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Revision 1.8 by root, Mon Nov 12 08:20:02 2007 UTC vs.
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	54	file descriptor being readable or a timeout occuring), and it will manage
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	97	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	98	to the C<double> type in C, and when you need to do any calculations on
		99	it, you should treat it as such.
		100
		101	=head1 GLOBAL FUNCTIONS
		102
		103	These functions can be called anytime, even before initialising the
		104	library in any way.
51		105
52	=over 4	106	=over 4
53		107
54	=item ev_tstamp ev_time ()	108	=item ev_tstamp ev_time ()
55		109
56	Returns the current time as libev would use it.	110	Returns the current time as libev would use it. Please note that the
		111	C<ev_now> function is usually faster and also often returns the timestamp
		112	you actually want to know.
57		113
58	=item int ev_version_major ()	114	=item int ev_version_major ()
59		115
60	=item int ev_version_minor ()	116	=item int ev_version_minor ()
61		117
…		…
63	you linked against by calling the functions C<ev_version_major> and	119	you linked against by calling the functions C<ev_version_major> and
64	C<ev_version_minor>. If you want, you can compare against the global	120	C<ev_version_minor>. If you want, you can compare against the global
65	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	122	version of the library your program was compiled against.
67		123
68	Usually, its a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	127	not a problem.
72		128
		129	Example: Make sure we haven't accidentally been linked against the wrong
		130	version.
		131
		132	assert (("libev version mismatch",
		133	ev_version_major () == EV_VERSION_MAJOR
		134	&& ev_version_minor () >= EV_VERSION_MINOR));
		135
		136	=item unsigned int ev_supported_backends ()
		137
		138	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		139	value) compiled into this binary of libev (independent of their
		140	availability on the system you are running on). See C<ev_default_loop> for
		141	a description of the set values.
		142
		143	Example: make sure we have the epoll method, because yeah this is cool and
		144	a must have and can we have a torrent of it please!!!11
		145
		146	assert (("sorry, no epoll, no sex",
		147	ev_supported_backends () & EVBACKEND_EPOLL));
		148
		149	=item unsigned int ev_recommended_backends ()
		150
		151	Return the set of all backends compiled into this binary of libev and also
		152	recommended for this platform. This set is often smaller than the one
		153	returned by C<ev_supported_backends>, as for example kqueue is broken on
		154	most BSDs and will not be autodetected unless you explicitly request it
		155	(assuming you know what you are doing). This is the set of backends that
		156	libev will probe for if you specify no backends explicitly.
		157
		158	=item unsigned int ev_embeddable_backends ()
		159
		160	Returns the set of backends that are embeddable in other event loops. This
		161	is the theoretical, all-platform, value. To find which backends
		162	might be supported on the current system, you would need to look at
		163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		164	recommended ones.
		165
		166	See the description of C<ev_embed> watchers for more info.
		167
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	168	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		169
75	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	171	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	172	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	173	memory needs to be allocated, the library might abort or take some
79	destructive action. The default is your system realloc function.	174	potentially destructive action. The default is your system realloc
		175	function.
80		176
81	You could override this function in high-availability programs to, say,	177	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,	178	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.	179	or even to sleep a while and retry until some memory is available.
		180
		181	Example: Replace the libev allocator with one that waits a bit and then
		182	retries).
		183
		184	static void *
		185	persistent_realloc (void *ptr, size_t size)
		186	{
		187	for (;;)
		188	{
		189	void *newptr = realloc (ptr, size);
		190
		191	if (newptr)
		192	return newptr;
		193
		194	sleep (60);
		195	}
		196	}
		197
		198	...
		199	ev_set_allocator (persistent_realloc);
84		200
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	201	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		202
87	Set the callback function to call on a retryable syscall error (such	203	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	204	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	206	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	207	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	208	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	209	(such as abort).
94		210
		211	Example: This is basically the same thing that libev does internally, too.
		212
		213	static void
		214	fatal_error (const char *msg)
		215	{
		216	perror (msg);
		217	abort ();
		218	}
		219
		220	...
		221	ev_set_syserr_cb (fatal_error);
		222
95	=back	223	=back
96		224
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	225	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		226
99	An event loop is described by a C<struct ev_loop *>. The library knows two	227	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	228	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	229	events, and dynamically created loops which do not.
102		230
103	If you use threads, a common model is to run the default event loop	231	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	232	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	233	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	234	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	235	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because its hideous and inefficient).	236	done correctly, because it's hideous and inefficient).
109		237
110	=over 4	238	=over 4
111		239
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	240	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		241
114	This will initialise the default event loop if it hasn't been initialised	242	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	243	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	244	false. If it already was initialised it simply returns it (and ignores the
117	flags).	245	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		246
119	If you don't know what event loop to use, use the one returned from this	247	If you don't know what event loop to use, use the one returned from this
120	function.	248	function.
121		249
122	The flags argument can be used to specify special behaviour or specific	250	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).	251	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		252
125	It supports the following flags:	253	The following flags are supported:
126		254
127	=over 4	255	=over 4
128		256
129	=item EVFLAG_AUTO	257	=item C<EVFLAG_AUTO>
130		258
131	The default flags value. Use this if you have no clue (its the right	259	The default flags value. Use this if you have no clue (it's the right
132	thing, believe me).	260	thing, believe me).
133		261
134	=item EVFLAG_NOENV	262	=item C<EVFLAG_NOENV>
135		263
136	If this flag bit is ored into the flag value (or the program runs setuid	264	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	265	or setgid) then libev will I<not> look at the environment variable
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	267	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	268	useful to try out specific backends to test their performance, or to work
141	around bugs.	269	around bugs.
142		270
		271	=item C<EVFLAG_FORKCHECK>
		272
		273	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		274	a fork, you can also make libev check for a fork in each iteration by
		275	enabling this flag.
		276
		277	This works by calling C<getpid ()> on every iteration of the loop,
		278	and thus this might slow down your event loop if you do a lot of loop
		279	iterations and little real work, but is usually not noticeable (on my
		280	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		281	without a syscall and thus I<very> fast, but my Linux system also has
		282	C<pthread_atfork> which is even faster).
		283
		284	The big advantage of this flag is that you can forget about fork (and
		285	forget about forgetting to tell libev about forking) when you use this
		286	flag.
		287
		288	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		289	environment variable.
		290
143	=item EVMETHOD_SELECT portable select backend	291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		292
145	=item EVMETHOD_POLL poll backend (everywhere except windows)	293	This is your standard select(2) backend. Not I<completely> standard, as
		294	libev tries to roll its own fd_set with no limits on the number of fds,
		295	but if that fails, expect a fairly low limit on the number of fds when
		296	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		297	the fastest backend for a low number of fds.
146		298
147	=item EVMETHOD_EPOLL linux only	299	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
148		300
149	=item EVMETHOD_KQUEUE some bsds only	301	And this is your standard poll(2) backend. It's more complicated than
		302	select, but handles sparse fds better and has no artificial limit on the
		303	number of fds you can use (except it will slow down considerably with a
		304	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
150		305
151	=item EVMETHOD_DEVPOLL solaris 8 only	306	=item C<EVBACKEND_EPOLL> (value 4, Linux)
152		307
153	=item EVMETHOD_PORT solaris 10 only	308	For few fds, this backend is a bit little slower than poll and select,
		309	but it scales phenomenally better. While poll and select usually scale like
		310	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		311	either O(1) or O(active_fds).
		312
		313	While stopping and starting an I/O watcher in the same iteration will
		314	result in some caching, there is still a syscall per such incident
		315	(because the fd could point to a different file description now), so its
		316	best to avoid that. Also, dup()ed file descriptors might not work very
		317	well if you register events for both fds.
		318
		319	Please note that epoll sometimes generates spurious notifications, so you
		320	need to use non-blocking I/O or other means to avoid blocking when no data
		321	(or space) is available.
		322
		323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		324
		325	Kqueue deserves special mention, as at the time of this writing, it
		326	was broken on all BSDs except NetBSD (usually it doesn't work with
		327	anything but sockets and pipes, except on Darwin, where of course its
		328	completely useless). For this reason its not being "autodetected"
		329	unless you explicitly specify it explicitly in the flags (i.e. using
		330	C<EVBACKEND_KQUEUE>).
		331
		332	It scales in the same way as the epoll backend, but the interface to the
		333	kernel is more efficient (which says nothing about its actual speed, of
		334	course). While starting and stopping an I/O watcher does not cause an
		335	extra syscall as with epoll, it still adds up to four event changes per
		336	incident, so its best to avoid that.
		337
		338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		339
		340	This is not implemented yet (and might never be).
		341
		342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		343
		344	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		345	it's really slow, but it still scales very well (O(active_fds)).
		346
		347	Please note that solaris ports can result in a lot of spurious
		348	notifications, so you need to use non-blocking I/O or other means to avoid
		349	blocking when no data (or space) is available.
		350
		351	=item C<EVBACKEND_ALL>
		352
		353	Try all backends (even potentially broken ones that wouldn't be tried
		354	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		356
		357	=back
154		358
155	If one or more of these are ored into the flags value, then only these	359	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	360	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	361	specified, most compiled-in backend will be tried, usually in reverse
		362	order of their flag values :)
158		363
159	=back	364	The most typical usage is like this:
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	Use whatever libev has to offer, but make sure that kqueue is used if
		375	available (warning, breaks stuff, best use only with your own private
		376	event loop and only if you know the OS supports your types of fds):
		377
		378	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		379
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	380	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		381
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	382	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	383	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	384	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).	385	undefined behaviour (or a failed assertion if assertions are enabled).
