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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as such.
51		104
52	=head1 GLOBAL FUNCTIONS	105	=head1 GLOBAL FUNCTIONS
53		106
54	These functions can be called anytime, even before initialising the	107	These functions can be called anytime, even before initialising the
55	library in any way.	108	library in any way.
…		…
64		117
65	=item int ev_version_major ()	118	=item int ev_version_major ()
66		119
67	=item int ev_version_minor ()	120	=item int ev_version_minor ()
68		121
69	You can find out the major and minor version numbers of the library	122	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	123	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	124	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	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
73	version of the library your program was compiled against.	126	version of the library your program was compiled against.
74		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
75	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	134	not a problem.
79		135
		136	Example: Make sure we haven't accidentally been linked against the wrong
		137	version.
		138
		139	assert (("libev version mismatch",
		140	ev_version_major () == EV_VERSION_MAJOR
		141	&& ev_version_minor () >= EV_VERSION_MINOR));
		142
		143	=item unsigned int ev_supported_backends ()
		144
		145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		146	value) compiled into this binary of libev (independent of their
		147	availability on the system you are running on). See C<ev_default_loop> for
		148	a description of the set values.
		149
		150	Example: make sure we have the epoll method, because yeah this is cool and
		151	a must have and can we have a torrent of it please!!!11
		152
		153	assert (("sorry, no epoll, no sex",
		154	ev_supported_backends () & EVBACKEND_EPOLL));
		155
		156	=item unsigned int ev_recommended_backends ()
		157
		158	Return the set of all backends compiled into this binary of libev and also
		159	recommended for this platform. This set is often smaller than the one
		160	returned by C<ev_supported_backends>, as for example kqueue is broken on
		161	most BSDs and will not be autodetected unless you explicitly request it
		162	(assuming you know what you are doing). This is the set of backends that
		163	libev will probe for if you specify no backends explicitly.
		164
		165	=item unsigned int ev_embeddable_backends ()
		166
		167	Returns the set of backends that are embeddable in other event loops. This
		168	is the theoretical, all-platform, value. To find which backends
		169	might be supported on the current system, you would need to look at
		170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		171	recommended ones.
		172
		173	See the description of C<ev_embed> watchers for more info.
		174
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		176
82	Sets the allocation function to use (the prototype is similar to the	177	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	178	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	179	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	180	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	181	potentially destructive action. The default is your system realloc
		182	function.
87		183
88	You could override this function in high-availability programs to, say,	184	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,	185	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.	186	or even to sleep a while and retry until some memory is available.
		187
		188	Example: Replace the libev allocator with one that waits a bit and then
		189	retries).
		190
		191	static void *
		192	persistent_realloc (void *ptr, size_t size)
		193	{
		194	for (;;)
		195	{
		196	void *newptr = realloc (ptr, size);
		197
		198	if (newptr)
		199	return newptr;
		200
		201	sleep (60);
		202	}
		203	}
		204
		205	...
		206	ev_set_allocator (persistent_realloc);
91		207
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	208	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		209
94	Set the callback function to call on a retryable syscall error (such	210	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	211	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	213	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	214	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	215	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	216	(such as abort).
101		217
		218	Example: This is basically the same thing that libev does internally, too.
		219
		220	static void
		221	fatal_error (const char *msg)
		222	{
		223	perror (msg);
		224	abort ();
		225	}
		226
		227	...
		228	ev_set_syserr_cb (fatal_error);
		229
102	=back	230	=back
103		231
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		233
106	An event loop is described by a C<struct ev_loop *>. The library knows two	234	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)	247	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		248
121	This will initialise the default event loop if it hasn't been initialised	249	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	250	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	251	false. If it already was initialised it simply returns it (and ignores the
124	flags).	252	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		253
126	If you don't know what event loop to use, use the one returned from this	254	If you don't know what event loop to use, use the one returned from this
127	function.	255	function.
128		256
129	The flags argument can be used to specify special behaviour or specific	257	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).	258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		259
132	It supports the following flags:	260	The following flags are supported:
133		261
134	=over 4	262	=over 4
135		263
136	=item C<EVFLAG_AUTO>	264	=item C<EVFLAG_AUTO>
137		265
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	274	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	275	useful to try out specific backends to test their performance, or to work
148	around bugs.	276	around bugs.
149		277
		278	=item C<EVFLAG_FORKCHECK>
		279
		280	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		281	a fork, you can also make libev check for a fork in each iteration by
		282	enabling this flag.
		283
		284	This works by calling C<getpid ()> on every iteration of the loop,
		285	and thus this might slow down your event loop if you do a lot of loop
		286	iterations and little real work, but is usually not noticeable (on my
		287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		288	without a syscall and thus I<very> fast, but my Linux system also has
		289	C<pthread_atfork> which is even faster).
		290
		291	The big advantage of this flag is that you can forget about fork (and
		292	forget about forgetting to tell libev about forking) when you use this
		293	flag.
		294
		295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		296	environment variable.
		297
150	=item C<EVMETHOD_SELECT> (value 1, portable select backend)	298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		299
152	This is your standard select(2) backend. Not I<completely> standard, as	300	This is your standard select(2) backend. Not I<completely> standard, as
153	libev tries to roll its own fd_set with no limits on the number of fds,	301	libev tries to roll its own fd_set with no limits on the number of fds,
154	but if that fails, expect a fairly low limit on the number of fds when	302	but if that fails, expect a fairly low limit on the number of fds when
155	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
156	the fastest backend for a low number of fds.	304	the fastest backend for a low number of fds.
157		305
158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)	306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
159		307
160	And this is your standard poll(2) backend. It's more complicated than	308	And this is your standard poll(2) backend. It's more complicated than
161	select, but handles sparse fds better and has no artificial limit on the	309	select, but handles sparse fds better and has no artificial limit on the
162	number of fds you can use (except it will slow down considerably with a	310	number of fds you can use (except it will slow down considerably with a
163	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
164		312
165	=item C<EVMETHOD_EPOLL> (value 4, Linux)	313	=item C<EVBACKEND_EPOLL> (value 4, Linux)
166		314
167	For few fds, this backend is a bit little slower than poll and select,	315	For few fds, this backend is a bit little slower than poll and select,
168	but it scales phenomenally better. While poll and select usually scale like	316	but it scales phenomenally better. While poll and select usually scale like
169	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
170	either O(1) or O(active_fds).	318	either O(1) or O(active_fds).
…		…
173	result in some caching, there is still a syscall per such incident	321	result in some caching, there is still a syscall per such incident
174	(because the fd could point to a different file description now), so its	322	(because the fd could point to a different file description now), so its
175	best to avoid that. Also, dup()ed file descriptors might not work very	323	best to avoid that. Also, dup()ed file descriptors might not work very
176	well if you register events for both fds.	324	well if you register events for both fds.
177		325
		326	Please note that epoll sometimes generates spurious notifications, so you
		327	need to use non-blocking I/O or other means to avoid blocking when no data
		328	(or space) is available.
		329
178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)	330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
179		331
180	Kqueue deserves special mention, as at the time of this writing, it	332	Kqueue deserves special mention, as at the time of this writing, it
181	was broken on all BSDs except NetBSD (usually it doesn't work with	333	was broken on all BSDs except NetBSD (usually it doesn't work with
182	anything but sockets and pipes, except on Darwin, where of course its	334	anything but sockets and pipes, except on Darwin, where of course its
183	completely useless). For this reason its not being "autodetected" unless	335	completely useless). For this reason its not being "autodetected"
184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	336	unless you explicitly specify it explicitly in the flags (i.e. using
		337	C<EVBACKEND_KQUEUE>).
185		338
186	It scales in the same way as the epoll backend, but the interface to the	339	It scales in the same way as the epoll backend, but the interface to the
187	kernel is more efficient (which says nothing about its actual speed, of	340	kernel is more efficient (which says nothing about its actual speed, of
188	course). While starting and stopping an I/O watcher does not cause an	341	course). While starting and stopping an I/O watcher does not cause an
189	extra syscall as with epoll, it still adds up to four event changes per	342	extra syscall as with epoll, it still adds up to four event changes per
190	incident, so its best to avoid that.	343	incident, so its best to avoid that.
191		344
192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)	345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
193		346
194	This is not implemented yet (and might never be).	347	This is not implemented yet (and might never be).
195		348
196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)	349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
197		350
198	This uses the Solaris 10 port mechanism. As with everything on Solaris,	351	This uses the Solaris 10 port mechanism. As with everything on Solaris,
199	it's really slow, but it still scales very well (O(active_fds)).	352	it's really slow, but it still scales very well (O(active_fds)).
200		353
		354	Please note that solaris ports can result in a lot of spurious
		355	notifications, so you need to use non-blocking I/O or other means to avoid
		356	blocking when no data (or space) is available.
		357
201	=item C<EVMETHOD_ALL>	358	=item C<EVBACKEND_ALL>
202		359
203	Try all backends (even potentially broken ones that wouldn't be tried	360	Try all backends (even potentially broken ones that wouldn't be tried
204	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.	362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
206		363
207	=back	364	=back
208		365
209	If one or more of these are ored into the flags value, then only these	366	If one or more of these are ored into the flags value, then only these
210	backends will be tried (in the reverse order as given here). If none are	367	backends will be tried (in the reverse order as given here). If none are
211	specified, most compiled-in backend will be tried, usually in reverse	368	specified, most compiled-in backend will be tried, usually in reverse
212	order of their flag values :)	369	order of their flag values :)
213		370
		371	The most typical usage is like this:
		372
		373	if (!ev_default_loop (0))
		374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		375
		376	Restrict libev to the select and poll backends, and do not allow
		377	environment settings to be taken into account:
		378
		379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		380
		381	Use whatever libev has to offer, but make sure that kqueue is used if
		382	available (warning, breaks stuff, best use only with your own private
		383	event loop and only if you know the OS supports your types of fds):
		384
		385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
		386
214	=item struct ev_loop *ev_loop_new (unsigned int flags)	387	=item struct ev_loop *ev_loop_new (unsigned int flags)
215		388
216	Similar to C<ev_default_loop>, but always creates a new event loop that is	389	Similar to C<ev_default_loop>, but always creates a new event loop that is
217	always distinct from the default loop. Unlike the default loop, it cannot	390	always distinct from the default loop. Unlike the default loop, it cannot
218	handle signal and child watchers, and attempts to do so will be greeted by	391	handle signal and child watchers, and attempts to do so will be greeted by
219	undefined behaviour (or a failed assertion if assertions are enabled).	392	undefined behaviour (or a failed assertion if assertions are enabled).
