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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
122	The flags argument can be used to specify special behaviour or specific	265	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).	266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		267
125	It supports the following flags:	268	The following flags are supported:
126		269
127	=over 4	270	=over 4
128		271
129	=item EVFLAG_AUTO	272	=item C<EVFLAG_AUTO>
130		273
131	The default flags value. Use this if you have no clue (its the right	274	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	275	thing, believe me).
133		276
134	=item EVFLAG_NOENV	277	=item C<EVFLAG_NOENV>
135		278
136	If this flag bit is ored into the flag value (or the program runs setuid	279	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	280	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	282	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	283	useful to try out specific backends to test their performance, or to work
141	around bugs.	284	around bugs.
142		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
143	=item EVMETHOD_SELECT portable select backend	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		307
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	308	This is your standard select(2) backend. Not I<completely> standard, as
		309	libev tries to roll its own fd_set with no limits on the number of fds,
		310	but if that fails, expect a fairly low limit on the number of fds when
		311	using this backend. It doesn't scale too well (O(highest_fd)), but its
		312	usually the fastest backend for a low number of (low-numbered :) fds.
146		313
147	=item EVMETHOD_EPOLL linux only	314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
148		320
149	=item EVMETHOD_KQUEUE some bsds only	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
150		322
151	=item EVMETHOD_DEVPOLL solaris 8 only	323	And this is your standard poll(2) backend. It's more complicated
		324	than select, but handles sparse fds better and has no artificial
		325	limit on the number of fds you can use (except it will slow down
		326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
152		329
153	=item EVMETHOD_PORT solaris 10 only	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		331
		332	For few fds, this backend is a bit little slower than poll and select,
		333	but it scales phenomenally better. While poll and select usually scale
		334	like O(total_fds) where n is the total number of fds (or the highest fd),
		335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
		339
		340	While stopping, setting and starting an I/O watcher in the same iteration
		341	will result in some caching, there is still a syscall per such incident
		342	(because the fd could point to a different file description now), so its
		343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		344	very well if you register events for both fds.
		345
		346	Please note that epoll sometimes generates spurious notifications, so you
		347	need to use non-blocking I/O or other means to avoid blocking when no data
		348	(or space) is available.
		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
		357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		358
		359	Kqueue deserves special mention, as at the time of this writing, it
		360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		361	with anything but sockets and pipes, except on Darwin, where of course
		362	it's completely useless). For this reason it's not being "autodetected"
		363	unless you explicitly specify it explicitly in the flags (i.e. using
		364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
		370
		371	It scales in the same way as the epoll backend, but the interface to the
		372	kernel is more efficient (which says nothing about its actual speed, of
		373	course). While stopping, setting and starting an I/O watcher does never
		374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
		375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
		386
		387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		388
		389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
		393
		394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		395
		396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		397	it's really slow, but it still scales very well (O(active_fds)).
		398
		399	Please note that solaris event ports can deliver a lot of spurious
		400	notifications, so you need to use non-blocking I/O or other means to avoid
		401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
		407
		408	On the positive side, ignoring the spurious readyness notifications, this
		409	backend actually performed to specification in all tests and is fully
		410	embeddable, which is a rare feat among the OS-specific backends.
		411
		412	=item C<EVBACKEND_ALL>
		413
		414	Try all backends (even potentially broken ones that wouldn't be tried
		415	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		416	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		417
		418	It is definitely not recommended to use this flag.
		419
		420	=back
154		421
155	If one or more of these are ored into the flags value, then only these	422	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	423	backends will be tried (in the reverse order as listed here). If none are
157	specified, any backend will do.	424	specified, all backends in C<ev_recommended_backends ()> will be tried.
158		425
159	=back	426	The most typical usage is like this:
		427
		428	if (!ev_default_loop (0))
		429	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		430
		431	Restrict libev to the select and poll backends, and do not allow
		432	environment settings to be taken into account:
		433
		434	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		435
		436	Use whatever libev has to offer, but make sure that kqueue is used if
		437	available (warning, breaks stuff, best use only with your own private
		438	event loop and only if you know the OS supports your types of fds):
		439
		440	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		441
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	442	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		443
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	444	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	445	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	446	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).	447	undefined behaviour (or a failed assertion if assertions are enabled).
167		448
		449	Example: Try to create a event loop that uses epoll and nothing else.
		450
		451	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		452	if (!epoller)
		453	fatal ("no epoll found here, maybe it hides under your chair");
		454
168	=item ev_default_destroy ()	455	=item ev_default_destroy ()
169		456
170	Destroys the default loop again (frees all memory and kernel state	457	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	458	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	459	sense, so e.g. C<ev_is_active> might still return true. It is your
		460	responsibility to either stop all watchers cleanly yoursef I<before>
		461	calling this function, or cope with the fact afterwards (which is usually
		462	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		463	for example).
		464
		465	Note that certain global state, such as signal state, will not be freed by
		466	this function, and related watchers (such as signal and child watchers)
		467	would need to be stopped manually.
		468
		469	In general it is not advisable to call this function except in the
		470	rare occasion where you really need to free e.g. the signal handling
		471	pipe fds. If you need dynamically allocated loops it is better to use
		472	C<ev_loop_new> and C<ev_loop_destroy>).
173		473
174	=item ev_loop_destroy (loop)	474	=item ev_loop_destroy (loop)
175		475
176	Like C<ev_default_destroy>, but destroys an event loop created by an	476	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	477	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	481	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	482	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	483	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	484	again makes little sense).
185		485
186	You I<must> call this function after forking if and only if you want to	486	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	487	only if you want to use the event library in both processes. If you just
188	have to call it.	488	fork+exec, you don't have to call it.
189		489
190	The function itself is quite fast and its usually not a problem to call	490	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	491	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>:	492	quite nicely into a call to C<pthread_atfork>:
193		493
194	pthread_atfork (0, 0, ev_default_fork);	494	pthread_atfork (0, 0, ev_default_fork);
		495
		496	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		497	without calling this function, so if you force one of those backends you
		498	do not need to care.
195		499
196	=item ev_loop_fork (loop)	500	=item ev_loop_fork (loop)
197		501
198	Like C<ev_default_fork>, but acts on an event loop created by	502	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	503	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.	504	after fork, and how you do this is entirely your own problem.
201		505
		506	=item unsigned int ev_loop_count (loop)
		507
		508	Returns the count of loop iterations for the loop, which is identical to
		509	the number of times libev did poll for new events. It starts at C<0> and
		510	happily wraps around with enough iterations.
		511
		512	This value can sometimes be useful as a generation counter of sorts (it
		513	"ticks" the number of loop iterations), as it roughly corresponds with
		514	C<ev_prepare> and C<ev_check> calls.
		515
202	=item unsigned int ev_method (loop)	516	=item unsigned int ev_backend (loop)
203		517
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	518	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	519	use.
206		520
207	=item ev_tstamp = ev_now (loop)	521	=item ev_tstamp ev_now (loop)
208		522
209	Returns the current "event loop time", which is the time the event loop	523	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	524	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	525	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	526	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).	527	event occurring (or more correctly, libev finding out about it).
214		528
215	=item ev_loop (loop, int flags)	529	=item ev_loop (loop, int flags)
216		530
217	Finally, this is it, the event handler. This function usually is called	531	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	532	after you initialised all your watchers and you want to start handling
219	events.	533	events.
220		534
221	If the flags argument is specified as 0, it will not return until either	535	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.	536	either no event watchers are active anymore or C<ev_unloop> was called.
		537
		538	Please note that an explicit C<ev_unloop> is usually better than
		539	relying on all watchers to be stopped when deciding when a program has
		540	finished (especially in interactive programs), but having a program that
		541	automatically loops as long as it has to and no longer by virtue of
		542	relying on its watchers stopping correctly is a thing of beauty.
223		543
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	544	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	545	those events and any outstanding ones, but will not block your process in
226	case there are no events.	546	case there are no events and will return after one iteration of the loop.
227		547
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	548	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	549	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	550	your process until at least one new event arrives, and will return after
		551	one iteration of the loop. This is useful if you are waiting for some
		552	external event in conjunction with something not expressible using other
		553	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		554	usually a better approach for this kind of thing.
231		555
232	This flags value could be used to implement alternative looping	556	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	557
234	more generic mechanism.	558	- Before the first iteration, call any pending watchers.
		559	* If EVFLAG_FORKCHECK was used, check for a fork.
		560	- If a fork was detected, queue and call all fork watchers.
		561	- Queue and call all prepare watchers.
		562	- If we have been forked, recreate the kernel state.
		563	- Update the kernel state with all outstanding changes.
		564	- Update the "event loop time".
		565	- Calculate for how long to sleep or block, if at all
		566	(active idle watchers, EVLOOP_NONBLOCK or not having
		567	any active watchers at all will result in not sleeping).
		568	- Sleep if the I/O and timer collect interval say so.
		569	- Block the process, waiting for any events.
		570	- Queue all outstanding I/O (fd) events.
		571	- Update the "event loop time" and do time jump handling.
		572	- Queue all outstanding timers.
		573	- Queue all outstanding periodics.
		574	- If no events are pending now, queue all idle watchers.
		575	- Queue all check watchers.
		576	- Call all queued watchers in reverse order (i.e. check watchers first).
		577	Signals and child watchers are implemented as I/O watchers, and will
		578	be handled here by queueing them when their watcher gets executed.
		579	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		580	were used, or there are no active watchers, return, otherwise
		581	continue with step *.
		582
		583	Example: Queue some jobs and then loop until no events are outstanding
		584	anymore.
		585
		586	... queue jobs here, make sure they register event watchers as long
		587	... as they still have work to do (even an idle watcher will do..)
		588	ev_loop (my_loop, 0);
		589	... jobs done. yeah!
235		590
236	=item ev_unloop (loop, how)	591	=item ev_unloop (loop, how)
237		592
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	593	Can be used to make a call to C<ev_loop> return early (but only after it
		594	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>	595	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>	596	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.	597
		598	This "unloop state" will be cleared when entering C<ev_loop> again.
242		599
243	=item ev_ref (loop)	600	=item ev_ref (loop)
244		601
245	=item ev_unref (loop)	602	=item ev_unref (loop)
246		603
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	604	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	605	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	606	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	607	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	608	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	609	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	610	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	611	no event watchers registered by it are active. It is also an excellent
255	before stop.	612	way to do this for generic recurring timers or from within third-party
		613	libraries. Just remember to I<unref after start> and I<ref before stop>
		614	(but only if the watcher wasn't active before, or was active before,
		615	respectively).
		616
		617	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		618	running when nothing else is active.
