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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	=head1 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
		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>.
10		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 occuring), 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
…		…
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	=head1 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	=head1 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	=head1 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 such.
		104
		105	=head1 GLOBAL FUNCTIONS
		106
		107	These functions can be called anytime, even before initialising the
		108	library in any way.
51		109
52	=over 4	110	=over 4
53		111
54	=item ev_tstamp ev_time ()	112	=item ev_tstamp ev_time ()
55		113
56	Returns the current time as libev would use it.	114	Returns the current time as libev would use it. Please note that the
		115	C<ev_now> function is usually faster and also often returns the timestamp
		116	you actually want to know.
57		117
58	=item int ev_version_major ()	118	=item int ev_version_major ()
59		119
60	=item int ev_version_minor ()	120	=item int ev_version_minor ()
61		121
…		…
68	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	131	not a problem.
72		132
		133	Example: Make sure we haven't accidentally been linked against the wrong
		134	version.
		135
		136	assert (("libev version mismatch",
		137	ev_version_major () == EV_VERSION_MAJOR
		138	&& ev_version_minor () >= EV_VERSION_MINOR));
		139
		140	=item unsigned int ev_supported_backends ()
		141
		142	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		143	value) compiled into this binary of libev (independent of their
		144	availability on the system you are running on). See C<ev_default_loop> for
		145	a description of the set values.
		146
		147	Example: make sure we have the epoll method, because yeah this is cool and
		148	a must have and can we have a torrent of it please!!!11
		149
		150	assert (("sorry, no epoll, no sex",
		151	ev_supported_backends () & EVBACKEND_EPOLL));
		152
		153	=item unsigned int ev_recommended_backends ()
		154
		155	Return the set of all backends compiled into this binary of libev and also
		156	recommended for this platform. This set is often smaller than the one
		157	returned by C<ev_supported_backends>, as for example kqueue is broken on
		158	most BSDs and will not be autodetected unless you explicitly request it
		159	(assuming you know what you are doing). This is the set of backends that
		160	libev will probe for if you specify no backends explicitly.
		161
		162	=item unsigned int ev_embeddable_backends ()
		163
		164	Returns the set of backends that are embeddable in other event loops. This
		165	is the theoretical, all-platform, value. To find which backends
		166	might be supported on the current system, you would need to look at
		167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		168	recommended ones.
		169
		170	See the description of C<ev_embed> watchers for more info.
		171
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		173
75	Sets the allocation function to use (the prototype is similar to the	174	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	175	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	176	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	177	memory needs to be allocated, the library might abort or take some
79	destructive action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
80		180
81	You could override this function in high-availability programs to, say,	181	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,	182	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.	183	or even to sleep a while and retry until some memory is available.
		184
		185	Example: Replace the libev allocator with one that waits a bit and then
		186	retries).
		187
		188	static void *
		189	persistent_realloc (void *ptr, size_t size)
		190	{
		191	for (;;)
		192	{
		193	void *newptr = realloc (ptr, size);
		194
		195	if (newptr)
		196	return newptr;
		197
		198	sleep (60);
		199	}
		200	}
		201
		202	...
		203	ev_set_allocator (persistent_realloc);
84		204
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	205	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		206
87	Set the callback function to call on a retryable syscall error (such	207	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	208	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	210	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	211	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	212	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	213	(such as abort).
94		214
		215	Example: This is basically the same thing that libev does internally, too.
		216
		217	static void
		218	fatal_error (const char *msg)
		219	{
		220	perror (msg);
		221	abort ();
		222	}
		223
		224	...
		225	ev_set_syserr_cb (fatal_error);
		226
95	=back	227	=back
96		228
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	229	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		230
99	An event loop is described by a C<struct ev_loop *>. The library knows two	231	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	232	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	233	events, and dynamically created loops which do not.
102		234
103	If you use threads, a common model is to run the default event loop	235	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	236	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	237	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	238	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	239	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	240	done correctly, because it's hideous and inefficient).
109		241
…		…
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	244	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		245
114	This will initialise the default event loop if it hasn't been initialised	246	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	247	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	248	false. If it already was initialised it simply returns it (and ignores the
117	flags).	249	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		250
119	If you don't know what event loop to use, use the one returned from this	251	If you don't know what event loop to use, use the one returned from this
120	function.	252	function.
121		253
122	The flags argument can be used to specify special behaviour or specific	254	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).	255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		256
125	It supports the following flags:	257	The following flags are supported:
126		258
127	=over 4	259	=over 4
128		260
129	=item C<EVFLAG_AUTO>	261	=item C<EVFLAG_AUTO>
130		262
…		…
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	271	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	272	useful to try out specific backends to test their performance, or to work
141	around bugs.	273	around bugs.
142		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
143	=item C<EVMETHOD_SELECT> (portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		296
		297	This is your standard select(2) backend. Not I<completely> standard, as
		298	libev tries to roll its own fd_set with no limits on the number of fds,
		299	but if that fails, expect a fairly low limit on the number of fds when
		300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		301	the fastest backend for a low number of fds.
		302
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		304
147	=item C<EVMETHOD_EPOLL> (linux only)	305	And this is your standard poll(2) backend. It's more complicated than
		306	select, but handles sparse fds better and has no artificial limit on the
		307	number of fds you can use (except it will slow down considerably with a
		308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148		309
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	310	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		311
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	312	For few fds, this backend is a bit little slower than poll and select,
		313	but it scales phenomenally better. While poll and select usually scale like
		314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		315	either O(1) or O(active_fds).
152		316
153	=item C<EVMETHOD_PORT> (solaris 10 only)	317	While stopping and starting an I/O watcher in the same iteration will
		318	result in some caching, there is still a syscall per such incident
		319	(because the fd could point to a different file description now), so its
		320	best to avoid that. Also, dup()ed file descriptors might not work very
		321	well if you register events for both fds.
		322
		323	Please note that epoll sometimes generates spurious notifications, so you
		324	need to use non-blocking I/O or other means to avoid blocking when no data
		325	(or space) is available.
		326
		327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		328
		329	Kqueue deserves special mention, as at the time of this writing, it
		330	was broken on all BSDs except NetBSD (usually it doesn't work with
		331	anything but sockets and pipes, except on Darwin, where of course its
		332	completely useless). For this reason its not being "autodetected"
		333	unless you explicitly specify it explicitly in the flags (i.e. using
		334	C<EVBACKEND_KQUEUE>).
		335
		336	It scales in the same way as the epoll backend, but the interface to the
		337	kernel is more efficient (which says nothing about its actual speed, of
		338	course). While starting and stopping an I/O watcher does not cause an
		339	extra syscall as with epoll, it still adds up to four event changes per
		340	incident, so its best to avoid that.
		341
		342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		343
		344	This is not implemented yet (and might never be).
		345
		346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		347
		348	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		349	it's really slow, but it still scales very well (O(active_fds)).
		350
		351	Please note that solaris ports can result in a lot of spurious
		352	notifications, so you need to use non-blocking I/O or other means to avoid
		353	blocking when no data (or space) is available.
		354
		355	=item C<EVBACKEND_ALL>
		356
		357	Try all backends (even potentially broken ones that wouldn't be tried
		358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		360
		361	=back
154		362
155	If one or more of these are ored into the flags value, then only these	363	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	364	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	365	specified, most compiled-in backend will be tried, usually in reverse
		366	order of their flag values :)
158		367
159	=back	368	The most typical usage is like this:
		369
		370	if (!ev_default_loop (0))
		371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		372
		373	Restrict libev to the select and poll backends, and do not allow
		374	environment settings to be taken into account:
		375
		376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		377
		378	Use whatever libev has to offer, but make sure that kqueue is used if
		379	available (warning, breaks stuff, best use only with your own private
		380	event loop and only if you know the OS supports your types of fds):
		381
		382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		383
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	384	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		385
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	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	387	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	388	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).	389	undefined behaviour (or a failed assertion if assertions are enabled).
167		390
		391	Example: Try to create a event loop that uses epoll and nothing else.
		392
		393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		394	if (!epoller)
		395	fatal ("no epoll found here, maybe it hides under your chair");
		396
168	=item ev_default_destroy ()	397	=item ev_default_destroy ()
169		398
170	Destroys the default loop again (frees all memory and kernel state	399	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	400	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cannot rely on this :).	401	sense, so e.g. C<ev_is_active> might still return true. It is your
		402	responsibility to either stop all watchers cleanly yoursef I<before>
		403	calling this function, or cope with the fact afterwards (which is usually
		404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		405	for example).
173		406
174	=item ev_loop_destroy (loop)	407	=item ev_loop_destroy (loop)
175		408
176	Like C<ev_default_destroy>, but destroys an event loop created by an	409	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	410	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	414	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	415	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	416	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	417	again makes little sense).
185		418
186	You I<must> call this function after forking if and only if you want to	419	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	420	only if you want to use the event library in both processes. If you just
188	have to call it.	421	fork+exec, you don't have to call it.
189		422
190	The function itself is quite fast and it's usually not a problem to call	423	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	424	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>:	425	quite nicely into a call to C<pthread_atfork>:
193		426
194	pthread_atfork (0, 0, ev_default_fork);	427	pthread_atfork (0, 0, ev_default_fork);
195		428
		429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		430	without calling this function, so if you force one of those backends you
		431	do not need to care.
		432
196	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
197		434
198	Like C<ev_default_fork>, but acts on an event loop created by	435	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	436	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.	437	after fork, and how you do this is entirely your own problem.
