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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>.
…		…
181	This function reinitialises the kernel state for backends that have	488	This function reinitialises the kernel state for backends that have
182	one. Despite the name, you can call it anytime, but it makes most sense	489	one. Despite the name, you can call it anytime, but it makes most sense
183	after forking, in either the parent or child process (or both, but that	490	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	491	again makes little sense).
185		492
186	You I<must> call this function after forking if and only if you want to	493	You I<must> call this function in the child process after forking if and
187	use the event library in both processes. If you just fork+exec, you don't	494	only if you want to use the event library in both processes. If you just
188	have to call it.	495	fork+exec, you don't have to call it.
189		496
190	The function itself is quite fast and its usually not a problem to call	497	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	498	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>:	499	quite nicely into a call to C<pthread_atfork>:
193		500
194	pthread_atfork (0, 0, ev_default_fork);	501	pthread_atfork (0, 0, ev_default_fork);
		502
		503	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		504	without calling this function, so if you force one of those backends you
		505	do not need to care.
195		506
196	=item ev_loop_fork (loop)	507	=item ev_loop_fork (loop)
197		508
198	Like C<ev_default_fork>, but acts on an event loop created by	509	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	510	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.	511	after fork, and how you do this is entirely your own problem.
201		512
		513	=item unsigned int ev_loop_count (loop)
		514
		515	Returns the count of loop iterations for the loop, which is identical to
		516	the number of times libev did poll for new events. It starts at C<0> and
		517	happily wraps around with enough iterations.
		518
		519	This value can sometimes be useful as a generation counter of sorts (it
		520	"ticks" the number of loop iterations), as it roughly corresponds with
		521	C<ev_prepare> and C<ev_check> calls.
		522
202	=item unsigned int ev_method (loop)	523	=item unsigned int ev_backend (loop)
203		524
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	525	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	526	use.
206		527
207	=item ev_tstamp = ev_now (loop)	528	=item ev_tstamp ev_now (loop)
208		529
209	Returns the current "event loop time", which is the time the event loop	530	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	531	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	532	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	533	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).	534	event occurring (or more correctly, libev finding out about it).
214		535
215	=item ev_loop (loop, int flags)	536	=item ev_loop (loop, int flags)
216		537
217	Finally, this is it, the event handler. This function usually is called	538	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	539	after you initialised all your watchers and you want to start handling
219	events.	540	events.
220		541
221	If the flags argument is specified as 0, it will not return until either	542	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.	543	either no event watchers are active anymore or C<ev_unloop> was called.
		544
		545	Please note that an explicit C<ev_unloop> is usually better than
		546	relying on all watchers to be stopped when deciding when a program has
		547	finished (especially in interactive programs), but having a program that
		548	automatically loops as long as it has to and no longer by virtue of
		549	relying on its watchers stopping correctly is a thing of beauty.
223		550
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	551	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	552	those events and any outstanding ones, but will not block your process in
226	case there are no events.	553	case there are no events and will return after one iteration of the loop.
227		554
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	555	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	556	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	557	your process until at least one new event arrives, and will return after
		558	one iteration of the loop. This is useful if you are waiting for some
		559	external event in conjunction with something not expressible using other
		560	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		561	usually a better approach for this kind of thing.
231		562
232	This flags value could be used to implement alternative looping	563	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	564
234	more generic mechanism.	565	- Before the first iteration, call any pending watchers.
		566	* If EVFLAG_FORKCHECK was used, check for a fork.
		567	- If a fork was detected, queue and call all fork watchers.
		568	- Queue and call all prepare watchers.
		569	- If we have been forked, recreate the kernel state.
		570	- Update the kernel state with all outstanding changes.
		571	- Update the "event loop time".
		572	- Calculate for how long to sleep or block, if at all
		573	(active idle watchers, EVLOOP_NONBLOCK or not having
		574	any active watchers at all will result in not sleeping).
		575	- Sleep if the I/O and timer collect interval say so.
		576	- Block the process, waiting for any events.
		577	- Queue all outstanding I/O (fd) events.
		578	- Update the "event loop time" and do time jump handling.
		579	- Queue all outstanding timers.
		580	- Queue all outstanding periodics.
		581	- If no events are pending now, queue all idle watchers.
		582	- Queue all check watchers.
		583	- Call all queued watchers in reverse order (i.e. check watchers first).
		584	Signals and child watchers are implemented as I/O watchers, and will
		585	be handled here by queueing them when their watcher gets executed.
		586	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		587	were used, or there are no active watchers, return, otherwise
		588	continue with step *.
		589
		590	Example: Queue some jobs and then loop until no events are outstanding
		591	anymore.
		592
		593	... queue jobs here, make sure they register event watchers as long
		594	... as they still have work to do (even an idle watcher will do..)
		595	ev_loop (my_loop, 0);
		596	... jobs done. yeah!
235		597
236	=item ev_unloop (loop, how)	598	=item ev_unloop (loop, how)
237		599
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	600	Can be used to make a call to C<ev_loop> return early (but only after it
		601	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>	602	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>	603	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.	604
		605	This "unloop state" will be cleared when entering C<ev_loop> again.
242		606
243	=item ev_ref (loop)	607	=item ev_ref (loop)
244		608
245	=item ev_unref (loop)	609	=item ev_unref (loop)
246		610
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	611	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	612	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	613	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	614	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	615	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	616	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	617	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	618	no event watchers registered by it are active. It is also an excellent
255	before stop.	619	way to do this for generic recurring timers or from within third-party
		620	libraries. Just remember to I<unref after start> and I<ref before stop>
		621	(but only if the watcher wasn't active before, or was active before,
		622	respectively).
		623
		624	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		625	running when nothing else is active.
		626
		627	struct ev_signal exitsig;
		628	ev_signal_init (&exitsig, sig_cb, SIGINT);
		629	ev_signal_start (loop, &exitsig);
		630	evf_unref (loop);
		631
		632	Example: For some weird reason, unregister the above signal handler again.
		633
		634	ev_ref (loop);
		635	ev_signal_stop (loop, &exitsig);
		636
		637	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		638
		639	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		640
		641	These advanced functions influence the time that libev will spend waiting
		642	for events. Both are by default C<0>, meaning that libev will try to
		643	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		644
		645	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		646	allows libev to delay invocation of I/O and timer/periodic callbacks to
		647	increase efficiency of loop iterations.
		648
		649	The background is that sometimes your program runs just fast enough to
		650	handle one (or very few) event(s) per loop iteration. While this makes
		651	the program responsive, it also wastes a lot of CPU time to poll for new
		652	events, especially with backends like C<select ()> which have a high
		653	overhead for the actual polling but can deliver many events at once.
		654
		655	By setting a higher I<io collect interval> you allow libev to spend more
		656	time collecting I/O events, so you can handle more events per iteration,
		657	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		658	C<ev_timer>) will be not affected. Setting this to a non-null value will
		659	introduce an additional C<ev_sleep ()> call into most loop iterations.
		660
		661	Likewise, by setting a higher I<timeout collect interval> you allow libev
		662	to spend more time collecting timeouts, at the expense of increased
		663	latency (the watcher callback will be called later). C<ev_io> watchers
		664	will not be affected. Setting this to a non-null value will not introduce
		665	any overhead in libev.
		666
		667	Many (busy) programs can usually benefit by setting the io collect
		668	interval to a value near C<0.1> or so, which is often enough for
		669	interactive servers (of course not for games), likewise for timeouts. It
		670	usually doesn't make much sense to set it to a lower value than C<0.01>,
		671	as this approsaches the timing granularity of most systems.
256		672
257	=back	673	=back
		674
258		675
259	=head1 ANATOMY OF A WATCHER	676	=head1 ANATOMY OF A WATCHER
260		677
261	A watcher is a structure that you create and register to record your	678	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	679	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:	680	become readable, you would create an C<ev_io> watcher for that:
264		681
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	682	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	683	{
267	ev_io_stop (w);	684	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	685	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	712	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	713	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		714
298	As long as your watcher is active (has been started but not stopped) you	715	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	716	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	717	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		718
307	Each and every callback receives the event loop pointer as first, the	719	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	720	registered watcher structure as second, and a bitset of received events as
309	third argument.	721	third argument.
310		722
311	The rceeived events usually include a single bit per event type received	723	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	724	(you can receive multiple events at the same time). The possible bit masks
313	are:	725	are:
314		726
315	=over 4	727	=over 4
316		728
317	=item EV_READ	729	=item C<EV_READ>
318		730
319	=item EV_WRITE	731	=item C<EV_WRITE>
320		732
321	The file descriptor in the ev_io watcher has become readable and/or	733	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	734	writable.
323		735
324	=item EV_TIMEOUT	736	=item C<EV_TIMEOUT>
325		737
326	The ev_timer watcher has timed out.	738	The C<ev_timer> watcher has timed out.
327		739
328	=item EV_PERIODIC	740	=item C<EV_PERIODIC>
329		741
330	The ev_periodic watcher has timed out.	742	The C<ev_periodic> watcher has timed out.
331		743
332	=item EV_SIGNAL	744	=item C<EV_SIGNAL>
333		745
334	The signal specified in the ev_signal watcher has been received by a thread.	746	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		747
336	=item EV_CHILD	748	=item C<EV_CHILD>
337		749
338	The pid specified in the ev_child watcher has received a status change.	750	The pid specified in the C<ev_child> watcher has received a status change.
339		751
		752	=item C<EV_STAT>
		753
		754	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		755
340	=item EV_IDLE	756	=item C<EV_IDLE>
341		757
342	The ev_idle watcher has determined that you have nothing better to do.	758	The C<ev_idle> watcher has determined that you have nothing better to do.
343		759
344	=item EV_PREPARE	760	=item C<EV_PREPARE>
345		761
346	=item EV_CHECK	762	=item C<EV_CHECK>
347		763
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	764	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	765	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	766	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	767	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	768	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	769	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	770	C<ev_loop> from blocking).
355		771
		772	=item C<EV_EMBED>
		773
		774	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		775
		776	=item C<EV_FORK>
		777
		778	The event loop has been resumed in the child process after fork (see
		779	C<ev_fork>).
		780
356	=item EV_ERROR	781	=item C<EV_ERROR>
357		782
358	An unspecified error has occured, the watcher has been stopped. This might	783	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	784	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	785	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	786	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	792	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	793	programs, though, so beware.