		619
		620	struct ev_signal exitsig;
		621	ev_signal_init (&exitsig, sig_cb, SIGINT);
		622	ev_signal_start (loop, &exitsig);
		623	evf_unref (loop);
		624
		625	Example: For some weird reason, unregister the above signal handler again.
		626
		627	ev_ref (loop);
		628	ev_signal_stop (loop, &exitsig);
		629
		630	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		631
		632	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		633
		634	These advanced functions influence the time that libev will spend waiting
		635	for events. Both are by default C<0>, meaning that libev will try to
		636	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		637
		638	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		639	allows libev to delay invocation of I/O and timer/periodic callbacks to
		640	increase efficiency of loop iterations.
		641
		642	The background is that sometimes your program runs just fast enough to
		643	handle one (or very few) event(s) per loop iteration. While this makes
		644	the program responsive, it also wastes a lot of CPU time to poll for new
		645	events, especially with backends like C<select ()> which have a high
		646	overhead for the actual polling but can deliver many events at once.
		647
		648	By setting a higher I<io collect interval> you allow libev to spend more
		649	time collecting I/O events, so you can handle more events per iteration,
		650	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		651	C<ev_timer>) will be not affected. Setting this to a non-null value will
		652	introduce an additional C<ev_sleep ()> call into most loop iterations.
		653
		654	Likewise, by setting a higher I<timeout collect interval> you allow libev
		655	to spend more time collecting timeouts, at the expense of increased
		656	latency (the watcher callback will be called later). C<ev_io> watchers
		657	will not be affected. Setting this to a non-null value will not introduce
		658	any overhead in libev.
		659
		660	Many (busy) programs can usually benefit by setting the io collect
		661	interval to a value near C<0.1> or so, which is often enough for
		662	interactive servers (of course not for games), likewise for timeouts. It
		663	usually doesn't make much sense to set it to a lower value than C<0.01>,
		664	as this approsaches the timing granularity of most systems.
256		665
257	=back	666	=back
		667
258		668
259	=head1 ANATOMY OF A WATCHER	669	=head1 ANATOMY OF A WATCHER
260		670
261	A watcher is a structure that you create and register to record your	671	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	672	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:	673	become readable, you would create an C<ev_io> watcher for that:
264		674
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	675	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	676	{
267	ev_io_stop (w);	677	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	678	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	705	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	706	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		707
298	As long as your watcher is active (has been started but not stopped) you	708	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	709	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	710	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		711
307	Each and every callback receives the event loop pointer as first, the	712	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	713	registered watcher structure as second, and a bitset of received events as
309	third argument.	714	third argument.
310		715
311	The rceeived events usually include a single bit per event type received	716	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	717	(you can receive multiple events at the same time). The possible bit masks
313	are:	718	are:
314		719
315	=over 4	720	=over 4
316		721
317	=item EV_READ	722	=item C<EV_READ>
318		723
319	=item EV_WRITE	724	=item C<EV_WRITE>
320		725
321	The file descriptor in the ev_io watcher has become readable and/or	726	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	727	writable.
323		728
324	=item EV_TIMEOUT	729	=item C<EV_TIMEOUT>
325		730
326	The ev_timer watcher has timed out.	731	The C<ev_timer> watcher has timed out.
327		732
328	=item EV_PERIODIC	733	=item C<EV_PERIODIC>
329		734
330	The ev_periodic watcher has timed out.	735	The C<ev_periodic> watcher has timed out.
331		736
332	=item EV_SIGNAL	737	=item C<EV_SIGNAL>
333		738
334	The signal specified in the ev_signal watcher has been received by a thread.	739	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		740
336	=item EV_CHILD	741	=item C<EV_CHILD>
337		742
338	The pid specified in the ev_child watcher has received a status change.	743	The pid specified in the C<ev_child> watcher has received a status change.
339		744
		745	=item C<EV_STAT>
		746
		747	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		748
340	=item EV_IDLE	749	=item C<EV_IDLE>
341		750
342	The ev_idle watcher has determined that you have nothing better to do.	751	The C<ev_idle> watcher has determined that you have nothing better to do.
343		752
344	=item EV_PREPARE	753	=item C<EV_PREPARE>
345		754
346	=item EV_CHECK	755	=item C<EV_CHECK>
347		756
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	757	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	758	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	759	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	760	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	761	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	762	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	763	C<ev_loop> from blocking).
355		764
		765	=item C<EV_EMBED>
		766
		767	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		768
		769	=item C<EV_FORK>
		770
		771	The event loop has been resumed in the child process after fork (see
		772	C<ev_fork>).
		773
356	=item EV_ERROR	774	=item C<EV_ERROR>
357		775
358	An unspecified error has occured, the watcher has been stopped. This might	776	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	777	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	778	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	779	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	785	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	786	programs, though, so beware.
369		787
370	=back	788	=back
371		789
		790	=head2 GENERIC WATCHER FUNCTIONS
		791
		792	In the following description, C<TYPE> stands for the watcher type,
		793	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		794
		795	=over 4
		796
		797	=item C<ev_init> (ev_TYPE *watcher, callback)
		798
		799	This macro initialises the generic portion of a watcher. The contents
		800	of the watcher object can be arbitrary (so C<malloc> will do). Only
		801	the generic parts of the watcher are initialised, you I<need> to call
		802	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		803	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		804	which rolls both calls into one.
		805
		806	You can reinitialise a watcher at any time as long as it has been stopped
		807	(or never started) and there are no pending events outstanding.
		808
		809	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		810	int revents)>.
		811
		812	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		813
		814	This macro initialises the type-specific parts of a watcher. You need to
		815	call C<ev_init> at least once before you call this macro, but you can
		816	call C<ev_TYPE_set> any number of times. You must not, however, call this
		817	macro on a watcher that is active (it can be pending, however, which is a
		818	difference to the C<ev_init> macro).
		819
		820	Although some watcher types do not have type-specific arguments
		821	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		822
		823	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		824
		825	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		826	calls into a single call. This is the most convinient method to initialise
		827	a watcher. The same limitations apply, of course.
		828
		829	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		830
		831	Starts (activates) the given watcher. Only active watchers will receive
		832	events. If the watcher is already active nothing will happen.
		833
		834	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		835
		836	Stops the given watcher again (if active) and clears the pending
		837	status. It is possible that stopped watchers are pending (for example,
		838	non-repeating timers are being stopped when they become pending), but
		839	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		840	you want to free or reuse the memory used by the watcher it is therefore a
		841	good idea to always call its C<ev_TYPE_stop> function.
		842
		843	=item bool ev_is_active (ev_TYPE *watcher)
		844
		845	Returns a true value iff the watcher is active (i.e. it has been started
		846	and not yet been stopped). As long as a watcher is active you must not modify
		847	it.
		848
		849	=item bool ev_is_pending (ev_TYPE *watcher)
		850
		851	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		852	events but its callback has not yet been invoked). As long as a watcher
		853	is pending (but not active) you must not call an init function on it (but
		854	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		855	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		856	it).
		857
		858	=item callback ev_cb (ev_TYPE *watcher)
		859
		860	Returns the callback currently set on the watcher.
		861
		862	=item ev_cb_set (ev_TYPE *watcher, callback)
		863
		864	Change the callback. You can change the callback at virtually any time
		865	(modulo threads).
		866
		867	=item ev_set_priority (ev_TYPE *watcher, priority)
		868
		869	=item int ev_priority (ev_TYPE *watcher)
		870
		871	Set and query the priority of the watcher. The priority is a small
		872	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		873	(default: C<-2>). Pending watchers with higher priority will be invoked
		874	before watchers with lower priority, but priority will not keep watchers
		875	from being executed (except for C<ev_idle> watchers).
		876
		877	This means that priorities are I<only> used for ordering callback
		878	invocation after new events have been received. This is useful, for
		879	example, to reduce latency after idling, or more often, to bind two
		880	watchers on the same event and make sure one is called first.
		881
		882	If you need to suppress invocation when higher priority events are pending
		883	you need to look at C<ev_idle> watchers, which provide this functionality.
		884
		885	You I<must not> change the priority of a watcher as long as it is active or
		886	pending.
		887
		888	The default priority used by watchers when no priority has been set is
		889	always C<0>, which is supposed to not be too high and not be too low :).
		890
		891	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		892	fine, as long as you do not mind that the priority value you query might
		893	or might not have been adjusted to be within valid range.
		894
		895	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		896
		897	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		898	C<loop> nor C<revents> need to be valid as long as the watcher callback
		899	can deal with that fact.
		900
		901	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		902
		903	If the watcher is pending, this function returns clears its pending status
		904	and returns its C<revents> bitset (as if its callback was invoked). If the
		905	watcher isn't pending it does nothing and returns C<0>.
		906
		907	=back
		908
		909
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	910	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		911
374	Each watcher has, by default, a member C<void *data> that you can change	912	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	913	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	914	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	915	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	916	member, you can also "subclass" the watcher type and provide your own
379	data:	917	data:
380		918
…		…
393	{	931	{
394	struct my_io *w = (struct my_io *)w_;	932	struct my_io *w = (struct my_io *)w_;
395	...	933	...
396	}	934	}
397		935
398	More interesting and less C-conformant ways of catsing your callback type	936	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	937	instead have been omitted.
		938
		939	Another common scenario is having some data structure with multiple
		940	watchers:
		941
		942	struct my_biggy
		943	{
		944	int some_data;
		945	ev_timer t1;
		946	ev_timer t2;
		947	}
		948
		949	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		950	you need to use C<offsetof>:
		951
		952	#include <stddef.h>
		953
		954	static void
		955	t1_cb (EV_P_ struct ev_timer *w, int revents)
		956	{
		957	struct my_biggy big = (struct my_biggy *
		958	(((char *)w) - offsetof (struct my_biggy, t1));
		959	}
		960
		961	static void
		962	t2_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, t2));
		966	}
400		967
401		968
402	=head1 WATCHER TYPES	969	=head1 WATCHER TYPES
403		970
404	This section describes each watcher in detail, but will not repeat	971	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	972	information given in the last section. Any initialisation/set macros,
		973	functions and members specific to the watcher type are explained.
406		974
		975	Members are additionally marked with either I<[read-only]>, meaning that,
		976	while the watcher is active, you can look at the member and expect some
		977	sensible content, but you must not modify it (you can modify it while the
		978	watcher is stopped to your hearts content), or I<[read-write]>, which
		979	means you can expect it to have some sensible content while the watcher
		980	is active, but you can also modify it. Modifying it may not do something
		981	sensible or take immediate effect (or do anything at all), but libev will
		982	not crash or malfunction in any way.
		983
		984
407	=head2 struct ev_io - is my file descriptor readable or writable	985	=head2 C<ev_io> - is this file descriptor readable or writable?
408		986
409	I/O watchers check whether a file descriptor is readable or writable	987	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	988	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	989	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	990	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	991	receiving events as long as the condition persists. Remember you can stop
		992	the watcher if you don't want to act on the event and neither want to
		993	receive future events.
