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Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.56 by root, Wed Nov 28 11:15:55 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
…		…
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). It also is quite	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
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	79	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	80	for example).
33		81
34	=head1 CONVENTIONS	82	=head1 CONVENTIONS
35		83
36	Libev is very configurable. In this manual the default configuration	84	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	85	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	86	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	87	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	88	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	89	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		90
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	91	=head1 TIME REPRESENTATION
45		92
46	Libev represents time as a single floating point number, representing the	93	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	94	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	95	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	96	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	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.
51		104
52	=over 4	105	=over 4
53		106
54	=item ev_tstamp ev_time ()	107	=item ev_tstamp ev_time ()
55		108
56	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.
57		112
58	=item int ev_version_major ()	113	=item int ev_version_major ()
59		114
60	=item int ev_version_minor ()	115	=item int ev_version_minor ()
61		116
…		…
63	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
64	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
65	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
66	version of the library your program was compiled against.	121	version of the library your program was compiled against.
67		122
68	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,
69	as this indicates an incompatible change. Minor versions are usually	124	as this indicates an incompatible change. Minor versions are usually
70	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
71	not a problem.	126	not a problem.
72		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
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	167	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))
74		168
75	Sets the allocation function to use (the prototype is similar to the	169	Sets the allocation function to use (the prototype and semantics are
76	realloc C function, the semantics are identical). It is used to allocate	170	identical to the realloc C function). It is used to allocate and free
77	and free memory (no surprises here). If it returns zero when memory	171	memory (no surprises here). If it returns zero when memory needs to be
78	needs to be allocated, the library might abort or take some potentially	172	allocated, the library might abort or take some potentially destructive
79	destructive action. The default is your system realloc function.	173	action. The default is your system realloc function.
80		174
81	You could override this function in high-availability programs to, say,	175	You could override this function in high-availability programs to, say,
82	free some memory if it cannot allocate memory, to use a special allocator,	176	free some memory if it cannot allocate memory, to use a special allocator,
83	or even to sleep a while and retry until some memory is available.	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);
84		198
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	199	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		200
87	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
88	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
…		…
90	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
91	matter what, when it returns. That is, libev will generally retry the	205	matter what, when it returns. That is, libev will generally retry the
92	requested operation, or, if the condition doesn't go away, do bad stuff	206	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	207	(such as abort).
94		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);
		220
95	=back	221	=back
96		222
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	223	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		224
99	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
100	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
101	events, and dynamically created loops which do not.	227	events, and dynamically created loops which do not.
102		228
103	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
104	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
105	create, you also create another event loop. Libev itself does no locking	231	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	232	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	233	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	234	done correctly, because it's hideous and inefficient).
109		235
110	=over 4	236	=over 4
111		237
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	238	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		239
114	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
115	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
116	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
117	flags).	243	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		244
119	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
120	function.	246	function.
121		247
122	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
123	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>).
124		250
125	It supports the following flags:	251	The following flags are supported:
126		252
127	=over 4	253	=over 4
128		254
129	=item EVFLAG_AUTO	255	=item C<EVFLAG_AUTO>
130		256
131	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
132	thing, believe me).	258	thing, believe me).
133		259
134	=item EVFLAG_NOENV	260	=item C<EVFLAG_NOENV>
135		261
136	If this flag bit is ored into the flag value (or the program runs setuid	262	If this flag bit is ored into the flag value (or the program runs setuid
137	or setgid) then libev will I<not> look at the environment variable	263	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	265	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	266	useful to try out specific backends to test their performance, or to work
141	around bugs.	267	around bugs.
142		268
143	=item EVMETHOD_SELECT portable select backend	269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		270
145	=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.
146		276
147	=item EVMETHOD_EPOLL linux only	277	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
148		278
149	=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).
150		283
151	=item EVMETHOD_DEVPOLL solaris 8 only	284	=item C<EVBACKEND_EPOLL> (value 4, Linux)
152		285
153	=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
154		336
155	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
156	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
157	specified, any backend will do.	339	specified, most compiled-in backend will be tried, usually in reverse
		340	order of their flag values :)
158		341
159	=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);
160		357
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	358	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		359
163	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
164	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
165	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
166	undefined behaviour (or a failed assertion if assertions are enabled).	363	undefined behaviour (or a failed assertion if assertions are enabled).
167		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
168	=item ev_default_destroy ()	371	=item ev_default_destroy ()
169		372
170	Destroys the default loop again (frees all memory and kernel state	373	Destroys the default loop again (frees all memory and kernel state
171	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
172	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).
173		380
174	=item ev_loop_destroy (loop)	381	=item ev_loop_destroy (loop)
175		382
176	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
177	earlier call to C<ev_loop_new>.	384	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	388	This function reinitialises the kernel state for backends that have
182	one. Despite the name, you can call it anytime, but it makes most sense	389	one. Despite the name, you can call it anytime, but it makes most sense
183	after forking, in either the parent or child process (or both, but that	390	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	391	again makes little sense).
185		392
186	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
187	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
188	have to call it.	395	fork+exec, you don't have to call it.
189		396
190	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
191	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
192	quite nicely into a call to C<pthread_atfork>:	399	quite nicely into a call to C<pthread_atfork>:
193		400
194	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.
195		406
196	=item ev_loop_fork (loop)	407	=item ev_loop_fork (loop)
197		408
198	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
199	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
200	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.
201		412
202	=item unsigned int ev_method (loop)	413	=item unsigned int ev_backend (loop)
203		414
204	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
205	use.	416	use.
206		417
207	=item ev_tstamp = ev_now (loop)	418	=item ev_tstamp ev_now (loop)
208		419
209	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
210	got events and started processing them. This timestamp does not change	421	received events and started processing them. This timestamp does not
211	as long as callbacks are being processed, and this is also the base time	422	change as long as callbacks are being processed, and this is also the base
212	used for relative timers. You can treat it as the timestamp of the event	423	time used for relative timers. You can treat it as the timestamp of the
213	occuring (or more correctly, the mainloop finding out about it).	424	event occuring (or more correctly, libev finding out about it).
214		425
215	=item ev_loop (loop, int flags)	426	=item ev_loop (loop, int flags)
216		427
217	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
218	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
219	events.	430	events.
220		431
221	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
222	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.
223		440
224	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
225	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
226	case there are no events.	443	case there are no events and will return after one iteration of the loop.
227		444
228	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
229	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
230	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.
231		452
232	This flags value could be used to implement alternative looping	453	Here are the gory details of what C<ev_loop> does:
233	constructs, but the C<prepare> and C<check> watchers provide a better and	454
234	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!
235		481
236	=item ev_unloop (loop, how)	482	=item ev_unloop (loop, how)
237		483
238	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
239	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
240	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.
241	calls return.
242		488
243	=item ev_ref (loop)	489	=item ev_ref (loop)
244		490
245	=item ev_unref (loop)	491	=item ev_unref (loop)
246		492
247	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
248	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
249	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
250	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
251	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
252	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
253	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
254	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
255	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);
256		516
257	=back	517	=back
		518
258		519
259	=head1 ANATOMY OF A WATCHER	520	=head1 ANATOMY OF A WATCHER
260		521
261	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
262	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
263	become readable, you would create an ev_io watcher for that:	524	become readable, you would create an C<ev_io> watcher for that:
264		525
265	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)
266	{	527	{
267	ev_io_stop (w);	528	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	529	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), 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
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	557	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		558
298	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
299	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
300	reinitialise it or call its set method.	561	reinitialise it or call its C<set> macro.
301
302	You cna check whether an event is active by calling the C<ev_is_active
303	(watcher *)> macro. To see whether an event is outstanding (but the
304	callback for it has not been called yet) you cna use the C<ev_is_pending
305	(watcher *)> macro.
306		562
307	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
308	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
309	third argument.	565	third argument.
