poll(2) backend. It's more complicated
		367	than select, but handles sparse fds better and has no artificial
		368	limit on the number of fds you can use (except it will slow down
		369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
148		372
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		374
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	375	For few fds, this backend is a bit little slower than poll and select,
		376	but it scales phenomenally better. While poll and select usually scale
		377	like O(total_fds) where n is the total number of fds (or the highest fd),
		378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
152		382
153	=item C<EVMETHOD_PORT> (solaris 10 only)	383	While stopping, setting and starting an I/O watcher in the same iteration
		384	will result in some caching, there is still a system call per such incident
		385	(because the fd could point to a different file description now), so its
		386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		387	very well if you register events for both fds.
154		388
155	If one or more of these are ored into the flags value, then only these	389	Please note that epoll sometimes generates spurious notifications, so you
156	backends will be tried (in the reverse order as given here). If one are	390	need to use non-blocking I/O or other means to avoid blocking when no data
157	specified, any backend will do.	391	(or space) is available.
		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
		400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		401
		402	Kqueue deserves special mention, as at the time of this writing, it
		403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		404	with anything but sockets and pipes, except on Darwin, where of course
		405	it's completely useless). For this reason it's not being "auto-detected"
		406	unless you explicitly specify it explicitly in the flags (i.e. using
		407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
		413
		414	It scales in the same way as the epoll backend, but the interface to the
		415	kernel is more efficient (which says nothing about its actual speed, of
		416	course). While stopping, setting and starting an I/O watcher does never
		417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
		418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
		429
		430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		431
		432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
		436
		437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		438
		439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		440	it's really slow, but it still scales very well (O(active_fds)).
		441
		442	Please note that Solaris event ports can deliver a lot of spurious
		443	notifications, so you need to use non-blocking I/O or other means to avoid
		444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
		454
		455	=item C<EVBACKEND_ALL>
		456
		457	Try all backends (even potentially broken ones that wouldn't be tried
		458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		460
		461	It is definitely not recommended to use this flag.
158		462
159	=back	463	=back
		464
		465	If one or more of these are or'ed into the flags value, then only these
		466	backends will be tried (in the reverse order as listed here). If none are
		467	specified, all backends in C<ev_recommended_backends ()> will be tried.
		468
		469	The most typical usage is like this:
		470
		471	if (!ev_default_loop (0))
		472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		473
		474	Restrict libev to the select and poll backends, and do not allow
		475	environment settings to be taken into account:
		476
		477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		478
		479	Use whatever libev has to offer, but make sure that kqueue is used if
		480	available (warning, breaks stuff, best use only with your own private
		481	event loop and only if you know the OS supports your types of fds):
		482
		483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		484
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		486
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
164	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
165	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
166	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
167		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
		496	Example: Try to create a event loop that uses epoll and nothing else.
		497
		498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		499	if (!epoller)
		500	fatal ("no epoll found here, maybe it hides under your chair");
		501
168	=item ev_default_destroy ()	502	=item ev_default_destroy ()
169		503
170	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	505	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cannot rely on this :).	506	sense, so e.g. C<ev_is_active> might still return true. It is your
		507	responsibility to either stop all watchers cleanly yourself I<before>
		508	calling this function, or cope with the fact afterwards (which is usually
		509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
173		520
174	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
175		522
176	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
178		525
179	=item ev_default_fork ()	526	=item ev_default_fork ()
180		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
181	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
182	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
183	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
184	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
185		534
186	You I<must> call this function after forking if and only if you want to	535	On the other hand, you only need to call this function in the child
187	use the event library in both processes. If you just fork+exec, you don't	536	process if and only if you want to use the event library in the child. If
188	have to call it.	537	you just fork+exec, you don't have to call it at all.
189		538
190	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
191	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
192	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
193		542
…		…
197		546
198	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
199	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
200	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
201		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
		554
		555	=item unsigned int ev_loop_count (loop)
		556
		557	Returns the count of loop iterations for the loop, which is identical to
		558	the number of times libev did poll for new events. It starts at C<0> and
		559	happily wraps around with enough iterations.
		560
		561	This value can sometimes be useful as a generation counter of sorts (it
		562	"ticks" the number of loop iterations), as it roughly corresponds with
		563	C<ev_prepare> and C<ev_check> calls.
		564
202	=item unsigned int ev_method (loop)	565	=item unsigned int ev_backend (loop)
203		566
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	568	use.
206		569
207	=item ev_tstamp ev_now (loop)	570	=item ev_tstamp ev_now (loop)
208		571
209	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
210	got events and started processing them. This timestamp does not change	573	received events and started processing them. This timestamp does not
211	as long as callbacks are being processed, and this is also the base time	574	change as long as callbacks are being processed, and this is also the base
212	used for relative timers. You can treat it as the timestamp of the event	575	time used for relative timers. You can treat it as the timestamp of the
213	occuring (or more correctly, the mainloop finding out about it).	576	event occurring (or more correctly, libev finding out about it).
214		577
215	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
216		579
217	Finally, this is it, the event handler. This function usually is called	580	Finally, this is it, the event handler. This function usually is called
218	after you initialised all your watchers and you want to start handling	581	after you initialised all your watchers and you want to start handling
219	events.	582	events.
220		583
221	If the flags argument is specified as 0, it will not return until either	584	If the flags argument is specified as C<0>, it will not return until
222	no event watchers are active anymore or C<ev_unloop> was called.	585	either no event watchers are active anymore or C<ev_unloop> was called.
		586
		587	Please note that an explicit C<ev_unloop> is usually better than
		588	relying on all watchers to be stopped when deciding when a program has
		589	finished (especially in interactive programs), but having a program that
		590	automatically loops as long as it has to and no longer by virtue of
		591	relying on its watchers stopping correctly is a thing of beauty.
223		592
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
225	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
226	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
227		596
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
229	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
231	one iteration of the loop.	600	one iteration of the loop. This is useful if you are waiting for some
		601	external event in conjunction with something not expressible using other
		602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		603	usually a better approach for this kind of thing.
232		604
233	This flags value could be used to implement alternative looping	605	Here are the gory details of what C<ev_loop> does:
234	constructs, but the C<prepare> and C<check> watchers provide a better and	606
235	more generic mechanism.	607	- Before the first iteration, call any pending watchers.
		608	* If EVFLAG_FORKCHECK was used, check for a fork.
		609	- If a fork was detected (by any means), queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
		611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
		613	- Update the kernel state with all outstanding changes.
		614	- Update the "event loop time" (ev_now ()).
		615	- Calculate for how long to sleep or block, if at all
		616	(active idle watchers, EVLOOP_NONBLOCK or not having
		617	any active watchers at all will result in not sleeping).
		618	- Sleep if the I/O and timer collect interval say so.
		619	- Block the process, waiting for any events.
		620	- Queue all outstanding I/O (fd) events.
		621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
		622	- Queue all outstanding timers.
		623	- Queue all outstanding periodics.
		624	- Unless any events are pending now, queue all idle watchers.
		625	- Queue all check watchers.
		626	- Call all queued watchers in reverse order (i.e. check watchers first).
		627	Signals and child watchers are implemented as I/O watchers, and will
		628	be handled here by queueing them when their watcher gets executed.
		629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
		632
		633	Example: Queue some jobs and then loop until no events are outstanding
		634	anymore.
		635
		636	... queue jobs here, make sure they register event watchers as long
		637	... as they still have work to do (even an idle watcher will do..)
		638	ev_loop (my_loop, 0);
		639	... jobs done or somebody called unloop. yeah!
236		640
237	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
238		642
239	Can be used to make a call to C<ev_loop> return early (but only after it	643	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	644	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		647
		648	This "unloop state" will be cleared when entering C<ev_loop> again.
243		649
244	=item ev_ref (loop)	650	=item ev_ref (loop)
245		651
246	=item ev_unref (loop)	652	=item ev_unref (loop)
247		653
…		…
252	returning, ev_unref() after starting, and ev_ref() before stopping it. For	658	returning, ev_unref() after starting, and ev_ref() before stopping it. For
253	example, libev itself uses this for its internal signal pipe: It is not	659	example, libev itself uses this for its internal signal pipe: It is not
254	visible to the libev user and should not keep C<ev_loop> from exiting if	660	visible to the libev user and should not keep C<ev_loop> from exiting if
255	no event watchers registered by it are active. It is also an excellent	661	no event watchers registered by it are active. It is also an excellent
256	way to do this for generic recurring timers or from within third-party	662	way to do this for generic recurring timers or from within third-party
257	libraries. Just remember to I<unref after start> and I<ref before stop>.	663	libraries. Just remember to I<unref after start> and I<ref before stop>
		664	(but only if the watcher wasn't active before, or was active before,
		665	respectively).
		666
		667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		668	running when nothing else is active.
		669
		670	struct ev_signal exitsig;
		671	ev_signal_init (&exitsig, sig_cb, SIGINT);
		672	ev_signal_start (loop, &exitsig);
		673	evf_unref (loop);
		674
		675	Example: For some weird reason, unregister the above signal handler again.
		676
		677	ev_ref (loop);
		678	ev_signal_stop (loop, &exitsig);
		679
		680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		681
		682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		683
		684	These advanced functions influence the time that libev will spend waiting
		685	for events. Both time intervals are by default C<0>, meaning that libev
		686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
		688
		689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		690	allows libev to delay invocation of I/O and timer/periodic callbacks
		691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
		693
		694	The background is that sometimes your program runs just fast enough to
		695	handle one (or very few) event(s) per loop iteration. While this makes
		696	the program responsive, it also wastes a lot of CPU time to poll for new
		697	events, especially with backends like C<select ()> which have a high
		698	overhead for the actual polling but can deliver many events at once.
		699
		700	By setting a higher I<io collect interval> you allow libev to spend more
		701	time collecting I/O events, so you can handle more events per iteration,
		702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		703	C<ev_timer>) will be not affected. Setting this to a non-null value will
		704	introduce an additional C<ev_sleep ()> call into most loop iterations.
		705
		706	Likewise, by setting a higher I<timeout collect interval> you allow libev
		707	to spend more time collecting timeouts, at the expense of increased
		708	latency (the watcher callback will be called later). C<ev_io> watchers
		709	will not be affected. Setting this to a non-null value will not introduce
		710	any overhead in libev.
		711
		712	Many (busy) programs can usually benefit by setting the I/O collect
		713	interval to a value near C<0.1> or so, which is often enough for
		714	interactive servers (of course not for games), likewise for timeouts. It
		715	usually doesn't make much sense to set it to a lower value than C<0.01>,
		716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
258		735
259	=back	736	=back
		737
260		738
261	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
262		740
263	A watcher is a structure that you create and register to record your	741	A watcher is a structure that you create and register to record your
264	interest in some event. For instance, if you want to wait for STDIN to	742	interest in some event. For instance, if you want to wait for STDIN to
265	become readable, you would create an C<ev_io> watcher for that:	743	become readable, you would create an C<ev_io> watcher for that:
266		744
267	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
268	{	746	{
269	ev_io_stop (w);	747	ev_io_stop (w);
270	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
271	}	749	}
272		750
273	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
274	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
275	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
276	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
277	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
278	ev_loop (loop, 0);	756	ev_loop (loop, 0);
279		757
280	As you can see, you are responsible for allocating the memory for your	758	As you can see, you are responsible for allocating the memory for your
281	watcher structures (and it is usually a bad idea to do this on the stack,	759	watcher structures (and it is usually a bad idea to do this on the stack,
282	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
283		761
284	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
285	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
286	callback gets invoked each time the event occurs (or, in the case of io	764	callback gets invoked each time the event occurs (or, in the case of I/O
287	watchers, each time the event loop detects that the file descriptor given	765	watchers, each time the event loop detects that the file descriptor given
288	is readable and/or writable).	766	is readable and/or writable).
289		767
290	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
291	with arguments specific to this watcher type. There is also a macro	769	with arguments specific to this watcher type. There is also a macro
…		…
297	*) >>), and you can stop watching for events at any time by calling the	775	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		777
300	As long as your watcher is active (has been started but not stopped) you	778	As long as your watcher is active (has been started but not stopped) you
301	must not touch the values stored in it. Most specifically you must never	779	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	780	reinitialise it or call its C<set> macro.
303
304	You can check whether an event is active by calling the C<ev_is_active
305	(watcher *)> macro. To see whether an event is outstanding (but the
306	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.
308		781
309	Each and every callback receives the event loop pointer as first, the	782	Each and every callback receives the event loop pointer as first, the
310	registered watcher structure as second, and a bitset of received events as	783	registered watcher structure as second, and a bitset of received events as
311	third argument.	784	third argument.
312		785
…		…
336	The signal specified in the C<ev_signal> watcher has been received by a thread.	809	The signal specified in the C<ev_signal> watcher has been received by a thread.
337		810
338	=item C<EV_CHILD>	811	=item C<EV_CHILD>
339		812
340	The pid specified in the C<ev_child> watcher has received a status change.	813	The pid specified in the C<ev_child> watcher has received a status change.
		814
		815	=item C<EV_STAT>
		816
		817	The path specified in the C<ev_stat> watcher changed its attributes somehow.
341		818
342	=item C<EV_IDLE>	819	=item C<EV_IDLE>
343		820
344	The C<ev_idle> watcher has determined that you have nothing better to do.	821	The C<ev_idle> watcher has determined that you have nothing better to do.
345		822
…		…
353	received events. Callbacks of both watcher types can start and stop as	830	received events. Callbacks of both watcher types can start and stop as
354	many watchers as they want, and all of them will be taken into account	831	many watchers as they want, and all of them will be taken into account
355	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	832	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
356	C<ev_loop> from blocking).	833	C<ev_loop> from blocking).
357		834
		835	=item C<EV_EMBED>
		836
		837	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		838
		839	=item C<EV_FORK>
		840
		841	The event loop has been resumed in the child process after fork (see
		842	C<ev_fork>).
		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
358	=item C<EV_ERROR>	848	=item C<EV_ERROR>
359		849
360	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
361	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
362	ran out of memory, a file descriptor was found to be closed or any other	852	ran out of memory, a file descriptor was found to be closed or any other
363	problem. You best act on it by reporting the problem and somehow coping	853	problem. You best act on it by reporting the problem and somehow coping
364	with the watcher being stopped.	854	with the watcher being stopped.
