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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as such.
51		104
52	=head1 GLOBAL FUNCTIONS	105	=head1 GLOBAL FUNCTIONS
53		106
54	These functions can be called anytime, even before initialising the	107	These functions can be called anytime, even before initialising the
55	library in any way.	108	library in any way.
…		…
75	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	131	not a problem.
79		132
		133	Example: Make sure we haven't accidentally been linked against the wrong
		134	version.
		135
		136	assert (("libev version mismatch",
		137	ev_version_major () == EV_VERSION_MAJOR
		138	&& ev_version_minor () >= EV_VERSION_MINOR));
		139
		140	=item unsigned int ev_supported_backends ()
		141
		142	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		143	value) compiled into this binary of libev (independent of their
		144	availability on the system you are running on). See C<ev_default_loop> for
		145	a description of the set values.
		146
		147	Example: make sure we have the epoll method, because yeah this is cool and
		148	a must have and can we have a torrent of it please!!!11
		149
		150	assert (("sorry, no epoll, no sex",
		151	ev_supported_backends () & EVBACKEND_EPOLL));
		152
		153	=item unsigned int ev_recommended_backends ()
		154
		155	Return the set of all backends compiled into this binary of libev and also
		156	recommended for this platform. This set is often smaller than the one
		157	returned by C<ev_supported_backends>, as for example kqueue is broken on
		158	most BSDs and will not be autodetected unless you explicitly request it
		159	(assuming you know what you are doing). This is the set of backends that
		160	libev will probe for if you specify no backends explicitly.
		161
		162	=item unsigned int ev_embeddable_backends ()
		163
		164	Returns the set of backends that are embeddable in other event loops. This
		165	is the theoretical, all-platform, value. To find which backends
		166	might be supported on the current system, you would need to look at
		167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		168	recommended ones.
		169
		170	See the description of C<ev_embed> watchers for more info.
		171
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		173
82	Sets the allocation function to use (the prototype is similar to the	174	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	175	semantics is identical - to the realloc C function). It is used to
84	and free memory (no surprises here). If it returns zero when memory	176	allocate and free memory (no surprises here). If it returns zero when
85	needs to be allocated, the library might abort or take some potentially	177	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
87		180
88	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
89	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
90	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
		184
		185	Example: Replace the libev allocator with one that waits a bit and then
		186	retries).
		187
		188	static void *
		189	persistent_realloc (void *ptr, size_t size)
		190	{
		191	for (;;)
		192	{
		193	void *newptr = realloc (ptr, size);
		194
		195	if (newptr)
		196	return newptr;
		197
		198	sleep (60);
		199	}
		200	}
		201
		202	...
		203	ev_set_allocator (persistent_realloc);
91		204
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	205	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		206
94	Set the callback function to call on a retryable syscall error (such	207	Set the callback function to call on a retryable syscall error (such
95	as failed select, poll, epoll_wait). The message is a printable string	208	as failed select, poll, epoll_wait). The message is a printable string
…		…
97	callback is set, then libev will expect it to remedy the sitution, no	210	callback is set, then libev will expect it to remedy the sitution, no
98	matter what, when it returns. That is, libev will generally retry the	211	matter what, when it returns. That is, libev will generally retry the
99	requested operation, or, if the condition doesn't go away, do bad stuff	212	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	213	(such as abort).
101		214
		215	Example: This is basically the same thing that libev does internally, too.
		216
		217	static void
		218	fatal_error (const char *msg)
		219	{
		220	perror (msg);
		221	abort ();
		222	}
		223
		224	...
		225	ev_set_syserr_cb (fatal_error);
		226
102	=back	227	=back
103		228
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	229	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		230
106	An event loop is described by a C<struct ev_loop *>. The library knows two	231	An event loop is described by a C<struct ev_loop *>. The library knows two
…		…
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	244	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		245
121	This will initialise the default event loop if it hasn't been initialised	246	This will initialise the default event loop if it hasn't been initialised
122	yet and return it. If the default loop could not be initialised, returns	247	yet and return it. If the default loop could not be initialised, returns
123	false. If it already was initialised it simply returns it (and ignores the	248	false. If it already was initialised it simply returns it (and ignores the
124	flags).	249	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		250
126	If you don't know what event loop to use, use the one returned from this	251	If you don't know what event loop to use, use the one returned from this
127	function.	252	function.
128		253
129	The flags argument can be used to specify special behaviour or specific	254	The flags argument can be used to specify special behaviour or specific
130	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		256
132	It supports the following flags:	257	The following flags are supported:
133		258
134	=over 4	259	=over 4
135		260
136	=item C<EVFLAG_AUTO>	261	=item C<EVFLAG_AUTO>
137		262
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
147	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
148	around bugs.	273	around bugs.
149		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
150	=item C<EVMETHOD_SELECT> (portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		296
		297	This is your standard select(2) backend. Not I<completely> standard, as
		298	libev tries to roll its own fd_set with no limits on the number of fds,
		299	but if that fails, expect a fairly low limit on the number of fds when
		300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		301	the fastest backend for a low number of fds.
		302
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		304
154	=item C<EVMETHOD_EPOLL> (linux only)	305	And this is your standard poll(2) backend. It's more complicated than
		306	select, but handles sparse fds better and has no artificial limit on the
		307	number of fds you can use (except it will slow down considerably with a
		308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
155		309
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	310	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		311
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	312	For few fds, this backend is a bit little slower than poll and select,
		313	but it scales phenomenally better. While poll and select usually scale like
		314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		315	either O(1) or O(active_fds).
159		316
160	=item C<EVMETHOD_PORT> (solaris 10 only)	317	While stopping and starting an I/O watcher in the same iteration will
		318	result in some caching, there is still a syscall per such incident
		319	(because the fd could point to a different file description now), so its
		320	best to avoid that. Also, dup()ed file descriptors might not work very
		321	well if you register events for both fds.
		322
		323	Please note that epoll sometimes generates spurious notifications, so you
		324	need to use non-blocking I/O or other means to avoid blocking when no data
		325	(or space) is available.
		326
		327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		328
		329	Kqueue deserves special mention, as at the time of this writing, it
		330	was broken on all BSDs except NetBSD (usually it doesn't work with
		331	anything but sockets and pipes, except on Darwin, where of course its
		332	completely useless). For this reason its not being "autodetected"
		333	unless you explicitly specify it explicitly in the flags (i.e. using
		334	C<EVBACKEND_KQUEUE>).
		335
		336	It scales in the same way as the epoll backend, but the interface to the
		337	kernel is more efficient (which says nothing about its actual speed, of
		338	course). While starting and stopping an I/O watcher does not cause an
		339	extra syscall as with epoll, it still adds up to four event changes per
		340	incident, so its best to avoid that.
		341
		342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		343
		344	This is not implemented yet (and might never be).
		345
		346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		347
		348	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		349	it's really slow, but it still scales very well (O(active_fds)).
		350
		351	Please note that solaris ports can result in a lot of spurious
		352	notifications, so you need to use non-blocking I/O or other means to avoid
		353	blocking when no data (or space) is available.
		354
		355	=item C<EVBACKEND_ALL>
		356
		357	Try all backends (even potentially broken ones that wouldn't be tried
		358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		360
		361	=back
161		362
162	If one or more of these are ored into the flags value, then only these	363	If one or more of these are ored into the flags value, then only these
163	backends will be tried (in the reverse order as given here). If one are	364	backends will be tried (in the reverse order as given here). If none are
164	specified, any backend will do.	365	specified, most compiled-in backend will be tried, usually in reverse
		366	order of their flag values :)
165		367
166	=back	368	The most typical usage is like this:
		369
		370	if (!ev_default_loop (0))
		371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		372
		373	Restrict libev to the select and poll backends, and do not allow
		374	environment settings to be taken into account:
		375
		376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		377
		378	Use whatever libev has to offer, but make sure that kqueue is used if
		379	available (warning, breaks stuff, best use only with your own private
		380	event loop and only if you know the OS supports your types of fds):
		381
		382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
167		383
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	384	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		385
170	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	Similar to C<ev_default_loop>, but always creates a new event loop that is
171	always distinct from the default loop. Unlike the default loop, it cannot	387	always distinct from the default loop. Unlike the default loop, it cannot
172	handle signal and child watchers, and attempts to do so will be greeted by	388	handle signal and child watchers, and attempts to do so will be greeted by
173	undefined behaviour (or a failed assertion if assertions are enabled).	389	undefined behaviour (or a failed assertion if assertions are enabled).
174		390
		391	Example: Try to create a event loop that uses epoll and nothing else.
		392
		393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		394	if (!epoller)
		395	fatal ("no epoll found here, maybe it hides under your chair");
		396
175	=item ev_default_destroy ()	397	=item ev_default_destroy ()
176		398
177	Destroys the default loop again (frees all memory and kernel state	399	Destroys the default loop again (frees all memory and kernel state
178	etc.). This stops all registered event watchers (by not touching them in	400	etc.). None of the active event watchers will be stopped in the normal
179	any way whatsoever, although you cannot rely on this :).	401	sense, so e.g. C<ev_is_active> might still return true. It is your
		402	responsibility to either stop all watchers cleanly yoursef I<before>
		403	calling this function, or cope with the fact afterwards (which is usually
		404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		405	for example).
180		406
181	=item ev_loop_destroy (loop)	407	=item ev_loop_destroy (loop)
182		408
183	Like C<ev_default_destroy>, but destroys an event loop created by an	409	Like C<ev_default_destroy>, but destroys an event loop created by an
184	earlier call to C<ev_loop_new>.	410	earlier call to C<ev_loop_new>.