310		566
311	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
312	(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
313	are:	569	are:
314		570
315	=over 4	571	=over 4
316		572
317	=item EV_READ	573	=item C<EV_READ>
318		574
319	=item EV_WRITE	575	=item C<EV_WRITE>
320		576
321	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
322	writable.	578	writable.
323		579
324	=item EV_TIMEOUT	580	=item C<EV_TIMEOUT>
325		581
326	The ev_timer watcher has timed out.	582	The C<ev_timer> watcher has timed out.
327		583
328	=item EV_PERIODIC	584	=item C<EV_PERIODIC>
329		585
330	The ev_periodic watcher has timed out.	586	The C<ev_periodic> watcher has timed out.
331		587
332	=item EV_SIGNAL	588	=item C<EV_SIGNAL>
333		589
334	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.
335		591
336	=item EV_CHILD	592	=item C<EV_CHILD>
337		593
338	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.
339		595
		596	=item C<EV_STAT>
		597
		598	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		599
340	=item EV_IDLE	600	=item C<EV_IDLE>
341		601
342	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.
343		603
344	=item EV_PREPARE	604	=item C<EV_PREPARE>
345		605
346	=item EV_CHECK	606	=item C<EV_CHECK>
347		607
348	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
349	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
350	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
351	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
352	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
353	(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
354	C<ev_loop> from blocking).	614	C<ev_loop> from blocking).
355		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
356	=item EV_ERROR	625	=item C<EV_ERROR>
357		626
358	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
359	happen because the watcher could not be properly started because libev	628	happen because the watcher could not be properly started because libev
360	ran out of memory, a file descriptor was found to be closed or any other	629	ran out of memory, a file descriptor was found to be closed or any other
361	problem. You best act on it by reporting the problem and somehow coping	630	problem. You best act on it by reporting the problem and somehow coping
…		…
367	with the error from read() or write(). This will not work in multithreaded	636	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	637	programs, though, so beware.
369		638
370	=back	639	=back
371		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
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		721
374	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
375	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
376	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
377	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
378	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
379	data:	727	data:
380		728
…		…
393	{	741	{
394	struct my_io *w = (struct my_io *)w_;	742	struct my_io *w = (struct my_io *)w_;
395	...	743	...
396	}	744	}
397		745
398	More interesting and less C-conformant ways of catsing your callback type	746	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	747	instead have been omitted.
		748
		749	Another common scenario is having some data structure with multiple
		750	watchers:
		751
		752	struct my_biggy
		753	{
		754	int some_data;
		755	ev_timer t1;
		756	ev_timer t2;
		757	}
		758
		759	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		760	you need to use C<offsetof>:
		761
		762	#include <stddef.h>
		763
		764	static void
		765	t1_cb (EV_P_ struct ev_timer *w, int revents)
		766	{
		767	struct my_biggy big = (struct my_biggy *
		768	(((char *)w) - offsetof (struct my_biggy, t1));
		769	}
		770
		771	static void
		772	t2_cb (EV_P_ struct ev_timer *w, int revents)
		773	{
		774	struct my_biggy big = (struct my_biggy *
		775	(((char *)w) - offsetof (struct my_biggy, t2));
		776	}
400		777
401		778
402	=head1 WATCHER TYPES	779	=head1 WATCHER TYPES
403		780
404	This section describes each watcher in detail, but will not repeat	781	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	782	information given in the last section. Any initialisation/set macros,
		783	functions and members specific to the watcher type are explained.
406		784
		785	Members are additionally marked with either I<[read-only]>, meaning that,
		786	while the watcher is active, you can look at the member and expect some
		787	sensible content, but you must not modify it (you can modify it while the
		788	watcher is stopped to your hearts content), or I<[read-write]>, which
		789	means you can expect it to have some sensible content while the watcher
		790	is active, but you can also modify it. Modifying it may not do something
		791	sensible or take immediate effect (or do anything at all), but libev will
		792	not crash or malfunction in any way.
		793
		794
407	=head2 struct ev_io - is my file descriptor readable or writable	795	=head2 C<ev_io> - is this file descriptor readable or writable?
408		796
409	I/O watchers check whether a file descriptor is readable or writable	797	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	798	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	799	would not block the process and writing would at least be able to write
412	condition persists. Remember you cna stop the watcher if you don't want to	800	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	801	receiving events as long as the condition persists. Remember you can stop
		802	the watcher if you don't want to act on the event and neither want to
		803	receive future events.
414		804
415	In general you can register as many read and/or write event watchers oer	805	In general you can register as many read and/or write event watchers per
416	fd as you want (as long as you don't confuse yourself). Setting all file	806	fd as you want (as long as you don't confuse yourself). Setting all file
417	descriptors to non-blocking mode is also usually a good idea (but not	807	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	808	required if you know what you are doing).
419		809
420	You have to be careful with dup'ed file descriptors, though. Some backends	810	You have to be careful with dup'ed file descriptors, though. Some backends
421	(the linux epoll backend is a notable example) cannot handle dup'ed file	811	(the linux epoll backend is a notable example) cannot handle dup'ed file
422	descriptors correctly if you register interest in two or more fds pointing	812	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	813	to the same underlying file/socket/etc. description (that is, they share
		814	the same underlying "file open").
424		815
425	If you must do this, then force the use of a known-to-be-good backend	816	If you must do this, then force the use of a known-to-be-good backend
426	(at the time of this writing, this includes only EVMETHOD_SELECT and	817	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	818	C<EVBACKEND_POLL>).
		819
		820	Another thing you have to watch out for is that it is quite easy to
		821	receive "spurious" readyness notifications, that is your callback might
		822	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		823	because there is no data. Not only are some backends known to create a
		824	lot of those (for example solaris ports), it is very easy to get into
		825	this situation even with a relatively standard program structure. Thus
		826	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		827	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		828
		829	If you cannot run the fd in non-blocking mode (for example you should not
		830	play around with an Xlib connection), then you have to seperately re-test
		831	wether a file descriptor is really ready with a known-to-be good interface
		832	such as poll (fortunately in our Xlib example, Xlib already does this on
		833	its own, so its quite safe to use).
428		834
429	=over 4	835	=over 4
430		836
431	=item ev_io_init (ev_io *, callback, int fd, int events)	837	=item ev_io_init (ev_io *, callback, int fd, int events)
432		838
433	=item ev_io_set (ev_io *, int fd, int events)	839	=item ev_io_set (ev_io *, int fd, int events)
434		840
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	841	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
436	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	842	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	843	C<EV_READ | EV_WRITE> to receive the given events.
		844
		845	=item int fd [read-only]
		846
		847	The file descriptor being watched.
		848
		849	=item int events [read-only]
		850
		851	The events being watched.
438		852
439	=back	853	=back
440		854
		855	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		856	readable, but only once. Since it is likely line-buffered, you could
		857	attempt to read a whole line in the callback.
		858
		859	static void
		860	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		861	{
		862	ev_io_stop (loop, w);
		863	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		864	}
		865
		866	...
		867	struct ev_loop *loop = ev_default_init (0);
		868	struct ev_io stdin_readable;
		869	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		870	ev_io_start (loop, &stdin_readable);
		871	ev_loop (loop, 0);
		872
		873
441	=head2 struct ev_timer - relative and optionally recurring timeouts	874	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		875
443	Timer watchers are simple relative timers that generate an event after a	876	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	877	given time, and optionally repeating in regular intervals after that.
445		878
446	The timers are based on real time, that is, if you register an event that	879	The timers are based on real time, that is, if you register an event that
447	times out after an hour and youreset your system clock to last years	880	times out after an hour and you reset your system clock to last years
448	time, it will still time out after (roughly) and hour. "Roughly" because	881	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	882	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	883	monotonic clock option helps a lot here).
		884
		885	The relative timeouts are calculated relative to the C<ev_now ()>
		886	time. This is usually the right thing as this timestamp refers to the time
		887	of the event triggering whatever timeout you are modifying/starting. If
		888	you suspect event processing to be delayed and you I<need> to base the timeout
		889	on the current time, use something like this to adjust for this:
		890
		891	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		892
		893	The callback is guarenteed to be invoked only when its timeout has passed,
		894	but if multiple timers become ready during the same loop iteration then
		895	order of execution is undefined.
