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Revision 1.1 by root, Mon Nov 12 07:58:13 2007 UTC vs.
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		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	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	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	54	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program events.	55	these event sources and provide your program with events.
14		56
15	To do this, it must take more or less complete control over your process	57	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	58	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	59	communicate events via a callback mechanism.
18		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	bsd-specific C<kqueue> and the solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),
29	events (related to SIGCHLD), and event watchers dealing with the event	71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous
30	loop mechanism itself (idle, prepare and check watchers).	72	signals (C<ev_signal>), process status change events (C<ev_child>), and
		73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,
		74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		75	file watchers (C<ev_stat>) and even limited support for fork events
		76	(C<ev_fork>).
		77
		78	It also is quite fast (see this
		79	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
		80	for example).
31		81
32	=head1 CONVENTIONS	82	=head1 CONVENTIONS
33		83
34	Libev is very configurable. In this manual the default configuration	84	Libev is very configurable. In this manual the default configuration will
35	will be described, which supports multiple event loops. For more info	85	be described, which supports multiple event loops. For more info about
36	about various configuraiton options please have a look at the file	86	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	87	this manual. If libev was configured without support for multiple event
38	support for multiple event loops, then all functions taking an initial	88	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 *>)	89	(which is always of type C<struct ev_loop *>) will not have this argument.
40	will not have this argument.
41		90
42	=head1 TIME AND OTHER GLOBAL FUNCTIONS	91	=head1 TIME REPRESENTATION
43		92
44	Libev represents time as a single floating point number. This type is	93	Libev represents time as a single floating point number, representing the
		94	(fractional) number of seconds since the (POSIX) epoch (somewhere near
		95	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	96	called C<ev_tstamp>, which is what you should use too. It usually aliases
46	to the double type in C.	97	to the C<double> type in C, and when you need to do any calculations on
		98	it, you should treat it as such.
		99
		100	=head1 GLOBAL FUNCTIONS
		101
		102	These functions can be called anytime, even before initialising the
		103	library in any way.
47		104
48	=over 4	105	=over 4
49		106
50	=item ev_tstamp ev_time ()	107	=item ev_tstamp ev_time ()
51		108
52	Returns the current time as libev would use it.	109	Returns the current time as libev would use it. Please note that the
		110	C<ev_now> function is usually faster and also often returns the timestamp
		111	you actually want to know.
53		112
54	=item int ev_version_major ()	113	=item int ev_version_major ()
55		114
56	=item int ev_version_minor ()	115	=item int ev_version_minor ()
57		116
…		…
59	you linked against by calling the functions C<ev_version_major> and	118	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	119	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	120	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
62	version of the library your program was compiled against.	121	version of the library your program was compiled against.
63		122
64	Usually, its a good idea to terminate if the major versions mismatch,	123	Usually, it's a good idea to terminate if the major versions mismatch,
65	as this indicates an incompatible change. Minor versions are usually	124	as this indicates an incompatible change. Minor versions are usually
66	compatible to older versions, so a larger minor version alone is usually	125	compatible to older versions, so a larger minor version alone is usually
67	not a problem.	126	not a problem.
68		127
		128	Example: Make sure we haven't accidentally been linked against the wrong
		129	version.
		130
		131	assert (("libev version mismatch",
		132	ev_version_major () == EV_VERSION_MAJOR
		133	&& ev_version_minor () >= EV_VERSION_MINOR));
		134
		135	=item unsigned int ev_supported_backends ()
		136
		137	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		138	value) compiled into this binary of libev (independent of their
		139	availability on the system you are running on). See C<ev_default_loop> for
		140	a description of the set values.
		141
		142	Example: make sure we have the epoll method, because yeah this is cool and
		143	a must have and can we have a torrent of it please!!!11
		144
		145	assert (("sorry, no epoll, no sex",
		146	ev_supported_backends () & EVBACKEND_EPOLL));
		147
		148	=item unsigned int ev_recommended_backends ()
		149
		150	Return the set of all backends compiled into this binary of libev and also
		151	recommended for this platform. This set is often smaller than the one
		152	returned by C<ev_supported_backends>, as for example kqueue is broken on
		153	most BSDs and will not be autodetected unless you explicitly request it
		154	(assuming you know what you are doing). This is the set of backends that
		155	libev will probe for if you specify no backends explicitly.
		156
		157	=item unsigned int ev_embeddable_backends ()
		158
		159	Returns the set of backends that are embeddable in other event loops. This
		160	is the theoretical, all-platform, value. To find which backends
		161	might be supported on the current system, you would need to look at
		162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		163	recommended ones.
		164
		165	See the description of C<ev_embed> watchers for more info.
		166
69	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	167	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))
70		168
71	Sets the allocation function to use (the prototype is similar to the	169	Sets the allocation function to use (the prototype and semantics are
72	realloc function). It is used to allocate and free memory (no surprises	170	identical to the realloc C function). It is used to allocate and free
73	here). If it returns zero when memory needs to be allocated, the library	171	memory (no surprises here). If it returns zero when memory needs to be
74	might abort or take some potentially destructive action. The default is	172	allocated, the library might abort or take some potentially destructive
75	your system realloc function.	173	action. The default is your system realloc function.
76		174
77	You could override this function in high-availability programs to, say,	175	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,	176	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.	177	or even to sleep a while and retry until some memory is available.
		178
		179	Example: Replace the libev allocator with one that waits a bit and then
		180	retries).
		181
		182	static void *
		183	persistent_realloc (void *ptr, size_t size)
		184	{
		185	for (;;)
		186	{
		187	void *newptr = realloc (ptr, size);
		188
		189	if (newptr)
		190	return newptr;
		191
		192	sleep (60);
		193	}
		194	}
		195
		196	...
		197	ev_set_allocator (persistent_realloc);
80		198
81	=item ev_set_syserr_cb (void (*cb)(const char *msg));	199	=item ev_set_syserr_cb (void (*cb)(const char *msg));
82		200
83	Set the callback function to call on a retryable syscall error (such	201	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	202	as failed select, poll, epoll_wait). The message is a printable string
85	indicating the system call or subsystem causing the problem. If this	203	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	204	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	205	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	206	requested operation, or, if the condition doesn't go away, do bad stuff
89	(such as abort).	207	(such as abort).
		208
		209	Example: This is basically the same thing that libev does internally, too.
		210
		211	static void
		212	fatal_error (const char *msg)
		213	{
		214	perror (msg);
		215	abort ();
		216	}
		217
		218	...
		219	ev_set_syserr_cb (fatal_error);
90		220
91	=back	221	=back
92		222
93	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	223	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
94		224
95	An event loop is described by a C<struct ev_loop *>. The library knows two	225	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	226	types of such loops, the I<default> loop, which supports signals and child
97	events, and dynamically created loops which do not.	227	events, and dynamically created loops which do not.
98		228
99	If you use threads, a common model is to run the default event loop	229	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	230	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	231	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	232	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).	233	threads, make sure you lock (this is usually a bad idea, though, even if
		234	done correctly, because it's hideous and inefficient).
104		235
105	=over 4	236	=over 4
106		237
107	=item struct ev_loop *ev_default_loop (unsigned int flags)	238	=item struct ev_loop *ev_default_loop (unsigned int flags)
108		239
109	This will initialise the default event loop if it hasn't been initialised	240	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	241	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	242	false. If it already was initialised it simply returns it (and ignores the
112	flags).	243	flags. If that is troubling you, check C<ev_backend ()> afterwards).
113		244
114	If you don't know what event loop to use, use the one returned from this	245	If you don't know what event loop to use, use the one returned from this
115	function.	246	function.
116		247
117	The flags argument can be used to specify special behaviour or specific	248	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)	249	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
119		250
120	It supports the following flags:	251	The following flags are supported:
121		252
122	=over 4	253	=over 4
123		254
124	=item EVFLAG_AUTO	255	=item C<EVFLAG_AUTO>
125		256
126	The default flags value. Use this if you have no clue (its the right	257	The default flags value. Use this if you have no clue (it's the right
127	thing, believe me).	258	thing, believe me).
128		259
129	=item EVFLAG_NOENV	260	=item C<EVFLAG_NOENV>
130		261
131	If this flag bit is ored into the flag value then libev will I<not> look	262	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	263	or setgid) then libev will I<not> look at the environment variable
133	environment variable will override the flags completely. This is useful	264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		265	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	266	useful to try out specific backends to test their performance, or to work
135	bugs.	267	around bugs.
136		268
137	=item EVMETHOD_SELECT portable select backend	269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
138		270
139	=item EVMETHOD_POLL poll backend (everywhere except windows)	271	This is your standard select(2) backend. Not I<completely> standard, as
		272	libev tries to roll its own fd_set with no limits on the number of fds,
		273	but if that fails, expect a fairly low limit on the number of fds when
		274	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		275	the fastest backend for a low number of fds.
140		276
141	=item EVMETHOD_EPOLL linux only	277	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
142		278
143	=item EVMETHOD_KQUEUE some bsds only	279	And this is your standard poll(2) backend. It's more complicated than
		280	select, but handles sparse fds better and has no artificial limit on the
		281	number of fds you can use (except it will slow down considerably with a
		282	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
144		283
145	=item EVMETHOD_DEVPOLL solaris 8 only	284	=item C<EVBACKEND_EPOLL> (value 4, Linux)
146		285
147	=item EVMETHOD_PORT solaris 10 only	286	For few fds, this backend is a bit little slower than poll and select,
		287	but it scales phenomenally better. While poll and select usually scale like
		288	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		289	either O(1) or O(active_fds).
