ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC

…		…
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 I<all> BSDs (usually it doesn't work with anything but
		345	sockets and pipes, except on Darwin, where of course it's completely
		346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
		347	is used by default there). For this reason it's not being "autodetected"
		348	unless you explicitly specify it explicitly in the flags (i.e. using
		349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		350	system like NetBSD.
		351
		352	It scales in the same way as the epoll backend, but the interface to the
		353	kernel is more efficient (which says nothing about its actual speed,
		354	of course). While stopping, setting and starting an I/O watcher does
		355	never cause an extra syscall as with epoll, it still adds up to two event
		356	changes per incident, support for C<fork ()> is very bad and it drops fds
		357	silently in similarly hard-to-detetc cases.
		358
		359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		360
		361	This is not implemented yet (and might never be).
		362
		363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		364
		365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		366	it's really slow, but it still scales very well (O(active_fds)).
		367
		368	Please note that solaris event ports can deliver a lot of spurious
		369	notifications, so you need to use non-blocking I/O or other means to avoid
		370	blocking when no data (or space) is available.
		371
		372	=item C<EVBACKEND_ALL>
		373
		374	Try all backends (even potentially broken ones that wouldn't be tried
		375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		377
		378	=back
154		379
155	If one or more of these are ored into the flags value, then only these	380	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	381	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	382	specified, most compiled-in backend will be tried, usually in reverse
		383	order of their flag values :)
158		384
159	=back	385	The most typical usage is like this:
		386
		387	if (!ev_default_loop (0))
		388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		389
		390	Restrict libev to the select and poll backends, and do not allow
		391	environment settings to be taken into account:
		392
		393	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		394
		395	Use whatever libev has to offer, but make sure that kqueue is used if
		396	available (warning, breaks stuff, best use only with your own private
		397	event loop and only if you know the OS supports your types of fds):
		398
		399	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		400
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	401	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		402
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	403	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	404	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	405	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).	406	undefined behaviour (or a failed assertion if assertions are enabled).
167		407
		408	Example: Try to create a event loop that uses epoll and nothing else.
		409
		410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		411	if (!epoller)
		412	fatal ("no epoll found here, maybe it hides under your chair");
		413
168	=item ev_default_destroy ()	414	=item ev_default_destroy ()
169		415
170	Destroys the default loop again (frees all memory and kernel state	416	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	417	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	418	sense, so e.g. C<ev_is_active> might still return true. It is your
		419	responsibility to either stop all watchers cleanly yoursef I<before>
		420	calling this function, or cope with the fact afterwards (which is usually
		421	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		422	for example).
		423
		424	Note that certain global state, such as signal state, will not be freed by
		425	this function, and related watchers (such as signal and child watchers)
		426	would need to be stopped manually.
		427
		428	In general it is not advisable to call this function except in the
		429	rare occasion where you really need to free e.g. the signal handling
		430	pipe fds. If you need dynamically allocated loops it is better to use
		431	C<ev_loop_new> and C<ev_loop_destroy>).
173		432
174	=item ev_loop_destroy (loop)	433	=item ev_loop_destroy (loop)
175		434
176	Like C<ev_default_destroy>, but destroys an event loop created by an	435	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	436	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	440	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	441	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	442	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	443	again makes little sense).
185		444
186	You I<must> call this function after forking if and only if you want to	445	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	446	only if you want to use the event library in both processes. If you just
188	have to call it.	447	fork+exec, you don't have to call it.
189		448
190	The function itself is quite fast and its usually not a problem to call	449	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	450	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>:	451	quite nicely into a call to C<pthread_atfork>:
193		452
194	pthread_atfork (0, 0, ev_default_fork);	453	pthread_atfork (0, 0, ev_default_fork);
		454
		455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		456	without calling this function, so if you force one of those backends you
		457	do not need to care.
195		458
196	=item ev_loop_fork (loop)	459	=item ev_loop_fork (loop)
197		460
198	Like C<ev_default_fork>, but acts on an event loop created by	461	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	462	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.	463	after fork, and how you do this is entirely your own problem.
201		464
		465	=item unsigned int ev_loop_count (loop)
		466
		467	Returns the count of loop iterations for the loop, which is identical to
		468	the number of times libev did poll for new events. It starts at C<0> and
		469	happily wraps around with enough iterations.
		470
		471	This value can sometimes be useful as a generation counter of sorts (it
		472	"ticks" the number of loop iterations), as it roughly corresponds with
		473	C<ev_prepare> and C<ev_check> calls.
		474
202	=item unsigned int ev_method (loop)	475	=item unsigned int ev_backend (loop)
203		476
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	477	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	478	use.
206		479
207	=item ev_tstamp = ev_now (loop)	480	=item ev_tstamp ev_now (loop)
208		481
209	Returns the current "event loop time", which is the time the event loop	482	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	483	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	484	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	485	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).	486	event occurring (or more correctly, libev finding out about it).
214		487
215	=item ev_loop (loop, int flags)	488	=item ev_loop (loop, int flags)
216		489
217	Finally, this is it, the event handler. This function usually is called	490	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	491	after you initialised all your watchers and you want to start handling
219	events.	492	events.
220		493
221	If the flags argument is specified as 0, it will not return until either	494	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.	495	either no event watchers are active anymore or C<ev_unloop> was called.
		496
		497	Please note that an explicit C<ev_unloop> is usually better than
		498	relying on all watchers to be stopped when deciding when a program has
		499	finished (especially in interactive programs), but having a program that
		500	automatically loops as long as it has to and no longer by virtue of
		501	relying on its watchers stopping correctly is a thing of beauty.
223		502
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	503	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	504	those events and any outstanding ones, but will not block your process in
226	case there are no events.	505	case there are no events and will return after one iteration of the loop.
227		506
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	507	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	508	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	509	your process until at least one new event arrives, and will return after
		510	one iteration of the loop. This is useful if you are waiting for some
		511	external event in conjunction with something not expressible using other
		512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		513	usually a better approach for this kind of thing.
231		514
232	This flags value could be used to implement alternative looping	515	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	516
234	more generic mechanism.	517	- Before the first iteration, call any pending watchers.
		518	* If there are no active watchers (reference count is zero), return.
		519	- Queue all prepare watchers and then call all outstanding watchers.
		520	- If we have been forked, recreate the kernel state.
		521	- Update the kernel state with all outstanding changes.
		522	- Update the "event loop time".
		523	- Calculate for how long to block.
		524	- Block the process, waiting for any events.
		525	- Queue all outstanding I/O (fd) events.
		526	- Update the "event loop time" and do time jump handling.
		527	- Queue all outstanding timers.
		528	- Queue all outstanding periodics.
		529	- If no events are pending now, queue all idle watchers.
		530	- Queue all check watchers.
		531	- Call all queued watchers in reverse order (i.e. check watchers first).
		532	Signals and child watchers are implemented as I/O watchers, and will
		533	be handled here by queueing them when their watcher gets executed.
		534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		535	were used, return, otherwise continue with step *.
		536
		537	Example: Queue some jobs and then loop until no events are outsanding
		538	anymore.
		539
		540	... queue jobs here, make sure they register event watchers as long
		541	... as they still have work to do (even an idle watcher will do..)
		542	ev_loop (my_loop, 0);
		543	... jobs done. yeah!
235		544
236	=item ev_unloop (loop, how)	545	=item ev_unloop (loop, how)
237		546
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	547	Can be used to make a call to C<ev_loop> return early (but only after it
		548	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>	549	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>	550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.
242		551
243	=item ev_ref (loop)	552	=item ev_ref (loop)
244		553
245	=item ev_unref (loop)	554	=item ev_unref (loop)
246		555
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	556	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	557	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	558	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	559	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	560	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	561	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	562	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	563	no event watchers registered by it are active. It is also an excellent
255	before stop.	564	way to do this for generic recurring timers or from within third-party
		565	libraries. Just remember to I<unref after start> and I<ref before stop>.
		566
		567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		568	running when nothing else is active.
		569
		570	struct ev_signal exitsig;
		571	ev_signal_init (&exitsig, sig_cb, SIGINT);
		572	ev_signal_start (loop, &exitsig);
		573	evf_unref (loop);
		574
		575	Example: For some weird reason, unregister the above signal handler again.
		576
		577	ev_ref (loop);
		578	ev_signal_stop (loop, &exitsig);
		579
		580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		581
		582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		583
		584	These advanced functions influence the time that libev will spend waiting
		585	for events. Both are by default C<0>, meaning that libev will try to
		586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		587
		588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		589	allows libev to delay invocation of I/O and timer/periodic callbacks to
		590	increase efficiency of loop iterations.
		591
		592	The background is that sometimes your program runs just fast enough to
		593	handle one (or very few) event(s) per loop iteration. While this makes
		594	the program responsive, it also wastes a lot of CPU time to poll for new
		595	events, especially with backends like C<select ()> which have a high
		596	overhead for the actual polling but can deliver many events at once.
		597
		598	By setting a higher I<io collect interval> you allow libev to spend more
		599	time collecting I/O events, so you can handle more events per iteration,
		600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		601	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will
		602	introduce an additional C<ev_sleep ()> call into most loop iterations.
		603
		604	Likewise, by setting a higher I<timeout collect interval> you allow libev
		605	to spend more time collecting timeouts, at the expense of increased
		606	latency (the watcher callback will be called later). C<ev_io> watchers
		607	will not be affected. Setting this to a non-null value will not introduce
		608	any overhead in libev.
		609
		610	Many (busy) programs can usually benefit by setting the io collect
		611	interval to a value near C<0.1> or so, which is often enough for
		612	interactive servers (of course not for games), likewise for timeouts. It
		613	usually doesn't make much sense to set it to a lower value than C<0.01>,
		614	as this approsaches the timing granularity of most systems.
