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Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC vs.
Revision 1.173 by root, Thu Aug 7 19:24:56 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 REPRESENTATION	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
51		142
52	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
53		144
54	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
55	library in any way.	146	library in any way.
…		…
60		151
61	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
62	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
63	you actually want to know.	154	you actually want to know.
64		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 ()>.
		161
65	=item int ev_version_major ()	162	=item int ev_version_major ()
66		163
67	=item int ev_version_minor ()	164	=item int ev_version_minor ()
68		165
69	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
70	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
71	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
72	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
73	version of the library your program was compiled against.	170	version of the library your program was compiled against.
74		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
75	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,
76	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
77	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
78	not a problem.	178	not a problem.
79		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
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		220
82	Sets the allocation function to use (the prototype is similar to the	221	Sets the allocation function to use (the prototype is similar - the
83	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
84	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
85	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
86	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.
87		230
88	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
89	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,
90	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.
91		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
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		256
94	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
95	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
96	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
97	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
98	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
99	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
100	(such as abort).	263	(such as abort).
101		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
102	=back	277	=back
103		278
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		280
106	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
107	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
108	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
109		284
110	If you use threads, a common model is to run the default event loop
111	in your main thread (or in a separate thread) and for each thread you
112	create, you also create another event loop. Libev itself does no locking
113	whatsoever, so if you mix calls to the same event loop in different
114	threads, make sure you lock (this is usually a bad idea, though, even if
115	done correctly, because it's hideous and inefficient).
116
117	=over 4	285	=over 4
118		286
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		288
121	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
122	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
123	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
124	flags).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		293
126	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
127	function.	295	function.
128		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
129	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
130	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>).
131		310
132	It supports the following flags:	311	The following flags are supported:
133		312
134	=over 4	313	=over 4
135		314
136	=item C<EVFLAG_AUTO>	315	=item C<EVFLAG_AUTO>
137		316
138	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
139	thing, believe me).	318	thing, believe me).
140		319
141	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
142		321
143	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
144	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
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	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
147	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
148	around bugs.	327	around bugs.
149		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
150	=item C<EVMETHOD_SELECT> (portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		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
152	=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)
153		365
154	=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.
155		372
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		374
158	=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.
159		382
160	=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.
161		388
162	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
163	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
164	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.
165		462
166	=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);
167		484
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		486
170	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
171	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
172	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
173	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
174		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
175	=item ev_default_destroy ()	502	=item ev_default_destroy ()
176		503
177	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
178	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
179	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>).
180		520
181	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
182		522
183	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
184	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
185		525
186	=item ev_default_fork ()	526	=item ev_default_fork ()
187		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
188	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
189	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
190	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
191	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.
192		534
193	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
194	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
195	have to call it.	537	you just fork+exec, you don't have to call it at all.
196		538
197	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
198	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
199	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
200		542
…		…
204		546
205	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
206	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
207	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.
208		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
209	=item unsigned int ev_method (loop)	565	=item unsigned int ev_backend (loop)
210		566
211	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
212	use.	568	use.
213		569
214	=item ev_tstamp ev_now (loop)	570	=item ev_tstamp ev_now (loop)
215		571
216	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
217	got events and started processing them. This timestamp does not change	573	received events and started processing them. This timestamp does not
218	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
219	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
220	occuring (or more correctly, the mainloop finding out about it).	576	event occurring (or more correctly, libev finding out about it).
221		577
222	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
223		579
224	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
225	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
226	events.	582	events.
227		583
228	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
229	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.
230		592
231	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
232	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
233	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.
234		596
235	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
236	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
237	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
238	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.
239		604
240	This flags value could be used to implement alternative looping
241	constructs, but the C<prepare> and C<check> watchers provide a better and
242	more generic mechanism.
243
244	Here are the gory details of what ev_loop does:	605	Here are the gory details of what C<ev_loop> does:
245		606
246	1. If there are no active watchers (reference count is zero), return.	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.
247	2. Queue and immediately call all prepare watchers.	610	- Queue and call all prepare watchers.
248	3. If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
249	4. Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
251	6. Calculate for how long to block.	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.
252	7. Block the process, waiting for events.	619	- Block the process, waiting for any events.
		620	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
254	9. Queue all outstanding timers.	622	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	623	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	625	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	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.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	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!
261		640
262	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
263		642
264	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
265	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
266	C<EVUNLOOP_ONE>, 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
267	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.
268		649
269	=item ev_ref (loop)	650	=item ev_ref (loop)
270		651
271	=item ev_unref (loop)	652	=item ev_unref (loop)
272		653
…		…
277	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
278	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
279	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
280	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
281	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
282	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.
283		735
284	=back	736	=back
		737
285		738
286	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
287		740
288	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
289	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
290	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:
291		744
292	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)
293	{	746	{
294	ev_io_stop (w);	747	ev_io_stop (w);
295	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
296	}	749	}
297		750
298	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
299	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
300	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
301	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
302	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
303	ev_loop (loop, 0);	756	ev_loop (loop, 0);
304		757
305	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
306	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,
307	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
308		761
309	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
310	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
311	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
312	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
313	is readable and/or writable).	766	is readable and/or writable).
314		767
315	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
316	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
…		…
322	*) >>), 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
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		777
325	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
326	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
327	reinitialise it or call its set method.	780	reinitialise it or call its C<set> macro.
328
329	You can check whether an event is active by calling the C<ev_is_active
330	(watcher *)> macro. To see whether an event is outstanding (but the
331	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.
333		781
334	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
335	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
336	third argument.	784	third argument.
337		785
…		…
361	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.
362		810
363	=item C<EV_CHILD>	811	=item C<EV_CHILD>
364		812
365	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.
366		818
367	=item C<EV_IDLE>	819	=item C<EV_IDLE>
368		820
369	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.
370		822
…		…
378	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
379	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
380	(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
381	C<ev_loop> from blocking).	833	C<ev_loop> from blocking).
382		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
383	=item C<EV_ERROR>	848	=item C<EV_ERROR>
384		849
385	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
386	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
387	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
388	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
389	with the watcher being stopped.	854	with the watcher being stopped.
390		855
391	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,
392	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
393	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
394	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
395	programs, though, so beware.	860	programs, though, so beware.
396		861
397	=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
398		983
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		985
401	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
402	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
403	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
404	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
405	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
406	data:	991	data:
407		992
408	struct my_io	993	struct my_io
409	{	994	{
410	struct ev_io io;	995	struct ev_io io;
411	int otherfd;	996	int otherfd;
412	void *somedata;	997	void *somedata;
413	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
414	}	999	}
415		1000
416	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
417	can cast it back to your own type:	1002	can cast it back to your own type:
418		1003
419	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)
420	{	1005	{
421	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
422	...	1007	...
423	}	1008	}
424		1009
425	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
426	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	}
427		1041
428		1042
429	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
430		1044
431	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
432	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.
433		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
434	=head2 C<ev_io> - is this file descriptor readable or writable	1059	=head2 C<ev_io> - is this file descriptor readable or writable?
435		1060
436	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
437	in each iteration of the event loop (This behaviour is called	1062	in each iteration of the event loop, or, more precisely, when reading
438	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
439	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
440	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.
441		1068
442	In general you can register as many read and/or write event watchers per	1069	In general you can register as many read and/or write event watchers per
443	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
444	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
445	required if you know what you are doing).	1072	required if you know what you are doing).
446		1073
447	You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing
450	to the same underlying file/socket etc. description (that is, they share
451	the same underlying "file open").
452
453	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
454	(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
455	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 reading from a pipe whose other end has been closed, your program
		1140	gets send a SIGPIPE, which, by default, aborts your program. For most
		1141	programs this is sensible behaviour, for daemons, this is usually
		1142	undesirable.
		1143
		1144	So when you encounter spurious, unexplained daemon exits, make sure you
		1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1146	somewhere, as that would have given you a big clue).
		1147
		1148
		1149	=head3 Watcher-Specific Functions
456		1150
457	=over 4	1151	=over 4
458		1152
459	=item ev_io_init (ev_io *, callback, int fd, int events)	1153	=item ev_io_init (ev_io *, callback, int fd, int events)
460		1154
461	=item ev_io_set (ev_io *, int fd, int events)	1155	=item ev_io_set (ev_io *, int fd, int events)
462		1156
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
464	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
465	EV_WRITE> to receive the given events.	1159	C<EV_READ | EV_WRITE> to receive the given events.
		1160
		1161	=item int fd [read-only]
		1162
		1163	The file descriptor being watched.
		1164
		1165	=item int events [read-only]
		1166
		1167	The events being watched.
466		1168
467	=back	1169	=back
468		1170
		1171	=head3 Examples
		1172
		1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1174	readable, but only once. Since it is likely line-buffered, you could
		1175	attempt to read a whole line in the callback.
		1176
		1177	static void
		1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1179	{
		1180	ev_io_stop (loop, w);
		1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1182	}
		1183
		1184	...
		1185	struct ev_loop *loop = ev_default_init (0);
		1186	struct ev_io stdin_readable;
		1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1188	ev_io_start (loop, &stdin_readable);
		1189	ev_loop (loop, 0);
		1190
		1191
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	1192	=head2 C<ev_timer> - relative and optionally repeating timeouts
470		1193
471	Timer watchers are simple relative timers that generate an event after a	1194	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	1195	given time, and optionally repeating in regular intervals after that.
473		1196
474	The timers are based on real time, that is, if you register an event that	1197	The timers are based on real time, that is, if you register an event that
475	times out after an hour and you reset your system clock to last years	1198	times out after an hour and you reset your system clock to January last
476	time, it will still time out after (roughly) and hour. "Roughly" because	1199	year, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	1201	monotonic clock option helps a lot here).
479		1202
480	The relative timeouts are calculated relative to the C<ev_now ()>	1203	The relative timeouts are calculated relative to the C<ev_now ()>
481	time. This is usually the right thing as this timestamp refers to the time	1204	time. This is usually the right thing as this timestamp refers to the time
482	of the event triggering whatever timeout you are modifying/starting. If	1205	of the event triggering whatever timeout you are modifying/starting. If
483	you suspect event processing to be delayed and you *need* to base the timeout	1206	you suspect event processing to be delayed and you I<need> to base the timeout
484	on the current time, use something like this to adjust for this:	1207	on the current time, use something like this to adjust for this:
485		1208
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
487		1210
		1211	The callback is guaranteed to be invoked only after its timeout has passed,
		1212	but if multiple timers become ready during the same loop iteration then
		1213	order of execution is undefined.
		1214
		1215	=head3 Watcher-Specific Functions and Data Members
		1216
488	=over 4	1217	=over 4
489		1218
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1219	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		1220
492	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1221	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
493		1222
494	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1223	Configure the timer to trigger after C<after> seconds. If C<repeat>
495	C<0.>, then it will automatically be stopped. If it is positive, then the	1224	is C<0.>, then it will automatically be stopped once the timeout is
496	timer will automatically be configured to trigger again C<repeat> seconds	1225	reached. If it is positive, then the timer will automatically be
497	later, again, and again, until stopped manually.	1226	configured to trigger again C<repeat> seconds later, again, and again,
		1227	until stopped manually.
498		1228
499	The timer itself will do a best-effort at avoiding drift, that is, if you	1229	The timer itself will do a best-effort at avoiding drift, that is, if
500	configure a timer to trigger every 10 seconds, then it will trigger at	1230	you configure a timer to trigger every 10 seconds, then it will normally
501	exactly 10 second intervals. If, however, your program cannot keep up with	1231	trigger at exactly 10 second intervals. If, however, your program cannot
502	the timer (because it takes longer than those 10 seconds to do stuff) the	1232	keep up with the timer (because it takes longer than those 10 seconds to
503	timer will not fire more than once per event loop iteration.	1233	do stuff) the timer will not fire more than once per event loop iteration.
504		1234
505	=item ev_timer_again (loop)	1235	=item ev_timer_again (loop, ev_timer *)
506		1236
507	This will act as if the timer timed out and restart it again if it is	1237	This will act as if the timer timed out and restart it again if it is
508	repeating. The exact semantics are:	1238	repeating. The exact semantics are:
509		1239
		1240	If the timer is pending, its pending status is cleared.
		1241
510	If the timer is started but nonrepeating, stop it.	1242	If the timer is started but non-repeating, stop it (as if it timed out).