201		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
		448
202	=item unsigned int ev_method (loop)	449	=item unsigned int ev_backend (loop)
203		450
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	452	use.
206		453
207	=item ev_tstamp ev_now (loop)	454	=item ev_tstamp ev_now (loop)
208		455
209	Returns the current "event loop time", which is the time the event loop	456	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	457	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	458	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	459	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).	460	event occuring (or more correctly, libev finding out about it).
214		461
215	=item ev_loop (loop, int flags)	462	=item ev_loop (loop, int flags)
216		463
217	Finally, this is it, the event handler. This function usually is called	464	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	465	after you initialised all your watchers and you want to start handling
219	events.	466	events.
220		467
221	If the flags argument is specified as 0, it will not return until either	468	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.	469	either no event watchers are active anymore or C<ev_unloop> was called.
		470
		471	Please note that an explicit C<ev_unloop> is usually better than
		472	relying on all watchers to be stopped when deciding when a program has
		473	finished (especially in interactive programs), but having a program that
		474	automatically loops as long as it has to and no longer by virtue of
		475	relying on its watchers stopping correctly is a thing of beauty.
223		476
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	477	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	478	those events and any outstanding ones, but will not block your process in
226	case there are no events and will return after one iteration of the loop.	479	case there are no events and will return after one iteration of the loop.
227		480
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	481	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	482	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives, and will return after	483	your process until at least one new event arrives, and will return after
231	one iteration of the loop.	484	one iteration of the loop. This is useful if you are waiting for some
		485	external event in conjunction with something not expressible using other
		486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		487	usually a better approach for this kind of thing.
232		488
233	This flags value could be used to implement alternative looping	489	Here are the gory details of what C<ev_loop> does:
234	constructs, but the C<prepare> and C<check> watchers provide a better and	490
235	more generic mechanism.	491	* If there are no active watchers (reference count is zero), return.
		492	- Queue prepare watchers and then call all outstanding watchers.
		493	- If we have been forked, recreate the kernel state.
		494	- Update the kernel state with all outstanding changes.
		495	- Update the "event loop time".
		496	- Calculate for how long to block.
		497	- Block the process, waiting for any events.
		498	- Queue all outstanding I/O (fd) events.
		499	- Update the "event loop time" and do time jump handling.
		500	- Queue all outstanding timers.
		501	- Queue all outstanding periodics.
		502	- If no events are pending now, queue all idle watchers.
		503	- Queue all check watchers.
		504	- Call all queued watchers in reverse order (i.e. check watchers first).
		505	Signals and child watchers are implemented as I/O watchers, and will
		506	be handled here by queueing them when their watcher gets executed.
		507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		508	were used, return, otherwise continue with step *.
		509
		510	Example: Queue some jobs and then loop until no events are outsanding
		511	anymore.
		512
		513	... queue jobs here, make sure they register event watchers as long
		514	... as they still have work to do (even an idle watcher will do..)
		515	ev_loop (my_loop, 0);
		516	... jobs done. yeah!
236		517
237	=item ev_unloop (loop, how)	518	=item ev_unloop (loop, how)
238		519
239	Can be used to make a call to C<ev_loop> return early (but only after it	520	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	521	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		524
244	=item ev_ref (loop)	525	=item ev_ref (loop)
245		526
246	=item ev_unref (loop)	527	=item ev_unref (loop)
…		…
254	visible to the libev user and should not keep C<ev_loop> from exiting if	535	visible to the libev user and should not keep C<ev_loop> from exiting if
255	no event watchers registered by it are active. It is also an excellent	536	no event watchers registered by it are active. It is also an excellent
256	way to do this for generic recurring timers or from within third-party	537	way to do this for generic recurring timers or from within third-party
257	libraries. Just remember to I<unref after start> and I<ref before stop>.	538	libraries. Just remember to I<unref after start> and I<ref before stop>.
258		539
		540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		541	running when nothing else is active.
		542
		543	struct ev_signal exitsig;
		544	ev_signal_init (&exitsig, sig_cb, SIGINT);
		545	ev_signal_start (loop, &exitsig);
		546	evf_unref (loop);
		547
		548	Example: For some weird reason, unregister the above signal handler again.
		549
		550	ev_ref (loop);
		551	ev_signal_stop (loop, &exitsig);
		552
259	=back	553	=back
		554
260		555
261	=head1 ANATOMY OF A WATCHER	556	=head1 ANATOMY OF A WATCHER
262		557
263	A watcher is a structure that you create and register to record your	558	A watcher is a structure that you create and register to record your
264	interest in some event. For instance, if you want to wait for STDIN to	559	interest in some event. For instance, if you want to wait for STDIN to
…		…
297	*) >>), and you can stop watching for events at any time by calling the	592	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	593	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		594
300	As long as your watcher is active (has been started but not stopped) you	595	As long as your watcher is active (has been started but not stopped) you
301	must not touch the values stored in it. Most specifically you must never	596	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	597	reinitialise it or call its C<set> macro.
303
304	You can check whether an event is active by calling the C<ev_is_active
305	(watcher *)> macro. To see whether an event is outstanding (but the
306	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.
308		598
309	Each and every callback receives the event loop pointer as first, the	599	Each and every callback receives the event loop pointer as first, the
310	registered watcher structure as second, and a bitset of received events as	600	registered watcher structure as second, and a bitset of received events as
311	third argument.	601	third argument.
312		602
…		…
336	The signal specified in the C<ev_signal> watcher has been received by a thread.	626	The signal specified in the C<ev_signal> watcher has been received by a thread.
337		627
338	=item C<EV_CHILD>	628	=item C<EV_CHILD>
339		629
340	The pid specified in the C<ev_child> watcher has received a status change.	630	The pid specified in the C<ev_child> watcher has received a status change.
		631
		632	=item C<EV_STAT>
		633
		634	The path specified in the C<ev_stat> watcher changed its attributes somehow.
341		635
342	=item C<EV_IDLE>	636	=item C<EV_IDLE>
343		637
344	The C<ev_idle> watcher has determined that you have nothing better to do.	638	The C<ev_idle> watcher has determined that you have nothing better to do.
345		639
…		…
353	received events. Callbacks of both watcher types can start and stop as	647	received events. Callbacks of both watcher types can start and stop as
354	many watchers as they want, and all of them will be taken into account	648	many watchers as they want, and all of them will be taken into account
355	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	649	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
356	C<ev_loop> from blocking).	650	C<ev_loop> from blocking).
357		651
		652	=item C<EV_EMBED>
		653
		654	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		655
		656	=item C<EV_FORK>
		657
		658	The event loop has been resumed in the child process after fork (see
		659	C<ev_fork>).
		660
358	=item C<EV_ERROR>	661	=item C<EV_ERROR>
359		662
360	An unspecified error has occured, the watcher has been stopped. This might	663	An unspecified error has occured, the watcher has been stopped. This might
361	happen because the watcher could not be properly started because libev	664	happen because the watcher could not be properly started because libev
362	ran out of memory, a file descriptor was found to be closed or any other	665	ran out of memory, a file descriptor was found to be closed or any other
…		…
368	your callbacks is well-written it can just attempt the operation and cope	671	your callbacks is well-written it can just attempt the operation and cope
369	with the error from read() or write(). This will not work in multithreaded	672	with the error from read() or write(). This will not work in multithreaded
370	programs, though, so beware.	673	programs, though, so beware.
371		674
372	=back	675	=back
		676
		677	=head2 GENERIC WATCHER FUNCTIONS
		678
		679	In the following description, C<TYPE> stands for the watcher type,
		680	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		681
		682	=over 4
		683
		684	=item C<ev_init> (ev_TYPE *watcher, callback)
		685
		686	This macro initialises the generic portion of a watcher. The contents
		687	of the watcher object can be arbitrary (so C<malloc> will do). Only
		688	the generic parts of the watcher are initialised, you I<need> to call
		689	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		690	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		691	which rolls both calls into one.
		692
		693	You can reinitialise a watcher at any time as long as it has been stopped
		694	(or never started) and there are no pending events outstanding.
		695
		696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		697	int revents)>.
		698
		699	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		700
		701	This macro initialises the type-specific parts of a watcher. You need to
		702	call C<ev_init> at least once before you call this macro, but you can
		703	call C<ev_TYPE_set> any number of times. You must not, however, call this
		704	macro on a watcher that is active (it can be pending, however, which is a
		705	difference to the C<ev_init> macro).
		706
		707	Although some watcher types do not have type-specific arguments
		708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		709
		710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		711
		712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		713	calls into a single call. This is the most convinient method to initialise
		714	a watcher. The same limitations apply, of course.
		715
		716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		717
		718	Starts (activates) the given watcher. Only active watchers will receive
		719	events. If the watcher is already active nothing will happen.
		720
		721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		722
		723	Stops the given watcher again (if active) and clears the pending
		724	status. It is possible that stopped watchers are pending (for example,
		725	non-repeating timers are being stopped when they become pending), but
		726	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		727	you want to free or reuse the memory used by the watcher it is therefore a
		728	good idea to always call its C<ev_TYPE_stop> function.
		729
		730	=item bool ev_is_active (ev_TYPE *watcher)
		731
		732	Returns a true value iff the watcher is active (i.e. it has been started
		733	and not yet been stopped). As long as a watcher is active you must not modify
		734	it.
		735
		736	=item bool ev_is_pending (ev_TYPE *watcher)
		737
		738	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		739	events but its callback has not yet been invoked). As long as a watcher
		740	is pending (but not active) you must not call an init function on it (but
		741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		742	libev (e.g. you cnanot C<free ()> it).
