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Revision 1.3 by root, Mon Nov 12 08:03:31 2007 UTC vs.
Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
		7	/* this is the only header you need */
7	#include <ev.h>	8	#include <ev.h>
		9
		10	/* what follows is a fully working example program */
		11	ev_io stdin_watcher;
		12	ev_timer timeout_watcher;
		13
		14	/* called when data readable on stdin */
		15	static void
		16	stdin_cb (EV_P_ struct ev_io *w, int revents)
		17	{
		18	/* puts ("stdin ready"); */
		19	ev_io_stop (EV_A_ w); /* just a syntax example */
		20	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		21	}
		22
		23	static void
		24	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		25	{
		26	/* puts ("timeout"); */
		27	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		28	}
		29
		30	int
		31	main (void)
		32	{
		33	struct ev_loop *loop = ev_default_loop (0);
		34
		35	/* initialise an io watcher, then start it */
		36	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		37	ev_io_start (loop, &stdin_watcher);
		38
		39	/* simple non-repeating 5.5 second timeout */
		40	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		41	ev_timer_start (loop, &timeout_watcher);
		42
		43	/* loop till timeout or data ready */
		44	ev_loop (loop, 0);
		45
		46	return 0;
		47	}
8		48
9	=head1 DESCRIPTION	49	=head1 DESCRIPTION
10		50
11	Libev is an event loop: you register interest in certain events (such as a	51	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	52	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program events.	53	these event sources and provide your program with events.
14		54
15	To do this, it must take more or less complete control over your process	55	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	56	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	57	communicate events via a callback mechanism.
18		58
…		…
25		65
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	66	Libev supports select, poll, the linux-specific epoll and the bsd-specific
27	kqueue mechanisms for file descriptor events, relative timers, absolute	67	kqueue mechanisms for file descriptor events, relative timers, absolute
28	timers with customised rescheduling, signal events, process status change	68	timers with customised rescheduling, signal events, process status change
29	events (related to SIGCHLD), and event watchers dealing with the event	69	events (related to SIGCHLD), and event watchers dealing with the event
30	loop mechanism itself (idle, prepare and check watchers).	70	loop mechanism itself (idle, prepare and check watchers). It also is quite
		71	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
		72	it to libevent for example).
31		73
32	=head1 CONVENTIONS	74	=head1 CONVENTIONS
33		75
34	Libev is very configurable. In this manual the default configuration	76	Libev is very configurable. In this manual the default configuration
35	will be described, which supports multiple event loops. For more info	77	will be described, which supports multiple event loops. For more info
36	about various configuraiton options please have a look at the file	78	about various configuration options please have a look at the file
37	F<README.embed> in the libev distribution. If libev was configured without	79	F<README.embed> in the libev distribution. If libev was configured without
38	support for multiple event loops, then all functions taking an initial	80	support for multiple event loops, then all functions taking an initial
39	argument of name C<loop> (which is always of type C<struct ev_loop *>)	81	argument of name C<loop> (which is always of type C<struct ev_loop *>)
40	will not have this argument.	82	will not have this argument.
41		83
42	=head1 TIME AND OTHER GLOBAL FUNCTIONS	84	=head1 TIME REPRESENTATION
43		85
44	Libev represents time as a single floating point number, representing the	86	Libev represents time as a single floating point number, representing the
45	(fractional) number of seconds since the (POSIX) epoch (somewhere near	87	(fractional) number of seconds since the (POSIX) epoch (somewhere near
46	the beginning of 1970, details are complicated, don't ask). This type is	88	the beginning of 1970, details are complicated, don't ask). This type is
47	called C<ev_tstamp>, which is what you should use too. It usually aliases	89	called C<ev_tstamp>, which is what you should use too. It usually aliases
48	to the double type in C.	90	to the C<double> type in C, and when you need to do any calculations on
		91	it, you should treat it as such.
		92
		93	=head1 GLOBAL FUNCTIONS
		94
		95	These functions can be called anytime, even before initialising the
		96	library in any way.
49		97
50	=over 4	98	=over 4
51		99
52	=item ev_tstamp ev_time ()	100	=item ev_tstamp ev_time ()
53		101
54	Returns the current time as libev would use it.	102	Returns the current time as libev would use it. Please note that the
		103	C<ev_now> function is usually faster and also often returns the timestamp
		104	you actually want to know.
55		105
56	=item int ev_version_major ()	106	=item int ev_version_major ()
57		107
58	=item int ev_version_minor ()	108	=item int ev_version_minor ()
59		109
…		…
61	you linked against by calling the functions C<ev_version_major> and	111	you linked against by calling the functions C<ev_version_major> and
62	C<ev_version_minor>. If you want, you can compare against the global	112	C<ev_version_minor>. If you want, you can compare against the global
63	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	113	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
64	version of the library your program was compiled against.	114	version of the library your program was compiled against.
65		115
66	Usually, its a good idea to terminate if the major versions mismatch,	116	Usually, it's a good idea to terminate if the major versions mismatch,
67	as this indicates an incompatible change. Minor versions are usually	117	as this indicates an incompatible change. Minor versions are usually
68	compatible to older versions, so a larger minor version alone is usually	118	compatible to older versions, so a larger minor version alone is usually
69	not a problem.	119	not a problem.
70		120
		121	Example: make sure we haven't accidentally been linked against the wrong
		122	version:
		123
		124	assert (("libev version mismatch",
		125	ev_version_major () == EV_VERSION_MAJOR
		126	&& ev_version_minor () >= EV_VERSION_MINOR));
		127
		128	=item unsigned int ev_supported_backends ()
		129
		130	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		131	value) compiled into this binary of libev (independent of their
		132	availability on the system you are running on). See C<ev_default_loop> for
		133	a description of the set values.
