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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 events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
18		64
…		…
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).	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
		84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
		85	for example).
31		86
32	=head1 CONVENTIONS	87	=head1 CONVENTIONS
33		88
34	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
35	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
36	about various configuraiton options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
37	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
38	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
39	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.
40	will not have this argument.
41		95
42	=head1 TIME AND OTHER GLOBAL FUNCTIONS	96	=head1 TIME REPRESENTATION
43		97
44	Libev represents time as a single floating point number. This type is	98	Libev represents time as a single floating point number, representing the
		99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
		100	the beginning of 1970, details are complicated, don't ask). This type is
45	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
46	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
		106
		107	=head1 GLOBAL FUNCTIONS
		108
		109	These functions can be called anytime, even before initialising the
		110	library in any way.
47		111
48	=over 4	112	=over 4
49		113
50	=item ev_tstamp ev_time ()	114	=item ev_tstamp ev_time ()
51		115
52	Returns the current time as libev would use it.	116	Returns the current time as libev would use it. Please note that the
		117	C<ev_now> function is usually faster and also often returns the timestamp
		118	you actually want to know.
53		119
54	=item int ev_version_major ()	120	=item int ev_version_major ()
55		121
56	=item int ev_version_minor ()	122	=item int ev_version_minor ()
57		123
58	You can find out the major and minor version numbers of the library	124	You can find out the major and minor ABI version numbers of the library
59	you linked against by calling the functions C<ev_version_major> and	125	you linked against by calling the functions C<ev_version_major> and
60	C<ev_version_minor>. If you want, you can compare against the global	126	C<ev_version_minor>. If you want, you can compare against the global
61	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
62	version of the library your program was compiled against.	128	version of the library your program was compiled against.
63		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
64	Usually, its a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
65	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
66	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
67	not a problem.	136	not a problem.
68		137
		138	Example: Make sure we haven't accidentally been linked against the wrong
		139	version.
		140
		141	assert (("libev version mismatch",
		142	ev_version_major () == EV_VERSION_MAJOR
		143	&& ev_version_minor () >= EV_VERSION_MINOR));
		144
		145	=item unsigned int ev_supported_backends ()
		146
		147	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		148	value) compiled into this binary of libev (independent of their
		149	availability on the system you are running on). See C<ev_default_loop> for
		150	a description of the set values.
		151
		152	Example: make sure we have the epoll method, because yeah this is cool and
		153	a must have and can we have a torrent of it please!!!11
		154
		155	assert (("sorry, no epoll, no sex",
		156	ev_supported_backends () & EVBACKEND_EPOLL));
		157
		158	=item unsigned int ev_recommended_backends ()
		159
		160	Return the set of all backends compiled into this binary of libev and also
		161	recommended for this platform. This set is often smaller than the one
		162	returned by C<ev_supported_backends>, as for example kqueue is broken on
		163	most BSDs and will not be autodetected unless you explicitly request it
		164	(assuming you know what you are doing). This is the set of backends that
		165	libev will probe for if you specify no backends explicitly.
		166
		167	=item unsigned int ev_embeddable_backends ()
		168
		169	Returns the set of backends that are embeddable in other event loops. This
		170	is the theoretical, all-platform, value. To find which backends
		171	might be supported on the current system, you would need to look at
		172	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		173	recommended ones.
		174
		175	See the description of C<ev_embed> watchers for more info.
		176
69	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
70		178
71	Sets the allocation function to use (the prototype is similar to the	179	Sets the allocation function to use (the prototype is similar - the
72	realloc function). It is used to allocate and free memory (no surprises	180	semantics is identical - to the realloc C function). It is used to
73	here). If it returns zero when memory needs to be allocated, the library	181	allocate and free memory (no surprises here). If it returns zero when
74	might abort or take some potentially destructive action. The default is	182	memory needs to be allocated, the library might abort or take some
75	your system realloc function.	183	potentially destructive action. The default is your system realloc
		184	function.
76		185
77	You could override this function in high-availability programs to, say,	186	You could override this function in high-availability programs to, say,
78	free some memory if it cannot allocate memory, to use a special allocator,	187	free some memory if it cannot allocate memory, to use a special allocator,
79	or even to sleep a while and retry until some memory is available.	188	or even to sleep a while and retry until some memory is available.
		189
		190	Example: Replace the libev allocator with one that waits a bit and then
		191	retries).
		192
		193	static void *
		194	persistent_realloc (void *ptr, size_t size)
		195	{
		196	for (;;)
		197	{
		198	void *newptr = realloc (ptr, size);
		199
		200	if (newptr)
		201	return newptr;
		202
		203	sleep (60);
		204	}
		205	}
		206
		207	...
		208	ev_set_allocator (persistent_realloc);
80		209
81	=item ev_set_syserr_cb (void (*cb)(const char *msg));	210	=item ev_set_syserr_cb (void (*cb)(const char *msg));
82		211
83	Set the callback function to call on a retryable syscall error (such	212	Set the callback function to call on a retryable syscall error (such
84	as failed select, poll, epoll_wait). The message is a printable string	213	as failed select, poll, epoll_wait). The message is a printable string
85	indicating the system call or subsystem causing the problem. If this	214	indicating the system call or subsystem causing the problem. If this
86	callback is set, then libev will expect it to remedy the sitution, no	215	callback is set, then libev will expect it to remedy the sitution, no
87	matter what, when it returns. That is, libev will geenrally retry the	216	matter what, when it returns. That is, libev will generally retry the
88	requested operation, or, if the condition doesn't go away, do bad stuff	217	requested operation, or, if the condition doesn't go away, do bad stuff
89	(such as abort).	218	(such as abort).
		219
		220	Example: This is basically the same thing that libev does internally, too.
		221
		222	static void
		223	fatal_error (const char *msg)
		224	{
		225	perror (msg);
		226	abort ();
		227	}
		228
		229	...
		230	ev_set_syserr_cb (fatal_error);
90		231
91	=back	232	=back
92		233
93	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
94		235
95	An event loop is described by a C<struct ev_loop *>. The library knows two	236	An event loop is described by a C<struct ev_loop *>. The library knows two
96	types of such loops, the I<default> loop, which supports signals and child	237	types of such loops, the I<default> loop, which supports signals and child
97	events, and dynamically created loops which do not.	238	events, and dynamically created loops which do not.
98		239
99	If you use threads, a common model is to run the default event loop	240	If you use threads, a common model is to run the default event loop
100	in your main thread (or in a separate thrad) and for each thread you	241	in your main thread (or in a separate thread) and for each thread you
101	create, you also create another event loop. Libev itself does no lockign	242	create, you also create another event loop. Libev itself does no locking
102	whatsoever, so if you mix calls to different event loops, make sure you	243	whatsoever, so if you mix calls to the same event loop in different
103	lock (this is usually a bad idea, though, even if done right).	244	threads, make sure you lock (this is usually a bad idea, though, even if
		245	done correctly, because it's hideous and inefficient).
104		246
105	=over 4	247	=over 4
106		248
107	=item struct ev_loop *ev_default_loop (unsigned int flags)	249	=item struct ev_loop *ev_default_loop (unsigned int flags)
108		250
109	This will initialise the default event loop if it hasn't been initialised	251	This will initialise the default event loop if it hasn't been initialised
110	yet and return it. If the default loop could not be initialised, returns	252	yet and return it. If the default loop could not be initialised, returns
111	false. If it already was initialised it simply returns it (and ignores the	253	false. If it already was initialised it simply returns it (and ignores the
112	flags).	254	flags. If that is troubling you, check C<ev_backend ()> afterwards).
113		255
114	If you don't know what event loop to use, use the one returned from this	256	If you don't know what event loop to use, use the one returned from this
115	function.	257	function.
116		258
117	The flags argument can be used to specify special behaviour or specific	259	The flags argument can be used to specify special behaviour or specific
118	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
119		261
120	It supports the following flags:	262	The following flags are supported:
121		263
122	=over 4	264	=over 4
123		265
124	=item EVFLAG_AUTO	266	=item C<EVFLAG_AUTO>
125		267
126	The default flags value. Use this if you have no clue (its the right	268	The default flags value. Use this if you have no clue (it's the right
127	thing, believe me).	269	thing, believe me).
128		270
129	=item EVFLAG_NOENV	271	=item C<EVFLAG_NOENV>
130		272
131	If this flag bit is ored into the flag value then libev will I<not> look	273	If this flag bit is ored into the flag value (or the program runs setuid
132	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	274	or setgid) then libev will I<not> look at the environment variable
133	environment variable will override the flags completely. This is useful	275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		276	override the flags completely if it is found in the environment. This is
134	to try out specific backends to tets their performance, or to work around	277	useful to try out specific backends to test their performance, or to work
135	bugs.	278	around bugs.
136		279
		280	=item C<EVFLAG_FORKCHECK>
		281
		282	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		283	a fork, you can also make libev check for a fork in each iteration by
		284	enabling this flag.
		285
		286	This works by calling C<getpid ()> on every iteration of the loop,
		287	and thus this might slow down your event loop if you do a lot of loop
		288	iterations and little real work, but is usually not noticeable (on my
		289	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		290	without a syscall and thus I<very> fast, but my Linux system also has
		291	C<pthread_atfork> which is even faster).
		292
		293	The big advantage of this flag is that you can forget about fork (and
		294	forget about forgetting to tell libev about forking) when you use this
		295	flag.
		296
		297	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		298	environment variable.
		299
137	=item EVMETHOD_SELECT portable select backend	300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
138		301
139	=item EVMETHOD_POLL poll backend (everywhere except windows)	302	This is your standard select(2) backend. Not I<completely> standard, as
		303	libev tries to roll its own fd_set with no limits on the number of fds,
		304	but if that fails, expect a fairly low limit on the number of fds when
		305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		306	the fastest backend for a low number of fds.
140		307
141	=item EVMETHOD_EPOLL linux only	308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
142		309
143	=item EVMETHOD_KQUEUE some bsds only	310	And this is your standard poll(2) backend. It's more complicated than
		311	select, but handles sparse fds better and has no artificial limit on the
		312	number of fds you can use (except it will slow down considerably with a
		313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
144		314
145	=item EVMETHOD_DEVPOLL solaris 8 only	315	=item C<EVBACKEND_EPOLL> (value 4, Linux)
146		316
147	=item EVMETHOD_PORT solaris 10 only	317	For few fds, this backend is a bit little slower than poll and select,
		318	but it scales phenomenally better. While poll and select usually scale like
		319	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		320	either O(1) or O(active_fds).
		321
		322	While stopping and starting an I/O watcher in the same iteration will
		323	result in some caching, there is still a syscall per such incident
		324	(because the fd could point to a different file description now), so its
		325	best to avoid that. Also, dup()ed file descriptors might not work very
		326	well if you register events for both fds.
		327
		328	Please note that epoll sometimes generates spurious notifications, so you
		329	need to use non-blocking I/O or other means to avoid blocking when no data
		330	(or space) is available.
		331
		332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		333
		334	Kqueue deserves special mention, as at the time of this writing, it
		335	was broken on all BSDs except NetBSD (usually it doesn't work with
		336	anything but sockets and pipes, except on Darwin, where of course its
		337	completely useless). For this reason its not being "autodetected"
		338	unless you explicitly specify it explicitly in the flags (i.e. using
		339	C<EVBACKEND_KQUEUE>).
		340
		341	It scales in the same way as the epoll backend, but the interface to the
		342	kernel is more efficient (which says nothing about its actual speed, of
		343	course). While starting and stopping an I/O watcher does not cause an
		344	extra syscall as with epoll, it still adds up to four event changes per
		345	incident, so its best to avoid that.
		346
		347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		348
		349	This is not implemented yet (and might never be).
		350
		351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		352
		353	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		354	it's really slow, but it still scales very well (O(active_fds)).
		355
		356	Please note that solaris ports can result in a lot of spurious
		357	notifications, so you need to use non-blocking I/O or other means to avoid
		358	blocking when no data (or space) is available.
