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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	=head2 EXAMPLE PROGRAM
		10
		11	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		66
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://cvs.schmorp.de/libev/ev.html>.
		70
11	Libev is an event loop: you register interest in certain events (such as a	71	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	72	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
21	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers).	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
31		96
		97	It also is quite fast (see this
		98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
		99	for example).
		100
32	=head1 CONVENTIONS	101	=head2 CONVENTIONS
33		102
34	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
35	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
36	about various configuraiton options please have a look at the file	105	more info about various configuration options please have a look at
37	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
38	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
39	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
40	will not have this argument.	109	this argument.
41		110
42	=head1 TIME AND OTHER GLOBAL FUNCTIONS	111	=head2 TIME REPRESENTATION
43		112
44	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
45	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
46	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
47	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
48	to the double type in C.	117	to the C<double> type in C, and when you need to do any calculations on
		118	it, you should treat it as some floatingpoint value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 GLOBAL FUNCTIONS
		123
		124	These functions can be called anytime, even before initialising the
		125	library in any way.
49		126
50	=over 4	127	=over 4
51		128
52	=item ev_tstamp ev_time ()	129	=item ev_tstamp ev_time ()
53		130
54	Returns the current time as libev would use it.	131	Returns the current time as libev would use it. Please note that the
		132	C<ev_now> function is usually faster and also often returns the timestamp
		133	you actually want to know.
		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
55		140
56	=item int ev_version_major ()	141	=item int ev_version_major ()
57		142
58	=item int ev_version_minor ()	143	=item int ev_version_minor ()
59		144
60	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
61	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
62	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
63	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
64	version of the library your program was compiled against.	149	version of the library your program was compiled against.
65		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
66	Usually, its a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
67	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
68	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
69	not a problem.	157	not a problem.
70		158
		159	Example: Make sure we haven't accidentally been linked against the wrong
		160	version.
		161
		162	assert (("libev version mismatch",
		163	ev_version_major () == EV_VERSION_MAJOR
		164	&& ev_version_minor () >= EV_VERSION_MINOR));
		165
		166	=item unsigned int ev_supported_backends ()
		167
		168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		169	value) compiled into this binary of libev (independent of their
		170	availability on the system you are running on). See C<ev_default_loop> for
		171	a description of the set values.
		172
		173	Example: make sure we have the epoll method, because yeah this is cool and
		174	a must have and can we have a torrent of it please!!!11
		175
		176	assert (("sorry, no epoll, no sex",
		177	ev_supported_backends () & EVBACKEND_EPOLL));
		178
		179	=item unsigned int ev_recommended_backends ()
		180
		181	Return the set of all backends compiled into this binary of libev and also
		182	recommended for this platform. This set is often smaller than the one
		183	returned by C<ev_supported_backends>, as for example kqueue is broken on
		184	most BSDs and will not be autodetected unless you explicitly request it
		185	(assuming you know what you are doing). This is the set of backends that
		186	libev will probe for if you specify no backends explicitly.
		187
		188	=item unsigned int ev_embeddable_backends ()
		189
		190	Returns the set of backends that are embeddable in other event loops. This
		191	is the theoretical, all-platform, value. To find which backends
		192	might be supported on the current system, you would need to look at
		193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		194	recommended ones.
		195
		196	See the description of C<ev_embed> watchers for more info.
		197
71	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
72		199
73	Sets the allocation function to use (the prototype is similar to the	200	Sets the allocation function to use (the prototype is similar - the
74	realloc function). It is used to allocate and free memory (no surprises	201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
75	here). If it returns zero when memory needs to be allocated, the library	202	used to allocate and free memory (no surprises here). If it returns zero
		203	when memory needs to be allocated (C<size != 0>), the library might abort
76	might abort or take some potentially destructive action. The default is	204	or take some potentially destructive action.
77	your system realloc function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
78		209
79	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
80	free some memory if it cannot allocate memory, to use a special allocator,	211	free some memory if it cannot allocate memory, to use a special allocator,
81	or even to sleep a while and retry until some memory is available.	212	or even to sleep a while and retry until some memory is available.
		213
		214	Example: Replace the libev allocator with one that waits a bit and then
		215	retries (example requires a standards-compliant C<realloc>).
		216
		217	static void *
		218	persistent_realloc (void *ptr, size_t size)
		219	{
		220	for (;;)
		221	{
		222	void *newptr = realloc (ptr, size);
		223
		224	if (newptr)
		225	return newptr;
		226
		227	sleep (60);
		228	}
		229	}
		230
		231	...
		232	ev_set_allocator (persistent_realloc);
82		233
83	=item ev_set_syserr_cb (void (*cb)(const char *msg));	234	=item ev_set_syserr_cb (void (*cb)(const char *msg));
84		235
85	Set the callback function to call on a retryable syscall error (such	236	Set the callback function to call on a retryable syscall error (such
86	as failed select, poll, epoll_wait). The message is a printable string	237	as failed select, poll, epoll_wait). The message is a printable string
87	indicating the system call or subsystem causing the problem. If this	238	indicating the system call or subsystem causing the problem. If this
88	callback is set, then libev will expect it to remedy the sitution, no	239	callback is set, then libev will expect it to remedy the sitution, no
89	matter what, when it returns. That is, libev will geenrally retry the	240	matter what, when it returns. That is, libev will generally retry the
90	requested operation, or, if the condition doesn't go away, do bad stuff	241	requested operation, or, if the condition doesn't go away, do bad stuff
91	(such as abort).	242	(such as abort).
		243
		244	Example: This is basically the same thing that libev does internally, too.
		245
		246	static void
		247	fatal_error (const char *msg)
		248	{
		249	perror (msg);
		250	abort ();
		251	}
		252
		253	...
		254	ev_set_syserr_cb (fatal_error);
92		255
93	=back	256	=back
94		257
95	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
96		259
97	An event loop is described by a C<struct ev_loop *>. The library knows two	260	An event loop is described by a C<struct ev_loop *>. The library knows two
98	types of such loops, the I<default> loop, which supports signals and child	261	types of such loops, the I<default> loop, which supports signals and child
99	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
100		263
101	If you use threads, a common model is to run the default event loop
102	in your main thread (or in a separate thrad) and for each thread you
103	create, you also create another event loop. Libev itself does no lockign
104	whatsoever, so if you mix calls to different event loops, make sure you
105	lock (this is usually a bad idea, though, even if done right).
106
107	=over 4	264	=over 4
108		265
109	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
110		267
111	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
112	yet and return it. If the default loop could not be initialised, returns	269	yet and return it. If the default loop could not be initialised, returns
113	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
114	flags).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
115		272
116	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
117	function.	274	function.
118		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
119	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
120	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
121		289
122	It supports the following flags:	290	The following flags are supported:
123		291
124	=over 4	292	=over 4
125		293
126	=item EVFLAG_AUTO	294	=item C<EVFLAG_AUTO>
127		295
128	The default flags value. Use this if you have no clue (its the right	296	The default flags value. Use this if you have no clue (it's the right
129	thing, believe me).	297	thing, believe me).
130		298
131	=item EVFLAG_NOENV	299	=item C<EVFLAG_NOENV>
132		300
133	If this flag bit is ored into the flag value then libev will I<not> look	301	If this flag bit is ored into the flag value (or the program runs setuid
134	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	302	or setgid) then libev will I<not> look at the environment variable
135	environment variable will override the flags completely. This is useful	303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		304	override the flags completely if it is found in the environment. This is
136	to try out specific backends to tets their performance, or to work around	305	useful to try out specific backends to test their performance, or to work
137	bugs.	306	around bugs.
138		307
		308	=item C<EVFLAG_FORKCHECK>
		309
		310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		311	a fork, you can also make libev check for a fork in each iteration by
		312	enabling this flag.
		313
		314	This works by calling C<getpid ()> on every iteration of the loop,
		315	and thus this might slow down your event loop if you do a lot of loop
		316	iterations and little real work, but is usually not noticeable (on my
		317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		319	C<pthread_atfork> which is even faster).
		320
		321	The big advantage of this flag is that you can forget about fork (and
		322	forget about forgetting to tell libev about forking) when you use this
		323	flag.
		324
		325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		326	environment variable.
		327
139	=item EVMETHOD_SELECT portable select backend	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
140		329
141	=item EVMETHOD_POLL poll backend (everywhere except windows)	330	This is your standard select(2) backend. Not I<completely> standard, as
		331	libev tries to roll its own fd_set with no limits on the number of fds,
		332	but if that fails, expect a fairly low limit on the number of fds when
		333	using this backend. It doesn't scale too well (O(highest_fd)), but its
		334	usually the fastest backend for a low number of (low-numbered :) fds.
142		335
143	=item EVMETHOD_EPOLL linux only	336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
144		342
145	=item EVMETHOD_KQUEUE some bsds only	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		344
147	=item EVMETHOD_DEVPOLL solaris 8 only	345	And this is your standard poll(2) backend. It's more complicated
		346	than select, but handles sparse fds better and has no artificial
		347	limit on the number of fds you can use (except it will slow down
		348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
148		351
149	=item EVMETHOD_PORT solaris 10 only	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		353
		354	For few fds, this backend is a bit little slower than poll and select,
		355	but it scales phenomenally better. While poll and select usually scale
		356	like O(total_fds) where n is the total number of fds (or the highest fd),
		357	epoll scales either O(1) or O(active_fds). The epoll design has a number
		358	of shortcomings, such as silently dropping events in some hard-to-detect
		359	cases and requiring a syscall per fd change, no fork support and bad
		360	support for dup.
		361
		362	While stopping, setting and starting an I/O watcher in the same iteration
		363	will result in some caching, there is still a syscall per such incident
		364	(because the fd could point to a different file description now), so its
		365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		366	very well if you register events for both fds.
		367
		368	Please note that epoll sometimes generates spurious notifications, so you
		369	need to use non-blocking I/O or other means to avoid blocking when no data
		370	(or space) is available.
		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
		379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		380
		381	Kqueue deserves special mention, as at the time of this writing, it
		382	was broken on all BSDs except NetBSD (usually it doesn't work reliably
		383	with anything but sockets and pipes, except on Darwin, where of course
		384	it's completely useless). For this reason it's not being "autodetected"
		385	unless you explicitly specify it explicitly in the flags (i.e. using
		386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		387	system like NetBSD.
		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
		392
		393	It scales in the same way as the epoll backend, but the interface to the
		394	kernel is more efficient (which says nothing about its actual speed, of
		395	course). While stopping, setting and starting an I/O watcher does never
		396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
		397	two event changes per incident, support for C<fork ()> is very bad and it
		398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
		408
		409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		410
		411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
		415
		416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		417
		418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		419	it's really slow, but it still scales very well (O(active_fds)).
		420
		421	Please note that solaris event ports can deliver a lot of spurious
		422	notifications, so you need to use non-blocking I/O or other means to avoid
		423	blocking when no data (or space) is available.
		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
		433
		434	=item C<EVBACKEND_ALL>
		435
		436	Try all backends (even potentially broken ones that wouldn't be tried
		437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		439
		440	It is definitely not recommended to use this flag.
		441
		442	=back
150		443
151	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
152	backends will be tried (in the reverse order as given here). If one are	445	backends will be tried (in the reverse order as listed here). If none are
153	specified, any backend will do.	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
154		447
155	=back	448	The most typical usage is like this:
		449
		450	if (!ev_default_loop (0))
		451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		452
		453	Restrict libev to the select and poll backends, and do not allow
		454	environment settings to be taken into account:
		455
		456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		457
		458	Use whatever libev has to offer, but make sure that kqueue is used if
		459	available (warning, breaks stuff, best use only with your own private
		460	event loop and only if you know the OS supports your types of fds):
		461
		462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
156		463
157	=item struct ev_loop *ev_loop_new (unsigned int flags)	464	=item struct ev_loop *ev_loop_new (unsigned int flags)
158		465
159	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	Similar to C<ev_default_loop>, but always creates a new event loop that is
160	always distinct from the default loop. Unlike the default loop, it cannot	467	always distinct from the default loop. Unlike the default loop, it cannot
161	handle signal and child watchers, and attempts to do so will be greeted by	468	handle signal and child watchers, and attempts to do so will be greeted by
162	undefined behaviour (or a failed assertion if assertions are enabled).	469	undefined behaviour (or a failed assertion if assertions are enabled).
163		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
		474
		475	Example: Try to create a event loop that uses epoll and nothing else.
		476
		477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		478	if (!epoller)
		479	fatal ("no epoll found here, maybe it hides under your chair");
		480
164	=item ev_default_destroy ()	481	=item ev_default_destroy ()
165		482
166	Destroys the default loop again (frees all memory and kernel state	483	Destroys the default loop again (frees all memory and kernel state
167	etc.). This stops all registered event watchers (by not touching them in	484	etc.). None of the active event watchers will be stopped in the normal
168	any way whatsoever, although you cnanot rely on this :).	485	sense, so e.g. C<ev_is_active> might still return true. It is your
		486	responsibility to either stop all watchers cleanly yoursef I<before>
		487	calling this function, or cope with the fact afterwards (which is usually
		488	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		489	for example).
		490
		491	Note that certain global state, such as signal state, will not be freed by
		492	this function, and related watchers (such as signal and child watchers)
		493	would need to be stopped manually.
		494
		495	In general it is not advisable to call this function except in the
		496	rare occasion where you really need to free e.g. the signal handling
		497	pipe fds. If you need dynamically allocated loops it is better to use
		498	C<ev_loop_new> and C<ev_loop_destroy>).
169		499
170	=item ev_loop_destroy (loop)	500	=item ev_loop_destroy (loop)
171		501
172	Like C<ev_default_destroy>, but destroys an event loop created by an	502	Like C<ev_default_destroy>, but destroys an event loop created by an
173	earlier call to C<ev_loop_new>.	503	earlier call to C<ev_loop_new>.
174		504
175	=item ev_default_fork ()	505	=item ev_default_fork ()
176		506
		507	This function sets a flag that causes subsequent C<ev_loop> iterations
177	This function reinitialises the kernel state for backends that have	508	to reinitialise the kernel state for backends that have one. Despite the
178	one. Despite the name, you can call it anytime, but it makes most sense	509	name, you can call it anytime, but it makes most sense after forking, in
179	after forking, in either the parent or child process (or both, but that	510	the child process (or both child and parent, but that again makes little
180	again makes little sense).	511	sense). You I<must> call it in the child before using any of the libev
		512	functions, and it will only take effect at the next C<ev_loop> iteration.
181		513
182	You I<must> call this function after forking if and only if you want to	514	On the other hand, you only need to call this function in the child
183	use the event library in both processes. If you just fork+exec, you don't	515	process if and only if you want to use the event library in the child. If
184	have to call it.	516	you just fork+exec, you don't have to call it at all.
185		517
186	The function itself is quite fast and its usually not a problem to call	518	The function itself is quite fast and it's usually not a problem to call
187	it just in case after a fork. To make this easy, the function will fit in	519	it just in case after a fork. To make this easy, the function will fit in
188	quite nicely into a call to C<pthread_atfork>:	520	quite nicely into a call to C<pthread_atfork>:
189		521
190	pthread_atfork (0, 0, ev_default_fork);	522	pthread_atfork (0, 0, ev_default_fork);
191		523
…		…
193		525
194	Like C<ev_default_fork>, but acts on an event loop created by	526	Like C<ev_default_fork>, but acts on an event loop created by
195	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
196	after fork, and how you do this is entirely your own problem.	528	after fork, and how you do this is entirely your own problem.
