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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	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	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	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	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	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	66	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	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head2 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head2 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	96	=head2 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	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	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
		106
		107	=head1 GLOBAL FUNCTIONS
		108
		109	These functions can be called anytime, even before initialising the
		110	library in any way.
51		111
52	=over 4	112	=over 4
53		113
54	=item ev_tstamp ev_time ()	114	=item ev_tstamp ev_time ()
55		115
56	Returns the current time as libev would use it.	116	Returns the current time as libev would use it. Please note that the
		117	C<ev_now> function is usually faster and also often returns the timestamp
		118	you actually want to know.
		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
57		125
58	=item int ev_version_major ()	126	=item int ev_version_major ()
59		127
60	=item int ev_version_minor ()	128	=item int ev_version_minor ()
61		129
62	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
63	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
64	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
65	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	134	version of the library your program was compiled against.
67		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
68	Usually, its a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	142	not a problem.
72		143
		144	Example: Make sure we haven't accidentally been linked against the wrong
		145	version.
		146
		147	assert (("libev version mismatch",
		148	ev_version_major () == EV_VERSION_MAJOR
		149	&& ev_version_minor () >= EV_VERSION_MINOR));
		150
		151	=item unsigned int ev_supported_backends ()
		152
		153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		154	value) compiled into this binary of libev (independent of their
		155	availability on the system you are running on). See C<ev_default_loop> for
		156	a description of the set values.
		157
		158	Example: make sure we have the epoll method, because yeah this is cool and
		159	a must have and can we have a torrent of it please!!!11
		160
		161	assert (("sorry, no epoll, no sex",
		162	ev_supported_backends () & EVBACKEND_EPOLL));
		163
		164	=item unsigned int ev_recommended_backends ()
		165
		166	Return the set of all backends compiled into this binary of libev and also
		167	recommended for this platform. This set is often smaller than the one
		168	returned by C<ev_supported_backends>, as for example kqueue is broken on
		169	most BSDs and will not be autodetected unless you explicitly request it
		170	(assuming you know what you are doing). This is the set of backends that
		171	libev will probe for if you specify no backends explicitly.
		172
		173	=item unsigned int ev_embeddable_backends ()
		174
		175	Returns the set of backends that are embeddable in other event loops. This
		176	is the theoretical, all-platform, value. To find which backends
		177	might be supported on the current system, you would need to look at
		178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		179	recommended ones.
		180
		181	See the description of C<ev_embed> watchers for more info.
		182
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		184
75	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
77	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
78	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
79	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
80		191
81	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
82	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
83	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
		195
		196	Example: Replace the libev allocator with one that waits a bit and then
		197	retries).
		198
		199	static void *
		200	persistent_realloc (void *ptr, size_t size)
		201	{
		202	for (;;)
		203	{
		204	void *newptr = realloc (ptr, size);
		205
		206	if (newptr)
		207	return newptr;
		208
		209	sleep (60);
		210	}
		211	}
		212
		213	...
		214	ev_set_allocator (persistent_realloc);
84		215
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	216	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		217
87	Set the callback function to call on a retryable syscall error (such	218	Set the callback function to call on a retryable syscall error (such
88	as failed select, poll, epoll_wait). The message is a printable string	219	as failed select, poll, epoll_wait). The message is a printable string
…		…
90	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
91	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
92	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	224	(such as abort).
94		225
		226	Example: This is basically the same thing that libev does internally, too.
		227
		228	static void
		229	fatal_error (const char *msg)
		230	{
		231	perror (msg);
		232	abort ();
		233	}
		234
		235	...
		236	ev_set_syserr_cb (fatal_error);
		237
95	=back	238	=back
96		239
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		241
99	An event loop is described by a C<struct ev_loop *>. The library knows two	242	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	243	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	244	events, and dynamically created loops which do not.
102		245
103	If you use threads, a common model is to run the default event loop	246	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	247	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	248	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	249	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	250	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	251	done correctly, because it's hideous and inefficient).
109		252
110	=over 4	253	=over 4
111		254
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	255	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		256
114	This will initialise the default event loop if it hasn't been initialised	257	This will initialise the default event loop if it hasn't been initialised
115	yet and return it. If the default loop could not be initialised, returns	258	yet and return it. If the default loop could not be initialised, returns
116	false. If it already was initialised it simply returns it (and ignores the	259	false. If it already was initialised it simply returns it (and ignores the
117	flags).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		261
119	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
120	function.	263	function.
121		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
122	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
123	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		274
125	It supports the following flags:	275	The following flags are supported:
126		276
127	=over 4	277	=over 4
128		278
129	=item EVFLAG_AUTO	279	=item C<EVFLAG_AUTO>
130		280
131	The default flags value. Use this if you have no clue (its the right	281	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	282	thing, believe me).
133		283
134	=item EVFLAG_NOENV	284	=item C<EVFLAG_NOENV>
135		285
136	If this flag bit is ored into the flag value (or the program runs setuid	286	If this flag bit is ored into the flag value (or the program runs setuid
137	or setgid) then libev will I<not> look at the environment variable	287	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	289	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	290	useful to try out specific backends to test their performance, or to work
141	around bugs.	291	around bugs.
142		292
		293	=item C<EVFLAG_FORKCHECK>
		294
		295	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		296	a fork, you can also make libev check for a fork in each iteration by
		297	enabling this flag.
		298
		299	This works by calling C<getpid ()> on every iteration of the loop,
		300	and thus this might slow down your event loop if you do a lot of loop
		301	iterations and little real work, but is usually not noticeable (on my
		302	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		303	without a syscall and thus I<very> fast, but my Linux system also has
		304	C<pthread_atfork> which is even faster).
		305
		306	The big advantage of this flag is that you can forget about fork (and
		307	forget about forgetting to tell libev about forking) when you use this
		308	flag.
		309
		310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		311	environment variable.
		312
143	=item EVMETHOD_SELECT portable select backend	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		314
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	315	This is your standard select(2) backend. Not I<completely> standard, as
		316	libev tries to roll its own fd_set with no limits on the number of fds,
		317	but if that fails, expect a fairly low limit on the number of fds when
		318	using this backend. It doesn't scale too well (O(highest_fd)), but its
		319	usually the fastest backend for a low number of (low-numbered :) fds.
146		320
147	=item EVMETHOD_EPOLL linux only	321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
148		327
149	=item EVMETHOD_KQUEUE some bsds only	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
150		329
151	=item EVMETHOD_DEVPOLL solaris 8 only	330	And this is your standard poll(2) backend. It's more complicated
		331	than select, but handles sparse fds better and has no artificial
		332	limit on the number of fds you can use (except it will slow down
		333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
152		336
153	=item EVMETHOD_PORT solaris 10 only	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		338
		339	For few fds, this backend is a bit little slower than poll and select,
		340	but it scales phenomenally better. While poll and select usually scale
		341	like O(total_fds) where n is the total number of fds (or the highest fd),
		342	epoll scales either O(1) or O(active_fds). The epoll design has a number
		343	of shortcomings, such as silently dropping events in some hard-to-detect
		344	cases and rewiring a syscall per fd change, no fork support and bad
		345	support for dup.
		346
		347	While stopping, setting and starting an I/O watcher in the same iteration
		348	will result in some caching, there is still a syscall per such incident
		349	(because the fd could point to a different file description now), so its
		350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		351	very well if you register events for both fds.
		352
		353	Please note that epoll sometimes generates spurious notifications, so you
		354	need to use non-blocking I/O or other means to avoid blocking when no data
		355	(or space) is available.
		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
		364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		365
		366	Kqueue deserves special mention, as at the time of this writing, it
		367	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		368	with anything but sockets and pipes, except on Darwin, where of course
		369	it's completely useless). For this reason it's not being "autodetected"
		370	unless you explicitly specify it explicitly in the flags (i.e. using
		371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		372	system like NetBSD.
		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
		377
		378	It scales in the same way as the epoll backend, but the interface to the
		379	kernel is more efficient (which says nothing about its actual speed, of
		380	course). While stopping, setting and starting an I/O watcher does never
		381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
		382	two event changes per incident, support for C<fork ()> is very bad and it
		383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
		393
		394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		395
		396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
		400
		401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		402
		403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		404	it's really slow, but it still scales very well (O(active_fds)).
		405
		406	Please note that solaris event ports can deliver a lot of spurious
		407	notifications, so you need to use non-blocking I/O or other means to avoid
		408	blocking when no data (or space) is available.
		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
		418
		419	=item C<EVBACKEND_ALL>
		420
		421	Try all backends (even potentially broken ones that wouldn't be tried
		422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		424
		425	It is definitely not recommended to use this flag.
		426
		427	=back
154		428
155	If one or more of these are ored into the flags value, then only these	429	If one or more of these are ored into the flags value, then only these
156	backends will be tried (in the reverse order as given here). If one are	430	backends will be tried (in the reverse order as listed here). If none are
157	specified, any backend will do.	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
158		432
159	=back	433	The most typical usage is like this:
		434
		435	if (!ev_default_loop (0))
		436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		437
		438	Restrict libev to the select and poll backends, and do not allow
		439	environment settings to be taken into account:
		440
		441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		442
		443	Use whatever libev has to offer, but make sure that kqueue is used if
		444	available (warning, breaks stuff, best use only with your own private
		445	event loop and only if you know the OS supports your types of fds):
		446
		447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		448
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	449	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		450
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	451	Similar to C<ev_default_loop>, but always creates a new event loop that is
164	always distinct from the default loop. Unlike the default loop, it cannot	452	always distinct from the default loop. Unlike the default loop, it cannot
165	handle signal and child watchers, and attempts to do so will be greeted by	453	handle signal and child watchers, and attempts to do so will be greeted by
166	undefined behaviour (or a failed assertion if assertions are enabled).	454	undefined behaviour (or a failed assertion if assertions are enabled).
167		455
		456	Example: Try to create a event loop that uses epoll and nothing else.
		457
		458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		459	if (!epoller)
		460	fatal ("no epoll found here, maybe it hides under your chair");
		461
168	=item ev_default_destroy ()	462	=item ev_default_destroy ()
169		463
170	Destroys the default loop again (frees all memory and kernel state	464	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	465	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	466	sense, so e.g. C<ev_is_active> might still return true. It is your
		467	responsibility to either stop all watchers cleanly yoursef I<before>
		468	calling this function, or cope with the fact afterwards (which is usually
		469	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		470	for example).
		471
		472	Note that certain global state, such as signal state, will not be freed by
		473	this function, and related watchers (such as signal and child watchers)
		474	would need to be stopped manually.
		475
		476	In general it is not advisable to call this function except in the
		477	rare occasion where you really need to free e.g. the signal handling
		478	pipe fds. If you need dynamically allocated loops it is better to use
		479	C<ev_loop_new> and C<ev_loop_destroy>).
173		480
174	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
175		482
176	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
178		485
179	=item ev_default_fork ()	486	=item ev_default_fork ()
180		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
181	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
182	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
183	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
184	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
185		494
186	You I<must> call this function after forking if and only if you want to	495	On the other hand, you only need to call this function in the child
187	use the event library in both processes. If you just fork+exec, you don't	496	process if and only if you want to use the event library in the child. If
188	have to call it.	497	you just fork+exec, you don't have to call it at all.
189		498
190	The function itself is quite fast and its usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
191	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
192	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
193		502
194	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
195		504
…		…
197		506
198	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
199	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
200	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
201		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
		514
		515	=item unsigned int ev_loop_count (loop)
		516
		517	Returns the count of loop iterations for the loop, which is identical to
		518	the number of times libev did poll for new events. It starts at C<0> and
		519	happily wraps around with enough iterations.
		520
		521	This value can sometimes be useful as a generation counter of sorts (it
		522	"ticks" the number of loop iterations), as it roughly corresponds with
		523	C<ev_prepare> and C<ev_check> calls.
		524
202	=item unsigned int ev_method (loop)	525	=item unsigned int ev_backend (loop)
203		526
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	527	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	528	use.
206		529
207	=item ev_tstamp = ev_now (loop)	530	=item ev_tstamp ev_now (loop)
208		531
209	Returns the current "event loop time", which is the time the event loop	532	Returns the current "event loop time", which is the time the event loop
210	got events and started processing them. This timestamp does not change	533	received events and started processing them. This timestamp does not
211	as long as callbacks are being processed, and this is also the base time	534	change as long as callbacks are being processed, and this is also the base
212	used for relative timers. You can treat it as the timestamp of the event	535	time used for relative timers. You can treat it as the timestamp of the
213	occuring (or more correctly, the mainloop finding out about it).	536	event occurring (or more correctly, libev finding out about it).
214		537
215	=item ev_loop (loop, int flags)	538	=item ev_loop (loop, int flags)
216		539
217	Finally, this is it, the event handler. This function usually is called	540	Finally, this is it, the event handler. This function usually is called
218	after you initialised all your watchers and you want to start handling	541	after you initialised all your watchers and you want to start handling
219	events.	542	events.