369		794
370	=back	795	=back
371		796
		797	=head2 GENERIC WATCHER FUNCTIONS
		798
		799	In the following description, C<TYPE> stands for the watcher type,
		800	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		801
		802	=over 4
		803
		804	=item C<ev_init> (ev_TYPE *watcher, callback)
		805
		806	This macro initialises the generic portion of a watcher. The contents
		807	of the watcher object can be arbitrary (so C<malloc> will do). Only
		808	the generic parts of the watcher are initialised, you I<need> to call
		809	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		810	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		811	which rolls both calls into one.
		812
		813	You can reinitialise a watcher at any time as long as it has been stopped
		814	(or never started) and there are no pending events outstanding.
		815
		816	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		817	int revents)>.
		818
		819	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		820
		821	This macro initialises the type-specific parts of a watcher. You need to
		822	call C<ev_init> at least once before you call this macro, but you can
		823	call C<ev_TYPE_set> any number of times. You must not, however, call this
		824	macro on a watcher that is active (it can be pending, however, which is a
		825	difference to the C<ev_init> macro).
		826
		827	Although some watcher types do not have type-specific arguments
		828	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		829
		830	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		831
		832	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		833	calls into a single call. This is the most convinient method to initialise
		834	a watcher. The same limitations apply, of course.
		835
		836	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		837
		838	Starts (activates) the given watcher. Only active watchers will receive
		839	events. If the watcher is already active nothing will happen.
		840
		841	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		842
		843	Stops the given watcher again (if active) and clears the pending
		844	status. It is possible that stopped watchers are pending (for example,
		845	non-repeating timers are being stopped when they become pending), but
		846	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		847	you want to free or reuse the memory used by the watcher it is therefore a
		848	good idea to always call its C<ev_TYPE_stop> function.
		849
		850	=item bool ev_is_active (ev_TYPE *watcher)
		851
		852	Returns a true value iff the watcher is active (i.e. it has been started
		853	and not yet been stopped). As long as a watcher is active you must not modify
		854	it.
		855
		856	=item bool ev_is_pending (ev_TYPE *watcher)
		857
		858	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		859	events but its callback has not yet been invoked). As long as a watcher
		860	is pending (but not active) you must not call an init function on it (but
		861	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		862	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		863	it).
		864
		865	=item callback ev_cb (ev_TYPE *watcher)
		866
		867	Returns the callback currently set on the watcher.
		868
		869	=item ev_cb_set (ev_TYPE *watcher, callback)
		870
		871	Change the callback. You can change the callback at virtually any time
		872	(modulo threads).
		873
		874	=item ev_set_priority (ev_TYPE *watcher, priority)
		875
		876	=item int ev_priority (ev_TYPE *watcher)
		877
		878	Set and query the priority of the watcher. The priority is a small
		879	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		880	(default: C<-2>). Pending watchers with higher priority will be invoked
		881	before watchers with lower priority, but priority will not keep watchers
		882	from being executed (except for C<ev_idle> watchers).
		883
		884	This means that priorities are I<only> used for ordering callback
		885	invocation after new events have been received. This is useful, for
		886	example, to reduce latency after idling, or more often, to bind two
		887	watchers on the same event and make sure one is called first.
		888
		889	If you need to suppress invocation when higher priority events are pending
		890	you need to look at C<ev_idle> watchers, which provide this functionality.
		891
		892	You I<must not> change the priority of a watcher as long as it is active or
		893	pending.
		894
		895	The default priority used by watchers when no priority has been set is
		896	always C<0>, which is supposed to not be too high and not be too low :).
		897
		898	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		899	fine, as long as you do not mind that the priority value you query might
		900	or might not have been adjusted to be within valid range.
		901
		902	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		903
		904	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		905	C<loop> nor C<revents> need to be valid as long as the watcher callback
		906	can deal with that fact.
		907
		908	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		909
		910	If the watcher is pending, this function returns clears its pending status
		911	and returns its C<revents> bitset (as if its callback was invoked). If the
		912	watcher isn't pending it does nothing and returns C<0>.
		913
		914	=back
		915
		916
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	917	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		918
374	Each watcher has, by default, a member C<void *data> that you can change	919	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	920	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	921	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	922	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	923	member, you can also "subclass" the watcher type and provide your own
379	data:	924	data:
380		925
…		…
393	{	938	{
394	struct my_io *w = (struct my_io *)w_;	939	struct my_io *w = (struct my_io *)w_;
395	...	940	...
396	}	941	}
397		942
398	More interesting and less C-conformant ways of catsing your callback type	943	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	944	instead have been omitted.
		945
		946	Another common scenario is having some data structure with multiple
		947	watchers:
		948
		949	struct my_biggy
		950	{
		951	int some_data;
		952	ev_timer t1;
		953	ev_timer t2;
		954	}
		955
		956	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		957	you need to use C<offsetof>:
		958
		959	#include <stddef.h>
		960
		961	static void
		962	t1_cb (EV_P_ struct ev_timer *w, int revents)
		963	{
		964	struct my_biggy big = (struct my_biggy *
		965	(((char *)w) - offsetof (struct my_biggy, t1));
		966	}
		967
		968	static void
		969	t2_cb (EV_P_ struct ev_timer *w, int revents)
		970	{
		971	struct my_biggy big = (struct my_biggy *
		972	(((char *)w) - offsetof (struct my_biggy, t2));
		973	}
400		974
401		975
402	=head1 WATCHER TYPES	976	=head1 WATCHER TYPES
403		977
404	This section describes each watcher in detail, but will not repeat	978	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	979	information given in the last section. Any initialisation/set macros,
		980	functions and members specific to the watcher type are explained.
406		981
		982	Members are additionally marked with either I<[read-only]>, meaning that,
		983	while the watcher is active, you can look at the member and expect some
		984	sensible content, but you must not modify it (you can modify it while the
		985	watcher is stopped to your hearts content), or I<[read-write]>, which
		986	means you can expect it to have some sensible content while the watcher
		987	is active, but you can also modify it. Modifying it may not do something
		988	sensible or take immediate effect (or do anything at all), but libev will
		989	not crash or malfunction in any way.
		990
		991
407	=head2 struct ev_io - is my file descriptor readable or writable	992	=head2 C<ev_io> - is this file descriptor readable or writable?
408		993
409	I/O watchers check whether a file descriptor is readable or writable	994	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	995	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	996	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	997	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	998	receiving events as long as the condition persists. Remember you can stop
		999	the watcher if you don't want to act on the event and neither want to
		1000	receive future events.
414		1001
415	In general you can register as many read and/or write event watchers oer	1002	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	1003	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	1004	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	1005	required if you know what you are doing).
419		1006
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	1007	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	1008	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	1009	C<EVBACKEND_POLL>).
		1010
		1011	Another thing you have to watch out for is that it is quite easy to
		1012	receive "spurious" readyness notifications, that is your callback might
		1013	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1014	because there is no data. Not only are some backends known to create a
		1015	lot of those (for example solaris ports), it is very easy to get into
		1016	this situation even with a relatively standard program structure. Thus
		1017	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1018	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1019
		1020	If you cannot run the fd in non-blocking mode (for example you should not
		1021	play around with an Xlib connection), then you have to seperately re-test
		1022	whether a file descriptor is really ready with a known-to-be good interface
		1023	such as poll (fortunately in our Xlib example, Xlib already does this on
		1024	its own, so its quite safe to use).
		1025
		1026	=head3 The special problem of disappearing file descriptors
		1027
		1028	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1029	descriptor (either by calling C<close> explicitly or by any other means,
		1030	such as C<dup>). The reason is that you register interest in some file
		1031	descriptor, but when it goes away, the operating system will silently drop
		1032	this interest. If another file descriptor with the same number then is
		1033	registered with libev, there is no efficient way to see that this is, in
		1034	fact, a different file descriptor.
		1035
		1036	To avoid having to explicitly tell libev about such cases, libev follows
		1037	the following policy: Each time C<ev_io_set> is being called, libev
		1038	will assume that this is potentially a new file descriptor, otherwise
		1039	it is assumed that the file descriptor stays the same. That means that
		1040	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1041	descriptor even if the file descriptor number itself did not change.
		1042
		1043	This is how one would do it normally anyway, the important point is that
		1044	the libev application should not optimise around libev but should leave
		1045	optimisations to libev.
		1046
		1047	=head3 The special problem of dup'ed file descriptors
		1048
		1049	Some backends (e.g. epoll), cannot register events for file descriptors,
		1050	but only events for the underlying file descriptions. That means when you
		1051	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1052	events for them, only one file descriptor might actually receive events.
		1053
		1054	There is no workaround possible except not registering events
		1055	for potentially C<dup ()>'ed file descriptors, or to resort to
		1056	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1057
		1058	=head3 The special problem of fork
		1059
		1060	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1061	useless behaviour. Libev fully supports fork, but needs to be told about
		1062	it in the child.
		1063
		1064	To support fork in your programs, you either have to call
		1065	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1066	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1067	C<EVBACKEND_POLL>.
		1068
		1069
		1070	=head3 Watcher-Specific Functions
428		1071
429	=over 4	1072	=over 4
430		1073
431	=item ev_io_init (ev_io *, callback, int fd, int events)	1074	=item ev_io_init (ev_io *, callback, int fd, int events)
432		1075
433	=item ev_io_set (ev_io *, int fd, int events)	1076	=item ev_io_set (ev_io *, int fd, int events)
434		1077
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1078	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 |	1079	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	1080	C<EV_READ | EV_WRITE> to receive the given events.
		1081
		1082	=item int fd [read-only]
		1083
		1084	The file descriptor being watched.
		1085
		1086	=item int events [read-only]
		1087
		1088	The events being watched.
438		1089
439	=back	1090	=back
440		1091
		1092	=head3 Examples
		1093
		1094	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1095	readable, but only once. Since it is likely line-buffered, you could
		1096	attempt to read a whole line in the callback.
		1097
		1098	static void
		1099	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1100	{
		1101	ev_io_stop (loop, w);
		1102	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1103	}
		1104
		1105	...