197		529
		530	=item int ev_is_default_loop (loop)
		531
		532	Returns true when the given loop actually is the default loop, false otherwise.
		533
		534	=item unsigned int ev_loop_count (loop)
		535
		536	Returns the count of loop iterations for the loop, which is identical to
		537	the number of times libev did poll for new events. It starts at C<0> and
		538	happily wraps around with enough iterations.
		539
		540	This value can sometimes be useful as a generation counter of sorts (it
		541	"ticks" the number of loop iterations), as it roughly corresponds with
		542	C<ev_prepare> and C<ev_check> calls.
		543
198	=item unsigned int ev_method (loop)	544	=item unsigned int ev_backend (loop)
199		545
200	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
201	use.	547	use.
202		548
203	=item ev_tstamp = ev_now (loop)	549	=item ev_tstamp ev_now (loop)
204		550
205	Returns the current "event loop time", which is the time the event loop	551	Returns the current "event loop time", which is the time the event loop
206	got events and started processing them. This timestamp does not change	552	received events and started processing them. This timestamp does not
207	as long as callbacks are being processed, and this is also the base time	553	change as long as callbacks are being processed, and this is also the base
208	used for relative timers. You can treat it as the timestamp of the event	554	time used for relative timers. You can treat it as the timestamp of the
209	occuring (or more correctly, the mainloop finding out about it).	555	event occurring (or more correctly, libev finding out about it).
210		556
211	=item ev_loop (loop, int flags)	557	=item ev_loop (loop, int flags)
212		558
213	Finally, this is it, the event handler. This function usually is called	559	Finally, this is it, the event handler. This function usually is called
214	after you initialised all your watchers and you want to start handling	560	after you initialised all your watchers and you want to start handling
215	events.	561	events.
216		562
217	If the flags argument is specified as 0, it will not return until either	563	If the flags argument is specified as C<0>, it will not return until
218	no event watchers are active anymore or C<ev_unloop> was called.	564	either no event watchers are active anymore or C<ev_unloop> was called.
		565
		566	Please note that an explicit C<ev_unloop> is usually better than
		567	relying on all watchers to be stopped when deciding when a program has
		568	finished (especially in interactive programs), but having a program that
		569	automatically loops as long as it has to and no longer by virtue of
		570	relying on its watchers stopping correctly is a thing of beauty.
219		571
220	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
221	those events and any outstanding ones, but will not block your process in	573	those events and any outstanding ones, but will not block your process in
222	case there are no events.	574	case there are no events and will return after one iteration of the loop.
223		575
224	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
225	neccessary) and will handle those and any outstanding ones. It will block	577	neccessary) and will handle those and any outstanding ones. It will block
226	your process until at least one new event arrives.	578	your process until at least one new event arrives, and will return after
		579	one iteration of the loop. This is useful if you are waiting for some
		580	external event in conjunction with something not expressible using other
		581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		582	usually a better approach for this kind of thing.
227		583
228	This flags value could be used to implement alternative looping	584	Here are the gory details of what C<ev_loop> does:
229	constructs, but the C<prepare> and C<check> watchers provide a better and	585
230	more generic mechanism.	586	- Before the first iteration, call any pending watchers.
		587	* If EVFLAG_FORKCHECK was used, check for a fork.
		588	- If a fork was detected, queue and call all fork watchers.
		589	- Queue and call all prepare watchers.
		590	- If we have been forked, recreate the kernel state.
		591	- Update the kernel state with all outstanding changes.
		592	- Update the "event loop time".
		593	- Calculate for how long to sleep or block, if at all
		594	(active idle watchers, EVLOOP_NONBLOCK or not having
		595	any active watchers at all will result in not sleeping).
		596	- Sleep if the I/O and timer collect interval say so.
		597	- Block the process, waiting for any events.
		598	- Queue all outstanding I/O (fd) events.
		599	- Update the "event loop time" and do time jump handling.
		600	- Queue all outstanding timers.
		601	- Queue all outstanding periodics.
		602	- If no events are pending now, queue all idle watchers.
		603	- Queue all check watchers.
		604	- Call all queued watchers in reverse order (i.e. check watchers first).
		605	Signals and child watchers are implemented as I/O watchers, and will
		606	be handled here by queueing them when their watcher gets executed.
		607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		608	were used, or there are no active watchers, return, otherwise
		609	continue with step *.
		610
		611	Example: Queue some jobs and then loop until no events are outstanding
		612	anymore.
		613
		614	... queue jobs here, make sure they register event watchers as long
		615	... as they still have work to do (even an idle watcher will do..)
		616	ev_loop (my_loop, 0);
		617	... jobs done. yeah!
231		618
232	=item ev_unloop (loop, how)	619	=item ev_unloop (loop, how)
233		620
234	Can be used to make a call to C<ev_loop> return early. The C<how> argument	621	Can be used to make a call to C<ev_loop> return early (but only after it
		622	has processed all outstanding events). The C<how> argument must be either
235	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
236	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
237	calls return.	625
		626	This "unloop state" will be cleared when entering C<ev_loop> again.
238		627
239	=item ev_ref (loop)	628	=item ev_ref (loop)
240		629
241	=item ev_unref (loop)	630	=item ev_unref (loop)
242		631
243	Ref/unref can be used to add or remove a refcount on the event loop: Every	632	Ref/unref can be used to add or remove a reference count on the event
244	watcher keeps one reference. If you have a long-runing watcher you never	633	loop: Every watcher keeps one reference, and as long as the reference
245	unregister that should not keep ev_loop from running, ev_unref() after	634	count is nonzero, C<ev_loop> will not return on its own. If you have
246	starting, and ev_ref() before stopping it. Libev itself uses this for	635	a watcher you never unregister that should not keep C<ev_loop> from
247	example for its internal signal pipe: It is not visible to you as a user	636	returning, ev_unref() after starting, and ev_ref() before stopping it. For
248	and should not keep C<ev_loop> from exiting if the work is done. It is	637	example, libev itself uses this for its internal signal pipe: It is not
249	also an excellent way to do this for generic recurring timers or from	638	visible to the libev user and should not keep C<ev_loop> from exiting if
250	within third-party libraries. Just remember to unref after start and ref	639	no event watchers registered by it are active. It is also an excellent
251	before stop.	640	way to do this for generic recurring timers or from within third-party
		641	libraries. Just remember to I<unref after start> and I<ref before stop>
		642	(but only if the watcher wasn't active before, or was active before,
		643	respectively).
		644
		645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		646	running when nothing else is active.
		647
		648	struct ev_signal exitsig;
		649	ev_signal_init (&exitsig, sig_cb, SIGINT);
		650	ev_signal_start (loop, &exitsig);
		651	evf_unref (loop);
		652
		653	Example: For some weird reason, unregister the above signal handler again.
		654
		655	ev_ref (loop);
		656	ev_signal_stop (loop, &exitsig);
		657
		658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		659
		660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		661
		662	These advanced functions influence the time that libev will spend waiting
		663	for events. Both are by default C<0>, meaning that libev will try to
		664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		665
		666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		667	allows libev to delay invocation of I/O and timer/periodic callbacks to
		668	increase efficiency of loop iterations.
		669
		670	The background is that sometimes your program runs just fast enough to
		671	handle one (or very few) event(s) per loop iteration. While this makes
		672	the program responsive, it also wastes a lot of CPU time to poll for new
		673	events, especially with backends like C<select ()> which have a high
		674	overhead for the actual polling but can deliver many events at once.
		675
		676	By setting a higher I<io collect interval> you allow libev to spend more
		677	time collecting I/O events, so you can handle more events per iteration,
		678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		679	C<ev_timer>) will be not affected. Setting this to a non-null value will
		680	introduce an additional C<ev_sleep ()> call into most loop iterations.
		681
		682	Likewise, by setting a higher I<timeout collect interval> you allow libev
		683	to spend more time collecting timeouts, at the expense of increased
		684	latency (the watcher callback will be called later). C<ev_io> watchers
		685	will not be affected. Setting this to a non-null value will not introduce
		686	any overhead in libev.
		687
		688	Many (busy) programs can usually benefit by setting the io collect
		689	interval to a value near C<0.1> or so, which is often enough for
		690	interactive servers (of course not for games), likewise for timeouts. It
		691	usually doesn't make much sense to set it to a lower value than C<0.01>,
		692	as this approsaches the timing granularity of most systems.
252		693
253	=back	694	=back
		695
254		696
255	=head1 ANATOMY OF A WATCHER	697	=head1 ANATOMY OF A WATCHER
256		698
257	A watcher is a structure that you create and register to record your	699	A watcher is a structure that you create and register to record your
258	interest in some event. For instance, if you want to wait for STDIN to	700	interest in some event. For instance, if you want to wait for STDIN to
259	become readable, you would create an ev_io watcher for that:	701	become readable, you would create an C<ev_io> watcher for that:
260		702
261	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
262	{	704	{
263	ev_io_stop (w);	705	ev_io_stop (w);
264	ev_unloop (loop, EVUNLOOP_ALL);	706	ev_unloop (loop, EVUNLOOP_ALL);
…		…
291	*) >>), and you can stop watching for events at any time by calling the	733	*) >>), and you can stop watching for events at any time by calling the
292	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
293		735
294	As long as your watcher is active (has been started but not stopped) you	736	As long as your watcher is active (has been started but not stopped) you
295	must not touch the values stored in it. Most specifically you must never	737	must not touch the values stored in it. Most specifically you must never
296	reinitialise it or call its set method.	738	reinitialise it or call its C<set> macro.
297
298	You cna check whether an event is active by calling the C<ev_is_active
299	(watcher *)> macro. To see whether an event is outstanding (but the
300	callback for it has not been called yet) you cna use the C<ev_is_pending
301	(watcher *)> macro.
302		739
303	Each and every callback receives the event loop pointer as first, the	740	Each and every callback receives the event loop pointer as first, the
304	registered watcher structure as second, and a bitset of received events as	741	registered watcher structure as second, and a bitset of received events as
305	third argument.	742	third argument.
306		743
307	The rceeived events usually include a single bit per event type received	744	The received events usually include a single bit per event type received
308	(you can receive multiple events at the same time). The possible bit masks	745	(you can receive multiple events at the same time). The possible bit masks
309	are:	746	are:
310		747
311	=over 4	748	=over 4
312		749
313	=item EV_READ	750	=item C<EV_READ>
314		751
315	=item EV_WRITE	752	=item C<EV_WRITE>
316		753
317	The file descriptor in the ev_io watcher has become readable and/or	754	The file descriptor in the C<ev_io> watcher has become readable and/or
318	writable.	755	writable.
319		756
320	=item EV_TIMEOUT	757	=item C<EV_TIMEOUT>
321		758
322	The ev_timer watcher has timed out.	759	The C<ev_timer> watcher has timed out.
323		760
324	=item EV_PERIODIC	761	=item C<EV_PERIODIC>
325		762
326	The ev_periodic watcher has timed out.	763	The C<ev_periodic> watcher has timed out.
327		764
328	=item EV_SIGNAL	765	=item C<EV_SIGNAL>
329		766
330	The signal specified in the ev_signal watcher has been received by a thread.	767	The signal specified in the C<ev_signal> watcher has been received by a thread.
331		768
332	=item EV_CHILD	769	=item C<EV_CHILD>
333		770
334	The pid specified in the ev_child watcher has received a status change.	771	The pid specified in the C<ev_child> watcher has received a status change.
335		772
		773	=item C<EV_STAT>
		774
		775	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		776
336	=item EV_IDLE	777	=item C<EV_IDLE>
337		778
338	The ev_idle watcher has determined that you have nothing better to do.	779	The C<ev_idle> watcher has determined that you have nothing better to do.
339		780
340	=item EV_PREPARE	781	=item C<EV_PREPARE>
341		782
342	=item EV_CHECK	783	=item C<EV_CHECK>
343		784
344	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	785	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
345	to gather new events, and all ev_check watchers are invoked just after	786	to gather new events, and all C<ev_check> watchers are invoked just after
346	C<ev_loop> has gathered them, but before it invokes any callbacks for any	787	C<ev_loop> has gathered them, but before it invokes any callbacks for any
347	received events. Callbacks of both watcher types can start and stop as	788	received events. Callbacks of both watcher types can start and stop as
348	many watchers as they want, and all of them will be taken into account	789	many watchers as they want, and all of them will be taken into account
349	(for example, a ev_prepare watcher might start an idle watcher to keep	790	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
350	C<ev_loop> from blocking).	791	C<ev_loop> from blocking).
351		792
		793	=item C<EV_EMBED>
		794
		795	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		796
		797	=item C<EV_FORK>
		798
		799	The event loop has been resumed in the child process after fork (see
		800	C<ev_fork>).
		801
		802	=item C<EV_ASYNC>
		803
		804	The given async watcher has been asynchronously notified (see C<ev_async>).
		805
352	=item EV_ERROR	806	=item C<EV_ERROR>
353		807
354	An unspecified error has occured, the watcher has been stopped. This might	808	An unspecified error has occured, the watcher has been stopped. This might
355	happen because the watcher could not be properly started because libev	809	happen because the watcher could not be properly started because libev
356	ran out of memory, a file descriptor was found to be closed or any other	810	ran out of memory, a file descriptor was found to be closed or any other
357	problem. You best act on it by reporting the problem and somehow coping	811	problem. You best act on it by reporting the problem and somehow coping
…		…
363	with the error from read() or write(). This will not work in multithreaded	817	with the error from read() or write(). This will not work in multithreaded
364	programs, though, so beware.	818	programs, though, so beware.
365		819
366	=back	820	=back
367		821
		822	=head2 GENERIC WATCHER FUNCTIONS
		823
		824	In the following description, C<TYPE> stands for the watcher type,
		825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		826
		827	=over 4
		828
		829	=item C<ev_init> (ev_TYPE *watcher, callback)
		830
		831	This macro initialises the generic portion of a watcher. The contents
		832	of the watcher object can be arbitrary (so C<malloc> will do). Only
		833	the generic parts of the watcher are initialised, you I<need> to call
		834	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		835	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		836	which rolls both calls into one.
		837
		838	You can reinitialise a watcher at any time as long as it has been stopped
		839	(or never started) and there are no pending events outstanding.
		840
		841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		842	int revents)>.
		843
		844	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		845
		846	This macro initialises the type-specific parts of a watcher. You need to
		847	call C<ev_init> at least once before you call this macro, but you can
		848	call C<ev_TYPE_set> any number of times. You must not, however, call this
		849	macro on a watcher that is active (it can be pending, however, which is a
		850	difference to the C<ev_init> macro).
		851
		852	Although some watcher types do not have type-specific arguments
		853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		854
		855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		856
		857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		858	calls into a single call. This is the most convinient method to initialise
		859	a watcher. The same limitations apply, of course.
		860
		861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		862
		863	Starts (activates) the given watcher. Only active watchers will receive
		864	events. If the watcher is already active nothing will happen.