414		994
415	In general you can register as many read and/or write event watchers oer	995	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	996	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	997	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	998	required if you know what you are doing).
419		999
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	1000	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	1001	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	1002	C<EVBACKEND_POLL>).
		1003
		1004	Another thing you have to watch out for is that it is quite easy to
		1005	receive "spurious" readyness notifications, that is your callback might
		1006	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1007	because there is no data. Not only are some backends known to create a
		1008	lot of those (for example solaris ports), it is very easy to get into
		1009	this situation even with a relatively standard program structure. Thus
		1010	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1011	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1012
		1013	If you cannot run the fd in non-blocking mode (for example you should not
		1014	play around with an Xlib connection), then you have to seperately re-test
		1015	whether a file descriptor is really ready with a known-to-be good interface
		1016	such as poll (fortunately in our Xlib example, Xlib already does this on
		1017	its own, so its quite safe to use).
		1018
		1019	=head3 The special problem of disappearing file descriptors
		1020
		1021	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1022	descriptor (either by calling C<close> explicitly or by any other means,
		1023	such as C<dup>). The reason is that you register interest in some file
		1024	descriptor, but when it goes away, the operating system will silently drop
		1025	this interest. If another file descriptor with the same number then is
		1026	registered with libev, there is no efficient way to see that this is, in
		1027	fact, a different file descriptor.
		1028
		1029	To avoid having to explicitly tell libev about such cases, libev follows
		1030	the following policy: Each time C<ev_io_set> is being called, libev
		1031	will assume that this is potentially a new file descriptor, otherwise
		1032	it is assumed that the file descriptor stays the same. That means that
		1033	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1034	descriptor even if the file descriptor number itself did not change.
		1035
		1036	This is how one would do it normally anyway, the important point is that
		1037	the libev application should not optimise around libev but should leave
		1038	optimisations to libev.
		1039
		1040	=head3 The special problem of dup'ed file descriptors
		1041
		1042	Some backends (e.g. epoll), cannot register events for file descriptors,
		1043	but only events for the underlying file descriptions. That means when you
		1044	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1045	events for them, only one file descriptor might actually receive events.
		1046
		1047	There is no workaround possible except not registering events
		1048	for potentially C<dup ()>'ed file descriptors, or to resort to
		1049	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1050
		1051	=head3 The special problem of fork
		1052
		1053	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1054	useless behaviour. Libev fully supports fork, but needs to be told about
		1055	it in the child.
		1056
		1057	To support fork in your programs, you either have to call
		1058	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1059	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1060	C<EVBACKEND_POLL>.
		1061
		1062
		1063	=head3 Watcher-Specific Functions
428		1064
429	=over 4	1065	=over 4
430		1066
431	=item ev_io_init (ev_io *, callback, int fd, int events)	1067	=item ev_io_init (ev_io *, callback, int fd, int events)
432		1068
433	=item ev_io_set (ev_io *, int fd, int events)	1069	=item ev_io_set (ev_io *, int fd, int events)
434		1070
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1071	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 |	1072	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	1073	C<EV_READ | EV_WRITE> to receive the given events.
		1074
		1075	=item int fd [read-only]
		1076
		1077	The file descriptor being watched.
		1078
		1079	=item int events [read-only]
		1080
		1081	The events being watched.
438		1082
439	=back	1083	=back
440		1084
		1085	=head3 Examples
		1086
		1087	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1088	readable, but only once. Since it is likely line-buffered, you could
		1089	attempt to read a whole line in the callback.
		1090
		1091	static void
		1092	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1093	{
		1094	ev_io_stop (loop, w);
		1095	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1096	}
		1097
		1098	...
		1099	struct ev_loop *loop = ev_default_init (0);
		1100	struct ev_io stdin_readable;
		1101	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1102	ev_io_start (loop, &stdin_readable);
		1103	ev_loop (loop, 0);
		1104
		1105
441	=head2 struct ev_timer - relative and optionally recurring timeouts	1106	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		1107
443	Timer watchers are simple relative timers that generate an event after a	1108	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	1109	given time, and optionally repeating in regular intervals after that.
445		1110
446	The timers are based on real time, that is, if you register an event that	1111	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	1112	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	1113	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1114	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	1115	monotonic clock option helps a lot here).
		1116
		1117	The relative timeouts are calculated relative to the C<ev_now ()>
		1118	time. This is usually the right thing as this timestamp refers to the time
		1119	of the event triggering whatever timeout you are modifying/starting. If
		1120	you suspect event processing to be delayed and you I<need> to base the timeout
		1121	on the current time, use something like this to adjust for this:
		1122
		1123	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1124
		1125	The callback is guarenteed to be invoked only when its timeout has passed,
		1126	but if multiple timers become ready during the same loop iteration then
		1127	order of execution is undefined.
		1128
		1129	=head3 Watcher-Specific Functions and Data Members
451		1130
452	=over 4	1131	=over 4
453		1132
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1133	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		1134
…		…
461	later, again, and again, until stopped manually.	1140	later, again, and again, until stopped manually.
462		1141
463	The timer itself will do a best-effort at avoiding drift, that is, if you	1142	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	1143	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	1144	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	1145	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.	1146	timer will not fire more than once per event loop iteration.
468		1147
469	=item ev_timer_again (loop)	1148	=item ev_timer_again (loop)
470		1149
471	This will act as if the timer timed out and restart it again if it is	1150	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	1151	repeating. The exact semantics are:
473		1152
		1153	If the timer is pending, its pending status is cleared.
		1154
474	If the timer is started but nonrepeating, stop it.	1155	If the timer is started but nonrepeating, stop it (as if it timed out).
475		1156
476	If the timer is repeating, either start it if necessary (with the repeat	1157	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	1158	C<repeat> value), or reset the running timer to the C<repeat> value.
478		1159
479	This sounds a bit complicated, but here is a useful and typical	1160	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	1161	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	1162	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	1163	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	1164	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	1165	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	1166	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.	1167	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1168	automatically restart it if need be.
		1169
		1170	That means you can ignore the C<after> value and C<ev_timer_start>
		1171	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1172
		1173	ev_timer_init (timer, callback, 0., 5.);
		1174	ev_timer_again (loop, timer);
		1175	...
		1176	timer->again = 17.;
		1177	ev_timer_again (loop, timer);
		1178	...
		1179	timer->again = 10.;
		1180	ev_timer_again (loop, timer);
		1181
		1182	This is more slightly efficient then stopping/starting the timer each time
		1183	you want to modify its timeout value.
		1184
		1185	=item ev_tstamp repeat [read-write]
		1186
		1187	The current C<repeat> value. Will be used each time the watcher times out
		1188	or C<ev_timer_again> is called and determines the next timeout (if any),
		1189	which is also when any modifications are taken into account.
487		1190
488	=back	1191	=back
489		1192
		1193	=head3 Examples
		1194
		1195	Example: Create a timer that fires after 60 seconds.
		1196
		1197	static void
		1198	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1199	{
		1200	.. one minute over, w is actually stopped right here
		1201	}
		1202
		1203	struct ev_timer mytimer;
		1204	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1205	ev_timer_start (loop, &mytimer);
		1206
		1207	Example: Create a timeout timer that times out after 10 seconds of
		1208	inactivity.
		1209
		1210	static void
		1211	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1212	{
		1213	.. ten seconds without any activity
		1214	}
		1215
		1216	struct ev_timer mytimer;
		1217	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1218	ev_timer_again (&mytimer); /* start timer */
		1219	ev_loop (loop, 0);
		1220
		1221	// and in some piece of code that gets executed on any "activity":
		1222	// reset the timeout to start ticking again at 10 seconds
		1223	ev_timer_again (&mytimer);
		1224
		1225
490	=head2 ev_periodic - to cron or not to cron it	1226	=head2 C<ev_periodic> - to cron or not to cron?
491		1227
492	Periodic watchers are also timers of a kind, but they are very versatile	1228	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1229	(and unfortunately a bit complex).
494		1230
495	Unlike ev_timer's, they are not based on real time (or relative time)	1231	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	1232	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	1233	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 ()	1234	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	1235	+ 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	1236	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	1237	roughly 10 seconds later).
502	again).
503		1238
504	They can also be used to implement vastly more complex timers, such as	1239	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1240	triggering an event on each midnight, local time or other, complicated,
		1241	rules.
		1242
		1243	As with timers, the callback is guarenteed to be invoked only when the
		1244	time (C<at>) has been passed, but if multiple periodic timers become ready
		1245	during the same loop iteration then order of execution is undefined.
		1246
		1247	=head3 Watcher-Specific Functions and Data Members
506		1248
507	=over 4	1249	=over 4
508		1250
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1251	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1252
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1253	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1254
513	Lots of arguments, lets sort it out... There are basically three modes of	1255	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1256	operation, and we will explain them from simplest to complex:
515		1257
516
517	=over 4	1258	=over 4
518		1259
519	=item * absolute timer (interval = reschedule_cb = 0)	1260	=item * absolute timer (at = time, interval = reschedule_cb = 0)
520		1261
521	In this configuration the watcher triggers an event at the wallclock time	1262	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,	1263	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	1264	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.	1265	system time reaches or surpasses this time.
525		1266
526	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1267	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
527		1268
528	In this mode the watcher will always be scheduled to time out at the next	1269	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	1270	C<at + N * interval> time (for some integer N, which can also be negative)
530	of any time jumps.	1271	and then repeat, regardless of any time jumps.
531		1272
532	This can be used to create timers that do not drift with respect to system	1273	This can be used to create timers that do not drift with respect to system
533	time:	1274	time:
534		1275
535	ev_periodic_set (&periodic, 0., 3600., 0);	1276	ev_periodic_set (&periodic, 0., 3600., 0);
536		1277
537	This doesn't mean there will always be 3600 seconds in between triggers,	1278	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	1279	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	1280	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1281	by 3600.
541		1282
542	Another way to think about it (for the mathematically inclined) is that	1283	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	1284	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.	1285	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1286
		1287	For numerical stability it is preferable that the C<at> value is near
		1288	C<ev_now ()> (the current time), but there is no range requirement for
		1289	this value.
		1290
546	=item * manual reschedule mode (reschedule_cb = callback)	1291	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
547		1292
548	In this mode the values for C<interval> and C<at> are both being	1293	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	1294	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1295	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1296	current time as second argument.
552		1297
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1298	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	1299	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.	1300	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1301	starting an C<ev_prepare> watcher, which is legal).
556		1302
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1303	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1304	ev_tstamp now)>, e.g.:
559		1305
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1306	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1307	{
562	return now + 60.;	1308	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1311	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	1312	(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	1313	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1314	might be called at other times, too.
569		1315
		1316	NOTE: I<< This callback must always return a time that is later than the
		1317	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1318
570	This can be used to create very complex timers, such as a timer that	1319	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	1320	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	1321	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1322	you do this is, again, up to you (but it is not trivial, which is the main
		1323	reason I omitted it as an example).