		1106	struct ev_loop *loop = ev_default_init (0);
		1107	struct ev_io stdin_readable;
		1108	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1109	ev_io_start (loop, &stdin_readable);
		1110	ev_loop (loop, 0);
		1111
		1112
441	=head2 struct ev_timer - relative and optionally recurring timeouts	1113	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		1114
443	Timer watchers are simple relative timers that generate an event after a	1115	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	1116	given time, and optionally repeating in regular intervals after that.
445		1117
446	The timers are based on real time, that is, if you register an event that	1118	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	1119	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	1120	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1121	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	1122	monotonic clock option helps a lot here).
		1123
		1124	The relative timeouts are calculated relative to the C<ev_now ()>
		1125	time. This is usually the right thing as this timestamp refers to the time
		1126	of the event triggering whatever timeout you are modifying/starting. If
		1127	you suspect event processing to be delayed and you I<need> to base the timeout
		1128	on the current time, use something like this to adjust for this:
		1129
		1130	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1131
		1132	The callback is guarenteed to be invoked only when its timeout has passed,
		1133	but if multiple timers become ready during the same loop iteration then
		1134	order of execution is undefined.
		1135
		1136	=head3 Watcher-Specific Functions and Data Members
451		1137
452	=over 4	1138	=over 4
453		1139
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1140	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		1141
…		…
461	later, again, and again, until stopped manually.	1147	later, again, and again, until stopped manually.
462		1148
463	The timer itself will do a best-effort at avoiding drift, that is, if you	1149	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	1150	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	1151	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	1152	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.	1153	timer will not fire more than once per event loop iteration.
468		1154
469	=item ev_timer_again (loop)	1155	=item ev_timer_again (loop)
470		1156
471	This will act as if the timer timed out and restart it again if it is	1157	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	1158	repeating. The exact semantics are:
473		1159
		1160	If the timer is pending, its pending status is cleared.
		1161
474	If the timer is started but nonrepeating, stop it.	1162	If the timer is started but nonrepeating, stop it (as if it timed out).
475		1163
476	If the timer is repeating, either start it if necessary (with the repeat	1164	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	1165	C<repeat> value), or reset the running timer to the C<repeat> value.
478		1166
479	This sounds a bit complicated, but here is a useful and typical	1167	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	1168	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	1169	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	1170	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	1171	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	1172	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	1173	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.	1174	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1175	automatically restart it if need be.
		1176
		1177	That means you can ignore the C<after> value and C<ev_timer_start>
		1178	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1179
		1180	ev_timer_init (timer, callback, 0., 5.);
		1181	ev_timer_again (loop, timer);
		1182	...
		1183	timer->again = 17.;
		1184	ev_timer_again (loop, timer);
		1185	...
		1186	timer->again = 10.;
		1187	ev_timer_again (loop, timer);
		1188
		1189	This is more slightly efficient then stopping/starting the timer each time
		1190	you want to modify its timeout value.
		1191
		1192	=item ev_tstamp repeat [read-write]
		1193
		1194	The current C<repeat> value. Will be used each time the watcher times out
		1195	or C<ev_timer_again> is called and determines the next timeout (if any),
		1196	which is also when any modifications are taken into account.
487		1197
488	=back	1198	=back
489		1199
		1200	=head3 Examples
		1201
		1202	Example: Create a timer that fires after 60 seconds.
		1203
		1204	static void
		1205	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1206	{
		1207	.. one minute over, w is actually stopped right here
		1208	}
		1209
		1210	struct ev_timer mytimer;
		1211	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1212	ev_timer_start (loop, &mytimer);
		1213
		1214	Example: Create a timeout timer that times out after 10 seconds of
		1215	inactivity.
		1216
		1217	static void
		1218	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1219	{
		1220	.. ten seconds without any activity
		1221	}
		1222
		1223	struct ev_timer mytimer;
		1224	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1225	ev_timer_again (&mytimer); /* start timer */
		1226	ev_loop (loop, 0);
		1227
		1228	// and in some piece of code that gets executed on any "activity":
		1229	// reset the timeout to start ticking again at 10 seconds
		1230	ev_timer_again (&mytimer);
		1231
		1232
490	=head2 ev_periodic - to cron or not to cron it	1233	=head2 C<ev_periodic> - to cron or not to cron?
491		1234
492	Periodic watchers are also timers of a kind, but they are very versatile	1235	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1236	(and unfortunately a bit complex).
494		1237
495	Unlike ev_timer's, they are not based on real time (or relative time)	1238	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	1239	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	1240	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 ()	1241	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	1242	+ 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	1243	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	1244	roughly 10 seconds later).
502	again).
503		1245
504	They can also be used to implement vastly more complex timers, such as	1246	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1247	triggering an event on each midnight, local time or other, complicated,
		1248	rules.
		1249
		1250	As with timers, the callback is guarenteed to be invoked only when the
		1251	time (C<at>) has been passed, but if multiple periodic timers become ready
		1252	during the same loop iteration then order of execution is undefined.
		1253
		1254	=head3 Watcher-Specific Functions and Data Members
506		1255
507	=over 4	1256	=over 4
508		1257
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1258	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1259
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1260	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1261
513	Lots of arguments, lets sort it out... There are basically three modes of	1262	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1263	operation, and we will explain them from simplest to complex:
515		1264
516
517	=over 4	1265	=over 4
518		1266
519	=item * absolute timer (interval = reschedule_cb = 0)	1267	=item * absolute timer (at = time, interval = reschedule_cb = 0)
520		1268
521	In this configuration the watcher triggers an event at the wallclock time	1269	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,	1270	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	1271	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.	1272	system time reaches or surpasses this time.
525		1273
526	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1274	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
527		1275
528	In this mode the watcher will always be scheduled to time out at the next	1276	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	1277	C<at + N * interval> time (for some integer N, which can also be negative)
530	of any time jumps.	1278	and then repeat, regardless of any time jumps.
531		1279
532	This can be used to create timers that do not drift with respect to system	1280	This can be used to create timers that do not drift with respect to system
533	time:	1281	time:
534		1282
535	ev_periodic_set (&periodic, 0., 3600., 0);	1283	ev_periodic_set (&periodic, 0., 3600., 0);
536		1284
537	This doesn't mean there will always be 3600 seconds in between triggers,	1285	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	1286	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	1287	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1288	by 3600.
541		1289
542	Another way to think about it (for the mathematically inclined) is that	1290	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	1291	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.	1292	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1293
		1294	For numerical stability it is preferable that the C<at> value is near
		1295	C<ev_now ()> (the current time), but there is no range requirement for
		1296	this value.
		1297
546	=item * manual reschedule mode (reschedule_cb = callback)	1298	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
547		1299
548	In this mode the values for C<interval> and C<at> are both being	1300	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	1301	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1302	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1303	current time as second argument.
552		1304
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1305	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	1306	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.	1307	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1308	starting an C<ev_prepare> watcher, which is legal).
556		1309
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1310	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1311	ev_tstamp now)>, e.g.:
559		1312
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1313	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1314	{
562	return now + 60.;	1315	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1318	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	1319	(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	1320	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1321	might be called at other times, too.
569		1322
		1323	NOTE: I<< This callback must always return a time that is later than the
		1324	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1325
570	This can be used to create very complex timers, such as a timer that	1326	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	1327	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	1328	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1329	you do this is, again, up to you (but it is not trivial, which is the main
		1330	reason I omitted it as an example).
574		1331
575	=back	1332	=back
576		1333
577	=item ev_periodic_again (loop, ev_periodic *)	1334	=item ev_periodic_again (loop, ev_periodic *)
578		1335
579	Simply stops and restarts the periodic watcher again. This is only useful	1336	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1337	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	1338	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1339	program when the crontabs have changed).
583		1340
		1341	=item ev_tstamp offset [read-write]
		1342
		1343	When repeating, this contains the offset value, otherwise this is the
		1344	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1345
		1346	Can be modified any time, but changes only take effect when the periodic
		1347	timer fires or C<ev_periodic_again> is being called.
		1348
		1349	=item ev_tstamp interval [read-write]
		1350
		1351	The current interval value. Can be modified any time, but changes only
		1352	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1353	called.
		1354
		1355	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1356
		1357	The current reschedule callback, or C<0>, if this functionality is
		1358	switched off. Can be changed any time, but changes only take effect when
		1359	the periodic timer fires or C<ev_periodic_again> is being called.
		1360
		1361	=item ev_tstamp at [read-only]
		1362
		1363	When active, contains the absolute time that the watcher is supposed to
		1364	trigger next.
		1365
584	=back	1366	=back
585		1367
		1368	=head3 Examples
		1369
		1370	Example: Call a callback every hour, or, more precisely, whenever the
		1371	system clock is divisible by 3600. The callback invocation times have
		1372	potentially a lot of jittering, but good long-term stability.
		1373
		1374	static void
		1375	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1376	{
		1377	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1378	}
		1379
		1380	struct ev_periodic hourly_tick;
		1381	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1382	ev_periodic_start (loop, &hourly_tick);
		1383
		1384	Example: The same as above, but use a reschedule callback to do it:
		1385
		1386	#include <math.h>
		1387
		1388	static ev_tstamp
		1389	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1390	{
		1391	return fmod (now, 3600.) + 3600.;
		1392	}
		1393
		1394	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1395
		1396	Example: Call a callback every hour, starting now:
		1397
		1398	struct ev_periodic hourly_tick;
		1399	ev_periodic_init (&hourly_tick, clock_cb,
		1400	fmod (ev_now (loop), 3600.), 3600., 0);
		1401	ev_periodic_start (loop, &hourly_tick);
		1402
		1403
586	=head2 ev_signal - signal me when a signal gets signalled	1404	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1405
588	Signal watchers will trigger an event when the process receives a specific	1406	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	1407	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	1408	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1409	normal event processing, like any other event.
592		1410
593	You cna configure as many watchers as you like per signal. Only when the	1411	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	1412	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	1413	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	1414	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	1415	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1416	SIG_DFL (regardless of what it was set to before).
