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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
		106
		107	=head1 GLOBAL FUNCTIONS
		108
		109	These functions can be called anytime, even before initialising the
		110	library in any way.
51		111
52	=over 4	112	=over 4
53		113
54	=item ev_tstamp ev_time ()	114	=item ev_tstamp ev_time ()
55		115
56	Returns the current time as libev would use it.	116	Returns the current time as libev would use it. Please note that the
		117	C<ev_now> function is usually faster and also often returns the timestamp
		118	you actually want to know.
		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
57		125
58	=item int ev_version_major ()	126	=item int ev_version_major ()
59		127
60	=item int ev_version_minor ()	128	=item int ev_version_minor ()
61		129
62	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
63	you linked against by calling the functions C<ev_version_major> and	131	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	132	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	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	134	version of the library your program was compiled against.
67		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
68	Usually, its a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	142	not a problem.
72		143
		144	Example: Make sure we haven't accidentally been linked against the wrong
		145	version.
		146
		147	assert (("libev version mismatch",
		148	ev_version_major () == EV_VERSION_MAJOR
		149	&& ev_version_minor () >= EV_VERSION_MINOR));
		150
		151	=item unsigned int ev_supported_backends ()
		152
		153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		154	value) compiled into this binary of libev (independent of their
		155	availability on the system you are running on). See C<ev_default_loop> for
		156	a description of the set values.
		157
		158	Example: make sure we have the epoll method, because yeah this is cool and
		159	a must have and can we have a torrent of it please!!!11
		160
		161	assert (("sorry, no epoll, no sex",
		162	ev_supported_backends () & EVBACKEND_EPOLL));
		163
		164	=item unsigned int ev_recommended_backends ()
		165
		166	Return the set of all backends compiled into this binary of libev and also
		167	recommended for this platform. This set is often smaller than the one
		168	returned by C<ev_supported_backends>, as for example kqueue is broken on
		169	most BSDs and will not be autodetected unless you explicitly request it
		170	(assuming you know what you are doing). This is the set of backends that
		171	libev will probe for if you specify no backends explicitly.
		172
		173	=item unsigned int ev_embeddable_backends ()
		174
		175	Returns the set of backends that are embeddable in other event loops. This
		176	is the theoretical, all-platform, value. To find which backends
		177	might be supported on the current system, you would need to look at
		178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		179	recommended ones.
		180
		181	See the description of C<ev_embed> watchers for more info.
		182
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		184
75	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
77	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
78	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
79	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
80		191
81	You could override this function in high-availability programs to, say,	192	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,	193	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.	194	or even to sleep a while and retry until some memory is available.
		195
		196	Example: Replace the libev allocator with one that waits a bit and then
		197	retries).
		198
		199	static void *
		200	persistent_realloc (void *ptr, size_t size)
		201	{
		202	for (;;)
		203	{
		204	void *newptr = realloc (ptr, size);
		205
		206	if (newptr)
		207	return newptr;
		208
		209	sleep (60);
		210	}
		211	}
		212
		213	...
		214	ev_set_allocator (persistent_realloc);
84		215
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	216	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		217
87	Set the callback function to call on a retryable syscall error (such	218	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	219	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	221	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	222	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	223	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	224	(such as abort).
94		225
		226	Example: This is basically the same thing that libev does internally, too.
		227
		228	static void
		229	fatal_error (const char *msg)
		230	{
		231	perror (msg);
		232	abort ();
		233	}
		234
		235	...
		236	ev_set_syserr_cb (fatal_error);
		237
95	=back	238	=back
96		239
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		241
99	An event loop is described by a C<struct ev_loop *>. The library knows two	242	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	243	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	244	events, and dynamically created loops which do not.
102		245
103	If you use threads, a common model is to run the default event loop	246	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	247	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	248	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	249	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	250	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	251	done correctly, because it's hideous and inefficient).
109		252
110	=over 4	253	=over 4
111		254
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	255	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		256
114	This will initialise the default event loop if it hasn't been initialised	257	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	258	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	259	false. If it already was initialised it simply returns it (and ignores the
117	flags).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		261
119	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
120	function.	263	function.
121		264
122	The flags argument can be used to specify special behaviour or specific	265	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).	266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		267
125	It supports the following flags:	268	The following flags are supported:
126		269
127	=over 4	270	=over 4
128		271
129	=item EVFLAG_AUTO	272	=item C<EVFLAG_AUTO>
130		273
131	The default flags value. Use this if you have no clue (its the right	274	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	275	thing, believe me).
133		276
134	=item EVFLAG_NOENV	277	=item C<EVFLAG_NOENV>
135		278
136	If this flag bit is ored into the flag value (or the program runs setuid	279	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	280	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	282	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	283	useful to try out specific backends to test their performance, or to work
141	around bugs.	284	around bugs.
142		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
143	=item EVMETHOD_SELECT portable select backend	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		307
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	308	This is your standard select(2) backend. Not I<completely> standard, as
		309	libev tries to roll its own fd_set with no limits on the number of fds,
		310	but if that fails, expect a fairly low limit on the number of fds when
		311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		312	the fastest backend for a low number of fds.
146		313
147	=item EVMETHOD_EPOLL linux only	314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
148		315
149	=item EVMETHOD_KQUEUE some bsds only	316	And this is your standard poll(2) backend. It's more complicated than
		317	select, but handles sparse fds better and has no artificial limit on the
		318	number of fds you can use (except it will slow down considerably with a
		319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
150		320
151	=item EVMETHOD_DEVPOLL solaris 8 only	321	=item C<EVBACKEND_EPOLL> (value 4, Linux)
152		322
153	=item EVMETHOD_PORT solaris 10 only	323	For few fds, this backend is a bit little slower than poll and select,
		324	but it scales phenomenally better. While poll and select usually scale
		325	like O(total_fds) where n is the total number of fds (or the highest fd),
		326	epoll scales either O(1) or O(active_fds). The epoll design has a number
		327	of shortcomings, such as silently dropping events in some hard-to-detect
		328	cases and rewiring a syscall per fd change, no fork support and bad
		329	support for dup:
		330
		331	While stopping, setting and starting an I/O watcher in the same iteration
		332	will result in some caching, there is still a syscall per such incident
		333	(because the fd could point to a different file description now), so its
		334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		335	very well if you register events for both fds.
		336
		337	Please note that epoll sometimes generates spurious notifications, so you
		338	need to use non-blocking I/O or other means to avoid blocking when no data
		339	(or space) is available.
		340
		341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		342
		343	Kqueue deserves special mention, as at the time of this writing, it
		344	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		345	with anything but sockets and pipes, except on Darwin, where of course
		346	it's completely useless). For this reason it's not being "autodetected"
		347	unless you explicitly specify it explicitly in the flags (i.e. using
		348	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		349	system like NetBSD.
		350
		351	You still can embed kqueue into a normal poll or select backend and use it
		352	only for sockets (after having made sure that sockets work with kqueue on
		353	the target platform). See C<ev_embed> watchers for more info.
		354
		355	It scales in the same way as the epoll backend, but the interface to the
		356	kernel is more efficient (which says nothing about its actual speed, of
		357	course). While stopping, setting and starting an I/O watcher does never
		358	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
		359	two event changes per incident, support for C<fork ()> is very bad and it
		360	drops fds silently in similarly hard-to-detect cases.
		361
		362	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		363
		364	This is not implemented yet (and might never be).
		365
		366	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		367
		368	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		369	it's really slow, but it still scales very well (O(active_fds)).
		370
		371	Please note that solaris event ports can deliver a lot of spurious
		372	notifications, so you need to use non-blocking I/O or other means to avoid
		373	blocking when no data (or space) is available.
		374
		375	=item C<EVBACKEND_ALL>
		376
		377	Try all backends (even potentially broken ones that wouldn't be tried
		378	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		379	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		380
		381	=back
154		382
155	If one or more of these are ored into the flags value, then only these	383	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	384	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	385	specified, most compiled-in backend will be tried, usually in reverse
		386	order of their flag values :)
158		387
159	=back	388	The most typical usage is like this:
		389
		390	if (!ev_default_loop (0))
		391	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		392
		393	Restrict libev to the select and poll backends, and do not allow
		394	environment settings to be taken into account:
		395
		396	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		397
		398	Use whatever libev has to offer, but make sure that kqueue is used if
		399	available (warning, breaks stuff, best use only with your own private
		400	event loop and only if you know the OS supports your types of fds):
		401
		402	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		403
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	404	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		405
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	406	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	407	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	408	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).	409	undefined behaviour (or a failed assertion if assertions are enabled).
167		410
		411	Example: Try to create a event loop that uses epoll and nothing else.
		412
		413	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		414	if (!epoller)
		415	fatal ("no epoll found here, maybe it hides under your chair");
		416
168	=item ev_default_destroy ()	417	=item ev_default_destroy ()
169		418
170	Destroys the default loop again (frees all memory and kernel state	419	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	420	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	421	sense, so e.g. C<ev_is_active> might still return true. It is your
		422	responsibility to either stop all watchers cleanly yoursef I<before>
		423	calling this function, or cope with the fact afterwards (which is usually
		424	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		425	for example).
		426
		427	Note that certain global state, such as signal state, will not be freed by
		428	this function, and related watchers (such as signal and child watchers)
		429	would need to be stopped manually.
		430
		431	In general it is not advisable to call this function except in the
		432	rare occasion where you really need to free e.g. the signal handling
		433	pipe fds. If you need dynamically allocated loops it is better to use
		434	C<ev_loop_new> and C<ev_loop_destroy>).
173		435
174	=item ev_loop_destroy (loop)	436	=item ev_loop_destroy (loop)
175		437
176	Like C<ev_default_destroy>, but destroys an event loop created by an	438	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	439	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	443	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	444	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	445	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	446	again makes little sense).
185		447
186	You I<must> call this function after forking if and only if you want to	448	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	449	only if you want to use the event library in both processes. If you just
188	have to call it.	450	fork+exec, you don't have to call it.
189		451
190	The function itself is quite fast and its usually not a problem to call	452	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	453	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>:	454	quite nicely into a call to C<pthread_atfork>:
193		455
194	pthread_atfork (0, 0, ev_default_fork);	456	pthread_atfork (0, 0, ev_default_fork);
		457
		458	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		459	without calling this function, so if you force one of those backends you
		460	do not need to care.
195		461
196	=item ev_loop_fork (loop)	462	=item ev_loop_fork (loop)
197		463
198	Like C<ev_default_fork>, but acts on an event loop created by	464	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	465	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.	466	after fork, and how you do this is entirely your own problem.