		134
		135	Example: make sure we have the epoll method, because yeah this is cool and
		136	a must have and can we have a torrent of it please!!!11
		137
		138	assert (("sorry, no epoll, no sex",
		139	ev_supported_backends () & EVBACKEND_EPOLL));
		140
		141	=item unsigned int ev_recommended_backends ()
		142
		143	Return the set of all backends compiled into this binary of libev and also
		144	recommended for this platform. This set is often smaller than the one
		145	returned by C<ev_supported_backends>, as for example kqueue is broken on
		146	most BSDs and will not be autodetected unless you explicitly request it
		147	(assuming you know what you are doing). This is the set of backends that
		148	libev will probe for if you specify no backends explicitly.
		149
		150	=item unsigned int ev_embeddable_backends ()
		151
		152	Returns the set of backends that are embeddable in other event loops. This
		153	is the theoretical, all-platform, value. To find which backends
		154	might be supported on the current system, you would need to look at
		155	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		156	recommended ones.
		157
		158	See the description of C<ev_embed> watchers for more info.
		159
71	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	160	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))
72		161
73	Sets the allocation function to use (the prototype is similar to the	162	Sets the allocation function to use (the prototype and semantics are
74	realloc function). It is used to allocate and free memory (no surprises	163	identical to the realloc C function). It is used to allocate and free
75	here). If it returns zero when memory needs to be allocated, the library	164	memory (no surprises here). If it returns zero when memory needs to be
76	might abort or take some potentially destructive action. The default is	165	allocated, the library might abort or take some potentially destructive
77	your system realloc function.	166	action. The default is your system realloc function.
78		167
79	You could override this function in high-availability programs to, say,	168	You could override this function in high-availability programs to, say,
80	free some memory if it cannot allocate memory, to use a special allocator,	169	free some memory if it cannot allocate memory, to use a special allocator,
81	or even to sleep a while and retry until some memory is available.	170	or even to sleep a while and retry until some memory is available.
		171
		172	Example: replace the libev allocator with one that waits a bit and then
		173	retries: better than mine).
		174
		175	static void *
		176	persistent_realloc (void *ptr, size_t size)
		177	{
		178	for (;;)
		179	{
		180	void *newptr = realloc (ptr, size);
		181
		182	if (newptr)
		183	return newptr;
		184
		185	sleep (60);
		186	}
		187	}
		188
		189	...
		190	ev_set_allocator (persistent_realloc);
82		191
83	=item ev_set_syserr_cb (void (*cb)(const char *msg));	192	=item ev_set_syserr_cb (void (*cb)(const char *msg));
84		193
85	Set the callback function to call on a retryable syscall error (such	194	Set the callback function to call on a retryable syscall error (such
86	as failed select, poll, epoll_wait). The message is a printable string	195	as failed select, poll, epoll_wait). The message is a printable string
87	indicating the system call or subsystem causing the problem. If this	196	indicating the system call or subsystem causing the problem. If this
88	callback is set, then libev will expect it to remedy the sitution, no	197	callback is set, then libev will expect it to remedy the sitution, no
89	matter what, when it returns. That is, libev will geenrally retry the	198	matter what, when it returns. That is, libev will generally retry the
90	requested operation, or, if the condition doesn't go away, do bad stuff	199	requested operation, or, if the condition doesn't go away, do bad stuff
91	(such as abort).	200	(such as abort).
		201
		202	Example: do the same thing as libev does internally:
		203
		204	static void
		205	fatal_error (const char *msg)
		206	{
		207	perror (msg);
		208	abort ();
		209	}
		210
		211	...
		212	ev_set_syserr_cb (fatal_error);
92		213
93	=back	214	=back
94		215
95	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	216	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
96		217
97	An event loop is described by a C<struct ev_loop *>. The library knows two	218	An event loop is described by a C<struct ev_loop *>. The library knows two
98	types of such loops, the I<default> loop, which supports signals and child	219	types of such loops, the I<default> loop, which supports signals and child
99	events, and dynamically created loops which do not.	220	events, and dynamically created loops which do not.
100		221
101	If you use threads, a common model is to run the default event loop	222	If you use threads, a common model is to run the default event loop
102	in your main thread (or in a separate thrad) and for each thread you	223	in your main thread (or in a separate thread) and for each thread you
103	create, you also create another event loop. Libev itself does no lockign	224	create, you also create another event loop. Libev itself does no locking
104	whatsoever, so if you mix calls to different event loops, make sure you	225	whatsoever, so if you mix calls to the same event loop in different
105	lock (this is usually a bad idea, though, even if done right).	226	threads, make sure you lock (this is usually a bad idea, though, even if
		227	done correctly, because it's hideous and inefficient).
106		228
107	=over 4	229	=over 4
108		230
109	=item struct ev_loop *ev_default_loop (unsigned int flags)	231	=item struct ev_loop *ev_default_loop (unsigned int flags)
110		232
111	This will initialise the default event loop if it hasn't been initialised	233	This will initialise the default event loop if it hasn't been initialised
112	yet and return it. If the default loop could not be initialised, returns	234	yet and return it. If the default loop could not be initialised, returns
113	false. If it already was initialised it simply returns it (and ignores the	235	false. If it already was initialised it simply returns it (and ignores the
114	flags).	236	flags. If that is troubling you, check C<ev_backend ()> afterwards).