599		1417
		1418	=head3 Watcher-Specific Functions and Data Members
		1419
600	=over 4	1420	=over 4
601		1421
602	=item ev_signal_init (ev_signal *, callback, int signum)	1422	=item ev_signal_init (ev_signal *, callback, int signum)
603		1423
604	=item ev_signal_set (ev_signal *, int signum)	1424	=item ev_signal_set (ev_signal *, int signum)
605		1425
606	Configures the watcher to trigger on the given signal number (usually one	1426	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1427	of the C<SIGxxx> constants).
608		1428
		1429	=item int signum [read-only]
		1430
		1431	The signal the watcher watches out for.
		1432
609	=back	1433	=back
610		1434
		1435
611	=head2 ev_child - wait for pid status changes	1436	=head2 C<ev_child> - watch out for process status changes
612		1437
613	Child watchers trigger when your process receives a SIGCHLD in response to	1438	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).	1439	some child status changes (most typically when a child of yours dies).
		1440
		1441	=head3 Watcher-Specific Functions and Data Members
615		1442
616	=over 4	1443	=over 4
617		1444
618	=item ev_child_init (ev_child *, callback, int pid)	1445	=item ev_child_init (ev_child *, callback, int pid)
619		1446
620	=item ev_child_set (ev_child *, int pid)	1447	=item ev_child_set (ev_child *, int pid)
621		1448
622	Configures the watcher to wait for status changes of process C<pid> (or	1449	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	1450	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	1451	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	1452	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.	1453	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1454	process causing the status change.
		1455
		1456	=item int pid [read-only]
		1457
		1458	The process id this watcher watches out for, or C<0>, meaning any process id.
		1459
		1460	=item int rpid [read-write]
		1461
		1462	The process id that detected a status change.
		1463
		1464	=item int rstatus [read-write]
		1465
		1466	The process exit/trace status caused by C<rpid> (see your systems
		1467	C<waitpid> and C<sys/wait.h> documentation for details).
627		1468
628	=back	1469	=back
629		1470
		1471	=head3 Examples
		1472
		1473	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1474
		1475	static void
		1476	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1477	{
		1478	ev_unloop (loop, EVUNLOOP_ALL);
		1479	}
		1480
		1481	struct ev_signal signal_watcher;
		1482	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1483	ev_signal_start (loop, &sigint_cb);
		1484
		1485
		1486	=head2 C<ev_stat> - did the file attributes just change?
		1487
		1488	This watches a filesystem path for attribute changes. That is, it calls
		1489	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1490	compared to the last time, invoking the callback if it did.
		1491
		1492	The path does not need to exist: changing from "path exists" to "path does
		1493	not exist" is a status change like any other. The condition "path does
		1494	not exist" is signified by the C<st_nlink> field being zero (which is
		1495	otherwise always forced to be at least one) and all the other fields of
		1496	the stat buffer having unspecified contents.
		1497
		1498	The path I<should> be absolute and I<must not> end in a slash. If it is
		1499	relative and your working directory changes, the behaviour is undefined.
		1500
		1501	Since there is no standard to do this, the portable implementation simply
		1502	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1503	can specify a recommended polling interval for this case. If you specify
		1504	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1505	unspecified default> value will be used (which you can expect to be around
		1506	five seconds, although this might change dynamically). Libev will also
		1507	impose a minimum interval which is currently around C<0.1>, but thats
		1508	usually overkill.
		1509
		1510	This watcher type is not meant for massive numbers of stat watchers,
		1511	as even with OS-supported change notifications, this can be
		1512	resource-intensive.
		1513
		1514	At the time of this writing, only the Linux inotify interface is
		1515	implemented (implementing kqueue support is left as an exercise for the
		1516	reader). Inotify will be used to give hints only and should not change the
		1517	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1518	to fall back to regular polling again even with inotify, but changes are
		1519	usually detected immediately, and if the file exists there will be no
		1520	polling.
		1521
		1522	=head3 Inotify
		1523
		1524	When C<inotify (7)> support has been compiled into libev (generally only
		1525	available on Linux) and present at runtime, it will be used to speed up
		1526	change detection where possible. The inotify descriptor will be created lazily
		1527	when the first C<ev_stat> watcher is being started.
		1528
		1529	Inotify presense does not change the semantics of C<ev_stat> watchers
		1530	except that changes might be detected earlier, and in some cases, to avoid
		1531	making regular C<stat> calls. Even in the presense of inotify support
		1532	there are many cases where libev has to resort to regular C<stat> polling.
		1533
		1534	(There is no support for kqueue, as apparently it cannot be used to
		1535	implement this functionality, due to the requirement of having a file
		1536	descriptor open on the object at all times).
		1537
		1538	=head3 The special problem of stat time resolution
		1539
		1540	The C<stat ()> syscall only supports full-second resolution portably, and
		1541	even on systems where the resolution is higher, many filesystems still
		1542	only support whole seconds.
		1543
		1544	That means that, if the time is the only thing that changes, you might
		1545	miss updates: on the first update, C<ev_stat> detects a change and calls
		1546	your callback, which does something. When there is another update within
		1547	the same second, C<ev_stat> will be unable to detect it.
		1548
		1549	The solution to this is to delay acting on a change for a second (or till
		1550	the next second boundary), using a roughly one-second delay C<ev_timer>
		1551	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1552	is added to work around small timing inconsistencies of some operating
		1553	systems.
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
		1556
		1557	=over 4
		1558
		1559	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1560
		1561	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1562
		1563	Configures the watcher to wait for status changes of the given
		1564	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1565	be detected and should normally be specified as C<0> to let libev choose
		1566	a suitable value. The memory pointed to by C<path> must point to the same
		1567	path for as long as the watcher is active.
		1568
		1569	The callback will be receive C<EV_STAT> when a change was detected,
		1570	relative to the attributes at the time the watcher was started (or the
		1571	last change was detected).
		1572
		1573	=item ev_stat_stat (ev_stat *)
		1574
		1575	Updates the stat buffer immediately with new values. If you change the
		1576	watched path in your callback, you could call this fucntion to avoid
		1577	detecting this change (while introducing a race condition). Can also be
		1578	useful simply to find out the new values.
		1579
		1580	=item ev_statdata attr [read-only]
		1581
		1582	The most-recently detected attributes of the file. Although the type is of
		1583	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1584	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1585	was some error while C<stat>ing the file.
		1586
		1587	=item ev_statdata prev [read-only]
		1588
		1589	The previous attributes of the file. The callback gets invoked whenever
		1590	C<prev> != C<attr>.
		1591
		1592	=item ev_tstamp interval [read-only]
		1593
		1594	The specified interval.
		1595
		1596	=item const char *path [read-only]
		1597
		1598	The filesystem path that is being watched.
		1599
		1600	=back
		1601
		1602	=head3 Examples
		1603
		1604	Example: Watch C</etc/passwd> for attribute changes.
		1605
		1606	static void
		1607	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1608	{
		1609	/* /etc/passwd changed in some way */
		1610	if (w->attr.st_nlink)
		1611	{
		1612	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1613	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1614	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1615	}
		1616	else
		1617	/* you shalt not abuse printf for puts */
		1618	puts ("wow, /etc/passwd is not there, expect problems. "
		1619	"if this is windows, they already arrived\n");
		1620	}
		1621
		1622	...
		1623	ev_stat passwd;
		1624
		1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1626	ev_stat_start (loop, &passwd);
		1627
		1628	Example: Like above, but additionally use a one-second delay so we do not
		1629	miss updates (however, frequent updates will delay processing, too, so
		1630	one might do the work both on C<ev_stat> callback invocation I<and> on
		1631	C<ev_timer> callback invocation).
		1632
		1633	static ev_stat passwd;
		1634	static ev_timer timer;
		1635
		1636	static void
		1637	timer_cb (EV_P_ ev_timer *w, int revents)
		1638	{
		1639	ev_timer_stop (EV_A_ w);
		1640
		1641	/* now it's one second after the most recent passwd change */
		1642	}
		1643
		1644	static void
		1645	stat_cb (EV_P_ ev_stat *w, int revents)
		1646	{
		1647	/* reset the one-second timer */
		1648	ev_timer_again (EV_A_ &timer);
		1649	}
		1650
		1651	...
		1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1653	ev_stat_start (loop, &passwd);
		1654	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1655
		1656
630	=head2 ev_idle - when you've got nothing better to do	1657	=head2 C<ev_idle> - when you've got nothing better to do...
631		1658
632	Idle watchers trigger events when there are no other I/O or timer (or	1659	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	1660	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	1661	count).
635	is idle all idle watchers are being called again and again - until	1662
		1663	That is, as long as your process is busy handling sockets or timeouts
		1664	(or even signals, imagine) of the same or higher priority it will not be
		1665	triggered. But when your process is idle (or only lower-priority watchers
		1666	are pending), the idle watchers are being called once per event loop
636	stopped, that is, or your process receives more events.	1667	iteration - until stopped, that is, or your process receives more events
		1668	and becomes busy again with higher priority stuff.
637		1669
638	The most noteworthy effect is that as long as any idle watchers are	1670	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.	1671	active, the process will not block when waiting for new events.
640		1672
641	Apart from keeping your process non-blocking (which is a useful	1673	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	1674	effect on its own sometimes), idle watchers are a good place to do
643	"pseudo-background processing", or delay processing stuff to after the	1675	"pseudo-background processing", or delay processing stuff to after the
644	event loop has handled all outstanding events.	1676	event loop has handled all outstanding events.
645		1677
		1678	=head3 Watcher-Specific Functions and Data Members
		1679
646	=over 4	1680	=over 4
647		1681
648	=item ev_idle_init (ev_signal *, callback)	1682	=item ev_idle_init (ev_signal *, callback)
649		1683
650	Initialises and configures the idle watcher - it has no parameters of any	1684	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,	1685	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1686	believe me.
653		1687
654	=back	1688	=back
655		1689
656	=head2 prepare and check - your hooks into the event loop	1690	=head3 Examples
657		1691
		1692	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1693	callback, free it. Also, use no error checking, as usual.
		1694
		1695	static void
		1696	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1697	{
		1698	free (w);
		1699	// now do something you wanted to do when the program has
		1700	// no longer asnything immediate to do.
		1701	}
		1702
		1703	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1704	ev_idle_init (idle_watcher, idle_cb);
		1705	ev_idle_start (loop, idle_cb);
		1706
		1707
		1708	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1709
658	Prepare and check watchers usually (but not always) are used in	1710	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1711	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1712	afterwards.