201		467
		468	=item unsigned int ev_loop_count (loop)
		469
		470	Returns the count of loop iterations for the loop, which is identical to
		471	the number of times libev did poll for new events. It starts at C<0> and
		472	happily wraps around with enough iterations.
		473
		474	This value can sometimes be useful as a generation counter of sorts (it
		475	"ticks" the number of loop iterations), as it roughly corresponds with
		476	C<ev_prepare> and C<ev_check> calls.
		477
202	=item unsigned int ev_method (loop)	478	=item unsigned int ev_backend (loop)
203		479
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	480	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	481	use.
206		482
207	=item ev_tstamp = ev_now (loop)	483	=item ev_tstamp ev_now (loop)
208		484
209	Returns the current "event loop time", which is the time the event loop	485	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	486	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	487	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	488	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).	489	event occurring (or more correctly, libev finding out about it).
214		490
215	=item ev_loop (loop, int flags)	491	=item ev_loop (loop, int flags)
216		492
217	Finally, this is it, the event handler. This function usually is called	493	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	494	after you initialised all your watchers and you want to start handling
219	events.	495	events.
220		496
221	If the flags argument is specified as 0, it will not return until either	497	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.	498	either no event watchers are active anymore or C<ev_unloop> was called.
		499
		500	Please note that an explicit C<ev_unloop> is usually better than
		501	relying on all watchers to be stopped when deciding when a program has
		502	finished (especially in interactive programs), but having a program that
		503	automatically loops as long as it has to and no longer by virtue of
		504	relying on its watchers stopping correctly is a thing of beauty.
223		505
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	506	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	507	those events and any outstanding ones, but will not block your process in
226	case there are no events.	508	case there are no events and will return after one iteration of the loop.
227		509
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	510	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	511	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	512	your process until at least one new event arrives, and will return after
		513	one iteration of the loop. This is useful if you are waiting for some
		514	external event in conjunction with something not expressible using other
		515	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		516	usually a better approach for this kind of thing.
231		517
232	This flags value could be used to implement alternative looping	518	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	519
234	more generic mechanism.	520	- Before the first iteration, call any pending watchers.
		521	* If there are no active watchers (reference count is zero), return.
		522	- Queue all prepare watchers and then call all outstanding watchers.
		523	- If we have been forked, recreate the kernel state.
		524	- Update the kernel state with all outstanding changes.
		525	- Update the "event loop time".
		526	- Calculate for how long to block.
		527	- Block the process, waiting for any events.
		528	- Queue all outstanding I/O (fd) events.
		529	- Update the "event loop time" and do time jump handling.
		530	- Queue all outstanding timers.
		531	- Queue all outstanding periodics.
		532	- If no events are pending now, queue all idle watchers.
		533	- Queue all check watchers.
		534	- Call all queued watchers in reverse order (i.e. check watchers first).
		535	Signals and child watchers are implemented as I/O watchers, and will
		536	be handled here by queueing them when their watcher gets executed.
		537	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		538	were used, return, otherwise continue with step *.
		539
		540	Example: Queue some jobs and then loop until no events are outsanding
		541	anymore.
		542
		543	... queue jobs here, make sure they register event watchers as long
		544	... as they still have work to do (even an idle watcher will do..)
		545	ev_loop (my_loop, 0);
		546	... jobs done. yeah!
235		547
236	=item ev_unloop (loop, how)	548	=item ev_unloop (loop, how)
237		549
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	550	Can be used to make a call to C<ev_loop> return early (but only after it
		551	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>	552	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>	553	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.
242		554
243	=item ev_ref (loop)	555	=item ev_ref (loop)
244		556
245	=item ev_unref (loop)	557	=item ev_unref (loop)
246		558
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	559	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	560	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	561	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	562	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	563	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	564	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	565	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	566	no event watchers registered by it are active. It is also an excellent
255	before stop.	567	way to do this for generic recurring timers or from within third-party
		568	libraries. Just remember to I<unref after start> and I<ref before stop>.
		569
		570	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		571	running when nothing else is active.
		572
		573	struct ev_signal exitsig;
		574	ev_signal_init (&exitsig, sig_cb, SIGINT);
		575	ev_signal_start (loop, &exitsig);
		576	evf_unref (loop);
		577
		578	Example: For some weird reason, unregister the above signal handler again.
		579
		580	ev_ref (loop);
		581	ev_signal_stop (loop, &exitsig);
		582
		583	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		584
		585	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		586
		587	These advanced functions influence the time that libev will spend waiting
		588	for events. Both are by default C<0>, meaning that libev will try to
		589	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		590
		591	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		592	allows libev to delay invocation of I/O and timer/periodic callbacks to
		593	increase efficiency of loop iterations.
		594
		595	The background is that sometimes your program runs just fast enough to
		596	handle one (or very few) event(s) per loop iteration. While this makes
		597	the program responsive, it also wastes a lot of CPU time to poll for new
		598	events, especially with backends like C<select ()> which have a high
		599	overhead for the actual polling but can deliver many events at once.
		600
		601	By setting a higher I<io collect interval> you allow libev to spend more
		602	time collecting I/O events, so you can handle more events per iteration,
		603	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		604	C<ev_timer>) will be not affected. Setting this to a non-null value will
		605	introduce an additional C<ev_sleep ()> call into most loop iterations.
		606
		607	Likewise, by setting a higher I<timeout collect interval> you allow libev
		608	to spend more time collecting timeouts, at the expense of increased
		609	latency (the watcher callback will be called later). C<ev_io> watchers
		610	will not be affected. Setting this to a non-null value will not introduce
		611	any overhead in libev.
		612
		613	Many (busy) programs can usually benefit by setting the io collect
		614	interval to a value near C<0.1> or so, which is often enough for
		615	interactive servers (of course not for games), likewise for timeouts. It
		616	usually doesn't make much sense to set it to a lower value than C<0.01>,
		617	as this approsaches the timing granularity of most systems.
256		618
257	=back	619	=back
		620
258		621
259	=head1 ANATOMY OF A WATCHER	622	=head1 ANATOMY OF A WATCHER
260		623
261	A watcher is a structure that you create and register to record your	624	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	625	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:	626	become readable, you would create an C<ev_io> watcher for that:
264		627
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	628	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	629	{
267	ev_io_stop (w);	630	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	631	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	658	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	659	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		660
298	As long as your watcher is active (has been started but not stopped) you	661	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	662	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	663	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		664
307	Each and every callback receives the event loop pointer as first, the	665	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	666	registered watcher structure as second, and a bitset of received events as
309	third argument.	667	third argument.
310		668
311	The rceeived events usually include a single bit per event type received	669	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	670	(you can receive multiple events at the same time). The possible bit masks
313	are:	671	are:
314		672
315	=over 4	673	=over 4
316		674
317	=item EV_READ	675	=item C<EV_READ>
318		676
319	=item EV_WRITE	677	=item C<EV_WRITE>
320		678
321	The file descriptor in the ev_io watcher has become readable and/or	679	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	680	writable.
323		681
324	=item EV_TIMEOUT	682	=item C<EV_TIMEOUT>
325		683
326	The ev_timer watcher has timed out.	684	The C<ev_timer> watcher has timed out.
327		685
328	=item EV_PERIODIC	686	=item C<EV_PERIODIC>
329		687
330	The ev_periodic watcher has timed out.	688	The C<ev_periodic> watcher has timed out.
331		689
332	=item EV_SIGNAL	690	=item C<EV_SIGNAL>
333		691
334	The signal specified in the ev_signal watcher has been received by a thread.	692	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		693
336	=item EV_CHILD	694	=item C<EV_CHILD>
337		695
338	The pid specified in the ev_child watcher has received a status change.	696	The pid specified in the C<ev_child> watcher has received a status change.
339		697
		698	=item C<EV_STAT>
		699
		700	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		701
340	=item EV_IDLE	702	=item C<EV_IDLE>
341		703
342	The ev_idle watcher has determined that you have nothing better to do.	704	The C<ev_idle> watcher has determined that you have nothing better to do.
343		705
344	=item EV_PREPARE	706	=item C<EV_PREPARE>
345		707
346	=item EV_CHECK	708	=item C<EV_CHECK>
347		709
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	710	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	711	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	712	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	713	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	714	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	715	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	716	C<ev_loop> from blocking).
355		717
		718	=item C<EV_EMBED>
		719
		720	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		721
		722	=item C<EV_FORK>
		723
		724	The event loop has been resumed in the child process after fork (see
		725	C<ev_fork>).
		726
356	=item EV_ERROR	727	=item C<EV_ERROR>
357		728
358	An unspecified error has occured, the watcher has been stopped. This might	729	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	730	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	731	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	732	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	738	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	739	programs, though, so beware.
369		740
370	=back	741	=back
371		742
		743	=head2 GENERIC WATCHER FUNCTIONS
		744
		745	In the following description, C<TYPE> stands for the watcher type,
		746	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		747
		748	=over 4
		749
		750	=item C<ev_init> (ev_TYPE *watcher, callback)
		751
		752	This macro initialises the generic portion of a watcher. The contents
		753	of the watcher object can be arbitrary (so C<malloc> will do). Only
		754	the generic parts of the watcher are initialised, you I<need> to call
		755	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		756	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		757	which rolls both calls into one.
		758
		759	You can reinitialise a watcher at any time as long as it has been stopped
		760	(or never started) and there are no pending events outstanding.
		761
		762	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		763	int revents)>.
		764
		765	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		766
		767	This macro initialises the type-specific parts of a watcher. You need to
		768	call C<ev_init> at least once before you call this macro, but you can
		769	call C<ev_TYPE_set> any number of times. You must not, however, call this
		770	macro on a watcher that is active (it can be pending, however, which is a
		771	difference to the C<ev_init> macro).
		772
		773	Although some watcher types do not have type-specific arguments
		774	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		775
		776	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		777
		778	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		779	calls into a single call. This is the most convinient method to initialise
		780	a watcher. The same limitations apply, of course.
		781
		782	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		783
		784	Starts (activates) the given watcher. Only active watchers will receive
		785	events. If the watcher is already active nothing will happen.
		786
		787	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		788
		789	Stops the given watcher again (if active) and clears the pending
		790	status. It is possible that stopped watchers are pending (for example,
		791	non-repeating timers are being stopped when they become pending), but
		792	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		793	you want to free or reuse the memory used by the watcher it is therefore a
		794	good idea to always call its C<ev_TYPE_stop> function.
		795
		796	=item bool ev_is_active (ev_TYPE *watcher)
		797
		798	Returns a true value iff the watcher is active (i.e. it has been started
		799	and not yet been stopped). As long as a watcher is active you must not modify
		800	it.