256		615
257	=back	616	=back
		617
258		618
259	=head1 ANATOMY OF A WATCHER	619	=head1 ANATOMY OF A WATCHER
260		620
261	A watcher is a structure that you create and register to record your	621	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	622	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:	623	become readable, you would create an C<ev_io> watcher for that:
264		624
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	625	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	626	{
267	ev_io_stop (w);	627	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	628	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	655	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	656	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		657
298	As long as your watcher is active (has been started but not stopped) you	658	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	659	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	660	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		661
307	Each and every callback receives the event loop pointer as first, the	662	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	663	registered watcher structure as second, and a bitset of received events as
309	third argument.	664	third argument.
310		665
311	The rceeived events usually include a single bit per event type received	666	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	667	(you can receive multiple events at the same time). The possible bit masks
313	are:	668	are:
314		669
315	=over 4	670	=over 4
316		671
317	=item EV_READ	672	=item C<EV_READ>
318		673
319	=item EV_WRITE	674	=item C<EV_WRITE>
320		675
321	The file descriptor in the ev_io watcher has become readable and/or	676	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	677	writable.
323		678
324	=item EV_TIMEOUT	679	=item C<EV_TIMEOUT>
325		680
326	The ev_timer watcher has timed out.	681	The C<ev_timer> watcher has timed out.
327		682
328	=item EV_PERIODIC	683	=item C<EV_PERIODIC>
329		684
330	The ev_periodic watcher has timed out.	685	The C<ev_periodic> watcher has timed out.
331		686
332	=item EV_SIGNAL	687	=item C<EV_SIGNAL>
333		688
334	The signal specified in the ev_signal watcher has been received by a thread.	689	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		690
336	=item EV_CHILD	691	=item C<EV_CHILD>
337		692
338	The pid specified in the ev_child watcher has received a status change.	693	The pid specified in the C<ev_child> watcher has received a status change.
339		694
		695	=item C<EV_STAT>
		696
		697	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		698
340	=item EV_IDLE	699	=item C<EV_IDLE>
341		700
342	The ev_idle watcher has determined that you have nothing better to do.	701	The C<ev_idle> watcher has determined that you have nothing better to do.
343		702
344	=item EV_PREPARE	703	=item C<EV_PREPARE>
345		704
346	=item EV_CHECK	705	=item C<EV_CHECK>
347		706
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	707	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	708	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	709	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	710	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	711	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	712	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	713	C<ev_loop> from blocking).
355		714
		715	=item C<EV_EMBED>
		716
		717	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		718
		719	=item C<EV_FORK>
		720
		721	The event loop has been resumed in the child process after fork (see
		722	C<ev_fork>).
		723
356	=item EV_ERROR	724	=item C<EV_ERROR>
357		725
358	An unspecified error has occured, the watcher has been stopped. This might	726	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	727	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	728	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	729	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	735	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	736	programs, though, so beware.
369		737
370	=back	738	=back
371		739
		740	=head2 GENERIC WATCHER FUNCTIONS
		741
		742	In the following description, C<TYPE> stands for the watcher type,
		743	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		744
		745	=over 4
		746
		747	=item C<ev_init> (ev_TYPE *watcher, callback)
		748
		749	This macro initialises the generic portion of a watcher. The contents
		750	of the watcher object can be arbitrary (so C<malloc> will do). Only
		751	the generic parts of the watcher are initialised, you I<need> to call
		752	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		753	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		754	which rolls both calls into one.
		755
		756	You can reinitialise a watcher at any time as long as it has been stopped
		757	(or never started) and there are no pending events outstanding.
		758
		759	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		760	int revents)>.
		761
		762	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		763
		764	This macro initialises the type-specific parts of a watcher. You need to
		765	call C<ev_init> at least once before you call this macro, but you can
		766	call C<ev_TYPE_set> any number of times. You must not, however, call this
		767	macro on a watcher that is active (it can be pending, however, which is a
		768	difference to the C<ev_init> macro).
		769
		770	Although some watcher types do not have type-specific arguments
		771	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		772
		773	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		774
		775	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		776	calls into a single call. This is the most convinient method to initialise
		777	a watcher. The same limitations apply, of course.
		778
		779	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		780
		781	Starts (activates) the given watcher. Only active watchers will receive
		782	events. If the watcher is already active nothing will happen.
		783
		784	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		785
		786	Stops the given watcher again (if active) and clears the pending
		787	status. It is possible that stopped watchers are pending (for example,
		788	non-repeating timers are being stopped when they become pending), but
		789	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		790	you want to free or reuse the memory used by the watcher it is therefore a
		791	good idea to always call its C<ev_TYPE_stop> function.
		792
		793	=item bool ev_is_active (ev_TYPE *watcher)
		794
		795	Returns a true value iff the watcher is active (i.e. it has been started
		796	and not yet been stopped). As long as a watcher is active you must not modify
		797	it.
		798
		799	=item bool ev_is_pending (ev_TYPE *watcher)
		800
		801	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		802	events but its callback has not yet been invoked). As long as a watcher
		803	is pending (but not active) you must not call an init function on it (but
		804	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		805	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		806	it).
		807
		808	=item callback ev_cb (ev_TYPE *watcher)
		809
		810	Returns the callback currently set on the watcher.
		811
		812	=item ev_cb_set (ev_TYPE *watcher, callback)
		813
		814	Change the callback. You can change the callback at virtually any time
		815	(modulo threads).
		816
		817	=item ev_set_priority (ev_TYPE *watcher, priority)
		818
		819	=item int ev_priority (ev_TYPE *watcher)
		820
		821	Set and query the priority of the watcher. The priority is a small
		822	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		823	(default: C<-2>). Pending watchers with higher priority will be invoked
		824	before watchers with lower priority, but priority will not keep watchers
		825	from being executed (except for C<ev_idle> watchers).
		826
		827	This means that priorities are I<only> used for ordering callback
		828	invocation after new events have been received. This is useful, for
		829	example, to reduce latency after idling, or more often, to bind two
		830	watchers on the same event and make sure one is called first.
		831
		832	If you need to suppress invocation when higher priority events are pending
		833	you need to look at C<ev_idle> watchers, which provide this functionality.
		834
		835	You I<must not> change the priority of a watcher as long as it is active or
		836	pending.
		837
		838	The default priority used by watchers when no priority has been set is
		839	always C<0>, which is supposed to not be too high and not be too low :).
		840
		841	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		842	fine, as long as you do not mind that the priority value you query might
		843	or might not have been adjusted to be within valid range.
		844
		845	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		846
		847	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		848	C<loop> nor C<revents> need to be valid as long as the watcher callback
		849	can deal with that fact.
		850
		851	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		852
		853	If the watcher is pending, this function returns clears its pending status
		854	and returns its C<revents> bitset (as if its callback was invoked). If the
		855	watcher isn't pending it does nothing and returns C<0>.
		856
		857	=back
		858
		859
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	860	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		861
374	Each watcher has, by default, a member C<void *data> that you can change	862	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	863	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	864	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	865	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	866	member, you can also "subclass" the watcher type and provide your own
379	data:	867	data:
380		868
…		…
393	{	881	{
394	struct my_io *w = (struct my_io *)w_;	882	struct my_io *w = (struct my_io *)w_;
395	...	883	...
396	}	884	}
397		885
398	More interesting and less C-conformant ways of catsing your callback type	886	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	887	instead have been omitted.
		888
		889	Another common scenario is having some data structure with multiple
		890	watchers:
		891
		892	struct my_biggy
		893	{
		894	int some_data;
		895	ev_timer t1;
		896	ev_timer t2;
		897	}
		898
		899	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		900	you need to use C<offsetof>:
		901
		902	#include <stddef.h>
		903
		904	static void
		905	t1_cb (EV_P_ struct ev_timer *w, int revents)
		906	{
		907	struct my_biggy big = (struct my_biggy *
		908	(((char *)w) - offsetof (struct my_biggy, t1));
		909	}
		910
		911	static void
		912	t2_cb (EV_P_ struct ev_timer *w, int revents)
		913	{
		914	struct my_biggy big = (struct my_biggy *
		915	(((char *)w) - offsetof (struct my_biggy, t2));
		916	}
400		917
401		918
402	=head1 WATCHER TYPES	919	=head1 WATCHER TYPES
403		920
404	This section describes each watcher in detail, but will not repeat	921	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	922	information given in the last section. Any initialisation/set macros,
		923	functions and members specific to the watcher type are explained.
406		924
		925	Members are additionally marked with either I<[read-only]>, meaning that,
		926	while the watcher is active, you can look at the member and expect some
		927	sensible content, but you must not modify it (you can modify it while the
		928	watcher is stopped to your hearts content), or I<[read-write]>, which
		929	means you can expect it to have some sensible content while the watcher
		930	is active, but you can also modify it. Modifying it may not do something
		931	sensible or take immediate effect (or do anything at all), but libev will
		932	not crash or malfunction in any way.
		933
		934
407	=head2 struct ev_io - is my file descriptor readable or writable	935	=head2 C<ev_io> - is this file descriptor readable or writable?
408		936
409	I/O watchers check whether a file descriptor is readable or writable	937	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	938	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	939	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	940	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	941	receiving events as long as the condition persists. Remember you can stop
		942	the watcher if you don't want to act on the event and neither want to
		943	receive future events.
414		944
415	In general you can register as many read and/or write event watchers oer	945	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	946	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	947	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	948	required if you know what you are doing).
419		949
420	You have to be careful with dup'ed file descriptors, though. Some backends	950	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	951	(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	952	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	953	to the same underlying file/socket/etc. description (that is, they share
		954	the same underlying "file open").