		359
		360	=item C<EVBACKEND_ALL>
		361
		362	Try all backends (even potentially broken ones that wouldn't be tried
		363	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		365
		366	=back
148		367
149	If one or more of these are ored into the flags value, then only these	368	If one or more of these are ored into the flags value, then only these
150	backends will be tried (in the reverse order as given here). If one are	369	backends will be tried (in the reverse order as given here). If none are
151	specified, any backend will do.	370	specified, most compiled-in backend will be tried, usually in reverse
		371	order of their flag values :)
152		372
153	=back	373	The most typical usage is like this:
		374
		375	if (!ev_default_loop (0))
		376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		377
		378	Restrict libev to the select and poll backends, and do not allow
		379	environment settings to be taken into account:
		380
		381	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		382
		383	Use whatever libev has to offer, but make sure that kqueue is used if
		384	available (warning, breaks stuff, best use only with your own private
		385	event loop and only if you know the OS supports your types of fds):
		386
		387	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
154		388
155	=item struct ev_loop *ev_loop_new (unsigned int flags)	389	=item struct ev_loop *ev_loop_new (unsigned int flags)
156		390
157	Similar to C<ev_default_loop>, but always creates a new event loop that is	391	Similar to C<ev_default_loop>, but always creates a new event loop that is
158	always distinct from the default loop. Unlike the default loop, it cannot	392	always distinct from the default loop. Unlike the default loop, it cannot
159	handle signal and child watchers, and attempts to do so will be greeted by	393	handle signal and child watchers, and attempts to do so will be greeted by
160	undefined behaviour (or a failed assertion if assertions are enabled).	394	undefined behaviour (or a failed assertion if assertions are enabled).
161		395
		396	Example: Try to create a event loop that uses epoll and nothing else.
		397
		398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		399	if (!epoller)
		400	fatal ("no epoll found here, maybe it hides under your chair");
		401
162	=item ev_default_destroy ()	402	=item ev_default_destroy ()
163		403
164	Destroys the default loop again (frees all memory and kernel state	404	Destroys the default loop again (frees all memory and kernel state
165	etc.). This stops all registered event watchers (by not touching them in	405	etc.). None of the active event watchers will be stopped in the normal
166	any way whatsoever, although you cnanot rely on this :).	406	sense, so e.g. C<ev_is_active> might still return true. It is your
		407	responsibility to either stop all watchers cleanly yoursef I<before>
		408	calling this function, or cope with the fact afterwards (which is usually
		409	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		410	for example).
167		411
168	=item ev_loop_destroy (loop)	412	=item ev_loop_destroy (loop)
169		413
170	Like C<ev_default_destroy>, but destroys an event loop created by an	414	Like C<ev_default_destroy>, but destroys an event loop created by an
171	earlier call to C<ev_loop_new>.	415	earlier call to C<ev_loop_new>.
…		…
175	This function reinitialises the kernel state for backends that have	419	This function reinitialises the kernel state for backends that have
176	one. Despite the name, you can call it anytime, but it makes most sense	420	one. Despite the name, you can call it anytime, but it makes most sense
177	after forking, in either the parent or child process (or both, but that	421	after forking, in either the parent or child process (or both, but that
178	again makes little sense).	422	again makes little sense).
179		423
180	You I<must> call this function after forking if and only if you want to	424	You I<must> call this function in the child process after forking if and
181	use the event library in both processes. If you just fork+exec, you don't	425	only if you want to use the event library in both processes. If you just
182	have to call it.	426	fork+exec, you don't have to call it.
183		427
184	The function itself is quite fast and its usually not a problem to call	428	The function itself is quite fast and it's usually not a problem to call
185	it just in case after a fork. To make this easy, the function will fit in	429	it just in case after a fork. To make this easy, the function will fit in
186	quite nicely into a call to C<pthread_atfork>:	430	quite nicely into a call to C<pthread_atfork>:
187		431
188	pthread_atfork (0, 0, ev_default_fork);	432	pthread_atfork (0, 0, ev_default_fork);
		433
		434	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		435	without calling this function, so if you force one of those backends you
		436	do not need to care.
189		437
190	=item ev_loop_fork (loop)	438	=item ev_loop_fork (loop)
191		439
192	Like C<ev_default_fork>, but acts on an event loop created by	440	Like C<ev_default_fork>, but acts on an event loop created by
193	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	441	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
194	after fork, and how you do this is entirely your own problem.	442	after fork, and how you do this is entirely your own problem.
195		443
		444	=item unsigned int ev_loop_count (loop)
		445
		446	Returns the count of loop iterations for the loop, which is identical to
		447	the number of times libev did poll for new events. It starts at C<0> and
		448	happily wraps around with enough iterations.
		449
		450	This value can sometimes be useful as a generation counter of sorts (it
		451	"ticks" the number of loop iterations), as it roughly corresponds with
		452	C<ev_prepare> and C<ev_check> calls.
		453
196	=item unsigned int ev_method (loop)	454	=item unsigned int ev_backend (loop)
197		455
198	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	456	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
199	use.	457	use.
200		458
201	=item ev_tstamp = ev_now (loop)	459	=item ev_tstamp ev_now (loop)
202		460
203	Returns the current "event loop time", which is the time the event loop	461	Returns the current "event loop time", which is the time the event loop
204	got events and started processing them. This timestamp does not change	462	received events and started processing them. This timestamp does not
205	as long as callbacks are being processed, and this is also the base time	463	change as long as callbacks are being processed, and this is also the base
206	used for relative timers. You can treat it as the timestamp of the event	464	time used for relative timers. You can treat it as the timestamp of the
207	occuring (or more correctly, the mainloop finding out about it).	465	event occuring (or more correctly, libev finding out about it).
208		466
209	=item ev_loop (loop, int flags)	467	=item ev_loop (loop, int flags)
210		468
211	Finally, this is it, the event handler. This function usually is called	469	Finally, this is it, the event handler. This function usually is called
212	after you initialised all your watchers and you want to start handling	470	after you initialised all your watchers and you want to start handling
213	events.	471	events.
214		472
215	If the flags argument is specified as 0, it will not return until either	473	If the flags argument is specified as C<0>, it will not return until
216	no event watchers are active anymore or C<ev_unloop> was called.	474	either no event watchers are active anymore or C<ev_unloop> was called.
		475
		476	Please note that an explicit C<ev_unloop> is usually better than
		477	relying on all watchers to be stopped when deciding when a program has
		478	finished (especially in interactive programs), but having a program that
		479	automatically loops as long as it has to and no longer by virtue of
		480	relying on its watchers stopping correctly is a thing of beauty.
217		481
218	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	482	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
219	those events and any outstanding ones, but will not block your process in	483	those events and any outstanding ones, but will not block your process in
220	case there are no events.	484	case there are no events and will return after one iteration of the loop.
221		485
222	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	486	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
223	neccessary) and will handle those and any outstanding ones. It will block	487	neccessary) and will handle those and any outstanding ones. It will block
224	your process until at least one new event arrives.	488	your process until at least one new event arrives, and will return after
		489	one iteration of the loop. This is useful if you are waiting for some
		490	external event in conjunction with something not expressible using other
		491	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		492	usually a better approach for this kind of thing.
225		493
226	This flags value could be used to implement alternative looping	494	Here are the gory details of what C<ev_loop> does:
227	constructs, but the C<prepare> and C<check> watchers provide a better and	495
228	more generic mechanism.	496	- Before the first iteration, call any pending watchers.
		497	* If there are no active watchers (reference count is zero), return.
		498	- Queue all prepare watchers and then call all outstanding watchers.
		499	- If we have been forked, recreate the kernel state.
		500	- Update the kernel state with all outstanding changes.
		501	- Update the "event loop time".
		502	- Calculate for how long to block.
		503	- Block the process, waiting for any events.
		504	- Queue all outstanding I/O (fd) events.
		505	- Update the "event loop time" and do time jump handling.
		506	- Queue all outstanding timers.
		507	- Queue all outstanding periodics.
		508	- If no events are pending now, queue all idle watchers.
		509	- Queue all check watchers.
		510	- Call all queued watchers in reverse order (i.e. check watchers first).
		511	Signals and child watchers are implemented as I/O watchers, and will
		512	be handled here by queueing them when their watcher gets executed.
		513	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		514	were used, return, otherwise continue with step *.
		515
		516	Example: Queue some jobs and then loop until no events are outsanding
		517	anymore.
		518
		519	... queue jobs here, make sure they register event watchers as long
		520	... as they still have work to do (even an idle watcher will do..)
		521	ev_loop (my_loop, 0);
		522	... jobs done. yeah!
229		523
230	=item ev_unloop (loop, how)	524	=item ev_unloop (loop, how)
231		525
232	Can be used to make a call to C<ev_loop> return early. The C<how> argument	526	Can be used to make a call to C<ev_loop> return early (but only after it
		527	has processed all outstanding events). The C<how> argument must be either
233	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	528	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
234	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	529	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
235	calls return.
236		530
237	=item ev_ref (loop)	531	=item ev_ref (loop)
238		532
239	=item ev_unref (loop)	533	=item ev_unref (loop)
240		534
241	Ref/unref can be used to add or remove a refcount on the event loop: Every	535	Ref/unref can be used to add or remove a reference count on the event
242	watcher keeps one reference. If you have a long-runing watcher you never	536	loop: Every watcher keeps one reference, and as long as the reference
243	unregister that should not keep ev_loop from running, ev_unref() after	537	count is nonzero, C<ev_loop> will not return on its own. If you have
244	starting, and ev_ref() before stopping it. Libev itself uses this for	538	a watcher you never unregister that should not keep C<ev_loop> from
245	example for its internal signal pipe: It is not visible to you as a user	539	returning, ev_unref() after starting, and ev_ref() before stopping it. For
246	and should not keep C<ev_loop> from exiting if the work is done. It is	540	example, libev itself uses this for its internal signal pipe: It is not
247	also an excellent way to do this for generic recurring timers or from	541	visible to the libev user and should not keep C<ev_loop> from exiting if
248	within third-party libraries. Just remember to unref after start and ref	542	no event watchers registered by it are active. It is also an excellent
249	before stop.	543	way to do this for generic recurring timers or from within third-party
		544	libraries. Just remember to I<unref after start> and I<ref before stop>.
		545
		546	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		547	running when nothing else is active.
		548
		549	struct ev_signal exitsig;
		550	ev_signal_init (&exitsig, sig_cb, SIGINT);
		551	ev_signal_start (loop, &exitsig);
		552	evf_unref (loop);
		553
		554	Example: For some weird reason, unregister the above signal handler again.
		555
		556	ev_ref (loop);
		557	ev_signal_stop (loop, &exitsig);
250		558
251	=back	559	=back
		560
252		561
253	=head1 ANATOMY OF A WATCHER	562	=head1 ANATOMY OF A WATCHER
254		563
255	A watcher is a structure that you create and register to record your	564	A watcher is a structure that you create and register to record your
256	interest in some event. For instance, if you want to wait for STDIN to	565	interest in some event. For instance, if you want to wait for STDIN to
257	become readable, you would create an ev_io watcher for that:	566	become readable, you would create an C<ev_io> watcher for that:
258		567
259	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	568	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
260	{	569	{
261	ev_io_stop (w);	570	ev_io_stop (w);
262	ev_unloop (loop, EVUNLOOP_ALL);	571	ev_unloop (loop, EVUNLOOP_ALL);
…		…
289	*) >>), and you can stop watching for events at any time by calling the	598	*) >>), and you can stop watching for events at any time by calling the
290	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	599	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
291		600
292	As long as your watcher is active (has been started but not stopped) you	601	As long as your watcher is active (has been started but not stopped) you
293	must not touch the values stored in it. Most specifically you must never	602	must not touch the values stored in it. Most specifically you must never
294	reinitialise it or call its set method.	603	reinitialise it or call its C<set> macro.
295
296	You cna check wether an event is active by calling the C<ev_is_active
297	(watcher *)> macro. To see wether an event is outstanding (but the
298	callback for it has not been called yet) you cna use the C<ev_is_pending
299	(watcher *)> macro.
300		604
301	Each and every callback receives the event loop pointer as first, the	605	Each and every callback receives the event loop pointer as first, the
302	registered watcher structure as second, and a bitset of received events as	606	registered watcher structure as second, and a bitset of received events as
303	third argument.	607	third argument.
304		608
305	The rceeived events usually include a single bit per event type received	609	The received events usually include a single bit per event type received
306	(you can receive multiple events at the same time). The possible bit masks	610	(you can receive multiple events at the same time). The possible bit masks
307	are:	611	are:
308		612
309	=over 4	613	=over 4
310		614
311	=item EV_READ	615	=item C<EV_READ>
312		616
313	=item EV_WRITE	617	=item C<EV_WRITE>
314		618
315	The file descriptor in the ev_io watcher has become readable and/or	619	The file descriptor in the C<ev_io> watcher has become readable and/or
316	writable.	620	writable.
317		621
318	=item EV_TIMEOUT	622	=item C<EV_TIMEOUT>
319		623
320	The ev_timer watcher has timed out.	624	The C<ev_timer> watcher has timed out.
321		625
322	=item EV_PERIODIC	626	=item C<EV_PERIODIC>
323		627
324	The ev_periodic watcher has timed out.	628	The C<ev_periodic> watcher has timed out.
325		629
326	=item EV_SIGNAL	630	=item C<EV_SIGNAL>
327		631
328	The signal specified in the ev_signal watcher has been received by a thread.	632	The signal specified in the C<ev_signal> watcher has been received by a thread.