		801
		802	=item bool ev_is_pending (ev_TYPE *watcher)
		803
		804	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		805	events but its callback has not yet been invoked). As long as a watcher
		806	is pending (but not active) you must not call an init function on it (but
		807	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		808	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		809	it).
		810
		811	=item callback ev_cb (ev_TYPE *watcher)
		812
		813	Returns the callback currently set on the watcher.
		814
		815	=item ev_cb_set (ev_TYPE *watcher, callback)
		816
		817	Change the callback. You can change the callback at virtually any time
		818	(modulo threads).
		819
		820	=item ev_set_priority (ev_TYPE *watcher, priority)
		821
		822	=item int ev_priority (ev_TYPE *watcher)
		823
		824	Set and query the priority of the watcher. The priority is a small
		825	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		826	(default: C<-2>). Pending watchers with higher priority will be invoked
		827	before watchers with lower priority, but priority will not keep watchers
		828	from being executed (except for C<ev_idle> watchers).
		829
		830	This means that priorities are I<only> used for ordering callback
		831	invocation after new events have been received. This is useful, for
		832	example, to reduce latency after idling, or more often, to bind two
		833	watchers on the same event and make sure one is called first.
		834
		835	If you need to suppress invocation when higher priority events are pending
		836	you need to look at C<ev_idle> watchers, which provide this functionality.
		837
		838	You I<must not> change the priority of a watcher as long as it is active or
		839	pending.
		840
		841	The default priority used by watchers when no priority has been set is
		842	always C<0>, which is supposed to not be too high and not be too low :).
		843
		844	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		845	fine, as long as you do not mind that the priority value you query might
		846	or might not have been adjusted to be within valid range.
		847
		848	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		849
		850	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		851	C<loop> nor C<revents> need to be valid as long as the watcher callback
		852	can deal with that fact.
		853
		854	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		855
		856	If the watcher is pending, this function returns clears its pending status
		857	and returns its C<revents> bitset (as if its callback was invoked). If the
		858	watcher isn't pending it does nothing and returns C<0>.
		859
		860	=back
		861
		862
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	863	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		864
374	Each watcher has, by default, a member C<void *data> that you can change	865	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	866	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	867	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	868	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	869	member, you can also "subclass" the watcher type and provide your own
379	data:	870	data:
380		871
…		…
393	{	884	{
394	struct my_io *w = (struct my_io *)w_;	885	struct my_io *w = (struct my_io *)w_;
395	...	886	...
396	}	887	}
397		888
398	More interesting and less C-conformant ways of catsing your callback type	889	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	890	instead have been omitted.
		891
		892	Another common scenario is having some data structure with multiple
		893	watchers:
		894
		895	struct my_biggy
		896	{
		897	int some_data;
		898	ev_timer t1;
		899	ev_timer t2;
		900	}
		901
		902	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		903	you need to use C<offsetof>:
		904
		905	#include <stddef.h>
		906
		907	static void
		908	t1_cb (EV_P_ struct ev_timer *w, int revents)
		909	{
		910	struct my_biggy big = (struct my_biggy *
		911	(((char *)w) - offsetof (struct my_biggy, t1));
		912	}
		913
		914	static void
		915	t2_cb (EV_P_ struct ev_timer *w, int revents)
		916	{
		917	struct my_biggy big = (struct my_biggy *
		918	(((char *)w) - offsetof (struct my_biggy, t2));
		919	}
400		920
401		921
402	=head1 WATCHER TYPES	922	=head1 WATCHER TYPES
403		923
404	This section describes each watcher in detail, but will not repeat	924	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	925	information given in the last section. Any initialisation/set macros,
		926	functions and members specific to the watcher type are explained.
406		927
		928	Members are additionally marked with either I<[read-only]>, meaning that,
		929	while the watcher is active, you can look at the member and expect some
		930	sensible content, but you must not modify it (you can modify it while the
		931	watcher is stopped to your hearts content), or I<[read-write]>, which
		932	means you can expect it to have some sensible content while the watcher
		933	is active, but you can also modify it. Modifying it may not do something
		934	sensible or take immediate effect (or do anything at all), but libev will
		935	not crash or malfunction in any way.
		936
		937
407	=head2 struct ev_io - is my file descriptor readable or writable	938	=head2 C<ev_io> - is this file descriptor readable or writable?
408		939
409	I/O watchers check whether a file descriptor is readable or writable	940	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	941	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	942	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	943	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	944	receiving events as long as the condition persists. Remember you can stop
		945	the watcher if you don't want to act on the event and neither want to
		946	receive future events.
414		947
415	In general you can register as many read and/or write event watchers oer	948	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	949	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	950	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	951	required if you know what you are doing).
419		952
420	You have to be careful with dup'ed file descriptors, though. Some backends	953	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	954	(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	955	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	956	to the same underlying file/socket/etc. description (that is, they share
		957	the same underlying "file open").
424		958
425	If you must do this, then force the use of a known-to-be-good backend	959	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	960	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	961	C<EVBACKEND_POLL>).
		962
		963	Another thing you have to watch out for is that it is quite easy to
		964	receive "spurious" readyness notifications, that is your callback might
		965	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		966	because there is no data. Not only are some backends known to create a
		967	lot of those (for example solaris ports), it is very easy to get into
		968	this situation even with a relatively standard program structure. Thus
		969	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		970	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		971
		972	If you cannot run the fd in non-blocking mode (for example you should not
		973	play around with an Xlib connection), then you have to seperately re-test
		974	whether a file descriptor is really ready with a known-to-be good interface
		975	such as poll (fortunately in our Xlib example, Xlib already does this on
		976	its own, so its quite safe to use).
		977
		978	=head3 The special problem of disappearing file descriptors
		979
		980	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		981	descriptor (either by calling C<close> explicitly or by any other means,
		982	such as C<dup>). The reason is that you register interest in some file
		983	descriptor, but when it goes away, the operating system will silently drop
		984	this interest. If another file descriptor with the same number then is
		985	registered with libev, there is no efficient way to see that this is, in
		986	fact, a different file descriptor.
		987
		988	To avoid having to explicitly tell libev about such cases, libev follows
		989	the following policy: Each time C<ev_io_set> is being called, libev
		990	will assume that this is potentially a new file descriptor, otherwise
		991	it is assumed that the file descriptor stays the same. That means that
		992	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		993	descriptor even if the file descriptor number itself did not change.
		994
		995	This is how one would do it normally anyway, the important point is that
		996	the libev application should not optimise around libev but should leave
		997	optimisations to libev.
		998
		999	=head3 The special problem of dup'ed file descriptors
		1000
		1001	Some backends (e.g. epoll), cannot register events for file descriptors,
		1002	but only events for the underlying file descriptions. That menas when you
		1003	have C<dup ()>'ed file descriptors and register events for them, only one
		1004	file descriptor might actually receive events.
		1005
		1006	There is no workaorund possible except not registering events
		1007	for potentially C<dup ()>'ed file descriptors or to resort to
		1008	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1009
		1010	=head3 The special problem of fork
		1011
		1012	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1013	useless behaviour. Libev fully supports fork, but needs to be told about
		1014	it in the child.
		1015
		1016	To support fork in your programs, you either have to call
		1017	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1018	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1019	C<EVBACKEND_POLL>.
		1020
		1021
		1022	=head3 Watcher-Specific Functions
428		1023
429	=over 4	1024	=over 4
430		1025
431	=item ev_io_init (ev_io *, callback, int fd, int events)	1026	=item ev_io_init (ev_io *, callback, int fd, int events)
432		1027
433	=item ev_io_set (ev_io *, int fd, int events)	1028	=item ev_io_set (ev_io *, int fd, int events)
434		1029
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1030	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 |	1031	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	1032	C<EV_READ | EV_WRITE> to receive the given events.
		1033
		1034	=item int fd [read-only]
		1035
		1036	The file descriptor being watched.
		1037
		1038	=item int events [read-only]
		1039
		1040	The events being watched.
438		1041
439	=back	1042	=back
440		1043
		1044	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1045	readable, but only once. Since it is likely line-buffered, you could
		1046	attempt to read a whole line in the callback.
		1047
		1048	static void
		1049	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1050	{
		1051	ev_io_stop (loop, w);
		1052	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1053	}
		1054
		1055	...
		1056	struct ev_loop *loop = ev_default_init (0);
		1057	struct ev_io stdin_readable;
		1058	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1059	ev_io_start (loop, &stdin_readable);
		1060	ev_loop (loop, 0);
		1061
		1062
441	=head2 struct ev_timer - relative and optionally recurring timeouts	1063	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		1064
443	Timer watchers are simple relative timers that generate an event after a	1065	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	1066	given time, and optionally repeating in regular intervals after that.
445		1067
446	The timers are based on real time, that is, if you register an event that	1068	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	1069	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	1070	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1071	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	1072	monotonic clock option helps a lot here).
		1073
		1074	The relative timeouts are calculated relative to the C<ev_now ()>
		1075	time. This is usually the right thing as this timestamp refers to the time
		1076	of the event triggering whatever timeout you are modifying/starting. If
		1077	you suspect event processing to be delayed and you I<need> to base the timeout
		1078	on the current time, use something like this to adjust for this:
		1079
		1080	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1081
		1082	The callback is guarenteed to be invoked only when its timeout has passed,
		1083	but if multiple timers become ready during the same loop iteration then
		1084	order of execution is undefined.
		1085
		1086	=head3 Watcher-Specific Functions and Data Members
451		1087
452	=over 4	1088	=over 4
453		1089
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1090	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		1091
…		…
461	later, again, and again, until stopped manually.	1097	later, again, and again, until stopped manually.
462		1098
463	The timer itself will do a best-effort at avoiding drift, that is, if you	1099	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	1100	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	1101	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	1102	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.	1103	timer will not fire more than once per event loop iteration.
468		1104
469	=item ev_timer_again (loop)	1105	=item ev_timer_again (loop)
470		1106
471	This will act as if the timer timed out and restart it again if it is	1107	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	1108	repeating. The exact semantics are:
473		1109
		1110	If the timer is pending, its pending status is cleared.
		1111
474	If the timer is started but nonrepeating, stop it.	1112	If the timer is started but nonrepeating, stop it (as if it timed out).
475		1113
476	If the timer is repeating, either start it if necessary (with the repeat	1114	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	1115	C<repeat> value), or reset the running timer to the C<repeat> value.
478		1116
479	This sounds a bit complicated, but here is a useful and typical	1117	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	1118	example: Imagine you have a tcp connection and you want a so-called idle
481	timeout, that is, you want to be called when there have been, say, 60	1119	timeout, that is, you want to be called when there have been, say, 60
482	seconds of inactivity on the socket. The easiest way to do this is to	1120	seconds of inactivity on the socket. The easiest way to do this is to
483	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1121	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
484	time you successfully read or write some data. If you go into an idle	1122	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	1123	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.	1124	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1125	automatically restart it if need be.