424		955
425	If you must do this, then force the use of a known-to-be-good backend	956	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	957	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	958	C<EVBACKEND_POLL>).
		959
		960	Another thing you have to watch out for is that it is quite easy to
		961	receive "spurious" readyness notifications, that is your callback might
		962	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		963	because there is no data. Not only are some backends known to create a
		964	lot of those (for example solaris ports), it is very easy to get into
		965	this situation even with a relatively standard program structure. Thus
		966	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		967	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		968
		969	If you cannot run the fd in non-blocking mode (for example you should not
		970	play around with an Xlib connection), then you have to seperately re-test
		971	whether a file descriptor is really ready with a known-to-be good interface
		972	such as poll (fortunately in our Xlib example, Xlib already does this on
		973	its own, so its quite safe to use).
		974
		975	=head3 The special problem of disappearing file descriptors
		976
		977	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		978	descriptor (either by calling C<close> explicitly or by any other means,
		979	such as C<dup>). The reason is that you register interest in some file
		980	descriptor, but when it goes away, the operating system will silently drop
		981	this interest. If another file descriptor with the same number then is
		982	registered with libev, there is no efficient way to see that this is, in
		983	fact, a different file descriptor.
		984
		985	To avoid having to explicitly tell libev about such cases, libev follows
		986	the following policy: Each time C<ev_io_set> is being called, libev
		987	will assume that this is potentially a new file descriptor, otherwise
		988	it is assumed that the file descriptor stays the same. That means that
		989	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		990	descriptor even if the file descriptor number itself did not change.
		991
		992	This is how one would do it normally anyway, the important point is that
		993	the libev application should not optimise around libev but should leave
		994	optimisations to libev.
		995
		996	=head3 The special problem of dup'ed file descriptors
		997
		998	Some backends (e.g. epoll), cannot register events for file descriptors,
		999	but only events for the underlying file descriptions. That menas when you
		1000	have C<dup ()>'ed file descriptors and register events for them, only one
		1001	file descriptor might actually receive events.
		1002
		1003	There is no workaorund possible except not registering events
		1004	for potentially C<dup ()>'ed file descriptors or to resort to
		1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1006
		1007	=head3 The special problem of fork
		1008
		1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1010	useless behaviour. Libev fully supports fork, but needs to be told about
		1011	it in the child.
		1012
		1013	To support fork in your programs, you either have to call
		1014	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1015	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1016	C<EVBACKEND_POLL>.
		1017
		1018
		1019	=head3 Watcher-Specific Functions
428		1020
429	=over 4	1021	=over 4
430		1022
431	=item ev_io_init (ev_io *, callback, int fd, int events)	1023	=item ev_io_init (ev_io *, callback, int fd, int events)
432		1024
433	=item ev_io_set (ev_io *, int fd, int events)	1025	=item ev_io_set (ev_io *, int fd, int events)
434		1026
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1027	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 |	1028	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	1029	C<EV_READ | EV_WRITE> to receive the given events.
		1030
		1031	=item int fd [read-only]
		1032
		1033	The file descriptor being watched.
		1034
		1035	=item int events [read-only]
		1036
		1037	The events being watched.
438		1038
439	=back	1039	=back
440		1040
		1041	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1042	readable, but only once. Since it is likely line-buffered, you could
		1043	attempt to read a whole line in the callback.
		1044
		1045	static void
		1046	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1047	{
		1048	ev_io_stop (loop, w);
		1049	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1050	}
		1051
		1052	...
		1053	struct ev_loop *loop = ev_default_init (0);
		1054	struct ev_io stdin_readable;
		1055	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1056	ev_io_start (loop, &stdin_readable);
		1057	ev_loop (loop, 0);
		1058
		1059
441	=head2 struct ev_timer - relative and optionally recurring timeouts	1060	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		1061
443	Timer watchers are simple relative timers that generate an event after a	1062	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	1063	given time, and optionally repeating in regular intervals after that.
445		1064
446	The timers are based on real time, that is, if you register an event that	1065	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	1066	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	1067	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1068	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	1069	monotonic clock option helps a lot here).
		1070
		1071	The relative timeouts are calculated relative to the C<ev_now ()>
		1072	time. This is usually the right thing as this timestamp refers to the time
		1073	of the event triggering whatever timeout you are modifying/starting. If
		1074	you suspect event processing to be delayed and you I<need> to base the timeout
		1075	on the current time, use something like this to adjust for this:
		1076
		1077	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1078
		1079	The callback is guarenteed to be invoked only when its timeout has passed,
		1080	but if multiple timers become ready during the same loop iteration then
		1081	order of execution is undefined.
		1082
		1083	=head3 Watcher-Specific Functions and Data Members
451		1084
452	=over 4	1085	=over 4
453		1086
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1087	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		1088
…		…
461	later, again, and again, until stopped manually.	1094	later, again, and again, until stopped manually.
462		1095
463	The timer itself will do a best-effort at avoiding drift, that is, if you	1096	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	1097	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	1098	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	1099	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.	1100	timer will not fire more than once per event loop iteration.
468		1101
469	=item ev_timer_again (loop)	1102	=item ev_timer_again (loop)
470		1103
471	This will act as if the timer timed out and restart it again if it is	1104	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	1105	repeating. The exact semantics are:
473		1106
		1107	If the timer is pending, its pending status is cleared.
		1108
474	If the timer is started but nonrepeating, stop it.	1109	If the timer is started but nonrepeating, stop it (as if it timed out).
475		1110
476	If the timer is repeating, either start it if necessary (with the repeat	1111	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	1112	C<repeat> value), or reset the running timer to the C<repeat> value.
478		1113
479	This sounds a bit complicated, but here is a useful and typical	1114	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	1115	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	1116	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	1117	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	1118	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	1119	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	1120	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.	1121	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1122	automatically restart it if need be.
		1123
		1124	That means you can ignore the C<after> value and C<ev_timer_start>
		1125	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1126
		1127	ev_timer_init (timer, callback, 0., 5.);
		1128	ev_timer_again (loop, timer);
		1129	...
		1130	timer->again = 17.;
		1131	ev_timer_again (loop, timer);
		1132	...
		1133	timer->again = 10.;
		1134	ev_timer_again (loop, timer);
		1135
		1136	This is more slightly efficient then stopping/starting the timer each time
		1137	you want to modify its timeout value.
		1138
		1139	=item ev_tstamp repeat [read-write]
		1140
		1141	The current C<repeat> value. Will be used each time the watcher times out
		1142	or C<ev_timer_again> is called and determines the next timeout (if any),
		1143	which is also when any modifications are taken into account.
487		1144
488	=back	1145	=back
489		1146
		1147	Example: Create a timer that fires after 60 seconds.
		1148
		1149	static void
		1150	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1151	{
		1152	.. one minute over, w is actually stopped right here
		1153	}
		1154
		1155	struct ev_timer mytimer;
		1156	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1157	ev_timer_start (loop, &mytimer);
		1158
		1159	Example: Create a timeout timer that times out after 10 seconds of
		1160	inactivity.
		1161
		1162	static void
		1163	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1164	{
		1165	.. ten seconds without any activity
		1166	}
		1167
		1168	struct ev_timer mytimer;
		1169	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1170	ev_timer_again (&mytimer); /* start timer */
		1171	ev_loop (loop, 0);
		1172
		1173	// and in some piece of code that gets executed on any "activity":
		1174	// reset the timeout to start ticking again at 10 seconds
		1175	ev_timer_again (&mytimer);
		1176
		1177
490	=head2 ev_periodic - to cron or not to cron it	1178	=head2 C<ev_periodic> - to cron or not to cron?
491		1179
492	Periodic watchers are also timers of a kind, but they are very versatile	1180	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1181	(and unfortunately a bit complex).
494		1182
495	Unlike ev_timer's, they are not based on real time (or relative time)	1183	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	1184	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	1185	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 ()	1186	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	1187	+ 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	1188	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	1189	roughly 10 seconds later).
502	again).
503		1190
504	They can also be used to implement vastly more complex timers, such as	1191	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1192	triggering an event on each midnight, local time or other, complicated,
		1193	rules.
		1194
		1195	As with timers, the callback is guarenteed to be invoked only when the
		1196	time (C<at>) has been passed, but if multiple periodic timers become ready
		1197	during the same loop iteration then order of execution is undefined.
		1198
		1199	=head3 Watcher-Specific Functions and Data Members
506		1200
507	=over 4	1201	=over 4
508		1202
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1203	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1204
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1205	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1206
513	Lots of arguments, lets sort it out... There are basically three modes of	1207	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1208	operation, and we will explain them from simplest to complex:
515		1209
516
517	=over 4	1210	=over 4
518		1211
519	=item * absolute timer (interval = reschedule_cb = 0)	1212	=item * absolute timer (at = time, interval = reschedule_cb = 0)
520		1213
521	In this configuration the watcher triggers an event at the wallclock time	1214	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,	1215	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	1216	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.	1217	system time reaches or surpasses this time.
525		1218
526	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1219	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
527		1220
528	In this mode the watcher will always be scheduled to time out at the next	1221	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	1222	C<at + N * interval> time (for some integer N, which can also be negative)
530	of any time jumps.	1223	and then repeat, regardless of any time jumps.
531		1224
532	This can be used to create timers that do not drift with respect to system	1225	This can be used to create timers that do not drift with respect to system
533	time:	1226	time:
534		1227
535	ev_periodic_set (&periodic, 0., 3600., 0);	1228	ev_periodic_set (&periodic, 0., 3600., 0);
536		1229
537	This doesn't mean there will always be 3600 seconds in between triggers,	1230	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	1231	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	1232	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1233	by 3600.