574		1324
575	=back	1325	=back
576		1326
577	=item ev_periodic_again (loop, ev_periodic *)	1327	=item ev_periodic_again (loop, ev_periodic *)
578		1328
579	Simply stops and restarts the periodic watcher again. This is only useful	1329	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1330	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	1331	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1332	program when the crontabs have changed).
583		1333
		1334	=item ev_tstamp offset [read-write]
		1335
		1336	When repeating, this contains the offset value, otherwise this is the
		1337	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1338
		1339	Can be modified any time, but changes only take effect when the periodic
		1340	timer fires or C<ev_periodic_again> is being called.
		1341
		1342	=item ev_tstamp interval [read-write]
		1343
		1344	The current interval value. Can be modified any time, but changes only
		1345	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1346	called.
		1347
		1348	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1349
		1350	The current reschedule callback, or C<0>, if this functionality is
		1351	switched off. Can be changed any time, but changes only take effect when
		1352	the periodic timer fires or C<ev_periodic_again> is being called.
		1353
		1354	=item ev_tstamp at [read-only]
		1355
		1356	When active, contains the absolute time that the watcher is supposed to
		1357	trigger next.
		1358
584	=back	1359	=back
585		1360
		1361	=head3 Examples
		1362
		1363	Example: Call a callback every hour, or, more precisely, whenever the
		1364	system clock is divisible by 3600. The callback invocation times have
		1365	potentially a lot of jittering, but good long-term stability.
		1366
		1367	static void
		1368	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1369	{
		1370	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1371	}
		1372
		1373	struct ev_periodic hourly_tick;
		1374	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1375	ev_periodic_start (loop, &hourly_tick);
		1376
		1377	Example: The same as above, but use a reschedule callback to do it:
		1378
		1379	#include <math.h>
		1380
		1381	static ev_tstamp
		1382	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1383	{
		1384	return fmod (now, 3600.) + 3600.;
		1385	}
		1386
		1387	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1388
		1389	Example: Call a callback every hour, starting now:
		1390
		1391	struct ev_periodic hourly_tick;
		1392	ev_periodic_init (&hourly_tick, clock_cb,
		1393	fmod (ev_now (loop), 3600.), 3600., 0);
		1394	ev_periodic_start (loop, &hourly_tick);
		1395
		1396
586	=head2 ev_signal - signal me when a signal gets signalled	1397	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1398
588	Signal watchers will trigger an event when the process receives a specific	1399	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	1400	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	1401	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1402	normal event processing, like any other event.
592		1403
593	You cna configure as many watchers as you like per signal. Only when the	1404	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	1405	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	1406	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	1407	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	1408	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1409	SIG_DFL (regardless of what it was set to before).
599		1410
		1411	=head3 Watcher-Specific Functions and Data Members
		1412
600	=over 4	1413	=over 4
601		1414
602	=item ev_signal_init (ev_signal *, callback, int signum)	1415	=item ev_signal_init (ev_signal *, callback, int signum)
603		1416
604	=item ev_signal_set (ev_signal *, int signum)	1417	=item ev_signal_set (ev_signal *, int signum)
605		1418
606	Configures the watcher to trigger on the given signal number (usually one	1419	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1420	of the C<SIGxxx> constants).
608		1421
		1422	=item int signum [read-only]
		1423
		1424	The signal the watcher watches out for.
		1425
609	=back	1426	=back
610		1427
		1428
611	=head2 ev_child - wait for pid status changes	1429	=head2 C<ev_child> - watch out for process status changes
612		1430
613	Child watchers trigger when your process receives a SIGCHLD in response to	1431	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).	1432	some child status changes (most typically when a child of yours dies).
		1433
		1434	=head3 Watcher-Specific Functions and Data Members
615		1435
616	=over 4	1436	=over 4
617		1437
618	=item ev_child_init (ev_child *, callback, int pid)	1438	=item ev_child_init (ev_child *, callback, int pid)
619		1439
620	=item ev_child_set (ev_child *, int pid)	1440	=item ev_child_set (ev_child *, int pid)
621		1441
622	Configures the watcher to wait for status changes of process C<pid> (or	1442	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	1443	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	1444	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	1445	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.	1446	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1447	process causing the status change.
		1448
		1449	=item int pid [read-only]
		1450
		1451	The process id this watcher watches out for, or C<0>, meaning any process id.
		1452
		1453	=item int rpid [read-write]
		1454
		1455	The process id that detected a status change.
		1456
		1457	=item int rstatus [read-write]
		1458
		1459	The process exit/trace status caused by C<rpid> (see your systems
		1460	C<waitpid> and C<sys/wait.h> documentation for details).
627		1461
628	=back	1462	=back
629		1463
		1464	=head3 Examples
		1465
		1466	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1467
		1468	static void
		1469	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1470	{
		1471	ev_unloop (loop, EVUNLOOP_ALL);
		1472	}
		1473
		1474	struct ev_signal signal_watcher;
		1475	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1476	ev_signal_start (loop, &sigint_cb);
		1477
		1478
		1479	=head2 C<ev_stat> - did the file attributes just change?
		1480
		1481	This watches a filesystem path for attribute changes. That is, it calls
		1482	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1483	compared to the last time, invoking the callback if it did.
		1484
		1485	The path does not need to exist: changing from "path exists" to "path does
		1486	not exist" is a status change like any other. The condition "path does
		1487	not exist" is signified by the C<st_nlink> field being zero (which is
		1488	otherwise always forced to be at least one) and all the other fields of
		1489	the stat buffer having unspecified contents.
		1490
		1491	The path I<should> be absolute and I<must not> end in a slash. If it is
		1492	relative and your working directory changes, the behaviour is undefined.
		1493
		1494	Since there is no standard to do this, the portable implementation simply
		1495	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1496	can specify a recommended polling interval for this case. If you specify
		1497	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1498	unspecified default> value will be used (which you can expect to be around
		1499	five seconds, although this might change dynamically). Libev will also
		1500	impose a minimum interval which is currently around C<0.1>, but thats
		1501	usually overkill.
		1502
		1503	This watcher type is not meant for massive numbers of stat watchers,
		1504	as even with OS-supported change notifications, this can be
		1505	resource-intensive.
		1506
		1507	At the time of this writing, only the Linux inotify interface is
		1508	implemented (implementing kqueue support is left as an exercise for the
		1509	reader). Inotify will be used to give hints only and should not change the
		1510	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1511	to fall back to regular polling again even with inotify, but changes are
		1512	usually detected immediately, and if the file exists there will be no
		1513	polling.
		1514
		1515	=head3 Inotify
		1516
		1517	When C<inotify (7)> support has been compiled into libev (generally only
		1518	available on Linux) and present at runtime, it will be used to speed up
		1519	change detection where possible. The inotify descriptor will be created lazily
		1520	when the first C<ev_stat> watcher is being started.
		1521
		1522	Inotify presense does not change the semantics of C<ev_stat> watchers
		1523	except that changes might be detected earlier, and in some cases, to avoid
		1524	making regular C<stat> calls. Even in the presense of inotify support
		1525	there are many cases where libev has to resort to regular C<stat> polling.
		1526
		1527	(There is no support for kqueue, as apparently it cannot be used to
		1528	implement this functionality, due to the requirement of having a file
		1529	descriptor open on the object at all times).
		1530
		1531	=head3 The special problem of stat time resolution
		1532
		1533	The C<stat ()> syscall only supports full-second resolution portably, and
		1534	even on systems where the resolution is higher, many filesystems still
		1535	only support whole seconds.
		1536
		1537	That means that, if the time is the only thing that changes, you might
		1538	miss updates: on the first update, C<ev_stat> detects a change and calls
		1539	your callback, which does something. When there is another update within
		1540	the same second, C<ev_stat> will be unable to detect it.
		1541
		1542	The solution to this is to delay acting on a change for a second (or till
		1543	the next second boundary), using a roughly one-second delay C<ev_timer>
		1544	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1545	is added to work around small timing inconsistencies of some operating
		1546	systems.
		1547
		1548	=head3 Watcher-Specific Functions and Data Members
		1549
		1550	=over 4
		1551
		1552	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1553
		1554	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1555
		1556	Configures the watcher to wait for status changes of the given
		1557	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1558	be detected and should normally be specified as C<0> to let libev choose
		1559	a suitable value. The memory pointed to by C<path> must point to the same
		1560	path for as long as the watcher is active.
		1561
		1562	The callback will be receive C<EV_STAT> when a change was detected,
		1563	relative to the attributes at the time the watcher was started (or the
		1564	last change was detected).
		1565
		1566	=item ev_stat_stat (ev_stat *)
		1567
		1568	Updates the stat buffer immediately with new values. If you change the
		1569	watched path in your callback, you could call this fucntion to avoid
		1570	detecting this change (while introducing a race condition). Can also be
		1571	useful simply to find out the new values.
		1572
		1573	=item ev_statdata attr [read-only]
		1574
		1575	The most-recently detected attributes of the file. Although the type is of
		1576	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1577	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1578	was some error while C<stat>ing the file.
		1579
		1580	=item ev_statdata prev [read-only]
		1581
		1582	The previous attributes of the file. The callback gets invoked whenever
		1583	C<prev> != C<attr>.
		1584
		1585	=item ev_tstamp interval [read-only]
		1586
		1587	The specified interval.
		1588
		1589	=item const char *path [read-only]
		1590
		1591	The filesystem path that is being watched.
		1592
		1593	=back
		1594
		1595	=head3 Examples
		1596
		1597	Example: Watch C</etc/passwd> for attribute changes.
		1598
		1599	static void
		1600	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1601	{
		1602	/* /etc/passwd changed in some way */
		1603	if (w->attr.st_nlink)
		1604	{
		1605	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1606	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1607	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1608	}
		1609	else
		1610	/* you shalt not abuse printf for puts */
		1611	puts ("wow, /etc/passwd is not there, expect problems. "
		1612	"if this is windows, they already arrived\n");
		1613	}
		1614
		1615	...
		1616	ev_stat passwd;
		1617
		1618	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1619	ev_stat_start (loop, &passwd);
		1620
		1621	Example: Like above, but additionally use a one-second delay so we do not
		1622	miss updates (however, frequent updates will delay processing, too, so
		1623	one might do the work both on C<ev_stat> callback invocation I<and> on
		1624	C<ev_timer> callback invocation).
		1625
		1626	static ev_stat passwd;
		1627	static ev_timer timer;
		1628
		1629	static void
		1630	timer_cb (EV_P_ ev_timer *w, int revents)
		1631	{
		1632	ev_timer_stop (EV_A_ w);
		1633
		1634	/* now it's one second after the most recent passwd change */
		1635	}
		1636
		1637	static void
		1638	stat_cb (EV_P_ ev_stat *w, int revents)
		1639	{
		1640	/* reset the one-second timer */
		1641	ev_timer_again (EV_A_ &timer);
		1642	}
		1643
		1644	...