		290
		291	While stopping and starting an I/O watcher in the same iteration will
		292	result in some caching, there is still a syscall per such incident
		293	(because the fd could point to a different file description now), so its
		294	best to avoid that. Also, dup()ed file descriptors might not work very
		295	well if you register events for both fds.
		296
		297	Please note that epoll sometimes generates spurious notifications, so you
		298	need to use non-blocking I/O or other means to avoid blocking when no data
		299	(or space) is available.
		300
		301	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		302
		303	Kqueue deserves special mention, as at the time of this writing, it
		304	was broken on all BSDs except NetBSD (usually it doesn't work with
		305	anything but sockets and pipes, except on Darwin, where of course its
		306	completely useless). For this reason its not being "autodetected"
		307	unless you explicitly specify it explicitly in the flags (i.e. using
		308	C<EVBACKEND_KQUEUE>).
		309
		310	It scales in the same way as the epoll backend, but the interface to the
		311	kernel is more efficient (which says nothing about its actual speed, of
		312	course). While starting and stopping an I/O watcher does not cause an
		313	extra syscall as with epoll, it still adds up to four event changes per
		314	incident, so its best to avoid that.
		315
		316	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		317
		318	This is not implemented yet (and might never be).
		319
		320	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		321
		322	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		323	it's really slow, but it still scales very well (O(active_fds)).
		324
		325	Please note that solaris ports can result in a lot of spurious
		326	notifications, so you need to use non-blocking I/O or other means to avoid
		327	blocking when no data (or space) is available.
		328
		329	=item C<EVBACKEND_ALL>
		330
		331	Try all backends (even potentially broken ones that wouldn't be tried
		332	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		333	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		334
		335	=back
148		336
149	If one or more of these are ored into the flags value, then only these	337	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	338	backends will be tried (in the reverse order as given here). If none are
151	specified, any backend will do.	339	specified, most compiled-in backend will be tried, usually in reverse
		340	order of their flag values :)
152		341
153	=back	342	The most typical usage is like this:
		343
		344	if (!ev_default_loop (0))
		345	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		346
		347	Restrict libev to the select and poll backends, and do not allow
		348	environment settings to be taken into account:
		349
		350	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		351
		352	Use whatever libev has to offer, but make sure that kqueue is used if
		353	available (warning, breaks stuff, best use only with your own private
		354	event loop and only if you know the OS supports your types of fds):
		355
		356	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
154		357
155	=item struct ev_loop *ev_loop_new (unsigned int flags)	358	=item struct ev_loop *ev_loop_new (unsigned int flags)
156		359
157	Similar to C<ev_default_loop>, but always creates a new event loop that is	360	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	361	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	362	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).	363	undefined behaviour (or a failed assertion if assertions are enabled).
161		364
		365	Example: Try to create a event loop that uses epoll and nothing else.
		366
		367	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		368	if (!epoller)
		369	fatal ("no epoll found here, maybe it hides under your chair");
		370
162	=item ev_default_destroy ()	371	=item ev_default_destroy ()
163		372
164	Destroys the default loop again (frees all memory and kernel state	373	Destroys the default loop again (frees all memory and kernel state
165	etc.). This stops all registered event watchers (by not touching them in	374	etc.). None of the active event watchers will be stopped in the normal
166	any way whatsoever, although you cnanot rely on this :).	375	sense, so e.g. C<ev_is_active> might still return true. It is your
		376	responsibility to either stop all watchers cleanly yoursef I<before>
		377	calling this function, or cope with the fact afterwards (which is usually
		378	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		379	for example).
167		380
168	=item ev_loop_destroy (loop)	381	=item ev_loop_destroy (loop)
169		382
170	Like C<ev_default_destroy>, but destroys an event loop created by an	383	Like C<ev_default_destroy>, but destroys an event loop created by an
171	earlier call to C<ev_loop_new>.	384	earlier call to C<ev_loop_new>.
…		…
175	This function reinitialises the kernel state for backends that have	388	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	389	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	390	after forking, in either the parent or child process (or both, but that
178	again makes little sense).	391	again makes little sense).
179		392
180	You I<must> call this function after forking if and only if you want to	393	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	394	only if you want to use the event library in both processes. If you just
182	have to call it.	395	fork+exec, you don't have to call it.
183		396
184	The function itself is quite fast and its usually not a problem to call	397	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	398	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>:	399	quite nicely into a call to C<pthread_atfork>:
187		400
188	pthread_atfork (0, 0, ev_default_fork);	401	pthread_atfork (0, 0, ev_default_fork);
		402
		403	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		404	without calling this function, so if you force one of those backends you
		405	do not need to care.
189		406
190	=item ev_loop_fork (loop)	407	=item ev_loop_fork (loop)
191		408
192	Like C<ev_default_fork>, but acts on an event loop created by	409	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	410	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.	411	after fork, and how you do this is entirely your own problem.
195		412
196	=item unsigned int ev_method (loop)	413	=item unsigned int ev_backend (loop)
197		414
198	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	415	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
199	use.	416	use.
200		417
201	=item ev_tstamp = ev_now (loop)	418	=item ev_tstamp ev_now (loop)
202		419
203	Returns the current "event loop time", which is the time the event loop	420	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	421	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	422	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	423	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).	424	event occuring (or more correctly, libev finding out about it).
208		425
209	=item ev_loop (loop, int flags)	426	=item ev_loop (loop, int flags)
210		427
211	Finally, this is it, the event handler. This function usually is called	428	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	429	after you initialised all your watchers and you want to start handling
213	events.	430	events.
214		431
215	If the flags argument is specified as 0, it will not return until either	432	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.	433	either no event watchers are active anymore or C<ev_unloop> was called.
		434
		435	Please note that an explicit C<ev_unloop> is usually better than
		436	relying on all watchers to be stopped when deciding when a program has
		437	finished (especially in interactive programs), but having a program that
		438	automatically loops as long as it has to and no longer by virtue of
		439	relying on its watchers stopping correctly is a thing of beauty.
217		440
218	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	441	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	442	those events and any outstanding ones, but will not block your process in
220	case there are no events.	443	case there are no events and will return after one iteration of the loop.
221		444
222	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	445	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	446	neccessary) and will handle those and any outstanding ones. It will block
224	your process until at least one new event arrives.	447	your process until at least one new event arrives, and will return after
		448	one iteration of the loop. This is useful if you are waiting for some
		449	external event in conjunction with something not expressible using other
		450	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		451	usually a better approach for this kind of thing.
225		452
226	This flags value could be used to implement alternative looping	453	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	454
228	more generic mechanism.	455	* If there are no active watchers (reference count is zero), return.
		456	- Queue prepare watchers and then call all outstanding watchers.
		457	- If we have been forked, recreate the kernel state.
		458	- Update the kernel state with all outstanding changes.
		459	- Update the "event loop time".
		460	- Calculate for how long to block.
		461	- Block the process, waiting for any events.
		462	- Queue all outstanding I/O (fd) events.
		463	- Update the "event loop time" and do time jump handling.
		464	- Queue all outstanding timers.
		465	- Queue all outstanding periodics.
		466	- If no events are pending now, queue all idle watchers.
		467	- Queue all check watchers.
		468	- Call all queued watchers in reverse order (i.e. check watchers first).
		469	Signals and child watchers are implemented as I/O watchers, and will
		470	be handled here by queueing them when their watcher gets executed.
		471	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		472	were used, return, otherwise continue with step *.
		473
		474	Example: Queue some jobs and then loop until no events are outsanding
		475	anymore.
		476
		477	... queue jobs here, make sure they register event watchers as long
		478	... as they still have work to do (even an idle watcher will do..)
		479	ev_loop (my_loop, 0);
		480	... jobs done. yeah!
229		481
230	=item ev_unloop (loop, how)	482	=item ev_unloop (loop, how)
231		483
232	Can be used to make a call to C<ev_loop> return early. The C<how> argument	484	Can be used to make a call to C<ev_loop> return early (but only after it
		485	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>	486	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>	487	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
235	calls return.
236		488
237	=item ev_ref (loop)	489	=item ev_ref (loop)
238		490
239	=item ev_unref (loop)	491	=item ev_unref (loop)
240		492
241	Ref/unref can be used to add or remove a refcount on the event loop: Every	493	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	494	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	495	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	496	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	497	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	498	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	499	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	500	no event watchers registered by it are active. It is also an excellent
249	before stop.	501	way to do this for generic recurring timers or from within third-party
		502	libraries. Just remember to I<unref after start> and I<ref before stop>.
		503
		504	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		505	running when nothing else is active.
		506
		507	struct ev_signal exitsig;
		508	ev_signal_init (&exitsig, sig_cb, SIGINT);
		509	ev_signal_start (loop, &exitsig);
		510	evf_unref (loop);
		511
		512	Example: For some weird reason, unregister the above signal handler again.
		513
		514	ev_ref (loop);
		515	ev_signal_stop (loop, &exitsig);
250		516
251	=back	517	=back
		518
252		519
253	=head1 ANATOMY OF A WATCHER	520	=head1 ANATOMY OF A WATCHER
254		521
255	A watcher is a structure that you create and register to record your	522	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	523	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:	524	become readable, you would create an C<ev_io> watcher for that:
258		525
259	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	526	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
260	{	527	{
261	ev_io_stop (w);	528	ev_io_stop (w);
262	ev_unloop (loop, EVUNLOOP_ALL);	529	ev_unloop (loop, EVUNLOOP_ALL);
…		…
289	*) >>), and you can stop watching for events at any time by calling the	556	*) >>), and you can stop watching for events at any time by calling the
290	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	557	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
291		558
292	As long as your watcher is active (has been started but not stopped) you	559	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	560	must not touch the values stored in it. Most specifically you must never
294	reinitialise it or call its set method.	561	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		562
301	Each and every callback receives the event loop pointer as first, the	563	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	564	registered watcher structure as second, and a bitset of received events as
303	third argument.	565	third argument.
