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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
51		106
52	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
53		108
54	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
55	library in any way.	110	library in any way.
…		…
64		119
65	=item int ev_version_major ()	120	=item int ev_version_major ()
66		121
67	=item int ev_version_minor ()	122	=item int ev_version_minor ()
68		123
69	You can find out the major and minor version numbers of the library	124	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	125	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	126	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	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
73	version of the library your program was compiled against.	128	version of the library your program was compiled against.
74		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
75	Usually, it's a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	136	not a problem.
79		137
		138	Example: Make sure we haven't accidentally been linked against the wrong
		139	version.
		140
		141	assert (("libev version mismatch",
		142	ev_version_major () == EV_VERSION_MAJOR
		143	&& ev_version_minor () >= EV_VERSION_MINOR));
		144
		145	=item unsigned int ev_supported_backends ()
		146
		147	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		148	value) compiled into this binary of libev (independent of their
		149	availability on the system you are running on). See C<ev_default_loop> for
		150	a description of the set values.
		151
		152	Example: make sure we have the epoll method, because yeah this is cool and
		153	a must have and can we have a torrent of it please!!!11
		154
		155	assert (("sorry, no epoll, no sex",
		156	ev_supported_backends () & EVBACKEND_EPOLL));
		157
		158	=item unsigned int ev_recommended_backends ()
		159
		160	Return the set of all backends compiled into this binary of libev and also
		161	recommended for this platform. This set is often smaller than the one
		162	returned by C<ev_supported_backends>, as for example kqueue is broken on
		163	most BSDs and will not be autodetected unless you explicitly request it
		164	(assuming you know what you are doing). This is the set of backends that
		165	libev will probe for if you specify no backends explicitly.
		166
		167	=item unsigned int ev_embeddable_backends ()
		168
		169	Returns the set of backends that are embeddable in other event loops. This
		170	is the theoretical, all-platform, value. To find which backends
		171	might be supported on the current system, you would need to look at
		172	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		173	recommended ones.
		174
		175	See the description of C<ev_embed> watchers for more info.
		176
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		178
82	Sets the allocation function to use (the prototype is similar to the	179	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	180	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	181	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	182	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	183	potentially destructive action. The default is your system realloc
		184	function.
87		185
88	You could override this function in high-availability programs to, say,	186	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,	187	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.	188	or even to sleep a while and retry until some memory is available.
		189
		190	Example: Replace the libev allocator with one that waits a bit and then
		191	retries).
		192
		193	static void *
		194	persistent_realloc (void *ptr, size_t size)
		195	{
		196	for (;;)
		197	{
		198	void *newptr = realloc (ptr, size);
		199
		200	if (newptr)
		201	return newptr;
		202
		203	sleep (60);
		204	}
		205	}
		206
		207	...
		208	ev_set_allocator (persistent_realloc);
91		209
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	210	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		211
94	Set the callback function to call on a retryable syscall error (such	212	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	213	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	215	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	216	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	217	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	218	(such as abort).
101		219
		220	Example: This is basically the same thing that libev does internally, too.
		221
		222	static void
		223	fatal_error (const char *msg)
		224	{
		225	perror (msg);
		226	abort ();
		227	}
		228
		229	...
		230	ev_set_syserr_cb (fatal_error);
		231
102	=back	232	=back
103		233
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		235
106	An event loop is described by a C<struct ev_loop *>. The library knows two	236	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)	249	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		250
121	This will initialise the default event loop if it hasn't been initialised	251	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	252	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	253	false. If it already was initialised it simply returns it (and ignores the
124	flags).	254	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		255
126	If you don't know what event loop to use, use the one returned from this	256	If you don't know what event loop to use, use the one returned from this
127	function.	257	function.
128		258
129	The flags argument can be used to specify special behaviour or specific	259	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).	260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		261
132	It supports the following flags:	262	The following flags are supported:
133		263
134	=over 4	264	=over 4
135		265
136	=item C<EVFLAG_AUTO>	266	=item C<EVFLAG_AUTO>
137		267
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	276	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	277	useful to try out specific backends to test their performance, or to work
148	around bugs.	278	around bugs.
149		279
		280	=item C<EVFLAG_FORKCHECK>
		281
		282	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		283	a fork, you can also make libev check for a fork in each iteration by
		284	enabling this flag.
		285
		286	This works by calling C<getpid ()> on every iteration of the loop,
		287	and thus this might slow down your event loop if you do a lot of loop
		288	iterations and little real work, but is usually not noticeable (on my
		289	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		290	without a syscall and thus I<very> fast, but my Linux system also has
		291	C<pthread_atfork> which is even faster).
		292
		293	The big advantage of this flag is that you can forget about fork (and
		294	forget about forgetting to tell libev about forking) when you use this
		295	flag.
		296
		297	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		298	environment variable.
		299
150	=item C<EVMETHOD_SELECT> (portable select backend)	300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		301
		302	This is your standard select(2) backend. Not I<completely> standard, as
		303	libev tries to roll its own fd_set with no limits on the number of fds,
		304	but if that fails, expect a fairly low limit on the number of fds when
		305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		306	the fastest backend for a low number of fds.
		307
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		309
154	=item C<EVMETHOD_EPOLL> (linux only)	310	And this is your standard poll(2) backend. It's more complicated than
		311	select, but handles sparse fds better and has no artificial limit on the
		312	number of fds you can use (except it will slow down considerably with a
		313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
155		314
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	315	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		316
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	317	For few fds, this backend is a bit little slower than poll and select,
		318	but it scales phenomenally better. While poll and select usually scale like
		319	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		320	either O(1) or O(active_fds).
159		321
160	=item C<EVMETHOD_PORT> (solaris 10 only)	322	While stopping and starting an I/O watcher in the same iteration will
		323	result in some caching, there is still a syscall per such incident
		324	(because the fd could point to a different file description now), so its
		325	best to avoid that. Also, dup()ed file descriptors might not work very
		326	well if you register events for both fds.
		327
		328	Please note that epoll sometimes generates spurious notifications, so you
		329	need to use non-blocking I/O or other means to avoid blocking when no data
		330	(or space) is available.
		331
		332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		333
		334	Kqueue deserves special mention, as at the time of this writing, it
		335	was broken on all BSDs except NetBSD (usually it doesn't work with
		336	anything but sockets and pipes, except on Darwin, where of course its
		337	completely useless). For this reason its not being "autodetected"
		338	unless you explicitly specify it explicitly in the flags (i.e. using
		339	C<EVBACKEND_KQUEUE>).
		340
		341	It scales in the same way as the epoll backend, but the interface to the
		342	kernel is more efficient (which says nothing about its actual speed, of
		343	course). While starting and stopping an I/O watcher does not cause an
		344	extra syscall as with epoll, it still adds up to four event changes per
		345	incident, so its best to avoid that.
		346
		347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		348
		349	This is not implemented yet (and might never be).
		350
		351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		352
		353	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		354	it's really slow, but it still scales very well (O(active_fds)).
		355
		356	Please note that solaris ports can result in a lot of spurious
		357	notifications, so you need to use non-blocking I/O or other means to avoid
		358	blocking when no data (or space) is available.
		359
		360	=item C<EVBACKEND_ALL>
		361
		362	Try all backends (even potentially broken ones that wouldn't be tried
		363	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		365
		366	=back
161		367
162	If one or more of these are ored into the flags value, then only these	368	If one or more of these are ored into the flags value, then only these
163	backends will be tried (in the reverse order as given here). If one are	369	backends will be tried (in the reverse order as given here). If none are
164	specified, any backend will do.	370	specified, most compiled-in backend will be tried, usually in reverse
		371	order of their flag values :)
165		372
166	=back	373	The most typical usage is like this:
		374
		375	if (!ev_default_loop (0))
		376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		377
		378	Restrict libev to the select and poll backends, and do not allow
		379	environment settings to be taken into account:
		380
		381	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		382
		383	Use whatever libev has to offer, but make sure that kqueue is used if
		384	available (warning, breaks stuff, best use only with your own private
		385	event loop and only if you know the OS supports your types of fds):
		386
		387	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
167		388
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	389	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		390
170	Similar to C<ev_default_loop>, but always creates a new event loop that is	391	Similar to C<ev_default_loop>, but always creates a new event loop that is
171	always distinct from the default loop. Unlike the default loop, it cannot	392	always distinct from the default loop. Unlike the default loop, it cannot
172	handle signal and child watchers, and attempts to do so will be greeted by	393	handle signal and child watchers, and attempts to do so will be greeted by
173	undefined behaviour (or a failed assertion if assertions are enabled).	394	undefined behaviour (or a failed assertion if assertions are enabled).
174		395
		396	Example: Try to create a event loop that uses epoll and nothing else.
		397
		398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		399	if (!epoller)
		400	fatal ("no epoll found here, maybe it hides under your chair");
		401
175	=item ev_default_destroy ()	402	=item ev_default_destroy ()
176		403
177	Destroys the default loop again (frees all memory and kernel state	404	Destroys the default loop again (frees all memory and kernel state
178	etc.). This stops all registered event watchers (by not touching them in	405	etc.). None of the active event watchers will be stopped in the normal
179	any way whatsoever, although you cannot rely on this :).	406	sense, so e.g. C<ev_is_active> might still return true. It is your
		407	responsibility to either stop all watchers cleanly yoursef I<before>
		408	calling this function, or cope with the fact afterwards (which is usually
		409	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		410	for example).
		411
		412	Note that certain global state, such as signal state, will not be freed by
		413	this function, and related watchers (such as signal and child watchers)
		414	would need to be stopped manually.
		415
		416	In general it is not advisable to call this function except in the
		417	rare occasion where you really need to free e.g. the signal handling
		418	pipe fds. If you need dynamically allocated loops it is better to use
		419	C<ev_loop_new> and C<ev_loop_destroy>).
180		420
181	=item ev_loop_destroy (loop)	421	=item ev_loop_destroy (loop)
182		422
183	Like C<ev_default_destroy>, but destroys an event loop created by an	423	Like C<ev_default_destroy>, but destroys an event loop created by an
184	earlier call to C<ev_loop_new>.	424	earlier call to C<ev_loop_new>.
…		…
188	This function reinitialises the kernel state for backends that have	428	This function reinitialises the kernel state for backends that have
189	one. Despite the name, you can call it anytime, but it makes most sense	429	one. Despite the name, you can call it anytime, but it makes most sense
190	after forking, in either the parent or child process (or both, but that	430	after forking, in either the parent or child process (or both, but that
191	again makes little sense).	431	again makes little sense).
192		432
193	You I<must> call this function after forking if and only if you want to	433	You I<must> call this function in the child process after forking if and
194	use the event library in both processes. If you just fork+exec, you don't	434	only if you want to use the event library in both processes. If you just
195	have to call it.	435	fork+exec, you don't have to call it.
