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Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.58 by root, Wed Nov 28 11:31:34 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>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	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	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	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 *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	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	97	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	98	to the C<double> type in C, and when you need to do any calculations on
		99	it, you should treat it as such.
		100
		101	=head1 GLOBAL FUNCTIONS
		102
		103	These functions can be called anytime, even before initialising the
		104	library in any way.
51		105
52	=over 4	106	=over 4
53		107
54	=item ev_tstamp ev_time ()	108	=item ev_tstamp ev_time ()
55		109
56	Returns the current time as libev would use it.	110	Returns the current time as libev would use it. Please note that the
		111	C<ev_now> function is usually faster and also often returns the timestamp
		112	you actually want to know.
57		113
58	=item int ev_version_major ()	114	=item int ev_version_major ()
59		115
60	=item int ev_version_minor ()	116	=item int ev_version_minor ()
61		117
…		…
63	you linked against by calling the functions C<ev_version_major> and	119	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	120	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	121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	122	version of the library your program was compiled against.
67		123
68	Usually, its a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	127	not a problem.
72		128
		129	Example: Make sure we haven't accidentally been linked against the wrong
		130	version.
		131
		132	assert (("libev version mismatch",
		133	ev_version_major () == EV_VERSION_MAJOR
		134	&& ev_version_minor () >= EV_VERSION_MINOR));
		135
		136	=item unsigned int ev_supported_backends ()
		137
		138	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		139	value) compiled into this binary of libev (independent of their
		140	availability on the system you are running on). See C<ev_default_loop> for
		141	a description of the set values.
		142
		143	Example: make sure we have the epoll method, because yeah this is cool and
		144	a must have and can we have a torrent of it please!!!11
		145
		146	assert (("sorry, no epoll, no sex",
		147	ev_supported_backends () & EVBACKEND_EPOLL));
		148
		149	=item unsigned int ev_recommended_backends ()
		150
		151	Return the set of all backends compiled into this binary of libev and also
		152	recommended for this platform. This set is often smaller than the one
		153	returned by C<ev_supported_backends>, as for example kqueue is broken on
		154	most BSDs and will not be autodetected unless you explicitly request it
		155	(assuming you know what you are doing). This is the set of backends that
		156	libev will probe for if you specify no backends explicitly.
		157
		158	=item unsigned int ev_embeddable_backends ()
		159
		160	Returns the set of backends that are embeddable in other event loops. This
		161	is the theoretical, all-platform, value. To find which backends
		162	might be supported on the current system, you would need to look at
		163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		164	recommended ones.
		165
		166	See the description of C<ev_embed> watchers for more info.
		167
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	168	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))
74		169
75	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype and semantics are
76	realloc C function, the semantics are identical). It is used to allocate	171	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	172	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	173	allocated, the library might abort or take some potentially destructive
79	destructive action. The default is your system realloc function.	174	action. The default is your system realloc function.
80		175
81	You could override this function in high-availability programs to, say,	176	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,	177	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.	178	or even to sleep a while and retry until some memory is available.
		179
		180	Example: Replace the libev allocator with one that waits a bit and then
		181	retries).
		182
		183	static void *
		184	persistent_realloc (void *ptr, size_t size)
		185	{
		186	for (;;)
		187	{
		188	void *newptr = realloc (ptr, size);
		189
		190	if (newptr)
		191	return newptr;
		192
		193	sleep (60);
		194	}
		195	}
		196
		197	...
		198	ev_set_allocator (persistent_realloc);
84		199
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	200	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		201
87	Set the callback function to call on a retryable syscall error (such	202	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	203	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	205	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	206	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	207	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	208	(such as abort).
94		209
		210	Example: This is basically the same thing that libev does internally, too.
		211
		212	static void
		213	fatal_error (const char *msg)
		214	{
		215	perror (msg);
		216	abort ();
		217	}
		218
		219	...
		220	ev_set_syserr_cb (fatal_error);
		221
95	=back	222	=back
96		223
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	224	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		225
99	An event loop is described by a C<struct ev_loop *>. The library knows two	226	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	227	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	228	events, and dynamically created loops which do not.
102		229
103	If you use threads, a common model is to run the default event loop	230	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	231	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	232	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	233	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	234	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	235	done correctly, because it's hideous and inefficient).
109		236
110	=over 4	237	=over 4
111		238
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	239	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		240
114	This will initialise the default event loop if it hasn't been initialised	241	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	242	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	243	false. If it already was initialised it simply returns it (and ignores the
117	flags).	244	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		245
119	If you don't know what event loop to use, use the one returned from this	246	If you don't know what event loop to use, use the one returned from this
120	function.	247	function.
121		248
122	The flags argument can be used to specify special behaviour or specific	249	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).	250	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		251
125	It supports the following flags:	252	The following flags are supported:
126		253
127	=over 4	254	=over 4
128		255
129	=item EVFLAG_AUTO	256	=item C<EVFLAG_AUTO>
130		257
131	The default flags value. Use this if you have no clue (its the right	258	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	259	thing, believe me).
133		260
134	=item EVFLAG_NOENV	261	=item C<EVFLAG_NOENV>
135		262
136	If this flag bit is ored into the flag value (or the program runs setuid	263	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	264	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	265	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	266	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	267	useful to try out specific backends to test their performance, or to work
141	around bugs.	268	around bugs.
142		269
143	=item EVMETHOD_SELECT portable select backend	270	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		271
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	272	This is your standard select(2) backend. Not I<completely> standard, as
		273	libev tries to roll its own fd_set with no limits on the number of fds,
		274	but if that fails, expect a fairly low limit on the number of fds when
		275	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		276	the fastest backend for a low number of fds.
146		277
147	=item EVMETHOD_EPOLL linux only	278	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
148		279
149	=item EVMETHOD_KQUEUE some bsds only	280	And this is your standard poll(2) backend. It's more complicated than
		281	select, but handles sparse fds better and has no artificial limit on the
		282	number of fds you can use (except it will slow down considerably with a
		283	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
150		284
151	=item EVMETHOD_DEVPOLL solaris 8 only	285	=item C<EVBACKEND_EPOLL> (value 4, Linux)
152		286
153	=item EVMETHOD_PORT solaris 10 only	287	For few fds, this backend is a bit little slower than poll and select,
		288	but it scales phenomenally better. While poll and select usually scale like
		289	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		290	either O(1) or O(active_fds).
		291
		292	While stopping and starting an I/O watcher in the same iteration will
		293	result in some caching, there is still a syscall per such incident
		294	(because the fd could point to a different file description now), so its
		295	best to avoid that. Also, dup()ed file descriptors might not work very
		296	well if you register events for both fds.
		297
		298	Please note that epoll sometimes generates spurious notifications, so you
		299	need to use non-blocking I/O or other means to avoid blocking when no data
		300	(or space) is available.
		301
		302	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		303
		304	Kqueue deserves special mention, as at the time of this writing, it
		305	was broken on all BSDs except NetBSD (usually it doesn't work with
		306	anything but sockets and pipes, except on Darwin, where of course its
		307	completely useless). For this reason its not being "autodetected"
		308	unless you explicitly specify it explicitly in the flags (i.e. using
		309	C<EVBACKEND_KQUEUE>).
		310
		311	It scales in the same way as the epoll backend, but the interface to the
		312	kernel is more efficient (which says nothing about its actual speed, of
		313	course). While starting and stopping an I/O watcher does not cause an
		314	extra syscall as with epoll, it still adds up to four event changes per
		315	incident, so its best to avoid that.
		316
		317	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		318
		319	This is not implemented yet (and might never be).
		320
		321	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		322
		323	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		324	it's really slow, but it still scales very well (O(active_fds)).
		325
		326	Please note that solaris ports can result in a lot of spurious
		327	notifications, so you need to use non-blocking I/O or other means to avoid
		328	blocking when no data (or space) is available.
		329
		330	=item C<EVBACKEND_ALL>
		331
		332	Try all backends (even potentially broken ones that wouldn't be tried
		333	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		334	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		335
		336	=back
154		337
155	If one or more of these are ored into the flags value, then only these	338	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	339	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	340	specified, most compiled-in backend will be tried, usually in reverse
		341	order of their flag values :)
158		342
159	=back	343	The most typical usage is like this:
		344
		345	if (!ev_default_loop (0))
		346	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		347
		348	Restrict libev to the select and poll backends, and do not allow
		349	environment settings to be taken into account:
		350
		351	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		352
		353	Use whatever libev has to offer, but make sure that kqueue is used if
		354	available (warning, breaks stuff, best use only with your own private
		355	event loop and only if you know the OS supports your types of fds):
		356
		357	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		358
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	359	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		360
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	361	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	362	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	363	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).	364	undefined behaviour (or a failed assertion if assertions are enabled).