…		…
188	This function reinitialises the kernel state for backends that have	414	This function reinitialises the kernel state for backends that have
189	one. Despite the name, you can call it anytime, but it makes most sense	415	one. Despite the name, you can call it anytime, but it makes most sense
190	after forking, in either the parent or child process (or both, but that	416	after forking, in either the parent or child process (or both, but that
191	again makes little sense).	417	again makes little sense).
192		418
193	You I<must> call this function after forking if and only if you want to	419	You I<must> call this function in the child process after forking if and
194	use the event library in both processes. If you just fork+exec, you don't	420	only if you want to use the event library in both processes. If you just
195	have to call it.	421	fork+exec, you don't have to call it.
196		422
197	The function itself is quite fast and it's usually not a problem to call	423	The function itself is quite fast and it's usually not a problem to call
198	it just in case after a fork. To make this easy, the function will fit in	424	it just in case after a fork. To make this easy, the function will fit in
199	quite nicely into a call to C<pthread_atfork>:	425	quite nicely into a call to C<pthread_atfork>:
200		426
201	pthread_atfork (0, 0, ev_default_fork);	427	pthread_atfork (0, 0, ev_default_fork);
202		428
		429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		430	without calling this function, so if you force one of those backends you
		431	do not need to care.
		432
203	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
204		434
205	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
206	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
207	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
208		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
		448
209	=item unsigned int ev_method (loop)	449	=item unsigned int ev_backend (loop)
210		450
211	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
212	use.	452	use.
213		453
214	=item ev_tstamp ev_now (loop)	454	=item ev_tstamp ev_now (loop)
215		455
216	Returns the current "event loop time", which is the time the event loop	456	Returns the current "event loop time", which is the time the event loop
217	got events and started processing them. This timestamp does not change	457	received events and started processing them. This timestamp does not
218	as long as callbacks are being processed, and this is also the base time	458	change as long as callbacks are being processed, and this is also the base
219	used for relative timers. You can treat it as the timestamp of the event	459	time used for relative timers. You can treat it as the timestamp of the
220	occuring (or more correctly, the mainloop finding out about it).	460	event occuring (or more correctly, libev finding out about it).
221		461
222	=item ev_loop (loop, int flags)	462	=item ev_loop (loop, int flags)
223		463
224	Finally, this is it, the event handler. This function usually is called	464	Finally, this is it, the event handler. This function usually is called
225	after you initialised all your watchers and you want to start handling	465	after you initialised all your watchers and you want to start handling
226	events.	466	events.
227		467
228	If the flags argument is specified as 0, it will not return until either	468	If the flags argument is specified as C<0>, it will not return until
229	no event watchers are active anymore or C<ev_unloop> was called.	469	either no event watchers are active anymore or C<ev_unloop> was called.
		470
		471	Please note that an explicit C<ev_unloop> is usually better than
		472	relying on all watchers to be stopped when deciding when a program has
		473	finished (especially in interactive programs), but having a program that
		474	automatically loops as long as it has to and no longer by virtue of
		475	relying on its watchers stopping correctly is a thing of beauty.
230		476
231	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
232	those events and any outstanding ones, but will not block your process in	478	those events and any outstanding ones, but will not block your process in
233	case there are no events and will return after one iteration of the loop.	479	case there are no events and will return after one iteration of the loop.
234		480
235	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
236	neccessary) and will handle those and any outstanding ones. It will block	482	neccessary) and will handle those and any outstanding ones. It will block
237	your process until at least one new event arrives, and will return after	483	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	484	one iteration of the loop. This is useful if you are waiting for some
		485	external event in conjunction with something not expressible using other
		486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		487	usually a better approach for this kind of thing.
239		488
240	This flags value could be used to implement alternative looping
241	constructs, but the C<prepare> and C<check> watchers provide a better and
242	more generic mechanism.
243
244	Here are the gory details of what ev_loop does:	489	Here are the gory details of what C<ev_loop> does:
245		490
246	1. If there are no active watchers (reference count is zero), return.	491	* If there are no active watchers (reference count is zero), return.
247	2. Queue and immediately call all prepare watchers.	492	- Queue prepare watchers and then call all outstanding watchers.
248	3. If we have been forked, recreate the kernel state.	493	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	494	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	495	- Update the "event loop time".
251	6. Calculate for how long to block.	496	- Calculate for how long to block.
252	7. Block the process, waiting for events.	497	- Block the process, waiting for any events.
		498	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	499	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	500	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	501	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	502	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	503	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	504	- Call all queued watchers in reverse order (i.e. check watchers first).
		505	Signals and child watchers are implemented as I/O watchers, and will
		506	be handled here by queueing them when their watcher gets executed.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	508	were used, return, otherwise continue with step *.
		509
		510	Example: Queue some jobs and then loop until no events are outsanding
		511	anymore.
		512
		513	... queue jobs here, make sure they register event watchers as long
		514	... as they still have work to do (even an idle watcher will do..)
		515	ev_loop (my_loop, 0);
		516	... jobs done. yeah!
261		517
262	=item ev_unloop (loop, how)	518	=item ev_unloop (loop, how)
263		519
264	Can be used to make a call to C<ev_loop> return early (but only after it	520	Can be used to make a call to C<ev_loop> return early (but only after it
265	has processed all outstanding events). The C<how> argument must be either	521	has processed all outstanding events). The C<how> argument must be either
…		…
279	visible to the libev user and should not keep C<ev_loop> from exiting if	535	visible to the libev user and should not keep C<ev_loop> from exiting if
280	no event watchers registered by it are active. It is also an excellent	536	no event watchers registered by it are active. It is also an excellent
281	way to do this for generic recurring timers or from within third-party	537	way to do this for generic recurring timers or from within third-party
282	libraries. Just remember to I<unref after start> and I<ref before stop>.	538	libraries. Just remember to I<unref after start> and I<ref before stop>.
283		539
		540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		541	running when nothing else is active.
		542
		543	struct ev_signal exitsig;
		544	ev_signal_init (&exitsig, sig_cb, SIGINT);
		545	ev_signal_start (loop, &exitsig);
		546	evf_unref (loop);
		547
		548	Example: For some weird reason, unregister the above signal handler again.
		549
		550	ev_ref (loop);
		551	ev_signal_stop (loop, &exitsig);
		552
284	=back	553	=back
		554
285		555
286	=head1 ANATOMY OF A WATCHER	556	=head1 ANATOMY OF A WATCHER
287		557
288	A watcher is a structure that you create and register to record your	558	A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	559	interest in some event. For instance, if you want to wait for STDIN to
…		…
322	*) >>), and you can stop watching for events at any time by calling the	592	*) >>), and you can stop watching for events at any time by calling the
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	593	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		594
325	As long as your watcher is active (has been started but not stopped) you	595	As long as your watcher is active (has been started but not stopped) you
326	must not touch the values stored in it. Most specifically you must never	596	must not touch the values stored in it. Most specifically you must never
327	reinitialise it or call its set method.	597	reinitialise it or call its C<set> macro.
328
329	You can check whether an event is active by calling the C<ev_is_active
330	(watcher *)> macro. To see whether an event is outstanding (but the
331	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.
333		598
334	Each and every callback receives the event loop pointer as first, the	599	Each and every callback receives the event loop pointer as first, the
335	registered watcher structure as second, and a bitset of received events as	600	registered watcher structure as second, and a bitset of received events as
336	third argument.	601	third argument.
337		602
…		…
361	The signal specified in the C<ev_signal> watcher has been received by a thread.	626	The signal specified in the C<ev_signal> watcher has been received by a thread.
362		627
363	=item C<EV_CHILD>	628	=item C<EV_CHILD>
364		629
365	The pid specified in the C<ev_child> watcher has received a status change.	630	The pid specified in the C<ev_child> watcher has received a status change.
		631
		632	=item C<EV_STAT>
		633
		634	The path specified in the C<ev_stat> watcher changed its attributes somehow.
366		635
367	=item C<EV_IDLE>	636	=item C<EV_IDLE>
368		637
369	The C<ev_idle> watcher has determined that you have nothing better to do.	638	The C<ev_idle> watcher has determined that you have nothing better to do.
370		639
…		…
378	received events. Callbacks of both watcher types can start and stop as	647	received events. Callbacks of both watcher types can start and stop as
379	many watchers as they want, and all of them will be taken into account	648	many watchers as they want, and all of them will be taken into account
380	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	649	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
381	C<ev_loop> from blocking).	650	C<ev_loop> from blocking).
382		651
		652	=item C<EV_EMBED>
		653
		654	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		655
		656	=item C<EV_FORK>
		657
		658	The event loop has been resumed in the child process after fork (see
		659	C<ev_fork>).
		660
383	=item C<EV_ERROR>	661	=item C<EV_ERROR>
384		662
385	An unspecified error has occured, the watcher has been stopped. This might	663	An unspecified error has occured, the watcher has been stopped. This might
386	happen because the watcher could not be properly started because libev	664	happen because the watcher could not be properly started because libev
387	ran out of memory, a file descriptor was found to be closed or any other	665	ran out of memory, a file descriptor was found to be closed or any other
…		…
393	your callbacks is well-written it can just attempt the operation and cope	671	your callbacks is well-written it can just attempt the operation and cope
394	with the error from read() or write(). This will not work in multithreaded	672	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.	673	programs, though, so beware.