196		436
197	The function itself is quite fast and it's usually not a problem to call	437	The function itself is quite fast and it's usually not a problem to call
198	it just in case after a fork. To make this easy, the function will fit in	438	it just in case after a fork. To make this easy, the function will fit in
199	quite nicely into a call to C<pthread_atfork>:	439	quite nicely into a call to C<pthread_atfork>:
200		440
201	pthread_atfork (0, 0, ev_default_fork);	441	pthread_atfork (0, 0, ev_default_fork);
202		442
		443	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		444	without calling this function, so if you force one of those backends you
		445	do not need to care.
		446
203	=item ev_loop_fork (loop)	447	=item ev_loop_fork (loop)
204		448
205	Like C<ev_default_fork>, but acts on an event loop created by	449	Like C<ev_default_fork>, but acts on an event loop created by
206	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	450	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
207	after fork, and how you do this is entirely your own problem.	451	after fork, and how you do this is entirely your own problem.
208		452
		453	=item unsigned int ev_loop_count (loop)
		454
		455	Returns the count of loop iterations for the loop, which is identical to
		456	the number of times libev did poll for new events. It starts at C<0> and
		457	happily wraps around with enough iterations.
		458
		459	This value can sometimes be useful as a generation counter of sorts (it
		460	"ticks" the number of loop iterations), as it roughly corresponds with
		461	C<ev_prepare> and C<ev_check> calls.
		462
209	=item unsigned int ev_method (loop)	463	=item unsigned int ev_backend (loop)
210		464
211	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	465	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
212	use.	466	use.
213		467
214	=item ev_tstamp ev_now (loop)	468	=item ev_tstamp ev_now (loop)
215		469
216	Returns the current "event loop time", which is the time the event loop	470	Returns the current "event loop time", which is the time the event loop
217	got events and started processing them. This timestamp does not change	471	received events and started processing them. This timestamp does not
218	as long as callbacks are being processed, and this is also the base time	472	change as long as callbacks are being processed, and this is also the base
219	used for relative timers. You can treat it as the timestamp of the event	473	time used for relative timers. You can treat it as the timestamp of the
220	occuring (or more correctly, the mainloop finding out about it).	474	event occuring (or more correctly, libev finding out about it).
221		475
222	=item ev_loop (loop, int flags)	476	=item ev_loop (loop, int flags)
223		477
224	Finally, this is it, the event handler. This function usually is called	478	Finally, this is it, the event handler. This function usually is called
225	after you initialised all your watchers and you want to start handling	479	after you initialised all your watchers and you want to start handling
226	events.	480	events.
227		481
228	If the flags argument is specified as 0, it will not return until either	482	If the flags argument is specified as C<0>, it will not return until
229	no event watchers are active anymore or C<ev_unloop> was called.	483	either no event watchers are active anymore or C<ev_unloop> was called.
		484
		485	Please note that an explicit C<ev_unloop> is usually better than
		486	relying on all watchers to be stopped when deciding when a program has
		487	finished (especially in interactive programs), but having a program that
		488	automatically loops as long as it has to and no longer by virtue of
		489	relying on its watchers stopping correctly is a thing of beauty.
230		490
231	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	491	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
232	those events and any outstanding ones, but will not block your process in	492	those events and any outstanding ones, but will not block your process in
233	case there are no events and will return after one iteration of the loop.	493	case there are no events and will return after one iteration of the loop.
234		494
235	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	495	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
236	neccessary) and will handle those and any outstanding ones. It will block	496	neccessary) and will handle those and any outstanding ones. It will block
237	your process until at least one new event arrives, and will return after	497	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	498	one iteration of the loop. This is useful if you are waiting for some
		499	external event in conjunction with something not expressible using other
		500	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		501	usually a better approach for this kind of thing.
239		502
240	This flags value could be used to implement alternative looping
241	constructs, but the C<prepare> and C<check> watchers provide a better and
242	more generic mechanism.
243
244	Here are the gory details of what ev_loop does:	503	Here are the gory details of what C<ev_loop> does:
245		504
		505	- Before the first iteration, call any pending watchers.
246	1. If there are no active watchers (reference count is zero), return.	506	* If there are no active watchers (reference count is zero), return.
247	2. Queue and immediately call all prepare watchers.	507	- Queue all prepare watchers and then call all outstanding watchers.
248	3. If we have been forked, recreate the kernel state.	508	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	509	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	510	- Update the "event loop time".
251	6. Calculate for how long to block.	511	- Calculate for how long to block.
252	7. Block the process, waiting for events.	512	- Block the process, waiting for any events.
		513	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	514	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	515	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	516	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	517	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	518	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	519	- Call all queued watchers in reverse order (i.e. check watchers first).
		520	Signals and child watchers are implemented as I/O watchers, and will
		521	be handled here by queueing them when their watcher gets executed.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	522	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	523	were used, return, otherwise continue with step *.
		524
		525	Example: Queue some jobs and then loop until no events are outsanding
		526	anymore.
		527
		528	... queue jobs here, make sure they register event watchers as long
		529	... as they still have work to do (even an idle watcher will do..)
		530	ev_loop (my_loop, 0);
		531	... jobs done. yeah!
261		532
262	=item ev_unloop (loop, how)	533	=item ev_unloop (loop, how)
263		534
264	Can be used to make a call to C<ev_loop> return early (but only after it	535	Can be used to make a call to C<ev_loop> return early (but only after it
265	has processed all outstanding events). The C<how> argument must be either	536	has processed all outstanding events). The C<how> argument must be either
…		…
279	visible to the libev user and should not keep C<ev_loop> from exiting if	550	visible to the libev user and should not keep C<ev_loop> from exiting if
280	no event watchers registered by it are active. It is also an excellent	551	no event watchers registered by it are active. It is also an excellent
281	way to do this for generic recurring timers or from within third-party	552	way to do this for generic recurring timers or from within third-party
282	libraries. Just remember to I<unref after start> and I<ref before stop>.	553	libraries. Just remember to I<unref after start> and I<ref before stop>.
283		554
		555	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		556	running when nothing else is active.
		557
		558	struct ev_signal exitsig;
		559	ev_signal_init (&exitsig, sig_cb, SIGINT);
		560	ev_signal_start (loop, &exitsig);
		561	evf_unref (loop);
		562
		563	Example: For some weird reason, unregister the above signal handler again.
		564
		565	ev_ref (loop);
		566	ev_signal_stop (loop, &exitsig);
		567
284	=back	568	=back
		569
285		570
286	=head1 ANATOMY OF A WATCHER	571	=head1 ANATOMY OF A WATCHER
287		572
288	A watcher is a structure that you create and register to record your	573	A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	574	interest in some event. For instance, if you want to wait for STDIN to
…		…
322	*) >>), and you can stop watching for events at any time by calling the	607	*) >>), and you can stop watching for events at any time by calling the
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	608	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		609
325	As long as your watcher is active (has been started but not stopped) you	610	As long as your watcher is active (has been started but not stopped) you
326	must not touch the values stored in it. Most specifically you must never	611	must not touch the values stored in it. Most specifically you must never
327	reinitialise it or call its set method.	612	reinitialise it or call its C<set> macro.
328
329	You can check whether an event is active by calling the C<ev_is_active
330	(watcher *)> macro. To see whether an event is outstanding (but the
331	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.
333		613
334	Each and every callback receives the event loop pointer as first, the	614	Each and every callback receives the event loop pointer as first, the
335	registered watcher structure as second, and a bitset of received events as	615	registered watcher structure as second, and a bitset of received events as
336	third argument.	616	third argument.
337		617
…		…
361	The signal specified in the C<ev_signal> watcher has been received by a thread.	641	The signal specified in the C<ev_signal> watcher has been received by a thread.
362		642
363	=item C<EV_CHILD>	643	=item C<EV_CHILD>
364		644
365	The pid specified in the C<ev_child> watcher has received a status change.	645	The pid specified in the C<ev_child> watcher has received a status change.
		646
		647	=item C<EV_STAT>
		648
		649	The path specified in the C<ev_stat> watcher changed its attributes somehow.
366		650
367	=item C<EV_IDLE>	651	=item C<EV_IDLE>
368		652
369	The C<ev_idle> watcher has determined that you have nothing better to do.	653	The C<ev_idle> watcher has determined that you have nothing better to do.
370		654
…		…
378	received events. Callbacks of both watcher types can start and stop as	662	received events. Callbacks of both watcher types can start and stop as
379	many watchers as they want, and all of them will be taken into account	663	many watchers as they want, and all of them will be taken into account
380	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	664	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
381	C<ev_loop> from blocking).	665	C<ev_loop> from blocking).
382		666
		667	=item C<EV_EMBED>
		668
		669	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		670
		671	=item C<EV_FORK>
		672
		673	The event loop has been resumed in the child process after fork (see
		674	C<ev_fork>).
		675
383	=item C<EV_ERROR>	676	=item C<EV_ERROR>
384		677
385	An unspecified error has occured, the watcher has been stopped. This might	678	An unspecified error has occured, the watcher has been stopped. This might
386	happen because the watcher could not be properly started because libev	679	happen because the watcher could not be properly started because libev
387	ran out of memory, a file descriptor was found to be closed or any other	680	ran out of memory, a file descriptor was found to be closed or any other
…		…
393	your callbacks is well-written it can just attempt the operation and cope	686	your callbacks is well-written it can just attempt the operation and cope
394	with the error from read() or write(). This will not work in multithreaded	687	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.	688	programs, though, so beware.
396		689
397	=back	690	=back
		691
		692	=head2 GENERIC WATCHER FUNCTIONS
		693
		694	In the following description, C<TYPE> stands for the watcher type,
		695	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		696
		697	=over 4
		698
		699	=item C<ev_init> (ev_TYPE *watcher, callback)
		700
		701	This macro initialises the generic portion of a watcher. The contents
		702	of the watcher object can be arbitrary (so C<malloc> will do). Only
		703	the generic parts of the watcher are initialised, you I<need> to call
		704	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		705	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		706	which rolls both calls into one.
		707
		708	You can reinitialise a watcher at any time as long as it has been stopped
		709	(or never started) and there are no pending events outstanding.
		710
		711	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		712	int revents)>.
		713
		714	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		715
		716	This macro initialises the type-specific parts of a watcher. You need to
		717	call C<ev_init> at least once before you call this macro, but you can
		718	call C<ev_TYPE_set> any number of times. You must not, however, call this
		719	macro on a watcher that is active (it can be pending, however, which is a
		720	difference to the C<ev_init> macro).
		721
		722	Although some watcher types do not have type-specific arguments
		723	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		724
		725	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		726
		727	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		728	calls into a single call. This is the most convinient method to initialise
		729	a watcher. The same limitations apply, of course.
		730
		731	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		732
		733	Starts (activates) the given watcher. Only active watchers will receive
		734	events. If the watcher is already active nothing will happen.
		735
		736	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		737
		738	Stops the given watcher again (if active) and clears the pending
		739	status. It is possible that stopped watchers are pending (for example,
		740	non-repeating timers are being stopped when they become pending), but
		741	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		742	you want to free or reuse the memory used by the watcher it is therefore a
		743	good idea to always call its C<ev_TYPE_stop> function.