541		1234
542	Another way to think about it (for the mathematically inclined) is that	1235	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	1236	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.	1237	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1238
		1239	For numerical stability it is preferable that the C<at> value is near
		1240	C<ev_now ()> (the current time), but there is no range requirement for
		1241	this value.
		1242
546	=item * manual reschedule mode (reschedule_cb = callback)	1243	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
547		1244
548	In this mode the values for C<interval> and C<at> are both being	1245	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	1246	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1247	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1248	current time as second argument.
552		1249
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1250	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	1251	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.	1252	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1253	starting an C<ev_prepare> watcher, which is legal).
556		1254
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1255	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1256	ev_tstamp now)>, e.g.:
559		1257
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1258	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1259	{
562	return now + 60.;	1260	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1263	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	1264	(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	1265	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1266	might be called at other times, too.
569		1267
		1268	NOTE: I<< This callback must always return a time that is later than the
		1269	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1270
570	This can be used to create very complex timers, such as a timer that	1271	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	1272	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	1273	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1274	you do this is, again, up to you (but it is not trivial, which is the main
		1275	reason I omitted it as an example).
574		1276
575	=back	1277	=back
576		1278
577	=item ev_periodic_again (loop, ev_periodic *)	1279	=item ev_periodic_again (loop, ev_periodic *)
578		1280
579	Simply stops and restarts the periodic watcher again. This is only useful	1281	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1282	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	1283	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1284	program when the crontabs have changed).
583		1285
		1286	=item ev_tstamp offset [read-write]
		1287
		1288	When repeating, this contains the offset value, otherwise this is the
		1289	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1290
		1291	Can be modified any time, but changes only take effect when the periodic
		1292	timer fires or C<ev_periodic_again> is being called.
		1293
		1294	=item ev_tstamp interval [read-write]
		1295
		1296	The current interval value. Can be modified any time, but changes only
		1297	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1298	called.
		1299
		1300	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1301
		1302	The current reschedule callback, or C<0>, if this functionality is
		1303	switched off. Can be changed any time, but changes only take effect when
		1304	the periodic timer fires or C<ev_periodic_again> is being called.
		1305
		1306	=item ev_tstamp at [read-only]
		1307
		1308	When active, contains the absolute time that the watcher is supposed to
		1309	trigger next.
		1310
584	=back	1311	=back
585		1312
		1313	Example: Call a callback every hour, or, more precisely, whenever the
		1314	system clock is divisible by 3600. The callback invocation times have
		1315	potentially a lot of jittering, but good long-term stability.
		1316
		1317	static void
		1318	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1319	{
		1320	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1321	}
		1322
		1323	struct ev_periodic hourly_tick;
		1324	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1325	ev_periodic_start (loop, &hourly_tick);
		1326
		1327	Example: The same as above, but use a reschedule callback to do it:
		1328
		1329	#include <math.h>
		1330
		1331	static ev_tstamp
		1332	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1333	{
		1334	return fmod (now, 3600.) + 3600.;
		1335	}
		1336
		1337	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1338
		1339	Example: Call a callback every hour, starting now:
		1340
		1341	struct ev_periodic hourly_tick;
		1342	ev_periodic_init (&hourly_tick, clock_cb,
		1343	fmod (ev_now (loop), 3600.), 3600., 0);
		1344	ev_periodic_start (loop, &hourly_tick);
		1345
		1346
586	=head2 ev_signal - signal me when a signal gets signalled	1347	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1348
588	Signal watchers will trigger an event when the process receives a specific	1349	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	1350	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	1351	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1352	normal event processing, like any other event.
592		1353
593	You cna configure as many watchers as you like per signal. Only when the	1354	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	1355	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	1356	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	1357	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	1358	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1359	SIG_DFL (regardless of what it was set to before).
599		1360
		1361	=head3 Watcher-Specific Functions and Data Members
		1362
600	=over 4	1363	=over 4
601		1364
602	=item ev_signal_init (ev_signal *, callback, int signum)	1365	=item ev_signal_init (ev_signal *, callback, int signum)
603		1366
604	=item ev_signal_set (ev_signal *, int signum)	1367	=item ev_signal_set (ev_signal *, int signum)
605		1368
606	Configures the watcher to trigger on the given signal number (usually one	1369	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1370	of the C<SIGxxx> constants).
608		1371
		1372	=item int signum [read-only]
		1373
		1374	The signal the watcher watches out for.
		1375
609	=back	1376	=back
610		1377
		1378
611	=head2 ev_child - wait for pid status changes	1379	=head2 C<ev_child> - watch out for process status changes
612		1380
613	Child watchers trigger when your process receives a SIGCHLD in response to	1381	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).	1382	some child status changes (most typically when a child of yours dies).
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
615		1385
616	=over 4	1386	=over 4
617		1387
618	=item ev_child_init (ev_child *, callback, int pid)	1388	=item ev_child_init (ev_child *, callback, int pid)
619		1389
620	=item ev_child_set (ev_child *, int pid)	1390	=item ev_child_set (ev_child *, int pid)
621		1391
622	Configures the watcher to wait for status changes of process C<pid> (or	1392	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	1393	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	1394	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	1395	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.	1396	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1397	process causing the status change.
		1398
		1399	=item int pid [read-only]
		1400
		1401	The process id this watcher watches out for, or C<0>, meaning any process id.
		1402
		1403	=item int rpid [read-write]
		1404
		1405	The process id that detected a status change.
		1406
		1407	=item int rstatus [read-write]
		1408
		1409	The process exit/trace status caused by C<rpid> (see your systems
		1410	C<waitpid> and C<sys/wait.h> documentation for details).
627		1411
628	=back	1412	=back
629		1413
		1414	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1415
		1416	static void
		1417	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1418	{
		1419	ev_unloop (loop, EVUNLOOP_ALL);
		1420	}
		1421
		1422	struct ev_signal signal_watcher;
		1423	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1424	ev_signal_start (loop, &sigint_cb);
		1425
		1426
		1427	=head2 C<ev_stat> - did the file attributes just change?
		1428
		1429	This watches a filesystem path for attribute changes. That is, it calls
		1430	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1431	compared to the last time, invoking the callback if it did.
		1432
		1433	The path does not need to exist: changing from "path exists" to "path does
		1434	not exist" is a status change like any other. The condition "path does
		1435	not exist" is signified by the C<st_nlink> field being zero (which is
		1436	otherwise always forced to be at least one) and all the other fields of
		1437	the stat buffer having unspecified contents.
		1438
		1439	The path I<should> be absolute and I<must not> end in a slash. If it is
		1440	relative and your working directory changes, the behaviour is undefined.
		1441
		1442	Since there is no standard to do this, the portable implementation simply
		1443	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1444	can specify a recommended polling interval for this case. If you specify
		1445	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1446	unspecified default> value will be used (which you can expect to be around
		1447	five seconds, although this might change dynamically). Libev will also
		1448	impose a minimum interval which is currently around C<0.1>, but thats
		1449	usually overkill.
		1450
		1451	This watcher type is not meant for massive numbers of stat watchers,
		1452	as even with OS-supported change notifications, this can be
		1453	resource-intensive.
		1454
		1455	At the time of this writing, only the Linux inotify interface is
		1456	implemented (implementing kqueue support is left as an exercise for the
		1457	reader). Inotify will be used to give hints only and should not change the
		1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1459	to fall back to regular polling again even with inotify, but changes are
		1460	usually detected immediately, and if the file exists there will be no
		1461	polling.
		1462
		1463	=head3 Watcher-Specific Functions and Data Members
		1464
		1465	=over 4
		1466
		1467	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1468
		1469	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1470
		1471	Configures the watcher to wait for status changes of the given
		1472	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1473	be detected and should normally be specified as C<0> to let libev choose
		1474	a suitable value. The memory pointed to by C<path> must point to the same
		1475	path for as long as the watcher is active.
		1476
		1477	The callback will be receive C<EV_STAT> when a change was detected,
		1478	relative to the attributes at the time the watcher was started (or the
		1479	last change was detected).
		1480
		1481	=item ev_stat_stat (ev_stat *)
		1482
		1483	Updates the stat buffer immediately with new values. If you change the
		1484	watched path in your callback, you could call this fucntion to avoid
		1485	detecting this change (while introducing a race condition). Can also be
		1486	useful simply to find out the new values.
		1487
		1488	=item ev_statdata attr [read-only]
		1489
		1490	The most-recently detected attributes of the file. Although the type is of
		1491	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1492	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1493	was some error while C<stat>ing the file.
		1494
		1495	=item ev_statdata prev [read-only]
		1496
		1497	The previous attributes of the file. The callback gets invoked whenever
		1498	C<prev> != C<attr>.
		1499
		1500	=item ev_tstamp interval [read-only]
		1501
		1502	The specified interval.
		1503
		1504	=item const char *path [read-only]
		1505
		1506	The filesystem path that is being watched.
		1507
		1508	=back
		1509
		1510	Example: Watch C</etc/passwd> for attribute changes.
		1511
		1512	static void
		1513	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1514	{
		1515	/* /etc/passwd changed in some way */
		1516	if (w->attr.st_nlink)
		1517	{
		1518	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1519	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1520	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1521	}
		1522	else
		1523	/* you shalt not abuse printf for puts */
		1524	puts ("wow, /etc/passwd is not there, expect problems. "
		1525	"if this is windows, they already arrived\n");
		1526	}
		1527
		1528	...
		1529	ev_stat passwd;
		1530
		1531	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1532	ev_stat_start (loop, &passwd);
		1533
		1534
630	=head2 ev_idle - when you've got nothing better to do	1535	=head2 C<ev_idle> - when you've got nothing better to do...
631		1536
632	Idle watchers trigger events when there are no other I/O or timer (or	1537	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	1538	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	1539	count).