220		543
221	If the flags argument is specified as 0, it will not return until either	544	If the flags argument is specified as C<0>, it will not return until
222	no event watchers are active anymore or C<ev_unloop> was called.	545	either no event watchers are active anymore or C<ev_unloop> was called.
		546
		547	Please note that an explicit C<ev_unloop> is usually better than
		548	relying on all watchers to be stopped when deciding when a program has
		549	finished (especially in interactive programs), but having a program that
		550	automatically loops as long as it has to and no longer by virtue of
		551	relying on its watchers stopping correctly is a thing of beauty.
223		552
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	553	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
225	those events and any outstanding ones, but will not block your process in	554	those events and any outstanding ones, but will not block your process in
226	case there are no events.	555	case there are no events and will return after one iteration of the loop.
227		556
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	557	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
229	neccessary) and will handle those and any outstanding ones. It will block	558	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	559	your process until at least one new event arrives, and will return after
		560	one iteration of the loop. This is useful if you are waiting for some
		561	external event in conjunction with something not expressible using other
		562	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		563	usually a better approach for this kind of thing.
231		564
232	This flags value could be used to implement alternative looping	565	Here are the gory details of what C<ev_loop> does:
233	constructs, but the C<prepare> and C<check> watchers provide a better and	566
234	more generic mechanism.	567	- Before the first iteration, call any pending watchers.
		568	* If EVFLAG_FORKCHECK was used, check for a fork.
		569	- If a fork was detected, queue and call all fork watchers.
		570	- Queue and call all prepare watchers.
		571	- If we have been forked, recreate the kernel state.
		572	- Update the kernel state with all outstanding changes.
		573	- Update the "event loop time".
		574	- Calculate for how long to sleep or block, if at all
		575	(active idle watchers, EVLOOP_NONBLOCK or not having
		576	any active watchers at all will result in not sleeping).
		577	- Sleep if the I/O and timer collect interval say so.
		578	- Block the process, waiting for any events.
		579	- Queue all outstanding I/O (fd) events.
		580	- Update the "event loop time" and do time jump handling.
		581	- Queue all outstanding timers.
		582	- Queue all outstanding periodics.
		583	- If no events are pending now, queue all idle watchers.
		584	- Queue all check watchers.
		585	- Call all queued watchers in reverse order (i.e. check watchers first).
		586	Signals and child watchers are implemented as I/O watchers, and will
		587	be handled here by queueing them when their watcher gets executed.
		588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		589	were used, or there are no active watchers, return, otherwise
		590	continue with step *.
		591
		592	Example: Queue some jobs and then loop until no events are outstanding
		593	anymore.
		594
		595	... queue jobs here, make sure they register event watchers as long
		596	... as they still have work to do (even an idle watcher will do..)
		597	ev_loop (my_loop, 0);
		598	... jobs done. yeah!
235		599
236	=item ev_unloop (loop, how)	600	=item ev_unloop (loop, how)
237		601
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	602	Can be used to make a call to C<ev_loop> return early (but only after it
		603	has processed all outstanding events). The C<how> argument must be either
239	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
240	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.	606
		607	This "unloop state" will be cleared when entering C<ev_loop> again.
242		608
243	=item ev_ref (loop)	609	=item ev_ref (loop)
244		610
245	=item ev_unref (loop)	611	=item ev_unref (loop)
246		612
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	613	Ref/unref can be used to add or remove a reference count on the event
248	watcher keeps one reference. If you have a long-runing watcher you never	614	loop: Every watcher keeps one reference, and as long as the reference
249	unregister that should not keep ev_loop from running, ev_unref() after	615	count is nonzero, C<ev_loop> will not return on its own. If you have
250	starting, and ev_ref() before stopping it. Libev itself uses this for	616	a watcher you never unregister that should not keep C<ev_loop> from
251	example for its internal signal pipe: It is not visible to you as a user	617	returning, ev_unref() after starting, and ev_ref() before stopping it. For
252	and should not keep C<ev_loop> from exiting if the work is done. It is	618	example, libev itself uses this for its internal signal pipe: It is not
253	also an excellent way to do this for generic recurring timers or from	619	visible to the libev user and should not keep C<ev_loop> from exiting if
254	within third-party libraries. Just remember to unref after start and ref	620	no event watchers registered by it are active. It is also an excellent
255	before stop.	621	way to do this for generic recurring timers or from within third-party
		622	libraries. Just remember to I<unref after start> and I<ref before stop>
		623	(but only if the watcher wasn't active before, or was active before,
		624	respectively).
		625
		626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		627	running when nothing else is active.
		628
		629	struct ev_signal exitsig;
		630	ev_signal_init (&exitsig, sig_cb, SIGINT);
		631	ev_signal_start (loop, &exitsig);
		632	evf_unref (loop);
		633
		634	Example: For some weird reason, unregister the above signal handler again.
		635
		636	ev_ref (loop);
		637	ev_signal_stop (loop, &exitsig);
		638
		639	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		640
		641	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		642
		643	These advanced functions influence the time that libev will spend waiting
		644	for events. Both are by default C<0>, meaning that libev will try to
		645	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		646
		647	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		648	allows libev to delay invocation of I/O and timer/periodic callbacks to
		649	increase efficiency of loop iterations.
		650
		651	The background is that sometimes your program runs just fast enough to
		652	handle one (or very few) event(s) per loop iteration. While this makes
		653	the program responsive, it also wastes a lot of CPU time to poll for new
		654	events, especially with backends like C<select ()> which have a high
		655	overhead for the actual polling but can deliver many events at once.
		656
		657	By setting a higher I<io collect interval> you allow libev to spend more
		658	time collecting I/O events, so you can handle more events per iteration,
		659	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		660	C<ev_timer>) will be not affected. Setting this to a non-null value will
		661	introduce an additional C<ev_sleep ()> call into most loop iterations.
		662
		663	Likewise, by setting a higher I<timeout collect interval> you allow libev
		664	to spend more time collecting timeouts, at the expense of increased
		665	latency (the watcher callback will be called later). C<ev_io> watchers
		666	will not be affected. Setting this to a non-null value will not introduce
		667	any overhead in libev.
		668
		669	Many (busy) programs can usually benefit by setting the io collect
		670	interval to a value near C<0.1> or so, which is often enough for
		671	interactive servers (of course not for games), likewise for timeouts. It
		672	usually doesn't make much sense to set it to a lower value than C<0.01>,
		673	as this approsaches the timing granularity of most systems.
256		674
257	=back	675	=back
		676
258		677
259	=head1 ANATOMY OF A WATCHER	678	=head1 ANATOMY OF A WATCHER
260		679
261	A watcher is a structure that you create and register to record your	680	A watcher is a structure that you create and register to record your
262	interest in some event. For instance, if you want to wait for STDIN to	681	interest in some event. For instance, if you want to wait for STDIN to
263	become readable, you would create an ev_io watcher for that:	682	become readable, you would create an C<ev_io> watcher for that:
264		683
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	684	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	685	{
267	ev_io_stop (w);	686	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	687	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	714	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	715	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		716
298	As long as your watcher is active (has been started but not stopped) you	717	As long as your watcher is active (has been started but not stopped) you
299	must not touch the values stored in it. Most specifically you must never	718	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	719	reinitialise it or call its C<set> macro.
301
302	You cna check whether an event is active by calling the C<ev_is_active
303	(watcher *)> macro. To see whether an event is outstanding (but the
304	callback for it has not been called yet) you cna use the C<ev_is_pending
305	(watcher *)> macro.
306		720
307	Each and every callback receives the event loop pointer as first, the	721	Each and every callback receives the event loop pointer as first, the
308	registered watcher structure as second, and a bitset of received events as	722	registered watcher structure as second, and a bitset of received events as
309	third argument.	723	third argument.
310		724
311	The rceeived events usually include a single bit per event type received	725	The received events usually include a single bit per event type received
312	(you can receive multiple events at the same time). The possible bit masks	726	(you can receive multiple events at the same time). The possible bit masks
313	are:	727	are:
314		728
315	=over 4	729	=over 4
316		730
317	=item EV_READ	731	=item C<EV_READ>
318		732
319	=item EV_WRITE	733	=item C<EV_WRITE>
320		734
321	The file descriptor in the ev_io watcher has become readable and/or	735	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	736	writable.
323		737
324	=item EV_TIMEOUT	738	=item C<EV_TIMEOUT>
325		739
326	The ev_timer watcher has timed out.	740	The C<ev_timer> watcher has timed out.
327		741
328	=item EV_PERIODIC	742	=item C<EV_PERIODIC>
329		743
330	The ev_periodic watcher has timed out.	744	The C<ev_periodic> watcher has timed out.
331		745
332	=item EV_SIGNAL	746	=item C<EV_SIGNAL>
333		747
334	The signal specified in the ev_signal watcher has been received by a thread.	748	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		749
336	=item EV_CHILD	750	=item C<EV_CHILD>
337		751
338	The pid specified in the ev_child watcher has received a status change.	752	The pid specified in the C<ev_child> watcher has received a status change.
339		753
		754	=item C<EV_STAT>
		755
		756	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		757
340	=item EV_IDLE	758	=item C<EV_IDLE>
341		759
342	The ev_idle watcher has determined that you have nothing better to do.	760	The C<ev_idle> watcher has determined that you have nothing better to do.
343		761
344	=item EV_PREPARE	762	=item C<EV_PREPARE>
345		763
346	=item EV_CHECK	764	=item C<EV_CHECK>
347		765
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	766	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
349	to gather new events, and all ev_check watchers are invoked just after	767	to gather new events, and all C<ev_check> watchers are invoked just after
350	C<ev_loop> has gathered them, but before it invokes any callbacks for any	768	C<ev_loop> has gathered them, but before it invokes any callbacks for any
351	received events. Callbacks of both watcher types can start and stop as	769	received events. Callbacks of both watcher types can start and stop as
352	many watchers as they want, and all of them will be taken into account	770	many watchers as they want, and all of them will be taken into account
353	(for example, a ev_prepare watcher might start an idle watcher to keep	771	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	772	C<ev_loop> from blocking).
355		773
		774	=item C<EV_EMBED>
		775
		776	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		777
		778	=item C<EV_FORK>
		779
		780	The event loop has been resumed in the child process after fork (see
		781	C<ev_fork>).
		782
		783	=item C<EV_ASYNC>
		784
		785	The given async watcher has been asynchronously notified (see C<ev_async>).
		786
356	=item EV_ERROR	787	=item C<EV_ERROR>
357		788
358	An unspecified error has occured, the watcher has been stopped. This might	789	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	790	happen because the watcher could not be properly started because libev
360	ran out of memory, a file descriptor was found to be closed or any other	791	ran out of memory, a file descriptor was found to be closed or any other
361	problem. You best act on it by reporting the problem and somehow coping	792	problem. You best act on it by reporting the problem and somehow coping
…		…
367	with the error from read() or write(). This will not work in multithreaded	798	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	799	programs, though, so beware.
369		800
370	=back	801	=back
371		802
		803	=head2 GENERIC WATCHER FUNCTIONS
		804
		805	In the following description, C<TYPE> stands for the watcher type,
		806	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		807
		808	=over 4
		809
		810	=item C<ev_init> (ev_TYPE *watcher, callback)
		811
		812	This macro initialises the generic portion of a watcher. The contents
		813	of the watcher object can be arbitrary (so C<malloc> will do). Only
		814	the generic parts of the watcher are initialised, you I<need> to call
		815	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		816	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		817	which rolls both calls into one.
		818
		819	You can reinitialise a watcher at any time as long as it has been stopped
		820	(or never started) and there are no pending events outstanding.
		821
		822	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		823	int revents)>.
		824
		825	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		826
		827	This macro initialises the type-specific parts of a watcher. You need to
		828	call C<ev_init> at least once before you call this macro, but you can
		829	call C<ev_TYPE_set> any number of times. You must not, however, call this
		830	macro on a watcher that is active (it can be pending, however, which is a
		831	difference to the C<ev_init> macro).
		832
		833	Although some watcher types do not have type-specific arguments
		834	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		835
		836	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		837
		838	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		839	calls into a single call. This is the most convinient method to initialise
		840	a watcher. The same limitations apply, of course.
		841
		842	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		843
		844	Starts (activates) the given watcher. Only active watchers will receive
		845	events. If the watcher is already active nothing will happen.
		846
		847	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		848
		849	Stops the given watcher again (if active) and clears the pending
		850	status. It is possible that stopped watchers are pending (for example,
		851	non-repeating timers are being stopped when they become pending), but
		852	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		853	you want to free or reuse the memory used by the watcher it is therefore a
		854	good idea to always call its C<ev_TYPE_stop> function.