167		365
		366	Example: Try to create a event loop that uses epoll and nothing else.
		367
		368	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		369	if (!epoller)
		370	fatal ("no epoll found here, maybe it hides under your chair");
		371
168	=item ev_default_destroy ()	372	=item ev_default_destroy ()
169		373
170	Destroys the default loop again (frees all memory and kernel state	374	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	375	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	376	sense, so e.g. C<ev_is_active> might still return true. It is your
		377	responsibility to either stop all watchers cleanly yoursef I<before>
		378	calling this function, or cope with the fact afterwards (which is usually
		379	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		380	for example).
173		381
174	=item ev_loop_destroy (loop)	382	=item ev_loop_destroy (loop)
175		383
176	Like C<ev_default_destroy>, but destroys an event loop created by an	384	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	385	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	389	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	390	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	391	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	392	again makes little sense).
185		393
186	You I<must> call this function after forking if and only if you want to	394	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	395	only if you want to use the event library in both processes. If you just
188	have to call it.	396	fork+exec, you don't have to call it.
189		397
190	The function itself is quite fast and its usually not a problem to call	398	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	399	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>:	400	quite nicely into a call to C<pthread_atfork>:
193		401
194	pthread_atfork (0, 0, ev_default_fork);	402	pthread_atfork (0, 0, ev_default_fork);
		403
		404	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		405	without calling this function, so if you force one of those backends you
		406	do not need to care.
195		407
196	=item ev_loop_fork (loop)	408	=item ev_loop_fork (loop)
197		409
198	Like C<ev_default_fork>, but acts on an event loop created by	410	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	411	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.	412	after fork, and how you do this is entirely your own problem.
201		413
202	=item unsigned int ev_method (loop)	414	=item unsigned int ev_backend (loop)
203		415
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	416	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	417	use.
206		418
207	=item ev_tstamp = ev_now (loop)	419	=item ev_tstamp ev_now (loop)
208		420
209	Returns the current "event loop time", which is the time the event loop	421	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	422	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	423	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	424	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).	425	event occuring (or more correctly, libev finding out about it).
214		426
215	=item ev_loop (loop, int flags)	427	=item ev_loop (loop, int flags)
216		428
217	Finally, this is it, the event handler. This function usually is called	429	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	430	after you initialised all your watchers and you want to start handling
219	events.	431	events.
220		432
221	If the flags argument is specified as 0, it will not return until either	433	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.	434	either no event watchers are active anymore or C<ev_unloop> was called.
		435
		436	Please note that an explicit C<ev_unloop> is usually better than
		437	relying on all watchers to be stopped when deciding when a program has
		438	finished (especially in interactive programs), but having a program that
		439	automatically loops as long as it has to and no longer by virtue of
		440	relying on its watchers stopping correctly is a thing of beauty.
223		441
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	442	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	443	those events and any outstanding ones, but will not block your process in
226	case there are no events.	444	case there are no events and will return after one iteration of the loop.
227		445
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	446	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	447	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	448	your process until at least one new event arrives, and will return after
		449	one iteration of the loop. This is useful if you are waiting for some
		450	external event in conjunction with something not expressible using other
		451	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		452	usually a better approach for this kind of thing.
231		453
232	This flags value could be used to implement alternative looping	454	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	455
234	more generic mechanism.	456	* If there are no active watchers (reference count is zero), return.
		457	- Queue prepare watchers and then call all outstanding watchers.
		458	- If we have been forked, recreate the kernel state.
		459	- Update the kernel state with all outstanding changes.
		460	- Update the "event loop time".
		461	- Calculate for how long to block.
		462	- Block the process, waiting for any events.
		463	- Queue all outstanding I/O (fd) events.
		464	- Update the "event loop time" and do time jump handling.
		465	- Queue all outstanding timers.
		466	- Queue all outstanding periodics.
		467	- If no events are pending now, queue all idle watchers.
		468	- Queue all check watchers.
		469	- Call all queued watchers in reverse order (i.e. check watchers first).
		470	Signals and child watchers are implemented as I/O watchers, and will
		471	be handled here by queueing them when their watcher gets executed.
		472	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		473	were used, return, otherwise continue with step *.
		474
		475	Example: Queue some jobs and then loop until no events are outsanding
		476	anymore.
		477
		478	... queue jobs here, make sure they register event watchers as long
		479	... as they still have work to do (even an idle watcher will do..)
		480	ev_loop (my_loop, 0);
		481	... jobs done. yeah!
235		482
236	=item ev_unloop (loop, how)	483	=item ev_unloop (loop, how)
237		484
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	485	Can be used to make a call to C<ev_loop> return early (but only after it
		486	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>	487	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>	488	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.
242		489
243	=item ev_ref (loop)	490	=item ev_ref (loop)
244		491
245	=item ev_unref (loop)	492	=item ev_unref (loop)
246		493
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	494	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	495	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	496	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	497	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	498	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	499	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	500	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	501	no event watchers registered by it are active. It is also an excellent
255	before stop.	502	way to do this for generic recurring timers or from within third-party
		503	libraries. Just remember to I<unref after start> and I<ref before stop>.
		504
		505	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		506	running when nothing else is active.
		507
		508	struct ev_signal exitsig;
		509	ev_signal_init (&exitsig, sig_cb, SIGINT);
		510	ev_signal_start (loop, &exitsig);
		511	evf_unref (loop);
		512
		513	Example: For some weird reason, unregister the above signal handler again.
		514
		515	ev_ref (loop);
		516	ev_signal_stop (loop, &exitsig);
256		517
257	=back	518	=back
		519
258		520
259	=head1 ANATOMY OF A WATCHER	521	=head1 ANATOMY OF A WATCHER
260		522
261	A watcher is a structure that you create and register to record your	523	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	524	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:	525	become readable, you would create an C<ev_io> watcher for that:
264		526
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	527	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	528	{
267	ev_io_stop (w);	529	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	530	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	557	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	558	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		559
298	As long as your watcher is active (has been started but not stopped) you	560	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	561	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	562	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		563
307	Each and every callback receives the event loop pointer as first, the	564	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	565	registered watcher structure as second, and a bitset of received events as
309	third argument.	566	third argument.
310		567
311	The rceeived events usually include a single bit per event type received	568	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	569	(you can receive multiple events at the same time). The possible bit masks
313	are:	570	are:
314		571
315	=over 4	572	=over 4
316		573
317	=item EV_READ	574	=item C<EV_READ>
318		575
319	=item EV_WRITE	576	=item C<EV_WRITE>
320		577
321	The file descriptor in the ev_io watcher has become readable and/or	578	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	579	writable.
323		580
324	=item EV_TIMEOUT	581	=item C<EV_TIMEOUT>
325		582
326	The ev_timer watcher has timed out.	583	The C<ev_timer> watcher has timed out.
327		584
328	=item EV_PERIODIC	585	=item C<EV_PERIODIC>
329		586
330	The ev_periodic watcher has timed out.	587	The C<ev_periodic> watcher has timed out.
331		588
332	=item EV_SIGNAL	589	=item C<EV_SIGNAL>
333		590
334	The signal specified in the ev_signal watcher has been received by a thread.	591	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		592
336	=item EV_CHILD	593	=item C<EV_CHILD>
337		594
338	The pid specified in the ev_child watcher has received a status change.	595	The pid specified in the C<ev_child> watcher has received a status change.
339		596
		597	=item C<EV_STAT>
		598
		599	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		600
340	=item EV_IDLE	601	=item C<EV_IDLE>
341		602
342	The ev_idle watcher has determined that you have nothing better to do.	603	The C<ev_idle> watcher has determined that you have nothing better to do.
343		604
344	=item EV_PREPARE	605	=item C<EV_PREPARE>
345		606
346	=item EV_CHECK	607	=item C<EV_CHECK>
347		608
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	609	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	610	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	611	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	612	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	613	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	614	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	615	C<ev_loop> from blocking).
355		616
		617	=item C<EV_EMBED>
		618
		619	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		620
		621	=item C<EV_FORK>
		622
		623	The event loop has been resumed in the child process after fork (see
		624	C<ev_fork>).
		625
356	=item EV_ERROR	626	=item C<EV_ERROR>
357		627
358	An unspecified error has occured, the watcher has been stopped. This might	628	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	629	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	630	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	631	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	637	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	638	programs, though, so beware.