		1126
		1127	That means you can ignore the C<after> value and C<ev_timer_start>
		1128	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1129
		1130	ev_timer_init (timer, callback, 0., 5.);
		1131	ev_timer_again (loop, timer);
		1132	...
		1133	timer->again = 17.;
		1134	ev_timer_again (loop, timer);
		1135	...
		1136	timer->again = 10.;
		1137	ev_timer_again (loop, timer);
		1138
		1139	This is more slightly efficient then stopping/starting the timer each time
		1140	you want to modify its timeout value.
		1141
		1142	=item ev_tstamp repeat [read-write]
		1143
		1144	The current C<repeat> value. Will be used each time the watcher times out
		1145	or C<ev_timer_again> is called and determines the next timeout (if any),
		1146	which is also when any modifications are taken into account.
487		1147
488	=back	1148	=back
489		1149
		1150	Example: Create a timer that fires after 60 seconds.
		1151
		1152	static void
		1153	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1154	{
		1155	.. one minute over, w is actually stopped right here
		1156	}
		1157
		1158	struct ev_timer mytimer;
		1159	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1160	ev_timer_start (loop, &mytimer);
		1161
		1162	Example: Create a timeout timer that times out after 10 seconds of
		1163	inactivity.
		1164
		1165	static void
		1166	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1167	{
		1168	.. ten seconds without any activity
		1169	}
		1170
		1171	struct ev_timer mytimer;
		1172	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1173	ev_timer_again (&mytimer); /* start timer */
		1174	ev_loop (loop, 0);
		1175
		1176	// and in some piece of code that gets executed on any "activity":
		1177	// reset the timeout to start ticking again at 10 seconds
		1178	ev_timer_again (&mytimer);
		1179
		1180
490	=head2 ev_periodic - to cron or not to cron it	1181	=head2 C<ev_periodic> - to cron or not to cron?
491		1182
492	Periodic watchers are also timers of a kind, but they are very versatile	1183	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1184	(and unfortunately a bit complex).
494		1185
495	Unlike ev_timer's, they are not based on real time (or relative time)	1186	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	1187	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	1188	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 ()	1189	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	1190	+ 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	1191	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	1192	roughly 10 seconds later).
502	again).
503		1193
504	They can also be used to implement vastly more complex timers, such as	1194	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1195	triggering an event on each midnight, local time or other, complicated,
		1196	rules.
		1197
		1198	As with timers, the callback is guarenteed to be invoked only when the
		1199	time (C<at>) has been passed, but if multiple periodic timers become ready
		1200	during the same loop iteration then order of execution is undefined.
		1201
		1202	=head3 Watcher-Specific Functions and Data Members
506		1203
507	=over 4	1204	=over 4
508		1205
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1206	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1207
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1208	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1209
513	Lots of arguments, lets sort it out... There are basically three modes of	1210	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1211	operation, and we will explain them from simplest to complex:
515		1212
516
517	=over 4	1213	=over 4
518		1214
519	=item * absolute timer (interval = reschedule_cb = 0)	1215	=item * absolute timer (at = time, interval = reschedule_cb = 0)
520		1216
521	In this configuration the watcher triggers an event at the wallclock time	1217	In this configuration the watcher triggers an event at the wallclock time
522	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1218	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
523	that is, if it is to be run at January 1st 2011 then it will run when the	1219	that is, if it is to be run at January 1st 2011 then it will run when the
524	system time reaches or surpasses this time.	1220	system time reaches or surpasses this time.
525		1221
526	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1222	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
527		1223
528	In this mode the watcher will always be scheduled to time out at the next	1224	In this mode the watcher will always be scheduled to time out at the next
529	C<at + N * interval> time (for some integer N) and then repeat, regardless	1225	C<at + N * interval> time (for some integer N, which can also be negative)
530	of any time jumps.	1226	and then repeat, regardless of any time jumps.
531		1227
532	This can be used to create timers that do not drift with respect to system	1228	This can be used to create timers that do not drift with respect to system
533	time:	1229	time:
534		1230
535	ev_periodic_set (&periodic, 0., 3600., 0);	1231	ev_periodic_set (&periodic, 0., 3600., 0);
536		1232
537	This doesn't mean there will always be 3600 seconds in between triggers,	1233	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	1234	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	1235	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1236	by 3600.
541		1237
542	Another way to think about it (for the mathematically inclined) is that	1238	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	1239	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.	1240	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1241
		1242	For numerical stability it is preferable that the C<at> value is near
		1243	C<ev_now ()> (the current time), but there is no range requirement for
		1244	this value.
		1245
546	=item * manual reschedule mode (reschedule_cb = callback)	1246	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
547		1247
548	In this mode the values for C<interval> and C<at> are both being	1248	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	1249	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1250	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1251	current time as second argument.
552		1252
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1253	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	1254	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.	1255	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1256	starting an C<ev_prepare> watcher, which is legal).
556		1257
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1258	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1259	ev_tstamp now)>, e.g.:
559		1260
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1261	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1262	{
562	return now + 60.;	1263	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1266	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	1267	(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	1268	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1269	might be called at other times, too.
569		1270
		1271	NOTE: I<< This callback must always return a time that is later than the
		1272	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1273
570	This can be used to create very complex timers, such as a timer that	1274	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	1275	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	1276	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1277	you do this is, again, up to you (but it is not trivial, which is the main
		1278	reason I omitted it as an example).
574		1279
575	=back	1280	=back
576		1281
577	=item ev_periodic_again (loop, ev_periodic *)	1282	=item ev_periodic_again (loop, ev_periodic *)
578		1283
579	Simply stops and restarts the periodic watcher again. This is only useful	1284	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1285	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	1286	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1287	program when the crontabs have changed).
583		1288
		1289	=item ev_tstamp offset [read-write]
		1290
		1291	When repeating, this contains the offset value, otherwise this is the
		1292	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1293
		1294	Can be modified any time, but changes only take effect when the periodic
		1295	timer fires or C<ev_periodic_again> is being called.
		1296
		1297	=item ev_tstamp interval [read-write]
		1298
		1299	The current interval value. Can be modified any time, but changes only
		1300	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1301	called.
		1302
		1303	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1304
		1305	The current reschedule callback, or C<0>, if this functionality is
		1306	switched off. Can be changed any time, but changes only take effect when
		1307	the periodic timer fires or C<ev_periodic_again> is being called.
		1308
		1309	=item ev_tstamp at [read-only]
		1310
		1311	When active, contains the absolute time that the watcher is supposed to
		1312	trigger next.
		1313
584	=back	1314	=back
585		1315
		1316	Example: Call a callback every hour, or, more precisely, whenever the
		1317	system clock is divisible by 3600. The callback invocation times have
		1318	potentially a lot of jittering, but good long-term stability.
		1319
		1320	static void
		1321	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1322	{
		1323	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1324	}
		1325
		1326	struct ev_periodic hourly_tick;
		1327	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1328	ev_periodic_start (loop, &hourly_tick);
		1329
		1330	Example: The same as above, but use a reschedule callback to do it:
		1331
		1332	#include <math.h>
		1333
		1334	static ev_tstamp
		1335	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1336	{
		1337	return fmod (now, 3600.) + 3600.;
		1338	}
		1339
		1340	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1341
		1342	Example: Call a callback every hour, starting now:
		1343
		1344	struct ev_periodic hourly_tick;
		1345	ev_periodic_init (&hourly_tick, clock_cb,
		1346	fmod (ev_now (loop), 3600.), 3600., 0);
		1347	ev_periodic_start (loop, &hourly_tick);
		1348
		1349
586	=head2 ev_signal - signal me when a signal gets signalled	1350	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1351
588	Signal watchers will trigger an event when the process receives a specific	1352	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	1353	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	1354	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1355	normal event processing, like any other event.
592		1356
593	You cna configure as many watchers as you like per signal. Only when the	1357	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	1358	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	1359	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	1360	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	1361	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1362	SIG_DFL (regardless of what it was set to before).
599		1363
		1364	=head3 Watcher-Specific Functions and Data Members
		1365
600	=over 4	1366	=over 4
601		1367
602	=item ev_signal_init (ev_signal *, callback, int signum)	1368	=item ev_signal_init (ev_signal *, callback, int signum)
603		1369
604	=item ev_signal_set (ev_signal *, int signum)	1370	=item ev_signal_set (ev_signal *, int signum)
605		1371
606	Configures the watcher to trigger on the given signal number (usually one	1372	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1373	of the C<SIGxxx> constants).
608		1374
		1375	=item int signum [read-only]
		1376
		1377	The signal the watcher watches out for.
		1378
609	=back	1379	=back
610		1380
		1381
611	=head2 ev_child - wait for pid status changes	1382	=head2 C<ev_child> - watch out for process status changes
612		1383
613	Child watchers trigger when your process receives a SIGCHLD in response to	1384	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).	1385	some child status changes (most typically when a child of yours dies).
		1386
		1387	=head3 Watcher-Specific Functions and Data Members
615		1388
616	=over 4	1389	=over 4
617		1390
618	=item ev_child_init (ev_child *, callback, int pid)	1391	=item ev_child_init (ev_child *, callback, int pid)
619		1392
620	=item ev_child_set (ev_child *, int pid)	1393	=item ev_child_set (ev_child *, int pid)
621		1394
622	Configures the watcher to wait for status changes of process C<pid> (or	1395	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	1396	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	1397	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	1398	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.	1399	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1400	process causing the status change.
		1401
		1402	=item int pid [read-only]
		1403
		1404	The process id this watcher watches out for, or C<0>, meaning any process id.
		1405
		1406	=item int rpid [read-write]
		1407
		1408	The process id that detected a status change.
		1409
		1410	=item int rstatus [read-write]
		1411
		1412	The process exit/trace status caused by C<rpid> (see your systems
		1413	C<waitpid> and C<sys/wait.h> documentation for details).
627		1414
628	=back	1415	=back
629		1416
		1417	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1418
		1419	static void
		1420	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1421	{
		1422	ev_unloop (loop, EVUNLOOP_ALL);
		1423	}
		1424
		1425	struct ev_signal signal_watcher;
		1426	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1427	ev_signal_start (loop, &sigint_cb);
		1428
		1429
		1430	=head2 C<ev_stat> - did the file attributes just change?
		1431
		1432	This watches a filesystem path for attribute changes. That is, it calls
		1433	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1434	compared to the last time, invoking the callback if it did.