115		237
116	If you don't know what event loop to use, use the one returned from this	238	If you don't know what event loop to use, use the one returned from this
117	function.	239	function.
118		240
119	The flags argument can be used to specify special behaviour or specific	241	The flags argument can be used to specify special behaviour or specific
120	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	242	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
121		243
122	It supports the following flags:	244	The following flags are supported:
123		245
124	=over 4	246	=over 4
125		247
126	=item EVFLAG_AUTO	248	=item C<EVFLAG_AUTO>
127		249
128	The default flags value. Use this if you have no clue (its the right	250	The default flags value. Use this if you have no clue (it's the right
129	thing, believe me).	251	thing, believe me).
130		252
131	=item EVFLAG_NOENV	253	=item C<EVFLAG_NOENV>
132		254
133	If this flag bit is ored into the flag value then libev will I<not> look	255	If this flag bit is ored into the flag value (or the program runs setuid
134	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	256	or setgid) then libev will I<not> look at the environment variable
135	environment variable will override the flags completely. This is useful	257	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		258	override the flags completely if it is found in the environment. This is
136	to try out specific backends to tets their performance, or to work around	259	useful to try out specific backends to test their performance, or to work
137	bugs.	260	around bugs.
138		261
139	=item EVMETHOD_SELECT portable select backend	262	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
140		263
141	=item EVMETHOD_POLL poll backend (everywhere except windows)	264	This is your standard select(2) backend. Not I<completely> standard, as
		265	libev tries to roll its own fd_set with no limits on the number of fds,
		266	but if that fails, expect a fairly low limit on the number of fds when
		267	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		268	the fastest backend for a low number of fds.
142		269
143	=item EVMETHOD_EPOLL linux only	270	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
144		271
145	=item EVMETHOD_KQUEUE some bsds only	272	And this is your standard poll(2) backend. It's more complicated than
		273	select, but handles sparse fds better and has no artificial limit on the
		274	number of fds you can use (except it will slow down considerably with a
		275	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
146		276
147	=item EVMETHOD_DEVPOLL solaris 8 only	277	=item C<EVBACKEND_EPOLL> (value 4, Linux)
148		278
149	=item EVMETHOD_PORT solaris 10 only	279	For few fds, this backend is a bit little slower than poll and select,
		280	but it scales phenomenally better. While poll and select usually scale like
		281	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		282	either O(1) or O(active_fds).
		283
		284	While stopping and starting an I/O watcher in the same iteration will
		285	result in some caching, there is still a syscall per such incident
		286	(because the fd could point to a different file description now), so its
		287	best to avoid that. Also, dup()ed file descriptors might not work very
		288	well if you register events for both fds.
		289
		290	Please note that epoll sometimes generates spurious notifications, so you
		291	need to use non-blocking I/O or other means to avoid blocking when no data
		292	(or space) is available.
		293
		294	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		295
		296	Kqueue deserves special mention, as at the time of this writing, it
		297	was broken on all BSDs except NetBSD (usually it doesn't work with
		298	anything but sockets and pipes, except on Darwin, where of course its
		299	completely useless). For this reason its not being "autodetected"
		300	unless you explicitly specify it explicitly in the flags (i.e. using
		301	C<EVBACKEND_KQUEUE>).
		302
		303	It scales in the same way as the epoll backend, but the interface to the
		304	kernel is more efficient (which says nothing about its actual speed, of
		305	course). While starting and stopping an I/O watcher does not cause an
		306	extra syscall as with epoll, it still adds up to four event changes per
		307	incident, so its best to avoid that.
		308
		309	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		310
		311	This is not implemented yet (and might never be).
		312
		313	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		314
		315	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		316	it's really slow, but it still scales very well (O(active_fds)).
		317
		318	Please note that solaris ports can result in a lot of spurious
		319	notifications, so you need to use non-blocking I/O or other means to avoid
		320	blocking when no data (or space) is available.
		321
		322	=item C<EVBACKEND_ALL>
		323
		324	Try all backends (even potentially broken ones that wouldn't be tried
		325	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		326	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		327
		328	=back
150		329
151	If one or more of these are ored into the flags value, then only these	330	If one or more of these are ored into the flags value, then only these
152	backends will be tried (in the reverse order as given here). If one are	331	backends will be tried (in the reverse order as given here). If none are
153	specified, any backend will do.	332	specified, most compiled-in backend will be tried, usually in reverse
		333	order of their flag values :)
154		334
155	=back	335	The most typical usage is like this:
		336
		337	if (!ev_default_loop (0))
		338	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		339
		340	Restrict libev to the select and poll backends, and do not allow
		341	environment settings to be taken into account:
		342
		343	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		344
		345	Use whatever libev has to offer, but make sure that kqueue is used if
		346	available (warning, breaks stuff, best use only with your own private
		347	event loop and only if you know the OS supports your types of fds):
		348
		349	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
156		350
157	=item struct ev_loop *ev_loop_new (unsigned int flags)	351	=item struct ev_loop *ev_loop_new (unsigned int flags)
158		352
159	Similar to C<ev_default_loop>, but always creates a new event loop that is	353	Similar to C<ev_default_loop>, but always creates a new event loop that is
160	always distinct from the default loop. Unlike the default loop, it cannot	354	always distinct from the default loop. Unlike the default loop, it cannot
161	handle signal and child watchers, and attempts to do so will be greeted by	355	handle signal and child watchers, and attempts to do so will be greeted by
162	undefined behaviour (or a failed assertion if assertions are enabled).	356	undefined behaviour (or a failed assertion if assertions are enabled).