451		896
452	=over 4	897	=over 4
453		898
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	899	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		900
…		…
461	later, again, and again, until stopped manually.	906	later, again, and again, until stopped manually.
462		907
463	The timer itself will do a best-effort at avoiding drift, that is, if you	908	The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	909	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	910	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	911	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.	912	timer will not fire more than once per event loop iteration.
468		913
469	=item ev_timer_again (loop)	914	=item ev_timer_again (loop)
470		915
471	This will act as if the timer timed out and restart it again if it is	916	This will act as if the timer timed out and restart it again if it is
…		…
475		920
476	If the timer is repeating, either start it if necessary (with the repeat	921	If the timer is repeating, either start it if necessary (with the repeat
477	value), or reset the running timer to the repeat value.	922	value), or reset the running timer to the repeat value.
478		923
479	This sounds a bit complicated, but here is a useful and typical	924	This sounds a bit complicated, but here is a useful and typical
480	example: Imagine you have a tcp connection and you want a so-called idle	925	example: Imagine you have a tcp connection and you want a so-called
481	timeout, that is, you want to be called when there have been, say, 60	926	idle timeout, that is, you want to be called when there have been,
482	seconds of inactivity on the socket. The easiest way to do this is to	927	say, 60 seconds of inactivity on the socket. The easiest way to do
483	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	928	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
484	time you successfully read or write some data. If you go into an idle	929	C<ev_timer_again> each time you successfully read or write some data. If
485	state where you do not expect data to travel on the socket, you can stop	930	you go into an idle state where you do not expect data to travel on the
486	the timer, and again will automatically restart it if need be.	931	socket, you can stop the timer, and again will automatically restart it if
		932	need be.
		933
		934	You can also ignore the C<after> value and C<ev_timer_start> altogether
		935	and only ever use the C<repeat> value:
		936
		937	ev_timer_init (timer, callback, 0., 5.);
		938	ev_timer_again (loop, timer);
		939	...
		940	timer->again = 17.;
		941	ev_timer_again (loop, timer);
		942	...
		943	timer->again = 10.;
		944	ev_timer_again (loop, timer);
		945
		946	This is more efficient then stopping/starting the timer eahc time you want
		947	to modify its timeout value.
		948
		949	=item ev_tstamp repeat [read-write]
		950
		951	The current C<repeat> value. Will be used each time the watcher times out
		952	or C<ev_timer_again> is called and determines the next timeout (if any),
		953	which is also when any modifications are taken into account.
487		954
488	=back	955	=back
489		956
		957	Example: Create a timer that fires after 60 seconds.
		958
		959	static void
		960	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		961	{
		962	.. one minute over, w is actually stopped right here
		963	}
		964
		965	struct ev_timer mytimer;
		966	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		967	ev_timer_start (loop, &mytimer);
		968
		969	Example: Create a timeout timer that times out after 10 seconds of
		970	inactivity.
		971
		972	static void
		973	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		974	{
		975	.. ten seconds without any activity
		976	}
		977
		978	struct ev_timer mytimer;
		979	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		980	ev_timer_again (&mytimer); /* start timer */
		981	ev_loop (loop, 0);
		982
		983	// and in some piece of code that gets executed on any "activity":
		984	// reset the timeout to start ticking again at 10 seconds
		985	ev_timer_again (&mytimer);
		986
		987
490	=head2 ev_periodic - to cron or not to cron it	988	=head2 C<ev_periodic> - to cron or not to cron?
491		989
492	Periodic watchers are also timers of a kind, but they are very versatile	990	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	991	(and unfortunately a bit complex).
494		992
495	Unlike ev_timer's, they are not based on real time (or relative time)	993	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
496	but on wallclock time (absolute time). You can tell a periodic watcher	994	but on wallclock time (absolute time). You can tell a periodic watcher
497	to trigger "at" some specific point in time. For example, if you tell a	995	to trigger "at" some specific point in time. For example, if you tell a
498	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	996	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
499	+ 10.>) and then reset your system clock to the last year, then it will	997	+ 10.>) and then reset your system clock to the last year, then it will
500	take a year to trigger the event (unlike an ev_timer, which would trigger	998	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
501	roughly 10 seconds later and of course not if you reset your system time	999	roughly 10 seconds later and of course not if you reset your system time
502	again).	1000	again).
503		1001
504	They can also be used to implement vastly more complex timers, such as	1002	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1003	triggering an event on eahc midnight, local time.
506		1004
		1005	As with timers, the callback is guarenteed to be invoked only when the
		1006	time (C<at>) has been passed, but if multiple periodic timers become ready
		1007	during the same loop iteration then order of execution is undefined.
		1008
507	=over 4	1009	=over 4
508		1010
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1011	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1012
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1013	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1014
513	Lots of arguments, lets sort it out... There are basically three modes of	1015	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1016	operation, and we will explain them from simplest to complex:
515
516		1017
517	=over 4	1018	=over 4
518		1019
519	=item * absolute timer (interval = reschedule_cb = 0)	1020	=item * absolute timer (interval = reschedule_cb = 0)
520		1021
…		…
534		1035
535	ev_periodic_set (&periodic, 0., 3600., 0);	1036	ev_periodic_set (&periodic, 0., 3600., 0);
536		1037
537	This doesn't mean there will always be 3600 seconds in between triggers,	1038	This doesn't mean there will always be 3600 seconds in between triggers,
538	but only that the the callback will be called when the system time shows a	1039	but only that the the callback will be called when the system time shows a
539	full hour (UTC), or more correct, when the system time is evenly divisible	1040	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1041	by 3600.
541		1042
542	Another way to think about it (for the mathematically inclined) is that	1043	Another way to think about it (for the mathematically inclined) is that
543	ev_periodic will try to run the callback in this mode at the next possible	1044	C<ev_periodic> will try to run the callback in this mode at the next possible
544	time where C<time = at (mod interval)>, regardless of any time jumps.	1045	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1046
546	=item * manual reschedule mode (reschedule_cb = callback)	1047	=item * manual reschedule mode (reschedule_cb = callback)
547		1048
548	In this mode the values for C<interval> and C<at> are both being	1049	In this mode the values for C<interval> and C<at> are both being
549	ignored. Instead, each time the periodic watcher gets scheduled, the	1050	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1051	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1052	current time as second argument.
552		1053
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1054	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
554	periodic watcher, ever, or make any event loop modificstions>. If you need	1055	ever, or make any event loop modifications>. If you need to stop it,
555	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	1056	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1057	starting a prepare watcher).
556		1058
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1059	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1060	ev_tstamp now)>, e.g.:
559		1061
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1062	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1063	{
562	return now + 60.;	1064	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1067	It must return the next time to trigger, based on the passed time value
566	(that is, the lowest time value larger than to the second argument). It	1068	(that is, the lowest time value larger than to the second argument). It
567	will usually be called just before the callback will be triggered, but	1069	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1070	might be called at other times, too.
569		1071
		1072	NOTE: I<< This callback must always return a time that is later than the
		1073	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1074
570	This can be used to create very complex timers, such as a timer that	1075	This can be used to create very complex timers, such as a timer that
571	triggers on each midnight, local time. To do this, you would calculate the	1076	triggers on each midnight, local time. To do this, you would calculate the
572	next midnight after C<now> and return the timestamp value for this. How you do this	1077	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1078	you do this is, again, up to you (but it is not trivial, which is the main
		1079	reason I omitted it as an example).
574		1080
575	=back	1081	=back
576		1082
577	=item ev_periodic_again (loop, ev_periodic *)	1083	=item ev_periodic_again (loop, ev_periodic *)
578		1084
579	Simply stops and restarts the periodic watcher again. This is only useful	1085	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1086	when you changed some parameters or the reschedule callback would return
581	a different time than the last time it was called (e.g. in a crond like	1087	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1088	program when the crontabs have changed).