167		386
		387	Example: Try to create a event loop that uses epoll and nothing else.
		388
		389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		390	if (!epoller)
		391	fatal ("no epoll found here, maybe it hides under your chair");
		392
168	=item ev_default_destroy ()	393	=item ev_default_destroy ()
169		394
170	Destroys the default loop again (frees all memory and kernel state	395	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	396	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cnanot rely on this :).	397	sense, so e.g. C<ev_is_active> might still return true. It is your
		398	responsibility to either stop all watchers cleanly yoursef I<before>
		399	calling this function, or cope with the fact afterwards (which is usually
		400	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		401	for example).
173		402
174	=item ev_loop_destroy (loop)	403	=item ev_loop_destroy (loop)
175		404
176	Like C<ev_default_destroy>, but destroys an event loop created by an	405	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	406	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	410	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	411	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	412	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	413	again makes little sense).
185		414
186	You I<must> call this function after forking if and only if you want to	415	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	416	only if you want to use the event library in both processes. If you just
188	have to call it.	417	fork+exec, you don't have to call it.
189		418
190	The function itself is quite fast and its usually not a problem to call	419	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	420	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>:	421	quite nicely into a call to C<pthread_atfork>:
193		422
194	pthread_atfork (0, 0, ev_default_fork);	423	pthread_atfork (0, 0, ev_default_fork);
		424
		425	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		426	without calling this function, so if you force one of those backends you
		427	do not need to care.
195		428
196	=item ev_loop_fork (loop)	429	=item ev_loop_fork (loop)
197		430
198	Like C<ev_default_fork>, but acts on an event loop created by	431	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	432	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.	433	after fork, and how you do this is entirely your own problem.
201		434
		435	=item unsigned int ev_loop_count (loop)
		436
		437	Returns the count of loop iterations for the loop, which is identical to
		438	the number of times libev did poll for new events. It starts at C<0> and
		439	happily wraps around with enough iterations.
		440
		441	This value can sometimes be useful as a generation counter of sorts (it
		442	"ticks" the number of loop iterations), as it roughly corresponds with
		443	C<ev_prepare> and C<ev_check> calls.
		444
202	=item unsigned int ev_method (loop)	445	=item unsigned int ev_backend (loop)
203		446
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	447	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	448	use.
206		449
207	=item ev_tstamp = ev_now (loop)	450	=item ev_tstamp ev_now (loop)
208		451
209	Returns the current "event loop time", which is the time the event loop	452	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	453	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	454	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	455	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).	456	event occuring (or more correctly, libev finding out about it).
214		457
215	=item ev_loop (loop, int flags)	458	=item ev_loop (loop, int flags)
216		459
217	Finally, this is it, the event handler. This function usually is called	460	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	461	after you initialised all your watchers and you want to start handling
219	events.	462	events.
220		463
221	If the flags argument is specified as 0, it will not return until either	464	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.	465	either no event watchers are active anymore or C<ev_unloop> was called.
		466
		467	Please note that an explicit C<ev_unloop> is usually better than
		468	relying on all watchers to be stopped when deciding when a program has
		469	finished (especially in interactive programs), but having a program that
		470	automatically loops as long as it has to and no longer by virtue of
		471	relying on its watchers stopping correctly is a thing of beauty.
223		472
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	473	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	474	those events and any outstanding ones, but will not block your process in
226	case there are no events.	475	case there are no events and will return after one iteration of the loop.
227		476
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	477	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	478	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives.	479	your process until at least one new event arrives, and will return after
		480	one iteration of the loop. This is useful if you are waiting for some
		481	external event in conjunction with something not expressible using other
		482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		483	usually a better approach for this kind of thing.
231		484
232	This flags value could be used to implement alternative looping	485	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	486
234	more generic mechanism.	487	* If there are no active watchers (reference count is zero), return.
		488	- Queue prepare watchers and then call all outstanding watchers.
		489	- If we have been forked, recreate the kernel state.
		490	- Update the kernel state with all outstanding changes.
		491	- Update the "event loop time".
		492	- Calculate for how long to block.
		493	- Block the process, waiting for any events.
		494	- Queue all outstanding I/O (fd) events.
		495	- Update the "event loop time" and do time jump handling.
		496	- Queue all outstanding timers.
		497	- Queue all outstanding periodics.
		498	- If no events are pending now, queue all idle watchers.
		499	- Queue all check watchers.
		500	- Call all queued watchers in reverse order (i.e. check watchers first).
		501	Signals and child watchers are implemented as I/O watchers, and will
		502	be handled here by queueing them when their watcher gets executed.
		503	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		504	were used, return, otherwise continue with step *.
		505
		506	Example: Queue some jobs and then loop until no events are outsanding
		507	anymore.
		508
		509	... queue jobs here, make sure they register event watchers as long
		510	... as they still have work to do (even an idle watcher will do..)
		511	ev_loop (my_loop, 0);
		512	... jobs done. yeah!
235		513
236	=item ev_unloop (loop, how)	514	=item ev_unloop (loop, how)
237		515
238	Can be used to make a call to C<ev_loop> return early. The C<how> argument	516	Can be used to make a call to C<ev_loop> return early (but only after it
		517	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>	518	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>	519	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
241	calls return.
242		520
243	=item ev_ref (loop)	521	=item ev_ref (loop)
244		522
245	=item ev_unref (loop)	523	=item ev_unref (loop)
246		524
247	Ref/unref can be used to add or remove a refcount on the event loop: Every	525	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	526	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	527	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	528	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	529	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	530	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	531	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	532	no event watchers registered by it are active. It is also an excellent
255	before stop.	533	way to do this for generic recurring timers or from within third-party
		534	libraries. Just remember to I<unref after start> and I<ref before stop>.
		535
		536	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		537	running when nothing else is active.
		538
		539	struct ev_signal exitsig;
		540	ev_signal_init (&exitsig, sig_cb, SIGINT);
		541	ev_signal_start (loop, &exitsig);
		542	evf_unref (loop);
		543
		544	Example: For some weird reason, unregister the above signal handler again.
		545
		546	ev_ref (loop);
		547	ev_signal_stop (loop, &exitsig);
256		548
257	=back	549	=back
		550
258		551
259	=head1 ANATOMY OF A WATCHER	552	=head1 ANATOMY OF A WATCHER
260		553
261	A watcher is a structure that you create and register to record your	554	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	555	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:	556	become readable, you would create an C<ev_io> watcher for that:
264		557
265	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	558	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
266	{	559	{
267	ev_io_stop (w);	560	ev_io_stop (w);
268	ev_unloop (loop, EVUNLOOP_ALL);	561	ev_unloop (loop, EVUNLOOP_ALL);
…		…
295	*) >>), and you can stop watching for events at any time by calling the	588	*) >>), and you can stop watching for events at any time by calling the
296	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	589	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
297		590
298	As long as your watcher is active (has been started but not stopped) you	591	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	592	must not touch the values stored in it. Most specifically you must never
300	reinitialise it or call its set method.	593	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		594
307	Each and every callback receives the event loop pointer as first, the	595	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	596	registered watcher structure as second, and a bitset of received events as
309	third argument.	597	third argument.
310		598
311	The rceeived events usually include a single bit per event type received	599	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	600	(you can receive multiple events at the same time). The possible bit masks
313	are:	601	are:
314		602
315	=over 4	603	=over 4
316		604
317	=item EV_READ	605	=item C<EV_READ>
318		606
319	=item EV_WRITE	607	=item C<EV_WRITE>
320		608
321	The file descriptor in the ev_io watcher has become readable and/or	609	The file descriptor in the C<ev_io> watcher has become readable and/or
322	writable.	610	writable.
323		611
324	=item EV_TIMEOUT	612	=item C<EV_TIMEOUT>
325		613
326	The ev_timer watcher has timed out.	614	The C<ev_timer> watcher has timed out.
327		615
328	=item EV_PERIODIC	616	=item C<EV_PERIODIC>
329		617
330	The ev_periodic watcher has timed out.	618	The C<ev_periodic> watcher has timed out.
331		619
332	=item EV_SIGNAL	620	=item C<EV_SIGNAL>
333		621
334	The signal specified in the ev_signal watcher has been received by a thread.	622	The signal specified in the C<ev_signal> watcher has been received by a thread.
335		623
336	=item EV_CHILD	624	=item C<EV_CHILD>
337		625
338	The pid specified in the ev_child watcher has received a status change.	626	The pid specified in the C<ev_child> watcher has received a status change.
339		627
		628	=item C<EV_STAT>
		629
		630	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		631
340	=item EV_IDLE	632	=item C<EV_IDLE>
341		633
342	The ev_idle watcher has determined that you have nothing better to do.	634	The C<ev_idle> watcher has determined that you have nothing better to do.