163		357
		358	Example: try to create a event loop that uses epoll and nothing else.
		359
		360	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		361	if (!epoller)
		362	fatal ("no epoll found here, maybe it hides under your chair");
		363
164	=item ev_default_destroy ()	364	=item ev_default_destroy ()
165		365
166	Destroys the default loop again (frees all memory and kernel state	366	Destroys the default loop again (frees all memory and kernel state
167	etc.). This stops all registered event watchers (by not touching them in	367	etc.). None of the active event watchers will be stopped in the normal
168	any way whatsoever, although you cnanot rely on this :).	368	sense, so e.g. C<ev_is_active> might still return true. It is your
		369	responsibility to either stop all watchers cleanly yoursef I<before>
		370	calling this function, or cope with the fact afterwards (which is usually
		371	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		372	for example).
169		373
170	=item ev_loop_destroy (loop)	374	=item ev_loop_destroy (loop)
171		375
172	Like C<ev_default_destroy>, but destroys an event loop created by an	376	Like C<ev_default_destroy>, but destroys an event loop created by an
173	earlier call to C<ev_loop_new>.	377	earlier call to C<ev_loop_new>.
…		…
177	This function reinitialises the kernel state for backends that have	381	This function reinitialises the kernel state for backends that have
178	one. Despite the name, you can call it anytime, but it makes most sense	382	one. Despite the name, you can call it anytime, but it makes most sense
179	after forking, in either the parent or child process (or both, but that	383	after forking, in either the parent or child process (or both, but that
180	again makes little sense).	384	again makes little sense).
181		385
182	You I<must> call this function after forking if and only if you want to	386	You I<must> call this function in the child process after forking if and
183	use the event library in both processes. If you just fork+exec, you don't	387	only if you want to use the event library in both processes. If you just
184	have to call it.	388	fork+exec, you don't have to call it.
185		389
186	The function itself is quite fast and its usually not a problem to call	390	The function itself is quite fast and it's usually not a problem to call
187	it just in case after a fork. To make this easy, the function will fit in	391	it just in case after a fork. To make this easy, the function will fit in
188	quite nicely into a call to C<pthread_atfork>:	392	quite nicely into a call to C<pthread_atfork>:
189		393
190	pthread_atfork (0, 0, ev_default_fork);	394	pthread_atfork (0, 0, ev_default_fork);
		395
		396	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		397	without calling this function, so if you force one of those backends you
		398	do not need to care.
191		399
192	=item ev_loop_fork (loop)	400	=item ev_loop_fork (loop)
193		401
194	Like C<ev_default_fork>, but acts on an event loop created by	402	Like C<ev_default_fork>, but acts on an event loop created by
195	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	403	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
196	after fork, and how you do this is entirely your own problem.	404	after fork, and how you do this is entirely your own problem.
197		405
198	=item unsigned int ev_method (loop)	406	=item unsigned int ev_backend (loop)
199		407
200	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	408	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
201	use.	409	use.
202		410
203	=item ev_tstamp = ev_now (loop)	411	=item ev_tstamp ev_now (loop)
204		412
205	Returns the current "event loop time", which is the time the event loop	413	Returns the current "event loop time", which is the time the event loop
206	got events and started processing them. This timestamp does not change	414	received events and started processing them. This timestamp does not
207	as long as callbacks are being processed, and this is also the base time	415	change as long as callbacks are being processed, and this is also the base
208	used for relative timers. You can treat it as the timestamp of the event	416	time used for relative timers. You can treat it as the timestamp of the
209	occuring (or more correctly, the mainloop finding out about it).	417	event occuring (or more correctly, libev finding out about it).
210		418
211	=item ev_loop (loop, int flags)	419	=item ev_loop (loop, int flags)
212		420
213	Finally, this is it, the event handler. This function usually is called	421	Finally, this is it, the event handler. This function usually is called
214	after you initialised all your watchers and you want to start handling	422	after you initialised all your watchers and you want to start handling
215	events.	423	events.
216		424
217	If the flags argument is specified as 0, it will not return until either	425	If the flags argument is specified as C<0>, it will not return until
218	no event watchers are active anymore or C<ev_unloop> was called.	426	either no event watchers are active anymore or C<ev_unloop> was called.
		427
		428	Please note that an explicit C<ev_unloop> is usually better than
		429	relying on all watchers to be stopped when deciding when a program has
		430	finished (especially in interactive programs), but having a program that
		431	automatically loops as long as it has to and no longer by virtue of
		432	relying on its watchers stopping correctly is a thing of beauty.
219		433
220	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	434	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
221	those events and any outstanding ones, but will not block your process in	435	those events and any outstanding ones, but will not block your process in
222	case there are no events.	436	case there are no events and will return after one iteration of the loop.
223		437
224	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	438	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
225	neccessary) and will handle those and any outstanding ones. It will block	439	neccessary) and will handle those and any outstanding ones. It will block
226	your process until at least one new event arrives.	440	your process until at least one new event arrives, and will return after
		441	one iteration of the loop. This is useful if you are waiting for some
		442	external event in conjunction with something not expressible using other
		443	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		444	usually a better approach for this kind of thing.
227		445
228	This flags value could be used to implement alternative looping	446	Here are the gory details of what C<ev_loop> does:
229	constructs, but the C<prepare> and C<check> watchers provide a better and	447
230	more generic mechanism.	448	* If there are no active watchers (reference count is zero), return.
		449	- Queue prepare watchers and then call all outstanding watchers.
		450	- If we have been forked, recreate the kernel state.
		451	- Update the kernel state with all outstanding changes.