304		566
305	The rceeived events usually include a single bit per event type received	567	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	568	(you can receive multiple events at the same time). The possible bit masks
307	are:	569	are:
308		570
309	=over 4	571	=over 4
310		572
311	=item EV_READ	573	=item C<EV_READ>
312		574
313	=item EV_WRITE	575	=item C<EV_WRITE>
314		576
315	The file descriptor in the ev_io watcher has become readable and/or	577	The file descriptor in the C<ev_io> watcher has become readable and/or
316	writable.	578	writable.
317		579
318	=item EV_TIMEOUT	580	=item C<EV_TIMEOUT>
319		581
320	The ev_timer watcher has timed out.	582	The C<ev_timer> watcher has timed out.
321		583
322	=item EV_PERIODIC	584	=item C<EV_PERIODIC>
323		585
324	The ev_periodic watcher has timed out.	586	The C<ev_periodic> watcher has timed out.
325		587
326	=item EV_SIGNAL	588	=item C<EV_SIGNAL>
327		589
328	The signal specified in the ev_signal watcher has been received by a thread.	590	The signal specified in the C<ev_signal> watcher has been received by a thread.
329		591
330	=item EV_CHILD	592	=item C<EV_CHILD>
331		593
332	The pid specified in the ev_child watcher has received a status change.	594	The pid specified in the C<ev_child> watcher has received a status change.
333		595
		596	=item C<EV_STAT>
		597
		598	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		599
334	=item EV_IDLE	600	=item C<EV_IDLE>
335		601
336	The ev_idle watcher has determined that you have nothing better to do.	602	The C<ev_idle> watcher has determined that you have nothing better to do.
337		603
338	=item EV_PREPARE	604	=item C<EV_PREPARE>
339		605
340	=item EV_CHECK	606	=item C<EV_CHECK>
341		607
342	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	608	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	609	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	610	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	611	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	612	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	613	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
348	C<ev_loop> from blocking).	614	C<ev_loop> from blocking).
349		615
		616	=item C<EV_EMBED>
		617
		618	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		619
		620	=item C<EV_FORK>
		621
		622	The event loop has been resumed in the child process after fork (see
		623	C<ev_fork>).
		624
350	=item EV_ERROR	625	=item C<EV_ERROR>
351		626
352	An unspecified error has occured, the watcher has been stopped. This might	627	An unspecified error has occured, the watcher has been stopped. This might
353	happen because the watcher could not be properly started because libev	628	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	629	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	630	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	636	with the error from read() or write(). This will not work in multithreaded
362	programs, though, so beware.	637	programs, though, so beware.
363		638
364	=back	639	=back
365		640
		641	=head2 GENERIC WATCHER FUNCTIONS
		642
		643	In the following description, C<TYPE> stands for the watcher type,
		644	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		645
		646	=over 4
		647
		648	=item C<ev_init> (ev_TYPE *watcher, callback)
		649
		650	This macro initialises the generic portion of a watcher. The contents
		651	of the watcher object can be arbitrary (so C<malloc> will do). Only
		652	the generic parts of the watcher are initialised, you I<need> to call
		653	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		654	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		655	which rolls both calls into one.
		656
		657	You can reinitialise a watcher at any time as long as it has been stopped
		658	(or never started) and there are no pending events outstanding.
		659
		660	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		661	int revents)>.
		662
		663	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		664
		665	This macro initialises the type-specific parts of a watcher. You need to
		666	call C<ev_init> at least once before you call this macro, but you can
		667	call C<ev_TYPE_set> any number of times. You must not, however, call this
		668	macro on a watcher that is active (it can be pending, however, which is a
		669	difference to the C<ev_init> macro).
		670
		671	Although some watcher types do not have type-specific arguments
		672	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		673
		674	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		675
		676	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		677	calls into a single call. This is the most convinient method to initialise
		678	a watcher. The same limitations apply, of course.
		679
		680	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		681
		682	Starts (activates) the given watcher. Only active watchers will receive
		683	events. If the watcher is already active nothing will happen.
		684
		685	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		686
		687	Stops the given watcher again (if active) and clears the pending
		688	status. It is possible that stopped watchers are pending (for example,
		689	non-repeating timers are being stopped when they become pending), but
		690	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		691	you want to free or reuse the memory used by the watcher it is therefore a
		692	good idea to always call its C<ev_TYPE_stop> function.
		693
		694	=item bool ev_is_active (ev_TYPE *watcher)
		695
		696	Returns a true value iff the watcher is active (i.e. it has been started
		697	and not yet been stopped). As long as a watcher is active you must not modify
		698	it.
		699
		700	=item bool ev_is_pending (ev_TYPE *watcher)
		701
		702	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		703	events but its callback has not yet been invoked). As long as a watcher
		704	is pending (but not active) you must not call an init function on it (but
		705	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		706	libev (e.g. you cnanot C<free ()> it).
		707
		708	=item callback = ev_cb (ev_TYPE *watcher)
		709
		710	Returns the callback currently set on the watcher.
		711
		712	=item ev_cb_set (ev_TYPE *watcher, callback)
		713
		714	Change the callback. You can change the callback at virtually any time
		715	(modulo threads).
		716
		717	=back
		718
		719
366	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
367		721
368	Each watcher has, by default, a member C<void *data> that you can change	722	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	723	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	724	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	725	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	726	member, you can also "subclass" the watcher type and provide your own
373	data:	727	data:
374		728
…		…
394		748
395		749
396	=head1 WATCHER TYPES	750	=head1 WATCHER TYPES
397		751
398	This section describes each watcher in detail, but will not repeat	752	This section describes each watcher in detail, but will not repeat
399	information given in the last section.	753	information given in the last section. Any initialisation/set macros,
		754	functions and members specific to the watcher type are explained.
400		755
		756	Members are additionally marked with either I<[read-only]>, meaning that,
		757	while the watcher is active, you can look at the member and expect some
		758	sensible content, but you must not modify it (you can modify it while the
		759	watcher is stopped to your hearts content), or I<[read-write]>, which
		760	means you can expect it to have some sensible content while the watcher
		761	is active, but you can also modify it. Modifying it may not do something
		762	sensible or take immediate effect (or do anything at all), but libev will
		763	not crash or malfunction in any way.
		764
		765
401	=head2 struct ev_io - is my file descriptor readable or writable	766	=head2 C<ev_io> - is this file descriptor readable or writable?
402		767
403	I/O watchers check wether a file descriptor is readable or writable	768	I/O watchers check whether a file descriptor is readable or writable
404	in each iteration of the event loop (This behaviour is called	769	in each iteration of the event loop, or, more precisely, when reading
405	level-triggering because you keep receiving events as long as the	770	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	771	some data. This behaviour is called level-triggering because you keep
407	act on the event and neither want to receive future events).	772	receiving events as long as the condition persists. Remember you can stop
		773	the watcher if you don't want to act on the event and neither want to
		774	receive future events.
		775
		776	In general you can register as many read and/or write event watchers per
		777	fd as you want (as long as you don't confuse yourself). Setting all file
		778	descriptors to non-blocking mode is also usually a good idea (but not
		779	required if you know what you are doing).
		780
		781	You have to be careful with dup'ed file descriptors, though. Some backends
		782	(the linux epoll backend is a notable example) cannot handle dup'ed file
		783	descriptors correctly if you register interest in two or more fds pointing
		784	to the same underlying file/socket/etc. description (that is, they share
		785	the same underlying "file open").
		786
		787	If you must do this, then force the use of a known-to-be-good backend
		788	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		789	C<EVBACKEND_POLL>).
		790
		791	Another thing you have to watch out for is that it is quite easy to
		792	receive "spurious" readyness notifications, that is your callback might
		793	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		794	because there is no data. Not only are some backends known to create a
		795	lot of those (for example solaris ports), it is very easy to get into
		796	this situation even with a relatively standard program structure. Thus
		797	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		798	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		799
		800	If you cannot run the fd in non-blocking mode (for example you should not
		801	play around with an Xlib connection), then you have to seperately re-test
		802	wether a file descriptor is really ready with a known-to-be good interface
		803	such as poll (fortunately in our Xlib example, Xlib already does this on
		804	its own, so its quite safe to use).
408		805
409	=over 4	806	=over 4
410		807
411	=item ev_io_init (ev_io *, callback, int fd, int events)	808	=item ev_io_init (ev_io *, callback, int fd, int events)
412		809
413	=item ev_io_set (ev_io *, int fd, int events)	810	=item ev_io_set (ev_io *, int fd, int events)
414		811
415	Configures an ev_io watcher. The fd is the file descriptor to rceeive	812	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 |	813	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
417	EV_WRITE> to receive the given events.	814	C<EV_READ | EV_WRITE> to receive the given events.
		815
		816	=item int fd [read-only]
		817
		818	The file descriptor being watched.
		819
		820	=item int events [read-only]
		821
		822	The events being watched.
418		823
419	=back	824	=back
420		825
		826	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		827	readable, but only once. Since it is likely line-buffered, you could
		828	attempt to read a whole line in the callback.