220		393
		394	Example: Try to create a event loop that uses epoll and nothing else.
		395
		396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		397	if (!epoller)
		398	fatal ("no epoll found here, maybe it hides under your chair");
		399
221	=item ev_default_destroy ()	400	=item ev_default_destroy ()
222		401
223	Destroys the default loop again (frees all memory and kernel state	402	Destroys the default loop again (frees all memory and kernel state
224	etc.). This stops all registered event watchers (by not touching them in	403	etc.). None of the active event watchers will be stopped in the normal
225	any way whatsoever, although you cannot rely on this :).	404	sense, so e.g. C<ev_is_active> might still return true. It is your
		405	responsibility to either stop all watchers cleanly yoursef I<before>
		406	calling this function, or cope with the fact afterwards (which is usually
		407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		408	for example).
226		409
227	=item ev_loop_destroy (loop)	410	=item ev_loop_destroy (loop)
228		411
229	Like C<ev_default_destroy>, but destroys an event loop created by an	412	Like C<ev_default_destroy>, but destroys an event loop created by an
230	earlier call to C<ev_loop_new>.	413	earlier call to C<ev_loop_new>.
…		…
244	it just in case after a fork. To make this easy, the function will fit in	427	it just in case after a fork. To make this easy, the function will fit in
245	quite nicely into a call to C<pthread_atfork>:	428	quite nicely into a call to C<pthread_atfork>:
246		429
247	pthread_atfork (0, 0, ev_default_fork);	430	pthread_atfork (0, 0, ev_default_fork);
248		431
		432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		433	without calling this function, so if you force one of those backends you
		434	do not need to care.
		435
249	=item ev_loop_fork (loop)	436	=item ev_loop_fork (loop)
250		437
251	Like C<ev_default_fork>, but acts on an event loop created by	438	Like C<ev_default_fork>, but acts on an event loop created by
252	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
253	after fork, and how you do this is entirely your own problem.	440	after fork, and how you do this is entirely your own problem.
254		441
		442	=item unsigned int ev_loop_count (loop)
		443
		444	Returns the count of loop iterations for the loop, which is identical to
		445	the number of times libev did poll for new events. It starts at C<0> and
		446	happily wraps around with enough iterations.
		447
		448	This value can sometimes be useful as a generation counter of sorts (it
		449	"ticks" the number of loop iterations), as it roughly corresponds with
		450	C<ev_prepare> and C<ev_check> calls.
		451
255	=item unsigned int ev_method (loop)	452	=item unsigned int ev_backend (loop)
256		453
257	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	454	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
258	use.	455	use.
259		456
260	=item ev_tstamp ev_now (loop)	457	=item ev_tstamp ev_now (loop)
261		458
262	Returns the current "event loop time", which is the time the event loop	459	Returns the current "event loop time", which is the time the event loop
263	got events and started processing them. This timestamp does not change	460	received events and started processing them. This timestamp does not
264	as long as callbacks are being processed, and this is also the base time	461	change as long as callbacks are being processed, and this is also the base
265	used for relative timers. You can treat it as the timestamp of the event	462	time used for relative timers. You can treat it as the timestamp of the
266	occuring (or more correctly, the mainloop finding out about it).	463	event occuring (or more correctly, libev finding out about it).
267		464
268	=item ev_loop (loop, int flags)	465	=item ev_loop (loop, int flags)
269		466
270	Finally, this is it, the event handler. This function usually is called	467	Finally, this is it, the event handler. This function usually is called
271	after you initialised all your watchers and you want to start handling	468	after you initialised all your watchers and you want to start handling
272	events.	469	events.
273		470
274	If the flags argument is specified as 0, it will not return until either	471	If the flags argument is specified as C<0>, it will not return until
275	no event watchers are active anymore or C<ev_unloop> was called.	472	either no event watchers are active anymore or C<ev_unloop> was called.
		473
		474	Please note that an explicit C<ev_unloop> is usually better than
		475	relying on all watchers to be stopped when deciding when a program has
		476	finished (especially in interactive programs), but having a program that
		477	automatically loops as long as it has to and no longer by virtue of
		478	relying on its watchers stopping correctly is a thing of beauty.
276		479
277	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
278	those events and any outstanding ones, but will not block your process in	481	those events and any outstanding ones, but will not block your process in
279	case there are no events and will return after one iteration of the loop.	482	case there are no events and will return after one iteration of the loop.
280		483
281	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
282	neccessary) and will handle those and any outstanding ones. It will block	485	neccessary) and will handle those and any outstanding ones. It will block
283	your process until at least one new event arrives, and will return after	486	your process until at least one new event arrives, and will return after
284	one iteration of the loop.	487	one iteration of the loop. This is useful if you are waiting for some
		488	external event in conjunction with something not expressible using other
		489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		490	usually a better approach for this kind of thing.
285		491
286	This flags value could be used to implement alternative looping
287	constructs, but the C<prepare> and C<check> watchers provide a better and
288	more generic mechanism.
289
290	Here are the gory details of what ev_loop does:	492	Here are the gory details of what C<ev_loop> does:
291		493
		494	- Before the first iteration, call any pending watchers.
292	1. If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
293	2. Queue and immediately call all prepare watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
294	3. If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
295	4. Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
296	5. Update the "event loop time".	499	- Update the "event loop time".
297	6. Calculate for how long to block.	500	- Calculate for how long to block.
298	7. Block the process, waiting for events.	501	- Block the process, waiting for any events.
		502	- Queue all outstanding I/O (fd) events.
299	8. Update the "event loop time" and do time jump handling.	503	- Update the "event loop time" and do time jump handling.
300	9. Queue all outstanding timers.	504	- Queue all outstanding timers.
301	10. Queue all outstanding periodics.	505	- Queue all outstanding periodics.
302	11. If no events are pending now, queue all idle watchers.	506	- If no events are pending now, queue all idle watchers.
303	12. Queue all check watchers.	507	- Queue all check watchers.
304	13. Call all queued watchers in reverse order (i.e. check watchers first).	508	- Call all queued watchers in reverse order (i.e. check watchers first).
		509	Signals and child watchers are implemented as I/O watchers, and will
		510	be handled here by queueing them when their watcher gets executed.
305	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
306	was used, return, otherwise continue with step #1.	512	were used, return, otherwise continue with step *.
		513
		514	Example: Queue some jobs and then loop until no events are outsanding
		515	anymore.
		516
		517	... queue jobs here, make sure they register event watchers as long
		518	... as they still have work to do (even an idle watcher will do..)
		519	ev_loop (my_loop, 0);
		520	... jobs done. yeah!
307		521
308	=item ev_unloop (loop, how)	522	=item ev_unloop (loop, how)
309		523
310	Can be used to make a call to C<ev_loop> return early (but only after it	524	Can be used to make a call to C<ev_loop> return early (but only after it
311	has processed all outstanding events). The C<how> argument must be either	525	has processed all outstanding events). The C<how> argument must be either
…		…
325	visible to the libev user and should not keep C<ev_loop> from exiting if	539	visible to the libev user and should not keep C<ev_loop> from exiting if
326	no event watchers registered by it are active. It is also an excellent	540	no event watchers registered by it are active. It is also an excellent
327	way to do this for generic recurring timers or from within third-party	541	way to do this for generic recurring timers or from within third-party
328	libraries. Just remember to I<unref after start> and I<ref before stop>.	542	libraries. Just remember to I<unref after start> and I<ref before stop>.
329		543
		544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		545	running when nothing else is active.
		546
		547	struct ev_signal exitsig;
		548	ev_signal_init (&exitsig, sig_cb, SIGINT);
		549	ev_signal_start (loop, &exitsig);
		550	evf_unref (loop);
		551
		552	Example: For some weird reason, unregister the above signal handler again.
		553
		554	ev_ref (loop);
		555	ev_signal_stop (loop, &exitsig);
		556
330	=back	557	=back
		558
331		559
332	=head1 ANATOMY OF A WATCHER	560	=head1 ANATOMY OF A WATCHER
333		561
334	A watcher is a structure that you create and register to record your	562	A watcher is a structure that you create and register to record your
335	interest in some event. For instance, if you want to wait for STDIN to	563	interest in some event. For instance, if you want to wait for STDIN to
…		…
368	*) >>), and you can stop watching for events at any time by calling the	596	*) >>), and you can stop watching for events at any time by calling the
369	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	597	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
370		598
371	As long as your watcher is active (has been started but not stopped) you	599	As long as your watcher is active (has been started but not stopped) you
372	must not touch the values stored in it. Most specifically you must never	600	must not touch the values stored in it. Most specifically you must never
373	reinitialise it or call its set method.	601	reinitialise it or call its C<set> macro.
374
375	You can check whether an event is active by calling the C<ev_is_active
376	(watcher *)> macro. To see whether an event is outstanding (but the
377	callback for it has not been called yet) you can use the C<ev_is_pending
378	(watcher *)> macro.
379		602
380	Each and every callback receives the event loop pointer as first, the	603	Each and every callback receives the event loop pointer as first, the
381	registered watcher structure as second, and a bitset of received events as	604	registered watcher structure as second, and a bitset of received events as
382	third argument.	605	third argument.
383		606
…		…
407	The signal specified in the C<ev_signal> watcher has been received by a thread.	630	The signal specified in the C<ev_signal> watcher has been received by a thread.
408		631
409	=item C<EV_CHILD>	632	=item C<EV_CHILD>
410		633
411	The pid specified in the C<ev_child> watcher has received a status change.	634	The pid specified in the C<ev_child> watcher has received a status change.
		635
		636	=item C<EV_STAT>
		637
		638	The path specified in the C<ev_stat> watcher changed its attributes somehow.
412		639
413	=item C<EV_IDLE>	640	=item C<EV_IDLE>
414		641
415	The C<ev_idle> watcher has determined that you have nothing better to do.	642	The C<ev_idle> watcher has determined that you have nothing better to do.
416		643
…		…
424	received events. Callbacks of both watcher types can start and stop as	651	received events. Callbacks of both watcher types can start and stop as
425	many watchers as they want, and all of them will be taken into account	652	many watchers as they want, and all of them will be taken into account
426	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	653	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
427	C<ev_loop> from blocking).	654	C<ev_loop> from blocking).
428		655
		656	=item C<EV_EMBED>
		657
		658	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		659
		660	=item C<EV_FORK>
		661
		662	The event loop has been resumed in the child process after fork (see
		663	C<ev_fork>).
		664
429	=item C<EV_ERROR>	665	=item C<EV_ERROR>
430		666
431	An unspecified error has occured, the watcher has been stopped. This might	667	An unspecified error has occured, the watcher has been stopped. This might
432	happen because the watcher could not be properly started because libev	668	happen because the watcher could not be properly started because libev
433	ran out of memory, a file descriptor was found to be closed or any other	669	ran out of memory, a file descriptor was found to be closed or any other
…		…
439	your callbacks is well-written it can just attempt the operation and cope	675	your callbacks is well-written it can just attempt the operation and cope
440	with the error from read() or write(). This will not work in multithreaded	676	with the error from read() or write(). This will not work in multithreaded
441	programs, though, so beware.	677	programs, though, so beware.