583		1089
		1090	=item ev_tstamp interval [read-write]
		1091
		1092	The current interval value. Can be modified any time, but changes only
		1093	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1094	called.
		1095
		1096	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1097
		1098	The current reschedule callback, or C<0>, if this functionality is
		1099	switched off. Can be changed any time, but changes only take effect when
		1100	the periodic timer fires or C<ev_periodic_again> is being called.
		1101
584	=back	1102	=back
585		1103
		1104	Example: Call a callback every hour, or, more precisely, whenever the
		1105	system clock is divisible by 3600. The callback invocation times have
		1106	potentially a lot of jittering, but good long-term stability.
		1107
		1108	static void
		1109	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1110	{
		1111	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1112	}
		1113
		1114	struct ev_periodic hourly_tick;
		1115	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1116	ev_periodic_start (loop, &hourly_tick);
		1117
		1118	Example: The same as above, but use a reschedule callback to do it:
		1119
		1120	#include <math.h>
		1121
		1122	static ev_tstamp
		1123	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1124	{
		1125	return fmod (now, 3600.) + 3600.;
		1126	}
		1127
		1128	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1129
		1130	Example: Call a callback every hour, starting now:
		1131
		1132	struct ev_periodic hourly_tick;
		1133	ev_periodic_init (&hourly_tick, clock_cb,
		1134	fmod (ev_now (loop), 3600.), 3600., 0);
		1135	ev_periodic_start (loop, &hourly_tick);
		1136
		1137
586	=head2 ev_signal - signal me when a signal gets signalled	1138	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1139
588	Signal watchers will trigger an event when the process receives a specific	1140	Signal watchers will trigger an event when the process receives a specific
589	signal one or more times. Even though signals are very asynchronous, libev	1141	signal one or more times. Even though signals are very asynchronous, libev
590	will try its best to deliver signals synchronously, i.e. as part of the	1142	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1143	normal event processing, like any other event.
592		1144
593	You cna configure as many watchers as you like per signal. Only when the	1145	You can configure as many watchers as you like per signal. Only when the
594	first watcher gets started will libev actually register a signal watcher	1146	first watcher gets started will libev actually register a signal watcher
595	with the kernel (thus it coexists with your own signal handlers as long	1147	with the kernel (thus it coexists with your own signal handlers as long
596	as you don't register any with libev). Similarly, when the last signal	1148	as you don't register any with libev). Similarly, when the last signal
597	watcher for a signal is stopped libev will reset the signal handler to	1149	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1150	SIG_DFL (regardless of what it was set to before).
…		…
604	=item ev_signal_set (ev_signal *, int signum)	1156	=item ev_signal_set (ev_signal *, int signum)
605		1157
606	Configures the watcher to trigger on the given signal number (usually one	1158	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1159	of the C<SIGxxx> constants).
608		1160
		1161	=item int signum [read-only]
		1162
		1163	The signal the watcher watches out for.
		1164
609	=back	1165	=back
610		1166
		1167
611	=head2 ev_child - wait for pid status changes	1168	=head2 C<ev_child> - watch out for process status changes
612		1169
613	Child watchers trigger when your process receives a SIGCHLD in response to	1170	Child watchers trigger when your process receives a SIGCHLD in response to
614	some child status changes (most typically when a child of yours dies).	1171	some child status changes (most typically when a child of yours dies).
615		1172
616	=over 4	1173	=over 4
…		…
620	=item ev_child_set (ev_child *, int pid)	1177	=item ev_child_set (ev_child *, int pid)
621		1178
622	Configures the watcher to wait for status changes of process C<pid> (or	1179	Configures the watcher to wait for status changes of process C<pid> (or
623	I<any> process if C<pid> is specified as C<0>). The callback can look	1180	I<any> process if C<pid> is specified as C<0>). The callback can look
624	at the C<rstatus> member of the C<ev_child> watcher structure to see	1181	at the C<rstatus> member of the C<ev_child> watcher structure to see
625	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1182	the status word (use the macros from C<sys/wait.h> and see your systems
626	contains the pid of the process causing the status change.	1183	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1184	process causing the status change.
		1185
		1186	=item int pid [read-only]
		1187
		1188	The process id this watcher watches out for, or C<0>, meaning any process id.
		1189
		1190	=item int rpid [read-write]
		1191
		1192	The process id that detected a status change.
		1193
		1194	=item int rstatus [read-write]
		1195
		1196	The process exit/trace status caused by C<rpid> (see your systems
		1197	C<waitpid> and C<sys/wait.h> documentation for details).
627		1198
628	=back	1199	=back
629		1200
		1201	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1202
		1203	static void
		1204	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1205	{
		1206	ev_unloop (loop, EVUNLOOP_ALL);
		1207	}
		1208
		1209	struct ev_signal signal_watcher;
		1210	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1211	ev_signal_start (loop, &sigint_cb);
		1212
		1213
		1214	=head2 C<ev_stat> - did the file attributes just change?
		1215
		1216	This watches a filesystem path for attribute changes. That is, it calls
		1217	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1218	compared to the last time, invoking the callback if it did.
		1219
		1220	The path does not need to exist: changing from "path exists" to "path does
		1221	not exist" is a status change like any other. The condition "path does
		1222	not exist" is signified by the C<st_nlink> field being zero (which is
		1223	otherwise always forced to be at least one) and all the other fields of
		1224	the stat buffer having unspecified contents.
		1225
		1226	Since there is no standard to do this, the portable implementation simply
		1227	calls C<stat (2)> regulalry on the path to see if it changed somehow. You
		1228	can specify a recommended polling interval for this case. If you specify
		1229	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1230	unspecified default> value will be used (which you can expect to be around
		1231	five seconds, although this might change dynamically). Libev will also
		1232	impose a minimum interval which is currently around C<0.1>, but thats
		1233	usually overkill.
		1234
		1235	This watcher type is not meant for massive numbers of stat watchers,
		1236	as even with OS-supported change notifications, this can be
		1237	resource-intensive.
		1238
		1239	At the time of this writing, no specific OS backends are implemented, but
		1240	if demand increases, at least a kqueue and inotify backend will be added.
		1241
		1242	=over 4
		1243
		1244	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1245
		1246	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1247
		1248	Configures the watcher to wait for status changes of the given
		1249	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1250	be detected and should normally be specified as C<0> to let libev choose
		1251	a suitable value. The memory pointed to by C<path> must point to the same
		1252	path for as long as the watcher is active.
		1253
		1254	The callback will be receive C<EV_STAT> when a change was detected,
		1255	relative to the attributes at the time the watcher was started (or the
		1256	last change was detected).
		1257
		1258	=item ev_stat_stat (ev_stat *)
		1259
		1260	Updates the stat buffer immediately with new values. If you change the
		1261	watched path in your callback, you could call this fucntion to avoid
		1262	detecting this change (while introducing a race condition). Can also be
		1263	useful simply to find out the new values.
		1264
		1265	=item ev_statdata attr [read-only]
		1266
		1267	The most-recently detected attributes of the file. Although the type is of
		1268	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1269	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1270	was some error while C<stat>ing the file.
		1271
		1272	=item ev_statdata prev [read-only]
		1273
		1274	The previous attributes of the file. The callback gets invoked whenever
		1275	C<prev> != C<attr>.
		1276
		1277	=item ev_tstamp interval [read-only]
		1278
		1279	The specified interval.
		1280
		1281	=item const char *path [read-only]
		1282
		1283	The filesystem path that is being watched.
		1284
		1285	=back
		1286
		1287	Example: Watch C</etc/passwd> for attribute changes.
		1288
		1289	static void
		1290	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1291	{
		1292	/* /etc/passwd changed in some way */
		1293	if (w->attr.st_nlink)
		1294	{
		1295	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1296	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1297	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1298	}
		1299	else
		1300	/* you shalt not abuse printf for puts */
		1301	puts ("wow, /etc/passwd is not there, expect problems. "
		1302	"if this is windows, they already arrived\n");
		1303	}
		1304
		1305	...