329		633
330	=item EV_CHILD	634	=item C<EV_CHILD>
331		635
332	The pid specified in the ev_child watcher has received a status change.	636	The pid specified in the C<ev_child> watcher has received a status change.
333		637
		638	=item C<EV_STAT>
		639
		640	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		641
334	=item EV_IDLE	642	=item C<EV_IDLE>
335		643
336	The ev_idle watcher has determined that you have nothing better to do.	644	The C<ev_idle> watcher has determined that you have nothing better to do.
337		645
338	=item EV_PREPARE	646	=item C<EV_PREPARE>
339		647
340	=item EV_CHECK	648	=item C<EV_CHECK>
341		649
342	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	650	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
343	to gather new events, and all ev_check watchers are invoked just after	651	to gather new events, and all C<ev_check> watchers are invoked just after
344	C<ev_loop> has gathered them, but before it invokes any callbacks for any	652	C<ev_loop> has gathered them, but before it invokes any callbacks for any
345	received events. Callbacks of both watcher types can start and stop as	653	received events. Callbacks of both watcher types can start and stop as
346	many watchers as they want, and all of them will be taken into account	654	many watchers as they want, and all of them will be taken into account
347	(for example, a ev_prepare watcher might start an idle watcher to keep	655	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
348	C<ev_loop> from blocking).	656	C<ev_loop> from blocking).
349		657
		658	=item C<EV_EMBED>
		659
		660	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		661
		662	=item C<EV_FORK>
		663
		664	The event loop has been resumed in the child process after fork (see
		665	C<ev_fork>).
		666
350	=item EV_ERROR	667	=item C<EV_ERROR>
351		668
352	An unspecified error has occured, the watcher has been stopped. This might	669	An unspecified error has occured, the watcher has been stopped. This might
353	happen because the watcher could not be properly started because libev	670	happen because the watcher could not be properly started because libev
354	ran out of memory, a file descriptor was found to be closed or any other	671	ran out of memory, a file descriptor was found to be closed or any other
355	problem. You best act on it by reporting the problem and somehow coping	672	problem. You best act on it by reporting the problem and somehow coping
…		…
361	with the error from read() or write(). This will not work in multithreaded	678	with the error from read() or write(). This will not work in multithreaded
362	programs, though, so beware.	679	programs, though, so beware.
363		680
364	=back	681	=back
365		682
		683	=head2 GENERIC WATCHER FUNCTIONS
		684
		685	In the following description, C<TYPE> stands for the watcher type,
		686	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		687
		688	=over 4
		689
		690	=item C<ev_init> (ev_TYPE *watcher, callback)
		691
		692	This macro initialises the generic portion of a watcher. The contents
		693	of the watcher object can be arbitrary (so C<malloc> will do). Only
		694	the generic parts of the watcher are initialised, you I<need> to call
		695	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		696	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		697	which rolls both calls into one.
		698
		699	You can reinitialise a watcher at any time as long as it has been stopped
		700	(or never started) and there are no pending events outstanding.
		701
		702	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		703	int revents)>.
		704
		705	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		706
		707	This macro initialises the type-specific parts of a watcher. You need to
		708	call C<ev_init> at least once before you call this macro, but you can
		709	call C<ev_TYPE_set> any number of times. You must not, however, call this
		710	macro on a watcher that is active (it can be pending, however, which is a
		711	difference to the C<ev_init> macro).
		712
		713	Although some watcher types do not have type-specific arguments
		714	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		715
		716	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		717
		718	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		719	calls into a single call. This is the most convinient method to initialise
		720	a watcher. The same limitations apply, of course.
		721
		722	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		723
		724	Starts (activates) the given watcher. Only active watchers will receive
		725	events. If the watcher is already active nothing will happen.
		726
		727	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		728
		729	Stops the given watcher again (if active) and clears the pending
		730	status. It is possible that stopped watchers are pending (for example,
		731	non-repeating timers are being stopped when they become pending), but
		732	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		733	you want to free or reuse the memory used by the watcher it is therefore a
		734	good idea to always call its C<ev_TYPE_stop> function.
		735
		736	=item bool ev_is_active (ev_TYPE *watcher)
		737
		738	Returns a true value iff the watcher is active (i.e. it has been started
		739	and not yet been stopped). As long as a watcher is active you must not modify
		740	it.
		741
		742	=item bool ev_is_pending (ev_TYPE *watcher)
		743
		744	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		745	events but its callback has not yet been invoked). As long as a watcher
		746	is pending (but not active) you must not call an init function on it (but
		747	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		748	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		749	it).
		750
		751	=item callback ev_cb (ev_TYPE *watcher)
		752
		753	Returns the callback currently set on the watcher.
		754
		755	=item ev_cb_set (ev_TYPE *watcher, callback)
		756
		757	Change the callback. You can change the callback at virtually any time
		758	(modulo threads).
		759
		760	=item ev_set_priority (ev_TYPE *watcher, priority)
		761
		762	=item int ev_priority (ev_TYPE *watcher)
		763
		764	Set and query the priority of the watcher. The priority is a small
		765	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		766	(default: C<-2>). Pending watchers with higher priority will be invoked
		767	before watchers with lower priority, but priority will not keep watchers
		768	from being executed (except for C<ev_idle> watchers).
		769
		770	This means that priorities are I<only> used for ordering callback
		771	invocation after new events have been received. This is useful, for
		772	example, to reduce latency after idling, or more often, to bind two
		773	watchers on the same event and make sure one is called first.
		774
		775	If you need to suppress invocation when higher priority events are pending
		776	you need to look at C<ev_idle> watchers, which provide this functionality.
		777
		778	You I<must not> change the priority of a watcher as long as it is active or
		779	pending.
		780
		781	The default priority used by watchers when no priority has been set is
		782	always C<0>, which is supposed to not be too high and not be too low :).
		783
		784	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		785	fine, as long as you do not mind that the priority value you query might
		786	or might not have been adjusted to be within valid range.
		787
		788	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		789
		790	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		791	C<loop> nor C<revents> need to be valid as long as the watcher callback
		792	can deal with that fact.
		793
		794	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		795
		796	If the watcher is pending, this function returns clears its pending status
		797	and returns its C<revents> bitset (as if its callback was invoked). If the
		798	watcher isn't pending it does nothing and returns C<0>.
		799
		800	=back
		801
		802
366	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	803	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
367		804
368	Each watcher has, by default, a member C<void *data> that you can change	805	Each watcher has, by default, a member C<void *data> that you can change
369	and read at any time, libev will completely ignore it. This cna be used	806	and read at any time, libev will completely ignore it. This can be used
370	to associate arbitrary data with your watcher. If you need more data and	807	to associate arbitrary data with your watcher. If you need more data and
371	don't want to allocate memory and store a pointer to it in that data	808	don't want to allocate memory and store a pointer to it in that data
372	member, you can also "subclass" the watcher type and provide your own	809	member, you can also "subclass" the watcher type and provide your own
373	data:	810	data:
374		811
…		…
387	{	824	{
388	struct my_io *w = (struct my_io *)w_;	825	struct my_io *w = (struct my_io *)w_;
389	...	826	...
390	}	827	}
391		828
392	More interesting and less C-conformant ways of catsing your callback type	829	More interesting and less C-conformant ways of casting your callback type
393	have been omitted....	830	instead have been omitted.
		831
		832	Another common scenario is having some data structure with multiple
		833	watchers:
		834
		835	struct my_biggy
		836	{
		837	int some_data;
		838	ev_timer t1;
		839	ev_timer t2;
		840	}
		841
		842	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		843	you need to use C<offsetof>:
		844
		845	#include <stddef.h>
		846
		847	static void
		848	t1_cb (EV_P_ struct ev_timer *w, int revents)
		849	{
		850	struct my_biggy big = (struct my_biggy *
		851	(((char *)w) - offsetof (struct my_biggy, t1));
		852	}
		853
		854	static void
		855	t2_cb (EV_P_ struct ev_timer *w, int revents)
		856	{
		857	struct my_biggy big = (struct my_biggy *
		858	(((char *)w) - offsetof (struct my_biggy, t2));
		859	}
394		860
395		861
396	=head1 WATCHER TYPES	862	=head1 WATCHER TYPES
397		863
398	This section describes each watcher in detail, but will not repeat	864	This section describes each watcher in detail, but will not repeat
399	information given in the last section.	865	information given in the last section. Any initialisation/set macros,
		866	functions and members specific to the watcher type are explained.
400		867
		868	Members are additionally marked with either I<[read-only]>, meaning that,
		869	while the watcher is active, you can look at the member and expect some
		870	sensible content, but you must not modify it (you can modify it while the
		871	watcher is stopped to your hearts content), or I<[read-write]>, which
		872	means you can expect it to have some sensible content while the watcher
		873	is active, but you can also modify it. Modifying it may not do something
		874	sensible or take immediate effect (or do anything at all), but libev will
		875	not crash or malfunction in any way.
		876
		877
401	=head2 struct ev_io - is my file descriptor readable or writable	878	=head2 C<ev_io> - is this file descriptor readable or writable?
402		879
403	I/O watchers check wether a file descriptor is readable or writable	880	I/O watchers check whether a file descriptor is readable or writable
404	in each iteration of the event loop (This behaviour is called	881	in each iteration of the event loop, or, more precisely, when reading
405	level-triggering because you keep receiving events as long as the	882	would not block the process and writing would at least be able to write
406	condition persists. Remember you cna stop the watcher if you don't want to	883	some data. This behaviour is called level-triggering because you keep
407	act on the event and neither want to receive future events).	884	receiving events as long as the condition persists. Remember you can stop
		885	the watcher if you don't want to act on the event and neither want to
		886	receive future events.
		887
		888	In general you can register as many read and/or write event watchers per
		889	fd as you want (as long as you don't confuse yourself). Setting all file
		890	descriptors to non-blocking mode is also usually a good idea (but not
		891	required if you know what you are doing).
		892
		893	You have to be careful with dup'ed file descriptors, though. Some backends
		894	(the linux epoll backend is a notable example) cannot handle dup'ed file
		895	descriptors correctly if you register interest in two or more fds pointing
		896	to the same underlying file/socket/etc. description (that is, they share
		897	the same underlying "file open").
		898
		899	If you must do this, then force the use of a known-to-be-good backend
		900	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		901	C<EVBACKEND_POLL>).
		902
		903	Another thing you have to watch out for is that it is quite easy to
		904	receive "spurious" readyness notifications, that is your callback might
		905	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		906	because there is no data. Not only are some backends known to create a
		907	lot of those (for example solaris ports), it is very easy to get into
		908	this situation even with a relatively standard program structure. Thus
		909	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		910	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		911
		912	If you cannot run the fd in non-blocking mode (for example you should not
		913	play around with an Xlib connection), then you have to seperately re-test
		914	whether a file descriptor is really ready with a known-to-be good interface
		915	such as poll (fortunately in our Xlib example, Xlib already does this on
		916	its own, so its quite safe to use).
		917
		918	=head3 The special problem of disappearing file descriptors
		919
		920	Some backends (e.g kqueue, epoll) need to be told about closing a file
		921	descriptor (either by calling C<close> explicitly or by any other means,
		922	such as C<dup>). The reason is that you register interest in some file
		923	descriptor, but when it goes away, the operating system will silently drop
		924	this interest. If another file descriptor with the same number then is
		925	registered with libev, there is no efficient way to see that this is, in
		926	fact, a different file descriptor.
		927
		928	To avoid having to explicitly tell libev about such cases, libev follows
		929	the following policy: Each time C<ev_io_set> is being called, libev
		930	will assume that this is potentially a new file descriptor, otherwise
		931	it is assumed that the file descriptor stays the same. That means that
		932	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		933	descriptor even if the file descriptor number itself did not change.
		934
		935	This is how one would do it normally anyway, the important point is that
		936	the libev application should not optimise around libev but should leave
		937	optimisations to libev.
		938
		939
		940	=head3 Watcher-Specific Functions
408		941
409	=over 4	942	=over 4
410		943
411	=item ev_io_init (ev_io *, callback, int fd, int events)	944	=item ev_io_init (ev_io *, callback, int fd, int events)
412		945
413	=item ev_io_set (ev_io *, int fd, int events)	946	=item ev_io_set (ev_io *, int fd, int events)
414		947
415	Configures an ev_io watcher. The fd is the file descriptor to rceeive	948	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
416	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	949	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
417	EV_WRITE> to receive the given events.	950	C<EV_READ | EV_WRITE> to receive the given events.
		951
		952	=item int fd [read-only]
		953
		954	The file descriptor being watched.
		955
		956	=item int events [read-only]
		957
		958	The events being watched.
418		959
419	=back	960	=back
420		961
		962	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		963	readable, but only once. Since it is likely line-buffered, you could
		964	attempt to read a whole line in the callback.