442		678
443	=back	679	=back
		680
		681	=head2 GENERIC WATCHER FUNCTIONS
		682
		683	In the following description, C<TYPE> stands for the watcher type,
		684	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		685
		686	=over 4
		687
		688	=item C<ev_init> (ev_TYPE *watcher, callback)
		689
		690	This macro initialises the generic portion of a watcher. The contents
		691	of the watcher object can be arbitrary (so C<malloc> will do). Only
		692	the generic parts of the watcher are initialised, you I<need> to call
		693	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		694	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		695	which rolls both calls into one.
		696
		697	You can reinitialise a watcher at any time as long as it has been stopped
		698	(or never started) and there are no pending events outstanding.
		699
		700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		701	int revents)>.
		702
		703	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		704
		705	This macro initialises the type-specific parts of a watcher. You need to
		706	call C<ev_init> at least once before you call this macro, but you can
		707	call C<ev_TYPE_set> any number of times. You must not, however, call this
		708	macro on a watcher that is active (it can be pending, however, which is a
		709	difference to the C<ev_init> macro).
		710
		711	Although some watcher types do not have type-specific arguments
		712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		713
		714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		715
		716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		717	calls into a single call. This is the most convinient method to initialise
		718	a watcher. The same limitations apply, of course.
		719
		720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		721
		722	Starts (activates) the given watcher. Only active watchers will receive
		723	events. If the watcher is already active nothing will happen.
		724
		725	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		726
		727	Stops the given watcher again (if active) and clears the pending
		728	status. It is possible that stopped watchers are pending (for example,
		729	non-repeating timers are being stopped when they become pending), but
		730	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		731	you want to free or reuse the memory used by the watcher it is therefore a
		732	good idea to always call its C<ev_TYPE_stop> function.
		733
		734	=item bool ev_is_active (ev_TYPE *watcher)
		735
		736	Returns a true value iff the watcher is active (i.e. it has been started
		737	and not yet been stopped). As long as a watcher is active you must not modify
		738	it.
		739
		740	=item bool ev_is_pending (ev_TYPE *watcher)
		741
		742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		743	events but its callback has not yet been invoked). As long as a watcher
		744	is pending (but not active) you must not call an init function on it (but
		745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
		748
		749	=item callback ev_cb (ev_TYPE *watcher)
		750
		751	Returns the callback currently set on the watcher.
		752
		753	=item ev_cb_set (ev_TYPE *watcher, callback)
		754
		755	Change the callback. You can change the callback at virtually any time
		756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
		797
		798	=back
		799
444		800
445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
446		802
447	Each watcher has, by default, a member C<void *data> that you can change	803	Each watcher has, by default, a member C<void *data> that you can change
448	and read at any time, libev will completely ignore it. This can be used	804	and read at any time, libev will completely ignore it. This can be used
…		…
466	{	822	{
467	struct my_io *w = (struct my_io *)w_;	823	struct my_io *w = (struct my_io *)w_;
468	...	824	...
469	}	825	}
470		826
471	More interesting and less C-conformant ways of catsing your callback type	827	More interesting and less C-conformant ways of casting your callback type
472	have been omitted....	828	instead have been omitted.
		829
		830	Another common scenario is having some data structure with multiple
		831	watchers:
		832
		833	struct my_biggy
		834	{
		835	int some_data;
		836	ev_timer t1;
		837	ev_timer t2;
		838	}
		839
		840	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		841	you need to use C<offsetof>:
		842
		843	#include <stddef.h>
		844
		845	static void
		846	t1_cb (EV_P_ struct ev_timer *w, int revents)
		847	{
		848	struct my_biggy big = (struct my_biggy *
		849	(((char *)w) - offsetof (struct my_biggy, t1));
		850	}
		851
		852	static void
		853	t2_cb (EV_P_ struct ev_timer *w, int revents)
		854	{
		855	struct my_biggy big = (struct my_biggy *
		856	(((char *)w) - offsetof (struct my_biggy, t2));
		857	}
473		858
474		859
475	=head1 WATCHER TYPES	860	=head1 WATCHER TYPES
476		861
477	This section describes each watcher in detail, but will not repeat	862	This section describes each watcher in detail, but will not repeat
478	information given in the last section.	863	information given in the last section. Any initialisation/set macros,
		864	functions and members specific to the watcher type are explained.
479		865
		866	Members are additionally marked with either I<[read-only]>, meaning that,
		867	while the watcher is active, you can look at the member and expect some
		868	sensible content, but you must not modify it (you can modify it while the
		869	watcher is stopped to your hearts content), or I<[read-write]>, which
		870	means you can expect it to have some sensible content while the watcher
		871	is active, but you can also modify it. Modifying it may not do something
		872	sensible or take immediate effect (or do anything at all), but libev will
		873	not crash or malfunction in any way.
		874
		875
480	=head2 C<ev_io> - is this file descriptor readable or writable	876	=head2 C<ev_io> - is this file descriptor readable or writable?
481		877
482	I/O watchers check whether a file descriptor is readable or writable	878	I/O watchers check whether a file descriptor is readable or writable
483	in each iteration of the event loop (This behaviour is called	879	in each iteration of the event loop, or, more precisely, when reading
484	level-triggering because you keep receiving events as long as the	880	would not block the process and writing would at least be able to write
485	condition persists. Remember you can stop the watcher if you don't want to	881	some data. This behaviour is called level-triggering because you keep
486	act on the event and neither want to receive future events).	882	receiving events as long as the condition persists. Remember you can stop
		883	the watcher if you don't want to act on the event and neither want to
		884	receive future events.
487		885
488	In general you can register as many read and/or write event watchers per	886	In general you can register as many read and/or write event watchers per
489	fd as you want (as long as you don't confuse yourself). Setting all file	887	fd as you want (as long as you don't confuse yourself). Setting all file
490	descriptors to non-blocking mode is also usually a good idea (but not	888	descriptors to non-blocking mode is also usually a good idea (but not
491	required if you know what you are doing).	889	required if you know what you are doing).
492		890
493	You have to be careful with dup'ed file descriptors, though. Some backends	891	You have to be careful with dup'ed file descriptors, though. Some backends
494	(the linux epoll backend is a notable example) cannot handle dup'ed file	892	(the linux epoll backend is a notable example) cannot handle dup'ed file
495	descriptors correctly if you register interest in two or more fds pointing	893	descriptors correctly if you register interest in two or more fds pointing
496	to the same underlying file/socket etc. description (that is, they share	894	to the same underlying file/socket/etc. description (that is, they share
497	the same underlying "file open").	895	the same underlying "file open").
498		896
499	If you must do this, then force the use of a known-to-be-good backend	897	If you must do this, then force the use of a known-to-be-good backend
500	(at the time of this writing, this includes only EVMETHOD_SELECT and	898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
501	EVMETHOD_POLL).	899	C<EVBACKEND_POLL>).
		900
		901	Another thing you have to watch out for is that it is quite easy to
		902	receive "spurious" readyness notifications, that is your callback might
		903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		904	because there is no data. Not only are some backends known to create a
		905	lot of those (for example solaris ports), it is very easy to get into
		906	this situation even with a relatively standard program structure. Thus
		907	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		909
		910	If you cannot run the fd in non-blocking mode (for example you should not
		911	play around with an Xlib connection), then you have to seperately re-test
		912	whether a file descriptor is really ready with a known-to-be good interface
		913	such as poll (fortunately in our Xlib example, Xlib already does this on
		914	its own, so its quite safe to use).
		915
		916	=head3 The special problem of disappearing file descriptors
		917
		918	Some backends (e.g kqueue, epoll) need to be told about closing a file
		919	descriptor (either by calling C<close> explicitly or by any other means,
		920	such as C<dup>). The reason is that you register interest in some file
		921	descriptor, but when it goes away, the operating system will silently drop
		922	this interest. If another file descriptor with the same number then is
		923	registered with libev, there is no efficient way to see that this is, in
		924	fact, a different file descriptor.
		925
		926	To avoid having to explicitly tell libev about such cases, libev follows
		927	the following policy: Each time C<ev_io_set> is being called, libev
		928	will assume that this is potentially a new file descriptor, otherwise
		929	it is assumed that the file descriptor stays the same. That means that
		930	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		931	descriptor even if the file descriptor number itself did not change.
		932
		933	This is how one would do it normally anyway, the important point is that
		934	the libev application should not optimise around libev but should leave
		935	optimisations to libev.
		936
502		937
503	=over 4	938	=over 4
504		939
505	=item ev_io_init (ev_io *, callback, int fd, int events)	940	=item ev_io_init (ev_io *, callback, int fd, int events)
506		941
507	=item ev_io_set (ev_io *, int fd, int events)	942	=item ev_io_set (ev_io *, int fd, int events)
508		943
509	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	944	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
510	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	945	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
511	EV_WRITE> to receive the given events.	946	C<EV_READ | EV_WRITE> to receive the given events.
		947
		948	=item int fd [read-only]
		949
		950	The file descriptor being watched.
		951
		952	=item int events [read-only]
		953
		954	The events being watched.
512		955
513	=back	956	=back
514		957
		958	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		959	readable, but only once. Since it is likely line-buffered, you could
		960	attempt to read a whole line in the callback.
		961
		962	static void
		963	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		964	{
		965	ev_io_stop (loop, w);
		966	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		967	}
		968
		969	...
		970	struct ev_loop *loop = ev_default_init (0);
		971	struct ev_io stdin_readable;
		972	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		973	ev_io_start (loop, &stdin_readable);
		974	ev_loop (loop, 0);
		975
		976
515	=head2 C<ev_timer> - relative and optionally recurring timeouts	977	=head2 C<ev_timer> - relative and optionally repeating timeouts
516		978
517	Timer watchers are simple relative timers that generate an event after a	979	Timer watchers are simple relative timers that generate an event after a
518	given time, and optionally repeating in regular intervals after that.	980	given time, and optionally repeating in regular intervals after that.
519		981
520	The timers are based on real time, that is, if you register an event that	982	The timers are based on real time, that is, if you register an event that
…		…
555	=item ev_timer_again (loop)	1017	=item ev_timer_again (loop)
556		1018
557	This will act as if the timer timed out and restart it again if it is	1019	This will act as if the timer timed out and restart it again if it is
558	repeating. The exact semantics are:	1020	repeating. The exact semantics are:
559		1021
		1022	If the timer is pending, its pending status is cleared.
		1023
560	If the timer is started but nonrepeating, stop it.	1024	If the timer is started but nonrepeating, stop it (as if it timed out).