		1306	ev_stat passwd;
		1307
		1308	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1309	ev_stat_start (loop, &passwd);
		1310
		1311
630	=head2 ev_idle - when you've got nothing better to do	1312	=head2 C<ev_idle> - when you've got nothing better to do...
631		1313
632	Idle watchers trigger events when there are no other I/O or timer (or	1314	Idle watchers trigger events when there are no other events are pending
633	periodic) events pending. That is, as long as your process is busy	1315	(prepare, check and other idle watchers do not count). That is, as long
634	handling sockets or timeouts it will not be called. But when your process	1316	as your process is busy handling sockets or timeouts (or even signals,
635	is idle all idle watchers are being called again and again - until	1317	imagine) it will not be triggered. But when your process is idle all idle
		1318	watchers are being called again and again, once per event loop iteration -
636	stopped, that is, or your process receives more events.	1319	until stopped, that is, or your process receives more events and becomes
		1320	busy.
637		1321
638	The most noteworthy effect is that as long as any idle watchers are	1322	The most noteworthy effect is that as long as any idle watchers are
639	active, the process will not block when waiting for new events.	1323	active, the process will not block when waiting for new events.
640		1324
641	Apart from keeping your process non-blocking (which is a useful	1325	Apart from keeping your process non-blocking (which is a useful
…		…
651	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1335	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1336	believe me.
653		1337
654	=back	1338	=back
655		1339
656	=head2 prepare and check - your hooks into the event loop	1340	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1341	callback, free it. Also, use no error checking, as usual.
657		1342
		1343	static void
		1344	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1345	{
		1346	free (w);
		1347	// now do something you wanted to do when the program has
		1348	// no longer asnything immediate to do.
		1349	}
		1350
		1351	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1352	ev_idle_init (idle_watcher, idle_cb);
		1353	ev_idle_start (loop, idle_cb);
		1354
		1355
		1356	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1357
658	Prepare and check watchers usually (but not always) are used in	1358	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1359	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1360	afterwards.
661		1361
		1362	You I<must not> call C<ev_loop> or similar functions that enter
		1363	the current event loop from either C<ev_prepare> or C<ev_check>
		1364	watchers. Other loops than the current one are fine, however. The
		1365	rationale behind this is that you do not need to check for recursion in
		1366	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1367	C<ev_check> so if you have one watcher of each kind they will always be
		1368	called in pairs bracketing the blocking call.
		1369
662	Their main purpose is to integrate other event mechanisms into libev. This	1370	Their main purpose is to integrate other event mechanisms into libev and
663	could be used, for example, to track variable changes, implement your own	1371	their use is somewhat advanced. This could be used, for example, to track
664	watchers, integrate net-snmp or a coroutine library and lots more.	1372	variable changes, implement your own watchers, integrate net-snmp or a
		1373	coroutine library and lots more. They are also occasionally useful if
		1374	you cache some data and want to flush it before blocking (for example,
		1375	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1376	watcher).
665		1377
666	This is done by examining in each prepare call which file descriptors need	1378	This is done by examining in each prepare call which file descriptors need
667	to be watched by the other library, registering ev_io watchers for them	1379	to be watched by the other library, registering C<ev_io> watchers for
668	and starting an ev_timer watcher for any timeouts (many libraries provide	1380	them and starting an C<ev_timer> watcher for any timeouts (many libraries
669	just this functionality). Then, in the check watcher you check for any	1381	provide just this functionality). Then, in the check watcher you check for
670	events that occured (by making your callbacks set soem flags for example)	1382	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1383	and stopping them) and call back into the library. The I/O and timer
		1384	callbacks will never actually be called (but must be valid nevertheless,
		1385	because you never know, you know?).
672		1386
673	As another example, the perl Coro module uses these hooks to integrate	1387	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1388	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1389	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1390	are ready to run (it's actually more complicated: it only runs coroutines
		1391	with priority higher than or equal to the event loop and one coroutine
		1392	of lower priority, but only once, using idle watchers to keep the event
		1393	loop from blocking if lower-priority coroutines are active, thus mapping
		1394	low-priority coroutines to idle/background tasks).
677		1395
678	=over 4	1396	=over 4
679		1397
680	=item ev_prepare_init (ev_prepare *, callback)	1398	=item ev_prepare_init (ev_prepare *, callback)
681		1399
682	=item ev_check_init (ev_check *, callback)	1400	=item ev_check_init (ev_check *, callback)
683		1401
684	Initialises and configures the prepare or check watcher - they have no	1402	Initialises and configures the prepare or check watcher - they have no
685	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1403	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1404	macros, but using them is utterly, utterly and completely pointless.
687		1405
688	=back	1406	=back
689		1407
		1408	Example: To include a library such as adns, you would add IO watchers
		1409	and a timeout watcher in a prepare handler, as required by libadns, and
		1410	in a check watcher, destroy them and call into libadns. What follows is
		1411	pseudo-code only of course:
		1412
		1413	static ev_io iow [nfd];
		1414	static ev_timer tw;
		1415
		1416	static void
		1417	io_cb (ev_loop *loop, ev_io *w, int revents)
		1418	{
		1419	// set the relevant poll flags
		1420	// could also call adns_processreadable etc. here
		1421	struct pollfd *fd = (struct pollfd *)w->data;
		1422	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1423	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1424	}
		1425
		1426	// create io watchers for each fd and a timer before blocking
		1427	static void
		1428	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1429	{
		1430	int timeout = 3600000;truct pollfd fds [nfd];
		1431	// actual code will need to loop here and realloc etc.
		1432	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1433
		1434	/* the callback is illegal, but won't be called as we stop during check */
		1435	ev_timer_init (&tw, 0, timeout * 1e-3);
		1436	ev_timer_start (loop, &tw);
		1437
		1438	// create on ev_io per pollfd
		1439	for (int i = 0; i < nfd; ++i)
		1440	{
		1441	ev_io_init (iow + i, io_cb, fds [i].fd,
		1442	((fds [i].events & POLLIN ? EV_READ : 0)
		1443	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1444
		1445	fds [i].revents = 0;
		1446	iow [i].data = fds + i;
		1447	ev_io_start (loop, iow + i);
		1448	}
		1449	}
		1450
		1451	// stop all watchers after blocking
		1452	static void
		1453	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1454	{
		1455	ev_timer_stop (loop, &tw);
		1456
		1457	for (int i = 0; i < nfd; ++i)
		1458	ev_io_stop (loop, iow + i);
		1459
		1460	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1461	}
		1462
		1463
		1464	=head2 C<ev_embed> - when one backend isn't enough...
		1465
		1466	This is a rather advanced watcher type that lets you embed one event loop
		1467	into another (currently only C<ev_io> events are supported in the embedded
		1468	loop, other types of watchers might be handled in a delayed or incorrect
		1469	fashion and must not be used).
		1470
		1471	There are primarily two reasons you would want that: work around bugs and
		1472	prioritise I/O.
		1473
		1474	As an example for a bug workaround, the kqueue backend might only support
		1475	sockets on some platform, so it is unusable as generic backend, but you
		1476	still want to make use of it because you have many sockets and it scales
		1477	so nicely. In this case, you would create a kqueue-based loop and embed it
		1478	into your default loop (which might use e.g. poll). Overall operation will
		1479	be a bit slower because first libev has to poll and then call kevent, but
		1480	at least you can use both at what they are best.
		1481
		1482	As for prioritising I/O: rarely you have the case where some fds have
		1483	to be watched and handled very quickly (with low latency), and even
		1484	priorities and idle watchers might have too much overhead. In this case
		1485	you would put all the high priority stuff in one loop and all the rest in
		1486	a second one, and embed the second one in the first.
