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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). It also is quite	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>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	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
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	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
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	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
49	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
50	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.
51		121
52	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
53		123
54	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
55	library in any way.	125	library in any way.
…		…
60		130
61	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
62	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
63	you actually want to know.	133	you actually want to know.
64		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 ()>.
		140
65	=item int ev_version_major ()	141	=item int ev_version_major ()
66		142
67	=item int ev_version_minor ()	143	=item int ev_version_minor ()
68		144
69	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
70	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
71	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
72	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
73	version of the library your program was compiled against.	149	version of the library your program was compiled against.
74		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
75	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
77	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
78	not a problem.	157	not a problem.
79		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
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		199
82	Sets the allocation function to use (the prototype is similar to the	200	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	201	semantics is identical - to the realloc C function). It is used to
84	and free memory (no surprises here). If it returns zero when memory	202	allocate and free memory (no surprises here). If it returns zero when
85	needs to be allocated, the library might abort or take some potentially	203	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	204	potentially destructive action. The default is your system realloc
		205	function.
87		206
88	You could override this function in high-availability programs to, say,	207	You could override this function in high-availability programs to, say,
89	free some memory if it cannot allocate memory, to use a special allocator,	208	free some memory if it cannot allocate memory, to use a special allocator,
90	or even to sleep a while and retry until some memory is available.	209	or even to sleep a while and retry until some memory is available.
		210
		211	Example: Replace the libev allocator with one that waits a bit and then
		212	retries).
		213
		214	static void *
		215	persistent_realloc (void *ptr, size_t size)
		216	{
		217	for (;;)
		218	{
		219	void *newptr = realloc (ptr, size);
		220
		221	if (newptr)
		222	return newptr;
		223
		224	sleep (60);
		225	}
		226	}
		227
		228	...
		229	ev_set_allocator (persistent_realloc);
91		230
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	231	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		232
94	Set the callback function to call on a retryable syscall error (such	233	Set the callback function to call on a retryable syscall error (such
95	as failed select, poll, epoll_wait). The message is a printable string	234	as failed select, poll, epoll_wait). The message is a printable string
…		…
97	callback is set, then libev will expect it to remedy the sitution, no	236	callback is set, then libev will expect it to remedy the sitution, no
98	matter what, when it returns. That is, libev will generally retry the	237	matter what, when it returns. That is, libev will generally retry the
99	requested operation, or, if the condition doesn't go away, do bad stuff	238	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	239	(such as abort).
101		240
		241	Example: This is basically the same thing that libev does internally, too.
		242
		243	static void
		244	fatal_error (const char *msg)
		245	{
		246	perror (msg);
		247	abort ();
		248	}
		249
		250	...
		251	ev_set_syserr_cb (fatal_error);
		252
102	=back	253	=back
103		254
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		256
106	An event loop is described by a C<struct ev_loop *>. The library knows two	257	An event loop is described by a C<struct ev_loop *>. The library knows two
…		…
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	270	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		271
121	This will initialise the default event loop if it hasn't been initialised	272	This will initialise the default event loop if it hasn't been initialised
122	yet and return it. If the default loop could not be initialised, returns	273	yet and return it. If the default loop could not be initialised, returns
123	false. If it already was initialised it simply returns it (and ignores the	274	false. If it already was initialised it simply returns it (and ignores the
124	flags).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		276
126	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
127	function.	278	function.
128		279
		280	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
129	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
130	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		293
132	It supports the following flags:	294	The following flags are supported:
133		295
134	=over 4	296	=over 4
135		297
136	=item C<EVFLAG_AUTO>	298	=item C<EVFLAG_AUTO>
137		299
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	308	override the flags completely if it is found in the environment. This is
147	useful to try out specific backends to test their performance, or to work	309	useful to try out specific backends to test their performance, or to work
148	around bugs.	310	around bugs.
149		311
		312	=item C<EVFLAG_FORKCHECK>
		313
		314	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		315	a fork, you can also make libev check for a fork in each iteration by
		316	enabling this flag.
		317
		318	This works by calling C<getpid ()> on every iteration of the loop,
		319	and thus this might slow down your event loop if you do a lot of loop
		320	iterations and little real work, but is usually not noticeable (on my
		321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		323	C<pthread_atfork> which is even faster).
		324
		325	The big advantage of this flag is that you can forget about fork (and
		326	forget about forgetting to tell libev about forking) when you use this
		327	flag.
		328
		329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		330	environment variable.
		331
150	=item C<EVMETHOD_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		333
152	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
153	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
154	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
155	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
156	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
157		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
		346
158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
159		348
160	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
161	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
162	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
163	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
164		355
165	=item C<EVMETHOD_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
166		357
167	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
168	but it scales phenomenally better. While poll and select usually scale like	359	but it scales phenomenally better. While poll and select usually scale
169	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	360	like O(total_fds) where n is the total number of fds (or the highest fd),
170	either O(1) or O(active_fds).	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
		362	of shortcomings, such as silently dropping events in some hard-to-detect
		363	cases and rewiring a syscall per fd change, no fork support and bad
		364	support for dup.
171		365
172	While stopping and starting an I/O watcher in the same iteration will	366	While stopping, setting and starting an I/O watcher in the same iteration
173	result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
174	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
175	best to avoid that. Also, dup()ed file descriptors might not work very	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
176	well if you register events for both fds.	370	very well if you register events for both fds.
177		371
		372	Please note that epoll sometimes generates spurious notifications, so you
		373	need to use non-blocking I/O or other means to avoid blocking when no data
		374	(or space) is available.
		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
179		384
180	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
181	was broken on all BSDs except NetBSD (usually it doesn't work with	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
182	anything but sockets and pipes, except on Darwin, where of course its	387	with anything but sockets and pipes, except on Darwin, where of course
183	completely useless). For this reason its not being "autodetected" unless	388	it's completely useless). For this reason it's not being "autodetected"
184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	389	unless you explicitly specify it explicitly in the flags (i.e. using
		390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		391	system like NetBSD.
		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
185		396
186	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
187	kernel is more efficient (which says nothing about its actual speed, of	398	kernel is more efficient (which says nothing about its actual speed, of
188	course). While starting and stopping an I/O watcher does not cause an	399	course). While stopping, setting and starting an I/O watcher does never
189	extra syscall as with epoll, it still adds up to four event changes per	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
190	incident, so its best to avoid that.	401	two event changes per incident, support for C<fork ()> is very bad and it
		402	drops fds silently in similarly hard-to-detect cases.
191		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
		412
192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
193		414
194	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
195		419
196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
197		421
198	This uses the Solaris 10 port mechanism. As with everything on Solaris,	422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
199	it's really slow, but it still scales very well (O(active_fds)).	423	it's really slow, but it still scales very well (O(active_fds)).
200		424
		425	Please note that solaris event ports can deliver a lot of spurious
		426	notifications, so you need to use non-blocking I/O or other means to avoid
		427	blocking when no data (or space) is available.
		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
		437
201	=item C<EVMETHOD_ALL>	438	=item C<EVBACKEND_ALL>
202		439
203	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
204	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		443
		444	It is definitely not recommended to use this flag.
206		445
207	=back	446	=back
208		447
209	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
210	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
211	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
212	order of their flag values :)	451
		452	The most typical usage is like this:
		453
		454	if (!ev_default_loop (0))
		455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		456
		457	Restrict libev to the select and poll backends, and do not allow
		458	environment settings to be taken into account:
		459
		460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		461
		462	Use whatever libev has to offer, but make sure that kqueue is used if
		463	available (warning, breaks stuff, best use only with your own private
		464	event loop and only if you know the OS supports your types of fds):
		465
		466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
213		467
214	=item struct ev_loop *ev_loop_new (unsigned int flags)	468	=item struct ev_loop *ev_loop_new (unsigned int flags)
215		469
216	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
217	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
218	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
219	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
220		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
		478
		479	Example: Try to create a event loop that uses epoll and nothing else.
		480
		481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		482	if (!epoller)
		483	fatal ("no epoll found here, maybe it hides under your chair");
		484
221	=item ev_default_destroy ()	485	=item ev_default_destroy ()
222		486
223	Destroys the default loop again (frees all memory and kernel state	487	Destroys the default loop again (frees all memory and kernel state
224	etc.). This stops all registered event watchers (by not touching them in	488	etc.). None of the active event watchers will be stopped in the normal
225	any way whatsoever, although you cannot rely on this :).	489	sense, so e.g. C<ev_is_active> might still return true. It is your
		490	responsibility to either stop all watchers cleanly yoursef I<before>
		491	calling this function, or cope with the fact afterwards (which is usually
		492	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		493	for example).
		494
		495	Note that certain global state, such as signal state, will not be freed by
		496	this function, and related watchers (such as signal and child watchers)
		497	would need to be stopped manually.
		498
		499	In general it is not advisable to call this function except in the
		500	rare occasion where you really need to free e.g. the signal handling
		501	pipe fds. If you need dynamically allocated loops it is better to use
		502	C<ev_loop_new> and C<ev_loop_destroy>).
226		503
227	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
228		505
229	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
230	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
231		508
232	=item ev_default_fork ()	509	=item ev_default_fork ()
233		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
234	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
235	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
236	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
237	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
238		517
239	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
240	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
241	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
242		521
243	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
244	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
245	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
246		525
…		…
250		529
251	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
252	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
253	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
254		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
		537
		538	=item unsigned int ev_loop_count (loop)
		539
		540	Returns the count of loop iterations for the loop, which is identical to
		541	the number of times libev did poll for new events. It starts at C<0> and
		542	happily wraps around with enough iterations.
		543
		544	This value can sometimes be useful as a generation counter of sorts (it
		545	"ticks" the number of loop iterations), as it roughly corresponds with
		546	C<ev_prepare> and C<ev_check> calls.
		547
255	=item unsigned int ev_method (loop)	548	=item unsigned int ev_backend (loop)
256		549
257	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	550	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
258	use.	551	use.
259		552
260	=item ev_tstamp ev_now (loop)	553	=item ev_tstamp ev_now (loop)
261		554
262	Returns the current "event loop time", which is the time the event loop	555	Returns the current "event loop time", which is the time the event loop
263	got events and started processing them. This timestamp does not change	556	received events and started processing them. This timestamp does not
264	as long as callbacks are being processed, and this is also the base time	557	change as long as callbacks are being processed, and this is also the base
265	used for relative timers. You can treat it as the timestamp of the event	558	time used for relative timers. You can treat it as the timestamp of the
266	occuring (or more correctly, the mainloop finding out about it).	559	event occurring (or more correctly, libev finding out about it).
267		560
268	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
269		562
270	Finally, this is it, the event handler. This function usually is called	563	Finally, this is it, the event handler. This function usually is called
271	after you initialised all your watchers and you want to start handling	564	after you initialised all your watchers and you want to start handling
272	events.	565	events.
273		566
274	If the flags argument is specified as 0, it will not return until either	567	If the flags argument is specified as C<0>, it will not return until
275	no event watchers are active anymore or C<ev_unloop> was called.	568	either no event watchers are active anymore or C<ev_unloop> was called.
		569
		570	Please note that an explicit C<ev_unloop> is usually better than
		571	relying on all watchers to be stopped when deciding when a program has
		572	finished (especially in interactive programs), but having a program that
		573	automatically loops as long as it has to and no longer by virtue of
		574	relying on its watchers stopping correctly is a thing of beauty.