561		1025
562	If the timer is repeating, either start it if necessary (with the repeat	1026	If the timer is repeating, either start it if necessary (with the
563	value), or reset the running timer to the repeat value.	1027	C<repeat> value), or reset the running timer to the C<repeat> value.
564		1028
565	This sounds a bit complicated, but here is a useful and typical	1029	This sounds a bit complicated, but here is a useful and typical
566	example: Imagine you have a tcp connection and you want a so-called idle	1030	example: Imagine you have a tcp connection and you want a so-called idle
567	timeout, that is, you want to be called when there have been, say, 60	1031	timeout, that is, you want to be called when there have been, say, 60
568	seconds of inactivity on the socket. The easiest way to do this is to	1032	seconds of inactivity on the socket. The easiest way to do this is to
569	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1033	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
570	time you successfully read or write some data. If you go into an idle	1034	C<ev_timer_again> each time you successfully read or write some data. If
571	state where you do not expect data to travel on the socket, you can stop	1035	you go into an idle state where you do not expect data to travel on the
572	the timer, and again will automatically restart it if need be.	1036	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1037	automatically restart it if need be.
		1038
		1039	That means you can ignore the C<after> value and C<ev_timer_start>
		1040	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1041
		1042	ev_timer_init (timer, callback, 0., 5.);
		1043	ev_timer_again (loop, timer);
		1044	...
		1045	timer->again = 17.;
		1046	ev_timer_again (loop, timer);
		1047	...
		1048	timer->again = 10.;
		1049	ev_timer_again (loop, timer);
		1050
		1051	This is more slightly efficient then stopping/starting the timer each time
		1052	you want to modify its timeout value.
		1053
		1054	=item ev_tstamp repeat [read-write]
		1055
		1056	The current C<repeat> value. Will be used each time the watcher times out
		1057	or C<ev_timer_again> is called and determines the next timeout (if any),
		1058	which is also when any modifications are taken into account.
573		1059
574	=back	1060	=back
575		1061
		1062	Example: Create a timer that fires after 60 seconds.
		1063
		1064	static void
		1065	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1066	{
		1067	.. one minute over, w is actually stopped right here
		1068	}
		1069
		1070	struct ev_timer mytimer;
		1071	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1072	ev_timer_start (loop, &mytimer);
		1073
		1074	Example: Create a timeout timer that times out after 10 seconds of
		1075	inactivity.
		1076
		1077	static void
		1078	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1079	{
		1080	.. ten seconds without any activity
		1081	}
		1082
		1083	struct ev_timer mytimer;
		1084	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1085	ev_timer_again (&mytimer); /* start timer */
		1086	ev_loop (loop, 0);
		1087
		1088	// and in some piece of code that gets executed on any "activity":
		1089	// reset the timeout to start ticking again at 10 seconds
		1090	ev_timer_again (&mytimer);
		1091
		1092
576	=head2 C<ev_periodic> - to cron or not to cron	1093	=head2 C<ev_periodic> - to cron or not to cron?
577		1094
578	Periodic watchers are also timers of a kind, but they are very versatile	1095	Periodic watchers are also timers of a kind, but they are very versatile
579	(and unfortunately a bit complex).	1096	(and unfortunately a bit complex).
580		1097
581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1098	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
582	but on wallclock time (absolute time). You can tell a periodic watcher	1099	but on wallclock time (absolute time). You can tell a periodic watcher
583	to trigger "at" some specific point in time. For example, if you tell a	1100	to trigger "at" some specific point in time. For example, if you tell a
584	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1101	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
585	+ 10.>) and then reset your system clock to the last year, then it will	1102	+ 10.>) and then reset your system clock to the last year, then it will
586	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1103	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
587	roughly 10 seconds later and of course not if you reset your system time	1104	roughly 10 seconds later).
588	again).
589		1105
590	They can also be used to implement vastly more complex timers, such as	1106	They can also be used to implement vastly more complex timers, such as
591	triggering an event on eahc midnight, local time.	1107	triggering an event on each midnight, local time or other, complicated,
		1108	rules.
592		1109
593	As with timers, the callback is guarenteed to be invoked only when the	1110	As with timers, the callback is guarenteed to be invoked only when the
594	time (C<at>) has been passed, but if multiple periodic timers become ready	1111	time (C<at>) has been passed, but if multiple periodic timers become ready
595	during the same loop iteration then order of execution is undefined.	1112	during the same loop iteration then order of execution is undefined.
596		1113
…		…
603	Lots of arguments, lets sort it out... There are basically three modes of	1120	Lots of arguments, lets sort it out... There are basically three modes of
604	operation, and we will explain them from simplest to complex:	1121	operation, and we will explain them from simplest to complex:
605		1122
606	=over 4	1123	=over 4
607		1124
608	=item * absolute timer (interval = reschedule_cb = 0)	1125	=item * absolute timer (at = time, interval = reschedule_cb = 0)
609		1126
610	In this configuration the watcher triggers an event at the wallclock time	1127	In this configuration the watcher triggers an event at the wallclock time
611	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1128	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
612	that is, if it is to be run at January 1st 2011 then it will run when the	1129	that is, if it is to be run at January 1st 2011 then it will run when the
613	system time reaches or surpasses this time.	1130	system time reaches or surpasses this time.
614		1131
615	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1132	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
616		1133
617	In this mode the watcher will always be scheduled to time out at the next	1134	In this mode the watcher will always be scheduled to time out at the next
618	C<at + N * interval> time (for some integer N) and then repeat, regardless	1135	C<at + N * interval> time (for some integer N, which can also be negative)
619	of any time jumps.	1136	and then repeat, regardless of any time jumps.
620		1137
621	This can be used to create timers that do not drift with respect to system	1138	This can be used to create timers that do not drift with respect to system
622	time:	1139	time:
623		1140
624	ev_periodic_set (&periodic, 0., 3600., 0);	1141	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
630		1147
631	Another way to think about it (for the mathematically inclined) is that	1148	Another way to think about it (for the mathematically inclined) is that
632	C<ev_periodic> will try to run the callback in this mode at the next possible	1149	C<ev_periodic> will try to run the callback in this mode at the next possible
633	time where C<time = at (mod interval)>, regardless of any time jumps.	1150	time where C<time = at (mod interval)>, regardless of any time jumps.
634		1151
		1152	For numerical stability it is preferable that the C<at> value is near
		1153	C<ev_now ()> (the current time), but there is no range requirement for
		1154	this value.
		1155
635	=item * manual reschedule mode (reschedule_cb = callback)	1156	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
636		1157
637	In this mode the values for C<interval> and C<at> are both being	1158	In this mode the values for C<interval> and C<at> are both being
638	ignored. Instead, each time the periodic watcher gets scheduled, the	1159	ignored. Instead, each time the periodic watcher gets scheduled, the
639	reschedule callback will be called with the watcher as first, and the	1160	reschedule callback will be called with the watcher as first, and the
640	current time as second argument.	1161	current time as second argument.
641		1162
642	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1163	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
643	ever, or make any event loop modifications>. If you need to stop it,	1164	ever, or make any event loop modifications>. If you need to stop it,
644	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1165	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
645	starting a prepare watcher).	1166	starting an C<ev_prepare> watcher, which is legal).
646		1167
647	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1168	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
648	ev_tstamp now)>, e.g.:	1169	ev_tstamp now)>, e.g.:
649		1170
650	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1171	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
673	Simply stops and restarts the periodic watcher again. This is only useful	1194	Simply stops and restarts the periodic watcher again. This is only useful
674	when you changed some parameters or the reschedule callback would return	1195	when you changed some parameters or the reschedule callback would return
675	a different time than the last time it was called (e.g. in a crond like	1196	a different time than the last time it was called (e.g. in a crond like
676	program when the crontabs have changed).	1197	program when the crontabs have changed).
677		1198
		1199	=item ev_tstamp offset [read-write]
		1200
		1201	When repeating, this contains the offset value, otherwise this is the
		1202	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1203
		1204	Can be modified any time, but changes only take effect when the periodic
		1205	timer fires or C<ev_periodic_again> is being called.
		1206
		1207	=item ev_tstamp interval [read-write]
		1208
		1209	The current interval value. Can be modified any time, but changes only
		1210	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1211	called.
		1212
		1213	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1214
		1215	The current reschedule callback, or C<0>, if this functionality is
		1216	switched off. Can be changed any time, but changes only take effect when
		1217	the periodic timer fires or C<ev_periodic_again> is being called.
		1218
678	=back	1219	=back
679		1220
		1221	Example: Call a callback every hour, or, more precisely, whenever the
		1222	system clock is divisible by 3600. The callback invocation times have
		1223	potentially a lot of jittering, but good long-term stability.
		1224
		1225	static void
		1226	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1227	{
		1228	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1229	}
		1230
		1231	struct ev_periodic hourly_tick;
		1232	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1233	ev_periodic_start (loop, &hourly_tick);
		1234
		1235	Example: The same as above, but use a reschedule callback to do it:
		1236
		1237	#include <math.h>
		1238
		1239	static ev_tstamp
		1240	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1241	{
		1242	return fmod (now, 3600.) + 3600.;
		1243	}
		1244
		1245	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1246
		1247	Example: Call a callback every hour, starting now:
		1248
		1249	struct ev_periodic hourly_tick;
		1250	ev_periodic_init (&hourly_tick, clock_cb,
		1251	fmod (ev_now (loop), 3600.), 3600., 0);
		1252	ev_periodic_start (loop, &hourly_tick);
		1253
		1254
680	=head2 C<ev_signal> - signal me when a signal gets signalled	1255	=head2 C<ev_signal> - signal me when a signal gets signalled!
681		1256
682	Signal watchers will trigger an event when the process receives a specific	1257	Signal watchers will trigger an event when the process receives a specific
683	signal one or more times. Even though signals are very asynchronous, libev	1258	signal one or more times. Even though signals are very asynchronous, libev
684	will try it's best to deliver signals synchronously, i.e. as part of the	1259	will try it's best to deliver signals synchronously, i.e. as part of the
685	normal event processing, like any other event.	1260	normal event processing, like any other event.
…		…
698	=item ev_signal_set (ev_signal *, int signum)	1273	=item ev_signal_set (ev_signal *, int signum)
699		1274
700	Configures the watcher to trigger on the given signal number (usually one	1275	Configures the watcher to trigger on the given signal number (usually one
701	of the C<SIGxxx> constants).	1276	of the C<SIGxxx> constants).