		1487
		1488	As long as the watcher is active, the callback will be invoked every time
		1489	there might be events pending in the embedded loop. The callback must then
		1490	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1491	their callbacks (you could also start an idle watcher to give the embedded
		1492	loop strictly lower priority for example). You can also set the callback
		1493	to C<0>, in which case the embed watcher will automatically execute the
		1494	embedded loop sweep.
		1495
		1496	As long as the watcher is started it will automatically handle events. The
		1497	callback will be invoked whenever some events have been handled. You can
		1498	set the callback to C<0> to avoid having to specify one if you are not
		1499	interested in that.
		1500
		1501	Also, there have not currently been made special provisions for forking:
		1502	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1503	but you will also have to stop and restart any C<ev_embed> watchers
		1504	yourself.
		1505
		1506	Unfortunately, not all backends are embeddable, only the ones returned by
		1507	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1508	portable one.
		1509
		1510	So when you want to use this feature you will always have to be prepared
		1511	that you cannot get an embeddable loop. The recommended way to get around
		1512	this is to have a separate variables for your embeddable loop, try to
		1513	create it, and if that fails, use the normal loop for everything:
		1514
		1515	struct ev_loop *loop_hi = ev_default_init (0);
		1516	struct ev_loop *loop_lo = 0;
		1517	struct ev_embed embed;
		1518
		1519	// see if there is a chance of getting one that works
		1520	// (remember that a flags value of 0 means autodetection)
		1521	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1522	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1523	: 0;
		1524
		1525	// if we got one, then embed it, otherwise default to loop_hi
		1526	if (loop_lo)
		1527	{
		1528	ev_embed_init (&embed, 0, loop_lo);
		1529	ev_embed_start (loop_hi, &embed);
		1530	}
		1531	else
		1532	loop_lo = loop_hi;
		1533
		1534	=over 4
		1535
		1536	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1537
		1538	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1539
		1540	Configures the watcher to embed the given loop, which must be
		1541	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1542	invoked automatically, otherwise it is the responsibility of the callback
		1543	to invoke it (it will continue to be called until the sweep has been done,
		1544	if you do not want thta, you need to temporarily stop the embed watcher).
		1545
		1546	=item ev_embed_sweep (loop, ev_embed *)
		1547
		1548	Make a single, non-blocking sweep over the embedded loop. This works
		1549	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1550	apropriate way for embedded loops.
		1551
		1552	=item struct ev_loop *loop [read-only]
		1553
		1554	The embedded event loop.
		1555
		1556	=back
		1557
		1558
		1559	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1560
		1561	Fork watchers are called when a C<fork ()> was detected (usually because
		1562	whoever is a good citizen cared to tell libev about it by calling
		1563	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1564	event loop blocks next and before C<ev_check> watchers are being called,
		1565	and only in the child after the fork. If whoever good citizen calling
		1566	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1567	handlers will be invoked, too, of course.
		1568
		1569	=over 4
		1570
		1571	=item ev_fork_init (ev_signal *, callback)
		1572
		1573	Initialises and configures the fork watcher - it has no parameters of any
		1574	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1575	believe me.
		1576
		1577	=back
		1578
		1579
690	=head1 OTHER FUNCTIONS	1580	=head1 OTHER FUNCTIONS
691		1581
692	There are some other fucntions of possible interest. Described. Here. Now.	1582	There are some other functions of possible interest. Described. Here. Now.
693		1583
694	=over 4	1584	=over 4
695		1585
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1586	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		1587
698	This function combines a simple timer and an I/O watcher, calls your	1588	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	1589	callback on whichever event happens first and automatically stop both
700	watchers. This is useful if you want to wait for a single event on an fd	1590	watchers. This is useful if you want to wait for a single event on an fd
701	or timeout without havign to allocate/configure/start/stop/free one or	1591	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	1592	more watchers yourself.
703		1593
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	1594	If C<fd> is less than 0, then no I/O watcher will be started and events
705	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1595	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	1596	C<events> set will be craeted and started.
707		1597
708	If C<timeout> is less than 0, then no timeout watcher will be	1598	If C<timeout> is less than 0, then no timeout watcher will be
709	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1599	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	1600	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1601	dubious value.
711		1602
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	1603	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
713	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1604	passed an C<revents> set like normal event callbacks (a combination of
714	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1605	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1606	value passed to C<ev_once>:
715		1607
716	static void stdin_ready (int revents, void *arg)	1608	static void stdin_ready (int revents, void *arg)
717	{	1609	{
718	if (revents & EV_TIMEOUT)	1610	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	1611	/* doh, nothing entered */;
720	else if (revents & EV_READ)	1612	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	1613	/* stdin might have data for us, joy! */;
722	}	1614	}
723		1615
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1616	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		1617
726	=item ev_feed_event (loop, watcher, int events)	1618	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		1619
728	Feeds the given event set into the event loop, as if the specified event	1620	Feeds the given event set into the event loop, as if the specified event
729	has happened for the specified watcher (which must be a pointer to an	1621	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	1622	initialised but not necessarily started event watcher).
731		1623
732	=item ev_feed_fd_event (loop, int fd, int revents)	1624	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		1625
734	Feed an event on the given fd, as if a file descriptor backend detected it.	1626	Feed an event on the given fd, as if a file descriptor backend detected
		1627	the given events it.
735		1628
736	=item ev_feed_signal_event (loop, int signum)	1629	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		1630
738	Feed an event as if the given signal occured (loop must be the default loop!).	1631	Feed an event as if the given signal occured (C<loop> must be the default
		1632	loop!).
739		1633
740	=back	1634	=back
741		1635
		1636
		1637	=head1 LIBEVENT EMULATION
		1638
		1639	Libev offers a compatibility emulation layer for libevent. It cannot
		1640	emulate the internals of libevent, so here are some usage hints:
		1641
		1642	=over 4
		1643
		1644	=item * Use it by including <event.h>, as usual.
		1645
		1646	=item * The following members are fully supported: ev_base, ev_callback,
		1647	ev_arg, ev_fd, ev_res, ev_events.
		1648
		1649	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1650	maintained by libev, it does not work exactly the same way as in libevent (consider
		1651	it a private API).
		1652
		1653	=item * Priorities are not currently supported. Initialising priorities
		1654	will fail and all watchers will have the same priority, even though there
		1655	is an ev_pri field.
		1656
		1657	=item * Other members are not supported.
		1658
		1659	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1660	to use the libev header file and library.
		1661
		1662	=back
		1663
		1664	=head1 C++ SUPPORT
		1665
		1666	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1667	you to use some convinience methods to start/stop watchers and also change
		1668	the callback model to a model using method callbacks on objects.
		1669
		1670	To use it,
		1671
		1672	#include <ev++.h>
		1673
		1674	(it is not installed by default). This automatically includes F<ev.h>
		1675	and puts all of its definitions (many of them macros) into the global
		1676	namespace. All C++ specific things are put into the C<ev> namespace.
		1677
		1678	It should support all the same embedding options as F<ev.h>, most notably
		1679	C<EV_MULTIPLICITY>.
		1680
		1681	Here is a list of things available in the C<ev> namespace:
		1682
		1683	=over 4
		1684
		1685	=item C<ev::READ>, C<ev::WRITE> etc.
		1686
		1687	These are just enum values with the same values as the C<EV_READ> etc.
		1688	macros from F<ev.h>.
		1689
		1690	=item C<ev::tstamp>, C<ev::now>
		1691
		1692	Aliases to the same types/functions as with the C<ev_> prefix.
		1693
		1694	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1695
		1696	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1697	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1698	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1699	defines by many implementations.
		1700
		1701	All of those classes have these methods:
		1702
		1703	=over 4
		1704
		1705	=item ev::TYPE::TYPE (object *, object::method *)
		1706
		1707	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1708
		1709	=item ev::TYPE::~TYPE
		1710
		1711	The constructor takes a pointer to an object and a method pointer to
		1712	the event handler callback to call in this class. The constructor calls
		1713	C<ev_init> for you, which means you have to call the C<set> method
		1714	before starting it. If you do not specify a loop then the constructor
		1715	automatically associates the default loop with this watcher.