		965
		966	static void
		967	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		968	{
		969	ev_io_stop (loop, w);
		970	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		971	}
		972
		973	...
		974	struct ev_loop *loop = ev_default_init (0);
		975	struct ev_io stdin_readable;
		976	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		977	ev_io_start (loop, &stdin_readable);
		978	ev_loop (loop, 0);
		979
		980
421	=head2 struct ev_timer - relative and optionally recurring timeouts	981	=head2 C<ev_timer> - relative and optionally repeating timeouts
422		982
423	Timer watchers are simple relative timers that generate an event after a	983	Timer watchers are simple relative timers that generate an event after a
424	given time, and optionally repeating in regular intervals after that.	984	given time, and optionally repeating in regular intervals after that.
425		985
426	The timers are based on real time, that is, if you register an event that	986	The timers are based on real time, that is, if you register an event that
427	times out after an hour and youreset your system clock to last years	987	times out after an hour and you reset your system clock to last years
428	time, it will still time out after (roughly) and hour. "Roughly" because	988	time, it will still time out after (roughly) and hour. "Roughly" because
429	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	989	detecting time jumps is hard, and some inaccuracies are unavoidable (the
430	monotonic clock option helps a lot here).	990	monotonic clock option helps a lot here).
		991
		992	The relative timeouts are calculated relative to the C<ev_now ()>
		993	time. This is usually the right thing as this timestamp refers to the time
		994	of the event triggering whatever timeout you are modifying/starting. If
		995	you suspect event processing to be delayed and you I<need> to base the timeout
		996	on the current time, use something like this to adjust for this:
		997
		998	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		999
		1000	The callback is guarenteed to be invoked only when its timeout has passed,
		1001	but if multiple timers become ready during the same loop iteration then
		1002	order of execution is undefined.
		1003
		1004	=head3 Watcher-Specific Functions and Data Members
431		1005
432	=over 4	1006	=over 4
433		1007
434	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1008	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
435		1009
…		…
441	later, again, and again, until stopped manually.	1015	later, again, and again, until stopped manually.
442		1016
443	The timer itself will do a best-effort at avoiding drift, that is, if you	1017	The timer itself will do a best-effort at avoiding drift, that is, if you
444	configure a timer to trigger every 10 seconds, then it will trigger at	1018	configure a timer to trigger every 10 seconds, then it will trigger at
445	exactly 10 second intervals. If, however, your program cannot keep up with	1019	exactly 10 second intervals. If, however, your program cannot keep up with
446	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1020	the timer (because it takes longer than those 10 seconds to do stuff) the
447	timer will not fire more than once per event loop iteration.	1021	timer will not fire more than once per event loop iteration.
448		1022
449	=item ev_timer_again (loop)	1023	=item ev_timer_again (loop)
450		1024
451	This will act as if the timer timed out and restart it again if it is	1025	This will act as if the timer timed out and restart it again if it is
452	repeating. The exact semantics are:	1026	repeating. The exact semantics are:
453		1027
		1028	If the timer is pending, its pending status is cleared.
		1029
454	If the timer is started but nonrepeating, stop it.	1030	If the timer is started but nonrepeating, stop it (as if it timed out).
455		1031
456	If the timer is repeating, either start it if necessary (with the repeat	1032	If the timer is repeating, either start it if necessary (with the
457	value), or reset the running timer to the repeat value.	1033	C<repeat> value), or reset the running timer to the C<repeat> value.
458		1034
459	This sounds a bit complicated, but here is a useful and typical	1035	This sounds a bit complicated, but here is a useful and typical
460	example: Imagine you have a tcp connection and you want a so-called idle	1036	example: Imagine you have a tcp connection and you want a so-called idle
461	timeout, that is, you want to be called when there have been, say, 60	1037	timeout, that is, you want to be called when there have been, say, 60
462	seconds of inactivity on the socket. The easiest way to do this is to	1038	seconds of inactivity on the socket. The easiest way to do this is to
463	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1039	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
464	time you successfully read or write some data. If you go into an idle	1040	C<ev_timer_again> each time you successfully read or write some data. If
465	state where you do not expect data to travel on the socket, you can stop	1041	you go into an idle state where you do not expect data to travel on the
466	the timer, and again will automatically restart it if need be.	1042	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1043	automatically restart it if need be.
		1044
		1045	That means you can ignore the C<after> value and C<ev_timer_start>
		1046	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1047
		1048	ev_timer_init (timer, callback, 0., 5.);
		1049	ev_timer_again (loop, timer);
		1050	...
		1051	timer->again = 17.;
		1052	ev_timer_again (loop, timer);
		1053	...
		1054	timer->again = 10.;
		1055	ev_timer_again (loop, timer);
		1056
		1057	This is more slightly efficient then stopping/starting the timer each time
		1058	you want to modify its timeout value.
		1059
		1060	=item ev_tstamp repeat [read-write]
		1061
		1062	The current C<repeat> value. Will be used each time the watcher times out
		1063	or C<ev_timer_again> is called and determines the next timeout (if any),
		1064	which is also when any modifications are taken into account.
467		1065
468	=back	1066	=back
469		1067
470	=head2 ev_periodic	1068	Example: Create a timer that fires after 60 seconds.
		1069
		1070	static void
		1071	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1072	{
		1073	.. one minute over, w is actually stopped right here
		1074	}
		1075
		1076	struct ev_timer mytimer;
		1077	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1078	ev_timer_start (loop, &mytimer);
		1079
		1080	Example: Create a timeout timer that times out after 10 seconds of
		1081	inactivity.
		1082
		1083	static void
		1084	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1085	{
		1086	.. ten seconds without any activity
		1087	}
		1088
		1089	struct ev_timer mytimer;
		1090	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1091	ev_timer_again (&mytimer); /* start timer */
		1092	ev_loop (loop, 0);
		1093
		1094	// and in some piece of code that gets executed on any "activity":
		1095	// reset the timeout to start ticking again at 10 seconds
		1096	ev_timer_again (&mytimer);
		1097
		1098
		1099	=head2 C<ev_periodic> - to cron or not to cron?
471		1100
472	Periodic watchers are also timers of a kind, but they are very versatile	1101	Periodic watchers are also timers of a kind, but they are very versatile
473	(and unfortunately a bit complex).	1102	(and unfortunately a bit complex).
474		1103
475	Unlike ev_timer's, they are not based on real time (or relative time)	1104	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
476	but on wallclock time (absolute time). You can tell a periodic watcher	1105	but on wallclock time (absolute time). You can tell a periodic watcher
477	to trigger "at" some specific point in time. For example, if you tell a	1106	to trigger "at" some specific point in time. For example, if you tell a
478	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1107	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
479	+ 10.>) and then reset your system clock to the last year, then it will	1108	+ 10.>) and then reset your system clock to the last year, then it will
480	take a year to trigger the event (unlike an ev_timer, which would trigger	1109	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
481	roughly 10 seconds later and of course not if you reset your system time	1110	roughly 10 seconds later).
482	again).
483		1111
484	They can also be used to implement vastly more complex timers, such as	1112	They can also be used to implement vastly more complex timers, such as
485	triggering an event on eahc midnight, local time.	1113	triggering an event on each midnight, local time or other, complicated,
		1114	rules.
		1115
		1116	As with timers, the callback is guarenteed to be invoked only when the
		1117	time (C<at>) has been passed, but if multiple periodic timers become ready
		1118	during the same loop iteration then order of execution is undefined.
		1119
		1120	=head3 Watcher-Specific Functions and Data Members
486		1121
487	=over 4	1122	=over 4
488		1123
489	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1124	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
490		1125
491	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1126	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
492		1127
493	Lots of arguments, lets sort it out... There are basically three modes of	1128	Lots of arguments, lets sort it out... There are basically three modes of
494	operation, and we will explain them from simplest to complex:	1129	operation, and we will explain them from simplest to complex:
495		1130
496
497	=over 4	1131	=over 4
498		1132
499	=item * absolute timer (interval = reschedule_cb = 0)	1133	=item * absolute timer (at = time, interval = reschedule_cb = 0)
500		1134
501	In this configuration the watcher triggers an event at the wallclock time	1135	In this configuration the watcher triggers an event at the wallclock time
502	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1136	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
503	that is, if it is to be run at January 1st 2011 then it will run when the	1137	that is, if it is to be run at January 1st 2011 then it will run when the
504	system time reaches or surpasses this time.	1138	system time reaches or surpasses this time.
505		1139
506	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1140	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
507		1141
508	In this mode the watcher will always be scheduled to time out at the next	1142	In this mode the watcher will always be scheduled to time out at the next
509	C<at + N * interval> time (for some integer N) and then repeat, regardless	1143	C<at + N * interval> time (for some integer N, which can also be negative)
510	of any time jumps.	1144	and then repeat, regardless of any time jumps.
511		1145
512	This can be used to create timers that do not drift with respect to system	1146	This can be used to create timers that do not drift with respect to system
513	time:	1147	time:
514		1148
515	ev_periodic_set (&periodic, 0., 3600., 0);	1149	ev_periodic_set (&periodic, 0., 3600., 0);
516		1150
517	This doesn't mean there will always be 3600 seconds in between triggers,	1151	This doesn't mean there will always be 3600 seconds in between triggers,
518	but only that the the callback will be called when the system time shows a	1152	but only that the the callback will be called when the system time shows a
519	full hour (UTC), or more correct, when the system time is evenly divisible	1153	full hour (UTC), or more correctly, when the system time is evenly divisible
520	by 3600.	1154	by 3600.
521		1155
522	Another way to think about it (for the mathematically inclined) is that	1156	Another way to think about it (for the mathematically inclined) is that
523	ev_periodic will try to run the callback in this mode at the next possible	1157	C<ev_periodic> will try to run the callback in this mode at the next possible
524	time where C<time = at (mod interval)>, regardless of any time jumps.	1158	time where C<time = at (mod interval)>, regardless of any time jumps.
525		1159
		1160	For numerical stability it is preferable that the C<at> value is near
		1161	C<ev_now ()> (the current time), but there is no range requirement for
		1162	this value.
		1163
526	=item * manual reschedule mode (reschedule_cb = callback)	1164	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
527		1165
528	In this mode the values for C<interval> and C<at> are both being	1166	In this mode the values for C<interval> and C<at> are both being
529	ignored. Instead, each time the periodic watcher gets scheduled, the	1167	ignored. Instead, each time the periodic watcher gets scheduled, the
530	reschedule callback will be called with the watcher as first, and the	1168	reschedule callback will be called with the watcher as first, and the
531	current time as second argument.	1169	current time as second argument.
532		1170
533	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1171	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
534	periodic watcher, ever, or make any event loop modificstions>. If you need	1172	ever, or make any event loop modifications>. If you need to stop it,
535	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	1173	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1174	starting an C<ev_prepare> watcher, which is legal).
536		1175
537	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1176	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
538	ev_tstamp now)>, e.g.:	1177	ev_tstamp now)>, e.g.:
539		1178
540	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1179	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
541	{	1180	{
542	return now + 60.;	1181	return now + 60.;
…		…
545	It must return the next time to trigger, based on the passed time value	1184	It must return the next time to trigger, based on the passed time value
546	(that is, the lowest time value larger than to the second argument). It	1185	(that is, the lowest time value larger than to the second argument). It
547	will usually be called just before the callback will be triggered, but	1186	will usually be called just before the callback will be triggered, but
548	might be called at other times, too.	1187	might be called at other times, too.
549		1188
		1189	NOTE: I<< This callback must always return a time that is later than the
		1190	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1191
550	This can be used to create very complex timers, such as a timer that	1192	This can be used to create very complex timers, such as a timer that
551	triggers on each midnight, local time. To do this, you would calculate the	1193	triggers on each midnight, local time. To do this, you would calculate the
552	next midnight after C<now> and return the timestamp value for this. How you do this	1194	next midnight after C<now> and return the timestamp value for this. How
553	is, again, up to you (but it is not trivial).	1195	you do this is, again, up to you (but it is not trivial, which is the main
		1196	reason I omitted it as an example).