		865
		866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		867
		868	Stops the given watcher again (if active) and clears the pending
		869	status. It is possible that stopped watchers are pending (for example,
		870	non-repeating timers are being stopped when they become pending), but
		871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		872	you want to free or reuse the memory used by the watcher it is therefore a
		873	good idea to always call its C<ev_TYPE_stop> function.
		874
		875	=item bool ev_is_active (ev_TYPE *watcher)
		876
		877	Returns a true value iff the watcher is active (i.e. it has been started
		878	and not yet been stopped). As long as a watcher is active you must not modify
		879	it.
		880
		881	=item bool ev_is_pending (ev_TYPE *watcher)
		882
		883	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		884	events but its callback has not yet been invoked). As long as a watcher
		885	is pending (but not active) you must not call an init function on it (but
		886	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		887	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		888	it).
		889
		890	=item callback ev_cb (ev_TYPE *watcher)
		891
		892	Returns the callback currently set on the watcher.
		893
		894	=item ev_cb_set (ev_TYPE *watcher, callback)
		895
		896	Change the callback. You can change the callback at virtually any time
		897	(modulo threads).
		898
		899	=item ev_set_priority (ev_TYPE *watcher, priority)
		900
		901	=item int ev_priority (ev_TYPE *watcher)
		902
		903	Set and query the priority of the watcher. The priority is a small
		904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		905	(default: C<-2>). Pending watchers with higher priority will be invoked
		906	before watchers with lower priority, but priority will not keep watchers
		907	from being executed (except for C<ev_idle> watchers).
		908
		909	This means that priorities are I<only> used for ordering callback
		910	invocation after new events have been received. This is useful, for
		911	example, to reduce latency after idling, or more often, to bind two
		912	watchers on the same event and make sure one is called first.
		913
		914	If you need to suppress invocation when higher priority events are pending
		915	you need to look at C<ev_idle> watchers, which provide this functionality.
		916
		917	You I<must not> change the priority of a watcher as long as it is active or
		918	pending.
		919
		920	The default priority used by watchers when no priority has been set is
		921	always C<0>, which is supposed to not be too high and not be too low :).
		922
		923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		924	fine, as long as you do not mind that the priority value you query might
		925	or might not have been adjusted to be within valid range.
		926
		927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		928
		929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		930	C<loop> nor C<revents> need to be valid as long as the watcher callback
		931	can deal with that fact.
		932
		933	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		934
		935	If the watcher is pending, this function returns clears its pending status
		936	and returns its C<revents> bitset (as if its callback was invoked). If the
		937	watcher isn't pending it does nothing and returns C<0>.
		938
		939	=back
		940
		941
368	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
369		943
370	Each watcher has, by default, a member C<void *data> that you can change	944	Each watcher has, by default, a member C<void *data> that you can change
371	and read at any time, libev will completely ignore it. This cna be used	945	and read at any time, libev will completely ignore it. This can be used
372	to associate arbitrary data with your watcher. If you need more data and	946	to associate arbitrary data with your watcher. If you need more data and
373	don't want to allocate memory and store a pointer to it in that data	947	don't want to allocate memory and store a pointer to it in that data
374	member, you can also "subclass" the watcher type and provide your own	948	member, you can also "subclass" the watcher type and provide your own
375	data:	949	data:
376		950
…		…
389	{	963	{
390	struct my_io *w = (struct my_io *)w_;	964	struct my_io *w = (struct my_io *)w_;
391	...	965	...
392	}	966	}
393		967
394	More interesting and less C-conformant ways of catsing your callback type	968	More interesting and less C-conformant ways of casting your callback type
395	have been omitted....	969	instead have been omitted.
		970
		971	Another common scenario is having some data structure with multiple
		972	watchers:
		973
		974	struct my_biggy
		975	{
		976	int some_data;
		977	ev_timer t1;
		978	ev_timer t2;
		979	}
		980
		981	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		982	you need to use C<offsetof>:
		983
		984	#include <stddef.h>
		985
		986	static void
		987	t1_cb (EV_P_ struct ev_timer *w, int revents)
		988	{
		989	struct my_biggy big = (struct my_biggy *
		990	(((char *)w) - offsetof (struct my_biggy, t1));
		991	}
		992
		993	static void
		994	t2_cb (EV_P_ struct ev_timer *w, int revents)
		995	{
		996	struct my_biggy big = (struct my_biggy *
		997	(((char *)w) - offsetof (struct my_biggy, t2));
		998	}
396		999
397		1000
398	=head1 WATCHER TYPES	1001	=head1 WATCHER TYPES
399		1002
400	This section describes each watcher in detail, but will not repeat	1003	This section describes each watcher in detail, but will not repeat
401	information given in the last section.	1004	information given in the last section. Any initialisation/set macros,
		1005	functions and members specific to the watcher type are explained.
402		1006
		1007	Members are additionally marked with either I<[read-only]>, meaning that,
		1008	while the watcher is active, you can look at the member and expect some
		1009	sensible content, but you must not modify it (you can modify it while the
		1010	watcher is stopped to your hearts content), or I<[read-write]>, which
		1011	means you can expect it to have some sensible content while the watcher
		1012	is active, but you can also modify it. Modifying it may not do something
		1013	sensible or take immediate effect (or do anything at all), but libev will
		1014	not crash or malfunction in any way.
		1015
		1016
403	=head2 struct ev_io - is my file descriptor readable or writable	1017	=head2 C<ev_io> - is this file descriptor readable or writable?
404		1018
405	I/O watchers check whether a file descriptor is readable or writable	1019	I/O watchers check whether a file descriptor is readable or writable
406	in each iteration of the event loop (This behaviour is called	1020	in each iteration of the event loop, or, more precisely, when reading
407	level-triggering because you keep receiving events as long as the	1021	would not block the process and writing would at least be able to write
408	condition persists. Remember you cna stop the watcher if you don't want to	1022	some data. This behaviour is called level-triggering because you keep
409	act on the event and neither want to receive future events).	1023	receiving events as long as the condition persists. Remember you can stop
		1024	the watcher if you don't want to act on the event and neither want to
		1025	receive future events.
		1026
		1027	In general you can register as many read and/or write event watchers per
		1028	fd as you want (as long as you don't confuse yourself). Setting all file
		1029	descriptors to non-blocking mode is also usually a good idea (but not
		1030	required if you know what you are doing).
		1031
		1032	If you must do this, then force the use of a known-to-be-good backend
		1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		1034	C<EVBACKEND_POLL>).
		1035
		1036	Another thing you have to watch out for is that it is quite easy to
		1037	receive "spurious" readyness notifications, that is your callback might
		1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1039	because there is no data. Not only are some backends known to create a
		1040	lot of those (for example solaris ports), it is very easy to get into
		1041	this situation even with a relatively standard program structure. Thus
		1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1044
		1045	If you cannot run the fd in non-blocking mode (for example you should not
		1046	play around with an Xlib connection), then you have to seperately re-test
		1047	whether a file descriptor is really ready with a known-to-be good interface
		1048	such as poll (fortunately in our Xlib example, Xlib already does this on
		1049	its own, so its quite safe to use).
		1050
		1051	=head3 The special problem of disappearing file descriptors
		1052
		1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1054	descriptor (either by calling C<close> explicitly or by any other means,
		1055	such as C<dup>). The reason is that you register interest in some file
		1056	descriptor, but when it goes away, the operating system will silently drop
		1057	this interest. If another file descriptor with the same number then is
		1058	registered with libev, there is no efficient way to see that this is, in
		1059	fact, a different file descriptor.
		1060
		1061	To avoid having to explicitly tell libev about such cases, libev follows
		1062	the following policy: Each time C<ev_io_set> is being called, libev
		1063	will assume that this is potentially a new file descriptor, otherwise
		1064	it is assumed that the file descriptor stays the same. That means that
		1065	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1066	descriptor even if the file descriptor number itself did not change.
		1067
		1068	This is how one would do it normally anyway, the important point is that
		1069	the libev application should not optimise around libev but should leave
		1070	optimisations to libev.
		1071
		1072	=head3 The special problem of dup'ed file descriptors
		1073
		1074	Some backends (e.g. epoll), cannot register events for file descriptors,
		1075	but only events for the underlying file descriptions. That means when you
		1076	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1077	events for them, only one file descriptor might actually receive events.
		1078
		1079	There is no workaround possible except not registering events
		1080	for potentially C<dup ()>'ed file descriptors, or to resort to
		1081	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1082
		1083	=head3 The special problem of fork
		1084
		1085	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1086	useless behaviour. Libev fully supports fork, but needs to be told about
		1087	it in the child.
		1088
		1089	To support fork in your programs, you either have to call
		1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1092	C<EVBACKEND_POLL>.
		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
		1106
		1107	=head3 Watcher-Specific Functions
410		1108
411	=over 4	1109	=over 4
412		1110
413	=item ev_io_init (ev_io *, callback, int fd, int events)	1111	=item ev_io_init (ev_io *, callback, int fd, int events)
414		1112
415	=item ev_io_set (ev_io *, int fd, int events)	1113	=item ev_io_set (ev_io *, int fd, int events)
416		1114
417	Configures an ev_io watcher. The fd is the file descriptor to rceeive	1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
418	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
419	EV_WRITE> to receive the given events.	1117	C<EV_READ | EV_WRITE> to receive the given events.
		1118
		1119	=item int fd [read-only]
		1120
		1121	The file descriptor being watched.
		1122
		1123	=item int events [read-only]
		1124
		1125	The events being watched.
420		1126
421	=back	1127	=back
422		1128
		1129	=head3 Examples
		1130
		1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1132	readable, but only once. Since it is likely line-buffered, you could
		1133	attempt to read a whole line in the callback.
		1134
		1135	static void
		1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1137	{
		1138	ev_io_stop (loop, w);
		1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1140	}
		1141
		1142	...
		1143	struct ev_loop *loop = ev_default_init (0);
		1144	struct ev_io stdin_readable;
		1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1146	ev_io_start (loop, &stdin_readable);
		1147	ev_loop (loop, 0);
		1148
		1149
423	=head2 struct ev_timer - relative and optionally recurring timeouts	1150	=head2 C<ev_timer> - relative and optionally repeating timeouts
424		1151
425	Timer watchers are simple relative timers that generate an event after a	1152	Timer watchers are simple relative timers that generate an event after a
426	given time, and optionally repeating in regular intervals after that.	1153	given time, and optionally repeating in regular intervals after that.
427		1154
428	The timers are based on real time, that is, if you register an event that	1155	The timers are based on real time, that is, if you register an event that
429	times out after an hour and youreset your system clock to last years	1156	times out after an hour and you reset your system clock to last years
430	time, it will still time out after (roughly) and hour. "Roughly" because	1157	time, it will still time out after (roughly) and hour. "Roughly" because
431	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the
432	monotonic clock option helps a lot here).	1159	monotonic clock option helps a lot here).
		1160
		1161	The relative timeouts are calculated relative to the C<ev_now ()>
		1162	time. This is usually the right thing as this timestamp refers to the time
		1163	of the event triggering whatever timeout you are modifying/starting. If
		1164	you suspect event processing to be delayed and you I<need> to base the timeout
		1165	on the current time, use something like this to adjust for this:
		1166
		1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1168
		1169	The callback is guarenteed to be invoked only when its timeout has passed,
		1170	but if multiple timers become ready during the same loop iteration then
		1171	order of execution is undefined.
		1172
		1173	=head3 Watcher-Specific Functions and Data Members
433		1174
434	=over 4	1175	=over 4
435		1176
436	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
437		1178
…		…
443	later, again, and again, until stopped manually.	1184	later, again, and again, until stopped manually.
444		1185
445	The timer itself will do a best-effort at avoiding drift, that is, if you	1186	The timer itself will do a best-effort at avoiding drift, that is, if you
446	configure a timer to trigger every 10 seconds, then it will trigger at	1187	configure a timer to trigger every 10 seconds, then it will trigger at
447	exactly 10 second intervals. If, however, your program cannot keep up with	1188	exactly 10 second intervals. If, however, your program cannot keep up with
448	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1189	the timer (because it takes longer than those 10 seconds to do stuff) the
449	timer will not fire more than once per event loop iteration.	1190	timer will not fire more than once per event loop iteration.
450		1191
451	=item ev_timer_again (loop)	1192	=item ev_timer_again (loop, ev_timer *)
452		1193
453	This will act as if the timer timed out and restart it again if it is	1194	This will act as if the timer timed out and restart it again if it is
454	repeating. The exact semantics are:	1195	repeating. The exact semantics are:
455		1196
		1197	If the timer is pending, its pending status is cleared.
		1198
456	If the timer is started but nonrepeating, stop it.	1199	If the timer is started but nonrepeating, stop it (as if it timed out).
457		1200
458	If the timer is repeating, either start it if necessary (with the repeat	1201	If the timer is repeating, either start it if necessary (with the
459	value), or reset the running timer to the repeat value.	1202	C<repeat> value), or reset the running timer to the C<repeat> value.
460		1203
461	This sounds a bit complicated, but here is a useful and typical	1204	This sounds a bit complicated, but here is a useful and typical
462	example: Imagine you have a tcp connection and you want a so-called idle	1205	example: Imagine you have a tcp connection and you want a so-called idle
463	timeout, that is, you want to be called when there have been, say, 60	1206	timeout, that is, you want to be called when there have been, say, 60
464	seconds of inactivity on the socket. The easiest way to do this is to	1207	seconds of inactivity on the socket. The easiest way to do this is to
465	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
466	time you successfully read or write some data. If you go into an idle	1209	C<ev_timer_again> each time you successfully read or write some data. If
467	state where you do not expect data to travel on the socket, you can stop	1210	you go into an idle state where you do not expect data to travel on the
468	the timer, and again will automatically restart it if need be.	1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1212	automatically restart it if need be.
		1213
		1214	That means you can ignore the C<after> value and C<ev_timer_start>
		1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1216
		1217	ev_timer_init (timer, callback, 0., 5.);
		1218	ev_timer_again (loop, timer);
		1219	...
		1220	timer->again = 17.;
		1221	ev_timer_again (loop, timer);
		1222	...
		1223	timer->again = 10.;
		1224	ev_timer_again (loop, timer);
		1225
		1226	This is more slightly efficient then stopping/starting the timer each time
		1227	you want to modify its timeout value.
		1228
		1229	=item ev_tstamp repeat [read-write]
		1230
		1231	The current C<repeat> value. Will be used each time the watcher times out
		1232	or C<ev_timer_again> is called and determines the next timeout (if any),
		1233	which is also when any modifications are taken into account.
469		1234
470	=back	1235	=back
471		1236
		1237	=head3 Examples
		1238
		1239	Example: Create a timer that fires after 60 seconds.
		1240
		1241	static void
		1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1243	{
		1244	.. one minute over, w is actually stopped right here
		1245	}
		1246
		1247	struct ev_timer mytimer;
		1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1249	ev_timer_start (loop, &mytimer);
		1250
		1251	Example: Create a timeout timer that times out after 10 seconds of
		1252	inactivity.
		1253
		1254	static void
		1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1256	{
		1257	.. ten seconds without any activity
		1258	}
		1259
		1260	struct ev_timer mytimer;
		1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1262	ev_timer_again (&mytimer); /* start timer */
		1263	ev_loop (loop, 0);
		1264
		1265	// and in some piece of code that gets executed on any "activity":
		1266	// reset the timeout to start ticking again at 10 seconds
		1267	ev_timer_again (&mytimer);
		1268
		1269
472	=head2 ev_periodic - to cron or not to cron it	1270	=head2 C<ev_periodic> - to cron or not to cron?