635	is idle all idle watchers are being called again and again - until	1540
		1541	That is, as long as your process is busy handling sockets or timeouts
		1542	(or even signals, imagine) of the same or higher priority it will not be
		1543	triggered. But when your process is idle (or only lower-priority watchers
		1544	are pending), the idle watchers are being called once per event loop
636	stopped, that is, or your process receives more events.	1545	iteration - until stopped, that is, or your process receives more events
		1546	and becomes busy again with higher priority stuff.
637		1547
638	The most noteworthy effect is that as long as any idle watchers are	1548	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.	1549	active, the process will not block when waiting for new events.
640		1550
641	Apart from keeping your process non-blocking (which is a useful	1551	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	1552	effect on its own sometimes), idle watchers are a good place to do
643	"pseudo-background processing", or delay processing stuff to after the	1553	"pseudo-background processing", or delay processing stuff to after the
644	event loop has handled all outstanding events.	1554	event loop has handled all outstanding events.
645		1555
		1556	=head3 Watcher-Specific Functions and Data Members
		1557
646	=over 4	1558	=over 4
647		1559
648	=item ev_idle_init (ev_signal *, callback)	1560	=item ev_idle_init (ev_signal *, callback)
649		1561
650	Initialises and configures the idle watcher - it has no parameters of any	1562	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,	1563	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1564	believe me.
653		1565
654	=back	1566	=back
655		1567
656	=head2 prepare and check - your hooks into the event loop	1568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1569	callback, free it. Also, use no error checking, as usual.
657		1570
		1571	static void
		1572	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1573	{
		1574	free (w);
		1575	// now do something you wanted to do when the program has
		1576	// no longer asnything immediate to do.
		1577	}
		1578
		1579	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1580	ev_idle_init (idle_watcher, idle_cb);
		1581	ev_idle_start (loop, idle_cb);
		1582
		1583
		1584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1585
658	Prepare and check watchers usually (but not always) are used in	1586	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1587	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1588	afterwards.
661		1589
		1590	You I<must not> call C<ev_loop> or similar functions that enter
		1591	the current event loop from either C<ev_prepare> or C<ev_check>
		1592	watchers. Other loops than the current one are fine, however. The
		1593	rationale behind this is that you do not need to check for recursion in
		1594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1595	C<ev_check> so if you have one watcher of each kind they will always be
		1596	called in pairs bracketing the blocking call.
		1597
662	Their main purpose is to integrate other event mechanisms into libev. This	1598	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	1599	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.	1600	variable changes, implement your own watchers, integrate net-snmp or a
		1601	coroutine library and lots more. They are also occasionally useful if
		1602	you cache some data and want to flush it before blocking (for example,
		1603	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1604	watcher).
665		1605
666	This is done by examining in each prepare call which file descriptors need	1606	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	1607	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	1608	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	1609	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)	1610	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1611	and stopping them) and call back into the library. The I/O and timer
		1612	callbacks will never actually be called (but must be valid nevertheless,
		1613	because you never know, you know?).
672		1614
673	As another example, the perl Coro module uses these hooks to integrate	1615	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1616	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1617	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1618	are ready to run (it's actually more complicated: it only runs coroutines
		1619	with priority higher than or equal to the event loop and one coroutine
		1620	of lower priority, but only once, using idle watchers to keep the event
		1621	loop from blocking if lower-priority coroutines are active, thus mapping
		1622	low-priority coroutines to idle/background tasks).
		1623
		1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1625	priority, to ensure that they are being run before any other watchers
		1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1627	too) should not activate ("feed") events into libev. While libev fully
		1628	supports this, they will be called before other C<ev_check> watchers did
		1629	their job. As C<ev_check> watchers are often used to embed other event
		1630	loops those other event loops might be in an unusable state until their
		1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1632	others).
		1633
		1634	=head3 Watcher-Specific Functions and Data Members
677		1635
678	=over 4	1636	=over 4
679		1637
680	=item ev_prepare_init (ev_prepare *, callback)	1638	=item ev_prepare_init (ev_prepare *, callback)
681		1639
682	=item ev_check_init (ev_check *, callback)	1640	=item ev_check_init (ev_check *, callback)
683		1641
684	Initialises and configures the prepare or check watcher - they have no	1642	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>	1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1644	macros, but using them is utterly, utterly and completely pointless.
687		1645
688	=back	1646	=back
689		1647
		1648	There are a number of principal ways to embed other event loops or modules
		1649	into libev. Here are some ideas on how to include libadns into libev
		1650	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1651	use for an actually working example. Another Perl module named C<EV::Glib>
		1652	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1653	into the Glib event loop).
		1654
		1655	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1656	and in a check watcher, destroy them and call into libadns. What follows
		1657	is pseudo-code only of course. This requires you to either use a low
		1658	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1659	the callbacks for the IO/timeout watchers might not have been called yet.
		1660
		1661	static ev_io iow [nfd];
		1662	static ev_timer tw;
		1663
		1664	static void
		1665	io_cb (ev_loop *loop, ev_io *w, int revents)
		1666	{
		1667	}
		1668
		1669	// create io watchers for each fd and a timer before blocking
		1670	static void
		1671	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1672	{
		1673	int timeout = 3600000;
		1674	struct pollfd fds [nfd];
		1675	// actual code will need to loop here and realloc etc.
		1676	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1677
		1678	/* the callback is illegal, but won't be called as we stop during check */
		1679	ev_timer_init (&tw, 0, timeout * 1e-3);
		1680	ev_timer_start (loop, &tw);
		1681
		1682	// create one ev_io per pollfd
		1683	for (int i = 0; i < nfd; ++i)
		1684	{
		1685	ev_io_init (iow + i, io_cb, fds [i].fd,
		1686	((fds [i].events & POLLIN ? EV_READ : 0)
		1687	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1688
		1689	fds [i].revents = 0;
		1690	ev_io_start (loop, iow + i);
		1691	}
		1692	}
		1693
		1694	// stop all watchers after blocking
		1695	static void
		1696	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1697	{
		1698	ev_timer_stop (loop, &tw);
		1699
		1700	for (int i = 0; i < nfd; ++i)
		1701	{
		1702	// set the relevant poll flags
		1703	// could also call adns_processreadable etc. here
		1704	struct pollfd *fd = fds + i;
		1705	int revents = ev_clear_pending (iow + i);
		1706	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1707	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1708
		1709	// now stop the watcher
		1710	ev_io_stop (loop, iow + i);
		1711	}
		1712
		1713	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1714	}
		1715
		1716	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1717	in the prepare watcher and would dispose of the check watcher.
		1718
		1719	Method 3: If the module to be embedded supports explicit event
		1720	notification (adns does), you can also make use of the actual watcher
		1721	callbacks, and only destroy/create the watchers in the prepare watcher.
		1722
		1723	static void
		1724	timer_cb (EV_P_ ev_timer *w, int revents)
		1725	{
		1726	adns_state ads = (adns_state)w->data;
		1727	update_now (EV_A);
		1728
		1729	adns_processtimeouts (ads, &tv_now);
		1730	}
		1731
		1732	static void
		1733	io_cb (EV_P_ ev_io *w, int revents)
		1734	{
		1735	adns_state ads = (adns_state)w->data;
		1736	update_now (EV_A);
		1737
		1738	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1739	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1740	}
		1741
		1742	// do not ever call adns_afterpoll
		1743
		1744	Method 4: Do not use a prepare or check watcher because the module you
		1745	want to embed is too inflexible to support it. Instead, youc na override
		1746	their poll function. The drawback with this solution is that the main
		1747	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1748	this.
		1749
		1750	static gint
		1751	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1752	{
		1753	int got_events = 0;
		1754
		1755	for (n = 0; n < nfds; ++n)
		1756	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1757
		1758	if (timeout >= 0)
		1759	// create/start timer
		1760
		1761	// poll
		1762	ev_loop (EV_A_ 0);
		1763
		1764	// stop timer again
		1765	if (timeout >= 0)
		1766	ev_timer_stop (EV_A_ &to);
		1767
		1768	// stop io watchers again - their callbacks should have set
		1769	for (n = 0; n < nfds; ++n)
		1770	ev_io_stop (EV_A_ iow [n]);
		1771
		1772	return got_events;
		1773	}
		1774
		1775
		1776	=head2 C<ev_embed> - when one backend isn't enough...
		1777
		1778	This is a rather advanced watcher type that lets you embed one event loop
		1779	into another (currently only C<ev_io> events are supported in the embedded
		1780	loop, other types of watchers might be handled in a delayed or incorrect
		1781	fashion and must not be used). (See portability notes, below).
		1782
		1783	There are primarily two reasons you would want that: work around bugs and
		1784	prioritise I/O.
		1785
		1786	As an example for a bug workaround, the kqueue backend might only support
		1787	sockets on some platform, so it is unusable as generic backend, but you
		1788	still want to make use of it because you have many sockets and it scales
		1789	so nicely. In this case, you would create a kqueue-based loop and embed it
		1790	into your default loop (which might use e.g. poll). Overall operation will
		1791	be a bit slower because first libev has to poll and then call kevent, but
		1792	at least you can use both at what they are best.
		1793
		1794	As for prioritising I/O: rarely you have the case where some fds have
		1795	to be watched and handled very quickly (with low latency), and even
		1796	priorities and idle watchers might have too much overhead. In this case
		1797	you would put all the high priority stuff in one loop and all the rest in
		1798	a second one, and embed the second one in the first.
		1799
		1800	As long as the watcher is active, the callback will be invoked every time
		1801	there might be events pending in the embedded loop. The callback must then
		1802	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1803	their callbacks (you could also start an idle watcher to give the embedded
		1804	loop strictly lower priority for example). You can also set the callback
		1805	to C<0>, in which case the embed watcher will automatically execute the
		1806	embedded loop sweep.