		743
		744	=item callback ev_cb (ev_TYPE *watcher)
		745
		746	Returns the callback currently set on the watcher.
		747
		748	=item ev_cb_set (ev_TYPE *watcher, callback)
		749
		750	Change the callback. You can change the callback at virtually any time
		751	(modulo threads).
		752
		753	=item ev_set_priority (ev_TYPE *watcher, priority)
		754
		755	=item int ev_priority (ev_TYPE *watcher)
		756
		757	Set and query the priority of the watcher. The priority is a small
		758	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		759	(default: C<-2>). Pending watchers with higher priority will be invoked
		760	before watchers with lower priority, but priority will not keep watchers
		761	from being executed (except for C<ev_idle> watchers).
		762
		763	This means that priorities are I<only> used for ordering callback
		764	invocation after new events have been received. This is useful, for
		765	example, to reduce latency after idling, or more often, to bind two
		766	watchers on the same event and make sure one is called first.
		767
		768	If you need to suppress invocation when higher priority events are pending
		769	you need to look at C<ev_idle> watchers, which provide this functionality.
		770
		771	The default priority used by watchers when no priority has been set is
		772	always C<0>, which is supposed to not be too high and not be too low :).
		773
		774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		775	fine, as long as you do not mind that the priority value you query might
		776	or might not have been adjusted to be within valid range.
		777
		778	=back
		779
373		780
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		782
376	Each watcher has, by default, a member C<void *data> that you can change	783	Each watcher has, by default, a member C<void *data> that you can change
377	and read at any time, libev will completely ignore it. This can be used	784	and read at any time, libev will completely ignore it. This can be used
…		…
395	{	802	{
396	struct my_io *w = (struct my_io *)w_;	803	struct my_io *w = (struct my_io *)w_;
397	...	804	...
398	}	805	}
399		806
400	More interesting and less C-conformant ways of catsing your callback type	807	More interesting and less C-conformant ways of casting your callback type
401	have been omitted....	808	instead have been omitted.
		809
		810	Another common scenario is having some data structure with multiple
		811	watchers:
		812
		813	struct my_biggy
		814	{
		815	int some_data;
		816	ev_timer t1;
		817	ev_timer t2;
		818	}
		819
		820	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		821	you need to use C<offsetof>:
		822
		823	#include <stddef.h>
		824
		825	static void
		826	t1_cb (EV_P_ struct ev_timer *w, int revents)
		827	{
		828	struct my_biggy big = (struct my_biggy *
		829	(((char *)w) - offsetof (struct my_biggy, t1));
		830	}
		831
		832	static void
		833	t2_cb (EV_P_ struct ev_timer *w, int revents)
		834	{
		835	struct my_biggy big = (struct my_biggy *
		836	(((char *)w) - offsetof (struct my_biggy, t2));
		837	}
402		838
403		839
404	=head1 WATCHER TYPES	840	=head1 WATCHER TYPES
405		841
406	This section describes each watcher in detail, but will not repeat	842	This section describes each watcher in detail, but will not repeat
407	information given in the last section.	843	information given in the last section. Any initialisation/set macros,
		844	functions and members specific to the watcher type are explained.
408		845
		846	Members are additionally marked with either I<[read-only]>, meaning that,
		847	while the watcher is active, you can look at the member and expect some
		848	sensible content, but you must not modify it (you can modify it while the
		849	watcher is stopped to your hearts content), or I<[read-write]>, which
		850	means you can expect it to have some sensible content while the watcher
		851	is active, but you can also modify it. Modifying it may not do something
		852	sensible or take immediate effect (or do anything at all), but libev will
		853	not crash or malfunction in any way.
		854
		855
409	=head2 C<ev_io> - is this file descriptor readable or writable	856	=head2 C<ev_io> - is this file descriptor readable or writable?
410		857
411	I/O watchers check whether a file descriptor is readable or writable	858	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	859	in each iteration of the event loop, or, more precisely, when reading
413	level-triggering because you keep receiving events as long as the	860	would not block the process and writing would at least be able to write
414	condition persists. Remember you can stop the watcher if you don't want to	861	some data. This behaviour is called level-triggering because you keep
415	act on the event and neither want to receive future events).	862	receiving events as long as the condition persists. Remember you can stop
		863	the watcher if you don't want to act on the event and neither want to
		864	receive future events.
416		865
417	In general you can register as many read and/or write event watchers oer	866	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	867	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	868	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	869	required if you know what you are doing).
421		870
422	You have to be careful with dup'ed file descriptors, though. Some backends	871	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file	872	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing	873	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	874	to the same underlying file/socket/etc. description (that is, they share
		875	the same underlying "file open").
426		876
427	If you must do this, then force the use of a known-to-be-good backend	877	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	879	C<EVBACKEND_POLL>).
		880
		881	Another thing you have to watch out for is that it is quite easy to
		882	receive "spurious" readyness notifications, that is your callback might
		883	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		884	because there is no data. Not only are some backends known to create a
		885	lot of those (for example solaris ports), it is very easy to get into
		886	this situation even with a relatively standard program structure. Thus
		887	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		888	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		889
		890	If you cannot run the fd in non-blocking mode (for example you should not
		891	play around with an Xlib connection), then you have to seperately re-test
		892	whether a file descriptor is really ready with a known-to-be good interface
		893	such as poll (fortunately in our Xlib example, Xlib already does this on
		894	its own, so its quite safe to use).
430		895
431	=over 4	896	=over 4
432		897
433	=item ev_io_init (ev_io *, callback, int fd, int events)	898	=item ev_io_init (ev_io *, callback, int fd, int events)
434		899
435	=item ev_io_set (ev_io *, int fd, int events)	900	=item ev_io_set (ev_io *, int fd, int events)
436		901
437	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	902	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
438	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	903	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
439	EV_WRITE> to receive the given events.	904	C<EV_READ | EV_WRITE> to receive the given events.
		905
		906	=item int fd [read-only]
		907
		908	The file descriptor being watched.
		909
		910	=item int events [read-only]
		911
		912	The events being watched.
440		913
441	=back	914	=back
442		915
		916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		917	readable, but only once. Since it is likely line-buffered, you could
		918	attempt to read a whole line in the callback.
		919
		920	static void
		921	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		922	{
		923	ev_io_stop (loop, w);
		924	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		925	}
		926
		927	...
		928	struct ev_loop *loop = ev_default_init (0);
		929	struct ev_io stdin_readable;
		930	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		931	ev_io_start (loop, &stdin_readable);
		932	ev_loop (loop, 0);
		933
		934
443	=head2 C<ev_timer> - relative and optionally recurring timeouts	935	=head2 C<ev_timer> - relative and optionally repeating timeouts
444		936
445	Timer watchers are simple relative timers that generate an event after a	937	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	938	given time, and optionally repeating in regular intervals after that.
447		939
448	The timers are based on real time, that is, if you register an event that	940	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	941	times out after an hour and you reset your system clock to last years
450	time, it will still time out after (roughly) and hour. "Roughly" because	942	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	943	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	944	monotonic clock option helps a lot here).
453		945
454	The relative timeouts are calculated relative to the C<ev_now ()>	946	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	947	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	948	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you *need* to base the timeout	949	you suspect event processing to be delayed and you I<need> to base the timeout
458	ion the current time, use something like this to adjust for this:	950	on the current time, use something like this to adjust for this:
459		951
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		953
		954	The callback is guarenteed to be invoked only when its timeout has passed,
		955	but if multiple timers become ready during the same loop iteration then
		956	order of execution is undefined.
461		957
462	=over 4	958	=over 4
463		959
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		961
…		…
471	later, again, and again, until stopped manually.	967	later, again, and again, until stopped manually.
472		968
473	The timer itself will do a best-effort at avoiding drift, that is, if you	969	The timer itself will do a best-effort at avoiding drift, that is, if you
474	configure a timer to trigger every 10 seconds, then it will trigger at	970	configure a timer to trigger every 10 seconds, then it will trigger at
475	exactly 10 second intervals. If, however, your program cannot keep up with	971	exactly 10 second intervals. If, however, your program cannot keep up with
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	972	the timer (because it takes longer than those 10 seconds to do stuff) the
477	timer will not fire more than once per event loop iteration.	973	timer will not fire more than once per event loop iteration.
478		974
479	=item ev_timer_again (loop)	975	=item ev_timer_again (loop)
480		976
481	This will act as if the timer timed out and restart it again if it is	977	This will act as if the timer timed out and restart it again if it is
482	repeating. The exact semantics are:	978	repeating. The exact semantics are:
483		979
		980	If the timer is pending, its pending status is cleared.
		981
484	If the timer is started but nonrepeating, stop it.	982	If the timer is started but nonrepeating, stop it (as if it timed out).
485		983
486	If the timer is repeating, either start it if necessary (with the repeat	984	If the timer is repeating, either start it if necessary (with the
487	value), or reset the running timer to the repeat value.	985	C<repeat> value), or reset the running timer to the C<repeat> value.
488		986
489	This sounds a bit complicated, but here is a useful and typical	987	This sounds a bit complicated, but here is a useful and typical
490	example: Imagine you have a tcp connection and you want a so-called idle	988	example: Imagine you have a tcp connection and you want a so-called idle
491	timeout, that is, you want to be called when there have been, say, 60	989	timeout, that is, you want to be called when there have been, say, 60
492	seconds of inactivity on the socket. The easiest way to do this is to	990	seconds of inactivity on the socket. The easiest way to do this is to
493	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	991	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
494	time you successfully read or write some data. If you go into an idle	992	C<ev_timer_again> each time you successfully read or write some data. If
495	state where you do not expect data to travel on the socket, you can stop	993	you go into an idle state where you do not expect data to travel on the
496	the timer, and again will automatically restart it if need be.	994	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		995	automatically restart it if need be.