343		635
344	=item EV_PREPARE	636	=item C<EV_PREPARE>
345		637
346	=item EV_CHECK	638	=item C<EV_CHECK>
347		639
348	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	640	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	641	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	642	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	643	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	644	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	645	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
354	C<ev_loop> from blocking).	646	C<ev_loop> from blocking).
355		647
		648	=item C<EV_EMBED>
		649
		650	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		651
		652	=item C<EV_FORK>
		653
		654	The event loop has been resumed in the child process after fork (see
		655	C<ev_fork>).
		656
356	=item EV_ERROR	657	=item C<EV_ERROR>
357		658
358	An unspecified error has occured, the watcher has been stopped. This might	659	An unspecified error has occured, the watcher has been stopped. This might
359	happen because the watcher could not be properly started because libev	660	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	661	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	662	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	668	with the error from read() or write(). This will not work in multithreaded
368	programs, though, so beware.	669	programs, though, so beware.
369		670
370	=back	671	=back
371		672
		673	=head2 GENERIC WATCHER FUNCTIONS
		674
		675	In the following description, C<TYPE> stands for the watcher type,
		676	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		677
		678	=over 4
		679
		680	=item C<ev_init> (ev_TYPE *watcher, callback)
		681
		682	This macro initialises the generic portion of a watcher. The contents
		683	of the watcher object can be arbitrary (so C<malloc> will do). Only
		684	the generic parts of the watcher are initialised, you I<need> to call
		685	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		686	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		687	which rolls both calls into one.
		688
		689	You can reinitialise a watcher at any time as long as it has been stopped
		690	(or never started) and there are no pending events outstanding.
		691
		692	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		693	int revents)>.
		694
		695	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		696
		697	This macro initialises the type-specific parts of a watcher. You need to
		698	call C<ev_init> at least once before you call this macro, but you can
		699	call C<ev_TYPE_set> any number of times. You must not, however, call this
		700	macro on a watcher that is active (it can be pending, however, which is a
		701	difference to the C<ev_init> macro).
		702
		703	Although some watcher types do not have type-specific arguments
		704	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		705
		706	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		707
		708	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		709	calls into a single call. This is the most convinient method to initialise
		710	a watcher. The same limitations apply, of course.
		711
		712	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		713
		714	Starts (activates) the given watcher. Only active watchers will receive
		715	events. If the watcher is already active nothing will happen.
		716
		717	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		718
		719	Stops the given watcher again (if active) and clears the pending
		720	status. It is possible that stopped watchers are pending (for example,
		721	non-repeating timers are being stopped when they become pending), but
		722	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		723	you want to free or reuse the memory used by the watcher it is therefore a
		724	good idea to always call its C<ev_TYPE_stop> function.
		725
		726	=item bool ev_is_active (ev_TYPE *watcher)
		727
		728	Returns a true value iff the watcher is active (i.e. it has been started
		729	and not yet been stopped). As long as a watcher is active you must not modify
		730	it.
		731
		732	=item bool ev_is_pending (ev_TYPE *watcher)
		733
		734	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		735	events but its callback has not yet been invoked). As long as a watcher
		736	is pending (but not active) you must not call an init function on it (but
		737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		738	libev (e.g. you cnanot C<free ()> it).
		739
		740	=item callback ev_cb (ev_TYPE *watcher)
		741
		742	Returns the callback currently set on the watcher.
		743
		744	=item ev_cb_set (ev_TYPE *watcher, callback)
		745
		746	Change the callback. You can change the callback at virtually any time
		747	(modulo threads).
		748
		749	=back
		750
		751
372	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
373		753
374	Each watcher has, by default, a member C<void *data> that you can change	754	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	755	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	756	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	757	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	758	member, you can also "subclass" the watcher type and provide your own
379	data:	759	data:
380		760
…		…
393	{	773	{
394	struct my_io *w = (struct my_io *)w_;	774	struct my_io *w = (struct my_io *)w_;
395	...	775	...
396	}	776	}
397		777
398	More interesting and less C-conformant ways of catsing your callback type	778	More interesting and less C-conformant ways of casting your callback type
399	have been omitted....	779	instead have been omitted.
		780
		781	Another common scenario is having some data structure with multiple
		782	watchers:
		783
		784	struct my_biggy
		785	{
		786	int some_data;
		787	ev_timer t1;
		788	ev_timer t2;
		789	}
		790
		791	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		792	you need to use C<offsetof>:
		793
		794	#include <stddef.h>
		795
		796	static void
		797	t1_cb (EV_P_ struct ev_timer *w, int revents)
		798	{
		799	struct my_biggy big = (struct my_biggy *
		800	(((char *)w) - offsetof (struct my_biggy, t1));
		801	}
		802
		803	static void
		804	t2_cb (EV_P_ struct ev_timer *w, int revents)
		805	{
		806	struct my_biggy big = (struct my_biggy *
		807	(((char *)w) - offsetof (struct my_biggy, t2));
		808	}
400		809
401		810
402	=head1 WATCHER TYPES	811	=head1 WATCHER TYPES
403		812
404	This section describes each watcher in detail, but will not repeat	813	This section describes each watcher in detail, but will not repeat
405	information given in the last section.	814	information given in the last section. Any initialisation/set macros,
		815	functions and members specific to the watcher type are explained.
406		816
		817	Members are additionally marked with either I<[read-only]>, meaning that,
		818	while the watcher is active, you can look at the member and expect some
		819	sensible content, but you must not modify it (you can modify it while the
		820	watcher is stopped to your hearts content), or I<[read-write]>, which
		821	means you can expect it to have some sensible content while the watcher
		822	is active, but you can also modify it. Modifying it may not do something
		823	sensible or take immediate effect (or do anything at all), but libev will
		824	not crash or malfunction in any way.
		825
		826
407	=head2 struct ev_io - is my file descriptor readable or writable	827	=head2 C<ev_io> - is this file descriptor readable or writable?
408		828
409	I/O watchers check whether a file descriptor is readable or writable	829	I/O watchers check whether a file descriptor is readable or writable
410	in each iteration of the event loop (This behaviour is called	830	in each iteration of the event loop, or, more precisely, when reading
411	level-triggering because you keep receiving events as long as the	831	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	832	some data. This behaviour is called level-triggering because you keep
413	act on the event and neither want to receive future events).	833	receiving events as long as the condition persists. Remember you can stop
		834	the watcher if you don't want to act on the event and neither want to
		835	receive future events.
414		836
415	In general you can register as many read and/or write event watchers oer	837	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	838	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	839	descriptors to non-blocking mode is also usually a good idea (but not
418	required if you know what you are doing).	840	required if you know what you are doing).
419		841
420	You have to be careful with dup'ed file descriptors, though. Some backends	842	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	843	(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	844	descriptors correctly if you register interest in two or more fds pointing
423	to the same file/socket etc. description.	845	to the same underlying file/socket/etc. description (that is, they share
		846	the same underlying "file open").
424		847
425	If you must do this, then force the use of a known-to-be-good backend	848	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	849	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
427	EVMETHOD_POLL).	850	C<EVBACKEND_POLL>).
		851
		852	Another thing you have to watch out for is that it is quite easy to
		853	receive "spurious" readyness notifications, that is your callback might
		854	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		855	because there is no data. Not only are some backends known to create a
		856	lot of those (for example solaris ports), it is very easy to get into
		857	this situation even with a relatively standard program structure. Thus
		858	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		859	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		860
		861	If you cannot run the fd in non-blocking mode (for example you should not
		862	play around with an Xlib connection), then you have to seperately re-test
		863	wether a file descriptor is really ready with a known-to-be good interface
		864	such as poll (fortunately in our Xlib example, Xlib already does this on
		865	its own, so its quite safe to use).
428		866
429	=over 4	867	=over 4
430		868
431	=item ev_io_init (ev_io *, callback, int fd, int events)	869	=item ev_io_init (ev_io *, callback, int fd, int events)
432		870
433	=item ev_io_set (ev_io *, int fd, int events)	871	=item ev_io_set (ev_io *, int fd, int events)
434		872
435	Configures an ev_io watcher. The fd is the file descriptor to rceeive	873	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 |	874	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
437	EV_WRITE> to receive the given events.	875	C<EV_READ | EV_WRITE> to receive the given events.
		876
		877	=item int fd [read-only]
		878
		879	The file descriptor being watched.
		880
		881	=item int events [read-only]
		882
		883	The events being watched.
438		884
439	=back	885	=back
440		886
		887	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		888	readable, but only once. Since it is likely line-buffered, you could
		889	attempt to read a whole line in the callback.
		890
		891	static void
		892	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		893	{
		894	ev_io_stop (loop, w);
		895	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		896	}
		897
		898	...
		899	struct ev_loop *loop = ev_default_init (0);
		900	struct ev_io stdin_readable;
		901	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		902	ev_io_start (loop, &stdin_readable);
		903	ev_loop (loop, 0);
		904
		905
441	=head2 struct ev_timer - relative and optionally recurring timeouts	906	=head2 C<ev_timer> - relative and optionally repeating timeouts
442		907
443	Timer watchers are simple relative timers that generate an event after a	908	Timer watchers are simple relative timers that generate an event after a
444	given time, and optionally repeating in regular intervals after that.	909	given time, and optionally repeating in regular intervals after that.
445		910
446	The timers are based on real time, that is, if you register an event that	911	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	912	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	913	time, it will still time out after (roughly) and hour. "Roughly" because
449	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	914	detecting time jumps is hard, and some inaccuracies are unavoidable (the
450	monotonic clock option helps a lot here).	915	monotonic clock option helps a lot here).