		829
		830	static void
		831	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		832	{
		833	ev_io_stop (loop, w);
		834	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		835	}
		836
		837	...
		838	struct ev_loop *loop = ev_default_init (0);
		839	struct ev_io stdin_readable;
		840	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		841	ev_io_start (loop, &stdin_readable);
		842	ev_loop (loop, 0);
		843
		844
421	=head2 struct ev_timer - relative and optionally recurring timeouts	845	=head2 C<ev_timer> - relative and optionally repeating timeouts
422		846
423	Timer watchers are simple relative timers that generate an event after a	847	Timer watchers are simple relative timers that generate an event after a
424	given time, and optionally repeating in regular intervals after that.	848	given time, and optionally repeating in regular intervals after that.
425		849
426	The timers are based on real time, that is, if you register an event that	850	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	851	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	852	time, it will still time out after (roughly) and hour. "Roughly" because
429	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	853	detecting time jumps is hard, and some inaccuracies are unavoidable (the
430	monotonic clock option helps a lot here).	854	monotonic clock option helps a lot here).
		855
		856	The relative timeouts are calculated relative to the C<ev_now ()>
		857	time. This is usually the right thing as this timestamp refers to the time
		858	of the event triggering whatever timeout you are modifying/starting. If
		859	you suspect event processing to be delayed and you I<need> to base the timeout
		860	on the current time, use something like this to adjust for this:
		861
		862	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		863
		864	The callback is guarenteed to be invoked only when its timeout has passed,
		865	but if multiple timers become ready during the same loop iteration then
		866	order of execution is undefined.
431		867
432	=over 4	868	=over 4
433		869
434	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	870	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
435		871
…		…
441	later, again, and again, until stopped manually.	877	later, again, and again, until stopped manually.
442		878
443	The timer itself will do a best-effort at avoiding drift, that is, if you	879	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	880	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	881	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	882	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.	883	timer will not fire more than once per event loop iteration.
448		884
449	=item ev_timer_again (loop)	885	=item ev_timer_again (loop)
450		886
451	This will act as if the timer timed out and restart it again if it is	887	This will act as if the timer timed out and restart it again if it is
…		…
455		891
456	If the timer is repeating, either start it if necessary (with the repeat	892	If the timer is repeating, either start it if necessary (with the repeat
457	value), or reset the running timer to the repeat value.	893	value), or reset the running timer to the repeat value.
458		894
459	This sounds a bit complicated, but here is a useful and typical	895	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	896	example: Imagine you have a tcp connection and you want a so-called
461	timeout, that is, you want to be called when there have been, say, 60	897	idle timeout, that is, you want to be called when there have been,
462	seconds of inactivity on the socket. The easiest way to do this is to	898	say, 60 seconds of inactivity on the socket. The easiest way to do
463	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	899	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
464	time you successfully read or write some data. If you go into an idle	900	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	901	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.	902	socket, you can stop the timer, and again will automatically restart it if
		903	need be.
		904
		905	You can also ignore the C<after> value and C<ev_timer_start> altogether
		906	and only ever use the C<repeat> value:
		907
		908	ev_timer_init (timer, callback, 0., 5.);
		909	ev_timer_again (loop, timer);
		910	...
		911	timer->again = 17.;
		912	ev_timer_again (loop, timer);
		913	...
		914	timer->again = 10.;
		915	ev_timer_again (loop, timer);
		916
		917	This is more efficient then stopping/starting the timer eahc time you want
		918	to modify its timeout value.
		919
		920	=item ev_tstamp repeat [read-write]
		921
		922	The current C<repeat> value. Will be used each time the watcher times out
		923	or C<ev_timer_again> is called and determines the next timeout (if any),
		924	which is also when any modifications are taken into account.
467		925
468	=back	926	=back
469		927
470	=head2 ev_periodic	928	Example: Create a timer that fires after 60 seconds.
		929
		930	static void
		931	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		932	{
		933	.. one minute over, w is actually stopped right here
		934	}
		935
		936	struct ev_timer mytimer;
		937	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		938	ev_timer_start (loop, &mytimer);
		939
		940	Example: Create a timeout timer that times out after 10 seconds of
		941	inactivity.
		942
		943	static void
		944	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		945	{
		946	.. ten seconds without any activity
		947	}
		948
		949	struct ev_timer mytimer;
		950	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		951	ev_timer_again (&mytimer); /* start timer */
		952	ev_loop (loop, 0);
		953
		954	// and in some piece of code that gets executed on any "activity":
		955	// reset the timeout to start ticking again at 10 seconds
		956	ev_timer_again (&mytimer);
		957
		958
		959	=head2 C<ev_periodic> - to cron or not to cron?
471		960
472	Periodic watchers are also timers of a kind, but they are very versatile	961	Periodic watchers are also timers of a kind, but they are very versatile
473	(and unfortunately a bit complex).	962	(and unfortunately a bit complex).
474		963
475	Unlike ev_timer's, they are not based on real time (or relative time)	964	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	965	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	966	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 ()	967	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	968	+ 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	969	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	970	roughly 10 seconds later and of course not if you reset your system time
482	again).	971	again).
483		972
484	They can also be used to implement vastly more complex timers, such as	973	They can also be used to implement vastly more complex timers, such as
485	triggering an event on eahc midnight, local time.	974	triggering an event on eahc midnight, local time.
486		975
		976	As with timers, the callback is guarenteed to be invoked only when the
		977	time (C<at>) has been passed, but if multiple periodic timers become ready
		978	during the same loop iteration then order of execution is undefined.
		979
487	=over 4	980	=over 4
488		981
489	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	982	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
490		983
491	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	984	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
492		985
493	Lots of arguments, lets sort it out... There are basically three modes of	986	Lots of arguments, lets sort it out... There are basically three modes of
494	operation, and we will explain them from simplest to complex:	987	operation, and we will explain them from simplest to complex:
495
496		988
497	=over 4	989	=over 4
498		990
499	=item * absolute timer (interval = reschedule_cb = 0)	991	=item * absolute timer (interval = reschedule_cb = 0)
500		992
…		…
514		1006
515	ev_periodic_set (&periodic, 0., 3600., 0);	1007	ev_periodic_set (&periodic, 0., 3600., 0);
516		1008
517	This doesn't mean there will always be 3600 seconds in between triggers,	1009	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	1010	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	1011	full hour (UTC), or more correctly, when the system time is evenly divisible
520	by 3600.	1012	by 3600.
521		1013
522	Another way to think about it (for the mathematically inclined) is that	1014	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	1015	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.	1016	time where C<time = at (mod interval)>, regardless of any time jumps.
525		1017
526	=item * manual reschedule mode (reschedule_cb = callback)	1018	=item * manual reschedule mode (reschedule_cb = callback)
527		1019
528	In this mode the values for C<interval> and C<at> are both being	1020	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	1021	ignored. Instead, each time the periodic watcher gets scheduled, the
530	reschedule callback will be called with the watcher as first, and the	1022	reschedule callback will be called with the watcher as first, and the
531	current time as second argument.	1023	current time as second argument.
532		1024
533	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1025	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	1026	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.	1027	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1028	starting a prepare watcher).
536		1029
537	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1030	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
538	ev_tstamp now)>, e.g.:	1031	ev_tstamp now)>, e.g.:
539		1032
540	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1033	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
541	{	1034	{
542	return now + 60.;	1035	return now + 60.;
…		…
545	It must return the next time to trigger, based on the passed time value	1038	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	1039	(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	1040	will usually be called just before the callback will be triggered, but
548	might be called at other times, too.	1041	might be called at other times, too.
549		1042
		1043	NOTE: I<< This callback must always return a time that is later than the
		1044	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1045
550	This can be used to create very complex timers, such as a timer that	1046	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	1047	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	1048	next midnight after C<now> and return the timestamp value for this. How
553	is, again, up to you (but it is not trivial).	1049	you do this is, again, up to you (but it is not trivial, which is the main
		1050	reason I omitted it as an example).
554		1051
555	=back	1052	=back
556		1053
557	=item ev_periodic_again (loop, ev_periodic *)	1054	=item ev_periodic_again (loop, ev_periodic *)
558		1055
559	Simply stops and restarts the periodic watcher again. This is only useful	1056	Simply stops and restarts the periodic watcher again. This is only useful
560	when you changed some parameters or the reschedule callback would return	1057	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	1058	a different time than the last time it was called (e.g. in a crond like
562	program when the crontabs have changed).	1059	program when the crontabs have changed).
563		1060
		1061	=item ev_tstamp interval [read-write]
		1062
		1063	The current interval value. Can be modified any time, but changes only
		1064	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1065	called.
		1066
		1067	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1068
		1069	The current reschedule callback, or C<0>, if this functionality is
		1070	switched off. Can be changed any time, but changes only take effect when
		1071	the periodic timer fires or C<ev_periodic_again> is being called.
		1072
564	=back	1073	=back
565		1074
		1075	Example: Call a callback every hour, or, more precisely, whenever the
		1076	system clock is divisible by 3600. The callback invocation times have
		1077	potentially a lot of jittering, but good long-term stability.