		1435
		1436	The path does not need to exist: changing from "path exists" to "path does
		1437	not exist" is a status change like any other. The condition "path does
		1438	not exist" is signified by the C<st_nlink> field being zero (which is
		1439	otherwise always forced to be at least one) and all the other fields of
		1440	the stat buffer having unspecified contents.
		1441
		1442	The path I<should> be absolute and I<must not> end in a slash. If it is
		1443	relative and your working directory changes, the behaviour is undefined.
		1444
		1445	Since there is no standard to do this, the portable implementation simply
		1446	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1447	can specify a recommended polling interval for this case. If you specify
		1448	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1449	unspecified default> value will be used (which you can expect to be around
		1450	five seconds, although this might change dynamically). Libev will also
		1451	impose a minimum interval which is currently around C<0.1>, but thats
		1452	usually overkill.
		1453
		1454	This watcher type is not meant for massive numbers of stat watchers,
		1455	as even with OS-supported change notifications, this can be
		1456	resource-intensive.
		1457
		1458	At the time of this writing, only the Linux inotify interface is
		1459	implemented (implementing kqueue support is left as an exercise for the
		1460	reader). Inotify will be used to give hints only and should not change the
		1461	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1462	to fall back to regular polling again even with inotify, but changes are
		1463	usually detected immediately, and if the file exists there will be no
		1464	polling.
		1465
		1466	=head3 Watcher-Specific Functions and Data Members
		1467
		1468	=over 4
		1469
		1470	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1471
		1472	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1473
		1474	Configures the watcher to wait for status changes of the given
		1475	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1476	be detected and should normally be specified as C<0> to let libev choose
		1477	a suitable value. The memory pointed to by C<path> must point to the same
		1478	path for as long as the watcher is active.
		1479
		1480	The callback will be receive C<EV_STAT> when a change was detected,
		1481	relative to the attributes at the time the watcher was started (or the
		1482	last change was detected).
		1483
		1484	=item ev_stat_stat (ev_stat *)
		1485
		1486	Updates the stat buffer immediately with new values. If you change the
		1487	watched path in your callback, you could call this fucntion to avoid
		1488	detecting this change (while introducing a race condition). Can also be
		1489	useful simply to find out the new values.
		1490
		1491	=item ev_statdata attr [read-only]
		1492
		1493	The most-recently detected attributes of the file. Although the type is of
		1494	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1495	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1496	was some error while C<stat>ing the file.
		1497
		1498	=item ev_statdata prev [read-only]
		1499
		1500	The previous attributes of the file. The callback gets invoked whenever
		1501	C<prev> != C<attr>.
		1502
		1503	=item ev_tstamp interval [read-only]
		1504
		1505	The specified interval.
		1506
		1507	=item const char *path [read-only]
		1508
		1509	The filesystem path that is being watched.
		1510
		1511	=back
		1512
		1513	Example: Watch C</etc/passwd> for attribute changes.
		1514
		1515	static void
		1516	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1517	{
		1518	/* /etc/passwd changed in some way */
		1519	if (w->attr.st_nlink)
		1520	{
		1521	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1522	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1523	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1524	}
		1525	else
		1526	/* you shalt not abuse printf for puts */
		1527	puts ("wow, /etc/passwd is not there, expect problems. "
		1528	"if this is windows, they already arrived\n");
		1529	}
		1530
		1531	...
		1532	ev_stat passwd;
		1533
		1534	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1535	ev_stat_start (loop, &passwd);
		1536
		1537
630	=head2 ev_idle - when you've got nothing better to do	1538	=head2 C<ev_idle> - when you've got nothing better to do...
631		1539
632	Idle watchers trigger events when there are no other I/O or timer (or	1540	Idle watchers trigger events when no other events of the same or higher
633	periodic) events pending. That is, as long as your process is busy	1541	priority are pending (prepare, check and other idle watchers do not
634	handling sockets or timeouts it will not be called. But when your process	1542	count).
635	is idle all idle watchers are being called again and again - until	1543
		1544	That is, as long as your process is busy handling sockets or timeouts
		1545	(or even signals, imagine) of the same or higher priority it will not be
		1546	triggered. But when your process is idle (or only lower-priority watchers
		1547	are pending), the idle watchers are being called once per event loop
636	stopped, that is, or your process receives more events.	1548	iteration - until stopped, that is, or your process receives more events
		1549	and becomes busy again with higher priority stuff.
637		1550
638	The most noteworthy effect is that as long as any idle watchers are	1551	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.	1552	active, the process will not block when waiting for new events.
640		1553
641	Apart from keeping your process non-blocking (which is a useful	1554	Apart from keeping your process non-blocking (which is a useful
642	effect on its own sometimes), idle watchers are a good place to do	1555	effect on its own sometimes), idle watchers are a good place to do
643	"pseudo-background processing", or delay processing stuff to after the	1556	"pseudo-background processing", or delay processing stuff to after the
644	event loop has handled all outstanding events.	1557	event loop has handled all outstanding events.
645		1558
		1559	=head3 Watcher-Specific Functions and Data Members
		1560
646	=over 4	1561	=over 4
647		1562
648	=item ev_idle_init (ev_signal *, callback)	1563	=item ev_idle_init (ev_signal *, callback)
649		1564
650	Initialises and configures the idle watcher - it has no parameters of any	1565	Initialises and configures the idle watcher - it has no parameters of any
651	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1566	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1567	believe me.
653		1568
654	=back	1569	=back
655		1570
656	=head2 prepare and check - your hooks into the event loop	1571	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1572	callback, free it. Also, use no error checking, as usual.
657		1573
		1574	static void
		1575	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1576	{
		1577	free (w);
		1578	// now do something you wanted to do when the program has
		1579	// no longer asnything immediate to do.
		1580	}
		1581
		1582	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1583	ev_idle_init (idle_watcher, idle_cb);
		1584	ev_idle_start (loop, idle_cb);
		1585
		1586
		1587	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1588
658	Prepare and check watchers usually (but not always) are used in	1589	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1590	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1591	afterwards.
661		1592
		1593	You I<must not> call C<ev_loop> or similar functions that enter
		1594	the current event loop from either C<ev_prepare> or C<ev_check>
		1595	watchers. Other loops than the current one are fine, however. The
		1596	rationale behind this is that you do not need to check for recursion in
		1597	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1598	C<ev_check> so if you have one watcher of each kind they will always be
		1599	called in pairs bracketing the blocking call.
		1600
662	Their main purpose is to integrate other event mechanisms into libev. This	1601	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	1602	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.	1603	variable changes, implement your own watchers, integrate net-snmp or a
		1604	coroutine library and lots more. They are also occasionally useful if
		1605	you cache some data and want to flush it before blocking (for example,
		1606	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1607	watcher).
665		1608
666	This is done by examining in each prepare call which file descriptors need	1609	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	1610	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	1611	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	1612	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)	1613	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1614	and stopping them) and call back into the library. The I/O and timer
		1615	callbacks will never actually be called (but must be valid nevertheless,
		1616	because you never know, you know?).
672		1617
673	As another example, the perl Coro module uses these hooks to integrate	1618	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1619	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1620	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1621	are ready to run (it's actually more complicated: it only runs coroutines
		1622	with priority higher than or equal to the event loop and one coroutine
		1623	of lower priority, but only once, using idle watchers to keep the event
		1624	loop from blocking if lower-priority coroutines are active, thus mapping
		1625	low-priority coroutines to idle/background tasks).
		1626
		1627	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1628	priority, to ensure that they are being run before any other watchers
		1629	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1630	too) should not activate ("feed") events into libev. While libev fully
		1631	supports this, they will be called before other C<ev_check> watchers
		1632	did their job. As C<ev_check> watchers are often used to embed other
		1633	(non-libev) event loops those other event loops might be in an unusable
		1634	state until their C<ev_check> watcher ran (always remind yourself to
		1635	coexist peacefully with others).
		1636
		1637	=head3 Watcher-Specific Functions and Data Members
677		1638
678	=over 4	1639	=over 4
679		1640
680	=item ev_prepare_init (ev_prepare *, callback)	1641	=item ev_prepare_init (ev_prepare *, callback)
681		1642
682	=item ev_check_init (ev_check *, callback)	1643	=item ev_check_init (ev_check *, callback)
683		1644
684	Initialises and configures the prepare or check watcher - they have no	1645	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>	1646	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1647	macros, but using them is utterly, utterly and completely pointless.
687		1648
688	=back	1649	=back
689		1650
		1651	There are a number of principal ways to embed other event loops or modules
		1652	into libev. Here are some ideas on how to include libadns into libev
		1653	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1654	use for an actually working example. Another Perl module named C<EV::Glib>
		1655	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1656	into the Glib event loop).
		1657
		1658	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1659	and in a check watcher, destroy them and call into libadns. What follows
		1660	is pseudo-code only of course. This requires you to either use a low
		1661	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1662	the callbacks for the IO/timeout watchers might not have been called yet.
		1663
		1664	static ev_io iow [nfd];
		1665	static ev_timer tw;
		1666
		1667	static void
		1668	io_cb (ev_loop *loop, ev_io *w, int revents)
		1669	{
		1670	}
		1671
		1672	// create io watchers for each fd and a timer before blocking
		1673	static void
		1674	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1675	{
		1676	int timeout = 3600000;
		1677	struct pollfd fds [nfd];
		1678	// actual code will need to loop here and realloc etc.
		1679	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1680
		1681	/* the callback is illegal, but won't be called as we stop during check */
		1682	ev_timer_init (&tw, 0, timeout * 1e-3);
		1683	ev_timer_start (loop, &tw);
		1684
		1685	// create one ev_io per pollfd
		1686	for (int i = 0; i < nfd; ++i)
		1687	{
		1688	ev_io_init (iow + i, io_cb, fds [i].fd,
		1689	((fds [i].events & POLLIN ? EV_READ : 0)
		1690	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1691
		1692	fds [i].revents = 0;
		1693	ev_io_start (loop, iow + i);
		1694	}
		1695	}
		1696
		1697	// stop all watchers after blocking
		1698	static void
		1699	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1700	{
		1701	ev_timer_stop (loop, &tw);
		1702
		1703	for (int i = 0; i < nfd; ++i)
		1704	{
		1705	// set the relevant poll flags
		1706	// could also call adns_processreadable etc. here
		1707	struct pollfd *fd = fds + i;
		1708	int revents = ev_clear_pending (iow + i);
		1709	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1710	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1711
		1712	// now stop the watcher
		1713	ev_io_stop (loop, iow + i);
		1714	}
		1715
		1716	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1717	}
		1718
		1719	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1720	in the prepare watcher and would dispose of the check watcher.
		1721
		1722	Method 3: If the module to be embedded supports explicit event
		1723	notification (adns does), you can also make use of the actual watcher
		1724	callbacks, and only destroy/create the watchers in the prepare watcher.
		1725
		1726	static void
		1727	timer_cb (EV_P_ ev_timer *w, int revents)
		1728	{
		1729	adns_state ads = (adns_state)w->data;
		1730	update_now (EV_A);
		1731
		1732	adns_processtimeouts (ads, &tv_now);
		1733	}
		1734
		1735	static void
		1736	io_cb (EV_P_ ev_io *w, int revents)
		1737	{
		1738	adns_state ads = (adns_state)w->data;
		1739	update_now (EV_A);
		1740
		1741	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1742	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1743	}
		1744
		1745	// do not ever call adns_afterpoll
		1746
		1747	Method 4: Do not use a prepare or check watcher because the module you
		1748	want to embed is too inflexible to support it. Instead, youc na override
		1749	their poll function. The drawback with this solution is that the main
		1750	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1751	this.
		1752
		1753	static gint
		1754	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1755	{
		1756	int got_events = 0;
		1757
		1758	for (n = 0; n < nfds; ++n)
		1759	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1760
		1761	if (timeout >= 0)
		1762	// create/start timer
		1763
		1764	// poll
		1765	ev_loop (EV_A_ 0);
		1766
		1767	// stop timer again
		1768	if (timeout >= 0)
		1769	ev_timer_stop (EV_A_ &to);
		1770
		1771	// stop io watchers again - their callbacks should have set
		1772	for (n = 0; n < nfds; ++n)
		1773	ev_io_stop (EV_A_ iow [n]);
		1774
		1775	return got_events;
		1776	}
		1777
		1778
		1779	=head2 C<ev_embed> - when one backend isn't enough...
		1780
		1781	This is a rather advanced watcher type that lets you embed one event loop
		1782	into another (currently only C<ev_io> events are supported in the embedded
		1783	loop, other types of watchers might be handled in a delayed or incorrect
		1784	fashion and must not be used).
		1785
		1786	There are primarily two reasons you would want that: work around bugs and
		1787	prioritise I/O.
		1788
		1789	As an example for a bug workaround, the kqueue backend might only support
		1790	sockets on some platform, so it is unusable as generic backend, but you
		1791	still want to make use of it because you have many sockets and it scales
		1792	so nicely. In this case, you would create a kqueue-based loop and embed it
		1793	into your default loop (which might use e.g. poll). Overall operation will
		1794	be a bit slower because first libev has to poll and then call kevent, but
		1795	at least you can use both at what they are best.
		1796
		1797	As for prioritising I/O: rarely you have the case where some fds have
		1798	to be watched and handled very quickly (with low latency), and even
		1799	priorities and idle watchers might have too much overhead. In this case
		1800	you would put all the high priority stuff in one loop and all the rest in
		1801	a second one, and embed the second one in the first.
		1802
		1803	As long as the watcher is active, the callback will be invoked every time
		1804	there might be events pending in the embedded loop. The callback must then
		1805	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1806	their callbacks (you could also start an idle watcher to give the embedded
		1807	loop strictly lower priority for example). You can also set the callback
		1808	to C<0>, in which case the embed watcher will automatically execute the
		1809	embedded loop sweep.
		1810
		1811	As long as the watcher is started it will automatically handle events. The
		1812	callback will be invoked whenever some events have been handled. You can
		1813	set the callback to C<0> to avoid having to specify one if you are not
		1814	interested in that.
		1815
		1816	Also, there have not currently been made special provisions for forking:
		1817	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1818	but you will also have to stop and restart any C<ev_embed> watchers
		1819	yourself.
		1820
		1821	Unfortunately, not all backends are embeddable, only the ones returned by
		1822	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1823	portable one.
		1824
		1825	So when you want to use this feature you will always have to be prepared
		1826	that you cannot get an embeddable loop. The recommended way to get around
		1827	this is to have a separate variables for your embeddable loop, try to
		1828	create it, and if that fails, use the normal loop for everything:
		1829
		1830	struct ev_loop *loop_hi = ev_default_init (0);
		1831	struct ev_loop *loop_lo = 0;
		1832	struct ev_embed embed;
		1833
		1834	// see if there is a chance of getting one that works
		1835	// (remember that a flags value of 0 means autodetection)
		1836	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1837	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1838	: 0;
		1839
		1840	// if we got one, then embed it, otherwise default to loop_hi
		1841	if (loop_lo)
		1842	{
		1843	ev_embed_init (&embed, 0, loop_lo);
		1844	ev_embed_start (loop_hi, &embed);
		1845	}
		1846	else
		1847	loop_lo = loop_hi;
		1848
		1849	=head3 Watcher-Specific Functions and Data Members
		1850
		1851	=over 4
		1852
		1853	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1854
		1855	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1856
		1857	Configures the watcher to embed the given loop, which must be
		1858	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1859	invoked automatically, otherwise it is the responsibility of the callback
		1860	to invoke it (it will continue to be called until the sweep has been done,
		1861	if you do not want thta, you need to temporarily stop the embed watcher).
		1862
		1863	=item ev_embed_sweep (loop, ev_embed *)
		1864
		1865	Make a single, non-blocking sweep over the embedded loop. This works
		1866	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1867	apropriate way for embedded loops.
		1868
		1869	=item struct ev_loop *other [read-only]
		1870
		1871	The embedded event loop.
		1872
		1873	=back
		1874
		1875
		1876	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1877
		1878	Fork watchers are called when a C<fork ()> was detected (usually because
		1879	whoever is a good citizen cared to tell libev about it by calling
		1880	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1881	event loop blocks next and before C<ev_check> watchers are being called,
		1882	and only in the child after the fork. If whoever good citizen calling
		1883	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1884	handlers will be invoked, too, of course.
		1885
		1886	=head3 Watcher-Specific Functions and Data Members
		1887
		1888	=over 4
		1889
		1890	=item ev_fork_init (ev_signal *, callback)
		1891
		1892	Initialises and configures the fork watcher - it has no parameters of any
		1893	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1894	believe me.
		1895
		1896	=back
		1897
		1898
690	=head1 OTHER FUNCTIONS	1899	=head1 OTHER FUNCTIONS
691		1900
692	There are some other fucntions of possible interest. Described. Here. Now.	1901	There are some other functions of possible interest. Described. Here. Now.
693		1902
694	=over 4	1903	=over 4
695		1904
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1905	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		1906
698	This function combines a simple timer and an I/O watcher, calls your	1907	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	1908	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	1909	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	1910	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	1911	more watchers yourself.
703		1912
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	1913	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	1914	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	1915	C<events> set will be craeted and started.
707		1916
708	If C<timeout> is less than 0, then no timeout watcher will be	1917	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	1918	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	1919	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1920	dubious value.
711		1921
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	1922	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,	1923	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>:	1924	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1925	value passed to C<ev_once>:
715		1926
716	static void stdin_ready (int revents, void *arg)	1927	static void stdin_ready (int revents, void *arg)
717	{	1928	{
718	if (revents & EV_TIMEOUT)	1929	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	1930	/* doh, nothing entered */;
720	else if (revents & EV_READ)	1931	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	1932	/* stdin might have data for us, joy! */;
722	}	1933	}
723		1934
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1935	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		1936
726	=item ev_feed_event (loop, watcher, int events)	1937	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		1938
728	Feeds the given event set into the event loop, as if the specified event	1939	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	1940	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	1941	initialised but not necessarily started event watcher).
731		1942
732	=item ev_feed_fd_event (loop, int fd, int revents)	1943	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		1944
734	Feed an event on the given fd, as if a file descriptor backend detected it.	1945	Feed an event on the given fd, as if a file descriptor backend detected
		1946	the given events it.
735		1947
736	=item ev_feed_signal_event (loop, int signum)	1948	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		1949
738	Feed an event as if the given signal occured (loop must be the default loop!).	1950	Feed an event as if the given signal occured (C<loop> must be the default
		1951	loop!).
739		1952
740	=back	1953	=back
741		1954
		1955
		1956	=head1 LIBEVENT EMULATION
		1957
		1958	Libev offers a compatibility emulation layer for libevent. It cannot
		1959	emulate the internals of libevent, so here are some usage hints:
		1960
		1961	=over 4
		1962
		1963	=item * Use it by including <event.h>, as usual.
		1964
		1965	=item * The following members are fully supported: ev_base, ev_callback,
		1966	ev_arg, ev_fd, ev_res, ev_events.
		1967
		1968	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1969	maintained by libev, it does not work exactly the same way as in libevent (consider
		1970	it a private API).
		1971
		1972	=item * Priorities are not currently supported. Initialising priorities
		1973	will fail and all watchers will have the same priority, even though there
		1974	is an ev_pri field.
		1975
		1976	=item * Other members are not supported.
		1977
		1978	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1979	to use the libev header file and library.
		1980
		1981	=back
		1982
		1983	=head1 C++ SUPPORT
		1984
		1985	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1986	you to use some convinience methods to start/stop watchers and also change
		1987	the callback model to a model using method callbacks on objects.
		1988
		1989	To use it,
		1990
		1991	#include <ev++.h>
		1992
		1993	This automatically includes F<ev.h> and puts all of its definitions (many
		1994	of them macros) into the global namespace. All C++ specific things are
		1995	put into the C<ev> namespace. It should support all the same embedding
		1996	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1997
		1998	Care has been taken to keep the overhead low. The only data member the C++
		1999	classes add (compared to plain C-style watchers) is the event loop pointer
		2000	that the watcher is associated with (or no additional members at all if
		2001	you disable C<EV_MULTIPLICITY> when embedding libev).
		2002
		2003	Currently, functions, and static and non-static member functions can be
		2004	used as callbacks. Other types should be easy to add as long as they only
		2005	need one additional pointer for context. If you need support for other
		2006	types of functors please contact the author (preferably after implementing
		2007	it).
		2008
		2009	Here is a list of things available in the C<ev> namespace:
		2010
		2011	=over 4
		2012
		2013	=item C<ev::READ>, C<ev::WRITE> etc.
		2014
		2015	These are just enum values with the same values as the C<EV_READ> etc.
		2016	macros from F<ev.h>.
		2017
		2018	=item C<ev::tstamp>, C<ev::now>
		2019
		2020	Aliases to the same types/functions as with the C<ev_> prefix.
		2021
		2022	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2023
		2024	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2025	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2026	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2027	defines by many implementations.