		916
		917	The relative timeouts are calculated relative to the C<ev_now ()>
		918	time. This is usually the right thing as this timestamp refers to the time
		919	of the event triggering whatever timeout you are modifying/starting. If
		920	you suspect event processing to be delayed and you I<need> to base the timeout
		921	on the current time, use something like this to adjust for this:
		922
		923	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		924
		925	The callback is guarenteed to be invoked only when its timeout has passed,
		926	but if multiple timers become ready during the same loop iteration then
		927	order of execution is undefined.
451		928
452	=over 4	929	=over 4
453		930
454	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	931	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
455		932
…		…
461	later, again, and again, until stopped manually.	938	later, again, and again, until stopped manually.
462		939
463	The timer itself will do a best-effort at avoiding drift, that is, if you	940	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	941	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	942	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	943	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.	944	timer will not fire more than once per event loop iteration.
468		945
469	=item ev_timer_again (loop)	946	=item ev_timer_again (loop)
470		947
471	This will act as if the timer timed out and restart it again if it is	948	This will act as if the timer timed out and restart it again if it is
472	repeating. The exact semantics are:	949	repeating. The exact semantics are:
473		950
		951	If the timer is pending, its pending status is cleared.
		952
474	If the timer is started but nonrepeating, stop it.	953	If the timer is started but nonrepeating, stop it (as if it timed out).
475		954
476	If the timer is repeating, either start it if necessary (with the repeat	955	If the timer is repeating, either start it if necessary (with the
477	value), or reset the running timer to the repeat value.	956	C<repeat> value), or reset the running timer to the C<repeat> value.
478		957
479	This sounds a bit complicated, but here is a useful and typical	958	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	959	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	960	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	961	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	962	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	963	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	964	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.	965	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		966	automatically restart it if need be.
		967
		968	That means you can ignore the C<after> value and C<ev_timer_start>
		969	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		970
		971	ev_timer_init (timer, callback, 0., 5.);
		972	ev_timer_again (loop, timer);
		973	...
		974	timer->again = 17.;
		975	ev_timer_again (loop, timer);
		976	...
		977	timer->again = 10.;
		978	ev_timer_again (loop, timer);
		979
		980	This is more slightly efficient then stopping/starting the timer each time
		981	you want to modify its timeout value.
		982
		983	=item ev_tstamp repeat [read-write]
		984
		985	The current C<repeat> value. Will be used each time the watcher times out
		986	or C<ev_timer_again> is called and determines the next timeout (if any),
		987	which is also when any modifications are taken into account.
487		988
488	=back	989	=back
489		990
		991	Example: Create a timer that fires after 60 seconds.
		992
		993	static void
		994	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		995	{
		996	.. one minute over, w is actually stopped right here
		997	}
		998
		999	struct ev_timer mytimer;
		1000	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1001	ev_timer_start (loop, &mytimer);
		1002
		1003	Example: Create a timeout timer that times out after 10 seconds of
		1004	inactivity.
		1005
		1006	static void
		1007	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1008	{
		1009	.. ten seconds without any activity
		1010	}
		1011
		1012	struct ev_timer mytimer;
		1013	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1014	ev_timer_again (&mytimer); /* start timer */
		1015	ev_loop (loop, 0);
		1016
		1017	// and in some piece of code that gets executed on any "activity":
		1018	// reset the timeout to start ticking again at 10 seconds
		1019	ev_timer_again (&mytimer);
		1020
		1021
490	=head2 ev_periodic - to cron or not to cron it	1022	=head2 C<ev_periodic> - to cron or not to cron?
491		1023
492	Periodic watchers are also timers of a kind, but they are very versatile	1024	Periodic watchers are also timers of a kind, but they are very versatile
493	(and unfortunately a bit complex).	1025	(and unfortunately a bit complex).
494		1026
495	Unlike ev_timer's, they are not based on real time (or relative time)	1027	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	1028	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	1029	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 ()	1030	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	1031	+ 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	1032	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	1033	roughly 10 seconds later and of course not if you reset your system time
502	again).	1034	again).
503		1035
504	They can also be used to implement vastly more complex timers, such as	1036	They can also be used to implement vastly more complex timers, such as
505	triggering an event on eahc midnight, local time.	1037	triggering an event on eahc midnight, local time.
506		1038
		1039	As with timers, the callback is guarenteed to be invoked only when the
		1040	time (C<at>) has been passed, but if multiple periodic timers become ready
		1041	during the same loop iteration then order of execution is undefined.
		1042
507	=over 4	1043	=over 4
508		1044
509	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1045	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
510		1046
511	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1047	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
512		1048
513	Lots of arguments, lets sort it out... There are basically three modes of	1049	Lots of arguments, lets sort it out... There are basically three modes of
514	operation, and we will explain them from simplest to complex:	1050	operation, and we will explain them from simplest to complex:
515
516		1051
517	=over 4	1052	=over 4
518		1053
519	=item * absolute timer (interval = reschedule_cb = 0)	1054	=item * absolute timer (interval = reschedule_cb = 0)
520		1055
…		…
534		1069
535	ev_periodic_set (&periodic, 0., 3600., 0);	1070	ev_periodic_set (&periodic, 0., 3600., 0);
536		1071
537	This doesn't mean there will always be 3600 seconds in between triggers,	1072	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	1073	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	1074	full hour (UTC), or more correctly, when the system time is evenly divisible
540	by 3600.	1075	by 3600.
541		1076
542	Another way to think about it (for the mathematically inclined) is that	1077	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	1078	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.	1079	time where C<time = at (mod interval)>, regardless of any time jumps.
545		1080
546	=item * manual reschedule mode (reschedule_cb = callback)	1081	=item * manual reschedule mode (reschedule_cb = callback)
547		1082
548	In this mode the values for C<interval> and C<at> are both being	1083	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	1084	ignored. Instead, each time the periodic watcher gets scheduled, the
550	reschedule callback will be called with the watcher as first, and the	1085	reschedule callback will be called with the watcher as first, and the
551	current time as second argument.	1086	current time as second argument.
552		1087
553	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1088	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	1089	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.	1090	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1091	starting a prepare watcher).
556		1092
557	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1093	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
558	ev_tstamp now)>, e.g.:	1094	ev_tstamp now)>, e.g.:
559		1095
560	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
561	{	1097	{
562	return now + 60.;	1098	return now + 60.;
…		…
565	It must return the next time to trigger, based on the passed time value	1101	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	1102	(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	1103	will usually be called just before the callback will be triggered, but
568	might be called at other times, too.	1104	might be called at other times, too.
569		1105
		1106	NOTE: I<< This callback must always return a time that is later than the
		1107	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1108
570	This can be used to create very complex timers, such as a timer that	1109	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	1110	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	1111	next midnight after C<now> and return the timestamp value for this. How
573	is, again, up to you (but it is not trivial).	1112	you do this is, again, up to you (but it is not trivial, which is the main
		1113	reason I omitted it as an example).
574		1114
575	=back	1115	=back
576		1116
577	=item ev_periodic_again (loop, ev_periodic *)	1117	=item ev_periodic_again (loop, ev_periodic *)
578		1118
579	Simply stops and restarts the periodic watcher again. This is only useful	1119	Simply stops and restarts the periodic watcher again. This is only useful
580	when you changed some parameters or the reschedule callback would return	1120	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	1121	a different time than the last time it was called (e.g. in a crond like
582	program when the crontabs have changed).	1122	program when the crontabs have changed).
583		1123
		1124	=item ev_tstamp interval [read-write]
		1125
		1126	The current interval value. Can be modified any time, but changes only
		1127	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1128	called.
		1129
		1130	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1131
		1132	The current reschedule callback, or C<0>, if this functionality is
		1133	switched off. Can be changed any time, but changes only take effect when
		1134	the periodic timer fires or C<ev_periodic_again> is being called.
		1135
584	=back	1136	=back
585		1137
		1138	Example: Call a callback every hour, or, more precisely, whenever the
		1139	system clock is divisible by 3600. The callback invocation times have
		1140	potentially a lot of jittering, but good long-term stability.
		1141
		1142	static void
		1143	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1144	{
		1145	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1146	}
		1147
		1148	struct ev_periodic hourly_tick;
		1149	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1150	ev_periodic_start (loop, &hourly_tick);
		1151
		1152	Example: The same as above, but use a reschedule callback to do it:
		1153
		1154	#include <math.h>
		1155
		1156	static ev_tstamp
		1157	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1158	{
		1159	return fmod (now, 3600.) + 3600.;
		1160	}
		1161
		1162	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1163
		1164	Example: Call a callback every hour, starting now:
		1165
		1166	struct ev_periodic hourly_tick;
		1167	ev_periodic_init (&hourly_tick, clock_cb,
		1168	fmod (ev_now (loop), 3600.), 3600., 0);
		1169	ev_periodic_start (loop, &hourly_tick);
		1170
		1171
586	=head2 ev_signal - signal me when a signal gets signalled	1172	=head2 C<ev_signal> - signal me when a signal gets signalled!
587		1173
588	Signal watchers will trigger an event when the process receives a specific	1174	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	1175	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	1176	will try it's best to deliver signals synchronously, i.e. as part of the
591	normal event processing, like any other event.	1177	normal event processing, like any other event.