		855
		856	=item bool ev_is_active (ev_TYPE *watcher)
		857
		858	Returns a true value iff the watcher is active (i.e. it has been started
		859	and not yet been stopped). As long as a watcher is active you must not modify
		860	it.
		861
		862	=item bool ev_is_pending (ev_TYPE *watcher)
		863
		864	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		865	events but its callback has not yet been invoked). As long as a watcher
		866	is pending (but not active) you must not call an init function on it (but
		867	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		868	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		869	it).
		870
		871	=item callback ev_cb (ev_TYPE *watcher)
		872
		873	Returns the callback currently set on the watcher.
		874
		875	=item ev_cb_set (ev_TYPE *watcher, callback)
		876
		877	Change the callback. You can change the callback at virtually any time
		878	(modulo threads).
		879
		880	=item ev_set_priority (ev_TYPE *watcher, priority)
		881
		882	=item int ev_priority (ev_TYPE *watcher)
		883
		884	Set and query the priority of the watcher. The priority is a small
		885	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		886	(default: C<-2>). Pending watchers with higher priority will be invoked
		887	before watchers with lower priority, but priority will not keep watchers
		888	from being executed (except for C<ev_idle> watchers).
		889
		890	This means that priorities are I<only> used for ordering callback
		891	invocation after new events have been received. This is useful, for
		892	example, to reduce latency after idling, or more often, to bind two
		893	watchers on the same event and make sure one is called first.
		894
		895	If you need to suppress invocation when higher priority events are pending
		896	you need to look at C<ev_idle> watchers, which provide this functionality.
		897
		898	You I<must not> change the priority of a watcher as long as it is active or
		899	pending.
		900
		901	The default priority used by watchers when no priority has been set is
		902	always C<0>, which is supposed to not be too high and not be too low :).
		903
		904	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		905	fine, as long as you do not mind that the priority value you query might
		906	or might not have been adjusted to be within valid range.
		907
		908	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		909
		910	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		911	C<loop> nor C<revents> need to be valid as long as the watcher callback
		912	can deal with that fact.
		913
		914	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		915
		916	If the watcher is pending, this function returns clears its pending status
		917	and returns its C<revents> bitset (as if its callback was invoked). If the
		918	watcher isn't pending it does nothing and returns C<0>.
		919
		920	=back
		921
		922
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	923	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		924
374	Each watcher has, by default, a member C<void *data> that you can change	925	Each watcher has, by default, a member C<void *data> that you can change
375	and read at any time, libev will completely ignore it. This cna be used	926	and read at any time, libev will completely ignore it. This can be used
376	to associate arbitrary data with your watcher. If you need more data and	927	to associate arbitrary data with your watcher. If you need more data and
377	don't want to allocate memory and store a pointer to it in that data	928	don't want to allocate memory and store a pointer to it in that data
378	member, you can also "subclass" the watcher type and provide your own	929	member, you can also "subclass" the watcher type and provide your own
379	data:	930	data:
380		931
…		…
393	{	944	{
394	struct my_io *w = (struct my_io *)w_;	945	struct my_io *w = (struct my_io *)w_;
395	...	946	...
396	}	947	}
397		948
398	More interesting and less C-conformant ways of catsing your callback type	949	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	950	instead have been omitted.
		951
		952	Another common scenario is having some data structure with multiple
		953	watchers:
		954
		955	struct my_biggy
		956	{
		957	int some_data;
		958	ev_timer t1;
		959	ev_timer t2;
		960	}
		961
		962	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		963	you need to use C<offsetof>:
		964
		965	#include <stddef.h>
		966
		967	static void
		968	t1_cb (EV_P_ struct ev_timer *w, int revents)
		969	{
		970	struct my_biggy big = (struct my_biggy *
		971	(((char *)w) - offsetof (struct my_biggy, t1));
		972	}
		973
		974	static void
		975	t2_cb (EV_P_ struct ev_timer *w, int revents)
		976	{
		977	struct my_biggy big = (struct my_biggy *
		978	(((char *)w) - offsetof (struct my_biggy, t2));
		979	}
400		980
401		981
402	=head1 WATCHER TYPES	982	=head1 WATCHER TYPES
403		983
404	This section describes each watcher in detail, but will not repeat	984	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	985	information given in the last section. Any initialisation/set macros,
		986	functions and members specific to the watcher type are explained.
406		987
		988	Members are additionally marked with either I<[read-only]>, meaning that,
		989	while the watcher is active, you can look at the member and expect some
		990	sensible content, but you must not modify it (you can modify it while the
		991	watcher is stopped to your hearts content), or I<[read-write]>, which
		992	means you can expect it to have some sensible content while the watcher
		993	is active, but you can also modify it. Modifying it may not do something
		994	sensible or take immediate effect (or do anything at all), but libev will
		995	not crash or malfunction in any way.
		996
		997
407	=head2 struct ev_io - is my file descriptor readable or writable	998	=head2 C<ev_io> - is this file descriptor readable or writable?
408		999
409	I/O watchers check whether a file descriptor is readable or writable	1000	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	1001	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	1002	would not block the process and writing would at least be able to write
412	condition persists. Remember you cna stop the watcher if you don't want to	1003	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	1004	receiving events as long as the condition persists. Remember you can stop
		1005	the watcher if you don't want to act on the event and neither want to
		1006	receive future events.
414		1007
415	In general you can register as many read and/or write event watchers oer	1008	In general you can register as many read and/or write event watchers per
416	fd as you want (as long as you don't confuse yourself). Setting all file	1009	fd as you want (as long as you don't confuse yourself). Setting all file
417	descriptors to non-blocking mode is also usually a good idea (but not	1010	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	1011	required if you know what you are doing).
419		1012
420	You have to be careful with dup'ed file descriptors, though. Some backends
421	(the linux epoll backend is a notable example) cannot handle dup'ed file
422	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.
424
425	If you must do this, then force the use of a known-to-be-good backend	1013	If you must do this, then force the use of a known-to-be-good backend
426	(at the time of this writing, this includes only EVMETHOD_SELECT and	1014	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	1015	C<EVBACKEND_POLL>).
		1016
		1017	Another thing you have to watch out for is that it is quite easy to
		1018	receive "spurious" readyness notifications, that is your callback might
		1019	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1020	because there is no data. Not only are some backends known to create a
		1021	lot of those (for example solaris ports), it is very easy to get into
		1022	this situation even with a relatively standard program structure. Thus
		1023	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1024	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1025
		1026	If you cannot run the fd in non-blocking mode (for example you should not
		1027	play around with an Xlib connection), then you have to seperately re-test
		1028	whether a file descriptor is really ready with a known-to-be good interface
		1029	such as poll (fortunately in our Xlib example, Xlib already does this on
		1030	its own, so its quite safe to use).
		1031
		1032	=head3 The special problem of disappearing file descriptors
		1033
		1034	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1035	descriptor (either by calling C<close> explicitly or by any other means,
		1036	such as C<dup>). The reason is that you register interest in some file
		1037	descriptor, but when it goes away, the operating system will silently drop
		1038	this interest. If another file descriptor with the same number then is
		1039	registered with libev, there is no efficient way to see that this is, in
		1040	fact, a different file descriptor.
		1041
		1042	To avoid having to explicitly tell libev about such cases, libev follows
		1043	the following policy: Each time C<ev_io_set> is being called, libev
		1044	will assume that this is potentially a new file descriptor, otherwise
		1045	it is assumed that the file descriptor stays the same. That means that
		1046	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1047	descriptor even if the file descriptor number itself did not change.
		1048
		1049	This is how one would do it normally anyway, the important point is that
		1050	the libev application should not optimise around libev but should leave
		1051	optimisations to libev.
		1052
		1053	=head3 The special problem of dup'ed file descriptors
		1054
		1055	Some backends (e.g. epoll), cannot register events for file descriptors,
		1056	but only events for the underlying file descriptions. That means when you
		1057	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1058	events for them, only one file descriptor might actually receive events.
		1059
		1060	There is no workaround possible except not registering events
		1061	for potentially C<dup ()>'ed file descriptors, or to resort to
		1062	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1063
		1064	=head3 The special problem of fork
		1065
		1066	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1067	useless behaviour. Libev fully supports fork, but needs to be told about
		1068	it in the child.
		1069
		1070	To support fork in your programs, you either have to call
		1071	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1072	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1073	C<EVBACKEND_POLL>.
		1074
		1075
		1076	=head3 Watcher-Specific Functions
428		1077
429	=over 4	1078	=over 4
430		1079
431	=item ev_io_init (ev_io *, callback, int fd, int events)	1080	=item ev_io_init (ev_io *, callback, int fd, int events)
432		1081
433	=item ev_io_set (ev_io *, int fd, int events)	1082	=item ev_io_set (ev_io *, int fd, int events)
434		1083
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1084	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
436	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1085	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	1086	C<EV_READ | EV_WRITE> to receive the given events.
		1087
		1088	=item int fd [read-only]
		1089
		1090	The file descriptor being watched.
		1091
		1092	=item int events [read-only]
		1093
		1094	The events being watched.
438		1095
439	=back	1096	=back
440		1097
		1098	=head3 Examples
		1099
		1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1101	readable, but only once. Since it is likely line-buffered, you could
		1102	attempt to read a whole line in the callback.
		1103
		1104	static void
		1105	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1106	{
		1107	ev_io_stop (loop, w);
		1108	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1109	}
		1110
		1111	...
		1112	struct ev_loop *loop = ev_default_init (0);
		1113	struct ev_io stdin_readable;
		1114	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1115	ev_io_start (loop, &stdin_readable);
		1116	ev_loop (loop, 0);
		1117
		1118
441	=head2 struct ev_timer - relative and optionally recurring timeouts	1119	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		1120
443	Timer watchers are simple relative timers that generate an event after a	1121	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	1122	given time, and optionally repeating in regular intervals after that.
445		1123
446	The timers are based on real time, that is, if you register an event that	1124	The timers are based on real time, that is, if you register an event that
447	times out after an hour and youreset your system clock to last years	1125	times out after an hour and you reset your system clock to last years
448	time, it will still time out after (roughly) and hour. "Roughly" because	1126	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1127	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	1128	monotonic clock option helps a lot here).
		1129
		1130	The relative timeouts are calculated relative to the C<ev_now ()>
		1131	time. This is usually the right thing as this timestamp refers to the time
		1132	of the event triggering whatever timeout you are modifying/starting. If
		1133	you suspect event processing to be delayed and you I<need> to base the timeout
		1134	on the current time, use something like this to adjust for this:
		1135
		1136	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1137
		1138	The callback is guarenteed to be invoked only when its timeout has passed,
		1139	but if multiple timers become ready during the same loop iteration then
		1140	order of execution is undefined.
		1141
		1142	=head3 Watcher-Specific Functions and Data Members
451		1143
452	=over 4	1144	=over 4
453		1145
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1146	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		1147
…		…
461	later, again, and again, until stopped manually.	1153	later, again, and again, until stopped manually.
462		1154
463	The timer itself will do a best-effort at avoiding drift, that is, if you	1155	The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
468		1160
469	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
470		1162
471	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
473		1165
		1166	If the timer is pending, its pending status is cleared.
		1167
474	If the timer is started but nonrepeating, stop it.	1168	If the timer is started but nonrepeating, stop it (as if it timed out).
475		1169
476	If the timer is repeating, either start it if necessary (with the repeat	1170	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	1171	C<repeat> value), or reset the running timer to the C<repeat> value.
478		1172
479	This sounds a bit complicated, but here is a useful and typical	1173	This sounds a bit complicated, but here is a useful and typical
480	example: Imagine you have a tcp connection and you want a so-called idle	1174	example: Imagine you have a tcp connection and you want a so-called idle
481	timeout, that is, you want to be called when there have been, say, 60	1175	timeout, that is, you want to be called when there have been, say, 60
482	seconds of inactivity on the socket. The easiest way to do this is to	1176	seconds of inactivity on the socket. The easiest way to do this is to
483	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1177	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
484	time you successfully read or write some data. If you go into an idle	1178	C<ev_timer_again> each time you successfully read or write some data. If
485	state where you do not expect data to travel on the socket, you can stop	1179	you go into an idle state where you do not expect data to travel on the
486	the timer, and again will automatically restart it if need be.	1180	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1181	automatically restart it if need be.
		1182
		1183	That means you can ignore the C<after> value and C<ev_timer_start>
		1184	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1185
		1186	ev_timer_init (timer, callback, 0., 5.);
		1187	ev_timer_again (loop, timer);
		1188	...
		1189	timer->again = 17.;
		1190	ev_timer_again (loop, timer);
		1191	...
		1192	timer->again = 10.;
		1193	ev_timer_again (loop, timer);
		1194
		1195	This is more slightly efficient then stopping/starting the timer each time
		1196	you want to modify its timeout value.