554		1197
555	=back	1198	=back
556		1199
557	=item ev_periodic_again (loop, ev_periodic *)	1200	=item ev_periodic_again (loop, ev_periodic *)
558		1201
559	Simply stops and restarts the periodic watcher again. This is only useful	1202	Simply stops and restarts the periodic watcher again. This is only useful
560	when you changed some parameters or the reschedule callback would return	1203	when you changed some parameters or the reschedule callback would return
561	a different time than the last time it was called (e.g. in a crond like	1204	a different time than the last time it was called (e.g. in a crond like
562	program when the crontabs have changed).	1205	program when the crontabs have changed).
563		1206
		1207	=item ev_tstamp offset [read-write]
		1208
		1209	When repeating, this contains the offset value, otherwise this is the
		1210	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1211
		1212	Can be modified any time, but changes only take effect when the periodic
		1213	timer fires or C<ev_periodic_again> is being called.
		1214
		1215	=item ev_tstamp interval [read-write]
		1216
		1217	The current interval value. Can be modified any time, but changes only
		1218	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1219	called.
		1220
		1221	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1222
		1223	The current reschedule callback, or C<0>, if this functionality is
		1224	switched off. Can be changed any time, but changes only take effect when
		1225	the periodic timer fires or C<ev_periodic_again> is being called.
		1226
		1227	=item ev_tstamp at [read-only]
		1228
		1229	When active, contains the absolute time that the watcher is supposed to
		1230	trigger next.
		1231
564	=back	1232	=back
565		1233
		1234	Example: Call a callback every hour, or, more precisely, whenever the
		1235	system clock is divisible by 3600. The callback invocation times have
		1236	potentially a lot of jittering, but good long-term stability.
		1237
		1238	static void
		1239	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1240	{
		1241	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1242	}
		1243
		1244	struct ev_periodic hourly_tick;
		1245	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1246	ev_periodic_start (loop, &hourly_tick);
		1247
		1248	Example: The same as above, but use a reschedule callback to do it:
		1249
		1250	#include <math.h>
		1251
		1252	static ev_tstamp
		1253	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1254	{
		1255	return fmod (now, 3600.) + 3600.;
		1256	}
		1257
		1258	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1259
		1260	Example: Call a callback every hour, starting now:
		1261
		1262	struct ev_periodic hourly_tick;
		1263	ev_periodic_init (&hourly_tick, clock_cb,
		1264	fmod (ev_now (loop), 3600.), 3600., 0);
		1265	ev_periodic_start (loop, &hourly_tick);
		1266
		1267
566	=head2 ev_signal - signal me when a signal gets signalled	1268	=head2 C<ev_signal> - signal me when a signal gets signalled!
567		1269
568	Signal watchers will trigger an event when the process receives a specific	1270	Signal watchers will trigger an event when the process receives a specific
569	signal one or more times. Even though signals are very asynchronous, libev	1271	signal one or more times. Even though signals are very asynchronous, libev
570	will try its best to deliver signals synchronously, i.e. as part of the	1272	will try it's best to deliver signals synchronously, i.e. as part of the
571	normal event processing, like any other event.	1273	normal event processing, like any other event.
572		1274
573	You cna configure as many watchers as you like per signal. Only when the	1275	You can configure as many watchers as you like per signal. Only when the
574	first watcher gets started will libev actually register a signal watcher	1276	first watcher gets started will libev actually register a signal watcher
575	with the kernel (thus it coexists with your own signal handlers as long	1277	with the kernel (thus it coexists with your own signal handlers as long
576	as you don't register any with libev). Similarly, when the last signal	1278	as you don't register any with libev). Similarly, when the last signal
577	watcher for a signal is stopped libev will reset the signal handler to	1279	watcher for a signal is stopped libev will reset the signal handler to
578	SIG_DFL (regardless of what it was set to before).	1280	SIG_DFL (regardless of what it was set to before).
579		1281
		1282	=head3 Watcher-Specific Functions and Data Members
		1283
580	=over 4	1284	=over 4
581		1285
582	=item ev_signal_init (ev_signal *, callback, int signum)	1286	=item ev_signal_init (ev_signal *, callback, int signum)
583		1287
584	=item ev_signal_set (ev_signal *, int signum)	1288	=item ev_signal_set (ev_signal *, int signum)
585		1289
586	Configures the watcher to trigger on the given signal number (usually one	1290	Configures the watcher to trigger on the given signal number (usually one
587	of the C<SIGxxx> constants).	1291	of the C<SIGxxx> constants).
588		1292
		1293	=item int signum [read-only]
		1294
		1295	The signal the watcher watches out for.
		1296
589	=back	1297	=back
590		1298
		1299
591	=head2 ev_child - wait for pid status changes	1300	=head2 C<ev_child> - watch out for process status changes
592		1301
593	Child watchers trigger when your process receives a SIGCHLD in response to	1302	Child watchers trigger when your process receives a SIGCHLD in response to
594	some child status changes (most typically when a child of yours dies).	1303	some child status changes (most typically when a child of yours dies).
		1304
		1305	=head3 Watcher-Specific Functions and Data Members
595		1306
596	=over 4	1307	=over 4
597		1308
598	=item ev_child_init (ev_child *, callback, int pid)	1309	=item ev_child_init (ev_child *, callback, int pid)
599		1310
600	=item ev_child_set (ev_child *, int pid)	1311	=item ev_child_set (ev_child *, int pid)
601		1312
602	Configures the watcher to wait for status changes of process C<pid> (or	1313	Configures the watcher to wait for status changes of process C<pid> (or
603	I<any> process if C<pid> is specified as C<0>). The callback can look	1314	I<any> process if C<pid> is specified as C<0>). The callback can look
604	at the C<rstatus> member of the C<ev_child> watcher structure to see	1315	at the C<rstatus> member of the C<ev_child> watcher structure to see
605	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1316	the status word (use the macros from C<sys/wait.h> and see your systems
606	contains the pid of the process causing the status change.	1317	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1318	process causing the status change.
		1319
		1320	=item int pid [read-only]
		1321
		1322	The process id this watcher watches out for, or C<0>, meaning any process id.
		1323
		1324	=item int rpid [read-write]
		1325
		1326	The process id that detected a status change.
		1327
		1328	=item int rstatus [read-write]
		1329
		1330	The process exit/trace status caused by C<rpid> (see your systems
		1331	C<waitpid> and C<sys/wait.h> documentation for details).
607		1332
608	=back	1333	=back
609		1334
		1335	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1336
		1337	static void
		1338	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1339	{
		1340	ev_unloop (loop, EVUNLOOP_ALL);
		1341	}
		1342
		1343	struct ev_signal signal_watcher;
		1344	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1345	ev_signal_start (loop, &sigint_cb);
		1346
		1347
		1348	=head2 C<ev_stat> - did the file attributes just change?
		1349
		1350	This watches a filesystem path for attribute changes. That is, it calls
		1351	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1352	compared to the last time, invoking the callback if it did.
		1353
		1354	The path does not need to exist: changing from "path exists" to "path does
		1355	not exist" is a status change like any other. The condition "path does
		1356	not exist" is signified by the C<st_nlink> field being zero (which is
		1357	otherwise always forced to be at least one) and all the other fields of
		1358	the stat buffer having unspecified contents.
		1359
		1360	The path I<should> be absolute and I<must not> end in a slash. If it is
		1361	relative and your working directory changes, the behaviour is undefined.
		1362
		1363	Since there is no standard to do this, the portable implementation simply
		1364	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1365	can specify a recommended polling interval for this case. If you specify
		1366	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1367	unspecified default> value will be used (which you can expect to be around
		1368	five seconds, although this might change dynamically). Libev will also
		1369	impose a minimum interval which is currently around C<0.1>, but thats
		1370	usually overkill.
		1371
		1372	This watcher type is not meant for massive numbers of stat watchers,
		1373	as even with OS-supported change notifications, this can be
		1374	resource-intensive.
		1375
		1376	At the time of this writing, only the Linux inotify interface is
		1377	implemented (implementing kqueue support is left as an exercise for the
		1378	reader). Inotify will be used to give hints only and should not change the
		1379	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1380	to fall back to regular polling again even with inotify, but changes are
		1381	usually detected immediately, and if the file exists there will be no
		1382	polling.
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
		1385
		1386	=over 4
		1387
		1388	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1389
		1390	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1391
		1392	Configures the watcher to wait for status changes of the given
		1393	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1394	be detected and should normally be specified as C<0> to let libev choose
		1395	a suitable value. The memory pointed to by C<path> must point to the same
		1396	path for as long as the watcher is active.
		1397
		1398	The callback will be receive C<EV_STAT> when a change was detected,
		1399	relative to the attributes at the time the watcher was started (or the
		1400	last change was detected).
		1401
		1402	=item ev_stat_stat (ev_stat *)
		1403
		1404	Updates the stat buffer immediately with new values. If you change the
		1405	watched path in your callback, you could call this fucntion to avoid
		1406	detecting this change (while introducing a race condition). Can also be
		1407	useful simply to find out the new values.
		1408
		1409	=item ev_statdata attr [read-only]
		1410
		1411	The most-recently detected attributes of the file. Although the type is of
		1412	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1413	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1414	was some error while C<stat>ing the file.
		1415
		1416	=item ev_statdata prev [read-only]
		1417
		1418	The previous attributes of the file. The callback gets invoked whenever
		1419	C<prev> != C<attr>.
		1420
		1421	=item ev_tstamp interval [read-only]
		1422
		1423	The specified interval.
		1424
		1425	=item const char *path [read-only]
		1426
		1427	The filesystem path that is being watched.
		1428
		1429	=back
		1430
		1431	Example: Watch C</etc/passwd> for attribute changes.
		1432
		1433	static void
		1434	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1435	{
		1436	/* /etc/passwd changed in some way */
		1437	if (w->attr.st_nlink)
		1438	{
		1439	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1440	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1441	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1442	}
		1443	else
		1444	/* you shalt not abuse printf for puts */
		1445	puts ("wow, /etc/passwd is not there, expect problems. "
		1446	"if this is windows, they already arrived\n");
		1447	}
		1448
		1449	...
		1450	ev_stat passwd;
		1451
		1452	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1453	ev_stat_start (loop, &passwd);
		1454
		1455
610	=head2 ev_idle - when you've got nothing better to do	1456	=head2 C<ev_idle> - when you've got nothing better to do...
611		1457
612	Idle watchers trigger events when there are no other I/O or timer (or	1458	Idle watchers trigger events when no other events of the same or higher
613	periodic) events pending. That is, as long as your process is busy	1459	priority are pending (prepare, check and other idle watchers do not
614	handling sockets or timeouts it will not be called. But when your process	1460	count).
615	is idle all idle watchers are being called again and again - until	1461
		1462	That is, as long as your process is busy handling sockets or timeouts
		1463	(or even signals, imagine) of the same or higher priority it will not be
		1464	triggered. But when your process is idle (or only lower-priority watchers
		1465	are pending), the idle watchers are being called once per event loop
616	stopped, that is, or your process receives more events.	1466	iteration - until stopped, that is, or your process receives more events
		1467	and becomes busy again with higher priority stuff.
617		1468
618	The most noteworthy effect is that as long as any idle watchers are	1469	The most noteworthy effect is that as long as any idle watchers are
619	active, the process will not block when waiting for new events.	1470	active, the process will not block when waiting for new events.
620		1471
621	Apart from keeping your process non-blocking (which is a useful	1472	Apart from keeping your process non-blocking (which is a useful
622	effect on its own sometimes), idle watchers are a good place to do	1473	effect on its own sometimes), idle watchers are a good place to do
623	"pseudo-background processing", or delay processing stuff to after the	1474	"pseudo-background processing", or delay processing stuff to after the
624	event loop has handled all outstanding events.	1475	event loop has handled all outstanding events.
625		1476
		1477	=head3 Watcher-Specific Functions and Data Members
		1478
626	=over 4	1479	=over 4
627		1480
628	=item ev_idle_init (ev_signal *, callback)	1481	=item ev_idle_init (ev_signal *, callback)
629		1482
630	Initialises and configures the idle watcher - it has no parameters of any	1483	Initialises and configures the idle watcher - it has no parameters of any
631	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1484	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
632	believe me.	1485	believe me.
633		1486
634	=back	1487	=back
635		1488
636	=head2 prepare and check - your hooks into the event loop	1489	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1490	callback, free it. Also, use no error checking, as usual.
637		1491
		1492	static void
		1493	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1494	{
		1495	free (w);
		1496	// now do something you wanted to do when the program has
		1497	// no longer asnything immediate to do.