592		1178
593	You cna configure as many watchers as you like per signal. Only when the	1179	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	1180	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	1181	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	1182	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	1183	watcher for a signal is stopped libev will reset the signal handler to
598	SIG_DFL (regardless of what it was set to before).	1184	SIG_DFL (regardless of what it was set to before).
…		…
604	=item ev_signal_set (ev_signal *, int signum)	1190	=item ev_signal_set (ev_signal *, int signum)
605		1191
606	Configures the watcher to trigger on the given signal number (usually one	1192	Configures the watcher to trigger on the given signal number (usually one
607	of the C<SIGxxx> constants).	1193	of the C<SIGxxx> constants).
608		1194
		1195	=item int signum [read-only]
		1196
		1197	The signal the watcher watches out for.
		1198
609	=back	1199	=back
610		1200
		1201
611	=head2 ev_child - wait for pid status changes	1202	=head2 C<ev_child> - watch out for process status changes
612		1203
613	Child watchers trigger when your process receives a SIGCHLD in response to	1204	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).	1205	some child status changes (most typically when a child of yours dies).
615		1206
616	=over 4	1207	=over 4
…		…
620	=item ev_child_set (ev_child *, int pid)	1211	=item ev_child_set (ev_child *, int pid)
621		1212
622	Configures the watcher to wait for status changes of process C<pid> (or	1213	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	1214	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	1215	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	1216	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.	1217	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1218	process causing the status change.
		1219
		1220	=item int pid [read-only]
		1221
		1222	The process id this watcher watches out for, or C<0>, meaning any process id.
		1223
		1224	=item int rpid [read-write]
		1225
		1226	The process id that detected a status change.
		1227
		1228	=item int rstatus [read-write]
		1229
		1230	The process exit/trace status caused by C<rpid> (see your systems
		1231	C<waitpid> and C<sys/wait.h> documentation for details).
627		1232
628	=back	1233	=back
629		1234
		1235	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1236
		1237	static void
		1238	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1239	{
		1240	ev_unloop (loop, EVUNLOOP_ALL);
		1241	}
		1242
		1243	struct ev_signal signal_watcher;
		1244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1245	ev_signal_start (loop, &sigint_cb);
		1246
		1247
		1248	=head2 C<ev_stat> - did the file attributes just change?
		1249
		1250	This watches a filesystem path for attribute changes. That is, it calls
		1251	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1252	compared to the last time, invoking the callback if it did.
		1253
		1254	The path does not need to exist: changing from "path exists" to "path does
		1255	not exist" is a status change like any other. The condition "path does
		1256	not exist" is signified by the C<st_nlink> field being zero (which is
		1257	otherwise always forced to be at least one) and all the other fields of
		1258	the stat buffer having unspecified contents.
		1259
		1260	The path I<should> be absolute and I<must not> end in a slash. If it is
		1261	relative and your working directory changes, the behaviour is undefined.
		1262
		1263	Since there is no standard to do this, the portable implementation simply
		1264	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1265	can specify a recommended polling interval for this case. If you specify
		1266	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1267	unspecified default> value will be used (which you can expect to be around
		1268	five seconds, although this might change dynamically). Libev will also
		1269	impose a minimum interval which is currently around C<0.1>, but thats
		1270	usually overkill.
		1271
		1272	This watcher type is not meant for massive numbers of stat watchers,
		1273	as even with OS-supported change notifications, this can be
		1274	resource-intensive.
		1275
		1276	At the time of this writing, only the Linux inotify interface is
		1277	implemented (implementing kqueue support is left as an exercise for the
		1278	reader). Inotify will be used to give hints only and should not change the
		1279	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1280	to fall back to regular polling again even with inotify, but changes are
		1281	usually detected immediately, and if the file exists there will be no
		1282	polling.
		1283
		1284	=over 4
		1285
		1286	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1287
		1288	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1289
		1290	Configures the watcher to wait for status changes of the given
		1291	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1292	be detected and should normally be specified as C<0> to let libev choose
		1293	a suitable value. The memory pointed to by C<path> must point to the same
		1294	path for as long as the watcher is active.
		1295
		1296	The callback will be receive C<EV_STAT> when a change was detected,
		1297	relative to the attributes at the time the watcher was started (or the
		1298	last change was detected).
		1299
		1300	=item ev_stat_stat (ev_stat *)
		1301
		1302	Updates the stat buffer immediately with new values. If you change the
		1303	watched path in your callback, you could call this fucntion to avoid
		1304	detecting this change (while introducing a race condition). Can also be
		1305	useful simply to find out the new values.
		1306
		1307	=item ev_statdata attr [read-only]
		1308
		1309	The most-recently detected attributes of the file. Although the type is of
		1310	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1311	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1312	was some error while C<stat>ing the file.
		1313
		1314	=item ev_statdata prev [read-only]
		1315
		1316	The previous attributes of the file. The callback gets invoked whenever
		1317	C<prev> != C<attr>.
		1318
		1319	=item ev_tstamp interval [read-only]
		1320
		1321	The specified interval.
		1322
		1323	=item const char *path [read-only]
		1324
		1325	The filesystem path that is being watched.
		1326
		1327	=back
		1328
		1329	Example: Watch C</etc/passwd> for attribute changes.
		1330
		1331	static void
		1332	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1333	{
		1334	/* /etc/passwd changed in some way */
		1335	if (w->attr.st_nlink)
		1336	{
		1337	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1338	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1339	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1340	}
		1341	else
		1342	/* you shalt not abuse printf for puts */
		1343	puts ("wow, /etc/passwd is not there, expect problems. "
		1344	"if this is windows, they already arrived\n");
		1345	}
		1346
		1347	...
		1348	ev_stat passwd;
		1349
		1350	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1351	ev_stat_start (loop, &passwd);
		1352
		1353
630	=head2 ev_idle - when you've got nothing better to do	1354	=head2 C<ev_idle> - when you've got nothing better to do...
631		1355
632	Idle watchers trigger events when there are no other I/O or timer (or	1356	Idle watchers trigger events when there are no other events are pending
633	periodic) events pending. That is, as long as your process is busy	1357	(prepare, check and other idle watchers do not count). That is, as long
634	handling sockets or timeouts it will not be called. But when your process	1358	as your process is busy handling sockets or timeouts (or even signals,
635	is idle all idle watchers are being called again and again - until	1359	imagine) it will not be triggered. But when your process is idle all idle
		1360	watchers are being called again and again, once per event loop iteration -
636	stopped, that is, or your process receives more events.	1361	until stopped, that is, or your process receives more events and becomes
		1362	busy.
637		1363
638	The most noteworthy effect is that as long as any idle watchers are	1364	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.	1365	active, the process will not block when waiting for new events.
640		1366
641	Apart from keeping your process non-blocking (which is a useful	1367	Apart from keeping your process non-blocking (which is a useful
…		…
651	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1377	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
652	believe me.	1378	believe me.
653		1379
654	=back	1380	=back
655		1381
656	=head2 prepare and check - your hooks into the event loop	1382	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1383	callback, free it. Also, use no error checking, as usual.
657		1384
		1385	static void
		1386	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1387	{
		1388	free (w);
		1389	// now do something you wanted to do when the program has
		1390	// no longer asnything immediate to do.
		1391	}
		1392
		1393	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1394	ev_idle_init (idle_watcher, idle_cb);
		1395	ev_idle_start (loop, idle_cb);
		1396
		1397
		1398	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1399
658	Prepare and check watchers usually (but not always) are used in	1400	Prepare and check watchers are usually (but not always) used in tandem:
659	tandom. Prepare watchers get invoked before the process blocks and check	1401	prepare watchers get invoked before the process blocks and check watchers
660	watchers afterwards.	1402	afterwards.
661		1403
		1404	You I<must not> call C<ev_loop> or similar functions that enter
		1405	the current event loop from either C<ev_prepare> or C<ev_check>
		1406	watchers. Other loops than the current one are fine, however. The
		1407	rationale behind this is that you do not need to check for recursion in
		1408	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1409	C<ev_check> so if you have one watcher of each kind they will always be
		1410	called in pairs bracketing the blocking call.
		1411
662	Their main purpose is to integrate other event mechanisms into libev. This	1412	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	1413	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.	1414	variable changes, implement your own watchers, integrate net-snmp or a
		1415	coroutine library and lots more. They are also occasionally useful if
		1416	you cache some data and want to flush it before blocking (for example,
		1417	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1418	watcher).
665		1419
666	This is done by examining in each prepare call which file descriptors need	1420	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	1421	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	1422	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	1423	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)	1424	any events that occured (by checking the pending status of all watchers
671	and call back into the library.	1425	and stopping them) and call back into the library. The I/O and timer
		1426	callbacks will never actually be called (but must be valid nevertheless,
		1427	because you never know, you know?).
672		1428
673	As another example, the perl Coro module uses these hooks to integrate	1429	As another example, the Perl Coro module uses these hooks to integrate
674	coroutines into libev programs, by yielding to other active coroutines	1430	coroutines into libev programs, by yielding to other active coroutines
675	during each prepare and only letting the process block if no coroutines	1431	during each prepare and only letting the process block if no coroutines
676	are ready to run.	1432	are ready to run (it's actually more complicated: it only runs coroutines
		1433	with priority higher than or equal to the event loop and one coroutine
		1434	of lower priority, but only once, using idle watchers to keep the event
		1435	loop from blocking if lower-priority coroutines are active, thus mapping
		1436	low-priority coroutines to idle/background tasks).