		996
		997	That means you can ignore the C<after> value and C<ev_timer_start>
		998	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		999
		1000	ev_timer_init (timer, callback, 0., 5.);
		1001	ev_timer_again (loop, timer);
		1002	...
		1003	timer->again = 17.;
		1004	ev_timer_again (loop, timer);
		1005	...
		1006	timer->again = 10.;
		1007	ev_timer_again (loop, timer);
		1008
		1009	This is more slightly efficient then stopping/starting the timer each time
		1010	you want to modify its timeout value.
		1011
		1012	=item ev_tstamp repeat [read-write]
		1013
		1014	The current C<repeat> value. Will be used each time the watcher times out
		1015	or C<ev_timer_again> is called and determines the next timeout (if any),
		1016	which is also when any modifications are taken into account.
497		1017
498	=back	1018	=back
499		1019
		1020	Example: Create a timer that fires after 60 seconds.
		1021
		1022	static void
		1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1024	{
		1025	.. one minute over, w is actually stopped right here
		1026	}
		1027
		1028	struct ev_timer mytimer;
		1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1030	ev_timer_start (loop, &mytimer);
		1031
		1032	Example: Create a timeout timer that times out after 10 seconds of
		1033	inactivity.
		1034
		1035	static void
		1036	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1037	{
		1038	.. ten seconds without any activity
		1039	}
		1040
		1041	struct ev_timer mytimer;
		1042	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1043	ev_timer_again (&mytimer); /* start timer */
		1044	ev_loop (loop, 0);
		1045
		1046	// and in some piece of code that gets executed on any "activity":
		1047	// reset the timeout to start ticking again at 10 seconds
		1048	ev_timer_again (&mytimer);
		1049
		1050
500	=head2 C<ev_periodic> - to cron or not to cron	1051	=head2 C<ev_periodic> - to cron or not to cron?
501		1052
502	Periodic watchers are also timers of a kind, but they are very versatile	1053	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	1054	(and unfortunately a bit complex).
504		1055
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1056	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
506	but on wallclock time (absolute time). You can tell a periodic watcher	1057	but on wallclock time (absolute time). You can tell a periodic watcher
507	to trigger "at" some specific point in time. For example, if you tell a	1058	to trigger "at" some specific point in time. For example, if you tell a
508	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
509	+ 10.>) and then reset your system clock to the last year, then it will	1060	+ 10.>) and then reset your system clock to the last year, then it will
510	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
511	roughly 10 seconds later and of course not if you reset your system time	1062	roughly 10 seconds later and of course not if you reset your system time
512	again).	1063	again).
513		1064
514	They can also be used to implement vastly more complex timers, such as	1065	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	1066	triggering an event on eahc midnight, local time.
516		1067
		1068	As with timers, the callback is guarenteed to be invoked only when the
		1069	time (C<at>) has been passed, but if multiple periodic timers become ready
		1070	during the same loop iteration then order of execution is undefined.
		1071
517	=over 4	1072	=over 4
518		1073
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		1075
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		1077
523	Lots of arguments, lets sort it out... There are basically three modes of	1078	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	1079	operation, and we will explain them from simplest to complex:
525
526		1080
527	=over 4	1081	=over 4
528		1082
529	=item * absolute timer (interval = reschedule_cb = 0)	1083	=item * absolute timer (interval = reschedule_cb = 0)
530		1084
…		…
558	In this mode the values for C<interval> and C<at> are both being	1112	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	1113	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	1114	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	1115	current time as second argument.
562		1116
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	1118	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		1120	starting a prepare watcher).
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569		1121
570	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571	ev_tstamp now)>, e.g.:	1123	ev_tstamp now)>, e.g.:
572		1124
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
578	It must return the next time to trigger, based on the passed time value	1130	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	1131	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	1132	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	1133	might be called at other times, too.
582		1134
		1135	NOTE: I<< This callback must always return a time that is later than the
		1136	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1137
583	This can be used to create very complex timers, such as a timer that	1138	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	1139	triggers on each midnight, local time. To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	1140	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	1141	you do this is, again, up to you (but it is not trivial, which is the main
		1142	reason I omitted it as an example).
587		1143
588	=back	1144	=back
589		1145
590	=item ev_periodic_again (loop, ev_periodic *)	1146	=item ev_periodic_again (loop, ev_periodic *)
591		1147
592	Simply stops and restarts the periodic watcher again. This is only useful	1148	Simply stops and restarts the periodic watcher again. This is only useful
593	when you changed some parameters or the reschedule callback would return	1149	when you changed some parameters or the reschedule callback would return
594	a different time than the last time it was called (e.g. in a crond like	1150	a different time than the last time it was called (e.g. in a crond like
595	program when the crontabs have changed).	1151	program when the crontabs have changed).
596		1152
		1153	=item ev_tstamp interval [read-write]
		1154
		1155	The current interval value. Can be modified any time, but changes only
		1156	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1157	called.
		1158
		1159	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1160
		1161	The current reschedule callback, or C<0>, if this functionality is
		1162	switched off. Can be changed any time, but changes only take effect when
		1163	the periodic timer fires or C<ev_periodic_again> is being called.
		1164
597	=back	1165	=back
598		1166
		1167	Example: Call a callback every hour, or, more precisely, whenever the
		1168	system clock is divisible by 3600. The callback invocation times have
		1169	potentially a lot of jittering, but good long-term stability.
		1170
		1171	static void
		1172	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1173	{
		1174	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1175	}
		1176
		1177	struct ev_periodic hourly_tick;
		1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1179	ev_periodic_start (loop, &hourly_tick);
		1180
		1181	Example: The same as above, but use a reschedule callback to do it:
		1182
		1183	#include <math.h>
		1184
		1185	static ev_tstamp
		1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1187	{
		1188	return fmod (now, 3600.) + 3600.;
		1189	}
		1190
		1191	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1192
		1193	Example: Call a callback every hour, starting now:
		1194
		1195	struct ev_periodic hourly_tick;
		1196	ev_periodic_init (&hourly_tick, clock_cb,
		1197	fmod (ev_now (loop), 3600.), 3600., 0);
		1198	ev_periodic_start (loop, &hourly_tick);
		1199
		1200
599	=head2 C<ev_signal> - signal me when a signal gets signalled	1201	=head2 C<ev_signal> - signal me when a signal gets signalled!
600		1202
601	Signal watchers will trigger an event when the process receives a specific	1203	Signal watchers will trigger an event when the process receives a specific
602	signal one or more times. Even though signals are very asynchronous, libev	1204	signal one or more times. Even though signals are very asynchronous, libev
603	will try it's best to deliver signals synchronously, i.e. as part of the	1205	will try it's best to deliver signals synchronously, i.e. as part of the
604	normal event processing, like any other event.	1206	normal event processing, like any other event.
…		…
617	=item ev_signal_set (ev_signal *, int signum)	1219	=item ev_signal_set (ev_signal *, int signum)
618		1220
619	Configures the watcher to trigger on the given signal number (usually one	1221	Configures the watcher to trigger on the given signal number (usually one
620	of the C<SIGxxx> constants).	1222	of the C<SIGxxx> constants).
621		1223
		1224	=item int signum [read-only]
		1225
		1226	The signal the watcher watches out for.
		1227
622	=back	1228	=back
623		1229
		1230
624	=head2 C<ev_child> - wait for pid status changes	1231	=head2 C<ev_child> - watch out for process status changes
625		1232
626	Child watchers trigger when your process receives a SIGCHLD in response to	1233	Child watchers trigger when your process receives a SIGCHLD in response to
627	some child status changes (most typically when a child of yours dies).	1234	some child status changes (most typically when a child of yours dies).
628		1235
629	=over 4	1236	=over 4
…		…
637	at the C<rstatus> member of the C<ev_child> watcher structure to see	1244	at the C<rstatus> member of the C<ev_child> watcher structure to see
638	the status word (use the macros from C<sys/wait.h> and see your systems	1245	the status word (use the macros from C<sys/wait.h> and see your systems
639	C<waitpid> documentation). The C<rpid> member contains the pid of the	1246	C<waitpid> documentation). The C<rpid> member contains the pid of the
640	process causing the status change.	1247	process causing the status change.
641		1248
		1249	=item int pid [read-only]
		1250
		1251	The process id this watcher watches out for, or C<0>, meaning any process id.
		1252
		1253	=item int rpid [read-write]
		1254
		1255	The process id that detected a status change.
		1256
		1257	=item int rstatus [read-write]
		1258
		1259	The process exit/trace status caused by C<rpid> (see your systems
		1260	C<waitpid> and C<sys/wait.h> documentation for details).
		1261
642	=back	1262	=back
643		1263
		1264	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1265
		1266	static void
		1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1268	{
		1269	ev_unloop (loop, EVUNLOOP_ALL);
		1270	}
		1271
		1272	struct ev_signal signal_watcher;
		1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1274	ev_signal_start (loop, &sigint_cb);
		1275
		1276
		1277	=head2 C<ev_stat> - did the file attributes just change?
		1278
		1279	This watches a filesystem path for attribute changes. That is, it calls
		1280	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1281	compared to the last time, invoking the callback if it did.
		1282
		1283	The path does not need to exist: changing from "path exists" to "path does
		1284	not exist" is a status change like any other. The condition "path does
		1285	not exist" is signified by the C<st_nlink> field being zero (which is
		1286	otherwise always forced to be at least one) and all the other fields of
		1287	the stat buffer having unspecified contents.
		1288
		1289	The path I<should> be absolute and I<must not> end in a slash. If it is
		1290	relative and your working directory changes, the behaviour is undefined.
		1291
		1292	Since there is no standard to do this, the portable implementation simply
		1293	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1294	can specify a recommended polling interval for this case. If you specify
		1295	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1296	unspecified default> value will be used (which you can expect to be around
		1297	five seconds, although this might change dynamically). Libev will also
		1298	impose a minimum interval which is currently around C<0.1>, but thats
		1299	usually overkill.
		1300
		1301	This watcher type is not meant for massive numbers of stat watchers,
		1302	as even with OS-supported change notifications, this can be
		1303	resource-intensive.
		1304
		1305	At the time of this writing, only the Linux inotify interface is
		1306	implemented (implementing kqueue support is left as an exercise for the
		1307	reader). Inotify will be used to give hints only and should not change the
		1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1309	to fall back to regular polling again even with inotify, but changes are
		1310	usually detected immediately, and if the file exists there will be no
		1311	polling.
		1312
		1313	=over 4
		1314
		1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1316
		1317	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1318
		1319	Configures the watcher to wait for status changes of the given
		1320	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1321	be detected and should normally be specified as C<0> to let libev choose
		1322	a suitable value. The memory pointed to by C<path> must point to the same
		1323	path for as long as the watcher is active.
		1324
		1325	The callback will be receive C<EV_STAT> when a change was detected,
		1326	relative to the attributes at the time the watcher was started (or the
		1327	last change was detected).
		1328
		1329	=item ev_stat_stat (ev_stat *)
		1330
		1331	Updates the stat buffer immediately with new values. If you change the
		1332	watched path in your callback, you could call this fucntion to avoid
		1333	detecting this change (while introducing a race condition). Can also be
		1334	useful simply to find out the new values.
		1335
		1336	=item ev_statdata attr [read-only]
		1337
		1338	The most-recently detected attributes of the file. Although the type is of
		1339	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1340	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1341	was some error while C<stat>ing the file.
		1342
		1343	=item ev_statdata prev [read-only]
		1344
		1345	The previous attributes of the file. The callback gets invoked whenever
		1346	C<prev> != C<attr>.
		1347
		1348	=item ev_tstamp interval [read-only]
		1349
		1350	The specified interval.
		1351
		1352	=item const char *path [read-only]
		1353
		1354	The filesystem path that is being watched.
		1355
		1356	=back
		1357
		1358	Example: Watch C</etc/passwd> for attribute changes.
		1359
		1360	static void
		1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1362	{
		1363	/* /etc/passwd changed in some way */
		1364	if (w->attr.st_nlink)
		1365	{
		1366	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1367	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1368	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1369	}
		1370	else
		1371	/* you shalt not abuse printf for puts */
		1372	puts ("wow, /etc/passwd is not there, expect problems. "
		1373	"if this is windows, they already arrived\n");
		1374	}
		1375
		1376	...
		1377	ev_stat passwd;
		1378
		1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1380	ev_stat_start (loop, &passwd);
		1381
		1382
644	=head2 C<ev_idle> - when you've got nothing better to do	1383	=head2 C<ev_idle> - when you've got nothing better to do...
645		1384
646	Idle watchers trigger events when there are no other events are pending	1385	Idle watchers trigger events when no other events of the same or higher
647	(prepare, check and other idle watchers do not count). That is, as long	1386	priority are pending (prepare, check and other idle watchers do not
648	as your process is busy handling sockets or timeouts (or even signals,	1387	count).
649	imagine) it will not be triggered. But when your process is idle all idle	1388
650	watchers are being called again and again, once per event loop iteration -	1389	That is, as long as your process is busy handling sockets or timeouts
		1390	(or even signals, imagine) of the same or higher priority it will not be
		1391	triggered. But when your process is idle (or only lower-priority watchers
		1392	are pending), the idle watchers are being called once per event loop
651	until stopped, that is, or your process receives more events and becomes	1393	iteration - until stopped, that is, or your process receives more events
652	busy.	1394	and becomes busy again with higher priority stuff.
653		1395
654	The most noteworthy effect is that as long as any idle watchers are	1396	The most noteworthy effect is that as long as any idle watchers are
655	active, the process will not block when waiting for new events.	1397	active, the process will not block when waiting for new events.
656		1398
657	Apart from keeping your process non-blocking (which is a useful	1399	Apart from keeping your process non-blocking (which is a useful
…		…
667	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
668	believe me.	1410	believe me.
669		1411
670	=back	1412	=back
671		1413
		1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1415	callback, free it. Also, use no error checking, as usual.
		1416
		1417	static void
		1418	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1419	{
		1420	free (w);
		1421	// now do something you wanted to do when the program has
		1422	// no longer asnything immediate to do.
		1423	}
		1424
		1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1426	ev_idle_init (idle_watcher, idle_cb);
		1427	ev_idle_start (loop, idle_cb);
		1428
		1429
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1430	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
673		1431
674	Prepare and check watchers are usually (but not always) used in tandem:	1432	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1433	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	1434	afterwards.
677		1435
		1436	You I<must not> call C<ev_loop> or similar functions that enter
		1437	the current event loop from either C<ev_prepare> or C<ev_check>
		1438	watchers. Other loops than the current one are fine, however. The
		1439	rationale behind this is that you do not need to check for recursion in
		1440	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1441	C<ev_check> so if you have one watcher of each kind they will always be
		1442	called in pairs bracketing the blocking call.
		1443
678	Their main purpose is to integrate other event mechanisms into libev. This	1444	Their main purpose is to integrate other event mechanisms into libev and
679	could be used, for example, to track variable changes, implement your own	1445	their use is somewhat advanced. This could be used, for example, to track
680	watchers, integrate net-snmp or a coroutine library and lots more.	1446	variable changes, implement your own watchers, integrate net-snmp or a
		1447	coroutine library and lots more. They are also occasionally useful if
		1448	you cache some data and want to flush it before blocking (for example,
		1449	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1450	watcher).
681		1451
682	This is done by examining in each prepare call which file descriptors need	1452	This is done by examining in each prepare call which file descriptors need
683	to be watched by the other library, registering C<ev_io> watchers for	1453	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1454	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	1455	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	1456	any events that occured (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	1457	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	1458	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	1459	because you never know, you know?).
690		1460
691	As another example, the Perl Coro module uses these hooks to integrate	1461	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	1462	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	1463	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	1464	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	1465	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	1466	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	1467	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	1468	low-priority coroutines to idle/background tasks).
699		1469
700	=over 4	1470	=over 4
701		1471
702	=item ev_prepare_init (ev_prepare *, callback)	1472	=item ev_prepare_init (ev_prepare *, callback)
703		1473
…		…
707	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
708	macros, but using them is utterly, utterly and completely pointless.	1478	macros, but using them is utterly, utterly and completely pointless.
709		1479
710	=back	1480	=back
711		1481
		1482	Example: To include a library such as adns, you would add IO watchers
		1483	and a timeout watcher in a prepare handler, as required by libadns, and
		1484	in a check watcher, destroy them and call into libadns. What follows is
		1485	pseudo-code only of course:
		1486
		1487	static ev_io iow [nfd];
		1488	static ev_timer tw;
		1489
		1490	static void
		1491	io_cb (ev_loop *loop, ev_io *w, int revents)
		1492	{
		1493	// set the relevant poll flags
		1494	// could also call adns_processreadable etc. here
		1495	struct pollfd *fd = (struct pollfd *)w->data;
		1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1498	}
		1499
		1500	// create io watchers for each fd and a timer before blocking
		1501	static void
		1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1503	{
		1504	int timeout = 3600000;
		1505	struct pollfd fds [nfd];
		1506	// actual code will need to loop here and realloc etc.
		1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1508
		1509	/* the callback is illegal, but won't be called as we stop during check */
		1510	ev_timer_init (&tw, 0, timeout * 1e-3);
		1511	ev_timer_start (loop, &tw);
		1512
		1513	// create on ev_io per pollfd
		1514	for (int i = 0; i < nfd; ++i)
		1515	{
		1516	ev_io_init (iow + i, io_cb, fds [i].fd,
		1517	((fds [i].events & POLLIN ? EV_READ : 0)
		1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1519
		1520	fds [i].revents = 0;
		1521	iow [i].data = fds + i;
		1522	ev_io_start (loop, iow + i);
		1523	}
		1524	}
		1525
		1526	// stop all watchers after blocking
		1527	static void
		1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1529	{
		1530	ev_timer_stop (loop, &tw);
		1531
		1532	for (int i = 0; i < nfd; ++i)
		1533	ev_io_stop (loop, iow + i);
		1534
		1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1536	}
		1537
		1538
		1539	=head2 C<ev_embed> - when one backend isn't enough...
		1540
		1541	This is a rather advanced watcher type that lets you embed one event loop
		1542	into another (currently only C<ev_io> events are supported in the embedded
		1543	loop, other types of watchers might be handled in a delayed or incorrect
		1544	fashion and must not be used).
		1545
		1546	There are primarily two reasons you would want that: work around bugs and
		1547	prioritise I/O.
		1548
		1549	As an example for a bug workaround, the kqueue backend might only support
		1550	sockets on some platform, so it is unusable as generic backend, but you
		1551	still want to make use of it because you have many sockets and it scales
		1552	so nicely. In this case, you would create a kqueue-based loop and embed it
		1553	into your default loop (which might use e.g. poll). Overall operation will
		1554	be a bit slower because first libev has to poll and then call kevent, but
		1555	at least you can use both at what they are best.
		1556
		1557	As for prioritising I/O: rarely you have the case where some fds have
		1558	to be watched and handled very quickly (with low latency), and even
		1559	priorities and idle watchers might have too much overhead. In this case
		1560	you would put all the high priority stuff in one loop and all the rest in
		1561	a second one, and embed the second one in the first.
		1562
		1563	As long as the watcher is active, the callback will be invoked every time
		1564	there might be events pending in the embedded loop. The callback must then
		1565	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1566	their callbacks (you could also start an idle watcher to give the embedded
		1567	loop strictly lower priority for example). You can also set the callback
		1568	to C<0>, in which case the embed watcher will automatically execute the
		1569	embedded loop sweep.
		1570
		1571	As long as the watcher is started it will automatically handle events. The
		1572	callback will be invoked whenever some events have been handled. You can
		1573	set the callback to C<0> to avoid having to specify one if you are not
		1574	interested in that.
		1575
		1576	Also, there have not currently been made special provisions for forking:
		1577	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1578	but you will also have to stop and restart any C<ev_embed> watchers
		1579	yourself.
		1580
		1581	Unfortunately, not all backends are embeddable, only the ones returned by
		1582	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1583	portable one.
		1584
		1585	So when you want to use this feature you will always have to be prepared
		1586	that you cannot get an embeddable loop. The recommended way to get around
		1587	this is to have a separate variables for your embeddable loop, try to
		1588	create it, and if that fails, use the normal loop for everything:
		1589
		1590	struct ev_loop *loop_hi = ev_default_init (0);
		1591	struct ev_loop *loop_lo = 0;
		1592	struct ev_embed embed;
		1593
		1594	// see if there is a chance of getting one that works
		1595	// (remember that a flags value of 0 means autodetection)
		1596	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1597	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1598	: 0;
		1599
		1600	// if we got one, then embed it, otherwise default to loop_hi
		1601	if (loop_lo)
		1602	{
		1603	ev_embed_init (&embed, 0, loop_lo);
		1604	ev_embed_start (loop_hi, &embed);
		1605	}
		1606	else
		1607	loop_lo = loop_hi;
		1608
		1609	=over 4
		1610
		1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1612
		1613	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1614
		1615	Configures the watcher to embed the given loop, which must be
		1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1617	invoked automatically, otherwise it is the responsibility of the callback
		1618	to invoke it (it will continue to be called until the sweep has been done,
		1619	if you do not want thta, you need to temporarily stop the embed watcher).
		1620
		1621	=item ev_embed_sweep (loop, ev_embed *)
		1622
		1623	Make a single, non-blocking sweep over the embedded loop. This works
		1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1625	apropriate way for embedded loops.
		1626
		1627	=item struct ev_loop *loop [read-only]
		1628
		1629	The embedded event loop.
		1630
		1631	=back
		1632
		1633
		1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1635
		1636	Fork watchers are called when a C<fork ()> was detected (usually because
		1637	whoever is a good citizen cared to tell libev about it by calling
		1638	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1639	event loop blocks next and before C<ev_check> watchers are being called,
		1640	and only in the child after the fork. If whoever good citizen calling
		1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1642	handlers will be invoked, too, of course.
		1643
		1644	=over 4
		1645
		1646	=item ev_fork_init (ev_signal *, callback)
		1647
		1648	Initialises and configures the fork watcher - it has no parameters of any
		1649	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1650	believe me.
		1651
		1652	=back
		1653
		1654
712	=head1 OTHER FUNCTIONS	1655	=head1 OTHER FUNCTIONS
713		1656
714	There are some other functions of possible interest. Described. Here. Now.	1657	There are some other functions of possible interest. Described. Here. Now.
715		1658
716	=over 4	1659	=over 4
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1661	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		1662
720	This function combines a simple timer and an I/O watcher, calls your	1663	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	1664	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	1665	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	1666	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	1667	more watchers yourself.
725		1668
726	If C<fd> is less than 0, then no I/O watcher will be started and events	1669	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	1670	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	1671	C<events> set will be craeted and started.
…		…
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	1674	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	1675	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	1676	dubious value.
734		1677
735	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	1678	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	1679	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	1680	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	1681	value passed to C<ev_once>:
739		1682
740	static void stdin_ready (int revents, void *arg)	1683	static void stdin_ready (int revents, void *arg)
741	{	1684	{
…		…
745	/* stdin might have data for us, joy! */;	1688	/* stdin might have data for us, joy! */;
746	}	1689	}
747		1690
748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1691	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
749		1692
750	=item ev_feed_event (loop, watcher, int events)	1693	=item ev_feed_event (ev_loop *, watcher *, int revents)
751		1694
752	Feeds the given event set into the event loop, as if the specified event	1695	Feeds the given event set into the event loop, as if the specified event
753	had happened for the specified watcher (which must be a pointer to an	1696	had happened for the specified watcher (which must be a pointer to an
754	initialised but not necessarily started event watcher).	1697	initialised but not necessarily started event watcher).
755		1698
756	=item ev_feed_fd_event (loop, int fd, int revents)	1699	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
757		1700
758	Feed an event on the given fd, as if a file descriptor backend detected	1701	Feed an event on the given fd, as if a file descriptor backend detected
759	the given events it.	1702	the given events it.
760		1703
761	=item ev_feed_signal_event (loop, int signum)	1704	=item ev_feed_signal_event (ev_loop *loop, int signum)
762		1705
763	Feed an event as if the given signal occured (loop must be the default loop!).	1706	Feed an event as if the given signal occured (C<loop> must be the default
		1707	loop!).
764		1708
765	=back	1709	=back
766		1710
		1711
		1712	=head1 LIBEVENT EMULATION
		1713
		1714	Libev offers a compatibility emulation layer for libevent. It cannot
		1715	emulate the internals of libevent, so here are some usage hints:
		1716
		1717	=over 4
		1718
		1719	=item * Use it by including <event.h>, as usual.
		1720
		1721	=item * The following members are fully supported: ev_base, ev_callback,
		1722	ev_arg, ev_fd, ev_res, ev_events.
		1723
		1724	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1725	maintained by libev, it does not work exactly the same way as in libevent (consider
		1726	it a private API).
		1727
		1728	=item * Priorities are not currently supported. Initialising priorities
		1729	will fail and all watchers will have the same priority, even though there
		1730	is an ev_pri field.
		1731
		1732	=item * Other members are not supported.
		1733
		1734	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1735	to use the libev header file and library.
		1736
		1737	=back
		1738
		1739	=head1 C++ SUPPORT
		1740
		1741	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1742	you to use some convinience methods to start/stop watchers and also change
		1743	the callback model to a model using method callbacks on objects.
		1744
		1745	To use it,
		1746
		1747	#include <ev++.h>
		1748
		1749	This automatically includes F<ev.h> and puts all of its definitions (many
		1750	of them macros) into the global namespace. All C++ specific things are
		1751	put into the C<ev> namespace. It should support all the same embedding
		1752	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1753
		1754	Care has been taken to keep the overhead low. The only data member the C++
		1755	classes add (compared to plain C-style watchers) is the event loop pointer
		1756	that the watcher is associated with (or no additional members at all if
		1757	you disable C<EV_MULTIPLICITY> when embedding libev).
		1758
		1759	Currently, functions, and static and non-static member functions can be
		1760	used as callbacks. Other types should be easy to add as long as they only
		1761	need one additional pointer for context. If you need support for other
		1762	types of functors please contact the author (preferably after implementing
		1763	it).
		1764
		1765	Here is a list of things available in the C<ev> namespace:
		1766
		1767	=over 4
		1768
		1769	=item C<ev::READ>, C<ev::WRITE> etc.
		1770
		1771	These are just enum values with the same values as the C<EV_READ> etc.
		1772	macros from F<ev.h>.
		1773
		1774	=item C<ev::tstamp>, C<ev::now>
		1775
		1776	Aliases to the same types/functions as with the C<ev_> prefix.
		1777
		1778	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1779
		1780	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1781	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1782	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1783	defines by many implementations.
		1784
		1785	All of those classes have these methods:
		1786
		1787	=over 4
		1788
		1789	=item ev::TYPE::TYPE ()
		1790
		1791	=item ev::TYPE::TYPE (struct ev_loop *)
		1792
		1793	=item ev::TYPE::~TYPE
		1794
		1795	The constructor (optionally) takes an event loop to associate the watcher
		1796	with. If it is omitted, it will use C<EV_DEFAULT>.
		1797
		1798	The constructor calls C<ev_init> for you, which means you have to call the
		1799	C<set> method before starting it.
		1800
		1801	It will not set a callback, however: You have to call the templated C<set>
		1802	method to set a callback before you can start the watcher.
		1803
		1804	(The reason why you have to use a method is a limitation in C++ which does
		1805	not allow explicit template arguments for constructors).
		1806
		1807	The destructor automatically stops the watcher if it is active.
		1808
		1809	=item w->set<class, &class::method> (object *)
		1810
		1811	This method sets the callback method to call. The method has to have a
		1812	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1813	first argument and the C<revents> as second. The object must be given as
		1814	parameter and is stored in the C<data> member of the watcher.