369		639
370	=back	640	=back
371		641
		642	=head2 GENERIC WATCHER FUNCTIONS
		643
		644	In the following description, C<TYPE> stands for the watcher type,
		645	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		646
		647	=over 4
		648
		649	=item C<ev_init> (ev_TYPE *watcher, callback)
		650
		651	This macro initialises the generic portion of a watcher. The contents
		652	of the watcher object can be arbitrary (so C<malloc> will do). Only
		653	the generic parts of the watcher are initialised, you I<need> to call
		654	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		655	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		656	which rolls both calls into one.
		657
		658	You can reinitialise a watcher at any time as long as it has been stopped
		659	(or never started) and there are no pending events outstanding.
		660
		661	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		662	int revents)>.
		663
		664	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		665
		666	This macro initialises the type-specific parts of a watcher. You need to
		667	call C<ev_init> at least once before you call this macro, but you can
		668	call C<ev_TYPE_set> any number of times. You must not, however, call this
		669	macro on a watcher that is active (it can be pending, however, which is a
		670	difference to the C<ev_init> macro).
		671
		672	Although some watcher types do not have type-specific arguments
		673	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		674
		675	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		676
		677	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		678	calls into a single call. This is the most convinient method to initialise
		679	a watcher. The same limitations apply, of course.
		680
		681	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		682
		683	Starts (activates) the given watcher. Only active watchers will receive
		684	events. If the watcher is already active nothing will happen.
		685
		686	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		687
		688	Stops the given watcher again (if active) and clears the pending
		689	status. It is possible that stopped watchers are pending (for example,
		690	non-repeating timers are being stopped when they become pending), but
		691	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		692	you want to free or reuse the memory used by the watcher it is therefore a
		693	good idea to always call its C<ev_TYPE_stop> function.
		694
		695	=item bool ev_is_active (ev_TYPE *watcher)
		696
		697	Returns a true value iff the watcher is active (i.e. it has been started
		698	and not yet been stopped). As long as a watcher is active you must not modify
		699	it.
		700
		701	=item bool ev_is_pending (ev_TYPE *watcher)
		702
		703	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		704	events but its callback has not yet been invoked). As long as a watcher
		705	is pending (but not active) you must not call an init function on it (but
		706	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		707	libev (e.g. you cnanot C<free ()> it).
		708
		709	=item callback ev_cb (ev_TYPE *watcher)
		710
		711	Returns the callback currently set on the watcher.
		712
		713	=item ev_cb_set (ev_TYPE *watcher, callback)
		714
		715	Change the callback. You can change the callback at virtually any time
		716	(modulo threads).
		717
		718	=back
		719
		720
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	721	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		722
374	Each watcher has, by default, a member C<void *data> that you can change	723	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	724	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	725	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	726	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	727	member, you can also "subclass" the watcher type and provide your own
379	data:	728	data:
380		729
…		…
393	{	742	{
394	struct my_io *w = (struct my_io *)w_;	743	struct my_io *w = (struct my_io *)w_;
395	...	744	...
396	}	745	}
397		746
398	More interesting and less C-conformant ways of catsing your callback type	747	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	748	instead have been omitted.
		749
		750	Another common scenario is having some data structure with multiple
		751	watchers:
		752
		753	struct my_biggy
		754	{
		755	int some_data;
		756	ev_timer t1;
		757	ev_timer t2;
		758	}
		759
		760	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		761	you need to use C<offsetof>:
		762
		763	#include <stddef.h>
		764
		765	static void
		766	t1_cb (EV_P_ struct ev_timer *w, int revents)
		767	{
		768	struct my_biggy big = (struct my_biggy *
		769	(((char *)w) - offsetof (struct my_biggy, t1));
		770	}
		771
		772	static void
		773	t2_cb (EV_P_ struct ev_timer *w, int revents)
		774	{
		775	struct my_biggy big = (struct my_biggy *
		776	(((char *)w) - offsetof (struct my_biggy, t2));
		777	}
400		778
401		779
402	=head1 WATCHER TYPES	780	=head1 WATCHER TYPES
403		781
404	This section describes each watcher in detail, but will not repeat	782	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	783	information given in the last section. Any initialisation/set macros,
		784	functions and members specific to the watcher type are explained.
406		785
		786	Members are additionally marked with either I<[read-only]>, meaning that,
		787	while the watcher is active, you can look at the member and expect some
		788	sensible content, but you must not modify it (you can modify it while the
		789	watcher is stopped to your hearts content), or I<[read-write]>, which
		790	means you can expect it to have some sensible content while the watcher
		791	is active, but you can also modify it. Modifying it may not do something
		792	sensible or take immediate effect (or do anything at all), but libev will
		793	not crash or malfunction in any way.
		794
		795
407	=head2 struct ev_io - is my file descriptor readable or writable	796	=head2 C<ev_io> - is this file descriptor readable or writable?
408		797
409	I/O watchers check whether a file descriptor is readable or writable	798	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	799	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	800	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	801	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	802	receiving events as long as the condition persists. Remember you can stop
		803	the watcher if you don't want to act on the event and neither want to
		804	receive future events.
414		805
415	In general you can register as many read and/or write event watchers oer	806	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	807	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	808	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	809	required if you know what you are doing).
419		810
420	You have to be careful with dup'ed file descriptors, though. Some backends	811	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	812	(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	813	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	814	to the same underlying file/socket/etc. description (that is, they share
		815	the same underlying "file open").
424		816
425	If you must do this, then force the use of a known-to-be-good backend	817	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	818	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	819	C<EVBACKEND_POLL>).
		820
		821	Another thing you have to watch out for is that it is quite easy to
		822	receive "spurious" readyness notifications, that is your callback might
		823	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		824	because there is no data. Not only are some backends known to create a
		825	lot of those (for example solaris ports), it is very easy to get into
		826	this situation even with a relatively standard program structure. Thus
		827	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		828	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		829
		830	If you cannot run the fd in non-blocking mode (for example you should not
		831	play around with an Xlib connection), then you have to seperately re-test
		832	wether a file descriptor is really ready with a known-to-be good interface
		833	such as poll (fortunately in our Xlib example, Xlib already does this on
		834	its own, so its quite safe to use).
428		835
429	=over 4	836	=over 4
430		837
431	=item ev_io_init (ev_io *, callback, int fd, int events)	838	=item ev_io_init (ev_io *, callback, int fd, int events)
432		839
433	=item ev_io_set (ev_io *, int fd, int events)	840	=item ev_io_set (ev_io *, int fd, int events)
434		841
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	842	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 |	843	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	844	C<EV_READ | EV_WRITE> to receive the given events.
		845
		846	=item int fd [read-only]
		847
		848	The file descriptor being watched.
		849
		850	=item int events [read-only]
		851
		852	The events being watched.
438		853
439	=back	854	=back
440		855
		856	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		857	readable, but only once. Since it is likely line-buffered, you could
		858	attempt to read a whole line in the callback.
		859
		860	static void
		861	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		862	{
		863	ev_io_stop (loop, w);
		864	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		865	}
		866
		867	...
		868	struct ev_loop *loop = ev_default_init (0);
		869	struct ev_io stdin_readable;
		870	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		871	ev_io_start (loop, &stdin_readable);
		872	ev_loop (loop, 0);
		873
		874
441	=head2 struct ev_timer - relative and optionally recurring timeouts	875	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		876
443	Timer watchers are simple relative timers that generate an event after a	877	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	878	given time, and optionally repeating in regular intervals after that.
445		879
446	The timers are based on real time, that is, if you register an event that	880	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	881	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	882	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	883	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	884	monotonic clock option helps a lot here).
		885
		886	The relative timeouts are calculated relative to the C<ev_now ()>
		887	time. This is usually the right thing as this timestamp refers to the time
		888	of the event triggering whatever timeout you are modifying/starting. If
		889	you suspect event processing to be delayed and you I<need> to base the timeout
		890	on the current time, use something like this to adjust for this:
		891
		892	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		893
		894	The callback is guarenteed to be invoked only when its timeout has passed,
		895	but if multiple timers become ready during the same loop iteration then
		896	order of execution is undefined.
451		897
452	=over 4	898	=over 4
453		899
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	900	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		901
…		…
461	later, again, and again, until stopped manually.	907	later, again, and again, until stopped manually.