		1078
		1079	static void
		1080	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1081	{
		1082	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1083	}
		1084
		1085	struct ev_periodic hourly_tick;
		1086	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1087	ev_periodic_start (loop, &hourly_tick);
		1088
		1089	Example: The same as above, but use a reschedule callback to do it:
		1090
		1091	#include <math.h>
		1092
		1093	static ev_tstamp
		1094	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1095	{
		1096	return fmod (now, 3600.) + 3600.;
		1097	}
		1098
		1099	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1100
		1101	Example: Call a callback every hour, starting now:
		1102
		1103	struct ev_periodic hourly_tick;
		1104	ev_periodic_init (&hourly_tick, clock_cb,
		1105	fmod (ev_now (loop), 3600.), 3600., 0);
		1106	ev_periodic_start (loop, &hourly_tick);
		1107
		1108
566	=head2 ev_signal - signal me when a signal gets signalled	1109	=head2 C<ev_signal> - signal me when a signal gets signalled!
567		1110
568	Signal watchers will trigger an event when the process receives a specific	1111	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	1112	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	1113	will try it's best to deliver signals synchronously, i.e. as part of the
571	normal event processing, like any other event.	1114	normal event processing, like any other event.
572		1115
573	You cna configure as many watchers as you like per signal. Only when the	1116	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	1117	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	1118	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	1119	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	1120	watcher for a signal is stopped libev will reset the signal handler to
578	SIG_DFL (regardless of what it was set to before).	1121	SIG_DFL (regardless of what it was set to before).
…		…
584	=item ev_signal_set (ev_signal *, int signum)	1127	=item ev_signal_set (ev_signal *, int signum)
585		1128
586	Configures the watcher to trigger on the given signal number (usually one	1129	Configures the watcher to trigger on the given signal number (usually one
587	of the C<SIGxxx> constants).	1130	of the C<SIGxxx> constants).
588		1131
		1132	=item int signum [read-only]
		1133
		1134	The signal the watcher watches out for.
		1135
589	=back	1136	=back
590		1137
		1138
591	=head2 ev_child - wait for pid status changes	1139	=head2 C<ev_child> - watch out for process status changes
592		1140
593	Child watchers trigger when your process receives a SIGCHLD in response to	1141	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).	1142	some child status changes (most typically when a child of yours dies).
595		1143
596	=over 4	1144	=over 4
…		…
600	=item ev_child_set (ev_child *, int pid)	1148	=item ev_child_set (ev_child *, int pid)
601		1149
602	Configures the watcher to wait for status changes of process C<pid> (or	1150	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	1151	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	1152	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	1153	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.	1154	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1155	process causing the status change.
		1156
		1157	=item int pid [read-only]
		1158
		1159	The process id this watcher watches out for, or C<0>, meaning any process id.
		1160
		1161	=item int rpid [read-write]
		1162
		1163	The process id that detected a status change.
		1164
		1165	=item int rstatus [read-write]
		1166
		1167	The process exit/trace status caused by C<rpid> (see your systems
		1168	C<waitpid> and C<sys/wait.h> documentation for details).
607		1169
608	=back	1170	=back
609		1171
		1172	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1173
		1174	static void
		1175	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1176	{
		1177	ev_unloop (loop, EVUNLOOP_ALL);
		1178	}
		1179
		1180	struct ev_signal signal_watcher;
		1181	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1182	ev_signal_start (loop, &sigint_cb);
		1183
		1184
		1185	=head2 C<ev_stat> - did the file attributes just change?
		1186
		1187	This watches a filesystem path for attribute changes. That is, it calls
		1188	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1189	compared to the last time, invoking the callback if it did.
		1190
		1191	The path does not need to exist: changing from "path exists" to "path does
		1192	not exist" is a status change like any other. The condition "path does
		1193	not exist" is signified by the C<st_nlink> field being zero (which is
		1194	otherwise always forced to be at least one) and all the other fields of
		1195	the stat buffer having unspecified contents.
		1196
		1197	Since there is no standard to do this, the portable implementation simply
		1198	calls C<stat (2)> regulalry on the path to see if it changed somehow. You
		1199	can specify a recommended polling interval for this case. If you specify
		1200	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1201	unspecified default> value will be used (which you can expect to be around
		1202	five seconds, although this might change dynamically). Libev will also
		1203	impose a minimum interval which is currently around C<0.1>, but thats
		1204	usually overkill.
		1205
		1206	This watcher type is not meant for massive numbers of stat watchers,
		1207	as even with OS-supported change notifications, this can be
		1208	resource-intensive.
		1209
		1210	At the time of this writing, no specific OS backends are implemented, but
		1211	if demand increases, at least a kqueue and inotify backend will be added.
		1212
		1213	=over 4
		1214
		1215	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1216
		1217	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1218
		1219	Configures the watcher to wait for status changes of the given
		1220	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1221	be detected and should normally be specified as C<0> to let libev choose
		1222	a suitable value. The memory pointed to by C<path> must point to the same
		1223	path for as long as the watcher is active.
		1224
		1225	The callback will be receive C<EV_STAT> when a change was detected,
		1226	relative to the attributes at the time the watcher was started (or the
		1227	last change was detected).
		1228
		1229	=item ev_stat_stat (ev_stat *)
		1230
		1231	Updates the stat buffer immediately with new values. If you change the
		1232	watched path in your callback, you could call this fucntion to avoid
		1233	detecting this change (while introducing a race condition). Can also be
		1234	useful simply to find out the new values.
		1235
		1236	=item ev_statdata attr [read-only]
		1237
		1238	The most-recently detected attributes of the file. Although the type is of
		1239	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1240	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1241	was some error while C<stat>ing the file.
		1242
		1243	=item ev_statdata prev [read-only]
		1244
		1245	The previous attributes of the file. The callback gets invoked whenever
		1246	C<prev> != C<attr>.
		1247
		1248	=item ev_tstamp interval [read-only]
		1249
		1250	The specified interval.
		1251
		1252	=item const char *path [read-only]
		1253
		1254	The filesystem path that is being watched.
		1255
		1256	=back
		1257
		1258	Example: Watch C</etc/passwd> for attribute changes.
		1259
		1260	static void
		1261	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1262	{
		1263	/* /etc/passwd changed in some way */
		1264	if (w->attr.st_nlink)
		1265	{
		1266	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1267	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1268	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1269	}
		1270	else
		1271	/* you shalt not abuse printf for puts */
		1272	puts ("wow, /etc/passwd is not there, expect problems. "
		1273	"if this is windows, they already arrived\n");
		1274	}
		1275
		1276	...
		1277	ev_stat passwd;
		1278
		1279	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1280	ev_stat_start (loop, &passwd);
		1281
		1282
610	=head2 ev_idle - when you've got nothing better to do	1283	=head2 C<ev_idle> - when you've got nothing better to do...
611		1284
612	Idle watchers trigger events when there are no other I/O or timer (or	1285	Idle watchers trigger events when there are no other events are pending
613	periodic) events pending. That is, as long as your process is busy	1286	(prepare, check and other idle watchers do not count). That is, as long
614	handling sockets or timeouts it will not be called. But when your process	1287	as your process is busy handling sockets or timeouts (or even signals,
615	is idle all idle watchers are being called again and again - until	1288	imagine) it will not be triggered. But when your process is idle all idle
		1289	watchers are being called again and again, once per event loop iteration -
616	stopped, that is, or your process receives more events.	1290	until stopped, that is, or your process receives more events and becomes
		1291	busy.
617		1292
618	The most noteworthy effect is that as long as any idle watchers are	1293	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.	1294	active, the process will not block when waiting for new events.
620		1295
621	Apart from keeping your process non-blocking (which is a useful	1296	Apart from keeping your process non-blocking (which is a useful
…		…
631	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1306	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
632	believe me.	1307	believe me.
633		1308
634	=back	1309	=back
635		1310
636	=head2 prepare and check - your hooks into the event loop	1311	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1312	callback, free it. Also, use no error checking, as usual.
637		1313
		1314	static void
		1315	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1316	{
		1317	free (w);
		1318	// now do something you wanted to do when the program has
		1319	// no longer asnything immediate to do.
		1320	}
		1321
		1322	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1323	ev_idle_init (idle_watcher, idle_cb);
		1324	ev_idle_start (loop, idle_cb);
		1325
		1326
		1327	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1328
638	Prepare and check watchers usually (but not always) are used in	1329	Prepare and check watchers are usually (but not always) used in tandem:
639	tandom. Prepare watchers get invoked before the process blocks and check	1330	prepare watchers get invoked before the process blocks and check watchers
640	watchers afterwards.	1331	afterwards.
641		1332
		1333	You I<must not> call C<ev_loop> or similar functions that enter
		1334	the current event loop from either C<ev_prepare> or C<ev_check>
		1335	watchers. Other loops than the current one are fine, however. The
		1336	rationale behind this is that you do not need to check for recursion in
		1337	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1338	C<ev_check> so if you have one watcher of each kind they will always be
		1339	called in pairs bracketing the blocking call.
		1340
642	Their main purpose is to integrate other event mechanisms into libev. This	1341	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	1342	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.	1343	variable changes, implement your own watchers, integrate net-snmp or a
		1344	coroutine library and lots more. They are also occasionally useful if
		1345	you cache some data and want to flush it before blocking (for example,
		1346	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1347	watcher).