		1807
		1808	As long as the watcher is started it will automatically handle events. The
		1809	callback will be invoked whenever some events have been handled. You can
		1810	set the callback to C<0> to avoid having to specify one if you are not
		1811	interested in that.
		1812
		1813	Also, there have not currently been made special provisions for forking:
		1814	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1815	but you will also have to stop and restart any C<ev_embed> watchers
		1816	yourself.
		1817
		1818	Unfortunately, not all backends are embeddable, only the ones returned by
		1819	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1820	portable one.
		1821
		1822	So when you want to use this feature you will always have to be prepared
		1823	that you cannot get an embeddable loop. The recommended way to get around
		1824	this is to have a separate variables for your embeddable loop, try to
		1825	create it, and if that fails, use the normal loop for everything:
		1826
		1827	struct ev_loop *loop_hi = ev_default_init (0);
		1828	struct ev_loop *loop_lo = 0;
		1829	struct ev_embed embed;
		1830
		1831	// see if there is a chance of getting one that works
		1832	// (remember that a flags value of 0 means autodetection)
		1833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1835	: 0;
		1836
		1837	// if we got one, then embed it, otherwise default to loop_hi
		1838	if (loop_lo)
		1839	{
		1840	ev_embed_init (&embed, 0, loop_lo);
		1841	ev_embed_start (loop_hi, &embed);
		1842	}
		1843	else
		1844	loop_lo = loop_hi;
		1845
		1846	=head2 Portability notes
		1847
		1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1849	tried, in various ways. Usually the embedded event loop will simply never
		1850	receive events, sometimes it will only trigger a few times, sometimes in a
		1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1852	will always eport the epoll fd as ready, even when no events are pending.
		1853
		1854	While libev allows embedding these backends (they are contained in
		1855	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1856	work.
		1857
		1858	When in doubt, create a dynamic event loop forced to use sockets (this
		1859	usually works) and possibly another thread and a pipe or so to report to
		1860	your main event loop.
		1861
		1862	=head3 Watcher-Specific Functions and Data Members
		1863
		1864	=over 4
		1865
		1866	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1867
		1868	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1869
		1870	Configures the watcher to embed the given loop, which must be
		1871	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1872	invoked automatically, otherwise it is the responsibility of the callback
		1873	to invoke it (it will continue to be called until the sweep has been done,
		1874	if you do not want thta, you need to temporarily stop the embed watcher).
		1875
		1876	=item ev_embed_sweep (loop, ev_embed *)
		1877
		1878	Make a single, non-blocking sweep over the embedded loop. This works
		1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1880	apropriate way for embedded loops.
		1881
		1882	=item struct ev_loop *other [read-only]
		1883
		1884	The embedded event loop.
		1885
		1886	=back
		1887
		1888
		1889	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1890
		1891	Fork watchers are called when a C<fork ()> was detected (usually because
		1892	whoever is a good citizen cared to tell libev about it by calling
		1893	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1894	event loop blocks next and before C<ev_check> watchers are being called,
		1895	and only in the child after the fork. If whoever good citizen calling
		1896	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1897	handlers will be invoked, too, of course.
		1898
		1899	=head3 Watcher-Specific Functions and Data Members
		1900
		1901	=over 4
		1902
		1903	=item ev_fork_init (ev_signal *, callback)
		1904
		1905	Initialises and configures the fork watcher - it has no parameters of any
		1906	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1907	believe me.
		1908
		1909	=back
		1910
		1911
690	=head1 OTHER FUNCTIONS	1912	=head1 OTHER FUNCTIONS
691		1913
692	There are some other fucntions of possible interest. Described. Here. Now.	1914	There are some other functions of possible interest. Described. Here. Now.
693		1915
694	=over 4	1916	=over 4
695		1917
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1918	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		1919
698	This function combines a simple timer and an I/O watcher, calls your	1920	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	1921	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	1922	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	1923	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	1924	more watchers yourself.
703		1925
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	1926	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	1927	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	1928	C<events> set will be craeted and started.
707		1929
708	If C<timeout> is less than 0, then no timeout watcher will be	1930	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	1931	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	1932	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1933	dubious value.
711		1934
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	1935	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,	1936	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>:	1937	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1938	value passed to C<ev_once>:
715		1939
716	static void stdin_ready (int revents, void *arg)	1940	static void stdin_ready (int revents, void *arg)
717	{	1941	{
718	if (revents & EV_TIMEOUT)	1942	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	1943	/* doh, nothing entered */;
720	else if (revents & EV_READ)	1944	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	1945	/* stdin might have data for us, joy! */;
722	}	1946	}
723		1947
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1948	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		1949
726	=item ev_feed_event (loop, watcher, int events)	1950	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		1951
728	Feeds the given event set into the event loop, as if the specified event	1952	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	1953	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	1954	initialised but not necessarily started event watcher).
731		1955
732	=item ev_feed_fd_event (loop, int fd, int revents)	1956	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		1957
734	Feed an event on the given fd, as if a file descriptor backend detected it.	1958	Feed an event on the given fd, as if a file descriptor backend detected
		1959	the given events it.
735		1960
736	=item ev_feed_signal_event (loop, int signum)	1961	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		1962
738	Feed an event as if the given signal occured (loop must be the default loop!).	1963	Feed an event as if the given signal occured (C<loop> must be the default
		1964	loop!).
739		1965
740	=back	1966	=back
741		1967
		1968
		1969	=head1 LIBEVENT EMULATION
		1970
		1971	Libev offers a compatibility emulation layer for libevent. It cannot
		1972	emulate the internals of libevent, so here are some usage hints:
		1973
		1974	=over 4
		1975
		1976	=item * Use it by including <event.h>, as usual.
		1977
		1978	=item * The following members are fully supported: ev_base, ev_callback,
		1979	ev_arg, ev_fd, ev_res, ev_events.
		1980
		1981	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1982	maintained by libev, it does not work exactly the same way as in libevent (consider
		1983	it a private API).
		1984
		1985	=item * Priorities are not currently supported. Initialising priorities
		1986	will fail and all watchers will have the same priority, even though there
		1987	is an ev_pri field.
		1988
		1989	=item * Other members are not supported.
		1990
		1991	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1992	to use the libev header file and library.
		1993
		1994	=back
		1995
		1996	=head1 C++ SUPPORT
		1997
		1998	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1999	you to use some convinience methods to start/stop watchers and also change
		2000	the callback model to a model using method callbacks on objects.
		2001
		2002	To use it,
		2003
		2004	#include <ev++.h>
		2005
		2006	This automatically includes F<ev.h> and puts all of its definitions (many
		2007	of them macros) into the global namespace. All C++ specific things are
		2008	put into the C<ev> namespace. It should support all the same embedding
		2009	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2010
		2011	Care has been taken to keep the overhead low. The only data member the C++
		2012	classes add (compared to plain C-style watchers) is the event loop pointer
		2013	that the watcher is associated with (or no additional members at all if
		2014	you disable C<EV_MULTIPLICITY> when embedding libev).
		2015
		2016	Currently, functions, and static and non-static member functions can be
		2017	used as callbacks. Other types should be easy to add as long as they only
		2018	need one additional pointer for context. If you need support for other
		2019	types of functors please contact the author (preferably after implementing
		2020	it).
		2021
		2022	Here is a list of things available in the C<ev> namespace:
		2023
		2024	=over 4
		2025
		2026	=item C<ev::READ>, C<ev::WRITE> etc.
		2027
		2028	These are just enum values with the same values as the C<EV_READ> etc.
		2029	macros from F<ev.h>.
		2030
		2031	=item C<ev::tstamp>, C<ev::now>
		2032
		2033	Aliases to the same types/functions as with the C<ev_> prefix.
		2034
		2035	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2036
		2037	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2038	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2039	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2040	defines by many implementations.
		2041
		2042	All of those classes have these methods:
		2043
		2044	=over 4
		2045
		2046	=item ev::TYPE::TYPE ()
		2047
		2048	=item ev::TYPE::TYPE (struct ev_loop *)
		2049
		2050	=item ev::TYPE::~TYPE
		2051
		2052	The constructor (optionally) takes an event loop to associate the watcher
		2053	with. If it is omitted, it will use C<EV_DEFAULT>.
		2054
		2055	The constructor calls C<ev_init> for you, which means you have to call the
		2056	C<set> method before starting it.
		2057
		2058	It will not set a callback, however: You have to call the templated C<set>
		2059	method to set a callback before you can start the watcher.
		2060
		2061	(The reason why you have to use a method is a limitation in C++ which does
		2062	not allow explicit template arguments for constructors).
		2063
		2064	The destructor automatically stops the watcher if it is active.
		2065
		2066	=item w->set<class, &class::method> (object *)
		2067
		2068	This method sets the callback method to call. The method has to have a
		2069	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2070	first argument and the C<revents> as second. The object must be given as
		2071	parameter and is stored in the C<data> member of the watcher.
		2072
		2073	This method synthesizes efficient thunking code to call your method from
		2074	the C callback that libev requires. If your compiler can inline your
		2075	callback (i.e. it is visible to it at the place of the C<set> call and
		2076	your compiler is good :), then the method will be fully inlined into the
		2077	thunking function, making it as fast as a direct C callback.