462		908
463	The timer itself will do a best-effort at avoiding drift, that is, if you	909	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	910	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	911	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	912	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.	913	timer will not fire more than once per event loop iteration.
468		914
469	=item ev_timer_again (loop)	915	=item ev_timer_again (loop)
470		916
471	This will act as if the timer timed out and restart it again if it is	917	This will act as if the timer timed out and restart it again if it is
…		…
475		921
476	If the timer is repeating, either start it if necessary (with the repeat	922	If the timer is repeating, either start it if necessary (with the repeat
477	value), or reset the running timer to the repeat value.	923	value), or reset the running timer to the repeat value.
478		924
479	This sounds a bit complicated, but here is a useful and typical	925	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	926	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	927	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	928	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	929	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	930	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	931	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.	932	socket, you can stop the timer, and again will automatically restart it if
		933	need be.
		934
		935	You can also ignore the C<after> value and C<ev_timer_start> altogether
		936	and only ever use the C<repeat> value:
		937
		938	ev_timer_init (timer, callback, 0., 5.);
		939	ev_timer_again (loop, timer);
		940	...
		941	timer->again = 17.;
		942	ev_timer_again (loop, timer);
		943	...
		944	timer->again = 10.;
		945	ev_timer_again (loop, timer);
		946
		947	This is more efficient then stopping/starting the timer eahc time you want
		948	to modify its timeout value.
		949
		950	=item ev_tstamp repeat [read-write]
		951
		952	The current C<repeat> value. Will be used each time the watcher times out
		953	or C<ev_timer_again> is called and determines the next timeout (if any),
		954	which is also when any modifications are taken into account.
487		955
488	=back	956	=back
489		957
		958	Example: Create a timer that fires after 60 seconds.
		959
		960	static void
		961	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		962	{
		963	.. one minute over, w is actually stopped right here
		964	}
		965
		966	struct ev_timer mytimer;
		967	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		968	ev_timer_start (loop, &mytimer);
		969
		970	Example: Create a timeout timer that times out after 10 seconds of
		971	inactivity.
		972
		973	static void
		974	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		975	{
		976	.. ten seconds without any activity
		977	}
		978
		979	struct ev_timer mytimer;
		980	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		981	ev_timer_again (&mytimer); /* start timer */
		982	ev_loop (loop, 0);
		983
		984	// and in some piece of code that gets executed on any "activity":
		985	// reset the timeout to start ticking again at 10 seconds
		986	ev_timer_again (&mytimer);
		987
		988
490	=head2 ev_periodic - to cron or not to cron it	989	=head2 C<ev_periodic> - to cron or not to cron?
491		990
492	Periodic watchers are also timers of a kind, but they are very versatile	991	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	992	(and unfortunately a bit complex).
494		993
495	Unlike ev_timer's, they are not based on real time (or relative time)	994	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	995	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	996	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 ()	997	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	998	+ 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	999	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	1000	roughly 10 seconds later and of course not if you reset your system time
502	again).	1001	again).
503		1002
504	They can also be used to implement vastly more complex timers, such as	1003	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1004	triggering an event on eahc midnight, local time.
506		1005
		1006	As with timers, the callback is guarenteed to be invoked only when the
		1007	time (C<at>) has been passed, but if multiple periodic timers become ready
		1008	during the same loop iteration then order of execution is undefined.
		1009
507	=over 4	1010	=over 4
508		1011
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1012	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1013
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1014	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1015
513	Lots of arguments, lets sort it out... There are basically three modes of	1016	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1017	operation, and we will explain them from simplest to complex:
515
516		1018
517	=over 4	1019	=over 4
518		1020
519	=item * absolute timer (interval = reschedule_cb = 0)	1021	=item * absolute timer (interval = reschedule_cb = 0)
520		1022
…		…
534		1036
535	ev_periodic_set (&periodic, 0., 3600., 0);	1037	ev_periodic_set (&periodic, 0., 3600., 0);
536		1038
537	This doesn't mean there will always be 3600 seconds in between triggers,	1039	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	1040	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	1041	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1042	by 3600.
541		1043
542	Another way to think about it (for the mathematically inclined) is that	1044	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	1045	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.	1046	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1047
546	=item * manual reschedule mode (reschedule_cb = callback)	1048	=item * manual reschedule mode (reschedule_cb = callback)
547		1049
548	In this mode the values for C<interval> and C<at> are both being	1050	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	1051	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1052	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1053	current time as second argument.
552		1054
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1055	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	1056	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.	1057	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1058	starting a prepare watcher).
556		1059
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1060	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1061	ev_tstamp now)>, e.g.:
559		1062
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1063	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1064	{
562	return now + 60.;	1065	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1068	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	1069	(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	1070	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1071	might be called at other times, too.
569		1072
		1073	NOTE: I<< This callback must always return a time that is later than the
		1074	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1075
570	This can be used to create very complex timers, such as a timer that	1076	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	1077	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	1078	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1079	you do this is, again, up to you (but it is not trivial, which is the main
		1080	reason I omitted it as an example).
574		1081
575	=back	1082	=back
576		1083
577	=item ev_periodic_again (loop, ev_periodic *)	1084	=item ev_periodic_again (loop, ev_periodic *)
578		1085
579	Simply stops and restarts the periodic watcher again. This is only useful	1086	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1087	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	1088	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1089	program when the crontabs have changed).
583		1090
		1091	=item ev_tstamp interval [read-write]
		1092
		1093	The current interval value. Can be modified any time, but changes only
		1094	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1095	called.
		1096
		1097	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1098
		1099	The current reschedule callback, or C<0>, if this functionality is
		1100	switched off. Can be changed any time, but changes only take effect when
		1101	the periodic timer fires or C<ev_periodic_again> is being called.
		1102
584	=back	1103	=back
585		1104
		1105	Example: Call a callback every hour, or, more precisely, whenever the
		1106	system clock is divisible by 3600. The callback invocation times have
		1107	potentially a lot of jittering, but good long-term stability.
		1108
		1109	static void
		1110	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1111	{
		1112	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1113	}
		1114
		1115	struct ev_periodic hourly_tick;
		1116	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1117	ev_periodic_start (loop, &hourly_tick);
		1118
		1119	Example: The same as above, but use a reschedule callback to do it:
		1120
		1121	#include <math.h>
		1122
		1123	static ev_tstamp
		1124	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1125	{
		1126	return fmod (now, 3600.) + 3600.;
		1127	}
		1128
		1129	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1130
		1131	Example: Call a callback every hour, starting now:
		1132
		1133	struct ev_periodic hourly_tick;
		1134	ev_periodic_init (&hourly_tick, clock_cb,
		1135	fmod (ev_now (loop), 3600.), 3600., 0);
		1136	ev_periodic_start (loop, &hourly_tick);
		1137
		1138
586	=head2 ev_signal - signal me when a signal gets signalled	1139	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1140
588	Signal watchers will trigger an event when the process receives a specific	1141	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	1142	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	1143	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1144	normal event processing, like any other event.
592		1145
593	You cna configure as many watchers as you like per signal. Only when the	1146	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	1147	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	1148	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	1149	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	1150	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1151	SIG_DFL (regardless of what it was set to before).
…		…
604	=item ev_signal_set (ev_signal *, int signum)	1157	=item ev_signal_set (ev_signal *, int signum)
605		1158
606	Configures the watcher to trigger on the given signal number (usually one	1159	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1160	of the C<SIGxxx> constants).
608		1161
		1162	=item int signum [read-only]
		1163
		1164	The signal the watcher watches out for.
		1165
609	=back	1166	=back
610		1167
		1168
611	=head2 ev_child - wait for pid status changes	1169	=head2 C<ev_child> - watch out for process status changes
612		1170
613	Child watchers trigger when your process receives a SIGCHLD in response to	1171	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).	1172	some child status changes (most typically when a child of yours dies).
615		1173
616	=over 4	1174	=over 4
…		…
620	=item ev_child_set (ev_child *, int pid)	1178	=item ev_child_set (ev_child *, int pid)
621		1179
622	Configures the watcher to wait for status changes of process C<pid> (or	1180	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	1181	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	1182	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	1183	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.	1184	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1185	process causing the status change.