396		674
397	=back	675	=back
		676
		677	=head2 GENERIC WATCHER FUNCTIONS
		678
		679	In the following description, C<TYPE> stands for the watcher type,
		680	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		681
		682	=over 4
		683
		684	=item C<ev_init> (ev_TYPE *watcher, callback)
		685
		686	This macro initialises the generic portion of a watcher. The contents
		687	of the watcher object can be arbitrary (so C<malloc> will do). Only
		688	the generic parts of the watcher are initialised, you I<need> to call
		689	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		690	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		691	which rolls both calls into one.
		692
		693	You can reinitialise a watcher at any time as long as it has been stopped
		694	(or never started) and there are no pending events outstanding.
		695
		696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		697	int revents)>.
		698
		699	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		700
		701	This macro initialises the type-specific parts of a watcher. You need to
		702	call C<ev_init> at least once before you call this macro, but you can
		703	call C<ev_TYPE_set> any number of times. You must not, however, call this
		704	macro on a watcher that is active (it can be pending, however, which is a
		705	difference to the C<ev_init> macro).
		706
		707	Although some watcher types do not have type-specific arguments
		708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		709
		710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		711
		712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		713	calls into a single call. This is the most convinient method to initialise
		714	a watcher. The same limitations apply, of course.
		715
		716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		717
		718	Starts (activates) the given watcher. Only active watchers will receive
		719	events. If the watcher is already active nothing will happen.
		720
		721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		722
		723	Stops the given watcher again (if active) and clears the pending
		724	status. It is possible that stopped watchers are pending (for example,
		725	non-repeating timers are being stopped when they become pending), but
		726	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		727	you want to free or reuse the memory used by the watcher it is therefore a
		728	good idea to always call its C<ev_TYPE_stop> function.
		729
		730	=item bool ev_is_active (ev_TYPE *watcher)
		731
		732	Returns a true value iff the watcher is active (i.e. it has been started
		733	and not yet been stopped). As long as a watcher is active you must not modify
		734	it.
		735
		736	=item bool ev_is_pending (ev_TYPE *watcher)
		737
		738	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		739	events but its callback has not yet been invoked). As long as a watcher
		740	is pending (but not active) you must not call an init function on it (but
		741	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		742	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		743	it).
		744
		745	=item callback ev_cb (ev_TYPE *watcher)
		746
		747	Returns the callback currently set on the watcher.
		748
		749	=item ev_cb_set (ev_TYPE *watcher, callback)
		750
		751	Change the callback. You can change the callback at virtually any time
		752	(modulo threads).
		753
		754	=item ev_set_priority (ev_TYPE *watcher, priority)
		755
		756	=item int ev_priority (ev_TYPE *watcher)
		757
		758	Set and query the priority of the watcher. The priority is a small
		759	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		760	(default: C<-2>). Pending watchers with higher priority will be invoked
		761	before watchers with lower priority, but priority will not keep watchers
		762	from being executed (except for C<ev_idle> watchers).
		763
		764	This means that priorities are I<only> used for ordering callback
		765	invocation after new events have been received. This is useful, for
		766	example, to reduce latency after idling, or more often, to bind two
		767	watchers on the same event and make sure one is called first.
		768
		769	If you need to suppress invocation when higher priority events are pending
		770	you need to look at C<ev_idle> watchers, which provide this functionality.
		771
		772	You I<must not> change the priority of a watcher as long as it is active or
		773	pending.
		774
		775	The default priority used by watchers when no priority has been set is
		776	always C<0>, which is supposed to not be too high and not be too low :).
		777
		778	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		779	fine, as long as you do not mind that the priority value you query might
		780	or might not have been adjusted to be within valid range.
		781
		782	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		783
		784	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		785	C<loop> nor C<revents> need to be valid as long as the watcher callback
		786	can deal with that fact.
		787
		788	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		789
		790	If the watcher is pending, this function returns clears its pending status
		791	and returns its C<revents> bitset (as if its callback was invoked). If the
		792	watcher isn't pending it does nothing and returns C<0>.
		793
		794	=back
		795
398		796
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		798
401	Each watcher has, by default, a member C<void *data> that you can change	799	Each watcher has, by default, a member C<void *data> that you can change
402	and read at any time, libev will completely ignore it. This can be used	800	and read at any time, libev will completely ignore it. This can be used
…		…
420	{	818	{
421	struct my_io *w = (struct my_io *)w_;	819	struct my_io *w = (struct my_io *)w_;
422	...	820	...
423	}	821	}
424		822
425	More interesting and less C-conformant ways of catsing your callback type	823	More interesting and less C-conformant ways of casting your callback type
426	have been omitted....	824	instead have been omitted.
		825
		826	Another common scenario is having some data structure with multiple
		827	watchers:
		828
		829	struct my_biggy
		830	{
		831	int some_data;
		832	ev_timer t1;
		833	ev_timer t2;
		834	}
		835
		836	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		837	you need to use C<offsetof>:
		838
		839	#include <stddef.h>
		840
		841	static void
		842	t1_cb (EV_P_ struct ev_timer *w, int revents)
		843	{
		844	struct my_biggy big = (struct my_biggy *
		845	(((char *)w) - offsetof (struct my_biggy, t1));
		846	}
		847
		848	static void
		849	t2_cb (EV_P_ struct ev_timer *w, int revents)
		850	{
		851	struct my_biggy big = (struct my_biggy *
		852	(((char *)w) - offsetof (struct my_biggy, t2));
		853	}
427		854
428		855
429	=head1 WATCHER TYPES	856	=head1 WATCHER TYPES
430		857
431	This section describes each watcher in detail, but will not repeat	858	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	859	information given in the last section. Any initialisation/set macros,
		860	functions and members specific to the watcher type are explained.
433		861
		862	Members are additionally marked with either I<[read-only]>, meaning that,
		863	while the watcher is active, you can look at the member and expect some
		864	sensible content, but you must not modify it (you can modify it while the
		865	watcher is stopped to your hearts content), or I<[read-write]>, which
		866	means you can expect it to have some sensible content while the watcher
		867	is active, but you can also modify it. Modifying it may not do something
		868	sensible or take immediate effect (or do anything at all), but libev will
		869	not crash or malfunction in any way.
		870
		871
434	=head2 C<ev_io> - is this file descriptor readable or writable	872	=head2 C<ev_io> - is this file descriptor readable or writable?
435		873
436	I/O watchers check whether a file descriptor is readable or writable	874	I/O watchers check whether a file descriptor is readable or writable
437	in each iteration of the event loop (This behaviour is called	875	in each iteration of the event loop, or, more precisely, when reading
438	level-triggering because you keep receiving events as long as the	876	would not block the process and writing would at least be able to write
439	condition persists. Remember you can stop the watcher if you don't want to	877	some data. This behaviour is called level-triggering because you keep
440	act on the event and neither want to receive future events).	878	receiving events as long as the condition persists. Remember you can stop
		879	the watcher if you don't want to act on the event and neither want to
		880	receive future events.
441		881
442	In general you can register as many read and/or write event watchers per	882	In general you can register as many read and/or write event watchers per
443	fd as you want (as long as you don't confuse yourself). Setting all file	883	fd as you want (as long as you don't confuse yourself). Setting all file
444	descriptors to non-blocking mode is also usually a good idea (but not	884	descriptors to non-blocking mode is also usually a good idea (but not
445	required if you know what you are doing).	885	required if you know what you are doing).
446		886
447	You have to be careful with dup'ed file descriptors, though. Some backends	887	You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	888	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	889	descriptors correctly if you register interest in two or more fds pointing
450	to the same underlying file/socket etc. description (that is, they share	890	to the same underlying file/socket/etc. description (that is, they share
451	the same underlying "file open").	891	the same underlying "file open").
452		892
453	If you must do this, then force the use of a known-to-be-good backend	893	If you must do this, then force the use of a known-to-be-good backend
454	(at the time of this writing, this includes only EVMETHOD_SELECT and	894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	895	C<EVBACKEND_POLL>).
		896
		897	Another thing you have to watch out for is that it is quite easy to
		898	receive "spurious" readyness notifications, that is your callback might
		899	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		900	because there is no data. Not only are some backends known to create a
		901	lot of those (for example solaris ports), it is very easy to get into
		902	this situation even with a relatively standard program structure. Thus
		903	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		904	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		905
		906	If you cannot run the fd in non-blocking mode (for example you should not
		907	play around with an Xlib connection), then you have to seperately re-test
		908	whether a file descriptor is really ready with a known-to-be good interface
		909	such as poll (fortunately in our Xlib example, Xlib already does this on
		910	its own, so its quite safe to use).
456		911
457	=over 4	912	=over 4
458		913
459	=item ev_io_init (ev_io *, callback, int fd, int events)	914	=item ev_io_init (ev_io *, callback, int fd, int events)
460		915
461	=item ev_io_set (ev_io *, int fd, int events)	916	=item ev_io_set (ev_io *, int fd, int events)
462		917
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	918	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
464	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	919	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
465	EV_WRITE> to receive the given events.	920	C<EV_READ | EV_WRITE> to receive the given events.
		921
		922	=item int fd [read-only]
		923
		924	The file descriptor being watched.
		925
		926	=item int events [read-only]
		927
		928	The events being watched.
466		929
467	=back	930	=back
468		931
		932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		933	readable, but only once. Since it is likely line-buffered, you could
		934	attempt to read a whole line in the callback.
		935
		936	static void
		937	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		938	{
		939	ev_io_stop (loop, w);
		940	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		941	}
		942
		943	...