511		1243
512	If the timer is repeating, either start it if necessary (with the repeat	1244	If the timer is repeating, either start it if necessary (with the
513	value), or reset the running timer to the repeat value.	1245	C<repeat> value), or reset the running timer to the C<repeat> value.
514		1246
515	This sounds a bit complicated, but here is a useful and typical	1247	This sounds a bit complicated, but here is a useful and typical
516	example: Imagine you have a tcp connection and you want a so-called idle	1248	example: Imagine you have a TCP connection and you want a so-called idle
517	timeout, that is, you want to be called when there have been, say, 60	1249	timeout, that is, you want to be called when there have been, say, 60
518	seconds of inactivity on the socket. The easiest way to do this is to	1250	seconds of inactivity on the socket. The easiest way to do this is to
519	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
520	time you successfully read or write some data. If you go into an idle	1252	C<ev_timer_again> each time you successfully read or write some data. If
521	state where you do not expect data to travel on the socket, you can stop	1253	you go into an idle state where you do not expect data to travel on the
522	the timer, and again will automatically restart it if need be.	1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1255	automatically restart it if need be.
		1256
		1257	That means you can ignore the C<after> value and C<ev_timer_start>
		1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1259
		1260	ev_timer_init (timer, callback, 0., 5.);
		1261	ev_timer_again (loop, timer);
		1262	...
		1263	timer->again = 17.;
		1264	ev_timer_again (loop, timer);
		1265	...
		1266	timer->again = 10.;
		1267	ev_timer_again (loop, timer);
		1268
		1269	This is more slightly efficient then stopping/starting the timer each time
		1270	you want to modify its timeout value.
		1271
		1272	=item ev_tstamp repeat [read-write]
		1273
		1274	The current C<repeat> value. Will be used each time the watcher times out
		1275	or C<ev_timer_again> is called and determines the next timeout (if any),
		1276	which is also when any modifications are taken into account.
523		1277
524	=back	1278	=back
525		1279
		1280	=head3 Examples
		1281
		1282	Example: Create a timer that fires after 60 seconds.
		1283
		1284	static void
		1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1286	{
		1287	.. one minute over, w is actually stopped right here
		1288	}
		1289
		1290	struct ev_timer mytimer;
		1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1292	ev_timer_start (loop, &mytimer);
		1293
		1294	Example: Create a timeout timer that times out after 10 seconds of
		1295	inactivity.
		1296
		1297	static void
		1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1299	{
		1300	.. ten seconds without any activity
		1301	}
		1302
		1303	struct ev_timer mytimer;
		1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1305	ev_timer_again (&mytimer); /* start timer */
		1306	ev_loop (loop, 0);
		1307
		1308	// and in some piece of code that gets executed on any "activity":
		1309	// reset the timeout to start ticking again at 10 seconds
		1310	ev_timer_again (&mytimer);
		1311
		1312
526	=head2 C<ev_periodic> - to cron or not to cron	1313	=head2 C<ev_periodic> - to cron or not to cron?
527		1314
528	Periodic watchers are also timers of a kind, but they are very versatile	1315	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	1316	(and unfortunately a bit complex).
530		1317
531	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
532	but on wallclock time (absolute time). You can tell a periodic watcher	1319	but on wall clock time (absolute time). You can tell a periodic watcher
533	to trigger "at" some specific point in time. For example, if you tell a	1320	to trigger after some specific point in time. For example, if you tell a
534	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
535	+ 10.>) and then reset your system clock to the last year, then it will	1322	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1323	clock to January of the previous year, then it will take more than year
536	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
537	roughly 10 seconds later and of course not if you reset your system time	1325	roughly 10 seconds later as it uses a relative timeout).
538	again).
539		1326
540	They can also be used to implement vastly more complex timers, such as	1327	C<ev_periodic>s can also be used to implement vastly more complex timers,
541	triggering an event on eahc midnight, local time.	1328	such as triggering an event on each "midnight, local time", or other
		1329	complicated, rules.
		1330
		1331	As with timers, the callback is guaranteed to be invoked only when the
		1332	time (C<at>) has passed, but if multiple periodic timers become ready
		1333	during the same loop iteration then order of execution is undefined.
		1334
		1335	=head3 Watcher-Specific Functions and Data Members
542		1336
543	=over 4	1337	=over 4
544		1338
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		1340
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		1342
549	Lots of arguments, lets sort it out... There are basically three modes of	1343	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	1344	operation, and we will explain them from simplest to complex:
551		1345
552
553	=over 4	1346	=over 4
554		1347
555	=item * absolute timer (interval = reschedule_cb = 0)	1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)
556		1349
557	In this configuration the watcher triggers an event at the wallclock time	1350	In this configuration the watcher triggers an event after the wall clock
558	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1351	time C<at> has passed and doesn't repeat. It will not adjust when a time
559	that is, if it is to be run at January 1st 2011 then it will run when the	1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will
560	system time reaches or surpasses this time.	1353	run when the system time reaches or surpasses this time.
561		1354
562	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
563		1356
564	In this mode the watcher will always be scheduled to time out at the next	1357	In this mode the watcher will always be scheduled to time out at the next
565	C<at + N * interval> time (for some integer N) and then repeat, regardless	1358	C<at + N * interval> time (for some integer N, which can also be negative)
566	of any time jumps.	1359	and then repeat, regardless of any time jumps.
567		1360
568	This can be used to create timers that do not drift with respect to system	1361	This can be used to create timers that do not drift with respect to system
569	time:	1362	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1363	the hour:
570		1364
571	ev_periodic_set (&periodic, 0., 3600., 0);	1365	ev_periodic_set (&periodic, 0., 3600., 0);
572		1366
573	This doesn't mean there will always be 3600 seconds in between triggers,	1367	This doesn't mean there will always be 3600 seconds in between triggers,
574	but only that the the callback will be called when the system time shows a	1368	but only that the callback will be called when the system time shows a
575	full hour (UTC), or more correctly, when the system time is evenly divisible	1369	full hour (UTC), or more correctly, when the system time is evenly divisible
576	by 3600.	1370	by 3600.
577		1371
578	Another way to think about it (for the mathematically inclined) is that	1372	Another way to think about it (for the mathematically inclined) is that
579	C<ev_periodic> will try to run the callback in this mode at the next possible	1373	C<ev_periodic> will try to run the callback in this mode at the next possible
580	time where C<time = at (mod interval)>, regardless of any time jumps.	1374	time where C<time = at (mod interval)>, regardless of any time jumps.
581		1375
		1376	For numerical stability it is preferable that the C<at> value is near
		1377	C<ev_now ()> (the current time), but there is no range requirement for
		1378	this value, and in fact is often specified as zero.
		1379
		1380	Note also that there is an upper limit to how often a timer can fire (CPU
		1381	speed for example), so if C<interval> is very small then timing stability
		1382	will of course deteriorate. Libev itself tries to be exact to be about one
		1383	millisecond (if the OS supports it and the machine is fast enough).
		1384
582	=item * manual reschedule mode (reschedule_cb = callback)	1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
583		1386
584	In this mode the values for C<interval> and C<at> are both being	1387	In this mode the values for C<interval> and C<at> are both being
585	ignored. Instead, each time the periodic watcher gets scheduled, the	1388	ignored. Instead, each time the periodic watcher gets scheduled, the
586	reschedule callback will be called with the watcher as first, and the	1389	reschedule callback will be called with the watcher as first, and the
587	current time as second argument.	1390	current time as second argument.
588		1391
589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
590	ever, or make any event loop modifications>. If you need to stop it,	1393	ever, or make ANY event loop modifications whatsoever>.
591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
592	starting a prepare watcher).
593		1394
		1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1397	only event loop modification you are allowed to do).
		1398
594	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
595	ev_tstamp now)>, e.g.:	1400	*w, ev_tstamp now)>, e.g.:
596		1401
597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
598	{	1403	{
599	return now + 60.;	1404	return now + 60.;
600	}	1405	}
…		…
602	It must return the next time to trigger, based on the passed time value	1407	It must return the next time to trigger, based on the passed time value
603	(that is, the lowest time value larger than to the second argument). It	1408	(that is, the lowest time value larger than to the second argument). It
604	will usually be called just before the callback will be triggered, but	1409	will usually be called just before the callback will be triggered, but
605	might be called at other times, too.	1410	might be called at other times, too.
606		1411
607	NOTE: I<< This callback must always return a time that is later than the	1412	NOTE: I<< This callback must always return a time that is higher than or
608	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1413	equal to the passed C<now> value >>.
609		1414
610	This can be used to create very complex timers, such as a timer that	1415	This can be used to create very complex timers, such as a timer that
611	triggers on each midnight, local time. To do this, you would calculate the	1416	triggers on "next midnight, local time". To do this, you would calculate the
612	next midnight after C<now> and return the timestamp value for this. How	1417	next midnight after C<now> and return the timestamp value for this. How
613	you do this is, again, up to you (but it is not trivial, which is the main	1418	you do this is, again, up to you (but it is not trivial, which is the main
614	reason I omitted it as an example).	1419	reason I omitted it as an example).
615		1420
616	=back	1421	=back
…		…
620	Simply stops and restarts the periodic watcher again. This is only useful	1425	Simply stops and restarts the periodic watcher again. This is only useful
621	when you changed some parameters or the reschedule callback would return	1426	when you changed some parameters or the reschedule callback would return
622	a different time than the last time it was called (e.g. in a crond like	1427	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	1428	program when the crontabs have changed).
624		1429
		1430	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1431
		1432	When active, returns the absolute time that the watcher is supposed to
		1433	trigger next.
		1434
		1435	=item ev_tstamp offset [read-write]
		1436
		1437	When repeating, this contains the offset value, otherwise this is the
		1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1439
		1440	Can be modified any time, but changes only take effect when the periodic
		1441	timer fires or C<ev_periodic_again> is being called.
		1442
		1443	=item ev_tstamp interval [read-write]
		1444
		1445	The current interval value. Can be modified any time, but changes only
		1446	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1447	called.
		1448
		1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1450
		1451	The current reschedule callback, or C<0>, if this functionality is
		1452	switched off. Can be changed any time, but changes only take effect when
		1453	the periodic timer fires or C<ev_periodic_again> is being called.
		1454
625	=back	1455	=back
626		1456
		1457	=head3 Examples
		1458
		1459	Example: Call a callback every hour, or, more precisely, whenever the
		1460	system clock is divisible by 3600. The callback invocation times have
		1461	potentially a lot of jitter, but good long-term stability.
		1462
		1463	static void
		1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1465	{
		1466	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1467	}
		1468
		1469	struct ev_periodic hourly_tick;
		1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1471	ev_periodic_start (loop, &hourly_tick);
		1472
		1473	Example: The same as above, but use a reschedule callback to do it:
		1474
		1475	#include <math.h>
		1476
		1477	static ev_tstamp
		1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1479	{
		1480	return fmod (now, 3600.) + 3600.;
		1481	}
		1482
		1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1484
		1485	Example: Call a callback every hour, starting now:
		1486
		1487	struct ev_periodic hourly_tick;
		1488	ev_periodic_init (&hourly_tick, clock_cb,
		1489	fmod (ev_now (loop), 3600.), 3600., 0);
		1490	ev_periodic_start (loop, &hourly_tick);
		1491
		1492
627	=head2 C<ev_signal> - signal me when a signal gets signalled	1493	=head2 C<ev_signal> - signal me when a signal gets signalled!
628		1494
629	Signal watchers will trigger an event when the process receives a specific	1495	Signal watchers will trigger an event when the process receives a specific
630	signal one or more times. Even though signals are very asynchronous, libev	1496	signal one or more times. Even though signals are very asynchronous, libev
631	will try it's best to deliver signals synchronously, i.e. as part of the	1497	will try it's best to deliver signals synchronously, i.e. as part of the
632	normal event processing, like any other event.	1498	normal event processing, like any other event.
…		…
636	with the kernel (thus it coexists with your own signal handlers as long	1502	with the kernel (thus it coexists with your own signal handlers as long
637	as you don't register any with libev). Similarly, when the last signal	1503	as you don't register any with libev). Similarly, when the last signal
638	watcher for a signal is stopped libev will reset the signal handler to	1504	watcher for a signal is stopped libev will reset the signal handler to
639	SIG_DFL (regardless of what it was set to before).	1505	SIG_DFL (regardless of what it was set to before).
640		1506
		1507	If possible and supported, libev will install its handlers with
		1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1509	interrupted. If you have a problem with system calls getting interrupted by
		1510	signals you can block all signals in an C<ev_check> watcher and unblock
		1511	them in an C<ev_prepare> watcher.