		1186
		1187	=item int pid [read-only]
		1188
		1189	The process id this watcher watches out for, or C<0>, meaning any process id.
		1190
		1191	=item int rpid [read-write]
		1192
		1193	The process id that detected a status change.
		1194
		1195	=item int rstatus [read-write]
		1196
		1197	The process exit/trace status caused by C<rpid> (see your systems
		1198	C<waitpid> and C<sys/wait.h> documentation for details).
627		1199
628	=back	1200	=back
629		1201
		1202	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1203
		1204	static void
		1205	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1206	{
		1207	ev_unloop (loop, EVUNLOOP_ALL);
		1208	}
		1209
		1210	struct ev_signal signal_watcher;
		1211	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1212	ev_signal_start (loop, &sigint_cb);
		1213
		1214
		1215	=head2 C<ev_stat> - did the file attributes just change?
		1216
		1217	This watches a filesystem path for attribute changes. That is, it calls
		1218	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1219	compared to the last time, invoking the callback if it did.
		1220
		1221	The path does not need to exist: changing from "path exists" to "path does
		1222	not exist" is a status change like any other. The condition "path does
		1223	not exist" is signified by the C<st_nlink> field being zero (which is
		1224	otherwise always forced to be at least one) and all the other fields of
		1225	the stat buffer having unspecified contents.
		1226
		1227	Since there is no standard to do this, the portable implementation simply
		1228	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1229	can specify a recommended polling interval for this case. If you specify
		1230	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1231	unspecified default> value will be used (which you can expect to be around
		1232	five seconds, although this might change dynamically). Libev will also
		1233	impose a minimum interval which is currently around C<0.1>, but thats
		1234	usually overkill.
		1235
		1236	This watcher type is not meant for massive numbers of stat watchers,
		1237	as even with OS-supported change notifications, this can be
		1238	resource-intensive.
		1239
		1240	At the time of this writing, only the Linux inotify interface is
		1241	implemented (implementing kqueue support is left as an exercise for the
		1242	reader). Inotify will be used to give hints only and should not change the
		1243	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1244	to fall back to regular polling again even with inotify, but changes are
		1245	usually detected immediately, and if the file exists there will be no
		1246	polling.
		1247
		1248	=over 4
		1249
		1250	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1251
		1252	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1253
		1254	Configures the watcher to wait for status changes of the given
		1255	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1256	be detected and should normally be specified as C<0> to let libev choose
		1257	a suitable value. The memory pointed to by C<path> must point to the same
		1258	path for as long as the watcher is active.
		1259
		1260	The callback will be receive C<EV_STAT> when a change was detected,
		1261	relative to the attributes at the time the watcher was started (or the
		1262	last change was detected).
		1263
		1264	=item ev_stat_stat (ev_stat *)
		1265
		1266	Updates the stat buffer immediately with new values. If you change the
		1267	watched path in your callback, you could call this fucntion to avoid
		1268	detecting this change (while introducing a race condition). Can also be
		1269	useful simply to find out the new values.
		1270
		1271	=item ev_statdata attr [read-only]
		1272
		1273	The most-recently detected attributes of the file. Although the type is of
		1274	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1275	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1276	was some error while C<stat>ing the file.
		1277
		1278	=item ev_statdata prev [read-only]
		1279
		1280	The previous attributes of the file. The callback gets invoked whenever
		1281	C<prev> != C<attr>.
		1282
		1283	=item ev_tstamp interval [read-only]
		1284
		1285	The specified interval.
		1286
		1287	=item const char *path [read-only]
		1288
		1289	The filesystem path that is being watched.
		1290
		1291	=back
		1292
		1293	Example: Watch C</etc/passwd> for attribute changes.
		1294
		1295	static void
		1296	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1297	{
		1298	/* /etc/passwd changed in some way */
		1299	if (w->attr.st_nlink)
		1300	{
		1301	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1302	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1303	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1304	}
		1305	else
		1306	/* you shalt not abuse printf for puts */
		1307	puts ("wow, /etc/passwd is not there, expect problems. "
		1308	"if this is windows, they already arrived\n");
		1309	}
		1310
		1311	...
		1312	ev_stat passwd;
		1313
		1314	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1315	ev_stat_start (loop, &passwd);
		1316
		1317
630	=head2 ev_idle - when you've got nothing better to do	1318	=head2 C<ev_idle> - when you've got nothing better to do...
631		1319
632	Idle watchers trigger events when there are no other I/O or timer (or	1320	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	1321	(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	1322	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	1323	imagine) it will not be triggered. But when your process is idle all idle
		1324	watchers are being called again and again, once per event loop iteration -
636	stopped, that is, or your process receives more events.	1325	until stopped, that is, or your process receives more events and becomes
		1326	busy.
637		1327
638	The most noteworthy effect is that as long as any idle watchers are	1328	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.	1329	active, the process will not block when waiting for new events.
640		1330
641	Apart from keeping your process non-blocking (which is a useful	1331	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,	1341	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1342	believe me.
653		1343
654	=back	1344	=back
655		1345
656	=head2 prepare and check - your hooks into the event loop	1346	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1347	callback, free it. Also, use no error checking, as usual.
657		1348
		1349	static void
		1350	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1351	{
		1352	free (w);
		1353	// now do something you wanted to do when the program has
		1354	// no longer asnything immediate to do.
		1355	}
		1356
		1357	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1358	ev_idle_init (idle_watcher, idle_cb);
		1359	ev_idle_start (loop, idle_cb);
		1360
		1361
		1362	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1363
658	Prepare and check watchers usually (but not always) are used in	1364	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1365	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1366	afterwards.
661		1367
		1368	You I<must not> call C<ev_loop> or similar functions that enter
		1369	the current event loop from either C<ev_prepare> or C<ev_check>
		1370	watchers. Other loops than the current one are fine, however. The
		1371	rationale behind this is that you do not need to check for recursion in
		1372	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1373	C<ev_check> so if you have one watcher of each kind they will always be
		1374	called in pairs bracketing the blocking call.
		1375
662	Their main purpose is to integrate other event mechanisms into libev. This	1376	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	1377	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.	1378	variable changes, implement your own watchers, integrate net-snmp or a
		1379	coroutine library and lots more. They are also occasionally useful if
		1380	you cache some data and want to flush it before blocking (for example,
		1381	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1382	watcher).
665		1383
666	This is done by examining in each prepare call which file descriptors need	1384	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	1385	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	1386	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	1387	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)	1388	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1389	and stopping them) and call back into the library. The I/O and timer
		1390	callbacks will never actually be called (but must be valid nevertheless,
		1391	because you never know, you know?).
672		1392
673	As another example, the perl Coro module uses these hooks to integrate	1393	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1394	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1395	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1396	are ready to run (it's actually more complicated: it only runs coroutines
		1397	with priority higher than or equal to the event loop and one coroutine
		1398	of lower priority, but only once, using idle watchers to keep the event
		1399	loop from blocking if lower-priority coroutines are active, thus mapping
		1400	low-priority coroutines to idle/background tasks).
677		1401
678	=over 4	1402	=over 4
679		1403
680	=item ev_prepare_init (ev_prepare *, callback)	1404	=item ev_prepare_init (ev_prepare *, callback)
681		1405
682	=item ev_check_init (ev_check *, callback)	1406	=item ev_check_init (ev_check *, callback)
683		1407
684	Initialises and configures the prepare or check watcher - they have no	1408	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>	1409	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1410	macros, but using them is utterly, utterly and completely pointless.
687		1411
688	=back	1412	=back
689		1413
		1414	Example: To include a library such as adns, you would add IO watchers
		1415	and a timeout watcher in a prepare handler, as required by libadns, and
		1416	in a check watcher, destroy them and call into libadns. What follows is
		1417	pseudo-code only of course:
		1418
		1419	static ev_io iow [nfd];
		1420	static ev_timer tw;
		1421
		1422	static void
		1423	io_cb (ev_loop *loop, ev_io *w, int revents)
		1424	{
		1425	// set the relevant poll flags
		1426	// could also call adns_processreadable etc. here
		1427	struct pollfd *fd = (struct pollfd *)w->data;
		1428	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1429	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1430	}
		1431
		1432	// create io watchers for each fd and a timer before blocking
		1433	static void
		1434	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1435	{
		1436	int timeout = 3600000;truct pollfd fds [nfd];
		1437	// actual code will need to loop here and realloc etc.