276		575
277	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
278	those events and any outstanding ones, but will not block your process in	577	those events and any outstanding ones, but will not block your process in
279	case there are no events and will return after one iteration of the loop.	578	case there are no events and will return after one iteration of the loop.
280		579
281	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
282	neccessary) and will handle those and any outstanding ones. It will block	581	neccessary) and will handle those and any outstanding ones. It will block
283	your process until at least one new event arrives, and will return after	582	your process until at least one new event arrives, and will return after
284	one iteration of the loop.	583	one iteration of the loop. This is useful if you are waiting for some
		584	external event in conjunction with something not expressible using other
		585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		586	usually a better approach for this kind of thing.
285		587
286	This flags value could be used to implement alternative looping
287	constructs, but the C<prepare> and C<check> watchers provide a better and
288	more generic mechanism.
289
290	Here are the gory details of what ev_loop does:	588	Here are the gory details of what C<ev_loop> does:
291		589
292	1. If there are no active watchers (reference count is zero), return.	590	- Before the first iteration, call any pending watchers.
		591	* If EVFLAG_FORKCHECK was used, check for a fork.
		592	- If a fork was detected, queue and call all fork watchers.
293	2. Queue and immediately call all prepare watchers.	593	- Queue and call all prepare watchers.
294	3. If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
295	4. Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
296	5. Update the "event loop time".	596	- Update the "event loop time".
297	6. Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
298	7. Block the process, waiting for events.	601	- Block the process, waiting for any events.
		602	- Queue all outstanding I/O (fd) events.
299	8. Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
300	9. Queue all outstanding timers.	604	- Queue all outstanding timers.
301	10. Queue all outstanding periodics.	605	- Queue all outstanding periodics.
302	11. If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
303	12. Queue all check watchers.	607	- Queue all check watchers.
304	13. Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
		609	Signals and child watchers are implemented as I/O watchers, and will
		610	be handled here by queueing them when their watcher gets executed.
305	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
306	was used, return, otherwise continue with step #1.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
		614
		615	Example: Queue some jobs and then loop until no events are outstanding
		616	anymore.
		617
		618	... queue jobs here, make sure they register event watchers as long
		619	... as they still have work to do (even an idle watcher will do..)
		620	ev_loop (my_loop, 0);
		621	... jobs done. yeah!
307		622
308	=item ev_unloop (loop, how)	623	=item ev_unloop (loop, how)
309		624
310	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
311	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
312	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
313	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
314		631
315	=item ev_ref (loop)	632	=item ev_ref (loop)
316		633
317	=item ev_unref (loop)	634	=item ev_unref (loop)
318		635
…		…
323	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
324	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
325	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
326	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
327	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
328	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
		648
		649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		650	running when nothing else is active.
		651
		652	struct ev_signal exitsig;
		653	ev_signal_init (&exitsig, sig_cb, SIGINT);
		654	ev_signal_start (loop, &exitsig);
		655	evf_unref (loop);
		656
		657	Example: For some weird reason, unregister the above signal handler again.
		658
		659	ev_ref (loop);
		660	ev_signal_stop (loop, &exitsig);
		661
		662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		663
		664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		665
		666	These advanced functions influence the time that libev will spend waiting
		667	for events. Both are by default C<0>, meaning that libev will try to
		668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		669
		670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		671	allows libev to delay invocation of I/O and timer/periodic callbacks to
		672	increase efficiency of loop iterations.
		673
		674	The background is that sometimes your program runs just fast enough to
		675	handle one (or very few) event(s) per loop iteration. While this makes
		676	the program responsive, it also wastes a lot of CPU time to poll for new
		677	events, especially with backends like C<select ()> which have a high
		678	overhead for the actual polling but can deliver many events at once.
		679
		680	By setting a higher I<io collect interval> you allow libev to spend more
		681	time collecting I/O events, so you can handle more events per iteration,
		682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
		685
		686	Likewise, by setting a higher I<timeout collect interval> you allow libev
		687	to spend more time collecting timeouts, at the expense of increased
		688	latency (the watcher callback will be called later). C<ev_io> watchers
		689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
		691
		692	Many (busy) programs can usually benefit by setting the io collect
		693	interval to a value near C<0.1> or so, which is often enough for
		694	interactive servers (of course not for games), likewise for timeouts. It
		695	usually doesn't make much sense to set it to a lower value than C<0.01>,
		696	as this approsaches the timing granularity of most systems.
329		697
330	=back	698	=back
		699
331		700
332	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
333		702
334	A watcher is a structure that you create and register to record your	703	A watcher is a structure that you create and register to record your
335	interest in some event. For instance, if you want to wait for STDIN to	704	interest in some event. For instance, if you want to wait for STDIN to
…		…
368	*) >>), and you can stop watching for events at any time by calling the	737	*) >>), and you can stop watching for events at any time by calling the
369	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
370		739
371	As long as your watcher is active (has been started but not stopped) you	740	As long as your watcher is active (has been started but not stopped) you
372	must not touch the values stored in it. Most specifically you must never	741	must not touch the values stored in it. Most specifically you must never
373	reinitialise it or call its set method.	742	reinitialise it or call its C<set> macro.
374
375	You can check whether an event is active by calling the C<ev_is_active
376	(watcher *)> macro. To see whether an event is outstanding (but the
377	callback for it has not been called yet) you can use the C<ev_is_pending
378	(watcher *)> macro.
379		743
380	Each and every callback receives the event loop pointer as first, the	744	Each and every callback receives the event loop pointer as first, the
381	registered watcher structure as second, and a bitset of received events as	745	registered watcher structure as second, and a bitset of received events as
382	third argument.	746	third argument.
383		747
…		…
407	The signal specified in the C<ev_signal> watcher has been received by a thread.	771	The signal specified in the C<ev_signal> watcher has been received by a thread.
408		772
409	=item C<EV_CHILD>	773	=item C<EV_CHILD>
410		774
411	The pid specified in the C<ev_child> watcher has received a status change.	775	The pid specified in the C<ev_child> watcher has received a status change.
		776
		777	=item C<EV_STAT>
		778
		779	The path specified in the C<ev_stat> watcher changed its attributes somehow.
412		780
413	=item C<EV_IDLE>	781	=item C<EV_IDLE>
414		782
415	The C<ev_idle> watcher has determined that you have nothing better to do.	783	The C<ev_idle> watcher has determined that you have nothing better to do.
416		784
…		…
424	received events. Callbacks of both watcher types can start and stop as	792	received events. Callbacks of both watcher types can start and stop as
425	many watchers as they want, and all of them will be taken into account	793	many watchers as they want, and all of them will be taken into account
426	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	794	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
427	C<ev_loop> from blocking).	795	C<ev_loop> from blocking).
428		796
		797	=item C<EV_EMBED>
		798
		799	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		800
		801	=item C<EV_FORK>
		802
		803	The event loop has been resumed in the child process after fork (see
		804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
		809
429	=item C<EV_ERROR>	810	=item C<EV_ERROR>
430		811
431	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
432	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
433	ran out of memory, a file descriptor was found to be closed or any other	814	ran out of memory, a file descriptor was found to be closed or any other
…		…
439	your callbacks is well-written it can just attempt the operation and cope	820	your callbacks is well-written it can just attempt the operation and cope
440	with the error from read() or write(). This will not work in multithreaded	821	with the error from read() or write(). This will not work in multithreaded
441	programs, though, so beware.	822	programs, though, so beware.
442		823
443	=back	824	=back
		825
		826	=head2 GENERIC WATCHER FUNCTIONS
		827
		828	In the following description, C<TYPE> stands for the watcher type,
		829	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		830
		831	=over 4
		832
		833	=item C<ev_init> (ev_TYPE *watcher, callback)
		834
		835	This macro initialises the generic portion of a watcher. The contents
		836	of the watcher object can be arbitrary (so C<malloc> will do). Only
		837	the generic parts of the watcher are initialised, you I<need> to call
		838	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		839	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		840	which rolls both calls into one.
		841
		842	You can reinitialise a watcher at any time as long as it has been stopped
		843	(or never started) and there are no pending events outstanding.
		844
		845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		846	int revents)>.
		847
		848	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		849
		850	This macro initialises the type-specific parts of a watcher. You need to
		851	call C<ev_init> at least once before you call this macro, but you can
		852	call C<ev_TYPE_set> any number of times. You must not, however, call this
		853	macro on a watcher that is active (it can be pending, however, which is a
		854	difference to the C<ev_init> macro).
		855
		856	Although some watcher types do not have type-specific arguments
		857	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		858
		859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		860
		861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		862	calls into a single call. This is the most convinient method to initialise
		863	a watcher. The same limitations apply, of course.
		864
		865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		866
		867	Starts (activates) the given watcher. Only active watchers will receive
		868	events. If the watcher is already active nothing will happen.
		869
		870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		871
		872	Stops the given watcher again (if active) and clears the pending
		873	status. It is possible that stopped watchers are pending (for example,
		874	non-repeating timers are being stopped when they become pending), but
		875	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		876	you want to free or reuse the memory used by the watcher it is therefore a
		877	good idea to always call its C<ev_TYPE_stop> function.
		878
		879	=item bool ev_is_active (ev_TYPE *watcher)
		880
		881	Returns a true value iff the watcher is active (i.e. it has been started
		882	and not yet been stopped). As long as a watcher is active you must not modify
		883	it.
		884
		885	=item bool ev_is_pending (ev_TYPE *watcher)
		886
		887	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		888	events but its callback has not yet been invoked). As long as a watcher
		889	is pending (but not active) you must not call an init function on it (but
		890	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		891	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		892	it).
		893
		894	=item callback ev_cb (ev_TYPE *watcher)
		895
		896	Returns the callback currently set on the watcher.
		897
		898	=item ev_cb_set (ev_TYPE *watcher, callback)
		899
		900	Change the callback. You can change the callback at virtually any time
		901	(modulo threads).
		902
		903	=item ev_set_priority (ev_TYPE *watcher, priority)
		904
		905	=item int ev_priority (ev_TYPE *watcher)
		906
		907	Set and query the priority of the watcher. The priority is a small
		908	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		909	(default: C<-2>). Pending watchers with higher priority will be invoked
		910	before watchers with lower priority, but priority will not keep watchers
		911	from being executed (except for C<ev_idle> watchers).
		912
		913	This means that priorities are I<only> used for ordering callback
		914	invocation after new events have been received. This is useful, for
		915	example, to reduce latency after idling, or more often, to bind two
		916	watchers on the same event and make sure one is called first.
		917
		918	If you need to suppress invocation when higher priority events are pending
		919	you need to look at C<ev_idle> watchers, which provide this functionality.
		920
		921	You I<must not> change the priority of a watcher as long as it is active or
		922	pending.
		923
		924	The default priority used by watchers when no priority has been set is
		925	always C<0>, which is supposed to not be too high and not be too low :).
		926
		927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		928	fine, as long as you do not mind that the priority value you query might
		929	or might not have been adjusted to be within valid range.
		930
		931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		932
		933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		934	C<loop> nor C<revents> need to be valid as long as the watcher callback
		935	can deal with that fact.
		936
		937	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		938
		939	If the watcher is pending, this function returns clears its pending status
		940	and returns its C<revents> bitset (as if its callback was invoked). If the
		941	watcher isn't pending it does nothing and returns C<0>.