473		1271
474	Periodic watchers are also timers of a kind, but they are very versatile	1272	Periodic watchers are also timers of a kind, but they are very versatile
475	(and unfortunately a bit complex).	1273	(and unfortunately a bit complex).
476		1274
477	Unlike ev_timer's, they are not based on real time (or relative time)	1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
478	but on wallclock time (absolute time). You can tell a periodic watcher	1276	but on wallclock time (absolute time). You can tell a periodic watcher
479	to trigger "at" some specific point in time. For example, if you tell a	1277	to trigger "at" some specific point in time. For example, if you tell a
480	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
481	+ 10.>) and then reset your system clock to the last year, then it will	1279	+ 10.>) and then reset your system clock to the last year, then it will
482	take a year to trigger the event (unlike an ev_timer, which would trigger	1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
483	roughly 10 seconds later and of course not if you reset your system time	1281	roughly 10 seconds later).
484	again).
485		1282
486	They can also be used to implement vastly more complex timers, such as	1283	They can also be used to implement vastly more complex timers, such as
487	triggering an event on eahc midnight, local time.	1284	triggering an event on each midnight, local time or other, complicated,
		1285	rules.
		1286
		1287	As with timers, the callback is guarenteed to be invoked only when the
		1288	time (C<at>) has been passed, but if multiple periodic timers become ready
		1289	during the same loop iteration then order of execution is undefined.
		1290
		1291	=head3 Watcher-Specific Functions and Data Members
488		1292
489	=over 4	1293	=over 4
490		1294
491	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
492		1296
493	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
494		1298
495	Lots of arguments, lets sort it out... There are basically three modes of	1299	Lots of arguments, lets sort it out... There are basically three modes of
496	operation, and we will explain them from simplest to complex:	1300	operation, and we will explain them from simplest to complex:
497		1301
498
499	=over 4	1302	=over 4
500		1303
501	=item * absolute timer (interval = reschedule_cb = 0)	1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)
502		1305
503	In this configuration the watcher triggers an event at the wallclock time	1306	In this configuration the watcher triggers an event at the wallclock time
504	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
505	that is, if it is to be run at January 1st 2011 then it will run when the	1308	that is, if it is to be run at January 1st 2011 then it will run when the
506	system time reaches or surpasses this time.	1309	system time reaches or surpasses this time.
507		1310
508	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
509		1312
510	In this mode the watcher will always be scheduled to time out at the next	1313	In this mode the watcher will always be scheduled to time out at the next
511	C<at + N * interval> time (for some integer N) and then repeat, regardless	1314	C<at + N * interval> time (for some integer N, which can also be negative)
512	of any time jumps.	1315	and then repeat, regardless of any time jumps.
513		1316
514	This can be used to create timers that do not drift with respect to system	1317	This can be used to create timers that do not drift with respect to system
515	time:	1318	time:
516		1319
517	ev_periodic_set (&periodic, 0., 3600., 0);	1320	ev_periodic_set (&periodic, 0., 3600., 0);
518		1321
519	This doesn't mean there will always be 3600 seconds in between triggers,	1322	This doesn't mean there will always be 3600 seconds in between triggers,
520	but only that the the callback will be called when the system time shows a	1323	but only that the the callback will be called when the system time shows a
521	full hour (UTC), or more correct, when the system time is evenly divisible	1324	full hour (UTC), or more correctly, when the system time is evenly divisible
522	by 3600.	1325	by 3600.
523		1326
524	Another way to think about it (for the mathematically inclined) is that	1327	Another way to think about it (for the mathematically inclined) is that
525	ev_periodic will try to run the callback in this mode at the next possible	1328	C<ev_periodic> will try to run the callback in this mode at the next possible
526	time where C<time = at (mod interval)>, regardless of any time jumps.	1329	time where C<time = at (mod interval)>, regardless of any time jumps.
527		1330
		1331	For numerical stability it is preferable that the C<at> value is near
		1332	C<ev_now ()> (the current time), but there is no range requirement for
		1333	this value.
		1334
528	=item * manual reschedule mode (reschedule_cb = callback)	1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
529		1336
530	In this mode the values for C<interval> and C<at> are both being	1337	In this mode the values for C<interval> and C<at> are both being
531	ignored. Instead, each time the periodic watcher gets scheduled, the	1338	ignored. Instead, each time the periodic watcher gets scheduled, the
532	reschedule callback will be called with the watcher as first, and the	1339	reschedule callback will be called with the watcher as first, and the
533	current time as second argument.	1340	current time as second argument.
534		1341
535	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
536	periodic watcher, ever, or make any event loop modificstions>. If you need	1343	ever, or make any event loop modifications>. If you need to stop it,
537	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1345	starting an C<ev_prepare> watcher, which is legal).
538		1346
539	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
540	ev_tstamp now)>, e.g.:	1348	ev_tstamp now)>, e.g.:
541		1349
542	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
543	{	1351	{
544	return now + 60.;	1352	return now + 60.;
…		…
547	It must return the next time to trigger, based on the passed time value	1355	It must return the next time to trigger, based on the passed time value
548	(that is, the lowest time value larger than to the second argument). It	1356	(that is, the lowest time value larger than to the second argument). It
549	will usually be called just before the callback will be triggered, but	1357	will usually be called just before the callback will be triggered, but
550	might be called at other times, too.	1358	might be called at other times, too.
551		1359
		1360	NOTE: I<< This callback must always return a time that is later than the
		1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1362
552	This can be used to create very complex timers, such as a timer that	1363	This can be used to create very complex timers, such as a timer that
553	triggers on each midnight, local time. To do this, you would calculate the	1364	triggers on each midnight, local time. To do this, you would calculate the
554	next midnight after C<now> and return the timestamp value for this. How you do this	1365	next midnight after C<now> and return the timestamp value for this. How
555	is, again, up to you (but it is not trivial).	1366	you do this is, again, up to you (but it is not trivial, which is the main
		1367	reason I omitted it as an example).
556		1368
557	=back	1369	=back
558		1370
559	=item ev_periodic_again (loop, ev_periodic *)	1371	=item ev_periodic_again (loop, ev_periodic *)
560		1372
561	Simply stops and restarts the periodic watcher again. This is only useful	1373	Simply stops and restarts the periodic watcher again. This is only useful
562	when you changed some parameters or the reschedule callback would return	1374	when you changed some parameters or the reschedule callback would return
563	a different time than the last time it was called (e.g. in a crond like	1375	a different time than the last time it was called (e.g. in a crond like
564	program when the crontabs have changed).	1376	program when the crontabs have changed).
565		1377
		1378	=item ev_tstamp offset [read-write]
		1379
		1380	When repeating, this contains the offset value, otherwise this is the
		1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1382
		1383	Can be modified any time, but changes only take effect when the periodic
		1384	timer fires or C<ev_periodic_again> is being called.
		1385
		1386	=item ev_tstamp interval [read-write]
		1387
		1388	The current interval value. Can be modified any time, but changes only
		1389	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1390	called.
		1391
		1392	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1393
		1394	The current reschedule callback, or C<0>, if this functionality is
		1395	switched off. Can be changed any time, but changes only take effect when
		1396	the periodic timer fires or C<ev_periodic_again> is being called.
		1397
		1398	=item ev_tstamp at [read-only]
		1399
		1400	When active, contains the absolute time that the watcher is supposed to
		1401	trigger next.
		1402
566	=back	1403	=back
567		1404
		1405	=head3 Examples
		1406
		1407	Example: Call a callback every hour, or, more precisely, whenever the
		1408	system clock is divisible by 3600. The callback invocation times have
		1409	potentially a lot of jittering, but good long-term stability.
		1410
		1411	static void
		1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1413	{
		1414	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1415	}
		1416
		1417	struct ev_periodic hourly_tick;
		1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1419	ev_periodic_start (loop, &hourly_tick);
		1420
		1421	Example: The same as above, but use a reschedule callback to do it:
		1422
		1423	#include <math.h>
		1424
		1425	static ev_tstamp
		1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1427	{
		1428	return fmod (now, 3600.) + 3600.;
		1429	}
		1430
		1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1432
		1433	Example: Call a callback every hour, starting now:
		1434
		1435	struct ev_periodic hourly_tick;
		1436	ev_periodic_init (&hourly_tick, clock_cb,
		1437	fmod (ev_now (loop), 3600.), 3600., 0);
		1438	ev_periodic_start (loop, &hourly_tick);
		1439
		1440
568	=head2 ev_signal - signal me when a signal gets signalled	1441	=head2 C<ev_signal> - signal me when a signal gets signalled!
569		1442
570	Signal watchers will trigger an event when the process receives a specific	1443	Signal watchers will trigger an event when the process receives a specific
571	signal one or more times. Even though signals are very asynchronous, libev	1444	signal one or more times. Even though signals are very asynchronous, libev
572	will try its best to deliver signals synchronously, i.e. as part of the	1445	will try it's best to deliver signals synchronously, i.e. as part of the
573	normal event processing, like any other event.	1446	normal event processing, like any other event.
574		1447
575	You cna configure as many watchers as you like per signal. Only when the	1448	You can configure as many watchers as you like per signal. Only when the
576	first watcher gets started will libev actually register a signal watcher	1449	first watcher gets started will libev actually register a signal watcher
577	with the kernel (thus it coexists with your own signal handlers as long	1450	with the kernel (thus it coexists with your own signal handlers as long
578	as you don't register any with libev). Similarly, when the last signal	1451	as you don't register any with libev). Similarly, when the last signal
579	watcher for a signal is stopped libev will reset the signal handler to	1452	watcher for a signal is stopped libev will reset the signal handler to
580	SIG_DFL (regardless of what it was set to before).	1453	SIG_DFL (regardless of what it was set to before).
581		1454
		1455	If possible and supported, libev will install its handlers with
		1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1457	interrupted. If you have a problem with syscalls getting interrupted by
		1458	signals you can block all signals in an C<ev_check> watcher and unblock
		1459	them in an C<ev_prepare> watcher.
		1460
		1461	=head3 Watcher-Specific Functions and Data Members
		1462
582	=over 4	1463	=over 4
583		1464
584	=item ev_signal_init (ev_signal *, callback, int signum)	1465	=item ev_signal_init (ev_signal *, callback, int signum)
585		1466
586	=item ev_signal_set (ev_signal *, int signum)	1467	=item ev_signal_set (ev_signal *, int signum)
587		1468
588	Configures the watcher to trigger on the given signal number (usually one	1469	Configures the watcher to trigger on the given signal number (usually one
589	of the C<SIGxxx> constants).	1470	of the C<SIGxxx> constants).
590		1471
		1472	=item int signum [read-only]
		1473
		1474	The signal the watcher watches out for.
		1475
591	=back	1476	=back
592		1477
		1478	=head3 Examples
		1479
		1480	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1481
		1482	static void
		1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1484	{
		1485	ev_unloop (loop, EVUNLOOP_ALL);
		1486	}
		1487
		1488	struct ev_signal signal_watcher;
		1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1490	ev_signal_start (loop, &sigint_cb);
		1491
		1492
593	=head2 ev_child - wait for pid status changes	1493	=head2 C<ev_child> - watch out for process status changes
594		1494
595	Child watchers trigger when your process receives a SIGCHLD in response to	1495	Child watchers trigger when your process receives a SIGCHLD in response to
596	some child status changes (most typically when a child of yours dies).	1496	some child status changes (most typically when a child of yours dies). It
		1497	is permissible to install a child watcher I<after> the child has been
		1498	forked (which implies it might have already exited), as long as the event
		1499	loop isn't entered (or is continued from a watcher).
		1500
		1501	Only the default event loop is capable of handling signals, and therefore
		1502	you can only rgeister child watchers in the default event loop.
		1503
		1504	=head3 Process Interaction
		1505
		1506	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1507	initialised. This is necessary to guarantee proper behaviour even if
		1508	the first child watcher is started after the child exits. The occurance
		1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1510	synchronously as part of the event loop processing. Libev always reaps all
		1511	children, even ones not watched.
		1512
		1513	=head3 Overriding the Built-In Processing
		1514
		1515	Libev offers no special support for overriding the built-in child
		1516	processing, but if your application collides with libev's default child
		1517	handler, you can override it easily by installing your own handler for
		1518	C<SIGCHLD> after initialising the default loop, and making sure the
		1519	default loop never gets destroyed. You are encouraged, however, to use an
		1520	event-based approach to child reaping and thus use libev's support for
		1521	that, so other libev users can use C<ev_child> watchers freely.
		1522
		1523	=head3 Watcher-Specific Functions and Data Members
597		1524
598	=over 4	1525	=over 4
599		1526
600	=item ev_child_init (ev_child *, callback, int pid)	1527	=item ev_child_init (ev_child *, callback, int pid, int trace)
601		1528
602	=item ev_child_set (ev_child *, int pid)	1529	=item ev_child_set (ev_child *, int pid, int trace)
603		1530
604	Configures the watcher to wait for status changes of process C<pid> (or	1531	Configures the watcher to wait for status changes of process C<pid> (or
605	I<any> process if C<pid> is specified as C<0>). The callback can look	1532	I<any> process if C<pid> is specified as C<0>). The callback can look
606	at the C<rstatus> member of the C<ev_child> watcher structure to see	1533	at the C<rstatus> member of the C<ev_child> watcher structure to see
607	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1534	the status word (use the macros from C<sys/wait.h> and see your systems
608	contains the pid of the process causing the status change.	1535	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1536	process causing the status change. C<trace> must be either C<0> (only
		1537	activate the watcher when the process terminates) or C<1> (additionally
		1538	activate the watcher when the process is stopped or continued).
		1539
		1540	=item int pid [read-only]
		1541
		1542	The process id this watcher watches out for, or C<0>, meaning any process id.
		1543
		1544	=item int rpid [read-write]
		1545
		1546	The process id that detected a status change.
		1547
		1548	=item int rstatus [read-write]
		1549
		1550	The process exit/trace status caused by C<rpid> (see your systems
		1551	C<waitpid> and C<sys/wait.h> documentation for details).
609		1552
610	=back	1553	=back
611		1554
		1555	=head3 Examples
		1556
		1557	Example: C<fork()> a new process and install a child handler to wait for
		1558	its completion.
		1559
		1560	ev_child cw;
		1561
		1562	static void
		1563	child_cb (EV_P_ struct ev_child *w, int revents)
		1564	{
		1565	ev_child_stop (EV_A_ w);
		1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1567	}
		1568
		1569	pid_t pid = fork ();
		1570
		1571	if (pid < 0)
		1572	// error
		1573	else if (pid == 0)
		1574	{
		1575	// the forked child executes here
		1576	exit (1);
		1577	}
		1578	else
		1579	{
		1580	ev_child_init (&cw, child_cb, pid, 0);
		1581	ev_child_start (EV_DEFAULT_ &cw);
		1582	}
		1583
		1584
		1585	=head2 C<ev_stat> - did the file attributes just change?
		1586
		1587	This watches a filesystem path for attribute changes. That is, it calls
		1588	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1589	compared to the last time, invoking the callback if it did.
		1590
		1591	The path does not need to exist: changing from "path exists" to "path does
		1592	not exist" is a status change like any other. The condition "path does
		1593	not exist" is signified by the C<st_nlink> field being zero (which is
		1594	otherwise always forced to be at least one) and all the other fields of
		1595	the stat buffer having unspecified contents.
		1596
		1597	The path I<should> be absolute and I<must not> end in a slash. If it is
		1598	relative and your working directory changes, the behaviour is undefined.
		1599
		1600	Since there is no standard to do this, the portable implementation simply
		1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1602	can specify a recommended polling interval for this case. If you specify
		1603	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1604	unspecified default> value will be used (which you can expect to be around
		1605	five seconds, although this might change dynamically). Libev will also
		1606	impose a minimum interval which is currently around C<0.1>, but thats
		1607	usually overkill.
		1608
		1609	This watcher type is not meant for massive numbers of stat watchers,
		1610	as even with OS-supported change notifications, this can be
		1611	resource-intensive.
		1612
		1613	At the time of this writing, only the Linux inotify interface is
		1614	implemented (implementing kqueue support is left as an exercise for the
		1615	reader). Inotify will be used to give hints only and should not change the
		1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1617	to fall back to regular polling again even with inotify, but changes are
		1618	usually detected immediately, and if the file exists there will be no
		1619	polling.
		1620
		1621	=head3 ABI Issues (Largefile Support)
		1622
		1623	Libev by default (unless the user overrides this) uses the default
		1624	compilation environment, which means that on systems with optionally
		1625	disabled large file support, you get the 32 bit version of the stat
		1626	structure. When using the library from programs that change the ABI to
		1627	use 64 bit file offsets the programs will fail. In that case you have to
		1628	compile libev with the same flags to get binary compatibility. This is
		1629	obviously the case with any flags that change the ABI, but the problem is
		1630	most noticably with ev_stat and largefile support.
		1631
		1632	=head3 Inotify
		1633
		1634	When C<inotify (7)> support has been compiled into libev (generally only
		1635	available on Linux) and present at runtime, it will be used to speed up
		1636	change detection where possible. The inotify descriptor will be created lazily
		1637	when the first C<ev_stat> watcher is being started.
		1638
		1639	Inotify presence does not change the semantics of C<ev_stat> watchers
		1640	except that changes might be detected earlier, and in some cases, to avoid
		1641	making regular C<stat> calls. Even in the presence of inotify support
		1642	there are many cases where libev has to resort to regular C<stat> polling.
		1643
		1644	(There is no support for kqueue, as apparently it cannot be used to
		1645	implement this functionality, due to the requirement of having a file
		1646	descriptor open on the object at all times).
		1647
		1648	=head3 The special problem of stat time resolution
		1649
		1650	The C<stat ()> syscall only supports full-second resolution portably, and
		1651	even on systems where the resolution is higher, many filesystems still
		1652	only support whole seconds.
		1653
		1654	That means that, if the time is the only thing that changes, you might
		1655	miss updates: on the first update, C<ev_stat> detects a change and calls
		1656	your callback, which does something. When there is another update within
		1657	the same second, C<ev_stat> will be unable to detect it.
		1658
		1659	The solution to this is to delay acting on a change for a second (or till
		1660	the next second boundary), using a roughly one-second delay C<ev_timer>
		1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1662	is added to work around small timing inconsistencies of some operating
		1663	systems.
		1664
		1665	=head3 Watcher-Specific Functions and Data Members
		1666
		1667	=over 4
		1668
		1669	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1670
		1671	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1672
		1673	Configures the watcher to wait for status changes of the given
		1674	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1675	be detected and should normally be specified as C<0> to let libev choose
		1676	a suitable value. The memory pointed to by C<path> must point to the same
		1677	path for as long as the watcher is active.
		1678
		1679	The callback will be receive C<EV_STAT> when a change was detected,
		1680	relative to the attributes at the time the watcher was started (or the
		1681	last change was detected).
		1682
		1683	=item ev_stat_stat (loop, ev_stat *)
		1684
		1685	Updates the stat buffer immediately with new values. If you change the
		1686	watched path in your callback, you could call this fucntion to avoid
		1687	detecting this change (while introducing a race condition). Can also be
		1688	useful simply to find out the new values.
		1689
		1690	=item ev_statdata attr [read-only]
		1691
		1692	The most-recently detected attributes of the file. Although the type is of
		1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1694	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1695	was some error while C<stat>ing the file.
		1696
		1697	=item ev_statdata prev [read-only]
		1698
		1699	The previous attributes of the file. The callback gets invoked whenever
		1700	C<prev> != C<attr>.
		1701
		1702	=item ev_tstamp interval [read-only]
		1703
		1704	The specified interval.
		1705
		1706	=item const char *path [read-only]
		1707
		1708	The filesystem path that is being watched.
		1709
		1710	=back
		1711
		1712	=head3 Examples
		1713
		1714	Example: Watch C</etc/passwd> for attribute changes.
		1715
		1716	static void
		1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1718	{
		1719	/* /etc/passwd changed in some way */
		1720	if (w->attr.st_nlink)
		1721	{
		1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1725	}
		1726	else
		1727	/* you shalt not abuse printf for puts */
		1728	puts ("wow, /etc/passwd is not there, expect problems. "
		1729	"if this is windows, they already arrived\n");
		1730	}
		1731
		1732	...
		1733	ev_stat passwd;
		1734
		1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1736	ev_stat_start (loop, &passwd);
		1737
		1738	Example: Like above, but additionally use a one-second delay so we do not
		1739	miss updates (however, frequent updates will delay processing, too, so
		1740	one might do the work both on C<ev_stat> callback invocation I<and> on
		1741	C<ev_timer> callback invocation).
		1742
		1743	static ev_stat passwd;
		1744	static ev_timer timer;
		1745
		1746	static void
		1747	timer_cb (EV_P_ ev_timer *w, int revents)
		1748	{
		1749	ev_timer_stop (EV_A_ w);
		1750
		1751	/* now it's one second after the most recent passwd change */
		1752	}
		1753
		1754	static void
		1755	stat_cb (EV_P_ ev_stat *w, int revents)
		1756	{
		1757	/* reset the one-second timer */
		1758	ev_timer_again (EV_A_ &timer);
		1759	}
		1760
		1761	...
		1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1763	ev_stat_start (loop, &passwd);
		1764	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1765
		1766
612	=head2 ev_idle - when you've got nothing better to do	1767	=head2 C<ev_idle> - when you've got nothing better to do...
613		1768
614	Idle watchers trigger events when there are no other I/O or timer (or	1769	Idle watchers trigger events when no other events of the same or higher
615	periodic) events pending. That is, as long as your process is busy	1770	priority are pending (prepare, check and other idle watchers do not
616	handling sockets or timeouts it will not be called. But when your process	1771	count).
617	is idle all idle watchers are being called again and again - until	1772
		1773	That is, as long as your process is busy handling sockets or timeouts
		1774	(or even signals, imagine) of the same or higher priority it will not be
		1775	triggered. But when your process is idle (or only lower-priority watchers
		1776	are pending), the idle watchers are being called once per event loop
618	stopped, that is, or your process receives more events.	1777	iteration - until stopped, that is, or your process receives more events
		1778	and becomes busy again with higher priority stuff.
619		1779
620	The most noteworthy effect is that as long as any idle watchers are	1780	The most noteworthy effect is that as long as any idle watchers are
621	active, the process will not block when waiting for new events.	1781	active, the process will not block when waiting for new events.
622		1782
623	Apart from keeping your process non-blocking (which is a useful	1783	Apart from keeping your process non-blocking (which is a useful
624	effect on its own sometimes), idle watchers are a good place to do	1784	effect on its own sometimes), idle watchers are a good place to do
625	"pseudo-background processing", or delay processing stuff to after the	1785	"pseudo-background processing", or delay processing stuff to after the
626	event loop has handled all outstanding events.	1786	event loop has handled all outstanding events.
627		1787
		1788	=head3 Watcher-Specific Functions and Data Members
		1789
628	=over 4	1790	=over 4
629		1791
630	=item ev_idle_init (ev_signal *, callback)	1792	=item ev_idle_init (ev_signal *, callback)
631		1793
632	Initialises and configures the idle watcher - it has no parameters of any	1794	Initialises and configures the idle watcher - it has no parameters of any
633	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
634	believe me.	1796	believe me.
635		1797
636	=back	1798	=back
637		1799
638	=head2 prepare and check - your hooks into the event loop	1800	=head3 Examples
639		1801
		1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1803	callback, free it. Also, use no error checking, as usual.
		1804
		1805	static void
		1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1807	{
		1808	free (w);
		1809	// now do something you wanted to do when the program has
		1810	// no longer anything immediate to do.
		1811	}
		1812
		1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1814	ev_idle_init (idle_watcher, idle_cb);
		1815	ev_idle_start (loop, idle_cb);
		1816
		1817
		1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1819
640	Prepare and check watchers usually (but not always) are used in	1820	Prepare and check watchers are usually (but not always) used in tandem:
641	tandom. Prepare watchers get invoked before the process blocks and check	1821	prepare watchers get invoked before the process blocks and check watchers
642	watchers afterwards.	1822	afterwards.
643		1823
		1824	You I<must not> call C<ev_loop> or similar functions that enter
		1825	the current event loop from either C<ev_prepare> or C<ev_check>
		1826	watchers. Other loops than the current one are fine, however. The
		1827	rationale behind this is that you do not need to check for recursion in
		1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1829	C<ev_check> so if you have one watcher of each kind they will always be
		1830	called in pairs bracketing the blocking call.
		1831
644	Their main purpose is to integrate other event mechanisms into libev. This	1832	Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1833	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.	1834	variable changes, implement your own watchers, integrate net-snmp or a
		1835	coroutine library and lots more. They are also occasionally useful if
		1836	you cache some data and want to flush it before blocking (for example,
		1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1838	watcher).
647		1839
648	This is done by examining in each prepare call which file descriptors need	1840	This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1841	to be watched by the other library, registering C<ev_io> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1843	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1844	any events that occured (by checking the pending status of all watchers
653	and call back into the library.	1845	and stopping them) and call back into the library. The I/O and timer
		1846	callbacks will never actually be called (but must be valid nevertheless,
		1847	because you never know, you know?).
654		1848
655	As another example, the perl Coro module uses these hooks to integrate	1849	As another example, the Perl Coro module uses these hooks to integrate
656	coroutines into libev programs, by yielding to other active coroutines	1850	coroutines into libev programs, by yielding to other active coroutines
657	during each prepare and only letting the process block if no coroutines	1851	during each prepare and only letting the process block if no coroutines
658	are ready to run.	1852	are ready to run (it's actually more complicated: it only runs coroutines
		1853	with priority higher than or equal to the event loop and one coroutine
		1854	of lower priority, but only once, using idle watchers to keep the event
		1855	loop from blocking if lower-priority coroutines are active, thus mapping
		1856	low-priority coroutines to idle/background tasks).
		1857
		1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1859	priority, to ensure that they are being run before any other watchers
		1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1861	too) should not activate ("feed") events into libev. While libev fully
		1862	supports this, they will be called before other C<ev_check> watchers
		1863	did their job. As C<ev_check> watchers are often used to embed other
		1864	(non-libev) event loops those other event loops might be in an unusable
		1865	state until their C<ev_check> watcher ran (always remind yourself to
		1866	coexist peacefully with others).
		1867
		1868	=head3 Watcher-Specific Functions and Data Members
659		1869
660	=over 4	1870	=over 4
661		1871
662	=item ev_prepare_init (ev_prepare *, callback)	1872	=item ev_prepare_init (ev_prepare *, callback)
663		1873
664	=item ev_check_init (ev_check *, callback)	1874	=item ev_check_init (ev_check *, callback)
665		1875
666	Initialises and configures the prepare or check watcher - they have no	1876	Initialises and configures the prepare or check watcher - they have no
667	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
668	macros, but using them is utterly, utterly pointless.	1878	macros, but using them is utterly, utterly and completely pointless.
669		1879
670	=back	1880	=back
671		1881
		1882	=head3 Examples
		1883
		1884	There are a number of principal ways to embed other event loops or modules
		1885	into libev. Here are some ideas on how to include libadns into libev
		1886	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1887	use for an actually working example. Another Perl module named C<EV::Glib>
		1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1889	into the Glib event loop).
		1890
		1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1892	and in a check watcher, destroy them and call into libadns. What follows
		1893	is pseudo-code only of course. This requires you to either use a low
		1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1895	the callbacks for the IO/timeout watchers might not have been called yet.
		1896
		1897	static ev_io iow [nfd];
		1898	static ev_timer tw;
		1899
		1900	static void
		1901	io_cb (ev_loop *loop, ev_io *w, int revents)
		1902	{
		1903	}
		1904
		1905	// create io watchers for each fd and a timer before blocking
		1906	static void
		1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1908	{
		1909	int timeout = 3600000;
		1910	struct pollfd fds [nfd];
		1911	// actual code will need to loop here and realloc etc.
		1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1913
		1914	/* the callback is illegal, but won't be called as we stop during check */
		1915	ev_timer_init (&tw, 0, timeout * 1e-3);
		1916	ev_timer_start (loop, &tw);
		1917
		1918	// create one ev_io per pollfd
		1919	for (int i = 0; i < nfd; ++i)
		1920	{
		1921	ev_io_init (iow + i, io_cb, fds [i].fd,
		1922	((fds [i].events & POLLIN ? EV_READ : 0)
		1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1924
		1925	fds [i].revents = 0;
		1926	ev_io_start (loop, iow + i);
		1927	}
		1928	}
		1929
		1930	// stop all watchers after blocking
		1931	static void
		1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1933	{
		1934	ev_timer_stop (loop, &tw);
		1935
		1936	for (int i = 0; i < nfd; ++i)
		1937	{
		1938	// set the relevant poll flags
		1939	// could also call adns_processreadable etc. here
		1940	struct pollfd *fd = fds + i;
		1941	int revents = ev_clear_pending (iow + i);
		1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1944
		1945	// now stop the watcher
		1946	ev_io_stop (loop, iow + i);
		1947	}
		1948
		1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1950	}
		1951
		1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1953	in the prepare watcher and would dispose of the check watcher.
		1954
		1955	Method 3: If the module to be embedded supports explicit event
		1956	notification (adns does), you can also make use of the actual watcher
		1957	callbacks, and only destroy/create the watchers in the prepare watcher.
		1958
		1959	static void
		1960	timer_cb (EV_P_ ev_timer *w, int revents)
		1961	{
		1962	adns_state ads = (adns_state)w->data;
		1963	update_now (EV_A);
		1964
		1965	adns_processtimeouts (ads, &tv_now);
		1966	}
		1967
		1968	static void
		1969	io_cb (EV_P_ ev_io *w, int revents)
		1970	{
		1971	adns_state ads = (adns_state)w->data;
		1972	update_now (EV_A);
		1973
		1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1976	}
		1977
		1978	// do not ever call adns_afterpoll
		1979
		1980	Method 4: Do not use a prepare or check watcher because the module you
		1981	want to embed is too inflexible to support it. Instead, youc na override
		1982	their poll function. The drawback with this solution is that the main
		1983	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1984	this.
		1985
		1986	static gint
		1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1988	{
		1989	int got_events = 0;
		1990
		1991	for (n = 0; n < nfds; ++n)
		1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1993
		1994	if (timeout >= 0)
		1995	// create/start timer
		1996
		1997	// poll
		1998	ev_loop (EV_A_ 0);
		1999
		2000	// stop timer again
		2001	if (timeout >= 0)
		2002	ev_timer_stop (EV_A_ &to);
		2003
		2004	// stop io watchers again - their callbacks should have set
		2005	for (n = 0; n < nfds; ++n)
		2006	ev_io_stop (EV_A_ iow [n]);
		2007
		2008	return got_events;
		2009	}
		2010
		2011
		2012	=head2 C<ev_embed> - when one backend isn't enough...
		2013
		2014	This is a rather advanced watcher type that lets you embed one event loop
		2015	into another (currently only C<ev_io> events are supported in the embedded
		2016	loop, other types of watchers might be handled in a delayed or incorrect
		2017	fashion and must not be used).
		2018
		2019	There are primarily two reasons you would want that: work around bugs and
		2020	prioritise I/O.
		2021
		2022	As an example for a bug workaround, the kqueue backend might only support
		2023	sockets on some platform, so it is unusable as generic backend, but you
		2024	still want to make use of it because you have many sockets and it scales
		2025	so nicely. In this case, you would create a kqueue-based loop and embed it
		2026	into your default loop (which might use e.g. poll). Overall operation will
		2027	be a bit slower because first libev has to poll and then call kevent, but
		2028	at least you can use both at what they are best.
		2029
		2030	As for prioritising I/O: rarely you have the case where some fds have
		2031	to be watched and handled very quickly (with low latency), and even
		2032	priorities and idle watchers might have too much overhead. In this case
		2033	you would put all the high priority stuff in one loop and all the rest in
		2034	a second one, and embed the second one in the first.
		2035
		2036	As long as the watcher is active, the callback will be invoked every time
		2037	there might be events pending in the embedded loop. The callback must then
		2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		2039	their callbacks (you could also start an idle watcher to give the embedded
		2040	loop strictly lower priority for example). You can also set the callback
		2041	to C<0>, in which case the embed watcher will automatically execute the
		2042	embedded loop sweep.
		2043
		2044	As long as the watcher is started it will automatically handle events. The
		2045	callback will be invoked whenever some events have been handled. You can
		2046	set the callback to C<0> to avoid having to specify one if you are not
		2047	interested in that.
		2048
		2049	Also, there have not currently been made special provisions for forking:
		2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2051	but you will also have to stop and restart any C<ev_embed> watchers
		2052	yourself.
		2053
		2054	Unfortunately, not all backends are embeddable, only the ones returned by
		2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2056	portable one.
		2057
		2058	So when you want to use this feature you will always have to be prepared
		2059	that you cannot get an embeddable loop. The recommended way to get around
		2060	this is to have a separate variables for your embeddable loop, try to
		2061	create it, and if that fails, use the normal loop for everything.
		2062
		2063	=head3 Watcher-Specific Functions and Data Members
		2064
		2065	=over 4
		2066
		2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2068
		2069	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2070
		2071	Configures the watcher to embed the given loop, which must be
		2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2073	invoked automatically, otherwise it is the responsibility of the callback
		2074	to invoke it (it will continue to be called until the sweep has been done,
		2075	if you do not want thta, you need to temporarily stop the embed watcher).
		2076
		2077	=item ev_embed_sweep (loop, ev_embed *)
		2078
		2079	Make a single, non-blocking sweep over the embedded loop. This works
		2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2081	apropriate way for embedded loops.
		2082
		2083	=item struct ev_loop *other [read-only]
		2084
		2085	The embedded event loop.
		2086
		2087	=back
		2088
		2089	=head3 Examples
		2090
		2091	Example: Try to get an embeddable event loop and embed it into the default
		2092	event loop. If that is not possible, use the default loop. The default
		2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2095	used).
		2096
		2097	struct ev_loop *loop_hi = ev_default_init (0);
		2098	struct ev_loop *loop_lo = 0;
		2099	struct ev_embed embed;
		2100
		2101	// see if there is a chance of getting one that works
		2102	// (remember that a flags value of 0 means autodetection)
		2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2105	: 0;
		2106
		2107	// if we got one, then embed it, otherwise default to loop_hi
		2108	if (loop_lo)
		2109	{
		2110	ev_embed_init (&embed, 0, loop_lo);
		2111	ev_embed_start (loop_hi, &embed);
		2112	}
		2113	else
		2114	loop_lo = loop_hi;
		2115
		2116	Example: Check if kqueue is available but not recommended and create
		2117	a kqueue backend for use with sockets (which usually work with any
		2118	kqueue implementation). Store the kqueue/socket-only event loop in
		2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2120
		2121	struct ev_loop *loop = ev_default_init (0);
		2122	struct ev_loop *loop_socket = 0;
		2123	struct ev_embed embed;
		2124
		2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2127	{
		2128	ev_embed_init (&embed, 0, loop_socket);
		2129	ev_embed_start (loop, &embed);
		2130	}
		2131
		2132	if (!loop_socket)
		2133	loop_socket = loop;
		2134
		2135	// now use loop_socket for all sockets, and loop for everything else
		2136
		2137
		2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2139
		2140	Fork watchers are called when a C<fork ()> was detected (usually because
		2141	whoever is a good citizen cared to tell libev about it by calling
		2142	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2143	event loop blocks next and before C<ev_check> watchers are being called,
		2144	and only in the child after the fork. If whoever good citizen calling
		2145	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2146	handlers will be invoked, too, of course.
		2147
		2148	=head3 Watcher-Specific Functions and Data Members
		2149
		2150	=over 4
		2151
		2152	=item ev_fork_init (ev_signal *, callback)
		2153
		2154	Initialises and configures the fork watcher - it has no parameters of any
		2155	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2156	believe me.
		2157
		2158	=back
		2159
		2160
		2161	=head2 C<ev_async> - how to wake up another event loop
		2162
		2163	In general, you cannot use an C<ev_loop> from multiple threads or other
		2164	asynchronous sources such as signal handlers (as opposed to multiple event
		2165	loops - those are of course safe to use in different threads).
		2166
		2167	Sometimes, however, you need to wake up another event loop you do not
		2168	control, for example because it belongs to another thread. This is what
		2169	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2170	can signal it by calling C<ev_async_send>, which is thread- and signal
		2171	safe.
		2172
		2173	This functionality is very similar to C<ev_signal> watchers, as signals,
		2174	too, are asynchronous in nature, and signals, too, will be compressed
		2175	(i.e. the number of callback invocations may be less than the number of
		2176	C<ev_async_sent> calls).
		2177
		2178	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2179	just the default loop.
		2180
		2181	=head3 Queueing
		2182
		2183	C<ev_async> does not support queueing of data in any way. The reason
		2184	is that the author does not know of a simple (or any) algorithm for a
		2185	multiple-writer-single-reader queue that works in all cases and doesn't
		2186	need elaborate support such as pthreads.
		2187
		2188	That means that if you want to queue data, you have to provide your own
		2189	queue. But at least I can tell you would implement locking around your
		2190	queue:
		2191
		2192	=over 4
		2193
		2194	=item queueing from a signal handler context
		2195
		2196	To implement race-free queueing, you simply add to the queue in the signal
		2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2198	some fictitiuous SIGUSR1 handler:
		2199
		2200	static ev_async mysig;
		2201
		2202	static void
		2203	sigusr1_handler (void)
		2204	{
		2205	sometype data;
		2206
		2207	// no locking etc.
		2208	queue_put (data);
		2209	ev_async_send (EV_DEFAULT_ &mysig);
		2210	}
		2211
		2212	static void
		2213	mysig_cb (EV_P_ ev_async *w, int revents)
		2214	{
		2215	sometype data;
		2216	sigset_t block, prev;
		2217
		2218	sigemptyset (&block);
		2219	sigaddset (&block, SIGUSR1);
		2220	sigprocmask (SIG_BLOCK, &block, &prev);
		2221
		2222	while (queue_get (&data))
		2223	process (data);
		2224
		2225	if (sigismember (&prev, SIGUSR1)
		2226	sigprocmask (SIG_UNBLOCK, &block, 0);
		2227	}
		2228
		2229	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2230	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2231	either...).
		2232
		2233	=item queueing from a thread context
		2234
		2235	The strategy for threads is different, as you cannot (easily) block
		2236	threads but you can easily preempt them, so to queue safely you need to
		2237	employ a traditional mutex lock, such as in this pthread example:
		2238
		2239	static ev_async mysig;
		2240	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2241
		2242	static void
		2243	otherthread (void)
		2244	{
		2245	// only need to lock the actual queueing operation
		2246	pthread_mutex_lock (&mymutex);
		2247	queue_put (data);
		2248	pthread_mutex_unlock (&mymutex);
		2249
		2250	ev_async_send (EV_DEFAULT_ &mysig);
		2251	}
		2252
		2253	static void
		2254	mysig_cb (EV_P_ ev_async *w, int revents)
		2255	{
		2256	pthread_mutex_lock (&mymutex);
		2257
		2258	while (queue_get (&data))
		2259	process (data);
		2260
		2261	pthread_mutex_unlock (&mymutex);
		2262	}
		2263
		2264	=back
		2265
		2266
		2267	=head3 Watcher-Specific Functions and Data Members
		2268
		2269	=over 4
		2270
		2271	=item ev_async_init (ev_async *, callback)
		2272
		2273	Initialises and configures the async watcher - it has no parameters of any
		2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2275	believe me.
		2276
		2277	=item ev_async_send (loop, ev_async *)
		2278
		2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2281	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2283	section below on what exactly this means).
		2284
		2285	This call incurs the overhead of a syscall only once per loop iteration,
		2286	so while the overhead might be noticable, it doesn't apply to repeated
		2287	calls to C<ev_async_send>.
		2288
		2289	=item bool = ev_async_pending (ev_async *)
		2290
		2291	Returns a non-zero value when C<ev_async_send> has been called on the
		2292	watcher but the event has not yet been processed (or even noted) by the
		2293	event loop.
		2294
		2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2296	the loop iterates next and checks for the watcher to have become active,
		2297	it will reset the flag again. C<ev_async_pending> can be used to very
		2298	quickly check wether invoking the loop might be a good idea.
		2299
		2300	Not that this does I<not> check wether the watcher itself is pending, only
		2301	wether it has been requested to make this watcher pending.
		2302
		2303	=back
		2304
		2305
672	=head1 OTHER FUNCTIONS	2306	=head1 OTHER FUNCTIONS
673		2307
674	There are some other fucntions of possible interest. Described. Here. Now.	2308	There are some other functions of possible interest. Described. Here. Now.
675		2309
676	=over 4	2310	=over 4
677		2311
678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
679		2313
680	This function combines a simple timer and an I/O watcher, calls your	2314	This function combines a simple timer and an I/O watcher, calls your
681	callback on whichever event happens first and automatically stop both	2315	callback on whichever event happens first and automatically stop both
682	watchers. This is useful if you want to wait for a single event on an fd	2316	watchers. This is useful if you want to wait for a single event on an fd
683	or timeout without havign to allocate/configure/start/stop/free one or	2317	or timeout without having to allocate/configure/start/stop/free one or
684	more watchers yourself.	2318	more watchers yourself.
685		2319
686	If C<fd> is less than 0, then no I/O watcher will be started and events is	2320	If C<fd> is less than 0, then no I/O watcher will be started and events
687	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
688	will be craeted and started.	2322	C<events> set will be craeted and started.
689		2323
690	If C<timeout> is less than 0, then no timeout watcher will be	2324	If C<timeout> is less than 0, then no timeout watcher will be
691	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
692	= 0) will be started.	2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		2327	dubious value.
693		2328
694	The callback has the type C<void (*cb)(int revents, void *arg)> and	2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
695	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	2330	passed an C<revents> set like normal event callbacks (a combination of
696	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		2332	value passed to C<ev_once>:
697		2333
698	static void stdin_ready (int revents, void *arg)	2334	static void stdin_ready (int revents, void *arg)
699	{	2335	{
700	if (revents & EV_TIMEOUT)	2336	if (revents & EV_TIMEOUT)
701	/* doh, nothing entered */	2337	/* doh, nothing entered */;
702	else if (revents & EV_READ)	2338	else if (revents & EV_READ)
703	/* stdin might have data for us, joy! */	2339	/* stdin might have data for us, joy! */;
704	}	2340	}
705		2341
706	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
707		2343
708	=item ev_feed_event (loop, watcher, int events)	2344	=item ev_feed_event (ev_loop *, watcher *, int revents)
709		2345
710	Feeds the given event set into the event loop, as if the specified event	2346	Feeds the given event set into the event loop, as if the specified event
711	has happened for the specified watcher (which must be a pointer to an	2347	had happened for the specified watcher (which must be a pointer to an
712	initialised but not necessarily active event watcher).	2348	initialised but not necessarily started event watcher).
713		2349
714	=item ev_feed_fd_event (loop, int fd, int revents)	2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
715		2351
716	Feed an event on the given fd, as if a file descriptor backend detected it.	2352	Feed an event on the given fd, as if a file descriptor backend detected
		2353	the given events it.
717		2354
718	=item ev_feed_signal_event (loop, int signum)	2355	=item ev_feed_signal_event (ev_loop *loop, int signum)
719		2356
720	Feed an event as if the given signal occured (loop must be the default loop!).	2357	Feed an event as if the given signal occured (C<loop> must be the default
		2358	loop!).
721		2359
722	=back	2360	=back
723		2361
		2362
		2363	=head1 LIBEVENT EMULATION
		2364
		2365	Libev offers a compatibility emulation layer for libevent. It cannot
		2366	emulate the internals of libevent, so here are some usage hints:
		2367
		2368	=over 4
		2369
		2370	=item * Use it by including <event.h>, as usual.
		2371
		2372	=item * The following members are fully supported: ev_base, ev_callback,
		2373	ev_arg, ev_fd, ev_res, ev_events.
		2374
		2375	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		2376	maintained by libev, it does not work exactly the same way as in libevent (consider
		2377	it a private API).
		2378
		2379	=item * Priorities are not currently supported. Initialising priorities
		2380	will fail and all watchers will have the same priority, even though there
		2381	is an ev_pri field.
		2382
		2383	=item * In libevent, the last base created gets the signals, in libev, the
		2384	first base created (== the default loop) gets the signals.
		2385
		2386	=item * Other members are not supported.
		2387
		2388	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		2389	to use the libev header file and library.
		2390
		2391	=back
		2392
		2393	=head1 C++ SUPPORT
		2394
		2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2396	you to use some convinience methods to start/stop watchers and also change
		2397	the callback model to a model using method callbacks on objects.
		2398
		2399	To use it,
		2400
		2401	#include <ev++.h>
		2402
		2403	This automatically includes F<ev.h> and puts all of its definitions (many
		2404	of them macros) into the global namespace. All C++ specific things are
		2405	put into the C<ev> namespace. It should support all the same embedding
		2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2407
		2408	Care has been taken to keep the overhead low. The only data member the C++
		2409	classes add (compared to plain C-style watchers) is the event loop pointer
		2410	that the watcher is associated with (or no additional members at all if
		2411	you disable C<EV_MULTIPLICITY> when embedding libev).
		2412
		2413	Currently, functions, and static and non-static member functions can be
		2414	used as callbacks. Other types should be easy to add as long as they only
		2415	need one additional pointer for context. If you need support for other
		2416	types of functors please contact the author (preferably after implementing
		2417	it).
		2418
		2419	Here is a list of things available in the C<ev> namespace:
		2420
		2421	=over 4
		2422
		2423	=item C<ev::READ>, C<ev::WRITE> etc.
		2424
		2425	These are just enum values with the same values as the C<EV_READ> etc.
		2426	macros from F<ev.h>.
		2427
		2428	=item C<ev::tstamp>, C<ev::now>
		2429
		2430	Aliases to the same types/functions as with the C<ev_> prefix.
		2431
		2432	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2433
		2434	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2435	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2436	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2437	defines by many implementations.
		2438
		2439	All of those classes have these methods:
		2440
		2441	=over 4
		2442
		2443	=item ev::TYPE::TYPE ()
		2444
		2445	=item ev::TYPE::TYPE (struct ev_loop *)
		2446
		2447	=item ev::TYPE::~TYPE
		2448
		2449	The constructor (optionally) takes an event loop to associate the watcher
		2450	with. If it is omitted, it will use C<EV_DEFAULT>.
		2451
		2452	The constructor calls C<ev_init> for you, which means you have to call the
		2453	C<set> method before starting it.
		2454
		2455	It will not set a callback, however: You have to call the templated C<set>
		2456	method to set a callback before you can start the watcher.
		2457
		2458	(The reason why you have to use a method is a limitation in C++ which does
		2459	not allow explicit template arguments for constructors).
		2460
		2461	The destructor automatically stops the watcher if it is active.
		2462
		2463	=item w->set<class, &class::method> (object *)
		2464
		2465	This method sets the callback method to call. The method has to have a
		2466	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2467	first argument and the C<revents> as second. The object must be given as
		2468	parameter and is stored in the C<data> member of the watcher.
		2469
		2470	This method synthesizes efficient thunking code to call your method from
		2471	the C callback that libev requires. If your compiler can inline your
		2472	callback (i.e. it is visible to it at the place of the C<set> call and
		2473	your compiler is good :), then the method will be fully inlined into the
		2474	thunking function, making it as fast as a direct C callback.
		2475
		2476	Example: simple class declaration and watcher initialisation
		2477
		2478	struct myclass
		2479	{
		2480	void io_cb (ev::io &w, int revents) { }
		2481	}
		2482
		2483	myclass obj;
		2484	ev::io iow;
		2485	iow.set <myclass, &myclass::io_cb> (&obj);
		2486
		2487	=item w->set<function> (void *data = 0)
		2488
		2489	Also sets a callback, but uses a static method or plain function as
		2490	callback. The optional C<data> argument will be stored in the watcher's
		2491	C<data> member and is free for you to use.
		2492
		2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2494
		2495	See the method-C<set> above for more details.
		2496
		2497	Example:
		2498
		2499	static void io_cb (ev::io &w, int revents) { }
		2500	iow.set <io_cb> ();
		2501
		2502	=item w->set (struct ev_loop *)
		2503
		2504	Associates a different C<struct ev_loop> with this watcher. You can only
		2505	do this when the watcher is inactive (and not pending either).
		2506
		2507	=item w->set ([args])
		2508
		2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2510	called at least once. Unlike the C counterpart, an active watcher gets
		2511	automatically stopped and restarted when reconfiguring it with this
		2512	method.
		2513
		2514	=item w->start ()
		2515
		2516	Starts the watcher. Note that there is no C<loop> argument, as the
		2517	constructor already stores the event loop.
		2518
		2519	=item w->stop ()
		2520
		2521	Stops the watcher if it is active. Again, no C<loop> argument.
		2522
		2523	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2524
		2525	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2526	C<ev_TYPE_again> function.
		2527
		2528	=item w->sweep () (C<ev::embed> only)
		2529
		2530	Invokes C<ev_embed_sweep>.
		2531
		2532	=item w->update () (C<ev::stat> only)
		2533
		2534	Invokes C<ev_stat_stat>.
		2535
		2536	=back
		2537
		2538	=back
		2539
		2540	Example: Define a class with an IO and idle watcher, start one of them in
		2541	the constructor.
		2542
		2543	class myclass
		2544	{
		2545	ev::io io; void io_cb (ev::io &w, int revents);
		2546	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2547
		2548	myclass (int fd)
		2549	{
		2550	io .set <myclass, &myclass::io_cb > (this);
		2551	idle.set <myclass, &myclass::idle_cb> (this);
		2552
		2553	io.start (fd, ev::READ);
		2554	}
		2555	};
		2556
		2557
		2558	=head1 OTHER LANGUAGE BINDINGS
		2559
		2560	Libev does not offer other language bindings itself, but bindings for a
		2561	numbe rof languages exist in the form of third-party packages. If you know
		2562	any interesting language binding in addition to the ones listed here, drop
		2563	me a note.
		2564
		2565	=over 4
		2566
		2567	=item Perl
		2568
		2569	The EV module implements the full libev API and is actually used to test
		2570	libev. EV is developed together with libev. Apart from the EV core module,
		2571	there are additional modules that implement libev-compatible interfaces
		2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2574
		2575	It can be found and installed via CPAN, its homepage is found at
		2576	L<http://software.schmorp.de/pkg/EV>.
		2577
		2578	=item Ruby
		2579
		2580	Tony Arcieri has written a ruby extension that offers access to a subset
		2581	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2582	more on top of it. It can be found via gem servers. Its homepage is at
		2583	L<http://rev.rubyforge.org/>.
		2584
		2585	=item D
		2586
		2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2589
		2590	=back
		2591
		2592
		2593	=head1 MACRO MAGIC
		2594
		2595	Libev can be compiled with a variety of options, the most fundamantal
		2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2597	functions and callbacks have an initial C<struct ev_loop *> argument.
		2598
		2599	To make it easier to write programs that cope with either variant, the
		2600	following macros are defined:
		2601
		2602	=over 4
		2603
		2604	=item C<EV_A>, C<EV_A_>
		2605
		2606	This provides the loop I<argument> for functions, if one is required ("ev
		2607	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2608	C<EV_A_> is used when other arguments are following. Example:
		2609
		2610	ev_unref (EV_A);
		2611	ev_timer_add (EV_A_ watcher);
		2612	ev_loop (EV_A_ 0);
		2613
		2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2615	which is often provided by the following macro.
		2616
		2617	=item C<EV_P>, C<EV_P_>
		2618
		2619	This provides the loop I<parameter> for functions, if one is required ("ev
		2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2621	C<EV_P_> is used when other parameters are following. Example:
		2622
		2623	// this is how ev_unref is being declared
		2624	static void ev_unref (EV_P);
		2625
		2626	// this is how you can declare your typical callback
		2627	static void cb (EV_P_ ev_timer *w, int revents)
		2628
		2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2630	suitable for use with C<EV_A>.
		2631
		2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2633
		2634	Similar to the other two macros, this gives you the value of the default
		2635	loop, if multiple loops are supported ("ev loop default").
		2636
		2637	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2638
		2639	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2640	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2641	is undefined when the default loop has not been initialised by a previous
		2642	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2643
		2644	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2645	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2646
		2647	=back
		2648
		2649	Example: Declare and initialise a check watcher, utilising the above
		2650	macros so it will work regardless of whether multiple loops are supported
		2651	or not.
		2652
		2653	static void
		2654	check_cb (EV_P_ ev_timer *w, int revents)
		2655	{
		2656	ev_check_stop (EV_A_ w);
		2657	}
		2658
		2659	ev_check check;
		2660	ev_check_init (&check, check_cb);
		2661	ev_check_start (EV_DEFAULT_ &check);
		2662	ev_loop (EV_DEFAULT_ 0);
		2663
		2664	=head1 EMBEDDING
		2665
		2666	Libev can (and often is) directly embedded into host
		2667	applications. Examples of applications that embed it include the Deliantra
		2668	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2669	and rxvt-unicode.
		2670
		2671	The goal is to enable you to just copy the necessary files into your
		2672	source directory without having to change even a single line in them, so
		2673	you can easily upgrade by simply copying (or having a checked-out copy of
		2674	libev somewhere in your source tree).
		2675
		2676	=head2 FILESETS
		2677
		2678	Depending on what features you need you need to include one or more sets of files
		2679	in your app.
		2680
		2681	=head3 CORE EVENT LOOP
		2682
		2683	To include only the libev core (all the C<ev_*> functions), with manual
		2684	configuration (no autoconf):
		2685
		2686	#define EV_STANDALONE 1
		2687	#include "ev.c"
		2688
		2689	This will automatically include F<ev.h>, too, and should be done in a
		2690	single C source file only to provide the function implementations. To use
		2691	it, do the same for F<ev.h> in all files wishing to use this API (best
		2692	done by writing a wrapper around F<ev.h> that you can include instead and
		2693	where you can put other configuration options):
		2694
		2695	#define EV_STANDALONE 1
		2696	#include "ev.h"
		2697
		2698	Both header files and implementation files can be compiled with a C++
		2699	compiler (at least, thats a stated goal, and breakage will be treated
		2700	as a bug).
		2701
		2702	You need the following files in your source tree, or in a directory
		2703	in your include path (e.g. in libev/ when using -Ilibev):
		2704
		2705	ev.h
		2706	ev.c
		2707	ev_vars.h
		2708	ev_wrap.h
		2709
		2710	ev_win32.c required on win32 platforms only
		2711
		2712	ev_select.c only when select backend is enabled (which is enabled by default)
		2713	ev_poll.c only when poll backend is enabled (disabled by default)
		2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2716	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2717
		2718	F<ev.c> includes the backend files directly when enabled, so you only need
		2719	to compile this single file.
		2720
		2721	=head3 LIBEVENT COMPATIBILITY API
		2722
		2723	To include the libevent compatibility API, also include:
		2724
		2725	#include "event.c"
		2726
		2727	in the file including F<ev.c>, and:
		2728
		2729	#include "event.h"
		2730
		2731	in the files that want to use the libevent API. This also includes F<ev.h>.
		2732
		2733	You need the following additional files for this:
		2734
		2735	event.h
		2736	event.c
		2737
		2738	=head3 AUTOCONF SUPPORT
		2739
		2740	Instead of using C<EV_STANDALONE=1> and providing your config in
		2741	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2743	include F<config.h> and configure itself accordingly.
		2744
		2745	For this of course you need the m4 file:
		2746
		2747	libev.m4
		2748
		2749	=head2 PREPROCESSOR SYMBOLS/MACROS
		2750
		2751	Libev can be configured via a variety of preprocessor symbols you have to
		2752	define before including any of its files. The default in the absense of
		2753	autoconf is noted for every option.
		2754
		2755	=over 4
		2756
		2757	=item EV_STANDALONE
		2758
		2759	Must always be C<1> if you do not use autoconf configuration, which
		2760	keeps libev from including F<config.h>, and it also defines dummy
		2761	implementations for some libevent functions (such as logging, which is not
		2762	supported). It will also not define any of the structs usually found in
		2763	F<event.h> that are not directly supported by the libev core alone.
		2764
		2765	=item EV_USE_MONOTONIC
		2766
		2767	If defined to be C<1>, libev will try to detect the availability of the
		2768	monotonic clock option at both compiletime and runtime. Otherwise no use
		2769	of the monotonic clock option will be attempted. If you enable this, you
		2770	usually have to link against librt or something similar. Enabling it when
		2771	the functionality isn't available is safe, though, although you have
		2772	to make sure you link against any libraries where the C<clock_gettime>
		2773	function is hiding in (often F<-lrt>).
		2774
		2775	=item EV_USE_REALTIME
		2776
		2777	If defined to be C<1>, libev will try to detect the availability of the
		2778	realtime clock option at compiletime (and assume its availability at
		2779	runtime if successful). Otherwise no use of the realtime clock option will
		2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2783
		2784	=item EV_USE_NANOSLEEP
		2785
		2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2787	and will use it for delays. Otherwise it will use C<select ()>.
		2788
		2789	=item EV_USE_EVENTFD
		2790
		2791	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2792	available and will probe for kernel support at runtime. This will improve
		2793	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2794	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2795	2.7 or newer, otherwise disabled.
		2796
		2797	=item EV_USE_SELECT
		2798
		2799	If undefined or defined to be C<1>, libev will compile in support for the
		2800	C<select>(2) backend. No attempt at autodetection will be done: if no
		2801	other method takes over, select will be it. Otherwise the select backend
		2802	will not be compiled in.
		2803
		2804	=item EV_SELECT_USE_FD_SET
		2805
		2806	If defined to C<1>, then the select backend will use the system C<fd_set>
		2807	structure. This is useful if libev doesn't compile due to a missing
		2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2809	exotic systems. This usually limits the range of file descriptors to some
		2810	low limit such as 1024 or might have other limitations (winsocket only
		2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2812	influence the size of the C<fd_set> used.
		2813
		2814	=item EV_SELECT_IS_WINSOCKET
		2815
		2816	When defined to C<1>, the select backend will assume that
		2817	select/socket/connect etc. don't understand file descriptors but
		2818	wants osf handles on win32 (this is the case when the select to
		2819	be used is the winsock select). This means that it will call
		2820	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2821	it is assumed that all these functions actually work on fds, even
		2822	on win32. Should not be defined on non-win32 platforms.
		2823
		2824	=item EV_FD_TO_WIN32_HANDLE
		2825
		2826	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2827	file descriptors to socket handles. When not defining this symbol (the
		2828	default), then libev will call C<_get_osfhandle>, which is usually
		2829	correct. In some cases, programs use their own file descriptor management,
		2830	in which case they can provide this function to map fds to socket handles.
		2831
		2832	=item EV_USE_POLL
		2833
		2834	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2835	backend. Otherwise it will be enabled on non-win32 platforms. It
		2836	takes precedence over select.
		2837
		2838	=item EV_USE_EPOLL
		2839
		2840	If defined to be C<1>, libev will compile in support for the Linux
		2841	C<epoll>(7) backend. Its availability will be detected at runtime,
		2842	otherwise another method will be used as fallback. This is the preferred
		2843	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2844	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2845
		2846	=item EV_USE_KQUEUE
		2847
		2848	If defined to be C<1>, libev will compile in support for the BSD style
		2849	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2850	otherwise another method will be used as fallback. This is the preferred
		2851	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2852	supports some types of fds correctly (the only platform we found that
		2853	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2854	not be used unless explicitly requested. The best way to use it is to find
		2855	out whether kqueue supports your type of fd properly and use an embedded
		2856	kqueue loop.
		2857
		2858	=item EV_USE_PORT
		2859
		2860	If defined to be C<1>, libev will compile in support for the Solaris
		2861	10 port style backend. Its availability will be detected at runtime,
		2862	otherwise another method will be used as fallback. This is the preferred
		2863	backend for Solaris 10 systems.
		2864
		2865	=item EV_USE_DEVPOLL
		2866
		2867	reserved for future expansion, works like the USE symbols above.