		1716
		1717	The destructor automatically stops the watcher if it is active.
		1718
		1719	=item w->set (struct ev_loop *)
		1720
		1721	Associates a different C<struct ev_loop> with this watcher. You can only
		1722	do this when the watcher is inactive (and not pending either).
		1723
		1724	=item w->set ([args])
		1725
		1726	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1727	called at least once. Unlike the C counterpart, an active watcher gets
		1728	automatically stopped and restarted.
		1729
		1730	=item w->start ()
		1731
		1732	Starts the watcher. Note that there is no C<loop> argument as the
		1733	constructor already takes the loop.
		1734
		1735	=item w->stop ()
		1736
		1737	Stops the watcher if it is active. Again, no C<loop> argument.
		1738
		1739	=item w->again () C<ev::timer>, C<ev::periodic> only
		1740
		1741	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1742	C<ev_TYPE_again> function.
		1743
		1744	=item w->sweep () C<ev::embed> only
		1745
		1746	Invokes C<ev_embed_sweep>.
		1747
		1748	=item w->update () C<ev::stat> only
		1749
		1750	Invokes C<ev_stat_stat>.
		1751
		1752	=back
		1753
		1754	=back
		1755
		1756	Example: Define a class with an IO and idle watcher, start one of them in
		1757	the constructor.
		1758
		1759	class myclass
		1760	{
		1761	ev_io io; void io_cb (ev::io &w, int revents);
		1762	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1763
		1764	myclass ();
		1765	}
		1766
		1767	myclass::myclass (int fd)
		1768	: io (this, &myclass::io_cb),
		1769	idle (this, &myclass::idle_cb)
		1770	{
		1771	io.start (fd, ev::READ);
		1772	}
		1773
		1774
		1775	=head1 MACRO MAGIC
		1776
		1777	Libev can be compiled with a variety of options, the most fundemantal is
		1778	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1779	callbacks have an initial C<struct ev_loop *> argument.
		1780
		1781	To make it easier to write programs that cope with either variant, the
		1782	following macros are defined:
		1783
		1784	=over 4
		1785
		1786	=item C<EV_A>, C<EV_A_>
		1787
		1788	This provides the loop I<argument> for functions, if one is required ("ev
		1789	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1790	C<EV_A_> is used when other arguments are following. Example:
		1791
		1792	ev_unref (EV_A);
		1793	ev_timer_add (EV_A_ watcher);
		1794	ev_loop (EV_A_ 0);
		1795
		1796	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1797	which is often provided by the following macro.
		1798
		1799	=item C<EV_P>, C<EV_P_>
		1800
		1801	This provides the loop I<parameter> for functions, if one is required ("ev
		1802	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1803	C<EV_P_> is used when other parameters are following. Example:
		1804
		1805	// this is how ev_unref is being declared
		1806	static void ev_unref (EV_P);
		1807
		1808	// this is how you can declare your typical callback
		1809	static void cb (EV_P_ ev_timer *w, int revents)
		1810
		1811	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1812	suitable for use with C<EV_A>.
		1813
		1814	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1815
		1816	Similar to the other two macros, this gives you the value of the default
		1817	loop, if multiple loops are supported ("ev loop default").
		1818
		1819	=back
		1820
		1821	Example: Declare and initialise a check watcher, working regardless of
		1822	wether multiple loops are supported or not.
		1823
		1824	static void
		1825	check_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_check_stop (EV_A_ w);
		1828	}
		1829
		1830	ev_check check;
		1831	ev_check_init (&check, check_cb);
		1832	ev_check_start (EV_DEFAULT_ &check);
		1833	ev_loop (EV_DEFAULT_ 0);
		1834
		1835
		1836	=head1 EMBEDDING
		1837
		1838	Libev can (and often is) directly embedded into host
		1839	applications. Examples of applications that embed it include the Deliantra
		1840	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1841	and rxvt-unicode.
		1842
		1843	The goal is to enable you to just copy the neecssary files into your
		1844	source directory without having to change even a single line in them, so
		1845	you can easily upgrade by simply copying (or having a checked-out copy of
		1846	libev somewhere in your source tree).
		1847
		1848	=head2 FILESETS
		1849
		1850	Depending on what features you need you need to include one or more sets of files
		1851	in your app.
		1852
		1853	=head3 CORE EVENT LOOP
		1854
		1855	To include only the libev core (all the C<ev_*> functions), with manual
		1856	configuration (no autoconf):
		1857
		1858	#define EV_STANDALONE 1
		1859	#include "ev.c"
		1860
		1861	This will automatically include F<ev.h>, too, and should be done in a
		1862	single C source file only to provide the function implementations. To use
		1863	it, do the same for F<ev.h> in all files wishing to use this API (best
		1864	done by writing a wrapper around F<ev.h> that you can include instead and
		1865	where you can put other configuration options):
		1866
		1867	#define EV_STANDALONE 1
		1868	#include "ev.h"
		1869
		1870	Both header files and implementation files can be compiled with a C++
		1871	compiler (at least, thats a stated goal, and breakage will be treated
		1872	as a bug).
		1873
		1874	You need the following files in your source tree, or in a directory
		1875	in your include path (e.g. in libev/ when using -Ilibev):
		1876
		1877	ev.h
		1878	ev.c
		1879	ev_vars.h
		1880	ev_wrap.h
		1881
		1882	ev_win32.c required on win32 platforms only
		1883
		1884	ev_select.c only when select backend is enabled (which is by default)
		1885	ev_poll.c only when poll backend is enabled (disabled by default)
		1886	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1887	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1888	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1889
		1890	F<ev.c> includes the backend files directly when enabled, so you only need
		1891	to compile this single file.
		1892
		1893	=head3 LIBEVENT COMPATIBILITY API
		1894
		1895	To include the libevent compatibility API, also include:
		1896
		1897	#include "event.c"
		1898
		1899	in the file including F<ev.c>, and:
		1900
		1901	#include "event.h"
		1902
		1903	in the files that want to use the libevent API. This also includes F<ev.h>.
		1904
		1905	You need the following additional files for this:
		1906
		1907	event.h
		1908	event.c
		1909
		1910	=head3 AUTOCONF SUPPORT
		1911
		1912	Instead of using C<EV_STANDALONE=1> and providing your config in
		1913	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1914	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1915	include F<config.h> and configure itself accordingly.
		1916
		1917	For this of course you need the m4 file:
		1918
		1919	libev.m4
		1920
		1921	=head2 PREPROCESSOR SYMBOLS/MACROS
		1922
		1923	Libev can be configured via a variety of preprocessor symbols you have to define
		1924	before including any of its files. The default is not to build for multiplicity
		1925	and only include the select backend.
		1926
		1927	=over 4
		1928
		1929	=item EV_STANDALONE
		1930
		1931	Must always be C<1> if you do not use autoconf configuration, which
		1932	keeps libev from including F<config.h>, and it also defines dummy
		1933	implementations for some libevent functions (such as logging, which is not
		1934	supported). It will also not define any of the structs usually found in
		1935	F<event.h> that are not directly supported by the libev core alone.
		1936
		1937	=item EV_USE_MONOTONIC
		1938
		1939	If defined to be C<1>, libev will try to detect the availability of the
		1940	monotonic clock option at both compiletime and runtime. Otherwise no use
		1941	of the monotonic clock option will be attempted. If you enable this, you
		1942	usually have to link against librt or something similar. Enabling it when
		1943	the functionality isn't available is safe, though, althoguh you have
		1944	to make sure you link against any libraries where the C<clock_gettime>
		1945	function is hiding in (often F<-lrt>).
		1946
		1947	=item EV_USE_REALTIME
		1948
		1949	If defined to be C<1>, libev will try to detect the availability of the
		1950	realtime clock option at compiletime (and assume its availability at
		1951	runtime if successful). Otherwise no use of the realtime clock option will
		1952	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1953	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1954	in the description of C<EV_USE_MONOTONIC>, though.