661		1713
		1714	You I<must not> call C<ev_loop> or similar functions that enter
		1715	the current event loop from either C<ev_prepare> or C<ev_check>
		1716	watchers. Other loops than the current one are fine, however. The
		1717	rationale behind this is that you do not need to check for recursion in
		1718	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1719	C<ev_check> so if you have one watcher of each kind they will always be
		1720	called in pairs bracketing the blocking call.
		1721
662	Their main purpose is to integrate other event mechanisms into libev. This	1722	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	1723	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.	1724	variable changes, implement your own watchers, integrate net-snmp or a
		1725	coroutine library and lots more. They are also occasionally useful if
		1726	you cache some data and want to flush it before blocking (for example,
		1727	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1728	watcher).
665		1729
666	This is done by examining in each prepare call which file descriptors need	1730	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	1731	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	1732	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	1733	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)	1734	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1735	and stopping them) and call back into the library. The I/O and timer
		1736	callbacks will never actually be called (but must be valid nevertheless,
		1737	because you never know, you know?).
672		1738
673	As another example, the perl Coro module uses these hooks to integrate	1739	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1740	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1741	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1742	are ready to run (it's actually more complicated: it only runs coroutines
		1743	with priority higher than or equal to the event loop and one coroutine
		1744	of lower priority, but only once, using idle watchers to keep the event
		1745	loop from blocking if lower-priority coroutines are active, thus mapping
		1746	low-priority coroutines to idle/background tasks).
		1747
		1748	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1749	priority, to ensure that they are being run before any other watchers
		1750	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1751	too) should not activate ("feed") events into libev. While libev fully
		1752	supports this, they will be called before other C<ev_check> watchers
		1753	did their job. As C<ev_check> watchers are often used to embed other
		1754	(non-libev) event loops those other event loops might be in an unusable
		1755	state until their C<ev_check> watcher ran (always remind yourself to
		1756	coexist peacefully with others).
		1757
		1758	=head3 Watcher-Specific Functions and Data Members
677		1759
678	=over 4	1760	=over 4
679		1761
680	=item ev_prepare_init (ev_prepare *, callback)	1762	=item ev_prepare_init (ev_prepare *, callback)
681		1763
682	=item ev_check_init (ev_check *, callback)	1764	=item ev_check_init (ev_check *, callback)
683		1765
684	Initialises and configures the prepare or check watcher - they have no	1766	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>	1767	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1768	macros, but using them is utterly, utterly and completely pointless.
687		1769
688	=back	1770	=back
689		1771
		1772	=head3 Examples
		1773
		1774	There are a number of principal ways to embed other event loops or modules
		1775	into libev. Here are some ideas on how to include libadns into libev
		1776	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1777	use for an actually working example. Another Perl module named C<EV::Glib>
		1778	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1779	into the Glib event loop).
		1780
		1781	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1782	and in a check watcher, destroy them and call into libadns. What follows
		1783	is pseudo-code only of course. This requires you to either use a low
		1784	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1785	the callbacks for the IO/timeout watchers might not have been called yet.
		1786
		1787	static ev_io iow [nfd];
		1788	static ev_timer tw;
		1789
		1790	static void
		1791	io_cb (ev_loop *loop, ev_io *w, int revents)
		1792	{
		1793	}
		1794
		1795	// create io watchers for each fd and a timer before blocking
		1796	static void
		1797	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1798	{
		1799	int timeout = 3600000;
		1800	struct pollfd fds [nfd];
		1801	// actual code will need to loop here and realloc etc.
		1802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1803
		1804	/* the callback is illegal, but won't be called as we stop during check */
		1805	ev_timer_init (&tw, 0, timeout * 1e-3);
		1806	ev_timer_start (loop, &tw);
		1807
		1808	// create one ev_io per pollfd
		1809	for (int i = 0; i < nfd; ++i)
		1810	{
		1811	ev_io_init (iow + i, io_cb, fds [i].fd,
		1812	((fds [i].events & POLLIN ? EV_READ : 0)
		1813	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1814
		1815	fds [i].revents = 0;
		1816	ev_io_start (loop, iow + i);
		1817	}
		1818	}
		1819
		1820	// stop all watchers after blocking
		1821	static void
		1822	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1823	{
		1824	ev_timer_stop (loop, &tw);
		1825
		1826	for (int i = 0; i < nfd; ++i)
		1827	{
		1828	// set the relevant poll flags
		1829	// could also call adns_processreadable etc. here
		1830	struct pollfd *fd = fds + i;
		1831	int revents = ev_clear_pending (iow + i);
		1832	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1833	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1834
		1835	// now stop the watcher
		1836	ev_io_stop (loop, iow + i);
		1837	}
		1838
		1839	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1840	}
		1841
		1842	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1843	in the prepare watcher and would dispose of the check watcher.
		1844
		1845	Method 3: If the module to be embedded supports explicit event
		1846	notification (adns does), you can also make use of the actual watcher
		1847	callbacks, and only destroy/create the watchers in the prepare watcher.
		1848
		1849	static void
		1850	timer_cb (EV_P_ ev_timer *w, int revents)
		1851	{
		1852	adns_state ads = (adns_state)w->data;
		1853	update_now (EV_A);
		1854
		1855	adns_processtimeouts (ads, &tv_now);
		1856	}
		1857
		1858	static void
		1859	io_cb (EV_P_ ev_io *w, int revents)
		1860	{
		1861	adns_state ads = (adns_state)w->data;
		1862	update_now (EV_A);
		1863
		1864	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1865	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1866	}
		1867
		1868	// do not ever call adns_afterpoll
		1869
		1870	Method 4: Do not use a prepare or check watcher because the module you
		1871	want to embed is too inflexible to support it. Instead, youc na override
		1872	their poll function. The drawback with this solution is that the main
		1873	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1874	this.
		1875
		1876	static gint
		1877	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1878	{
		1879	int got_events = 0;
		1880
		1881	for (n = 0; n < nfds; ++n)
		1882	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1883
		1884	if (timeout >= 0)
		1885	// create/start timer
		1886
		1887	// poll
		1888	ev_loop (EV_A_ 0);
		1889
		1890	// stop timer again
		1891	if (timeout >= 0)
		1892	ev_timer_stop (EV_A_ &to);
		1893
		1894	// stop io watchers again - their callbacks should have set
		1895	for (n = 0; n < nfds; ++n)
		1896	ev_io_stop (EV_A_ iow [n]);
		1897
		1898	return got_events;
		1899	}
		1900
		1901
		1902	=head2 C<ev_embed> - when one backend isn't enough...
		1903
		1904	This is a rather advanced watcher type that lets you embed one event loop
		1905	into another (currently only C<ev_io> events are supported in the embedded
		1906	loop, other types of watchers might be handled in a delayed or incorrect
		1907	fashion and must not be used).
		1908
		1909	There are primarily two reasons you would want that: work around bugs and
		1910	prioritise I/O.
		1911
		1912	As an example for a bug workaround, the kqueue backend might only support
		1913	sockets on some platform, so it is unusable as generic backend, but you
		1914	still want to make use of it because you have many sockets and it scales
		1915	so nicely. In this case, you would create a kqueue-based loop and embed it
		1916	into your default loop (which might use e.g. poll). Overall operation will
		1917	be a bit slower because first libev has to poll and then call kevent, but
		1918	at least you can use both at what they are best.
		1919
		1920	As for prioritising I/O: rarely you have the case where some fds have
		1921	to be watched and handled very quickly (with low latency), and even
		1922	priorities and idle watchers might have too much overhead. In this case
		1923	you would put all the high priority stuff in one loop and all the rest in
		1924	a second one, and embed the second one in the first.
		1925
		1926	As long as the watcher is active, the callback will be invoked every time
		1927	there might be events pending in the embedded loop. The callback must then
		1928	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1929	their callbacks (you could also start an idle watcher to give the embedded
		1930	loop strictly lower priority for example). You can also set the callback
		1931	to C<0>, in which case the embed watcher will automatically execute the
		1932	embedded loop sweep.
		1933
		1934	As long as the watcher is started it will automatically handle events. The
		1935	callback will be invoked whenever some events have been handled. You can
		1936	set the callback to C<0> to avoid having to specify one if you are not
		1937	interested in that.
		1938
		1939	Also, there have not currently been made special provisions for forking:
		1940	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1941	but you will also have to stop and restart any C<ev_embed> watchers
		1942	yourself.
		1943
		1944	Unfortunately, not all backends are embeddable, only the ones returned by
		1945	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1946	portable one.
		1947
		1948	So when you want to use this feature you will always have to be prepared
		1949	that you cannot get an embeddable loop. The recommended way to get around
		1950	this is to have a separate variables for your embeddable loop, try to
		1951	create it, and if that fails, use the normal loop for everything.
		1952
		1953	=head3 Watcher-Specific Functions and Data Members
		1954
		1955	=over 4
		1956
		1957	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1958
		1959	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1960
		1961	Configures the watcher to embed the given loop, which must be
		1962	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1963	invoked automatically, otherwise it is the responsibility of the callback
		1964	to invoke it (it will continue to be called until the sweep has been done,
		1965	if you do not want thta, you need to temporarily stop the embed watcher).
		1966
		1967	=item ev_embed_sweep (loop, ev_embed *)
		1968
		1969	Make a single, non-blocking sweep over the embedded loop. This works
		1970	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1971	apropriate way for embedded loops.
		1972
		1973	=item struct ev_loop *other [read-only]
		1974
		1975	The embedded event loop.
		1976
		1977	=back
		1978
		1979	=head3 Examples
		1980
		1981	Example: Try to get an embeddable event loop and embed it into the default
		1982	event loop. If that is not possible, use the default loop. The default
		1983	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1984	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1985	used).