702		1277
		1278	=item int signum [read-only]
		1279
		1280	The signal the watcher watches out for.
		1281
703	=back	1282	=back
704		1283
		1284
705	=head2 C<ev_child> - wait for pid status changes	1285	=head2 C<ev_child> - watch out for process status changes
706		1286
707	Child watchers trigger when your process receives a SIGCHLD in response to	1287	Child watchers trigger when your process receives a SIGCHLD in response to
708	some child status changes (most typically when a child of yours dies).	1288	some child status changes (most typically when a child of yours dies).
709		1289
710	=over 4	1290	=over 4
…		…
718	at the C<rstatus> member of the C<ev_child> watcher structure to see	1298	at the C<rstatus> member of the C<ev_child> watcher structure to see
719	the status word (use the macros from C<sys/wait.h> and see your systems	1299	the status word (use the macros from C<sys/wait.h> and see your systems
720	C<waitpid> documentation). The C<rpid> member contains the pid of the	1300	C<waitpid> documentation). The C<rpid> member contains the pid of the
721	process causing the status change.	1301	process causing the status change.
722		1302
		1303	=item int pid [read-only]
		1304
		1305	The process id this watcher watches out for, or C<0>, meaning any process id.
		1306
		1307	=item int rpid [read-write]
		1308
		1309	The process id that detected a status change.
		1310
		1311	=item int rstatus [read-write]
		1312
		1313	The process exit/trace status caused by C<rpid> (see your systems
		1314	C<waitpid> and C<sys/wait.h> documentation for details).
		1315
723	=back	1316	=back
724		1317
		1318	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1319
		1320	static void
		1321	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1322	{
		1323	ev_unloop (loop, EVUNLOOP_ALL);
		1324	}
		1325
		1326	struct ev_signal signal_watcher;
		1327	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1328	ev_signal_start (loop, &sigint_cb);
		1329
		1330
		1331	=head2 C<ev_stat> - did the file attributes just change?
		1332
		1333	This watches a filesystem path for attribute changes. That is, it calls
		1334	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1335	compared to the last time, invoking the callback if it did.
		1336
		1337	The path does not need to exist: changing from "path exists" to "path does
		1338	not exist" is a status change like any other. The condition "path does
		1339	not exist" is signified by the C<st_nlink> field being zero (which is
		1340	otherwise always forced to be at least one) and all the other fields of
		1341	the stat buffer having unspecified contents.
		1342
		1343	The path I<should> be absolute and I<must not> end in a slash. If it is
		1344	relative and your working directory changes, the behaviour is undefined.
		1345
		1346	Since there is no standard to do this, the portable implementation simply
		1347	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1348	can specify a recommended polling interval for this case. If you specify
		1349	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1350	unspecified default> value will be used (which you can expect to be around
		1351	five seconds, although this might change dynamically). Libev will also
		1352	impose a minimum interval which is currently around C<0.1>, but thats
		1353	usually overkill.
		1354
		1355	This watcher type is not meant for massive numbers of stat watchers,
		1356	as even with OS-supported change notifications, this can be
		1357	resource-intensive.
		1358
		1359	At the time of this writing, only the Linux inotify interface is
		1360	implemented (implementing kqueue support is left as an exercise for the
		1361	reader). Inotify will be used to give hints only and should not change the
		1362	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1363	to fall back to regular polling again even with inotify, but changes are
		1364	usually detected immediately, and if the file exists there will be no
		1365	polling.
		1366
		1367	=over 4
		1368
		1369	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1370
		1371	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1372
		1373	Configures the watcher to wait for status changes of the given
		1374	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1375	be detected and should normally be specified as C<0> to let libev choose
		1376	a suitable value. The memory pointed to by C<path> must point to the same
		1377	path for as long as the watcher is active.
		1378
		1379	The callback will be receive C<EV_STAT> when a change was detected,
		1380	relative to the attributes at the time the watcher was started (or the
		1381	last change was detected).
		1382
		1383	=item ev_stat_stat (ev_stat *)
		1384
		1385	Updates the stat buffer immediately with new values. If you change the
		1386	watched path in your callback, you could call this fucntion to avoid
		1387	detecting this change (while introducing a race condition). Can also be
		1388	useful simply to find out the new values.
		1389
		1390	=item ev_statdata attr [read-only]
		1391
		1392	The most-recently detected attributes of the file. Although the type is of
		1393	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1394	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1395	was some error while C<stat>ing the file.
		1396
		1397	=item ev_statdata prev [read-only]
		1398
		1399	The previous attributes of the file. The callback gets invoked whenever
		1400	C<prev> != C<attr>.
		1401
		1402	=item ev_tstamp interval [read-only]
		1403
		1404	The specified interval.
		1405
		1406	=item const char *path [read-only]
		1407
		1408	The filesystem path that is being watched.
		1409
		1410	=back
		1411
		1412	Example: Watch C</etc/passwd> for attribute changes.
		1413
		1414	static void
		1415	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1416	{
		1417	/* /etc/passwd changed in some way */
		1418	if (w->attr.st_nlink)
		1419	{
		1420	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1421	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1422	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1423	}
		1424	else
		1425	/* you shalt not abuse printf for puts */
		1426	puts ("wow, /etc/passwd is not there, expect problems. "
		1427	"if this is windows, they already arrived\n");
		1428	}
		1429
		1430	...
		1431	ev_stat passwd;
		1432
		1433	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1434	ev_stat_start (loop, &passwd);
		1435
		1436
725	=head2 C<ev_idle> - when you've got nothing better to do	1437	=head2 C<ev_idle> - when you've got nothing better to do...
726		1438
727	Idle watchers trigger events when there are no other events are pending	1439	Idle watchers trigger events when no other events of the same or higher
728	(prepare, check and other idle watchers do not count). That is, as long	1440	priority are pending (prepare, check and other idle watchers do not
729	as your process is busy handling sockets or timeouts (or even signals,	1441	count).
730	imagine) it will not be triggered. But when your process is idle all idle	1442
731	watchers are being called again and again, once per event loop iteration -	1443	That is, as long as your process is busy handling sockets or timeouts
		1444	(or even signals, imagine) of the same or higher priority it will not be
		1445	triggered. But when your process is idle (or only lower-priority watchers
		1446	are pending), the idle watchers are being called once per event loop
732	until stopped, that is, or your process receives more events and becomes	1447	iteration - until stopped, that is, or your process receives more events
733	busy.	1448	and becomes busy again with higher priority stuff.
734		1449
735	The most noteworthy effect is that as long as any idle watchers are	1450	The most noteworthy effect is that as long as any idle watchers are
736	active, the process will not block when waiting for new events.	1451	active, the process will not block when waiting for new events.
737		1452
738	Apart from keeping your process non-blocking (which is a useful	1453	Apart from keeping your process non-blocking (which is a useful
…		…
748	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1463	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
749	believe me.	1464	believe me.
750		1465
751	=back	1466	=back
752		1467
		1468	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1469	callback, free it. Also, use no error checking, as usual.
		1470
		1471	static void
		1472	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1473	{
		1474	free (w);
		1475	// now do something you wanted to do when the program has
		1476	// no longer asnything immediate to do.
		1477	}
		1478
		1479	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1480	ev_idle_init (idle_watcher, idle_cb);
		1481	ev_idle_start (loop, idle_cb);
		1482
		1483
753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1484	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
754		1485
755	Prepare and check watchers are usually (but not always) used in tandem:	1486	Prepare and check watchers are usually (but not always) used in tandem:
756	prepare watchers get invoked before the process blocks and check watchers	1487	prepare watchers get invoked before the process blocks and check watchers
757	afterwards.	1488	afterwards.
758		1489
		1490	You I<must not> call C<ev_loop> or similar functions that enter
		1491	the current event loop from either C<ev_prepare> or C<ev_check>
		1492	watchers. Other loops than the current one are fine, however. The
		1493	rationale behind this is that you do not need to check for recursion in
		1494	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1495	C<ev_check> so if you have one watcher of each kind they will always be
		1496	called in pairs bracketing the blocking call.
		1497
759	Their main purpose is to integrate other event mechanisms into libev. This	1498	Their main purpose is to integrate other event mechanisms into libev and
760	could be used, for example, to track variable changes, implement your own	1499	their use is somewhat advanced. This could be used, for example, to track
761	watchers, integrate net-snmp or a coroutine library and lots more.	1500	variable changes, implement your own watchers, integrate net-snmp or a
		1501	coroutine library and lots more. They are also occasionally useful if
		1502	you cache some data and want to flush it before blocking (for example,
		1503	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1504	watcher).
762		1505
763	This is done by examining in each prepare call which file descriptors need	1506	This is done by examining in each prepare call which file descriptors need
764	to be watched by the other library, registering C<ev_io> watchers for	1507	to be watched by the other library, registering C<ev_io> watchers for
765	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1508	them and starting an C<ev_timer> watcher for any timeouts (many libraries
766	provide just this functionality). Then, in the check watcher you check for	1509	provide just this functionality). Then, in the check watcher you check for
…		…
776	with priority higher than or equal to the event loop and one coroutine	1519	with priority higher than or equal to the event loop and one coroutine
777	of lower priority, but only once, using idle watchers to keep the event	1520	of lower priority, but only once, using idle watchers to keep the event
778	loop from blocking if lower-priority coroutines are active, thus mapping	1521	loop from blocking if lower-priority coroutines are active, thus mapping
779	low-priority coroutines to idle/background tasks).	1522	low-priority coroutines to idle/background tasks).
780		1523
		1524	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1525	priority, to ensure that they are being run before any other watchers
		1526	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1527	too) should not activate ("feed") events into libev. While libev fully
		1528	supports this, they will be called before other C<ev_check> watchers did
		1529	their job. As C<ev_check> watchers are often used to embed other event
		1530	loops those other event loops might be in an unusable state until their
		1531	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1532	others).
		1533
781	=over 4	1534	=over 4
782		1535
783	=item ev_prepare_init (ev_prepare *, callback)	1536	=item ev_prepare_init (ev_prepare *, callback)
784		1537
785	=item ev_check_init (ev_check *, callback)	1538	=item ev_check_init (ev_check *, callback)
…		…
787	Initialises and configures the prepare or check watcher - they have no	1540	Initialises and configures the prepare or check watcher - they have no
788	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1541	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
789	macros, but using them is utterly, utterly and completely pointless.	1542	macros, but using them is utterly, utterly and completely pointless.
790		1543
791	=back	1544	=back
		1545
		1546	There are a number of principal ways to embed other event loops or modules
		1547	into libev. Here are some ideas on how to include libadns into libev
		1548	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1549	use for an actually working example. Another Perl module named C<EV::Glib>
		1550	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1551	into the Glib event loop).