		452	- Update the "event loop time".
		453	- Calculate for how long to block.
		454	- Block the process, waiting for any events.
		455	- Queue all outstanding I/O (fd) events.
		456	- Update the "event loop time" and do time jump handling.
		457	- Queue all outstanding timers.
		458	- Queue all outstanding periodics.
		459	- If no events are pending now, queue all idle watchers.
		460	- Queue all check watchers.
		461	- Call all queued watchers in reverse order (i.e. check watchers first).
		462	Signals and child watchers are implemented as I/O watchers, and will
		463	be handled here by queueing them when their watcher gets executed.
		464	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		465	were used, return, otherwise continue with step *.
		466
		467	Example: queue some jobs and then loop until no events are outsanding
		468	anymore.
		469
		470	... queue jobs here, make sure they register event watchers as long
		471	... as they still have work to do (even an idle watcher will do..)
		472	ev_loop (my_loop, 0);
		473	... jobs done. yeah!
231		474
232	=item ev_unloop (loop, how)	475	=item ev_unloop (loop, how)
233		476
234	Can be used to make a call to C<ev_loop> return early. The C<how> argument	477	Can be used to make a call to C<ev_loop> return early (but only after it
		478	has processed all outstanding events). The C<how> argument must be either
235	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	479	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
236	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	480	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
237	calls return.
238		481
239	=item ev_ref (loop)	482	=item ev_ref (loop)
240		483
241	=item ev_unref (loop)	484	=item ev_unref (loop)
242		485
243	Ref/unref can be used to add or remove a refcount on the event loop: Every	486	Ref/unref can be used to add or remove a reference count on the event
244	watcher keeps one reference. If you have a long-runing watcher you never	487	loop: Every watcher keeps one reference, and as long as the reference
245	unregister that should not keep ev_loop from running, ev_unref() after	488	count is nonzero, C<ev_loop> will not return on its own. If you have
246	starting, and ev_ref() before stopping it. Libev itself uses this for	489	a watcher you never unregister that should not keep C<ev_loop> from
247	example for its internal signal pipe: It is not visible to you as a user	490	returning, ev_unref() after starting, and ev_ref() before stopping it. For
248	and should not keep C<ev_loop> from exiting if the work is done. It is	491	example, libev itself uses this for its internal signal pipe: It is not
249	also an excellent way to do this for generic recurring timers or from	492	visible to the libev user and should not keep C<ev_loop> from exiting if
250	within third-party libraries. Just remember to unref after start and ref	493	no event watchers registered by it are active. It is also an excellent
251	before stop.	494	way to do this for generic recurring timers or from within third-party
		495	libraries. Just remember to I<unref after start> and I<ref before stop>.
		496
		497	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		498	running when nothing else is active.
		499
		500	struct dv_signal exitsig;
		501	ev_signal_init (&exitsig, sig_cb, SIGINT);
		502	ev_signal_start (myloop, &exitsig);
		503	evf_unref (myloop);
		504
		505	Example: for some weird reason, unregister the above signal handler again.
		506
		507	ev_ref (myloop);
		508	ev_signal_stop (myloop, &exitsig);
252		509
253	=back	510	=back
		511
254		512
255	=head1 ANATOMY OF A WATCHER	513	=head1 ANATOMY OF A WATCHER
256		514
257	A watcher is a structure that you create and register to record your	515	A watcher is a structure that you create and register to record your
258	interest in some event. For instance, if you want to wait for STDIN to	516	interest in some event. For instance, if you want to wait for STDIN to
259	become readable, you would create an ev_io watcher for that:	517	become readable, you would create an C<ev_io> watcher for that:
260		518
261	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	519	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
262	{	520	{
263	ev_io_stop (w);	521	ev_io_stop (w);
264	ev_unloop (loop, EVUNLOOP_ALL);	522	ev_unloop (loop, EVUNLOOP_ALL);
…		…
291	*) >>), and you can stop watching for events at any time by calling the	549	*) >>), and you can stop watching for events at any time by calling the
292	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	550	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
293		551
294	As long as your watcher is active (has been started but not stopped) you	552	As long as your watcher is active (has been started but not stopped) you
295	must not touch the values stored in it. Most specifically you must never	553	must not touch the values stored in it. Most specifically you must never
296	reinitialise it or call its set method.	554	reinitialise it or call its C<set> macro.
297
298	You cna check wether an event is active by calling the C<ev_is_active
299	(watcher *)> macro. To see wether an event is outstanding (but the
300	callback for it has not been called yet) you cna use the C<ev_is_pending
301	(watcher *)> macro.
302		555
303	Each and every callback receives the event loop pointer as first, the	556	Each and every callback receives the event loop pointer as first, the
304	registered watcher structure as second, and a bitset of received events as	557	registered watcher structure as second, and a bitset of received events as
305	third argument.	558	third argument.
306		559
307	The rceeived events usually include a single bit per event type received	560	The received events usually include a single bit per event type received
308	(you can receive multiple events at the same time). The possible bit masks	561	(you can receive multiple events at the same time). The possible bit masks
309	are:	562	are:
310		563
311	=over 4	564	=over 4
312		565
313	=item EV_READ	566	=item C<EV_READ>
314		567
315	=item EV_WRITE	568	=item C<EV_WRITE>
316		569
317	The file descriptor in the ev_io watcher has become readable and/or	570	The file descriptor in the C<ev_io> watcher has become readable and/or
318	writable.	571	writable.