		944	struct ev_loop *loop = ev_default_init (0);
		945	struct ev_io stdin_readable;
		946	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		947	ev_io_start (loop, &stdin_readable);
		948	ev_loop (loop, 0);
		949
		950
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	951	=head2 C<ev_timer> - relative and optionally repeating timeouts
470		952
471	Timer watchers are simple relative timers that generate an event after a	953	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	954	given time, and optionally repeating in regular intervals after that.
473		955
474	The timers are based on real time, that is, if you register an event that	956	The timers are based on real time, that is, if you register an event that
475	times out after an hour and you reset your system clock to last years	957	times out after an hour and you reset your system clock to last years
476	time, it will still time out after (roughly) and hour. "Roughly" because	958	time, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	959	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	960	monotonic clock option helps a lot here).
479		961
480	The relative timeouts are calculated relative to the C<ev_now ()>	962	The relative timeouts are calculated relative to the C<ev_now ()>
481	time. This is usually the right thing as this timestamp refers to the time	963	time. This is usually the right thing as this timestamp refers to the time
482	of the event triggering whatever timeout you are modifying/starting. If	964	of the event triggering whatever timeout you are modifying/starting. If
483	you suspect event processing to be delayed and you *need* to base the timeout	965	you suspect event processing to be delayed and you I<need> to base the timeout
484	on the current time, use something like this to adjust for this:	966	on the current time, use something like this to adjust for this:
485		967
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		969
		970	The callback is guarenteed to be invoked only when its timeout has passed,
		971	but if multiple timers become ready during the same loop iteration then
		972	order of execution is undefined.
487		973
488	=over 4	974	=over 4
489		975
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		977
…		…
505	=item ev_timer_again (loop)	991	=item ev_timer_again (loop)
506		992
507	This will act as if the timer timed out and restart it again if it is	993	This will act as if the timer timed out and restart it again if it is
508	repeating. The exact semantics are:	994	repeating. The exact semantics are:
509		995
		996	If the timer is pending, its pending status is cleared.
		997
510	If the timer is started but nonrepeating, stop it.	998	If the timer is started but nonrepeating, stop it (as if it timed out).
511		999
512	If the timer is repeating, either start it if necessary (with the repeat	1000	If the timer is repeating, either start it if necessary (with the
513	value), or reset the running timer to the repeat value.	1001	C<repeat> value), or reset the running timer to the C<repeat> value.
514		1002
515	This sounds a bit complicated, but here is a useful and typical	1003	This sounds a bit complicated, but here is a useful and typical
516	example: Imagine you have a tcp connection and you want a so-called idle	1004	example: Imagine you have a tcp connection and you want a so-called idle
517	timeout, that is, you want to be called when there have been, say, 60	1005	timeout, that is, you want to be called when there have been, say, 60
518	seconds of inactivity on the socket. The easiest way to do this is to	1006	seconds of inactivity on the socket. The easiest way to do this is to
519	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1007	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
520	time you successfully read or write some data. If you go into an idle	1008	C<ev_timer_again> each time you successfully read or write some data. If
521	state where you do not expect data to travel on the socket, you can stop	1009	you go into an idle state where you do not expect data to travel on the
522	the timer, and again will automatically restart it if need be.	1010	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1011	automatically restart it if need be.
		1012
		1013	That means you can ignore the C<after> value and C<ev_timer_start>
		1014	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1015
		1016	ev_timer_init (timer, callback, 0., 5.);
		1017	ev_timer_again (loop, timer);
		1018	...
		1019	timer->again = 17.;
		1020	ev_timer_again (loop, timer);
		1021	...
		1022	timer->again = 10.;
		1023	ev_timer_again (loop, timer);
		1024
		1025	This is more slightly efficient then stopping/starting the timer each time
		1026	you want to modify its timeout value.
		1027
		1028	=item ev_tstamp repeat [read-write]
		1029
		1030	The current C<repeat> value. Will be used each time the watcher times out
		1031	or C<ev_timer_again> is called and determines the next timeout (if any),
		1032	which is also when any modifications are taken into account.
523		1033
524	=back	1034	=back
525		1035
		1036	Example: Create a timer that fires after 60 seconds.
		1037
		1038	static void
		1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1040	{
		1041	.. one minute over, w is actually stopped right here
		1042	}
		1043
		1044	struct ev_timer mytimer;
		1045	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1046	ev_timer_start (loop, &mytimer);
		1047
		1048	Example: Create a timeout timer that times out after 10 seconds of
		1049	inactivity.
		1050
		1051	static void
		1052	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1053	{
		1054	.. ten seconds without any activity
		1055	}
		1056
		1057	struct ev_timer mytimer;
		1058	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1059	ev_timer_again (&mytimer); /* start timer */
		1060	ev_loop (loop, 0);
		1061
		1062	// and in some piece of code that gets executed on any "activity":
		1063	// reset the timeout to start ticking again at 10 seconds
		1064	ev_timer_again (&mytimer);
		1065
		1066
526	=head2 C<ev_periodic> - to cron or not to cron	1067	=head2 C<ev_periodic> - to cron or not to cron?
527		1068
528	Periodic watchers are also timers of a kind, but they are very versatile	1069	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	1070	(and unfortunately a bit complex).
530		1071
531	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
532	but on wallclock time (absolute time). You can tell a periodic watcher	1073	but on wallclock time (absolute time). You can tell a periodic watcher
533	to trigger "at" some specific point in time. For example, if you tell a	1074	to trigger "at" some specific point in time. For example, if you tell a
534	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
535	+ 10.>) and then reset your system clock to the last year, then it will	1076	+ 10.>) and then reset your system clock to the last year, then it will
536	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
537	roughly 10 seconds later and of course not if you reset your system time	1078	roughly 10 seconds later and of course not if you reset your system time
538	again).	1079	again).
539		1080
540	They can also be used to implement vastly more complex timers, such as	1081	They can also be used to implement vastly more complex timers, such as
541	triggering an event on eahc midnight, local time.	1082	triggering an event on eahc midnight, local time.
542		1083
		1084	As with timers, the callback is guarenteed to be invoked only when the
		1085	time (C<at>) has been passed, but if multiple periodic timers become ready
		1086	during the same loop iteration then order of execution is undefined.
		1087
543	=over 4	1088	=over 4
544		1089
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		1091
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1092	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		1093
549	Lots of arguments, lets sort it out... There are basically three modes of	1094	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	1095	operation, and we will explain them from simplest to complex:
551
552		1096
553	=over 4	1097	=over 4
554		1098
555	=item * absolute timer (interval = reschedule_cb = 0)	1099	=item * absolute timer (interval = reschedule_cb = 0)
556		1100
…		…
620	Simply stops and restarts the periodic watcher again. This is only useful	1164	Simply stops and restarts the periodic watcher again. This is only useful
621	when you changed some parameters or the reschedule callback would return	1165	when you changed some parameters or the reschedule callback would return
622	a different time than the last time it was called (e.g. in a crond like	1166	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	1167	program when the crontabs have changed).
624		1168
		1169	=item ev_tstamp interval [read-write]
		1170
		1171	The current interval value. Can be modified any time, but changes only
		1172	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1173	called.
		1174
		1175	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1176
		1177	The current reschedule callback, or C<0>, if this functionality is
		1178	switched off. Can be changed any time, but changes only take effect when
		1179	the periodic timer fires or C<ev_periodic_again> is being called.
		1180
625	=back	1181	=back
626		1182
		1183	Example: Call a callback every hour, or, more precisely, whenever the
		1184	system clock is divisible by 3600. The callback invocation times have
		1185	potentially a lot of jittering, but good long-term stability.
		1186
		1187	static void
		1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1189	{
		1190	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1191	}
		1192
		1193	struct ev_periodic hourly_tick;
		1194	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1195	ev_periodic_start (loop, &hourly_tick);
		1196
		1197	Example: The same as above, but use a reschedule callback to do it:
		1198
		1199	#include <math.h>
		1200
		1201	static ev_tstamp
		1202	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1203	{
		1204	return fmod (now, 3600.) + 3600.;
		1205	}
		1206
		1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1208
		1209	Example: Call a callback every hour, starting now:
		1210
		1211	struct ev_periodic hourly_tick;
		1212	ev_periodic_init (&hourly_tick, clock_cb,
		1213	fmod (ev_now (loop), 3600.), 3600., 0);
		1214	ev_periodic_start (loop, &hourly_tick);
		1215
		1216
627	=head2 C<ev_signal> - signal me when a signal gets signalled	1217	=head2 C<ev_signal> - signal me when a signal gets signalled!
628		1218
629	Signal watchers will trigger an event when the process receives a specific	1219	Signal watchers will trigger an event when the process receives a specific
630	signal one or more times. Even though signals are very asynchronous, libev	1220	signal one or more times. Even though signals are very asynchronous, libev
631	will try it's best to deliver signals synchronously, i.e. as part of the	1221	will try it's best to deliver signals synchronously, i.e. as part of the
632	normal event processing, like any other event.	1222	normal event processing, like any other event.
…		…
645	=item ev_signal_set (ev_signal *, int signum)	1235	=item ev_signal_set (ev_signal *, int signum)
646		1236
647	Configures the watcher to trigger on the given signal number (usually one	1237	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1238	of the C<SIGxxx> constants).
649		1239
		1240	=item int signum [read-only]
		1241
		1242	The signal the watcher watches out for.
		1243
650	=back	1244	=back
651		1245
		1246
652	=head2 C<ev_child> - wait for pid status changes	1247	=head2 C<ev_child> - watch out for process status changes
653		1248
654	Child watchers trigger when your process receives a SIGCHLD in response to	1249	Child watchers trigger when your process receives a SIGCHLD in response to
655	some child status changes (most typically when a child of yours dies).	1250	some child status changes (most typically when a child of yours dies).