		942
		943	=back
		944
444		945
445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
446		947
447	Each watcher has, by default, a member C<void *data> that you can change	948	Each watcher has, by default, a member C<void *data> that you can change
448	and read at any time, libev will completely ignore it. This can be used	949	and read at any time, libev will completely ignore it. This can be used
…		…
466	{	967	{
467	struct my_io *w = (struct my_io *)w_;	968	struct my_io *w = (struct my_io *)w_;
468	...	969	...
469	}	970	}
470		971
471	More interesting and less C-conformant ways of catsing your callback type	972	More interesting and less C-conformant ways of casting your callback type
472	have been omitted....	973	instead have been omitted.
		974
		975	Another common scenario is having some data structure with multiple
		976	watchers:
		977
		978	struct my_biggy
		979	{
		980	int some_data;
		981	ev_timer t1;
		982	ev_timer t2;
		983	}
		984
		985	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		986	you need to use C<offsetof>:
		987
		988	#include <stddef.h>
		989
		990	static void
		991	t1_cb (EV_P_ struct ev_timer *w, int revents)
		992	{
		993	struct my_biggy big = (struct my_biggy *
		994	(((char *)w) - offsetof (struct my_biggy, t1));
		995	}
		996
		997	static void
		998	t2_cb (EV_P_ struct ev_timer *w, int revents)
		999	{
		1000	struct my_biggy big = (struct my_biggy *
		1001	(((char *)w) - offsetof (struct my_biggy, t2));
		1002	}
473		1003
474		1004
475	=head1 WATCHER TYPES	1005	=head1 WATCHER TYPES
476		1006
477	This section describes each watcher in detail, but will not repeat	1007	This section describes each watcher in detail, but will not repeat
478	information given in the last section.	1008	information given in the last section. Any initialisation/set macros,
		1009	functions and members specific to the watcher type are explained.
479		1010
		1011	Members are additionally marked with either I<[read-only]>, meaning that,
		1012	while the watcher is active, you can look at the member and expect some
		1013	sensible content, but you must not modify it (you can modify it while the
		1014	watcher is stopped to your hearts content), or I<[read-write]>, which
		1015	means you can expect it to have some sensible content while the watcher
		1016	is active, but you can also modify it. Modifying it may not do something
		1017	sensible or take immediate effect (or do anything at all), but libev will
		1018	not crash or malfunction in any way.
		1019
		1020
480	=head2 C<ev_io> - is this file descriptor readable or writable	1021	=head2 C<ev_io> - is this file descriptor readable or writable?
481		1022
482	I/O watchers check whether a file descriptor is readable or writable	1023	I/O watchers check whether a file descriptor is readable or writable
483	in each iteration of the event loop (This behaviour is called	1024	in each iteration of the event loop, or, more precisely, when reading
484	level-triggering because you keep receiving events as long as the	1025	would not block the process and writing would at least be able to write
485	condition persists. Remember you can stop the watcher if you don't want to	1026	some data. This behaviour is called level-triggering because you keep
486	act on the event and neither want to receive future events).	1027	receiving events as long as the condition persists. Remember you can stop
		1028	the watcher if you don't want to act on the event and neither want to
		1029	receive future events.
487		1030
488	In general you can register as many read and/or write event watchers per	1031	In general you can register as many read and/or write event watchers per
489	fd as you want (as long as you don't confuse yourself). Setting all file	1032	fd as you want (as long as you don't confuse yourself). Setting all file
490	descriptors to non-blocking mode is also usually a good idea (but not	1033	descriptors to non-blocking mode is also usually a good idea (but not
491	required if you know what you are doing).	1034	required if you know what you are doing).
492		1035
493	You have to be careful with dup'ed file descriptors, though. Some backends
494	(the linux epoll backend is a notable example) cannot handle dup'ed file
495	descriptors correctly if you register interest in two or more fds pointing
496	to the same underlying file/socket etc. description (that is, they share
497	the same underlying "file open").
498
499	If you must do this, then force the use of a known-to-be-good backend	1036	If you must do this, then force the use of a known-to-be-good backend
500	(at the time of this writing, this includes only EVMETHOD_SELECT and	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
501	EVMETHOD_POLL).	1038	C<EVBACKEND_POLL>).
		1039
		1040	Another thing you have to watch out for is that it is quite easy to
		1041	receive "spurious" readyness notifications, that is your callback might
		1042	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1043	because there is no data. Not only are some backends known to create a
		1044	lot of those (for example solaris ports), it is very easy to get into
		1045	this situation even with a relatively standard program structure. Thus
		1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1048
		1049	If you cannot run the fd in non-blocking mode (for example you should not
		1050	play around with an Xlib connection), then you have to seperately re-test
		1051	whether a file descriptor is really ready with a known-to-be good interface
		1052	such as poll (fortunately in our Xlib example, Xlib already does this on
		1053	its own, so its quite safe to use).
		1054
		1055	=head3 The special problem of disappearing file descriptors
		1056
		1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1058	descriptor (either by calling C<close> explicitly or by any other means,
		1059	such as C<dup>). The reason is that you register interest in some file
		1060	descriptor, but when it goes away, the operating system will silently drop
		1061	this interest. If another file descriptor with the same number then is
		1062	registered with libev, there is no efficient way to see that this is, in
		1063	fact, a different file descriptor.
		1064
		1065	To avoid having to explicitly tell libev about such cases, libev follows
		1066	the following policy: Each time C<ev_io_set> is being called, libev
		1067	will assume that this is potentially a new file descriptor, otherwise
		1068	it is assumed that the file descriptor stays the same. That means that
		1069	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1070	descriptor even if the file descriptor number itself did not change.
		1071
		1072	This is how one would do it normally anyway, the important point is that
		1073	the libev application should not optimise around libev but should leave
		1074	optimisations to libev.
		1075
		1076	=head3 The special problem of dup'ed file descriptors
		1077
		1078	Some backends (e.g. epoll), cannot register events for file descriptors,
		1079	but only events for the underlying file descriptions. That means when you
		1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1081	events for them, only one file descriptor might actually receive events.
		1082
		1083	There is no workaround possible except not registering events
		1084	for potentially C<dup ()>'ed file descriptors, or to resort to
		1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1086
		1087	=head3 The special problem of fork
		1088
		1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1090	useless behaviour. Libev fully supports fork, but needs to be told about
		1091	it in the child.
		1092
		1093	To support fork in your programs, you either have to call
		1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1096	C<EVBACKEND_POLL>.
		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
		1110
		1111	=head3 Watcher-Specific Functions
502		1112
503	=over 4	1113	=over 4
504		1114
505	=item ev_io_init (ev_io *, callback, int fd, int events)	1115	=item ev_io_init (ev_io *, callback, int fd, int events)
506		1116
507	=item ev_io_set (ev_io *, int fd, int events)	1117	=item ev_io_set (ev_io *, int fd, int events)
508		1118
509	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
510	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1120	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
511	EV_WRITE> to receive the given events.	1121	C<EV_READ | EV_WRITE> to receive the given events.
		1122
		1123	=item int fd [read-only]
		1124
		1125	The file descriptor being watched.
		1126
		1127	=item int events [read-only]
		1128
		1129	The events being watched.
512		1130
513	=back	1131	=back
514		1132
		1133	=head3 Examples
		1134
		1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1136	readable, but only once. Since it is likely line-buffered, you could
		1137	attempt to read a whole line in the callback.
		1138
		1139	static void
		1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1141	{
		1142	ev_io_stop (loop, w);
		1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1144	}
		1145
		1146	...
		1147	struct ev_loop *loop = ev_default_init (0);
		1148	struct ev_io stdin_readable;
		1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1150	ev_io_start (loop, &stdin_readable);
		1151	ev_loop (loop, 0);
		1152
		1153
515	=head2 C<ev_timer> - relative and optionally recurring timeouts	1154	=head2 C<ev_timer> - relative and optionally repeating timeouts
516		1155
517	Timer watchers are simple relative timers that generate an event after a	1156	Timer watchers are simple relative timers that generate an event after a
518	given time, and optionally repeating in regular intervals after that.	1157	given time, and optionally repeating in regular intervals after that.
519		1158
520	The timers are based on real time, that is, if you register an event that	1159	The timers are based on real time, that is, if you register an event that
…		…
533		1172
534	The callback is guarenteed to be invoked only when its timeout has passed,	1173	The callback is guarenteed to be invoked only when its timeout has passed,
535	but if multiple timers become ready during the same loop iteration then	1174	but if multiple timers become ready during the same loop iteration then
536	order of execution is undefined.	1175	order of execution is undefined.
537		1176
		1177	=head3 Watcher-Specific Functions and Data Members
		1178
538	=over 4	1179	=over 4
539		1180
540	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
541		1182
542	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
550	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
551	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
552	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
553	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
554		1195
555	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
556		1197
557	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
558	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
559		1200
		1201	If the timer is pending, its pending status is cleared.
		1202
560	If the timer is started but nonrepeating, stop it.	1203	If the timer is started but nonrepeating, stop it (as if it timed out).
561		1204
562	If the timer is repeating, either start it if necessary (with the repeat	1205	If the timer is repeating, either start it if necessary (with the
563	value), or reset the running timer to the repeat value.	1206	C<repeat> value), or reset the running timer to the C<repeat> value.
564		1207
565	This sounds a bit complicated, but here is a useful and typical	1208	This sounds a bit complicated, but here is a useful and typical
566	example: Imagine you have a tcp connection and you want a so-called idle	1209	example: Imagine you have a tcp connection and you want a so-called idle
567	timeout, that is, you want to be called when there have been, say, 60	1210	timeout, that is, you want to be called when there have been, say, 60
568	seconds of inactivity on the socket. The easiest way to do this is to	1211	seconds of inactivity on the socket. The easiest way to do this is to
569	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1212	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
570	time you successfully read or write some data. If you go into an idle	1213	C<ev_timer_again> each time you successfully read or write some data. If
571	state where you do not expect data to travel on the socket, you can stop	1214	you go into an idle state where you do not expect data to travel on the
572	the timer, and again will automatically restart it if need be.	1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1216	automatically restart it if need be.
		1217
		1218	That means you can ignore the C<after> value and C<ev_timer_start>
		1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1220
		1221	ev_timer_init (timer, callback, 0., 5.);
		1222	ev_timer_again (loop, timer);
		1223	...
		1224	timer->again = 17.;
		1225	ev_timer_again (loop, timer);
		1226	...
		1227	timer->again = 10.;
		1228	ev_timer_again (loop, timer);
		1229
		1230	This is more slightly efficient then stopping/starting the timer each time
		1231	you want to modify its timeout value.
		1232
		1233	=item ev_tstamp repeat [read-write]
		1234
		1235	The current C<repeat> value. Will be used each time the watcher times out
		1236	or C<ev_timer_again> is called and determines the next timeout (if any),
		1237	which is also when any modifications are taken into account.
573		1238
574	=back	1239	=back
575		1240
		1241	=head3 Examples
		1242
		1243	Example: Create a timer that fires after 60 seconds.
		1244
		1245	static void
		1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1247	{
		1248	.. one minute over, w is actually stopped right here
		1249	}
		1250
		1251	struct ev_timer mytimer;
		1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1253	ev_timer_start (loop, &mytimer);
		1254
		1255	Example: Create a timeout timer that times out after 10 seconds of
		1256	inactivity.