		1815
		1816	This method synthesizes efficient thunking code to call your method from
		1817	the C callback that libev requires. If your compiler can inline your
		1818	callback (i.e. it is visible to it at the place of the C<set> call and
		1819	your compiler is good :), then the method will be fully inlined into the
		1820	thunking function, making it as fast as a direct C callback.
		1821
		1822	Example: simple class declaration and watcher initialisation
		1823
		1824	struct myclass
		1825	{
		1826	void io_cb (ev::io &w, int revents) { }
		1827	}
		1828
		1829	myclass obj;
		1830	ev::io iow;
		1831	iow.set <myclass, &myclass::io_cb> (&obj);
		1832
		1833	=item w->set (void (*function)(watcher &w, int), void *data = 0)
		1834
		1835	Also sets a callback, but uses a static method or plain function as
		1836	callback. The optional C<data> argument will be stored in the watcher's
		1837	C<data> member and is free for you to use.
		1838
		1839	See the method-C<set> above for more details.
		1840
		1841	=item w->set (struct ev_loop *)
		1842
		1843	Associates a different C<struct ev_loop> with this watcher. You can only
		1844	do this when the watcher is inactive (and not pending either).
		1845
		1846	=item w->set ([args])
		1847
		1848	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1849	called at least once. Unlike the C counterpart, an active watcher gets
		1850	automatically stopped and restarted when reconfiguring it with this
		1851	method.
		1852
		1853	=item w->start ()
		1854
		1855	Starts the watcher. Note that there is no C<loop> argument, as the
		1856	constructor already stores the event loop.
		1857
		1858	=item w->stop ()
		1859
		1860	Stops the watcher if it is active. Again, no C<loop> argument.
		1861
		1862	=item w->again () C<ev::timer>, C<ev::periodic> only
		1863
		1864	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1865	C<ev_TYPE_again> function.
		1866
		1867	=item w->sweep () C<ev::embed> only
		1868
		1869	Invokes C<ev_embed_sweep>.
		1870
		1871	=item w->update () C<ev::stat> only
		1872
		1873	Invokes C<ev_stat_stat>.
		1874
		1875	=back
		1876
		1877	=back
		1878
		1879	Example: Define a class with an IO and idle watcher, start one of them in
		1880	the constructor.
		1881
		1882	class myclass
		1883	{
		1884	ev_io io; void io_cb (ev::io &w, int revents);
		1885	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1886
		1887	myclass ();
		1888	}
		1889
		1890	myclass::myclass (int fd)
		1891	{
		1892	io .set <myclass, &myclass::io_cb > (this);
		1893	idle.set <myclass, &myclass::idle_cb> (this);
		1894
		1895	io.start (fd, ev::READ);
		1896	}
		1897
		1898
		1899	=head1 MACRO MAGIC
		1900
		1901	Libev can be compiled with a variety of options, the most fundemantal is
		1902	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		1903	callbacks have an initial C<struct ev_loop *> argument.
		1904
		1905	To make it easier to write programs that cope with either variant, the
		1906	following macros are defined:
		1907
		1908	=over 4
		1909
		1910	=item C<EV_A>, C<EV_A_>
		1911
		1912	This provides the loop I<argument> for functions, if one is required ("ev
		1913	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1914	C<EV_A_> is used when other arguments are following. Example:
		1915
		1916	ev_unref (EV_A);
		1917	ev_timer_add (EV_A_ watcher);
		1918	ev_loop (EV_A_ 0);
		1919
		1920	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1921	which is often provided by the following macro.
		1922
		1923	=item C<EV_P>, C<EV_P_>
		1924
		1925	This provides the loop I<parameter> for functions, if one is required ("ev
		1926	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1927	C<EV_P_> is used when other parameters are following. Example:
		1928
		1929	// this is how ev_unref is being declared
		1930	static void ev_unref (EV_P);
		1931
		1932	// this is how you can declare your typical callback
		1933	static void cb (EV_P_ ev_timer *w, int revents)
		1934
		1935	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1936	suitable for use with C<EV_A>.
		1937
		1938	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1939
		1940	Similar to the other two macros, this gives you the value of the default
		1941	loop, if multiple loops are supported ("ev loop default").
		1942
		1943	=back
		1944
		1945	Example: Declare and initialise a check watcher, utilising the above
		1946	macros so it will work regardless of whether multiple loops are supported
		1947	or not.
		1948
		1949	static void
		1950	check_cb (EV_P_ ev_timer *w, int revents)
		1951	{
		1952	ev_check_stop (EV_A_ w);
		1953	}
		1954
		1955	ev_check check;
		1956	ev_check_init (&check, check_cb);
		1957	ev_check_start (EV_DEFAULT_ &check);
		1958	ev_loop (EV_DEFAULT_ 0);
		1959
		1960	=head1 EMBEDDING
		1961
		1962	Libev can (and often is) directly embedded into host
		1963	applications. Examples of applications that embed it include the Deliantra
		1964	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1965	and rxvt-unicode.
		1966
		1967	The goal is to enable you to just copy the neecssary files into your
		1968	source directory without having to change even a single line in them, so
		1969	you can easily upgrade by simply copying (or having a checked-out copy of
		1970	libev somewhere in your source tree).
		1971
		1972	=head2 FILESETS
		1973
		1974	Depending on what features you need you need to include one or more sets of files
		1975	in your app.
		1976
		1977	=head3 CORE EVENT LOOP
		1978
		1979	To include only the libev core (all the C<ev_*> functions), with manual
		1980	configuration (no autoconf):
		1981
		1982	#define EV_STANDALONE 1
		1983	#include "ev.c"
		1984
		1985	This will automatically include F<ev.h>, too, and should be done in a
		1986	single C source file only to provide the function implementations. To use
		1987	it, do the same for F<ev.h> in all files wishing to use this API (best
		1988	done by writing a wrapper around F<ev.h> that you can include instead and
		1989	where you can put other configuration options):
		1990
		1991	#define EV_STANDALONE 1
		1992	#include "ev.h"
		1993
		1994	Both header files and implementation files can be compiled with a C++
		1995	compiler (at least, thats a stated goal, and breakage will be treated
		1996	as a bug).
		1997
		1998	You need the following files in your source tree, or in a directory
		1999	in your include path (e.g. in libev/ when using -Ilibev):
		2000
		2001	ev.h
		2002	ev.c
		2003	ev_vars.h
		2004	ev_wrap.h
		2005
		2006	ev_win32.c required on win32 platforms only
		2007
		2008	ev_select.c only when select backend is enabled (which is enabled by default)
		2009	ev_poll.c only when poll backend is enabled (disabled by default)
		2010	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2011	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2012	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2013
		2014	F<ev.c> includes the backend files directly when enabled, so you only need
		2015	to compile this single file.
		2016
		2017	=head3 LIBEVENT COMPATIBILITY API
		2018
		2019	To include the libevent compatibility API, also include:
		2020
		2021	#include "event.c"
		2022
		2023	in the file including F<ev.c>, and:
		2024
		2025	#include "event.h"
		2026
		2027	in the files that want to use the libevent API. This also includes F<ev.h>.
		2028
		2029	You need the following additional files for this:
		2030
		2031	event.h
		2032	event.c
		2033
		2034	=head3 AUTOCONF SUPPORT
		2035
		2036	Instead of using C<EV_STANDALONE=1> and providing your config in
		2037	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2038	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2039	include F<config.h> and configure itself accordingly.
		2040
		2041	For this of course you need the m4 file:
		2042
		2043	libev.m4
		2044
		2045	=head2 PREPROCESSOR SYMBOLS/MACROS
		2046
		2047	Libev can be configured via a variety of preprocessor symbols you have to define
		2048	before including any of its files. The default is not to build for multiplicity
		2049	and only include the select backend.
		2050
		2051	=over 4
		2052
		2053	=item EV_STANDALONE
		2054
		2055	Must always be C<1> if you do not use autoconf configuration, which
		2056	keeps libev from including F<config.h>, and it also defines dummy
		2057	implementations for some libevent functions (such as logging, which is not
		2058	supported). It will also not define any of the structs usually found in
		2059	F<event.h> that are not directly supported by the libev core alone.
		2060
		2061	=item EV_USE_MONOTONIC
		2062
		2063	If defined to be C<1>, libev will try to detect the availability of the
		2064	monotonic clock option at both compiletime and runtime. Otherwise no use
		2065	of the monotonic clock option will be attempted. If you enable this, you
		2066	usually have to link against librt or something similar. Enabling it when
		2067	the functionality isn't available is safe, though, althoguh you have
		2068	to make sure you link against any libraries where the C<clock_gettime>
		2069	function is hiding in (often F<-lrt>).
		2070
		2071	=item EV_USE_REALTIME
		2072
		2073	If defined to be C<1>, libev will try to detect the availability of the
		2074	realtime clock option at compiletime (and assume its availability at
		2075	runtime if successful). Otherwise no use of the realtime clock option will
		2076	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2077	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2078	in the description of C<EV_USE_MONOTONIC>, though.
		2079
		2080	=item EV_USE_SELECT
		2081
		2082	If undefined or defined to be C<1>, libev will compile in support for the
		2083	C<select>(2) backend. No attempt at autodetection will be done: if no
		2084	other method takes over, select will be it. Otherwise the select backend
		2085	will not be compiled in.
		2086
		2087	=item EV_SELECT_USE_FD_SET
		2088
		2089	If defined to C<1>, then the select backend will use the system C<fd_set>
		2090	structure. This is useful if libev doesn't compile due to a missing
		2091	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2092	exotic systems. This usually limits the range of file descriptors to some
		2093	low limit such as 1024 or might have other limitations (winsocket only
		2094	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2095	influence the size of the C<fd_set> used.