		2078
		2079	Example: simple class declaration and watcher initialisation
		2080
		2081	struct myclass
		2082	{
		2083	void io_cb (ev::io &w, int revents) { }
		2084	}
		2085
		2086	myclass obj;
		2087	ev::io iow;
		2088	iow.set <myclass, &myclass::io_cb> (&obj);
		2089
		2090	=item w->set<function> (void *data = 0)
		2091
		2092	Also sets a callback, but uses a static method or plain function as
		2093	callback. The optional C<data> argument will be stored in the watcher's
		2094	C<data> member and is free for you to use.
		2095
		2096	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2097
		2098	See the method-C<set> above for more details.
		2099
		2100	Example:
		2101
		2102	static void io_cb (ev::io &w, int revents) { }
		2103	iow.set <io_cb> ();
		2104
		2105	=item w->set (struct ev_loop *)
		2106
		2107	Associates a different C<struct ev_loop> with this watcher. You can only
		2108	do this when the watcher is inactive (and not pending either).
		2109
		2110	=item w->set ([args])
		2111
		2112	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2113	called at least once. Unlike the C counterpart, an active watcher gets
		2114	automatically stopped and restarted when reconfiguring it with this
		2115	method.
		2116
		2117	=item w->start ()
		2118
		2119	Starts the watcher. Note that there is no C<loop> argument, as the
		2120	constructor already stores the event loop.
		2121
		2122	=item w->stop ()
		2123
		2124	Stops the watcher if it is active. Again, no C<loop> argument.
		2125
		2126	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2127
		2128	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2129	C<ev_TYPE_again> function.
		2130
		2131	=item w->sweep () (C<ev::embed> only)
		2132
		2133	Invokes C<ev_embed_sweep>.
		2134
		2135	=item w->update () (C<ev::stat> only)
		2136
		2137	Invokes C<ev_stat_stat>.
		2138
		2139	=back
		2140
		2141	=back
		2142
		2143	Example: Define a class with an IO and idle watcher, start one of them in
		2144	the constructor.
		2145
		2146	class myclass
		2147	{
		2148	ev_io io; void io_cb (ev::io &w, int revents);
		2149	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2150
		2151	myclass ();
		2152	}
		2153
		2154	myclass::myclass (int fd)
		2155	{
		2156	io .set <myclass, &myclass::io_cb > (this);
		2157	idle.set <myclass, &myclass::idle_cb> (this);
		2158
		2159	io.start (fd, ev::READ);
		2160	}
		2161
		2162
		2163	=head1 MACRO MAGIC
		2164
		2165	Libev can be compiled with a variety of options, the most fundamantal
		2166	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2167	functions and callbacks have an initial C<struct ev_loop *> argument.
		2168
		2169	To make it easier to write programs that cope with either variant, the
		2170	following macros are defined:
		2171
		2172	=over 4
		2173
		2174	=item C<EV_A>, C<EV_A_>
		2175
		2176	This provides the loop I<argument> for functions, if one is required ("ev
		2177	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2178	C<EV_A_> is used when other arguments are following. Example:
		2179
		2180	ev_unref (EV_A);
		2181	ev_timer_add (EV_A_ watcher);
		2182	ev_loop (EV_A_ 0);
		2183
		2184	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2185	which is often provided by the following macro.
		2186
		2187	=item C<EV_P>, C<EV_P_>
		2188
		2189	This provides the loop I<parameter> for functions, if one is required ("ev
		2190	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2191	C<EV_P_> is used when other parameters are following. Example:
		2192
		2193	// this is how ev_unref is being declared
		2194	static void ev_unref (EV_P);
		2195
		2196	// this is how you can declare your typical callback
		2197	static void cb (EV_P_ ev_timer *w, int revents)
		2198
		2199	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2200	suitable for use with C<EV_A>.
		2201
		2202	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2203
		2204	Similar to the other two macros, this gives you the value of the default
		2205	loop, if multiple loops are supported ("ev loop default").
		2206
		2207	=back
		2208
		2209	Example: Declare and initialise a check watcher, utilising the above
		2210	macros so it will work regardless of whether multiple loops are supported
		2211	or not.
		2212
		2213	static void
		2214	check_cb (EV_P_ ev_timer *w, int revents)
		2215	{
		2216	ev_check_stop (EV_A_ w);
		2217	}
		2218
		2219	ev_check check;
		2220	ev_check_init (&check, check_cb);
		2221	ev_check_start (EV_DEFAULT_ &check);
		2222	ev_loop (EV_DEFAULT_ 0);
		2223
		2224	=head1 EMBEDDING
		2225
		2226	Libev can (and often is) directly embedded into host
		2227	applications. Examples of applications that embed it include the Deliantra
		2228	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2229	and rxvt-unicode.
		2230
		2231	The goal is to enable you to just copy the necessary files into your
		2232	source directory without having to change even a single line in them, so
		2233	you can easily upgrade by simply copying (or having a checked-out copy of
		2234	libev somewhere in your source tree).
		2235
		2236	=head2 FILESETS
		2237
		2238	Depending on what features you need you need to include one or more sets of files
		2239	in your app.
		2240
		2241	=head3 CORE EVENT LOOP
		2242
		2243	To include only the libev core (all the C<ev_*> functions), with manual
		2244	configuration (no autoconf):
		2245
		2246	#define EV_STANDALONE 1
		2247	#include "ev.c"
		2248
		2249	This will automatically include F<ev.h>, too, and should be done in a
		2250	single C source file only to provide the function implementations. To use
		2251	it, do the same for F<ev.h> in all files wishing to use this API (best
		2252	done by writing a wrapper around F<ev.h> that you can include instead and
		2253	where you can put other configuration options):
		2254
		2255	#define EV_STANDALONE 1
		2256	#include "ev.h"
		2257
		2258	Both header files and implementation files can be compiled with a C++
		2259	compiler (at least, thats a stated goal, and breakage will be treated
		2260	as a bug).
		2261
		2262	You need the following files in your source tree, or in a directory
		2263	in your include path (e.g. in libev/ when using -Ilibev):
		2264
		2265	ev.h
		2266	ev.c
		2267	ev_vars.h
		2268	ev_wrap.h
		2269
		2270	ev_win32.c required on win32 platforms only
		2271
		2272	ev_select.c only when select backend is enabled (which is enabled by default)
		2273	ev_poll.c only when poll backend is enabled (disabled by default)
		2274	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2275	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2276	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2277
		2278	F<ev.c> includes the backend files directly when enabled, so you only need
		2279	to compile this single file.
		2280
		2281	=head3 LIBEVENT COMPATIBILITY API
		2282
		2283	To include the libevent compatibility API, also include:
		2284
		2285	#include "event.c"
		2286
		2287	in the file including F<ev.c>, and:
		2288
		2289	#include "event.h"
		2290
		2291	in the files that want to use the libevent API. This also includes F<ev.h>.
		2292
		2293	You need the following additional files for this:
		2294
		2295	event.h
		2296	event.c
		2297
		2298	=head3 AUTOCONF SUPPORT
		2299
		2300	Instead of using C<EV_STANDALONE=1> and providing your config in
		2301	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2302	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2303	include F<config.h> and configure itself accordingly.
		2304
		2305	For this of course you need the m4 file:
		2306
		2307	libev.m4
		2308
		2309	=head2 PREPROCESSOR SYMBOLS/MACROS
		2310
		2311	Libev can be configured via a variety of preprocessor symbols you have to define
		2312	before including any of its files. The default is not to build for multiplicity
		2313	and only include the select backend.
		2314
		2315	=over 4
		2316
		2317	=item EV_STANDALONE
		2318
		2319	Must always be C<1> if you do not use autoconf configuration, which
		2320	keeps libev from including F<config.h>, and it also defines dummy
		2321	implementations for some libevent functions (such as logging, which is not
		2322	supported). It will also not define any of the structs usually found in
		2323	F<event.h> that are not directly supported by the libev core alone.
		2324
		2325	=item EV_USE_MONOTONIC
		2326
		2327	If defined to be C<1>, libev will try to detect the availability of the
		2328	monotonic clock option at both compiletime and runtime. Otherwise no use
		2329	of the monotonic clock option will be attempted. If you enable this, you
		2330	usually have to link against librt or something similar. Enabling it when
		2331	the functionality isn't available is safe, though, although you have
		2332	to make sure you link against any libraries where the C<clock_gettime>
		2333	function is hiding in (often F<-lrt>).
		2334
		2335	=item EV_USE_REALTIME
		2336
		2337	If defined to be C<1>, libev will try to detect the availability of the
		2338	realtime clock option at compiletime (and assume its availability at
		2339	runtime if successful). Otherwise no use of the realtime clock option will
		2340	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2341	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2342	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2343
		2344	=item EV_USE_NANOSLEEP
		2345
		2346	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2347	and will use it for delays. Otherwise it will use C<select ()>.
		2348
		2349	=item EV_USE_SELECT
		2350
		2351	If undefined or defined to be C<1>, libev will compile in support for the
		2352	C<select>(2) backend. No attempt at autodetection will be done: if no
		2353	other method takes over, select will be it. Otherwise the select backend
		2354	will not be compiled in.
		2355
		2356	=item EV_SELECT_USE_FD_SET
		2357
		2358	If defined to C<1>, then the select backend will use the system C<fd_set>
		2359	structure. This is useful if libev doesn't compile due to a missing
		2360	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2361	exotic systems. This usually limits the range of file descriptors to some
		2362	low limit such as 1024 or might have other limitations (winsocket only
		2363	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2364	influence the size of the C<fd_set> used.
		2365
		2366	=item EV_SELECT_IS_WINSOCKET
		2367
		2368	When defined to C<1>, the select backend will assume that
		2369	select/socket/connect etc. don't understand file descriptors but
		2370	wants osf handles on win32 (this is the case when the select to
		2371	be used is the winsock select). This means that it will call
		2372	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2373	it is assumed that all these functions actually work on fds, even
		2374	on win32. Should not be defined on non-win32 platforms.
		2375
		2376	=item EV_USE_POLL
		2377
		2378	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2379	backend. Otherwise it will be enabled on non-win32 platforms. It
		2380	takes precedence over select.