		1257
		1258	static void
		1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1260	{
		1261	.. ten seconds without any activity
		1262	}
		1263
		1264	struct ev_timer mytimer;
		1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1266	ev_timer_again (&mytimer); /* start timer */
		1267	ev_loop (loop, 0);
		1268
		1269	// and in some piece of code that gets executed on any "activity":
		1270	// reset the timeout to start ticking again at 10 seconds
		1271	ev_timer_again (&mytimer);
		1272
		1273
576	=head2 C<ev_periodic> - to cron or not to cron	1274	=head2 C<ev_periodic> - to cron or not to cron?
577		1275
578	Periodic watchers are also timers of a kind, but they are very versatile	1276	Periodic watchers are also timers of a kind, but they are very versatile
579	(and unfortunately a bit complex).	1277	(and unfortunately a bit complex).
580		1278
581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
582	but on wallclock time (absolute time). You can tell a periodic watcher	1280	but on wallclock time (absolute time). You can tell a periodic watcher
583	to trigger "at" some specific point in time. For example, if you tell a	1281	to trigger "at" some specific point in time. For example, if you tell a
584	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
585	+ 10.>) and then reset your system clock to the last year, then it will	1283	+ 10.>) and then reset your system clock to the last year, then it will
586	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
587	roughly 10 seconds later and of course not if you reset your system time	1285	roughly 10 seconds later).
588	again).
589		1286
590	They can also be used to implement vastly more complex timers, such as	1287	They can also be used to implement vastly more complex timers, such as
591	triggering an event on eahc midnight, local time.	1288	triggering an event on each midnight, local time or other, complicated,
		1289	rules.
592		1290
593	As with timers, the callback is guarenteed to be invoked only when the	1291	As with timers, the callback is guarenteed to be invoked only when the
594	time (C<at>) has been passed, but if multiple periodic timers become ready	1292	time (C<at>) has been passed, but if multiple periodic timers become ready
595	during the same loop iteration then order of execution is undefined.	1293	during the same loop iteration then order of execution is undefined.
596		1294
		1295	=head3 Watcher-Specific Functions and Data Members
		1296
597	=over 4	1297	=over 4
598		1298
599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
600		1300
601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
603	Lots of arguments, lets sort it out... There are basically three modes of	1303	Lots of arguments, lets sort it out... There are basically three modes of
604	operation, and we will explain them from simplest to complex:	1304	operation, and we will explain them from simplest to complex:
605		1305
606	=over 4	1306	=over 4
607		1307
608	=item * absolute timer (interval = reschedule_cb = 0)	1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)
609		1309
610	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
611	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
612	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
613	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
614		1314
615	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
616		1316
617	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
618	C<at + N * interval> time (for some integer N) and then repeat, regardless	1318	C<at + N * interval> time (for some integer N, which can also be negative)
619	of any time jumps.	1319	and then repeat, regardless of any time jumps.
620		1320
621	This can be used to create timers that do not drift with respect to system	1321	This can be used to create timers that do not drift with respect to system
622	time:	1322	time:
623		1323
624	ev_periodic_set (&periodic, 0., 3600., 0);	1324	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
630		1330
631	Another way to think about it (for the mathematically inclined) is that	1331	Another way to think about it (for the mathematically inclined) is that
632	C<ev_periodic> will try to run the callback in this mode at the next possible	1332	C<ev_periodic> will try to run the callback in this mode at the next possible
633	time where C<time = at (mod interval)>, regardless of any time jumps.	1333	time where C<time = at (mod interval)>, regardless of any time jumps.
634		1334
		1335	For numerical stability it is preferable that the C<at> value is near
		1336	C<ev_now ()> (the current time), but there is no range requirement for
		1337	this value.
		1338
635	=item * manual reschedule mode (reschedule_cb = callback)	1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
636		1340
637	In this mode the values for C<interval> and C<at> are both being	1341	In this mode the values for C<interval> and C<at> are both being
638	ignored. Instead, each time the periodic watcher gets scheduled, the	1342	ignored. Instead, each time the periodic watcher gets scheduled, the
639	reschedule callback will be called with the watcher as first, and the	1343	reschedule callback will be called with the watcher as first, and the
640	current time as second argument.	1344	current time as second argument.
641		1345
642	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
643	ever, or make any event loop modifications>. If you need to stop it,	1347	ever, or make any event loop modifications>. If you need to stop it,
644	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
645	starting a prepare watcher).	1349	starting an C<ev_prepare> watcher, which is legal).
646		1350
647	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
648	ev_tstamp now)>, e.g.:	1352	ev_tstamp now)>, e.g.:
649		1353
650	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
673	Simply stops and restarts the periodic watcher again. This is only useful	1377	Simply stops and restarts the periodic watcher again. This is only useful
674	when you changed some parameters or the reschedule callback would return	1378	when you changed some parameters or the reschedule callback would return
675	a different time than the last time it was called (e.g. in a crond like	1379	a different time than the last time it was called (e.g. in a crond like
676	program when the crontabs have changed).	1380	program when the crontabs have changed).
677		1381
		1382	=item ev_tstamp offset [read-write]
		1383
		1384	When repeating, this contains the offset value, otherwise this is the
		1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1386
		1387	Can be modified any time, but changes only take effect when the periodic
		1388	timer fires or C<ev_periodic_again> is being called.
		1389
		1390	=item ev_tstamp interval [read-write]
		1391
		1392	The current interval value. Can be modified any time, but changes only
		1393	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1394	called.
		1395
		1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1397
		1398	The current reschedule callback, or C<0>, if this functionality is
		1399	switched off. Can be changed any time, but changes only take effect when
		1400	the periodic timer fires or C<ev_periodic_again> is being called.
		1401
		1402	=item ev_tstamp at [read-only]
		1403
		1404	When active, contains the absolute time that the watcher is supposed to
		1405	trigger next.
		1406
678	=back	1407	=back
679		1408
		1409	=head3 Examples
		1410
		1411	Example: Call a callback every hour, or, more precisely, whenever the
		1412	system clock is divisible by 3600. The callback invocation times have
		1413	potentially a lot of jittering, but good long-term stability.
		1414
		1415	static void
		1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1417	{
		1418	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1419	}
		1420
		1421	struct ev_periodic hourly_tick;
		1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1423	ev_periodic_start (loop, &hourly_tick);
		1424
		1425	Example: The same as above, but use a reschedule callback to do it:
		1426
		1427	#include <math.h>
		1428
		1429	static ev_tstamp
		1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1431	{
		1432	return fmod (now, 3600.) + 3600.;
		1433	}
		1434
		1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1436
		1437	Example: Call a callback every hour, starting now:
		1438
		1439	struct ev_periodic hourly_tick;
		1440	ev_periodic_init (&hourly_tick, clock_cb,
		1441	fmod (ev_now (loop), 3600.), 3600., 0);
		1442	ev_periodic_start (loop, &hourly_tick);
		1443
		1444
680	=head2 C<ev_signal> - signal me when a signal gets signalled	1445	=head2 C<ev_signal> - signal me when a signal gets signalled!
681		1446
682	Signal watchers will trigger an event when the process receives a specific	1447	Signal watchers will trigger an event when the process receives a specific
683	signal one or more times. Even though signals are very asynchronous, libev	1448	signal one or more times. Even though signals are very asynchronous, libev
684	will try it's best to deliver signals synchronously, i.e. as part of the	1449	will try it's best to deliver signals synchronously, i.e. as part of the
685	normal event processing, like any other event.	1450	normal event processing, like any other event.
…		…
689	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
690	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
691	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
692	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
693		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
		1465	=head3 Watcher-Specific Functions and Data Members
		1466
694	=over 4	1467	=over 4
695		1468
696	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
697		1470
698	=item ev_signal_set (ev_signal *, int signum)	1471	=item ev_signal_set (ev_signal *, int signum)
699		1472
700	Configures the watcher to trigger on the given signal number (usually one	1473	Configures the watcher to trigger on the given signal number (usually one
701	of the C<SIGxxx> constants).	1474	of the C<SIGxxx> constants).
702		1475
		1476	=item int signum [read-only]
		1477
		1478	The signal the watcher watches out for.
		1479
703	=back	1480	=back
704		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
		1496
705	=head2 C<ev_child> - wait for pid status changes	1497	=head2 C<ev_child> - watch out for process status changes
706		1498
707	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
708	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
		1526
		1527	=head3 Watcher-Specific Functions and Data Members
709		1528
710	=over 4	1529	=over 4
711		1530
712	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
713		1532
714	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
715		1534
716	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
717	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
718	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
719	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
720	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
721	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
		1543
		1544	=item int pid [read-only]
		1545
		1546	The process id this watcher watches out for, or C<0>, meaning any process id.
		1547
		1548	=item int rpid [read-write]
		1549
		1550	The process id that detected a status change.
		1551
		1552	=item int rstatus [read-write]
		1553
		1554	The process exit/trace status caused by C<rpid> (see your systems
		1555	C<waitpid> and C<sys/wait.h> documentation for details).
722		1556
723	=back	1557	=back
724		1558
		1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
		1565
		1566	static void
		1567	child_cb (EV_P_ struct ev_child *w, int revents)
		1568	{
		1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
		1571	}
		1572
		1573	pid_t pid = fork ();
		1574
		1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
		1587
		1588
		1589	=head2 C<ev_stat> - did the file attributes just change?
		1590
		1591	This watches a filesystem path for attribute changes. That is, it calls
		1592	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1593	compared to the last time, invoking the callback if it did.
		1594
		1595	The path does not need to exist: changing from "path exists" to "path does
		1596	not exist" is a status change like any other. The condition "path does
		1597	not exist" is signified by the C<st_nlink> field being zero (which is
		1598	otherwise always forced to be at least one) and all the other fields of
		1599	the stat buffer having unspecified contents.
		1600
		1601	The path I<should> be absolute and I<must not> end in a slash. If it is
		1602	relative and your working directory changes, the behaviour is undefined.
		1603
		1604	Since there is no standard to do this, the portable implementation simply
		1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1606	can specify a recommended polling interval for this case. If you specify
		1607	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1608	unspecified default> value will be used (which you can expect to be around
		1609	five seconds, although this might change dynamically). Libev will also
		1610	impose a minimum interval which is currently around C<0.1>, but thats
		1611	usually overkill.
		1612
		1613	This watcher type is not meant for massive numbers of stat watchers,
		1614	as even with OS-supported change notifications, this can be
		1615	resource-intensive.
		1616
		1617	At the time of this writing, only the Linux inotify interface is
		1618	implemented (implementing kqueue support is left as an exercise for the
		1619	reader). Inotify will be used to give hints only and should not change the
		1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1621	to fall back to regular polling again even with inotify, but changes are
		1622	usually detected immediately, and if the file exists there will be no
		1623	polling.
		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
		1669	=head3 Watcher-Specific Functions and Data Members
		1670
		1671	=over 4
		1672
		1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1674
		1675	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1676
		1677	Configures the watcher to wait for status changes of the given
		1678	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1679	be detected and should normally be specified as C<0> to let libev choose
		1680	a suitable value. The memory pointed to by C<path> must point to the same
		1681	path for as long as the watcher is active.
		1682
		1683	The callback will be receive C<EV_STAT> when a change was detected,
		1684	relative to the attributes at the time the watcher was started (or the
		1685	last change was detected).