656		1251
657	=over 4	1252	=over 4
…		…
665	at the C<rstatus> member of the C<ev_child> watcher structure to see	1260	at the C<rstatus> member of the C<ev_child> watcher structure to see
666	the status word (use the macros from C<sys/wait.h> and see your systems	1261	the status word (use the macros from C<sys/wait.h> and see your systems
667	C<waitpid> documentation). The C<rpid> member contains the pid of the	1262	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1263	process causing the status change.
669		1264
		1265	=item int pid [read-only]
		1266
		1267	The process id this watcher watches out for, or C<0>, meaning any process id.
		1268
		1269	=item int rpid [read-write]
		1270
		1271	The process id that detected a status change.
		1272
		1273	=item int rstatus [read-write]
		1274
		1275	The process exit/trace status caused by C<rpid> (see your systems
		1276	C<waitpid> and C<sys/wait.h> documentation for details).
		1277
670	=back	1278	=back
671		1279
		1280	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1281
		1282	static void
		1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1284	{
		1285	ev_unloop (loop, EVUNLOOP_ALL);
		1286	}
		1287
		1288	struct ev_signal signal_watcher;
		1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1290	ev_signal_start (loop, &sigint_cb);
		1291
		1292
		1293	=head2 C<ev_stat> - did the file attributes just change?
		1294
		1295	This watches a filesystem path for attribute changes. That is, it calls
		1296	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1297	compared to the last time, invoking the callback if it did.
		1298
		1299	The path does not need to exist: changing from "path exists" to "path does
		1300	not exist" is a status change like any other. The condition "path does
		1301	not exist" is signified by the C<st_nlink> field being zero (which is
		1302	otherwise always forced to be at least one) and all the other fields of
		1303	the stat buffer having unspecified contents.
		1304
		1305	The path I<should> be absolute and I<must not> end in a slash. If it is
		1306	relative and your working directory changes, the behaviour is undefined.
		1307
		1308	Since there is no standard to do this, the portable implementation simply
		1309	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1310	can specify a recommended polling interval for this case. If you specify
		1311	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1312	unspecified default> value will be used (which you can expect to be around
		1313	five seconds, although this might change dynamically). Libev will also
		1314	impose a minimum interval which is currently around C<0.1>, but thats
		1315	usually overkill.
		1316
		1317	This watcher type is not meant for massive numbers of stat watchers,
		1318	as even with OS-supported change notifications, this can be
		1319	resource-intensive.
		1320
		1321	At the time of this writing, only the Linux inotify interface is
		1322	implemented (implementing kqueue support is left as an exercise for the
		1323	reader). Inotify will be used to give hints only and should not change the
		1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1325	to fall back to regular polling again even with inotify, but changes are
		1326	usually detected immediately, and if the file exists there will be no
		1327	polling.
		1328
		1329	=over 4
		1330
		1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1332
		1333	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1334
		1335	Configures the watcher to wait for status changes of the given
		1336	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1337	be detected and should normally be specified as C<0> to let libev choose
		1338	a suitable value. The memory pointed to by C<path> must point to the same
		1339	path for as long as the watcher is active.
		1340
		1341	The callback will be receive C<EV_STAT> when a change was detected,
		1342	relative to the attributes at the time the watcher was started (or the
		1343	last change was detected).
		1344
		1345	=item ev_stat_stat (ev_stat *)
		1346
		1347	Updates the stat buffer immediately with new values. If you change the
		1348	watched path in your callback, you could call this fucntion to avoid
		1349	detecting this change (while introducing a race condition). Can also be
		1350	useful simply to find out the new values.
		1351
		1352	=item ev_statdata attr [read-only]
		1353
		1354	The most-recently detected attributes of the file. Although the type is of
		1355	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1356	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1357	was some error while C<stat>ing the file.
		1358
		1359	=item ev_statdata prev [read-only]
		1360
		1361	The previous attributes of the file. The callback gets invoked whenever
		1362	C<prev> != C<attr>.
		1363
		1364	=item ev_tstamp interval [read-only]
		1365
		1366	The specified interval.
		1367
		1368	=item const char *path [read-only]
		1369
		1370	The filesystem path that is being watched.
		1371
		1372	=back
		1373
		1374	Example: Watch C</etc/passwd> for attribute changes.
		1375
		1376	static void
		1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1378	{
		1379	/* /etc/passwd changed in some way */
		1380	if (w->attr.st_nlink)
		1381	{
		1382	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1383	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1384	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1385	}
		1386	else
		1387	/* you shalt not abuse printf for puts */
		1388	puts ("wow, /etc/passwd is not there, expect problems. "
		1389	"if this is windows, they already arrived\n");
		1390	}
		1391
		1392	...
		1393	ev_stat passwd;
		1394
		1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1396	ev_stat_start (loop, &passwd);
		1397
		1398
672	=head2 C<ev_idle> - when you've got nothing better to do	1399	=head2 C<ev_idle> - when you've got nothing better to do...
673		1400
674	Idle watchers trigger events when there are no other events are pending	1401	Idle watchers trigger events when no other events of the same or higher
675	(prepare, check and other idle watchers do not count). That is, as long	1402	priority are pending (prepare, check and other idle watchers do not
676	as your process is busy handling sockets or timeouts (or even signals,	1403	count).
677	imagine) it will not be triggered. But when your process is idle all idle	1404
678	watchers are being called again and again, once per event loop iteration -	1405	That is, as long as your process is busy handling sockets or timeouts
		1406	(or even signals, imagine) of the same or higher priority it will not be
		1407	triggered. But when your process is idle (or only lower-priority watchers
		1408	are pending), the idle watchers are being called once per event loop
679	until stopped, that is, or your process receives more events and becomes	1409	iteration - until stopped, that is, or your process receives more events
680	busy.	1410	and becomes busy again with higher priority stuff.
681		1411
682	The most noteworthy effect is that as long as any idle watchers are	1412	The most noteworthy effect is that as long as any idle watchers are
683	active, the process will not block when waiting for new events.	1413	active, the process will not block when waiting for new events.
684		1414
685	Apart from keeping your process non-blocking (which is a useful	1415	Apart from keeping your process non-blocking (which is a useful
…		…
695	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1426	believe me.
697		1427
698	=back	1428	=back
699		1429
		1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1431	callback, free it. Also, use no error checking, as usual.
		1432
		1433	static void
		1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1435	{
		1436	free (w);
		1437	// now do something you wanted to do when the program has
		1438	// no longer asnything immediate to do.
		1439	}
		1440
		1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1442	ev_idle_init (idle_watcher, idle_cb);
		1443	ev_idle_start (loop, idle_cb);
		1444
		1445
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1446	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
701		1447
702	Prepare and check watchers are usually (but not always) used in tandem:	1448	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1449	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1450	afterwards.
705		1451
		1452	You I<must not> call C<ev_loop> or similar functions that enter
		1453	the current event loop from either C<ev_prepare> or C<ev_check>
		1454	watchers. Other loops than the current one are fine, however. The
		1455	rationale behind this is that you do not need to check for recursion in
		1456	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1457	C<ev_check> so if you have one watcher of each kind they will always be
		1458	called in pairs bracketing the blocking call.
		1459
706	Their main purpose is to integrate other event mechanisms into libev. This	1460	Their main purpose is to integrate other event mechanisms into libev and
707	could be used, for example, to track variable changes, implement your own	1461	their use is somewhat advanced. This could be used, for example, to track
708	watchers, integrate net-snmp or a coroutine library and lots more.	1462	variable changes, implement your own watchers, integrate net-snmp or a
		1463	coroutine library and lots more. They are also occasionally useful if
		1464	you cache some data and want to flush it before blocking (for example,
		1465	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1466	watcher).
709		1467
710	This is done by examining in each prepare call which file descriptors need	1468	This is done by examining in each prepare call which file descriptors need
711	to be watched by the other library, registering C<ev_io> watchers for	1469	to be watched by the other library, registering C<ev_io> watchers for
712	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1470	them and starting an C<ev_timer> watcher for any timeouts (many libraries
713	provide just this functionality). Then, in the check watcher you check for	1471	provide just this functionality). Then, in the check watcher you check for
…		…
735	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
736	macros, but using them is utterly, utterly and completely pointless.	1494	macros, but using them is utterly, utterly and completely pointless.
737		1495
738	=back	1496	=back
739		1497
		1498	Example: To include a library such as adns, you would add IO watchers
		1499	and a timeout watcher in a prepare handler, as required by libadns, and
		1500	in a check watcher, destroy them and call into libadns. What follows is
		1501	pseudo-code only of course:
		1502
		1503	static ev_io iow [nfd];
		1504	static ev_timer tw;
		1505
		1506	static void
		1507	io_cb (ev_loop *loop, ev_io *w, int revents)
		1508	{
		1509	// set the relevant poll flags
		1510	// could also call adns_processreadable etc. here
		1511	struct pollfd *fd = (struct pollfd *)w->data;
		1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1514	}
		1515
		1516	// create io watchers for each fd and a timer before blocking
		1517	static void
		1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1519	{
		1520	int timeout = 3600000;
		1521	struct pollfd fds [nfd];
		1522	// actual code will need to loop here and realloc etc.