		2028
		2029	All of those classes have these methods:
		2030
		2031	=over 4
		2032
		2033	=item ev::TYPE::TYPE ()
		2034
		2035	=item ev::TYPE::TYPE (struct ev_loop *)
		2036
		2037	=item ev::TYPE::~TYPE
		2038
		2039	The constructor (optionally) takes an event loop to associate the watcher
		2040	with. If it is omitted, it will use C<EV_DEFAULT>.
		2041
		2042	The constructor calls C<ev_init> for you, which means you have to call the
		2043	C<set> method before starting it.
		2044
		2045	It will not set a callback, however: You have to call the templated C<set>
		2046	method to set a callback before you can start the watcher.
		2047
		2048	(The reason why you have to use a method is a limitation in C++ which does
		2049	not allow explicit template arguments for constructors).
		2050
		2051	The destructor automatically stops the watcher if it is active.
		2052
		2053	=item w->set<class, &class::method> (object *)
		2054
		2055	This method sets the callback method to call. The method has to have a
		2056	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2057	first argument and the C<revents> as second. The object must be given as
		2058	parameter and is stored in the C<data> member of the watcher.
		2059
		2060	This method synthesizes efficient thunking code to call your method from
		2061	the C callback that libev requires. If your compiler can inline your
		2062	callback (i.e. it is visible to it at the place of the C<set> call and
		2063	your compiler is good :), then the method will be fully inlined into the
		2064	thunking function, making it as fast as a direct C callback.
		2065
		2066	Example: simple class declaration and watcher initialisation
		2067
		2068	struct myclass
		2069	{
		2070	void io_cb (ev::io &w, int revents) { }
		2071	}
		2072
		2073	myclass obj;
		2074	ev::io iow;
		2075	iow.set <myclass, &myclass::io_cb> (&obj);
		2076
		2077	=item w->set<function> (void *data = 0)
		2078
		2079	Also sets a callback, but uses a static method or plain function as
		2080	callback. The optional C<data> argument will be stored in the watcher's
		2081	C<data> member and is free for you to use.
		2082
		2083	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2084
		2085	See the method-C<set> above for more details.
		2086
		2087	Example:
		2088
		2089	static void io_cb (ev::io &w, int revents) { }
		2090	iow.set <io_cb> ();
		2091
		2092	=item w->set (struct ev_loop *)
		2093
		2094	Associates a different C<struct ev_loop> with this watcher. You can only
		2095	do this when the watcher is inactive (and not pending either).
		2096
		2097	=item w->set ([args])
		2098
		2099	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2100	called at least once. Unlike the C counterpart, an active watcher gets
		2101	automatically stopped and restarted when reconfiguring it with this
		2102	method.
		2103
		2104	=item w->start ()
		2105
		2106	Starts the watcher. Note that there is no C<loop> argument, as the
		2107	constructor already stores the event loop.
		2108
		2109	=item w->stop ()
		2110
		2111	Stops the watcher if it is active. Again, no C<loop> argument.
		2112
		2113	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2114
		2115	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2116	C<ev_TYPE_again> function.
		2117
		2118	=item w->sweep () (C<ev::embed> only)
		2119
		2120	Invokes C<ev_embed_sweep>.
		2121
		2122	=item w->update () (C<ev::stat> only)
		2123
		2124	Invokes C<ev_stat_stat>.
		2125
		2126	=back
		2127
		2128	=back
		2129
		2130	Example: Define a class with an IO and idle watcher, start one of them in
		2131	the constructor.
		2132
		2133	class myclass
		2134	{
		2135	ev_io io; void io_cb (ev::io &w, int revents);
		2136	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2137
		2138	myclass ();
		2139	}
		2140
		2141	myclass::myclass (int fd)
		2142	{
		2143	io .set <myclass, &myclass::io_cb > (this);
		2144	idle.set <myclass, &myclass::idle_cb> (this);
		2145
		2146	io.start (fd, ev::READ);
		2147	}
		2148
		2149
		2150	=head1 MACRO MAGIC
		2151
		2152	Libev can be compiled with a variety of options, the most fundamantal
		2153	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2154	functions and callbacks have an initial C<struct ev_loop *> argument.
		2155
		2156	To make it easier to write programs that cope with either variant, the
		2157	following macros are defined:
		2158
		2159	=over 4
		2160
		2161	=item C<EV_A>, C<EV_A_>
		2162
		2163	This provides the loop I<argument> for functions, if one is required ("ev
		2164	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2165	C<EV_A_> is used when other arguments are following. Example:
		2166
		2167	ev_unref (EV_A);
		2168	ev_timer_add (EV_A_ watcher);
		2169	ev_loop (EV_A_ 0);
		2170
		2171	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2172	which is often provided by the following macro.
		2173
		2174	=item C<EV_P>, C<EV_P_>
		2175
		2176	This provides the loop I<parameter> for functions, if one is required ("ev
		2177	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2178	C<EV_P_> is used when other parameters are following. Example:
		2179
		2180	// this is how ev_unref is being declared
		2181	static void ev_unref (EV_P);
		2182
		2183	// this is how you can declare your typical callback
		2184	static void cb (EV_P_ ev_timer *w, int revents)
		2185
		2186	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2187	suitable for use with C<EV_A>.
		2188
		2189	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2190
		2191	Similar to the other two macros, this gives you the value of the default
		2192	loop, if multiple loops are supported ("ev loop default").
		2193
		2194	=back
		2195
		2196	Example: Declare and initialise a check watcher, utilising the above
		2197	macros so it will work regardless of whether multiple loops are supported
		2198	or not.
		2199
		2200	static void
		2201	check_cb (EV_P_ ev_timer *w, int revents)
		2202	{
		2203	ev_check_stop (EV_A_ w);
		2204	}
		2205
		2206	ev_check check;
		2207	ev_check_init (&check, check_cb);
		2208	ev_check_start (EV_DEFAULT_ &check);
		2209	ev_loop (EV_DEFAULT_ 0);
		2210
		2211	=head1 EMBEDDING
		2212
		2213	Libev can (and often is) directly embedded into host
		2214	applications. Examples of applications that embed it include the Deliantra
		2215	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2216	and rxvt-unicode.
		2217
		2218	The goal is to enable you to just copy the necessary files into your
		2219	source directory without having to change even a single line in them, so
		2220	you can easily upgrade by simply copying (or having a checked-out copy of
		2221	libev somewhere in your source tree).
		2222
		2223	=head2 FILESETS
		2224
		2225	Depending on what features you need you need to include one or more sets of files
		2226	in your app.
		2227
		2228	=head3 CORE EVENT LOOP
		2229
		2230	To include only the libev core (all the C<ev_*> functions), with manual
		2231	configuration (no autoconf):
		2232
		2233	#define EV_STANDALONE 1
		2234	#include "ev.c"
		2235
		2236	This will automatically include F<ev.h>, too, and should be done in a
		2237	single C source file only to provide the function implementations. To use
		2238	it, do the same for F<ev.h> in all files wishing to use this API (best
		2239	done by writing a wrapper around F<ev.h> that you can include instead and
		2240	where you can put other configuration options):
		2241
		2242	#define EV_STANDALONE 1
		2243	#include "ev.h"
		2244
		2245	Both header files and implementation files can be compiled with a C++
		2246	compiler (at least, thats a stated goal, and breakage will be treated
		2247	as a bug).
		2248
		2249	You need the following files in your source tree, or in a directory
		2250	in your include path (e.g. in libev/ when using -Ilibev):
		2251
		2252	ev.h
		2253	ev.c
		2254	ev_vars.h
		2255	ev_wrap.h
		2256
		2257	ev_win32.c required on win32 platforms only
		2258
		2259	ev_select.c only when select backend is enabled (which is enabled by default)
		2260	ev_poll.c only when poll backend is enabled (disabled by default)
		2261	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2262	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2263	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2264
		2265	F<ev.c> includes the backend files directly when enabled, so you only need
		2266	to compile this single file.
		2267
		2268	=head3 LIBEVENT COMPATIBILITY API
		2269
		2270	To include the libevent compatibility API, also include:
		2271
		2272	#include "event.c"
		2273
		2274	in the file including F<ev.c>, and:
		2275
		2276	#include "event.h"
		2277
		2278	in the files that want to use the libevent API. This also includes F<ev.h>.
		2279
		2280	You need the following additional files for this:
		2281
		2282	event.h
		2283	event.c
		2284
		2285	=head3 AUTOCONF SUPPORT
		2286
		2287	Instead of using C<EV_STANDALONE=1> and providing your config in
		2288	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2289	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2290	include F<config.h> and configure itself accordingly.
		2291
		2292	For this of course you need the m4 file:
		2293
		2294	libev.m4
		2295
		2296	=head2 PREPROCESSOR SYMBOLS/MACROS
		2297
		2298	Libev can be configured via a variety of preprocessor symbols you have to define
		2299	before including any of its files. The default is not to build for multiplicity
		2300	and only include the select backend.
		2301
		2302	=over 4
		2303
		2304	=item EV_STANDALONE
		2305
		2306	Must always be C<1> if you do not use autoconf configuration, which
		2307	keeps libev from including F<config.h>, and it also defines dummy
		2308	implementations for some libevent functions (such as logging, which is not
		2309	supported). It will also not define any of the structs usually found in
		2310	F<event.h> that are not directly supported by the libev core alone.
		2311
		2312	=item EV_USE_MONOTONIC
		2313
		2314	If defined to be C<1>, libev will try to detect the availability of the
		2315	monotonic clock option at both compiletime and runtime. Otherwise no use
		2316	of the monotonic clock option will be attempted. If you enable this, you
		2317	usually have to link against librt or something similar. Enabling it when
		2318	the functionality isn't available is safe, though, although you have
		2319	to make sure you link against any libraries where the C<clock_gettime>
		2320	function is hiding in (often F<-lrt>).
		2321
		2322	=item EV_USE_REALTIME
		2323
		2324	If defined to be C<1>, libev will try to detect the availability of the
		2325	realtime clock option at compiletime (and assume its availability at
		2326	runtime if successful). Otherwise no use of the realtime clock option will
		2327	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2328	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2329	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2330
		2331	=item EV_USE_NANOSLEEP
		2332
		2333	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2334	and will use it for delays. Otherwise it will use C<select ()>.
		2335
		2336	=item EV_USE_SELECT
		2337
		2338	If undefined or defined to be C<1>, libev will compile in support for the
		2339	C<select>(2) backend. No attempt at autodetection will be done: if no
		2340	other method takes over, select will be it. Otherwise the select backend
		2341	will not be compiled in.