		1686
		1687	=item ev_stat_stat (loop, ev_stat *)
		1688
		1689	Updates the stat buffer immediately with new values. If you change the
		1690	watched path in your callback, you could call this fucntion to avoid
		1691	detecting this change (while introducing a race condition). Can also be
		1692	useful simply to find out the new values.
		1693
		1694	=item ev_statdata attr [read-only]
		1695
		1696	The most-recently detected attributes of the file. Although the type is of
		1697	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1698	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1699	was some error while C<stat>ing the file.
		1700
		1701	=item ev_statdata prev [read-only]
		1702
		1703	The previous attributes of the file. The callback gets invoked whenever
		1704	C<prev> != C<attr>.
		1705
		1706	=item ev_tstamp interval [read-only]
		1707
		1708	The specified interval.
		1709
		1710	=item const char *path [read-only]
		1711
		1712	The filesystem path that is being watched.
		1713
		1714	=back
		1715
		1716	=head3 Examples
		1717
		1718	Example: Watch C</etc/passwd> for attribute changes.
		1719
		1720	static void
		1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1722	{
		1723	/* /etc/passwd changed in some way */
		1724	if (w->attr.st_nlink)
		1725	{
		1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1729	}
		1730	else
		1731	/* you shalt not abuse printf for puts */
		1732	puts ("wow, /etc/passwd is not there, expect problems. "
		1733	"if this is windows, they already arrived\n");
		1734	}
		1735
		1736	...
		1737	ev_stat passwd;
		1738
		1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1740	ev_stat_start (loop, &passwd);
		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1769
		1770
725	=head2 C<ev_idle> - when you've got nothing better to do	1771	=head2 C<ev_idle> - when you've got nothing better to do...
726		1772
727	Idle watchers trigger events when there are no other events are pending	1773	Idle watchers trigger events when no other events of the same or higher
728	(prepare, check and other idle watchers do not count). That is, as long	1774	priority are pending (prepare, check and other idle watchers do not
729	as your process is busy handling sockets or timeouts (or even signals,	1775	count).
730	imagine) it will not be triggered. But when your process is idle all idle	1776
731	watchers are being called again and again, once per event loop iteration -	1777	That is, as long as your process is busy handling sockets or timeouts
		1778	(or even signals, imagine) of the same or higher priority it will not be
		1779	triggered. But when your process is idle (or only lower-priority watchers
		1780	are pending), the idle watchers are being called once per event loop
732	until stopped, that is, or your process receives more events and becomes	1781	iteration - until stopped, that is, or your process receives more events
733	busy.	1782	and becomes busy again with higher priority stuff.
734		1783
735	The most noteworthy effect is that as long as any idle watchers are	1784	The most noteworthy effect is that as long as any idle watchers are
736	active, the process will not block when waiting for new events.	1785	active, the process will not block when waiting for new events.
737		1786
738	Apart from keeping your process non-blocking (which is a useful	1787	Apart from keeping your process non-blocking (which is a useful
739	effect on its own sometimes), idle watchers are a good place to do	1788	effect on its own sometimes), idle watchers are a good place to do
740	"pseudo-background processing", or delay processing stuff to after the	1789	"pseudo-background processing", or delay processing stuff to after the
741	event loop has handled all outstanding events.	1790	event loop has handled all outstanding events.
742		1791
		1792	=head3 Watcher-Specific Functions and Data Members
		1793
743	=over 4	1794	=over 4
744		1795
745	=item ev_idle_init (ev_signal *, callback)	1796	=item ev_idle_init (ev_signal *, callback)
746		1797
747	Initialises and configures the idle watcher - it has no parameters of any	1798	Initialises and configures the idle watcher - it has no parameters of any
748	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
749	believe me.	1800	believe me.
750		1801
751	=back	1802	=back
752		1803
		1804	=head3 Examples
		1805
		1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1807	callback, free it. Also, use no error checking, as usual.
		1808
		1809	static void
		1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1811	{
		1812	free (w);
		1813	// now do something you wanted to do when the program has
		1814	// no longer anything immediate to do.
		1815	}
		1816
		1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1818	ev_idle_init (idle_watcher, idle_cb);
		1819	ev_idle_start (loop, idle_cb);
		1820
		1821
753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
754		1823
755	Prepare and check watchers are usually (but not always) used in tandem:	1824	Prepare and check watchers are usually (but not always) used in tandem:
756	prepare watchers get invoked before the process blocks and check watchers	1825	prepare watchers get invoked before the process blocks and check watchers
757	afterwards.	1826	afterwards.
758		1827
		1828	You I<must not> call C<ev_loop> or similar functions that enter
		1829	the current event loop from either C<ev_prepare> or C<ev_check>
		1830	watchers. Other loops than the current one are fine, however. The
		1831	rationale behind this is that you do not need to check for recursion in
		1832	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1833	C<ev_check> so if you have one watcher of each kind they will always be
		1834	called in pairs bracketing the blocking call.
		1835
759	Their main purpose is to integrate other event mechanisms into libev. This	1836	Their main purpose is to integrate other event mechanisms into libev and
760	could be used, for example, to track variable changes, implement your own	1837	their use is somewhat advanced. This could be used, for example, to track
761	watchers, integrate net-snmp or a coroutine library and lots more.	1838	variable changes, implement your own watchers, integrate net-snmp or a
		1839	coroutine library and lots more. They are also occasionally useful if
		1840	you cache some data and want to flush it before blocking (for example,
		1841	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1842	watcher).
762		1843
763	This is done by examining in each prepare call which file descriptors need	1844	This is done by examining in each prepare call which file descriptors need
764	to be watched by the other library, registering C<ev_io> watchers for	1845	to be watched by the other library, registering C<ev_io> watchers for
765	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1846	them and starting an C<ev_timer> watcher for any timeouts (many libraries
766	provide just this functionality). Then, in the check watcher you check for	1847	provide just this functionality). Then, in the check watcher you check for
…		…
776	with priority higher than or equal to the event loop and one coroutine	1857	with priority higher than or equal to the event loop and one coroutine
777	of lower priority, but only once, using idle watchers to keep the event	1858	of lower priority, but only once, using idle watchers to keep the event
778	loop from blocking if lower-priority coroutines are active, thus mapping	1859	loop from blocking if lower-priority coroutines are active, thus mapping
779	low-priority coroutines to idle/background tasks).	1860	low-priority coroutines to idle/background tasks).
780		1861
		1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1863	priority, to ensure that they are being run before any other watchers
		1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1865	too) should not activate ("feed") events into libev. While libev fully
		1866	supports this, they will be called before other C<ev_check> watchers
		1867	did their job. As C<ev_check> watchers are often used to embed other
		1868	(non-libev) event loops those other event loops might be in an unusable
		1869	state until their C<ev_check> watcher ran (always remind yourself to
		1870	coexist peacefully with others).
		1871
		1872	=head3 Watcher-Specific Functions and Data Members
		1873
781	=over 4	1874	=over 4
782		1875
783	=item ev_prepare_init (ev_prepare *, callback)	1876	=item ev_prepare_init (ev_prepare *, callback)
784		1877
785	=item ev_check_init (ev_check *, callback)	1878	=item ev_check_init (ev_check *, callback)
…		…
787	Initialises and configures the prepare or check watcher - they have no	1880	Initialises and configures the prepare or check watcher - they have no
788	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
789	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
790		1883
791	=back	1884	=back
		1885
		1886	=head3 Examples
		1887
		1888	There are a number of principal ways to embed other event loops or modules
		1889	into libev. Here are some ideas on how to include libadns into libev
		1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1891	use for an actually working example. Another Perl module named C<EV::Glib>
		1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1893	into the Glib event loop).
		1894
		1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1896	and in a check watcher, destroy them and call into libadns. What follows
		1897	is pseudo-code only of course. This requires you to either use a low
		1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1899	the callbacks for the IO/timeout watchers might not have been called yet.
		1900
		1901	static ev_io iow [nfd];
		1902	static ev_timer tw;
		1903
		1904	static void
		1905	io_cb (ev_loop *loop, ev_io *w, int revents)
		1906	{
		1907	}
		1908
		1909	// create io watchers for each fd and a timer before blocking
		1910	static void
		1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1912	{
		1913	int timeout = 3600000;
		1914	struct pollfd fds [nfd];
		1915	// actual code will need to loop here and realloc etc.
		1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1917
		1918	/* the callback is illegal, but won't be called as we stop during check */
		1919	ev_timer_init (&tw, 0, timeout * 1e-3);
		1920	ev_timer_start (loop, &tw);
		1921
		1922	// create one ev_io per pollfd
		1923	for (int i = 0; i < nfd; ++i)
		1924	{
		1925	ev_io_init (iow + i, io_cb, fds [i].fd,
		1926	((fds [i].events & POLLIN ? EV_READ : 0)
		1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1928
		1929	fds [i].revents = 0;
		1930	ev_io_start (loop, iow + i);
		1931	}
		1932	}
		1933
		1934	// stop all watchers after blocking
		1935	static void
		1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1937	{
		1938	ev_timer_stop (loop, &tw);
		1939
		1940	for (int i = 0; i < nfd; ++i)
		1941	{
		1942	// set the relevant poll flags
		1943	// could also call adns_processreadable etc. here
		1944	struct pollfd *fd = fds + i;
		1945	int revents = ev_clear_pending (iow + i);
		1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1948
		1949	// now stop the watcher
		1950	ev_io_stop (loop, iow + i);
		1951	}
		1952
		1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1954	}
		1955
		1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1957	in the prepare watcher and would dispose of the check watcher.
		1958
		1959	Method 3: If the module to be embedded supports explicit event
		1960	notification (adns does), you can also make use of the actual watcher
		1961	callbacks, and only destroy/create the watchers in the prepare watcher.
		1962
		1963	static void
		1964	timer_cb (EV_P_ ev_timer *w, int revents)
		1965	{
		1966	adns_state ads = (adns_state)w->data;
		1967	update_now (EV_A);
		1968
		1969	adns_processtimeouts (ads, &tv_now);
		1970	}
		1971
		1972	static void
		1973	io_cb (EV_P_ ev_io *w, int revents)
		1974	{
		1975	adns_state ads = (adns_state)w->data;
		1976	update_now (EV_A);
		1977
		1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1980	}
		1981
		1982	// do not ever call adns_afterpoll
		1983
		1984	Method 4: Do not use a prepare or check watcher because the module you
		1985	want to embed is too inflexible to support it. Instead, youc na override
		1986	their poll function. The drawback with this solution is that the main
		1987	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1988	this.
		1989
		1990	static gint
		1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1992	{
		1993	int got_events = 0;
		1994
		1995	for (n = 0; n < nfds; ++n)
		1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1997
		1998	if (timeout >= 0)
		1999	// create/start timer
		2000
		2001	// poll
		2002	ev_loop (EV_A_ 0);
		2003
		2004	// stop timer again
		2005	if (timeout >= 0)
		2006	ev_timer_stop (EV_A_ &to);
		2007
		2008	// stop io watchers again - their callbacks should have set
		2009	for (n = 0; n < nfds; ++n)
		2010	ev_io_stop (EV_A_ iow [n]);
		2011
		2012	return got_events;
		2013	}
		2014
		2015
		2016	=head2 C<ev_embed> - when one backend isn't enough...