		1512
		1513	=head3 Watcher-Specific Functions and Data Members
		1514
641	=over 4	1515	=over 4
642		1516
643	=item ev_signal_init (ev_signal *, callback, int signum)	1517	=item ev_signal_init (ev_signal *, callback, int signum)
644		1518
645	=item ev_signal_set (ev_signal *, int signum)	1519	=item ev_signal_set (ev_signal *, int signum)
646		1520
647	Configures the watcher to trigger on the given signal number (usually one	1521	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1522	of the C<SIGxxx> constants).
649		1523
		1524	=item int signum [read-only]
		1525
		1526	The signal the watcher watches out for.
		1527
650	=back	1528	=back
651		1529
		1530	=head3 Examples
		1531
		1532	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1533
		1534	static void
		1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1536	{
		1537	ev_unloop (loop, EVUNLOOP_ALL);
		1538	}
		1539
		1540	struct ev_signal signal_watcher;
		1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1542	ev_signal_start (loop, &sigint_cb);
		1543
		1544
652	=head2 C<ev_child> - wait for pid status changes	1545	=head2 C<ev_child> - watch out for process status changes
653		1546
654	Child watchers trigger when your process receives a SIGCHLD in response to	1547	Child watchers trigger when your process receives a SIGCHLD in response to
655	some child status changes (most typically when a child of yours dies).	1548	some child status changes (most typically when a child of yours dies). It
		1549	is permissible to install a child watcher I<after> the child has been
		1550	forked (which implies it might have already exited), as long as the event
		1551	loop isn't entered (or is continued from a watcher).
		1552
		1553	Only the default event loop is capable of handling signals, and therefore
		1554	you can only register child watchers in the default event loop.
		1555
		1556	=head3 Process Interaction
		1557
		1558	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1559	initialised. This is necessary to guarantee proper behaviour even if
		1560	the first child watcher is started after the child exits. The occurrence
		1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1562	synchronously as part of the event loop processing. Libev always reaps all
		1563	children, even ones not watched.
		1564
		1565	=head3 Overriding the Built-In Processing
		1566
		1567	Libev offers no special support for overriding the built-in child
		1568	processing, but if your application collides with libev's default child
		1569	handler, you can override it easily by installing your own handler for
		1570	C<SIGCHLD> after initialising the default loop, and making sure the
		1571	default loop never gets destroyed. You are encouraged, however, to use an
		1572	event-based approach to child reaping and thus use libev's support for
		1573	that, so other libev users can use C<ev_child> watchers freely.
		1574
		1575	=head3 Stopping the Child Watcher
		1576
		1577	Currently, the child watcher never gets stopped, even when the
		1578	child terminates, so normally one needs to stop the watcher in the
		1579	callback. Future versions of libev might stop the watcher automatically
		1580	when a child exit is detected.
		1581
		1582	=head3 Watcher-Specific Functions and Data Members
656		1583
657	=over 4	1584	=over 4
658		1585
659	=item ev_child_init (ev_child *, callback, int pid)	1586	=item ev_child_init (ev_child *, callback, int pid, int trace)
660		1587
661	=item ev_child_set (ev_child *, int pid)	1588	=item ev_child_set (ev_child *, int pid, int trace)
662		1589
663	Configures the watcher to wait for status changes of process C<pid> (or	1590	Configures the watcher to wait for status changes of process C<pid> (or
664	I<any> process if C<pid> is specified as C<0>). The callback can look	1591	I<any> process if C<pid> is specified as C<0>). The callback can look
665	at the C<rstatus> member of the C<ev_child> watcher structure to see	1592	at the C<rstatus> member of the C<ev_child> watcher structure to see
666	the status word (use the macros from C<sys/wait.h> and see your systems	1593	the status word (use the macros from C<sys/wait.h> and see your systems
667	C<waitpid> documentation). The C<rpid> member contains the pid of the	1594	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1595	process causing the status change. C<trace> must be either C<0> (only
		1596	activate the watcher when the process terminates) or C<1> (additionally
		1597	activate the watcher when the process is stopped or continued).
		1598
		1599	=item int pid [read-only]
		1600
		1601	The process id this watcher watches out for, or C<0>, meaning any process id.
		1602
		1603	=item int rpid [read-write]
		1604
		1605	The process id that detected a status change.
		1606
		1607	=item int rstatus [read-write]
		1608
		1609	The process exit/trace status caused by C<rpid> (see your systems
		1610	C<waitpid> and C<sys/wait.h> documentation for details).
669		1611
670	=back	1612	=back
671		1613
		1614	=head3 Examples
		1615
		1616	Example: C<fork()> a new process and install a child handler to wait for
		1617	its completion.
		1618
		1619	ev_child cw;
		1620
		1621	static void
		1622	child_cb (EV_P_ struct ev_child *w, int revents)
		1623	{
		1624	ev_child_stop (EV_A_ w);
		1625	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1626	}
		1627
		1628	pid_t pid = fork ();
		1629
		1630	if (pid < 0)
		1631	// error
		1632	else if (pid == 0)
		1633	{
		1634	// the forked child executes here
		1635	exit (1);
		1636	}
		1637	else
		1638	{
		1639	ev_child_init (&cw, child_cb, pid, 0);
		1640	ev_child_start (EV_DEFAULT_ &cw);
		1641	}
		1642
		1643
		1644	=head2 C<ev_stat> - did the file attributes just change?
		1645
		1646	This watches a file system path for attribute changes. That is, it calls
		1647	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1648	compared to the last time, invoking the callback if it did.
		1649
		1650	The path does not need to exist: changing from "path exists" to "path does
		1651	not exist" is a status change like any other. The condition "path does
		1652	not exist" is signified by the C<st_nlink> field being zero (which is
		1653	otherwise always forced to be at least one) and all the other fields of
		1654	the stat buffer having unspecified contents.
		1655
		1656	The path I<should> be absolute and I<must not> end in a slash. If it is
		1657	relative and your working directory changes, the behaviour is undefined.
		1658
		1659	Since there is no standard to do this, the portable implementation simply
		1660	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1661	can specify a recommended polling interval for this case. If you specify
		1662	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1663	unspecified default> value will be used (which you can expect to be around
		1664	five seconds, although this might change dynamically). Libev will also
		1665	impose a minimum interval which is currently around C<0.1>, but thats
		1666	usually overkill.
		1667
		1668	This watcher type is not meant for massive numbers of stat watchers,
		1669	as even with OS-supported change notifications, this can be
		1670	resource-intensive.
		1671
		1672	At the time of this writing, only the Linux inotify interface is
		1673	implemented (implementing kqueue support is left as an exercise for the
		1674	reader, note, however, that the author sees no way of implementing ev_stat
		1675	semantics with kqueue). Inotify will be used to give hints only and should
		1676	not change the semantics of C<ev_stat> watchers, which means that libev
		1677	sometimes needs to fall back to regular polling again even with inotify,
		1678	but changes are usually detected immediately, and if the file exists there
		1679	will be no polling.
		1680
		1681	=head3 ABI Issues (Largefile Support)
		1682
		1683	Libev by default (unless the user overrides this) uses the default
		1684	compilation environment, which means that on systems with large file
		1685	support disabled by default, you get the 32 bit version of the stat
		1686	structure. When using the library from programs that change the ABI to
		1687	use 64 bit file offsets the programs will fail. In that case you have to
		1688	compile libev with the same flags to get binary compatibility. This is
		1689	obviously the case with any flags that change the ABI, but the problem is
		1690	most noticeably disabled with ev_stat and large file support.
		1691
		1692	The solution for this is to lobby your distribution maker to make large
		1693	file interfaces available by default (as e.g. FreeBSD does) and not
		1694	optional. Libev cannot simply switch on large file support because it has
		1695	to exchange stat structures with application programs compiled using the
		1696	default compilation environment.
		1697
		1698	=head3 Inotify
		1699
		1700	When C<inotify (7)> support has been compiled into libev (generally only
		1701	available on Linux) and present at runtime, it will be used to speed up
		1702	change detection where possible. The inotify descriptor will be created lazily
		1703	when the first C<ev_stat> watcher is being started.
		1704
		1705	Inotify presence does not change the semantics of C<ev_stat> watchers
		1706	except that changes might be detected earlier, and in some cases, to avoid
		1707	making regular C<stat> calls. Even in the presence of inotify support
		1708	there are many cases where libev has to resort to regular C<stat> polling.
		1709
		1710	(There is no support for kqueue, as apparently it cannot be used to
		1711	implement this functionality, due to the requirement of having a file
		1712	descriptor open on the object at all times).
		1713
		1714	=head3 The special problem of stat time resolution
		1715
		1716	The C<stat ()> system call only supports full-second resolution portably, and
		1717	even on systems where the resolution is higher, many file systems still
		1718	only support whole seconds.
		1719
		1720	That means that, if the time is the only thing that changes, you can
		1721	easily miss updates: on the first update, C<ev_stat> detects a change and
		1722	calls your callback, which does something. When there is another update
		1723	within the same second, C<ev_stat> will be unable to detect it as the stat
		1724	data does not change.
		1725
		1726	The solution to this is to delay acting on a change for slightly more
		1727	than a second (or till slightly after the next full second boundary), using
		1728	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1729	ev_timer_again (loop, w)>).
		1730
		1731	The C<.02> offset is added to work around small timing inconsistencies
		1732	of some operating systems (where the second counter of the current time
		1733	might be be delayed. One such system is the Linux kernel, where a call to
		1734	C<gettimeofday> might return a timestamp with a full second later than
		1735	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1736	update file times then there will be a small window where the kernel uses
		1737	the previous second to update file times but libev might already execute
		1738	the timer callback).
		1739
		1740	=head3 Watcher-Specific Functions and Data Members
		1741
		1742	=over 4
		1743
		1744	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1745
		1746	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1747
		1748	Configures the watcher to wait for status changes of the given
		1749	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1750	be detected and should normally be specified as C<0> to let libev choose
		1751	a suitable value. The memory pointed to by C<path> must point to the same
		1752	path for as long as the watcher is active.
		1753
		1754	The callback will receive C<EV_STAT> when a change was detected, relative
		1755	to the attributes at the time the watcher was started (or the last change
		1756	was detected).
		1757
		1758	=item ev_stat_stat (loop, ev_stat *)
		1759
		1760	Updates the stat buffer immediately with new values. If you change the
		1761	watched path in your callback, you could call this function to avoid
		1762	detecting this change (while introducing a race condition if you are not
		1763	the only one changing the path). Can also be useful simply to find out the
		1764	new values.
		1765
		1766	=item ev_statdata attr [read-only]
		1767
		1768	The most-recently detected attributes of the file. Although the type is
		1769	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1770	suitable for your system, but you can only rely on the POSIX-standardised
		1771	members to be present. If the C<st_nlink> member is C<0>, then there was
		1772	some error while C<stat>ing the file.
		1773
		1774	=item ev_statdata prev [read-only]
		1775
		1776	The previous attributes of the file. The callback gets invoked whenever
		1777	C<prev> != C<attr>, or, more precisely, one or more of these members
		1778	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1779	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
		1780
		1781	=item ev_tstamp interval [read-only]
		1782
		1783	The specified interval.
		1784
		1785	=item const char *path [read-only]
		1786
		1787	The file system path that is being watched.
		1788
		1789	=back
		1790
		1791	=head3 Examples
		1792
		1793	Example: Watch C</etc/passwd> for attribute changes.
		1794
		1795	static void
		1796	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1797	{
		1798	/* /etc/passwd changed in some way */
		1799	if (w->attr.st_nlink)
		1800	{
		1801	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1802	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1803	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1804	}
		1805	else
		1806	/* you shalt not abuse printf for puts */
		1807	puts ("wow, /etc/passwd is not there, expect problems. "
		1808	"if this is windows, they already arrived\n");
		1809	}
		1810
		1811	...