		1552
		1553	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1554	and in a check watcher, destroy them and call into libadns. What follows
		1555	is pseudo-code only of course. This requires you to either use a low
		1556	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1557	the callbacks for the IO/timeout watchers might not have been called yet.
		1558
		1559	static ev_io iow [nfd];
		1560	static ev_timer tw;
		1561
		1562	static void
		1563	io_cb (ev_loop *loop, ev_io *w, int revents)
		1564	{
		1565	}
		1566
		1567	// create io watchers for each fd and a timer before blocking
		1568	static void
		1569	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1570	{
		1571	int timeout = 3600000;
		1572	struct pollfd fds [nfd];
		1573	// actual code will need to loop here and realloc etc.
		1574	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1575
		1576	/* the callback is illegal, but won't be called as we stop during check */
		1577	ev_timer_init (&tw, 0, timeout * 1e-3);
		1578	ev_timer_start (loop, &tw);
		1579
		1580	// create one ev_io per pollfd
		1581	for (int i = 0; i < nfd; ++i)
		1582	{
		1583	ev_io_init (iow + i, io_cb, fds [i].fd,
		1584	((fds [i].events & POLLIN ? EV_READ : 0)
		1585	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1586
		1587	fds [i].revents = 0;
		1588	ev_io_start (loop, iow + i);
		1589	}
		1590	}
		1591
		1592	// stop all watchers after blocking
		1593	static void
		1594	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1595	{
		1596	ev_timer_stop (loop, &tw);
		1597
		1598	for (int i = 0; i < nfd; ++i)
		1599	{
		1600	// set the relevant poll flags
		1601	// could also call adns_processreadable etc. here
		1602	struct pollfd *fd = fds + i;
		1603	int revents = ev_clear_pending (iow + i);
		1604	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1605	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1606
		1607	// now stop the watcher
		1608	ev_io_stop (loop, iow + i);
		1609	}
		1610
		1611	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1612	}
		1613
		1614	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1615	in the prepare watcher and would dispose of the check watcher.
		1616
		1617	Method 3: If the module to be embedded supports explicit event
		1618	notification (adns does), you can also make use of the actual watcher
		1619	callbacks, and only destroy/create the watchers in the prepare watcher.
		1620
		1621	static void
		1622	timer_cb (EV_P_ ev_timer *w, int revents)
		1623	{
		1624	adns_state ads = (adns_state)w->data;
		1625	update_now (EV_A);
		1626
		1627	adns_processtimeouts (ads, &tv_now);
		1628	}
		1629
		1630	static void
		1631	io_cb (EV_P_ ev_io *w, int revents)
		1632	{
		1633	adns_state ads = (adns_state)w->data;
		1634	update_now (EV_A);
		1635
		1636	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1637	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1638	}
		1639
		1640	// do not ever call adns_afterpoll
		1641
		1642	Method 4: Do not use a prepare or check watcher because the module you
		1643	want to embed is too inflexible to support it. Instead, youc na override
		1644	their poll function. The drawback with this solution is that the main
		1645	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1646	this.
		1647
		1648	static gint
		1649	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1650	{
		1651	int got_events = 0;
		1652
		1653	for (n = 0; n < nfds; ++n)
		1654	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1655
		1656	if (timeout >= 0)
		1657	// create/start timer
		1658
		1659	// poll
		1660	ev_loop (EV_A_ 0);
		1661
		1662	// stop timer again
		1663	if (timeout >= 0)
		1664	ev_timer_stop (EV_A_ &to);
		1665
		1666	// stop io watchers again - their callbacks should have set
		1667	for (n = 0; n < nfds; ++n)
		1668	ev_io_stop (EV_A_ iow [n]);
		1669
		1670	return got_events;
		1671	}
		1672
		1673
		1674	=head2 C<ev_embed> - when one backend isn't enough...
		1675
		1676	This is a rather advanced watcher type that lets you embed one event loop
		1677	into another (currently only C<ev_io> events are supported in the embedded
		1678	loop, other types of watchers might be handled in a delayed or incorrect
		1679	fashion and must not be used).
		1680
		1681	There are primarily two reasons you would want that: work around bugs and
		1682	prioritise I/O.
		1683
		1684	As an example for a bug workaround, the kqueue backend might only support
		1685	sockets on some platform, so it is unusable as generic backend, but you
		1686	still want to make use of it because you have many sockets and it scales
		1687	so nicely. In this case, you would create a kqueue-based loop and embed it
		1688	into your default loop (which might use e.g. poll). Overall operation will
		1689	be a bit slower because first libev has to poll and then call kevent, but
		1690	at least you can use both at what they are best.
		1691
		1692	As for prioritising I/O: rarely you have the case where some fds have
		1693	to be watched and handled very quickly (with low latency), and even
		1694	priorities and idle watchers might have too much overhead. In this case
		1695	you would put all the high priority stuff in one loop and all the rest in
		1696	a second one, and embed the second one in the first.
		1697
		1698	As long as the watcher is active, the callback will be invoked every time
		1699	there might be events pending in the embedded loop. The callback must then
		1700	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1701	their callbacks (you could also start an idle watcher to give the embedded
		1702	loop strictly lower priority for example). You can also set the callback
		1703	to C<0>, in which case the embed watcher will automatically execute the
		1704	embedded loop sweep.
		1705
		1706	As long as the watcher is started it will automatically handle events. The
		1707	callback will be invoked whenever some events have been handled. You can
		1708	set the callback to C<0> to avoid having to specify one if you are not
		1709	interested in that.
		1710
		1711	Also, there have not currently been made special provisions for forking:
		1712	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1713	but you will also have to stop and restart any C<ev_embed> watchers
		1714	yourself.
		1715
		1716	Unfortunately, not all backends are embeddable, only the ones returned by
		1717	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1718	portable one.
		1719
		1720	So when you want to use this feature you will always have to be prepared
		1721	that you cannot get an embeddable loop. The recommended way to get around
		1722	this is to have a separate variables for your embeddable loop, try to
		1723	create it, and if that fails, use the normal loop for everything:
		1724
		1725	struct ev_loop *loop_hi = ev_default_init (0);
		1726	struct ev_loop *loop_lo = 0;
		1727	struct ev_embed embed;
		1728
		1729	// see if there is a chance of getting one that works
		1730	// (remember that a flags value of 0 means autodetection)
		1731	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1732	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1733	: 0;
		1734
		1735	// if we got one, then embed it, otherwise default to loop_hi
		1736	if (loop_lo)
		1737	{
		1738	ev_embed_init (&embed, 0, loop_lo);
		1739	ev_embed_start (loop_hi, &embed);
		1740	}
		1741	else
		1742	loop_lo = loop_hi;
		1743
		1744	=over 4
		1745
		1746	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1747
		1748	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1749
		1750	Configures the watcher to embed the given loop, which must be
		1751	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1752	invoked automatically, otherwise it is the responsibility of the callback
		1753	to invoke it (it will continue to be called until the sweep has been done,
		1754	if you do not want thta, you need to temporarily stop the embed watcher).
		1755
		1756	=item ev_embed_sweep (loop, ev_embed *)
		1757
		1758	Make a single, non-blocking sweep over the embedded loop. This works
		1759	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1760	apropriate way for embedded loops.
		1761
		1762	=item struct ev_loop *loop [read-only]
		1763
		1764	The embedded event loop.
		1765
		1766	=back
		1767
		1768
		1769	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1770
		1771	Fork watchers are called when a C<fork ()> was detected (usually because
		1772	whoever is a good citizen cared to tell libev about it by calling
		1773	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1774	event loop blocks next and before C<ev_check> watchers are being called,
		1775	and only in the child after the fork. If whoever good citizen calling
		1776	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1777	handlers will be invoked, too, of course.
		1778
		1779	=over 4
		1780
		1781	=item ev_fork_init (ev_signal *, callback)
		1782
		1783	Initialises and configures the fork watcher - it has no parameters of any
		1784	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1785	believe me.
		1786
		1787	=back
		1788
792		1789
793	=head1 OTHER FUNCTIONS	1790	=head1 OTHER FUNCTIONS
794		1791
795	There are some other functions of possible interest. Described. Here. Now.	1792	There are some other functions of possible interest. Described. Here. Now.
796		1793
…		…
826	/* stdin might have data for us, joy! */;	1823	/* stdin might have data for us, joy! */;
827	}	1824	}
828		1825
829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1826	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
830		1827
831	=item ev_feed_event (loop, watcher, int events)	1828	=item ev_feed_event (ev_loop *, watcher *, int revents)
832		1829
833	Feeds the given event set into the event loop, as if the specified event	1830	Feeds the given event set into the event loop, as if the specified event
834	had happened for the specified watcher (which must be a pointer to an	1831	had happened for the specified watcher (which must be a pointer to an
835	initialised but not necessarily started event watcher).	1832	initialised but not necessarily started event watcher).
836		1833
837	=item ev_feed_fd_event (loop, int fd, int revents)	1834	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
838		1835
839	Feed an event on the given fd, as if a file descriptor backend detected	1836	Feed an event on the given fd, as if a file descriptor backend detected
840	the given events it.	1837	the given events it.
841		1838
842	=item ev_feed_signal_event (loop, int signum)	1839	=item ev_feed_signal_event (ev_loop *loop, int signum)
843		1840
844	Feed an event as if the given signal occured (loop must be the default loop!).	1841	Feed an event as if the given signal occured (C<loop> must be the default
		1842	loop!).
845		1843
846	=back	1844	=back
		1845
847		1846
848	=head1 LIBEVENT EMULATION	1847	=head1 LIBEVENT EMULATION
849		1848
850	Libev offers a compatibility emulation layer for libevent. It cannot	1849	Libev offers a compatibility emulation layer for libevent. It cannot
851	emulate the internals of libevent, so here are some usage hints:	1850	emulate the internals of libevent, so here are some usage hints:
…		…
872		1871
873	=back	1872	=back
874		1873
875	=head1 C++ SUPPORT	1874	=head1 C++ SUPPORT
876		1875
877	TBD.	1876	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1877	you to use some convinience methods to start/stop watchers and also change
		1878	the callback model to a model using method callbacks on objects.
		1879
		1880	To use it,
		1881
		1882	#include <ev++.h>
		1883
		1884	This automatically includes F<ev.h> and puts all of its definitions (many
		1885	of them macros) into the global namespace. All C++ specific things are
		1886	put into the C<ev> namespace. It should support all the same embedding
		1887	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1888
		1889	Care has been taken to keep the overhead low. The only data member the C++
		1890	classes add (compared to plain C-style watchers) is the event loop pointer
		1891	that the watcher is associated with (or no additional members at all if
		1892	you disable C<EV_MULTIPLICITY> when embedding libev).