		744
		745	=item bool ev_is_active (ev_TYPE *watcher)
		746
		747	Returns a true value iff the watcher is active (i.e. it has been started
		748	and not yet been stopped). As long as a watcher is active you must not modify
		749	it.
		750
		751	=item bool ev_is_pending (ev_TYPE *watcher)
		752
		753	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		754	events but its callback has not yet been invoked). As long as a watcher
		755	is pending (but not active) you must not call an init function on it (but
		756	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		757	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		758	it).
		759
		760	=item callback ev_cb (ev_TYPE *watcher)
		761
		762	Returns the callback currently set on the watcher.
		763
		764	=item ev_cb_set (ev_TYPE *watcher, callback)
		765
		766	Change the callback. You can change the callback at virtually any time
		767	(modulo threads).
		768
		769	=item ev_set_priority (ev_TYPE *watcher, priority)
		770
		771	=item int ev_priority (ev_TYPE *watcher)
		772
		773	Set and query the priority of the watcher. The priority is a small
		774	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		775	(default: C<-2>). Pending watchers with higher priority will be invoked
		776	before watchers with lower priority, but priority will not keep watchers
		777	from being executed (except for C<ev_idle> watchers).
		778
		779	This means that priorities are I<only> used for ordering callback
		780	invocation after new events have been received. This is useful, for
		781	example, to reduce latency after idling, or more often, to bind two
		782	watchers on the same event and make sure one is called first.
		783
		784	If you need to suppress invocation when higher priority events are pending
		785	you need to look at C<ev_idle> watchers, which provide this functionality.
		786
		787	You I<must not> change the priority of a watcher as long as it is active or
		788	pending.
		789
		790	The default priority used by watchers when no priority has been set is
		791	always C<0>, which is supposed to not be too high and not be too low :).
		792
		793	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		794	fine, as long as you do not mind that the priority value you query might
		795	or might not have been adjusted to be within valid range.
		796
		797	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		798
		799	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		800	C<loop> nor C<revents> need to be valid as long as the watcher callback
		801	can deal with that fact.
		802
		803	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		804
		805	If the watcher is pending, this function returns clears its pending status
		806	and returns its C<revents> bitset (as if its callback was invoked). If the
		807	watcher isn't pending it does nothing and returns C<0>.
		808
		809	=back
		810
398		811
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	812	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		813
401	Each watcher has, by default, a member C<void *data> that you can change	814	Each watcher has, by default, a member C<void *data> that you can change
402	and read at any time, libev will completely ignore it. This can be used	815	and read at any time, libev will completely ignore it. This can be used
…		…
420	{	833	{
421	struct my_io *w = (struct my_io *)w_;	834	struct my_io *w = (struct my_io *)w_;
422	...	835	...
423	}	836	}
424		837
425	More interesting and less C-conformant ways of catsing your callback type	838	More interesting and less C-conformant ways of casting your callback type
426	have been omitted....	839	instead have been omitted.
		840
		841	Another common scenario is having some data structure with multiple
		842	watchers:
		843
		844	struct my_biggy
		845	{
		846	int some_data;
		847	ev_timer t1;
		848	ev_timer t2;
		849	}
		850
		851	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		852	you need to use C<offsetof>:
		853
		854	#include <stddef.h>
		855
		856	static void
		857	t1_cb (EV_P_ struct ev_timer *w, int revents)
		858	{
		859	struct my_biggy big = (struct my_biggy *
		860	(((char *)w) - offsetof (struct my_biggy, t1));
		861	}
		862
		863	static void
		864	t2_cb (EV_P_ struct ev_timer *w, int revents)
		865	{
		866	struct my_biggy big = (struct my_biggy *
		867	(((char *)w) - offsetof (struct my_biggy, t2));
		868	}
427		869
428		870
429	=head1 WATCHER TYPES	871	=head1 WATCHER TYPES
430		872
431	This section describes each watcher in detail, but will not repeat	873	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	874	information given in the last section. Any initialisation/set macros,
		875	functions and members specific to the watcher type are explained.
433		876
		877	Members are additionally marked with either I<[read-only]>, meaning that,
		878	while the watcher is active, you can look at the member and expect some
		879	sensible content, but you must not modify it (you can modify it while the
		880	watcher is stopped to your hearts content), or I<[read-write]>, which
		881	means you can expect it to have some sensible content while the watcher
		882	is active, but you can also modify it. Modifying it may not do something
		883	sensible or take immediate effect (or do anything at all), but libev will
		884	not crash or malfunction in any way.
		885
		886
434	=head2 C<ev_io> - is this file descriptor readable or writable	887	=head2 C<ev_io> - is this file descriptor readable or writable?
435		888
436	I/O watchers check whether a file descriptor is readable or writable	889	I/O watchers check whether a file descriptor is readable or writable
437	in each iteration of the event loop (This behaviour is called	890	in each iteration of the event loop, or, more precisely, when reading
438	level-triggering because you keep receiving events as long as the	891	would not block the process and writing would at least be able to write
439	condition persists. Remember you can stop the watcher if you don't want to	892	some data. This behaviour is called level-triggering because you keep
440	act on the event and neither want to receive future events).	893	receiving events as long as the condition persists. Remember you can stop
		894	the watcher if you don't want to act on the event and neither want to
		895	receive future events.
441		896
442	In general you can register as many read and/or write event watchers per	897	In general you can register as many read and/or write event watchers per
443	fd as you want (as long as you don't confuse yourself). Setting all file	898	fd as you want (as long as you don't confuse yourself). Setting all file
444	descriptors to non-blocking mode is also usually a good idea (but not	899	descriptors to non-blocking mode is also usually a good idea (but not
445	required if you know what you are doing).	900	required if you know what you are doing).
446		901
447	You have to be careful with dup'ed file descriptors, though. Some backends	902	You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	903	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	904	descriptors correctly if you register interest in two or more fds pointing
450	to the same underlying file/socket etc. description (that is, they share	905	to the same underlying file/socket/etc. description (that is, they share
451	the same underlying "file open").	906	the same underlying "file open").
452		907
453	If you must do this, then force the use of a known-to-be-good backend	908	If you must do this, then force the use of a known-to-be-good backend
454	(at the time of this writing, this includes only EVMETHOD_SELECT and	909	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	910	C<EVBACKEND_POLL>).
		911
		912	Another thing you have to watch out for is that it is quite easy to
		913	receive "spurious" readyness notifications, that is your callback might
		914	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		915	because there is no data. Not only are some backends known to create a
		916	lot of those (for example solaris ports), it is very easy to get into
		917	this situation even with a relatively standard program structure. Thus
		918	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		919	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		920
		921	If you cannot run the fd in non-blocking mode (for example you should not
		922	play around with an Xlib connection), then you have to seperately re-test
		923	whether a file descriptor is really ready with a known-to-be good interface
		924	such as poll (fortunately in our Xlib example, Xlib already does this on
		925	its own, so its quite safe to use).
		926
		927	=head3 The special problem of disappearing file descriptors
		928
		929	Some backends (e.g kqueue, epoll) need to be told about closing a file
		930	descriptor (either by calling C<close> explicitly or by any other means,
		931	such as C<dup>). The reason is that you register interest in some file
		932	descriptor, but when it goes away, the operating system will silently drop
		933	this interest. If another file descriptor with the same number then is
		934	registered with libev, there is no efficient way to see that this is, in
		935	fact, a different file descriptor.
		936
		937	To avoid having to explicitly tell libev about such cases, libev follows
		938	the following policy: Each time C<ev_io_set> is being called, libev
		939	will assume that this is potentially a new file descriptor, otherwise
		940	it is assumed that the file descriptor stays the same. That means that
		941	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		942	descriptor even if the file descriptor number itself did not change.
		943
		944	This is how one would do it normally anyway, the important point is that
		945	the libev application should not optimise around libev but should leave
		946	optimisations to libev.
		947
		948
		949	=head3 Watcher-Specific Functions
456		950
457	=over 4	951	=over 4
458		952
459	=item ev_io_init (ev_io *, callback, int fd, int events)	953	=item ev_io_init (ev_io *, callback, int fd, int events)
460		954
461	=item ev_io_set (ev_io *, int fd, int events)	955	=item ev_io_set (ev_io *, int fd, int events)
462		956
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	957	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
464	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	958	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
465	EV_WRITE> to receive the given events.	959	C<EV_READ | EV_WRITE> to receive the given events.
		960
		961	=item int fd [read-only]
		962
		963	The file descriptor being watched.
		964
		965	=item int events [read-only]
		966
		967	The events being watched.
466		968
467	=back	969	=back
468		970
		971	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		972	readable, but only once. Since it is likely line-buffered, you could
		973	attempt to read a whole line in the callback.
		974
		975	static void
		976	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		977	{
		978	ev_io_stop (loop, w);
		979	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		980	}
		981
		982	...
		983	struct ev_loop *loop = ev_default_init (0);
		984	struct ev_io stdin_readable;
		985	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		986	ev_io_start (loop, &stdin_readable);
		987	ev_loop (loop, 0);
		988
		989
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	990	=head2 C<ev_timer> - relative and optionally repeating timeouts
470		991
471	Timer watchers are simple relative timers that generate an event after a	992	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	993	given time, and optionally repeating in regular intervals after that.
473		994
474	The timers are based on real time, that is, if you register an event that	995	The timers are based on real time, that is, if you register an event that
475	times out after an hour and you reset your system clock to last years	996	times out after an hour and you reset your system clock to last years
476	time, it will still time out after (roughly) and hour. "Roughly" because	997	time, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	998	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	999	monotonic clock option helps a lot here).
479		1000
480	The relative timeouts are calculated relative to the C<ev_now ()>	1001	The relative timeouts are calculated relative to the C<ev_now ()>
481	time. This is usually the right thing as this timestamp refers to the time	1002	time. This is usually the right thing as this timestamp refers to the time
482	of the event triggering whatever timeout you are modifying/starting. If	1003	of the event triggering whatever timeout you are modifying/starting. If
483	you suspect event processing to be delayed and you *need* to base the timeout	1004	you suspect event processing to be delayed and you I<need> to base the timeout
484	on the current time, use something like this to adjust for this:	1005	on the current time, use something like this to adjust for this:
485		1006
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1007	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1008
		1009	The callback is guarenteed to be invoked only when its timeout has passed,
		1010	but if multiple timers become ready during the same loop iteration then
		1011	order of execution is undefined.
		1012
		1013	=head3 Watcher-Specific Functions and Data Members
487		1014
488	=over 4	1015	=over 4
489		1016
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1017	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		1018
…		…
505	=item ev_timer_again (loop)	1032	=item ev_timer_again (loop)
506		1033
507	This will act as if the timer timed out and restart it again if it is	1034	This will act as if the timer timed out and restart it again if it is
508	repeating. The exact semantics are:	1035	repeating. The exact semantics are:
509		1036
		1037	If the timer is pending, its pending status is cleared.
		1038
510	If the timer is started but nonrepeating, stop it.	1039	If the timer is started but nonrepeating, stop it (as if it timed out).