		2342
		2343	=item EV_SELECT_USE_FD_SET
		2344
		2345	If defined to C<1>, then the select backend will use the system C<fd_set>
		2346	structure. This is useful if libev doesn't compile due to a missing
		2347	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2348	exotic systems. This usually limits the range of file descriptors to some
		2349	low limit such as 1024 or might have other limitations (winsocket only
		2350	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2351	influence the size of the C<fd_set> used.
		2352
		2353	=item EV_SELECT_IS_WINSOCKET
		2354
		2355	When defined to C<1>, the select backend will assume that
		2356	select/socket/connect etc. don't understand file descriptors but
		2357	wants osf handles on win32 (this is the case when the select to
		2358	be used is the winsock select). This means that it will call
		2359	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2360	it is assumed that all these functions actually work on fds, even
		2361	on win32. Should not be defined on non-win32 platforms.
		2362
		2363	=item EV_USE_POLL
		2364
		2365	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2366	backend. Otherwise it will be enabled on non-win32 platforms. It
		2367	takes precedence over select.
		2368
		2369	=item EV_USE_EPOLL
		2370
		2371	If defined to be C<1>, libev will compile in support for the Linux
		2372	C<epoll>(7) backend. Its availability will be detected at runtime,
		2373	otherwise another method will be used as fallback. This is the
		2374	preferred backend for GNU/Linux systems.
		2375
		2376	=item EV_USE_KQUEUE
		2377
		2378	If defined to be C<1>, libev will compile in support for the BSD style
		2379	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2380	otherwise another method will be used as fallback. This is the preferred
		2381	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2382	supports some types of fds correctly (the only platform we found that
		2383	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2384	not be used unless explicitly requested. The best way to use it is to find
		2385	out whether kqueue supports your type of fd properly and use an embedded
		2386	kqueue loop.
		2387
		2388	=item EV_USE_PORT
		2389
		2390	If defined to be C<1>, libev will compile in support for the Solaris
		2391	10 port style backend. Its availability will be detected at runtime,
		2392	otherwise another method will be used as fallback. This is the preferred
		2393	backend for Solaris 10 systems.
		2394
		2395	=item EV_USE_DEVPOLL
		2396
		2397	reserved for future expansion, works like the USE symbols above.
		2398
		2399	=item EV_USE_INOTIFY
		2400
		2401	If defined to be C<1>, libev will compile in support for the Linux inotify
		2402	interface to speed up C<ev_stat> watchers. Its actual availability will
		2403	be detected at runtime.
		2404
		2405	=item EV_H
		2406
		2407	The name of the F<ev.h> header file used to include it. The default if
		2408	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2409	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2410
		2411	=item EV_CONFIG_H
		2412
		2413	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2414	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2415	C<EV_H>, above.
		2416
		2417	=item EV_EVENT_H
		2418
		2419	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2420	of how the F<event.h> header can be found.
		2421
		2422	=item EV_PROTOTYPES
		2423
		2424	If defined to be C<0>, then F<ev.h> will not define any function
		2425	prototypes, but still define all the structs and other symbols. This is
		2426	occasionally useful if you want to provide your own wrapper functions
		2427	around libev functions.
		2428
		2429	=item EV_MULTIPLICITY
		2430
		2431	If undefined or defined to C<1>, then all event-loop-specific functions
		2432	will have the C<struct ev_loop *> as first argument, and you can create
		2433	additional independent event loops. Otherwise there will be no support
		2434	for multiple event loops and there is no first event loop pointer
		2435	argument. Instead, all functions act on the single default loop.
		2436
		2437	=item EV_MINPRI
		2438
		2439	=item EV_MAXPRI
		2440
		2441	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2442	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2443	provide for more priorities by overriding those symbols (usually defined
		2444	to be C<-2> and C<2>, respectively).
		2445
		2446	When doing priority-based operations, libev usually has to linearly search
		2447	all the priorities, so having many of them (hundreds) uses a lot of space
		2448	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2449	fine.
		2450
		2451	If your embedding app does not need any priorities, defining these both to
		2452	C<0> will save some memory and cpu.
		2453
		2454	=item EV_PERIODIC_ENABLE
		2455
		2456	If undefined or defined to be C<1>, then periodic timers are supported. If
		2457	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2458	code.
		2459
		2460	=item EV_IDLE_ENABLE
		2461
		2462	If undefined or defined to be C<1>, then idle watchers are supported. If
		2463	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2464	code.
		2465
		2466	=item EV_EMBED_ENABLE
		2467
		2468	If undefined or defined to be C<1>, then embed watchers are supported. If
		2469	defined to be C<0>, then they are not.
		2470
		2471	=item EV_STAT_ENABLE
		2472
		2473	If undefined or defined to be C<1>, then stat watchers are supported. If
		2474	defined to be C<0>, then they are not.
		2475
		2476	=item EV_FORK_ENABLE
		2477
		2478	If undefined or defined to be C<1>, then fork watchers are supported. If
		2479	defined to be C<0>, then they are not.
		2480
		2481	=item EV_MINIMAL
		2482
		2483	If you need to shave off some kilobytes of code at the expense of some
		2484	speed, define this symbol to C<1>. Currently only used for gcc to override
		2485	some inlining decisions, saves roughly 30% codesize of amd64.
		2486
		2487	=item EV_PID_HASHSIZE
		2488
		2489	C<ev_child> watchers use a small hash table to distribute workload by
		2490	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2491	than enough. If you need to manage thousands of children you might want to
		2492	increase this value (I<must> be a power of two).
		2493
		2494	=item EV_INOTIFY_HASHSIZE
		2495
		2496	C<ev_staz> watchers use a small hash table to distribute workload by
		2497	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2498	usually more than enough. If you need to manage thousands of C<ev_stat>
		2499	watchers you might want to increase this value (I<must> be a power of
		2500	two).
		2501
		2502	=item EV_COMMON
		2503
		2504	By default, all watchers have a C<void *data> member. By redefining
		2505	this macro to a something else you can include more and other types of
		2506	members. You have to define it each time you include one of the files,
		2507	though, and it must be identical each time.
		2508
		2509	For example, the perl EV module uses something like this:
		2510
		2511	#define EV_COMMON \
		2512	SV *self; /* contains this struct */ \
		2513	SV *cb_sv, *fh /* note no trailing ";" */
		2514
		2515	=item EV_CB_DECLARE (type)
		2516
		2517	=item EV_CB_INVOKE (watcher, revents)
		2518
		2519	=item ev_set_cb (ev, cb)
		2520
		2521	Can be used to change the callback member declaration in each watcher,
		2522	and the way callbacks are invoked and set. Must expand to a struct member
		2523	definition and a statement, respectively. See the F<ev.h> header file for
		2524	their default definitions. One possible use for overriding these is to
		2525	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2526	method calls instead of plain function calls in C++.
		2527
		2528	=head2 EXPORTED API SYMBOLS
		2529
		2530	If you need to re-export the API (e.g. via a dll) and you need a list of
		2531	exported symbols, you can use the provided F<Symbol.*> files which list
		2532	all public symbols, one per line:
		2533
		2534	Symbols.ev for libev proper
		2535	Symbols.event for the libevent emulation
		2536
		2537	This can also be used to rename all public symbols to avoid clashes with
		2538	multiple versions of libev linked together (which is obviously bad in
		2539	itself, but sometimes it is inconvinient to avoid this).
		2540
		2541	A sed command like this will create wrapper C<#define>'s that you need to
		2542	include before including F<ev.h>:
		2543
		2544	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2545
		2546	This would create a file F<wrap.h> which essentially looks like this:
		2547
		2548	#define ev_backend myprefix_ev_backend
		2549	#define ev_check_start myprefix_ev_check_start
		2550	#define ev_check_stop myprefix_ev_check_stop
		2551	...
		2552
		2553	=head2 EXAMPLES
		2554
		2555	For a real-world example of a program the includes libev
		2556	verbatim, you can have a look at the EV perl module
		2557	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2558	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2559	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2560	will be compiled. It is pretty complex because it provides its own header
		2561	file.
		2562
		2563	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2564	that everybody includes and which overrides some configure choices:
		2565
		2566	#define EV_MINIMAL 1
		2567	#define EV_USE_POLL 0
		2568	#define EV_MULTIPLICITY 0
		2569	#define EV_PERIODIC_ENABLE 0
		2570	#define EV_STAT_ENABLE 0
		2571	#define EV_FORK_ENABLE 0
		2572	#define EV_CONFIG_H <config.h>
		2573	#define EV_MINPRI 0
		2574	#define EV_MAXPRI 0
		2575
		2576	#include "ev++.h"
		2577
		2578	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2579
		2580	#include "ev_cpp.h"
		2581	#include "ev.c"
		2582
		2583
		2584	=head1 COMPLEXITIES
		2585
		2586	In this section the complexities of (many of) the algorithms used inside
		2587	libev will be explained. For complexity discussions about backends see the
		2588	documentation for C<ev_default_init>.
		2589
		2590	All of the following are about amortised time: If an array needs to be
		2591	extended, libev needs to realloc and move the whole array, but this
		2592	happens asymptotically never with higher number of elements, so O(1) might
		2593	mean it might do a lengthy realloc operation in rare cases, but on average
		2594	it is much faster and asymptotically approaches constant time.
		2595
		2596	=over 4
		2597
		2598	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2599
		2600	This means that, when you have a watcher that triggers in one hour and
		2601	there are 100 watchers that would trigger before that then inserting will
		2602	have to skip those 100 watchers.
		2603
		2604	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2605
		2606	That means that for changing a timer costs less than removing/adding them
		2607	as only the relative motion in the event queue has to be paid for.
		2608
		2609	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2610
		2611	These just add the watcher into an array or at the head of a list.
		2612	=item Stopping check/prepare/idle watchers: O(1)
		2613
		2614	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2615
		2616	These watchers are stored in lists then need to be walked to find the
		2617	correct watcher to remove. The lists are usually short (you don't usually
		2618	have many watchers waiting for the same fd or signal).
		2619
		2620	=item Finding the next timer per loop iteration: O(1)
		2621
		2622	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2623
		2624	A change means an I/O watcher gets started or stopped, which requires
		2625	libev to recalculate its status (and possibly tell the kernel).
		2626
		2627	=item Activating one watcher: O(1)
		2628
		2629	=item Priority handling: O(number_of_priorities)
		2630
		2631	Priorities are implemented by allocating some space for each
		2632	priority. When doing priority-based operations, libev usually has to
		2633	linearly search all the priorities.
		2634
		2635	=back
		2636
		2637
742	=head1 AUTHOR	2638	=head1 AUTHOR
743		2639
744	Marc Lehmann <libev@schmorp.de>.	2640	Marc Lehmann <libev@schmorp.de>.
745		2641

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