		1893
		1894	Currently, functions, and static and non-static member functions can be
		1895	used as callbacks. Other types should be easy to add as long as they only
		1896	need one additional pointer for context. If you need support for other
		1897	types of functors please contact the author (preferably after implementing
		1898	it).
		1899
		1900	Here is a list of things available in the C<ev> namespace:
		1901
		1902	=over 4
		1903
		1904	=item C<ev::READ>, C<ev::WRITE> etc.
		1905
		1906	These are just enum values with the same values as the C<EV_READ> etc.
		1907	macros from F<ev.h>.
		1908
		1909	=item C<ev::tstamp>, C<ev::now>
		1910
		1911	Aliases to the same types/functions as with the C<ev_> prefix.
		1912
		1913	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1914
		1915	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1916	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1917	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1918	defines by many implementations.
		1919
		1920	All of those classes have these methods:
		1921
		1922	=over 4
		1923
		1924	=item ev::TYPE::TYPE ()
		1925
		1926	=item ev::TYPE::TYPE (struct ev_loop *)
		1927
		1928	=item ev::TYPE::~TYPE
		1929
		1930	The constructor (optionally) takes an event loop to associate the watcher
		1931	with. If it is omitted, it will use C<EV_DEFAULT>.
		1932
		1933	The constructor calls C<ev_init> for you, which means you have to call the
		1934	C<set> method before starting it.
		1935
		1936	It will not set a callback, however: You have to call the templated C<set>
		1937	method to set a callback before you can start the watcher.
		1938
		1939	(The reason why you have to use a method is a limitation in C++ which does
		1940	not allow explicit template arguments for constructors).
		1941
		1942	The destructor automatically stops the watcher if it is active.
		1943
		1944	=item w->set<class, &class::method> (object *)
		1945
		1946	This method sets the callback method to call. The method has to have a
		1947	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1948	first argument and the C<revents> as second. The object must be given as
		1949	parameter and is stored in the C<data> member of the watcher.
		1950
		1951	This method synthesizes efficient thunking code to call your method from
		1952	the C callback that libev requires. If your compiler can inline your
		1953	callback (i.e. it is visible to it at the place of the C<set> call and
		1954	your compiler is good :), then the method will be fully inlined into the
		1955	thunking function, making it as fast as a direct C callback.
		1956
		1957	Example: simple class declaration and watcher initialisation
		1958
		1959	struct myclass
		1960	{
		1961	void io_cb (ev::io &w, int revents) { }
		1962	}
		1963
		1964	myclass obj;
		1965	ev::io iow;
		1966	iow.set <myclass, &myclass::io_cb> (&obj);
		1967
		1968	=item w->set<function> (void *data = 0)
		1969
		1970	Also sets a callback, but uses a static method or plain function as
		1971	callback. The optional C<data> argument will be stored in the watcher's
		1972	C<data> member and is free for you to use.
		1973
		1974	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1975
		1976	See the method-C<set> above for more details.
		1977
		1978	Example:
		1979
		1980	static void io_cb (ev::io &w, int revents) { }
		1981	iow.set <io_cb> ();
		1982
		1983	=item w->set (struct ev_loop *)
		1984
		1985	Associates a different C<struct ev_loop> with this watcher. You can only
		1986	do this when the watcher is inactive (and not pending either).
		1987
		1988	=item w->set ([args])
		1989
		1990	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1991	called at least once. Unlike the C counterpart, an active watcher gets
		1992	automatically stopped and restarted when reconfiguring it with this
		1993	method.
		1994
		1995	=item w->start ()
		1996
		1997	Starts the watcher. Note that there is no C<loop> argument, as the
		1998	constructor already stores the event loop.
		1999
		2000	=item w->stop ()
		2001
		2002	Stops the watcher if it is active. Again, no C<loop> argument.
		2003
		2004	=item w->again () C<ev::timer>, C<ev::periodic> only
		2005
		2006	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2007	C<ev_TYPE_again> function.
		2008
		2009	=item w->sweep () C<ev::embed> only
		2010
		2011	Invokes C<ev_embed_sweep>.
		2012
		2013	=item w->update () C<ev::stat> only
		2014
		2015	Invokes C<ev_stat_stat>.
		2016
		2017	=back
		2018
		2019	=back
		2020
		2021	Example: Define a class with an IO and idle watcher, start one of them in
		2022	the constructor.
		2023
		2024	class myclass
		2025	{
		2026	ev_io io; void io_cb (ev::io &w, int revents);
		2027	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2028
		2029	myclass ();
		2030	}
		2031
		2032	myclass::myclass (int fd)
		2033	{
		2034	io .set <myclass, &myclass::io_cb > (this);
		2035	idle.set <myclass, &myclass::idle_cb> (this);
		2036
		2037	io.start (fd, ev::READ);
		2038	}
		2039
		2040
		2041	=head1 MACRO MAGIC
		2042
		2043	Libev can be compiled with a variety of options, the most fundemantal is
		2044	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		2045	callbacks have an initial C<struct ev_loop *> argument.
		2046
		2047	To make it easier to write programs that cope with either variant, the
		2048	following macros are defined:
		2049
		2050	=over 4
		2051
		2052	=item C<EV_A>, C<EV_A_>
		2053
		2054	This provides the loop I<argument> for functions, if one is required ("ev
		2055	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2056	C<EV_A_> is used when other arguments are following. Example:
		2057
		2058	ev_unref (EV_A);
		2059	ev_timer_add (EV_A_ watcher);
		2060	ev_loop (EV_A_ 0);
		2061
		2062	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2063	which is often provided by the following macro.
		2064
		2065	=item C<EV_P>, C<EV_P_>
		2066
		2067	This provides the loop I<parameter> for functions, if one is required ("ev
		2068	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2069	C<EV_P_> is used when other parameters are following. Example:
		2070
		2071	// this is how ev_unref is being declared
		2072	static void ev_unref (EV_P);
		2073
		2074	// this is how you can declare your typical callback
		2075	static void cb (EV_P_ ev_timer *w, int revents)
		2076
		2077	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2078	suitable for use with C<EV_A>.
		2079
		2080	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2081
		2082	Similar to the other two macros, this gives you the value of the default
		2083	loop, if multiple loops are supported ("ev loop default").
		2084
		2085	=back
		2086
		2087	Example: Declare and initialise a check watcher, utilising the above
		2088	macros so it will work regardless of whether multiple loops are supported
		2089	or not.
		2090
		2091	static void
		2092	check_cb (EV_P_ ev_timer *w, int revents)
		2093	{
		2094	ev_check_stop (EV_A_ w);
		2095	}
		2096
		2097	ev_check check;
		2098	ev_check_init (&check, check_cb);
		2099	ev_check_start (EV_DEFAULT_ &check);
		2100	ev_loop (EV_DEFAULT_ 0);
		2101
		2102	=head1 EMBEDDING
		2103
		2104	Libev can (and often is) directly embedded into host
		2105	applications. Examples of applications that embed it include the Deliantra
		2106	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2107	and rxvt-unicode.
		2108
		2109	The goal is to enable you to just copy the neecssary files into your
		2110	source directory without having to change even a single line in them, so
		2111	you can easily upgrade by simply copying (or having a checked-out copy of
		2112	libev somewhere in your source tree).
		2113
		2114	=head2 FILESETS
		2115
		2116	Depending on what features you need you need to include one or more sets of files
		2117	in your app.
		2118
		2119	=head3 CORE EVENT LOOP
		2120
		2121	To include only the libev core (all the C<ev_*> functions), with manual
		2122	configuration (no autoconf):
		2123
		2124	#define EV_STANDALONE 1
		2125	#include "ev.c"
		2126
		2127	This will automatically include F<ev.h>, too, and should be done in a
		2128	single C source file only to provide the function implementations. To use
		2129	it, do the same for F<ev.h> in all files wishing to use this API (best
		2130	done by writing a wrapper around F<ev.h> that you can include instead and
		2131	where you can put other configuration options):
		2132
		2133	#define EV_STANDALONE 1
		2134	#include "ev.h"
		2135
		2136	Both header files and implementation files can be compiled with a C++
		2137	compiler (at least, thats a stated goal, and breakage will be treated
		2138	as a bug).
		2139
		2140	You need the following files in your source tree, or in a directory
		2141	in your include path (e.g. in libev/ when using -Ilibev):
		2142
		2143	ev.h
		2144	ev.c
		2145	ev_vars.h
		2146	ev_wrap.h
		2147
		2148	ev_win32.c required on win32 platforms only
		2149
		2150	ev_select.c only when select backend is enabled (which is enabled by default)
		2151	ev_poll.c only when poll backend is enabled (disabled by default)
		2152	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2153	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2154	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2155
		2156	F<ev.c> includes the backend files directly when enabled, so you only need
		2157	to compile this single file.
		2158
		2159	=head3 LIBEVENT COMPATIBILITY API
		2160
		2161	To include the libevent compatibility API, also include:
		2162
		2163	#include "event.c"
		2164
		2165	in the file including F<ev.c>, and:
		2166
		2167	#include "event.h"
		2168
		2169	in the files that want to use the libevent API. This also includes F<ev.h>.
		2170
		2171	You need the following additional files for this:
		2172
		2173	event.h
		2174	event.c
		2175
		2176	=head3 AUTOCONF SUPPORT
		2177
		2178	Instead of using C<EV_STANDALONE=1> and providing your config in
		2179	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2180	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2181	include F<config.h> and configure itself accordingly.
		2182
		2183	For this of course you need the m4 file:
		2184
		2185	libev.m4
		2186
		2187	=head2 PREPROCESSOR SYMBOLS/MACROS
		2188
		2189	Libev can be configured via a variety of preprocessor symbols you have to define
		2190	before including any of its files. The default is not to build for multiplicity
		2191	and only include the select backend.
		2192
		2193	=over 4
		2194
		2195	=item EV_STANDALONE
		2196
		2197	Must always be C<1> if you do not use autoconf configuration, which
		2198	keeps libev from including F<config.h>, and it also defines dummy
		2199	implementations for some libevent functions (such as logging, which is not
		2200	supported). It will also not define any of the structs usually found in
		2201	F<event.h> that are not directly supported by the libev core alone.
		2202
		2203	=item EV_USE_MONOTONIC
		2204
		2205	If defined to be C<1>, libev will try to detect the availability of the
		2206	monotonic clock option at both compiletime and runtime. Otherwise no use
		2207	of the monotonic clock option will be attempted. If you enable this, you
		2208	usually have to link against librt or something similar. Enabling it when
		2209	the functionality isn't available is safe, though, althoguh you have
		2210	to make sure you link against any libraries where the C<clock_gettime>
		2211	function is hiding in (often F<-lrt>).