677		1437
678	=over 4	1438	=over 4
679		1439
680	=item ev_prepare_init (ev_prepare *, callback)	1440	=item ev_prepare_init (ev_prepare *, callback)
681		1441
682	=item ev_check_init (ev_check *, callback)	1442	=item ev_check_init (ev_check *, callback)
683		1443
684	Initialises and configures the prepare or check watcher - they have no	1444	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>	1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
686	macros, but using them is utterly, utterly pointless.	1446	macros, but using them is utterly, utterly and completely pointless.
687		1447
688	=back	1448	=back
689		1449
		1450	Example: To include a library such as adns, you would add IO watchers
		1451	and a timeout watcher in a prepare handler, as required by libadns, and
		1452	in a check watcher, destroy them and call into libadns. What follows is
		1453	pseudo-code only of course:
		1454
		1455	static ev_io iow [nfd];
		1456	static ev_timer tw;
		1457
		1458	static void
		1459	io_cb (ev_loop *loop, ev_io *w, int revents)
		1460	{
		1461	// set the relevant poll flags
		1462	// could also call adns_processreadable etc. here
		1463	struct pollfd *fd = (struct pollfd *)w->data;
		1464	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1465	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1466	}
		1467
		1468	// create io watchers for each fd and a timer before blocking
		1469	static void
		1470	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1471	{
		1472	int timeout = 3600000;
		1473	struct pollfd fds [nfd];
		1474	// actual code will need to loop here and realloc etc.
		1475	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1476
		1477	/* the callback is illegal, but won't be called as we stop during check */
		1478	ev_timer_init (&tw, 0, timeout * 1e-3);
		1479	ev_timer_start (loop, &tw);
		1480
		1481	// create on ev_io per pollfd
		1482	for (int i = 0; i < nfd; ++i)
		1483	{
		1484	ev_io_init (iow + i, io_cb, fds [i].fd,
		1485	((fds [i].events & POLLIN ? EV_READ : 0)
		1486	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1487
		1488	fds [i].revents = 0;
		1489	iow [i].data = fds + i;
		1490	ev_io_start (loop, iow + i);
		1491	}
		1492	}
		1493
		1494	// stop all watchers after blocking
		1495	static void
		1496	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1497	{
		1498	ev_timer_stop (loop, &tw);
		1499
		1500	for (int i = 0; i < nfd; ++i)
		1501	ev_io_stop (loop, iow + i);
		1502
		1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1504	}
		1505
		1506
		1507	=head2 C<ev_embed> - when one backend isn't enough...
		1508
		1509	This is a rather advanced watcher type that lets you embed one event loop
		1510	into another (currently only C<ev_io> events are supported in the embedded
		1511	loop, other types of watchers might be handled in a delayed or incorrect
		1512	fashion and must not be used).
		1513
		1514	There are primarily two reasons you would want that: work around bugs and
		1515	prioritise I/O.
		1516
		1517	As an example for a bug workaround, the kqueue backend might only support
		1518	sockets on some platform, so it is unusable as generic backend, but you
		1519	still want to make use of it because you have many sockets and it scales
		1520	so nicely. In this case, you would create a kqueue-based loop and embed it
		1521	into your default loop (which might use e.g. poll). Overall operation will
		1522	be a bit slower because first libev has to poll and then call kevent, but
		1523	at least you can use both at what they are best.
		1524
		1525	As for prioritising I/O: rarely you have the case where some fds have
		1526	to be watched and handled very quickly (with low latency), and even
		1527	priorities and idle watchers might have too much overhead. In this case
		1528	you would put all the high priority stuff in one loop and all the rest in
		1529	a second one, and embed the second one in the first.
		1530
		1531	As long as the watcher is active, the callback will be invoked every time
		1532	there might be events pending in the embedded loop. The callback must then
		1533	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1534	their callbacks (you could also start an idle watcher to give the embedded
		1535	loop strictly lower priority for example). You can also set the callback
		1536	to C<0>, in which case the embed watcher will automatically execute the
		1537	embedded loop sweep.
		1538
		1539	As long as the watcher is started it will automatically handle events. The
		1540	callback will be invoked whenever some events have been handled. You can
		1541	set the callback to C<0> to avoid having to specify one if you are not
		1542	interested in that.
		1543
		1544	Also, there have not currently been made special provisions for forking:
		1545	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1546	but you will also have to stop and restart any C<ev_embed> watchers
		1547	yourself.
		1548
		1549	Unfortunately, not all backends are embeddable, only the ones returned by
		1550	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1551	portable one.
		1552
		1553	So when you want to use this feature you will always have to be prepared
		1554	that you cannot get an embeddable loop. The recommended way to get around
		1555	this is to have a separate variables for your embeddable loop, try to
		1556	create it, and if that fails, use the normal loop for everything:
		1557
		1558	struct ev_loop *loop_hi = ev_default_init (0);
		1559	struct ev_loop *loop_lo = 0;
		1560	struct ev_embed embed;
		1561
		1562	// see if there is a chance of getting one that works
		1563	// (remember that a flags value of 0 means autodetection)
		1564	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1565	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1566	: 0;
		1567
		1568	// if we got one, then embed it, otherwise default to loop_hi
		1569	if (loop_lo)
		1570	{
		1571	ev_embed_init (&embed, 0, loop_lo);
		1572	ev_embed_start (loop_hi, &embed);
		1573	}
		1574	else
		1575	loop_lo = loop_hi;
		1576
		1577	=over 4
		1578
		1579	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1580
		1581	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1582
		1583	Configures the watcher to embed the given loop, which must be
		1584	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1585	invoked automatically, otherwise it is the responsibility of the callback
		1586	to invoke it (it will continue to be called until the sweep has been done,
		1587	if you do not want thta, you need to temporarily stop the embed watcher).
		1588
		1589	=item ev_embed_sweep (loop, ev_embed *)
		1590
		1591	Make a single, non-blocking sweep over the embedded loop. This works
		1592	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1593	apropriate way for embedded loops.
		1594
		1595	=item struct ev_loop *loop [read-only]
		1596
		1597	The embedded event loop.
		1598
		1599	=back
		1600
		1601
		1602	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1603
		1604	Fork watchers are called when a C<fork ()> was detected (usually because
		1605	whoever is a good citizen cared to tell libev about it by calling
		1606	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1607	event loop blocks next and before C<ev_check> watchers are being called,
		1608	and only in the child after the fork. If whoever good citizen calling
		1609	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1610	handlers will be invoked, too, of course.
		1611
		1612	=over 4
		1613
		1614	=item ev_fork_init (ev_signal *, callback)
		1615
		1616	Initialises and configures the fork watcher - it has no parameters of any
		1617	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1618	believe me.
		1619
		1620	=back
		1621
		1622
690	=head1 OTHER FUNCTIONS	1623	=head1 OTHER FUNCTIONS
691		1624
692	There are some other fucntions of possible interest. Described. Here. Now.	1625	There are some other functions of possible interest. Described. Here. Now.
693		1626
694	=over 4	1627	=over 4
695		1628
696	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1629	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
697		1630
698	This function combines a simple timer and an I/O watcher, calls your	1631	This function combines a simple timer and an I/O watcher, calls your
699	callback on whichever event happens first and automatically stop both	1632	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	1633	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	1634	or timeout without having to allocate/configure/start/stop/free one or
702	more watchers yourself.	1635	more watchers yourself.
703		1636
704	If C<fd> is less than 0, then no I/O watcher will be started and events is	1637	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	1638	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
706	will be craeted and started.	1639	C<events> set will be craeted and started.
707		1640
708	If C<timeout> is less than 0, then no timeout watcher will be	1641	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	1642	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
710	= 0) will be started.	1643	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1644	dubious value.
711		1645
712	The callback has the type C<void (*cb)(int revents, void *arg)> and	1646	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,	1647	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>:	1648	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1649	value passed to C<ev_once>:
715		1650
716	static void stdin_ready (int revents, void *arg)	1651	static void stdin_ready (int revents, void *arg)
717	{	1652	{
718	if (revents & EV_TIMEOUT)	1653	if (revents & EV_TIMEOUT)
719	/* doh, nothing entered */	1654	/* doh, nothing entered */;
720	else if (revents & EV_READ)	1655	else if (revents & EV_READ)
721	/* stdin might have data for us, joy! */	1656	/* stdin might have data for us, joy! */;
722	}	1657	}
723		1658
724	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1659	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
725		1660
726	=item ev_feed_event (loop, watcher, int events)	1661	=item ev_feed_event (ev_loop *, watcher *, int revents)
727		1662
728	Feeds the given event set into the event loop, as if the specified event	1663	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	1664	had happened for the specified watcher (which must be a pointer to an
730	initialised but not necessarily active event watcher).	1665	initialised but not necessarily started event watcher).
731		1666
732	=item ev_feed_fd_event (loop, int fd, int revents)	1667	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
733		1668
734	Feed an event on the given fd, as if a file descriptor backend detected it.	1669	Feed an event on the given fd, as if a file descriptor backend detected
		1670	the given events it.
735		1671
736	=item ev_feed_signal_event (loop, int signum)	1672	=item ev_feed_signal_event (ev_loop *loop, int signum)
737		1673
738	Feed an event as if the given signal occured (loop must be the default loop!).	1674	Feed an event as if the given signal occured (C<loop> must be the default
		1675	loop!).