365		855
366	Libev will usually signal a few "dummy" events together with an error,	856	Libev will usually signal a few "dummy" events together with an error,
367	for example it might indicate that a fd is readable or writable, and if	857	for example it might indicate that a fd is readable or writable, and if
368	your callbacks is well-written it can just attempt the operation and cope	858	your callbacks is well-written it can just attempt the operation and cope
369	with the error from read() or write(). This will not work in multithreaded	859	with the error from read() or write(). This will not work in multi-threaded
370	programs, though, so beware.	860	programs, though, so beware.
371		861
372	=back	862	=back
		863
		864	=head2 GENERIC WATCHER FUNCTIONS
		865
		866	In the following description, C<TYPE> stands for the watcher type,
		867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		868
		869	=over 4
		870
		871	=item C<ev_init> (ev_TYPE *watcher, callback)
		872
		873	This macro initialises the generic portion of a watcher. The contents
		874	of the watcher object can be arbitrary (so C<malloc> will do). Only
		875	the generic parts of the watcher are initialised, you I<need> to call
		876	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		877	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		878	which rolls both calls into one.
		879
		880	You can reinitialise a watcher at any time as long as it has been stopped
		881	(or never started) and there are no pending events outstanding.
		882
		883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		884	int revents)>.
		885
		886	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		887
		888	This macro initialises the type-specific parts of a watcher. You need to
		889	call C<ev_init> at least once before you call this macro, but you can
		890	call C<ev_TYPE_set> any number of times. You must not, however, call this
		891	macro on a watcher that is active (it can be pending, however, which is a
		892	difference to the C<ev_init> macro).
		893
		894	Although some watcher types do not have type-specific arguments
		895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		896
		897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		898
		899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		900	calls into a single call. This is the most convenient method to initialise
		901	a watcher. The same limitations apply, of course.
		902
		903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		904
		905	Starts (activates) the given watcher. Only active watchers will receive
		906	events. If the watcher is already active nothing will happen.
		907
		908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		909
		910	Stops the given watcher again (if active) and clears the pending
		911	status. It is possible that stopped watchers are pending (for example,
		912	non-repeating timers are being stopped when they become pending), but
		913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		914	you want to free or reuse the memory used by the watcher it is therefore a
		915	good idea to always call its C<ev_TYPE_stop> function.
		916
		917	=item bool ev_is_active (ev_TYPE *watcher)
		918
		919	Returns a true value iff the watcher is active (i.e. it has been started
		920	and not yet been stopped). As long as a watcher is active you must not modify
		921	it.
		922
		923	=item bool ev_is_pending (ev_TYPE *watcher)
		924
		925	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		926	events but its callback has not yet been invoked). As long as a watcher
		927	is pending (but not active) you must not call an init function on it (but
		928	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		929	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		930	it).
		931
		932	=item callback ev_cb (ev_TYPE *watcher)
		933
		934	Returns the callback currently set on the watcher.
		935
		936	=item ev_cb_set (ev_TYPE *watcher, callback)
		937
		938	Change the callback. You can change the callback at virtually any time
		939	(modulo threads).
		940
		941	=item ev_set_priority (ev_TYPE *watcher, priority)
		942
		943	=item int ev_priority (ev_TYPE *watcher)
		944
		945	Set and query the priority of the watcher. The priority is a small
		946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		947	(default: C<-2>). Pending watchers with higher priority will be invoked
		948	before watchers with lower priority, but priority will not keep watchers
		949	from being executed (except for C<ev_idle> watchers).
		950
		951	This means that priorities are I<only> used for ordering callback
		952	invocation after new events have been received. This is useful, for
		953	example, to reduce latency after idling, or more often, to bind two
		954	watchers on the same event and make sure one is called first.
		955
		956	If you need to suppress invocation when higher priority events are pending
		957	you need to look at C<ev_idle> watchers, which provide this functionality.
		958
		959	You I<must not> change the priority of a watcher as long as it is active or
		960	pending.
		961
		962	The default priority used by watchers when no priority has been set is
		963	always C<0>, which is supposed to not be too high and not be too low :).
		964
		965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		966	fine, as long as you do not mind that the priority value you query might
		967	or might not have been adjusted to be within valid range.
		968
		969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		970
		971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		972	C<loop> nor C<revents> need to be valid as long as the watcher callback
		973	can deal with that fact.
		974
		975	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		976
		977	If the watcher is pending, this function returns clears its pending status
		978	and returns its C<revents> bitset (as if its callback was invoked). If the
		979	watcher isn't pending it does nothing and returns C<0>.
		980
		981	=back
		982
373		983
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		985
376	Each watcher has, by default, a member C<void *data> that you can change	986	Each watcher has, by default, a member C<void *data> that you can change
377	and read at any time, libev will completely ignore it. This can be used	987	and read at any time, libev will completely ignore it. This can be used
378	to associate arbitrary data with your watcher. If you need more data and	988	to associate arbitrary data with your watcher. If you need more data and
379	don't want to allocate memory and store a pointer to it in that data	989	don't want to allocate memory and store a pointer to it in that data
380	member, you can also "subclass" the watcher type and provide your own	990	member, you can also "subclass" the watcher type and provide your own
381	data:	991	data:
382		992
383	struct my_io	993	struct my_io
384	{	994	{
385	struct ev_io io;	995	struct ev_io io;
386	int otherfd;	996	int otherfd;
387	void *somedata;	997	void *somedata;
388	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
389	}	999	}
390		1000
391	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
392	can cast it back to your own type:	1002	can cast it back to your own type:
393		1003
394	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
395	{	1005	{
396	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
397	...	1007	...
398	}	1008	}
399		1009
400	More interesting and less C-conformant ways of catsing your callback type	1010	More interesting and less C-conformant ways of casting your callback type
401	have been omitted....	1011	instead have been omitted.
		1012
		1013	Another common scenario is having some data structure with multiple
		1014	watchers:
		1015
		1016	struct my_biggy
		1017	{
		1018	int some_data;
		1019	ev_timer t1;
		1020	ev_timer t2;
		1021	}
		1022
		1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		1024	you need to use C<offsetof>:
		1025
		1026	#include <stddef.h>
		1027
		1028	static void
		1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
		1030	{
		1031	struct my_biggy big = (struct my_biggy *
		1032	(((char *)w) - offsetof (struct my_biggy, t1));
		1033	}
		1034
		1035	static void
		1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
		1037	{
		1038	struct my_biggy big = (struct my_biggy *
		1039	(((char *)w) - offsetof (struct my_biggy, t2));
		1040	}
402		1041
403		1042
404	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
405		1044
406	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
407	information given in the last section.	1046	information given in the last section. Any initialisation/set macros,
		1047	functions and members specific to the watcher type are explained.
408		1048
		1049	Members are additionally marked with either I<[read-only]>, meaning that,
		1050	while the watcher is active, you can look at the member and expect some
		1051	sensible content, but you must not modify it (you can modify it while the
		1052	watcher is stopped to your hearts content), or I<[read-write]>, which
		1053	means you can expect it to have some sensible content while the watcher
		1054	is active, but you can also modify it. Modifying it may not do something
		1055	sensible or take immediate effect (or do anything at all), but libev will
		1056	not crash or malfunction in any way.
		1057
		1058
409	=head2 C<ev_io> - is this file descriptor readable or writable	1059	=head2 C<ev_io> - is this file descriptor readable or writable?
410		1060
411	I/O watchers check whether a file descriptor is readable or writable	1061	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	1062	in each iteration of the event loop, or, more precisely, when reading
413	level-triggering because you keep receiving events as long as the	1063	would not block the process and writing would at least be able to write
414	condition persists. Remember you can stop the watcher if you don't want to	1064	some data. This behaviour is called level-triggering because you keep
415	act on the event and neither want to receive future events).	1065	receiving events as long as the condition persists. Remember you can stop
		1066	the watcher if you don't want to act on the event and neither want to
		1067	receive future events.
416		1068
417	In general you can register as many read and/or write event watchers oer	1069	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	1070	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	1071	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	1072	required if you know what you are doing).
421		1073
422	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.
426
427	If you must do this, then force the use of a known-to-be-good backend	1074	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	1076	C<EVBACKEND_POLL>).
		1077
		1078	Another thing you have to watch out for is that it is quite easy to
		1079	receive "spurious" readiness notifications, that is your callback might
		1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1081	because there is no data. Not only are some backends known to create a
		1082	lot of those (for example Solaris ports), it is very easy to get into
		1083	this situation even with a relatively standard program structure. Thus
		1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1086
		1087	If you cannot run the fd in non-blocking mode (for example you should not
		1088	play around with an Xlib connection), then you have to separately re-test
		1089	whether a file descriptor is really ready with a known-to-be good interface
		1090	such as poll (fortunately in our Xlib example, Xlib already does this on
		1091	its own, so its quite safe to use).
		1092
		1093	=head3 The special problem of disappearing file descriptors
		1094
		1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1096	descriptor (either by calling C<close> explicitly or by any other means,
		1097	such as C<dup>). The reason is that you register interest in some file
		1098	descriptor, but when it goes away, the operating system will silently drop
		1099	this interest. If another file descriptor with the same number then is
		1100	registered with libev, there is no efficient way to see that this is, in
		1101	fact, a different file descriptor.
		1102
		1103	To avoid having to explicitly tell libev about such cases, libev follows
		1104	the following policy: Each time C<ev_io_set> is being called, libev
		1105	will assume that this is potentially a new file descriptor, otherwise
		1106	it is assumed that the file descriptor stays the same. That means that
		1107	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1108	descriptor even if the file descriptor number itself did not change.
		1109
		1110	This is how one would do it normally anyway, the important point is that
		1111	the libev application should not optimise around libev but should leave
		1112	optimisations to libev.
		1113
		1114	=head3 The special problem of dup'ed file descriptors
		1115
		1116	Some backends (e.g. epoll), cannot register events for file descriptors,
		1117	but only events for the underlying file descriptions. That means when you
		1118	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1119	events for them, only one file descriptor might actually receive events.
		1120
		1121	There is no workaround possible except not registering events
		1122	for potentially C<dup ()>'ed file descriptors, or to resort to
		1123	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1124
		1125	=head3 The special problem of fork
		1126
		1127	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1128	useless behaviour. Libev fully supports fork, but needs to be told about
		1129	it in the child.
		1130
		1131	To support fork in your programs, you either have to call
		1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1134	C<EVBACKEND_POLL>.
		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when writing to a pipe whose other end has been closed, your program gets
		1140	send a SIGPIPE, which, by default, aborts your program. For most programs
		1141	this is sensible behaviour, for daemons, this is usually undesirable.
		1142
		1143	So when you encounter spurious, unexplained daemon exits, make sure you
		1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1145	somewhere, as that would have given you a big clue).
		1146
		1147
		1148	=head3 Watcher-Specific Functions
430		1149
431	=over 4	1150	=over 4
432		1151
433	=item ev_io_init (ev_io *, callback, int fd, int events)	1152	=item ev_io_init (ev_io *, callback, int fd, int events)
434		1153
435	=item ev_io_set (ev_io *, int fd, int events)	1154	=item ev_io_set (ev_io *, int fd, int events)
436		1155
437	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
438	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
439	EV_WRITE> to receive the given events.	1158	C<EV_READ | EV_WRITE> to receive the given events.
		1159
		1160	=item int fd [read-only]
		1161
		1162	The file descriptor being watched.
		1163
		1164	=item int events [read-only]
		1165
		1166	The events being watched.
440		1167
441	=back	1168	=back
442		1169
		1170	=head3 Examples
		1171
		1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1173	readable, but only once. Since it is likely line-buffered, you could
		1174	attempt to read a whole line in the callback.
		1175
		1176	static void
		1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1178	{
		1179	ev_io_stop (loop, w);
		1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1181	}
		1182
		1183	...
		1184	struct ev_loop *loop = ev_default_init (0);
		1185	struct ev_io stdin_readable;
		1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1187	ev_io_start (loop, &stdin_readable);
		1188	ev_loop (loop, 0);
		1189
		1190
443	=head2 C<ev_timer> - relative and optionally recurring timeouts	1191	=head2 C<ev_timer> - relative and optionally repeating timeouts
444		1192
445	Timer watchers are simple relative timers that generate an event after a	1193	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	1194	given time, and optionally repeating in regular intervals after that.
447		1195
448	The timers are based on real time, that is, if you register an event that	1196	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	1197	times out after an hour and you reset your system clock to January last
450	time, it will still time out after (roughly) and hour. "Roughly" because	1198	year, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	1200	monotonic clock option helps a lot here).
453		1201
454	The relative timeouts are calculated relative to the C<ev_now ()>	1202	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	1203	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	1204	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you *need* to base the timeout	1205	you suspect event processing to be delayed and you I<need> to base the timeout
458	ion the current time, use something like this to adjust for this:	1206	on the current time, use something like this to adjust for this:
459		1207
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1208	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
461		1209
		1210	The callback is guaranteed to be invoked only after its timeout has passed,
		1211	but if multiple timers become ready during the same loop iteration then
		1212	order of execution is undefined.
		1213
		1214	=head3 Watcher-Specific Functions and Data Members
		1215
462	=over 4	1216	=over 4
463		1217
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1218	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		1219
466	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1220	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
467		1221
468	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1222	Configure the timer to trigger after C<after> seconds. If C<repeat>
469	C<0.>, then it will automatically be stopped. If it is positive, then the	1223	is C<0.>, then it will automatically be stopped once the timeout is
470	timer will automatically be configured to trigger again C<repeat> seconds	1224	reached. If it is positive, then the timer will automatically be
471	later, again, and again, until stopped manually.	1225	configured to trigger again C<repeat> seconds later, again, and again,
		1226	until stopped manually.
472		1227
473	The timer itself will do a best-effort at avoiding drift, that is, if you	1228	The timer itself will do a best-effort at avoiding drift, that is, if
474	configure a timer to trigger every 10 seconds, then it will trigger at	1229	you configure a timer to trigger every 10 seconds, then it will normally
475	exactly 10 second intervals. If, however, your program cannot keep up with	1230	trigger at exactly 10 second intervals. If, however, your program cannot
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1231	keep up with the timer (because it takes longer than those 10 seconds to
477	timer will not fire more than once per event loop iteration.	1232	do stuff) the timer will not fire more than once per event loop iteration.
478		1233
479	=item ev_timer_again (loop)	1234	=item ev_timer_again (loop, ev_timer *)
480		1235
481	This will act as if the timer timed out and restart it again if it is	1236	This will act as if the timer timed out and restart it again if it is
482	repeating. The exact semantics are:	1237	repeating. The exact semantics are:
483		1238
		1239	If the timer is pending, its pending status is cleared.
		1240
484	If the timer is started but nonrepeating, stop it.	1241	If the timer is started but non-repeating, stop it (as if it timed out).
485		1242
486	If the timer is repeating, either start it if necessary (with the repeat	1243	If the timer is repeating, either start it if necessary (with the
487	value), or reset the running timer to the repeat value.	1244	C<repeat> value), or reset the running timer to the C<repeat> value.
488		1245
489	This sounds a bit complicated, but here is a useful and typical	1246	This sounds a bit complicated, but here is a useful and typical
490	example: Imagine you have a tcp connection and you want a so-called idle	1247	example: Imagine you have a TCP connection and you want a so-called idle
491	timeout, that is, you want to be called when there have been, say, 60	1248	timeout, that is, you want to be called when there have been, say, 60
492	seconds of inactivity on the socket. The easiest way to do this is to	1249	seconds of inactivity on the socket. The easiest way to do this is to
493	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1250	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
494	time you successfully read or write some data. If you go into an idle	1251	C<ev_timer_again> each time you successfully read or write some data. If
495	state where you do not expect data to travel on the socket, you can stop	1252	you go into an idle state where you do not expect data to travel on the
496	the timer, and again will automatically restart it if need be.	1253	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1254	automatically restart it if need be.
		1255
		1256	That means you can ignore the C<after> value and C<ev_timer_start>
		1257	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1258
		1259	ev_timer_init (timer, callback, 0., 5.);
		1260	ev_timer_again (loop, timer);
		1261	...
		1262	timer->again = 17.;
		1263	ev_timer_again (loop, timer);
		1264	...
		1265	timer->again = 10.;
		1266	ev_timer_again (loop, timer);
		1267
		1268	This is more slightly efficient then stopping/starting the timer each time
		1269	you want to modify its timeout value.
		1270
		1271	=item ev_tstamp repeat [read-write]
		1272
		1273	The current C<repeat> value. Will be used each time the watcher times out
		1274	or C<ev_timer_again> is called and determines the next timeout (if any),
		1275	which is also when any modifications are taken into account.
497		1276
498	=back	1277	=back
499		1278
		1279	=head3 Examples
		1280
		1281	Example: Create a timer that fires after 60 seconds.
		1282
		1283	static void
		1284	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1285	{
		1286	.. one minute over, w is actually stopped right here
		1287	}
		1288
		1289	struct ev_timer mytimer;
		1290	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1291	ev_timer_start (loop, &mytimer);
		1292
		1293	Example: Create a timeout timer that times out after 10 seconds of
		1294	inactivity.
		1295
		1296	static void
		1297	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1298	{
		1299	.. ten seconds without any activity
		1300	}
		1301
		1302	struct ev_timer mytimer;
		1303	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1304	ev_timer_again (&mytimer); /* start timer */
		1305	ev_loop (loop, 0);
		1306
		1307	// and in some piece of code that gets executed on any "activity":
		1308	// reset the timeout to start ticking again at 10 seconds
		1309	ev_timer_again (&mytimer);
		1310
		1311
500	=head2 C<ev_periodic> - to cron or not to cron	1312	=head2 C<ev_periodic> - to cron or not to cron?
501		1313
502	Periodic watchers are also timers of a kind, but they are very versatile	1314	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	1315	(and unfortunately a bit complex).
504		1316
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1317	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
506	but on wallclock time (absolute time). You can tell a periodic watcher	1318	but on wall clock time (absolute time). You can tell a periodic watcher
507	to trigger "at" some specific point in time. For example, if you tell a	1319	to trigger after some specific point in time. For example, if you tell a
508	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1320	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
509	+ 10.>) and then reset your system clock to the last year, then it will	1321	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1322	clock to January of the previous year, then it will take more than year
510	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1323	to trigger the event (unlike an C<ev_timer>, which would still trigger
511	roughly 10 seconds later and of course not if you reset your system time	1324	roughly 10 seconds later as it uses a relative timeout).
512	again).
513		1325
514	They can also be used to implement vastly more complex timers, such as	1326	C<ev_periodic>s can also be used to implement vastly more complex timers,
515	triggering an event on eahc midnight, local time.	1327	such as triggering an event on each "midnight, local time", or other
		1328	complicated, rules.
		1329
		1330	As with timers, the callback is guaranteed to be invoked only when the
		1331	time (C<at>) has passed, but if multiple periodic timers become ready
		1332	during the same loop iteration then order of execution is undefined.
		1333
		1334	=head3 Watcher-Specific Functions and Data Members
516		1335
517	=over 4	1336	=over 4
518		1337
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1338	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		1339
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1340	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		1341
523	Lots of arguments, lets sort it out... There are basically three modes of	1342	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	1343	operation, and we will explain them from simplest to complex:
525		1344
526
527	=over 4	1345	=over 4
528		1346
529	=item * absolute timer (interval = reschedule_cb = 0)	1347	=item * absolute timer (at = time, interval = reschedule_cb = 0)
530		1348
531	In this configuration the watcher triggers an event at the wallclock time	1349	In this configuration the watcher triggers an event after the wall clock
532	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1350	time C<at> has passed and doesn't repeat. It will not adjust when a time
533	that is, if it is to be run at January 1st 2011 then it will run when the	1351	jump occurs, that is, if it is to be run at January 1st 2011 then it will
534	system time reaches or surpasses this time.	1352	run when the system time reaches or surpasses this time.
535		1353
536	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1354	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
537		1355
538	In this mode the watcher will always be scheduled to time out at the next	1356	In this mode the watcher will always be scheduled to time out at the next
539	C<at + N * interval> time (for some integer N) and then repeat, regardless	1357	C<at + N * interval> time (for some integer N, which can also be negative)
540	of any time jumps.	1358	and then repeat, regardless of any time jumps.
541		1359
542	This can be used to create timers that do not drift with respect to system	1360	This can be used to create timers that do not drift with respect to system
543	time:	1361	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1362	the hour:
544		1363
545	ev_periodic_set (&periodic, 0., 3600., 0);	1364	ev_periodic_set (&periodic, 0., 3600., 0);
546		1365
547	This doesn't mean there will always be 3600 seconds in between triggers,	1366	This doesn't mean there will always be 3600 seconds in between triggers,
548	but only that the the callback will be called when the system time shows a	1367	but only that the callback will be called when the system time shows a
549	full hour (UTC), or more correctly, when the system time is evenly divisible	1368	full hour (UTC), or more correctly, when the system time is evenly divisible
550	by 3600.	1369	by 3600.
551		1370
552	Another way to think about it (for the mathematically inclined) is that	1371	Another way to think about it (for the mathematically inclined) is that
553	C<ev_periodic> will try to run the callback in this mode at the next possible	1372	C<ev_periodic> will try to run the callback in this mode at the next possible
554	time where C<time = at (mod interval)>, regardless of any time jumps.	1373	time where C<time = at (mod interval)>, regardless of any time jumps.
555		1374
		1375	For numerical stability it is preferable that the C<at> value is near
		1376	C<ev_now ()> (the current time), but there is no range requirement for
		1377	this value, and in fact is often specified as zero.
		1378
		1379	Note also that there is an upper limit to how often a timer can fire (CPU
		1380	speed for example), so if C<interval> is very small then timing stability
		1381	will of course deteriorate. Libev itself tries to be exact to be about one
		1382	millisecond (if the OS supports it and the machine is fast enough).
		1383
556	=item * manual reschedule mode (reschedule_cb = callback)	1384	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
557		1385
558	In this mode the values for C<interval> and C<at> are both being	1386	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	1387	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	1388	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	1389	current time as second argument.
562		1390
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1391	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	1392	ever, or make ANY event loop modifications whatsoever>.
		1393
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	1394	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1395	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1396	only event loop modification you are allowed to do).
566		1397
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569
570	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1398	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
571	ev_tstamp now)>, e.g.:	1399	*w, ev_tstamp now)>, e.g.:
572		1400
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1401	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
574	{	1402	{
575	return now + 60.;	1403	return now + 60.;
576	}	1404	}
…		…
578	It must return the next time to trigger, based on the passed time value	1406	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	1407	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	1408	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	1409	might be called at other times, too.
582		1410
		1411	NOTE: I<< This callback must always return a time that is higher than or
		1412	equal to the passed C<now> value >>.
		1413
583	This can be used to create very complex timers, such as a timer that	1414	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	1415	triggers on "next midnight, local time". To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	1416	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	1417	you do this is, again, up to you (but it is not trivial, which is the main
		1418	reason I omitted it as an example).
587		1419
588	=back	1420	=back
589		1421
590	=item ev_periodic_again (loop, ev_periodic *)	1422	=item ev_periodic_again (loop, ev_periodic *)
591		1423
592	Simply stops and restarts the periodic watcher again. This is only useful	1424	Simply stops and restarts the periodic watcher again. This is only useful
593	when you changed some parameters or the reschedule callback would return	1425	when you changed some parameters or the reschedule callback would return
594	a different time than the last time it was called (e.g. in a crond like	1426	a different time than the last time it was called (e.g. in a crond like
595	program when the crontabs have changed).	1427	program when the crontabs have changed).
596		1428
		1429	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1430
		1431	When active, returns the absolute time that the watcher is supposed to
		1432	trigger next.
		1433
		1434	=item ev_tstamp offset [read-write]
		1435
		1436	When repeating, this contains the offset value, otherwise this is the
		1437	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1438
		1439	Can be modified any time, but changes only take effect when the periodic
		1440	timer fires or C<ev_periodic_again> is being called.
		1441
		1442	=item ev_tstamp interval [read-write]
		1443
		1444	The current interval value. Can be modified any time, but changes only
		1445	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1446	called.
		1447
		1448	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1449
		1450	The current reschedule callback, or C<0>, if this functionality is
		1451	switched off. Can be changed any time, but changes only take effect when
		1452	the periodic timer fires or C<ev_periodic_again> is being called.
		1453
597	=back	1454	=back
598		1455
		1456	=head3 Examples
		1457
		1458	Example: Call a callback every hour, or, more precisely, whenever the
		1459	system clock is divisible by 3600. The callback invocation times have
		1460	potentially a lot of jitter, but good long-term stability.
		1461
		1462	static void
		1463	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1464	{
		1465	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1466	}
		1467
		1468	struct ev_periodic hourly_tick;
		1469	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1470	ev_periodic_start (loop, &hourly_tick);
		1471
		1472	Example: The same as above, but use a reschedule callback to do it:
		1473
		1474	#include <math.h>
		1475
		1476	static ev_tstamp
		1477	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1478	{
		1479	return fmod (now, 3600.) + 3600.;
		1480	}
		1481
		1482	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1483
		1484	Example: Call a callback every hour, starting now:
		1485
		1486	struct ev_periodic hourly_tick;
		1487	ev_periodic_init (&hourly_tick, clock_cb,
		1488	fmod (ev_now (loop), 3600.), 3600., 0);
		1489	ev_periodic_start (loop, &hourly_tick);
		1490
		1491
599	=head2 C<ev_signal> - signal me when a signal gets signalled	1492	=head2 C<ev_signal> - signal me when a signal gets signalled!
600		1493
601	Signal watchers will trigger an event when the process receives a specific	1494	Signal watchers will trigger an event when the process receives a specific
602	signal one or more times. Even though signals are very asynchronous, libev	1495	signal one or more times. Even though signals are very asynchronous, libev
603	will try it's best to deliver signals synchronously, i.e. as part of the	1496	will try it's best to deliver signals synchronously, i.e. as part of the
604	normal event processing, like any other event.	1497	normal event processing, like any other event.
…		…
608	with the kernel (thus it coexists with your own signal handlers as long	1501	with the kernel (thus it coexists with your own signal handlers as long
609	as you don't register any with libev). Similarly, when the last signal	1502	as you don't register any with libev). Similarly, when the last signal
610	watcher for a signal is stopped libev will reset the signal handler to	1503	watcher for a signal is stopped libev will reset the signal handler to
611	SIG_DFL (regardless of what it was set to before).	1504	SIG_DFL (regardless of what it was set to before).
612		1505
		1506	If possible and supported, libev will install its handlers with
		1507	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1508	interrupted. If you have a problem with system calls getting interrupted by
		1509	signals you can block all signals in an C<ev_check> watcher and unblock
		1510	them in an C<ev_prepare> watcher.
		1511
		1512	=head3 Watcher-Specific Functions and Data Members
		1513
613	=over 4	1514	=over 4
614		1515
615	=item ev_signal_init (ev_signal *, callback, int signum)	1516	=item ev_signal_init (ev_signal *, callback, int signum)
616		1517
617	=item ev_signal_set (ev_signal *, int signum)	1518	=item ev_signal_set (ev_signal *, int signum)
618		1519
619	Configures the watcher to trigger on the given signal number (usually one	1520	Configures the watcher to trigger on the given signal number (usually one
620	of the C<SIGxxx> constants).	1521	of the C<SIGxxx> constants).
621		1522
		1523	=item int signum [read-only]
		1524
		1525	The signal the watcher watches out for.
		1526
622	=back	1527	=back
623		1528
		1529	=head3 Examples
		1530
		1531	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1532
		1533	static void
		1534	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1535	{
		1536	ev_unloop (loop, EVUNLOOP_ALL);
		1537	}
		1538
		1539	struct ev_signal signal_watcher;
		1540	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1541	ev_signal_start (loop, &sigint_cb);
		1542
		1543
624	=head2 C<ev_child> - wait for pid status changes	1544	=head2 C<ev_child> - watch out for process status changes
625		1545
626	Child watchers trigger when your process receives a SIGCHLD in response to	1546	Child watchers trigger when your process receives a SIGCHLD in response to
627	some child status changes (most typically when a child of yours dies).	1547	some child status changes (most typically when a child of yours dies). It
		1548	is permissible to install a child watcher I<after> the child has been
		1549	forked (which implies it might have already exited), as long as the event
		1550	loop isn't entered (or is continued from a watcher).
		1551
		1552	Only the default event loop is capable of handling signals, and therefore
		1553	you can only register child watchers in the default event loop.
		1554
		1555	=head3 Process Interaction
		1556
		1557	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1558	initialised. This is necessary to guarantee proper behaviour even if
		1559	the first child watcher is started after the child exits. The occurrence
		1560	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1561	synchronously as part of the event loop processing. Libev always reaps all
		1562	children, even ones not watched.
		1563
		1564	=head3 Overriding the Built-In Processing
		1565
		1566	Libev offers no special support for overriding the built-in child
		1567	processing, but if your application collides with libev's default child
		1568	handler, you can override it easily by installing your own handler for
		1569	C<SIGCHLD> after initialising the default loop, and making sure the
		1570	default loop never gets destroyed. You are encouraged, however, to use an
		1571	event-based approach to child reaping and thus use libev's support for
		1572	that, so other libev users can use C<ev_child> watchers freely.
		1573
		1574	=head3 Stopping the Child Watcher
		1575
		1576	Currently, the child watcher never gets stopped, even when the
		1577	child terminates, so normally one needs to stop the watcher in the
		1578	callback. Future versions of libev might stop the watcher automatically
		1579	when a child exit is detected.
		1580
		1581	=head3 Watcher-Specific Functions and Data Members
628		1582
629	=over 4	1583	=over 4
630		1584
631	=item ev_child_init (ev_child *, callback, int pid)	1585	=item ev_child_init (ev_child *, callback, int pid, int trace)
632		1586
633	=item ev_child_set (ev_child *, int pid)	1587	=item ev_child_set (ev_child *, int pid, int trace)
634		1588
635	Configures the watcher to wait for status changes of process C<pid> (or	1589	Configures the watcher to wait for status changes of process C<pid> (or
636	I<any> process if C<pid> is specified as C<0>). The callback can look	1590	I<any> process if C<pid> is specified as C<0>). The callback can look
637	at the C<rstatus> member of the C<ev_child> watcher structure to see	1591	at the C<rstatus> member of the C<ev_child> watcher structure to see
638	the status word (use the macros from C<sys/wait.h> and see your systems	1592	the status word (use the macros from C<sys/wait.h> and see your systems
639	C<waitpid> documentation). The C<rpid> member contains the pid of the	1593	C<waitpid> documentation). The C<rpid> member contains the pid of the
640	process causing the status change.	1594	process causing the status change. C<trace> must be either C<0> (only
		1595	activate the watcher when the process terminates) or C<1> (additionally
		1596	activate the watcher when the process is stopped or continued).
		1597
		1598	=item int pid [read-only]
		1599
		1600	The process id this watcher watches out for, or C<0>, meaning any process id.
		1601
		1602	=item int rpid [read-write]
		1603
		1604	The process id that detected a status change.
		1605
		1606	=item int rstatus [read-write]
		1607
		1608	The process exit/trace status caused by C<rpid> (see your systems
		1609	C<waitpid> and C<sys/wait.h> documentation for details).
641		1610
642	=back	1611	=back
643		1612
		1613	=head3 Examples
		1614
		1615	Example: C<fork()> a new process and install a child handler to wait for
		1616	its completion.
		1617
		1618	ev_child cw;
		1619
		1620	static void
		1621	child_cb (EV_P_ struct ev_child *w, int revents)
		1622	{
		1623	ev_child_stop (EV_A_ w);
		1624	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1625	}
		1626
		1627	pid_t pid = fork ();
		1628
		1629	if (pid < 0)
		1630	// error
		1631	else if (pid == 0)
		1632	{
		1633	// the forked child executes here
		1634	exit (1);
		1635	}
		1636	else
		1637	{
		1638	ev_child_init (&cw, child_cb, pid, 0);
		1639	ev_child_start (EV_DEFAULT_ &cw);
		1640	}
		1641
		1642
		1643	=head2 C<ev_stat> - did the file attributes just change?
		1644
		1645	This watches a file system path for attribute changes. That is, it calls
		1646	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1647	compared to the last time, invoking the callback if it did.
		1648
		1649	The path does not need to exist: changing from "path exists" to "path does
		1650	not exist" is a status change like any other. The condition "path does
		1651	not exist" is signified by the C<st_nlink> field being zero (which is
		1652	otherwise always forced to be at least one) and all the other fields of
		1653	the stat buffer having unspecified contents.
		1654
		1655	The path I<should> be absolute and I<must not> end in a slash. If it is
		1656	relative and your working directory changes, the behaviour is undefined.
		1657
		1658	Since there is no standard to do this, the portable implementation simply
		1659	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1660	can specify a recommended polling interval for this case. If you specify
		1661	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1662	unspecified default> value will be used (which you can expect to be around
		1663	five seconds, although this might change dynamically). Libev will also
		1664	impose a minimum interval which is currently around C<0.1>, but thats
		1665	usually overkill.
		1666
		1667	This watcher type is not meant for massive numbers of stat watchers,
		1668	as even with OS-supported change notifications, this can be
		1669	resource-intensive.
		1670
		1671	At the time of this writing, only the Linux inotify interface is
		1672	implemented (implementing kqueue support is left as an exercise for the
		1673	reader, note, however, that the author sees no way of implementing ev_stat
		1674	semantics with kqueue). Inotify will be used to give hints only and should
		1675	not change the semantics of C<ev_stat> watchers, which means that libev
		1676	sometimes needs to fall back to regular polling again even with inotify,
		1677	but changes are usually detected immediately, and if the file exists there
		1678	will be no polling.
		1679
		1680	=head3 ABI Issues (Largefile Support)
		1681
		1682	Libev by default (unless the user overrides this) uses the default
		1683	compilation environment, which means that on systems with large file
		1684	support disabled by default, you get the 32 bit version of the stat
		1685	structure. When using the library from programs that change the ABI to
		1686	use 64 bit file offsets the programs will fail. In that case you have to
		1687	compile libev with the same flags to get binary compatibility. This is
		1688	obviously the case with any flags that change the ABI, but the problem is
		1689	most noticeably disabled with ev_stat and large file support.
		1690
		1691	The solution for this is to lobby your distribution maker to make large
		1692	file interfaces available by default (as e.g. FreeBSD does) and not
		1693	optional. Libev cannot simply switch on large file support because it has
		1694	to exchange stat structures with application programs compiled using the
		1695	default compilation environment.
		1696
		1697	=head3 Inotify
		1698
		1699	When C<inotify (7)> support has been compiled into libev (generally only
		1700	available on Linux) and present at runtime, it will be used to speed up
		1701	change detection where possible. The inotify descriptor will be created lazily
		1702	when the first C<ev_stat> watcher is being started.
		1703
		1704	Inotify presence does not change the semantics of C<ev_stat> watchers
		1705	except that changes might be detected earlier, and in some cases, to avoid
		1706	making regular C<stat> calls. Even in the presence of inotify support
		1707	there are many cases where libev has to resort to regular C<stat> polling.
		1708
		1709	(There is no support for kqueue, as apparently it cannot be used to
		1710	implement this functionality, due to the requirement of having a file
		1711	descriptor open on the object at all times).
		1712
		1713	=head3 The special problem of stat time resolution
		1714
		1715	The C<stat ()> system call only supports full-second resolution portably, and
		1716	even on systems where the resolution is higher, many file systems still
		1717	only support whole seconds.
		1718
		1719	That means that, if the time is the only thing that changes, you can
		1720	easily miss updates: on the first update, C<ev_stat> detects a change and
		1721	calls your callback, which does something. When there is another update
		1722	within the same second, C<ev_stat> will be unable to detect it as the stat
		1723	data does not change.
		1724
		1725	The solution to this is to delay acting on a change for slightly more
		1726	than a second (or till slightly after the next full second boundary), using
		1727	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1728	ev_timer_again (loop, w)>).
		1729
		1730	The C<.02> offset is added to work around small timing inconsistencies
		1731	of some operating systems (where the second counter of the current time
		1732	might be be delayed. One such system is the Linux kernel, where a call to
		1733	C<gettimeofday> might return a timestamp with a full second later than
		1734	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1735	update file times then there will be a small window where the kernel uses
		1736	the previous second to update file times but libev might already execute
		1737	the timer callback).
		1738
		1739	=head3 Watcher-Specific Functions and Data Members
		1740
		1741	=over 4
		1742
		1743	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1744
		1745	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1746
		1747	Configures the watcher to wait for status changes of the given
		1748	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1749	be detected and should normally be specified as C<0> to let libev choose
		1750	a suitable value. The memory pointed to by C<path> must point to the same
		1751	path for as long as the watcher is active.
		1752
		1753	The callback will receive C<EV_STAT> when a change was detected, relative
		1754	to the attributes at the time the watcher was started (or the last change
		1755	was detected).
		1756
		1757	=item ev_stat_stat (loop, ev_stat *)
		1758
		1759	Updates the stat buffer immediately with new values. If you change the
		1760	watched path in your callback, you could call this function to avoid
		1761	detecting this change (while introducing a race condition if you are not
		1762	the only one changing the path). Can also be useful simply to find out the
		1763	new values.
		1764
		1765	=item ev_statdata attr [read-only]
		1766
		1767	The most-recently detected attributes of the file. Although the type is
		1768	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1769	suitable for your system, but you can only rely on the POSIX-standardised
		1770	members to be present. If the C<st_nlink> member is C<0>, then there was
		1771	some error while C<stat>ing the file.
		1772
		1773	=item ev_statdata prev [read-only]
		1774
		1775	The previous attributes of the file. The callback gets invoked whenever
		1776	C<prev> != C<attr>, or, more precisely, one or more of these members
		1777	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1778	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
		1779
		1780	=item ev_tstamp interval [read-only]
		1781
		1782	The specified interval.
		1783
		1784	=item const char *path [read-only]
		1785
		1786	The file system path that is being watched.
		1787
		1788	=back
		1789
		1790	=head3 Examples
		1791
		1792	Example: Watch C</etc/passwd> for attribute changes.
		1793
		1794	static void
		1795	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1796	{
		1797	/* /etc/passwd changed in some way */
		1798	if (w->attr.st_nlink)
		1799	{
		1800	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1801	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1802	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1803	}
		1804	else
		1805	/* you shalt not abuse printf for puts */
		1806	puts ("wow, /etc/passwd is not there, expect problems. "
		1807	"if this is windows, they already arrived\n");
		1808	}
		1809
		1810	...
		1811	ev_stat passwd;
		1812
		1813	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1814	ev_stat_start (loop, &passwd);
		1815
		1816	Example: Like above, but additionally use a one-second delay so we do not
		1817	miss updates (however, frequent updates will delay processing, too, so
		1818	one might do the work both on C<ev_stat> callback invocation I<and> on
		1819	C<ev_timer> callback invocation).
		1820
		1821	static ev_stat passwd;
		1822	static ev_timer timer;
		1823
		1824	static void
		1825	timer_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_timer_stop (EV_A_ w);
		1828
		1829	/* now it's one second after the most recent passwd change */
		1830	}
		1831
		1832	static void
		1833	stat_cb (EV_P_ ev_stat *w, int revents)
		1834	{
		1835	/* reset the one-second timer */
		1836	ev_timer_again (EV_A_ &timer);
		1837	}
		1838
		1839	...
		1840	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1841	ev_stat_start (loop, &passwd);
		1842	ev_timer_init (&timer, timer_cb, 0., 1.02);
		1843
		1844
644	=head2 C<ev_idle> - when you've got nothing better to do	1845	=head2 C<ev_idle> - when you've got nothing better to do...
645		1846
646	Idle watchers trigger events when there are no other events are pending	1847	Idle watchers trigger events when no other events of the same or higher
647	(prepare, check and other idle watchers do not count). That is, as long	1848	priority are pending (prepare, check and other idle watchers do not
648	as your process is busy handling sockets or timeouts (or even signals,	1849	count).
649	imagine) it will not be triggered. But when your process is idle all idle	1850
650	watchers are being called again and again, once per event loop iteration -	1851	That is, as long as your process is busy handling sockets or timeouts
		1852	(or even signals, imagine) of the same or higher priority it will not be
		1853	triggered. But when your process is idle (or only lower-priority watchers
		1854	are pending), the idle watchers are being called once per event loop
651	until stopped, that is, or your process receives more events and becomes	1855	iteration - until stopped, that is, or your process receives more events
652	busy.	1856	and becomes busy again with higher priority stuff.
653		1857
654	The most noteworthy effect is that as long as any idle watchers are	1858	The most noteworthy effect is that as long as any idle watchers are
655	active, the process will not block when waiting for new events.	1859	active, the process will not block when waiting for new events.
656		1860
657	Apart from keeping your process non-blocking (which is a useful	1861	Apart from keeping your process non-blocking (which is a useful
658	effect on its own sometimes), idle watchers are a good place to do	1862	effect on its own sometimes), idle watchers are a good place to do
659	"pseudo-background processing", or delay processing stuff to after the	1863	"pseudo-background processing", or delay processing stuff to after the
660	event loop has handled all outstanding events.	1864	event loop has handled all outstanding events.
661		1865
		1866	=head3 Watcher-Specific Functions and Data Members
		1867
662	=over 4	1868	=over 4
663		1869
664	=item ev_idle_init (ev_signal *, callback)	1870	=item ev_idle_init (ev_signal *, callback)
665		1871
666	Initialises and configures the idle watcher - it has no parameters of any	1872	Initialises and configures the idle watcher - it has no parameters of any
667	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
668	believe me.	1874	believe me.
669		1875
670	=back	1876	=back
671		1877
		1878	=head3 Examples
		1879
		1880	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1881	callback, free it. Also, use no error checking, as usual.
		1882
		1883	static void
		1884	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1885	{
		1886	free (w);
		1887	// now do something you wanted to do when the program has
		1888	// no longer anything immediate to do.
		1889	}
		1890
		1891	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1892	ev_idle_init (idle_watcher, idle_cb);
		1893	ev_idle_start (loop, idle_cb);
		1894
		1895
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1896	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
673		1897
674	Prepare and check watchers are usually (but not always) used in tandem:	1898	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1899	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	1900	afterwards.
677		1901
		1902	You I<must not> call C<ev_loop> or similar functions that enter
		1903	the current event loop from either C<ev_prepare> or C<ev_check>
		1904	watchers. Other loops than the current one are fine, however. The
		1905	rationale behind this is that you do not need to check for recursion in
		1906	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1907	C<ev_check> so if you have one watcher of each kind they will always be
		1908	called in pairs bracketing the blocking call.
		1909
678	Their main purpose is to integrate other event mechanisms into libev. This	1910	Their main purpose is to integrate other event mechanisms into libev and
679	could be used, for example, to track variable changes, implement your own	1911	their use is somewhat advanced. This could be used, for example, to track
680	watchers, integrate net-snmp or a coroutine library and lots more.	1912	variable changes, implement your own watchers, integrate net-snmp or a
		1913	coroutine library and lots more. They are also occasionally useful if
		1914	you cache some data and want to flush it before blocking (for example,
		1915	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1916	watcher).
681		1917
682	This is done by examining in each prepare call which file descriptors need	1918	This is done by examining in each prepare call which file descriptors need
683	to be watched by the other library, registering C<ev_io> watchers for	1919	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1920	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	1921	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	1922	any events that occurred (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	1923	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	1924	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	1925	because you never know, you know?).
690		1926
691	As another example, the Perl Coro module uses these hooks to integrate	1927	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	1928	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	1929	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	1930	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	1931	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	1932	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	1933	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	1934	low-priority coroutines to idle/background tasks).
		1935
		1936	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1937	priority, to ensure that they are being run before any other watchers
		1938	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1939	too) should not activate ("feed") events into libev. While libev fully
		1940	supports this, they might get executed before other C<ev_check> watchers
		1941	did their job. As C<ev_check> watchers are often used to embed other
		1942	(non-libev) event loops those other event loops might be in an unusable
		1943	state until their C<ev_check> watcher ran (always remind yourself to
		1944	coexist peacefully with others).
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
699		1947
700	=over 4	1948	=over 4
701		1949
702	=item ev_prepare_init (ev_prepare *, callback)	1950	=item ev_prepare_init (ev_prepare *, callback)
703		1951
…		…
707	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1955	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
708	macros, but using them is utterly, utterly and completely pointless.	1956	macros, but using them is utterly, utterly and completely pointless.
709		1957
710	=back	1958	=back
711		1959
		1960	=head3 Examples
		1961
		1962	There are a number of principal ways to embed other event loops or modules
		1963	into libev. Here are some ideas on how to include libadns into libev
		1964	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1965	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1966	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1967	Glib event loop).
		1968
		1969	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1970	and in a check watcher, destroy them and call into libadns. What follows
		1971	is pseudo-code only of course. This requires you to either use a low
		1972	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1973	the callbacks for the IO/timeout watchers might not have been called yet.
		1974
		1975	static ev_io iow [nfd];
		1976	static ev_timer tw;
		1977
		1978	static void
		1979	io_cb (ev_loop *loop, ev_io *w, int revents)
		1980	{
		1981	}
		1982
		1983	// create io watchers for each fd and a timer before blocking
		1984	static void
		1985	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1986	{
		1987	int timeout = 3600000;
		1988	struct pollfd fds [nfd];
		1989	// actual code will need to loop here and realloc etc.
		1990	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1991
		1992	/* the callback is illegal, but won't be called as we stop during check */
		1993	ev_timer_init (&tw, 0, timeout * 1e-3);
		1994	ev_timer_start (loop, &tw);
		1995
		1996	// create one ev_io per pollfd
		1997	for (int i = 0; i < nfd; ++i)
		1998	{
		1999	ev_io_init (iow + i, io_cb, fds [i].fd,
		2000	((fds [i].events & POLLIN ? EV_READ : 0)
		2001	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		2002
		2003	fds [i].revents = 0;
		2004	ev_io_start (loop, iow + i);
		2005	}
		2006	}
		2007
		2008	// stop all watchers after blocking
		2009	static void
		2010	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		2011	{
		2012	ev_timer_stop (loop, &tw);
		2013
		2014	for (int i = 0; i < nfd; ++i)
		2015	{
		2016	// set the relevant poll flags
		2017	// could also call adns_processreadable etc. here
		2018	struct pollfd *fd = fds + i;
		2019	int revents = ev_clear_pending (iow + i);
		2020	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2021	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2022
		2023	// now stop the watcher
		2024	ev_io_stop (loop, iow + i);
		2025	}
		2026
		2027	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		2028	}
		2029
		2030	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2031	in the prepare watcher and would dispose of the check watcher.
		2032
		2033	Method 3: If the module to be embedded supports explicit event
		2034	notification (libadns does), you can also make use of the actual watcher
		2035	callbacks, and only destroy/create the watchers in the prepare watcher.
		2036
		2037	static void
		2038	timer_cb (EV_P_ ev_timer *w, int revents)
		2039	{
		2040	adns_state ads = (adns_state)w->data;
		2041	update_now (EV_A);
		2042
		2043	adns_processtimeouts (ads, &tv_now);
		2044	}
		2045
		2046	static void
		2047	io_cb (EV_P_ ev_io *w, int revents)
		2048	{
		2049	adns_state ads = (adns_state)w->data;
		2050	update_now (EV_A);
		2051
		2052	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2053	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2054	}
		2055
		2056	// do not ever call adns_afterpoll
		2057
		2058	Method 4: Do not use a prepare or check watcher because the module you
		2059	want to embed is too inflexible to support it. Instead, you can override
		2060	their poll function. The drawback with this solution is that the main
		2061	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2062	this.
		2063
		2064	static gint
		2065	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2066	{
		2067	int got_events = 0;
		2068
		2069	for (n = 0; n < nfds; ++n)
		2070	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2071
		2072	if (timeout >= 0)
		2073	// create/start timer
		2074
		2075	// poll
		2076	ev_loop (EV_A_ 0);
		2077
		2078	// stop timer again
		2079	if (timeout >= 0)
		2080	ev_timer_stop (EV_A_ &to);
		2081
		2082	// stop io watchers again - their callbacks should have set
		2083	for (n = 0; n < nfds; ++n)
		2084	ev_io_stop (EV_A_ iow [n]);
		2085
		2086	return got_events;
		2087	}
		2088
		2089
		2090	=head2 C<ev_embed> - when one backend isn't enough...
		2091
		2092	This is a rather advanced watcher type that lets you embed one event loop
		2093	into another (currently only C<ev_io> events are supported in the embedded
		2094	loop, other types of watchers might be handled in a delayed or incorrect
		2095	fashion and must not be used).
		2096
		2097	There are primarily two reasons you would want that: work around bugs and
		2098	prioritise I/O.
		2099
		2100	As an example for a bug workaround, the kqueue backend might only support
		2101	sockets on some platform, so it is unusable as generic backend, but you
		2102	still want to make use of it because you have many sockets and it scales
		2103	so nicely. In this case, you would create a kqueue-based loop and embed it
		2104	into your default loop (which might use e.g. poll). Overall operation will
		2105	be a bit slower because first libev has to poll and then call kevent, but
		2106	at least you can use both at what they are best.
		2107
		2108	As for prioritising I/O: rarely you have the case where some fds have
		2109	to be watched and handled very quickly (with low latency), and even
		2110	priorities and idle watchers might have too much overhead. In this case
		2111	you would put all the high priority stuff in one loop and all the rest in
		2112	a second one, and embed the second one in the first.
		2113
		2114	As long as the watcher is active, the callback will be invoked every time
		2115	there might be events pending in the embedded loop. The callback must then
		2116	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		2117	their callbacks (you could also start an idle watcher to give the embedded
		2118	loop strictly lower priority for example). You can also set the callback
		2119	to C<0>, in which case the embed watcher will automatically execute the
		2120	embedded loop sweep.
		2121
		2122	As long as the watcher is started it will automatically handle events. The
		2123	callback will be invoked whenever some events have been handled. You can
		2124	set the callback to C<0> to avoid having to specify one if you are not
		2125	interested in that.
		2126
		2127	Also, there have not currently been made special provisions for forking:
		2128	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2129	but you will also have to stop and restart any C<ev_embed> watchers
		2130	yourself.
		2131
		2132	Unfortunately, not all backends are embeddable, only the ones returned by
		2133	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2134	portable one.
		2135
		2136	So when you want to use this feature you will always have to be prepared
		2137	that you cannot get an embeddable loop. The recommended way to get around
		2138	this is to have a separate variables for your embeddable loop, try to
		2139	create it, and if that fails, use the normal loop for everything.
		2140
		2141	=head3 Watcher-Specific Functions and Data Members
		2142
		2143	=over 4
		2144
		2145	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2146
		2147	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2148
		2149	Configures the watcher to embed the given loop, which must be
		2150	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2151	invoked automatically, otherwise it is the responsibility of the callback
		2152	to invoke it (it will continue to be called until the sweep has been done,
		2153	if you do not want that, you need to temporarily stop the embed watcher).
		2154
		2155	=item ev_embed_sweep (loop, ev_embed *)
		2156
		2157	Make a single, non-blocking sweep over the embedded loop. This works
		2158	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2159	appropriate way for embedded loops.
		2160
		2161	=item struct ev_loop *other [read-only]
		2162
		2163	The embedded event loop.
		2164
		2165	=back
		2166
		2167	=head3 Examples
		2168
		2169	Example: Try to get an embeddable event loop and embed it into the default
		2170	event loop. If that is not possible, use the default loop. The default
		2171	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2172	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2173	used).
		2174
		2175	struct ev_loop *loop_hi = ev_default_init (0);
		2176	struct ev_loop *loop_lo = 0;
		2177	struct ev_embed embed;
		2178
		2179	// see if there is a chance of getting one that works
		2180	// (remember that a flags value of 0 means autodetection)
		2181	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2182	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2183	: 0;
		2184
		2185	// if we got one, then embed it, otherwise default to loop_hi
		2186	if (loop_lo)
		2187	{
		2188	ev_embed_init (&embed, 0, loop_lo);
		2189	ev_embed_start (loop_hi, &embed);
		2190	}
		2191	else
		2192	loop_lo = loop_hi;
		2193
		2194	Example: Check if kqueue is available but not recommended and create
		2195	a kqueue backend for use with sockets (which usually work with any
		2196	kqueue implementation). Store the kqueue/socket-only event loop in
		2197	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2198
		2199	struct ev_loop *loop = ev_default_init (0);
		2200	struct ev_loop *loop_socket = 0;
		2201	struct ev_embed embed;
		2202
		2203	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2204	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2205	{
		2206	ev_embed_init (&embed, 0, loop_socket);
		2207	ev_embed_start (loop, &embed);
		2208	}
		2209
		2210	if (!loop_socket)
		2211	loop_socket = loop;
		2212
		2213	// now use loop_socket for all sockets, and loop for everything else
		2214
		2215
		2216	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2217
		2218	Fork watchers are called when a C<fork ()> was detected (usually because
		2219	whoever is a good citizen cared to tell libev about it by calling
		2220	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2221	event loop blocks next and before C<ev_check> watchers are being called,
		2222	and only in the child after the fork. If whoever good citizen calling
		2223	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2224	handlers will be invoked, too, of course.
		2225
		2226	=head3 Watcher-Specific Functions and Data Members
		2227
		2228	=over 4
		2229
		2230	=item ev_fork_init (ev_signal *, callback)
		2231
		2232	Initialises and configures the fork watcher - it has no parameters of any
		2233	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2234	believe me.
		2235
		2236	=back
		2237
		2238
		2239	=head2 C<ev_async> - how to wake up another event loop
		2240
		2241	In general, you cannot use an C<ev_loop> from multiple threads or other
		2242	asynchronous sources such as signal handlers (as opposed to multiple event
		2243	loops - those are of course safe to use in different threads).
		2244
		2245	Sometimes, however, you need to wake up another event loop you do not
		2246	control, for example because it belongs to another thread. This is what
		2247	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2248	can signal it by calling C<ev_async_send>, which is thread- and signal
		2249	safe.
		2250
		2251	This functionality is very similar to C<ev_signal> watchers, as signals,
		2252	too, are asynchronous in nature, and signals, too, will be compressed
		2253	(i.e. the number of callback invocations may be less than the number of
		2254	C<ev_async_sent> calls).
		2255
		2256	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2257	just the default loop.
		2258
		2259	=head3 Queueing
		2260
		2261	C<ev_async> does not support queueing of data in any way. The reason
		2262	is that the author does not know of a simple (or any) algorithm for a
		2263	multiple-writer-single-reader queue that works in all cases and doesn't
		2264	need elaborate support such as pthreads.
		2265
		2266	That means that if you want to queue data, you have to provide your own
		2267	queue. But at least I can tell you would implement locking around your
		2268	queue:
		2269
		2270	=over 4
		2271
		2272	=item queueing from a signal handler context
		2273
		2274	To implement race-free queueing, you simply add to the queue in the signal
		2275	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2276	some fictitious SIGUSR1 handler:
		2277
		2278	static ev_async mysig;
		2279
		2280	static void
		2281	sigusr1_handler (void)
		2282	{
		2283	sometype data;
		2284
		2285	// no locking etc.
		2286	queue_put (data);
		2287	ev_async_send (EV_DEFAULT_ &mysig);
		2288	}
		2289
		2290	static void
		2291	mysig_cb (EV_P_ ev_async *w, int revents)
		2292	{
		2293	sometype data;
		2294	sigset_t block, prev;
		2295
		2296	sigemptyset (&block);
		2297	sigaddset (&block, SIGUSR1);
		2298	sigprocmask (SIG_BLOCK, &block, &prev);
		2299
		2300	while (queue_get (&data))
		2301	process (data);
		2302
		2303	if (sigismember (&prev, SIGUSR1)
		2304	sigprocmask (SIG_UNBLOCK, &block, 0);
		2305	}
		2306
		2307	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2308	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2309	either...).
		2310
		2311	=item queueing from a thread context
		2312
		2313	The strategy for threads is different, as you cannot (easily) block
		2314	threads but you can easily preempt them, so to queue safely you need to
		2315	employ a traditional mutex lock, such as in this pthread example:
		2316
		2317	static ev_async mysig;
		2318	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2319
		2320	static void
		2321	otherthread (void)
		2322	{
		2323	// only need to lock the actual queueing operation
		2324	pthread_mutex_lock (&mymutex);
		2325	queue_put (data);
		2326	pthread_mutex_unlock (&mymutex);
		2327
		2328	ev_async_send (EV_DEFAULT_ &mysig);
		2329	}
		2330
		2331	static void
		2332	mysig_cb (EV_P_ ev_async *w, int revents)
		2333	{
		2334	pthread_mutex_lock (&mymutex);
		2335
		2336	while (queue_get (&data))
		2337	process (data);
		2338
		2339	pthread_mutex_unlock (&mymutex);
		2340	}
		2341
		2342	=back
		2343
		2344
		2345	=head3 Watcher-Specific Functions and Data Members
		2346
		2347	=over 4
		2348
		2349	=item ev_async_init (ev_async *, callback)
		2350
		2351	Initialises and configures the async watcher - it has no parameters of any
		2352	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2353	believe me.
		2354
		2355	=item ev_async_send (loop, ev_async *)
		2356
		2357	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2358	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2359	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2360	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2361	section below on what exactly this means).
		2362
		2363	This call incurs the overhead of a system call only once per loop iteration,
		2364	so while the overhead might be noticeable, it doesn't apply to repeated
		2365	calls to C<ev_async_send>.
		2366
		2367	=item bool = ev_async_pending (ev_async *)
		2368
		2369	Returns a non-zero value when C<ev_async_send> has been called on the
		2370	watcher but the event has not yet been processed (or even noted) by the
		2371	event loop.
		2372
		2373	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2374	the loop iterates next and checks for the watcher to have become active,
		2375	it will reset the flag again. C<ev_async_pending> can be used to very
		2376	quickly check whether invoking the loop might be a good idea.
		2377
		2378	Not that this does I<not> check whether the watcher itself is pending, only
		2379	whether it has been requested to make this watcher pending.
		2380
		2381	=back
		2382
		2383
712	=head1 OTHER FUNCTIONS	2384	=head1 OTHER FUNCTIONS
713		2385
714	There are some other functions of possible interest. Described. Here. Now.	2386	There are some other functions of possible interest. Described. Here. Now.
715		2387
716	=over 4	2388	=over 4
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2390	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		2391
720	This function combines a simple timer and an I/O watcher, calls your	2392	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	2393	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	2394	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	2395	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	2396	more watchers yourself.
725		2397
726	If C<fd> is less than 0, then no I/O watcher will be started and events	2398	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2399	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	2400	C<events> set will be created and started.
729		2401
730	If C<timeout> is less than 0, then no timeout watcher will be	2402	If C<timeout> is less than 0, then no timeout watcher will be
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2403	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2404	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	2405	dubious value.
734		2406
735	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2407	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	2408	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2409	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	2410	value passed to C<ev_once>:
739		2411
740	static void stdin_ready (int revents, void *arg)	2412	static void stdin_ready (int revents, void *arg)
741	{	2413	{
742	if (revents & EV_TIMEOUT)	2414	if (revents & EV_TIMEOUT)
743	/* doh, nothing entered */;	2415	/* doh, nothing entered */;
744	else if (revents & EV_READ)	2416	else if (revents & EV_READ)
745	/* stdin might have data for us, joy! */;	2417	/* stdin might have data for us, joy! */;
746	}	2418	}
747		2419
748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2420	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
749		2421
750	=item ev_feed_event (loop, watcher, int events)	2422	=item ev_feed_event (ev_loop *, watcher *, int revents)
751		2423
752	Feeds the given event set into the event loop, as if the specified event	2424	Feeds the given event set into the event loop, as if the specified event
753	had happened for the specified watcher (which must be a pointer to an	2425	had happened for the specified watcher (which must be a pointer to an
754	initialised but not necessarily started event watcher).	2426	initialised but not necessarily started event watcher).
755		2427
756	=item ev_feed_fd_event (loop, int fd, int revents)	2428	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
757		2429
758	Feed an event on the given fd, as if a file descriptor backend detected	2430	Feed an event on the given fd, as if a file descriptor backend detected
759	the given events it.	2431	the given events it.
760		2432
761	=item ev_feed_signal_event (loop, int signum)	2433	=item ev_feed_signal_event (ev_loop *loop, int signum)
762		2434
763	Feed an event as if the given signal occured (loop must be the default loop!).	2435	Feed an event as if the given signal occurred (C<loop> must be the default
		2436	loop!).
764		2437
765	=back	2438	=back
766		2439
		2440
		2441	=head1 LIBEVENT EMULATION
		2442
		2443	Libev offers a compatibility emulation layer for libevent. It cannot
		2444	emulate the internals of libevent, so here are some usage hints:
		2445
		2446	=over 4
		2447
		2448	=item * Use it by including <event.h>, as usual.
		2449
		2450	=item * The following members are fully supported: ev_base, ev_callback,
		2451	ev_arg, ev_fd, ev_res, ev_events.
		2452
		2453	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		2454	maintained by libev, it does not work exactly the same way as in libevent (consider
		2455	it a private API).
		2456
		2457	=item * Priorities are not currently supported. Initialising priorities
		2458	will fail and all watchers will have the same priority, even though there
		2459	is an ev_pri field.
		2460
		2461	=item * In libevent, the last base created gets the signals, in libev, the
		2462	first base created (== the default loop) gets the signals.
		2463
		2464	=item * Other members are not supported.
		2465
		2466	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		2467	to use the libev header file and library.
		2468
		2469	=back
		2470
		2471	=head1 C++ SUPPORT
		2472
		2473	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2474	you to use some convenience methods to start/stop watchers and also change
		2475	the callback model to a model using method callbacks on objects.
		2476
		2477	To use it,
		2478
		2479	#include <ev++.h>
		2480
		2481	This automatically includes F<ev.h> and puts all of its definitions (many
		2482	of them macros) into the global namespace. All C++ specific things are
		2483	put into the C<ev> namespace. It should support all the same embedding
		2484	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2485
		2486	Care has been taken to keep the overhead low. The only data member the C++
		2487	classes add (compared to plain C-style watchers) is the event loop pointer
		2488	that the watcher is associated with (or no additional members at all if
		2489	you disable C<EV_MULTIPLICITY> when embedding libev).
		2490
		2491	Currently, functions, and static and non-static member functions can be
		2492	used as callbacks. Other types should be easy to add as long as they only
		2493	need one additional pointer for context. If you need support for other
		2494	types of functors please contact the author (preferably after implementing
		2495	it).
		2496
		2497	Here is a list of things available in the C<ev> namespace:
		2498
		2499	=over 4
		2500
		2501	=item C<ev::READ>, C<ev::WRITE> etc.
		2502
		2503	These are just enum values with the same values as the C<EV_READ> etc.
		2504	macros from F<ev.h>.
		2505
		2506	=item C<ev::tstamp>, C<ev::now>
		2507
		2508	Aliases to the same types/functions as with the C<ev_> prefix.
		2509
		2510	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2511
		2512	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2513	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2514	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2515	defines by many implementations.
		2516
		2517	All of those classes have these methods:
		2518
		2519	=over 4
		2520
		2521	=item ev::TYPE::TYPE ()
		2522
		2523	=item ev::TYPE::TYPE (struct ev_loop *)
		2524
		2525	=item ev::TYPE::~TYPE
		2526
		2527	The constructor (optionally) takes an event loop to associate the watcher
		2528	with. If it is omitted, it will use C<EV_DEFAULT>.
		2529
		2530	The constructor calls C<ev_init> for you, which means you have to call the
		2531	C<set> method before starting it.
		2532
		2533	It will not set a callback, however: You have to call the templated C<set>
		2534	method to set a callback before you can start the watcher.
		2535
		2536	(The reason why you have to use a method is a limitation in C++ which does
		2537	not allow explicit template arguments for constructors).
		2538
		2539	The destructor automatically stops the watcher if it is active.
		2540
		2541	=item w->set<class, &class::method> (object *)
		2542
		2543	This method sets the callback method to call. The method has to have a
		2544	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2545	first argument and the C<revents> as second. The object must be given as
		2546	parameter and is stored in the C<data> member of the watcher.
		2547
		2548	This method synthesizes efficient thunking code to call your method from
		2549	the C callback that libev requires. If your compiler can inline your
		2550	callback (i.e. it is visible to it at the place of the C<set> call and
		2551	your compiler is good :), then the method will be fully inlined into the
		2552	thunking function, making it as fast as a direct C callback.
		2553
		2554	Example: simple class declaration and watcher initialisation
		2555
		2556	struct myclass
		2557	{
		2558	void io_cb (ev::io &w, int revents) { }
		2559	}
		2560
		2561	myclass obj;
		2562	ev::io iow;
		2563	iow.set <myclass, &myclass::io_cb> (&obj);
		2564
		2565	=item w->set<function> (void *data = 0)
		2566
		2567	Also sets a callback, but uses a static method or plain function as
		2568	callback. The optional C<data> argument will be stored in the watcher's
		2569	C<data> member and is free for you to use.
		2570
		2571	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2572
		2573	See the method-C<set> above for more details.
		2574
		2575	Example:
		2576
		2577	static void io_cb (ev::io &w, int revents) { }
		2578	iow.set <io_cb> ();
		2579
		2580	=item w->set (struct ev_loop *)
		2581
		2582	Associates a different C<struct ev_loop> with this watcher. You can only
		2583	do this when the watcher is inactive (and not pending either).
		2584
		2585	=item w->set ([arguments])
		2586
		2587	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
		2588	called at least once. Unlike the C counterpart, an active watcher gets
		2589	automatically stopped and restarted when reconfiguring it with this
		2590	method.
		2591
		2592	=item w->start ()
		2593
		2594	Starts the watcher. Note that there is no C<loop> argument, as the
		2595	constructor already stores the event loop.
		2596
		2597	=item w->stop ()
		2598
		2599	Stops the watcher if it is active. Again, no C<loop> argument.
		2600
		2601	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2602
		2603	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2604	C<ev_TYPE_again> function.
		2605
		2606	=item w->sweep () (C<ev::embed> only)
		2607
		2608	Invokes C<ev_embed_sweep>.
		2609
		2610	=item w->update () (C<ev::stat> only)
		2611
		2612	Invokes C<ev_stat_stat>.
		2613
		2614	=back
		2615
		2616	=back
		2617
		2618	Example: Define a class with an IO and idle watcher, start one of them in
		2619	the constructor.
		2620
		2621	class myclass
		2622	{
		2623	ev::io io; void io_cb (ev::io &w, int revents);
		2624	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2625
		2626	myclass (int fd)
		2627	{
		2628	io .set <myclass, &myclass::io_cb > (this);
		2629	idle.set <myclass, &myclass::idle_cb> (this);
		2630
		2631	io.start (fd, ev::READ);
		2632	}
		2633	};
		2634
		2635
		2636	=head1 OTHER LANGUAGE BINDINGS
		2637
		2638	Libev does not offer other language bindings itself, but bindings for a
		2639	number of languages exist in the form of third-party packages. If you know
		2640	any interesting language binding in addition to the ones listed here, drop
		2641	me a note.
		2642
		2643	=over 4
		2644
		2645	=item Perl
		2646
		2647	The EV module implements the full libev API and is actually used to test
		2648	libev. EV is developed together with libev. Apart from the EV core module,
		2649	there are additional modules that implement libev-compatible interfaces
		2650	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2651	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2652
		2653	It can be found and installed via CPAN, its homepage is at
		2654	L<http://software.schmorp.de/pkg/EV>.
		2655
		2656	=item Python
		2657
		2658	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2659	seems to be quite complete and well-documented. Note, however, that the
		2660	patch they require for libev is outright dangerous as it breaks the ABI
		2661	for everybody else, and therefore, should never be applied in an installed
		2662	libev (if python requires an incompatible ABI then it needs to embed
		2663	libev).
		2664
		2665	=item Ruby
		2666
		2667	Tony Arcieri has written a ruby extension that offers access to a subset
		2668	of the libev API and adds file handle abstractions, asynchronous DNS and
		2669	more on top of it. It can be found via gem servers. Its homepage is at
		2670	L<http://rev.rubyforge.org/>.
		2671
		2672	=item D
		2673
		2674	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2675	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2676
		2677	=back
		2678
		2679
		2680	=head1 MACRO MAGIC
		2681
		2682	Libev can be compiled with a variety of options, the most fundamental
		2683	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2684	functions and callbacks have an initial C<struct ev_loop *> argument.
		2685
		2686	To make it easier to write programs that cope with either variant, the
		2687	following macros are defined:
		2688
		2689	=over 4
		2690
		2691	=item C<EV_A>, C<EV_A_>
		2692
		2693	This provides the loop I<argument> for functions, if one is required ("ev
		2694	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2695	C<EV_A_> is used when other arguments are following. Example:
		2696
		2697	ev_unref (EV_A);
		2698	ev_timer_add (EV_A_ watcher);
		2699	ev_loop (EV_A_ 0);
		2700
		2701	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2702	which is often provided by the following macro.
		2703
		2704	=item C<EV_P>, C<EV_P_>
		2705
		2706	This provides the loop I<parameter> for functions, if one is required ("ev
		2707	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2708	C<EV_P_> is used when other parameters are following. Example:
		2709
		2710	// this is how ev_unref is being declared
		2711	static void ev_unref (EV_P);
		2712
		2713	// this is how you can declare your typical callback
		2714	static void cb (EV_P_ ev_timer *w, int revents)
		2715
		2716	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2717	suitable for use with C<EV_A>.
		2718
		2719	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2720
		2721	Similar to the other two macros, this gives you the value of the default
		2722	loop, if multiple loops are supported ("ev loop default").
		2723
		2724	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2725
		2726	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2727	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2728	is undefined when the default loop has not been initialised by a previous
		2729	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2730
		2731	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2732	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2733
		2734	=back
		2735
		2736	Example: Declare and initialise a check watcher, utilising the above
		2737	macros so it will work regardless of whether multiple loops are supported
		2738	or not.
		2739
		2740	static void
		2741	check_cb (EV_P_ ev_timer *w, int revents)
		2742	{
		2743	ev_check_stop (EV_A_ w);
		2744	}
		2745
		2746	ev_check check;
		2747	ev_check_init (&check, check_cb);
		2748	ev_check_start (EV_DEFAULT_ &check);
		2749	ev_loop (EV_DEFAULT_ 0);
		2750
		2751	=head1 EMBEDDING
		2752
		2753	Libev can (and often is) directly embedded into host
		2754	applications. Examples of applications that embed it include the Deliantra
		2755	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2756	and rxvt-unicode.
		2757
		2758	The goal is to enable you to just copy the necessary files into your
		2759	source directory without having to change even a single line in them, so
		2760	you can easily upgrade by simply copying (or having a checked-out copy of
		2761	libev somewhere in your source tree).
		2762
		2763	=head2 FILESETS
		2764
		2765	Depending on what features you need you need to include one or more sets of files
		2766	in your application.
		2767
		2768	=head3 CORE EVENT LOOP
		2769
		2770	To include only the libev core (all the C<ev_*> functions), with manual
		2771	configuration (no autoconf):
		2772
		2773	#define EV_STANDALONE 1
		2774	#include "ev.c"
		2775
		2776	This will automatically include F<ev.h>, too, and should be done in a
		2777	single C source file only to provide the function implementations. To use
		2778	it, do the same for F<ev.h> in all files wishing to use this API (best
		2779	done by writing a wrapper around F<ev.h> that you can include instead and
		2780	where you can put other configuration options):
		2781
		2782	#define EV_STANDALONE 1
		2783	#include "ev.h"
		2784
		2785	Both header files and implementation files can be compiled with a C++
		2786	compiler (at least, thats a stated goal, and breakage will be treated
		2787	as a bug).
		2788
		2789	You need the following files in your source tree, or in a directory
		2790	in your include path (e.g. in libev/ when using -Ilibev):
		2791
		2792	ev.h
		2793	ev.c
		2794	ev_vars.h
		2795	ev_wrap.h
		2796
		2797	ev_win32.c required on win32 platforms only
		2798
		2799	ev_select.c only when select backend is enabled (which is enabled by default)
		2800	ev_poll.c only when poll backend is enabled (disabled by default)
		2801	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2802	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2803	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2804
		2805	F<ev.c> includes the backend files directly when enabled, so you only need
		2806	to compile this single file.
		2807
		2808	=head3 LIBEVENT COMPATIBILITY API
		2809
		2810	To include the libevent compatibility API, also include:
		2811
		2812	#include "event.c"
		2813
		2814	in the file including F<ev.c>, and:
		2815
		2816	#include "event.h"
		2817
		2818	in the files that want to use the libevent API. This also includes F<ev.h>.
		2819
		2820	You need the following additional files for this:
		2821
		2822	event.h
		2823	event.c
		2824
		2825	=head3 AUTOCONF SUPPORT
		2826
		2827	Instead of using C<EV_STANDALONE=1> and providing your configuration in
		2828	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2829	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2830	include F<config.h> and configure itself accordingly.
		2831
		2832	For this of course you need the m4 file:
		2833
		2834	libev.m4
		2835
		2836	=head2 PREPROCESSOR SYMBOLS/MACROS
		2837
		2838	Libev can be configured via a variety of preprocessor symbols you have to
		2839	define before including any of its files. The default in the absence of
		2840	autoconf is noted for every option.
		2841
		2842	=over 4
		2843
		2844	=item EV_STANDALONE
		2845
		2846	Must always be C<1> if you do not use autoconf configuration, which
		2847	keeps libev from including F<config.h>, and it also defines dummy
		2848	implementations for some libevent functions (such as logging, which is not
		2849	supported). It will also not define any of the structs usually found in
		2850	F<event.h> that are not directly supported by the libev core alone.
		2851
		2852	=item EV_USE_MONOTONIC
		2853
		2854	If defined to be C<1>, libev will try to detect the availability of the
		2855	monotonic clock option at both compile time and runtime. Otherwise no use
		2856	of the monotonic clock option will be attempted. If you enable this, you
		2857	usually have to link against librt or something similar. Enabling it when
		2858	the functionality isn't available is safe, though, although you have
		2859	to make sure you link against any libraries where the C<clock_gettime>
		2860	function is hiding in (often F<-lrt>).
		2861
		2862	=item EV_USE_REALTIME
		2863
		2864	If defined to be C<1>, libev will try to detect the availability of the
		2865	real-time clock option at compile time (and assume its availability at
		2866	runtime if successful). Otherwise no use of the real-time clock option will
		2867	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2868	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2869	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2870
		2871	=item EV_USE_NANOSLEEP
		2872
		2873	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2874	and will use it for delays. Otherwise it will use C<select ()>.
		2875
		2876	=item EV_USE_EVENTFD
		2877
		2878	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2879	available and will probe for kernel support at runtime. This will improve
		2880	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2881	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2882	2.7 or newer, otherwise disabled.
		2883
		2884	=item EV_USE_SELECT
		2885
		2886	If undefined or defined to be C<1>, libev will compile in support for the
		2887	C<select>(2) backend. No attempt at auto-detection will be done: if no
		2888	other method takes over, select will be it. Otherwise the select backend
		2889	will not be compiled in.
		2890
		2891	=item EV_SELECT_USE_FD_SET
		2892
		2893	If defined to C<1>, then the select backend will use the system C<fd_set>
		2894	structure. This is useful if libev doesn't compile due to a missing
		2895	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
		2896	exotic systems. This usually limits the range of file descriptors to some
		2897	low limit such as 1024 or might have other limitations (winsocket only
		2898	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2899	influence the size of the C<fd_set> used.
		2900
		2901	=item EV_SELECT_IS_WINSOCKET
		2902
		2903	When defined to C<1>, the select backend will assume that
		2904	select/socket/connect etc. don't understand file descriptors but
		2905	wants osf handles on win32 (this is the case when the select to
		2906	be used is the winsock select). This means that it will call
		2907	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2908	it is assumed that all these functions actually work on fds, even
		2909	on win32. Should not be defined on non-win32 platforms.
		2910
		2911	=item EV_FD_TO_WIN32_HANDLE
		2912
		2913	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2914	file descriptors to socket handles. When not defining this symbol (the
		2915	default), then libev will call C<_get_osfhandle>, which is usually
		2916	correct. In some cases, programs use their own file descriptor management,
		2917	in which case they can provide this function to map fds to socket handles.
		2918
		2919	=item EV_USE_POLL
		2920
		2921	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2922	backend. Otherwise it will be enabled on non-win32 platforms. It
		2923	takes precedence over select.
		2924
		2925	=item EV_USE_EPOLL
		2926
		2927	If defined to be C<1>, libev will compile in support for the Linux
		2928	C<epoll>(7) backend. Its availability will be detected at runtime,
		2929	otherwise another method will be used as fallback. This is the preferred
		2930	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2931	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2932
		2933	=item EV_USE_KQUEUE
		2934
		2935	If defined to be C<1>, libev will compile in support for the BSD style
		2936	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2937	otherwise another method will be used as fallback. This is the preferred
		2938	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2939	supports some types of fds correctly (the only platform we found that
		2940	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2941	not be used unless explicitly requested. The best way to use it is to find
		2942	out whether kqueue supports your type of fd properly and use an embedded
		2943	kqueue loop.
		2944
		2945	=item EV_USE_PORT
		2946
		2947	If defined to be C<1>, libev will compile in support for the Solaris
		2948	10 port style backend. Its availability will be detected at runtime,
		2949	otherwise another method will be used as fallback. This is the preferred
		2950	backend for Solaris 10 systems.
		2951
		2952	=item EV_USE_DEVPOLL
		2953
		2954	Reserved for future expansion, works like the USE symbols above.
		2955
		2956	=item EV_USE_INOTIFY
		2957
		2958	If defined to be C<1>, libev will compile in support for the Linux inotify
		2959	interface to speed up C<ev_stat> watchers. Its actual availability will
		2960	be detected at runtime. If undefined, it will be enabled if the headers
		2961	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2962
		2963	=item EV_ATOMIC_T
		2964
		2965	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2966	access is atomic with respect to other threads or signal contexts. No such
		2967	type is easily found in the C language, so you can provide your own type
		2968	that you know is safe for your purposes. It is used both for signal handler "locking"
		2969	as well as for signal and thread safety in C<ev_async> watchers.
		2970
		2971	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2972	(from F<signal.h>), which is usually good enough on most platforms.
		2973
		2974	=item EV_H
		2975
		2976	The name of the F<ev.h> header file used to include it. The default if
		2977	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2978	used to virtually rename the F<ev.h> header file in case of conflicts.
		2979
		2980	=item EV_CONFIG_H
		2981
		2982	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2983	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2984	C<EV_H>, above.
		2985
		2986	=item EV_EVENT_H
		2987
		2988	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2989	of how the F<event.h> header can be found, the default is C<"event.h">.
		2990
		2991	=item EV_PROTOTYPES
		2992
		2993	If defined to be C<0>, then F<ev.h> will not define any function
		2994	prototypes, but still define all the structs and other symbols. This is
		2995	occasionally useful if you want to provide your own wrapper functions
		2996	around libev functions.
		2997
		2998	=item EV_MULTIPLICITY
		2999
		3000	If undefined or defined to C<1>, then all event-loop-specific functions
		3001	will have the C<struct ev_loop *> as first argument, and you can create
		3002	additional independent event loops. Otherwise there will be no support
		3003	for multiple event loops and there is no first event loop pointer
		3004	argument. Instead, all functions act on the single default loop.
		3005
		3006	=item EV_MINPRI
		3007
		3008	=item EV_MAXPRI
		3009
		3010	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3011	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3012	provide for more priorities by overriding those symbols (usually defined
		3013	to be C<-2> and C<2>, respectively).
		3014
		3015	When doing priority-based operations, libev usually has to linearly search
		3016	all the priorities, so having many of them (hundreds) uses a lot of space
		3017	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3018	fine.
		3019
		3020	If your embedding application does not need any priorities, defining these both to
		3021	C<0> will save some memory and CPU.
		3022
		3023	=item EV_PERIODIC_ENABLE
		3024
		3025	If undefined or defined to be C<1>, then periodic timers are supported. If
		3026	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3027	code.
		3028
		3029	=item EV_IDLE_ENABLE
		3030
		3031	If undefined or defined to be C<1>, then idle watchers are supported. If
		3032	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3033	code.
		3034
		3035	=item EV_EMBED_ENABLE
		3036
		3037	If undefined or defined to be C<1>, then embed watchers are supported. If
		3038	defined to be C<0>, then they are not.
		3039
		3040	=item EV_STAT_ENABLE
		3041
		3042	If undefined or defined to be C<1>, then stat watchers are supported. If
		3043	defined to be C<0>, then they are not.
		3044
		3045	=item EV_FORK_ENABLE
		3046
		3047	If undefined or defined to be C<1>, then fork watchers are supported. If
		3048	defined to be C<0>, then they are not.
		3049
		3050	=item EV_ASYNC_ENABLE
		3051
		3052	If undefined or defined to be C<1>, then async watchers are supported. If
		3053	defined to be C<0>, then they are not.
		3054
		3055	=item EV_MINIMAL
		3056
		3057	If you need to shave off some kilobytes of code at the expense of some
		3058	speed, define this symbol to C<1>. Currently this is used to override some
		3059	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3060	much smaller 2-heap for timer management over the default 4-heap.
		3061
		3062	=item EV_PID_HASHSIZE
		3063
		3064	C<ev_child> watchers use a small hash table to distribute workload by
		3065	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		3066	than enough. If you need to manage thousands of children you might want to
		3067	increase this value (I<must> be a power of two).
		3068
		3069	=item EV_INOTIFY_HASHSIZE
		3070
		3071	C<ev_stat> watchers use a small hash table to distribute workload by
		3072	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3073	usually more than enough. If you need to manage thousands of C<ev_stat>
		3074	watchers you might want to increase this value (I<must> be a power of
		3075	two).
		3076
		3077	=item EV_USE_4HEAP
		3078
		3079	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3080	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3081	to C<1>. The 4-heap uses more complicated (longer) code but has
		3082	noticeably faster performance with many (thousands) of watchers.
		3083
		3084	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3085	(disabled).
		3086
		3087	=item EV_HEAP_CACHE_AT
		3088
		3089	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3090	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3091	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3092	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3093	but avoids random read accesses on heap changes. This improves performance
		3094	noticeably with with many (hundreds) of watchers.
		3095
		3096	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3097	(disabled).
		3098
		3099	=item EV_VERIFY
		3100
		3101	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3102	be done: If set to C<0>, no internal verification code will be compiled
		3103	in. If set to C<1>, then verification code will be compiled in, but not
		3104	called. If set to C<2>, then the internal verification code will be
		3105	called once per loop, which can slow down libev. If set to C<3>, then the
		3106	verification code will be called very frequently, which will slow down
		3107	libev considerably.
		3108
		3109	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3110	C<0.>
		3111
		3112	=item EV_COMMON
		3113
		3114	By default, all watchers have a C<void *data> member. By redefining
		3115	this macro to a something else you can include more and other types of
		3116	members. You have to define it each time you include one of the files,
		3117	though, and it must be identical each time.
		3118
		3119	For example, the perl EV module uses something like this:
		3120
		3121	#define EV_COMMON \
		3122	SV *self; /* contains this struct */ \
		3123	SV *cb_sv, *fh /* note no trailing ";" */
		3124
		3125	=item EV_CB_DECLARE (type)
		3126
		3127	=item EV_CB_INVOKE (watcher, revents)
		3128
		3129	=item ev_set_cb (ev, cb)
		3130
		3131	Can be used to change the callback member declaration in each watcher,
		3132	and the way callbacks are invoked and set. Must expand to a struct member
		3133	definition and a statement, respectively. See the F<ev.h> header file for
		3134	their default definitions. One possible use for overriding these is to
		3135	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		3136	method calls instead of plain function calls in C++.
		3137
		3138	=head2 EXPORTED API SYMBOLS
		3139
		3140	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3141	exported symbols, you can use the provided F<Symbol.*> files which list
		3142	all public symbols, one per line:
		3143
		3144	Symbols.ev for libev proper
		3145	Symbols.event for the libevent emulation
		3146
		3147	This can also be used to rename all public symbols to avoid clashes with
		3148	multiple versions of libev linked together (which is obviously bad in
		3149	itself, but sometimes it is inconvenient to avoid this).
		3150
		3151	A sed command like this will create wrapper C<#define>'s that you need to
		3152	include before including F<ev.h>:
		3153
		3154	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3155
		3156	This would create a file F<wrap.h> which essentially looks like this:
		3157
		3158	#define ev_backend myprefix_ev_backend
		3159	#define ev_check_start myprefix_ev_check_start
		3160	#define ev_check_stop myprefix_ev_check_stop
		3161	...
		3162
		3163	=head2 EXAMPLES
		3164
		3165	For a real-world example of a program the includes libev
		3166	verbatim, you can have a look at the EV perl module
		3167	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		3168	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		3169	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		3170	will be compiled. It is pretty complex because it provides its own header
		3171	file.
		3172
		3173	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		3174	that everybody includes and which overrides some configure choices:
		3175
		3176	#define EV_MINIMAL 1
		3177	#define EV_USE_POLL 0
		3178	#define EV_MULTIPLICITY 0
		3179	#define EV_PERIODIC_ENABLE 0
		3180	#define EV_STAT_ENABLE 0
		3181	#define EV_FORK_ENABLE 0
		3182	#define EV_CONFIG_H <config.h>
		3183	#define EV_MINPRI 0
		3184	#define EV_MAXPRI 0
		3185
		3186	#include "ev++.h"
		3187
		3188	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		3189
		3190	#include "ev_cpp.h"
		3191	#include "ev.c"
		3192
		3193
		3194	=head1 THREADS AND COROUTINES
		3195
		3196	=head2 THREADS
		3197
		3198	Libev itself is completely thread-safe, but it uses no locking. This
		3199	means that you can use as many loops as you want in parallel, as long as
		3200	only one thread ever calls into one libev function with the same loop
		3201	parameter.
		3202
		3203	Or put differently: calls with different loop parameters can be done in
		3204	parallel from multiple threads, calls with the same loop parameter must be
		3205	done serially (but can be done from different threads, as long as only one
		3206	thread ever is inside a call at any point in time, e.g. by using a mutex
		3207	per loop).
		3208
		3209	If you want to know which design (one loop, locking, or multiple loops
		3210	without or something else still) is best for your problem, then I cannot
		3211	help you. I can give some generic advice however:
		3212
		3213	=over 4
		3214
		3215	=item * most applications have a main thread: use the default libev loop
		3216	in that thread, or create a separate thread running only the default loop.
		3217
		3218	This helps integrating other libraries or software modules that use libev
		3219	themselves and don't care/know about threading.
		3220
		3221	=item * one loop per thread is usually a good model.
		3222
		3223	Doing this is almost never wrong, sometimes a better-performance model
		3224	exists, but it is always a good start.
		3225
		3226	=item * other models exist, such as the leader/follower pattern, where one
		3227	loop is handed through multiple threads in a kind of round-robin fashion.
		3228
		3229	Choosing a model is hard - look around, learn, know that usually you can do
		3230	better than you currently do :-)
		3231
		3232	=item * often you need to talk to some other thread which blocks in the
		3233	event loop - C<ev_async> watchers can be used to wake them up from other
		3234	threads safely (or from signal contexts...).
		3235
		3236	=back
		3237
		3238	=head2 COROUTINES
		3239
		3240	Libev is much more accommodating to coroutines ("cooperative threads"):
		3241	libev fully supports nesting calls to it's functions from different
		3242	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3243	different coroutines and switch freely between both coroutines running the
		3244	loop, as long as you don't confuse yourself). The only exception is that
		3245	you must not do this from C<ev_periodic> reschedule callbacks.
		3246
		3247	Care has been invested into making sure that libev does not keep local
		3248	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3249	switches.
		3250
		3251
		3252	=head1 COMPLEXITIES
		3253
		3254	In this section the complexities of (many of) the algorithms used inside
		3255	libev will be explained. For complexity discussions about backends see the
		3256	documentation for C<ev_default_init>.
		3257
		3258	All of the following are about amortised time: If an array needs to be
		3259	extended, libev needs to realloc and move the whole array, but this
		3260	happens asymptotically never with higher number of elements, so O(1) might
		3261	mean it might do a lengthy realloc operation in rare cases, but on average
		3262	it is much faster and asymptotically approaches constant time.
		3263
		3264	=over 4
		3265
		3266	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3267
		3268	This means that, when you have a watcher that triggers in one hour and
		3269	there are 100 watchers that would trigger before that then inserting will
		3270	have to skip roughly seven (C<ld 100>) of these watchers.
		3271
		3272	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3273
		3274	That means that changing a timer costs less than removing/adding them
		3275	as only the relative motion in the event queue has to be paid for.
		3276
		3277	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3278
		3279	These just add the watcher into an array or at the head of a list.
		3280
		3281	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3282
		3283	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3284
		3285	These watchers are stored in lists then need to be walked to find the
		3286	correct watcher to remove. The lists are usually short (you don't usually
		3287	have many watchers waiting for the same fd or signal).
		3288
		3289	=item Finding the next timer in each loop iteration: O(1)
		3290
		3291	By virtue of using a binary or 4-heap, the next timer is always found at a
		3292	fixed position in the storage array.
		3293
		3294	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3295
		3296	A change means an I/O watcher gets started or stopped, which requires
		3297	libev to recalculate its status (and possibly tell the kernel, depending
		3298	on backend and whether C<ev_io_set> was used).
		3299
		3300	=item Activating one watcher (putting it into the pending state): O(1)
		3301
		3302	=item Priority handling: O(number_of_priorities)
		3303
		3304	Priorities are implemented by allocating some space for each
		3305	priority. When doing priority-based operations, libev usually has to
		3306	linearly search all the priorities, but starting/stopping and activating
		3307	watchers becomes O(1) w.r.t. priority handling.
		3308
		3309	=item Sending an ev_async: O(1)
		3310
		3311	=item Processing ev_async_send: O(number_of_async_watchers)
		3312
		3313	=item Processing signals: O(max_signal_number)
		3314
		3315	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3316	calls in the current loop iteration. Checking for async and signal events
		3317	involves iterating over all running async watchers or all signal numbers.
		3318
		3319	=back
		3320
		3321
		3322	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3323
		3324	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3325	requires, and its I/O model is fundamentally incompatible with the POSIX
		3326	model. Libev still offers limited functionality on this platform in
		3327	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3328	descriptors. This only applies when using Win32 natively, not when using
		3329	e.g. cygwin.
		3330
		3331	Lifting these limitations would basically require the full
		3332	re-implementation of the I/O system. If you are into these kinds of
		3333	things, then note that glib does exactly that for you in a very portable
		3334	way (note also that glib is the slowest event library known to man).
		3335
		3336	There is no supported compilation method available on windows except
		3337	embedding it into other applications.
		3338
		3339	Not a libev limitation but worth mentioning: windows apparently doesn't
		3340	accept large writes: instead of resulting in a partial write, windows will
		3341	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3342	so make sure you only write small amounts into your sockets (less than a
		3343	megabyte seems safe, but thsi apparently depends on the amount of memory
		3344	available).
		3345
		3346	Due to the many, low, and arbitrary limits on the win32 platform and
		3347	the abysmal performance of winsockets, using a large number of sockets
		3348	is not recommended (and not reasonable). If your program needs to use
		3349	more than a hundred or so sockets, then likely it needs to use a totally
		3350	different implementation for windows, as libev offers the POSIX readiness
		3351	notification model, which cannot be implemented efficiently on windows
		3352	(Microsoft monopoly games).
		3353
		3354	A typical way to use libev under windows is to embed it (see the embedding
		3355	section for details) and use the following F<evwrap.h> header file instead
		3356	of F<ev.h>:
		3357
		3358	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3359	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3360
		3361	#include "ev.h"
		3362
		3363	And compile the following F<evwrap.c> file into your project (make sure
		3364	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3365
		3366	#include "evwrap.h"
		3367	#include "ev.c"
		3368
		3369	=over 4
		3370
		3371	=item The winsocket select function
		3372
		3373	The winsocket C<select> function doesn't follow POSIX in that it
		3374	requires socket I<handles> and not socket I<file descriptors> (it is
		3375	also extremely buggy). This makes select very inefficient, and also
		3376	requires a mapping from file descriptors to socket handles (the Microsoft
		3377	C runtime provides the function C<_open_osfhandle> for this). See the
		3378	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3379	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3380
		3381	The configuration for a "naked" win32 using the Microsoft runtime
		3382	libraries and raw winsocket select is:
		3383
		3384	#define EV_USE_SELECT 1
		3385	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3386
		3387	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3388	complexity in the O(n²) range when using win32.
		3389
		3390	=item Limited number of file descriptors
		3391
		3392	Windows has numerous arbitrary (and low) limits on things.
		3393
		3394	Early versions of winsocket's select only supported waiting for a maximum
		3395	of C<64> handles (probably owning to the fact that all windows kernels
		3396	can only wait for C<64> things at the same time internally; Microsoft
		3397	recommends spawning a chain of threads and wait for 63 handles and the
		3398	previous thread in each. Great).
		3399
		3400	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3401	to some high number (e.g. C<2048>) before compiling the winsocket select
		3402	call (which might be in libev or elsewhere, for example, perl does its own
		3403	select emulation on windows).
		3404
		3405	Another limit is the number of file descriptors in the Microsoft runtime
		3406	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3407	or something like this inside Microsoft). You can increase this by calling
		3408	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3409	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3410	libraries.
		3411
		3412	This might get you to about C<512> or C<2048> sockets (depending on
		3413	windows version and/or the phase of the moon). To get more, you need to
		3414	wrap all I/O functions and provide your own fd management, but the cost of
		3415	calling select (O(n²)) will likely make this unworkable.
		3416
		3417	=back
		3418
		3419
		3420	=head1 PORTABILITY REQUIREMENTS
		3421
		3422	In addition to a working ISO-C implementation, libev relies on a few
		3423	additional extensions:
		3424
		3425	=over 4
		3426
		3427	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3428	calling conventions regardless of C<ev_watcher_type *>.
		3429
		3430	Libev assumes not only that all watcher pointers have the same internal
		3431	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3432	assumes that the same (machine) code can be used to call any watcher
		3433	callback: The watcher callbacks have different type signatures, but libev
		3434	calls them using an C<ev_watcher *> internally.
		3435
		3436	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3437
		3438	The type C<sig_atomic_t volatile> (or whatever is defined as
		3439	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3440	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3441	believed to be sufficiently portable.
		3442
		3443	=item C<sigprocmask> must work in a threaded environment
		3444
		3445	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3446	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3447	pthread implementations will either allow C<sigprocmask> in the "main
		3448	thread" or will block signals process-wide, both behaviours would
		3449	be compatible with libev. Interaction between C<sigprocmask> and
		3450	C<pthread_sigmask> could complicate things, however.
		3451
		3452	The most portable way to handle signals is to block signals in all threads
		3453	except the initial one, and run the default loop in the initial thread as
		3454	well.
		3455
		3456	=item C<long> must be large enough for common memory allocation sizes
		3457
		3458	To improve portability and simplify using libev, libev uses C<long>
		3459	internally instead of C<size_t> when allocating its data structures. On
		3460	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3461	is still at least 31 bits everywhere, which is enough for hundreds of
		3462	millions of watchers.
		3463
		3464	=item C<double> must hold a time value in seconds with enough accuracy
		3465
		3466	The type C<double> is used to represent timestamps. It is required to
		3467	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3468	enough for at least into the year 4000. This requirement is fulfilled by
		3469	implementations implementing IEEE 754 (basically all existing ones).
		3470
		3471	=back
		3472
		3473	If you know of other additional requirements drop me a note.
		3474
		3475
		3476	=head1 COMPILER WARNINGS
		3477
		3478	Depending on your compiler and compiler settings, you might get no or a
		3479	lot of warnings when compiling libev code. Some people are apparently
		3480	scared by this.
		3481
		3482	However, these are unavoidable for many reasons. For one, each compiler
		3483	has different warnings, and each user has different tastes regarding
		3484	warning options. "Warn-free" code therefore cannot be a goal except when
		3485	targeting a specific compiler and compiler-version.
		3486
		3487	Another reason is that some compiler warnings require elaborate
		3488	workarounds, or other changes to the code that make it less clear and less
		3489	maintainable.
		3490
		3491	And of course, some compiler warnings are just plain stupid, or simply
		3492	wrong (because they don't actually warn about the condition their message
		3493	seems to warn about).
		3494
		3495	While libev is written to generate as few warnings as possible,
		3496	"warn-free" code is not a goal, and it is recommended not to build libev
		3497	with any compiler warnings enabled unless you are prepared to cope with
		3498	them (e.g. by ignoring them). Remember that warnings are just that:
		3499	warnings, not errors, or proof of bugs.
		3500
		3501
		3502	=head1 VALGRIND
		3503
		3504	Valgrind has a special section here because it is a popular tool that is
		3505	highly useful, but valgrind reports are very hard to interpret.
		3506
		3507	If you think you found a bug (memory leak, uninitialised data access etc.)
		3508	in libev, then check twice: If valgrind reports something like:
		3509
		3510	==2274== definitely lost: 0 bytes in 0 blocks.
		3511	==2274== possibly lost: 0 bytes in 0 blocks.
		3512	==2274== still reachable: 256 bytes in 1 blocks.
		3513
		3514	Then there is no memory leak. Similarly, under some circumstances,
		3515	valgrind might report kernel bugs as if it were a bug in libev, or it
		3516	might be confused (it is a very good tool, but only a tool).
		3517
		3518	If you are unsure about something, feel free to contact the mailing list
		3519	with the full valgrind report and an explanation on why you think this is
		3520	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3521	no bug" answer and take the chance of learning how to interpret valgrind
		3522	properly.
		3523
		3524	If you need, for some reason, empty reports from valgrind for your project
		3525	I suggest using suppression lists.
		3526
		3527
767	=head1 AUTHOR	3528	=head1 AUTHOR
768		3529
769	Marc Lehmann <libev@schmorp.de>.	3530	Marc Lehmann <libev@schmorp.de>.
770		3531

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