		2017
		2018	This is a rather advanced watcher type that lets you embed one event loop
		2019	into another (currently only C<ev_io> events are supported in the embedded
		2020	loop, other types of watchers might be handled in a delayed or incorrect
		2021	fashion and must not be used).
		2022
		2023	There are primarily two reasons you would want that: work around bugs and
		2024	prioritise I/O.
		2025
		2026	As an example for a bug workaround, the kqueue backend might only support
		2027	sockets on some platform, so it is unusable as generic backend, but you
		2028	still want to make use of it because you have many sockets and it scales
		2029	so nicely. In this case, you would create a kqueue-based loop and embed it
		2030	into your default loop (which might use e.g. poll). Overall operation will
		2031	be a bit slower because first libev has to poll and then call kevent, but
		2032	at least you can use both at what they are best.
		2033
		2034	As for prioritising I/O: rarely you have the case where some fds have
		2035	to be watched and handled very quickly (with low latency), and even
		2036	priorities and idle watchers might have too much overhead. In this case
		2037	you would put all the high priority stuff in one loop and all the rest in
		2038	a second one, and embed the second one in the first.
		2039
		2040	As long as the watcher is active, the callback will be invoked every time
		2041	there might be events pending in the embedded loop. The callback must then
		2042	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		2043	their callbacks (you could also start an idle watcher to give the embedded
		2044	loop strictly lower priority for example). You can also set the callback
		2045	to C<0>, in which case the embed watcher will automatically execute the
		2046	embedded loop sweep.
		2047
		2048	As long as the watcher is started it will automatically handle events. The
		2049	callback will be invoked whenever some events have been handled. You can
		2050	set the callback to C<0> to avoid having to specify one if you are not
		2051	interested in that.
		2052
		2053	Also, there have not currently been made special provisions for forking:
		2054	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		2055	but you will also have to stop and restart any C<ev_embed> watchers
		2056	yourself.
		2057
		2058	Unfortunately, not all backends are embeddable, only the ones returned by
		2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		2060	portable one.
		2061
		2062	So when you want to use this feature you will always have to be prepared
		2063	that you cannot get an embeddable loop. The recommended way to get around
		2064	this is to have a separate variables for your embeddable loop, try to
		2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
		2100
		2101	struct ev_loop *loop_hi = ev_default_init (0);
		2102	struct ev_loop *loop_lo = 0;
		2103	struct ev_embed embed;
		2104
		2105	// see if there is a chance of getting one that works
		2106	// (remember that a flags value of 0 means autodetection)
		2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2109	: 0;
		2110
		2111	// if we got one, then embed it, otherwise default to loop_hi
		2112	if (loop_lo)
		2113	{
		2114	ev_embed_init (&embed, 0, loop_lo);
		2115	ev_embed_start (loop_hi, &embed);
		2116	}
		2117	else
		2118	loop_lo = loop_hi;
		2119
		2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2124
		2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
		2135
		2136	if (!loop_socket)
		2137	loop_socket = loop;
		2138
		2139	// now use loop_socket for all sockets, and loop for everything else
		2140
		2141
		2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2143
		2144	Fork watchers are called when a C<fork ()> was detected (usually because
		2145	whoever is a good citizen cared to tell libev about it by calling
		2146	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2147	event loop blocks next and before C<ev_check> watchers are being called,
		2148	and only in the child after the fork. If whoever good citizen calling
		2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2150	handlers will be invoked, too, of course.
		2151
		2152	=head3 Watcher-Specific Functions and Data Members
		2153
		2154	=over 4
		2155
		2156	=item ev_fork_init (ev_signal *, callback)
		2157
		2158	Initialises and configures the fork watcher - it has no parameters of any
		2159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2160	believe me.
		2161
		2162	=back
		2163
		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=back
		2294
792		2295
793	=head1 OTHER FUNCTIONS	2296	=head1 OTHER FUNCTIONS
794		2297
795	There are some other functions of possible interest. Described. Here. Now.	2298	There are some other functions of possible interest. Described. Here. Now.
796		2299
…		…
826	/* stdin might have data for us, joy! */;	2329	/* stdin might have data for us, joy! */;
827	}	2330	}
828		2331
829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2332	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
830		2333
831	=item ev_feed_event (loop, watcher, int events)	2334	=item ev_feed_event (ev_loop *, watcher *, int revents)
832		2335
833	Feeds the given event set into the event loop, as if the specified event	2336	Feeds the given event set into the event loop, as if the specified event
834	had happened for the specified watcher (which must be a pointer to an	2337	had happened for the specified watcher (which must be a pointer to an
835	initialised but not necessarily started event watcher).	2338	initialised but not necessarily started event watcher).
836		2339
837	=item ev_feed_fd_event (loop, int fd, int revents)	2340	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
838		2341
839	Feed an event on the given fd, as if a file descriptor backend detected	2342	Feed an event on the given fd, as if a file descriptor backend detected
840	the given events it.	2343	the given events it.
841		2344
842	=item ev_feed_signal_event (loop, int signum)	2345	=item ev_feed_signal_event (ev_loop *loop, int signum)
843		2346
844	Feed an event as if the given signal occured (loop must be the default loop!).	2347	Feed an event as if the given signal occured (C<loop> must be the default
		2348	loop!).
845		2349
846	=back	2350	=back
		2351
847		2352
848	=head1 LIBEVENT EMULATION	2353	=head1 LIBEVENT EMULATION
849		2354
850	Libev offers a compatibility emulation layer for libevent. It cannot	2355	Libev offers a compatibility emulation layer for libevent. It cannot
851	emulate the internals of libevent, so here are some usage hints:	2356	emulate the internals of libevent, so here are some usage hints:
…		…
872		2377
873	=back	2378	=back
874		2379
875	=head1 C++ SUPPORT	2380	=head1 C++ SUPPORT
876		2381
877	TBD.	2382	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2383	you to use some convinience methods to start/stop watchers and also change
		2384	the callback model to a model using method callbacks on objects.
		2385
		2386	To use it,
		2387
		2388	#include <ev++.h>
		2389
		2390	This automatically includes F<ev.h> and puts all of its definitions (many
		2391	of them macros) into the global namespace. All C++ specific things are
		2392	put into the C<ev> namespace. It should support all the same embedding
		2393	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2394
		2395	Care has been taken to keep the overhead low. The only data member the C++
		2396	classes add (compared to plain C-style watchers) is the event loop pointer
		2397	that the watcher is associated with (or no additional members at all if
		2398	you disable C<EV_MULTIPLICITY> when embedding libev).
		2399
		2400	Currently, functions, and static and non-static member functions can be
		2401	used as callbacks. Other types should be easy to add as long as they only
		2402	need one additional pointer for context. If you need support for other
		2403	types of functors please contact the author (preferably after implementing
		2404	it).
		2405
		2406	Here is a list of things available in the C<ev> namespace:
		2407
		2408	=over 4
		2409
		2410	=item C<ev::READ>, C<ev::WRITE> etc.
		2411
		2412	These are just enum values with the same values as the C<EV_READ> etc.
		2413	macros from F<ev.h>.
		2414
		2415	=item C<ev::tstamp>, C<ev::now>
		2416
		2417	Aliases to the same types/functions as with the C<ev_> prefix.
		2418
		2419	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2420
		2421	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2422	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2423	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2424	defines by many implementations.
		2425
		2426	All of those classes have these methods:
		2427
		2428	=over 4
		2429
		2430	=item ev::TYPE::TYPE ()
		2431
		2432	=item ev::TYPE::TYPE (struct ev_loop *)
		2433
		2434	=item ev::TYPE::~TYPE
		2435
		2436	The constructor (optionally) takes an event loop to associate the watcher
		2437	with. If it is omitted, it will use C<EV_DEFAULT>.
		2438
		2439	The constructor calls C<ev_init> for you, which means you have to call the
		2440	C<set> method before starting it.
		2441
		2442	It will not set a callback, however: You have to call the templated C<set>
		2443	method to set a callback before you can start the watcher.
		2444
		2445	(The reason why you have to use a method is a limitation in C++ which does
		2446	not allow explicit template arguments for constructors).
		2447
		2448	The destructor automatically stops the watcher if it is active.
		2449
		2450	=item w->set<class, &class::method> (object *)
		2451
		2452	This method sets the callback method to call. The method has to have a
		2453	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2454	first argument and the C<revents> as second. The object must be given as
		2455	parameter and is stored in the C<data> member of the watcher.
		2456
		2457	This method synthesizes efficient thunking code to call your method from
		2458	the C callback that libev requires. If your compiler can inline your
		2459	callback (i.e. it is visible to it at the place of the C<set> call and
		2460	your compiler is good :), then the method will be fully inlined into the
		2461	thunking function, making it as fast as a direct C callback.
		2462
		2463	Example: simple class declaration and watcher initialisation
		2464
		2465	struct myclass
		2466	{
		2467	void io_cb (ev::io &w, int revents) { }
		2468	}
		2469
		2470	myclass obj;
		2471	ev::io iow;
		2472	iow.set <myclass, &myclass::io_cb> (&obj);
		2473
		2474	=item w->set<function> (void *data = 0)
		2475
		2476	Also sets a callback, but uses a static method or plain function as
		2477	callback. The optional C<data> argument will be stored in the watcher's
		2478	C<data> member and is free for you to use.
		2479
		2480	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2481
		2482	See the method-C<set> above for more details.
		2483
		2484	Example:
		2485
		2486	static void io_cb (ev::io &w, int revents) { }
		2487	iow.set <io_cb> ();
		2488
		2489	=item w->set (struct ev_loop *)
		2490
		2491	Associates a different C<struct ev_loop> with this watcher. You can only
		2492	do this when the watcher is inactive (and not pending either).
		2493
		2494	=item w->set ([args])
		2495
		2496	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2497	called at least once. Unlike the C counterpart, an active watcher gets
		2498	automatically stopped and restarted when reconfiguring it with this
		2499	method.
		2500
		2501	=item w->start ()
		2502
		2503	Starts the watcher. Note that there is no C<loop> argument, as the
		2504	constructor already stores the event loop.
		2505
		2506	=item w->stop ()
		2507
		2508	Stops the watcher if it is active. Again, no C<loop> argument.
		2509
		2510	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2511
		2512	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2513	C<ev_TYPE_again> function.
		2514
		2515	=item w->sweep () (C<ev::embed> only)
		2516
		2517	Invokes C<ev_embed_sweep>.
		2518
		2519	=item w->update () (C<ev::stat> only)
		2520
		2521	Invokes C<ev_stat_stat>.
		2522
		2523	=back
		2524
		2525	=back
		2526
		2527	Example: Define a class with an IO and idle watcher, start one of them in
		2528	the constructor.
		2529
		2530	class myclass
		2531	{
		2532	ev::io io; void io_cb (ev::io &w, int revents);
		2533	ev:idle idle void idle_cb (ev::idle &w, int revents);
		2534
		2535	myclass (int fd)
		2536	{
		2537	io .set <myclass, &myclass::io_cb > (this);
		2538	idle.set <myclass, &myclass::idle_cb> (this);
		2539
		2540	io.start (fd, ev::READ);
		2541	}
		2542	};
		2543
		2544
		2545	=head1 OTHER LANGUAGE BINDINGS
		2546
		2547	Libev does not offer other language bindings itself, but bindings for a
		2548	numbe rof languages exist in the form of third-party packages. If you know
		2549	any interesting language binding in addition to the ones listed here, drop
		2550	me a note.