		1197
		1198	=item ev_tstamp repeat [read-write]
		1199
		1200	The current C<repeat> value. Will be used each time the watcher times out
		1201	or C<ev_timer_again> is called and determines the next timeout (if any),
		1202	which is also when any modifications are taken into account.
487		1203
488	=back	1204	=back
489		1205
		1206	=head3 Examples
		1207
		1208	Example: Create a timer that fires after 60 seconds.
		1209
		1210	static void
		1211	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1212	{
		1213	.. one minute over, w is actually stopped right here
		1214	}
		1215
		1216	struct ev_timer mytimer;
		1217	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1218	ev_timer_start (loop, &mytimer);
		1219
		1220	Example: Create a timeout timer that times out after 10 seconds of
		1221	inactivity.
		1222
		1223	static void
		1224	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1225	{
		1226	.. ten seconds without any activity
		1227	}
		1228
		1229	struct ev_timer mytimer;
		1230	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1231	ev_timer_again (&mytimer); /* start timer */
		1232	ev_loop (loop, 0);
		1233
		1234	// and in some piece of code that gets executed on any "activity":
		1235	// reset the timeout to start ticking again at 10 seconds
		1236	ev_timer_again (&mytimer);
		1237
		1238
490	=head2 ev_periodic - to cron or not to cron it	1239	=head2 C<ev_periodic> - to cron or not to cron?
491		1240
492	Periodic watchers are also timers of a kind, but they are very versatile	1241	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1242	(and unfortunately a bit complex).
494		1243
495	Unlike ev_timer's, they are not based on real time (or relative time)	1244	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
496	but on wallclock time (absolute time). You can tell a periodic watcher	1245	but on wallclock time (absolute time). You can tell a periodic watcher
497	to trigger "at" some specific point in time. For example, if you tell a	1246	to trigger "at" some specific point in time. For example, if you tell a
498	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1247	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
499	+ 10.>) and then reset your system clock to the last year, then it will	1248	+ 10.>) and then reset your system clock to the last year, then it will
500	take a year to trigger the event (unlike an ev_timer, which would trigger	1249	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
501	roughly 10 seconds later and of course not if you reset your system time	1250	roughly 10 seconds later).
502	again).
503		1251
504	They can also be used to implement vastly more complex timers, such as	1252	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1253	triggering an event on each midnight, local time or other, complicated,
		1254	rules.
		1255
		1256	As with timers, the callback is guarenteed to be invoked only when the
		1257	time (C<at>) has been passed, but if multiple periodic timers become ready
		1258	during the same loop iteration then order of execution is undefined.
		1259
		1260	=head3 Watcher-Specific Functions and Data Members
506		1261
507	=over 4	1262	=over 4
508		1263
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1264	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1265
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1266	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1267
513	Lots of arguments, lets sort it out... There are basically three modes of	1268	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1269	operation, and we will explain them from simplest to complex:
515		1270
516
517	=over 4	1271	=over 4
518		1272
519	=item * absolute timer (interval = reschedule_cb = 0)	1273	=item * absolute timer (at = time, interval = reschedule_cb = 0)
520		1274
521	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
522	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
523	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
524	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
525		1279
526	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
527		1281
528	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
529	C<at + N * interval> time (for some integer N) and then repeat, regardless	1283	C<at + N * interval> time (for some integer N, which can also be negative)
530	of any time jumps.	1284	and then repeat, regardless of any time jumps.
531		1285
532	This can be used to create timers that do not drift with respect to system	1286	This can be used to create timers that do not drift with respect to system
533	time:	1287	time:
534		1288
535	ev_periodic_set (&periodic, 0., 3600., 0);	1289	ev_periodic_set (&periodic, 0., 3600., 0);
536		1290
537	This doesn't mean there will always be 3600 seconds in between triggers,	1291	This doesn't mean there will always be 3600 seconds in between triggers,
538	but only that the the callback will be called when the system time shows a	1292	but only that the the callback will be called when the system time shows a
539	full hour (UTC), or more correct, when the system time is evenly divisible	1293	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1294	by 3600.
541		1295
542	Another way to think about it (for the mathematically inclined) is that	1296	Another way to think about it (for the mathematically inclined) is that
543	ev_periodic will try to run the callback in this mode at the next possible	1297	C<ev_periodic> will try to run the callback in this mode at the next possible
544	time where C<time = at (mod interval)>, regardless of any time jumps.	1298	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1299
		1300	For numerical stability it is preferable that the C<at> value is near
		1301	C<ev_now ()> (the current time), but there is no range requirement for
		1302	this value.
		1303
546	=item * manual reschedule mode (reschedule_cb = callback)	1304	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
547		1305
548	In this mode the values for C<interval> and C<at> are both being	1306	In this mode the values for C<interval> and C<at> are both being
549	ignored. Instead, each time the periodic watcher gets scheduled, the	1307	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1308	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1309	current time as second argument.
552		1310
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1311	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
554	periodic watcher, ever, or make any event loop modificstions>. If you need	1312	ever, or make any event loop modifications>. If you need to stop it,
555	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	1313	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1314	starting an C<ev_prepare> watcher, which is legal).
556		1315
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1316	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1317	ev_tstamp now)>, e.g.:
559		1318
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1319	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1320	{
562	return now + 60.;	1321	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1324	It must return the next time to trigger, based on the passed time value
566	(that is, the lowest time value larger than to the second argument). It	1325	(that is, the lowest time value larger than to the second argument). It
567	will usually be called just before the callback will be triggered, but	1326	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1327	might be called at other times, too.
569		1328
		1329	NOTE: I<< This callback must always return a time that is later than the
		1330	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1331
570	This can be used to create very complex timers, such as a timer that	1332	This can be used to create very complex timers, such as a timer that
571	triggers on each midnight, local time. To do this, you would calculate the	1333	triggers on each midnight, local time. To do this, you would calculate the
572	next midnight after C<now> and return the timestamp value for this. How you do this	1334	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1335	you do this is, again, up to you (but it is not trivial, which is the main
		1336	reason I omitted it as an example).
574		1337
575	=back	1338	=back
576		1339
577	=item ev_periodic_again (loop, ev_periodic *)	1340	=item ev_periodic_again (loop, ev_periodic *)
578		1341
579	Simply stops and restarts the periodic watcher again. This is only useful	1342	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1343	when you changed some parameters or the reschedule callback would return
581	a different time than the last time it was called (e.g. in a crond like	1344	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1345	program when the crontabs have changed).
583		1346
		1347	=item ev_tstamp offset [read-write]
		1348
		1349	When repeating, this contains the offset value, otherwise this is the
		1350	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1351
		1352	Can be modified any time, but changes only take effect when the periodic
		1353	timer fires or C<ev_periodic_again> is being called.
		1354
		1355	=item ev_tstamp interval [read-write]
		1356
		1357	The current interval value. Can be modified any time, but changes only
		1358	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1359	called.
		1360
		1361	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1362
		1363	The current reschedule callback, or C<0>, if this functionality is
		1364	switched off. Can be changed any time, but changes only take effect when
		1365	the periodic timer fires or C<ev_periodic_again> is being called.
		1366
		1367	=item ev_tstamp at [read-only]
		1368
		1369	When active, contains the absolute time that the watcher is supposed to
		1370	trigger next.
		1371
584	=back	1372	=back
585		1373
		1374	=head3 Examples
		1375
		1376	Example: Call a callback every hour, or, more precisely, whenever the
		1377	system clock is divisible by 3600. The callback invocation times have
		1378	potentially a lot of jittering, but good long-term stability.
		1379
		1380	static void
		1381	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1382	{
		1383	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1384	}
		1385
		1386	struct ev_periodic hourly_tick;
		1387	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1388	ev_periodic_start (loop, &hourly_tick);
		1389
		1390	Example: The same as above, but use a reschedule callback to do it:
		1391
		1392	#include <math.h>
		1393
		1394	static ev_tstamp
		1395	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1396	{
		1397	return fmod (now, 3600.) + 3600.;
		1398	}
		1399
		1400	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1401
		1402	Example: Call a callback every hour, starting now:
		1403
		1404	struct ev_periodic hourly_tick;
		1405	ev_periodic_init (&hourly_tick, clock_cb,
		1406	fmod (ev_now (loop), 3600.), 3600., 0);
		1407	ev_periodic_start (loop, &hourly_tick);
		1408
		1409
586	=head2 ev_signal - signal me when a signal gets signalled	1410	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1411
588	Signal watchers will trigger an event when the process receives a specific	1412	Signal watchers will trigger an event when the process receives a specific
589	signal one or more times. Even though signals are very asynchronous, libev	1413	signal one or more times. Even though signals are very asynchronous, libev
590	will try its best to deliver signals synchronously, i.e. as part of the	1414	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1415	normal event processing, like any other event.
592		1416
593	You cna configure as many watchers as you like per signal. Only when the	1417	You can configure as many watchers as you like per signal. Only when the
594	first watcher gets started will libev actually register a signal watcher	1418	first watcher gets started will libev actually register a signal watcher
595	with the kernel (thus it coexists with your own signal handlers as long	1419	with the kernel (thus it coexists with your own signal handlers as long
596	as you don't register any with libev). Similarly, when the last signal	1420	as you don't register any with libev). Similarly, when the last signal
597	watcher for a signal is stopped libev will reset the signal handler to	1421	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1422	SIG_DFL (regardless of what it was set to before).
599		1423
		1424	=head3 Watcher-Specific Functions and Data Members
		1425
600	=over 4	1426	=over 4
601		1427
602	=item ev_signal_init (ev_signal *, callback, int signum)	1428	=item ev_signal_init (ev_signal *, callback, int signum)
603		1429
604	=item ev_signal_set (ev_signal *, int signum)	1430	=item ev_signal_set (ev_signal *, int signum)
605		1431
606	Configures the watcher to trigger on the given signal number (usually one	1432	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1433	of the C<SIGxxx> constants).
608		1434
		1435	=item int signum [read-only]
		1436
		1437	The signal the watcher watches out for.
		1438
609	=back	1439	=back
610		1440
		1441	=head3 Examples
		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
		1455
611	=head2 ev_child - wait for pid status changes	1456	=head2 C<ev_child> - watch out for process status changes
612		1457
613	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
614	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
		1485
		1486	=head3 Watcher-Specific Functions and Data Members
615		1487
616	=over 4	1488	=over 4
617		1489
618	=item ev_child_init (ev_child *, callback, int pid)	1490	=item ev_child_init (ev_child *, callback, int pid, int trace)
619		1491
620	=item ev_child_set (ev_child *, int pid)	1492	=item ev_child_set (ev_child *, int pid, int trace)
621		1493
622	Configures the watcher to wait for status changes of process C<pid> (or	1494	Configures the watcher to wait for status changes of process C<pid> (or
623	I<any> process if C<pid> is specified as C<0>). The callback can look	1495	I<any> process if C<pid> is specified as C<0>). The callback can look
624	at the C<rstatus> member of the C<ev_child> watcher structure to see	1496	at the C<rstatus> member of the C<ev_child> watcher structure to see
625	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1497	the status word (use the macros from C<sys/wait.h> and see your systems
626	contains the pid of the process causing the status change.	1498	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1499	process causing the status change. C<trace> must be either C<0> (only
		1500	activate the watcher when the process terminates) or C<1> (additionally
		1501	activate the watcher when the process is stopped or continued).
		1502
		1503	=item int pid [read-only]
		1504
		1505	The process id this watcher watches out for, or C<0>, meaning any process id.
		1506
		1507	=item int rpid [read-write]
		1508
		1509	The process id that detected a status change.
		1510
		1511	=item int rstatus [read-write]
		1512
		1513	The process exit/trace status caused by C<rpid> (see your systems
		1514	C<waitpid> and C<sys/wait.h> documentation for details).
627		1515
628	=back	1516	=back
629		1517
		1518	=head3 Examples
		1519
		1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
		1524
		1525	static void
		1526	child_cb (EV_P_ struct ev_child *w, int revents)
		1527	{
		1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1530	}
		1531
		1532	pid_t pid = fork ();
		1533
		1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
		1546
		1547
		1548	=head2 C<ev_stat> - did the file attributes just change?
		1549
		1550	This watches a filesystem path for attribute changes. That is, it calls
		1551	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1552	compared to the last time, invoking the callback if it did.
		1553
		1554	The path does not need to exist: changing from "path exists" to "path does
		1555	not exist" is a status change like any other. The condition "path does
		1556	not exist" is signified by the C<st_nlink> field being zero (which is
		1557	otherwise always forced to be at least one) and all the other fields of
		1558	the stat buffer having unspecified contents.
		1559
		1560	The path I<should> be absolute and I<must not> end in a slash. If it is
		1561	relative and your working directory changes, the behaviour is undefined.