		1645	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1646	ev_stat_start (loop, &passwd);
		1647	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1648
		1649
630	=head2 ev_idle - when you've got nothing better to do	1650	=head2 C<ev_idle> - when you've got nothing better to do...
631		1651
632	Idle watchers trigger events when there are no other I/O or timer (or	1652	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	1653	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	1654	count).
635	is idle all idle watchers are being called again and again - until	1655
		1656	That is, as long as your process is busy handling sockets or timeouts
		1657	(or even signals, imagine) of the same or higher priority it will not be
		1658	triggered. But when your process is idle (or only lower-priority watchers
		1659	are pending), the idle watchers are being called once per event loop
636	stopped, that is, or your process receives more events.	1660	iteration - until stopped, that is, or your process receives more events
		1661	and becomes busy again with higher priority stuff.
637		1662
638	The most noteworthy effect is that as long as any idle watchers are	1663	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.	1664	active, the process will not block when waiting for new events.
640		1665
641	Apart from keeping your process non-blocking (which is a useful	1666	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	1667	effect on its own sometimes), idle watchers are a good place to do
643	"pseudo-background processing", or delay processing stuff to after the	1668	"pseudo-background processing", or delay processing stuff to after the
644	event loop has handled all outstanding events.	1669	event loop has handled all outstanding events.
645		1670
		1671	=head3 Watcher-Specific Functions and Data Members
		1672
646	=over 4	1673	=over 4
647		1674
648	=item ev_idle_init (ev_signal *, callback)	1675	=item ev_idle_init (ev_signal *, callback)
649		1676
650	Initialises and configures the idle watcher - it has no parameters of any	1677	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,	1678	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1679	believe me.
653		1680
654	=back	1681	=back
655		1682
656	=head2 prepare and check - your hooks into the event loop	1683	=head3 Examples
657		1684
		1685	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1686	callback, free it. Also, use no error checking, as usual.
		1687
		1688	static void
		1689	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1690	{
		1691	free (w);
		1692	// now do something you wanted to do when the program has
		1693	// no longer asnything immediate to do.
		1694	}
		1695
		1696	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1697	ev_idle_init (idle_watcher, idle_cb);
		1698	ev_idle_start (loop, idle_cb);
		1699
		1700
		1701	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1702
658	Prepare and check watchers usually (but not always) are used in	1703	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1704	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1705	afterwards.
661		1706
		1707	You I<must not> call C<ev_loop> or similar functions that enter
		1708	the current event loop from either C<ev_prepare> or C<ev_check>
		1709	watchers. Other loops than the current one are fine, however. The
		1710	rationale behind this is that you do not need to check for recursion in
		1711	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1712	C<ev_check> so if you have one watcher of each kind they will always be
		1713	called in pairs bracketing the blocking call.
		1714
662	Their main purpose is to integrate other event mechanisms into libev. This	1715	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	1716	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.	1717	variable changes, implement your own watchers, integrate net-snmp or a
		1718	coroutine library and lots more. They are also occasionally useful if
		1719	you cache some data and want to flush it before blocking (for example,
		1720	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1721	watcher).
665		1722
666	This is done by examining in each prepare call which file descriptors need	1723	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	1724	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	1725	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	1726	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)	1727	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1728	and stopping them) and call back into the library. The I/O and timer
		1729	callbacks will never actually be called (but must be valid nevertheless,
		1730	because you never know, you know?).
672		1731
673	As another example, the perl Coro module uses these hooks to integrate	1732	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1733	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1734	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1735	are ready to run (it's actually more complicated: it only runs coroutines
		1736	with priority higher than or equal to the event loop and one coroutine
		1737	of lower priority, but only once, using idle watchers to keep the event
		1738	loop from blocking if lower-priority coroutines are active, thus mapping
		1739	low-priority coroutines to idle/background tasks).
		1740
		1741	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1742	priority, to ensure that they are being run before any other watchers
		1743	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1744	too) should not activate ("feed") events into libev. While libev fully
		1745	supports this, they will be called before other C<ev_check> watchers
		1746	did their job. As C<ev_check> watchers are often used to embed other
		1747	(non-libev) event loops those other event loops might be in an unusable
		1748	state until their C<ev_check> watcher ran (always remind yourself to
		1749	coexist peacefully with others).
		1750
		1751	=head3 Watcher-Specific Functions and Data Members
677		1752
678	=over 4	1753	=over 4
679		1754
680	=item ev_prepare_init (ev_prepare *, callback)	1755	=item ev_prepare_init (ev_prepare *, callback)
681		1756
682	=item ev_check_init (ev_check *, callback)	1757	=item ev_check_init (ev_check *, callback)
683		1758
684	Initialises and configures the prepare or check watcher - they have no	1759	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>	1760	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1761	macros, but using them is utterly, utterly and completely pointless.
687		1762
688	=back	1763	=back
689		1764
		1765	=head3 Examples
		1766
		1767	There are a number of principal ways to embed other event loops or modules
		1768	into libev. Here are some ideas on how to include libadns into libev
		1769	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1770	use for an actually working example. Another Perl module named C<EV::Glib>
		1771	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1772	into the Glib event loop).
		1773
		1774	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1775	and in a check watcher, destroy them and call into libadns. What follows
		1776	is pseudo-code only of course. This requires you to either use a low
		1777	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1778	the callbacks for the IO/timeout watchers might not have been called yet.
		1779
		1780	static ev_io iow [nfd];
		1781	static ev_timer tw;
		1782
		1783	static void
		1784	io_cb (ev_loop *loop, ev_io *w, int revents)
		1785	{
		1786	}
		1787
		1788	// create io watchers for each fd and a timer before blocking
		1789	static void
		1790	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1791	{
		1792	int timeout = 3600000;
		1793	struct pollfd fds [nfd];
		1794	// actual code will need to loop here and realloc etc.
		1795	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1796
		1797	/* the callback is illegal, but won't be called as we stop during check */
		1798	ev_timer_init (&tw, 0, timeout * 1e-3);
		1799	ev_timer_start (loop, &tw);
		1800
		1801	// create one ev_io per pollfd
		1802	for (int i = 0; i < nfd; ++i)
		1803	{
		1804	ev_io_init (iow + i, io_cb, fds [i].fd,
		1805	((fds [i].events & POLLIN ? EV_READ : 0)
		1806	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1807
		1808	fds [i].revents = 0;
		1809	ev_io_start (loop, iow + i);
		1810	}
		1811	}
		1812
		1813	// stop all watchers after blocking
		1814	static void
		1815	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1816	{
		1817	ev_timer_stop (loop, &tw);
		1818
		1819	for (int i = 0; i < nfd; ++i)
		1820	{
		1821	// set the relevant poll flags
		1822	// could also call adns_processreadable etc. here
		1823	struct pollfd *fd = fds + i;
		1824	int revents = ev_clear_pending (iow + i);
		1825	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1826	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1827
		1828	// now stop the watcher
		1829	ev_io_stop (loop, iow + i);
		1830	}
		1831
		1832	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1833	}
		1834
		1835	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1836	in the prepare watcher and would dispose of the check watcher.
		1837
		1838	Method 3: If the module to be embedded supports explicit event
		1839	notification (adns does), you can also make use of the actual watcher
		1840	callbacks, and only destroy/create the watchers in the prepare watcher.
		1841
		1842	static void
		1843	timer_cb (EV_P_ ev_timer *w, int revents)
		1844	{
		1845	adns_state ads = (adns_state)w->data;
		1846	update_now (EV_A);
		1847
		1848	adns_processtimeouts (ads, &tv_now);
		1849	}
		1850
		1851	static void
		1852	io_cb (EV_P_ ev_io *w, int revents)
		1853	{
		1854	adns_state ads = (adns_state)w->data;
		1855	update_now (EV_A);
		1856
		1857	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1858	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1859	}
		1860
		1861	// do not ever call adns_afterpoll
		1862
		1863	Method 4: Do not use a prepare or check watcher because the module you
		1864	want to embed is too inflexible to support it. Instead, youc na override
		1865	their poll function. The drawback with this solution is that the main
		1866	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1867	this.
		1868
		1869	static gint
		1870	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1871	{
		1872	int got_events = 0;
		1873
		1874	for (n = 0; n < nfds; ++n)
		1875	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1876
		1877	if (timeout >= 0)
		1878	// create/start timer
		1879
		1880	// poll
		1881	ev_loop (EV_A_ 0);
		1882
		1883	// stop timer again
		1884	if (timeout >= 0)
		1885	ev_timer_stop (EV_A_ &to);
		1886
		1887	// stop io watchers again - their callbacks should have set
		1888	for (n = 0; n < nfds; ++n)
		1889	ev_io_stop (EV_A_ iow [n]);
		1890
		1891	return got_events;
		1892	}
		1893
		1894
		1895	=head2 C<ev_embed> - when one backend isn't enough...
		1896
		1897	This is a rather advanced watcher type that lets you embed one event loop
		1898	into another (currently only C<ev_io> events are supported in the embedded
		1899	loop, other types of watchers might be handled in a delayed or incorrect
		1900	fashion and must not be used).
		1901
		1902	There are primarily two reasons you would want that: work around bugs and
		1903	prioritise I/O.
		1904
		1905	As an example for a bug workaround, the kqueue backend might only support
		1906	sockets on some platform, so it is unusable as generic backend, but you
		1907	still want to make use of it because you have many sockets and it scales
		1908	so nicely. In this case, you would create a kqueue-based loop and embed it
		1909	into your default loop (which might use e.g. poll). Overall operation will
		1910	be a bit slower because first libev has to poll and then call kevent, but
		1911	at least you can use both at what they are best.
		1912
		1913	As for prioritising I/O: rarely you have the case where some fds have
		1914	to be watched and handled very quickly (with low latency), and even
		1915	priorities and idle watchers might have too much overhead. In this case
		1916	you would put all the high priority stuff in one loop and all the rest in
		1917	a second one, and embed the second one in the first.
		1918
		1919	As long as the watcher is active, the callback will be invoked every time
		1920	there might be events pending in the embedded loop. The callback must then
		1921	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1922	their callbacks (you could also start an idle watcher to give the embedded
		1923	loop strictly lower priority for example). You can also set the callback
		1924	to C<0>, in which case the embed watcher will automatically execute the
		1925	embedded loop sweep.
		1926
		1927	As long as the watcher is started it will automatically handle events. The
		1928	callback will be invoked whenever some events have been handled. You can
		1929	set the callback to C<0> to avoid having to specify one if you are not
		1930	interested in that.
		1931
		1932	Also, there have not currently been made special provisions for forking:
		1933	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1934	but you will also have to stop and restart any C<ev_embed> watchers
		1935	yourself.