		1498	}
		1499
		1500	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1501	ev_idle_init (idle_watcher, idle_cb);
		1502	ev_idle_start (loop, idle_cb);
		1503
		1504
		1505	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1506
638	Prepare and check watchers usually (but not always) are used in	1507	Prepare and check watchers are usually (but not always) used in tandem:
639	tandom. Prepare watchers get invoked before the process blocks and check	1508	prepare watchers get invoked before the process blocks and check watchers
640	watchers afterwards.	1509	afterwards.
641		1510
		1511	You I<must not> call C<ev_loop> or similar functions that enter
		1512	the current event loop from either C<ev_prepare> or C<ev_check>
		1513	watchers. Other loops than the current one are fine, however. The
		1514	rationale behind this is that you do not need to check for recursion in
		1515	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1516	C<ev_check> so if you have one watcher of each kind they will always be
		1517	called in pairs bracketing the blocking call.
		1518
642	Their main purpose is to integrate other event mechanisms into libev. This	1519	Their main purpose is to integrate other event mechanisms into libev and
643	could be used, for example, to track variable changes, implement your own	1520	their use is somewhat advanced. This could be used, for example, to track
644	watchers, integrate net-snmp or a coroutine library and lots more.	1521	variable changes, implement your own watchers, integrate net-snmp or a
		1522	coroutine library and lots more. They are also occasionally useful if
		1523	you cache some data and want to flush it before blocking (for example,
		1524	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1525	watcher).
645		1526
646	This is done by examining in each prepare call which file descriptors need	1527	This is done by examining in each prepare call which file descriptors need
647	to be watched by the other library, registering ev_io watchers for them	1528	to be watched by the other library, registering C<ev_io> watchers for
648	and starting an ev_timer watcher for any timeouts (many libraries provide	1529	them and starting an C<ev_timer> watcher for any timeouts (many libraries
649	just this functionality). Then, in the check watcher you check for any	1530	provide just this functionality). Then, in the check watcher you check for
650	events that occured (by making your callbacks set soem flags for example)	1531	any events that occured (by checking the pending status of all watchers
651	and call back into the library.	1532	and stopping them) and call back into the library. The I/O and timer
		1533	callbacks will never actually be called (but must be valid nevertheless,
		1534	because you never know, you know?).
652		1535
653	As another example, the perl Coro module uses these hooks to integrate	1536	As another example, the Perl Coro module uses these hooks to integrate
654	coroutines into libev programs, by yielding to other active coroutines	1537	coroutines into libev programs, by yielding to other active coroutines
655	during each prepare and only letting the process block if no coroutines	1538	during each prepare and only letting the process block if no coroutines
656	are ready to run.	1539	are ready to run (it's actually more complicated: it only runs coroutines
		1540	with priority higher than or equal to the event loop and one coroutine
		1541	of lower priority, but only once, using idle watchers to keep the event
		1542	loop from blocking if lower-priority coroutines are active, thus mapping
		1543	low-priority coroutines to idle/background tasks).
		1544
		1545	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1546	priority, to ensure that they are being run before any other watchers
		1547	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1548	too) should not activate ("feed") events into libev. While libev fully
		1549	supports this, they will be called before other C<ev_check> watchers did
		1550	their job. As C<ev_check> watchers are often used to embed other event
		1551	loops those other event loops might be in an unusable state until their
		1552	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1553	others).
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
657		1556
658	=over 4	1557	=over 4
659		1558
660	=item ev_prepare_init (ev_prepare *, callback)	1559	=item ev_prepare_init (ev_prepare *, callback)
661		1560
662	=item ev_check_init (ev_check *, callback)	1561	=item ev_check_init (ev_check *, callback)
663		1562
664	Initialises and configures the prepare or check watcher - they have no	1563	Initialises and configures the prepare or check watcher - they have no
665	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1564	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
666	macros, but using them is utterly, utterly pointless.	1565	macros, but using them is utterly, utterly and completely pointless.
667		1566
668	=back	1567	=back
669		1568
		1569	There are a number of principal ways to embed other event loops or modules
		1570	into libev. Here are some ideas on how to include libadns into libev
		1571	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1572	use for an actually working example. Another Perl module named C<EV::Glib>
		1573	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1574	into the Glib event loop).
		1575
		1576	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1577	and in a check watcher, destroy them and call into libadns. What follows
		1578	is pseudo-code only of course. This requires you to either use a low
		1579	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1580	the callbacks for the IO/timeout watchers might not have been called yet.
		1581
		1582	static ev_io iow [nfd];
		1583	static ev_timer tw;
		1584
		1585	static void
		1586	io_cb (ev_loop *loop, ev_io *w, int revents)
		1587	{
		1588	}
		1589
		1590	// create io watchers for each fd and a timer before blocking
		1591	static void
		1592	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1593	{
		1594	int timeout = 3600000;
		1595	struct pollfd fds [nfd];
		1596	// actual code will need to loop here and realloc etc.
		1597	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1598
		1599	/* the callback is illegal, but won't be called as we stop during check */
		1600	ev_timer_init (&tw, 0, timeout * 1e-3);
		1601	ev_timer_start (loop, &tw);
		1602
		1603	// create one ev_io per pollfd
		1604	for (int i = 0; i < nfd; ++i)
		1605	{
		1606	ev_io_init (iow + i, io_cb, fds [i].fd,
		1607	((fds [i].events & POLLIN ? EV_READ : 0)
		1608	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1609
		1610	fds [i].revents = 0;
		1611	ev_io_start (loop, iow + i);
		1612	}
		1613	}
		1614
		1615	// stop all watchers after blocking
		1616	static void
		1617	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1618	{
		1619	ev_timer_stop (loop, &tw);
		1620
		1621	for (int i = 0; i < nfd; ++i)
		1622	{
		1623	// set the relevant poll flags
		1624	// could also call adns_processreadable etc. here
		1625	struct pollfd *fd = fds + i;
		1626	int revents = ev_clear_pending (iow + i);
		1627	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1628	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1629
		1630	// now stop the watcher
		1631	ev_io_stop (loop, iow + i);
		1632	}
		1633
		1634	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1635	}
		1636
		1637	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1638	in the prepare watcher and would dispose of the check watcher.
		1639
		1640	Method 3: If the module to be embedded supports explicit event
		1641	notification (adns does), you can also make use of the actual watcher
		1642	callbacks, and only destroy/create the watchers in the prepare watcher.
		1643
		1644	static void
		1645	timer_cb (EV_P_ ev_timer *w, int revents)
		1646	{
		1647	adns_state ads = (adns_state)w->data;
		1648	update_now (EV_A);
		1649
		1650	adns_processtimeouts (ads, &tv_now);
		1651	}
		1652
		1653	static void
		1654	io_cb (EV_P_ ev_io *w, int revents)
		1655	{
		1656	adns_state ads = (adns_state)w->data;
		1657	update_now (EV_A);
		1658
		1659	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1660	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1661	}
		1662
		1663	// do not ever call adns_afterpoll
		1664
		1665	Method 4: Do not use a prepare or check watcher because the module you
		1666	want to embed is too inflexible to support it. Instead, youc na override
		1667	their poll function. The drawback with this solution is that the main
		1668	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1669	this.
		1670
		1671	static gint
		1672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1673	{
		1674	int got_events = 0;
		1675
		1676	for (n = 0; n < nfds; ++n)
		1677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1678
		1679	if (timeout >= 0)
		1680	// create/start timer
		1681
		1682	// poll
		1683	ev_loop (EV_A_ 0);
		1684
		1685	// stop timer again
		1686	if (timeout >= 0)
		1687	ev_timer_stop (EV_A_ &to);
		1688
		1689	// stop io watchers again - their callbacks should have set
		1690	for (n = 0; n < nfds; ++n)
		1691	ev_io_stop (EV_A_ iow [n]);
		1692
		1693	return got_events;
		1694	}
		1695
		1696
		1697	=head2 C<ev_embed> - when one backend isn't enough...
		1698
		1699	This is a rather advanced watcher type that lets you embed one event loop
		1700	into another (currently only C<ev_io> events are supported in the embedded
		1701	loop, other types of watchers might be handled in a delayed or incorrect
		1702	fashion and must not be used).
		1703
		1704	There are primarily two reasons you would want that: work around bugs and
		1705	prioritise I/O.
		1706
		1707	As an example for a bug workaround, the kqueue backend might only support
		1708	sockets on some platform, so it is unusable as generic backend, but you
		1709	still want to make use of it because you have many sockets and it scales
		1710	so nicely. In this case, you would create a kqueue-based loop and embed it
		1711	into your default loop (which might use e.g. poll). Overall operation will
		1712	be a bit slower because first libev has to poll and then call kevent, but
		1713	at least you can use both at what they are best.
		1714
		1715	As for prioritising I/O: rarely you have the case where some fds have
		1716	to be watched and handled very quickly (with low latency), and even
		1717	priorities and idle watchers might have too much overhead. In this case
		1718	you would put all the high priority stuff in one loop and all the rest in
		1719	a second one, and embed the second one in the first.
		1720
		1721	As long as the watcher is active, the callback will be invoked every time
		1722	there might be events pending in the embedded loop. The callback must then
		1723	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1724	their callbacks (you could also start an idle watcher to give the embedded
		1725	loop strictly lower priority for example). You can also set the callback
		1726	to C<0>, in which case the embed watcher will automatically execute the
		1727	embedded loop sweep.
		1728
		1729	As long as the watcher is started it will automatically handle events. The
		1730	callback will be invoked whenever some events have been handled. You can
		1731	set the callback to C<0> to avoid having to specify one if you are not
		1732	interested in that.
		1733
		1734	Also, there have not currently been made special provisions for forking:
		1735	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1736	but you will also have to stop and restart any C<ev_embed> watchers
		1737	yourself.
		1738
		1739	Unfortunately, not all backends are embeddable, only the ones returned by
		1740	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1741	portable one.
		1742
		1743	So when you want to use this feature you will always have to be prepared
		1744	that you cannot get an embeddable loop. The recommended way to get around
		1745	this is to have a separate variables for your embeddable loop, try to
		1746	create it, and if that fails, use the normal loop for everything:
		1747
		1748	struct ev_loop *loop_hi = ev_default_init (0);
		1749	struct ev_loop *loop_lo = 0;
		1750	struct ev_embed embed;
		1751
		1752	// see if there is a chance of getting one that works
		1753	// (remember that a flags value of 0 means autodetection)
		1754	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1755	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1756	: 0;
		1757
		1758	// if we got one, then embed it, otherwise default to loop_hi
		1759	if (loop_lo)
		1760	{
		1761	ev_embed_init (&embed, 0, loop_lo);
		1762	ev_embed_start (loop_hi, &embed);
		1763	}
		1764	else
		1765	loop_lo = loop_hi;
		1766
		1767	=head3 Watcher-Specific Functions and Data Members
		1768
		1769	=over 4
		1770
		1771	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1772
		1773	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1774
		1775	Configures the watcher to embed the given loop, which must be
		1776	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1777	invoked automatically, otherwise it is the responsibility of the callback
		1778	to invoke it (it will continue to be called until the sweep has been done,
		1779	if you do not want thta, you need to temporarily stop the embed watcher).
		1780
		1781	=item ev_embed_sweep (loop, ev_embed *)
		1782
		1783	Make a single, non-blocking sweep over the embedded loop. This works
		1784	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1785	apropriate way for embedded loops.
		1786
		1787	=item struct ev_loop *loop [read-only]
		1788
		1789	The embedded event loop.
		1790
		1791	=back
		1792
		1793
		1794	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1795
		1796	Fork watchers are called when a C<fork ()> was detected (usually because
		1797	whoever is a good citizen cared to tell libev about it by calling
		1798	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1799	event loop blocks next and before C<ev_check> watchers are being called,
		1800	and only in the child after the fork. If whoever good citizen calling
		1801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1802	handlers will be invoked, too, of course.
		1803
		1804	=head3 Watcher-Specific Functions and Data Members
		1805
		1806	=over 4
		1807
		1808	=item ev_fork_init (ev_signal *, callback)
		1809
		1810	Initialises and configures the fork watcher - it has no parameters of any
		1811	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1812	believe me.
		1813
		1814	=back
		1815
		1816
670	=head1 OTHER FUNCTIONS	1817	=head1 OTHER FUNCTIONS
671		1818
672	There are some other fucntions of possible interest. Described. Here. Now.	1819	There are some other functions of possible interest. Described. Here. Now.
673		1820
674	=over 4	1821	=over 4
675		1822
676	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1823	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
677		1824
678	This function combines a simple timer and an I/O watcher, calls your	1825	This function combines a simple timer and an I/O watcher, calls your
679	callback on whichever event happens first and automatically stop both	1826	callback on whichever event happens first and automatically stop both
680	watchers. This is useful if you want to wait for a single event on an fd	1827	watchers. This is useful if you want to wait for a single event on an fd
681	or timeout without havign to allocate/configure/start/stop/free one or	1828	or timeout without having to allocate/configure/start/stop/free one or
682	more watchers yourself.	1829	more watchers yourself.
683		1830
684	If C<fd> is less than 0, then no I/O watcher will be started and events is	1831	If C<fd> is less than 0, then no I/O watcher will be started and events
685	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1832	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
686	will be craeted and started.	1833	C<events> set will be craeted and started.
687		1834
688	If C<timeout> is less than 0, then no timeout watcher will be	1835	If C<timeout> is less than 0, then no timeout watcher will be
689	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1836	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
690	= 0) will be started.	1837	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1838	dubious value.
691		1839
692	The callback has the type C<void (*cb)(int revents, void *arg)> and	1840	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
693	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1841	passed an C<revents> set like normal event callbacks (a combination of
694	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1842	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1843	value passed to C<ev_once>:
695		1844
696	static void stdin_ready (int revents, void *arg)	1845	static void stdin_ready (int revents, void *arg)
697	{	1846	{
698	if (revents & EV_TIMEOUT)	1847	if (revents & EV_TIMEOUT)
699	/* doh, nothing entered */	1848	/* doh, nothing entered */;
700	else if (revents & EV_READ)	1849	else if (revents & EV_READ)
701	/* stdin might have data for us, joy! */	1850	/* stdin might have data for us, joy! */;
702	}	1851	}
703		1852
704	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1853	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
705		1854
706	=item ev_feed_event (loop, watcher, int events)	1855	=item ev_feed_event (ev_loop *, watcher *, int revents)
707		1856
708	Feeds the given event set into the event loop, as if the specified event	1857	Feeds the given event set into the event loop, as if the specified event
709	has happened for the specified watcher (which must be a pointer to an	1858	had happened for the specified watcher (which must be a pointer to an
710	initialised but not necessarily active event watcher).	1859	initialised but not necessarily started event watcher).
711		1860
712	=item ev_feed_fd_event (loop, int fd, int revents)	1861	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
713		1862
714	Feed an event on the given fd, as if a file descriptor backend detected it.	1863	Feed an event on the given fd, as if a file descriptor backend detected
		1864	the given events it.
715		1865
716	=item ev_feed_signal_event (loop, int signum)	1866	=item ev_feed_signal_event (ev_loop *loop, int signum)
717		1867
718	Feed an event as if the given signal occured (loop must be the default loop!).	1868	Feed an event as if the given signal occured (C<loop> must be the default
		1869	loop!).
719		1870
720	=back	1871	=back
721		1872
		1873
		1874	=head1 LIBEVENT EMULATION
		1875
		1876	Libev offers a compatibility emulation layer for libevent. It cannot
		1877	emulate the internals of libevent, so here are some usage hints:
		1878
		1879	=over 4
		1880
		1881	=item * Use it by including <event.h>, as usual.
		1882
		1883	=item * The following members are fully supported: ev_base, ev_callback,
		1884	ev_arg, ev_fd, ev_res, ev_events.
		1885
		1886	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1887	maintained by libev, it does not work exactly the same way as in libevent (consider
		1888	it a private API).
		1889
		1890	=item * Priorities are not currently supported. Initialising priorities
		1891	will fail and all watchers will have the same priority, even though there
		1892	is an ev_pri field.
		1893
		1894	=item * Other members are not supported.
		1895
		1896	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1897	to use the libev header file and library.
		1898
		1899	=back
		1900
		1901	=head1 C++ SUPPORT
		1902
		1903	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1904	you to use some convinience methods to start/stop watchers and also change
		1905	the callback model to a model using method callbacks on objects.
		1906
		1907	To use it,
		1908
		1909	#include <ev++.h>
		1910
		1911	This automatically includes F<ev.h> and puts all of its definitions (many
		1912	of them macros) into the global namespace. All C++ specific things are
		1913	put into the C<ev> namespace. It should support all the same embedding
		1914	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1915
		1916	Care has been taken to keep the overhead low. The only data member the C++
		1917	classes add (compared to plain C-style watchers) is the event loop pointer
		1918	that the watcher is associated with (or no additional members at all if
		1919	you disable C<EV_MULTIPLICITY> when embedding libev).
		1920
		1921	Currently, functions, and static and non-static member functions can be
		1922	used as callbacks. Other types should be easy to add as long as they only
		1923	need one additional pointer for context. If you need support for other
		1924	types of functors please contact the author (preferably after implementing
		1925	it).
		1926
		1927	Here is a list of things available in the C<ev> namespace:
		1928
		1929	=over 4
		1930
		1931	=item C<ev::READ>, C<ev::WRITE> etc.
		1932
		1933	These are just enum values with the same values as the C<EV_READ> etc.
		1934	macros from F<ev.h>.
		1935
		1936	=item C<ev::tstamp>, C<ev::now>
		1937
		1938	Aliases to the same types/functions as with the C<ev_> prefix.
		1939
		1940	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1941
		1942	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1943	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1944	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1945	defines by many implementations.
		1946
		1947	All of those classes have these methods:
		1948
		1949	=over 4
		1950
		1951	=item ev::TYPE::TYPE ()
		1952
		1953	=item ev::TYPE::TYPE (struct ev_loop *)
		1954
		1955	=item ev::TYPE::~TYPE
		1956
		1957	The constructor (optionally) takes an event loop to associate the watcher
		1958	with. If it is omitted, it will use C<EV_DEFAULT>.
		1959
		1960	The constructor calls C<ev_init> for you, which means you have to call the
		1961	C<set> method before starting it.
		1962
		1963	It will not set a callback, however: You have to call the templated C<set>
		1964	method to set a callback before you can start the watcher.
		1965
		1966	(The reason why you have to use a method is a limitation in C++ which does
		1967	not allow explicit template arguments for constructors).
		1968
		1969	The destructor automatically stops the watcher if it is active.
		1970
		1971	=item w->set<class, &class::method> (object *)
		1972
		1973	This method sets the callback method to call. The method has to have a
		1974	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1975	first argument and the C<revents> as second. The object must be given as
		1976	parameter and is stored in the C<data> member of the watcher.
		1977
		1978	This method synthesizes efficient thunking code to call your method from
		1979	the C callback that libev requires. If your compiler can inline your
		1980	callback (i.e. it is visible to it at the place of the C<set> call and
		1981	your compiler is good :), then the method will be fully inlined into the
		1982	thunking function, making it as fast as a direct C callback.
		1983
		1984	Example: simple class declaration and watcher initialisation
		1985
		1986	struct myclass
		1987	{
		1988	void io_cb (ev::io &w, int revents) { }
		1989	}
		1990
		1991	myclass obj;
		1992	ev::io iow;
		1993	iow.set <myclass, &myclass::io_cb> (&obj);
		1994
		1995	=item w->set<function> (void *data = 0)
		1996
		1997	Also sets a callback, but uses a static method or plain function as
		1998	callback. The optional C<data> argument will be stored in the watcher's
		1999	C<data> member and is free for you to use.
		2000
		2001	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2002
		2003	See the method-C<set> above for more details.
		2004
		2005	Example:
		2006
		2007	static void io_cb (ev::io &w, int revents) { }
		2008	iow.set <io_cb> ();
		2009
		2010	=item w->set (struct ev_loop *)
		2011
		2012	Associates a different C<struct ev_loop> with this watcher. You can only
		2013	do this when the watcher is inactive (and not pending either).
		2014
		2015	=item w->set ([args])
		2016
		2017	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2018	called at least once. Unlike the C counterpart, an active watcher gets
		2019	automatically stopped and restarted when reconfiguring it with this
		2020	method.
		2021
		2022	=item w->start ()
		2023
		2024	Starts the watcher. Note that there is no C<loop> argument, as the
		2025	constructor already stores the event loop.
		2026
		2027	=item w->stop ()
		2028
		2029	Stops the watcher if it is active. Again, no C<loop> argument.
		2030
		2031	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2032
		2033	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2034	C<ev_TYPE_again> function.
		2035
		2036	=item w->sweep () (C<ev::embed> only)
		2037
		2038	Invokes C<ev_embed_sweep>.
		2039
		2040	=item w->update () (C<ev::stat> only)
		2041
		2042	Invokes C<ev_stat_stat>.
		2043
		2044	=back
		2045
		2046	=back
		2047
		2048	Example: Define a class with an IO and idle watcher, start one of them in
		2049	the constructor.
		2050
		2051	class myclass
		2052	{
		2053	ev_io io; void io_cb (ev::io &w, int revents);
		2054	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2055
		2056	myclass ();
		2057	}
		2058
		2059	myclass::myclass (int fd)
		2060	{
		2061	io .set <myclass, &myclass::io_cb > (this);
		2062	idle.set <myclass, &myclass::idle_cb> (this);
		2063
		2064	io.start (fd, ev::READ);
		2065	}
		2066
		2067
		2068	=head1 MACRO MAGIC
		2069
		2070	Libev can be compiled with a variety of options, the most fundamantal
		2071	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2072	functions and callbacks have an initial C<struct ev_loop *> argument.
		2073
		2074	To make it easier to write programs that cope with either variant, the
		2075	following macros are defined:
		2076
		2077	=over 4
		2078
		2079	=item C<EV_A>, C<EV_A_>
		2080
		2081	This provides the loop I<argument> for functions, if one is required ("ev
		2082	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2083	C<EV_A_> is used when other arguments are following. Example:
		2084
		2085	ev_unref (EV_A);
		2086	ev_timer_add (EV_A_ watcher);
		2087	ev_loop (EV_A_ 0);
		2088
		2089	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2090	which is often provided by the following macro.
		2091
		2092	=item C<EV_P>, C<EV_P_>
		2093
		2094	This provides the loop I<parameter> for functions, if one is required ("ev
		2095	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2096	C<EV_P_> is used when other parameters are following. Example:
		2097
		2098	// this is how ev_unref is being declared
		2099	static void ev_unref (EV_P);
		2100
		2101	// this is how you can declare your typical callback
		2102	static void cb (EV_P_ ev_timer *w, int revents)
		2103
		2104	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2105	suitable for use with C<EV_A>.
		2106
		2107	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2108
		2109	Similar to the other two macros, this gives you the value of the default
		2110	loop, if multiple loops are supported ("ev loop default").
		2111
		2112	=back
		2113
		2114	Example: Declare and initialise a check watcher, utilising the above
		2115	macros so it will work regardless of whether multiple loops are supported
		2116	or not.
		2117
		2118	static void
		2119	check_cb (EV_P_ ev_timer *w, int revents)
		2120	{
		2121	ev_check_stop (EV_A_ w);
		2122	}
		2123
		2124	ev_check check;
		2125	ev_check_init (&check, check_cb);
		2126	ev_check_start (EV_DEFAULT_ &check);
		2127	ev_loop (EV_DEFAULT_ 0);
		2128
		2129	=head1 EMBEDDING
		2130
		2131	Libev can (and often is) directly embedded into host
		2132	applications. Examples of applications that embed it include the Deliantra
		2133	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2134	and rxvt-unicode.
		2135
		2136	The goal is to enable you to just copy the neecssary files into your
		2137	source directory without having to change even a single line in them, so
		2138	you can easily upgrade by simply copying (or having a checked-out copy of
		2139	libev somewhere in your source tree).
		2140
		2141	=head2 FILESETS
		2142
		2143	Depending on what features you need you need to include one or more sets of files
		2144	in your app.
		2145
		2146	=head3 CORE EVENT LOOP
		2147
		2148	To include only the libev core (all the C<ev_*> functions), with manual
		2149	configuration (no autoconf):
		2150
		2151	#define EV_STANDALONE 1
		2152	#include "ev.c"
		2153
		2154	This will automatically include F<ev.h>, too, and should be done in a
		2155	single C source file only to provide the function implementations. To use
		2156	it, do the same for F<ev.h> in all files wishing to use this API (best
		2157	done by writing a wrapper around F<ev.h> that you can include instead and
		2158	where you can put other configuration options):
		2159
		2160	#define EV_STANDALONE 1
		2161	#include "ev.h"
		2162
		2163	Both header files and implementation files can be compiled with a C++
		2164	compiler (at least, thats a stated goal, and breakage will be treated
		2165	as a bug).
		2166
		2167	You need the following files in your source tree, or in a directory
		2168	in your include path (e.g. in libev/ when using -Ilibev):
		2169
		2170	ev.h
		2171	ev.c
		2172	ev_vars.h
		2173	ev_wrap.h
		2174
		2175	ev_win32.c required on win32 platforms only
		2176
		2177	ev_select.c only when select backend is enabled (which is enabled by default)
		2178	ev_poll.c only when poll backend is enabled (disabled by default)
		2179	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2180	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2181	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2182
		2183	F<ev.c> includes the backend files directly when enabled, so you only need
		2184	to compile this single file.