		2551
		2552	=over 4
		2553
		2554	=item Perl
		2555
		2556	The EV module implements the full libev API and is actually used to test
		2557	libev. EV is developed together with libev. Apart from the EV core module,
		2558	there are additional modules that implement libev-compatible interfaces
		2559	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2560	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2561
		2562	It can be found and installed via CPAN, its homepage is found at
		2563	L<http://software.schmorp.de/pkg/EV>.
		2564
		2565	=item Ruby
		2566
		2567	Tony Arcieri has written a ruby extension that offers access to a subset
		2568	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2569	more on top of it. It can be found via gem servers. Its homepage is at
		2570	L<http://rev.rubyforge.org/>.
		2571
		2572	=item D
		2573
		2574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2575	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2576
		2577	=back
		2578
		2579
		2580	=head1 MACRO MAGIC
		2581
		2582	Libev can be compiled with a variety of options, the most fundamantal
		2583	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2584	functions and callbacks have an initial C<struct ev_loop *> argument.
		2585
		2586	To make it easier to write programs that cope with either variant, the
		2587	following macros are defined:
		2588
		2589	=over 4
		2590
		2591	=item C<EV_A>, C<EV_A_>
		2592
		2593	This provides the loop I<argument> for functions, if one is required ("ev
		2594	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2595	C<EV_A_> is used when other arguments are following. Example:
		2596
		2597	ev_unref (EV_A);
		2598	ev_timer_add (EV_A_ watcher);
		2599	ev_loop (EV_A_ 0);
		2600
		2601	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2602	which is often provided by the following macro.
		2603
		2604	=item C<EV_P>, C<EV_P_>
		2605
		2606	This provides the loop I<parameter> for functions, if one is required ("ev
		2607	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2608	C<EV_P_> is used when other parameters are following. Example:
		2609
		2610	// this is how ev_unref is being declared
		2611	static void ev_unref (EV_P);
		2612
		2613	// this is how you can declare your typical callback
		2614	static void cb (EV_P_ ev_timer *w, int revents)
		2615
		2616	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2617	suitable for use with C<EV_A>.
		2618
		2619	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2620
		2621	Similar to the other two macros, this gives you the value of the default
		2622	loop, if multiple loops are supported ("ev loop default").
		2623
		2624	=back
		2625
		2626	Example: Declare and initialise a check watcher, utilising the above
		2627	macros so it will work regardless of whether multiple loops are supported
		2628	or not.
		2629
		2630	static void
		2631	check_cb (EV_P_ ev_timer *w, int revents)
		2632	{
		2633	ev_check_stop (EV_A_ w);
		2634	}
		2635
		2636	ev_check check;
		2637	ev_check_init (&check, check_cb);
		2638	ev_check_start (EV_DEFAULT_ &check);
		2639	ev_loop (EV_DEFAULT_ 0);
		2640
		2641	=head1 EMBEDDING
		2642
		2643	Libev can (and often is) directly embedded into host
		2644	applications. Examples of applications that embed it include the Deliantra
		2645	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2646	and rxvt-unicode.
		2647
		2648	The goal is to enable you to just copy the necessary files into your
		2649	source directory without having to change even a single line in them, so
		2650	you can easily upgrade by simply copying (or having a checked-out copy of
		2651	libev somewhere in your source tree).
		2652
		2653	=head2 FILESETS
		2654
		2655	Depending on what features you need you need to include one or more sets of files
		2656	in your app.
		2657
		2658	=head3 CORE EVENT LOOP
		2659
		2660	To include only the libev core (all the C<ev_*> functions), with manual
		2661	configuration (no autoconf):
		2662
		2663	#define EV_STANDALONE 1
		2664	#include "ev.c"
		2665
		2666	This will automatically include F<ev.h>, too, and should be done in a
		2667	single C source file only to provide the function implementations. To use
		2668	it, do the same for F<ev.h> in all files wishing to use this API (best
		2669	done by writing a wrapper around F<ev.h> that you can include instead and
		2670	where you can put other configuration options):
		2671
		2672	#define EV_STANDALONE 1
		2673	#include "ev.h"
		2674
		2675	Both header files and implementation files can be compiled with a C++
		2676	compiler (at least, thats a stated goal, and breakage will be treated
		2677	as a bug).
		2678
		2679	You need the following files in your source tree, or in a directory
		2680	in your include path (e.g. in libev/ when using -Ilibev):
		2681
		2682	ev.h
		2683	ev.c
		2684	ev_vars.h
		2685	ev_wrap.h
		2686
		2687	ev_win32.c required on win32 platforms only
		2688
		2689	ev_select.c only when select backend is enabled (which is enabled by default)
		2690	ev_poll.c only when poll backend is enabled (disabled by default)
		2691	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2692	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2693	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2694
		2695	F<ev.c> includes the backend files directly when enabled, so you only need
		2696	to compile this single file.
		2697
		2698	=head3 LIBEVENT COMPATIBILITY API
		2699
		2700	To include the libevent compatibility API, also include:
		2701
		2702	#include "event.c"
		2703
		2704	in the file including F<ev.c>, and:
		2705
		2706	#include "event.h"
		2707
		2708	in the files that want to use the libevent API. This also includes F<ev.h>.
		2709
		2710	You need the following additional files for this:
		2711
		2712	event.h
		2713	event.c
		2714
		2715	=head3 AUTOCONF SUPPORT
		2716
		2717	Instead of using C<EV_STANDALONE=1> and providing your config in
		2718	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2719	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2720	include F<config.h> and configure itself accordingly.
		2721
		2722	For this of course you need the m4 file:
		2723
		2724	libev.m4
		2725
		2726	=head2 PREPROCESSOR SYMBOLS/MACROS
		2727
		2728	Libev can be configured via a variety of preprocessor symbols you have to define
		2729	before including any of its files. The default is not to build for multiplicity
		2730	and only include the select backend.
		2731
		2732	=over 4
		2733
		2734	=item EV_STANDALONE
		2735
		2736	Must always be C<1> if you do not use autoconf configuration, which
		2737	keeps libev from including F<config.h>, and it also defines dummy
		2738	implementations for some libevent functions (such as logging, which is not
		2739	supported). It will also not define any of the structs usually found in
		2740	F<event.h> that are not directly supported by the libev core alone.
		2741
		2742	=item EV_USE_MONOTONIC
		2743
		2744	If defined to be C<1>, libev will try to detect the availability of the
		2745	monotonic clock option at both compiletime and runtime. Otherwise no use
		2746	of the monotonic clock option will be attempted. If you enable this, you
		2747	usually have to link against librt or something similar. Enabling it when
		2748	the functionality isn't available is safe, though, although you have
		2749	to make sure you link against any libraries where the C<clock_gettime>
		2750	function is hiding in (often F<-lrt>).
		2751
		2752	=item EV_USE_REALTIME
		2753
		2754	If defined to be C<1>, libev will try to detect the availability of the
		2755	realtime clock option at compiletime (and assume its availability at
		2756	runtime if successful). Otherwise no use of the realtime clock option will
		2757	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2758	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2759	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2760
		2761	=item EV_USE_NANOSLEEP
		2762
		2763	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2764	and will use it for delays. Otherwise it will use C<select ()>.
		2765
		2766	=item EV_USE_SELECT
		2767
		2768	If undefined or defined to be C<1>, libev will compile in support for the
		2769	C<select>(2) backend. No attempt at autodetection will be done: if no
		2770	other method takes over, select will be it. Otherwise the select backend
		2771	will not be compiled in.
		2772
		2773	=item EV_SELECT_USE_FD_SET
		2774
		2775	If defined to C<1>, then the select backend will use the system C<fd_set>
		2776	structure. This is useful if libev doesn't compile due to a missing
		2777	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2778	exotic systems. This usually limits the range of file descriptors to some
		2779	low limit such as 1024 or might have other limitations (winsocket only
		2780	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2781	influence the size of the C<fd_set> used.
		2782
		2783	=item EV_SELECT_IS_WINSOCKET
		2784
		2785	When defined to C<1>, the select backend will assume that
		2786	select/socket/connect etc. don't understand file descriptors but
		2787	wants osf handles on win32 (this is the case when the select to
		2788	be used is the winsock select). This means that it will call
		2789	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2790	it is assumed that all these functions actually work on fds, even
		2791	on win32. Should not be defined on non-win32 platforms.
		2792
		2793	=item EV_FD_TO_WIN32_HANDLE
		2794
		2795	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2796	file descriptors to socket handles. When not defining this symbol (the
		2797	default), then libev will call C<_get_osfhandle>, which is usually
		2798	correct. In some cases, programs use their own file descriptor management,
		2799	in which case they can provide this function to map fds to socket handles.
		2800
		2801	=item EV_USE_POLL
		2802
		2803	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2804	backend. Otherwise it will be enabled on non-win32 platforms. It
		2805	takes precedence over select.
		2806
		2807	=item EV_USE_EPOLL
		2808
		2809	If defined to be C<1>, libev will compile in support for the Linux
		2810	C<epoll>(7) backend. Its availability will be detected at runtime,
		2811	otherwise another method will be used as fallback. This is the
		2812	preferred backend for GNU/Linux systems.
		2813
		2814	=item EV_USE_KQUEUE
		2815
		2816	If defined to be C<1>, libev will compile in support for the BSD style
		2817	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2818	otherwise another method will be used as fallback. This is the preferred
		2819	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2820	supports some types of fds correctly (the only platform we found that
		2821	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2822	not be used unless explicitly requested. The best way to use it is to find
		2823	out whether kqueue supports your type of fd properly and use an embedded
		2824	kqueue loop.
		2825
		2826	=item EV_USE_PORT
		2827
		2828	If defined to be C<1>, libev will compile in support for the Solaris
		2829	10 port style backend. Its availability will be detected at runtime,
		2830	otherwise another method will be used as fallback. This is the preferred
		2831	backend for Solaris 10 systems.
		2832
		2833	=item EV_USE_DEVPOLL
		2834
		2835	reserved for future expansion, works like the USE symbols above.
		2836
		2837	=item EV_USE_INOTIFY
		2838
		2839	If defined to be C<1>, libev will compile in support for the Linux inotify
		2840	interface to speed up C<ev_stat> watchers. Its actual availability will
		2841	be detected at runtime.
		2842
		2843	=item EV_ATOMIC_T
		2844
		2845	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2846	access is atomic with respect to other threads or signal contexts. No such
		2847	type is easily found in the C language, so you can provide your own type
		2848	that you know is safe for your purposes. It is used both for signal handler "locking"
		2849	as well as for signal and thread safety in C<ev_async> watchers.
		2850
		2851	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2852	(from F<signal.h>), which is usually good enough on most platforms.
		2853
		2854	=item EV_H
		2855
		2856	The name of the F<ev.h> header file used to include it. The default if
		2857	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
		2858	used to virtually rename the F<ev.h> header file in case of conflicts.
		2859
		2860	=item EV_CONFIG_H
		2861
		2862	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2863	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2864	C<EV_H>, above.
		2865
		2866	=item EV_EVENT_H
		2867
		2868	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2869	of how the F<event.h> header can be found, the default is C<"event.h">.