319		572
320	=item EV_TIMEOUT	573	=item C<EV_TIMEOUT>
321		574
322	The ev_timer watcher has timed out.	575	The C<ev_timer> watcher has timed out.
323		576
324	=item EV_PERIODIC	577	=item C<EV_PERIODIC>
325		578
326	The ev_periodic watcher has timed out.	579	The C<ev_periodic> watcher has timed out.
327		580
328	=item EV_SIGNAL	581	=item C<EV_SIGNAL>
329		582
330	The signal specified in the ev_signal watcher has been received by a thread.	583	The signal specified in the C<ev_signal> watcher has been received by a thread.
331		584
332	=item EV_CHILD	585	=item C<EV_CHILD>
333		586
334	The pid specified in the ev_child watcher has received a status change.	587	The pid specified in the C<ev_child> watcher has received a status change.
335		588
		589	=item C<EV_STAT>
		590
		591	The path specified in the C<ev_stat> watcher changed its attributes somehow.
		592
336	=item EV_IDLE	593	=item C<EV_IDLE>
337		594
338	The ev_idle watcher has determined that you have nothing better to do.	595	The C<ev_idle> watcher has determined that you have nothing better to do.
339		596
340	=item EV_PREPARE	597	=item C<EV_PREPARE>
341		598
342	=item EV_CHECK	599	=item C<EV_CHECK>
343		600
344	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	601	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
345	to gather new events, and all ev_check watchers are invoked just after	602	to gather new events, and all C<ev_check> watchers are invoked just after
346	C<ev_loop> has gathered them, but before it invokes any callbacks for any	603	C<ev_loop> has gathered them, but before it invokes any callbacks for any
347	received events. Callbacks of both watcher types can start and stop as	604	received events. Callbacks of both watcher types can start and stop as
348	many watchers as they want, and all of them will be taken into account	605	many watchers as they want, and all of them will be taken into account
349	(for example, a ev_prepare watcher might start an idle watcher to keep	606	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
350	C<ev_loop> from blocking).	607	C<ev_loop> from blocking).
351		608
		609	=item C<EV_EMBED>
		610
		611	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		612
		613	=item C<EV_FORK>
		614
		615	The event loop has been resumed in the child process after fork (see
		616	C<ev_fork>).
		617
352	=item EV_ERROR	618	=item C<EV_ERROR>
353		619
354	An unspecified error has occured, the watcher has been stopped. This might	620	An unspecified error has occured, the watcher has been stopped. This might
355	happen because the watcher could not be properly started because libev	621	happen because the watcher could not be properly started because libev
356	ran out of memory, a file descriptor was found to be closed or any other	622	ran out of memory, a file descriptor was found to be closed or any other
357	problem. You best act on it by reporting the problem and somehow coping	623	problem. You best act on it by reporting the problem and somehow coping
…		…
363	with the error from read() or write(). This will not work in multithreaded	629	with the error from read() or write(). This will not work in multithreaded
364	programs, though, so beware.	630	programs, though, so beware.
365		631
366	=back	632	=back
367		633
		634	=head2 GENERIC WATCHER FUNCTIONS
		635
		636	In the following description, C<TYPE> stands for the watcher type,
		637	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		638
		639	=over 4
		640
		641	=item C<ev_init> (ev_TYPE *watcher, callback)
		642
		643	This macro initialises the generic portion of a watcher. The contents
		644	of the watcher object can be arbitrary (so C<malloc> will do). Only
		645	the generic parts of the watcher are initialised, you I<need> to call
		646	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		647	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		648	which rolls both calls into one.
		649
		650	You can reinitialise a watcher at any time as long as it has been stopped
		651	(or never started) and there are no pending events outstanding.
		652
		653	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		654	int revents)>.
		655
		656	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		657
		658	This macro initialises the type-specific parts of a watcher. You need to
		659	call C<ev_init> at least once before you call this macro, but you can
		660	call C<ev_TYPE_set> any number of times. You must not, however, call this
		661	macro on a watcher that is active (it can be pending, however, which is a
		662	difference to the C<ev_init> macro).
		663
		664	Although some watcher types do not have type-specific arguments
		665	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		666
		667	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		668
		669	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		670	calls into a single call. This is the most convinient method to initialise
		671	a watcher. The same limitations apply, of course.
		672
		673	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		674
		675	Starts (activates) the given watcher. Only active watchers will receive
		676	events. If the watcher is already active nothing will happen.
		677
		678	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		679
		680	Stops the given watcher again (if active) and clears the pending
		681	status. It is possible that stopped watchers are pending (for example,
		682	non-repeating timers are being stopped when they become pending), but
		683	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		684	you want to free or reuse the memory used by the watcher it is therefore a
		685	good idea to always call its C<ev_TYPE_stop> function.
		686
		687	=item bool ev_is_active (ev_TYPE *watcher)
		688
		689	Returns a true value iff the watcher is active (i.e. it has been started
		690	and not yet been stopped). As long as a watcher is active you must not modify
		691	it.
		692
		693	=item bool ev_is_pending (ev_TYPE *watcher)
		694
		695	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		696	events but its callback has not yet been invoked). As long as a watcher
		697	is pending (but not active) you must not call an init function on it (but
		698	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		699	libev (e.g. you cnanot C<free ()> it).
		700
		701	=item callback = ev_cb (ev_TYPE *watcher)
		702
		703	Returns the callback currently set on the watcher.
		704
		705	=item ev_cb_set (ev_TYPE *watcher, callback)
		706
		707	Change the callback. You can change the callback at virtually any time
		708	(modulo threads).
		709
		710	=back
		711
		712
368	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	713	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
369		714
370	Each watcher has, by default, a member C<void *data> that you can change	715	Each watcher has, by default, a member C<void *data> that you can change
371	and read at any time, libev will completely ignore it. This cna be used	716	and read at any time, libev will completely ignore it. This can be used
372	to associate arbitrary data with your watcher. If you need more data and	717	to associate arbitrary data with your watcher. If you need more data and
373	don't want to allocate memory and store a pointer to it in that data	718	don't want to allocate memory and store a pointer to it in that data
374	member, you can also "subclass" the watcher type and provide your own	719	member, you can also "subclass" the watcher type and provide your own
375	data:	720	data:
376		721
…		…
396		741
397		742
398	=head1 WATCHER TYPES	743	=head1 WATCHER TYPES
399		744
400	This section describes each watcher in detail, but will not repeat	745	This section describes each watcher in detail, but will not repeat
401	information given in the last section.	746	information given in the last section. Any initialisation/set macros,
		747	functions and members specific to the watcher type are explained.
402		748
		749	Members are additionally marked with either I<[read-only]>, meaning that,
		750	while the watcher is active, you can look at the member and expect some
		751	sensible content, but you must not modify it (you can modify it while the
		752	watcher is stopped to your hearts content), or I<[read-write]>, which
		753	means you can expect it to have some sensible content while the watcher
		754	is active, but you can also modify it. Modifying it may not do something
		755	sensible or take immediate effect (or do anything at all), but libev will
		756	not crash or malfunction in any way.
		757
		758
403	=head2 struct ev_io - is my file descriptor readable or writable	759	=head2 C<ev_io> - is this file descriptor readable or writable?
404		760
405	I/O watchers check wether a file descriptor is readable or writable	761	I/O watchers check whether a file descriptor is readable or writable
406	in each iteration of the event loop (This behaviour is called	762	in each iteration of the event loop, or, more precisely, when reading
407	level-triggering because you keep receiving events as long as the	763	would not block the process and writing would at least be able to write
408	condition persists. Remember you cna stop the watcher if you don't want to	764	some data. This behaviour is called level-triggering because you keep
409	act on the event and neither want to receive future events).	765	receiving events as long as the condition persists. Remember you can stop
		766	the watcher if you don't want to act on the event and neither want to
		767	receive future events.
		768
		769	In general you can register as many read and/or write event watchers per
		770	fd as you want (as long as you don't confuse yourself). Setting all file
		771	descriptors to non-blocking mode is also usually a good idea (but not
		772	required if you know what you are doing).
		773
		774	You have to be careful with dup'ed file descriptors, though. Some backends
		775	(the linux epoll backend is a notable example) cannot handle dup'ed file
		776	descriptors correctly if you register interest in two or more fds pointing
		777	to the same underlying file/socket/etc. description (that is, they share
		778	the same underlying "file open").
		779
		780	If you must do this, then force the use of a known-to-be-good backend
		781	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		782	C<EVBACKEND_POLL>).
		783
		784	Another thing you have to watch out for is that it is quite easy to
		785	receive "spurious" readyness notifications, that is your callback might
		786	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		787	because there is no data. Not only are some backends known to create a
		788	lot of those (for example solaris ports), it is very easy to get into
		789	this situation even with a relatively standard program structure. Thus
		790	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		791	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		792
		793	If you cannot run the fd in non-blocking mode (for example you should not
		794	play around with an Xlib connection), then you have to seperately re-test
		795	wether a file descriptor is really ready with a known-to-be good interface
		796	such as poll (fortunately in our Xlib example, Xlib already does this on
		797	its own, so its quite safe to use).
410		798
411	=over 4	799	=over 4
412		800
413	=item ev_io_init (ev_io *, callback, int fd, int events)	801	=item ev_io_init (ev_io *, callback, int fd, int events)
414		802
415	=item ev_io_set (ev_io *, int fd, int events)	803	=item ev_io_set (ev_io *, int fd, int events)
416		804
417	Configures an ev_io watcher. The fd is the file descriptor to rceeive	805	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
418	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	806	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
419	EV_WRITE> to receive the given events.	807	C<EV_READ | EV_WRITE> to receive the given events.
		808
		809	=item int fd [read-only]
		810
		811	The file descriptor being watched.
		812
		813	=item int events [read-only]
		814
		815	The events being watched.
420		816
421	=back	817	=back
422		818
		819	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		820	readable, but only once. Since it is likely line-buffered, you could
		821	attempt to read a whole line in the callback:
		822
		823	static void
		824	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		825	{
		826	ev_io_stop (loop, w);
		827	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		828	}
		829
		830	...
		831	struct ev_loop *loop = ev_default_init (0);
		832	struct ev_io stdin_readable;
		833	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		834	ev_io_start (loop, &stdin_readable);
		835	ev_loop (loop, 0);
		836
		837
423	=head2 struct ev_timer - relative and optionally recurring timeouts	838	=head2 C<ev_timer> - relative and optionally repeating timeouts
424		839
425	Timer watchers are simple relative timers that generate an event after a	840	Timer watchers are simple relative timers that generate an event after a
426	given time, and optionally repeating in regular intervals after that.	841	given time, and optionally repeating in regular intervals after that.
427		842
428	The timers are based on real time, that is, if you register an event that	843	The timers are based on real time, that is, if you register an event that
429	times out after an hour and youreset your system clock to last years	844	times out after an hour and you reset your system clock to last years
430	time, it will still time out after (roughly) and hour. "Roughly" because	845	time, it will still time out after (roughly) and hour. "Roughly" because
431	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	846	detecting time jumps is hard, and some inaccuracies are unavoidable (the
432	monotonic clock option helps a lot here).	847	monotonic clock option helps a lot here).