		2185
		2186	=head3 LIBEVENT COMPATIBILITY API
		2187
		2188	To include the libevent compatibility API, also include:
		2189
		2190	#include "event.c"
		2191
		2192	in the file including F<ev.c>, and:
		2193
		2194	#include "event.h"
		2195
		2196	in the files that want to use the libevent API. This also includes F<ev.h>.
		2197
		2198	You need the following additional files for this:
		2199
		2200	event.h
		2201	event.c
		2202
		2203	=head3 AUTOCONF SUPPORT
		2204
		2205	Instead of using C<EV_STANDALONE=1> and providing your config in
		2206	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2207	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2208	include F<config.h> and configure itself accordingly.
		2209
		2210	For this of course you need the m4 file:
		2211
		2212	libev.m4
		2213
		2214	=head2 PREPROCESSOR SYMBOLS/MACROS
		2215
		2216	Libev can be configured via a variety of preprocessor symbols you have to define
		2217	before including any of its files. The default is not to build for multiplicity
		2218	and only include the select backend.
		2219
		2220	=over 4
		2221
		2222	=item EV_STANDALONE
		2223
		2224	Must always be C<1> if you do not use autoconf configuration, which
		2225	keeps libev from including F<config.h>, and it also defines dummy
		2226	implementations for some libevent functions (such as logging, which is not
		2227	supported). It will also not define any of the structs usually found in
		2228	F<event.h> that are not directly supported by the libev core alone.
		2229
		2230	=item EV_USE_MONOTONIC
		2231
		2232	If defined to be C<1>, libev will try to detect the availability of the
		2233	monotonic clock option at both compiletime and runtime. Otherwise no use
		2234	of the monotonic clock option will be attempted. If you enable this, you
		2235	usually have to link against librt or something similar. Enabling it when
		2236	the functionality isn't available is safe, though, althoguh you have
		2237	to make sure you link against any libraries where the C<clock_gettime>
		2238	function is hiding in (often F<-lrt>).
		2239
		2240	=item EV_USE_REALTIME
		2241
		2242	If defined to be C<1>, libev will try to detect the availability of the
		2243	realtime clock option at compiletime (and assume its availability at
		2244	runtime if successful). Otherwise no use of the realtime clock option will
		2245	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2246	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2247	in the description of C<EV_USE_MONOTONIC>, though.
		2248
		2249	=item EV_USE_SELECT
		2250
		2251	If undefined or defined to be C<1>, libev will compile in support for the
		2252	C<select>(2) backend. No attempt at autodetection will be done: if no
		2253	other method takes over, select will be it. Otherwise the select backend
		2254	will not be compiled in.
		2255
		2256	=item EV_SELECT_USE_FD_SET
		2257
		2258	If defined to C<1>, then the select backend will use the system C<fd_set>
		2259	structure. This is useful if libev doesn't compile due to a missing
		2260	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2261	exotic systems. This usually limits the range of file descriptors to some
		2262	low limit such as 1024 or might have other limitations (winsocket only
		2263	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2264	influence the size of the C<fd_set> used.
		2265
		2266	=item EV_SELECT_IS_WINSOCKET
		2267
		2268	When defined to C<1>, the select backend will assume that
		2269	select/socket/connect etc. don't understand file descriptors but
		2270	wants osf handles on win32 (this is the case when the select to
		2271	be used is the winsock select). This means that it will call
		2272	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2273	it is assumed that all these functions actually work on fds, even
		2274	on win32. Should not be defined on non-win32 platforms.
		2275
		2276	=item EV_USE_POLL
		2277
		2278	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2279	backend. Otherwise it will be enabled on non-win32 platforms. It
		2280	takes precedence over select.
		2281
		2282	=item EV_USE_EPOLL
		2283
		2284	If defined to be C<1>, libev will compile in support for the Linux
		2285	C<epoll>(7) backend. Its availability will be detected at runtime,
		2286	otherwise another method will be used as fallback. This is the
		2287	preferred backend for GNU/Linux systems.
		2288
		2289	=item EV_USE_KQUEUE
		2290
		2291	If defined to be C<1>, libev will compile in support for the BSD style
		2292	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2293	otherwise another method will be used as fallback. This is the preferred
		2294	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2295	supports some types of fds correctly (the only platform we found that
		2296	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2297	not be used unless explicitly requested. The best way to use it is to find
		2298	out whether kqueue supports your type of fd properly and use an embedded
		2299	kqueue loop.
		2300
		2301	=item EV_USE_PORT
		2302
		2303	If defined to be C<1>, libev will compile in support for the Solaris
		2304	10 port style backend. Its availability will be detected at runtime,
		2305	otherwise another method will be used as fallback. This is the preferred
		2306	backend for Solaris 10 systems.
		2307
		2308	=item EV_USE_DEVPOLL
		2309
		2310	reserved for future expansion, works like the USE symbols above.
		2311
		2312	=item EV_USE_INOTIFY
		2313
		2314	If defined to be C<1>, libev will compile in support for the Linux inotify
		2315	interface to speed up C<ev_stat> watchers. Its actual availability will
		2316	be detected at runtime.
		2317
		2318	=item EV_H
		2319
		2320	The name of the F<ev.h> header file used to include it. The default if
		2321	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2322	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2323
		2324	=item EV_CONFIG_H
		2325
		2326	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2327	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2328	C<EV_H>, above.
		2329
		2330	=item EV_EVENT_H
		2331
		2332	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2333	of how the F<event.h> header can be found.
		2334
		2335	=item EV_PROTOTYPES
		2336
		2337	If defined to be C<0>, then F<ev.h> will not define any function
		2338	prototypes, but still define all the structs and other symbols. This is
		2339	occasionally useful if you want to provide your own wrapper functions
		2340	around libev functions.
		2341
		2342	=item EV_MULTIPLICITY
		2343
		2344	If undefined or defined to C<1>, then all event-loop-specific functions
		2345	will have the C<struct ev_loop *> as first argument, and you can create
		2346	additional independent event loops. Otherwise there will be no support
		2347	for multiple event loops and there is no first event loop pointer
		2348	argument. Instead, all functions act on the single default loop.
		2349
		2350	=item EV_MINPRI
		2351
		2352	=item EV_MAXPRI
		2353
		2354	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2355	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2356	provide for more priorities by overriding those symbols (usually defined
		2357	to be C<-2> and C<2>, respectively).
		2358
		2359	When doing priority-based operations, libev usually has to linearly search
		2360	all the priorities, so having many of them (hundreds) uses a lot of space
		2361	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2362	fine.
		2363
		2364	If your embedding app does not need any priorities, defining these both to
		2365	C<0> will save some memory and cpu.
		2366
		2367	=item EV_PERIODIC_ENABLE
		2368
		2369	If undefined or defined to be C<1>, then periodic timers are supported. If
		2370	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2371	code.
		2372
		2373	=item EV_IDLE_ENABLE
		2374
		2375	If undefined or defined to be C<1>, then idle watchers are supported. If
		2376	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2377	code.
		2378
		2379	=item EV_EMBED_ENABLE
		2380
		2381	If undefined or defined to be C<1>, then embed watchers are supported. If
		2382	defined to be C<0>, then they are not.
		2383
		2384	=item EV_STAT_ENABLE
		2385
		2386	If undefined or defined to be C<1>, then stat watchers are supported. If
		2387	defined to be C<0>, then they are not.
		2388
		2389	=item EV_FORK_ENABLE
		2390
		2391	If undefined or defined to be C<1>, then fork watchers are supported. If
		2392	defined to be C<0>, then they are not.
		2393
		2394	=item EV_MINIMAL
		2395
		2396	If you need to shave off some kilobytes of code at the expense of some
		2397	speed, define this symbol to C<1>. Currently only used for gcc to override
		2398	some inlining decisions, saves roughly 30% codesize of amd64.
		2399
		2400	=item EV_PID_HASHSIZE
		2401
		2402	C<ev_child> watchers use a small hash table to distribute workload by
		2403	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2404	than enough. If you need to manage thousands of children you might want to
		2405	increase this value (I<must> be a power of two).
		2406
		2407	=item EV_INOTIFY_HASHSIZE
		2408
		2409	C<ev_staz> watchers use a small hash table to distribute workload by
		2410	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2411	usually more than enough. If you need to manage thousands of C<ev_stat>
		2412	watchers you might want to increase this value (I<must> be a power of
		2413	two).
		2414
		2415	=item EV_COMMON
		2416
		2417	By default, all watchers have a C<void *data> member. By redefining
		2418	this macro to a something else you can include more and other types of
		2419	members. You have to define it each time you include one of the files,
		2420	though, and it must be identical each time.
		2421
		2422	For example, the perl EV module uses something like this:
		2423
		2424	#define EV_COMMON \
		2425	SV *self; /* contains this struct */ \
		2426	SV *cb_sv, *fh /* note no trailing ";" */
		2427
		2428	=item EV_CB_DECLARE (type)
		2429
		2430	=item EV_CB_INVOKE (watcher, revents)
		2431
		2432	=item ev_set_cb (ev, cb)
		2433
		2434	Can be used to change the callback member declaration in each watcher,
		2435	and the way callbacks are invoked and set. Must expand to a struct member
		2436	definition and a statement, respectively. See the F<ev.v> header file for
		2437	their default definitions. One possible use for overriding these is to
		2438	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2439	method calls instead of plain function calls in C++.
		2440
		2441	=head2 EXAMPLES
		2442
		2443	For a real-world example of a program the includes libev
		2444	verbatim, you can have a look at the EV perl module
		2445	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2446	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2447	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2448	will be compiled. It is pretty complex because it provides its own header
		2449	file.
		2450
		2451	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2452	that everybody includes and which overrides some configure choices:
		2453
		2454	#define EV_MINIMAL 1
		2455	#define EV_USE_POLL 0
		2456	#define EV_MULTIPLICITY 0
		2457	#define EV_PERIODIC_ENABLE 0
		2458	#define EV_STAT_ENABLE 0
		2459	#define EV_FORK_ENABLE 0
		2460	#define EV_CONFIG_H <config.h>
		2461	#define EV_MINPRI 0
		2462	#define EV_MAXPRI 0
		2463
		2464	#include "ev++.h"
		2465
		2466	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2467
		2468	#include "ev_cpp.h"
		2469	#include "ev.c"
		2470
		2471
		2472	=head1 COMPLEXITIES
		2473
		2474	In this section the complexities of (many of) the algorithms used inside
		2475	libev will be explained. For complexity discussions about backends see the
		2476	documentation for C<ev_default_init>.
		2477
		2478	All of the following are about amortised time: If an array needs to be
		2479	extended, libev needs to realloc and move the whole array, but this
		2480	happens asymptotically never with higher number of elements, so O(1) might
		2481	mean it might do a lengthy realloc operation in rare cases, but on average
		2482	it is much faster and asymptotically approaches constant time.
		2483
		2484	=over 4
		2485
		2486	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2487
		2488	This means that, when you have a watcher that triggers in one hour and
		2489	there are 100 watchers that would trigger before that then inserting will
		2490	have to skip those 100 watchers.
		2491
		2492	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2493
		2494	That means that for changing a timer costs less than removing/adding them
		2495	as only the relative motion in the event queue has to be paid for.
		2496
		2497	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2498
		2499	These just add the watcher into an array or at the head of a list.
		2500	=item Stopping check/prepare/idle watchers: O(1)
		2501
		2502	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2503
		2504	These watchers are stored in lists then need to be walked to find the
		2505	correct watcher to remove. The lists are usually short (you don't usually
		2506	have many watchers waiting for the same fd or signal).
		2507
		2508	=item Finding the next timer per loop iteration: O(1)
		2509
		2510	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2511
		2512	A change means an I/O watcher gets started or stopped, which requires
		2513	libev to recalculate its status (and possibly tell the kernel).
		2514
		2515	=item Activating one watcher: O(1)
		2516
		2517	=item Priority handling: O(number_of_priorities)
		2518
		2519	Priorities are implemented by allocating some space for each
		2520	priority. When doing priority-based operations, libev usually has to
		2521	linearly search all the priorities.
		2522
		2523	=back
		2524
		2525
722	=head1 AUTHOR	2526	=head1 AUTHOR
723		2527
724	Marc Lehmann <libev@schmorp.de>.	2528	Marc Lehmann <libev@schmorp.de>.
725		2529

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