645		1348
646	This is done by examining in each prepare call which file descriptors need	1349	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	1350	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	1351	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	1352	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)	1353	any events that occured (by checking the pending status of all watchers
651	and call back into the library.	1354	and stopping them) and call back into the library. The I/O and timer
		1355	callbacks will never actually be called (but must be valid nevertheless,
		1356	because you never know, you know?).
652		1357
653	As another example, the perl Coro module uses these hooks to integrate	1358	As another example, the Perl Coro module uses these hooks to integrate
654	coroutines into libev programs, by yielding to other active coroutines	1359	coroutines into libev programs, by yielding to other active coroutines
655	during each prepare and only letting the process block if no coroutines	1360	during each prepare and only letting the process block if no coroutines
656	are ready to run.	1361	are ready to run (it's actually more complicated: it only runs coroutines
		1362	with priority higher than or equal to the event loop and one coroutine
		1363	of lower priority, but only once, using idle watchers to keep the event
		1364	loop from blocking if lower-priority coroutines are active, thus mapping
		1365	low-priority coroutines to idle/background tasks).
657		1366
658	=over 4	1367	=over 4
659		1368
660	=item ev_prepare_init (ev_prepare *, callback)	1369	=item ev_prepare_init (ev_prepare *, callback)
661		1370
662	=item ev_check_init (ev_check *, callback)	1371	=item ev_check_init (ev_check *, callback)
663		1372
664	Initialises and configures the prepare or check watcher - they have no	1373	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>	1374	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
666	macros, but using them is utterly, utterly pointless.	1375	macros, but using them is utterly, utterly and completely pointless.
667		1376
668	=back	1377	=back
669		1378
		1379	Example: To include a library such as adns, you would add IO watchers
		1380	and a timeout watcher in a prepare handler, as required by libadns, and
		1381	in a check watcher, destroy them and call into libadns. What follows is
		1382	pseudo-code only of course:
		1383
		1384	static ev_io iow [nfd];
		1385	static ev_timer tw;
		1386
		1387	static void
		1388	io_cb (ev_loop *loop, ev_io *w, int revents)
		1389	{
		1390	// set the relevant poll flags
		1391	// could also call adns_processreadable etc. here
		1392	struct pollfd *fd = (struct pollfd *)w->data;
		1393	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1394	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1395	}
		1396
		1397	// create io watchers for each fd and a timer before blocking
		1398	static void
		1399	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1400	{
		1401	int timeout = 3600000;truct pollfd fds [nfd];
		1402	// actual code will need to loop here and realloc etc.
		1403	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1404
		1405	/* the callback is illegal, but won't be called as we stop during check */
		1406	ev_timer_init (&tw, 0, timeout * 1e-3);
		1407	ev_timer_start (loop, &tw);
		1408
		1409	// create on ev_io per pollfd
		1410	for (int i = 0; i < nfd; ++i)
		1411	{
		1412	ev_io_init (iow + i, io_cb, fds [i].fd,
		1413	((fds [i].events & POLLIN ? EV_READ : 0)
		1414	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1415
		1416	fds [i].revents = 0;
		1417	iow [i].data = fds + i;
		1418	ev_io_start (loop, iow + i);
		1419	}
		1420	}
		1421
		1422	// stop all watchers after blocking
		1423	static void
		1424	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1425	{
		1426	ev_timer_stop (loop, &tw);
		1427
		1428	for (int i = 0; i < nfd; ++i)
		1429	ev_io_stop (loop, iow + i);
		1430
		1431	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1432	}
		1433
		1434
		1435	=head2 C<ev_embed> - when one backend isn't enough...
		1436
		1437	This is a rather advanced watcher type that lets you embed one event loop
		1438	into another (currently only C<ev_io> events are supported in the embedded
		1439	loop, other types of watchers might be handled in a delayed or incorrect
		1440	fashion and must not be used).
		1441
		1442	There are primarily two reasons you would want that: work around bugs and
		1443	prioritise I/O.
		1444
		1445	As an example for a bug workaround, the kqueue backend might only support
		1446	sockets on some platform, so it is unusable as generic backend, but you
		1447	still want to make use of it because you have many sockets and it scales
		1448	so nicely. In this case, you would create a kqueue-based loop and embed it
		1449	into your default loop (which might use e.g. poll). Overall operation will
		1450	be a bit slower because first libev has to poll and then call kevent, but
		1451	at least you can use both at what they are best.
		1452
		1453	As for prioritising I/O: rarely you have the case where some fds have
		1454	to be watched and handled very quickly (with low latency), and even
		1455	priorities and idle watchers might have too much overhead. In this case
		1456	you would put all the high priority stuff in one loop and all the rest in
		1457	a second one, and embed the second one in the first.
		1458
		1459	As long as the watcher is active, the callback will be invoked every time
		1460	there might be events pending in the embedded loop. The callback must then
		1461	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1462	their callbacks (you could also start an idle watcher to give the embedded
		1463	loop strictly lower priority for example). You can also set the callback
		1464	to C<0>, in which case the embed watcher will automatically execute the
		1465	embedded loop sweep.
		1466
		1467	As long as the watcher is started it will automatically handle events. The
		1468	callback will be invoked whenever some events have been handled. You can
		1469	set the callback to C<0> to avoid having to specify one if you are not
		1470	interested in that.
		1471
		1472	Also, there have not currently been made special provisions for forking:
		1473	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1474	but you will also have to stop and restart any C<ev_embed> watchers
		1475	yourself.
		1476
		1477	Unfortunately, not all backends are embeddable, only the ones returned by
		1478	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1479	portable one.
		1480
		1481	So when you want to use this feature you will always have to be prepared
		1482	that you cannot get an embeddable loop. The recommended way to get around
		1483	this is to have a separate variables for your embeddable loop, try to
		1484	create it, and if that fails, use the normal loop for everything:
		1485
		1486	struct ev_loop *loop_hi = ev_default_init (0);
		1487	struct ev_loop *loop_lo = 0;
		1488	struct ev_embed embed;
		1489
		1490	// see if there is a chance of getting one that works
		1491	// (remember that a flags value of 0 means autodetection)
		1492	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1493	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1494	: 0;
		1495
		1496	// if we got one, then embed it, otherwise default to loop_hi
		1497	if (loop_lo)
		1498	{
		1499	ev_embed_init (&embed, 0, loop_lo);
		1500	ev_embed_start (loop_hi, &embed);
		1501	}
		1502	else
		1503	loop_lo = loop_hi;
		1504
		1505	=over 4
		1506
		1507	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1508
		1509	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1510
		1511	Configures the watcher to embed the given loop, which must be
		1512	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1513	invoked automatically, otherwise it is the responsibility of the callback
		1514	to invoke it (it will continue to be called until the sweep has been done,
		1515	if you do not want thta, you need to temporarily stop the embed watcher).
		1516
		1517	=item ev_embed_sweep (loop, ev_embed *)
		1518
		1519	Make a single, non-blocking sweep over the embedded loop. This works
		1520	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1521	apropriate way for embedded loops.
		1522
		1523	=item struct ev_loop *loop [read-only]
		1524
		1525	The embedded event loop.
		1526
		1527	=back
		1528
		1529
		1530	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1531
		1532	Fork watchers are called when a C<fork ()> was detected (usually because
		1533	whoever is a good citizen cared to tell libev about it by calling
		1534	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1535	event loop blocks next and before C<ev_check> watchers are being called,
		1536	and only in the child after the fork. If whoever good citizen calling
		1537	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1538	handlers will be invoked, too, of course.
		1539
		1540	=over 4
		1541
		1542	=item ev_fork_init (ev_signal *, callback)
		1543
		1544	Initialises and configures the fork watcher - it has no parameters of any
		1545	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1546	believe me.
		1547
		1548	=back
		1549
		1550
670	=head1 OTHER FUNCTIONS	1551	=head1 OTHER FUNCTIONS
671		1552
672	There are some other fucntions of possible interest. Described. Here. Now.	1553	There are some other functions of possible interest. Described. Here. Now.
673		1554
674	=over 4	1555	=over 4
675		1556
676	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1557	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
677		1558
678	This function combines a simple timer and an I/O watcher, calls your	1559	This function combines a simple timer and an I/O watcher, calls your
679	callback on whichever event happens first and automatically stop both	1560	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	1561	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	1562	or timeout without having to allocate/configure/start/stop/free one or
682	more watchers yourself.	1563	more watchers yourself.
683		1564
684	If C<fd> is less than 0, then no I/O watcher will be started and events is	1565	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	1566	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
686	will be craeted and started.	1567	C<events> set will be craeted and started.
687		1568
688	If C<timeout> is less than 0, then no timeout watcher will be	1569	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	1570	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
690	= 0) will be started.	1571	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1572	dubious value.
691		1573
692	The callback has the type C<void (*cb)(int revents, void *arg)> and	1574	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,	1575	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>:	1576	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1577	value passed to C<ev_once>:
695		1578
696	static void stdin_ready (int revents, void *arg)	1579	static void stdin_ready (int revents, void *arg)
697	{	1580	{
698	if (revents & EV_TIMEOUT)	1581	if (revents & EV_TIMEOUT)
699	/* doh, nothing entered */	1582	/* doh, nothing entered */;
700	else if (revents & EV_READ)	1583	else if (revents & EV_READ)
701	/* stdin might have data for us, joy! */	1584	/* stdin might have data for us, joy! */;
702	}	1585	}
703		1586
704	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1587	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
705		1588
706	=item ev_feed_event (loop, watcher, int events)	1589	=item ev_feed_event (ev_loop *, watcher *, int revents)
707		1590
708	Feeds the given event set into the event loop, as if the specified event	1591	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	1592	had happened for the specified watcher (which must be a pointer to an
710	initialised but not necessarily active event watcher).	1593	initialised but not necessarily started event watcher).