739		1676
740	=back	1677	=back
741		1678
		1679
		1680	=head1 LIBEVENT EMULATION
		1681
		1682	Libev offers a compatibility emulation layer for libevent. It cannot
		1683	emulate the internals of libevent, so here are some usage hints:
		1684
		1685	=over 4
		1686
		1687	=item * Use it by including <event.h>, as usual.
		1688
		1689	=item * The following members are fully supported: ev_base, ev_callback,
		1690	ev_arg, ev_fd, ev_res, ev_events.
		1691
		1692	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1693	maintained by libev, it does not work exactly the same way as in libevent (consider
		1694	it a private API).
		1695
		1696	=item * Priorities are not currently supported. Initialising priorities
		1697	will fail and all watchers will have the same priority, even though there
		1698	is an ev_pri field.
		1699
		1700	=item * Other members are not supported.
		1701
		1702	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1703	to use the libev header file and library.
		1704
		1705	=back
		1706
		1707	=head1 C++ SUPPORT
		1708
		1709	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1710	you to use some convinience methods to start/stop watchers and also change
		1711	the callback model to a model using method callbacks on objects.
		1712
		1713	To use it,
		1714
		1715	#include <ev++.h>
		1716
		1717	(it is not installed by default). This automatically includes F<ev.h>
		1718	and puts all of its definitions (many of them macros) into the global
		1719	namespace. All C++ specific things are put into the C<ev> namespace.
		1720
		1721	It should support all the same embedding options as F<ev.h>, most notably
		1722	C<EV_MULTIPLICITY>.
		1723
		1724	Here is a list of things available in the C<ev> namespace:
		1725
		1726	=over 4
		1727
		1728	=item C<ev::READ>, C<ev::WRITE> etc.
		1729
		1730	These are just enum values with the same values as the C<EV_READ> etc.
		1731	macros from F<ev.h>.
		1732
		1733	=item C<ev::tstamp>, C<ev::now>
		1734
		1735	Aliases to the same types/functions as with the C<ev_> prefix.
		1736
		1737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1738
		1739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1740	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1741	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1742	defines by many implementations.
		1743
		1744	All of those classes have these methods:
		1745
		1746	=over 4
		1747
		1748	=item ev::TYPE::TYPE (object *, object::method *)
		1749
		1750	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1751
		1752	=item ev::TYPE::~TYPE
		1753
		1754	The constructor takes a pointer to an object and a method pointer to
		1755	the event handler callback to call in this class. The constructor calls
		1756	C<ev_init> for you, which means you have to call the C<set> method
		1757	before starting it. If you do not specify a loop then the constructor
		1758	automatically associates the default loop with this watcher.
		1759
		1760	The destructor automatically stops the watcher if it is active.
		1761
		1762	=item w->set (struct ev_loop *)
		1763
		1764	Associates a different C<struct ev_loop> with this watcher. You can only
		1765	do this when the watcher is inactive (and not pending either).
		1766
		1767	=item w->set ([args])
		1768
		1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1770	called at least once. Unlike the C counterpart, an active watcher gets
		1771	automatically stopped and restarted.
		1772
		1773	=item w->start ()
		1774
		1775	Starts the watcher. Note that there is no C<loop> argument as the
		1776	constructor already takes the loop.
		1777
		1778	=item w->stop ()
		1779
		1780	Stops the watcher if it is active. Again, no C<loop> argument.
		1781
		1782	=item w->again () C<ev::timer>, C<ev::periodic> only
		1783
		1784	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1785	C<ev_TYPE_again> function.
		1786
		1787	=item w->sweep () C<ev::embed> only
		1788
		1789	Invokes C<ev_embed_sweep>.
		1790
		1791	=item w->update () C<ev::stat> only
		1792
		1793	Invokes C<ev_stat_stat>.
		1794
		1795	=back
		1796
		1797	=back
		1798
		1799	Example: Define a class with an IO and idle watcher, start one of them in
		1800	the constructor.
		1801
		1802	class myclass
		1803	{
		1804	ev_io io; void io_cb (ev::io &w, int revents);
		1805	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1806
		1807	myclass ();
		1808	}
		1809
		1810	myclass::myclass (int fd)
		1811	: io (this, &myclass::io_cb),
		1812	idle (this, &myclass::idle_cb)
		1813	{
		1814	io.start (fd, ev::READ);
		1815	}
		1816
		1817
		1818	=head1 MACRO MAGIC
		1819
		1820	Libev can be compiled with a variety of options, the most fundemantal is
		1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1822	callbacks have an initial C<struct ev_loop *> argument.
		1823
		1824	To make it easier to write programs that cope with either variant, the
		1825	following macros are defined:
		1826
		1827	=over 4
		1828
		1829	=item C<EV_A>, C<EV_A_>
		1830
		1831	This provides the loop I<argument> for functions, if one is required ("ev
		1832	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1833	C<EV_A_> is used when other arguments are following. Example:
		1834
		1835	ev_unref (EV_A);
		1836	ev_timer_add (EV_A_ watcher);
		1837	ev_loop (EV_A_ 0);
		1838
		1839	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1840	which is often provided by the following macro.
		1841
		1842	=item C<EV_P>, C<EV_P_>
		1843
		1844	This provides the loop I<parameter> for functions, if one is required ("ev
		1845	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1846	C<EV_P_> is used when other parameters are following. Example:
		1847
		1848	// this is how ev_unref is being declared
		1849	static void ev_unref (EV_P);
		1850
		1851	// this is how you can declare your typical callback
		1852	static void cb (EV_P_ ev_timer *w, int revents)
		1853
		1854	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1855	suitable for use with C<EV_A>.
		1856
		1857	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1858
		1859	Similar to the other two macros, this gives you the value of the default
		1860	loop, if multiple loops are supported ("ev loop default").
		1861
		1862	=back
		1863
		1864	Example: Declare and initialise a check watcher, utilising the above
		1865	macros so it will work regardless of wether multiple loops are supported
		1866	or not.
		1867
		1868	static void
		1869	check_cb (EV_P_ ev_timer *w, int revents)
		1870	{
		1871	ev_check_stop (EV_A_ w);
		1872	}
		1873
		1874	ev_check check;
		1875	ev_check_init (&check, check_cb);
		1876	ev_check_start (EV_DEFAULT_ &check);
		1877	ev_loop (EV_DEFAULT_ 0);
		1878
		1879	=head1 EMBEDDING
		1880
		1881	Libev can (and often is) directly embedded into host
		1882	applications. Examples of applications that embed it include the Deliantra
		1883	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1884	and rxvt-unicode.
		1885
		1886	The goal is to enable you to just copy the neecssary files into your
		1887	source directory without having to change even a single line in them, so
		1888	you can easily upgrade by simply copying (or having a checked-out copy of
		1889	libev somewhere in your source tree).
		1890
		1891	=head2 FILESETS
		1892
		1893	Depending on what features you need you need to include one or more sets of files
		1894	in your app.
		1895
		1896	=head3 CORE EVENT LOOP
		1897
		1898	To include only the libev core (all the C<ev_*> functions), with manual
		1899	configuration (no autoconf):
		1900
		1901	#define EV_STANDALONE 1
		1902	#include "ev.c"
		1903
		1904	This will automatically include F<ev.h>, too, and should be done in a
		1905	single C source file only to provide the function implementations. To use
		1906	it, do the same for F<ev.h> in all files wishing to use this API (best
		1907	done by writing a wrapper around F<ev.h> that you can include instead and
		1908	where you can put other configuration options):
		1909
		1910	#define EV_STANDALONE 1
		1911	#include "ev.h"
		1912
		1913	Both header files and implementation files can be compiled with a C++
		1914	compiler (at least, thats a stated goal, and breakage will be treated
		1915	as a bug).
		1916
		1917	You need the following files in your source tree, or in a directory
		1918	in your include path (e.g. in libev/ when using -Ilibev):
		1919
		1920	ev.h
		1921	ev.c
		1922	ev_vars.h
		1923	ev_wrap.h
		1924
		1925	ev_win32.c required on win32 platforms only
		1926
		1927	ev_select.c only when select backend is enabled (which is enabled by default)
		1928	ev_poll.c only when poll backend is enabled (disabled by default)
		1929	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1930	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1931	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1932
		1933	F<ev.c> includes the backend files directly when enabled, so you only need
		1934	to compile this single file.
		1935
		1936	=head3 LIBEVENT COMPATIBILITY API
		1937
		1938	To include the libevent compatibility API, also include:
		1939
		1940	#include "event.c"
		1941
		1942	in the file including F<ev.c>, and:
		1943
		1944	#include "event.h"
		1945
		1946	in the files that want to use the libevent API. This also includes F<ev.h>.
		1947
		1948	You need the following additional files for this:
		1949
		1950	event.h
		1951	event.c
		1952
		1953	=head3 AUTOCONF SUPPORT
		1954
		1955	Instead of using C<EV_STANDALONE=1> and providing your config in
		1956	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1957	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1958	include F<config.h> and configure itself accordingly.
		1959
		1960	For this of course you need the m4 file:
		1961
		1962	libev.m4
		1963
		1964	=head2 PREPROCESSOR SYMBOLS/MACROS
		1965
		1966	Libev can be configured via a variety of preprocessor symbols you have to define
		1967	before including any of its files. The default is not to build for multiplicity
		1968	and only include the select backend.