		1523	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1524
		1525	/* the callback is illegal, but won't be called as we stop during check */
		1526	ev_timer_init (&tw, 0, timeout * 1e-3);
		1527	ev_timer_start (loop, &tw);
		1528
		1529	// create on ev_io per pollfd
		1530	for (int i = 0; i < nfd; ++i)
		1531	{
		1532	ev_io_init (iow + i, io_cb, fds [i].fd,
		1533	((fds [i].events & POLLIN ? EV_READ : 0)
		1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1535
		1536	fds [i].revents = 0;
		1537	iow [i].data = fds + i;
		1538	ev_io_start (loop, iow + i);
		1539	}
		1540	}
		1541
		1542	// stop all watchers after blocking
		1543	static void
		1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1545	{
		1546	ev_timer_stop (loop, &tw);
		1547
		1548	for (int i = 0; i < nfd; ++i)
		1549	ev_io_stop (loop, iow + i);
		1550
		1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1552	}
		1553
		1554
		1555	=head2 C<ev_embed> - when one backend isn't enough...
		1556
		1557	This is a rather advanced watcher type that lets you embed one event loop
		1558	into another (currently only C<ev_io> events are supported in the embedded
		1559	loop, other types of watchers might be handled in a delayed or incorrect
		1560	fashion and must not be used).
		1561
		1562	There are primarily two reasons you would want that: work around bugs and
		1563	prioritise I/O.
		1564
		1565	As an example for a bug workaround, the kqueue backend might only support
		1566	sockets on some platform, so it is unusable as generic backend, but you
		1567	still want to make use of it because you have many sockets and it scales
		1568	so nicely. In this case, you would create a kqueue-based loop and embed it
		1569	into your default loop (which might use e.g. poll). Overall operation will
		1570	be a bit slower because first libev has to poll and then call kevent, but
		1571	at least you can use both at what they are best.
		1572
		1573	As for prioritising I/O: rarely you have the case where some fds have
		1574	to be watched and handled very quickly (with low latency), and even
		1575	priorities and idle watchers might have too much overhead. In this case
		1576	you would put all the high priority stuff in one loop and all the rest in
		1577	a second one, and embed the second one in the first.
		1578
		1579	As long as the watcher is active, the callback will be invoked every time
		1580	there might be events pending in the embedded loop. The callback must then
		1581	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1582	their callbacks (you could also start an idle watcher to give the embedded
		1583	loop strictly lower priority for example). You can also set the callback
		1584	to C<0>, in which case the embed watcher will automatically execute the
		1585	embedded loop sweep.
		1586
		1587	As long as the watcher is started it will automatically handle events. The
		1588	callback will be invoked whenever some events have been handled. You can
		1589	set the callback to C<0> to avoid having to specify one if you are not
		1590	interested in that.
		1591
		1592	Also, there have not currently been made special provisions for forking:
		1593	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1594	but you will also have to stop and restart any C<ev_embed> watchers
		1595	yourself.
		1596
		1597	Unfortunately, not all backends are embeddable, only the ones returned by
		1598	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1599	portable one.
		1600
		1601	So when you want to use this feature you will always have to be prepared
		1602	that you cannot get an embeddable loop. The recommended way to get around
		1603	this is to have a separate variables for your embeddable loop, try to
		1604	create it, and if that fails, use the normal loop for everything:
		1605
		1606	struct ev_loop *loop_hi = ev_default_init (0);
		1607	struct ev_loop *loop_lo = 0;
		1608	struct ev_embed embed;
		1609
		1610	// see if there is a chance of getting one that works
		1611	// (remember that a flags value of 0 means autodetection)
		1612	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1613	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1614	: 0;
		1615
		1616	// if we got one, then embed it, otherwise default to loop_hi
		1617	if (loop_lo)
		1618	{
		1619	ev_embed_init (&embed, 0, loop_lo);
		1620	ev_embed_start (loop_hi, &embed);
		1621	}
		1622	else
		1623	loop_lo = loop_hi;
		1624
		1625	=over 4
		1626
		1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1628
		1629	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1630
		1631	Configures the watcher to embed the given loop, which must be
		1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1633	invoked automatically, otherwise it is the responsibility of the callback
		1634	to invoke it (it will continue to be called until the sweep has been done,
		1635	if you do not want thta, you need to temporarily stop the embed watcher).
		1636
		1637	=item ev_embed_sweep (loop, ev_embed *)
		1638
		1639	Make a single, non-blocking sweep over the embedded loop. This works
		1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1641	apropriate way for embedded loops.
		1642
		1643	=item struct ev_loop *loop [read-only]
		1644
		1645	The embedded event loop.
		1646
		1647	=back
		1648
		1649
		1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1651
		1652	Fork watchers are called when a C<fork ()> was detected (usually because
		1653	whoever is a good citizen cared to tell libev about it by calling
		1654	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1655	event loop blocks next and before C<ev_check> watchers are being called,
		1656	and only in the child after the fork. If whoever good citizen calling
		1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1658	handlers will be invoked, too, of course.
		1659
		1660	=over 4
		1661
		1662	=item ev_fork_init (ev_signal *, callback)
		1663
		1664	Initialises and configures the fork watcher - it has no parameters of any
		1665	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1666	believe me.
		1667
		1668	=back
		1669
		1670
740	=head1 OTHER FUNCTIONS	1671	=head1 OTHER FUNCTIONS
741		1672
742	There are some other functions of possible interest. Described. Here. Now.	1673	There are some other functions of possible interest. Described. Here. Now.
743		1674
744	=over 4	1675	=over 4
…		…
773	/* stdin might have data for us, joy! */;	1704	/* stdin might have data for us, joy! */;
774	}	1705	}
775		1706
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1707	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		1708
778	=item ev_feed_event (loop, watcher, int events)	1709	=item ev_feed_event (ev_loop *, watcher *, int revents)
779		1710
780	Feeds the given event set into the event loop, as if the specified event	1711	Feeds the given event set into the event loop, as if the specified event
781	had happened for the specified watcher (which must be a pointer to an	1712	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	1713	initialised but not necessarily started event watcher).
783		1714
784	=item ev_feed_fd_event (loop, int fd, int revents)	1715	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		1716
786	Feed an event on the given fd, as if a file descriptor backend detected	1717	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	1718	the given events it.
788		1719
789	=item ev_feed_signal_event (loop, int signum)	1720	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		1721
791	Feed an event as if the given signal occured (loop must be the default loop!).	1722	Feed an event as if the given signal occured (C<loop> must be the default
		1723	loop!).
792		1724
793	=back	1725	=back
		1726
794		1727
795	=head1 LIBEVENT EMULATION	1728	=head1 LIBEVENT EMULATION
796		1729
797	Libev offers a compatibility emulation layer for libevent. It cannot	1730	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	1731	emulate the internals of libevent, so here are some usage hints:
…		…
819		1752
820	=back	1753	=back
821		1754
822	=head1 C++ SUPPORT	1755	=head1 C++ SUPPORT
823		1756
824	TBD.	1757	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1758	you to use some convinience methods to start/stop watchers and also change
		1759	the callback model to a model using method callbacks on objects.
		1760
		1761	To use it,
		1762
		1763	#include <ev++.h>
		1764
		1765	This automatically includes F<ev.h> and puts all of its definitions (many
		1766	of them macros) into the global namespace. All C++ specific things are
		1767	put into the C<ev> namespace. It should support all the same embedding
		1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1769
		1770	Care has been taken to keep the overhead low. The only data member the C++
		1771	classes add (compared to plain C-style watchers) is the event loop pointer
		1772	that the watcher is associated with (or no additional members at all if
		1773	you disable C<EV_MULTIPLICITY> when embedding libev).
		1774
		1775	Currently, functions, and static and non-static member functions can be
		1776	used as callbacks. Other types should be easy to add as long as they only
		1777	need one additional pointer for context. If you need support for other
		1778	types of functors please contact the author (preferably after implementing
		1779	it).
		1780
		1781	Here is a list of things available in the C<ev> namespace:
		1782
		1783	=over 4
		1784
		1785	=item C<ev::READ>, C<ev::WRITE> etc.
		1786
		1787	These are just enum values with the same values as the C<EV_READ> etc.
		1788	macros from F<ev.h>.
		1789
		1790	=item C<ev::tstamp>, C<ev::now>
		1791
		1792	Aliases to the same types/functions as with the C<ev_> prefix.
		1793
		1794	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1795
		1796	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1797	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1798	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1799	defines by many implementations.
		1800
		1801	All of those classes have these methods:
		1802
		1803	=over 4
		1804
		1805	=item ev::TYPE::TYPE ()
		1806
		1807	=item ev::TYPE::TYPE (struct ev_loop *)
		1808
		1809	=item ev::TYPE::~TYPE
		1810
		1811	The constructor (optionally) takes an event loop to associate the watcher
		1812	with. If it is omitted, it will use C<EV_DEFAULT>.
		1813
		1814	The constructor calls C<ev_init> for you, which means you have to call the
		1815	C<set> method before starting it.
		1816
		1817	It will not set a callback, however: You have to call the templated C<set>
		1818	method to set a callback before you can start the watcher.
		1819
		1820	(The reason why you have to use a method is a limitation in C++ which does
		1821	not allow explicit template arguments for constructors).
		1822
		1823	The destructor automatically stops the watcher if it is active.
		1824
		1825	=item w->set<class, &class::method> (object *)
		1826
		1827	This method sets the callback method to call. The method has to have a
		1828	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1829	first argument and the C<revents> as second. The object must be given as
		1830	parameter and is stored in the C<data> member of the watcher.
		1831
		1832	This method synthesizes efficient thunking code to call your method from
		1833	the C callback that libev requires. If your compiler can inline your
		1834	callback (i.e. it is visible to it at the place of the C<set> call and
		1835	your compiler is good :), then the method will be fully inlined into the
		1836	thunking function, making it as fast as a direct C callback.