		1986
		1987	struct ev_loop *loop_hi = ev_default_init (0);
		1988	struct ev_loop *loop_lo = 0;
		1989	struct ev_embed embed;
		1990
		1991	// see if there is a chance of getting one that works
		1992	// (remember that a flags value of 0 means autodetection)
		1993	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1994	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1995	: 0;
		1996
		1997	// if we got one, then embed it, otherwise default to loop_hi
		1998	if (loop_lo)
		1999	{
		2000	ev_embed_init (&embed, 0, loop_lo);
		2001	ev_embed_start (loop_hi, &embed);
		2002	}
		2003	else
		2004	loop_lo = loop_hi;
		2005
		2006	Example: Check if kqueue is available but not recommended and create
		2007	a kqueue backend for use with sockets (which usually work with any
		2008	kqueue implementation). Store the kqueue/socket-only event loop in
		2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2010
		2011	struct ev_loop *loop = ev_default_init (0);
		2012	struct ev_loop *loop_socket = 0;
		2013	struct ev_embed embed;
		2014
		2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2017	{
		2018	ev_embed_init (&embed, 0, loop_socket);
		2019	ev_embed_start (loop, &embed);
		2020	}
		2021
		2022	if (!loop_socket)
		2023	loop_socket = loop;
		2024
		2025	// now use loop_socket for all sockets, and loop for everything else
		2026
		2027
		2028	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2029
		2030	Fork watchers are called when a C<fork ()> was detected (usually because
		2031	whoever is a good citizen cared to tell libev about it by calling
		2032	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2033	event loop blocks next and before C<ev_check> watchers are being called,
		2034	and only in the child after the fork. If whoever good citizen calling
		2035	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2036	handlers will be invoked, too, of course.
		2037
		2038	=head3 Watcher-Specific Functions and Data Members
		2039
		2040	=over 4
		2041
		2042	=item ev_fork_init (ev_signal *, callback)
		2043
		2044	Initialises and configures the fork watcher - it has no parameters of any
		2045	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2046	believe me.
		2047
		2048	=back
		2049
		2050
690	=head1 OTHER FUNCTIONS	2051	=head1 OTHER FUNCTIONS
691		2052
692	There are some other fucntions of possible interest. Described. Here. Now.	2053	There are some other functions of possible interest. Described. Here. Now.
693		2054
694	=over 4	2055	=over 4
695		2056
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2057	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		2058
698	This function combines a simple timer and an I/O watcher, calls your	2059	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	2060	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	2061	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	2062	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	2063	more watchers yourself.
703		2064
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	2065	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	2066	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	2067	C<events> set will be craeted and started.
707		2068
708	If C<timeout> is less than 0, then no timeout watcher will be	2069	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	2070	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	2071	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		2072	dubious value.
711		2073
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	2074	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,	2075	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>:	2076	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		2077	value passed to C<ev_once>:
715		2078
716	static void stdin_ready (int revents, void *arg)	2079	static void stdin_ready (int revents, void *arg)
717	{	2080	{
718	if (revents & EV_TIMEOUT)	2081	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	2082	/* doh, nothing entered */;
720	else if (revents & EV_READ)	2083	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	2084	/* stdin might have data for us, joy! */;
722	}	2085	}
723		2086
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	2087	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		2088
726	=item ev_feed_event (loop, watcher, int events)	2089	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		2090
728	Feeds the given event set into the event loop, as if the specified event	2091	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	2092	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	2093	initialised but not necessarily started event watcher).
731		2094
732	=item ev_feed_fd_event (loop, int fd, int revents)	2095	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		2096
734	Feed an event on the given fd, as if a file descriptor backend detected it.	2097	Feed an event on the given fd, as if a file descriptor backend detected
		2098	the given events it.
735		2099
736	=item ev_feed_signal_event (loop, int signum)	2100	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		2101
738	Feed an event as if the given signal occured (loop must be the default loop!).	2102	Feed an event as if the given signal occured (C<loop> must be the default
		2103	loop!).
739		2104
740	=back	2105	=back
741		2106
		2107
		2108	=head1 LIBEVENT EMULATION
		2109
		2110	Libev offers a compatibility emulation layer for libevent. It cannot
		2111	emulate the internals of libevent, so here are some usage hints:
		2112
		2113	=over 4
		2114
		2115	=item * Use it by including <event.h>, as usual.
		2116
		2117	=item * The following members are fully supported: ev_base, ev_callback,
		2118	ev_arg, ev_fd, ev_res, ev_events.
		2119
		2120	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		2121	maintained by libev, it does not work exactly the same way as in libevent (consider
		2122	it a private API).
		2123
		2124	=item * Priorities are not currently supported. Initialising priorities
		2125	will fail and all watchers will have the same priority, even though there
		2126	is an ev_pri field.
		2127
		2128	=item * Other members are not supported.
		2129
		2130	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		2131	to use the libev header file and library.
		2132
		2133	=back
		2134
		2135	=head1 C++ SUPPORT
		2136
		2137	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2138	you to use some convinience methods to start/stop watchers and also change
		2139	the callback model to a model using method callbacks on objects.
		2140
		2141	To use it,
		2142
		2143	#include <ev++.h>
		2144
		2145	This automatically includes F<ev.h> and puts all of its definitions (many
		2146	of them macros) into the global namespace. All C++ specific things are
		2147	put into the C<ev> namespace. It should support all the same embedding
		2148	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2149
		2150	Care has been taken to keep the overhead low. The only data member the C++
		2151	classes add (compared to plain C-style watchers) is the event loop pointer
		2152	that the watcher is associated with (or no additional members at all if
		2153	you disable C<EV_MULTIPLICITY> when embedding libev).
		2154
		2155	Currently, functions, and static and non-static member functions can be
		2156	used as callbacks. Other types should be easy to add as long as they only
		2157	need one additional pointer for context. If you need support for other
		2158	types of functors please contact the author (preferably after implementing
		2159	it).
		2160
		2161	Here is a list of things available in the C<ev> namespace:
		2162
		2163	=over 4
		2164
		2165	=item C<ev::READ>, C<ev::WRITE> etc.
		2166
		2167	These are just enum values with the same values as the C<EV_READ> etc.
		2168	macros from F<ev.h>.
		2169
		2170	=item C<ev::tstamp>, C<ev::now>
		2171
		2172	Aliases to the same types/functions as with the C<ev_> prefix.
		2173
		2174	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2175
		2176	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2177	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2178	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2179	defines by many implementations.
		2180
		2181	All of those classes have these methods:
		2182
		2183	=over 4
		2184
		2185	=item ev::TYPE::TYPE ()
		2186
		2187	=item ev::TYPE::TYPE (struct ev_loop *)
		2188
		2189	=item ev::TYPE::~TYPE
		2190
		2191	The constructor (optionally) takes an event loop to associate the watcher
		2192	with. If it is omitted, it will use C<EV_DEFAULT>.
		2193
		2194	The constructor calls C<ev_init> for you, which means you have to call the
		2195	C<set> method before starting it.
		2196
		2197	It will not set a callback, however: You have to call the templated C<set>
		2198	method to set a callback before you can start the watcher.
		2199
		2200	(The reason why you have to use a method is a limitation in C++ which does
		2201	not allow explicit template arguments for constructors).
		2202
		2203	The destructor automatically stops the watcher if it is active.
		2204
		2205	=item w->set<class, &class::method> (object *)
		2206
		2207	This method sets the callback method to call. The method has to have a
		2208	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2209	first argument and the C<revents> as second. The object must be given as
		2210	parameter and is stored in the C<data> member of the watcher.
		2211
		2212	This method synthesizes efficient thunking code to call your method from
		2213	the C callback that libev requires. If your compiler can inline your
		2214	callback (i.e. it is visible to it at the place of the C<set> call and
		2215	your compiler is good :), then the method will be fully inlined into the
		2216	thunking function, making it as fast as a direct C callback.
		2217
		2218	Example: simple class declaration and watcher initialisation
		2219
		2220	struct myclass
		2221	{
		2222	void io_cb (ev::io &w, int revents) { }
		2223	}
		2224
		2225	myclass obj;
		2226	ev::io iow;
		2227	iow.set <myclass, &myclass::io_cb> (&obj);
		2228
		2229	=item w->set<function> (void *data = 0)
		2230
		2231	Also sets a callback, but uses a static method or plain function as
		2232	callback. The optional C<data> argument will be stored in the watcher's
		2233	C<data> member and is free for you to use.
		2234
		2235	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2236
		2237	See the method-C<set> above for more details.
		2238
		2239	Example:
		2240
		2241	static void io_cb (ev::io &w, int revents) { }
		2242	iow.set <io_cb> ();
		2243
		2244	=item w->set (struct ev_loop *)
		2245
		2246	Associates a different C<struct ev_loop> with this watcher. You can only
		2247	do this when the watcher is inactive (and not pending either).
		2248
		2249	=item w->set ([args])
		2250
		2251	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2252	called at least once. Unlike the C counterpart, an active watcher gets
		2253	automatically stopped and restarted when reconfiguring it with this
		2254	method.
		2255
		2256	=item w->start ()
		2257
		2258	Starts the watcher. Note that there is no C<loop> argument, as the
		2259	constructor already stores the event loop.
		2260
		2261	=item w->stop ()
		2262
		2263	Stops the watcher if it is active. Again, no C<loop> argument.
		2264
		2265	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2266
		2267	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2268	C<ev_TYPE_again> function.
		2269
		2270	=item w->sweep () (C<ev::embed> only)
		2271
		2272	Invokes C<ev_embed_sweep>.
		2273
		2274	=item w->update () (C<ev::stat> only)
		2275
		2276	Invokes C<ev_stat_stat>.
		2277
		2278	=back
		2279
		2280	=back
		2281
		2282	Example: Define a class with an IO and idle watcher, start one of them in
		2283	the constructor.
		2284
		2285	class myclass
		2286	{
		2287	ev_io io; void io_cb (ev::io &w, int revents);
		2288	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2289
		2290	myclass ();
		2291	}
		2292
		2293	myclass::myclass (int fd)
		2294	{
		2295	io .set <myclass, &myclass::io_cb > (this);
		2296	idle.set <myclass, &myclass::idle_cb> (this);
		2297
		2298	io.start (fd, ev::READ);
		2299	}
		2300
		2301
		2302	=head1 MACRO MAGIC
		2303
		2304	Libev can be compiled with a variety of options, the most fundamantal
		2305	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2306	functions and callbacks have an initial C<struct ev_loop *> argument.