		2212
		2213	=item EV_USE_REALTIME
		2214
		2215	If defined to be C<1>, libev will try to detect the availability of the
		2216	realtime clock option at compiletime (and assume its availability at
		2217	runtime if successful). Otherwise no use of the realtime clock option will
		2218	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2219	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2220	in the description of C<EV_USE_MONOTONIC>, though.
		2221
		2222	=item EV_USE_SELECT
		2223
		2224	If undefined or defined to be C<1>, libev will compile in support for the
		2225	C<select>(2) backend. No attempt at autodetection will be done: if no
		2226	other method takes over, select will be it. Otherwise the select backend
		2227	will not be compiled in.
		2228
		2229	=item EV_SELECT_USE_FD_SET
		2230
		2231	If defined to C<1>, then the select backend will use the system C<fd_set>
		2232	structure. This is useful if libev doesn't compile due to a missing
		2233	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2234	exotic systems. This usually limits the range of file descriptors to some
		2235	low limit such as 1024 or might have other limitations (winsocket only
		2236	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2237	influence the size of the C<fd_set> used.
		2238
		2239	=item EV_SELECT_IS_WINSOCKET
		2240
		2241	When defined to C<1>, the select backend will assume that
		2242	select/socket/connect etc. don't understand file descriptors but
		2243	wants osf handles on win32 (this is the case when the select to
		2244	be used is the winsock select). This means that it will call
		2245	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2246	it is assumed that all these functions actually work on fds, even
		2247	on win32. Should not be defined on non-win32 platforms.
		2248
		2249	=item EV_USE_POLL
		2250
		2251	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2252	backend. Otherwise it will be enabled on non-win32 platforms. It
		2253	takes precedence over select.
		2254
		2255	=item EV_USE_EPOLL
		2256
		2257	If defined to be C<1>, libev will compile in support for the Linux
		2258	C<epoll>(7) backend. Its availability will be detected at runtime,
		2259	otherwise another method will be used as fallback. This is the
		2260	preferred backend for GNU/Linux systems.
		2261
		2262	=item EV_USE_KQUEUE
		2263
		2264	If defined to be C<1>, libev will compile in support for the BSD style
		2265	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2266	otherwise another method will be used as fallback. This is the preferred
		2267	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2268	supports some types of fds correctly (the only platform we found that
		2269	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2270	not be used unless explicitly requested. The best way to use it is to find
		2271	out whether kqueue supports your type of fd properly and use an embedded
		2272	kqueue loop.
		2273
		2274	=item EV_USE_PORT
		2275
		2276	If defined to be C<1>, libev will compile in support for the Solaris
		2277	10 port style backend. Its availability will be detected at runtime,
		2278	otherwise another method will be used as fallback. This is the preferred
		2279	backend for Solaris 10 systems.
		2280
		2281	=item EV_USE_DEVPOLL
		2282
		2283	reserved for future expansion, works like the USE symbols above.
		2284
		2285	=item EV_USE_INOTIFY
		2286
		2287	If defined to be C<1>, libev will compile in support for the Linux inotify
		2288	interface to speed up C<ev_stat> watchers. Its actual availability will
		2289	be detected at runtime.
		2290
		2291	=item EV_H
		2292
		2293	The name of the F<ev.h> header file used to include it. The default if
		2294	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2295	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2296
		2297	=item EV_CONFIG_H
		2298
		2299	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2300	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2301	C<EV_H>, above.
		2302
		2303	=item EV_EVENT_H
		2304
		2305	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2306	of how the F<event.h> header can be found.
		2307
		2308	=item EV_PROTOTYPES
		2309
		2310	If defined to be C<0>, then F<ev.h> will not define any function
		2311	prototypes, but still define all the structs and other symbols. This is
		2312	occasionally useful if you want to provide your own wrapper functions
		2313	around libev functions.
		2314
		2315	=item EV_MULTIPLICITY
		2316
		2317	If undefined or defined to C<1>, then all event-loop-specific functions
		2318	will have the C<struct ev_loop *> as first argument, and you can create
		2319	additional independent event loops. Otherwise there will be no support
		2320	for multiple event loops and there is no first event loop pointer
		2321	argument. Instead, all functions act on the single default loop.
		2322
		2323	=item EV_MINPRI
		2324
		2325	=item EV_MAXPRI
		2326
		2327	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2328	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2329	provide for more priorities by overriding those symbols (usually defined
		2330	to be C<-2> and C<2>, respectively).
		2331
		2332	When doing priority-based operations, libev usually has to linearly search
		2333	all the priorities, so having many of them (hundreds) uses a lot of space
		2334	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2335	fine.
		2336
		2337	If your embedding app does not need any priorities, defining these both to
		2338	C<0> will save some memory and cpu.
		2339
		2340	=item EV_PERIODIC_ENABLE
		2341
		2342	If undefined or defined to be C<1>, then periodic timers are supported. If
		2343	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2344	code.
		2345
		2346	=item EV_IDLE_ENABLE
		2347
		2348	If undefined or defined to be C<1>, then idle watchers are supported. If
		2349	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2350	code.
		2351
		2352	=item EV_EMBED_ENABLE
		2353
		2354	If undefined or defined to be C<1>, then embed watchers are supported. If
		2355	defined to be C<0>, then they are not.
		2356
		2357	=item EV_STAT_ENABLE
		2358
		2359	If undefined or defined to be C<1>, then stat watchers are supported. If
		2360	defined to be C<0>, then they are not.
		2361
		2362	=item EV_FORK_ENABLE
		2363
		2364	If undefined or defined to be C<1>, then fork watchers are supported. If
		2365	defined to be C<0>, then they are not.
		2366
		2367	=item EV_MINIMAL
		2368
		2369	If you need to shave off some kilobytes of code at the expense of some
		2370	speed, define this symbol to C<1>. Currently only used for gcc to override
		2371	some inlining decisions, saves roughly 30% codesize of amd64.
		2372
		2373	=item EV_PID_HASHSIZE
		2374
		2375	C<ev_child> watchers use a small hash table to distribute workload by
		2376	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2377	than enough. If you need to manage thousands of children you might want to
		2378	increase this value (I<must> be a power of two).
		2379
		2380	=item EV_INOTIFY_HASHSIZE
		2381
		2382	C<ev_staz> watchers use a small hash table to distribute workload by
		2383	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2384	usually more than enough. If you need to manage thousands of C<ev_stat>
		2385	watchers you might want to increase this value (I<must> be a power of
		2386	two).
		2387
		2388	=item EV_COMMON
		2389
		2390	By default, all watchers have a C<void *data> member. By redefining
		2391	this macro to a something else you can include more and other types of
		2392	members. You have to define it each time you include one of the files,
		2393	though, and it must be identical each time.
		2394
		2395	For example, the perl EV module uses something like this:
		2396
		2397	#define EV_COMMON \
		2398	SV *self; /* contains this struct */ \
		2399	SV *cb_sv, *fh /* note no trailing ";" */
		2400
		2401	=item EV_CB_DECLARE (type)
		2402
		2403	=item EV_CB_INVOKE (watcher, revents)
		2404
		2405	=item ev_set_cb (ev, cb)
		2406
		2407	Can be used to change the callback member declaration in each watcher,
		2408	and the way callbacks are invoked and set. Must expand to a struct member
		2409	definition and a statement, respectively. See the F<ev.v> header file for
		2410	their default definitions. One possible use for overriding these is to
		2411	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2412	method calls instead of plain function calls in C++.
		2413
		2414	=head2 EXAMPLES
		2415
		2416	For a real-world example of a program the includes libev
		2417	verbatim, you can have a look at the EV perl module
		2418	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2419	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2420	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2421	will be compiled. It is pretty complex because it provides its own header
		2422	file.
		2423
		2424	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2425	that everybody includes and which overrides some configure choices:
		2426
		2427	#define EV_MINIMAL 1
		2428	#define EV_USE_POLL 0
		2429	#define EV_MULTIPLICITY 0
		2430	#define EV_PERIODIC_ENABLE 0
		2431	#define EV_STAT_ENABLE 0
		2432	#define EV_FORK_ENABLE 0
		2433	#define EV_CONFIG_H <config.h>
		2434	#define EV_MINPRI 0
		2435	#define EV_MAXPRI 0
		2436
		2437	#include "ev++.h"
		2438
		2439	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2440
		2441	#include "ev_cpp.h"
		2442	#include "ev.c"
		2443
		2444
		2445	=head1 COMPLEXITIES
		2446
		2447	In this section the complexities of (many of) the algorithms used inside
		2448	libev will be explained. For complexity discussions about backends see the
		2449	documentation for C<ev_default_init>.
		2450
		2451	All of the following are about amortised time: If an array needs to be
		2452	extended, libev needs to realloc and move the whole array, but this
		2453	happens asymptotically never with higher number of elements, so O(1) might
		2454	mean it might do a lengthy realloc operation in rare cases, but on average
		2455	it is much faster and asymptotically approaches constant time.
		2456
		2457	=over 4
		2458
		2459	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2460
		2461	This means that, when you have a watcher that triggers in one hour and
		2462	there are 100 watchers that would trigger before that then inserting will
		2463	have to skip those 100 watchers.
		2464
		2465	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2466
		2467	That means that for changing a timer costs less than removing/adding them
		2468	as only the relative motion in the event queue has to be paid for.
		2469
		2470	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2471
		2472	These just add the watcher into an array or at the head of a list.
		2473	=item Stopping check/prepare/idle watchers: O(1)
		2474
		2475	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2476
		2477	These watchers are stored in lists then need to be walked to find the
		2478	correct watcher to remove. The lists are usually short (you don't usually
		2479	have many watchers waiting for the same fd or signal).
		2480
		2481	=item Finding the next timer per loop iteration: O(1)
		2482
		2483	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2484
		2485	A change means an I/O watcher gets started or stopped, which requires
		2486	libev to recalculate its status (and possibly tell the kernel).
		2487
		2488	=item Activating one watcher: O(1)
		2489
		2490	=item Priority handling: O(number_of_priorities)
		2491
		2492	Priorities are implemented by allocating some space for each
		2493	priority. When doing priority-based operations, libev usually has to
		2494	linearly search all the priorities.
		2495
		2496	=back
		2497
878		2498
879	=head1 AUTHOR	2499	=head1 AUTHOR
880		2500
881	Marc Lehmann <libev@schmorp.de>.	2501	Marc Lehmann <libev@schmorp.de>.
882		2502

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