		1837
		1838	Example: simple class declaration and watcher initialisation
		1839
		1840	struct myclass
		1841	{
		1842	void io_cb (ev::io &w, int revents) { }
		1843	}
		1844
		1845	myclass obj;
		1846	ev::io iow;
		1847	iow.set <myclass, &myclass::io_cb> (&obj);
		1848
		1849	=item w->set<function> (void *data = 0)
		1850
		1851	Also sets a callback, but uses a static method or plain function as
		1852	callback. The optional C<data> argument will be stored in the watcher's
		1853	C<data> member and is free for you to use.
		1854
		1855	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1856
		1857	See the method-C<set> above for more details.
		1858
		1859	Example:
		1860
		1861	static void io_cb (ev::io &w, int revents) { }
		1862	iow.set <io_cb> ();
		1863
		1864	=item w->set (struct ev_loop *)
		1865
		1866	Associates a different C<struct ev_loop> with this watcher. You can only
		1867	do this when the watcher is inactive (and not pending either).
		1868
		1869	=item w->set ([args])
		1870
		1871	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1872	called at least once. Unlike the C counterpart, an active watcher gets
		1873	automatically stopped and restarted when reconfiguring it with this
		1874	method.
		1875
		1876	=item w->start ()
		1877
		1878	Starts the watcher. Note that there is no C<loop> argument, as the
		1879	constructor already stores the event loop.
		1880
		1881	=item w->stop ()
		1882
		1883	Stops the watcher if it is active. Again, no C<loop> argument.
		1884
		1885	=item w->again () C<ev::timer>, C<ev::periodic> only
		1886
		1887	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1888	C<ev_TYPE_again> function.
		1889
		1890	=item w->sweep () C<ev::embed> only
		1891
		1892	Invokes C<ev_embed_sweep>.
		1893
		1894	=item w->update () C<ev::stat> only
		1895
		1896	Invokes C<ev_stat_stat>.
		1897
		1898	=back
		1899
		1900	=back
		1901
		1902	Example: Define a class with an IO and idle watcher, start one of them in
		1903	the constructor.
		1904
		1905	class myclass
		1906	{
		1907	ev_io io; void io_cb (ev::io &w, int revents);
		1908	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1909
		1910	myclass ();
		1911	}
		1912
		1913	myclass::myclass (int fd)
		1914	{
		1915	io .set <myclass, &myclass::io_cb > (this);
		1916	idle.set <myclass, &myclass::idle_cb> (this);
		1917
		1918	io.start (fd, ev::READ);
		1919	}
		1920
		1921
		1922	=head1 MACRO MAGIC
		1923
		1924	Libev can be compiled with a variety of options, the most fundemantal is
		1925	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		1926	callbacks have an initial C<struct ev_loop *> argument.
		1927
		1928	To make it easier to write programs that cope with either variant, the
		1929	following macros are defined:
		1930
		1931	=over 4
		1932
		1933	=item C<EV_A>, C<EV_A_>
		1934
		1935	This provides the loop I<argument> for functions, if one is required ("ev
		1936	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1937	C<EV_A_> is used when other arguments are following. Example:
		1938
		1939	ev_unref (EV_A);
		1940	ev_timer_add (EV_A_ watcher);
		1941	ev_loop (EV_A_ 0);
		1942
		1943	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1944	which is often provided by the following macro.
		1945
		1946	=item C<EV_P>, C<EV_P_>
		1947
		1948	This provides the loop I<parameter> for functions, if one is required ("ev
		1949	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1950	C<EV_P_> is used when other parameters are following. Example:
		1951
		1952	// this is how ev_unref is being declared
		1953	static void ev_unref (EV_P);
		1954
		1955	// this is how you can declare your typical callback
		1956	static void cb (EV_P_ ev_timer *w, int revents)
		1957
		1958	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1959	suitable for use with C<EV_A>.
		1960
		1961	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1962
		1963	Similar to the other two macros, this gives you the value of the default
		1964	loop, if multiple loops are supported ("ev loop default").
		1965
		1966	=back
		1967
		1968	Example: Declare and initialise a check watcher, utilising the above
		1969	macros so it will work regardless of whether multiple loops are supported
		1970	or not.
		1971
		1972	static void
		1973	check_cb (EV_P_ ev_timer *w, int revents)
		1974	{
		1975	ev_check_stop (EV_A_ w);
		1976	}
		1977
		1978	ev_check check;
		1979	ev_check_init (&check, check_cb);
		1980	ev_check_start (EV_DEFAULT_ &check);
		1981	ev_loop (EV_DEFAULT_ 0);
		1982
		1983	=head1 EMBEDDING
		1984
		1985	Libev can (and often is) directly embedded into host
		1986	applications. Examples of applications that embed it include the Deliantra
		1987	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1988	and rxvt-unicode.
		1989
		1990	The goal is to enable you to just copy the neecssary files into your
		1991	source directory without having to change even a single line in them, so
		1992	you can easily upgrade by simply copying (or having a checked-out copy of
		1993	libev somewhere in your source tree).
		1994
		1995	=head2 FILESETS
		1996
		1997	Depending on what features you need you need to include one or more sets of files
		1998	in your app.
		1999
		2000	=head3 CORE EVENT LOOP
		2001
		2002	To include only the libev core (all the C<ev_*> functions), with manual
		2003	configuration (no autoconf):
		2004
		2005	#define EV_STANDALONE 1
		2006	#include "ev.c"
		2007
		2008	This will automatically include F<ev.h>, too, and should be done in a
		2009	single C source file only to provide the function implementations. To use
		2010	it, do the same for F<ev.h> in all files wishing to use this API (best
		2011	done by writing a wrapper around F<ev.h> that you can include instead and
		2012	where you can put other configuration options):
		2013
		2014	#define EV_STANDALONE 1
		2015	#include "ev.h"
		2016
		2017	Both header files and implementation files can be compiled with a C++
		2018	compiler (at least, thats a stated goal, and breakage will be treated
		2019	as a bug).
		2020
		2021	You need the following files in your source tree, or in a directory
		2022	in your include path (e.g. in libev/ when using -Ilibev):
		2023
		2024	ev.h
		2025	ev.c
		2026	ev_vars.h
		2027	ev_wrap.h
		2028
		2029	ev_win32.c required on win32 platforms only
		2030
		2031	ev_select.c only when select backend is enabled (which is enabled by default)
		2032	ev_poll.c only when poll backend is enabled (disabled by default)
		2033	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2034	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2035	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2036
		2037	F<ev.c> includes the backend files directly when enabled, so you only need
		2038	to compile this single file.
		2039
		2040	=head3 LIBEVENT COMPATIBILITY API
		2041
		2042	To include the libevent compatibility API, also include:
		2043
		2044	#include "event.c"
		2045
		2046	in the file including F<ev.c>, and:
		2047
		2048	#include "event.h"
		2049
		2050	in the files that want to use the libevent API. This also includes F<ev.h>.
		2051
		2052	You need the following additional files for this:
		2053
		2054	event.h
		2055	event.c
		2056
		2057	=head3 AUTOCONF SUPPORT
		2058
		2059	Instead of using C<EV_STANDALONE=1> and providing your config in
		2060	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2061	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2062	include F<config.h> and configure itself accordingly.
		2063
		2064	For this of course you need the m4 file:
		2065
		2066	libev.m4
		2067
		2068	=head2 PREPROCESSOR SYMBOLS/MACROS
		2069
		2070	Libev can be configured via a variety of preprocessor symbols you have to define
		2071	before including any of its files. The default is not to build for multiplicity
		2072	and only include the select backend.
		2073
		2074	=over 4
		2075
		2076	=item EV_STANDALONE
		2077
		2078	Must always be C<1> if you do not use autoconf configuration, which
		2079	keeps libev from including F<config.h>, and it also defines dummy
		2080	implementations for some libevent functions (such as logging, which is not
		2081	supported). It will also not define any of the structs usually found in
		2082	F<event.h> that are not directly supported by the libev core alone.
		2083
		2084	=item EV_USE_MONOTONIC
		2085
		2086	If defined to be C<1>, libev will try to detect the availability of the
		2087	monotonic clock option at both compiletime and runtime. Otherwise no use
		2088	of the monotonic clock option will be attempted. If you enable this, you
		2089	usually have to link against librt or something similar. Enabling it when
		2090	the functionality isn't available is safe, though, althoguh you have
		2091	to make sure you link against any libraries where the C<clock_gettime>
		2092	function is hiding in (often F<-lrt>).
		2093
		2094	=item EV_USE_REALTIME
		2095
		2096	If defined to be C<1>, libev will try to detect the availability of the
		2097	realtime clock option at compiletime (and assume its availability at
		2098	runtime if successful). Otherwise no use of the realtime clock option will
		2099	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2100	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2101	in the description of C<EV_USE_MONOTONIC>, though.
		2102
		2103	=item EV_USE_SELECT
		2104
		2105	If undefined or defined to be C<1>, libev will compile in support for the
		2106	C<select>(2) backend. No attempt at autodetection will be done: if no
		2107	other method takes over, select will be it. Otherwise the select backend
		2108	will not be compiled in.
		2109
		2110	=item EV_SELECT_USE_FD_SET
		2111
		2112	If defined to C<1>, then the select backend will use the system C<fd_set>
		2113	structure. This is useful if libev doesn't compile due to a missing
		2114	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2115	exotic systems. This usually limits the range of file descriptors to some
		2116	low limit such as 1024 or might have other limitations (winsocket only
		2117	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2118	influence the size of the C<fd_set> used.