		1936
		1937	Unfortunately, not all backends are embeddable, only the ones returned by
		1938	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1939	portable one.
		1940
		1941	So when you want to use this feature you will always have to be prepared
		1942	that you cannot get an embeddable loop. The recommended way to get around
		1943	this is to have a separate variables for your embeddable loop, try to
		1944	create it, and if that fails, use the normal loop for everything.
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
		1947
		1948	=over 4
		1949
		1950	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1951
		1952	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1953
		1954	Configures the watcher to embed the given loop, which must be
		1955	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1956	invoked automatically, otherwise it is the responsibility of the callback
		1957	to invoke it (it will continue to be called until the sweep has been done,
		1958	if you do not want thta, you need to temporarily stop the embed watcher).
		1959
		1960	=item ev_embed_sweep (loop, ev_embed *)
		1961
		1962	Make a single, non-blocking sweep over the embedded loop. This works
		1963	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1964	apropriate way for embedded loops.
		1965
		1966	=item struct ev_loop *other [read-only]
		1967
		1968	The embedded event loop.
		1969
		1970	=back
		1971
		1972	=head3 Examples
		1973
		1974	Example: Try to get an embeddable event loop and embed it into the default
		1975	event loop. If that is not possible, use the default loop. The default
		1976	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1977	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1978	used).
		1979
		1980	struct ev_loop *loop_hi = ev_default_init (0);
		1981	struct ev_loop *loop_lo = 0;
		1982	struct ev_embed embed;
		1983
		1984	// see if there is a chance of getting one that works
		1985	// (remember that a flags value of 0 means autodetection)
		1986	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1987	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1988	: 0;
		1989
		1990	// if we got one, then embed it, otherwise default to loop_hi
		1991	if (loop_lo)
		1992	{
		1993	ev_embed_init (&embed, 0, loop_lo);
		1994	ev_embed_start (loop_hi, &embed);
		1995	}
		1996	else
		1997	loop_lo = loop_hi;
		1998
		1999	Example: Check if kqueue is available but not recommended and create
		2000	a kqueue backend for use with sockets (which usually work with any
		2001	kqueue implementation). Store the kqueue/socket-only event loop in
		2002	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2003
		2004	struct ev_loop *loop = ev_default_init (0);
		2005	struct ev_loop *loop_socket = 0;
		2006	struct ev_embed embed;
		2007
		2008	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2009	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2010	{
		2011	ev_embed_init (&embed, 0, loop_socket);
		2012	ev_embed_start (loop, &embed);
		2013	}
		2014
		2015	if (!loop_socket)
		2016	loop_socket = loop;
		2017
		2018	// now use loop_socket for all sockets, and loop for everything else
		2019
		2020
		2021	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2022
		2023	Fork watchers are called when a C<fork ()> was detected (usually because
		2024	whoever is a good citizen cared to tell libev about it by calling
		2025	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2026	event loop blocks next and before C<ev_check> watchers are being called,
		2027	and only in the child after the fork. If whoever good citizen calling
		2028	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2029	handlers will be invoked, too, of course.
		2030
		2031	=head3 Watcher-Specific Functions and Data Members
		2032
		2033	=over 4
		2034
		2035	=item ev_fork_init (ev_signal *, callback)
		2036
		2037	Initialises and configures the fork watcher - it has no parameters of any
		2038	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2039	believe me.
		2040
		2041	=back
		2042
		2043
690	=head1 OTHER FUNCTIONS	2044	=head1 OTHER FUNCTIONS
691		2045
692	There are some other fucntions of possible interest. Described. Here. Now.	2046	There are some other functions of possible interest. Described. Here. Now.
693		2047
694	=over 4	2048	=over 4
695		2049
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2050	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		2051
698	This function combines a simple timer and an I/O watcher, calls your	2052	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	2053	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	2054	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	2055	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	2056	more watchers yourself.
703		2057
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	2058	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	2059	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	2060	C<events> set will be craeted and started.
707		2061
708	If C<timeout> is less than 0, then no timeout watcher will be	2062	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	2063	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	2064	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		2065	dubious value.
711		2066
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	2067	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,	2068	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>:	2069	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		2070	value passed to C<ev_once>:
715		2071
716	static void stdin_ready (int revents, void *arg)	2072	static void stdin_ready (int revents, void *arg)
717	{	2073	{
718	if (revents & EV_TIMEOUT)	2074	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	2075	/* doh, nothing entered */;
720	else if (revents & EV_READ)	2076	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	2077	/* stdin might have data for us, joy! */;
722	}	2078	}
723		2079
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	2080	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		2081
726	=item ev_feed_event (loop, watcher, int events)	2082	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		2083
728	Feeds the given event set into the event loop, as if the specified event	2084	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	2085	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	2086	initialised but not necessarily started event watcher).
731		2087
732	=item ev_feed_fd_event (loop, int fd, int revents)	2088	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		2089
734	Feed an event on the given fd, as if a file descriptor backend detected it.	2090	Feed an event on the given fd, as if a file descriptor backend detected
		2091	the given events it.
735		2092
736	=item ev_feed_signal_event (loop, int signum)	2093	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		2094
738	Feed an event as if the given signal occured (loop must be the default loop!).	2095	Feed an event as if the given signal occured (C<loop> must be the default
		2096	loop!).
739		2097
740	=back	2098	=back
741		2099
		2100
		2101	=head1 LIBEVENT EMULATION
		2102
		2103	Libev offers a compatibility emulation layer for libevent. It cannot
		2104	emulate the internals of libevent, so here are some usage hints:
		2105
		2106	=over 4
		2107
		2108	=item * Use it by including <event.h>, as usual.
		2109
		2110	=item * The following members are fully supported: ev_base, ev_callback,
		2111	ev_arg, ev_fd, ev_res, ev_events.
		2112
		2113	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		2114	maintained by libev, it does not work exactly the same way as in libevent (consider
		2115	it a private API).
		2116
		2117	=item * Priorities are not currently supported. Initialising priorities
		2118	will fail and all watchers will have the same priority, even though there
		2119	is an ev_pri field.
		2120
		2121	=item * Other members are not supported.
		2122
		2123	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		2124	to use the libev header file and library.
		2125
		2126	=back
		2127
		2128	=head1 C++ SUPPORT
		2129
		2130	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2131	you to use some convinience methods to start/stop watchers and also change
		2132	the callback model to a model using method callbacks on objects.
		2133
		2134	To use it,
		2135
		2136	#include <ev++.h>
		2137
		2138	This automatically includes F<ev.h> and puts all of its definitions (many
		2139	of them macros) into the global namespace. All C++ specific things are
		2140	put into the C<ev> namespace. It should support all the same embedding
		2141	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2142
		2143	Care has been taken to keep the overhead low. The only data member the C++
		2144	classes add (compared to plain C-style watchers) is the event loop pointer
		2145	that the watcher is associated with (or no additional members at all if
		2146	you disable C<EV_MULTIPLICITY> when embedding libev).
		2147
		2148	Currently, functions, and static and non-static member functions can be
		2149	used as callbacks. Other types should be easy to add as long as they only
		2150	need one additional pointer for context. If you need support for other
		2151	types of functors please contact the author (preferably after implementing
		2152	it).
		2153
		2154	Here is a list of things available in the C<ev> namespace:
		2155
		2156	=over 4
		2157
		2158	=item C<ev::READ>, C<ev::WRITE> etc.
		2159
		2160	These are just enum values with the same values as the C<EV_READ> etc.
		2161	macros from F<ev.h>.
		2162
		2163	=item C<ev::tstamp>, C<ev::now>
		2164
		2165	Aliases to the same types/functions as with the C<ev_> prefix.
		2166
		2167	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2168
		2169	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2170	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2171	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2172	defines by many implementations.
		2173
		2174	All of those classes have these methods:
		2175
		2176	=over 4
		2177
		2178	=item ev::TYPE::TYPE ()
		2179
		2180	=item ev::TYPE::TYPE (struct ev_loop *)
		2181
		2182	=item ev::TYPE::~TYPE
		2183
		2184	The constructor (optionally) takes an event loop to associate the watcher
		2185	with. If it is omitted, it will use C<EV_DEFAULT>.
		2186
		2187	The constructor calls C<ev_init> for you, which means you have to call the
		2188	C<set> method before starting it.
		2189
		2190	It will not set a callback, however: You have to call the templated C<set>
		2191	method to set a callback before you can start the watcher.
		2192
		2193	(The reason why you have to use a method is a limitation in C++ which does
		2194	not allow explicit template arguments for constructors).
		2195
		2196	The destructor automatically stops the watcher if it is active.
		2197
		2198	=item w->set<class, &class::method> (object *)
		2199
		2200	This method sets the callback method to call. The method has to have a
		2201	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2202	first argument and the C<revents> as second. The object must be given as
		2203	parameter and is stored in the C<data> member of the watcher.
		2204
		2205	This method synthesizes efficient thunking code to call your method from
		2206	the C callback that libev requires. If your compiler can inline your
		2207	callback (i.e. it is visible to it at the place of the C<set> call and
		2208	your compiler is good :), then the method will be fully inlined into the
		2209	thunking function, making it as fast as a direct C callback.
		2210
		2211	Example: simple class declaration and watcher initialisation
		2212
		2213	struct myclass
		2214	{
		2215	void io_cb (ev::io &w, int revents) { }
		2216	}
		2217
		2218	myclass obj;
		2219	ev::io iow;
		2220	iow.set <myclass, &myclass::io_cb> (&obj);
		2221
		2222	=item w->set<function> (void *data = 0)
		2223
		2224	Also sets a callback, but uses a static method or plain function as
		2225	callback. The optional C<data> argument will be stored in the watcher's
		2226	C<data> member and is free for you to use.
		2227
		2228	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2229
		2230	See the method-C<set> above for more details.
		2231
		2232	Example:
		2233
		2234	static void io_cb (ev::io &w, int revents) { }
		2235	iow.set <io_cb> ();
		2236
		2237	=item w->set (struct ev_loop *)
		2238
		2239	Associates a different C<struct ev_loop> with this watcher. You can only
		2240	do this when the watcher is inactive (and not pending either).
		2241
		2242	=item w->set ([args])
		2243
		2244	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2245	called at least once. Unlike the C counterpart, an active watcher gets
		2246	automatically stopped and restarted when reconfiguring it with this
		2247	method.
		2248
		2249	=item w->start ()
		2250
		2251	Starts the watcher. Note that there is no C<loop> argument, as the
		2252	constructor already stores the event loop.
		2253
		2254	=item w->stop ()
		2255
		2256	Stops the watcher if it is active. Again, no C<loop> argument.
		2257
		2258	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2259
		2260	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2261	C<ev_TYPE_again> function.