511		1040
512	If the timer is repeating, either start it if necessary (with the repeat	1041	If the timer is repeating, either start it if necessary (with the
513	value), or reset the running timer to the repeat value.	1042	C<repeat> value), or reset the running timer to the C<repeat> value.
514		1043
515	This sounds a bit complicated, but here is a useful and typical	1044	This sounds a bit complicated, but here is a useful and typical
516	example: Imagine you have a tcp connection and you want a so-called idle	1045	example: Imagine you have a tcp connection and you want a so-called idle
517	timeout, that is, you want to be called when there have been, say, 60	1046	timeout, that is, you want to be called when there have been, say, 60
518	seconds of inactivity on the socket. The easiest way to do this is to	1047	seconds of inactivity on the socket. The easiest way to do this is to
519	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1048	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
520	time you successfully read or write some data. If you go into an idle	1049	C<ev_timer_again> each time you successfully read or write some data. If
521	state where you do not expect data to travel on the socket, you can stop	1050	you go into an idle state where you do not expect data to travel on the
522	the timer, and again will automatically restart it if need be.	1051	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1052	automatically restart it if need be.
		1053
		1054	That means you can ignore the C<after> value and C<ev_timer_start>
		1055	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1056
		1057	ev_timer_init (timer, callback, 0., 5.);
		1058	ev_timer_again (loop, timer);
		1059	...
		1060	timer->again = 17.;
		1061	ev_timer_again (loop, timer);
		1062	...
		1063	timer->again = 10.;
		1064	ev_timer_again (loop, timer);
		1065
		1066	This is more slightly efficient then stopping/starting the timer each time
		1067	you want to modify its timeout value.
		1068
		1069	=item ev_tstamp repeat [read-write]
		1070
		1071	The current C<repeat> value. Will be used each time the watcher times out
		1072	or C<ev_timer_again> is called and determines the next timeout (if any),
		1073	which is also when any modifications are taken into account.
523		1074
524	=back	1075	=back
525		1076
		1077	Example: Create a timer that fires after 60 seconds.
		1078
		1079	static void
		1080	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1081	{
		1082	.. one minute over, w is actually stopped right here
		1083	}
		1084
		1085	struct ev_timer mytimer;
		1086	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1087	ev_timer_start (loop, &mytimer);
		1088
		1089	Example: Create a timeout timer that times out after 10 seconds of
		1090	inactivity.
		1091
		1092	static void
		1093	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1094	{
		1095	.. ten seconds without any activity
		1096	}
		1097
		1098	struct ev_timer mytimer;
		1099	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1100	ev_timer_again (&mytimer); /* start timer */
		1101	ev_loop (loop, 0);
		1102
		1103	// and in some piece of code that gets executed on any "activity":
		1104	// reset the timeout to start ticking again at 10 seconds
		1105	ev_timer_again (&mytimer);
		1106
		1107
526	=head2 C<ev_periodic> - to cron or not to cron	1108	=head2 C<ev_periodic> - to cron or not to cron?
527		1109
528	Periodic watchers are also timers of a kind, but they are very versatile	1110	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	1111	(and unfortunately a bit complex).
530		1112
531	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1113	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
532	but on wallclock time (absolute time). You can tell a periodic watcher	1114	but on wallclock time (absolute time). You can tell a periodic watcher
533	to trigger "at" some specific point in time. For example, if you tell a	1115	to trigger "at" some specific point in time. For example, if you tell a
534	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1116	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
535	+ 10.>) and then reset your system clock to the last year, then it will	1117	+ 10.>) and then reset your system clock to the last year, then it will
536	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1118	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
537	roughly 10 seconds later and of course not if you reset your system time	1119	roughly 10 seconds later).
538	again).
539		1120
540	They can also be used to implement vastly more complex timers, such as	1121	They can also be used to implement vastly more complex timers, such as
541	triggering an event on eahc midnight, local time.	1122	triggering an event on each midnight, local time or other, complicated,
		1123	rules.
		1124
		1125	As with timers, the callback is guarenteed to be invoked only when the
		1126	time (C<at>) has been passed, but if multiple periodic timers become ready
		1127	during the same loop iteration then order of execution is undefined.
		1128
		1129	=head3 Watcher-Specific Functions and Data Members
542		1130
543	=over 4	1131	=over 4
544		1132
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1133	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		1134
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1135	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		1136
549	Lots of arguments, lets sort it out... There are basically three modes of	1137	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	1138	operation, and we will explain them from simplest to complex:
551		1139
552
553	=over 4	1140	=over 4
554		1141
555	=item * absolute timer (interval = reschedule_cb = 0)	1142	=item * absolute timer (at = time, interval = reschedule_cb = 0)
556		1143
557	In this configuration the watcher triggers an event at the wallclock time	1144	In this configuration the watcher triggers an event at the wallclock time
558	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1145	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
559	that is, if it is to be run at January 1st 2011 then it will run when the	1146	that is, if it is to be run at January 1st 2011 then it will run when the
560	system time reaches or surpasses this time.	1147	system time reaches or surpasses this time.
561		1148
562	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1149	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
563		1150
564	In this mode the watcher will always be scheduled to time out at the next	1151	In this mode the watcher will always be scheduled to time out at the next
565	C<at + N * interval> time (for some integer N) and then repeat, regardless	1152	C<at + N * interval> time (for some integer N, which can also be negative)
566	of any time jumps.	1153	and then repeat, regardless of any time jumps.
567		1154
568	This can be used to create timers that do not drift with respect to system	1155	This can be used to create timers that do not drift with respect to system
569	time:	1156	time:
570		1157
571	ev_periodic_set (&periodic, 0., 3600., 0);	1158	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
577		1164
578	Another way to think about it (for the mathematically inclined) is that	1165	Another way to think about it (for the mathematically inclined) is that
579	C<ev_periodic> will try to run the callback in this mode at the next possible	1166	C<ev_periodic> will try to run the callback in this mode at the next possible
580	time where C<time = at (mod interval)>, regardless of any time jumps.	1167	time where C<time = at (mod interval)>, regardless of any time jumps.
581		1168
		1169	For numerical stability it is preferable that the C<at> value is near
		1170	C<ev_now ()> (the current time), but there is no range requirement for
		1171	this value.
		1172
582	=item * manual reschedule mode (reschedule_cb = callback)	1173	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
583		1174
584	In this mode the values for C<interval> and C<at> are both being	1175	In this mode the values for C<interval> and C<at> are both being
585	ignored. Instead, each time the periodic watcher gets scheduled, the	1176	ignored. Instead, each time the periodic watcher gets scheduled, the
586	reschedule callback will be called with the watcher as first, and the	1177	reschedule callback will be called with the watcher as first, and the
587	current time as second argument.	1178	current time as second argument.
588		1179
589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1180	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
590	ever, or make any event loop modifications>. If you need to stop it,	1181	ever, or make any event loop modifications>. If you need to stop it,
591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1182	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
592	starting a prepare watcher).	1183	starting an C<ev_prepare> watcher, which is legal).
593		1184
594	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1185	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
595	ev_tstamp now)>, e.g.:	1186	ev_tstamp now)>, e.g.:
596		1187
597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1188	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
620	Simply stops and restarts the periodic watcher again. This is only useful	1211	Simply stops and restarts the periodic watcher again. This is only useful
621	when you changed some parameters or the reschedule callback would return	1212	when you changed some parameters or the reschedule callback would return
622	a different time than the last time it was called (e.g. in a crond like	1213	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	1214	program when the crontabs have changed).
624		1215
		1216	=item ev_tstamp offset [read-write]
		1217
		1218	When repeating, this contains the offset value, otherwise this is the
		1219	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1220
		1221	Can be modified any time, but changes only take effect when the periodic
		1222	timer fires or C<ev_periodic_again> is being called.
		1223
		1224	=item ev_tstamp interval [read-write]
		1225
		1226	The current interval value. Can be modified any time, but changes only
		1227	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1228	called.
		1229
		1230	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1231
		1232	The current reschedule callback, or C<0>, if this functionality is
		1233	switched off. Can be changed any time, but changes only take effect when
		1234	the periodic timer fires or C<ev_periodic_again> is being called.
		1235
		1236	=item ev_tstamp at [read-only]
		1237
		1238	When active, contains the absolute time that the watcher is supposed to
		1239	trigger next.
		1240
625	=back	1241	=back
626		1242
		1243	Example: Call a callback every hour, or, more precisely, whenever the
		1244	system clock is divisible by 3600. The callback invocation times have
		1245	potentially a lot of jittering, but good long-term stability.
		1246
		1247	static void
		1248	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1249	{
		1250	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1251	}
		1252
		1253	struct ev_periodic hourly_tick;
		1254	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1255	ev_periodic_start (loop, &hourly_tick);
		1256
		1257	Example: The same as above, but use a reschedule callback to do it:
		1258
		1259	#include <math.h>
		1260
		1261	static ev_tstamp
		1262	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1263	{
		1264	return fmod (now, 3600.) + 3600.;
		1265	}
		1266
		1267	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1268
		1269	Example: Call a callback every hour, starting now:
		1270
		1271	struct ev_periodic hourly_tick;
		1272	ev_periodic_init (&hourly_tick, clock_cb,
		1273	fmod (ev_now (loop), 3600.), 3600., 0);
		1274	ev_periodic_start (loop, &hourly_tick);
		1275
		1276
627	=head2 C<ev_signal> - signal me when a signal gets signalled	1277	=head2 C<ev_signal> - signal me when a signal gets signalled!
628		1278
629	Signal watchers will trigger an event when the process receives a specific	1279	Signal watchers will trigger an event when the process receives a specific
630	signal one or more times. Even though signals are very asynchronous, libev	1280	signal one or more times. Even though signals are very asynchronous, libev
631	will try it's best to deliver signals synchronously, i.e. as part of the	1281	will try it's best to deliver signals synchronously, i.e. as part of the
632	normal event processing, like any other event.	1282	normal event processing, like any other event.
…		…
636	with the kernel (thus it coexists with your own signal handlers as long	1286	with the kernel (thus it coexists with your own signal handlers as long
637	as you don't register any with libev). Similarly, when the last signal	1287	as you don't register any with libev). Similarly, when the last signal
638	watcher for a signal is stopped libev will reset the signal handler to	1288	watcher for a signal is stopped libev will reset the signal handler to
639	SIG_DFL (regardless of what it was set to before).	1289	SIG_DFL (regardless of what it was set to before).
640		1290
		1291	=head3 Watcher-Specific Functions and Data Members
		1292
641	=over 4	1293	=over 4
642		1294
643	=item ev_signal_init (ev_signal *, callback, int signum)	1295	=item ev_signal_init (ev_signal *, callback, int signum)
644		1296
645	=item ev_signal_set (ev_signal *, int signum)	1297	=item ev_signal_set (ev_signal *, int signum)
646		1298
647	Configures the watcher to trigger on the given signal number (usually one	1299	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1300	of the C<SIGxxx> constants).