		2868
		2869	=item EV_USE_INOTIFY
		2870
		2871	If defined to be C<1>, libev will compile in support for the Linux inotify
		2872	interface to speed up C<ev_stat> watchers. Its actual availability will
		2873	be detected at runtime. If undefined, it will be enabled if the headers
		2874	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2875
		2876	=item EV_ATOMIC_T
		2877
		2878	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2879	access is atomic with respect to other threads or signal contexts. No such
		2880	type is easily found in the C language, so you can provide your own type
		2881	that you know is safe for your purposes. It is used both for signal handler "locking"
		2882	as well as for signal and thread safety in C<ev_async> watchers.
		2883
		2884	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2885	(from F<signal.h>), which is usually good enough on most platforms.
		2886
		2887	=item EV_H
		2888
		2889	The name of the F<ev.h> header file used to include it. The default if
		2890	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2891	used to virtually rename the F<ev.h> header file in case of conflicts.
		2892
		2893	=item EV_CONFIG_H
		2894
		2895	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2896	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2897	C<EV_H>, above.
		2898
		2899	=item EV_EVENT_H
		2900
		2901	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2902	of how the F<event.h> header can be found, the default is C<"event.h">.
		2903
		2904	=item EV_PROTOTYPES
		2905
		2906	If defined to be C<0>, then F<ev.h> will not define any function
		2907	prototypes, but still define all the structs and other symbols. This is
		2908	occasionally useful if you want to provide your own wrapper functions
		2909	around libev functions.
		2910
		2911	=item EV_MULTIPLICITY
		2912
		2913	If undefined or defined to C<1>, then all event-loop-specific functions
		2914	will have the C<struct ev_loop *> as first argument, and you can create
		2915	additional independent event loops. Otherwise there will be no support
		2916	for multiple event loops and there is no first event loop pointer
		2917	argument. Instead, all functions act on the single default loop.
		2918
		2919	=item EV_MINPRI
		2920
		2921	=item EV_MAXPRI
		2922
		2923	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2924	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2925	provide for more priorities by overriding those symbols (usually defined
		2926	to be C<-2> and C<2>, respectively).
		2927
		2928	When doing priority-based operations, libev usually has to linearly search
		2929	all the priorities, so having many of them (hundreds) uses a lot of space
		2930	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2931	fine.
		2932
		2933	If your embedding app does not need any priorities, defining these both to
		2934	C<0> will save some memory and cpu.
		2935
		2936	=item EV_PERIODIC_ENABLE
		2937
		2938	If undefined or defined to be C<1>, then periodic timers are supported. If
		2939	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2940	code.
		2941
		2942	=item EV_IDLE_ENABLE
		2943
		2944	If undefined or defined to be C<1>, then idle watchers are supported. If
		2945	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2946	code.
		2947
		2948	=item EV_EMBED_ENABLE
		2949
		2950	If undefined or defined to be C<1>, then embed watchers are supported. If
		2951	defined to be C<0>, then they are not.
		2952
		2953	=item EV_STAT_ENABLE
		2954
		2955	If undefined or defined to be C<1>, then stat watchers are supported. If
		2956	defined to be C<0>, then they are not.
		2957
		2958	=item EV_FORK_ENABLE
		2959
		2960	If undefined or defined to be C<1>, then fork watchers are supported. If
		2961	defined to be C<0>, then they are not.
		2962
		2963	=item EV_ASYNC_ENABLE
		2964
		2965	If undefined or defined to be C<1>, then async watchers are supported. If
		2966	defined to be C<0>, then they are not.
		2967
		2968	=item EV_MINIMAL
		2969
		2970	If you need to shave off some kilobytes of code at the expense of some
		2971	speed, define this symbol to C<1>. Currently only used for gcc to override
		2972	some inlining decisions, saves roughly 30% codesize of amd64.
		2973
		2974	=item EV_PID_HASHSIZE
		2975
		2976	C<ev_child> watchers use a small hash table to distribute workload by
		2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2978	than enough. If you need to manage thousands of children you might want to
		2979	increase this value (I<must> be a power of two).
		2980
		2981	=item EV_INOTIFY_HASHSIZE
		2982
		2983	C<ev_stat> watchers use a small hash table to distribute workload by
		2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2985	usually more than enough. If you need to manage thousands of C<ev_stat>
		2986	watchers you might want to increase this value (I<must> be a power of
		2987	two).
		2988
		2989	=item EV_COMMON
		2990
		2991	By default, all watchers have a C<void *data> member. By redefining
		2992	this macro to a something else you can include more and other types of
		2993	members. You have to define it each time you include one of the files,
		2994	though, and it must be identical each time.
		2995
		2996	For example, the perl EV module uses something like this:
		2997
		2998	#define EV_COMMON \
		2999	SV *self; /* contains this struct */ \
		3000	SV *cb_sv, *fh /* note no trailing ";" */
		3001
		3002	=item EV_CB_DECLARE (type)
		3003
		3004	=item EV_CB_INVOKE (watcher, revents)
		3005
		3006	=item ev_set_cb (ev, cb)
		3007
		3008	Can be used to change the callback member declaration in each watcher,
		3009	and the way callbacks are invoked and set. Must expand to a struct member
		3010	definition and a statement, respectively. See the F<ev.h> header file for
		3011	their default definitions. One possible use for overriding these is to
		3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		3013	method calls instead of plain function calls in C++.
		3014
		3015	=head2 EXPORTED API SYMBOLS
		3016
		3017	If you need to re-export the API (e.g. via a dll) and you need a list of
		3018	exported symbols, you can use the provided F<Symbol.*> files which list
		3019	all public symbols, one per line:
		3020
		3021	Symbols.ev for libev proper
		3022	Symbols.event for the libevent emulation
		3023
		3024	This can also be used to rename all public symbols to avoid clashes with
		3025	multiple versions of libev linked together (which is obviously bad in
		3026	itself, but sometimes it is inconvinient to avoid this).
		3027
		3028	A sed command like this will create wrapper C<#define>'s that you need to
		3029	include before including F<ev.h>:
		3030
		3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3032
		3033	This would create a file F<wrap.h> which essentially looks like this:
		3034
		3035	#define ev_backend myprefix_ev_backend
		3036	#define ev_check_start myprefix_ev_check_start
		3037	#define ev_check_stop myprefix_ev_check_stop
		3038	...
		3039
		3040	=head2 EXAMPLES
		3041
		3042	For a real-world example of a program the includes libev
		3043	verbatim, you can have a look at the EV perl module
		3044	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		3045	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		3046	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		3047	will be compiled. It is pretty complex because it provides its own header
		3048	file.
		3049
		3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		3051	that everybody includes and which overrides some configure choices:
		3052
		3053	#define EV_MINIMAL 1
		3054	#define EV_USE_POLL 0
		3055	#define EV_MULTIPLICITY 0
		3056	#define EV_PERIODIC_ENABLE 0
		3057	#define EV_STAT_ENABLE 0
		3058	#define EV_FORK_ENABLE 0
		3059	#define EV_CONFIG_H <config.h>
		3060	#define EV_MINPRI 0
		3061	#define EV_MAXPRI 0
		3062
		3063	#include "ev++.h"
		3064
		3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		3066
		3067	#include "ev_cpp.h"
		3068	#include "ev.c"
		3069
		3070
		3071	=head1 THREADS AND COROUTINES
		3072
		3073	=head2 THREADS
		3074
		3075	Libev itself is completely threadsafe, but it uses no locking. This
		3076	means that you can use as many loops as you want in parallel, as long as
		3077	only one thread ever calls into one libev function with the same loop
		3078	parameter.
		3079
		3080	Or put differently: calls with different loop parameters can be done in
		3081	parallel from multiple threads, calls with the same loop parameter must be
		3082	done serially (but can be done from different threads, as long as only one
		3083	thread ever is inside a call at any point in time, e.g. by using a mutex
		3084	per loop).
		3085
		3086	If you want to know which design is best for your problem, then I cannot
		3087	help you but by giving some generic advice:
		3088
		3089	=over 4
		3090
		3091	=item * most applications have a main thread: use the default libev loop
		3092	in that thread, or create a seperate thread running only the default loop.
		3093
		3094	This helps integrating other libraries or software modules that use libev
		3095	themselves and don't care/know about threading.
		3096
		3097	=item * one loop per thread is usually a good model.
		3098
		3099	Doing this is almost never wrong, sometimes a better-performance model
		3100	exists, but it is always a good start.
		3101
		3102	=item * other models exist, such as the leader/follower pattern, where one
		3103	loop is handed through multiple threads in a kind of round-robbin fashion.
		3104
		3105	Chosing a model is hard - look around, learn, know that usually you cna do
		3106	better than you currently do :-)
		3107
		3108	=item * often you need to talk to some other thread which blocks in the
		3109	event loop - C<ev_async> watchers can be used to wake them up from other
		3110	threads safely (or from signal contexts...).
		3111
		3112	=back
		3113
		3114	=head2 COROUTINES
		3115
		3116	Libev is much more accomodating to coroutines ("cooperative threads"):
		3117	libev fully supports nesting calls to it's functions from different
		3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3119	different coroutines and switch freely between both coroutines running the
		3120	loop, as long as you don't confuse yourself). The only exception is that
		3121	you must not do this from C<ev_periodic> reschedule callbacks.
		3122
		3123	Care has been invested into making sure that libev does not keep local
		3124	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3125	switches.
		3126
		3127
		3128	=head1 COMPLEXITIES
		3129
		3130	In this section the complexities of (many of) the algorithms used inside
		3131	libev will be explained. For complexity discussions about backends see the
		3132	documentation for C<ev_default_init>.
		3133
		3134	All of the following are about amortised time: If an array needs to be
		3135	extended, libev needs to realloc and move the whole array, but this
		3136	happens asymptotically never with higher number of elements, so O(1) might
		3137	mean it might do a lengthy realloc operation in rare cases, but on average
		3138	it is much faster and asymptotically approaches constant time.
		3139
		3140	=over 4
		3141
		3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3143
		3144	This means that, when you have a watcher that triggers in one hour and
		3145	there are 100 watchers that would trigger before that then inserting will
		3146	have to skip roughly seven (C<ld 100>) of these watchers.
		3147
		3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3149
		3150	That means that changing a timer costs less than removing/adding them
		3151	as only the relative motion in the event queue has to be paid for.
		3152
		3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3154
		3155	These just add the watcher into an array or at the head of a list.
		3156
		3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3158
		3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3160
		3161	These watchers are stored in lists then need to be walked to find the
		3162	correct watcher to remove. The lists are usually short (you don't usually
		3163	have many watchers waiting for the same fd or signal).
		3164
		3165	=item Finding the next timer in each loop iteration: O(1)
		3166
		3167	By virtue of using a binary heap, the next timer is always found at the
		3168	beginning of the storage array.
		3169
		3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3171
		3172	A change means an I/O watcher gets started or stopped, which requires
		3173	libev to recalculate its status (and possibly tell the kernel, depending
		3174	on backend and wether C<ev_io_set> was used).
		3175
		3176	=item Activating one watcher (putting it into the pending state): O(1)
		3177
		3178	=item Priority handling: O(number_of_priorities)
		3179
		3180	Priorities are implemented by allocating some space for each
		3181	priority. When doing priority-based operations, libev usually has to
		3182	linearly search all the priorities, but starting/stopping and activating
		3183	watchers becomes O(1) w.r.t. priority handling.
		3184
		3185	=item Sending an ev_async: O(1)
		3186
		3187	=item Processing ev_async_send: O(number_of_async_watchers)
		3188
		3189	=item Processing signals: O(max_signal_number)
		3190
		3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3192	calls in the current loop iteration. Checking for async and signal events
		3193	involves iterating over all running async watchers or all signal numbers.
		3194
		3195	=back
		3196
		3197
		3198	=head1 Win32 platform limitations and workarounds
		3199
		3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3201	requires, and its I/O model is fundamentally incompatible with the POSIX
		3202	model. Libev still offers limited functionality on this platform in
		3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3204	descriptors. This only applies when using Win32 natively, not when using
		3205	e.g. cygwin.
		3206
		3207	There is no supported compilation method available on windows except
		3208	embedding it into other applications.
		3209
		3210	Due to the many, low, and arbitrary limits on the win32 platform and the
		3211	abysmal performance of winsockets, using a large number of sockets is not
		3212	recommended (and not reasonable). If your program needs to use more than
		3213	a hundred or so sockets, then likely it needs to use a totally different
		3214	implementation for windows, as libev offers the POSIX model, which cannot
		3215	be implemented efficiently on windows (microsoft monopoly games).
		3216
		3217	=over 4
		3218
		3219	=item The winsocket select function
		3220
		3221	The winsocket C<select> function doesn't follow POSIX in that it requires
		3222	socket I<handles> and not socket I<file descriptors>. This makes select
		3223	very inefficient, and also requires a mapping from file descriptors
		3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3226	symbols for more info.
		3227
		3228	The configuration for a "naked" win32 using the microsoft runtime
		3229	libraries and raw winsocket select is:
		3230
		3231	#define EV_USE_SELECT 1
		3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3233
		3234	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3235	complexity in the O(n²) range when using win32.
		3236
		3237	=item Limited number of file descriptors
		3238
		3239	Windows has numerous arbitrary (and low) limits on things. Early versions
		3240	of winsocket's select only supported waiting for a max. of C<64> handles
		3241	(probably owning to the fact that all windows kernels can only wait for
		3242	C<64> things at the same time internally; microsoft recommends spawning a
		3243	chain of threads and wait for 63 handles and the previous thread in each).
		3244
		3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3246	to some high number (e.g. C<2048>) before compiling the winsocket select
		3247	call (which might be in libev or elsewhere, for example, perl does its own
		3248	select emulation on windows).
		3249
		3250	Another limit is the number of file descriptors in the microsoft runtime
		3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3252	or something like this inside microsoft). You can increase this by calling
		3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3254	arbitrary limit), but is broken in many versions of the microsoft runtime
		3255	libraries.
		3256
		3257	This might get you to about C<512> or C<2048> sockets (depending on
		3258	windows version and/or the phase of the moon). To get more, you need to
		3259	wrap all I/O functions and provide your own fd management, but the cost of
		3260	calling select (O(n²)) will likely make this unworkable.
		3261
		3262	=back
		3263
		3264
		3265	=head1 PORTABILITY REQUIREMENTS
		3266
		3267	In addition to a working ISO-C implementation, libev relies on a few
		3268	additional extensions:
		3269
		3270	=over 4
		3271
		3272	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3273
		3274	The type C<sig_atomic_t volatile> (or whatever is defined as
		3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3276	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3277	believed to be sufficiently portable.
		3278
		3279	=item C<sigprocmask> must work in a threaded environment
		3280
		3281	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3282	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3283	pthread implementations will either allow C<sigprocmask> in the "main
		3284	thread" or will block signals process-wide, both behaviours would
		3285	be compatible with libev. Interaction between C<sigprocmask> and
		3286	C<pthread_sigmask> could complicate things, however.
		3287
		3288	The most portable way to handle signals is to block signals in all threads
		3289	except the initial one, and run the default loop in the initial thread as
		3290	well.
		3291
		3292	=back
		3293
		3294	If you know of other additional requirements drop me a note.
		3295
		3296
724	=head1 AUTHOR	3297	=head1 AUTHOR
725		3298
726	Marc Lehmann <libev@schmorp.de>.	3299	Marc Lehmann <libev@schmorp.de>.
727		3300

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