		2307
		2308	To make it easier to write programs that cope with either variant, the
		2309	following macros are defined:
		2310
		2311	=over 4
		2312
		2313	=item C<EV_A>, C<EV_A_>
		2314
		2315	This provides the loop I<argument> for functions, if one is required ("ev
		2316	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2317	C<EV_A_> is used when other arguments are following. Example:
		2318
		2319	ev_unref (EV_A);
		2320	ev_timer_add (EV_A_ watcher);
		2321	ev_loop (EV_A_ 0);
		2322
		2323	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2324	which is often provided by the following macro.
		2325
		2326	=item C<EV_P>, C<EV_P_>
		2327
		2328	This provides the loop I<parameter> for functions, if one is required ("ev
		2329	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2330	C<EV_P_> is used when other parameters are following. Example:
		2331
		2332	// this is how ev_unref is being declared
		2333	static void ev_unref (EV_P);
		2334
		2335	// this is how you can declare your typical callback
		2336	static void cb (EV_P_ ev_timer *w, int revents)
		2337
		2338	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2339	suitable for use with C<EV_A>.
		2340
		2341	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2342
		2343	Similar to the other two macros, this gives you the value of the default
		2344	loop, if multiple loops are supported ("ev loop default").
		2345
		2346	=back
		2347
		2348	Example: Declare and initialise a check watcher, utilising the above
		2349	macros so it will work regardless of whether multiple loops are supported
		2350	or not.
		2351
		2352	static void
		2353	check_cb (EV_P_ ev_timer *w, int revents)
		2354	{
		2355	ev_check_stop (EV_A_ w);
		2356	}
		2357
		2358	ev_check check;
		2359	ev_check_init (&check, check_cb);
		2360	ev_check_start (EV_DEFAULT_ &check);
		2361	ev_loop (EV_DEFAULT_ 0);
		2362
		2363	=head1 EMBEDDING
		2364
		2365	Libev can (and often is) directly embedded into host
		2366	applications. Examples of applications that embed it include the Deliantra
		2367	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2368	and rxvt-unicode.
		2369
		2370	The goal is to enable you to just copy the necessary files into your
		2371	source directory without having to change even a single line in them, so
		2372	you can easily upgrade by simply copying (or having a checked-out copy of
		2373	libev somewhere in your source tree).
		2374
		2375	=head2 FILESETS
		2376
		2377	Depending on what features you need you need to include one or more sets of files
		2378	in your app.
		2379
		2380	=head3 CORE EVENT LOOP
		2381
		2382	To include only the libev core (all the C<ev_*> functions), with manual
		2383	configuration (no autoconf):
		2384
		2385	#define EV_STANDALONE 1
		2386	#include "ev.c"
		2387
		2388	This will automatically include F<ev.h>, too, and should be done in a
		2389	single C source file only to provide the function implementations. To use
		2390	it, do the same for F<ev.h> in all files wishing to use this API (best
		2391	done by writing a wrapper around F<ev.h> that you can include instead and
		2392	where you can put other configuration options):
		2393
		2394	#define EV_STANDALONE 1
		2395	#include "ev.h"
		2396
		2397	Both header files and implementation files can be compiled with a C++
		2398	compiler (at least, thats a stated goal, and breakage will be treated
		2399	as a bug).
		2400
		2401	You need the following files in your source tree, or in a directory
		2402	in your include path (e.g. in libev/ when using -Ilibev):
		2403
		2404	ev.h
		2405	ev.c
		2406	ev_vars.h
		2407	ev_wrap.h
		2408
		2409	ev_win32.c required on win32 platforms only
		2410
		2411	ev_select.c only when select backend is enabled (which is enabled by default)
		2412	ev_poll.c only when poll backend is enabled (disabled by default)
		2413	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2414	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2415	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2416
		2417	F<ev.c> includes the backend files directly when enabled, so you only need
		2418	to compile this single file.
		2419
		2420	=head3 LIBEVENT COMPATIBILITY API
		2421
		2422	To include the libevent compatibility API, also include:
		2423
		2424	#include "event.c"
		2425
		2426	in the file including F<ev.c>, and:
		2427
		2428	#include "event.h"
		2429
		2430	in the files that want to use the libevent API. This also includes F<ev.h>.
		2431
		2432	You need the following additional files for this:
		2433
		2434	event.h
		2435	event.c
		2436
		2437	=head3 AUTOCONF SUPPORT
		2438
		2439	Instead of using C<EV_STANDALONE=1> and providing your config in
		2440	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2441	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2442	include F<config.h> and configure itself accordingly.
		2443
		2444	For this of course you need the m4 file:
		2445
		2446	libev.m4
		2447
		2448	=head2 PREPROCESSOR SYMBOLS/MACROS
		2449
		2450	Libev can be configured via a variety of preprocessor symbols you have to define
		2451	before including any of its files. The default is not to build for multiplicity
		2452	and only include the select backend.
		2453
		2454	=over 4
		2455
		2456	=item EV_STANDALONE
		2457
		2458	Must always be C<1> if you do not use autoconf configuration, which
		2459	keeps libev from including F<config.h>, and it also defines dummy
		2460	implementations for some libevent functions (such as logging, which is not
		2461	supported). It will also not define any of the structs usually found in
		2462	F<event.h> that are not directly supported by the libev core alone.
		2463
		2464	=item EV_USE_MONOTONIC
		2465
		2466	If defined to be C<1>, libev will try to detect the availability of the
		2467	monotonic clock option at both compiletime and runtime. Otherwise no use
		2468	of the monotonic clock option will be attempted. If you enable this, you
		2469	usually have to link against librt or something similar. Enabling it when
		2470	the functionality isn't available is safe, though, although you have
		2471	to make sure you link against any libraries where the C<clock_gettime>
		2472	function is hiding in (often F<-lrt>).
		2473
		2474	=item EV_USE_REALTIME
		2475
		2476	If defined to be C<1>, libev will try to detect the availability of the
		2477	realtime clock option at compiletime (and assume its availability at
		2478	runtime if successful). Otherwise no use of the realtime clock option will
		2479	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2480	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2481	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2482
		2483	=item EV_USE_NANOSLEEP
		2484
		2485	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2486	and will use it for delays. Otherwise it will use C<select ()>.
		2487
		2488	=item EV_USE_SELECT
		2489
		2490	If undefined or defined to be C<1>, libev will compile in support for the
		2491	C<select>(2) backend. No attempt at autodetection will be done: if no
		2492	other method takes over, select will be it. Otherwise the select backend
		2493	will not be compiled in.
		2494
		2495	=item EV_SELECT_USE_FD_SET
		2496
		2497	If defined to C<1>, then the select backend will use the system C<fd_set>
		2498	structure. This is useful if libev doesn't compile due to a missing
		2499	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2500	exotic systems. This usually limits the range of file descriptors to some
		2501	low limit such as 1024 or might have other limitations (winsocket only
		2502	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2503	influence the size of the C<fd_set> used.
		2504
		2505	=item EV_SELECT_IS_WINSOCKET
		2506
		2507	When defined to C<1>, the select backend will assume that
		2508	select/socket/connect etc. don't understand file descriptors but
		2509	wants osf handles on win32 (this is the case when the select to
		2510	be used is the winsock select). This means that it will call
		2511	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2512	it is assumed that all these functions actually work on fds, even
		2513	on win32. Should not be defined on non-win32 platforms.
		2514
		2515	=item EV_FD_TO_WIN32_HANDLE
		2516
		2517	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2518	file descriptors to socket handles. When not defining this symbol (the
		2519	default), then libev will call C<_get_osfhandle>, which is usually
		2520	correct. In some cases, programs use their own file descriptor management,
		2521	in which case they can provide this function to map fds to socket handles.
		2522
		2523	=item EV_USE_POLL
		2524
		2525	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2526	backend. Otherwise it will be enabled on non-win32 platforms. It
		2527	takes precedence over select.
		2528
		2529	=item EV_USE_EPOLL
		2530
		2531	If defined to be C<1>, libev will compile in support for the Linux
		2532	C<epoll>(7) backend. Its availability will be detected at runtime,
		2533	otherwise another method will be used as fallback. This is the
		2534	preferred backend for GNU/Linux systems.
		2535
		2536	=item EV_USE_KQUEUE
		2537
		2538	If defined to be C<1>, libev will compile in support for the BSD style
		2539	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2540	otherwise another method will be used as fallback. This is the preferred
		2541	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2542	supports some types of fds correctly (the only platform we found that
		2543	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2544	not be used unless explicitly requested. The best way to use it is to find
		2545	out whether kqueue supports your type of fd properly and use an embedded
		2546	kqueue loop.
		2547
		2548	=item EV_USE_PORT
		2549
		2550	If defined to be C<1>, libev will compile in support for the Solaris
		2551	10 port style backend. Its availability will be detected at runtime,
		2552	otherwise another method will be used as fallback. This is the preferred
		2553	backend for Solaris 10 systems.
		2554
		2555	=item EV_USE_DEVPOLL
		2556
		2557	reserved for future expansion, works like the USE symbols above.
		2558
		2559	=item EV_USE_INOTIFY
		2560
		2561	If defined to be C<1>, libev will compile in support for the Linux inotify
		2562	interface to speed up C<ev_stat> watchers. Its actual availability will
		2563	be detected at runtime.
		2564
		2565	=item EV_H
		2566
		2567	The name of the F<ev.h> header file used to include it. The default if
		2568	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2569	used to virtually rename the F<ev.h> header file in case of conflicts.
		2570
		2571	=item EV_CONFIG_H
		2572
		2573	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2574	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2575	C<EV_H>, above.
		2576
		2577	=item EV_EVENT_H
		2578
		2579	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2580	of how the F<event.h> header can be found, the default is C<"event.h">.
		2581
		2582	=item EV_PROTOTYPES
		2583
		2584	If defined to be C<0>, then F<ev.h> will not define any function
		2585	prototypes, but still define all the structs and other symbols. This is
		2586	occasionally useful if you want to provide your own wrapper functions
		2587	around libev functions.
		2588
		2589	=item EV_MULTIPLICITY
		2590
		2591	If undefined or defined to C<1>, then all event-loop-specific functions
		2592	will have the C<struct ev_loop *> as first argument, and you can create
		2593	additional independent event loops. Otherwise there will be no support
		2594	for multiple event loops and there is no first event loop pointer
		2595	argument. Instead, all functions act on the single default loop.