649		1301
		1302	=item int signum [read-only]
		1303
		1304	The signal the watcher watches out for.
		1305
650	=back	1306	=back
651		1307
		1308
652	=head2 C<ev_child> - wait for pid status changes	1309	=head2 C<ev_child> - watch out for process status changes
653		1310
654	Child watchers trigger when your process receives a SIGCHLD in response to	1311	Child watchers trigger when your process receives a SIGCHLD in response to
655	some child status changes (most typically when a child of yours dies).	1312	some child status changes (most typically when a child of yours dies).
		1313
		1314	=head3 Watcher-Specific Functions and Data Members
656		1315
657	=over 4	1316	=over 4
658		1317
659	=item ev_child_init (ev_child *, callback, int pid)	1318	=item ev_child_init (ev_child *, callback, int pid)
660		1319
…		…
665	at the C<rstatus> member of the C<ev_child> watcher structure to see	1324	at the C<rstatus> member of the C<ev_child> watcher structure to see
666	the status word (use the macros from C<sys/wait.h> and see your systems	1325	the status word (use the macros from C<sys/wait.h> and see your systems
667	C<waitpid> documentation). The C<rpid> member contains the pid of the	1326	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1327	process causing the status change.
669		1328
		1329	=item int pid [read-only]
		1330
		1331	The process id this watcher watches out for, or C<0>, meaning any process id.
		1332
		1333	=item int rpid [read-write]
		1334
		1335	The process id that detected a status change.
		1336
		1337	=item int rstatus [read-write]
		1338
		1339	The process exit/trace status caused by C<rpid> (see your systems
		1340	C<waitpid> and C<sys/wait.h> documentation for details).
		1341
670	=back	1342	=back
671		1343
		1344	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1345
		1346	static void
		1347	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1348	{
		1349	ev_unloop (loop, EVUNLOOP_ALL);
		1350	}
		1351
		1352	struct ev_signal signal_watcher;
		1353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1354	ev_signal_start (loop, &sigint_cb);
		1355
		1356
		1357	=head2 C<ev_stat> - did the file attributes just change?
		1358
		1359	This watches a filesystem path for attribute changes. That is, it calls
		1360	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1361	compared to the last time, invoking the callback if it did.
		1362
		1363	The path does not need to exist: changing from "path exists" to "path does
		1364	not exist" is a status change like any other. The condition "path does
		1365	not exist" is signified by the C<st_nlink> field being zero (which is
		1366	otherwise always forced to be at least one) and all the other fields of
		1367	the stat buffer having unspecified contents.
		1368
		1369	The path I<should> be absolute and I<must not> end in a slash. If it is
		1370	relative and your working directory changes, the behaviour is undefined.
		1371
		1372	Since there is no standard to do this, the portable implementation simply
		1373	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1374	can specify a recommended polling interval for this case. If you specify
		1375	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1376	unspecified default> value will be used (which you can expect to be around
		1377	five seconds, although this might change dynamically). Libev will also
		1378	impose a minimum interval which is currently around C<0.1>, but thats
		1379	usually overkill.
		1380
		1381	This watcher type is not meant for massive numbers of stat watchers,
		1382	as even with OS-supported change notifications, this can be
		1383	resource-intensive.
		1384
		1385	At the time of this writing, only the Linux inotify interface is
		1386	implemented (implementing kqueue support is left as an exercise for the
		1387	reader). Inotify will be used to give hints only and should not change the
		1388	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1389	to fall back to regular polling again even with inotify, but changes are
		1390	usually detected immediately, and if the file exists there will be no
		1391	polling.
		1392
		1393	=head3 Watcher-Specific Functions and Data Members
		1394
		1395	=over 4
		1396
		1397	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1398
		1399	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1400
		1401	Configures the watcher to wait for status changes of the given
		1402	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1403	be detected and should normally be specified as C<0> to let libev choose
		1404	a suitable value. The memory pointed to by C<path> must point to the same
		1405	path for as long as the watcher is active.
		1406
		1407	The callback will be receive C<EV_STAT> when a change was detected,
		1408	relative to the attributes at the time the watcher was started (or the
		1409	last change was detected).
		1410
		1411	=item ev_stat_stat (ev_stat *)
		1412
		1413	Updates the stat buffer immediately with new values. If you change the
		1414	watched path in your callback, you could call this fucntion to avoid
		1415	detecting this change (while introducing a race condition). Can also be
		1416	useful simply to find out the new values.
		1417
		1418	=item ev_statdata attr [read-only]
		1419
		1420	The most-recently detected attributes of the file. Although the type is of
		1421	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1422	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1423	was some error while C<stat>ing the file.
		1424
		1425	=item ev_statdata prev [read-only]
		1426
		1427	The previous attributes of the file. The callback gets invoked whenever
		1428	C<prev> != C<attr>.
		1429
		1430	=item ev_tstamp interval [read-only]
		1431
		1432	The specified interval.
		1433
		1434	=item const char *path [read-only]
		1435
		1436	The filesystem path that is being watched.
		1437
		1438	=back
		1439
		1440	Example: Watch C</etc/passwd> for attribute changes.
		1441
		1442	static void
		1443	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1444	{
		1445	/* /etc/passwd changed in some way */
		1446	if (w->attr.st_nlink)
		1447	{
		1448	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1449	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1450	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1451	}
		1452	else
		1453	/* you shalt not abuse printf for puts */
		1454	puts ("wow, /etc/passwd is not there, expect problems. "
		1455	"if this is windows, they already arrived\n");
		1456	}
		1457
		1458	...
		1459	ev_stat passwd;
		1460
		1461	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1462	ev_stat_start (loop, &passwd);
		1463
		1464
672	=head2 C<ev_idle> - when you've got nothing better to do	1465	=head2 C<ev_idle> - when you've got nothing better to do...
673		1466
674	Idle watchers trigger events when there are no other events are pending	1467	Idle watchers trigger events when no other events of the same or higher
675	(prepare, check and other idle watchers do not count). That is, as long	1468	priority are pending (prepare, check and other idle watchers do not
676	as your process is busy handling sockets or timeouts (or even signals,	1469	count).
677	imagine) it will not be triggered. But when your process is idle all idle	1470
678	watchers are being called again and again, once per event loop iteration -	1471	That is, as long as your process is busy handling sockets or timeouts
		1472	(or even signals, imagine) of the same or higher priority it will not be
		1473	triggered. But when your process is idle (or only lower-priority watchers
		1474	are pending), the idle watchers are being called once per event loop
679	until stopped, that is, or your process receives more events and becomes	1475	iteration - until stopped, that is, or your process receives more events
680	busy.	1476	and becomes busy again with higher priority stuff.
681		1477
682	The most noteworthy effect is that as long as any idle watchers are	1478	The most noteworthy effect is that as long as any idle watchers are
683	active, the process will not block when waiting for new events.	1479	active, the process will not block when waiting for new events.
684		1480
685	Apart from keeping your process non-blocking (which is a useful	1481	Apart from keeping your process non-blocking (which is a useful
686	effect on its own sometimes), idle watchers are a good place to do	1482	effect on its own sometimes), idle watchers are a good place to do
687	"pseudo-background processing", or delay processing stuff to after the	1483	"pseudo-background processing", or delay processing stuff to after the
688	event loop has handled all outstanding events.	1484	event loop has handled all outstanding events.
689		1485
		1486	=head3 Watcher-Specific Functions and Data Members
		1487
690	=over 4	1488	=over 4
691		1489
692	=item ev_idle_init (ev_signal *, callback)	1490	=item ev_idle_init (ev_signal *, callback)
693		1491
694	Initialises and configures the idle watcher - it has no parameters of any	1492	Initialises and configures the idle watcher - it has no parameters of any
695	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1493	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1494	believe me.
697		1495
698	=back	1496	=back
699		1497
		1498	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1499	callback, free it. Also, use no error checking, as usual.
		1500
		1501	static void
		1502	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1503	{
		1504	free (w);
		1505	// now do something you wanted to do when the program has
		1506	// no longer asnything immediate to do.
		1507	}
		1508
		1509	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1510	ev_idle_init (idle_watcher, idle_cb);
		1511	ev_idle_start (loop, idle_cb);
		1512
		1513
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1514	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
701		1515
702	Prepare and check watchers are usually (but not always) used in tandem:	1516	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1517	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1518	afterwards.
705		1519
		1520	You I<must not> call C<ev_loop> or similar functions that enter
		1521	the current event loop from either C<ev_prepare> or C<ev_check>
		1522	watchers. Other loops than the current one are fine, however. The
		1523	rationale behind this is that you do not need to check for recursion in
		1524	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1525	C<ev_check> so if you have one watcher of each kind they will always be
		1526	called in pairs bracketing the blocking call.
		1527
706	Their main purpose is to integrate other event mechanisms into libev. This	1528	Their main purpose is to integrate other event mechanisms into libev and
707	could be used, for example, to track variable changes, implement your own	1529	their use is somewhat advanced. This could be used, for example, to track
708	watchers, integrate net-snmp or a coroutine library and lots more.	1530	variable changes, implement your own watchers, integrate net-snmp or a
		1531	coroutine library and lots more. They are also occasionally useful if
		1532	you cache some data and want to flush it before blocking (for example,
		1533	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1534	watcher).
709		1535
710	This is done by examining in each prepare call which file descriptors need	1536	This is done by examining in each prepare call which file descriptors need
711	to be watched by the other library, registering C<ev_io> watchers for	1537	to be watched by the other library, registering C<ev_io> watchers for
712	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1538	them and starting an C<ev_timer> watcher for any timeouts (many libraries
713	provide just this functionality). Then, in the check watcher you check for	1539	provide just this functionality). Then, in the check watcher you check for
…		…
723	with priority higher than or equal to the event loop and one coroutine	1549	with priority higher than or equal to the event loop and one coroutine
724	of lower priority, but only once, using idle watchers to keep the event	1550	of lower priority, but only once, using idle watchers to keep the event
725	loop from blocking if lower-priority coroutines are active, thus mapping	1551	loop from blocking if lower-priority coroutines are active, thus mapping
726	low-priority coroutines to idle/background tasks).	1552	low-priority coroutines to idle/background tasks).
727		1553
		1554	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1555	priority, to ensure that they are being run before any other watchers
		1556	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1557	too) should not activate ("feed") events into libev. While libev fully
		1558	supports this, they will be called before other C<ev_check> watchers did
		1559	their job. As C<ev_check> watchers are often used to embed other event
		1560	loops those other event loops might be in an unusable state until their
		1561	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1562	others).
		1563
		1564	=head3 Watcher-Specific Functions and Data Members
		1565
728	=over 4	1566	=over 4
729		1567
730	=item ev_prepare_init (ev_prepare *, callback)	1568	=item ev_prepare_init (ev_prepare *, callback)
731		1569
732	=item ev_check_init (ev_check *, callback)	1570	=item ev_check_init (ev_check *, callback)
…		…
734	Initialises and configures the prepare or check watcher - they have no	1572	Initialises and configures the prepare or check watcher - they have no
735	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1573	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
736	macros, but using them is utterly, utterly and completely pointless.	1574	macros, but using them is utterly, utterly and completely pointless.