		1562
		1563	Since there is no standard to do this, the portable implementation simply
		1564	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1565	can specify a recommended polling interval for this case. If you specify
		1566	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1567	unspecified default> value will be used (which you can expect to be around
		1568	five seconds, although this might change dynamically). Libev will also
		1569	impose a minimum interval which is currently around C<0.1>, but thats
		1570	usually overkill.
		1571
		1572	This watcher type is not meant for massive numbers of stat watchers,
		1573	as even with OS-supported change notifications, this can be
		1574	resource-intensive.
		1575
		1576	At the time of this writing, only the Linux inotify interface is
		1577	implemented (implementing kqueue support is left as an exercise for the
		1578	reader). Inotify will be used to give hints only and should not change the
		1579	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1580	to fall back to regular polling again even with inotify, but changes are
		1581	usually detected immediately, and if the file exists there will be no
		1582	polling.
		1583
		1584	=head3 Inotify
		1585
		1586	When C<inotify (7)> support has been compiled into libev (generally only
		1587	available on Linux) and present at runtime, it will be used to speed up
		1588	change detection where possible. The inotify descriptor will be created lazily
		1589	when the first C<ev_stat> watcher is being started.
		1590
		1591	Inotify presense does not change the semantics of C<ev_stat> watchers
		1592	except that changes might be detected earlier, and in some cases, to avoid
		1593	making regular C<stat> calls. Even in the presense of inotify support
		1594	there are many cases where libev has to resort to regular C<stat> polling.
		1595
		1596	(There is no support for kqueue, as apparently it cannot be used to
		1597	implement this functionality, due to the requirement of having a file
		1598	descriptor open on the object at all times).
		1599
		1600	=head3 The special problem of stat time resolution
		1601
		1602	The C<stat ()> syscall only supports full-second resolution portably, and
		1603	even on systems where the resolution is higher, many filesystems still
		1604	only support whole seconds.
		1605
		1606	That means that, if the time is the only thing that changes, you might
		1607	miss updates: on the first update, C<ev_stat> detects a change and calls
		1608	your callback, which does something. When there is another update within
		1609	the same second, C<ev_stat> will be unable to detect it.
		1610
		1611	The solution to this is to delay acting on a change for a second (or till
		1612	the next second boundary), using a roughly one-second delay C<ev_timer>
		1613	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1614	is added to work around small timing inconsistencies of some operating
		1615	systems.
		1616
		1617	=head3 Watcher-Specific Functions and Data Members
		1618
		1619	=over 4
		1620
		1621	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1622
		1623	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1624
		1625	Configures the watcher to wait for status changes of the given
		1626	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1627	be detected and should normally be specified as C<0> to let libev choose
		1628	a suitable value. The memory pointed to by C<path> must point to the same
		1629	path for as long as the watcher is active.
		1630
		1631	The callback will be receive C<EV_STAT> when a change was detected,
		1632	relative to the attributes at the time the watcher was started (or the
		1633	last change was detected).
		1634
		1635	=item ev_stat_stat (loop, ev_stat *)
		1636
		1637	Updates the stat buffer immediately with new values. If you change the
		1638	watched path in your callback, you could call this fucntion to avoid
		1639	detecting this change (while introducing a race condition). Can also be
		1640	useful simply to find out the new values.
		1641
		1642	=item ev_statdata attr [read-only]
		1643
		1644	The most-recently detected attributes of the file. Although the type is of
		1645	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1646	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1647	was some error while C<stat>ing the file.
		1648
		1649	=item ev_statdata prev [read-only]
		1650
		1651	The previous attributes of the file. The callback gets invoked whenever
		1652	C<prev> != C<attr>.
		1653
		1654	=item ev_tstamp interval [read-only]
		1655
		1656	The specified interval.
		1657
		1658	=item const char *path [read-only]
		1659
		1660	The filesystem path that is being watched.
		1661
		1662	=back
		1663
		1664	=head3 Examples
		1665
		1666	Example: Watch C</etc/passwd> for attribute changes.
		1667
		1668	static void
		1669	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1670	{
		1671	/* /etc/passwd changed in some way */
		1672	if (w->attr.st_nlink)
		1673	{
		1674	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1675	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1676	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1677	}
		1678	else
		1679	/* you shalt not abuse printf for puts */
		1680	puts ("wow, /etc/passwd is not there, expect problems. "
		1681	"if this is windows, they already arrived\n");
		1682	}
		1683
		1684	...
		1685	ev_stat passwd;
		1686
		1687	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1688	ev_stat_start (loop, &passwd);
		1689
		1690	Example: Like above, but additionally use a one-second delay so we do not
		1691	miss updates (however, frequent updates will delay processing, too, so
		1692	one might do the work both on C<ev_stat> callback invocation I<and> on
		1693	C<ev_timer> callback invocation).
		1694
		1695	static ev_stat passwd;
		1696	static ev_timer timer;
		1697
		1698	static void
		1699	timer_cb (EV_P_ ev_timer *w, int revents)
		1700	{
		1701	ev_timer_stop (EV_A_ w);
		1702
		1703	/* now it's one second after the most recent passwd change */
		1704	}
		1705
		1706	static void
		1707	stat_cb (EV_P_ ev_stat *w, int revents)
		1708	{
		1709	/* reset the one-second timer */
		1710	ev_timer_again (EV_A_ &timer);
		1711	}
		1712
		1713	...
		1714	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1715	ev_stat_start (loop, &passwd);
		1716	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1717
		1718
630	=head2 ev_idle - when you've got nothing better to do	1719	=head2 C<ev_idle> - when you've got nothing better to do...
631		1720
632	Idle watchers trigger events when there are no other I/O or timer (or	1721	Idle watchers trigger events when no other events of the same or higher
633	periodic) events pending. That is, as long as your process is busy	1722	priority are pending (prepare, check and other idle watchers do not
634	handling sockets or timeouts it will not be called. But when your process	1723	count).
635	is idle all idle watchers are being called again and again - until	1724
		1725	That is, as long as your process is busy handling sockets or timeouts
		1726	(or even signals, imagine) of the same or higher priority it will not be
		1727	triggered. But when your process is idle (or only lower-priority watchers
		1728	are pending), the idle watchers are being called once per event loop
636	stopped, that is, or your process receives more events.	1729	iteration - until stopped, that is, or your process receives more events
		1730	and becomes busy again with higher priority stuff.
637		1731
638	The most noteworthy effect is that as long as any idle watchers are	1732	The most noteworthy effect is that as long as any idle watchers are
639	active, the process will not block when waiting for new events.	1733	active, the process will not block when waiting for new events.
640		1734
641	Apart from keeping your process non-blocking (which is a useful	1735	Apart from keeping your process non-blocking (which is a useful
642	effect on its own sometimes), idle watchers are a good place to do	1736	effect on its own sometimes), idle watchers are a good place to do
643	"pseudo-background processing", or delay processing stuff to after the	1737	"pseudo-background processing", or delay processing stuff to after the
644	event loop has handled all outstanding events.	1738	event loop has handled all outstanding events.
645		1739
		1740	=head3 Watcher-Specific Functions and Data Members
		1741
646	=over 4	1742	=over 4
647		1743
648	=item ev_idle_init (ev_signal *, callback)	1744	=item ev_idle_init (ev_signal *, callback)
649		1745
650	Initialises and configures the idle watcher - it has no parameters of any	1746	Initialises and configures the idle watcher - it has no parameters of any
651	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1747	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1748	believe me.
653		1749
654	=back	1750	=back
655		1751
656	=head2 prepare and check - your hooks into the event loop	1752	=head3 Examples
657		1753
		1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1755	callback, free it. Also, use no error checking, as usual.
		1756
		1757	static void
		1758	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1759	{
		1760	free (w);
		1761	// now do something you wanted to do when the program has
		1762	// no longer anything immediate to do.
		1763	}
		1764
		1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1766	ev_idle_init (idle_watcher, idle_cb);
		1767	ev_idle_start (loop, idle_cb);
		1768
		1769
		1770	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1771
658	Prepare and check watchers usually (but not always) are used in	1772	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1773	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1774	afterwards.
661		1775
		1776	You I<must not> call C<ev_loop> or similar functions that enter
		1777	the current event loop from either C<ev_prepare> or C<ev_check>
		1778	watchers. Other loops than the current one are fine, however. The
		1779	rationale behind this is that you do not need to check for recursion in
		1780	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1781	C<ev_check> so if you have one watcher of each kind they will always be
		1782	called in pairs bracketing the blocking call.
		1783
662	Their main purpose is to integrate other event mechanisms into libev. This	1784	Their main purpose is to integrate other event mechanisms into libev and
663	could be used, for example, to track variable changes, implement your own	1785	their use is somewhat advanced. This could be used, for example, to track
664	watchers, integrate net-snmp or a coroutine library and lots more.	1786	variable changes, implement your own watchers, integrate net-snmp or a
		1787	coroutine library and lots more. They are also occasionally useful if
		1788	you cache some data and want to flush it before blocking (for example,
		1789	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1790	watcher).
665		1791
666	This is done by examining in each prepare call which file descriptors need	1792	This is done by examining in each prepare call which file descriptors need
667	to be watched by the other library, registering ev_io watchers for them	1793	to be watched by the other library, registering C<ev_io> watchers for
668	and starting an ev_timer watcher for any timeouts (many libraries provide	1794	them and starting an C<ev_timer> watcher for any timeouts (many libraries
669	just this functionality). Then, in the check watcher you check for any	1795	provide just this functionality). Then, in the check watcher you check for
670	events that occured (by making your callbacks set soem flags for example)	1796	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1797	and stopping them) and call back into the library. The I/O and timer
		1798	callbacks will never actually be called (but must be valid nevertheless,
		1799	because you never know, you know?).
672		1800
673	As another example, the perl Coro module uses these hooks to integrate	1801	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1802	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1803	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1804	are ready to run (it's actually more complicated: it only runs coroutines
		1805	with priority higher than or equal to the event loop and one coroutine
		1806	of lower priority, but only once, using idle watchers to keep the event
		1807	loop from blocking if lower-priority coroutines are active, thus mapping
		1808	low-priority coroutines to idle/background tasks).
		1809
		1810	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1811	priority, to ensure that they are being run before any other watchers
		1812	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1813	too) should not activate ("feed") events into libev. While libev fully
		1814	supports this, they will be called before other C<ev_check> watchers
		1815	did their job. As C<ev_check> watchers are often used to embed other
		1816	(non-libev) event loops those other event loops might be in an unusable
		1817	state until their C<ev_check> watcher ran (always remind yourself to
		1818	coexist peacefully with others).
		1819
		1820	=head3 Watcher-Specific Functions and Data Members
677		1821
678	=over 4	1822	=over 4
679		1823
680	=item ev_prepare_init (ev_prepare *, callback)	1824	=item ev_prepare_init (ev_prepare *, callback)
681		1825
682	=item ev_check_init (ev_check *, callback)	1826	=item ev_check_init (ev_check *, callback)
683		1827
684	Initialises and configures the prepare or check watcher - they have no	1828	Initialises and configures the prepare or check watcher - they have no
685	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1830	macros, but using them is utterly, utterly and completely pointless.
687		1831
688	=back	1832	=back
689		1833
		1834	=head3 Examples
		1835
		1836	There are a number of principal ways to embed other event loops or modules
		1837	into libev. Here are some ideas on how to include libadns into libev
		1838	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1839	use for an actually working example. Another Perl module named C<EV::Glib>
		1840	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1841	into the Glib event loop).
		1842
		1843	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1844	and in a check watcher, destroy them and call into libadns. What follows
		1845	is pseudo-code only of course. This requires you to either use a low
		1846	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1847	the callbacks for the IO/timeout watchers might not have been called yet.
		1848
		1849	static ev_io iow [nfd];
		1850	static ev_timer tw;
		1851
		1852	static void
		1853	io_cb (ev_loop *loop, ev_io *w, int revents)
		1854	{
		1855	}
		1856
		1857	// create io watchers for each fd and a timer before blocking
		1858	static void
		1859	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1860	{
		1861	int timeout = 3600000;
		1862	struct pollfd fds [nfd];
		1863	// actual code will need to loop here and realloc etc.