		2119
		2120	=item EV_SELECT_IS_WINSOCKET
		2121
		2122	When defined to C<1>, the select backend will assume that
		2123	select/socket/connect etc. don't understand file descriptors but
		2124	wants osf handles on win32 (this is the case when the select to
		2125	be used is the winsock select). This means that it will call
		2126	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2127	it is assumed that all these functions actually work on fds, even
		2128	on win32. Should not be defined on non-win32 platforms.
		2129
		2130	=item EV_USE_POLL
		2131
		2132	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2133	backend. Otherwise it will be enabled on non-win32 platforms. It
		2134	takes precedence over select.
		2135
		2136	=item EV_USE_EPOLL
		2137
		2138	If defined to be C<1>, libev will compile in support for the Linux
		2139	C<epoll>(7) backend. Its availability will be detected at runtime,
		2140	otherwise another method will be used as fallback. This is the
		2141	preferred backend for GNU/Linux systems.
		2142
		2143	=item EV_USE_KQUEUE
		2144
		2145	If defined to be C<1>, libev will compile in support for the BSD style
		2146	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2147	otherwise another method will be used as fallback. This is the preferred
		2148	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2149	supports some types of fds correctly (the only platform we found that
		2150	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2151	not be used unless explicitly requested. The best way to use it is to find
		2152	out whether kqueue supports your type of fd properly and use an embedded
		2153	kqueue loop.
		2154
		2155	=item EV_USE_PORT
		2156
		2157	If defined to be C<1>, libev will compile in support for the Solaris
		2158	10 port style backend. Its availability will be detected at runtime,
		2159	otherwise another method will be used as fallback. This is the preferred
		2160	backend for Solaris 10 systems.
		2161
		2162	=item EV_USE_DEVPOLL
		2163
		2164	reserved for future expansion, works like the USE symbols above.
		2165
		2166	=item EV_USE_INOTIFY
		2167
		2168	If defined to be C<1>, libev will compile in support for the Linux inotify
		2169	interface to speed up C<ev_stat> watchers. Its actual availability will
		2170	be detected at runtime.
		2171
		2172	=item EV_H
		2173
		2174	The name of the F<ev.h> header file used to include it. The default if
		2175	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2176	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2177
		2178	=item EV_CONFIG_H
		2179
		2180	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2181	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2182	C<EV_H>, above.
		2183
		2184	=item EV_EVENT_H
		2185
		2186	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2187	of how the F<event.h> header can be found.
		2188
		2189	=item EV_PROTOTYPES
		2190
		2191	If defined to be C<0>, then F<ev.h> will not define any function
		2192	prototypes, but still define all the structs and other symbols. This is
		2193	occasionally useful if you want to provide your own wrapper functions
		2194	around libev functions.
		2195
		2196	=item EV_MULTIPLICITY
		2197
		2198	If undefined or defined to C<1>, then all event-loop-specific functions
		2199	will have the C<struct ev_loop *> as first argument, and you can create
		2200	additional independent event loops. Otherwise there will be no support
		2201	for multiple event loops and there is no first event loop pointer
		2202	argument. Instead, all functions act on the single default loop.
		2203
		2204	=item EV_MINPRI
		2205
		2206	=item EV_MAXPRI
		2207
		2208	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2209	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2210	provide for more priorities by overriding those symbols (usually defined
		2211	to be C<-2> and C<2>, respectively).
		2212
		2213	When doing priority-based operations, libev usually has to linearly search
		2214	all the priorities, so having many of them (hundreds) uses a lot of space
		2215	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2216	fine.
		2217
		2218	If your embedding app does not need any priorities, defining these both to
		2219	C<0> will save some memory and cpu.
		2220
		2221	=item EV_PERIODIC_ENABLE
		2222
		2223	If undefined or defined to be C<1>, then periodic timers are supported. If
		2224	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2225	code.
		2226
		2227	=item EV_IDLE_ENABLE
		2228
		2229	If undefined or defined to be C<1>, then idle watchers are supported. If
		2230	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2231	code.
		2232
		2233	=item EV_EMBED_ENABLE
		2234
		2235	If undefined or defined to be C<1>, then embed watchers are supported. If
		2236	defined to be C<0>, then they are not.
		2237
		2238	=item EV_STAT_ENABLE
		2239
		2240	If undefined or defined to be C<1>, then stat watchers are supported. If
		2241	defined to be C<0>, then they are not.
		2242
		2243	=item EV_FORK_ENABLE
		2244
		2245	If undefined or defined to be C<1>, then fork watchers are supported. If
		2246	defined to be C<0>, then they are not.
		2247
		2248	=item EV_MINIMAL
		2249
		2250	If you need to shave off some kilobytes of code at the expense of some
		2251	speed, define this symbol to C<1>. Currently only used for gcc to override
		2252	some inlining decisions, saves roughly 30% codesize of amd64.
		2253
		2254	=item EV_PID_HASHSIZE
		2255
		2256	C<ev_child> watchers use a small hash table to distribute workload by
		2257	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2258	than enough. If you need to manage thousands of children you might want to
		2259	increase this value (I<must> be a power of two).
		2260
		2261	=item EV_INOTIFY_HASHSIZE
		2262
		2263	C<ev_staz> watchers use a small hash table to distribute workload by
		2264	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2265	usually more than enough. If you need to manage thousands of C<ev_stat>
		2266	watchers you might want to increase this value (I<must> be a power of
		2267	two).
		2268
		2269	=item EV_COMMON
		2270
		2271	By default, all watchers have a C<void *data> member. By redefining
		2272	this macro to a something else you can include more and other types of
		2273	members. You have to define it each time you include one of the files,
		2274	though, and it must be identical each time.
		2275
		2276	For example, the perl EV module uses something like this:
		2277
		2278	#define EV_COMMON \
		2279	SV *self; /* contains this struct */ \
		2280	SV *cb_sv, *fh /* note no trailing ";" */
		2281
		2282	=item EV_CB_DECLARE (type)
		2283
		2284	=item EV_CB_INVOKE (watcher, revents)
		2285
		2286	=item ev_set_cb (ev, cb)
		2287
		2288	Can be used to change the callback member declaration in each watcher,
		2289	and the way callbacks are invoked and set. Must expand to a struct member
		2290	definition and a statement, respectively. See the F<ev.v> header file for
		2291	their default definitions. One possible use for overriding these is to
		2292	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2293	method calls instead of plain function calls in C++.
		2294
		2295	=head2 EXAMPLES
		2296
		2297	For a real-world example of a program the includes libev
		2298	verbatim, you can have a look at the EV perl module
		2299	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2300	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2301	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2302	will be compiled. It is pretty complex because it provides its own header
		2303	file.
		2304
		2305	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2306	that everybody includes and which overrides some configure choices:
		2307
		2308	#define EV_MINIMAL 1
		2309	#define EV_USE_POLL 0
		2310	#define EV_MULTIPLICITY 0
		2311	#define EV_PERIODIC_ENABLE 0
		2312	#define EV_STAT_ENABLE 0
		2313	#define EV_FORK_ENABLE 0
		2314	#define EV_CONFIG_H <config.h>
		2315	#define EV_MINPRI 0
		2316	#define EV_MAXPRI 0
		2317
		2318	#include "ev++.h"
		2319
		2320	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2321
		2322	#include "ev_cpp.h"
		2323	#include "ev.c"
		2324
		2325
		2326	=head1 COMPLEXITIES
		2327
		2328	In this section the complexities of (many of) the algorithms used inside
		2329	libev will be explained. For complexity discussions about backends see the
		2330	documentation for C<ev_default_init>.
		2331
		2332	All of the following are about amortised time: If an array needs to be
		2333	extended, libev needs to realloc and move the whole array, but this
		2334	happens asymptotically never with higher number of elements, so O(1) might
		2335	mean it might do a lengthy realloc operation in rare cases, but on average
		2336	it is much faster and asymptotically approaches constant time.
		2337
		2338	=over 4
		2339
		2340	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2341
		2342	This means that, when you have a watcher that triggers in one hour and
		2343	there are 100 watchers that would trigger before that then inserting will
		2344	have to skip those 100 watchers.
		2345
		2346	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2347
		2348	That means that for changing a timer costs less than removing/adding them
		2349	as only the relative motion in the event queue has to be paid for.
		2350
		2351	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2352
		2353	These just add the watcher into an array or at the head of a list.
		2354	=item Stopping check/prepare/idle watchers: O(1)
		2355
		2356	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2357
		2358	These watchers are stored in lists then need to be walked to find the
		2359	correct watcher to remove. The lists are usually short (you don't usually
		2360	have many watchers waiting for the same fd or signal).
		2361
		2362	=item Finding the next timer per loop iteration: O(1)
		2363
		2364	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2365
		2366	A change means an I/O watcher gets started or stopped, which requires
		2367	libev to recalculate its status (and possibly tell the kernel).
		2368
		2369	=item Activating one watcher: O(1)
		2370
		2371	=item Priority handling: O(number_of_priorities)
		2372
		2373	Priorities are implemented by allocating some space for each
		2374	priority. When doing priority-based operations, libev usually has to
		2375	linearly search all the priorities.
		2376
		2377	=back
		2378
825		2379
826	=head1 AUTHOR	2380	=head1 AUTHOR
827		2381
828	Marc Lehmann <libev@schmorp.de>.	2382	Marc Lehmann <libev@schmorp.de>.
829		2383

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