737		1575
738	=back	1576	=back
		1577
		1578	There are a number of principal ways to embed other event loops or modules
		1579	into libev. Here are some ideas on how to include libadns into libev
		1580	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1581	use for an actually working example. Another Perl module named C<EV::Glib>
		1582	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1583	into the Glib event loop).
		1584
		1585	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1586	and in a check watcher, destroy them and call into libadns. What follows
		1587	is pseudo-code only of course. This requires you to either use a low
		1588	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1589	the callbacks for the IO/timeout watchers might not have been called yet.
		1590
		1591	static ev_io iow [nfd];
		1592	static ev_timer tw;
		1593
		1594	static void
		1595	io_cb (ev_loop *loop, ev_io *w, int revents)
		1596	{
		1597	}
		1598
		1599	// create io watchers for each fd and a timer before blocking
		1600	static void
		1601	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1602	{
		1603	int timeout = 3600000;
		1604	struct pollfd fds [nfd];
		1605	// actual code will need to loop here and realloc etc.
		1606	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1607
		1608	/* the callback is illegal, but won't be called as we stop during check */
		1609	ev_timer_init (&tw, 0, timeout * 1e-3);
		1610	ev_timer_start (loop, &tw);
		1611
		1612	// create one ev_io per pollfd
		1613	for (int i = 0; i < nfd; ++i)
		1614	{
		1615	ev_io_init (iow + i, io_cb, fds [i].fd,
		1616	((fds [i].events & POLLIN ? EV_READ : 0)
		1617	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1618
		1619	fds [i].revents = 0;
		1620	ev_io_start (loop, iow + i);
		1621	}
		1622	}
		1623
		1624	// stop all watchers after blocking
		1625	static void
		1626	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1627	{
		1628	ev_timer_stop (loop, &tw);
		1629
		1630	for (int i = 0; i < nfd; ++i)
		1631	{
		1632	// set the relevant poll flags
		1633	// could also call adns_processreadable etc. here
		1634	struct pollfd *fd = fds + i;
		1635	int revents = ev_clear_pending (iow + i);
		1636	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1637	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1638
		1639	// now stop the watcher
		1640	ev_io_stop (loop, iow + i);
		1641	}
		1642
		1643	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1644	}
		1645
		1646	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1647	in the prepare watcher and would dispose of the check watcher.
		1648
		1649	Method 3: If the module to be embedded supports explicit event
		1650	notification (adns does), you can also make use of the actual watcher
		1651	callbacks, and only destroy/create the watchers in the prepare watcher.
		1652
		1653	static void
		1654	timer_cb (EV_P_ ev_timer *w, int revents)
		1655	{
		1656	adns_state ads = (adns_state)w->data;
		1657	update_now (EV_A);
		1658
		1659	adns_processtimeouts (ads, &tv_now);
		1660	}
		1661
		1662	static void
		1663	io_cb (EV_P_ ev_io *w, int revents)
		1664	{
		1665	adns_state ads = (adns_state)w->data;
		1666	update_now (EV_A);
		1667
		1668	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1669	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1670	}
		1671
		1672	// do not ever call adns_afterpoll
		1673
		1674	Method 4: Do not use a prepare or check watcher because the module you
		1675	want to embed is too inflexible to support it. Instead, youc na override
		1676	their poll function. The drawback with this solution is that the main
		1677	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1678	this.
		1679
		1680	static gint
		1681	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1682	{
		1683	int got_events = 0;
		1684
		1685	for (n = 0; n < nfds; ++n)
		1686	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1687
		1688	if (timeout >= 0)
		1689	// create/start timer
		1690
		1691	// poll
		1692	ev_loop (EV_A_ 0);
		1693
		1694	// stop timer again
		1695	if (timeout >= 0)
		1696	ev_timer_stop (EV_A_ &to);
		1697
		1698	// stop io watchers again - their callbacks should have set
		1699	for (n = 0; n < nfds; ++n)
		1700	ev_io_stop (EV_A_ iow [n]);
		1701
		1702	return got_events;
		1703	}
		1704
		1705
		1706	=head2 C<ev_embed> - when one backend isn't enough...
		1707
		1708	This is a rather advanced watcher type that lets you embed one event loop
		1709	into another (currently only C<ev_io> events are supported in the embedded
		1710	loop, other types of watchers might be handled in a delayed or incorrect
		1711	fashion and must not be used).
		1712
		1713	There are primarily two reasons you would want that: work around bugs and
		1714	prioritise I/O.
		1715
		1716	As an example for a bug workaround, the kqueue backend might only support
		1717	sockets on some platform, so it is unusable as generic backend, but you
		1718	still want to make use of it because you have many sockets and it scales
		1719	so nicely. In this case, you would create a kqueue-based loop and embed it
		1720	into your default loop (which might use e.g. poll). Overall operation will
		1721	be a bit slower because first libev has to poll and then call kevent, but
		1722	at least you can use both at what they are best.
		1723
		1724	As for prioritising I/O: rarely you have the case where some fds have
		1725	to be watched and handled very quickly (with low latency), and even
		1726	priorities and idle watchers might have too much overhead. In this case
		1727	you would put all the high priority stuff in one loop and all the rest in
		1728	a second one, and embed the second one in the first.
		1729
		1730	As long as the watcher is active, the callback will be invoked every time
		1731	there might be events pending in the embedded loop. The callback must then
		1732	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1733	their callbacks (you could also start an idle watcher to give the embedded
		1734	loop strictly lower priority for example). You can also set the callback
		1735	to C<0>, in which case the embed watcher will automatically execute the
		1736	embedded loop sweep.
		1737
		1738	As long as the watcher is started it will automatically handle events. The
		1739	callback will be invoked whenever some events have been handled. You can
		1740	set the callback to C<0> to avoid having to specify one if you are not
		1741	interested in that.
		1742
		1743	Also, there have not currently been made special provisions for forking:
		1744	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1745	but you will also have to stop and restart any C<ev_embed> watchers
		1746	yourself.
		1747
		1748	Unfortunately, not all backends are embeddable, only the ones returned by
		1749	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1750	portable one.
		1751
		1752	So when you want to use this feature you will always have to be prepared
		1753	that you cannot get an embeddable loop. The recommended way to get around
		1754	this is to have a separate variables for your embeddable loop, try to
		1755	create it, and if that fails, use the normal loop for everything:
		1756
		1757	struct ev_loop *loop_hi = ev_default_init (0);
		1758	struct ev_loop *loop_lo = 0;
		1759	struct ev_embed embed;
		1760
		1761	// see if there is a chance of getting one that works
		1762	// (remember that a flags value of 0 means autodetection)
		1763	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1764	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1765	: 0;
		1766
		1767	// if we got one, then embed it, otherwise default to loop_hi
		1768	if (loop_lo)
		1769	{
		1770	ev_embed_init (&embed, 0, loop_lo);
		1771	ev_embed_start (loop_hi, &embed);
		1772	}
		1773	else
		1774	loop_lo = loop_hi;
		1775
		1776	=head3 Watcher-Specific Functions and Data Members
		1777
		1778	=over 4
		1779
		1780	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1781
		1782	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1783
		1784	Configures the watcher to embed the given loop, which must be
		1785	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1786	invoked automatically, otherwise it is the responsibility of the callback
		1787	to invoke it (it will continue to be called until the sweep has been done,
		1788	if you do not want thta, you need to temporarily stop the embed watcher).
		1789
		1790	=item ev_embed_sweep (loop, ev_embed *)
		1791
		1792	Make a single, non-blocking sweep over the embedded loop. This works
		1793	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1794	apropriate way for embedded loops.
		1795
		1796	=item struct ev_loop *loop [read-only]
		1797
		1798	The embedded event loop.
		1799
		1800	=back
		1801
		1802
		1803	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1804
		1805	Fork watchers are called when a C<fork ()> was detected (usually because
		1806	whoever is a good citizen cared to tell libev about it by calling
		1807	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1808	event loop blocks next and before C<ev_check> watchers are being called,
		1809	and only in the child after the fork. If whoever good citizen calling
		1810	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1811	handlers will be invoked, too, of course.
		1812
		1813	=head3 Watcher-Specific Functions and Data Members
		1814
		1815	=over 4
		1816
		1817	=item ev_fork_init (ev_signal *, callback)
		1818
		1819	Initialises and configures the fork watcher - it has no parameters of any
		1820	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1821	believe me.
		1822
		1823	=back
		1824
739		1825
740	=head1 OTHER FUNCTIONS	1826	=head1 OTHER FUNCTIONS
741		1827
742	There are some other functions of possible interest. Described. Here. Now.	1828	There are some other functions of possible interest. Described. Here. Now.
743		1829
…		…
773	/* stdin might have data for us, joy! */;	1859	/* stdin might have data for us, joy! */;
774	}	1860	}
775		1861
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1862	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		1863
778	=item ev_feed_event (loop, watcher, int events)	1864	=item ev_feed_event (ev_loop *, watcher *, int revents)
779		1865
780	Feeds the given event set into the event loop, as if the specified event	1866	Feeds the given event set into the event loop, as if the specified event
781	had happened for the specified watcher (which must be a pointer to an	1867	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	1868	initialised but not necessarily started event watcher).
783		1869
784	=item ev_feed_fd_event (loop, int fd, int revents)	1870	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		1871
786	Feed an event on the given fd, as if a file descriptor backend detected	1872	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	1873	the given events it.
788		1874
789	=item ev_feed_signal_event (loop, int signum)	1875	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		1876
791	Feed an event as if the given signal occured (loop must be the default loop!).	1877	Feed an event as if the given signal occured (C<loop> must be the default
		1878	loop!).
792		1879
793	=back	1880	=back
		1881
794		1882
795	=head1 LIBEVENT EMULATION	1883	=head1 LIBEVENT EMULATION
796		1884
797	Libev offers a compatibility emulation layer for libevent. It cannot	1885	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	1886	emulate the internals of libevent, so here are some usage hints:
…		…
819		1907
820	=back	1908	=back
821		1909
822	=head1 C++ SUPPORT	1910	=head1 C++ SUPPORT
823		1911
824	TBD.	1912	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1913	you to use some convinience methods to start/stop watchers and also change
		1914	the callback model to a model using method callbacks on objects.
		1915
		1916	To use it,
		1917
		1918	#include <ev++.h>
		1919
		1920	This automatically includes F<ev.h> and puts all of its definitions (many
		1921	of them macros) into the global namespace. All C++ specific things are
		1922	put into the C<ev> namespace. It should support all the same embedding
		1923	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1924
		1925	Care has been taken to keep the overhead low. The only data member the C++
		1926	classes add (compared to plain C-style watchers) is the event loop pointer
		1927	that the watcher is associated with (or no additional members at all if
		1928	you disable C<EV_MULTIPLICITY> when embedding libev).