711		1594
712	=item ev_feed_fd_event (loop, int fd, int revents)	1595	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
713		1596
714	Feed an event on the given fd, as if a file descriptor backend detected it.	1597	Feed an event on the given fd, as if a file descriptor backend detected
		1598	the given events it.
715		1599
716	=item ev_feed_signal_event (loop, int signum)	1600	=item ev_feed_signal_event (ev_loop *loop, int signum)
717		1601
718	Feed an event as if the given signal occured (loop must be the default loop!).	1602	Feed an event as if the given signal occured (C<loop> must be the default
		1603	loop!).
719		1604
720	=back	1605	=back
721		1606
		1607
		1608	=head1 LIBEVENT EMULATION
		1609
		1610	Libev offers a compatibility emulation layer for libevent. It cannot
		1611	emulate the internals of libevent, so here are some usage hints:
		1612
		1613	=over 4
		1614
		1615	=item * Use it by including <event.h>, as usual.
		1616
		1617	=item * The following members are fully supported: ev_base, ev_callback,
		1618	ev_arg, ev_fd, ev_res, ev_events.
		1619
		1620	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1621	maintained by libev, it does not work exactly the same way as in libevent (consider
		1622	it a private API).
		1623
		1624	=item * Priorities are not currently supported. Initialising priorities
		1625	will fail and all watchers will have the same priority, even though there
		1626	is an ev_pri field.
		1627
		1628	=item * Other members are not supported.
		1629
		1630	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1631	to use the libev header file and library.
		1632
		1633	=back
		1634
		1635	=head1 C++ SUPPORT
		1636
		1637	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1638	you to use some convinience methods to start/stop watchers and also change
		1639	the callback model to a model using method callbacks on objects.
		1640
		1641	To use it,
		1642
		1643	#include <ev++.h>
		1644
		1645	(it is not installed by default). This automatically includes F<ev.h>
		1646	and puts all of its definitions (many of them macros) into the global
		1647	namespace. All C++ specific things are put into the C<ev> namespace.
		1648
		1649	It should support all the same embedding options as F<ev.h>, most notably
		1650	C<EV_MULTIPLICITY>.
		1651
		1652	Here is a list of things available in the C<ev> namespace:
		1653
		1654	=over 4
		1655
		1656	=item C<ev::READ>, C<ev::WRITE> etc.
		1657
		1658	These are just enum values with the same values as the C<EV_READ> etc.
		1659	macros from F<ev.h>.
		1660
		1661	=item C<ev::tstamp>, C<ev::now>
		1662
		1663	Aliases to the same types/functions as with the C<ev_> prefix.
		1664
		1665	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1666
		1667	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1668	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1669	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1670	defines by many implementations.
		1671
		1672	All of those classes have these methods:
		1673
		1674	=over 4
		1675
		1676	=item ev::TYPE::TYPE (object *, object::method *)
		1677
		1678	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1679
		1680	=item ev::TYPE::~TYPE
		1681
		1682	The constructor takes a pointer to an object and a method pointer to
		1683	the event handler callback to call in this class. The constructor calls
		1684	C<ev_init> for you, which means you have to call the C<set> method
		1685	before starting it. If you do not specify a loop then the constructor
		1686	automatically associates the default loop with this watcher.
		1687
		1688	The destructor automatically stops the watcher if it is active.
		1689
		1690	=item w->set (struct ev_loop *)
		1691
		1692	Associates a different C<struct ev_loop> with this watcher. You can only
		1693	do this when the watcher is inactive (and not pending either).
		1694
		1695	=item w->set ([args])
		1696
		1697	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1698	called at least once. Unlike the C counterpart, an active watcher gets
		1699	automatically stopped and restarted.
		1700
		1701	=item w->start ()
		1702
		1703	Starts the watcher. Note that there is no C<loop> argument as the
		1704	constructor already takes the loop.
		1705
		1706	=item w->stop ()
		1707
		1708	Stops the watcher if it is active. Again, no C<loop> argument.
		1709
		1710	=item w->again () C<ev::timer>, C<ev::periodic> only
		1711
		1712	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1713	C<ev_TYPE_again> function.
		1714
		1715	=item w->sweep () C<ev::embed> only
		1716
		1717	Invokes C<ev_embed_sweep>.
		1718
		1719	=item w->update () C<ev::stat> only
		1720
		1721	Invokes C<ev_stat_stat>.
		1722
		1723	=back
		1724
		1725	=back
		1726
		1727	Example: Define a class with an IO and idle watcher, start one of them in
		1728	the constructor.
		1729
		1730	class myclass
		1731	{
		1732	ev_io io; void io_cb (ev::io &w, int revents);
		1733	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1734
		1735	myclass ();
		1736	}
		1737
		1738	myclass::myclass (int fd)
		1739	: io (this, &myclass::io_cb),
		1740	idle (this, &myclass::idle_cb)
		1741	{
		1742	io.start (fd, ev::READ);
		1743	}
		1744
		1745
		1746	=head1 MACRO MAGIC
		1747
		1748	Libev can be compiled with a variety of options, the most fundemantal is
		1749	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1750	callbacks have an initial C<struct ev_loop *> argument.
		1751
		1752	To make it easier to write programs that cope with either variant, the
		1753	following macros are defined:
		1754
		1755	=over 4
		1756
		1757	=item C<EV_A>, C<EV_A_>
		1758
		1759	This provides the loop I<argument> for functions, if one is required ("ev
		1760	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1761	C<EV_A_> is used when other arguments are following. Example:
		1762
		1763	ev_unref (EV_A);
		1764	ev_timer_add (EV_A_ watcher);
		1765	ev_loop (EV_A_ 0);
		1766
		1767	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1768	which is often provided by the following macro.
		1769
		1770	=item C<EV_P>, C<EV_P_>
		1771
		1772	This provides the loop I<parameter> for functions, if one is required ("ev
		1773	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1774	C<EV_P_> is used when other parameters are following. Example:
		1775
		1776	// this is how ev_unref is being declared
		1777	static void ev_unref (EV_P);
		1778
		1779	// this is how you can declare your typical callback
		1780	static void cb (EV_P_ ev_timer *w, int revents)
		1781
		1782	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1783	suitable for use with C<EV_A>.
		1784
		1785	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1786
		1787	Similar to the other two macros, this gives you the value of the default
		1788	loop, if multiple loops are supported ("ev loop default").
		1789
		1790	=back
		1791
		1792	Example: Declare and initialise a check watcher, working regardless of
		1793	wether multiple loops are supported or not.
		1794
		1795	static void
		1796	check_cb (EV_P_ ev_timer *w, int revents)
		1797	{
		1798	ev_check_stop (EV_A_ w);
		1799	}
		1800
		1801	ev_check check;
		1802	ev_check_init (&check, check_cb);
		1803	ev_check_start (EV_DEFAULT_ &check);
		1804	ev_loop (EV_DEFAULT_ 0);
		1805
		1806
		1807	=head1 EMBEDDING
		1808
		1809	Libev can (and often is) directly embedded into host
		1810	applications. Examples of applications that embed it include the Deliantra
		1811	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1812	and rxvt-unicode.
		1813
		1814	The goal is to enable you to just copy the neecssary files into your
		1815	source directory without having to change even a single line in them, so
		1816	you can easily upgrade by simply copying (or having a checked-out copy of
		1817	libev somewhere in your source tree).
		1818
		1819	=head2 FILESETS
		1820
		1821	Depending on what features you need you need to include one or more sets of files
		1822	in your app.
		1823
		1824	=head3 CORE EVENT LOOP
		1825
		1826	To include only the libev core (all the C<ev_*> functions), with manual
		1827	configuration (no autoconf):
		1828
		1829	#define EV_STANDALONE 1
		1830	#include "ev.c"
		1831
		1832	This will automatically include F<ev.h>, too, and should be done in a
		1833	single C source file only to provide the function implementations. To use
		1834	it, do the same for F<ev.h> in all files wishing to use this API (best
		1835	done by writing a wrapper around F<ev.h> that you can include instead and
		1836	where you can put other configuration options):
		1837
		1838	#define EV_STANDALONE 1
		1839	#include "ev.h"
		1840
		1841	Both header files and implementation files can be compiled with a C++
		1842	compiler (at least, thats a stated goal, and breakage will be treated
		1843	as a bug).
		1844
		1845	You need the following files in your source tree, or in a directory
		1846	in your include path (e.g. in libev/ when using -Ilibev):
		1847
		1848	ev.h
		1849	ev.c
		1850	ev_vars.h
		1851	ev_wrap.h
		1852
		1853	ev_win32.c required on win32 platforms only
		1854
		1855	ev_select.c only when select backend is enabled (which is by default)
		1856	ev_poll.c only when poll backend is enabled (disabled by default)
		1857	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1858	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1859	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1860
		1861	F<ev.c> includes the backend files directly when enabled, so you only need
		1862	to compile this single file.
		1863
		1864	=head3 LIBEVENT COMPATIBILITY API
		1865
		1866	To include the libevent compatibility API, also include:
		1867
		1868	#include "event.c"
		1869
		1870	in the file including F<ev.c>, and:
		1871
		1872	#include "event.h"
		1873
		1874	in the files that want to use the libevent API. This also includes F<ev.h>.