		1438	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1439
		1440	/* the callback is illegal, but won't be called as we stop during check */
		1441	ev_timer_init (&tw, 0, timeout * 1e-3);
		1442	ev_timer_start (loop, &tw);
		1443
		1444	// create on ev_io per pollfd
		1445	for (int i = 0; i < nfd; ++i)
		1446	{
		1447	ev_io_init (iow + i, io_cb, fds [i].fd,
		1448	((fds [i].events & POLLIN ? EV_READ : 0)
		1449	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1450
		1451	fds [i].revents = 0;
		1452	iow [i].data = fds + i;
		1453	ev_io_start (loop, iow + i);
		1454	}
		1455	}
		1456
		1457	// stop all watchers after blocking
		1458	static void
		1459	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1460	{
		1461	ev_timer_stop (loop, &tw);
		1462
		1463	for (int i = 0; i < nfd; ++i)
		1464	ev_io_stop (loop, iow + i);
		1465
		1466	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1467	}
		1468
		1469
		1470	=head2 C<ev_embed> - when one backend isn't enough...
		1471
		1472	This is a rather advanced watcher type that lets you embed one event loop
		1473	into another (currently only C<ev_io> events are supported in the embedded
		1474	loop, other types of watchers might be handled in a delayed or incorrect
		1475	fashion and must not be used).
		1476
		1477	There are primarily two reasons you would want that: work around bugs and
		1478	prioritise I/O.
		1479
		1480	As an example for a bug workaround, the kqueue backend might only support
		1481	sockets on some platform, so it is unusable as generic backend, but you
		1482	still want to make use of it because you have many sockets and it scales
		1483	so nicely. In this case, you would create a kqueue-based loop and embed it
		1484	into your default loop (which might use e.g. poll). Overall operation will
		1485	be a bit slower because first libev has to poll and then call kevent, but
		1486	at least you can use both at what they are best.
		1487
		1488	As for prioritising I/O: rarely you have the case where some fds have
		1489	to be watched and handled very quickly (with low latency), and even
		1490	priorities and idle watchers might have too much overhead. In this case
		1491	you would put all the high priority stuff in one loop and all the rest in
		1492	a second one, and embed the second one in the first.
		1493
		1494	As long as the watcher is active, the callback will be invoked every time
		1495	there might be events pending in the embedded loop. The callback must then
		1496	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1497	their callbacks (you could also start an idle watcher to give the embedded
		1498	loop strictly lower priority for example). You can also set the callback
		1499	to C<0>, in which case the embed watcher will automatically execute the
		1500	embedded loop sweep.
		1501
		1502	As long as the watcher is started it will automatically handle events. The
		1503	callback will be invoked whenever some events have been handled. You can
		1504	set the callback to C<0> to avoid having to specify one if you are not
		1505	interested in that.
		1506
		1507	Also, there have not currently been made special provisions for forking:
		1508	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1509	but you will also have to stop and restart any C<ev_embed> watchers
		1510	yourself.
		1511
		1512	Unfortunately, not all backends are embeddable, only the ones returned by
		1513	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1514	portable one.
		1515
		1516	So when you want to use this feature you will always have to be prepared
		1517	that you cannot get an embeddable loop. The recommended way to get around
		1518	this is to have a separate variables for your embeddable loop, try to
		1519	create it, and if that fails, use the normal loop for everything:
		1520
		1521	struct ev_loop *loop_hi = ev_default_init (0);
		1522	struct ev_loop *loop_lo = 0;
		1523	struct ev_embed embed;
		1524
		1525	// see if there is a chance of getting one that works
		1526	// (remember that a flags value of 0 means autodetection)
		1527	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1528	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1529	: 0;
		1530
		1531	// if we got one, then embed it, otherwise default to loop_hi
		1532	if (loop_lo)
		1533	{
		1534	ev_embed_init (&embed, 0, loop_lo);
		1535	ev_embed_start (loop_hi, &embed);
		1536	}
		1537	else
		1538	loop_lo = loop_hi;
		1539
		1540	=over 4
		1541
		1542	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1543
		1544	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1545
		1546	Configures the watcher to embed the given loop, which must be
		1547	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1548	invoked automatically, otherwise it is the responsibility of the callback
		1549	to invoke it (it will continue to be called until the sweep has been done,
		1550	if you do not want thta, you need to temporarily stop the embed watcher).
		1551
		1552	=item ev_embed_sweep (loop, ev_embed *)
		1553
		1554	Make a single, non-blocking sweep over the embedded loop. This works
		1555	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1556	apropriate way for embedded loops.
		1557
		1558	=item struct ev_loop *loop [read-only]
		1559
		1560	The embedded event loop.
		1561
		1562	=back
		1563
		1564
		1565	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1566
		1567	Fork watchers are called when a C<fork ()> was detected (usually because
		1568	whoever is a good citizen cared to tell libev about it by calling
		1569	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1570	event loop blocks next and before C<ev_check> watchers are being called,
		1571	and only in the child after the fork. If whoever good citizen calling
		1572	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1573	handlers will be invoked, too, of course.
		1574
		1575	=over 4
		1576
		1577	=item ev_fork_init (ev_signal *, callback)
		1578
		1579	Initialises and configures the fork watcher - it has no parameters of any
		1580	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1581	believe me.
		1582
		1583	=back
		1584
		1585
690	=head1 OTHER FUNCTIONS	1586	=head1 OTHER FUNCTIONS
691		1587
692	There are some other fucntions of possible interest. Described. Here. Now.	1588	There are some other functions of possible interest. Described. Here. Now.
693		1589
694	=over 4	1590	=over 4
695		1591
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1592	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		1593
698	This function combines a simple timer and an I/O watcher, calls your	1594	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	1595	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	1596	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	1597	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	1598	more watchers yourself.
703		1599
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	1600	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	1601	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	1602	C<events> set will be craeted and started.
707		1603
708	If C<timeout> is less than 0, then no timeout watcher will be	1604	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	1605	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	1606	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1607	dubious value.
711		1608
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	1609	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,	1610	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>:	1611	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1612	value passed to C<ev_once>:
715		1613
716	static void stdin_ready (int revents, void *arg)	1614	static void stdin_ready (int revents, void *arg)
717	{	1615	{
718	if (revents & EV_TIMEOUT)	1616	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	1617	/* doh, nothing entered */;
720	else if (revents & EV_READ)	1618	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	1619	/* stdin might have data for us, joy! */;
722	}	1620	}
723		1621
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1622	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		1623
726	=item ev_feed_event (loop, watcher, int events)	1624	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		1625
728	Feeds the given event set into the event loop, as if the specified event	1626	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	1627	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	1628	initialised but not necessarily started event watcher).
731		1629
732	=item ev_feed_fd_event (loop, int fd, int revents)	1630	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		1631
734	Feed an event on the given fd, as if a file descriptor backend detected it.	1632	Feed an event on the given fd, as if a file descriptor backend detected
		1633	the given events it.
735		1634
736	=item ev_feed_signal_event (loop, int signum)	1635	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		1636
738	Feed an event as if the given signal occured (loop must be the default loop!).	1637	Feed an event as if the given signal occured (C<loop> must be the default
		1638	loop!).
739		1639
740	=back	1640	=back
741		1641
		1642
		1643	=head1 LIBEVENT EMULATION
		1644
		1645	Libev offers a compatibility emulation layer for libevent. It cannot
		1646	emulate the internals of libevent, so here are some usage hints:
		1647
		1648	=over 4
		1649
		1650	=item * Use it by including <event.h>, as usual.
		1651
		1652	=item * The following members are fully supported: ev_base, ev_callback,
		1653	ev_arg, ev_fd, ev_res, ev_events.
		1654
		1655	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1656	maintained by libev, it does not work exactly the same way as in libevent (consider
		1657	it a private API).
		1658
		1659	=item * Priorities are not currently supported. Initialising priorities
		1660	will fail and all watchers will have the same priority, even though there
		1661	is an ev_pri field.
		1662
		1663	=item * Other members are not supported.
		1664
		1665	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1666	to use the libev header file and library.
		1667
		1668	=back
		1669
		1670	=head1 C++ SUPPORT
		1671
		1672	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1673	you to use some convinience methods to start/stop watchers and also change
		1674	the callback model to a model using method callbacks on objects.
		1675
		1676	To use it,
		1677
		1678	#include <ev++.h>
		1679
		1680	(it is not installed by default). This automatically includes F<ev.h>
		1681	and puts all of its definitions (many of them macros) into the global
		1682	namespace. All C++ specific things are put into the C<ev> namespace.
		1683
		1684	It should support all the same embedding options as F<ev.h>, most notably
		1685	C<EV_MULTIPLICITY>.
		1686
		1687	Here is a list of things available in the C<ev> namespace:
		1688
		1689	=over 4
		1690
		1691	=item C<ev::READ>, C<ev::WRITE> etc.