		2262
		2263	=item w->sweep () (C<ev::embed> only)
		2264
		2265	Invokes C<ev_embed_sweep>.
		2266
		2267	=item w->update () (C<ev::stat> only)
		2268
		2269	Invokes C<ev_stat_stat>.
		2270
		2271	=back
		2272
		2273	=back
		2274
		2275	Example: Define a class with an IO and idle watcher, start one of them in
		2276	the constructor.
		2277
		2278	class myclass
		2279	{
		2280	ev_io io; void io_cb (ev::io &w, int revents);
		2281	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2282
		2283	myclass ();
		2284	}
		2285
		2286	myclass::myclass (int fd)
		2287	{
		2288	io .set <myclass, &myclass::io_cb > (this);
		2289	idle.set <myclass, &myclass::idle_cb> (this);
		2290
		2291	io.start (fd, ev::READ);
		2292	}
		2293
		2294
		2295	=head1 MACRO MAGIC
		2296
		2297	Libev can be compiled with a variety of options, the most fundamantal
		2298	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2299	functions and callbacks have an initial C<struct ev_loop *> argument.
		2300
		2301	To make it easier to write programs that cope with either variant, the
		2302	following macros are defined:
		2303
		2304	=over 4
		2305
		2306	=item C<EV_A>, C<EV_A_>
		2307
		2308	This provides the loop I<argument> for functions, if one is required ("ev
		2309	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2310	C<EV_A_> is used when other arguments are following. Example:
		2311
		2312	ev_unref (EV_A);
		2313	ev_timer_add (EV_A_ watcher);
		2314	ev_loop (EV_A_ 0);
		2315
		2316	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2317	which is often provided by the following macro.
		2318
		2319	=item C<EV_P>, C<EV_P_>
		2320
		2321	This provides the loop I<parameter> for functions, if one is required ("ev
		2322	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2323	C<EV_P_> is used when other parameters are following. Example:
		2324
		2325	// this is how ev_unref is being declared
		2326	static void ev_unref (EV_P);
		2327
		2328	// this is how you can declare your typical callback
		2329	static void cb (EV_P_ ev_timer *w, int revents)
		2330
		2331	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2332	suitable for use with C<EV_A>.
		2333
		2334	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2335
		2336	Similar to the other two macros, this gives you the value of the default
		2337	loop, if multiple loops are supported ("ev loop default").
		2338
		2339	=back
		2340
		2341	Example: Declare and initialise a check watcher, utilising the above
		2342	macros so it will work regardless of whether multiple loops are supported
		2343	or not.
		2344
		2345	static void
		2346	check_cb (EV_P_ ev_timer *w, int revents)
		2347	{
		2348	ev_check_stop (EV_A_ w);
		2349	}
		2350
		2351	ev_check check;
		2352	ev_check_init (&check, check_cb);
		2353	ev_check_start (EV_DEFAULT_ &check);
		2354	ev_loop (EV_DEFAULT_ 0);
		2355
		2356	=head1 EMBEDDING
		2357
		2358	Libev can (and often is) directly embedded into host
		2359	applications. Examples of applications that embed it include the Deliantra
		2360	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2361	and rxvt-unicode.
		2362
		2363	The goal is to enable you to just copy the necessary files into your
		2364	source directory without having to change even a single line in them, so
		2365	you can easily upgrade by simply copying (or having a checked-out copy of
		2366	libev somewhere in your source tree).
		2367
		2368	=head2 FILESETS
		2369
		2370	Depending on what features you need you need to include one or more sets of files
		2371	in your app.
		2372
		2373	=head3 CORE EVENT LOOP
		2374
		2375	To include only the libev core (all the C<ev_*> functions), with manual
		2376	configuration (no autoconf):
		2377
		2378	#define EV_STANDALONE 1
		2379	#include "ev.c"
		2380
		2381	This will automatically include F<ev.h>, too, and should be done in a
		2382	single C source file only to provide the function implementations. To use
		2383	it, do the same for F<ev.h> in all files wishing to use this API (best
		2384	done by writing a wrapper around F<ev.h> that you can include instead and
		2385	where you can put other configuration options):
		2386
		2387	#define EV_STANDALONE 1
		2388	#include "ev.h"
		2389
		2390	Both header files and implementation files can be compiled with a C++
		2391	compiler (at least, thats a stated goal, and breakage will be treated
		2392	as a bug).
		2393
		2394	You need the following files in your source tree, or in a directory
		2395	in your include path (e.g. in libev/ when using -Ilibev):
		2396
		2397	ev.h
		2398	ev.c
		2399	ev_vars.h
		2400	ev_wrap.h
		2401
		2402	ev_win32.c required on win32 platforms only
		2403
		2404	ev_select.c only when select backend is enabled (which is enabled by default)
		2405	ev_poll.c only when poll backend is enabled (disabled by default)
		2406	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2407	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2408	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2409
		2410	F<ev.c> includes the backend files directly when enabled, so you only need
		2411	to compile this single file.
		2412
		2413	=head3 LIBEVENT COMPATIBILITY API
		2414
		2415	To include the libevent compatibility API, also include:
		2416
		2417	#include "event.c"
		2418
		2419	in the file including F<ev.c>, and:
		2420
		2421	#include "event.h"
		2422
		2423	in the files that want to use the libevent API. This also includes F<ev.h>.
		2424
		2425	You need the following additional files for this:
		2426
		2427	event.h
		2428	event.c
		2429
		2430	=head3 AUTOCONF SUPPORT
		2431
		2432	Instead of using C<EV_STANDALONE=1> and providing your config in
		2433	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2434	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2435	include F<config.h> and configure itself accordingly.
		2436
		2437	For this of course you need the m4 file:
		2438
		2439	libev.m4
		2440
		2441	=head2 PREPROCESSOR SYMBOLS/MACROS
		2442
		2443	Libev can be configured via a variety of preprocessor symbols you have to define
		2444	before including any of its files. The default is not to build for multiplicity
		2445	and only include the select backend.
		2446
		2447	=over 4
		2448
		2449	=item EV_STANDALONE
		2450
		2451	Must always be C<1> if you do not use autoconf configuration, which
		2452	keeps libev from including F<config.h>, and it also defines dummy
		2453	implementations for some libevent functions (such as logging, which is not
		2454	supported). It will also not define any of the structs usually found in
		2455	F<event.h> that are not directly supported by the libev core alone.
		2456
		2457	=item EV_USE_MONOTONIC
		2458
		2459	If defined to be C<1>, libev will try to detect the availability of the
		2460	monotonic clock option at both compiletime and runtime. Otherwise no use
		2461	of the monotonic clock option will be attempted. If you enable this, you
		2462	usually have to link against librt or something similar. Enabling it when
		2463	the functionality isn't available is safe, though, although you have
		2464	to make sure you link against any libraries where the C<clock_gettime>
		2465	function is hiding in (often F<-lrt>).
		2466
		2467	=item EV_USE_REALTIME
		2468
		2469	If defined to be C<1>, libev will try to detect the availability of the
		2470	realtime clock option at compiletime (and assume its availability at
		2471	runtime if successful). Otherwise no use of the realtime clock option will
		2472	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2473	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2474	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2475
		2476	=item EV_USE_NANOSLEEP
		2477
		2478	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2479	and will use it for delays. Otherwise it will use C<select ()>.
		2480
		2481	=item EV_USE_SELECT
		2482
		2483	If undefined or defined to be C<1>, libev will compile in support for the
		2484	C<select>(2) backend. No attempt at autodetection will be done: if no
		2485	other method takes over, select will be it. Otherwise the select backend
		2486	will not be compiled in.
		2487
		2488	=item EV_SELECT_USE_FD_SET
		2489
		2490	If defined to C<1>, then the select backend will use the system C<fd_set>
		2491	structure. This is useful if libev doesn't compile due to a missing
		2492	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2493	exotic systems. This usually limits the range of file descriptors to some
		2494	low limit such as 1024 or might have other limitations (winsocket only
		2495	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2496	influence the size of the C<fd_set> used.
		2497
		2498	=item EV_SELECT_IS_WINSOCKET
		2499
		2500	When defined to C<1>, the select backend will assume that
		2501	select/socket/connect etc. don't understand file descriptors but
		2502	wants osf handles on win32 (this is the case when the select to
		2503	be used is the winsock select). This means that it will call
		2504	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2505	it is assumed that all these functions actually work on fds, even
		2506	on win32. Should not be defined on non-win32 platforms.
		2507
		2508	=item EV_FD_TO_WIN32_HANDLE
		2509
		2510	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2511	file descriptors to socket handles. When not defining this symbol (the
		2512	default), then libev will call C<_get_osfhandle>, which is usually
		2513	correct. In some cases, programs use their own file descriptor management,
		2514	in which case they can provide this function to map fds to socket handles.
		2515
		2516	=item EV_USE_POLL
		2517
		2518	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2519	backend. Otherwise it will be enabled on non-win32 platforms. It
		2520	takes precedence over select.
		2521
		2522	=item EV_USE_EPOLL
		2523
		2524	If defined to be C<1>, libev will compile in support for the Linux
		2525	C<epoll>(7) backend. Its availability will be detected at runtime,
		2526	otherwise another method will be used as fallback. This is the
		2527	preferred backend for GNU/Linux systems.
		2528
		2529	=item EV_USE_KQUEUE
		2530
		2531	If defined to be C<1>, libev will compile in support for the BSD style
		2532	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2533	otherwise another method will be used as fallback. This is the preferred
		2534	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2535	supports some types of fds correctly (the only platform we found that
		2536	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2537	not be used unless explicitly requested. The best way to use it is to find
		2538	out whether kqueue supports your type of fd properly and use an embedded
		2539	kqueue loop.
		2540
		2541	=item EV_USE_PORT
		2542
		2543	If defined to be C<1>, libev will compile in support for the Solaris
		2544	10 port style backend. Its availability will be detected at runtime,
		2545	otherwise another method will be used as fallback. This is the preferred
		2546	backend for Solaris 10 systems.
		2547
		2548	=item EV_USE_DEVPOLL
		2549
		2550	reserved for future expansion, works like the USE symbols above.
		2551
		2552	=item EV_USE_INOTIFY
		2553
		2554	If defined to be C<1>, libev will compile in support for the Linux inotify
		2555	interface to speed up C<ev_stat> watchers. Its actual availability will
		2556	be detected at runtime.
		2557
		2558	=item EV_H
		2559
		2560	The name of the F<ev.h> header file used to include it. The default if
		2561	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
		2562	virtually rename the F<ev.h> header file in case of conflicts.
		2563
		2564	=item EV_CONFIG_H
		2565
		2566	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2567	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2568	C<EV_H>, above.