		1929
		1930	Currently, functions, and static and non-static member functions can be
		1931	used as callbacks. Other types should be easy to add as long as they only
		1932	need one additional pointer for context. If you need support for other
		1933	types of functors please contact the author (preferably after implementing
		1934	it).
		1935
		1936	Here is a list of things available in the C<ev> namespace:
		1937
		1938	=over 4
		1939
		1940	=item C<ev::READ>, C<ev::WRITE> etc.
		1941
		1942	These are just enum values with the same values as the C<EV_READ> etc.
		1943	macros from F<ev.h>.
		1944
		1945	=item C<ev::tstamp>, C<ev::now>
		1946
		1947	Aliases to the same types/functions as with the C<ev_> prefix.
		1948
		1949	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1950
		1951	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1952	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1953	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1954	defines by many implementations.
		1955
		1956	All of those classes have these methods:
		1957
		1958	=over 4
		1959
		1960	=item ev::TYPE::TYPE ()
		1961
		1962	=item ev::TYPE::TYPE (struct ev_loop *)
		1963
		1964	=item ev::TYPE::~TYPE
		1965
		1966	The constructor (optionally) takes an event loop to associate the watcher
		1967	with. If it is omitted, it will use C<EV_DEFAULT>.
		1968
		1969	The constructor calls C<ev_init> for you, which means you have to call the
		1970	C<set> method before starting it.
		1971
		1972	It will not set a callback, however: You have to call the templated C<set>
		1973	method to set a callback before you can start the watcher.
		1974
		1975	(The reason why you have to use a method is a limitation in C++ which does
		1976	not allow explicit template arguments for constructors).
		1977
		1978	The destructor automatically stops the watcher if it is active.
		1979
		1980	=item w->set<class, &class::method> (object *)
		1981
		1982	This method sets the callback method to call. The method has to have a
		1983	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1984	first argument and the C<revents> as second. The object must be given as
		1985	parameter and is stored in the C<data> member of the watcher.
		1986
		1987	This method synthesizes efficient thunking code to call your method from
		1988	the C callback that libev requires. If your compiler can inline your
		1989	callback (i.e. it is visible to it at the place of the C<set> call and
		1990	your compiler is good :), then the method will be fully inlined into the
		1991	thunking function, making it as fast as a direct C callback.
		1992
		1993	Example: simple class declaration and watcher initialisation
		1994
		1995	struct myclass
		1996	{
		1997	void io_cb (ev::io &w, int revents) { }
		1998	}
		1999
		2000	myclass obj;
		2001	ev::io iow;
		2002	iow.set <myclass, &myclass::io_cb> (&obj);
		2003
		2004	=item w->set<function> (void *data = 0)
		2005
		2006	Also sets a callback, but uses a static method or plain function as
		2007	callback. The optional C<data> argument will be stored in the watcher's
		2008	C<data> member and is free for you to use.
		2009
		2010	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2011
		2012	See the method-C<set> above for more details.
		2013
		2014	Example:
		2015
		2016	static void io_cb (ev::io &w, int revents) { }
		2017	iow.set <io_cb> ();
		2018
		2019	=item w->set (struct ev_loop *)
		2020
		2021	Associates a different C<struct ev_loop> with this watcher. You can only
		2022	do this when the watcher is inactive (and not pending either).
		2023
		2024	=item w->set ([args])
		2025
		2026	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2027	called at least once. Unlike the C counterpart, an active watcher gets
		2028	automatically stopped and restarted when reconfiguring it with this
		2029	method.
		2030
		2031	=item w->start ()
		2032
		2033	Starts the watcher. Note that there is no C<loop> argument, as the
		2034	constructor already stores the event loop.
		2035
		2036	=item w->stop ()
		2037
		2038	Stops the watcher if it is active. Again, no C<loop> argument.
		2039
		2040	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2041
		2042	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2043	C<ev_TYPE_again> function.
		2044
		2045	=item w->sweep () (C<ev::embed> only)
		2046
		2047	Invokes C<ev_embed_sweep>.
		2048
		2049	=item w->update () (C<ev::stat> only)
		2050
		2051	Invokes C<ev_stat_stat>.
		2052
		2053	=back
		2054
		2055	=back
		2056
		2057	Example: Define a class with an IO and idle watcher, start one of them in
		2058	the constructor.
		2059
		2060	class myclass
		2061	{
		2062	ev_io io; void io_cb (ev::io &w, int revents);
		2063	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2064
		2065	myclass ();
		2066	}
		2067
		2068	myclass::myclass (int fd)
		2069	{
		2070	io .set <myclass, &myclass::io_cb > (this);
		2071	idle.set <myclass, &myclass::idle_cb> (this);
		2072
		2073	io.start (fd, ev::READ);
		2074	}
		2075
		2076
		2077	=head1 MACRO MAGIC
		2078
		2079	Libev can be compiled with a variety of options, the most fundamantal
		2080	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2081	functions and callbacks have an initial C<struct ev_loop *> argument.
		2082
		2083	To make it easier to write programs that cope with either variant, the
		2084	following macros are defined:
		2085
		2086	=over 4
		2087
		2088	=item C<EV_A>, C<EV_A_>
		2089
		2090	This provides the loop I<argument> for functions, if one is required ("ev
		2091	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2092	C<EV_A_> is used when other arguments are following. Example:
		2093
		2094	ev_unref (EV_A);
		2095	ev_timer_add (EV_A_ watcher);
		2096	ev_loop (EV_A_ 0);
		2097
		2098	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2099	which is often provided by the following macro.
		2100
		2101	=item C<EV_P>, C<EV_P_>
		2102
		2103	This provides the loop I<parameter> for functions, if one is required ("ev
		2104	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2105	C<EV_P_> is used when other parameters are following. Example:
		2106
		2107	// this is how ev_unref is being declared
		2108	static void ev_unref (EV_P);
		2109
		2110	// this is how you can declare your typical callback
		2111	static void cb (EV_P_ ev_timer *w, int revents)
		2112
		2113	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2114	suitable for use with C<EV_A>.
		2115
		2116	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2117
		2118	Similar to the other two macros, this gives you the value of the default
		2119	loop, if multiple loops are supported ("ev loop default").
		2120
		2121	=back
		2122
		2123	Example: Declare and initialise a check watcher, utilising the above
		2124	macros so it will work regardless of whether multiple loops are supported
		2125	or not.
		2126
		2127	static void
		2128	check_cb (EV_P_ ev_timer *w, int revents)
		2129	{
		2130	ev_check_stop (EV_A_ w);
		2131	}
		2132
		2133	ev_check check;
		2134	ev_check_init (&check, check_cb);
		2135	ev_check_start (EV_DEFAULT_ &check);
		2136	ev_loop (EV_DEFAULT_ 0);
		2137
		2138	=head1 EMBEDDING
		2139
		2140	Libev can (and often is) directly embedded into host
		2141	applications. Examples of applications that embed it include the Deliantra
		2142	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2143	and rxvt-unicode.
		2144
		2145	The goal is to enable you to just copy the neecssary files into your
		2146	source directory without having to change even a single line in them, so
		2147	you can easily upgrade by simply copying (or having a checked-out copy of
		2148	libev somewhere in your source tree).
		2149
		2150	=head2 FILESETS
		2151
		2152	Depending on what features you need you need to include one or more sets of files
		2153	in your app.
		2154
		2155	=head3 CORE EVENT LOOP
		2156
		2157	To include only the libev core (all the C<ev_*> functions), with manual
		2158	configuration (no autoconf):
		2159
		2160	#define EV_STANDALONE 1
		2161	#include "ev.c"
		2162
		2163	This will automatically include F<ev.h>, too, and should be done in a
		2164	single C source file only to provide the function implementations. To use
		2165	it, do the same for F<ev.h> in all files wishing to use this API (best
		2166	done by writing a wrapper around F<ev.h> that you can include instead and
		2167	where you can put other configuration options):
		2168
		2169	#define EV_STANDALONE 1
		2170	#include "ev.h"
		2171
		2172	Both header files and implementation files can be compiled with a C++
		2173	compiler (at least, thats a stated goal, and breakage will be treated
		2174	as a bug).
		2175
		2176	You need the following files in your source tree, or in a directory
		2177	in your include path (e.g. in libev/ when using -Ilibev):
		2178
		2179	ev.h
		2180	ev.c
		2181	ev_vars.h
		2182	ev_wrap.h
		2183
		2184	ev_win32.c required on win32 platforms only
		2185
		2186	ev_select.c only when select backend is enabled (which is enabled by default)
		2187	ev_poll.c only when poll backend is enabled (disabled by default)
		2188	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2189	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2190	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2191
		2192	F<ev.c> includes the backend files directly when enabled, so you only need
		2193	to compile this single file.
		2194
		2195	=head3 LIBEVENT COMPATIBILITY API
		2196
		2197	To include the libevent compatibility API, also include:
		2198
		2199	#include "event.c"
		2200
		2201	in the file including F<ev.c>, and:
		2202
		2203	#include "event.h"
		2204
		2205	in the files that want to use the libevent API. This also includes F<ev.h>.
		2206
		2207	You need the following additional files for this:
		2208
		2209	event.h
		2210	event.c
		2211
		2212	=head3 AUTOCONF SUPPORT
		2213
		2214	Instead of using C<EV_STANDALONE=1> and providing your config in
		2215	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2216	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2217	include F<config.h> and configure itself accordingly.
		2218
		2219	For this of course you need the m4 file:
		2220
		2221	libev.m4
		2222
		2223	=head2 PREPROCESSOR SYMBOLS/MACROS
		2224
		2225	Libev can be configured via a variety of preprocessor symbols you have to define
		2226	before including any of its files. The default is not to build for multiplicity
		2227	and only include the select backend.
		2228
		2229	=over 4
		2230
		2231	=item EV_STANDALONE
		2232
		2233	Must always be C<1> if you do not use autoconf configuration, which
		2234	keeps libev from including F<config.h>, and it also defines dummy
		2235	implementations for some libevent functions (such as logging, which is not
		2236	supported). It will also not define any of the structs usually found in
		2237	F<event.h> that are not directly supported by the libev core alone.
		2238
		2239	=item EV_USE_MONOTONIC
		2240
		2241	If defined to be C<1>, libev will try to detect the availability of the
		2242	monotonic clock option at both compiletime and runtime. Otherwise no use
		2243	of the monotonic clock option will be attempted. If you enable this, you
		2244	usually have to link against librt or something similar. Enabling it when
		2245	the functionality isn't available is safe, though, althoguh you have
		2246	to make sure you link against any libraries where the C<clock_gettime>
		2247	function is hiding in (often F<-lrt>).
		2248
		2249	=item EV_USE_REALTIME
		2250
		2251	If defined to be C<1>, libev will try to detect the availability of the
		2252	realtime clock option at compiletime (and assume its availability at
		2253	runtime if successful). Otherwise no use of the realtime clock option will
		2254	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2255	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2256	in the description of C<EV_USE_MONOTONIC>, though.