		1955
		1956	=item EV_USE_SELECT
		1957
		1958	If undefined or defined to be C<1>, libev will compile in support for the
		1959	C<select>(2) backend. No attempt at autodetection will be done: if no
		1960	other method takes over, select will be it. Otherwise the select backend
		1961	will not be compiled in.
		1962
		1963	=item EV_SELECT_USE_FD_SET
		1964
		1965	If defined to C<1>, then the select backend will use the system C<fd_set>
		1966	structure. This is useful if libev doesn't compile due to a missing
		1967	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1968	exotic systems. This usually limits the range of file descriptors to some
		1969	low limit such as 1024 or might have other limitations (winsocket only
		1970	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1971	influence the size of the C<fd_set> used.
		1972
		1973	=item EV_SELECT_IS_WINSOCKET
		1974
		1975	When defined to C<1>, the select backend will assume that
		1976	select/socket/connect etc. don't understand file descriptors but
		1977	wants osf handles on win32 (this is the case when the select to
		1978	be used is the winsock select). This means that it will call
		1979	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1980	it is assumed that all these functions actually work on fds, even
		1981	on win32. Should not be defined on non-win32 platforms.
		1982
		1983	=item EV_USE_POLL
		1984
		1985	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1986	backend. Otherwise it will be enabled on non-win32 platforms. It
		1987	takes precedence over select.
		1988
		1989	=item EV_USE_EPOLL
		1990
		1991	If defined to be C<1>, libev will compile in support for the Linux
		1992	C<epoll>(7) backend. Its availability will be detected at runtime,
		1993	otherwise another method will be used as fallback. This is the
		1994	preferred backend for GNU/Linux systems.
		1995
		1996	=item EV_USE_KQUEUE
		1997
		1998	If defined to be C<1>, libev will compile in support for the BSD style
		1999	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2000	otherwise another method will be used as fallback. This is the preferred
		2001	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2002	supports some types of fds correctly (the only platform we found that
		2003	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2004	not be used unless explicitly requested. The best way to use it is to find
		2005	out whether kqueue supports your type of fd properly and use an embedded
		2006	kqueue loop.
		2007
		2008	=item EV_USE_PORT
		2009
		2010	If defined to be C<1>, libev will compile in support for the Solaris
		2011	10 port style backend. Its availability will be detected at runtime,
		2012	otherwise another method will be used as fallback. This is the preferred
		2013	backend for Solaris 10 systems.
		2014
		2015	=item EV_USE_DEVPOLL
		2016
		2017	reserved for future expansion, works like the USE symbols above.
		2018
		2019	=item EV_USE_INOTIFY
		2020
		2021	If defined to be C<1>, libev will compile in support for the Linux inotify
		2022	interface to speed up C<ev_stat> watchers. Its actual availability will
		2023	be detected at runtime.
		2024
		2025	=item EV_H
		2026
		2027	The name of the F<ev.h> header file used to include it. The default if
		2028	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2029	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2030
		2031	=item EV_CONFIG_H
		2032
		2033	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2034	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2035	C<EV_H>, above.
		2036
		2037	=item EV_EVENT_H
		2038
		2039	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2040	of how the F<event.h> header can be found.
		2041
		2042	=item EV_PROTOTYPES
		2043
		2044	If defined to be C<0>, then F<ev.h> will not define any function
		2045	prototypes, but still define all the structs and other symbols. This is
		2046	occasionally useful if you want to provide your own wrapper functions
		2047	around libev functions.
		2048
		2049	=item EV_MULTIPLICITY
		2050
		2051	If undefined or defined to C<1>, then all event-loop-specific functions
		2052	will have the C<struct ev_loop *> as first argument, and you can create
		2053	additional independent event loops. Otherwise there will be no support
		2054	for multiple event loops and there is no first event loop pointer
		2055	argument. Instead, all functions act on the single default loop.
		2056
		2057	=item EV_PERIODIC_ENABLE
		2058
		2059	If undefined or defined to be C<1>, then periodic timers are supported. If
		2060	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2061	code.
		2062
		2063	=item EV_EMBED_ENABLE
		2064
		2065	If undefined or defined to be C<1>, then embed watchers are supported. If
		2066	defined to be C<0>, then they are not.
		2067
		2068	=item EV_STAT_ENABLE
		2069
		2070	If undefined or defined to be C<1>, then stat watchers are supported. If
		2071	defined to be C<0>, then they are not.
		2072
		2073	=item EV_FORK_ENABLE
		2074
		2075	If undefined or defined to be C<1>, then fork watchers are supported. If
		2076	defined to be C<0>, then they are not.
		2077
		2078	=item EV_MINIMAL
		2079
		2080	If you need to shave off some kilobytes of code at the expense of some
		2081	speed, define this symbol to C<1>. Currently only used for gcc to override
		2082	some inlining decisions, saves roughly 30% codesize of amd64.
		2083
		2084	=item EV_PID_HASHSIZE
		2085
		2086	C<ev_child> watchers use a small hash table to distribute workload by
		2087	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2088	than enough. If you need to manage thousands of children you might want to
		2089	increase this value (I<must> be a power of two).
		2090
		2091	=item EV_INOTIFY_HASHSIZE
		2092
		2093	C<ev_staz> watchers use a small hash table to distribute workload by
		2094	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2095	usually more than enough. If you need to manage thousands of C<ev_stat>
		2096	watchers you might want to increase this value (I<must> be a power of
		2097	two).
		2098
		2099	=item EV_COMMON
		2100
		2101	By default, all watchers have a C<void *data> member. By redefining
		2102	this macro to a something else you can include more and other types of
		2103	members. You have to define it each time you include one of the files,
		2104	though, and it must be identical each time.
		2105
		2106	For example, the perl EV module uses something like this:
		2107
		2108	#define EV_COMMON \
		2109	SV *self; /* contains this struct */ \
		2110	SV *cb_sv, *fh /* note no trailing ";" */
		2111
		2112	=item EV_CB_DECLARE (type)
		2113
		2114	=item EV_CB_INVOKE (watcher, revents)
		2115
		2116	=item ev_set_cb (ev, cb)
		2117
		2118	Can be used to change the callback member declaration in each watcher,
		2119	and the way callbacks are invoked and set. Must expand to a struct member
		2120	definition and a statement, respectively. See the F<ev.v> header file for
		2121	their default definitions. One possible use for overriding these is to
		2122	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2123	method calls instead of plain function calls in C++.
		2124
		2125	=head2 EXAMPLES
		2126
		2127	For a real-world example of a program the includes libev
		2128	verbatim, you can have a look at the EV perl module
		2129	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2130	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2131	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2132	will be compiled. It is pretty complex because it provides its own header
		2133	file.
		2134
		2135	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2136	that everybody includes and which overrides some autoconf choices:
		2137
		2138	#define EV_USE_POLL 0
		2139	#define EV_MULTIPLICITY 0
		2140	#define EV_PERIODICS 0
		2141	#define EV_CONFIG_H <config.h>
		2142
		2143	#include "ev++.h"
		2144
		2145	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2146
		2147	#include "ev_cpp.h"
		2148	#include "ev.c"
		2149
		2150
		2151	=head1 COMPLEXITIES
		2152
		2153	In this section the complexities of (many of) the algorithms used inside
		2154	libev will be explained. For complexity discussions about backends see the
		2155	documentation for C<ev_default_init>.
		2156
		2157	=over 4
		2158
		2159	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2160
		2161	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2162
		2163	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2164
		2165	=item Stopping check/prepare/idle watchers: O(1)
		2166
		2167	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2168
		2169	=item Finding the next timer per loop iteration: O(1)
		2170
		2171	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2172
		2173	=item Activating one watcher: O(1)
		2174
		2175	=back
		2176
		2177
742	=head1 AUTHOR	2178	=head1 AUTHOR
743		2179
744	Marc Lehmann <libev@schmorp.de>.	2180	Marc Lehmann <libev@schmorp.de>.
745		2181

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