		2569
		2570	=item EV_EVENT_H
		2571
		2572	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2573	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
		2574
		2575	=item EV_PROTOTYPES
		2576
		2577	If defined to be C<0>, then F<ev.h> will not define any function
		2578	prototypes, but still define all the structs and other symbols. This is
		2579	occasionally useful if you want to provide your own wrapper functions
		2580	around libev functions.
		2581
		2582	=item EV_MULTIPLICITY
		2583
		2584	If undefined or defined to C<1>, then all event-loop-specific functions
		2585	will have the C<struct ev_loop *> as first argument, and you can create
		2586	additional independent event loops. Otherwise there will be no support
		2587	for multiple event loops and there is no first event loop pointer
		2588	argument. Instead, all functions act on the single default loop.
		2589
		2590	=item EV_MINPRI
		2591
		2592	=item EV_MAXPRI
		2593
		2594	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2595	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2596	provide for more priorities by overriding those symbols (usually defined
		2597	to be C<-2> and C<2>, respectively).
		2598
		2599	When doing priority-based operations, libev usually has to linearly search
		2600	all the priorities, so having many of them (hundreds) uses a lot of space
		2601	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2602	fine.
		2603
		2604	If your embedding app does not need any priorities, defining these both to
		2605	C<0> will save some memory and cpu.
		2606
		2607	=item EV_PERIODIC_ENABLE
		2608
		2609	If undefined or defined to be C<1>, then periodic timers are supported. If
		2610	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2611	code.
		2612
		2613	=item EV_IDLE_ENABLE
		2614
		2615	If undefined or defined to be C<1>, then idle watchers are supported. If
		2616	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2617	code.
		2618
		2619	=item EV_EMBED_ENABLE
		2620
		2621	If undefined or defined to be C<1>, then embed watchers are supported. If
		2622	defined to be C<0>, then they are not.
		2623
		2624	=item EV_STAT_ENABLE
		2625
		2626	If undefined or defined to be C<1>, then stat watchers are supported. If
		2627	defined to be C<0>, then they are not.
		2628
		2629	=item EV_FORK_ENABLE
		2630
		2631	If undefined or defined to be C<1>, then fork watchers are supported. If
		2632	defined to be C<0>, then they are not.
		2633
		2634	=item EV_MINIMAL
		2635
		2636	If you need to shave off some kilobytes of code at the expense of some
		2637	speed, define this symbol to C<1>. Currently only used for gcc to override
		2638	some inlining decisions, saves roughly 30% codesize of amd64.
		2639
		2640	=item EV_PID_HASHSIZE
		2641
		2642	C<ev_child> watchers use a small hash table to distribute workload by
		2643	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2644	than enough. If you need to manage thousands of children you might want to
		2645	increase this value (I<must> be a power of two).
		2646
		2647	=item EV_INOTIFY_HASHSIZE
		2648
		2649	C<ev_stat> watchers use a small hash table to distribute workload by
		2650	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2651	usually more than enough. If you need to manage thousands of C<ev_stat>
		2652	watchers you might want to increase this value (I<must> be a power of
		2653	two).
		2654
		2655	=item EV_COMMON
		2656
		2657	By default, all watchers have a C<void *data> member. By redefining
		2658	this macro to a something else you can include more and other types of
		2659	members. You have to define it each time you include one of the files,
		2660	though, and it must be identical each time.
		2661
		2662	For example, the perl EV module uses something like this:
		2663
		2664	#define EV_COMMON \
		2665	SV *self; /* contains this struct */ \
		2666	SV *cb_sv, *fh /* note no trailing ";" */
		2667
		2668	=item EV_CB_DECLARE (type)
		2669
		2670	=item EV_CB_INVOKE (watcher, revents)
		2671
		2672	=item ev_set_cb (ev, cb)
		2673
		2674	Can be used to change the callback member declaration in each watcher,
		2675	and the way callbacks are invoked and set. Must expand to a struct member
		2676	definition and a statement, respectively. See the F<ev.h> header file for
		2677	their default definitions. One possible use for overriding these is to
		2678	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2679	method calls instead of plain function calls in C++.
		2680
		2681	=head2 EXPORTED API SYMBOLS
		2682
		2683	If you need to re-export the API (e.g. via a dll) and you need a list of
		2684	exported symbols, you can use the provided F<Symbol.*> files which list
		2685	all public symbols, one per line:
		2686
		2687	Symbols.ev for libev proper
		2688	Symbols.event for the libevent emulation
		2689
		2690	This can also be used to rename all public symbols to avoid clashes with
		2691	multiple versions of libev linked together (which is obviously bad in
		2692	itself, but sometimes it is inconvinient to avoid this).
		2693
		2694	A sed command like this will create wrapper C<#define>'s that you need to
		2695	include before including F<ev.h>:
		2696
		2697	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2698
		2699	This would create a file F<wrap.h> which essentially looks like this:
		2700
		2701	#define ev_backend myprefix_ev_backend
		2702	#define ev_check_start myprefix_ev_check_start
		2703	#define ev_check_stop myprefix_ev_check_stop
		2704	...
		2705
		2706	=head2 EXAMPLES
		2707
		2708	For a real-world example of a program the includes libev
		2709	verbatim, you can have a look at the EV perl module
		2710	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2711	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2712	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2713	will be compiled. It is pretty complex because it provides its own header
		2714	file.
		2715
		2716	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2717	that everybody includes and which overrides some configure choices:
		2718
		2719	#define EV_MINIMAL 1
		2720	#define EV_USE_POLL 0
		2721	#define EV_MULTIPLICITY 0
		2722	#define EV_PERIODIC_ENABLE 0
		2723	#define EV_STAT_ENABLE 0
		2724	#define EV_FORK_ENABLE 0
		2725	#define EV_CONFIG_H <config.h>
		2726	#define EV_MINPRI 0
		2727	#define EV_MAXPRI 0
		2728
		2729	#include "ev++.h"
		2730
		2731	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2732
		2733	#include "ev_cpp.h"
		2734	#include "ev.c"
		2735
		2736
		2737	=head1 COMPLEXITIES
		2738
		2739	In this section the complexities of (many of) the algorithms used inside
		2740	libev will be explained. For complexity discussions about backends see the
		2741	documentation for C<ev_default_init>.
		2742
		2743	All of the following are about amortised time: If an array needs to be
		2744	extended, libev needs to realloc and move the whole array, but this
		2745	happens asymptotically never with higher number of elements, so O(1) might
		2746	mean it might do a lengthy realloc operation in rare cases, but on average
		2747	it is much faster and asymptotically approaches constant time.
		2748
		2749	=over 4
		2750
		2751	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2752
		2753	This means that, when you have a watcher that triggers in one hour and
		2754	there are 100 watchers that would trigger before that then inserting will
		2755	have to skip roughly seven (C<ld 100>) of these watchers.
		2756
		2757	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2758
		2759	That means that changing a timer costs less than removing/adding them
		2760	as only the relative motion in the event queue has to be paid for.
		2761
		2762	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2763
		2764	These just add the watcher into an array or at the head of a list.
		2765
		2766	=item Stopping check/prepare/idle watchers: O(1)
		2767
		2768	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2769
		2770	These watchers are stored in lists then need to be walked to find the
		2771	correct watcher to remove. The lists are usually short (you don't usually
		2772	have many watchers waiting for the same fd or signal).
		2773
		2774	=item Finding the next timer in each loop iteration: O(1)
		2775
		2776	By virtue of using a binary heap, the next timer is always found at the
		2777	beginning of the storage array.
		2778
		2779	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2780
		2781	A change means an I/O watcher gets started or stopped, which requires
		2782	libev to recalculate its status (and possibly tell the kernel, depending
		2783	on backend and wether C<ev_io_set> was used).
		2784
		2785	=item Activating one watcher (putting it into the pending state): O(1)
		2786
		2787	=item Priority handling: O(number_of_priorities)
		2788
		2789	Priorities are implemented by allocating some space for each
		2790	priority. When doing priority-based operations, libev usually has to
		2791	linearly search all the priorities, but starting/stopping and activating
		2792	watchers becomes O(1) w.r.t. prioritiy handling.
		2793
		2794	=back
		2795
		2796
		2797	=head1 Win32 platform limitations and workarounds
		2798
		2799	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2800	requires, and its I/O model is fundamentally incompatible with the POSIX
		2801	model. Libev still offers limited functionality on this platform in
		2802	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2803	descriptors. This only applies when using Win32 natively, not when using
		2804	e.g. cygwin.
		2805
		2806	There is no supported compilation method available on windows except
		2807	embedding it into other applications.
		2808
		2809	Due to the many, low, and arbitrary limits on the win32 platform and the
		2810	abysmal performance of winsockets, using a large number of sockets is not
		2811	recommended (and not reasonable). If your program needs to use more than
		2812	a hundred or so sockets, then likely it needs to use a totally different
		2813	implementation for windows, as libev offers the POSIX model, which cannot
		2814	be implemented efficiently on windows (microsoft monopoly games).
		2815
		2816	=over 4
		2817
		2818	=item The winsocket select function
		2819
		2820	The winsocket C<select> function doesn't follow POSIX in that it requires
		2821	socket I<handles> and not socket I<file descriptors>. This makes select
		2822	very inefficient, and also requires a mapping from file descriptors
		2823	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2824	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2825	symbols for more info.
		2826
		2827	The configuration for a "naked" win32 using the microsoft runtime
		2828	libraries and raw winsocket select is:
		2829
		2830	#define EV_USE_SELECT 1
		2831	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2832
		2833	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2834	complexity in the O(n²) range when using win32.
		2835
		2836	=item Limited number of file descriptors
		2837
		2838	Windows has numerous arbitrary (and low) limits on things. Early versions
		2839	of winsocket's select only supported waiting for a max. of C<64> handles
		2840	(probably owning to the fact that all windows kernels can only wait for
		2841	C<64> things at the same time internally; microsoft recommends spawning a
		2842	chain of threads and wait for 63 handles and the previous thread in each).
		2843
		2844	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2845	to some high number (e.g. C<2048>) before compiling the winsocket select
		2846	call (which might be in libev or elsewhere, for example, perl does its own
		2847	select emulation on windows).
		2848
		2849	Another limit is the number of file descriptors in the microsoft runtime
		2850	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2851	or something like this inside microsoft). You can increase this by calling
		2852	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2853	arbitrary limit), but is broken in many versions of the microsoft runtime
		2854	libraries.
		2855
		2856	This might get you to about C<512> or C<2048> sockets (depending on
		2857	windows version and/or the phase of the moon). To get more, you need to
		2858	wrap all I/O functions and provide your own fd management, but the cost of
		2859	calling select (O(n²)) will likely make this unworkable.
		2860
		2861	=back
		2862
		2863
742	=head1 AUTHOR	2864	=head1 AUTHOR
743		2865
744	Marc Lehmann <libev@schmorp.de>.	2866	Marc Lehmann <libev@schmorp.de>.
745		2867

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