		2257
		2258	=item EV_USE_SELECT
		2259
		2260	If undefined or defined to be C<1>, libev will compile in support for the
		2261	C<select>(2) backend. No attempt at autodetection will be done: if no
		2262	other method takes over, select will be it. Otherwise the select backend
		2263	will not be compiled in.
		2264
		2265	=item EV_SELECT_USE_FD_SET
		2266
		2267	If defined to C<1>, then the select backend will use the system C<fd_set>
		2268	structure. This is useful if libev doesn't compile due to a missing
		2269	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2270	exotic systems. This usually limits the range of file descriptors to some
		2271	low limit such as 1024 or might have other limitations (winsocket only
		2272	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2273	influence the size of the C<fd_set> used.
		2274
		2275	=item EV_SELECT_IS_WINSOCKET
		2276
		2277	When defined to C<1>, the select backend will assume that
		2278	select/socket/connect etc. don't understand file descriptors but
		2279	wants osf handles on win32 (this is the case when the select to
		2280	be used is the winsock select). This means that it will call
		2281	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2282	it is assumed that all these functions actually work on fds, even
		2283	on win32. Should not be defined on non-win32 platforms.
		2284
		2285	=item EV_USE_POLL
		2286
		2287	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2288	backend. Otherwise it will be enabled on non-win32 platforms. It
		2289	takes precedence over select.
		2290
		2291	=item EV_USE_EPOLL
		2292
		2293	If defined to be C<1>, libev will compile in support for the Linux
		2294	C<epoll>(7) backend. Its availability will be detected at runtime,
		2295	otherwise another method will be used as fallback. This is the
		2296	preferred backend for GNU/Linux systems.
		2297
		2298	=item EV_USE_KQUEUE
		2299
		2300	If defined to be C<1>, libev will compile in support for the BSD style
		2301	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2302	otherwise another method will be used as fallback. This is the preferred
		2303	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2304	supports some types of fds correctly (the only platform we found that
		2305	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2306	not be used unless explicitly requested. The best way to use it is to find
		2307	out whether kqueue supports your type of fd properly and use an embedded
		2308	kqueue loop.
		2309
		2310	=item EV_USE_PORT
		2311
		2312	If defined to be C<1>, libev will compile in support for the Solaris
		2313	10 port style backend. Its availability will be detected at runtime,
		2314	otherwise another method will be used as fallback. This is the preferred
		2315	backend for Solaris 10 systems.
		2316
		2317	=item EV_USE_DEVPOLL
		2318
		2319	reserved for future expansion, works like the USE symbols above.
		2320
		2321	=item EV_USE_INOTIFY
		2322
		2323	If defined to be C<1>, libev will compile in support for the Linux inotify
		2324	interface to speed up C<ev_stat> watchers. Its actual availability will
		2325	be detected at runtime.
		2326
		2327	=item EV_H
		2328
		2329	The name of the F<ev.h> header file used to include it. The default if
		2330	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2331	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2332
		2333	=item EV_CONFIG_H
		2334
		2335	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2336	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2337	C<EV_H>, above.
		2338
		2339	=item EV_EVENT_H
		2340
		2341	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2342	of how the F<event.h> header can be found.
		2343
		2344	=item EV_PROTOTYPES
		2345
		2346	If defined to be C<0>, then F<ev.h> will not define any function
		2347	prototypes, but still define all the structs and other symbols. This is
		2348	occasionally useful if you want to provide your own wrapper functions
		2349	around libev functions.
		2350
		2351	=item EV_MULTIPLICITY
		2352
		2353	If undefined or defined to C<1>, then all event-loop-specific functions
		2354	will have the C<struct ev_loop *> as first argument, and you can create
		2355	additional independent event loops. Otherwise there will be no support
		2356	for multiple event loops and there is no first event loop pointer
		2357	argument. Instead, all functions act on the single default loop.
		2358
		2359	=item EV_MINPRI
		2360
		2361	=item EV_MAXPRI
		2362
		2363	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2364	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2365	provide for more priorities by overriding those symbols (usually defined
		2366	to be C<-2> and C<2>, respectively).
		2367
		2368	When doing priority-based operations, libev usually has to linearly search
		2369	all the priorities, so having many of them (hundreds) uses a lot of space
		2370	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2371	fine.
		2372
		2373	If your embedding app does not need any priorities, defining these both to
		2374	C<0> will save some memory and cpu.
		2375
		2376	=item EV_PERIODIC_ENABLE
		2377
		2378	If undefined or defined to be C<1>, then periodic timers are supported. If
		2379	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2380	code.
		2381
		2382	=item EV_IDLE_ENABLE
		2383
		2384	If undefined or defined to be C<1>, then idle watchers are supported. If
		2385	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2386	code.
		2387
		2388	=item EV_EMBED_ENABLE
		2389
		2390	If undefined or defined to be C<1>, then embed watchers are supported. If
		2391	defined to be C<0>, then they are not.
		2392
		2393	=item EV_STAT_ENABLE
		2394
		2395	If undefined or defined to be C<1>, then stat watchers are supported. If
		2396	defined to be C<0>, then they are not.
		2397
		2398	=item EV_FORK_ENABLE
		2399
		2400	If undefined or defined to be C<1>, then fork watchers are supported. If
		2401	defined to be C<0>, then they are not.
		2402
		2403	=item EV_MINIMAL
		2404
		2405	If you need to shave off some kilobytes of code at the expense of some
		2406	speed, define this symbol to C<1>. Currently only used for gcc to override
		2407	some inlining decisions, saves roughly 30% codesize of amd64.
		2408
		2409	=item EV_PID_HASHSIZE
		2410
		2411	C<ev_child> watchers use a small hash table to distribute workload by
		2412	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2413	than enough. If you need to manage thousands of children you might want to
		2414	increase this value (I<must> be a power of two).
		2415
		2416	=item EV_INOTIFY_HASHSIZE
		2417
		2418	C<ev_staz> watchers use a small hash table to distribute workload by
		2419	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2420	usually more than enough. If you need to manage thousands of C<ev_stat>
		2421	watchers you might want to increase this value (I<must> be a power of
		2422	two).
		2423
		2424	=item EV_COMMON
		2425
		2426	By default, all watchers have a C<void *data> member. By redefining
		2427	this macro to a something else you can include more and other types of
		2428	members. You have to define it each time you include one of the files,
		2429	though, and it must be identical each time.
		2430
		2431	For example, the perl EV module uses something like this:
		2432
		2433	#define EV_COMMON \
		2434	SV *self; /* contains this struct */ \
		2435	SV *cb_sv, *fh /* note no trailing ";" */
		2436
		2437	=item EV_CB_DECLARE (type)
		2438
		2439	=item EV_CB_INVOKE (watcher, revents)
		2440
		2441	=item ev_set_cb (ev, cb)
		2442
		2443	Can be used to change the callback member declaration in each watcher,
		2444	and the way callbacks are invoked and set. Must expand to a struct member
		2445	definition and a statement, respectively. See the F<ev.v> header file for
		2446	their default definitions. One possible use for overriding these is to
		2447	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2448	method calls instead of plain function calls in C++.
		2449
		2450	=head2 EXPORTED API SYMBOLS
		2451
		2452	If you need to re-export the API (e.g. via a dll) and you need a list of
		2453	exported symbols, you can use the provided F<Symbol.*> files which list
		2454	all public symbols, one per line:
		2455
		2456	Symbols.ev for libev proper
		2457	Symbols.event for the libevent emulation
		2458
		2459	This can also be used to rename all public symbols to avoid clashes with
		2460	multiple versions of libev linked together (which is obviously bad in
		2461	itself, but sometimes it is inconvinient to avoid this).
		2462
		2463	A sed comamnd like this will create wrapper C<#define>'s that you need to
		2464	include before including F<ev.h>:
		2465
		2466	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2467
		2468	This would create a file F<wrap.h> which essentially looks like this:
		2469
		2470	#define ev_backend myprefix_ev_backend
		2471	#define ev_check_start myprefix_ev_check_start
		2472	#define ev_check_stop myprefix_ev_check_stop
		2473	...
		2474
		2475	=head2 EXAMPLES
		2476
		2477	For a real-world example of a program the includes libev
		2478	verbatim, you can have a look at the EV perl module
		2479	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2480	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2481	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2482	will be compiled. It is pretty complex because it provides its own header
		2483	file.
		2484
		2485	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2486	that everybody includes and which overrides some configure choices:
		2487
		2488	#define EV_MINIMAL 1
		2489	#define EV_USE_POLL 0
		2490	#define EV_MULTIPLICITY 0
		2491	#define EV_PERIODIC_ENABLE 0
		2492	#define EV_STAT_ENABLE 0
		2493	#define EV_FORK_ENABLE 0
		2494	#define EV_CONFIG_H <config.h>
		2495	#define EV_MINPRI 0
		2496	#define EV_MAXPRI 0
		2497
		2498	#include "ev++.h"
		2499
		2500	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2501
		2502	#include "ev_cpp.h"
		2503	#include "ev.c"
		2504
		2505
		2506	=head1 COMPLEXITIES
		2507
		2508	In this section the complexities of (many of) the algorithms used inside
		2509	libev will be explained. For complexity discussions about backends see the
		2510	documentation for C<ev_default_init>.
		2511
		2512	All of the following are about amortised time: If an array needs to be
		2513	extended, libev needs to realloc and move the whole array, but this
		2514	happens asymptotically never with higher number of elements, so O(1) might
		2515	mean it might do a lengthy realloc operation in rare cases, but on average
		2516	it is much faster and asymptotically approaches constant time.
		2517
		2518	=over 4
		2519
		2520	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2521
		2522	This means that, when you have a watcher that triggers in one hour and
		2523	there are 100 watchers that would trigger before that then inserting will
		2524	have to skip those 100 watchers.
		2525
		2526	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2527
		2528	That means that for changing a timer costs less than removing/adding them
		2529	as only the relative motion in the event queue has to be paid for.
		2530
		2531	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2532
		2533	These just add the watcher into an array or at the head of a list.
		2534	=item Stopping check/prepare/idle watchers: O(1)
		2535
		2536	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2537
		2538	These watchers are stored in lists then need to be walked to find the
		2539	correct watcher to remove. The lists are usually short (you don't usually
		2540	have many watchers waiting for the same fd or signal).
		2541
		2542	=item Finding the next timer per loop iteration: O(1)
		2543
		2544	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2545
		2546	A change means an I/O watcher gets started or stopped, which requires
		2547	libev to recalculate its status (and possibly tell the kernel).
		2548
		2549	=item Activating one watcher: O(1)
		2550
		2551	=item Priority handling: O(number_of_priorities)
		2552
		2553	Priorities are implemented by allocating some space for each
		2554	priority. When doing priority-based operations, libev usually has to
		2555	linearly search all the priorities.
		2556
		2557	=back
		2558
825		2559
826	=head1 AUTHOR	2560	=head1 AUTHOR
827		2561
828	Marc Lehmann <libev@schmorp.de>.	2562	Marc Lehmann <libev@schmorp.de>.
829		2563

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