		1864	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1865
		1866	/* the callback is illegal, but won't be called as we stop during check */
		1867	ev_timer_init (&tw, 0, timeout * 1e-3);
		1868	ev_timer_start (loop, &tw);
		1869
		1870	// create one ev_io per pollfd
		1871	for (int i = 0; i < nfd; ++i)
		1872	{
		1873	ev_io_init (iow + i, io_cb, fds [i].fd,
		1874	((fds [i].events & POLLIN ? EV_READ : 0)
		1875	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1876
		1877	fds [i].revents = 0;
		1878	ev_io_start (loop, iow + i);
		1879	}
		1880	}
		1881
		1882	// stop all watchers after blocking
		1883	static void
		1884	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1885	{
		1886	ev_timer_stop (loop, &tw);
		1887
		1888	for (int i = 0; i < nfd; ++i)
		1889	{
		1890	// set the relevant poll flags
		1891	// could also call adns_processreadable etc. here
		1892	struct pollfd *fd = fds + i;
		1893	int revents = ev_clear_pending (iow + i);
		1894	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1895	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1896
		1897	// now stop the watcher
		1898	ev_io_stop (loop, iow + i);
		1899	}
		1900
		1901	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1902	}
		1903
		1904	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1905	in the prepare watcher and would dispose of the check watcher.
		1906
		1907	Method 3: If the module to be embedded supports explicit event
		1908	notification (adns does), you can also make use of the actual watcher
		1909	callbacks, and only destroy/create the watchers in the prepare watcher.
		1910
		1911	static void
		1912	timer_cb (EV_P_ ev_timer *w, int revents)
		1913	{
		1914	adns_state ads = (adns_state)w->data;
		1915	update_now (EV_A);
		1916
		1917	adns_processtimeouts (ads, &tv_now);
		1918	}
		1919
		1920	static void
		1921	io_cb (EV_P_ ev_io *w, int revents)
		1922	{
		1923	adns_state ads = (adns_state)w->data;
		1924	update_now (EV_A);
		1925
		1926	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1927	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1928	}
		1929
		1930	// do not ever call adns_afterpoll
		1931
		1932	Method 4: Do not use a prepare or check watcher because the module you
		1933	want to embed is too inflexible to support it. Instead, youc na override
		1934	their poll function. The drawback with this solution is that the main
		1935	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1936	this.
		1937
		1938	static gint
		1939	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1940	{
		1941	int got_events = 0;
		1942
		1943	for (n = 0; n < nfds; ++n)
		1944	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1945
		1946	if (timeout >= 0)
		1947	// create/start timer
		1948
		1949	// poll
		1950	ev_loop (EV_A_ 0);
		1951
		1952	// stop timer again
		1953	if (timeout >= 0)
		1954	ev_timer_stop (EV_A_ &to);
		1955
		1956	// stop io watchers again - their callbacks should have set
		1957	for (n = 0; n < nfds; ++n)
		1958	ev_io_stop (EV_A_ iow [n]);
		1959
		1960	return got_events;
		1961	}
		1962
		1963
		1964	=head2 C<ev_embed> - when one backend isn't enough...
		1965
		1966	This is a rather advanced watcher type that lets you embed one event loop
		1967	into another (currently only C<ev_io> events are supported in the embedded
		1968	loop, other types of watchers might be handled in a delayed or incorrect
		1969	fashion and must not be used).
		1970
		1971	There are primarily two reasons you would want that: work around bugs and
		1972	prioritise I/O.
		1973
		1974	As an example for a bug workaround, the kqueue backend might only support
		1975	sockets on some platform, so it is unusable as generic backend, but you
		1976	still want to make use of it because you have many sockets and it scales
		1977	so nicely. In this case, you would create a kqueue-based loop and embed it
		1978	into your default loop (which might use e.g. poll). Overall operation will
		1979	be a bit slower because first libev has to poll and then call kevent, but
		1980	at least you can use both at what they are best.
		1981
		1982	As for prioritising I/O: rarely you have the case where some fds have
		1983	to be watched and handled very quickly (with low latency), and even
		1984	priorities and idle watchers might have too much overhead. In this case
		1985	you would put all the high priority stuff in one loop and all the rest in
		1986	a second one, and embed the second one in the first.
		1987
		1988	As long as the watcher is active, the callback will be invoked every time
		1989	there might be events pending in the embedded loop. The callback must then
		1990	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1991	their callbacks (you could also start an idle watcher to give the embedded
		1992	loop strictly lower priority for example). You can also set the callback
		1993	to C<0>, in which case the embed watcher will automatically execute the
		1994	embedded loop sweep.
		1995
		1996	As long as the watcher is started it will automatically handle events. The
		1997	callback will be invoked whenever some events have been handled. You can
		1998	set the callback to C<0> to avoid having to specify one if you are not
		1999	interested in that.
		2000
		2001	Also, there have not currently been made special provisions for forking:
		2002	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2003	but you will also have to stop and restart any C<ev_embed> watchers
		2004	yourself.
		2005
		2006	Unfortunately, not all backends are embeddable, only the ones returned by
		2007	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2008	portable one.
		2009
		2010	So when you want to use this feature you will always have to be prepared
		2011	that you cannot get an embeddable loop. The recommended way to get around
		2012	this is to have a separate variables for your embeddable loop, try to
		2013	create it, and if that fails, use the normal loop for everything.
		2014
		2015	=head3 Watcher-Specific Functions and Data Members
		2016
		2017	=over 4
		2018
		2019	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2020
		2021	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2022
		2023	Configures the watcher to embed the given loop, which must be
		2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2025	invoked automatically, otherwise it is the responsibility of the callback
		2026	to invoke it (it will continue to be called until the sweep has been done,
		2027	if you do not want thta, you need to temporarily stop the embed watcher).
		2028
		2029	=item ev_embed_sweep (loop, ev_embed *)
		2030
		2031	Make a single, non-blocking sweep over the embedded loop. This works
		2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2033	apropriate way for embedded loops.
		2034
		2035	=item struct ev_loop *other [read-only]
		2036
		2037	The embedded event loop.
		2038
		2039	=back
		2040
		2041	=head3 Examples
		2042
		2043	Example: Try to get an embeddable event loop and embed it into the default
		2044	event loop. If that is not possible, use the default loop. The default
		2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2047	used).
		2048
		2049	struct ev_loop *loop_hi = ev_default_init (0);
		2050	struct ev_loop *loop_lo = 0;
		2051	struct ev_embed embed;
		2052
		2053	// see if there is a chance of getting one that works
		2054	// (remember that a flags value of 0 means autodetection)
		2055	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2056	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2057	: 0;
		2058
		2059	// if we got one, then embed it, otherwise default to loop_hi
		2060	if (loop_lo)
		2061	{
		2062	ev_embed_init (&embed, 0, loop_lo);
		2063	ev_embed_start (loop_hi, &embed);
		2064	}
		2065	else
		2066	loop_lo = loop_hi;
		2067
		2068	Example: Check if kqueue is available but not recommended and create
		2069	a kqueue backend for use with sockets (which usually work with any
		2070	kqueue implementation). Store the kqueue/socket-only event loop in
		2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2072
		2073	struct ev_loop *loop = ev_default_init (0);
		2074	struct ev_loop *loop_socket = 0;
		2075	struct ev_embed embed;
		2076
		2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2079	{
		2080	ev_embed_init (&embed, 0, loop_socket);
		2081	ev_embed_start (loop, &embed);
		2082	}
		2083
		2084	if (!loop_socket)
		2085	loop_socket = loop;
		2086
		2087	// now use loop_socket for all sockets, and loop for everything else
		2088
		2089
		2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2091
		2092	Fork watchers are called when a C<fork ()> was detected (usually because
		2093	whoever is a good citizen cared to tell libev about it by calling
		2094	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2095	event loop blocks next and before C<ev_check> watchers are being called,
		2096	and only in the child after the fork. If whoever good citizen calling
		2097	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2098	handlers will be invoked, too, of course.
		2099
		2100	=head3 Watcher-Specific Functions and Data Members
		2101
		2102	=over 4
		2103
		2104	=item ev_fork_init (ev_signal *, callback)
		2105
		2106	Initialises and configures the fork watcher - it has no parameters of any
		2107	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2108	believe me.
		2109
		2110	=back
		2111
		2112
		2113	=head2 C<ev_async> - how to wake up another event loop
		2114
		2115	In general, you cannot use an C<ev_loop> from multiple threads or other
		2116	asynchronous sources such as signal handlers (as opposed to multiple event
		2117	loops - those are of course safe to use in different threads).
		2118
		2119	Sometimes, however, you need to wake up another event loop you do not
		2120	control, for example because it belongs to another thread. This is what
		2121	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2122	can signal it by calling C<ev_async_send>, which is thread- and signal
		2123	safe.
		2124
		2125	This functionality is very similar to C<ev_signal> watchers, as signals,
		2126	too, are asynchronous in nature, and signals, too, will be compressed
		2127	(i.e. the number of callback invocations may be less than the number of
		2128	C<ev_async_sent> calls).
		2129
		2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2131	just the default loop.
		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
		2221	=over 4
		2222
		2223	=item ev_async_init (ev_async *, callback)
		2224
		2225	Initialises and configures the async watcher - it has no parameters of any
		2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2227	believe me.
		2228
		2229	=item ev_async_send (loop, ev_async *)
		2230
		2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2233	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2235	section below on what exactly this means).
		2236
		2237	This call incurs the overhead of a syscall only once per loop iteration,
		2238	so while the overhead might be noticable, it doesn't apply to repeated
		2239	calls to C<ev_async_send>.
		2240
		2241	=back
		2242
		2243
690	=head1 OTHER FUNCTIONS	2244	=head1 OTHER FUNCTIONS
691		2245
692	There are some other fucntions of possible interest. Described. Here. Now.	2246	There are some other functions of possible interest. Described. Here. Now.
693		2247
694	=over 4	2248	=over 4
695		2249
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2250	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		2251
698	This function combines a simple timer and an I/O watcher, calls your	2252	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	2253	callback on whichever event happens first and automatically stop both
700	watchers. This is useful if you want to wait for a single event on an fd	2254	watchers. This is useful if you want to wait for a single event on an fd
701	or timeout without havign to allocate/configure/start/stop/free one or	2255	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	2256	more watchers yourself.
703		2257
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	2258	If C<fd> is less than 0, then no I/O watcher will be started and events
705	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	2259	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	2260	C<events> set will be craeted and started.
707		2261
708	If C<timeout> is less than 0, then no timeout watcher will be	2262	If C<timeout> is less than 0, then no timeout watcher will be
709	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	2263	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	2264	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		2265	dubious value.
711		2266
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	2267	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
713	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	2268	passed an C<revents> set like normal event callbacks (a combination of
714	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	2269	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		2270	value passed to C<ev_once>:
715		2271
716	static void stdin_ready (int revents, void *arg)	2272	static void stdin_ready (int revents, void *arg)
717	{	2273	{
718	if (revents & EV_TIMEOUT)	2274	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	2275	/* doh, nothing entered */;
720	else if (revents & EV_READ)	2276	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	2277	/* stdin might have data for us, joy! */;
722	}	2278	}
723		2279
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	2280	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		2281
726	=item ev_feed_event (loop, watcher, int events)	2282	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		2283
728	Feeds the given event set into the event loop, as if the specified event	2284	Feeds the given event set into the event loop, as if the specified event
729	has happened for the specified watcher (which must be a pointer to an	2285	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	2286	initialised but not necessarily started event watcher).
731		2287
732	=item ev_feed_fd_event (loop, int fd, int revents)	2288	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		2289
734	Feed an event on the given fd, as if a file descriptor backend detected it.	2290	Feed an event on the given fd, as if a file descriptor backend detected
		2291	the given events it.
735		2292
736	=item ev_feed_signal_event (loop, int signum)	2293	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		2294
738	Feed an event as if the given signal occured (loop must be the default loop!).	2295	Feed an event as if the given signal occured (C<loop> must be the default
		2296	loop!).
739		2297
740	=back	2298	=back
741		2299
		2300
		2301	=head1 LIBEVENT EMULATION
		2302
		2303	Libev offers a compatibility emulation layer for libevent. It cannot
		2304	emulate the internals of libevent, so here are some usage hints:
		2305
		2306	=over 4
		2307
		2308	=item * Use it by including <event.h>, as usual.
		2309
		2310	=item * The following members are fully supported: ev_base, ev_callback,
		2311	ev_arg, ev_fd, ev_res, ev_events.
		2312
		2313	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		2314	maintained by libev, it does not work exactly the same way as in libevent (consider
		2315	it a private API).
		2316
		2317	=item * Priorities are not currently supported. Initialising priorities
		2318	will fail and all watchers will have the same priority, even though there
		2319	is an ev_pri field.
		2320
		2321	=item * Other members are not supported.
		2322
		2323	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		2324	to use the libev header file and library.
		2325
		2326	=back
		2327
		2328	=head1 C++ SUPPORT
		2329
		2330	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2331	you to use some convinience methods to start/stop watchers and also change
		2332	the callback model to a model using method callbacks on objects.