		2870
		2871	=item EV_PROTOTYPES
		2872
		2873	If defined to be C<0>, then F<ev.h> will not define any function
		2874	prototypes, but still define all the structs and other symbols. This is
		2875	occasionally useful if you want to provide your own wrapper functions
		2876	around libev functions.
		2877
		2878	=item EV_MULTIPLICITY
		2879
		2880	If undefined or defined to C<1>, then all event-loop-specific functions
		2881	will have the C<struct ev_loop *> as first argument, and you can create
		2882	additional independent event loops. Otherwise there will be no support
		2883	for multiple event loops and there is no first event loop pointer
		2884	argument. Instead, all functions act on the single default loop.
		2885
		2886	=item EV_MINPRI
		2887
		2888	=item EV_MAXPRI
		2889
		2890	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2891	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2892	provide for more priorities by overriding those symbols (usually defined
		2893	to be C<-2> and C<2>, respectively).
		2894
		2895	When doing priority-based operations, libev usually has to linearly search
		2896	all the priorities, so having many of them (hundreds) uses a lot of space
		2897	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2898	fine.
		2899
		2900	If your embedding app does not need any priorities, defining these both to
		2901	C<0> will save some memory and cpu.
		2902
		2903	=item EV_PERIODIC_ENABLE
		2904
		2905	If undefined or defined to be C<1>, then periodic timers are supported. If
		2906	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2907	code.
		2908
		2909	=item EV_IDLE_ENABLE
		2910
		2911	If undefined or defined to be C<1>, then idle watchers are supported. If
		2912	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2913	code.
		2914
		2915	=item EV_EMBED_ENABLE
		2916
		2917	If undefined or defined to be C<1>, then embed watchers are supported. If
		2918	defined to be C<0>, then they are not.
		2919
		2920	=item EV_STAT_ENABLE
		2921
		2922	If undefined or defined to be C<1>, then stat watchers are supported. If
		2923	defined to be C<0>, then they are not.
		2924
		2925	=item EV_FORK_ENABLE
		2926
		2927	If undefined or defined to be C<1>, then fork watchers are supported. If
		2928	defined to be C<0>, then they are not.
		2929
		2930	=item EV_ASYNC_ENABLE
		2931
		2932	If undefined or defined to be C<1>, then async watchers are supported. If
		2933	defined to be C<0>, then they are not.
		2934
		2935	=item EV_MINIMAL
		2936
		2937	If you need to shave off some kilobytes of code at the expense of some
		2938	speed, define this symbol to C<1>. Currently only used for gcc to override
		2939	some inlining decisions, saves roughly 30% codesize of amd64.
		2940
		2941	=item EV_PID_HASHSIZE
		2942
		2943	C<ev_child> watchers use a small hash table to distribute workload by
		2944	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2945	than enough. If you need to manage thousands of children you might want to
		2946	increase this value (I<must> be a power of two).
		2947
		2948	=item EV_INOTIFY_HASHSIZE
		2949
		2950	C<ev_stat> watchers use a small hash table to distribute workload by
		2951	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2952	usually more than enough. If you need to manage thousands of C<ev_stat>
		2953	watchers you might want to increase this value (I<must> be a power of
		2954	two).
		2955
		2956	=item EV_COMMON
		2957
		2958	By default, all watchers have a C<void *data> member. By redefining
		2959	this macro to a something else you can include more and other types of
		2960	members. You have to define it each time you include one of the files,
		2961	though, and it must be identical each time.
		2962
		2963	For example, the perl EV module uses something like this:
		2964
		2965	#define EV_COMMON \
		2966	SV *self; /* contains this struct */ \
		2967	SV *cb_sv, *fh /* note no trailing ";" */
		2968
		2969	=item EV_CB_DECLARE (type)
		2970
		2971	=item EV_CB_INVOKE (watcher, revents)
		2972
		2973	=item ev_set_cb (ev, cb)
		2974
		2975	Can be used to change the callback member declaration in each watcher,
		2976	and the way callbacks are invoked and set. Must expand to a struct member
		2977	definition and a statement, respectively. See the F<ev.h> header file for
		2978	their default definitions. One possible use for overriding these is to
		2979	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2980	method calls instead of plain function calls in C++.
		2981
		2982	=head2 EXPORTED API SYMBOLS
		2983
		2984	If you need to re-export the API (e.g. via a dll) and you need a list of
		2985	exported symbols, you can use the provided F<Symbol.*> files which list
		2986	all public symbols, one per line:
		2987
		2988	Symbols.ev for libev proper
		2989	Symbols.event for the libevent emulation
		2990
		2991	This can also be used to rename all public symbols to avoid clashes with
		2992	multiple versions of libev linked together (which is obviously bad in
		2993	itself, but sometimes it is inconvinient to avoid this).
		2994
		2995	A sed command like this will create wrapper C<#define>'s that you need to
		2996	include before including F<ev.h>:
		2997
		2998	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2999
		3000	This would create a file F<wrap.h> which essentially looks like this:
		3001
		3002	#define ev_backend myprefix_ev_backend
		3003	#define ev_check_start myprefix_ev_check_start
		3004	#define ev_check_stop myprefix_ev_check_stop
		3005	...
		3006
		3007	=head2 EXAMPLES
		3008
		3009	For a real-world example of a program the includes libev
		3010	verbatim, you can have a look at the EV perl module
		3011	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		3012	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		3013	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		3014	will be compiled. It is pretty complex because it provides its own header
		3015	file.
		3016
		3017	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		3018	that everybody includes and which overrides some configure choices:
		3019
		3020	#define EV_MINIMAL 1
		3021	#define EV_USE_POLL 0
		3022	#define EV_MULTIPLICITY 0
		3023	#define EV_PERIODIC_ENABLE 0
		3024	#define EV_STAT_ENABLE 0
		3025	#define EV_FORK_ENABLE 0
		3026	#define EV_CONFIG_H <config.h>
		3027	#define EV_MINPRI 0
		3028	#define EV_MAXPRI 0
		3029
		3030	#include "ev++.h"
		3031
		3032	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		3033
		3034	#include "ev_cpp.h"
		3035	#include "ev.c"
		3036
		3037
		3038	=head1 COMPLEXITIES
		3039
		3040	In this section the complexities of (many of) the algorithms used inside
		3041	libev will be explained. For complexity discussions about backends see the
		3042	documentation for C<ev_default_init>.
		3043
		3044	All of the following are about amortised time: If an array needs to be
		3045	extended, libev needs to realloc and move the whole array, but this
		3046	happens asymptotically never with higher number of elements, so O(1) might
		3047	mean it might do a lengthy realloc operation in rare cases, but on average
		3048	it is much faster and asymptotically approaches constant time.
		3049
		3050	=over 4
		3051
		3052	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3053
		3054	This means that, when you have a watcher that triggers in one hour and
		3055	there are 100 watchers that would trigger before that then inserting will
		3056	have to skip roughly seven (C<ld 100>) of these watchers.
		3057
		3058	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3059
		3060	That means that changing a timer costs less than removing/adding them
		3061	as only the relative motion in the event queue has to be paid for.
		3062
		3063	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3064
		3065	These just add the watcher into an array or at the head of a list.
		3066
		3067	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3068
		3069	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3070
		3071	These watchers are stored in lists then need to be walked to find the
		3072	correct watcher to remove. The lists are usually short (you don't usually
		3073	have many watchers waiting for the same fd or signal).
		3074
		3075	=item Finding the next timer in each loop iteration: O(1)
		3076
		3077	By virtue of using a binary heap, the next timer is always found at the
		3078	beginning of the storage array.
		3079
		3080	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3081
		3082	A change means an I/O watcher gets started or stopped, which requires
		3083	libev to recalculate its status (and possibly tell the kernel, depending
		3084	on backend and wether C<ev_io_set> was used).
		3085
		3086	=item Activating one watcher (putting it into the pending state): O(1)
		3087
		3088	=item Priority handling: O(number_of_priorities)
		3089
		3090	Priorities are implemented by allocating some space for each
		3091	priority. When doing priority-based operations, libev usually has to
		3092	linearly search all the priorities, but starting/stopping and activating
		3093	watchers becomes O(1) w.r.t. priority handling.
		3094
		3095	=item Sending an ev_async: O(1)
		3096
		3097	=item Processing ev_async_send: O(number_of_async_watchers)
		3098
		3099	=item Processing signals: O(max_signal_number)
		3100
		3101	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3102	calls in the current loop iteration. Checking for async and signal events
		3103	involves iterating over all running async watchers or all signal numbers.
		3104
		3105	=back
		3106
		3107
		3108	=head1 Win32 platform limitations and workarounds
		3109
		3110	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3111	requires, and its I/O model is fundamentally incompatible with the POSIX
		3112	model. Libev still offers limited functionality on this platform in
		3113	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3114	descriptors. This only applies when using Win32 natively, not when using
		3115	e.g. cygwin.
		3116
		3117	There is no supported compilation method available on windows except
		3118	embedding it into other applications.
		3119
		3120	Due to the many, low, and arbitrary limits on the win32 platform and the
		3121	abysmal performance of winsockets, using a large number of sockets is not
		3122	recommended (and not reasonable). If your program needs to use more than
		3123	a hundred or so sockets, then likely it needs to use a totally different
		3124	implementation for windows, as libev offers the POSIX model, which cannot
		3125	be implemented efficiently on windows (microsoft monopoly games).
		3126
		3127	=over 4
		3128
		3129	=item The winsocket select function
		3130
		3131	The winsocket C<select> function doesn't follow POSIX in that it requires
		3132	socket I<handles> and not socket I<file descriptors>. This makes select
		3133	very inefficient, and also requires a mapping from file descriptors
		3134	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3135	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3136	symbols for more info.
		3137
		3138	The configuration for a "naked" win32 using the microsoft runtime
		3139	libraries and raw winsocket select is:
		3140
		3141	#define EV_USE_SELECT 1
		3142	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3143
		3144	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3145	complexity in the O(n²) range when using win32.
		3146
		3147	=item Limited number of file descriptors
		3148
		3149	Windows has numerous arbitrary (and low) limits on things. Early versions
		3150	of winsocket's select only supported waiting for a max. of C<64> handles
		3151	(probably owning to the fact that all windows kernels can only wait for
		3152	C<64> things at the same time internally; microsoft recommends spawning a
		3153	chain of threads and wait for 63 handles and the previous thread in each).
		3154
		3155	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3156	to some high number (e.g. C<2048>) before compiling the winsocket select
		3157	call (which might be in libev or elsewhere, for example, perl does its own
		3158	select emulation on windows).
		3159
		3160	Another limit is the number of file descriptors in the microsoft runtime
		3161	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3162	or something like this inside microsoft). You can increase this by calling
		3163	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3164	arbitrary limit), but is broken in many versions of the microsoft runtime
		3165	libraries.
		3166
		3167	This might get you to about C<512> or C<2048> sockets (depending on
		3168	windows version and/or the phase of the moon). To get more, you need to
		3169	wrap all I/O functions and provide your own fd management, but the cost of
		3170	calling select (O(n²)) will likely make this unworkable.
		3171
		3172	=back
		3173
878		3174
879	=head1 AUTHOR	3175	=head1 AUTHOR
880		3176
881	Marc Lehmann <libev@schmorp.de>.	3177	Marc Lehmann <libev@schmorp.de>.
882		3178

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