		1692
		1693	These are just enum values with the same values as the C<EV_READ> etc.
		1694	macros from F<ev.h>.
		1695
		1696	=item C<ev::tstamp>, C<ev::now>
		1697
		1698	Aliases to the same types/functions as with the C<ev_> prefix.
		1699
		1700	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1701
		1702	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1703	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1704	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1705	defines by many implementations.
		1706
		1707	All of those classes have these methods:
		1708
		1709	=over 4
		1710
		1711	=item ev::TYPE::TYPE (object *, object::method *)
		1712
		1713	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1714
		1715	=item ev::TYPE::~TYPE
		1716
		1717	The constructor takes a pointer to an object and a method pointer to
		1718	the event handler callback to call in this class. The constructor calls
		1719	C<ev_init> for you, which means you have to call the C<set> method
		1720	before starting it. If you do not specify a loop then the constructor
		1721	automatically associates the default loop with this watcher.
		1722
		1723	The destructor automatically stops the watcher if it is active.
		1724
		1725	=item w->set (struct ev_loop *)
		1726
		1727	Associates a different C<struct ev_loop> with this watcher. You can only
		1728	do this when the watcher is inactive (and not pending either).
		1729
		1730	=item w->set ([args])
		1731
		1732	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1733	called at least once. Unlike the C counterpart, an active watcher gets
		1734	automatically stopped and restarted.
		1735
		1736	=item w->start ()
		1737
		1738	Starts the watcher. Note that there is no C<loop> argument as the
		1739	constructor already takes the loop.
		1740
		1741	=item w->stop ()
		1742
		1743	Stops the watcher if it is active. Again, no C<loop> argument.
		1744
		1745	=item w->again () C<ev::timer>, C<ev::periodic> only
		1746
		1747	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1748	C<ev_TYPE_again> function.
		1749
		1750	=item w->sweep () C<ev::embed> only
		1751
		1752	Invokes C<ev_embed_sweep>.
		1753
		1754	=item w->update () C<ev::stat> only
		1755
		1756	Invokes C<ev_stat_stat>.
		1757
		1758	=back
		1759
		1760	=back
		1761
		1762	Example: Define a class with an IO and idle watcher, start one of them in
		1763	the constructor.
		1764
		1765	class myclass
		1766	{
		1767	ev_io io; void io_cb (ev::io &w, int revents);
		1768	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1769
		1770	myclass ();
		1771	}
		1772
		1773	myclass::myclass (int fd)
		1774	: io (this, &myclass::io_cb),
		1775	idle (this, &myclass::idle_cb)
		1776	{
		1777	io.start (fd, ev::READ);
		1778	}
		1779
		1780
		1781	=head1 MACRO MAGIC
		1782
		1783	Libev can be compiled with a variety of options, the most fundemantal is
		1784	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1785	callbacks have an initial C<struct ev_loop *> argument.
		1786
		1787	To make it easier to write programs that cope with either variant, the
		1788	following macros are defined:
		1789
		1790	=over 4
		1791
		1792	=item C<EV_A>, C<EV_A_>
		1793
		1794	This provides the loop I<argument> for functions, if one is required ("ev
		1795	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1796	C<EV_A_> is used when other arguments are following. Example:
		1797
		1798	ev_unref (EV_A);
		1799	ev_timer_add (EV_A_ watcher);
		1800	ev_loop (EV_A_ 0);
		1801
		1802	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1803	which is often provided by the following macro.
		1804
		1805	=item C<EV_P>, C<EV_P_>
		1806
		1807	This provides the loop I<parameter> for functions, if one is required ("ev
		1808	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1809	C<EV_P_> is used when other parameters are following. Example:
		1810
		1811	// this is how ev_unref is being declared
		1812	static void ev_unref (EV_P);
		1813
		1814	// this is how you can declare your typical callback
		1815	static void cb (EV_P_ ev_timer *w, int revents)
		1816
		1817	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1818	suitable for use with C<EV_A>.
		1819
		1820	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1821
		1822	Similar to the other two macros, this gives you the value of the default
		1823	loop, if multiple loops are supported ("ev loop default").
		1824
		1825	=back
		1826
		1827	Example: Declare and initialise a check watcher, working regardless of
		1828	wether multiple loops are supported or not.
		1829
		1830	static void
		1831	check_cb (EV_P_ ev_timer *w, int revents)
		1832	{
		1833	ev_check_stop (EV_A_ w);
		1834	}
		1835
		1836	ev_check check;
		1837	ev_check_init (&check, check_cb);
		1838	ev_check_start (EV_DEFAULT_ &check);
		1839	ev_loop (EV_DEFAULT_ 0);
		1840
		1841
		1842	=head1 EMBEDDING
		1843
		1844	Libev can (and often is) directly embedded into host
		1845	applications. Examples of applications that embed it include the Deliantra
		1846	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1847	and rxvt-unicode.
		1848
		1849	The goal is to enable you to just copy the neecssary files into your
		1850	source directory without having to change even a single line in them, so
		1851	you can easily upgrade by simply copying (or having a checked-out copy of
		1852	libev somewhere in your source tree).
		1853
		1854	=head2 FILESETS
		1855
		1856	Depending on what features you need you need to include one or more sets of files
		1857	in your app.
		1858
		1859	=head3 CORE EVENT LOOP
		1860
		1861	To include only the libev core (all the C<ev_*> functions), with manual
		1862	configuration (no autoconf):
		1863
		1864	#define EV_STANDALONE 1
		1865	#include "ev.c"
		1866
		1867	This will automatically include F<ev.h>, too, and should be done in a
		1868	single C source file only to provide the function implementations. To use
		1869	it, do the same for F<ev.h> in all files wishing to use this API (best
		1870	done by writing a wrapper around F<ev.h> that you can include instead and
		1871	where you can put other configuration options):
		1872
		1873	#define EV_STANDALONE 1
		1874	#include "ev.h"
		1875
		1876	Both header files and implementation files can be compiled with a C++
		1877	compiler (at least, thats a stated goal, and breakage will be treated
		1878	as a bug).
		1879
		1880	You need the following files in your source tree, or in a directory
		1881	in your include path (e.g. in libev/ when using -Ilibev):
		1882
		1883	ev.h
		1884	ev.c
		1885	ev_vars.h
		1886	ev_wrap.h
		1887
		1888	ev_win32.c required on win32 platforms only
		1889
		1890	ev_select.c only when select backend is enabled (which is by default)
		1891	ev_poll.c only when poll backend is enabled (disabled by default)
		1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1894	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1895
		1896	F<ev.c> includes the backend files directly when enabled, so you only need
		1897	to compile this single file.
		1898
		1899	=head3 LIBEVENT COMPATIBILITY API
		1900
		1901	To include the libevent compatibility API, also include:
		1902
		1903	#include "event.c"
		1904
		1905	in the file including F<ev.c>, and:
		1906
		1907	#include "event.h"
		1908
		1909	in the files that want to use the libevent API. This also includes F<ev.h>.
		1910
		1911	You need the following additional files for this:
		1912
		1913	event.h
		1914	event.c
		1915
		1916	=head3 AUTOCONF SUPPORT
		1917
		1918	Instead of using C<EV_STANDALONE=1> and providing your config in
		1919	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1920	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1921	include F<config.h> and configure itself accordingly.
		1922
		1923	For this of course you need the m4 file:
		1924
		1925	libev.m4
		1926
		1927	=head2 PREPROCESSOR SYMBOLS/MACROS
		1928
		1929	Libev can be configured via a variety of preprocessor symbols you have to define
		1930	before including any of its files. The default is not to build for multiplicity
		1931	and only include the select backend.
		1932
		1933	=over 4
		1934
		1935	=item EV_STANDALONE
		1936
		1937	Must always be C<1> if you do not use autoconf configuration, which
		1938	keeps libev from including F<config.h>, and it also defines dummy
		1939	implementations for some libevent functions (such as logging, which is not
		1940	supported). It will also not define any of the structs usually found in
		1941	F<event.h> that are not directly supported by the libev core alone.
		1942
		1943	=item EV_USE_MONOTONIC
		1944
		1945	If defined to be C<1>, libev will try to detect the availability of the
		1946	monotonic clock option at both compiletime and runtime. Otherwise no use
		1947	of the monotonic clock option will be attempted. If you enable this, you
		1948	usually have to link against librt or something similar. Enabling it when
		1949	the functionality isn't available is safe, though, althoguh you have
		1950	to make sure you link against any libraries where the C<clock_gettime>
		1951	function is hiding in (often F<-lrt>).