		2333
		2334	To use it,
		2335
		2336	#include <ev++.h>
		2337
		2338	This automatically includes F<ev.h> and puts all of its definitions (many
		2339	of them macros) into the global namespace. All C++ specific things are
		2340	put into the C<ev> namespace. It should support all the same embedding
		2341	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2342
		2343	Care has been taken to keep the overhead low. The only data member the C++
		2344	classes add (compared to plain C-style watchers) is the event loop pointer
		2345	that the watcher is associated with (or no additional members at all if
		2346	you disable C<EV_MULTIPLICITY> when embedding libev).
		2347
		2348	Currently, functions, and static and non-static member functions can be
		2349	used as callbacks. Other types should be easy to add as long as they only
		2350	need one additional pointer for context. If you need support for other
		2351	types of functors please contact the author (preferably after implementing
		2352	it).
		2353
		2354	Here is a list of things available in the C<ev> namespace:
		2355
		2356	=over 4
		2357
		2358	=item C<ev::READ>, C<ev::WRITE> etc.
		2359
		2360	These are just enum values with the same values as the C<EV_READ> etc.
		2361	macros from F<ev.h>.
		2362
		2363	=item C<ev::tstamp>, C<ev::now>
		2364
		2365	Aliases to the same types/functions as with the C<ev_> prefix.
		2366
		2367	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2368
		2369	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2370	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2371	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2372	defines by many implementations.
		2373
		2374	All of those classes have these methods:
		2375
		2376	=over 4
		2377
		2378	=item ev::TYPE::TYPE ()
		2379
		2380	=item ev::TYPE::TYPE (struct ev_loop *)
		2381
		2382	=item ev::TYPE::~TYPE
		2383
		2384	The constructor (optionally) takes an event loop to associate the watcher
		2385	with. If it is omitted, it will use C<EV_DEFAULT>.
		2386
		2387	The constructor calls C<ev_init> for you, which means you have to call the
		2388	C<set> method before starting it.
		2389
		2390	It will not set a callback, however: You have to call the templated C<set>
		2391	method to set a callback before you can start the watcher.
		2392
		2393	(The reason why you have to use a method is a limitation in C++ which does
		2394	not allow explicit template arguments for constructors).
		2395
		2396	The destructor automatically stops the watcher if it is active.
		2397
		2398	=item w->set<class, &class::method> (object *)
		2399
		2400	This method sets the callback method to call. The method has to have a
		2401	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2402	first argument and the C<revents> as second. The object must be given as
		2403	parameter and is stored in the C<data> member of the watcher.
		2404
		2405	This method synthesizes efficient thunking code to call your method from
		2406	the C callback that libev requires. If your compiler can inline your
		2407	callback (i.e. it is visible to it at the place of the C<set> call and
		2408	your compiler is good :), then the method will be fully inlined into the
		2409	thunking function, making it as fast as a direct C callback.
		2410
		2411	Example: simple class declaration and watcher initialisation
		2412
		2413	struct myclass
		2414	{
		2415	void io_cb (ev::io &w, int revents) { }
		2416	}
		2417
		2418	myclass obj;
		2419	ev::io iow;
		2420	iow.set <myclass, &myclass::io_cb> (&obj);
		2421
		2422	=item w->set<function> (void *data = 0)
		2423
		2424	Also sets a callback, but uses a static method or plain function as
		2425	callback. The optional C<data> argument will be stored in the watcher's
		2426	C<data> member and is free for you to use.
		2427
		2428	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2429
		2430	See the method-C<set> above for more details.
		2431
		2432	Example:
		2433
		2434	static void io_cb (ev::io &w, int revents) { }
		2435	iow.set <io_cb> ();
		2436
		2437	=item w->set (struct ev_loop *)
		2438
		2439	Associates a different C<struct ev_loop> with this watcher. You can only
		2440	do this when the watcher is inactive (and not pending either).
		2441
		2442	=item w->set ([args])
		2443
		2444	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2445	called at least once. Unlike the C counterpart, an active watcher gets
		2446	automatically stopped and restarted when reconfiguring it with this
		2447	method.
		2448
		2449	=item w->start ()
		2450
		2451	Starts the watcher. Note that there is no C<loop> argument, as the
		2452	constructor already stores the event loop.
		2453
		2454	=item w->stop ()
		2455
		2456	Stops the watcher if it is active. Again, no C<loop> argument.
		2457
		2458	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2459
		2460	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2461	C<ev_TYPE_again> function.
		2462
		2463	=item w->sweep () (C<ev::embed> only)
		2464
		2465	Invokes C<ev_embed_sweep>.
		2466
		2467	=item w->update () (C<ev::stat> only)
		2468
		2469	Invokes C<ev_stat_stat>.
		2470
		2471	=back
		2472
		2473	=back
		2474
		2475	Example: Define a class with an IO and idle watcher, start one of them in
		2476	the constructor.
		2477
		2478	class myclass
		2479	{
		2480	ev::io io; void io_cb (ev::io &w, int revents);
		2481	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2482
		2483	myclass (int fd)
		2484	{
		2485	io .set <myclass, &myclass::io_cb > (this);
		2486	idle.set <myclass, &myclass::idle_cb> (this);
		2487
		2488	io.start (fd, ev::READ);
		2489	}
		2490	};
		2491
		2492
		2493	=head1 MACRO MAGIC
		2494
		2495	Libev can be compiled with a variety of options, the most fundamantal
		2496	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2497	functions and callbacks have an initial C<struct ev_loop *> argument.
		2498
		2499	To make it easier to write programs that cope with either variant, the
		2500	following macros are defined:
		2501
		2502	=over 4
		2503
		2504	=item C<EV_A>, C<EV_A_>
		2505
		2506	This provides the loop I<argument> for functions, if one is required ("ev
		2507	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2508	C<EV_A_> is used when other arguments are following. Example:
		2509
		2510	ev_unref (EV_A);
		2511	ev_timer_add (EV_A_ watcher);
		2512	ev_loop (EV_A_ 0);
		2513
		2514	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2515	which is often provided by the following macro.
		2516
		2517	=item C<EV_P>, C<EV_P_>
		2518
		2519	This provides the loop I<parameter> for functions, if one is required ("ev
		2520	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2521	C<EV_P_> is used when other parameters are following. Example:
		2522
		2523	// this is how ev_unref is being declared
		2524	static void ev_unref (EV_P);
		2525
		2526	// this is how you can declare your typical callback
		2527	static void cb (EV_P_ ev_timer *w, int revents)
		2528
		2529	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2530	suitable for use with C<EV_A>.
		2531
		2532	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2533
		2534	Similar to the other two macros, this gives you the value of the default
		2535	loop, if multiple loops are supported ("ev loop default").
		2536
		2537	=back
		2538
		2539	Example: Declare and initialise a check watcher, utilising the above
		2540	macros so it will work regardless of whether multiple loops are supported
		2541	or not.
		2542
		2543	static void
		2544	check_cb (EV_P_ ev_timer *w, int revents)
		2545	{
		2546	ev_check_stop (EV_A_ w);
		2547	}
		2548
		2549	ev_check check;
		2550	ev_check_init (&check, check_cb);
		2551	ev_check_start (EV_DEFAULT_ &check);
		2552	ev_loop (EV_DEFAULT_ 0);
		2553
		2554	=head1 EMBEDDING
		2555
		2556	Libev can (and often is) directly embedded into host
		2557	applications. Examples of applications that embed it include the Deliantra
		2558	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2559	and rxvt-unicode.
		2560
		2561	The goal is to enable you to just copy the necessary files into your
		2562	source directory without having to change even a single line in them, so
		2563	you can easily upgrade by simply copying (or having a checked-out copy of
		2564	libev somewhere in your source tree).
		2565
		2566	=head2 FILESETS
		2567
		2568	Depending on what features you need you need to include one or more sets of files
		2569	in your app.
		2570
		2571	=head3 CORE EVENT LOOP
		2572
		2573	To include only the libev core (all the C<ev_*> functions), with manual
		2574	configuration (no autoconf):
		2575
		2576	#define EV_STANDALONE 1
		2577	#include "ev.c"
		2578
		2579	This will automatically include F<ev.h>, too, and should be done in a
		2580	single C source file only to provide the function implementations. To use
		2581	it, do the same for F<ev.h> in all files wishing to use this API (best
		2582	done by writing a wrapper around F<ev.h> that you can include instead and
		2583	where you can put other configuration options):
		2584
		2585	#define EV_STANDALONE 1
		2586	#include "ev.h"
		2587
		2588	Both header files and implementation files can be compiled with a C++
		2589	compiler (at least, thats a stated goal, and breakage will be treated
		2590	as a bug).
		2591
		2592	You need the following files in your source tree, or in a directory
		2593	in your include path (e.g. in libev/ when using -Ilibev):
		2594
		2595	ev.h
		2596	ev.c
		2597	ev_vars.h
		2598	ev_wrap.h
		2599
		2600	ev_win32.c required on win32 platforms only
		2601
		2602	ev_select.c only when select backend is enabled (which is enabled by default)
		2603	ev_poll.c only when poll backend is enabled (disabled by default)
		2604	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2605	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2606	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2607
		2608	F<ev.c> includes the backend files directly when enabled, so you only need
		2609	to compile this single file.
		2610
		2611	=head3 LIBEVENT COMPATIBILITY API
		2612
		2613	To include the libevent compatibility API, also include:
		2614
		2615	#include "event.c"
		2616
		2617	in the file including F<ev.c>, and:
		2618
		2619	#include "event.h"
		2620
		2621	in the files that want to use the libevent API. This also includes F<ev.h>.
		2622
		2623	You need the following additional files for this:
		2624
		2625	event.h
		2626	event.c
		2627
		2628	=head3 AUTOCONF SUPPORT
		2629
		2630	Instead of using C<EV_STANDALONE=1> and providing your config in
		2631	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2632	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2633	include F<config.h> and configure itself accordingly.
		2634
		2635	For this of course you need the m4 file:
		2636
		2637	libev.m4
		2638
		2639	=head2 PREPROCESSOR SYMBOLS/MACROS
		2640
		2641	Libev can be configured via a variety of preprocessor symbols you have to define
		2642	before including any of its files. The default is not to build for multiplicity
		2643	and only include the select backend.
		2644
		2645	=over 4
		2646
		2647	=item EV_STANDALONE
		2648
		2649	Must always be C<1> if you do not use autoconf configuration, which
		2650	keeps libev from including F<config.h>, and it also defines dummy
		2651	implementations for some libevent functions (such as logging, which is not
		2652	supported). It will also not define any of the structs usually found in
		2653	F<event.h> that are not directly supported by the libev core alone.
		2654
		2655	=item EV_USE_MONOTONIC
		2656
		2657	If defined to be C<1>, libev will try to detect the availability of the
		2658	monotonic clock option at both compiletime and runtime. Otherwise no use
		2659	of the monotonic clock option will be attempted. If you enable this, you
		2660	usually have to link against librt or something similar. Enabling it when
		2661	the functionality isn't available is safe, though, although you have
		2662	to make sure you link against any libraries where the C<clock_gettime>
		2663	function is hiding in (often F<-lrt>).
		2664
		2665	=item EV_USE_REALTIME
		2666
		2667	If defined to be C<1>, libev will try to detect the availability of the
		2668	realtime clock option at compiletime (and assume its availability at
		2669	runtime if successful). Otherwise no use of the realtime clock option will
		2670	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2671	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2672	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2673
		2674	=item EV_USE_NANOSLEEP
		2675
		2676	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2677	and will use it for delays. Otherwise it will use C<select ()>.
		2678
		2679	=item EV_USE_SELECT
		2680
		2681	If undefined or defined to be C<1>, libev will compile in support for the
		2682	C<select>(2) backend. No attempt at autodetection will be done: if no
		2683	other method takes over, select will be it. Otherwise the select backend
		2684	will not be compiled in.
		2685
		2686	=item EV_SELECT_USE_FD_SET
		2687
		2688	If defined to C<1>, then the select backend will use the system C<fd_set>
		2689	structure. This is useful if libev doesn't compile due to a missing
		2690	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2691	exotic systems. This usually limits the range of file descriptors to some
		2692	low limit such as 1024 or might have other limitations (winsocket only
		2693	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2694	influence the size of the C<fd_set> used.
		2695
		2696	=item EV_SELECT_IS_WINSOCKET
		2697
		2698	When defined to C<1>, the select backend will assume that
		2699	select/socket/connect etc. don't understand file descriptors but
		2700	wants osf handles on win32 (this is the case when the select to
		2701	be used is the winsock select). This means that it will call
		2702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2703	it is assumed that all these functions actually work on fds, even
		2704	on win32. Should not be defined on non-win32 platforms.
		2705
		2706	=item EV_FD_TO_WIN32_HANDLE
		2707
		2708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2709	file descriptors to socket handles. When not defining this symbol (the
		2710	default), then libev will call C<_get_osfhandle>, which is usually
		2711	correct. In some cases, programs use their own file descriptor management,
		2712	in which case they can provide this function to map fds to socket handles.