		2596
		2597	=item EV_MINPRI
		2598
		2599	=item EV_MAXPRI
		2600
		2601	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2602	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2603	provide for more priorities by overriding those symbols (usually defined
		2604	to be C<-2> and C<2>, respectively).
		2605
		2606	When doing priority-based operations, libev usually has to linearly search
		2607	all the priorities, so having many of them (hundreds) uses a lot of space
		2608	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2609	fine.
		2610
		2611	If your embedding app does not need any priorities, defining these both to
		2612	C<0> will save some memory and cpu.
		2613
		2614	=item EV_PERIODIC_ENABLE
		2615
		2616	If undefined or defined to be C<1>, then periodic timers are supported. If
		2617	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2618	code.
		2619
		2620	=item EV_IDLE_ENABLE
		2621
		2622	If undefined or defined to be C<1>, then idle watchers are supported. If
		2623	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2624	code.
		2625
		2626	=item EV_EMBED_ENABLE
		2627
		2628	If undefined or defined to be C<1>, then embed watchers are supported. If
		2629	defined to be C<0>, then they are not.
		2630
		2631	=item EV_STAT_ENABLE
		2632
		2633	If undefined or defined to be C<1>, then stat watchers are supported. If
		2634	defined to be C<0>, then they are not.
		2635
		2636	=item EV_FORK_ENABLE
		2637
		2638	If undefined or defined to be C<1>, then fork watchers are supported. If
		2639	defined to be C<0>, then they are not.
		2640
		2641	=item EV_MINIMAL
		2642
		2643	If you need to shave off some kilobytes of code at the expense of some
		2644	speed, define this symbol to C<1>. Currently only used for gcc to override
		2645	some inlining decisions, saves roughly 30% codesize of amd64.
		2646
		2647	=item EV_PID_HASHSIZE
		2648
		2649	C<ev_child> watchers use a small hash table to distribute workload by
		2650	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2651	than enough. If you need to manage thousands of children you might want to
		2652	increase this value (I<must> be a power of two).
		2653
		2654	=item EV_INOTIFY_HASHSIZE
		2655
		2656	C<ev_stat> watchers use a small hash table to distribute workload by
		2657	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2658	usually more than enough. If you need to manage thousands of C<ev_stat>
		2659	watchers you might want to increase this value (I<must> be a power of
		2660	two).
		2661
		2662	=item EV_COMMON
		2663
		2664	By default, all watchers have a C<void *data> member. By redefining
		2665	this macro to a something else you can include more and other types of
		2666	members. You have to define it each time you include one of the files,
		2667	though, and it must be identical each time.
		2668
		2669	For example, the perl EV module uses something like this:
		2670
		2671	#define EV_COMMON \
		2672	SV *self; /* contains this struct */ \
		2673	SV *cb_sv, *fh /* note no trailing ";" */
		2674
		2675	=item EV_CB_DECLARE (type)
		2676
		2677	=item EV_CB_INVOKE (watcher, revents)
		2678
		2679	=item ev_set_cb (ev, cb)
		2680
		2681	Can be used to change the callback member declaration in each watcher,
		2682	and the way callbacks are invoked and set. Must expand to a struct member
		2683	definition and a statement, respectively. See the F<ev.h> header file for
		2684	their default definitions. One possible use for overriding these is to
		2685	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2686	method calls instead of plain function calls in C++.
		2687
		2688	=head2 EXPORTED API SYMBOLS
		2689
		2690	If you need to re-export the API (e.g. via a dll) and you need a list of
		2691	exported symbols, you can use the provided F<Symbol.*> files which list
		2692	all public symbols, one per line:
		2693
		2694	Symbols.ev for libev proper
		2695	Symbols.event for the libevent emulation
		2696
		2697	This can also be used to rename all public symbols to avoid clashes with
		2698	multiple versions of libev linked together (which is obviously bad in
		2699	itself, but sometimes it is inconvinient to avoid this).
		2700
		2701	A sed command like this will create wrapper C<#define>'s that you need to
		2702	include before including F<ev.h>:
		2703
		2704	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2705
		2706	This would create a file F<wrap.h> which essentially looks like this:
		2707
		2708	#define ev_backend myprefix_ev_backend
		2709	#define ev_check_start myprefix_ev_check_start
		2710	#define ev_check_stop myprefix_ev_check_stop
		2711	...
		2712
		2713	=head2 EXAMPLES
		2714
		2715	For a real-world example of a program the includes libev
		2716	verbatim, you can have a look at the EV perl module
		2717	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2718	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2719	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2720	will be compiled. It is pretty complex because it provides its own header
		2721	file.
		2722
		2723	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2724	that everybody includes and which overrides some configure choices:
		2725
		2726	#define EV_MINIMAL 1
		2727	#define EV_USE_POLL 0
		2728	#define EV_MULTIPLICITY 0
		2729	#define EV_PERIODIC_ENABLE 0
		2730	#define EV_STAT_ENABLE 0
		2731	#define EV_FORK_ENABLE 0
		2732	#define EV_CONFIG_H <config.h>
		2733	#define EV_MINPRI 0
		2734	#define EV_MAXPRI 0
		2735
		2736	#include "ev++.h"
		2737
		2738	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2739
		2740	#include "ev_cpp.h"
		2741	#include "ev.c"
		2742
		2743
		2744	=head1 COMPLEXITIES
		2745
		2746	In this section the complexities of (many of) the algorithms used inside
		2747	libev will be explained. For complexity discussions about backends see the
		2748	documentation for C<ev_default_init>.
		2749
		2750	All of the following are about amortised time: If an array needs to be
		2751	extended, libev needs to realloc and move the whole array, but this
		2752	happens asymptotically never with higher number of elements, so O(1) might
		2753	mean it might do a lengthy realloc operation in rare cases, but on average
		2754	it is much faster and asymptotically approaches constant time.
		2755
		2756	=over 4
		2757
		2758	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2759
		2760	This means that, when you have a watcher that triggers in one hour and
		2761	there are 100 watchers that would trigger before that then inserting will
		2762	have to skip roughly seven (C<ld 100>) of these watchers.
		2763
		2764	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2765
		2766	That means that changing a timer costs less than removing/adding them
		2767	as only the relative motion in the event queue has to be paid for.
		2768
		2769	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2770
		2771	These just add the watcher into an array or at the head of a list.
		2772
		2773	=item Stopping check/prepare/idle watchers: O(1)
		2774
		2775	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2776
		2777	These watchers are stored in lists then need to be walked to find the
		2778	correct watcher to remove. The lists are usually short (you don't usually
		2779	have many watchers waiting for the same fd or signal).
		2780
		2781	=item Finding the next timer in each loop iteration: O(1)
		2782
		2783	By virtue of using a binary heap, the next timer is always found at the
		2784	beginning of the storage array.
		2785
		2786	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2787
		2788	A change means an I/O watcher gets started or stopped, which requires
		2789	libev to recalculate its status (and possibly tell the kernel, depending
		2790	on backend and wether C<ev_io_set> was used).
		2791
		2792	=item Activating one watcher (putting it into the pending state): O(1)
		2793
		2794	=item Priority handling: O(number_of_priorities)
		2795
		2796	Priorities are implemented by allocating some space for each
		2797	priority. When doing priority-based operations, libev usually has to
		2798	linearly search all the priorities, but starting/stopping and activating
		2799	watchers becomes O(1) w.r.t. prioritiy handling.
		2800
		2801	=back
		2802
		2803
		2804	=head1 Win32 platform limitations and workarounds
		2805
		2806	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2807	requires, and its I/O model is fundamentally incompatible with the POSIX
		2808	model. Libev still offers limited functionality on this platform in
		2809	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2810	descriptors. This only applies when using Win32 natively, not when using
		2811	e.g. cygwin.
		2812
		2813	There is no supported compilation method available on windows except
		2814	embedding it into other applications.
		2815
		2816	Due to the many, low, and arbitrary limits on the win32 platform and the
		2817	abysmal performance of winsockets, using a large number of sockets is not
		2818	recommended (and not reasonable). If your program needs to use more than
		2819	a hundred or so sockets, then likely it needs to use a totally different
		2820	implementation for windows, as libev offers the POSIX model, which cannot
		2821	be implemented efficiently on windows (microsoft monopoly games).
		2822
		2823	=over 4
		2824
		2825	=item The winsocket select function
		2826
		2827	The winsocket C<select> function doesn't follow POSIX in that it requires
		2828	socket I<handles> and not socket I<file descriptors>. This makes select
		2829	very inefficient, and also requires a mapping from file descriptors
		2830	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2831	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2832	symbols for more info.
		2833
		2834	The configuration for a "naked" win32 using the microsoft runtime
		2835	libraries and raw winsocket select is:
		2836
		2837	#define EV_USE_SELECT 1
		2838	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2839
		2840	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2841	complexity in the O(n²) range when using win32.
		2842
		2843	=item Limited number of file descriptors
		2844
		2845	Windows has numerous arbitrary (and low) limits on things. Early versions
		2846	of winsocket's select only supported waiting for a max. of C<64> handles
		2847	(probably owning to the fact that all windows kernels can only wait for
		2848	C<64> things at the same time internally; microsoft recommends spawning a
		2849	chain of threads and wait for 63 handles and the previous thread in each).
		2850
		2851	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2852	to some high number (e.g. C<2048>) before compiling the winsocket select
		2853	call (which might be in libev or elsewhere, for example, perl does its own
		2854	select emulation on windows).
		2855
		2856	Another limit is the number of file descriptors in the microsoft runtime
		2857	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2858	or something like this inside microsoft). You can increase this by calling
		2859	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2860	arbitrary limit), but is broken in many versions of the microsoft runtime
		2861	libraries.
		2862
		2863	This might get you to about C<512> or C<2048> sockets (depending on
		2864	windows version and/or the phase of the moon). To get more, you need to
		2865	wrap all I/O functions and provide your own fd management, but the cost of
		2866	calling select (O(n²)) will likely make this unworkable.
		2867
		2868	=back
		2869
		2870
742	=head1 AUTHOR	2871	=head1 AUTHOR
743		2872
744	Marc Lehmann <libev@schmorp.de>.	2873	Marc Lehmann <libev@schmorp.de>.
745		2874

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