		1952
		1953	=item EV_USE_REALTIME
		1954
		1955	If defined to be C<1>, libev will try to detect the availability of the
		1956	realtime clock option at compiletime (and assume its availability at
		1957	runtime if successful). Otherwise no use of the realtime clock option will
		1958	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1959	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1960	in the description of C<EV_USE_MONOTONIC>, though.
		1961
		1962	=item EV_USE_SELECT
		1963
		1964	If undefined or defined to be C<1>, libev will compile in support for the
		1965	C<select>(2) backend. No attempt at autodetection will be done: if no
		1966	other method takes over, select will be it. Otherwise the select backend
		1967	will not be compiled in.
		1968
		1969	=item EV_SELECT_USE_FD_SET
		1970
		1971	If defined to C<1>, then the select backend will use the system C<fd_set>
		1972	structure. This is useful if libev doesn't compile due to a missing
		1973	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1974	exotic systems. This usually limits the range of file descriptors to some
		1975	low limit such as 1024 or might have other limitations (winsocket only
		1976	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1977	influence the size of the C<fd_set> used.
		1978
		1979	=item EV_SELECT_IS_WINSOCKET
		1980
		1981	When defined to C<1>, the select backend will assume that
		1982	select/socket/connect etc. don't understand file descriptors but
		1983	wants osf handles on win32 (this is the case when the select to
		1984	be used is the winsock select). This means that it will call
		1985	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1986	it is assumed that all these functions actually work on fds, even
		1987	on win32. Should not be defined on non-win32 platforms.
		1988
		1989	=item EV_USE_POLL
		1990
		1991	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1992	backend. Otherwise it will be enabled on non-win32 platforms. It
		1993	takes precedence over select.
		1994
		1995	=item EV_USE_EPOLL
		1996
		1997	If defined to be C<1>, libev will compile in support for the Linux
		1998	C<epoll>(7) backend. Its availability will be detected at runtime,
		1999	otherwise another method will be used as fallback. This is the
		2000	preferred backend for GNU/Linux systems.
		2001
		2002	=item EV_USE_KQUEUE
		2003
		2004	If defined to be C<1>, libev will compile in support for the BSD style
		2005	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2006	otherwise another method will be used as fallback. This is the preferred
		2007	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2008	supports some types of fds correctly (the only platform we found that
		2009	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2010	not be used unless explicitly requested. The best way to use it is to find
		2011	out whether kqueue supports your type of fd properly and use an embedded
		2012	kqueue loop.
		2013
		2014	=item EV_USE_PORT
		2015
		2016	If defined to be C<1>, libev will compile in support for the Solaris
		2017	10 port style backend. Its availability will be detected at runtime,
		2018	otherwise another method will be used as fallback. This is the preferred
		2019	backend for Solaris 10 systems.
		2020
		2021	=item EV_USE_DEVPOLL
		2022
		2023	reserved for future expansion, works like the USE symbols above.
		2024
		2025	=item EV_USE_INOTIFY
		2026
		2027	If defined to be C<1>, libev will compile in support for the Linux inotify
		2028	interface to speed up C<ev_stat> watchers. Its actual availability will
		2029	be detected at runtime.
		2030
		2031	=item EV_H
		2032
		2033	The name of the F<ev.h> header file used to include it. The default if
		2034	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2035	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2036
		2037	=item EV_CONFIG_H
		2038
		2039	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2040	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2041	C<EV_H>, above.
		2042
		2043	=item EV_EVENT_H
		2044
		2045	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2046	of how the F<event.h> header can be found.
		2047
		2048	=item EV_PROTOTYPES
		2049
		2050	If defined to be C<0>, then F<ev.h> will not define any function
		2051	prototypes, but still define all the structs and other symbols. This is
		2052	occasionally useful if you want to provide your own wrapper functions
		2053	around libev functions.
		2054
		2055	=item EV_MULTIPLICITY
		2056
		2057	If undefined or defined to C<1>, then all event-loop-specific functions
		2058	will have the C<struct ev_loop *> as first argument, and you can create
		2059	additional independent event loops. Otherwise there will be no support
		2060	for multiple event loops and there is no first event loop pointer
		2061	argument. Instead, all functions act on the single default loop.
		2062
		2063	=item EV_PERIODIC_ENABLE
		2064
		2065	If undefined or defined to be C<1>, then periodic timers are supported. If
		2066	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2067	code.
		2068
		2069	=item EV_EMBED_ENABLE
		2070
		2071	If undefined or defined to be C<1>, then embed watchers are supported. If
		2072	defined to be C<0>, then they are not.
		2073
		2074	=item EV_STAT_ENABLE
		2075
		2076	If undefined or defined to be C<1>, then stat watchers are supported. If
		2077	defined to be C<0>, then they are not.
		2078
		2079	=item EV_FORK_ENABLE
		2080
		2081	If undefined or defined to be C<1>, then fork watchers are supported. If
		2082	defined to be C<0>, then they are not.
		2083
		2084	=item EV_MINIMAL
		2085
		2086	If you need to shave off some kilobytes of code at the expense of some
		2087	speed, define this symbol to C<1>. Currently only used for gcc to override
		2088	some inlining decisions, saves roughly 30% codesize of amd64.
		2089
		2090	=item EV_PID_HASHSIZE
		2091
		2092	C<ev_child> watchers use a small hash table to distribute workload by
		2093	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2094	than enough. If you need to manage thousands of children you might want to
		2095	increase this value (I<must> be a power of two).
		2096
		2097	=item EV_INOTIFY_HASHSIZE
		2098
		2099	C<ev_staz> watchers use a small hash table to distribute workload by
		2100	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2101	usually more than enough. If you need to manage thousands of C<ev_stat>
		2102	watchers you might want to increase this value (I<must> be a power of
		2103	two).
		2104
		2105	=item EV_COMMON
		2106
		2107	By default, all watchers have a C<void *data> member. By redefining
		2108	this macro to a something else you can include more and other types of
		2109	members. You have to define it each time you include one of the files,
		2110	though, and it must be identical each time.
		2111
		2112	For example, the perl EV module uses something like this:
		2113
		2114	#define EV_COMMON \
		2115	SV *self; /* contains this struct */ \
		2116	SV *cb_sv, *fh /* note no trailing ";" */
		2117
		2118	=item EV_CB_DECLARE (type)
		2119
		2120	=item EV_CB_INVOKE (watcher, revents)
		2121
		2122	=item ev_set_cb (ev, cb)
		2123
		2124	Can be used to change the callback member declaration in each watcher,
		2125	and the way callbacks are invoked and set. Must expand to a struct member
		2126	definition and a statement, respectively. See the F<ev.v> header file for
		2127	their default definitions. One possible use for overriding these is to
		2128	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2129	method calls instead of plain function calls in C++.
		2130
		2131	=head2 EXAMPLES
		2132
		2133	For a real-world example of a program the includes libev
		2134	verbatim, you can have a look at the EV perl module
		2135	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2136	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2137	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2138	will be compiled. It is pretty complex because it provides its own header
		2139	file.
		2140
		2141	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2142	that everybody includes and which overrides some autoconf choices:
		2143
		2144	#define EV_USE_POLL 0
		2145	#define EV_MULTIPLICITY 0
		2146	#define EV_PERIODICS 0
		2147	#define EV_CONFIG_H <config.h>
		2148
		2149	#include "ev++.h"
		2150
		2151	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2152
		2153	#include "ev_cpp.h"
		2154	#include "ev.c"
		2155
		2156
		2157	=head1 COMPLEXITIES
		2158
		2159	In this section the complexities of (many of) the algorithms used inside
		2160	libev will be explained. For complexity discussions about backends see the
		2161	documentation for C<ev_default_init>.
		2162
		2163	=over 4
		2164
		2165	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2166
		2167	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2168
		2169	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2170
		2171	=item Stopping check/prepare/idle watchers: O(1)
		2172
		2173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2174
		2175	=item Finding the next timer per loop iteration: O(1)
		2176
		2177	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2178
		2179	=item Activating one watcher: O(1)
		2180
		2181	=back
		2182
		2183
742	=head1 AUTHOR	2184	=head1 AUTHOR
743		2185
744	Marc Lehmann <libev@schmorp.de>.	2186	Marc Lehmann <libev@schmorp.de>.
745		2187

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