		1812	ev_stat passwd;
		1813
		1814	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1815	ev_stat_start (loop, &passwd);
		1816
		1817	Example: Like above, but additionally use a one-second delay so we do not
		1818	miss updates (however, frequent updates will delay processing, too, so
		1819	one might do the work both on C<ev_stat> callback invocation I<and> on
		1820	C<ev_timer> callback invocation).
		1821
		1822	static ev_stat passwd;
		1823	static ev_timer timer;
		1824
		1825	static void
		1826	timer_cb (EV_P_ ev_timer *w, int revents)
		1827	{
		1828	ev_timer_stop (EV_A_ w);
		1829
		1830	/* now it's one second after the most recent passwd change */
		1831	}
		1832
		1833	static void
		1834	stat_cb (EV_P_ ev_stat *w, int revents)
		1835	{
		1836	/* reset the one-second timer */
		1837	ev_timer_again (EV_A_ &timer);
		1838	}
		1839
		1840	...
		1841	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1842	ev_stat_start (loop, &passwd);
		1843	ev_timer_init (&timer, timer_cb, 0., 1.02);
		1844
		1845
672	=head2 C<ev_idle> - when you've got nothing better to do	1846	=head2 C<ev_idle> - when you've got nothing better to do...
673		1847
674	Idle watchers trigger events when there are no other events are pending	1848	Idle watchers trigger events when no other events of the same or higher
675	(prepare, check and other idle watchers do not count). That is, as long	1849	priority are pending (prepare, check and other idle watchers do not
676	as your process is busy handling sockets or timeouts (or even signals,	1850	count).
677	imagine) it will not be triggered. But when your process is idle all idle	1851
678	watchers are being called again and again, once per event loop iteration -	1852	That is, as long as your process is busy handling sockets or timeouts
		1853	(or even signals, imagine) of the same or higher priority it will not be
		1854	triggered. But when your process is idle (or only lower-priority watchers
		1855	are pending), the idle watchers are being called once per event loop
679	until stopped, that is, or your process receives more events and becomes	1856	iteration - until stopped, that is, or your process receives more events
680	busy.	1857	and becomes busy again with higher priority stuff.
681		1858
682	The most noteworthy effect is that as long as any idle watchers are	1859	The most noteworthy effect is that as long as any idle watchers are
683	active, the process will not block when waiting for new events.	1860	active, the process will not block when waiting for new events.
684		1861
685	Apart from keeping your process non-blocking (which is a useful	1862	Apart from keeping your process non-blocking (which is a useful
686	effect on its own sometimes), idle watchers are a good place to do	1863	effect on its own sometimes), idle watchers are a good place to do
687	"pseudo-background processing", or delay processing stuff to after the	1864	"pseudo-background processing", or delay processing stuff to after the
688	event loop has handled all outstanding events.	1865	event loop has handled all outstanding events.
689		1866
		1867	=head3 Watcher-Specific Functions and Data Members
		1868
690	=over 4	1869	=over 4
691		1870
692	=item ev_idle_init (ev_signal *, callback)	1871	=item ev_idle_init (ev_signal *, callback)
693		1872
694	Initialises and configures the idle watcher - it has no parameters of any	1873	Initialises and configures the idle watcher - it has no parameters of any
695	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1874	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1875	believe me.
697		1876
698	=back	1877	=back
699		1878
		1879	=head3 Examples
		1880
		1881	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1882	callback, free it. Also, use no error checking, as usual.
		1883
		1884	static void
		1885	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1886	{
		1887	free (w);
		1888	// now do something you wanted to do when the program has
		1889	// no longer anything immediate to do.
		1890	}
		1891
		1892	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1893	ev_idle_init (idle_watcher, idle_cb);
		1894	ev_idle_start (loop, idle_cb);
		1895
		1896
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1897	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
701		1898
702	Prepare and check watchers are usually (but not always) used in tandem:	1899	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1900	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1901	afterwards.
705		1902
		1903	You I<must not> call C<ev_loop> or similar functions that enter
		1904	the current event loop from either C<ev_prepare> or C<ev_check>
		1905	watchers. Other loops than the current one are fine, however. The
		1906	rationale behind this is that you do not need to check for recursion in
		1907	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1908	C<ev_check> so if you have one watcher of each kind they will always be
		1909	called in pairs bracketing the blocking call.
		1910
706	Their main purpose is to integrate other event mechanisms into libev. This	1911	Their main purpose is to integrate other event mechanisms into libev and
707	could be used, for example, to track variable changes, implement your own	1912	their use is somewhat advanced. This could be used, for example, to track
708	watchers, integrate net-snmp or a coroutine library and lots more.	1913	variable changes, implement your own watchers, integrate net-snmp or a
		1914	coroutine library and lots more. They are also occasionally useful if
		1915	you cache some data and want to flush it before blocking (for example,
		1916	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1917	watcher).
709		1918
710	This is done by examining in each prepare call which file descriptors need	1919	This is done by examining in each prepare call which file descriptors need
711	to be watched by the other library, registering C<ev_io> watchers for	1920	to be watched by the other library, registering C<ev_io> watchers for
712	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1921	them and starting an C<ev_timer> watcher for any timeouts (many libraries
713	provide just this functionality). Then, in the check watcher you check for	1922	provide just this functionality). Then, in the check watcher you check for
714	any events that occured (by checking the pending status of all watchers	1923	any events that occurred (by checking the pending status of all watchers
715	and stopping them) and call back into the library. The I/O and timer	1924	and stopping them) and call back into the library. The I/O and timer
716	callbacks will never actually be called (but must be valid nevertheless,	1925	callbacks will never actually be called (but must be valid nevertheless,
717	because you never know, you know?).	1926	because you never know, you know?).
718		1927
719	As another example, the Perl Coro module uses these hooks to integrate	1928	As another example, the Perl Coro module uses these hooks to integrate
…		…
723	with priority higher than or equal to the event loop and one coroutine	1932	with priority higher than or equal to the event loop and one coroutine
724	of lower priority, but only once, using idle watchers to keep the event	1933	of lower priority, but only once, using idle watchers to keep the event
725	loop from blocking if lower-priority coroutines are active, thus mapping	1934	loop from blocking if lower-priority coroutines are active, thus mapping
726	low-priority coroutines to idle/background tasks).	1935	low-priority coroutines to idle/background tasks).
727		1936
		1937	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1938	priority, to ensure that they are being run before any other watchers
		1939	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1940	too) should not activate ("feed") events into libev. While libev fully
		1941	supports this, they might get executed before other C<ev_check> watchers
		1942	did their job. As C<ev_check> watchers are often used to embed other
		1943	(non-libev) event loops those other event loops might be in an unusable
		1944	state until their C<ev_check> watcher ran (always remind yourself to
		1945	coexist peacefully with others).
		1946
		1947	=head3 Watcher-Specific Functions and Data Members
		1948
728	=over 4	1949	=over 4
729		1950
730	=item ev_prepare_init (ev_prepare *, callback)	1951	=item ev_prepare_init (ev_prepare *, callback)
731		1952
732	=item ev_check_init (ev_check *, callback)	1953	=item ev_check_init (ev_check *, callback)
…		…
734	Initialises and configures the prepare or check watcher - they have no	1955	Initialises and configures the prepare or check watcher - they have no
735	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1956	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
736	macros, but using them is utterly, utterly and completely pointless.	1957	macros, but using them is utterly, utterly and completely pointless.
737		1958
738	=back	1959	=back
		1960
		1961	=head3 Examples
		1962
		1963	There are a number of principal ways to embed other event loops or modules
		1964	into libev. Here are some ideas on how to include libadns into libev
		1965	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1966	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1967	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1968	Glib event loop).
		1969
		1970	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1971	and in a check watcher, destroy them and call into libadns. What follows
		1972	is pseudo-code only of course. This requires you to either use a low
		1973	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1974	the callbacks for the IO/timeout watchers might not have been called yet.
		1975
		1976	static ev_io iow [nfd];
		1977	static ev_timer tw;
		1978
		1979	static void
		1980	io_cb (ev_loop *loop, ev_io *w, int revents)
		1981	{
		1982	}
		1983
		1984	// create io watchers for each fd and a timer before blocking
		1985	static void
		1986	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1987	{
		1988	int timeout = 3600000;
		1989	struct pollfd fds [nfd];
		1990	// actual code will need to loop here and realloc etc.
		1991	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1992
		1993	/* the callback is illegal, but won't be called as we stop during check */
		1994	ev_timer_init (&tw, 0, timeout * 1e-3);
		1995	ev_timer_start (loop, &tw);
		1996
		1997	// create one ev_io per pollfd
		1998	for (int i = 0; i < nfd; ++i)
		1999	{
		2000	ev_io_init (iow + i, io_cb, fds [i].fd,
		2001	((fds [i].events & POLLIN ? EV_READ : 0)
		2002	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		2003
		2004	fds [i].revents = 0;
		2005	ev_io_start (loop, iow + i);
		2006	}
		2007	}
		2008
		2009	// stop all watchers after blocking
		2010	static void
		2011	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		2012	{
		2013	ev_timer_stop (loop, &tw);
		2014
		2015	for (int i = 0; i < nfd; ++i)
		2016	{
		2017	// set the relevant poll flags
		2018	// could also call adns_processreadable etc. here
		2019	struct pollfd *fd = fds + i;
		2020	int revents = ev_clear_pending (iow + i);
		2021	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2022	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2023
		2024	// now stop the watcher
		2025	ev_io_stop (loop, iow + i);
		2026	}
		2027
		2028	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		2029	}
		2030
		2031	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2032	in the prepare watcher and would dispose of the check watcher.
		2033
		2034	Method 3: If the module to be embedded supports explicit event
		2035	notification (libadns does), you can also make use of the actual watcher
		2036	callbacks, and only destroy/create the watchers in the prepare watcher.
		2037
		2038	static void
		2039	timer_cb (EV_P_ ev_timer *w, int revents)
		2040	{
		2041	adns_state ads = (adns_state)w->data;
		2042	update_now (EV_A);
		2043
		2044	adns_processtimeouts (ads, &tv_now);
		2045	}
		2046
		2047	static void
		2048	io_cb (EV_P_ ev_io *w, int revents)
		2049	{
		2050	adns_state ads = (adns_state)w->data;
		2051	update_now (EV_A);
		2052
		2053	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2054	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2055	}
		2056
		2057	// do not ever call adns_afterpoll
		2058
		2059	Method 4: Do not use a prepare or check watcher because the module you
		2060	want to embed is too inflexible to support it. Instead, you can override
		2061	their poll function. The drawback with this solution is that the main
		2062	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2063	this.
		2064
		2065	static gint
		2066	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2067	{
		2068	int got_events = 0;
		2069
		2070	for (n = 0; n < nfds; ++n)
		2071	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2072
		2073	if (timeout >= 0)
		2074	// create/start timer
		2075
		2076	// poll
		2077	ev_loop (EV_A_ 0);
		2078
		2079	// stop timer again
		2080	if (timeout >= 0)
		2081	ev_timer_stop (EV_A_ &to);
		2082
		2083	// stop io watchers again - their callbacks should have set
		2084	for (n = 0; n < nfds; ++n)
		2085	ev_io_stop (EV_A_ iow [n]);
		2086
		2087	return got_events;
		2088	}
		2089
		2090
		2091	=head2 C<ev_embed> - when one backend isn't enough...
		2092
		2093	This is a rather advanced watcher type that lets you embed one event loop
		2094	into another (currently only C<ev_io> events are supported in the embedded
		2095	loop, other types of watchers might be handled in a delayed or incorrect
		2096	fashion and must not be used).
		2097
		2098	There are primarily two reasons you would want that: work around bugs and
		2099	prioritise I/O.
		2100
		2101	As an example for a bug workaround, the kqueue backend might only support
		2102	sockets on some platform, so it is unusable as generic backend, but you
		2103	still want to make use of it because you have many sockets and it scales
		2104	so nicely. In this case, you would create a kqueue-based loop and embed it
		2105	into your default loop (which might use e.g. poll). Overall operation will
		2106	be a bit slower because first libev has to poll and then call kevent, but
		2107	at least you can use both at what they are best.
		2108
		2109	As for prioritising I/O: rarely you have the case where some fds have
		2110	to be watched and handled very quickly (with low latency), and even
		2111	priorities and idle watchers might have too much overhead. In this case
		2112	you would put all the high priority stuff in one loop and all the rest in
		2113	a second one, and embed the second one in the first.
		2114
		2115	As long as the watcher is active, the callback will be invoked every time
		2116	there might be events pending in the embedded loop. The callback must then
		2117	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		2118	their callbacks (you could also start an idle watcher to give the embedded
		2119	loop strictly lower priority for example). You can also set the callback
		2120	to C<0>, in which case the embed watcher will automatically execute the
		2121	embedded loop sweep.