		2096
		2097	=item EV_SELECT_IS_WINSOCKET
		2098
		2099	When defined to C<1>, the select backend will assume that
		2100	select/socket/connect etc. don't understand file descriptors but
		2101	wants osf handles on win32 (this is the case when the select to
		2102	be used is the winsock select). This means that it will call
		2103	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2104	it is assumed that all these functions actually work on fds, even
		2105	on win32. Should not be defined on non-win32 platforms.
		2106
		2107	=item EV_USE_POLL
		2108
		2109	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2110	backend. Otherwise it will be enabled on non-win32 platforms. It
		2111	takes precedence over select.
		2112
		2113	=item EV_USE_EPOLL
		2114
		2115	If defined to be C<1>, libev will compile in support for the Linux
		2116	C<epoll>(7) backend. Its availability will be detected at runtime,
		2117	otherwise another method will be used as fallback. This is the
		2118	preferred backend for GNU/Linux systems.
		2119
		2120	=item EV_USE_KQUEUE
		2121
		2122	If defined to be C<1>, libev will compile in support for the BSD style
		2123	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2124	otherwise another method will be used as fallback. This is the preferred
		2125	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2126	supports some types of fds correctly (the only platform we found that
		2127	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2128	not be used unless explicitly requested. The best way to use it is to find
		2129	out whether kqueue supports your type of fd properly and use an embedded
		2130	kqueue loop.
		2131
		2132	=item EV_USE_PORT
		2133
		2134	If defined to be C<1>, libev will compile in support for the Solaris
		2135	10 port style backend. Its availability will be detected at runtime,
		2136	otherwise another method will be used as fallback. This is the preferred
		2137	backend for Solaris 10 systems.
		2138
		2139	=item EV_USE_DEVPOLL
		2140
		2141	reserved for future expansion, works like the USE symbols above.
		2142
		2143	=item EV_USE_INOTIFY
		2144
		2145	If defined to be C<1>, libev will compile in support for the Linux inotify
		2146	interface to speed up C<ev_stat> watchers. Its actual availability will
		2147	be detected at runtime.
		2148
		2149	=item EV_H
		2150
		2151	The name of the F<ev.h> header file used to include it. The default if
		2152	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2153	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2154
		2155	=item EV_CONFIG_H
		2156
		2157	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2158	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2159	C<EV_H>, above.
		2160
		2161	=item EV_EVENT_H
		2162
		2163	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2164	of how the F<event.h> header can be found.
		2165
		2166	=item EV_PROTOTYPES
		2167
		2168	If defined to be C<0>, then F<ev.h> will not define any function
		2169	prototypes, but still define all the structs and other symbols. This is
		2170	occasionally useful if you want to provide your own wrapper functions
		2171	around libev functions.
		2172
		2173	=item EV_MULTIPLICITY
		2174
		2175	If undefined or defined to C<1>, then all event-loop-specific functions
		2176	will have the C<struct ev_loop *> as first argument, and you can create
		2177	additional independent event loops. Otherwise there will be no support
		2178	for multiple event loops and there is no first event loop pointer
		2179	argument. Instead, all functions act on the single default loop.
		2180
		2181	=item EV_MINPRI
		2182
		2183	=item EV_MAXPRI
		2184
		2185	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2186	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2187	provide for more priorities by overriding those symbols (usually defined
		2188	to be C<-2> and C<2>, respectively).
		2189
		2190	When doing priority-based operations, libev usually has to linearly search
		2191	all the priorities, so having many of them (hundreds) uses a lot of space
		2192	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2193	fine.
		2194
		2195	If your embedding app does not need any priorities, defining these both to
		2196	C<0> will save some memory and cpu.
		2197
		2198	=item EV_PERIODIC_ENABLE
		2199
		2200	If undefined or defined to be C<1>, then periodic timers are supported. If
		2201	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2202	code.
		2203
		2204	=item EV_IDLE_ENABLE
		2205
		2206	If undefined or defined to be C<1>, then idle watchers are supported. If
		2207	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2208	code.
		2209
		2210	=item EV_EMBED_ENABLE
		2211
		2212	If undefined or defined to be C<1>, then embed watchers are supported. If
		2213	defined to be C<0>, then they are not.
		2214
		2215	=item EV_STAT_ENABLE
		2216
		2217	If undefined or defined to be C<1>, then stat watchers are supported. If
		2218	defined to be C<0>, then they are not.
		2219
		2220	=item EV_FORK_ENABLE
		2221
		2222	If undefined or defined to be C<1>, then fork watchers are supported. If
		2223	defined to be C<0>, then they are not.
		2224
		2225	=item EV_MINIMAL
		2226
		2227	If you need to shave off some kilobytes of code at the expense of some
		2228	speed, define this symbol to C<1>. Currently only used for gcc to override
		2229	some inlining decisions, saves roughly 30% codesize of amd64.
		2230
		2231	=item EV_PID_HASHSIZE
		2232
		2233	C<ev_child> watchers use a small hash table to distribute workload by
		2234	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2235	than enough. If you need to manage thousands of children you might want to
		2236	increase this value (I<must> be a power of two).
		2237
		2238	=item EV_INOTIFY_HASHSIZE
		2239
		2240	C<ev_staz> watchers use a small hash table to distribute workload by
		2241	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2242	usually more than enough. If you need to manage thousands of C<ev_stat>
		2243	watchers you might want to increase this value (I<must> be a power of
		2244	two).
		2245
		2246	=item EV_COMMON
		2247
		2248	By default, all watchers have a C<void *data> member. By redefining
		2249	this macro to a something else you can include more and other types of
		2250	members. You have to define it each time you include one of the files,
		2251	though, and it must be identical each time.
		2252
		2253	For example, the perl EV module uses something like this:
		2254
		2255	#define EV_COMMON \
		2256	SV *self; /* contains this struct */ \
		2257	SV *cb_sv, *fh /* note no trailing ";" */
		2258
		2259	=item EV_CB_DECLARE (type)
		2260
		2261	=item EV_CB_INVOKE (watcher, revents)
		2262
		2263	=item ev_set_cb (ev, cb)
		2264
		2265	Can be used to change the callback member declaration in each watcher,
		2266	and the way callbacks are invoked and set. Must expand to a struct member
		2267	definition and a statement, respectively. See the F<ev.v> header file for
		2268	their default definitions. One possible use for overriding these is to
		2269	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2270	method calls instead of plain function calls in C++.
		2271
		2272	=head2 EXAMPLES
		2273
		2274	For a real-world example of a program the includes libev
		2275	verbatim, you can have a look at the EV perl module
		2276	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2277	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2278	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2279	will be compiled. It is pretty complex because it provides its own header
		2280	file.
		2281
		2282	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2283	that everybody includes and which overrides some configure choices:
		2284
		2285	#define EV_MINIMAL 1
		2286	#define EV_USE_POLL 0
		2287	#define EV_MULTIPLICITY 0
		2288	#define EV_PERIODIC_ENABLE 0
		2289	#define EV_STAT_ENABLE 0
		2290	#define EV_FORK_ENABLE 0
		2291	#define EV_CONFIG_H <config.h>
		2292	#define EV_MINPRI 0
		2293	#define EV_MAXPRI 0
		2294
		2295	#include "ev++.h"
		2296
		2297	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2298
		2299	#include "ev_cpp.h"
		2300	#include "ev.c"
		2301
		2302
		2303	=head1 COMPLEXITIES
		2304
		2305	In this section the complexities of (many of) the algorithms used inside
		2306	libev will be explained. For complexity discussions about backends see the
		2307	documentation for C<ev_default_init>.
		2308
		2309	All of the following are about amortised time: If an array needs to be
		2310	extended, libev needs to realloc and move the whole array, but this
		2311	happens asymptotically never with higher number of elements, so O(1) might
		2312	mean it might do a lengthy realloc operation in rare cases, but on average
		2313	it is much faster and asymptotically approaches constant time.
		2314
		2315	=over 4
		2316
		2317	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2318
		2319	This means that, when you have a watcher that triggers in one hour and
		2320	there are 100 watchers that would trigger before that then inserting will
		2321	have to skip those 100 watchers.
		2322
		2323	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2324
		2325	That means that for changing a timer costs less than removing/adding them
		2326	as only the relative motion in the event queue has to be paid for.
		2327
		2328	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2329
		2330	These just add the watcher into an array or at the head of a list.
		2331	=item Stopping check/prepare/idle watchers: O(1)
		2332
		2333	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2334
		2335	These watchers are stored in lists then need to be walked to find the
		2336	correct watcher to remove. The lists are usually short (you don't usually
		2337	have many watchers waiting for the same fd or signal).
		2338
		2339	=item Finding the next timer per loop iteration: O(1)
		2340
		2341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2342
		2343	A change means an I/O watcher gets started or stopped, which requires
		2344	libev to recalculate its status (and possibly tell the kernel).
		2345
		2346	=item Activating one watcher: O(1)
		2347
		2348	=item Priority handling: O(number_of_priorities)
		2349
		2350	Priorities are implemented by allocating some space for each
		2351	priority. When doing priority-based operations, libev usually has to
		2352	linearly search all the priorities.
		2353
		2354	=back
		2355
		2356
767	=head1 AUTHOR	2357	=head1 AUTHOR
768		2358
769	Marc Lehmann <libev@schmorp.de>.	2359	Marc Lehmann <libev@schmorp.de>.
770		2360

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