		2381
		2382	=item EV_USE_EPOLL
		2383
		2384	If defined to be C<1>, libev will compile in support for the Linux
		2385	C<epoll>(7) backend. Its availability will be detected at runtime,
		2386	otherwise another method will be used as fallback. This is the
		2387	preferred backend for GNU/Linux systems.
		2388
		2389	=item EV_USE_KQUEUE
		2390
		2391	If defined to be C<1>, libev will compile in support for the BSD style
		2392	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2393	otherwise another method will be used as fallback. This is the preferred
		2394	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2395	supports some types of fds correctly (the only platform we found that
		2396	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2397	not be used unless explicitly requested. The best way to use it is to find
		2398	out whether kqueue supports your type of fd properly and use an embedded
		2399	kqueue loop.
		2400
		2401	=item EV_USE_PORT
		2402
		2403	If defined to be C<1>, libev will compile in support for the Solaris
		2404	10 port style backend. Its availability will be detected at runtime,
		2405	otherwise another method will be used as fallback. This is the preferred
		2406	backend for Solaris 10 systems.
		2407
		2408	=item EV_USE_DEVPOLL
		2409
		2410	reserved for future expansion, works like the USE symbols above.
		2411
		2412	=item EV_USE_INOTIFY
		2413
		2414	If defined to be C<1>, libev will compile in support for the Linux inotify
		2415	interface to speed up C<ev_stat> watchers. Its actual availability will
		2416	be detected at runtime.
		2417
		2418	=item EV_H
		2419
		2420	The name of the F<ev.h> header file used to include it. The default if
		2421	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2422	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2423
		2424	=item EV_CONFIG_H
		2425
		2426	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2427	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2428	C<EV_H>, above.
		2429
		2430	=item EV_EVENT_H
		2431
		2432	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2433	of how the F<event.h> header can be found.
		2434
		2435	=item EV_PROTOTYPES
		2436
		2437	If defined to be C<0>, then F<ev.h> will not define any function
		2438	prototypes, but still define all the structs and other symbols. This is
		2439	occasionally useful if you want to provide your own wrapper functions
		2440	around libev functions.
		2441
		2442	=item EV_MULTIPLICITY
		2443
		2444	If undefined or defined to C<1>, then all event-loop-specific functions
		2445	will have the C<struct ev_loop *> as first argument, and you can create
		2446	additional independent event loops. Otherwise there will be no support
		2447	for multiple event loops and there is no first event loop pointer
		2448	argument. Instead, all functions act on the single default loop.
		2449
		2450	=item EV_MINPRI
		2451
		2452	=item EV_MAXPRI
		2453
		2454	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2455	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2456	provide for more priorities by overriding those symbols (usually defined
		2457	to be C<-2> and C<2>, respectively).
		2458
		2459	When doing priority-based operations, libev usually has to linearly search
		2460	all the priorities, so having many of them (hundreds) uses a lot of space
		2461	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2462	fine.
		2463
		2464	If your embedding app does not need any priorities, defining these both to
		2465	C<0> will save some memory and cpu.
		2466
		2467	=item EV_PERIODIC_ENABLE
		2468
		2469	If undefined or defined to be C<1>, then periodic timers are supported. If
		2470	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2471	code.
		2472
		2473	=item EV_IDLE_ENABLE
		2474
		2475	If undefined or defined to be C<1>, then idle watchers are supported. If
		2476	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2477	code.
		2478
		2479	=item EV_EMBED_ENABLE
		2480
		2481	If undefined or defined to be C<1>, then embed watchers are supported. If
		2482	defined to be C<0>, then they are not.
		2483
		2484	=item EV_STAT_ENABLE
		2485
		2486	If undefined or defined to be C<1>, then stat watchers are supported. If
		2487	defined to be C<0>, then they are not.
		2488
		2489	=item EV_FORK_ENABLE
		2490
		2491	If undefined or defined to be C<1>, then fork watchers are supported. If
		2492	defined to be C<0>, then they are not.
		2493
		2494	=item EV_MINIMAL
		2495
		2496	If you need to shave off some kilobytes of code at the expense of some
		2497	speed, define this symbol to C<1>. Currently only used for gcc to override
		2498	some inlining decisions, saves roughly 30% codesize of amd64.
		2499
		2500	=item EV_PID_HASHSIZE
		2501
		2502	C<ev_child> watchers use a small hash table to distribute workload by
		2503	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2504	than enough. If you need to manage thousands of children you might want to
		2505	increase this value (I<must> be a power of two).
		2506
		2507	=item EV_INOTIFY_HASHSIZE
		2508
		2509	C<ev_staz> watchers use a small hash table to distribute workload by
		2510	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2511	usually more than enough. If you need to manage thousands of C<ev_stat>
		2512	watchers you might want to increase this value (I<must> be a power of
		2513	two).
		2514
		2515	=item EV_COMMON
		2516
		2517	By default, all watchers have a C<void *data> member. By redefining
		2518	this macro to a something else you can include more and other types of
		2519	members. You have to define it each time you include one of the files,
		2520	though, and it must be identical each time.
		2521
		2522	For example, the perl EV module uses something like this:
		2523
		2524	#define EV_COMMON \
		2525	SV *self; /* contains this struct */ \
		2526	SV *cb_sv, *fh /* note no trailing ";" */
		2527
		2528	=item EV_CB_DECLARE (type)
		2529
		2530	=item EV_CB_INVOKE (watcher, revents)
		2531
		2532	=item ev_set_cb (ev, cb)
		2533
		2534	Can be used to change the callback member declaration in each watcher,
		2535	and the way callbacks are invoked and set. Must expand to a struct member
		2536	definition and a statement, respectively. See the F<ev.h> header file for
		2537	their default definitions. One possible use for overriding these is to
		2538	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2539	method calls instead of plain function calls in C++.
		2540
		2541	=head2 EXPORTED API SYMBOLS
		2542
		2543	If you need to re-export the API (e.g. via a dll) and you need a list of
		2544	exported symbols, you can use the provided F<Symbol.*> files which list
		2545	all public symbols, one per line:
		2546
		2547	Symbols.ev for libev proper
		2548	Symbols.event for the libevent emulation
		2549
		2550	This can also be used to rename all public symbols to avoid clashes with
		2551	multiple versions of libev linked together (which is obviously bad in
		2552	itself, but sometimes it is inconvinient to avoid this).
		2553
		2554	A sed command like this will create wrapper C<#define>'s that you need to
		2555	include before including F<ev.h>:
		2556
		2557	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2558
		2559	This would create a file F<wrap.h> which essentially looks like this:
		2560
		2561	#define ev_backend myprefix_ev_backend
		2562	#define ev_check_start myprefix_ev_check_start
		2563	#define ev_check_stop myprefix_ev_check_stop
		2564	...
		2565
		2566	=head2 EXAMPLES
		2567
		2568	For a real-world example of a program the includes libev
		2569	verbatim, you can have a look at the EV perl module
		2570	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2571	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2572	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2573	will be compiled. It is pretty complex because it provides its own header
		2574	file.
		2575
		2576	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2577	that everybody includes and which overrides some configure choices:
		2578
		2579	#define EV_MINIMAL 1
		2580	#define EV_USE_POLL 0
		2581	#define EV_MULTIPLICITY 0
		2582	#define EV_PERIODIC_ENABLE 0
		2583	#define EV_STAT_ENABLE 0
		2584	#define EV_FORK_ENABLE 0
		2585	#define EV_CONFIG_H <config.h>
		2586	#define EV_MINPRI 0
		2587	#define EV_MAXPRI 0
		2588
		2589	#include "ev++.h"
		2590
		2591	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2592
		2593	#include "ev_cpp.h"
		2594	#include "ev.c"
		2595
		2596
		2597	=head1 COMPLEXITIES
		2598
		2599	In this section the complexities of (many of) the algorithms used inside
		2600	libev will be explained. For complexity discussions about backends see the
		2601	documentation for C<ev_default_init>.
		2602
		2603	All of the following are about amortised time: If an array needs to be
		2604	extended, libev needs to realloc and move the whole array, but this
		2605	happens asymptotically never with higher number of elements, so O(1) might
		2606	mean it might do a lengthy realloc operation in rare cases, but on average
		2607	it is much faster and asymptotically approaches constant time.
		2608
		2609	=over 4
		2610
		2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2612
		2613	This means that, when you have a watcher that triggers in one hour and
		2614	there are 100 watchers that would trigger before that then inserting will
		2615	have to skip those 100 watchers.
		2616
		2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2618
		2619	That means that for changing a timer costs less than removing/adding them
		2620	as only the relative motion in the event queue has to be paid for.
		2621
		2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2623
		2624	These just add the watcher into an array or at the head of a list.
		2625	=item Stopping check/prepare/idle watchers: O(1)
		2626
		2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2628
		2629	These watchers are stored in lists then need to be walked to find the
		2630	correct watcher to remove. The lists are usually short (you don't usually
		2631	have many watchers waiting for the same fd or signal).
		2632
		2633	=item Finding the next timer per loop iteration: O(1)
		2634
		2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2636
		2637	A change means an I/O watcher gets started or stopped, which requires
		2638	libev to recalculate its status (and possibly tell the kernel).
		2639
		2640	=item Activating one watcher: O(1)
		2641
		2642	=item Priority handling: O(number_of_priorities)
		2643
		2644	Priorities are implemented by allocating some space for each
		2645	priority. When doing priority-based operations, libev usually has to
		2646	linearly search all the priorities.
		2647
		2648	=back
		2649
		2650
742	=head1 AUTHOR	2651	=head1 AUTHOR
743		2652
744	Marc Lehmann <libev@schmorp.de>.	2653	Marc Lehmann <libev@schmorp.de>.
745		2654

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines