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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		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	}
		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://cvs.schmorp.de/libev/ev.html>.
		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 floatingpoint value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
51		121
52	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
53		123
54	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
55	library in any way.	125	library in any way.
…		…
60		130
61	Returns the current time as libev would use it. Please note that the	131	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	132	C<ev_now> function is usually faster and also often returns the timestamp
63	you actually want to know.	133	you actually want to know.
64		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
65	=item int ev_version_major ()	141	=item int ev_version_major ()
66		142
67	=item int ev_version_minor ()	143	=item int ev_version_minor ()
68		144
69	You can find out the major and minor version numbers of the library	145	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	146	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	147	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	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
73	version of the library your program was compiled against.	149	version of the library your program was compiled against.
74		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
75	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	157	not a problem.
79		158
		159	Example: Make sure we haven't accidentally been linked against the wrong
		160	version.
		161
		162	assert (("libev version mismatch",
		163	ev_version_major () == EV_VERSION_MAJOR
		164	&& ev_version_minor () >= EV_VERSION_MINOR));
		165
		166	=item unsigned int ev_supported_backends ()
		167
		168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		169	value) compiled into this binary of libev (independent of their
		170	availability on the system you are running on). See C<ev_default_loop> for
		171	a description of the set values.
		172
		173	Example: make sure we have the epoll method, because yeah this is cool and
		174	a must have and can we have a torrent of it please!!!11
		175
		176	assert (("sorry, no epoll, no sex",
		177	ev_supported_backends () & EVBACKEND_EPOLL));
		178
		179	=item unsigned int ev_recommended_backends ()
		180
		181	Return the set of all backends compiled into this binary of libev and also
		182	recommended for this platform. This set is often smaller than the one
		183	returned by C<ev_supported_backends>, as for example kqueue is broken on
		184	most BSDs and will not be autodetected unless you explicitly request it
		185	(assuming you know what you are doing). This is the set of backends that
		186	libev will probe for if you specify no backends explicitly.
		187
		188	=item unsigned int ev_embeddable_backends ()
		189
		190	Returns the set of backends that are embeddable in other event loops. This
		191	is the theoretical, all-platform, value. To find which backends
		192	might be supported on the current system, you would need to look at
		193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		194	recommended ones.
		195
		196	See the description of C<ev_embed> watchers for more info.
		197
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		199
82	Sets the allocation function to use (the prototype is similar to the	200	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	201	semantics is identical - to the realloc C function). It is used to
84	and free memory (no surprises here). If it returns zero when memory	202	allocate and free memory (no surprises here). If it returns zero when
85	needs to be allocated, the library might abort or take some potentially	203	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	204	potentially destructive action. The default is your system realloc
		205	function.
87		206
88	You could override this function in high-availability programs to, say,	207	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,	208	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.	209	or even to sleep a while and retry until some memory is available.
		210
		211	Example: Replace the libev allocator with one that waits a bit and then
		212	retries).
		213
		214	static void *
		215	persistent_realloc (void *ptr, size_t size)
		216	{
		217	for (;;)
		218	{
		219	void *newptr = realloc (ptr, size);
		220
		221	if (newptr)
		222	return newptr;
		223
		224	sleep (60);
		225	}
		226	}
		227
		228	...
		229	ev_set_allocator (persistent_realloc);
91		230
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	231	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		232
94	Set the callback function to call on a retryable syscall error (such	233	Set the callback function to call on a retryable syscall error (such
95	as failed select, poll, epoll_wait). The message is a printable string	234	as failed select, poll, epoll_wait). The message is a printable string
…		…
97	callback is set, then libev will expect it to remedy the sitution, no	236	callback is set, then libev will expect it to remedy the sitution, no
98	matter what, when it returns. That is, libev will generally retry the	237	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	238	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	239	(such as abort).
101		240
		241	Example: This is basically the same thing that libev does internally, too.
		242
		243	static void
		244	fatal_error (const char *msg)
		245	{
		246	perror (msg);
		247	abort ();
		248	}
		249
		250	...
		251	ev_set_syserr_cb (fatal_error);
		252
102	=back	253	=back
103		254
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		256
106	An event loop is described by a C<struct ev_loop *>. The library knows two	257	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	258	types of such loops, the I<default> loop, which supports signals and child
108	events, and dynamically created loops which do not.	259	events, and dynamically created loops which do not.
109		260
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	261	=over 4
118		262
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	263	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		264
121	This will initialise the default event loop if it hasn't been initialised	265	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	266	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	267	false. If it already was initialised it simply returns it (and ignores the
124	flags).	268	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		269
126	If you don't know what event loop to use, use the one returned from this	270	If you don't know what event loop to use, use the one returned from this
127	function.	271	function.
128		272
		273	Note that this function is I<not> thread-safe, so if you want to use it
		274	from multiple threads, you have to lock (note also that this is unlikely,
		275	as loops cannot bes hared easily between threads anyway).
		276
		277	The default loop is the only loop that can handle C<ev_signal> and
		278	C<ev_child> watchers, and to do this, it always registers a handler
		279	for C<SIGCHLD>. If this is a problem for your app you can either
		280	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		282	C<ev_default_init>.
		283
129	The flags argument can be used to specify special behaviour or specific	284	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).	285	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		286
132	It supports the following flags:	287	The following flags are supported:
133		288
134	=over 4	289	=over 4
135		290
136	=item C<EVFLAG_AUTO>	291	=item C<EVFLAG_AUTO>
137		292
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	300	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	301	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	302	useful to try out specific backends to test their performance, or to work
148	around bugs.	303	around bugs.
149		304
		305	=item C<EVFLAG_FORKCHECK>
		306
		307	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		308	a fork, you can also make libev check for a fork in each iteration by
		309	enabling this flag.
		310
		311	This works by calling C<getpid ()> on every iteration of the loop,
		312	and thus this might slow down your event loop if you do a lot of loop
		313	iterations and little real work, but is usually not noticeable (on my
		314	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		315	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		316	C<pthread_atfork> which is even faster).
		317
		318	The big advantage of this flag is that you can forget about fork (and
		319	forget about forgetting to tell libev about forking) when you use this
		320	flag.
		321
		322	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		323	environment variable.
		324
150	=item C<EVMETHOD_SELECT> (portable select backend)	325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		326
		327	This is your standard select(2) backend. Not I<completely> standard, as
		328	libev tries to roll its own fd_set with no limits on the number of fds,
		329	but if that fails, expect a fairly low limit on the number of fds when
		330	using this backend. It doesn't scale too well (O(highest_fd)), but its
		331	usually the fastest backend for a low number of (low-numbered :) fds.
		332
		333	To get good performance out of this backend you need a high amount of
		334	parallelity (most of the file descriptors should be busy). If you are
		335	writing a server, you should C<accept ()> in a loop to accept as many
		336	connections as possible during one iteration. You might also want to have
		337	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		338	readyness notifications you get per iteration.
		339
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	340	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		341
154	=item C<EVMETHOD_EPOLL> (linux only)	342	And this is your standard poll(2) backend. It's more complicated
		343	than select, but handles sparse fds better and has no artificial
		344	limit on the number of fds you can use (except it will slow down
		345	considerably with a lot of inactive fds). It scales similarly to select,
		346	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		347	performance tips.
155		348
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	349	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		350
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	351	For few fds, this backend is a bit little slower than poll and select,
		352	but it scales phenomenally better. While poll and select usually scale
		353	like O(total_fds) where n is the total number of fds (or the highest fd),
		354	epoll scales either O(1) or O(active_fds). The epoll design has a number
		355	of shortcomings, such as silently dropping events in some hard-to-detect
		356	cases and requiring a syscall per fd change, no fork support and bad
		357	support for dup.
159		358
160	=item C<EVMETHOD_PORT> (solaris 10 only)	359	While stopping, setting and starting an I/O watcher in the same iteration
		360	will result in some caching, there is still a syscall per such incident
		361	(because the fd could point to a different file description now), so its
		362	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		363	very well if you register events for both fds.
		364
		365	Please note that epoll sometimes generates spurious notifications, so you
		366	need to use non-blocking I/O or other means to avoid blocking when no data
		367	(or space) is available.
		368
		369	Best performance from this backend is achieved by not unregistering all
		370	watchers for a file descriptor until it has been closed, if possible, i.e.
		371	keep at least one watcher active per fd at all times.
		372
		373	While nominally embeddeble in other event loops, this feature is broken in
		374	all kernel versions tested so far.
		375
		376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		377
		378	Kqueue deserves special mention, as at the time of this writing, it
		379	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		380	with anything but sockets and pipes, except on Darwin, where of course
		381	it's completely useless). For this reason it's not being "autodetected"
		382	unless you explicitly specify it explicitly in the flags (i.e. using
		383	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		384	system like NetBSD.
		385
		386	You still can embed kqueue into a normal poll or select backend and use it
		387	only for sockets (after having made sure that sockets work with kqueue on
		388	the target platform). See C<ev_embed> watchers for more info.
		389
		390	It scales in the same way as the epoll backend, but the interface to the
		391	kernel is more efficient (which says nothing about its actual speed, of
		392	course). While stopping, setting and starting an I/O watcher does never
		393	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
		394	two event changes per incident, support for C<fork ()> is very bad and it
		395	drops fds silently in similarly hard-to-detect cases.
		396
		397	This backend usually performs well under most conditions.
		398
		399	While nominally embeddable in other event loops, this doesn't work
		400	everywhere, so you might need to test for this. And since it is broken
		401	almost everywhere, you should only use it when you have a lot of sockets
		402	(for which it usually works), by embedding it into another event loop
		403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		404	sockets.
		405
		406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		407
		408	This is not implemented yet (and might never be, unless you send me an
		409	implementation). According to reports, C</dev/poll> only supports sockets
		410	and is not embeddable, which would limit the usefulness of this backend
		411	immensely.
		412
		413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		414
		415	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		416	it's really slow, but it still scales very well (O(active_fds)).
		417
		418	Please note that solaris event ports can deliver a lot of spurious
		419	notifications, so you need to use non-blocking I/O or other means to avoid
		420	blocking when no data (or space) is available.
		421
		422	While this backend scales well, it requires one system call per active
		423	file descriptor per loop iteration. For small and medium numbers of file
		424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		425	might perform better.
		426
		427	On the positive side, ignoring the spurious readyness notifications, this
		428	backend actually performed to specification in all tests and is fully
		429	embeddable, which is a rare feat among the OS-specific backends.
		430
		431	=item C<EVBACKEND_ALL>
		432
		433	Try all backends (even potentially broken ones that wouldn't be tried
		434	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		435	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		436
		437	It is definitely not recommended to use this flag.
		438
		439	=back
161		440
162	If one or more of these are ored into the flags value, then only these	441	If one or more of these are ored into the flags value, then only these
163	backends will be tried (in the reverse order as given here). If one are	442	backends will be tried (in the reverse order as listed here). If none are
164	specified, any backend will do.	443	specified, all backends in C<ev_recommended_backends ()> will be tried.
165		444
166	=back	445	The most typical usage is like this:
		446
		447	if (!ev_default_loop (0))
		448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		449
		450	Restrict libev to the select and poll backends, and do not allow
		451	environment settings to be taken into account:
		452
		453	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		454
		455	Use whatever libev has to offer, but make sure that kqueue is used if
		456	available (warning, breaks stuff, best use only with your own private
		457	event loop and only if you know the OS supports your types of fds):
		458
		459	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
167		460
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	461	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		462
170	Similar to C<ev_default_loop>, but always creates a new event loop that is	463	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	464	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	465	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).	466	undefined behaviour (or a failed assertion if assertions are enabled).
174		467
		468	Note that this function I<is> thread-safe, and the recommended way to use
		469	libev with threads is indeed to create one loop per thread, and using the
		470	default loop in the "main" or "initial" thread.
		471
		472	Example: Try to create a event loop that uses epoll and nothing else.
		473
		474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		475	if (!epoller)
		476	fatal ("no epoll found here, maybe it hides under your chair");
		477
175	=item ev_default_destroy ()	478	=item ev_default_destroy ()
176		479
177	Destroys the default loop again (frees all memory and kernel state	480	Destroys the default loop again (frees all memory and kernel state
178	etc.). This stops all registered event watchers (by not touching them in	481	etc.). None of the active event watchers will be stopped in the normal
179	any way whatsoever, although you cannot rely on this :).	482	sense, so e.g. C<ev_is_active> might still return true. It is your
		483	responsibility to either stop all watchers cleanly yoursef I<before>
		484	calling this function, or cope with the fact afterwards (which is usually
		485	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		486	for example).
		487
		488	Note that certain global state, such as signal state, will not be freed by
		489	this function, and related watchers (such as signal and child watchers)
		490	would need to be stopped manually.
		491
		492	In general it is not advisable to call this function except in the
		493	rare occasion where you really need to free e.g. the signal handling
		494	pipe fds. If you need dynamically allocated loops it is better to use
		495	C<ev_loop_new> and C<ev_loop_destroy>).
180		496
181	=item ev_loop_destroy (loop)	497	=item ev_loop_destroy (loop)
182		498
183	Like C<ev_default_destroy>, but destroys an event loop created by an	499	Like C<ev_default_destroy>, but destroys an event loop created by an
184	earlier call to C<ev_loop_new>.	500	earlier call to C<ev_loop_new>.
185		501
186	=item ev_default_fork ()	502	=item ev_default_fork ()
187		503
		504	This function sets a flag that causes subsequent C<ev_loop> iterations
188	This function reinitialises the kernel state for backends that have	505	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	506	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	507	the child process (or both child and parent, but that again makes little
191	again makes little sense).	508	sense). You I<must> call it in the child before using any of the libev
		509	functions, and it will only take effect at the next C<ev_loop> iteration.
192		510
193	You I<must> call this function after forking if and only if you want to	511	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	512	process if and only if you want to use the event library in the child. If
195	have to call it.	513	you just fork+exec, you don't have to call it at all.
196		514
197	The function itself is quite fast and it's usually not a problem to call	515	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	516	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>:	517	quite nicely into a call to C<pthread_atfork>:
200		518
…		…
204		522
205	Like C<ev_default_fork>, but acts on an event loop created by	523	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	524	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.	525	after fork, and how you do this is entirely your own problem.
208		526
		527	=item int ev_is_default_loop (loop)
		528
		529	Returns true when the given loop actually is the default loop, false otherwise.
		530
		531	=item unsigned int ev_loop_count (loop)
		532
		533	Returns the count of loop iterations for the loop, which is identical to
		534	the number of times libev did poll for new events. It starts at C<0> and
		535	happily wraps around with enough iterations.
		536
		537	This value can sometimes be useful as a generation counter of sorts (it
		538	"ticks" the number of loop iterations), as it roughly corresponds with
		539	C<ev_prepare> and C<ev_check> calls.
		540
209	=item unsigned int ev_method (loop)	541	=item unsigned int ev_backend (loop)
210		542
211	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	543	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
212	use.	544	use.
213		545
214	=item ev_tstamp ev_now (loop)	546	=item ev_tstamp ev_now (loop)
215		547
216	Returns the current "event loop time", which is the time the event loop	548	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	549	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	550	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	551	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).	552	event occurring (or more correctly, libev finding out about it).
221		553
222	=item ev_loop (loop, int flags)	554	=item ev_loop (loop, int flags)
223		555
224	Finally, this is it, the event handler. This function usually is called	556	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	557	after you initialised all your watchers and you want to start handling
226	events.	558	events.
227		559
228	If the flags argument is specified as 0, it will not return until either	560	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.	561	either no event watchers are active anymore or C<ev_unloop> was called.
		562
		563	Please note that an explicit C<ev_unloop> is usually better than
		564	relying on all watchers to be stopped when deciding when a program has
		565	finished (especially in interactive programs), but having a program that
		566	automatically loops as long as it has to and no longer by virtue of
		567	relying on its watchers stopping correctly is a thing of beauty.
230		568
231	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	569	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	570	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.	571	case there are no events and will return after one iteration of the loop.
234		572
235	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	573	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	574	neccessary) 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	575	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	576	one iteration of the loop. This is useful if you are waiting for some
		577	external event in conjunction with something not expressible using other
		578	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		579	usually a better approach for this kind of thing.
239		580
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:	581	Here are the gory details of what C<ev_loop> does:
245		582
246	1. If there are no active watchers (reference count is zero), return.	583	- Before the first iteration, call any pending watchers.
		584	* If EVFLAG_FORKCHECK was used, check for a fork.
		585	- If a fork was detected, queue and call all fork watchers.
247	2. Queue and immediately call all prepare watchers.	586	- Queue and call all prepare watchers.
248	3. If we have been forked, recreate the kernel state.	587	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	588	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	589	- Update the "event loop time".
251	6. Calculate for how long to block.	590	- Calculate for how long to sleep or block, if at all
		591	(active idle watchers, EVLOOP_NONBLOCK or not having
		592	any active watchers at all will result in not sleeping).
		593	- Sleep if the I/O and timer collect interval say so.
252	7. Block the process, waiting for events.	594	- Block the process, waiting for any events.
		595	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	596	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	597	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	598	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	599	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	600	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	601	- Call all queued watchers in reverse order (i.e. check watchers first).
		602	Signals and child watchers are implemented as I/O watchers, and will
		603	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	604	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	605	were used, or there are no active watchers, return, otherwise
		606	continue with step *.
		607
		608	Example: Queue some jobs and then loop until no events are outstanding
		609	anymore.
		610
		611	... queue jobs here, make sure they register event watchers as long
		612	... as they still have work to do (even an idle watcher will do..)
		613	ev_loop (my_loop, 0);
		614	... jobs done. yeah!
261		615
262	=item ev_unloop (loop, how)	616	=item ev_unloop (loop, how)
263		617
264	Can be used to make a call to C<ev_loop> return early (but only after it	618	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	619	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	620	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.	621	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		622
		623	This "unloop state" will be cleared when entering C<ev_loop> again.
268		624
269	=item ev_ref (loop)	625	=item ev_ref (loop)
270		626
271	=item ev_unref (loop)	627	=item ev_unref (loop)
272		628
…		…
277	returning, ev_unref() after starting, and ev_ref() before stopping it. For	633	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	634	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	635	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	636	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	637	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>.	638	libraries. Just remember to I<unref after start> and I<ref before stop>
		639	(but only if the watcher wasn't active before, or was active before,
		640	respectively).
		641
		642	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		643	running when nothing else is active.
		644
		645	struct ev_signal exitsig;
		646	ev_signal_init (&exitsig, sig_cb, SIGINT);
		647	ev_signal_start (loop, &exitsig);
		648	evf_unref (loop);
		649
		650	Example: For some weird reason, unregister the above signal handler again.
		651
		652	ev_ref (loop);
		653	ev_signal_stop (loop, &exitsig);
		654
		655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		656
		657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		658
		659	These advanced functions influence the time that libev will spend waiting
		660	for events. Both are by default C<0>, meaning that libev will try to
		661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		662
		663	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		664	allows libev to delay invocation of I/O and timer/periodic callbacks to
		665	increase efficiency of loop iterations.
		666
		667	The background is that sometimes your program runs just fast enough to
		668	handle one (or very few) event(s) per loop iteration. While this makes
		669	the program responsive, it also wastes a lot of CPU time to poll for new
		670	events, especially with backends like C<select ()> which have a high
		671	overhead for the actual polling but can deliver many events at once.
		672
		673	By setting a higher I<io collect interval> you allow libev to spend more
		674	time collecting I/O events, so you can handle more events per iteration,
		675	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		676	C<ev_timer>) will be not affected. Setting this to a non-null value will
		677	introduce an additional C<ev_sleep ()> call into most loop iterations.
		678
		679	Likewise, by setting a higher I<timeout collect interval> you allow libev
		680	to spend more time collecting timeouts, at the expense of increased
		681	latency (the watcher callback will be called later). C<ev_io> watchers
		682	will not be affected. Setting this to a non-null value will not introduce
		683	any overhead in libev.
		684
		685	Many (busy) programs can usually benefit by setting the io collect
		686	interval to a value near C<0.1> or so, which is often enough for
		687	interactive servers (of course not for games), likewise for timeouts. It
		688	usually doesn't make much sense to set it to a lower value than C<0.01>,
		689	as this approsaches the timing granularity of most systems.
283		690
284	=back	691	=back
		692
285		693
286	=head1 ANATOMY OF A WATCHER	694	=head1 ANATOMY OF A WATCHER
287		695
288	A watcher is a structure that you create and register to record your	696	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	697	interest in some event. For instance, if you want to wait for STDIN to
…		…
322	*) >>), and you can stop watching for events at any time by calling the	730	*) >>), and you can stop watching for events at any time by calling the
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	731	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		732
325	As long as your watcher is active (has been started but not stopped) you	733	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	734	must not touch the values stored in it. Most specifically you must never
327	reinitialise it or call its set method.	735	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		736
334	Each and every callback receives the event loop pointer as first, the	737	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	738	registered watcher structure as second, and a bitset of received events as
336	third argument.	739	third argument.
337		740
…		…
361	The signal specified in the C<ev_signal> watcher has been received by a thread.	764	The signal specified in the C<ev_signal> watcher has been received by a thread.
362		765
363	=item C<EV_CHILD>	766	=item C<EV_CHILD>
364		767
365	The pid specified in the C<ev_child> watcher has received a status change.	768	The pid specified in the C<ev_child> watcher has received a status change.
		769
		770	=item C<EV_STAT>
		771
		772	The path specified in the C<ev_stat> watcher changed its attributes somehow.
366		773
367	=item C<EV_IDLE>	774	=item C<EV_IDLE>
368		775
369	The C<ev_idle> watcher has determined that you have nothing better to do.	776	The C<ev_idle> watcher has determined that you have nothing better to do.
370		777
…		…
378	received events. Callbacks of both watcher types can start and stop as	785	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	786	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	787	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
381	C<ev_loop> from blocking).	788	C<ev_loop> from blocking).
382		789
		790	=item C<EV_EMBED>
		791
		792	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		793
		794	=item C<EV_FORK>
		795
		796	The event loop has been resumed in the child process after fork (see
		797	C<ev_fork>).
		798
		799	=item C<EV_ASYNC>
		800
		801	The given async watcher has been asynchronously notified (see C<ev_async>).
		802
383	=item C<EV_ERROR>	803	=item C<EV_ERROR>
384		804
385	An unspecified error has occured, the watcher has been stopped. This might	805	An unspecified error has occured, the watcher has been stopped. This might
386	happen because the watcher could not be properly started because libev	806	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	807	ran out of memory, a file descriptor was found to be closed or any other
…		…
393	your callbacks is well-written it can just attempt the operation and cope	813	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	814	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.	815	programs, though, so beware.
396		816
397	=back	817	=back
		818
		819	=head2 GENERIC WATCHER FUNCTIONS
		820
		821	In the following description, C<TYPE> stands for the watcher type,
		822	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		823
		824	=over 4
		825
		826	=item C<ev_init> (ev_TYPE *watcher, callback)
		827
		828	This macro initialises the generic portion of a watcher. The contents
		829	of the watcher object can be arbitrary (so C<malloc> will do). Only
		830	the generic parts of the watcher are initialised, you I<need> to call
		831	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		832	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		833	which rolls both calls into one.
		834
		835	You can reinitialise a watcher at any time as long as it has been stopped
		836	(or never started) and there are no pending events outstanding.
		837
		838	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		839	int revents)>.
		840
		841	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		842
		843	This macro initialises the type-specific parts of a watcher. You need to
		844	call C<ev_init> at least once before you call this macro, but you can
		845	call C<ev_TYPE_set> any number of times. You must not, however, call this
		846	macro on a watcher that is active (it can be pending, however, which is a
		847	difference to the C<ev_init> macro).
		848
		849	Although some watcher types do not have type-specific arguments
		850	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		851
		852	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		853
		854	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		855	calls into a single call. This is the most convinient method to initialise
		856	a watcher. The same limitations apply, of course.
		857
		858	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		859
		860	Starts (activates) the given watcher. Only active watchers will receive
		861	events. If the watcher is already active nothing will happen.
		862
		863	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		864
		865	Stops the given watcher again (if active) and clears the pending
		866	status. It is possible that stopped watchers are pending (for example,
		867	non-repeating timers are being stopped when they become pending), but
		868	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		869	you want to free or reuse the memory used by the watcher it is therefore a
		870	good idea to always call its C<ev_TYPE_stop> function.
		871
		872	=item bool ev_is_active (ev_TYPE *watcher)
		873
		874	Returns a true value iff the watcher is active (i.e. it has been started
		875	and not yet been stopped). As long as a watcher is active you must not modify
		876	it.
		877
		878	=item bool ev_is_pending (ev_TYPE *watcher)
		879
		880	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		881	events but its callback has not yet been invoked). As long as a watcher
		882	is pending (but not active) you must not call an init function on it (but
		883	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		884	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		885	it).
		886
		887	=item callback ev_cb (ev_TYPE *watcher)
		888
		889	Returns the callback currently set on the watcher.
		890
		891	=item ev_cb_set (ev_TYPE *watcher, callback)
		892
		893	Change the callback. You can change the callback at virtually any time
		894	(modulo threads).
		895
		896	=item ev_set_priority (ev_TYPE *watcher, priority)
		897
		898	=item int ev_priority (ev_TYPE *watcher)
		899
		900	Set and query the priority of the watcher. The priority is a small
		901	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		902	(default: C<-2>). Pending watchers with higher priority will be invoked
		903	before watchers with lower priority, but priority will not keep watchers
		904	from being executed (except for C<ev_idle> watchers).
		905
		906	This means that priorities are I<only> used for ordering callback
		907	invocation after new events have been received. This is useful, for
		908	example, to reduce latency after idling, or more often, to bind two
		909	watchers on the same event and make sure one is called first.
		910
		911	If you need to suppress invocation when higher priority events are pending
		912	you need to look at C<ev_idle> watchers, which provide this functionality.
		913
		914	You I<must not> change the priority of a watcher as long as it is active or
		915	pending.
		916
		917	The default priority used by watchers when no priority has been set is
		918	always C<0>, which is supposed to not be too high and not be too low :).
		919
		920	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		921	fine, as long as you do not mind that the priority value you query might
		922	or might not have been adjusted to be within valid range.
		923
		924	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		925
		926	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		927	C<loop> nor C<revents> need to be valid as long as the watcher callback
		928	can deal with that fact.
		929
		930	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		931
		932	If the watcher is pending, this function returns clears its pending status
		933	and returns its C<revents> bitset (as if its callback was invoked). If the
		934	watcher isn't pending it does nothing and returns C<0>.
		935
		936	=back
		937
398		938
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	939	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		940
401	Each watcher has, by default, a member C<void *data> that you can change	941	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	942	and read at any time, libev will completely ignore it. This can be used
…		…
420	{	960	{
421	struct my_io *w = (struct my_io *)w_;	961	struct my_io *w = (struct my_io *)w_;
422	...	962	...
423	}	963	}
424		964
425	More interesting and less C-conformant ways of catsing your callback type	965	More interesting and less C-conformant ways of casting your callback type
426	have been omitted....	966	instead have been omitted.
		967
		968	Another common scenario is having some data structure with multiple
		969	watchers:
		970
		971	struct my_biggy
		972	{
		973	int some_data;
		974	ev_timer t1;
		975	ev_timer t2;
		976	}
		977
		978	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		979	you need to use C<offsetof>:
		980
		981	#include <stddef.h>
		982
		983	static void
		984	t1_cb (EV_P_ struct ev_timer *w, int revents)
		985	{
		986	struct my_biggy big = (struct my_biggy *
		987	(((char *)w) - offsetof (struct my_biggy, t1));
		988	}
		989
		990	static void
		991	t2_cb (EV_P_ struct ev_timer *w, int revents)
		992	{
		993	struct my_biggy big = (struct my_biggy *
		994	(((char *)w) - offsetof (struct my_biggy, t2));
		995	}
427		996
428		997
429	=head1 WATCHER TYPES	998	=head1 WATCHER TYPES
430		999
431	This section describes each watcher in detail, but will not repeat	1000	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	1001	information given in the last section. Any initialisation/set macros,
		1002	functions and members specific to the watcher type are explained.
433		1003
		1004	Members are additionally marked with either I<[read-only]>, meaning that,
		1005	while the watcher is active, you can look at the member and expect some
		1006	sensible content, but you must not modify it (you can modify it while the
		1007	watcher is stopped to your hearts content), or I<[read-write]>, which
		1008	means you can expect it to have some sensible content while the watcher
		1009	is active, but you can also modify it. Modifying it may not do something
		1010	sensible or take immediate effect (or do anything at all), but libev will
		1011	not crash or malfunction in any way.
		1012
		1013
434	=head2 C<ev_io> - is this file descriptor readable or writable	1014	=head2 C<ev_io> - is this file descriptor readable or writable?
435		1015
436	I/O watchers check whether a file descriptor is readable or writable	1016	I/O watchers check whether a file descriptor is readable or writable
437	in each iteration of the event loop (This behaviour is called	1017	in each iteration of the event loop, or, more precisely, when reading
438	level-triggering because you keep receiving events as long as the	1018	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	1019	some data. This behaviour is called level-triggering because you keep
440	act on the event and neither want to receive future events).	1020	receiving events as long as the condition persists. Remember you can stop
		1021	the watcher if you don't want to act on the event and neither want to
		1022	receive future events.
441		1023
442	In general you can register as many read and/or write event watchers per	1024	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	1025	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	1026	descriptors to non-blocking mode is also usually a good idea (but not
445	required if you know what you are doing).	1027	required if you know what you are doing).
446		1028
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	1029	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	1030	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	1031	C<EVBACKEND_POLL>).
		1032
		1033	Another thing you have to watch out for is that it is quite easy to
		1034	receive "spurious" readyness notifications, that is your callback might
		1035	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1036	because there is no data. Not only are some backends known to create a
		1037	lot of those (for example solaris ports), it is very easy to get into
		1038	this situation even with a relatively standard program structure. Thus
		1039	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1040	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1041
		1042	If you cannot run the fd in non-blocking mode (for example you should not
		1043	play around with an Xlib connection), then you have to seperately re-test
		1044	whether a file descriptor is really ready with a known-to-be good interface
		1045	such as poll (fortunately in our Xlib example, Xlib already does this on
		1046	its own, so its quite safe to use).
		1047
		1048	=head3 The special problem of disappearing file descriptors
		1049
		1050	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1051	descriptor (either by calling C<close> explicitly or by any other means,
		1052	such as C<dup>). The reason is that you register interest in some file
		1053	descriptor, but when it goes away, the operating system will silently drop
		1054	this interest. If another file descriptor with the same number then is
		1055	registered with libev, there is no efficient way to see that this is, in
		1056	fact, a different file descriptor.
		1057
		1058	To avoid having to explicitly tell libev about such cases, libev follows
		1059	the following policy: Each time C<ev_io_set> is being called, libev
		1060	will assume that this is potentially a new file descriptor, otherwise
		1061	it is assumed that the file descriptor stays the same. That means that
		1062	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1063	descriptor even if the file descriptor number itself did not change.
		1064
		1065	This is how one would do it normally anyway, the important point is that
		1066	the libev application should not optimise around libev but should leave
		1067	optimisations to libev.
		1068
		1069	=head3 The special problem of dup'ed file descriptors
		1070
		1071	Some backends (e.g. epoll), cannot register events for file descriptors,
		1072	but only events for the underlying file descriptions. That means when you
		1073	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1074	events for them, only one file descriptor might actually receive events.
		1075
		1076	There is no workaround possible except not registering events
		1077	for potentially C<dup ()>'ed file descriptors, or to resort to
		1078	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1079
		1080	=head3 The special problem of fork
		1081
		1082	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1083	useless behaviour. Libev fully supports fork, but needs to be told about
		1084	it in the child.
		1085
		1086	To support fork in your programs, you either have to call
		1087	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1088	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1089	C<EVBACKEND_POLL>.
		1090
		1091	=head3 The special problem of SIGPIPE
		1092
		1093	While not really specific to libev, it is easy to forget about SIGPIPE:
		1094	when reading from a pipe whose other end has been closed, your program
		1095	gets send a SIGPIPE, which, by default, aborts your program. For most
		1096	programs this is sensible behaviour, for daemons, this is usually
		1097	undesirable.
		1098
		1099	So when you encounter spurious, unexplained daemon exits, make sure you
		1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1101	somewhere, as that would have given you a big clue).
		1102
		1103
		1104	=head3 Watcher-Specific Functions
456		1105
457	=over 4	1106	=over 4
458		1107
459	=item ev_io_init (ev_io *, callback, int fd, int events)	1108	=item ev_io_init (ev_io *, callback, int fd, int events)
460		1109
461	=item ev_io_set (ev_io *, int fd, int events)	1110	=item ev_io_set (ev_io *, int fd, int events)
462		1111
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1112	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 |	1113	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
465	EV_WRITE> to receive the given events.	1114	C<EV_READ | EV_WRITE> to receive the given events.
		1115
		1116	=item int fd [read-only]
		1117
		1118	The file descriptor being watched.
		1119
		1120	=item int events [read-only]
		1121
		1122	The events being watched.
466		1123
467	=back	1124	=back
468		1125
		1126	=head3 Examples
		1127
		1128	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1129	readable, but only once. Since it is likely line-buffered, you could
		1130	attempt to read a whole line in the callback.
		1131
		1132	static void
		1133	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1134	{
		1135	ev_io_stop (loop, w);
		1136	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1137	}
		1138
		1139	...
		1140	struct ev_loop *loop = ev_default_init (0);
		1141	struct ev_io stdin_readable;
		1142	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1143	ev_io_start (loop, &stdin_readable);
		1144	ev_loop (loop, 0);
		1145
		1146
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	1147	=head2 C<ev_timer> - relative and optionally repeating timeouts
470		1148
471	Timer watchers are simple relative timers that generate an event after a	1149	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	1150	given time, and optionally repeating in regular intervals after that.
473		1151
474	The timers are based on real time, that is, if you register an event that	1152	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	1153	times out after an hour and you reset your system clock to last years
476	time, it will still time out after (roughly) and hour. "Roughly" because	1154	time, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1155	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	1156	monotonic clock option helps a lot here).
479		1157
480	The relative timeouts are calculated relative to the C<ev_now ()>	1158	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	1159	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	1160	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	1161	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:	1162	on the current time, use something like this to adjust for this:
485		1163
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1164	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1165
		1166	The callback is guarenteed to be invoked only when its timeout has passed,
		1167	but if multiple timers become ready during the same loop iteration then
		1168	order of execution is undefined.
		1169
		1170	=head3 Watcher-Specific Functions and Data Members
487		1171
488	=over 4	1172	=over 4
489		1173
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1174	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		1175
…		…
500	configure a timer to trigger every 10 seconds, then it will trigger at	1184	configure a timer to trigger every 10 seconds, then it will trigger at
501	exactly 10 second intervals. If, however, your program cannot keep up with	1185	exactly 10 second intervals. If, however, your program cannot keep up with
502	the timer (because it takes longer than those 10 seconds to do stuff) the	1186	the timer (because it takes longer than those 10 seconds to do stuff) the
503	timer will not fire more than once per event loop iteration.	1187	timer will not fire more than once per event loop iteration.
504		1188
505	=item ev_timer_again (loop)	1189	=item ev_timer_again (loop, ev_timer *)
506		1190
507	This will act as if the timer timed out and restart it again if it is	1191	This will act as if the timer timed out and restart it again if it is
508	repeating. The exact semantics are:	1192	repeating. The exact semantics are:
509		1193
		1194	If the timer is pending, its pending status is cleared.
		1195
510	If the timer is started but nonrepeating, stop it.	1196	If the timer is started but nonrepeating, stop it (as if it timed out).
511		1197
512	If the timer is repeating, either start it if necessary (with the repeat	1198	If the timer is repeating, either start it if necessary (with the
513	value), or reset the running timer to the repeat value.	1199	C<repeat> value), or reset the running timer to the C<repeat> value.
514		1200
515	This sounds a bit complicated, but here is a useful and typical	1201	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	1202	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	1203	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	1204	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	1205	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	1206	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	1207	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.	1208	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1209	automatically restart it if need be.
		1210
		1211	That means you can ignore the C<after> value and C<ev_timer_start>
		1212	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1213
		1214	ev_timer_init (timer, callback, 0., 5.);
		1215	ev_timer_again (loop, timer);
		1216	...
		1217	timer->again = 17.;
		1218	ev_timer_again (loop, timer);
		1219	...
		1220	timer->again = 10.;
		1221	ev_timer_again (loop, timer);
		1222
		1223	This is more slightly efficient then stopping/starting the timer each time
		1224	you want to modify its timeout value.
		1225
		1226	=item ev_tstamp repeat [read-write]
		1227
		1228	The current C<repeat> value. Will be used each time the watcher times out
		1229	or C<ev_timer_again> is called and determines the next timeout (if any),
		1230	which is also when any modifications are taken into account.
523		1231
524	=back	1232	=back
525		1233
		1234	=head3 Examples
		1235
		1236	Example: Create a timer that fires after 60 seconds.
		1237
		1238	static void
		1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1240	{
		1241	.. one minute over, w is actually stopped right here
		1242	}
		1243
		1244	struct ev_timer mytimer;
		1245	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1246	ev_timer_start (loop, &mytimer);
		1247
		1248	Example: Create a timeout timer that times out after 10 seconds of
		1249	inactivity.
		1250
		1251	static void
		1252	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1253	{
		1254	.. ten seconds without any activity
		1255	}
		1256
		1257	struct ev_timer mytimer;
		1258	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1259	ev_timer_again (&mytimer); /* start timer */
		1260	ev_loop (loop, 0);
		1261
		1262	// and in some piece of code that gets executed on any "activity":
		1263	// reset the timeout to start ticking again at 10 seconds
		1264	ev_timer_again (&mytimer);
		1265
		1266
526	=head2 C<ev_periodic> - to cron or not to cron	1267	=head2 C<ev_periodic> - to cron or not to cron?
527		1268
528	Periodic watchers are also timers of a kind, but they are very versatile	1269	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	1270	(and unfortunately a bit complex).
530		1271
531	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1272	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	1273	but on wallclock time (absolute time). You can tell a periodic watcher
533	to trigger "at" some specific point in time. For example, if you tell a	1274	to trigger "at" 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 ()	1275	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
535	+ 10.>) and then reset your system clock to the last year, then it will	1276	+ 10.>) and then reset your system clock to the last year, then it will
536	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1277	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
537	roughly 10 seconds later and of course not if you reset your system time	1278	roughly 10 seconds later).
538	again).
539		1279
540	They can also be used to implement vastly more complex timers, such as	1280	They can also be used to implement vastly more complex timers, such as
541	triggering an event on eahc midnight, local time.	1281	triggering an event on each midnight, local time or other, complicated,
		1282	rules.
		1283
		1284	As with timers, the callback is guarenteed to be invoked only when the
		1285	time (C<at>) has been passed, but if multiple periodic timers become ready
		1286	during the same loop iteration then order of execution is undefined.
		1287
		1288	=head3 Watcher-Specific Functions and Data Members
542		1289
543	=over 4	1290	=over 4
544		1291
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1292	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		1293
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1294	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		1295
549	Lots of arguments, lets sort it out... There are basically three modes of	1296	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	1297	operation, and we will explain them from simplest to complex:
551		1298
552
553	=over 4	1299	=over 4
554		1300
555	=item * absolute timer (interval = reschedule_cb = 0)	1301	=item * absolute timer (at = time, interval = reschedule_cb = 0)
556		1302
557	In this configuration the watcher triggers an event at the wallclock time	1303	In this configuration the watcher triggers an event at the wallclock time
558	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
559	that is, if it is to be run at January 1st 2011 then it will run when the	1305	that is, if it is to be run at January 1st 2011 then it will run when the
560	system time reaches or surpasses this time.	1306	system time reaches or surpasses this time.
561		1307
562	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
563		1309
564	In this mode the watcher will always be scheduled to time out at the next	1310	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	1311	C<at + N * interval> time (for some integer N, which can also be negative)
566	of any time jumps.	1312	and then repeat, regardless of any time jumps.
567		1313
568	This can be used to create timers that do not drift with respect to system	1314	This can be used to create timers that do not drift with respect to system
569	time:	1315	time:
570		1316
571	ev_periodic_set (&periodic, 0., 3600., 0);	1317	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
577		1323
578	Another way to think about it (for the mathematically inclined) is that	1324	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	1325	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.	1326	time where C<time = at (mod interval)>, regardless of any time jumps.
581		1327
		1328	For numerical stability it is preferable that the C<at> value is near
		1329	C<ev_now ()> (the current time), but there is no range requirement for
		1330	this value.
		1331
582	=item * manual reschedule mode (reschedule_cb = callback)	1332	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
583		1333
584	In this mode the values for C<interval> and C<at> are both being	1334	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	1335	ignored. Instead, each time the periodic watcher gets scheduled, the
586	reschedule callback will be called with the watcher as first, and the	1336	reschedule callback will be called with the watcher as first, and the
587	current time as second argument.	1337	current time as second argument.
588		1338
589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1339	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,	1340	ever, or make any event loop modifications>. If you need to stop it,
591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1341	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
592	starting a prepare watcher).	1342	starting an C<ev_prepare> watcher, which is legal).
593		1343
594	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1344	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
595	ev_tstamp now)>, e.g.:	1345	ev_tstamp now)>, e.g.:
596		1346
597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1347	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
620	Simply stops and restarts the periodic watcher again. This is only useful	1370	Simply stops and restarts the periodic watcher again. This is only useful
621	when you changed some parameters or the reschedule callback would return	1371	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	1372	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	1373	program when the crontabs have changed).
624		1374
		1375	=item ev_tstamp offset [read-write]
		1376
		1377	When repeating, this contains the offset value, otherwise this is the
		1378	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1379
		1380	Can be modified any time, but changes only take effect when the periodic
		1381	timer fires or C<ev_periodic_again> is being called.
		1382
		1383	=item ev_tstamp interval [read-write]
		1384
		1385	The current interval value. Can be modified any time, but changes only
		1386	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1387	called.
		1388
		1389	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1390
		1391	The current reschedule callback, or C<0>, if this functionality is
		1392	switched off. Can be changed any time, but changes only take effect when
		1393	the periodic timer fires or C<ev_periodic_again> is being called.
		1394
		1395	=item ev_tstamp at [read-only]
		1396
		1397	When active, contains the absolute time that the watcher is supposed to
		1398	trigger next.
		1399
625	=back	1400	=back
626		1401
		1402	=head3 Examples
		1403
		1404	Example: Call a callback every hour, or, more precisely, whenever the
		1405	system clock is divisible by 3600. The callback invocation times have
		1406	potentially a lot of jittering, but good long-term stability.
		1407
		1408	static void
		1409	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1410	{
		1411	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1412	}
		1413
		1414	struct ev_periodic hourly_tick;
		1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1416	ev_periodic_start (loop, &hourly_tick);
		1417
		1418	Example: The same as above, but use a reschedule callback to do it:
		1419
		1420	#include <math.h>
		1421
		1422	static ev_tstamp
		1423	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1424	{
		1425	return fmod (now, 3600.) + 3600.;
		1426	}
		1427
		1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1429
		1430	Example: Call a callback every hour, starting now:
		1431
		1432	struct ev_periodic hourly_tick;
		1433	ev_periodic_init (&hourly_tick, clock_cb,
		1434	fmod (ev_now (loop), 3600.), 3600., 0);
		1435	ev_periodic_start (loop, &hourly_tick);
		1436
		1437
627	=head2 C<ev_signal> - signal me when a signal gets signalled	1438	=head2 C<ev_signal> - signal me when a signal gets signalled!
628		1439
629	Signal watchers will trigger an event when the process receives a specific	1440	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	1441	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	1442	will try it's best to deliver signals synchronously, i.e. as part of the
632	normal event processing, like any other event.	1443	normal event processing, like any other event.
…		…
636	with the kernel (thus it coexists with your own signal handlers as long	1447	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	1448	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	1449	watcher for a signal is stopped libev will reset the signal handler to
639	SIG_DFL (regardless of what it was set to before).	1450	SIG_DFL (regardless of what it was set to before).
640		1451
		1452	If possible and supported, libev will install its handlers with
		1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1454	interrupted. If you have a problem with syscalls getting interrupted by
		1455	signals you can block all signals in an C<ev_check> watcher and unblock
		1456	them in an C<ev_prepare> watcher.
		1457
		1458	=head3 Watcher-Specific Functions and Data Members
		1459
641	=over 4	1460	=over 4
642		1461
643	=item ev_signal_init (ev_signal *, callback, int signum)	1462	=item ev_signal_init (ev_signal *, callback, int signum)
644		1463
645	=item ev_signal_set (ev_signal *, int signum)	1464	=item ev_signal_set (ev_signal *, int signum)
646		1465
647	Configures the watcher to trigger on the given signal number (usually one	1466	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1467	of the C<SIGxxx> constants).
649		1468
		1469	=item int signum [read-only]
		1470
		1471	The signal the watcher watches out for.
		1472
650	=back	1473	=back
651		1474
		1475	=head3 Examples
		1476
		1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1478
		1479	static void
		1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1481	{
		1482	ev_unloop (loop, EVUNLOOP_ALL);
		1483	}
		1484
		1485	struct ev_signal signal_watcher;
		1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1487	ev_signal_start (loop, &sigint_cb);
		1488
		1489
652	=head2 C<ev_child> - wait for pid status changes	1490	=head2 C<ev_child> - watch out for process status changes
653		1491
654	Child watchers trigger when your process receives a SIGCHLD in response to	1492	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).	1493	some child status changes (most typically when a child of yours dies). It
		1494	is permissible to install a child watcher I<after> the child has been
		1495	forked (which implies it might have already exited), as long as the event
		1496	loop isn't entered (or is continued from a watcher).
		1497
		1498	Only the default event loop is capable of handling signals, and therefore
		1499	you can only rgeister child watchers in the default event loop.
		1500
		1501	=head3 Process Interaction
		1502
		1503	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1504	initialised. This is necessary to guarantee proper behaviour even if
		1505	the first child watcher is started after the child exits. The occurance
		1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1507	synchronously as part of the event loop processing. Libev always reaps all
		1508	children, even ones not watched.
		1509
		1510	=head3 Overriding the Built-In Processing
		1511
		1512	Libev offers no special support for overriding the built-in child
		1513	processing, but if your application collides with libev's default child
		1514	handler, you can override it easily by installing your own handler for
		1515	C<SIGCHLD> after initialising the default loop, and making sure the
		1516	default loop never gets destroyed. You are encouraged, however, to use an
		1517	event-based approach to child reaping and thus use libev's support for
		1518	that, so other libev users can use C<ev_child> watchers freely.
		1519
		1520	=head3 Watcher-Specific Functions and Data Members
656		1521
657	=over 4	1522	=over 4
658		1523
659	=item ev_child_init (ev_child *, callback, int pid)	1524	=item ev_child_init (ev_child *, callback, int pid, int trace)
660		1525
661	=item ev_child_set (ev_child *, int pid)	1526	=item ev_child_set (ev_child *, int pid, int trace)
662		1527
663	Configures the watcher to wait for status changes of process C<pid> (or	1528	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	1529	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	1530	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	1531	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	1532	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1533	process causing the status change. C<trace> must be either C<0> (only
		1534	activate the watcher when the process terminates) or C<1> (additionally
		1535	activate the watcher when the process is stopped or continued).
		1536
		1537	=item int pid [read-only]
		1538
		1539	The process id this watcher watches out for, or C<0>, meaning any process id.
		1540
		1541	=item int rpid [read-write]
		1542
		1543	The process id that detected a status change.
		1544
		1545	=item int rstatus [read-write]
		1546
		1547	The process exit/trace status caused by C<rpid> (see your systems
		1548	C<waitpid> and C<sys/wait.h> documentation for details).
669		1549
670	=back	1550	=back
671		1551
		1552	=head3 Examples
		1553
		1554	Example: C<fork()> a new process and install a child handler to wait for
		1555	its completion.
		1556
		1557	ev_child cw;
		1558
		1559	static void
		1560	child_cb (EV_P_ struct ev_child *w, int revents)
		1561	{
		1562	ev_child_stop (EV_A_ w);
		1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1564	}
		1565
		1566	pid_t pid = fork ();
		1567
		1568	if (pid < 0)
		1569	// error
		1570	else if (pid == 0)
		1571	{
		1572	// the forked child executes here
		1573	exit (1);
		1574	}
		1575	else
		1576	{
		1577	ev_child_init (&cw, child_cb, pid, 0);
		1578	ev_child_start (EV_DEFAULT_ &cw);
		1579	}
		1580
		1581
		1582	=head2 C<ev_stat> - did the file attributes just change?
		1583
		1584	This watches a filesystem path for attribute changes. That is, it calls
		1585	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1586	compared to the last time, invoking the callback if it did.
		1587
		1588	The path does not need to exist: changing from "path exists" to "path does
		1589	not exist" is a status change like any other. The condition "path does
		1590	not exist" is signified by the C<st_nlink> field being zero (which is
		1591	otherwise always forced to be at least one) and all the other fields of
		1592	the stat buffer having unspecified contents.
		1593
		1594	The path I<should> be absolute and I<must not> end in a slash. If it is
		1595	relative and your working directory changes, the behaviour is undefined.
		1596
		1597	Since there is no standard to do this, the portable implementation simply
		1598	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1599	can specify a recommended polling interval for this case. If you specify
		1600	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1601	unspecified default> value will be used (which you can expect to be around
		1602	five seconds, although this might change dynamically). Libev will also
		1603	impose a minimum interval which is currently around C<0.1>, but thats
		1604	usually overkill.
		1605
		1606	This watcher type is not meant for massive numbers of stat watchers,
		1607	as even with OS-supported change notifications, this can be
		1608	resource-intensive.
		1609
		1610	At the time of this writing, only the Linux inotify interface is
		1611	implemented (implementing kqueue support is left as an exercise for the
		1612	reader). Inotify will be used to give hints only and should not change the
		1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1614	to fall back to regular polling again even with inotify, but changes are
		1615	usually detected immediately, and if the file exists there will be no
		1616	polling.
		1617
		1618	=head3 ABI Issues (Largefile Support)
		1619
		1620	Libev by default (unless the user overrides this) uses the default
		1621	compilation environment, which means that on systems with optionally
		1622	disabled large file support, you get the 32 bit version of the stat
		1623	structure. When using the library from programs that change the ABI to
		1624	use 64 bit file offsets the programs will fail. In that case you have to
		1625	compile libev with the same flags to get binary compatibility. This is
		1626	obviously the case with any flags that change the ABI, but the problem is
		1627	most noticably with ev_stat and largefile support.
		1628
		1629	=head3 Inotify
		1630
		1631	When C<inotify (7)> support has been compiled into libev (generally only
		1632	available on Linux) and present at runtime, it will be used to speed up
		1633	change detection where possible. The inotify descriptor will be created lazily
		1634	when the first C<ev_stat> watcher is being started.
		1635
		1636	Inotify presense does not change the semantics of C<ev_stat> watchers
		1637	except that changes might be detected earlier, and in some cases, to avoid
		1638	making regular C<stat> calls. Even in the presense of inotify support
		1639	there are many cases where libev has to resort to regular C<stat> polling.
		1640
		1641	(There is no support for kqueue, as apparently it cannot be used to
		1642	implement this functionality, due to the requirement of having a file
		1643	descriptor open on the object at all times).
		1644
		1645	=head3 The special problem of stat time resolution
		1646
		1647	The C<stat ()> syscall only supports full-second resolution portably, and
		1648	even on systems where the resolution is higher, many filesystems still
		1649	only support whole seconds.
		1650
		1651	That means that, if the time is the only thing that changes, you might
		1652	miss updates: on the first update, C<ev_stat> detects a change and calls
		1653	your callback, which does something. When there is another update within
		1654	the same second, C<ev_stat> will be unable to detect it.
		1655
		1656	The solution to this is to delay acting on a change for a second (or till
		1657	the next second boundary), using a roughly one-second delay C<ev_timer>
		1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1659	is added to work around small timing inconsistencies of some operating
		1660	systems.
		1661
		1662	=head3 Watcher-Specific Functions and Data Members
		1663
		1664	=over 4
		1665
		1666	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1667
		1668	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1669
		1670	Configures the watcher to wait for status changes of the given
		1671	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1672	be detected and should normally be specified as C<0> to let libev choose
		1673	a suitable value. The memory pointed to by C<path> must point to the same
		1674	path for as long as the watcher is active.
		1675
		1676	The callback will be receive C<EV_STAT> when a change was detected,
		1677	relative to the attributes at the time the watcher was started (or the
		1678	last change was detected).
		1679
		1680	=item ev_stat_stat (loop, ev_stat *)
		1681
		1682	Updates the stat buffer immediately with new values. If you change the
		1683	watched path in your callback, you could call this fucntion to avoid
		1684	detecting this change (while introducing a race condition). Can also be
		1685	useful simply to find out the new values.
		1686
		1687	=item ev_statdata attr [read-only]
		1688
		1689	The most-recently detected attributes of the file. Although the type is of
		1690	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1691	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1692	was some error while C<stat>ing the file.
		1693
		1694	=item ev_statdata prev [read-only]
		1695
		1696	The previous attributes of the file. The callback gets invoked whenever
		1697	C<prev> != C<attr>.
		1698
		1699	=item ev_tstamp interval [read-only]
		1700
		1701	The specified interval.
		1702
		1703	=item const char *path [read-only]
		1704
		1705	The filesystem path that is being watched.
		1706
		1707	=back
		1708
		1709	=head3 Examples
		1710
		1711	Example: Watch C</etc/passwd> for attribute changes.
		1712
		1713	static void
		1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1715	{
		1716	/* /etc/passwd changed in some way */
		1717	if (w->attr.st_nlink)
		1718	{
		1719	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1720	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1721	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1722	}
		1723	else
		1724	/* you shalt not abuse printf for puts */
		1725	puts ("wow, /etc/passwd is not there, expect problems. "
		1726	"if this is windows, they already arrived\n");
		1727	}
		1728
		1729	...
		1730	ev_stat passwd;
		1731
		1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1733	ev_stat_start (loop, &passwd);
		1734
		1735	Example: Like above, but additionally use a one-second delay so we do not
		1736	miss updates (however, frequent updates will delay processing, too, so
		1737	one might do the work both on C<ev_stat> callback invocation I<and> on
		1738	C<ev_timer> callback invocation).
		1739
		1740	static ev_stat passwd;
		1741	static ev_timer timer;
		1742
		1743	static void
		1744	timer_cb (EV_P_ ev_timer *w, int revents)
		1745	{
		1746	ev_timer_stop (EV_A_ w);
		1747
		1748	/* now it's one second after the most recent passwd change */
		1749	}
		1750
		1751	static void
		1752	stat_cb (EV_P_ ev_stat *w, int revents)
		1753	{
		1754	/* reset the one-second timer */
		1755	ev_timer_again (EV_A_ &timer);
		1756	}
		1757
		1758	...
		1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1760	ev_stat_start (loop, &passwd);
		1761	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1762
		1763
672	=head2 C<ev_idle> - when you've got nothing better to do	1764	=head2 C<ev_idle> - when you've got nothing better to do...
673		1765
674	Idle watchers trigger events when there are no other events are pending	1766	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	1767	priority are pending (prepare, check and other idle watchers do not
676	as your process is busy handling sockets or timeouts (or even signals,	1768	count).
677	imagine) it will not be triggered. But when your process is idle all idle	1769
678	watchers are being called again and again, once per event loop iteration -	1770	That is, as long as your process is busy handling sockets or timeouts
		1771	(or even signals, imagine) of the same or higher priority it will not be
		1772	triggered. But when your process is idle (or only lower-priority watchers
		1773	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	1774	iteration - until stopped, that is, or your process receives more events
680	busy.	1775	and becomes busy again with higher priority stuff.
681		1776
682	The most noteworthy effect is that as long as any idle watchers are	1777	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.	1778	active, the process will not block when waiting for new events.
684		1779
685	Apart from keeping your process non-blocking (which is a useful	1780	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	1781	effect on its own sometimes), idle watchers are a good place to do
687	"pseudo-background processing", or delay processing stuff to after the	1782	"pseudo-background processing", or delay processing stuff to after the
688	event loop has handled all outstanding events.	1783	event loop has handled all outstanding events.
689		1784
		1785	=head3 Watcher-Specific Functions and Data Members
		1786
690	=over 4	1787	=over 4
691		1788
692	=item ev_idle_init (ev_signal *, callback)	1789	=item ev_idle_init (ev_signal *, callback)
693		1790
694	Initialises and configures the idle watcher - it has no parameters of any	1791	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,	1792	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1793	believe me.
697		1794
698	=back	1795	=back
699		1796
		1797	=head3 Examples
		1798
		1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1800	callback, free it. Also, use no error checking, as usual.
		1801
		1802	static void
		1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1804	{
		1805	free (w);
		1806	// now do something you wanted to do when the program has
		1807	// no longer anything immediate to do.
		1808	}
		1809
		1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1811	ev_idle_init (idle_watcher, idle_cb);
		1812	ev_idle_start (loop, idle_cb);
		1813
		1814
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1815	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
701		1816
702	Prepare and check watchers are usually (but not always) used in tandem:	1817	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1818	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1819	afterwards.
705		1820
		1821	You I<must not> call C<ev_loop> or similar functions that enter
		1822	the current event loop from either C<ev_prepare> or C<ev_check>
		1823	watchers. Other loops than the current one are fine, however. The
		1824	rationale behind this is that you do not need to check for recursion in
		1825	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1826	C<ev_check> so if you have one watcher of each kind they will always be
		1827	called in pairs bracketing the blocking call.
		1828
706	Their main purpose is to integrate other event mechanisms into libev. This	1829	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	1830	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.	1831	variable changes, implement your own watchers, integrate net-snmp or a
		1832	coroutine library and lots more. They are also occasionally useful if
		1833	you cache some data and want to flush it before blocking (for example,
		1834	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1835	watcher).
709		1836
710	This is done by examining in each prepare call which file descriptors need	1837	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	1838	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	1839	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	1840	provide just this functionality). Then, in the check watcher you check for
…		…
723	with priority higher than or equal to the event loop and one coroutine	1850	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	1851	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	1852	loop from blocking if lower-priority coroutines are active, thus mapping
726	low-priority coroutines to idle/background tasks).	1853	low-priority coroutines to idle/background tasks).
727		1854
		1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1856	priority, to ensure that they are being run before any other watchers
		1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1858	too) should not activate ("feed") events into libev. While libev fully
		1859	supports this, they will be called before other C<ev_check> watchers
		1860	did their job. As C<ev_check> watchers are often used to embed other
		1861	(non-libev) event loops those other event loops might be in an unusable
		1862	state until their C<ev_check> watcher ran (always remind yourself to
		1863	coexist peacefully with others).
		1864
		1865	=head3 Watcher-Specific Functions and Data Members
		1866
728	=over 4	1867	=over 4
729		1868
730	=item ev_prepare_init (ev_prepare *, callback)	1869	=item ev_prepare_init (ev_prepare *, callback)
731		1870
732	=item ev_check_init (ev_check *, callback)	1871	=item ev_check_init (ev_check *, callback)
…		…
734	Initialises and configures the prepare or check watcher - they have no	1873	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>	1874	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.	1875	macros, but using them is utterly, utterly and completely pointless.
737		1876
738	=back	1877	=back
		1878
		1879	=head3 Examples
		1880
		1881	There are a number of principal ways to embed other event loops or modules
		1882	into libev. Here are some ideas on how to include libadns into libev
		1883	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1884	use for an actually working example. Another Perl module named C<EV::Glib>
		1885	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1886	into the Glib event loop).
		1887
		1888	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1889	and in a check watcher, destroy them and call into libadns. What follows
		1890	is pseudo-code only of course. This requires you to either use a low
		1891	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1892	the callbacks for the IO/timeout watchers might not have been called yet.
		1893
		1894	static ev_io iow [nfd];
		1895	static ev_timer tw;
		1896
		1897	static void
		1898	io_cb (ev_loop *loop, ev_io *w, int revents)
		1899	{
		1900	}
		1901
		1902	// create io watchers for each fd and a timer before blocking
		1903	static void
		1904	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1905	{
		1906	int timeout = 3600000;
		1907	struct pollfd fds [nfd];
		1908	// actual code will need to loop here and realloc etc.
		1909	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1910
		1911	/* the callback is illegal, but won't be called as we stop during check */
		1912	ev_timer_init (&tw, 0, timeout * 1e-3);
		1913	ev_timer_start (loop, &tw);
		1914
		1915	// create one ev_io per pollfd
		1916	for (int i = 0; i < nfd; ++i)
		1917	{
		1918	ev_io_init (iow + i, io_cb, fds [i].fd,
		1919	((fds [i].events & POLLIN ? EV_READ : 0)
		1920	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1921
		1922	fds [i].revents = 0;
		1923	ev_io_start (loop, iow + i);
		1924	}
		1925	}
		1926
		1927	// stop all watchers after blocking
		1928	static void
		1929	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1930	{
		1931	ev_timer_stop (loop, &tw);
		1932
		1933	for (int i = 0; i < nfd; ++i)
		1934	{
		1935	// set the relevant poll flags
		1936	// could also call adns_processreadable etc. here
		1937	struct pollfd *fd = fds + i;
		1938	int revents = ev_clear_pending (iow + i);
		1939	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1940	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1941
		1942	// now stop the watcher
		1943	ev_io_stop (loop, iow + i);
		1944	}
		1945
		1946	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1947	}
		1948
		1949	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1950	in the prepare watcher and would dispose of the check watcher.
		1951
		1952	Method 3: If the module to be embedded supports explicit event
		1953	notification (adns does), you can also make use of the actual watcher
		1954	callbacks, and only destroy/create the watchers in the prepare watcher.
		1955
		1956	static void
		1957	timer_cb (EV_P_ ev_timer *w, int revents)
		1958	{
		1959	adns_state ads = (adns_state)w->data;
		1960	update_now (EV_A);
		1961
		1962	adns_processtimeouts (ads, &tv_now);
		1963	}
		1964
		1965	static void
		1966	io_cb (EV_P_ ev_io *w, int revents)
		1967	{
		1968	adns_state ads = (adns_state)w->data;
		1969	update_now (EV_A);
		1970
		1971	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1972	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1973	}
		1974
		1975	// do not ever call adns_afterpoll
		1976
		1977	Method 4: Do not use a prepare or check watcher because the module you
		1978	want to embed is too inflexible to support it. Instead, youc na override
		1979	their poll function. The drawback with this solution is that the main
		1980	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1981	this.
		1982
		1983	static gint
		1984	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1985	{
		1986	int got_events = 0;
		1987
		1988	for (n = 0; n < nfds; ++n)
		1989	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1990
		1991	if (timeout >= 0)
		1992	// create/start timer
		1993
		1994	// poll
		1995	ev_loop (EV_A_ 0);
		1996
		1997	// stop timer again
		1998	if (timeout >= 0)
		1999	ev_timer_stop (EV_A_ &to);
		2000
		2001	// stop io watchers again - their callbacks should have set
		2002	for (n = 0; n < nfds; ++n)
		2003	ev_io_stop (EV_A_ iow [n]);
		2004
		2005	return got_events;
		2006	}
		2007
		2008
		2009	=head2 C<ev_embed> - when one backend isn't enough...
		2010
		2011	This is a rather advanced watcher type that lets you embed one event loop
		2012	into another (currently only C<ev_io> events are supported in the embedded
		2013	loop, other types of watchers might be handled in a delayed or incorrect
		2014	fashion and must not be used).
		2015
		2016	There are primarily two reasons you would want that: work around bugs and
		2017	prioritise I/O.
		2018
		2019	As an example for a bug workaround, the kqueue backend might only support
		2020	sockets on some platform, so it is unusable as generic backend, but you
		2021	still want to make use of it because you have many sockets and it scales
		2022	so nicely. In this case, you would create a kqueue-based loop and embed it
		2023	into your default loop (which might use e.g. poll). Overall operation will
		2024	be a bit slower because first libev has to poll and then call kevent, but
		2025	at least you can use both at what they are best.
		2026
		2027	As for prioritising I/O: rarely you have the case where some fds have
		2028	to be watched and handled very quickly (with low latency), and even
		2029	priorities and idle watchers might have too much overhead. In this case
		2030	you would put all the high priority stuff in one loop and all the rest in
		2031	a second one, and embed the second one in the first.
		2032
		2033	As long as the watcher is active, the callback will be invoked every time
		2034	there might be events pending in the embedded loop. The callback must then
		2035	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		2036	their callbacks (you could also start an idle watcher to give the embedded
		2037	loop strictly lower priority for example). You can also set the callback
		2038	to C<0>, in which case the embed watcher will automatically execute the
		2039	embedded loop sweep.
		2040
		2041	As long as the watcher is started it will automatically handle events. The
		2042	callback will be invoked whenever some events have been handled. You can
		2043	set the callback to C<0> to avoid having to specify one if you are not
		2044	interested in that.
		2045
		2046	Also, there have not currently been made special provisions for forking:
		2047	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2048	but you will also have to stop and restart any C<ev_embed> watchers
		2049	yourself.
		2050
		2051	Unfortunately, not all backends are embeddable, only the ones returned by
		2052	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2053	portable one.
		2054
		2055	So when you want to use this feature you will always have to be prepared
		2056	that you cannot get an embeddable loop. The recommended way to get around
		2057	this is to have a separate variables for your embeddable loop, try to
		2058	create it, and if that fails, use the normal loop for everything.
		2059
		2060	=head3 Watcher-Specific Functions and Data Members
		2061
		2062	=over 4
		2063
		2064	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2065
		2066	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2067
		2068	Configures the watcher to embed the given loop, which must be
		2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2070	invoked automatically, otherwise it is the responsibility of the callback
		2071	to invoke it (it will continue to be called until the sweep has been done,
		2072	if you do not want thta, you need to temporarily stop the embed watcher).
		2073
		2074	=item ev_embed_sweep (loop, ev_embed *)
		2075
		2076	Make a single, non-blocking sweep over the embedded loop. This works
		2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2078	apropriate way for embedded loops.
		2079
		2080	=item struct ev_loop *other [read-only]
		2081
		2082	The embedded event loop.
		2083
		2084	=back
		2085
		2086	=head3 Examples
		2087
		2088	Example: Try to get an embeddable event loop and embed it into the default
		2089	event loop. If that is not possible, use the default loop. The default
		2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2092	used).
		2093
		2094	struct ev_loop *loop_hi = ev_default_init (0);
		2095	struct ev_loop *loop_lo = 0;
		2096	struct ev_embed embed;
		2097
		2098	// see if there is a chance of getting one that works
		2099	// (remember that a flags value of 0 means autodetection)
		2100	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2101	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2102	: 0;
		2103
		2104	// if we got one, then embed it, otherwise default to loop_hi
		2105	if (loop_lo)
		2106	{
		2107	ev_embed_init (&embed, 0, loop_lo);
		2108	ev_embed_start (loop_hi, &embed);
		2109	}
		2110	else
		2111	loop_lo = loop_hi;
		2112
		2113	Example: Check if kqueue is available but not recommended and create
		2114	a kqueue backend for use with sockets (which usually work with any
		2115	kqueue implementation). Store the kqueue/socket-only event loop in
		2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2117
		2118	struct ev_loop *loop = ev_default_init (0);
		2119	struct ev_loop *loop_socket = 0;
		2120	struct ev_embed embed;
		2121
		2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2124	{
		2125	ev_embed_init (&embed, 0, loop_socket);
		2126	ev_embed_start (loop, &embed);
		2127	}
		2128
		2129	if (!loop_socket)
		2130	loop_socket = loop;
		2131
		2132	// now use loop_socket for all sockets, and loop for everything else
		2133
		2134
		2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2136
		2137	Fork watchers are called when a C<fork ()> was detected (usually because
		2138	whoever is a good citizen cared to tell libev about it by calling
		2139	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2140	event loop blocks next and before C<ev_check> watchers are being called,
		2141	and only in the child after the fork. If whoever good citizen calling
		2142	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2143	handlers will be invoked, too, of course.
		2144
		2145	=head3 Watcher-Specific Functions and Data Members
		2146
		2147	=over 4
		2148
		2149	=item ev_fork_init (ev_signal *, callback)
		2150
		2151	Initialises and configures the fork watcher - it has no parameters of any
		2152	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2153	believe me.
		2154
		2155	=back
		2156
		2157
		2158	=head2 C<ev_async> - how to wake up another event loop
		2159
		2160	In general, you cannot use an C<ev_loop> from multiple threads or other
		2161	asynchronous sources such as signal handlers (as opposed to multiple event
		2162	loops - those are of course safe to use in different threads).
		2163
		2164	Sometimes, however, you need to wake up another event loop you do not
		2165	control, for example because it belongs to another thread. This is what
		2166	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2167	can signal it by calling C<ev_async_send>, which is thread- and signal
		2168	safe.
		2169
		2170	This functionality is very similar to C<ev_signal> watchers, as signals,
		2171	too, are asynchronous in nature, and signals, too, will be compressed
		2172	(i.e. the number of callback invocations may be less than the number of
		2173	C<ev_async_sent> calls).
		2174
		2175	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2176	just the default loop.
		2177
		2178	=head3 Queueing
		2179
		2180	C<ev_async> does not support queueing of data in any way. The reason
		2181	is that the author does not know of a simple (or any) algorithm for a
		2182	multiple-writer-single-reader queue that works in all cases and doesn't
		2183	need elaborate support such as pthreads.
		2184
		2185	That means that if you want to queue data, you have to provide your own
		2186	queue. But at least I can tell you would implement locking around your
		2187	queue:
		2188
		2189	=over 4
		2190
		2191	=item queueing from a signal handler context
		2192
		2193	To implement race-free queueing, you simply add to the queue in the signal
		2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2195	some fictitiuous SIGUSR1 handler:
		2196
		2197	static ev_async mysig;
		2198
		2199	static void
		2200	sigusr1_handler (void)
		2201	{
		2202	sometype data;
		2203
		2204	// no locking etc.
		2205	queue_put (data);
		2206	ev_async_send (EV_DEFAULT_ &mysig);
		2207	}
		2208
		2209	static void
		2210	mysig_cb (EV_P_ ev_async *w, int revents)
		2211	{
		2212	sometype data;
		2213	sigset_t block, prev;
		2214
		2215	sigemptyset (&block);
		2216	sigaddset (&block, SIGUSR1);
		2217	sigprocmask (SIG_BLOCK, &block, &prev);
		2218
		2219	while (queue_get (&data))
		2220	process (data);
		2221
		2222	if (sigismember (&prev, SIGUSR1)
		2223	sigprocmask (SIG_UNBLOCK, &block, 0);
		2224	}
		2225
		2226	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2227	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2228	either...).
		2229
		2230	=item queueing from a thread context
		2231
		2232	The strategy for threads is different, as you cannot (easily) block
		2233	threads but you can easily preempt them, so to queue safely you need to
		2234	employ a traditional mutex lock, such as in this pthread example:
		2235
		2236	static ev_async mysig;
		2237	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2238
		2239	static void
		2240	otherthread (void)
		2241	{
		2242	// only need to lock the actual queueing operation
		2243	pthread_mutex_lock (&mymutex);
		2244	queue_put (data);
		2245	pthread_mutex_unlock (&mymutex);
		2246
		2247	ev_async_send (EV_DEFAULT_ &mysig);
		2248	}
		2249
		2250	static void
		2251	mysig_cb (EV_P_ ev_async *w, int revents)
		2252	{
		2253	pthread_mutex_lock (&mymutex);
		2254
		2255	while (queue_get (&data))
		2256	process (data);
		2257
		2258	pthread_mutex_unlock (&mymutex);
		2259	}
		2260
		2261	=back
		2262
		2263
		2264	=head3 Watcher-Specific Functions and Data Members
		2265
		2266	=over 4
		2267
		2268	=item ev_async_init (ev_async *, callback)
		2269
		2270	Initialises and configures the async watcher - it has no parameters of any
		2271	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2272	believe me.
		2273
		2274	=item ev_async_send (loop, ev_async *)
		2275
		2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2278	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2280	section below on what exactly this means).
		2281
		2282	This call incurs the overhead of a syscall only once per loop iteration,
		2283	so while the overhead might be noticable, it doesn't apply to repeated
		2284	calls to C<ev_async_send>.
		2285
		2286	=item bool = ev_async_pending (ev_async *)
		2287
		2288	Returns a non-zero value when C<ev_async_send> has been called on the
		2289	watcher but the event has not yet been processed (or even noted) by the
		2290	event loop.
		2291
		2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2293	the loop iterates next and checks for the watcher to have become active,
		2294	it will reset the flag again. C<ev_async_pending> can be used to very
		2295	quickly check wether invoking the loop might be a good idea.
		2296
		2297	Not that this does I<not> check wether the watcher itself is pending, only
		2298	wether it has been requested to make this watcher pending.
		2299
		2300	=back
		2301
739		2302
740	=head1 OTHER FUNCTIONS	2303	=head1 OTHER FUNCTIONS
741		2304
742	There are some other functions of possible interest. Described. Here. Now.	2305	There are some other functions of possible interest. Described. Here. Now.
743		2306
…		…
773	/* stdin might have data for us, joy! */;	2336	/* stdin might have data for us, joy! */;
774	}	2337	}
775		2338
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		2340
778	=item ev_feed_event (loop, watcher, int events)	2341	=item ev_feed_event (ev_loop *, watcher *, int revents)
779		2342
780	Feeds the given event set into the event loop, as if the specified event	2343	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	2344	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	2345	initialised but not necessarily started event watcher).
783		2346
784	=item ev_feed_fd_event (loop, int fd, int revents)	2347	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		2348
786	Feed an event on the given fd, as if a file descriptor backend detected	2349	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	2350	the given events it.
788		2351
789	=item ev_feed_signal_event (loop, int signum)	2352	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		2353
791	Feed an event as if the given signal occured (loop must be the default loop!).	2354	Feed an event as if the given signal occured (C<loop> must be the default
		2355	loop!).
792		2356
793	=back	2357	=back
		2358
794		2359
795	=head1 LIBEVENT EMULATION	2360	=head1 LIBEVENT EMULATION
796		2361
797	Libev offers a compatibility emulation layer for libevent. It cannot	2362	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	2363	emulate the internals of libevent, so here are some usage hints:
…		…
819		2384
820	=back	2385	=back
821		2386
822	=head1 C++ SUPPORT	2387	=head1 C++ SUPPORT
823		2388
824	TBD.	2389	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2390	you to use some convinience methods to start/stop watchers and also change
		2391	the callback model to a model using method callbacks on objects.
		2392
		2393	To use it,
		2394
		2395	#include <ev++.h>
		2396
		2397	This automatically includes F<ev.h> and puts all of its definitions (many
		2398	of them macros) into the global namespace. All C++ specific things are
		2399	put into the C<ev> namespace. It should support all the same embedding
		2400	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2401
		2402	Care has been taken to keep the overhead low. The only data member the C++
		2403	classes add (compared to plain C-style watchers) is the event loop pointer
		2404	that the watcher is associated with (or no additional members at all if
		2405	you disable C<EV_MULTIPLICITY> when embedding libev).
		2406
		2407	Currently, functions, and static and non-static member functions can be
		2408	used as callbacks. Other types should be easy to add as long as they only
		2409	need one additional pointer for context. If you need support for other
		2410	types of functors please contact the author (preferably after implementing
		2411	it).
		2412
		2413	Here is a list of things available in the C<ev> namespace:
		2414
		2415	=over 4
		2416
		2417	=item C<ev::READ>, C<ev::WRITE> etc.
		2418
		2419	These are just enum values with the same values as the C<EV_READ> etc.
		2420	macros from F<ev.h>.
		2421
		2422	=item C<ev::tstamp>, C<ev::now>
		2423
		2424	Aliases to the same types/functions as with the C<ev_> prefix.
		2425
		2426	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2427
		2428	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2429	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2430	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2431	defines by many implementations.
		2432
		2433	All of those classes have these methods:
		2434
		2435	=over 4
		2436
		2437	=item ev::TYPE::TYPE ()
		2438
		2439	=item ev::TYPE::TYPE (struct ev_loop *)
		2440
		2441	=item ev::TYPE::~TYPE
		2442
		2443	The constructor (optionally) takes an event loop to associate the watcher
		2444	with. If it is omitted, it will use C<EV_DEFAULT>.
		2445
		2446	The constructor calls C<ev_init> for you, which means you have to call the
		2447	C<set> method before starting it.
		2448
		2449	It will not set a callback, however: You have to call the templated C<set>
		2450	method to set a callback before you can start the watcher.
		2451
		2452	(The reason why you have to use a method is a limitation in C++ which does
		2453	not allow explicit template arguments for constructors).
		2454
		2455	The destructor automatically stops the watcher if it is active.
		2456
		2457	=item w->set<class, &class::method> (object *)
		2458
		2459	This method sets the callback method to call. The method has to have a
		2460	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2461	first argument and the C<revents> as second. The object must be given as
		2462	parameter and is stored in the C<data> member of the watcher.
		2463
		2464	This method synthesizes efficient thunking code to call your method from
		2465	the C callback that libev requires. If your compiler can inline your
		2466	callback (i.e. it is visible to it at the place of the C<set> call and
		2467	your compiler is good :), then the method will be fully inlined into the
		2468	thunking function, making it as fast as a direct C callback.
		2469
		2470	Example: simple class declaration and watcher initialisation
		2471
		2472	struct myclass
		2473	{
		2474	void io_cb (ev::io &w, int revents) { }
		2475	}
		2476
		2477	myclass obj;
		2478	ev::io iow;
		2479	iow.set <myclass, &myclass::io_cb> (&obj);
		2480
		2481	=item w->set<function> (void *data = 0)
		2482
		2483	Also sets a callback, but uses a static method or plain function as
		2484	callback. The optional C<data> argument will be stored in the watcher's
		2485	C<data> member and is free for you to use.
		2486
		2487	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2488
		2489	See the method-C<set> above for more details.
		2490
		2491	Example:
		2492
		2493	static void io_cb (ev::io &w, int revents) { }
		2494	iow.set <io_cb> ();
		2495
		2496	=item w->set (struct ev_loop *)
		2497
		2498	Associates a different C<struct ev_loop> with this watcher. You can only
		2499	do this when the watcher is inactive (and not pending either).
		2500
		2501	=item w->set ([args])
		2502
		2503	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2504	called at least once. Unlike the C counterpart, an active watcher gets
		2505	automatically stopped and restarted when reconfiguring it with this
		2506	method.
		2507
		2508	=item w->start ()
		2509
		2510	Starts the watcher. Note that there is no C<loop> argument, as the
		2511	constructor already stores the event loop.
		2512
		2513	=item w->stop ()
		2514
		2515	Stops the watcher if it is active. Again, no C<loop> argument.
		2516
		2517	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2518
		2519	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2520	C<ev_TYPE_again> function.
		2521
		2522	=item w->sweep () (C<ev::embed> only)
		2523
		2524	Invokes C<ev_embed_sweep>.
		2525
		2526	=item w->update () (C<ev::stat> only)
		2527
		2528	Invokes C<ev_stat_stat>.
		2529
		2530	=back
		2531
		2532	=back
		2533
		2534	Example: Define a class with an IO and idle watcher, start one of them in
		2535	the constructor.
		2536
		2537	class myclass
		2538	{
		2539	ev::io io; void io_cb (ev::io &w, int revents);
		2540	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2541
		2542	myclass (int fd)
		2543	{
		2544	io .set <myclass, &myclass::io_cb > (this);
		2545	idle.set <myclass, &myclass::idle_cb> (this);
		2546
		2547	io.start (fd, ev::READ);
		2548	}
		2549	};
		2550
		2551
		2552	=head1 OTHER LANGUAGE BINDINGS
		2553
		2554	Libev does not offer other language bindings itself, but bindings for a
		2555	numbe rof languages exist in the form of third-party packages. If you know
		2556	any interesting language binding in addition to the ones listed here, drop
		2557	me a note.
		2558
		2559	=over 4
		2560
		2561	=item Perl
		2562
		2563	The EV module implements the full libev API and is actually used to test
		2564	libev. EV is developed together with libev. Apart from the EV core module,
		2565	there are additional modules that implement libev-compatible interfaces
		2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2568
		2569	It can be found and installed via CPAN, its homepage is found at
		2570	L<http://software.schmorp.de/pkg/EV>.
		2571
		2572	=item Ruby
		2573
		2574	Tony Arcieri has written a ruby extension that offers access to a subset
		2575	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2576	more on top of it. It can be found via gem servers. Its homepage is at
		2577	L<http://rev.rubyforge.org/>.
		2578
		2579	=item D
		2580
		2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2583
		2584	=back
		2585
		2586
		2587	=head1 MACRO MAGIC
		2588
		2589	Libev can be compiled with a variety of options, the most fundamantal
		2590	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2591	functions and callbacks have an initial C<struct ev_loop *> argument.
		2592
		2593	To make it easier to write programs that cope with either variant, the
		2594	following macros are defined:
		2595
		2596	=over 4
		2597
		2598	=item C<EV_A>, C<EV_A_>
		2599
		2600	This provides the loop I<argument> for functions, if one is required ("ev
		2601	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2602	C<EV_A_> is used when other arguments are following. Example:
		2603
		2604	ev_unref (EV_A);
		2605	ev_timer_add (EV_A_ watcher);
		2606	ev_loop (EV_A_ 0);
		2607
		2608	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2609	which is often provided by the following macro.
		2610
		2611	=item C<EV_P>, C<EV_P_>
		2612
		2613	This provides the loop I<parameter> for functions, if one is required ("ev
		2614	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2615	C<EV_P_> is used when other parameters are following. Example:
		2616
		2617	// this is how ev_unref is being declared
		2618	static void ev_unref (EV_P);
		2619
		2620	// this is how you can declare your typical callback
		2621	static void cb (EV_P_ ev_timer *w, int revents)
		2622
		2623	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2624	suitable for use with C<EV_A>.
		2625
		2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2627
		2628	Similar to the other two macros, this gives you the value of the default
		2629	loop, if multiple loops are supported ("ev loop default").
		2630
		2631	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2632
		2633	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2634	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2635	is undefined when the default loop has not been initialised by a previous
		2636	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2637
		2638	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2639	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2640
		2641	=back
		2642
		2643	Example: Declare and initialise a check watcher, utilising the above
		2644	macros so it will work regardless of whether multiple loops are supported
		2645	or not.
		2646
		2647	static void
		2648	check_cb (EV_P_ ev_timer *w, int revents)
		2649	{
		2650	ev_check_stop (EV_A_ w);
		2651	}
		2652
		2653	ev_check check;
		2654	ev_check_init (&check, check_cb);
		2655	ev_check_start (EV_DEFAULT_ &check);
		2656	ev_loop (EV_DEFAULT_ 0);
		2657
		2658	=head1 EMBEDDING
		2659
		2660	Libev can (and often is) directly embedded into host
		2661	applications. Examples of applications that embed it include the Deliantra
		2662	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2663	and rxvt-unicode.
		2664
		2665	The goal is to enable you to just copy the necessary files into your
		2666	source directory without having to change even a single line in them, so
		2667	you can easily upgrade by simply copying (or having a checked-out copy of
		2668	libev somewhere in your source tree).
		2669
		2670	=head2 FILESETS
		2671
		2672	Depending on what features you need you need to include one or more sets of files
		2673	in your app.
		2674
		2675	=head3 CORE EVENT LOOP
		2676
		2677	To include only the libev core (all the C<ev_*> functions), with manual
		2678	configuration (no autoconf):
		2679
		2680	#define EV_STANDALONE 1
		2681	#include "ev.c"
		2682
		2683	This will automatically include F<ev.h>, too, and should be done in a
		2684	single C source file only to provide the function implementations. To use
		2685	it, do the same for F<ev.h> in all files wishing to use this API (best
		2686	done by writing a wrapper around F<ev.h> that you can include instead and
		2687	where you can put other configuration options):
		2688
		2689	#define EV_STANDALONE 1
		2690	#include "ev.h"
		2691
		2692	Both header files and implementation files can be compiled with a C++
		2693	compiler (at least, thats a stated goal, and breakage will be treated
		2694	as a bug).
		2695
		2696	You need the following files in your source tree, or in a directory
		2697	in your include path (e.g. in libev/ when using -Ilibev):
		2698
		2699	ev.h
		2700	ev.c
		2701	ev_vars.h
		2702	ev_wrap.h
		2703
		2704	ev_win32.c required on win32 platforms only
		2705
		2706	ev_select.c only when select backend is enabled (which is enabled by default)
		2707	ev_poll.c only when poll backend is enabled (disabled by default)
		2708	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2709	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2710	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2711
		2712	F<ev.c> includes the backend files directly when enabled, so you only need
		2713	to compile this single file.
		2714
		2715	=head3 LIBEVENT COMPATIBILITY API
		2716
		2717	To include the libevent compatibility API, also include:
		2718
		2719	#include "event.c"
		2720
		2721	in the file including F<ev.c>, and:
		2722
		2723	#include "event.h"
		2724
		2725	in the files that want to use the libevent API. This also includes F<ev.h>.
		2726
		2727	You need the following additional files for this:
		2728
		2729	event.h
		2730	event.c
		2731
		2732	=head3 AUTOCONF SUPPORT
		2733
		2734	Instead of using C<EV_STANDALONE=1> and providing your config in
		2735	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2736	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2737	include F<config.h> and configure itself accordingly.
		2738
		2739	For this of course you need the m4 file:
		2740
		2741	libev.m4
		2742
		2743	=head2 PREPROCESSOR SYMBOLS/MACROS
		2744
		2745	Libev can be configured via a variety of preprocessor symbols you have to
		2746	define before including any of its files. The default in the absense of
		2747	autoconf is noted for every option.
		2748
		2749	=over 4
		2750
		2751	=item EV_STANDALONE
		2752
		2753	Must always be C<1> if you do not use autoconf configuration, which
		2754	keeps libev from including F<config.h>, and it also defines dummy
		2755	implementations for some libevent functions (such as logging, which is not
		2756	supported). It will also not define any of the structs usually found in
		2757	F<event.h> that are not directly supported by the libev core alone.
		2758
		2759	=item EV_USE_MONOTONIC
		2760
		2761	If defined to be C<1>, libev will try to detect the availability of the
		2762	monotonic clock option at both compiletime and runtime. Otherwise no use
		2763	of the monotonic clock option will be attempted. If you enable this, you
		2764	usually have to link against librt or something similar. Enabling it when
		2765	the functionality isn't available is safe, though, although you have
		2766	to make sure you link against any libraries where the C<clock_gettime>
		2767	function is hiding in (often F<-lrt>).
		2768
		2769	=item EV_USE_REALTIME
		2770
		2771	If defined to be C<1>, libev will try to detect the availability of the
		2772	realtime clock option at compiletime (and assume its availability at
		2773	runtime if successful). Otherwise no use of the realtime clock option will
		2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2777
		2778	=item EV_USE_NANOSLEEP
		2779
		2780	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2781	and will use it for delays. Otherwise it will use C<select ()>.
		2782
		2783	=item EV_USE_EVENTFD
		2784
		2785	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2786	available and will probe for kernel support at runtime. This will improve
		2787	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2788	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2789	2.7 or newer, otherwise disabled.
		2790
		2791	=item EV_USE_SELECT
		2792
		2793	If undefined or defined to be C<1>, libev will compile in support for the
		2794	C<select>(2) backend. No attempt at autodetection will be done: if no
		2795	other method takes over, select will be it. Otherwise the select backend
		2796	will not be compiled in.
		2797
		2798	=item EV_SELECT_USE_FD_SET
		2799
		2800	If defined to C<1>, then the select backend will use the system C<fd_set>
		2801	structure. This is useful if libev doesn't compile due to a missing
		2802	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2803	exotic systems. This usually limits the range of file descriptors to some
		2804	low limit such as 1024 or might have other limitations (winsocket only
		2805	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2806	influence the size of the C<fd_set> used.
		2807
		2808	=item EV_SELECT_IS_WINSOCKET
		2809
		2810	When defined to C<1>, the select backend will assume that
		2811	select/socket/connect etc. don't understand file descriptors but
		2812	wants osf handles on win32 (this is the case when the select to
		2813	be used is the winsock select). This means that it will call
		2814	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2815	it is assumed that all these functions actually work on fds, even
		2816	on win32. Should not be defined on non-win32 platforms.
		2817
		2818	=item EV_FD_TO_WIN32_HANDLE
		2819
		2820	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2821	file descriptors to socket handles. When not defining this symbol (the
		2822	default), then libev will call C<_get_osfhandle>, which is usually
		2823	correct. In some cases, programs use their own file descriptor management,
		2824	in which case they can provide this function to map fds to socket handles.
		2825
		2826	=item EV_USE_POLL
		2827
		2828	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2829	backend. Otherwise it will be enabled on non-win32 platforms. It
		2830	takes precedence over select.
		2831
		2832	=item EV_USE_EPOLL
		2833
		2834	If defined to be C<1>, libev will compile in support for the Linux
		2835	C<epoll>(7) backend. Its availability will be detected at runtime,
		2836	otherwise another method will be used as fallback. This is the preferred
		2837	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2838	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2839
		2840	=item EV_USE_KQUEUE
		2841
		2842	If defined to be C<1>, libev will compile in support for the BSD style
		2843	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2844	otherwise another method will be used as fallback. This is the preferred
		2845	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2846	supports some types of fds correctly (the only platform we found that
		2847	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2848	not be used unless explicitly requested. The best way to use it is to find
		2849	out whether kqueue supports your type of fd properly and use an embedded
		2850	kqueue loop.
		2851
		2852	=item EV_USE_PORT
		2853
		2854	If defined to be C<1>, libev will compile in support for the Solaris
		2855	10 port style backend. Its availability will be detected at runtime,
		2856	otherwise another method will be used as fallback. This is the preferred
		2857	backend for Solaris 10 systems.
		2858
		2859	=item EV_USE_DEVPOLL
		2860
		2861	reserved for future expansion, works like the USE symbols above.
		2862
		2863	=item EV_USE_INOTIFY
		2864
		2865	If defined to be C<1>, libev will compile in support for the Linux inotify
		2866	interface to speed up C<ev_stat> watchers. Its actual availability will
		2867	be detected at runtime. If undefined, it will be enabled if the headers
		2868	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2869
		2870	=item EV_ATOMIC_T
		2871
		2872	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2873	access is atomic with respect to other threads or signal contexts. No such
		2874	type is easily found in the C language, so you can provide your own type
		2875	that you know is safe for your purposes. It is used both for signal handler "locking"
		2876	as well as for signal and thread safety in C<ev_async> watchers.
		2877
		2878	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2879	(from F<signal.h>), which is usually good enough on most platforms.
		2880
		2881	=item EV_H
		2882
		2883	The name of the F<ev.h> header file used to include it. The default if
		2884	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2885	used to virtually rename the F<ev.h> header file in case of conflicts.
		2886
		2887	=item EV_CONFIG_H
		2888
		2889	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2890	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2891	C<EV_H>, above.
		2892
		2893	=item EV_EVENT_H
		2894
		2895	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2896	of how the F<event.h> header can be found, the default is C<"event.h">.
		2897
		2898	=item EV_PROTOTYPES
		2899
		2900	If defined to be C<0>, then F<ev.h> will not define any function
		2901	prototypes, but still define all the structs and other symbols. This is
		2902	occasionally useful if you want to provide your own wrapper functions
		2903	around libev functions.
		2904
		2905	=item EV_MULTIPLICITY
		2906
		2907	If undefined or defined to C<1>, then all event-loop-specific functions
		2908	will have the C<struct ev_loop *> as first argument, and you can create
		2909	additional independent event loops. Otherwise there will be no support
		2910	for multiple event loops and there is no first event loop pointer
		2911	argument. Instead, all functions act on the single default loop.
		2912
		2913	=item EV_MINPRI
		2914
		2915	=item EV_MAXPRI
		2916
		2917	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2918	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2919	provide for more priorities by overriding those symbols (usually defined
		2920	to be C<-2> and C<2>, respectively).
		2921
		2922	When doing priority-based operations, libev usually has to linearly search
		2923	all the priorities, so having many of them (hundreds) uses a lot of space
		2924	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2925	fine.
		2926
		2927	If your embedding app does not need any priorities, defining these both to
		2928	C<0> will save some memory and cpu.
		2929
		2930	=item EV_PERIODIC_ENABLE
		2931
		2932	If undefined or defined to be C<1>, then periodic timers are supported. If
		2933	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2934	code.
		2935
		2936	=item EV_IDLE_ENABLE
		2937
		2938	If undefined or defined to be C<1>, then idle watchers are supported. If
		2939	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2940	code.
		2941
		2942	=item EV_EMBED_ENABLE
		2943
		2944	If undefined or defined to be C<1>, then embed watchers are supported. If
		2945	defined to be C<0>, then they are not.
		2946
		2947	=item EV_STAT_ENABLE
		2948
		2949	If undefined or defined to be C<1>, then stat watchers are supported. If
		2950	defined to be C<0>, then they are not.
		2951
		2952	=item EV_FORK_ENABLE
		2953
		2954	If undefined or defined to be C<1>, then fork watchers are supported. If
		2955	defined to be C<0>, then they are not.
		2956
		2957	=item EV_ASYNC_ENABLE
		2958
		2959	If undefined or defined to be C<1>, then async watchers are supported. If
		2960	defined to be C<0>, then they are not.
		2961
		2962	=item EV_MINIMAL
		2963
		2964	If you need to shave off some kilobytes of code at the expense of some
		2965	speed, define this symbol to C<1>. Currently only used for gcc to override
		2966	some inlining decisions, saves roughly 30% codesize of amd64.
		2967
		2968	=item EV_PID_HASHSIZE
		2969
		2970	C<ev_child> watchers use a small hash table to distribute workload by
		2971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2972	than enough. If you need to manage thousands of children you might want to
		2973	increase this value (I<must> be a power of two).
		2974
		2975	=item EV_INOTIFY_HASHSIZE
		2976
		2977	C<ev_stat> watchers use a small hash table to distribute workload by
		2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2979	usually more than enough. If you need to manage thousands of C<ev_stat>
		2980	watchers you might want to increase this value (I<must> be a power of
		2981	two).
		2982
		2983	=item EV_COMMON
		2984
		2985	By default, all watchers have a C<void *data> member. By redefining
		2986	this macro to a something else you can include more and other types of
		2987	members. You have to define it each time you include one of the files,
		2988	though, and it must be identical each time.
		2989
		2990	For example, the perl EV module uses something like this:
		2991
		2992	#define EV_COMMON \
		2993	SV *self; /* contains this struct */ \
		2994	SV *cb_sv, *fh /* note no trailing ";" */
		2995
		2996	=item EV_CB_DECLARE (type)
		2997
		2998	=item EV_CB_INVOKE (watcher, revents)
		2999
		3000	=item ev_set_cb (ev, cb)
		3001
		3002	Can be used to change the callback member declaration in each watcher,
		3003	and the way callbacks are invoked and set. Must expand to a struct member
		3004	definition and a statement, respectively. See the F<ev.h> header file for
		3005	their default definitions. One possible use for overriding these is to
		3006	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		3007	method calls instead of plain function calls in C++.
		3008
		3009	=head2 EXPORTED API SYMBOLS
		3010
		3011	If you need to re-export the API (e.g. via a dll) and you need a list of
		3012	exported symbols, you can use the provided F<Symbol.*> files which list
		3013	all public symbols, one per line:
		3014
		3015	Symbols.ev for libev proper
		3016	Symbols.event for the libevent emulation
		3017
		3018	This can also be used to rename all public symbols to avoid clashes with
		3019	multiple versions of libev linked together (which is obviously bad in
		3020	itself, but sometimes it is inconvinient to avoid this).
		3021
		3022	A sed command like this will create wrapper C<#define>'s that you need to
		3023	include before including F<ev.h>:
		3024
		3025	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3026
		3027	This would create a file F<wrap.h> which essentially looks like this:
		3028
		3029	#define ev_backend myprefix_ev_backend
		3030	#define ev_check_start myprefix_ev_check_start
		3031	#define ev_check_stop myprefix_ev_check_stop
		3032	...
		3033
		3034	=head2 EXAMPLES
		3035
		3036	For a real-world example of a program the includes libev
		3037	verbatim, you can have a look at the EV perl module
		3038	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		3039	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		3040	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		3041	will be compiled. It is pretty complex because it provides its own header
		3042	file.
		3043
		3044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		3045	that everybody includes and which overrides some configure choices:
		3046
		3047	#define EV_MINIMAL 1
		3048	#define EV_USE_POLL 0
		3049	#define EV_MULTIPLICITY 0
		3050	#define EV_PERIODIC_ENABLE 0
		3051	#define EV_STAT_ENABLE 0
		3052	#define EV_FORK_ENABLE 0
		3053	#define EV_CONFIG_H <config.h>
		3054	#define EV_MINPRI 0
		3055	#define EV_MAXPRI 0
		3056
		3057	#include "ev++.h"
		3058
		3059	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		3060
		3061	#include "ev_cpp.h"
		3062	#include "ev.c"
		3063
		3064
		3065	=head1 THREADS AND COROUTINES
		3066
		3067	=head2 THREADS
		3068
		3069	Libev itself is completely threadsafe, but it uses no locking. This
		3070	means that you can use as many loops as you want in parallel, as long as
		3071	only one thread ever calls into one libev function with the same loop
		3072	parameter.
		3073
		3074	Or put differently: calls with different loop parameters can be done in
		3075	parallel from multiple threads, calls with the same loop parameter must be
		3076	done serially (but can be done from different threads, as long as only one
		3077	thread ever is inside a call at any point in time, e.g. by using a mutex
		3078	per loop).
		3079
		3080	If you want to know which design is best for your problem, then I cannot
		3081	help you but by giving some generic advice:
		3082
		3083	=over 4
		3084
		3085	=item * most applications have a main thread: use the default libev loop
		3086	in that thread, or create a seperate thread running only the default loop.
		3087
		3088	This helps integrating other libraries or software modules that use libev
		3089	themselves and don't care/know about threading.
		3090
		3091	=item * one loop per thread is usually a good model.
		3092
		3093	Doing this is almost never wrong, sometimes a better-performance model
		3094	exists, but it is always a good start.
		3095
		3096	=item * other models exist, such as the leader/follower pattern, where one
		3097	loop is handed through multiple threads in a kind of round-robbin fashion.
		3098
		3099	Chosing a model is hard - look around, learn, know that usually you cna do
		3100	better than you currently do :-)
		3101
		3102	=item * often you need to talk to some other thread which blocks in the
		3103	event loop - C<ev_async> watchers can be used to wake them up from other
		3104	threads safely (or from signal contexts...).
		3105
		3106	=back
		3107
		3108	=head2 COROUTINES
		3109
		3110	Libev is much more accomodating to coroutines ("cooperative threads"):
		3111	libev fully supports nesting calls to it's functions from different
		3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3113	different coroutines and switch freely between both coroutines running the
		3114	loop, as long as you don't confuse yourself). The only exception is that
		3115	you must not do this from C<ev_periodic> reschedule callbacks.
		3116
		3117	Care has been invested into making sure that libev does not keep local
		3118	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3119	switches.
		3120
		3121
		3122	=head1 COMPLEXITIES
		3123
		3124	In this section the complexities of (many of) the algorithms used inside
		3125	libev will be explained. For complexity discussions about backends see the
		3126	documentation for C<ev_default_init>.
		3127
		3128	All of the following are about amortised time: If an array needs to be
		3129	extended, libev needs to realloc and move the whole array, but this
		3130	happens asymptotically never with higher number of elements, so O(1) might
		3131	mean it might do a lengthy realloc operation in rare cases, but on average
		3132	it is much faster and asymptotically approaches constant time.
		3133
		3134	=over 4
		3135
		3136	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3137
		3138	This means that, when you have a watcher that triggers in one hour and
		3139	there are 100 watchers that would trigger before that then inserting will
		3140	have to skip roughly seven (C<ld 100>) of these watchers.
		3141
		3142	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3143
		3144	That means that changing a timer costs less than removing/adding them
		3145	as only the relative motion in the event queue has to be paid for.
		3146
		3147	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3148
		3149	These just add the watcher into an array or at the head of a list.
		3150
		3151	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3152
		3153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3154
		3155	These watchers are stored in lists then need to be walked to find the
		3156	correct watcher to remove. The lists are usually short (you don't usually
		3157	have many watchers waiting for the same fd or signal).
		3158
		3159	=item Finding the next timer in each loop iteration: O(1)
		3160
		3161	By virtue of using a binary heap, the next timer is always found at the
		3162	beginning of the storage array.
		3163
		3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3165
		3166	A change means an I/O watcher gets started or stopped, which requires
		3167	libev to recalculate its status (and possibly tell the kernel, depending
		3168	on backend and wether C<ev_io_set> was used).
		3169
		3170	=item Activating one watcher (putting it into the pending state): O(1)
		3171
		3172	=item Priority handling: O(number_of_priorities)
		3173
		3174	Priorities are implemented by allocating some space for each
		3175	priority. When doing priority-based operations, libev usually has to
		3176	linearly search all the priorities, but starting/stopping and activating
		3177	watchers becomes O(1) w.r.t. priority handling.
		3178
		3179	=item Sending an ev_async: O(1)
		3180
		3181	=item Processing ev_async_send: O(number_of_async_watchers)
		3182
		3183	=item Processing signals: O(max_signal_number)
		3184
		3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3186	calls in the current loop iteration. Checking for async and signal events
		3187	involves iterating over all running async watchers or all signal numbers.
		3188
		3189	=back
		3190
		3191
		3192	=head1 Win32 platform limitations and workarounds
		3193
		3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3195	requires, and its I/O model is fundamentally incompatible with the POSIX
		3196	model. Libev still offers limited functionality on this platform in
		3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3198	descriptors. This only applies when using Win32 natively, not when using
		3199	e.g. cygwin.
		3200
		3201	There is no supported compilation method available on windows except
		3202	embedding it into other applications.
		3203
		3204	Due to the many, low, and arbitrary limits on the win32 platform and the
		3205	abysmal performance of winsockets, using a large number of sockets is not
		3206	recommended (and not reasonable). If your program needs to use more than
		3207	a hundred or so sockets, then likely it needs to use a totally different
		3208	implementation for windows, as libev offers the POSIX model, which cannot
		3209	be implemented efficiently on windows (microsoft monopoly games).
		3210
		3211	=over 4
		3212
		3213	=item The winsocket select function
		3214
		3215	The winsocket C<select> function doesn't follow POSIX in that it requires
		3216	socket I<handles> and not socket I<file descriptors>. This makes select
		3217	very inefficient, and also requires a mapping from file descriptors
		3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3220	symbols for more info.
		3221
		3222	The configuration for a "naked" win32 using the microsoft runtime
		3223	libraries and raw winsocket select is:
		3224
		3225	#define EV_USE_SELECT 1
		3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3227
		3228	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3229	complexity in the O(n²) range when using win32.
		3230
		3231	=item Limited number of file descriptors
		3232
		3233	Windows has numerous arbitrary (and low) limits on things. Early versions
		3234	of winsocket's select only supported waiting for a max. of C<64> handles
		3235	(probably owning to the fact that all windows kernels can only wait for
		3236	C<64> things at the same time internally; microsoft recommends spawning a
		3237	chain of threads and wait for 63 handles and the previous thread in each).
		3238
		3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3240	to some high number (e.g. C<2048>) before compiling the winsocket select
		3241	call (which might be in libev or elsewhere, for example, perl does its own
		3242	select emulation on windows).
		3243
		3244	Another limit is the number of file descriptors in the microsoft runtime
		3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3246	or something like this inside microsoft). You can increase this by calling
		3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3248	arbitrary limit), but is broken in many versions of the microsoft runtime
		3249	libraries.
		3250
		3251	This might get you to about C<512> or C<2048> sockets (depending on
		3252	windows version and/or the phase of the moon). To get more, you need to
		3253	wrap all I/O functions and provide your own fd management, but the cost of
		3254	calling select (O(n²)) will likely make this unworkable.
		3255
		3256	=back
		3257
825		3258
826	=head1 AUTHOR	3259	=head1 AUTHOR
827		3260
828	Marc Lehmann <libev@schmorp.de>.	3261	Marc Lehmann <libev@schmorp.de>.
829		3262

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