		1875
		1876	You need the following additional files for this:
		1877
		1878	event.h
		1879	event.c
		1880
		1881	=head3 AUTOCONF SUPPORT
		1882
		1883	Instead of using C<EV_STANDALONE=1> and providing your config in
		1884	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1885	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1886	include F<config.h> and configure itself accordingly.
		1887
		1888	For this of course you need the m4 file:
		1889
		1890	libev.m4
		1891
		1892	=head2 PREPROCESSOR SYMBOLS/MACROS
		1893
		1894	Libev can be configured via a variety of preprocessor symbols you have to define
		1895	before including any of its files. The default is not to build for multiplicity
		1896	and only include the select backend.
		1897
		1898	=over 4
		1899
		1900	=item EV_STANDALONE
		1901
		1902	Must always be C<1> if you do not use autoconf configuration, which
		1903	keeps libev from including F<config.h>, and it also defines dummy
		1904	implementations for some libevent functions (such as logging, which is not
		1905	supported). It will also not define any of the structs usually found in
		1906	F<event.h> that are not directly supported by the libev core alone.
		1907
		1908	=item EV_USE_MONOTONIC
		1909
		1910	If defined to be C<1>, libev will try to detect the availability of the
		1911	monotonic clock option at both compiletime and runtime. Otherwise no use
		1912	of the monotonic clock option will be attempted. If you enable this, you
		1913	usually have to link against librt or something similar. Enabling it when
		1914	the functionality isn't available is safe, though, althoguh you have
		1915	to make sure you link against any libraries where the C<clock_gettime>
		1916	function is hiding in (often F<-lrt>).
		1917
		1918	=item EV_USE_REALTIME
		1919
		1920	If defined to be C<1>, libev will try to detect the availability of the
		1921	realtime clock option at compiletime (and assume its availability at
		1922	runtime if successful). Otherwise no use of the realtime clock option will
		1923	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1924	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1925	in the description of C<EV_USE_MONOTONIC>, though.
		1926
		1927	=item EV_USE_SELECT
		1928
		1929	If undefined or defined to be C<1>, libev will compile in support for the
		1930	C<select>(2) backend. No attempt at autodetection will be done: if no
		1931	other method takes over, select will be it. Otherwise the select backend
		1932	will not be compiled in.
		1933
		1934	=item EV_SELECT_USE_FD_SET
		1935
		1936	If defined to C<1>, then the select backend will use the system C<fd_set>
		1937	structure. This is useful if libev doesn't compile due to a missing
		1938	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1939	exotic systems. This usually limits the range of file descriptors to some
		1940	low limit such as 1024 or might have other limitations (winsocket only
		1941	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1942	influence the size of the C<fd_set> used.
		1943
		1944	=item EV_SELECT_IS_WINSOCKET
		1945
		1946	When defined to C<1>, the select backend will assume that
		1947	select/socket/connect etc. don't understand file descriptors but
		1948	wants osf handles on win32 (this is the case when the select to
		1949	be used is the winsock select). This means that it will call
		1950	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1951	it is assumed that all these functions actually work on fds, even
		1952	on win32. Should not be defined on non-win32 platforms.
		1953
		1954	=item EV_USE_POLL
		1955
		1956	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1957	backend. Otherwise it will be enabled on non-win32 platforms. It
		1958	takes precedence over select.
		1959
		1960	=item EV_USE_EPOLL
		1961
		1962	If defined to be C<1>, libev will compile in support for the Linux
		1963	C<epoll>(7) backend. Its availability will be detected at runtime,
		1964	otherwise another method will be used as fallback. This is the
		1965	preferred backend for GNU/Linux systems.
		1966
		1967	=item EV_USE_KQUEUE
		1968
		1969	If defined to be C<1>, libev will compile in support for the BSD style
		1970	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1971	otherwise another method will be used as fallback. This is the preferred
		1972	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1973	supports some types of fds correctly (the only platform we found that
		1974	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1975	not be used unless explicitly requested. The best way to use it is to find
		1976	out whether kqueue supports your type of fd properly and use an embedded
		1977	kqueue loop.
		1978
		1979	=item EV_USE_PORT
		1980
		1981	If defined to be C<1>, libev will compile in support for the Solaris
		1982	10 port style backend. Its availability will be detected at runtime,
		1983	otherwise another method will be used as fallback. This is the preferred
		1984	backend for Solaris 10 systems.
		1985
		1986	=item EV_USE_DEVPOLL
		1987
		1988	reserved for future expansion, works like the USE symbols above.
		1989
		1990	=item EV_H
		1991
		1992	The name of the F<ev.h> header file used to include it. The default if
		1993	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1994	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1995
		1996	=item EV_CONFIG_H
		1997
		1998	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1999	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2000	C<EV_H>, above.
		2001
		2002	=item EV_EVENT_H
		2003
		2004	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2005	of how the F<event.h> header can be found.
		2006
		2007	=item EV_PROTOTYPES
		2008
		2009	If defined to be C<0>, then F<ev.h> will not define any function
		2010	prototypes, but still define all the structs and other symbols. This is
		2011	occasionally useful if you want to provide your own wrapper functions
		2012	around libev functions.
		2013
		2014	=item EV_MULTIPLICITY
		2015
		2016	If undefined or defined to C<1>, then all event-loop-specific functions
		2017	will have the C<struct ev_loop *> as first argument, and you can create
		2018	additional independent event loops. Otherwise there will be no support
		2019	for multiple event loops and there is no first event loop pointer
		2020	argument. Instead, all functions act on the single default loop.
		2021
		2022	=item EV_PERIODIC_ENABLE
		2023
		2024	If undefined or defined to be C<1>, then periodic timers are supported. If
		2025	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2026	code.
		2027
		2028	=item EV_EMBED_ENABLE
		2029
		2030	If undefined or defined to be C<1>, then embed watchers are supported. If
		2031	defined to be C<0>, then they are not.
		2032
		2033	=item EV_STAT_ENABLE
		2034
		2035	If undefined or defined to be C<1>, then stat watchers are supported. If
		2036	defined to be C<0>, then they are not.
		2037
		2038	=item EV_FORK_ENABLE
		2039
		2040	If undefined or defined to be C<1>, then fork watchers are supported. If
		2041	defined to be C<0>, then they are not.
		2042
		2043	=item EV_MINIMAL
		2044
		2045	If you need to shave off some kilobytes of code at the expense of some
		2046	speed, define this symbol to C<1>. Currently only used for gcc to override
		2047	some inlining decisions, saves roughly 30% codesize of amd64.
		2048
		2049	=item EV_PID_HASHSIZE
		2050
		2051	C<ev_child> watchers use a small hash table to distribute workload by
		2052	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2053	than enough. If you need to manage thousands of children you might want to
		2054	increase this value.
		2055
		2056	=item EV_COMMON
		2057
		2058	By default, all watchers have a C<void *data> member. By redefining
		2059	this macro to a something else you can include more and other types of
		2060	members. You have to define it each time you include one of the files,
		2061	though, and it must be identical each time.
		2062
		2063	For example, the perl EV module uses something like this:
		2064
		2065	#define EV_COMMON \
		2066	SV *self; /* contains this struct */ \
		2067	SV *cb_sv, *fh /* note no trailing ";" */
		2068
		2069	=item EV_CB_DECLARE (type)
		2070
		2071	=item EV_CB_INVOKE (watcher, revents)
		2072
		2073	=item ev_set_cb (ev, cb)
		2074
		2075	Can be used to change the callback member declaration in each watcher,
		2076	and the way callbacks are invoked and set. Must expand to a struct member
		2077	definition and a statement, respectively. See the F<ev.v> header file for
		2078	their default definitions. One possible use for overriding these is to
		2079	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2080	method calls instead of plain function calls in C++.
		2081
		2082	=head2 EXAMPLES
		2083
		2084	For a real-world example of a program the includes libev
		2085	verbatim, you can have a look at the EV perl module
		2086	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2087	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2088	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2089	will be compiled. It is pretty complex because it provides its own header
		2090	file.
		2091
		2092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2093	that everybody includes and which overrides some autoconf choices:
		2094
		2095	#define EV_USE_POLL 0
		2096	#define EV_MULTIPLICITY 0
		2097	#define EV_PERIODICS 0
		2098	#define EV_CONFIG_H <config.h>
		2099
		2100	#include "ev++.h"
		2101
		2102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2103
		2104	#include "ev_cpp.h"
		2105	#include "ev.c"
		2106
		2107
		2108	=head1 COMPLEXITIES
		2109
		2110	In this section the complexities of (many of) the algorithms used inside
		2111	libev will be explained. For complexity discussions about backends see the
		2112	documentation for C<ev_default_init>.
		2113
		2114	=over 4
		2115
		2116	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2117
		2118	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2119
		2120	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2121
		2122	=item Stopping check/prepare/idle watchers: O(1)
		2123
		2124	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		2125
		2126	=item Finding the next timer per loop iteration: O(1)
		2127
		2128	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2129
		2130	=item Activating one watcher: O(1)
		2131
		2132	=back
		2133
		2134
722	=head1 AUTHOR	2135	=head1 AUTHOR
723		2136
724	Marc Lehmann <libev@schmorp.de>.	2137	Marc Lehmann <libev@schmorp.de>.
725		2138

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