		1969
		1970	=over 4
		1971
		1972	=item EV_STANDALONE
		1973
		1974	Must always be C<1> if you do not use autoconf configuration, which
		1975	keeps libev from including F<config.h>, and it also defines dummy
		1976	implementations for some libevent functions (such as logging, which is not
		1977	supported). It will also not define any of the structs usually found in
		1978	F<event.h> that are not directly supported by the libev core alone.
		1979
		1980	=item EV_USE_MONOTONIC
		1981
		1982	If defined to be C<1>, libev will try to detect the availability of the
		1983	monotonic clock option at both compiletime and runtime. Otherwise no use
		1984	of the monotonic clock option will be attempted. If you enable this, you
		1985	usually have to link against librt or something similar. Enabling it when
		1986	the functionality isn't available is safe, though, althoguh you have
		1987	to make sure you link against any libraries where the C<clock_gettime>
		1988	function is hiding in (often F<-lrt>).
		1989
		1990	=item EV_USE_REALTIME
		1991
		1992	If defined to be C<1>, libev will try to detect the availability of the
		1993	realtime clock option at compiletime (and assume its availability at
		1994	runtime if successful). Otherwise no use of the realtime clock option will
		1995	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1996	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1997	in the description of C<EV_USE_MONOTONIC>, though.
		1998
		1999	=item EV_USE_SELECT
		2000
		2001	If undefined or defined to be C<1>, libev will compile in support for the
		2002	C<select>(2) backend. No attempt at autodetection will be done: if no
		2003	other method takes over, select will be it. Otherwise the select backend
		2004	will not be compiled in.
		2005
		2006	=item EV_SELECT_USE_FD_SET
		2007
		2008	If defined to C<1>, then the select backend will use the system C<fd_set>
		2009	structure. This is useful if libev doesn't compile due to a missing
		2010	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2011	exotic systems. This usually limits the range of file descriptors to some
		2012	low limit such as 1024 or might have other limitations (winsocket only
		2013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2014	influence the size of the C<fd_set> used.
		2015
		2016	=item EV_SELECT_IS_WINSOCKET
		2017
		2018	When defined to C<1>, the select backend will assume that
		2019	select/socket/connect etc. don't understand file descriptors but
		2020	wants osf handles on win32 (this is the case when the select to
		2021	be used is the winsock select). This means that it will call
		2022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2023	it is assumed that all these functions actually work on fds, even
		2024	on win32. Should not be defined on non-win32 platforms.
		2025
		2026	=item EV_USE_POLL
		2027
		2028	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2029	backend. Otherwise it will be enabled on non-win32 platforms. It
		2030	takes precedence over select.
		2031
		2032	=item EV_USE_EPOLL
		2033
		2034	If defined to be C<1>, libev will compile in support for the Linux
		2035	C<epoll>(7) backend. Its availability will be detected at runtime,
		2036	otherwise another method will be used as fallback. This is the
		2037	preferred backend for GNU/Linux systems.
		2038
		2039	=item EV_USE_KQUEUE
		2040
		2041	If defined to be C<1>, libev will compile in support for the BSD style
		2042	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2043	otherwise another method will be used as fallback. This is the preferred
		2044	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2045	supports some types of fds correctly (the only platform we found that
		2046	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2047	not be used unless explicitly requested. The best way to use it is to find
		2048	out whether kqueue supports your type of fd properly and use an embedded
		2049	kqueue loop.
		2050
		2051	=item EV_USE_PORT
		2052
		2053	If defined to be C<1>, libev will compile in support for the Solaris
		2054	10 port style backend. Its availability will be detected at runtime,
		2055	otherwise another method will be used as fallback. This is the preferred
		2056	backend for Solaris 10 systems.
		2057
		2058	=item EV_USE_DEVPOLL
		2059
		2060	reserved for future expansion, works like the USE symbols above.
		2061
		2062	=item EV_USE_INOTIFY
		2063
		2064	If defined to be C<1>, libev will compile in support for the Linux inotify
		2065	interface to speed up C<ev_stat> watchers. Its actual availability will
		2066	be detected at runtime.
		2067
		2068	=item EV_H
		2069
		2070	The name of the F<ev.h> header file used to include it. The default if
		2071	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2072	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2073
		2074	=item EV_CONFIG_H
		2075
		2076	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2077	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2078	C<EV_H>, above.
		2079
		2080	=item EV_EVENT_H
		2081
		2082	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2083	of how the F<event.h> header can be found.
		2084
		2085	=item EV_PROTOTYPES
		2086
		2087	If defined to be C<0>, then F<ev.h> will not define any function
		2088	prototypes, but still define all the structs and other symbols. This is
		2089	occasionally useful if you want to provide your own wrapper functions
		2090	around libev functions.
		2091
		2092	=item EV_MULTIPLICITY
		2093
		2094	If undefined or defined to C<1>, then all event-loop-specific functions
		2095	will have the C<struct ev_loop *> as first argument, and you can create
		2096	additional independent event loops. Otherwise there will be no support
		2097	for multiple event loops and there is no first event loop pointer
		2098	argument. Instead, all functions act on the single default loop.
		2099
		2100	=item EV_PERIODIC_ENABLE
		2101
		2102	If undefined or defined to be C<1>, then periodic timers are supported. If
		2103	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2104	code.
		2105
		2106	=item EV_EMBED_ENABLE
		2107
		2108	If undefined or defined to be C<1>, then embed watchers are supported. If
		2109	defined to be C<0>, then they are not.
		2110
		2111	=item EV_STAT_ENABLE
		2112
		2113	If undefined or defined to be C<1>, then stat watchers are supported. If
		2114	defined to be C<0>, then they are not.
		2115
		2116	=item EV_FORK_ENABLE
		2117
		2118	If undefined or defined to be C<1>, then fork watchers are supported. If
		2119	defined to be C<0>, then they are not.
		2120
		2121	=item EV_MINIMAL
		2122
		2123	If you need to shave off some kilobytes of code at the expense of some
		2124	speed, define this symbol to C<1>. Currently only used for gcc to override
		2125	some inlining decisions, saves roughly 30% codesize of amd64.
		2126
		2127	=item EV_PID_HASHSIZE
		2128
		2129	C<ev_child> watchers use a small hash table to distribute workload by
		2130	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2131	than enough. If you need to manage thousands of children you might want to
		2132	increase this value (I<must> be a power of two).
		2133
		2134	=item EV_INOTIFY_HASHSIZE
		2135
		2136	C<ev_staz> watchers use a small hash table to distribute workload by
		2137	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2138	usually more than enough. If you need to manage thousands of C<ev_stat>
		2139	watchers you might want to increase this value (I<must> be a power of
		2140	two).
		2141
		2142	=item EV_COMMON
		2143
		2144	By default, all watchers have a C<void *data> member. By redefining
		2145	this macro to a something else you can include more and other types of
		2146	members. You have to define it each time you include one of the files,
		2147	though, and it must be identical each time.
		2148
		2149	For example, the perl EV module uses something like this:
		2150
		2151	#define EV_COMMON \
		2152	SV *self; /* contains this struct */ \
		2153	SV *cb_sv, *fh /* note no trailing ";" */
		2154
		2155	=item EV_CB_DECLARE (type)
		2156
		2157	=item EV_CB_INVOKE (watcher, revents)
		2158
		2159	=item ev_set_cb (ev, cb)
		2160
		2161	Can be used to change the callback member declaration in each watcher,
		2162	and the way callbacks are invoked and set. Must expand to a struct member
		2163	definition and a statement, respectively. See the F<ev.v> header file for
		2164	their default definitions. One possible use for overriding these is to
		2165	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2166	method calls instead of plain function calls in C++.
		2167
		2168	=head2 EXAMPLES
		2169
		2170	For a real-world example of a program the includes libev
		2171	verbatim, you can have a look at the EV perl module
		2172	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2173	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2174	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2175	will be compiled. It is pretty complex because it provides its own header
		2176	file.
		2177
		2178	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2179	that everybody includes and which overrides some configure choices:
		2180
		2181	#define EV_MINIMAL 1
		2182	#define EV_USE_POLL 0
		2183	#define EV_MULTIPLICITY 0
		2184	#define EV_PERIODIC_ENABLE 0
		2185	#define EV_STAT_ENABLE 0
		2186	#define EV_FORK_ENABLE 0
		2187	#define EV_CONFIG_H <config.h>
		2188	#define EV_MINPRI 0
		2189	#define EV_MAXPRI 0
		2190
		2191	#include "ev++.h"
		2192
		2193	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2194
		2195	#include "ev_cpp.h"
		2196	#include "ev.c"
		2197
		2198
		2199	=head1 COMPLEXITIES
		2200
		2201	In this section the complexities of (many of) the algorithms used inside
		2202	libev will be explained. For complexity discussions about backends see the
		2203	documentation for C<ev_default_init>.
		2204
		2205	=over 4
		2206
		2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2208
		2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2210
		2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2212
		2213	=item Stopping check/prepare/idle watchers: O(1)
		2214
		2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2216
		2217	=item Finding the next timer per loop iteration: O(1)
		2218
		2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2220
		2221	=item Activating one watcher: O(1)
		2222
		2223	=back
		2224
		2225
742	=head1 AUTHOR	2226	=head1 AUTHOR
743		2227
744	Marc Lehmann <libev@schmorp.de>.	2228	Marc Lehmann <libev@schmorp.de>.
745		2229

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