		2713
		2714	=item EV_USE_POLL
		2715
		2716	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2717	backend. Otherwise it will be enabled on non-win32 platforms. It
		2718	takes precedence over select.
		2719
		2720	=item EV_USE_EPOLL
		2721
		2722	If defined to be C<1>, libev will compile in support for the Linux
		2723	C<epoll>(7) backend. Its availability will be detected at runtime,
		2724	otherwise another method will be used as fallback. This is the
		2725	preferred backend for GNU/Linux systems.
		2726
		2727	=item EV_USE_KQUEUE
		2728
		2729	If defined to be C<1>, libev will compile in support for the BSD style
		2730	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2731	otherwise another method will be used as fallback. This is the preferred
		2732	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2733	supports some types of fds correctly (the only platform we found that
		2734	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2735	not be used unless explicitly requested. The best way to use it is to find
		2736	out whether kqueue supports your type of fd properly and use an embedded
		2737	kqueue loop.
		2738
		2739	=item EV_USE_PORT
		2740
		2741	If defined to be C<1>, libev will compile in support for the Solaris
		2742	10 port style backend. Its availability will be detected at runtime,
		2743	otherwise another method will be used as fallback. This is the preferred
		2744	backend for Solaris 10 systems.
		2745
		2746	=item EV_USE_DEVPOLL
		2747
		2748	reserved for future expansion, works like the USE symbols above.
		2749
		2750	=item EV_USE_INOTIFY
		2751
		2752	If defined to be C<1>, libev will compile in support for the Linux inotify
		2753	interface to speed up C<ev_stat> watchers. Its actual availability will
		2754	be detected at runtime.
		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
		2767	=item EV_H
		2768
		2769	The name of the F<ev.h> header file used to include it. The default if
		2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2771	used to virtually rename the F<ev.h> header file in case of conflicts.
		2772
		2773	=item EV_CONFIG_H
		2774
		2775	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2776	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2777	C<EV_H>, above.
		2778
		2779	=item EV_EVENT_H
		2780
		2781	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2782	of how the F<event.h> header can be found, the default is C<"event.h">.
		2783
		2784	=item EV_PROTOTYPES
		2785
		2786	If defined to be C<0>, then F<ev.h> will not define any function
		2787	prototypes, but still define all the structs and other symbols. This is
		2788	occasionally useful if you want to provide your own wrapper functions
		2789	around libev functions.
		2790
		2791	=item EV_MULTIPLICITY
		2792
		2793	If undefined or defined to C<1>, then all event-loop-specific functions
		2794	will have the C<struct ev_loop *> as first argument, and you can create
		2795	additional independent event loops. Otherwise there will be no support
		2796	for multiple event loops and there is no first event loop pointer
		2797	argument. Instead, all functions act on the single default loop.
		2798
		2799	=item EV_MINPRI
		2800
		2801	=item EV_MAXPRI
		2802
		2803	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2804	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2805	provide for more priorities by overriding those symbols (usually defined
		2806	to be C<-2> and C<2>, respectively).
		2807
		2808	When doing priority-based operations, libev usually has to linearly search
		2809	all the priorities, so having many of them (hundreds) uses a lot of space
		2810	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2811	fine.
		2812
		2813	If your embedding app does not need any priorities, defining these both to
		2814	C<0> will save some memory and cpu.
		2815
		2816	=item EV_PERIODIC_ENABLE
		2817
		2818	If undefined or defined to be C<1>, then periodic timers are supported. If
		2819	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2820	code.
		2821
		2822	=item EV_IDLE_ENABLE
		2823
		2824	If undefined or defined to be C<1>, then idle watchers are supported. If
		2825	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2826	code.
		2827
		2828	=item EV_EMBED_ENABLE
		2829
		2830	If undefined or defined to be C<1>, then embed watchers are supported. If
		2831	defined to be C<0>, then they are not.
		2832
		2833	=item EV_STAT_ENABLE
		2834
		2835	If undefined or defined to be C<1>, then stat watchers are supported. If
		2836	defined to be C<0>, then they are not.
		2837
		2838	=item EV_FORK_ENABLE
		2839
		2840	If undefined or defined to be C<1>, then fork watchers are supported. If
		2841	defined to be C<0>, then they are not.
		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
		2846	defined to be C<0>, then they are not.
		2847
		2848	=item EV_MINIMAL
		2849
		2850	If you need to shave off some kilobytes of code at the expense of some
		2851	speed, define this symbol to C<1>. Currently only used for gcc to override
		2852	some inlining decisions, saves roughly 30% codesize of amd64.
		2853
		2854	=item EV_PID_HASHSIZE
		2855
		2856	C<ev_child> watchers use a small hash table to distribute workload by
		2857	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2858	than enough. If you need to manage thousands of children you might want to
		2859	increase this value (I<must> be a power of two).
		2860
		2861	=item EV_INOTIFY_HASHSIZE
		2862
		2863	C<ev_stat> watchers use a small hash table to distribute workload by
		2864	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2865	usually more than enough. If you need to manage thousands of C<ev_stat>
		2866	watchers you might want to increase this value (I<must> be a power of
		2867	two).
		2868
		2869	=item EV_COMMON
		2870
		2871	By default, all watchers have a C<void *data> member. By redefining
		2872	this macro to a something else you can include more and other types of
		2873	members. You have to define it each time you include one of the files,
		2874	though, and it must be identical each time.
		2875
		2876	For example, the perl EV module uses something like this:
		2877
		2878	#define EV_COMMON \
		2879	SV *self; /* contains this struct */ \
		2880	SV *cb_sv, *fh /* note no trailing ";" */
		2881
		2882	=item EV_CB_DECLARE (type)
		2883
		2884	=item EV_CB_INVOKE (watcher, revents)
		2885
		2886	=item ev_set_cb (ev, cb)
		2887
		2888	Can be used to change the callback member declaration in each watcher,
		2889	and the way callbacks are invoked and set. Must expand to a struct member
		2890	definition and a statement, respectively. See the F<ev.h> header file for
		2891	their default definitions. One possible use for overriding these is to
		2892	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2893	method calls instead of plain function calls in C++.
		2894
		2895	=head2 EXPORTED API SYMBOLS
		2896
		2897	If you need to re-export the API (e.g. via a dll) and you need a list of
		2898	exported symbols, you can use the provided F<Symbol.*> files which list
		2899	all public symbols, one per line:
		2900
		2901	Symbols.ev for libev proper
		2902	Symbols.event for the libevent emulation
		2903
		2904	This can also be used to rename all public symbols to avoid clashes with
		2905	multiple versions of libev linked together (which is obviously bad in
		2906	itself, but sometimes it is inconvinient to avoid this).
		2907
		2908	A sed command like this will create wrapper C<#define>'s that you need to
		2909	include before including F<ev.h>:
		2910
		2911	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2912
		2913	This would create a file F<wrap.h> which essentially looks like this:
		2914
		2915	#define ev_backend myprefix_ev_backend
		2916	#define ev_check_start myprefix_ev_check_start
		2917	#define ev_check_stop myprefix_ev_check_stop
		2918	...
		2919
		2920	=head2 EXAMPLES
		2921
		2922	For a real-world example of a program the includes libev
		2923	verbatim, you can have a look at the EV perl module
		2924	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2925	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2926	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2927	will be compiled. It is pretty complex because it provides its own header
		2928	file.
		2929
		2930	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2931	that everybody includes and which overrides some configure choices:
		2932
		2933	#define EV_MINIMAL 1
		2934	#define EV_USE_POLL 0
		2935	#define EV_MULTIPLICITY 0
		2936	#define EV_PERIODIC_ENABLE 0
		2937	#define EV_STAT_ENABLE 0
		2938	#define EV_FORK_ENABLE 0
		2939	#define EV_CONFIG_H <config.h>
		2940	#define EV_MINPRI 0
		2941	#define EV_MAXPRI 0
		2942
		2943	#include "ev++.h"
		2944
		2945	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2946
		2947	#include "ev_cpp.h"
		2948	#include "ev.c"
		2949
		2950
		2951	=head1 COMPLEXITIES
		2952
		2953	In this section the complexities of (many of) the algorithms used inside
		2954	libev will be explained. For complexity discussions about backends see the
		2955	documentation for C<ev_default_init>.
		2956
		2957	All of the following are about amortised time: If an array needs to be
		2958	extended, libev needs to realloc and move the whole array, but this
		2959	happens asymptotically never with higher number of elements, so O(1) might
		2960	mean it might do a lengthy realloc operation in rare cases, but on average
		2961	it is much faster and asymptotically approaches constant time.
		2962
		2963	=over 4
		2964
		2965	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2966
		2967	This means that, when you have a watcher that triggers in one hour and
		2968	there are 100 watchers that would trigger before that then inserting will
		2969	have to skip roughly seven (C<ld 100>) of these watchers.
		2970
		2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2972
		2973	That means that changing a timer costs less than removing/adding them
		2974	as only the relative motion in the event queue has to be paid for.
		2975
		2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		2977
		2978	These just add the watcher into an array or at the head of a list.
		2979
		2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		2981
		2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2983
		2984	These watchers are stored in lists then need to be walked to find the
		2985	correct watcher to remove. The lists are usually short (you don't usually
		2986	have many watchers waiting for the same fd or signal).
		2987
		2988	=item Finding the next timer in each loop iteration: O(1)
		2989
		2990	By virtue of using a binary heap, the next timer is always found at the
		2991	beginning of the storage array.
		2992
		2993	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2994
		2995	A change means an I/O watcher gets started or stopped, which requires
		2996	libev to recalculate its status (and possibly tell the kernel, depending
		2997	on backend and wether C<ev_io_set> was used).
		2998
		2999	=item Activating one watcher (putting it into the pending state): O(1)
		3000
		3001	=item Priority handling: O(number_of_priorities)
		3002
		3003	Priorities are implemented by allocating some space for each
		3004	priority. When doing priority-based operations, libev usually has to
		3005	linearly search all the priorities, but starting/stopping and activating
		3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
		3017
		3018	=back
		3019
		3020
		3021	=head1 Win32 platform limitations and workarounds
		3022
		3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3024	requires, and its I/O model is fundamentally incompatible with the POSIX
		3025	model. Libev still offers limited functionality on this platform in
		3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3027	descriptors. This only applies when using Win32 natively, not when using
		3028	e.g. cygwin.
		3029
		3030	There is no supported compilation method available on windows except
		3031	embedding it into other applications.
		3032
		3033	Due to the many, low, and arbitrary limits on the win32 platform and the
		3034	abysmal performance of winsockets, using a large number of sockets is not
		3035	recommended (and not reasonable). If your program needs to use more than
		3036	a hundred or so sockets, then likely it needs to use a totally different
		3037	implementation for windows, as libev offers the POSIX model, which cannot
		3038	be implemented efficiently on windows (microsoft monopoly games).
		3039
		3040	=over 4
		3041
		3042	=item The winsocket select function
		3043
		3044	The winsocket C<select> function doesn't follow POSIX in that it requires
		3045	socket I<handles> and not socket I<file descriptors>. This makes select
		3046	very inefficient, and also requires a mapping from file descriptors
		3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3049	symbols for more info.
		3050
		3051	The configuration for a "naked" win32 using the microsoft runtime
		3052	libraries and raw winsocket select is:
		3053
		3054	#define EV_USE_SELECT 1
		3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3056
		3057	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3058	complexity in the O(n²) range when using win32.
		3059
		3060	=item Limited number of file descriptors
		3061
		3062	Windows has numerous arbitrary (and low) limits on things. Early versions
		3063	of winsocket's select only supported waiting for a max. of C<64> handles
		3064	(probably owning to the fact that all windows kernels can only wait for
		3065	C<64> things at the same time internally; microsoft recommends spawning a
		3066	chain of threads and wait for 63 handles and the previous thread in each).
		3067
		3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3069	to some high number (e.g. C<2048>) before compiling the winsocket select
		3070	call (which might be in libev or elsewhere, for example, perl does its own
		3071	select emulation on windows).
		3072
		3073	Another limit is the number of file descriptors in the microsoft runtime
		3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3075	or something like this inside microsoft). You can increase this by calling
		3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3077	arbitrary limit), but is broken in many versions of the microsoft runtime
		3078	libraries.
		3079
		3080	This might get you to about C<512> or C<2048> sockets (depending on
		3081	windows version and/or the phase of the moon). To get more, you need to
		3082	wrap all I/O functions and provide your own fd management, but the cost of
		3083	calling select (O(n²)) will likely make this unworkable.
		3084
		3085	=back
		3086
		3087
742	=head1 AUTHOR	3088	=head1 AUTHOR
743		3089
744	Marc Lehmann <libev@schmorp.de>.	3090	Marc Lehmann <libev@schmorp.de>.
745		3091

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