		2122
		2123	As long as the watcher is started it will automatically handle events. The
		2124	callback will be invoked whenever some events have been handled. You can
		2125	set the callback to C<0> to avoid having to specify one if you are not
		2126	interested in that.
		2127
		2128	Also, there have not currently been made special provisions for forking:
		2129	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2130	but you will also have to stop and restart any C<ev_embed> watchers
		2131	yourself.
		2132
		2133	Unfortunately, not all backends are embeddable, only the ones returned by
		2134	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2135	portable one.
		2136
		2137	So when you want to use this feature you will always have to be prepared
		2138	that you cannot get an embeddable loop. The recommended way to get around
		2139	this is to have a separate variables for your embeddable loop, try to
		2140	create it, and if that fails, use the normal loop for everything.
		2141
		2142	=head3 Watcher-Specific Functions and Data Members
		2143
		2144	=over 4
		2145
		2146	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2147
		2148	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2149
		2150	Configures the watcher to embed the given loop, which must be
		2151	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2152	invoked automatically, otherwise it is the responsibility of the callback
		2153	to invoke it (it will continue to be called until the sweep has been done,
		2154	if you do not want that, you need to temporarily stop the embed watcher).
		2155
		2156	=item ev_embed_sweep (loop, ev_embed *)
		2157
		2158	Make a single, non-blocking sweep over the embedded loop. This works
		2159	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2160	appropriate way for embedded loops.
		2161
		2162	=item struct ev_loop *other [read-only]
		2163
		2164	The embedded event loop.
		2165
		2166	=back
		2167
		2168	=head3 Examples
		2169
		2170	Example: Try to get an embeddable event loop and embed it into the default
		2171	event loop. If that is not possible, use the default loop. The default
		2172	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2173	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2174	used).
		2175
		2176	struct ev_loop *loop_hi = ev_default_init (0);
		2177	struct ev_loop *loop_lo = 0;
		2178	struct ev_embed embed;
		2179
		2180	// see if there is a chance of getting one that works
		2181	// (remember that a flags value of 0 means autodetection)
		2182	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2183	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2184	: 0;
		2185
		2186	// if we got one, then embed it, otherwise default to loop_hi
		2187	if (loop_lo)
		2188	{
		2189	ev_embed_init (&embed, 0, loop_lo);
		2190	ev_embed_start (loop_hi, &embed);
		2191	}
		2192	else
		2193	loop_lo = loop_hi;
		2194
		2195	Example: Check if kqueue is available but not recommended and create
		2196	a kqueue backend for use with sockets (which usually work with any
		2197	kqueue implementation). Store the kqueue/socket-only event loop in
		2198	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2199
		2200	struct ev_loop *loop = ev_default_init (0);
		2201	struct ev_loop *loop_socket = 0;
		2202	struct ev_embed embed;
		2203
		2204	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2205	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2206	{
		2207	ev_embed_init (&embed, 0, loop_socket);
		2208	ev_embed_start (loop, &embed);
		2209	}
		2210
		2211	if (!loop_socket)
		2212	loop_socket = loop;
		2213
		2214	// now use loop_socket for all sockets, and loop for everything else
		2215
		2216
		2217	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2218
		2219	Fork watchers are called when a C<fork ()> was detected (usually because
		2220	whoever is a good citizen cared to tell libev about it by calling
		2221	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2222	event loop blocks next and before C<ev_check> watchers are being called,
		2223	and only in the child after the fork. If whoever good citizen calling
		2224	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2225	handlers will be invoked, too, of course.
		2226
		2227	=head3 Watcher-Specific Functions and Data Members
		2228
		2229	=over 4
		2230
		2231	=item ev_fork_init (ev_signal *, callback)
		2232
		2233	Initialises and configures the fork watcher - it has no parameters of any
		2234	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2235	believe me.
		2236
		2237	=back
		2238
		2239
		2240	=head2 C<ev_async> - how to wake up another event loop
		2241
		2242	In general, you cannot use an C<ev_loop> from multiple threads or other
		2243	asynchronous sources such as signal handlers (as opposed to multiple event
		2244	loops - those are of course safe to use in different threads).
		2245
		2246	Sometimes, however, you need to wake up another event loop you do not
		2247	control, for example because it belongs to another thread. This is what
		2248	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2249	can signal it by calling C<ev_async_send>, which is thread- and signal
		2250	safe.
		2251
		2252	This functionality is very similar to C<ev_signal> watchers, as signals,
		2253	too, are asynchronous in nature, and signals, too, will be compressed
		2254	(i.e. the number of callback invocations may be less than the number of
		2255	C<ev_async_sent> calls).
		2256
		2257	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2258	just the default loop.
		2259
		2260	=head3 Queueing
		2261
		2262	C<ev_async> does not support queueing of data in any way. The reason
		2263	is that the author does not know of a simple (or any) algorithm for a
		2264	multiple-writer-single-reader queue that works in all cases and doesn't
		2265	need elaborate support such as pthreads.
		2266
		2267	That means that if you want to queue data, you have to provide your own
		2268	queue. But at least I can tell you would implement locking around your
		2269	queue:
		2270
		2271	=over 4
		2272
		2273	=item queueing from a signal handler context
		2274
		2275	To implement race-free queueing, you simply add to the queue in the signal
		2276	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2277	some fictitious SIGUSR1 handler:
		2278
		2279	static ev_async mysig;
		2280
		2281	static void
		2282	sigusr1_handler (void)
		2283	{
		2284	sometype data;
		2285
		2286	// no locking etc.
		2287	queue_put (data);
		2288	ev_async_send (EV_DEFAULT_ &mysig);
		2289	}
		2290
		2291	static void
		2292	mysig_cb (EV_P_ ev_async *w, int revents)
		2293	{
		2294	sometype data;
		2295	sigset_t block, prev;
		2296
		2297	sigemptyset (&block);
		2298	sigaddset (&block, SIGUSR1);
		2299	sigprocmask (SIG_BLOCK, &block, &prev);
		2300
		2301	while (queue_get (&data))
		2302	process (data);
		2303
		2304	if (sigismember (&prev, SIGUSR1)
		2305	sigprocmask (SIG_UNBLOCK, &block, 0);
		2306	}
		2307
		2308	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2309	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2310	either...).
		2311
		2312	=item queueing from a thread context
		2313
		2314	The strategy for threads is different, as you cannot (easily) block
		2315	threads but you can easily preempt them, so to queue safely you need to
		2316	employ a traditional mutex lock, such as in this pthread example:
		2317
		2318	static ev_async mysig;
		2319	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2320
		2321	static void
		2322	otherthread (void)
		2323	{
		2324	// only need to lock the actual queueing operation
		2325	pthread_mutex_lock (&mymutex);
		2326	queue_put (data);
		2327	pthread_mutex_unlock (&mymutex);
		2328
		2329	ev_async_send (EV_DEFAULT_ &mysig);
		2330	}
		2331
		2332	static void
		2333	mysig_cb (EV_P_ ev_async *w, int revents)
		2334	{
		2335	pthread_mutex_lock (&mymutex);
		2336
		2337	while (queue_get (&data))
		2338	process (data);
		2339
		2340	pthread_mutex_unlock (&mymutex);
		2341	}
		2342
		2343	=back
		2344
		2345
		2346	=head3 Watcher-Specific Functions and Data Members
		2347
		2348	=over 4
		2349
		2350	=item ev_async_init (ev_async *, callback)
		2351
		2352	Initialises and configures the async watcher - it has no parameters of any
		2353	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2354	believe me.
		2355
		2356	=item ev_async_send (loop, ev_async *)
		2357
		2358	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2359	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2360	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2361	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2362	section below on what exactly this means).
		2363
		2364	This call incurs the overhead of a system call only once per loop iteration,
		2365	so while the overhead might be noticeable, it doesn't apply to repeated
		2366	calls to C<ev_async_send>.
		2367
		2368	=item bool = ev_async_pending (ev_async *)
		2369
		2370	Returns a non-zero value when C<ev_async_send> has been called on the
		2371	watcher but the event has not yet been processed (or even noted) by the
		2372	event loop.
		2373
		2374	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2375	the loop iterates next and checks for the watcher to have become active,
		2376	it will reset the flag again. C<ev_async_pending> can be used to very
		2377	quickly check whether invoking the loop might be a good idea.
		2378
		2379	Not that this does I<not> check whether the watcher itself is pending, only
		2380	whether it has been requested to make this watcher pending.
		2381
		2382	=back
		2383
739		2384
740	=head1 OTHER FUNCTIONS	2385	=head1 OTHER FUNCTIONS
741		2386
742	There are some other functions of possible interest. Described. Here. Now.	2387	There are some other functions of possible interest. Described. Here. Now.
743		2388
…		…
751	or timeout without having to allocate/configure/start/stop/free one or	2396	or timeout without having to allocate/configure/start/stop/free one or
752	more watchers yourself.	2397	more watchers yourself.
753		2398
754	If C<fd> is less than 0, then no I/O watcher will be started and events	2399	If C<fd> is less than 0, then no I/O watcher will be started and events
755	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2400	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
756	C<events> set will be craeted and started.	2401	C<events> set will be created and started.
757		2402
758	If C<timeout> is less than 0, then no timeout watcher will be	2403	If C<timeout> is less than 0, then no timeout watcher will be
759	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2404	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
760	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2405	repeat = 0) will be started. While C<0> is a valid timeout, it is of
761	dubious value.	2406	dubious value.
…		…
763	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2408	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
764	passed an C<revents> set like normal event callbacks (a combination of	2409	passed an C<revents> set like normal event callbacks (a combination of
765	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2410	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
766	value passed to C<ev_once>:	2411	value passed to C<ev_once>:
767		2412
768	static void stdin_ready (int revents, void *arg)	2413	static void stdin_ready (int revents, void *arg)
769	{	2414	{
770	if (revents & EV_TIMEOUT)	2415	if (revents & EV_TIMEOUT)
771	/* doh, nothing entered */;	2416	/* doh, nothing entered */;
772	else if (revents & EV_READ)	2417	else if (revents & EV_READ)
773	/* stdin might have data for us, joy! */;	2418	/* stdin might have data for us, joy! */;
774	}	2419	}
775		2420
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2421	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		2422
778	=item ev_feed_event (loop, watcher, int events)	2423	=item ev_feed_event (ev_loop *, watcher *, int revents)
779		2424
780	Feeds the given event set into the event loop, as if the specified event	2425	Feeds the given event set into the event loop, as if the specified event
781	had happened for the specified watcher (which must be a pointer to an	2426	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	2427	initialised but not necessarily started event watcher).
783		2428
784	=item ev_feed_fd_event (loop, int fd, int revents)	2429	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		2430
786	Feed an event on the given fd, as if a file descriptor backend detected	2431	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	2432	the given events it.
788		2433
789	=item ev_feed_signal_event (loop, int signum)	2434	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		2435
791	Feed an event as if the given signal occured (loop must be the default loop!).	2436	Feed an event as if the given signal occurred (C<loop> must be the default
		2437	loop!).
792		2438
793	=back	2439	=back
		2440
794		2441
795	=head1 LIBEVENT EMULATION	2442	=head1 LIBEVENT EMULATION
796		2443
797	Libev offers a compatibility emulation layer for libevent. It cannot	2444	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	2445	emulate the internals of libevent, so here are some usage hints:
…		…
810		2457
811	=item * Priorities are not currently supported. Initialising priorities	2458	=item * Priorities are not currently supported. Initialising priorities
812	will fail and all watchers will have the same priority, even though there	2459	will fail and all watchers will have the same priority, even though there
813	is an ev_pri field.	2460	is an ev_pri field.
814		2461
		2462	=item * In libevent, the last base created gets the signals, in libev, the
		2463	first base created (== the default loop) gets the signals.
		2464
815	=item * Other members are not supported.	2465	=item * Other members are not supported.
816		2466
817	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2467	=item * The libev emulation is I<not> ABI compatible to libevent, you need
818	to use the libev header file and library.	2468	to use the libev header file and library.
819		2469
820	=back	2470	=back
821		2471
822	=head1 C++ SUPPORT	2472	=head1 C++ SUPPORT
823		2473
824	TBD.	2474	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2475	you to use some convenience methods to start/stop watchers and also change
		2476	the callback model to a model using method callbacks on objects.
		2477
		2478	To use it,
		2479
		2480	#include <ev++.h>
		2481
		2482	This automatically includes F<ev.h> and puts all of its definitions (many
		2483	of them macros) into the global namespace. All C++ specific things are
		2484	put into the C<ev> namespace. It should support all the same embedding
		2485	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2486
		2487	Care has been taken to keep the overhead low. The only data member the C++
		2488	classes add (compared to plain C-style watchers) is the event loop pointer
		2489	that the watcher is associated with (or no additional members at all if
		2490	you disable C<EV_MULTIPLICITY> when embedding libev).
		2491
		2492	Currently, functions, and static and non-static member functions can be
		2493	used as callbacks. Other types should be easy to add as long as they only
		2494	need one additional pointer for context. If you need support for other
		2495	types of functors please contact the author (preferably after implementing
		2496	it).
		2497
		2498	Here is a list of things available in the C<ev> namespace:
		2499
		2500	=over 4
		2501
		2502	=item C<ev::READ>, C<ev::WRITE> etc.
		2503
		2504	These are just enum values with the same values as the C<EV_READ> etc.
		2505	macros from F<ev.h>.
		2506
		2507	=item C<ev::tstamp>, C<ev::now>
		2508
		2509	Aliases to the same types/functions as with the C<ev_> prefix.
		2510
		2511	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2512
		2513	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2514	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2515	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2516	defines by many implementations.
		2517
		2518	All of those classes have these methods:
		2519
		2520	=over 4
		2521
		2522	=item ev::TYPE::TYPE ()
		2523
		2524	=item ev::TYPE::TYPE (struct ev_loop *)
		2525
		2526	=item ev::TYPE::~TYPE
		2527
		2528	The constructor (optionally) takes an event loop to associate the watcher
		2529	with. If it is omitted, it will use C<EV_DEFAULT>.
		2530
		2531	The constructor calls C<ev_init> for you, which means you have to call the
		2532	C<set> method before starting it.
		2533
		2534	It will not set a callback, however: You have to call the templated C<set>
		2535	method to set a callback before you can start the watcher.
		2536
		2537	(The reason why you have to use a method is a limitation in C++ which does
		2538	not allow explicit template arguments for constructors).
		2539
		2540	The destructor automatically stops the watcher if it is active.
		2541
		2542	=item w->set<class, &class::method> (object *)
		2543
		2544	This method sets the callback method to call. The method has to have a
		2545	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2546	first argument and the C<revents> as second. The object must be given as
		2547	parameter and is stored in the C<data> member of the watcher.
		2548
		2549	This method synthesizes efficient thunking code to call your method from
		2550	the C callback that libev requires. If your compiler can inline your
		2551	callback (i.e. it is visible to it at the place of the C<set> call and
		2552	your compiler is good :), then the method will be fully inlined into the
		2553	thunking function, making it as fast as a direct C callback.
		2554
		2555	Example: simple class declaration and watcher initialisation
		2556
		2557	struct myclass
		2558	{
		2559	void io_cb (ev::io &w, int revents) { }
		2560	}
		2561
		2562	myclass obj;
		2563	ev::io iow;
		2564	iow.set <myclass, &myclass::io_cb> (&obj);
		2565
		2566	=item w->set<function> (void *data = 0)
		2567
		2568	Also sets a callback, but uses a static method or plain function as
		2569	callback. The optional C<data> argument will be stored in the watcher's
		2570	C<data> member and is free for you to use.
		2571
		2572	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2573
		2574	See the method-C<set> above for more details.
		2575
		2576	Example:
		2577
		2578	static void io_cb (ev::io &w, int revents) { }
		2579	iow.set <io_cb> ();
		2580
		2581	=item w->set (struct ev_loop *)
		2582
		2583	Associates a different C<struct ev_loop> with this watcher. You can only
		2584	do this when the watcher is inactive (and not pending either).
		2585
		2586	=item w->set ([arguments])
		2587
		2588	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
		2589	called at least once. Unlike the C counterpart, an active watcher gets
		2590	automatically stopped and restarted when reconfiguring it with this
		2591	method.
		2592
		2593	=item w->start ()
		2594
		2595	Starts the watcher. Note that there is no C<loop> argument, as the
		2596	constructor already stores the event loop.
		2597
		2598	=item w->stop ()
		2599
		2600	Stops the watcher if it is active. Again, no C<loop> argument.
		2601
		2602	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2603
		2604	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2605	C<ev_TYPE_again> function.
		2606
		2607	=item w->sweep () (C<ev::embed> only)
		2608
		2609	Invokes C<ev_embed_sweep>.
		2610
		2611	=item w->update () (C<ev::stat> only)
		2612
		2613	Invokes C<ev_stat_stat>.
		2614
		2615	=back
		2616
		2617	=back
		2618
		2619	Example: Define a class with an IO and idle watcher, start one of them in
		2620	the constructor.
		2621
		2622	class myclass
		2623	{
		2624	ev::io io; void io_cb (ev::io &w, int revents);
		2625	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2626
		2627	myclass (int fd)
		2628	{
		2629	io .set <myclass, &myclass::io_cb > (this);
		2630	idle.set <myclass, &myclass::idle_cb> (this);
		2631
		2632	io.start (fd, ev::READ);
		2633	}
		2634	};
		2635
		2636
		2637	=head1 OTHER LANGUAGE BINDINGS
		2638
		2639	Libev does not offer other language bindings itself, but bindings for a
		2640	number of languages exist in the form of third-party packages. If you know
		2641	any interesting language binding in addition to the ones listed here, drop
		2642	me a note.
		2643
		2644	=over 4
		2645
		2646	=item Perl
		2647
		2648	The EV module implements the full libev API and is actually used to test
		2649	libev. EV is developed together with libev. Apart from the EV core module,
		2650	there are additional modules that implement libev-compatible interfaces
		2651	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2652	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2653
		2654	It can be found and installed via CPAN, its homepage is at
		2655	L<http://software.schmorp.de/pkg/EV>.
		2656
		2657	=item Python
		2658
		2659	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2660	seems to be quite complete and well-documented. Note, however, that the
		2661	patch they require for libev is outright dangerous as it breaks the ABI
		2662	for everybody else, and therefore, should never be applied in an installed
		2663	libev (if python requires an incompatible ABI then it needs to embed
		2664	libev).
		2665
		2666	=item Ruby
		2667
		2668	Tony Arcieri has written a ruby extension that offers access to a subset
		2669	of the libev API and adds file handle abstractions, asynchronous DNS and
		2670	more on top of it. It can be found via gem servers. Its homepage is at
		2671	L<http://rev.rubyforge.org/>.
		2672
		2673	=item D
		2674
		2675	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2676	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2677
		2678	=back
		2679
		2680
		2681	=head1 MACRO MAGIC
		2682
		2683	Libev can be compiled with a variety of options, the most fundamental
		2684	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2685	functions and callbacks have an initial C<struct ev_loop *> argument.
		2686
		2687	To make it easier to write programs that cope with either variant, the
		2688	following macros are defined:
		2689
		2690	=over 4
		2691
		2692	=item C<EV_A>, C<EV_A_>
		2693
		2694	This provides the loop I<argument> for functions, if one is required ("ev
		2695	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2696	C<EV_A_> is used when other arguments are following. Example:
		2697
		2698	ev_unref (EV_A);
		2699	ev_timer_add (EV_A_ watcher);
		2700	ev_loop (EV_A_ 0);
		2701
		2702	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2703	which is often provided by the following macro.
		2704
		2705	=item C<EV_P>, C<EV_P_>
		2706
		2707	This provides the loop I<parameter> for functions, if one is required ("ev
		2708	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2709	C<EV_P_> is used when other parameters are following. Example:
		2710
		2711	// this is how ev_unref is being declared
		2712	static void ev_unref (EV_P);
		2713
		2714	// this is how you can declare your typical callback
		2715	static void cb (EV_P_ ev_timer *w, int revents)
		2716
		2717	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2718	suitable for use with C<EV_A>.
		2719
		2720	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2721
		2722	Similar to the other two macros, this gives you the value of the default
		2723	loop, if multiple loops are supported ("ev loop default").
		2724
		2725	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2726
		2727	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2728	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2729	is undefined when the default loop has not been initialised by a previous
		2730	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2731
		2732	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2733	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2734
		2735	=back
		2736
		2737	Example: Declare and initialise a check watcher, utilising the above
		2738	macros so it will work regardless of whether multiple loops are supported
		2739	or not.
		2740
		2741	static void
		2742	check_cb (EV_P_ ev_timer *w, int revents)
		2743	{
		2744	ev_check_stop (EV_A_ w);
		2745	}
		2746
		2747	ev_check check;
		2748	ev_check_init (&check, check_cb);
		2749	ev_check_start (EV_DEFAULT_ &check);
		2750	ev_loop (EV_DEFAULT_ 0);
		2751
		2752	=head1 EMBEDDING
		2753
		2754	Libev can (and often is) directly embedded into host
		2755	applications. Examples of applications that embed it include the Deliantra
		2756	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2757	and rxvt-unicode.
		2758
		2759	The goal is to enable you to just copy the necessary files into your
		2760	source directory without having to change even a single line in them, so
		2761	you can easily upgrade by simply copying (or having a checked-out copy of
		2762	libev somewhere in your source tree).
		2763
		2764	=head2 FILESETS
		2765
		2766	Depending on what features you need you need to include one or more sets of files
		2767	in your application.
		2768
		2769	=head3 CORE EVENT LOOP
		2770
		2771	To include only the libev core (all the C<ev_*> functions), with manual
		2772	configuration (no autoconf):
		2773
		2774	#define EV_STANDALONE 1
		2775	#include "ev.c"
		2776
		2777	This will automatically include F<ev.h>, too, and should be done in a
		2778	single C source file only to provide the function implementations. To use
		2779	it, do the same for F<ev.h> in all files wishing to use this API (best
		2780	done by writing a wrapper around F<ev.h> that you can include instead and
		2781	where you can put other configuration options):
		2782
		2783	#define EV_STANDALONE 1
		2784	#include "ev.h"
		2785
		2786	Both header files and implementation files can be compiled with a C++
		2787	compiler (at least, thats a stated goal, and breakage will be treated
		2788	as a bug).
		2789
		2790	You need the following files in your source tree, or in a directory
		2791	in your include path (e.g. in libev/ when using -Ilibev):
		2792
		2793	ev.h
		2794	ev.c
		2795	ev_vars.h
		2796	ev_wrap.h
		2797
		2798	ev_win32.c required on win32 platforms only
		2799
		2800	ev_select.c only when select backend is enabled (which is enabled by default)
		2801	ev_poll.c only when poll backend is enabled (disabled by default)
		2802	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2803	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2804	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2805
		2806	F<ev.c> includes the backend files directly when enabled, so you only need
		2807	to compile this single file.
		2808
		2809	=head3 LIBEVENT COMPATIBILITY API
		2810
		2811	To include the libevent compatibility API, also include:
		2812
		2813	#include "event.c"
		2814
		2815	in the file including F<ev.c>, and:
		2816
		2817	#include "event.h"
		2818
		2819	in the files that want to use the libevent API. This also includes F<ev.h>.
		2820
		2821	You need the following additional files for this:
		2822
		2823	event.h
		2824	event.c
		2825
		2826	=head3 AUTOCONF SUPPORT
		2827
		2828	Instead of using C<EV_STANDALONE=1> and providing your configuration in
		2829	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2830	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2831	include F<config.h> and configure itself accordingly.
		2832
		2833	For this of course you need the m4 file:
		2834
		2835	libev.m4
		2836
		2837	=head2 PREPROCESSOR SYMBOLS/MACROS
		2838
		2839	Libev can be configured via a variety of preprocessor symbols you have to
		2840	define before including any of its files. The default in the absence of
		2841	autoconf is noted for every option.
		2842
		2843	=over 4
		2844
		2845	=item EV_STANDALONE
		2846
		2847	Must always be C<1> if you do not use autoconf configuration, which
		2848	keeps libev from including F<config.h>, and it also defines dummy
		2849	implementations for some libevent functions (such as logging, which is not
		2850	supported). It will also not define any of the structs usually found in
		2851	F<event.h> that are not directly supported by the libev core alone.
		2852
		2853	=item EV_USE_MONOTONIC
		2854
		2855	If defined to be C<1>, libev will try to detect the availability of the
		2856	monotonic clock option at both compile time and runtime. Otherwise no use
		2857	of the monotonic clock option will be attempted. If you enable this, you
		2858	usually have to link against librt or something similar. Enabling it when
		2859	the functionality isn't available is safe, though, although you have
		2860	to make sure you link against any libraries where the C<clock_gettime>
		2861	function is hiding in (often F<-lrt>).
		2862
		2863	=item EV_USE_REALTIME
		2864
		2865	If defined to be C<1>, libev will try to detect the availability of the
		2866	real-time clock option at compile time (and assume its availability at
		2867	runtime if successful). Otherwise no use of the real-time clock option will
		2868	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2869	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2870	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2871
		2872	=item EV_USE_NANOSLEEP
		2873
		2874	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2875	and will use it for delays. Otherwise it will use C<select ()>.
		2876
		2877	=item EV_USE_EVENTFD
		2878
		2879	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2880	available and will probe for kernel support at runtime. This will improve
		2881	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2882	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2883	2.7 or newer, otherwise disabled.
		2884
		2885	=item EV_USE_SELECT
		2886
		2887	If undefined or defined to be C<1>, libev will compile in support for the
		2888	C<select>(2) backend. No attempt at auto-detection will be done: if no
		2889	other method takes over, select will be it. Otherwise the select backend
		2890	will not be compiled in.
		2891
		2892	=item EV_SELECT_USE_FD_SET
		2893
		2894	If defined to C<1>, then the select backend will use the system C<fd_set>
		2895	structure. This is useful if libev doesn't compile due to a missing
		2896	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
		2897	exotic systems. This usually limits the range of file descriptors to some
		2898	low limit such as 1024 or might have other limitations (winsocket only
		2899	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2900	influence the size of the C<fd_set> used.
		2901
		2902	=item EV_SELECT_IS_WINSOCKET
		2903
		2904	When defined to C<1>, the select backend will assume that
		2905	select/socket/connect etc. don't understand file descriptors but
		2906	wants osf handles on win32 (this is the case when the select to
		2907	be used is the winsock select). This means that it will call
		2908	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2909	it is assumed that all these functions actually work on fds, even
		2910	on win32. Should not be defined on non-win32 platforms.
		2911
		2912	=item EV_FD_TO_WIN32_HANDLE
		2913
		2914	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2915	file descriptors to socket handles. When not defining this symbol (the
		2916	default), then libev will call C<_get_osfhandle>, which is usually
		2917	correct. In some cases, programs use their own file descriptor management,
		2918	in which case they can provide this function to map fds to socket handles.
		2919
		2920	=item EV_USE_POLL
		2921
		2922	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2923	backend. Otherwise it will be enabled on non-win32 platforms. It
		2924	takes precedence over select.
		2925
		2926	=item EV_USE_EPOLL
		2927
		2928	If defined to be C<1>, libev will compile in support for the Linux
		2929	C<epoll>(7) backend. Its availability will be detected at runtime,
		2930	otherwise another method will be used as fallback. This is the preferred
		2931	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2932	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2933
		2934	=item EV_USE_KQUEUE
		2935
		2936	If defined to be C<1>, libev will compile in support for the BSD style
		2937	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2938	otherwise another method will be used as fallback. This is the preferred
		2939	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2940	supports some types of fds correctly (the only platform we found that
		2941	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2942	not be used unless explicitly requested. The best way to use it is to find
		2943	out whether kqueue supports your type of fd properly and use an embedded
		2944	kqueue loop.
		2945
		2946	=item EV_USE_PORT
		2947
		2948	If defined to be C<1>, libev will compile in support for the Solaris
		2949	10 port style backend. Its availability will be detected at runtime,
		2950	otherwise another method will be used as fallback. This is the preferred
		2951	backend for Solaris 10 systems.
		2952
		2953	=item EV_USE_DEVPOLL
		2954
		2955	Reserved for future expansion, works like the USE symbols above.
		2956
		2957	=item EV_USE_INOTIFY
		2958
		2959	If defined to be C<1>, libev will compile in support for the Linux inotify
		2960	interface to speed up C<ev_stat> watchers. Its actual availability will
		2961	be detected at runtime. If undefined, it will be enabled if the headers
		2962	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2963
		2964	=item EV_ATOMIC_T
		2965
		2966	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2967	access is atomic with respect to other threads or signal contexts. No such
		2968	type is easily found in the C language, so you can provide your own type
		2969	that you know is safe for your purposes. It is used both for signal handler "locking"
		2970	as well as for signal and thread safety in C<ev_async> watchers.
		2971
		2972	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2973	(from F<signal.h>), which is usually good enough on most platforms.
		2974
		2975	=item EV_H
		2976
		2977	The name of the F<ev.h> header file used to include it. The default if
		2978	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2979	used to virtually rename the F<ev.h> header file in case of conflicts.
		2980
		2981	=item EV_CONFIG_H
		2982
		2983	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2984	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2985	C<EV_H>, above.
		2986
		2987	=item EV_EVENT_H
		2988
		2989	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2990	of how the F<event.h> header can be found, the default is C<"event.h">.
		2991
		2992	=item EV_PROTOTYPES
		2993
		2994	If defined to be C<0>, then F<ev.h> will not define any function
		2995	prototypes, but still define all the structs and other symbols. This is
		2996	occasionally useful if you want to provide your own wrapper functions
		2997	around libev functions.
		2998
		2999	=item EV_MULTIPLICITY
		3000
		3001	If undefined or defined to C<1>, then all event-loop-specific functions
		3002	will have the C<struct ev_loop *> as first argument, and you can create
		3003	additional independent event loops. Otherwise there will be no support
		3004	for multiple event loops and there is no first event loop pointer
		3005	argument. Instead, all functions act on the single default loop.
		3006
		3007	=item EV_MINPRI
		3008
		3009	=item EV_MAXPRI
		3010
		3011	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3012	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3013	provide for more priorities by overriding those symbols (usually defined
		3014	to be C<-2> and C<2>, respectively).
		3015
		3016	When doing priority-based operations, libev usually has to linearly search
		3017	all the priorities, so having many of them (hundreds) uses a lot of space
		3018	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3019	fine.
		3020
		3021	If your embedding application does not need any priorities, defining these both to
		3022	C<0> will save some memory and CPU.
		3023
		3024	=item EV_PERIODIC_ENABLE
		3025
		3026	If undefined or defined to be C<1>, then periodic timers are supported. If
		3027	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3028	code.
		3029
		3030	=item EV_IDLE_ENABLE
		3031
		3032	If undefined or defined to be C<1>, then idle watchers are supported. If
		3033	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3034	code.
		3035
		3036	=item EV_EMBED_ENABLE
		3037
		3038	If undefined or defined to be C<1>, then embed watchers are supported. If
		3039	defined to be C<0>, then they are not.
		3040
		3041	=item EV_STAT_ENABLE
		3042
		3043	If undefined or defined to be C<1>, then stat watchers are supported. If
		3044	defined to be C<0>, then they are not.
		3045
		3046	=item EV_FORK_ENABLE
		3047
		3048	If undefined or defined to be C<1>, then fork watchers are supported. If
		3049	defined to be C<0>, then they are not.
		3050
		3051	=item EV_ASYNC_ENABLE
		3052
		3053	If undefined or defined to be C<1>, then async watchers are supported. If
		3054	defined to be C<0>, then they are not.
		3055
		3056	=item EV_MINIMAL
		3057
		3058	If you need to shave off some kilobytes of code at the expense of some
		3059	speed, define this symbol to C<1>. Currently this is used to override some
		3060	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3061	much smaller 2-heap for timer management over the default 4-heap.
		3062
		3063	=item EV_PID_HASHSIZE
		3064
		3065	C<ev_child> watchers use a small hash table to distribute workload by
		3066	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		3067	than enough. If you need to manage thousands of children you might want to
		3068	increase this value (I<must> be a power of two).
		3069
		3070	=item EV_INOTIFY_HASHSIZE
		3071
		3072	C<ev_stat> watchers use a small hash table to distribute workload by
		3073	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3074	usually more than enough. If you need to manage thousands of C<ev_stat>
		3075	watchers you might want to increase this value (I<must> be a power of
		3076	two).
		3077
		3078	=item EV_USE_4HEAP
		3079
		3080	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3081	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3082	to C<1>. The 4-heap uses more complicated (longer) code but has
		3083	noticeably faster performance with many (thousands) of watchers.
		3084
		3085	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3086	(disabled).
		3087
		3088	=item EV_HEAP_CACHE_AT
		3089
		3090	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3091	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3092	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3093	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3094	but avoids random read accesses on heap changes. This improves performance
		3095	noticeably with with many (hundreds) of watchers.
		3096
		3097	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3098	(disabled).
		3099
		3100	=item EV_VERIFY
		3101
		3102	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3103	be done: If set to C<0>, no internal verification code will be compiled
		3104	in. If set to C<1>, then verification code will be compiled in, but not
		3105	called. If set to C<2>, then the internal verification code will be
		3106	called once per loop, which can slow down libev. If set to C<3>, then the
		3107	verification code will be called very frequently, which will slow down
		3108	libev considerably.
		3109
		3110	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3111	C<0.>
		3112
		3113	=item EV_COMMON
		3114
		3115	By default, all watchers have a C<void *data> member. By redefining
		3116	this macro to a something else you can include more and other types of
		3117	members. You have to define it each time you include one of the files,
		3118	though, and it must be identical each time.
		3119
		3120	For example, the perl EV module uses something like this:
		3121
		3122	#define EV_COMMON \
		3123	SV *self; /* contains this struct */ \
		3124	SV *cb_sv, *fh /* note no trailing ";" */
		3125
		3126	=item EV_CB_DECLARE (type)
		3127
		3128	=item EV_CB_INVOKE (watcher, revents)
		3129
		3130	=item ev_set_cb (ev, cb)
		3131
		3132	Can be used to change the callback member declaration in each watcher,
		3133	and the way callbacks are invoked and set. Must expand to a struct member
		3134	definition and a statement, respectively. See the F<ev.h> header file for
		3135	their default definitions. One possible use for overriding these is to
		3136	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		3137	method calls instead of plain function calls in C++.
		3138
		3139	=head2 EXPORTED API SYMBOLS
		3140
		3141	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3142	exported symbols, you can use the provided F<Symbol.*> files which list
		3143	all public symbols, one per line:
		3144
		3145	Symbols.ev for libev proper
		3146	Symbols.event for the libevent emulation
		3147
		3148	This can also be used to rename all public symbols to avoid clashes with
		3149	multiple versions of libev linked together (which is obviously bad in
		3150	itself, but sometimes it is inconvenient to avoid this).
		3151
		3152	A sed command like this will create wrapper C<#define>'s that you need to
		3153	include before including F<ev.h>:
		3154
		3155	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3156
		3157	This would create a file F<wrap.h> which essentially looks like this:
		3158
		3159	#define ev_backend myprefix_ev_backend
		3160	#define ev_check_start myprefix_ev_check_start
		3161	#define ev_check_stop myprefix_ev_check_stop
		3162	...
		3163
		3164	=head2 EXAMPLES
		3165
		3166	For a real-world example of a program the includes libev
		3167	verbatim, you can have a look at the EV perl module
		3168	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		3169	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		3170	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		3171	will be compiled. It is pretty complex because it provides its own header
		3172	file.
		3173
		3174	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		3175	that everybody includes and which overrides some configure choices:
		3176
		3177	#define EV_MINIMAL 1
		3178	#define EV_USE_POLL 0
		3179	#define EV_MULTIPLICITY 0
		3180	#define EV_PERIODIC_ENABLE 0
		3181	#define EV_STAT_ENABLE 0
		3182	#define EV_FORK_ENABLE 0
		3183	#define EV_CONFIG_H <config.h>
		3184	#define EV_MINPRI 0
		3185	#define EV_MAXPRI 0
		3186
		3187	#include "ev++.h"
		3188
		3189	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		3190
		3191	#include "ev_cpp.h"
		3192	#include "ev.c"
		3193
		3194
		3195	=head1 THREADS AND COROUTINES
		3196
		3197	=head2 THREADS
		3198
		3199	Libev itself is completely thread-safe, but it uses no locking. This
		3200	means that you can use as many loops as you want in parallel, as long as
		3201	only one thread ever calls into one libev function with the same loop
		3202	parameter.
		3203
		3204	Or put differently: calls with different loop parameters can be done in
		3205	parallel from multiple threads, calls with the same loop parameter must be
		3206	done serially (but can be done from different threads, as long as only one
		3207	thread ever is inside a call at any point in time, e.g. by using a mutex
		3208	per loop).
		3209
		3210	If you want to know which design (one loop, locking, or multiple loops
		3211	without or something else still) is best for your problem, then I cannot
		3212	help you. I can give some generic advice however:
		3213
		3214	=over 4
		3215
		3216	=item * most applications have a main thread: use the default libev loop
		3217	in that thread, or create a separate thread running only the default loop.
		3218
		3219	This helps integrating other libraries or software modules that use libev
		3220	themselves and don't care/know about threading.
		3221
		3222	=item * one loop per thread is usually a good model.
		3223
		3224	Doing this is almost never wrong, sometimes a better-performance model
		3225	exists, but it is always a good start.
		3226
		3227	=item * other models exist, such as the leader/follower pattern, where one
		3228	loop is handed through multiple threads in a kind of round-robin fashion.
		3229
		3230	Choosing a model is hard - look around, learn, know that usually you can do
		3231	better than you currently do :-)
		3232
		3233	=item * often you need to talk to some other thread which blocks in the
		3234	event loop - C<ev_async> watchers can be used to wake them up from other
		3235	threads safely (or from signal contexts...).
		3236
		3237	=back
		3238
		3239	=head2 COROUTINES
		3240
		3241	Libev is much more accommodating to coroutines ("cooperative threads"):
		3242	libev fully supports nesting calls to it's functions from different
		3243	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3244	different coroutines and switch freely between both coroutines running the
		3245	loop, as long as you don't confuse yourself). The only exception is that
		3246	you must not do this from C<ev_periodic> reschedule callbacks.
		3247
		3248	Care has been invested into making sure that libev does not keep local
		3249	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3250	switches.
		3251
		3252
		3253	=head1 COMPLEXITIES
		3254
		3255	In this section the complexities of (many of) the algorithms used inside
		3256	libev will be explained. For complexity discussions about backends see the
		3257	documentation for C<ev_default_init>.
		3258
		3259	All of the following are about amortised time: If an array needs to be
		3260	extended, libev needs to realloc and move the whole array, but this
		3261	happens asymptotically never with higher number of elements, so O(1) might
		3262	mean it might do a lengthy realloc operation in rare cases, but on average
		3263	it is much faster and asymptotically approaches constant time.
		3264
		3265	=over 4
		3266
		3267	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3268
		3269	This means that, when you have a watcher that triggers in one hour and
		3270	there are 100 watchers that would trigger before that then inserting will
		3271	have to skip roughly seven (C<ld 100>) of these watchers.
		3272
		3273	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3274
		3275	That means that changing a timer costs less than removing/adding them
		3276	as only the relative motion in the event queue has to be paid for.
		3277
		3278	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3279
		3280	These just add the watcher into an array or at the head of a list.
		3281
		3282	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3283
		3284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3285
		3286	These watchers are stored in lists then need to be walked to find the
		3287	correct watcher to remove. The lists are usually short (you don't usually
		3288	have many watchers waiting for the same fd or signal).
		3289
		3290	=item Finding the next timer in each loop iteration: O(1)
		3291
		3292	By virtue of using a binary or 4-heap, the next timer is always found at a
		3293	fixed position in the storage array.
		3294
		3295	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3296
		3297	A change means an I/O watcher gets started or stopped, which requires
		3298	libev to recalculate its status (and possibly tell the kernel, depending
		3299	on backend and whether C<ev_io_set> was used).
		3300
		3301	=item Activating one watcher (putting it into the pending state): O(1)
		3302
		3303	=item Priority handling: O(number_of_priorities)
		3304
		3305	Priorities are implemented by allocating some space for each
		3306	priority. When doing priority-based operations, libev usually has to
		3307	linearly search all the priorities, but starting/stopping and activating
		3308	watchers becomes O(1) w.r.t. priority handling.
		3309
		3310	=item Sending an ev_async: O(1)
		3311
		3312	=item Processing ev_async_send: O(number_of_async_watchers)
		3313
		3314	=item Processing signals: O(max_signal_number)
		3315
		3316	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3317	calls in the current loop iteration. Checking for async and signal events
		3318	involves iterating over all running async watchers or all signal numbers.
		3319
		3320	=back
		3321
		3322
		3323	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3324
		3325	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3326	requires, and its I/O model is fundamentally incompatible with the POSIX
		3327	model. Libev still offers limited functionality on this platform in
		3328	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3329	descriptors. This only applies when using Win32 natively, not when using
		3330	e.g. cygwin.
		3331
		3332	Lifting these limitations would basically require the full
		3333	re-implementation of the I/O system. If you are into these kinds of
		3334	things, then note that glib does exactly that for you in a very portable
		3335	way (note also that glib is the slowest event library known to man).
		3336
		3337	There is no supported compilation method available on windows except
		3338	embedding it into other applications.
		3339
		3340	Not a libev limitation but worth mentioning: windows apparently doesn't
		3341	accept large writes: instead of resulting in a partial write, windows will
		3342	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3343	so make sure you only write small amounts into your sockets (less than a
		3344	megabyte seems safe, but thsi apparently depends on the amount of memory
		3345	available).
		3346
		3347	Due to the many, low, and arbitrary limits on the win32 platform and
		3348	the abysmal performance of winsockets, using a large number of sockets
		3349	is not recommended (and not reasonable). If your program needs to use
		3350	more than a hundred or so sockets, then likely it needs to use a totally
		3351	different implementation for windows, as libev offers the POSIX readiness
		3352	notification model, which cannot be implemented efficiently on windows
		3353	(Microsoft monopoly games).
		3354
		3355	A typical way to use libev under windows is to embed it (see the embedding
		3356	section for details) and use the following F<evwrap.h> header file instead
		3357	of F<ev.h>:
		3358
		3359	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3360	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3361
		3362	#include "ev.h"
		3363
		3364	And compile the following F<evwrap.c> file into your project (make sure
		3365	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3366
		3367	#include "evwrap.h"
		3368	#include "ev.c"
		3369
		3370	=over 4
		3371
		3372	=item The winsocket select function
		3373
		3374	The winsocket C<select> function doesn't follow POSIX in that it
		3375	requires socket I<handles> and not socket I<file descriptors> (it is
		3376	also extremely buggy). This makes select very inefficient, and also
		3377	requires a mapping from file descriptors to socket handles (the Microsoft
		3378	C runtime provides the function C<_open_osfhandle> for this). See the
		3379	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3380	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3381
		3382	The configuration for a "naked" win32 using the Microsoft runtime
		3383	libraries and raw winsocket select is:
		3384
		3385	#define EV_USE_SELECT 1
		3386	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3387
		3388	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3389	complexity in the O(n²) range when using win32.
		3390
		3391	=item Limited number of file descriptors
		3392
		3393	Windows has numerous arbitrary (and low) limits on things.
		3394
		3395	Early versions of winsocket's select only supported waiting for a maximum
		3396	of C<64> handles (probably owning to the fact that all windows kernels
		3397	can only wait for C<64> things at the same time internally; Microsoft
		3398	recommends spawning a chain of threads and wait for 63 handles and the
		3399	previous thread in each. Great).
		3400
		3401	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3402	to some high number (e.g. C<2048>) before compiling the winsocket select
		3403	call (which might be in libev or elsewhere, for example, perl does its own
		3404	select emulation on windows).
		3405
		3406	Another limit is the number of file descriptors in the Microsoft runtime
		3407	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3408	or something like this inside Microsoft). You can increase this by calling
		3409	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3410	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3411	libraries.
		3412
		3413	This might get you to about C<512> or C<2048> sockets (depending on
		3414	windows version and/or the phase of the moon). To get more, you need to
		3415	wrap all I/O functions and provide your own fd management, but the cost of
		3416	calling select (O(n²)) will likely make this unworkable.
		3417
		3418	=back
		3419
		3420
		3421	=head1 PORTABILITY REQUIREMENTS
		3422
		3423	In addition to a working ISO-C implementation, libev relies on a few
		3424	additional extensions:
		3425
		3426	=over 4
		3427
		3428	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3429	calling conventions regardless of C<ev_watcher_type *>.
		3430
		3431	Libev assumes not only that all watcher pointers have the same internal
		3432	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3433	assumes that the same (machine) code can be used to call any watcher
		3434	callback: The watcher callbacks have different type signatures, but libev
		3435	calls them using an C<ev_watcher *> internally.
		3436
		3437	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3438
		3439	The type C<sig_atomic_t volatile> (or whatever is defined as
		3440	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3441	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3442	believed to be sufficiently portable.
		3443
		3444	=item C<sigprocmask> must work in a threaded environment
		3445
		3446	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3447	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3448	pthread implementations will either allow C<sigprocmask> in the "main
		3449	thread" or will block signals process-wide, both behaviours would
		3450	be compatible with libev. Interaction between C<sigprocmask> and
		3451	C<pthread_sigmask> could complicate things, however.
		3452
		3453	The most portable way to handle signals is to block signals in all threads
		3454	except the initial one, and run the default loop in the initial thread as
		3455	well.
		3456
		3457	=item C<long> must be large enough for common memory allocation sizes
		3458
		3459	To improve portability and simplify using libev, libev uses C<long>
		3460	internally instead of C<size_t> when allocating its data structures. On
		3461	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3462	is still at least 31 bits everywhere, which is enough for hundreds of
		3463	millions of watchers.
		3464
		3465	=item C<double> must hold a time value in seconds with enough accuracy
		3466
		3467	The type C<double> is used to represent timestamps. It is required to
		3468	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3469	enough for at least into the year 4000. This requirement is fulfilled by
		3470	implementations implementing IEEE 754 (basically all existing ones).
		3471
		3472	=back
		3473
		3474	If you know of other additional requirements drop me a note.
		3475
		3476
		3477	=head1 COMPILER WARNINGS
		3478
		3479	Depending on your compiler and compiler settings, you might get no or a
		3480	lot of warnings when compiling libev code. Some people are apparently
		3481	scared by this.
		3482
		3483	However, these are unavoidable for many reasons. For one, each compiler
		3484	has different warnings, and each user has different tastes regarding
		3485	warning options. "Warn-free" code therefore cannot be a goal except when
		3486	targeting a specific compiler and compiler-version.
		3487
		3488	Another reason is that some compiler warnings require elaborate
		3489	workarounds, or other changes to the code that make it less clear and less
		3490	maintainable.
		3491
		3492	And of course, some compiler warnings are just plain stupid, or simply
		3493	wrong (because they don't actually warn about the condition their message
		3494	seems to warn about).
		3495
		3496	While libev is written to generate as few warnings as possible,
		3497	"warn-free" code is not a goal, and it is recommended not to build libev
		3498	with any compiler warnings enabled unless you are prepared to cope with
		3499	them (e.g. by ignoring them). Remember that warnings are just that:
		3500	warnings, not errors, or proof of bugs.
		3501
		3502
		3503	=head1 VALGRIND
		3504
		3505	Valgrind has a special section here because it is a popular tool that is
		3506	highly useful, but valgrind reports are very hard to interpret.
		3507
		3508	If you think you found a bug (memory leak, uninitialised data access etc.)
		3509	in libev, then check twice: If valgrind reports something like:
		3510
		3511	==2274== definitely lost: 0 bytes in 0 blocks.
		3512	==2274== possibly lost: 0 bytes in 0 blocks.
		3513	==2274== still reachable: 256 bytes in 1 blocks.
		3514
		3515	Then there is no memory leak. Similarly, under some circumstances,
		3516	valgrind might report kernel bugs as if it were a bug in libev, or it
		3517	might be confused (it is a very good tool, but only a tool).
		3518
		3519	If you are unsure about something, feel free to contact the mailing list
		3520	with the full valgrind report and an explanation on why you think this is
		3521	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3522	no bug" answer and take the chance of learning how to interpret valgrind
		3523	properly.
		3524
		3525	If you need, for some reason, empty reports from valgrind for your project
		3526	I suggest using suppression lists.
		3527
825		3528
826	=head1 AUTHOR	3529	=head1 AUTHOR
827		3530
828	Marc Lehmann <libev@schmorp.de>.	3531	Marc Lehmann <libev@schmorp.de>.
829		3532

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