		848
		849	The relative timeouts are calculated relative to the C<ev_now ()>
		850	time. This is usually the right thing as this timestamp refers to the time
		851	of the event triggering whatever timeout you are modifying/starting. If
		852	you suspect event processing to be delayed and you I<need> to base the timeout
		853	on the current time, use something like this to adjust for this:
		854
		855	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		856
		857	The callback is guarenteed to be invoked only when its timeout has passed,
		858	but if multiple timers become ready during the same loop iteration then
		859	order of execution is undefined.
433		860
434	=over 4	861	=over 4
435		862
436	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	863	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
437		864
…		…
443	later, again, and again, until stopped manually.	870	later, again, and again, until stopped manually.
444		871
445	The timer itself will do a best-effort at avoiding drift, that is, if you	872	The timer itself will do a best-effort at avoiding drift, that is, if you
446	configure a timer to trigger every 10 seconds, then it will trigger at	873	configure a timer to trigger every 10 seconds, then it will trigger at
447	exactly 10 second intervals. If, however, your program cannot keep up with	874	exactly 10 second intervals. If, however, your program cannot keep up with
448	the timer (ecause it takes longer than those 10 seconds to do stuff) the	875	the timer (because it takes longer than those 10 seconds to do stuff) the
449	timer will not fire more than once per event loop iteration.	876	timer will not fire more than once per event loop iteration.
450		877
451	=item ev_timer_again (loop)	878	=item ev_timer_again (loop)
452		879
453	This will act as if the timer timed out and restart it again if it is	880	This will act as if the timer timed out and restart it again if it is
…		…
457		884
458	If the timer is repeating, either start it if necessary (with the repeat	885	If the timer is repeating, either start it if necessary (with the repeat
459	value), or reset the running timer to the repeat value.	886	value), or reset the running timer to the repeat value.
460		887
461	This sounds a bit complicated, but here is a useful and typical	888	This sounds a bit complicated, but here is a useful and typical
462	example: Imagine you have a tcp connection and you want a so-called idle	889	example: Imagine you have a tcp connection and you want a so-called
463	timeout, that is, you want to be called when there have been, say, 60	890	idle timeout, that is, you want to be called when there have been,
464	seconds of inactivity on the socket. The easiest way to do this is to	891	say, 60 seconds of inactivity on the socket. The easiest way to do
465	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	892	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
466	time you successfully read or write some data. If you go into an idle	893	C<ev_timer_again> each time you successfully read or write some data. If
467	state where you do not expect data to travel on the socket, you can stop	894	you go into an idle state where you do not expect data to travel on the
468	the timer, and again will automatically restart it if need be.	895	socket, you can stop the timer, and again will automatically restart it if
		896	need be.
		897
		898	You can also ignore the C<after> value and C<ev_timer_start> altogether
		899	and only ever use the C<repeat> value:
		900
		901	ev_timer_init (timer, callback, 0., 5.);
		902	ev_timer_again (loop, timer);
		903	...
		904	timer->again = 17.;
		905	ev_timer_again (loop, timer);
		906	...
		907	timer->again = 10.;
		908	ev_timer_again (loop, timer);
		909
		910	This is more efficient then stopping/starting the timer eahc time you want
		911	to modify its timeout value.
		912
		913	=item ev_tstamp repeat [read-write]
		914
		915	The current C<repeat> value. Will be used each time the watcher times out
		916	or C<ev_timer_again> is called and determines the next timeout (if any),
		917	which is also when any modifications are taken into account.
469		918
470	=back	919	=back
471		920
		921	Example: create a timer that fires after 60 seconds.
		922
		923	static void
		924	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		925	{
		926	.. one minute over, w is actually stopped right here
		927	}
		928
		929	struct ev_timer mytimer;
		930	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		931	ev_timer_start (loop, &mytimer);
		932
		933	Example: create a timeout timer that times out after 10 seconds of
		934	inactivity.
		935
		936	static void
		937	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		938	{
		939	.. ten seconds without any activity
		940	}
		941
		942	struct ev_timer mytimer;
		943	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		944	ev_timer_again (&mytimer); /* start timer */
		945	ev_loop (loop, 0);
		946
		947	// and in some piece of code that gets executed on any "activity":
		948	// reset the timeout to start ticking again at 10 seconds
		949	ev_timer_again (&mytimer);
		950
		951
472	=head2 ev_periodic - to cron or not to cron it	952	=head2 C<ev_periodic> - to cron or not to cron?
473		953
474	Periodic watchers are also timers of a kind, but they are very versatile	954	Periodic watchers are also timers of a kind, but they are very versatile
475	(and unfortunately a bit complex).	955	(and unfortunately a bit complex).
476		956
477	Unlike ev_timer's, they are not based on real time (or relative time)	957	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
478	but on wallclock time (absolute time). You can tell a periodic watcher	958	but on wallclock time (absolute time). You can tell a periodic watcher
479	to trigger "at" some specific point in time. For example, if you tell a	959	to trigger "at" some specific point in time. For example, if you tell a
480	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	960	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
481	+ 10.>) and then reset your system clock to the last year, then it will	961	+ 10.>) and then reset your system clock to the last year, then it will
482	take a year to trigger the event (unlike an ev_timer, which would trigger	962	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
483	roughly 10 seconds later and of course not if you reset your system time	963	roughly 10 seconds later and of course not if you reset your system time
484	again).	964	again).
485		965
486	They can also be used to implement vastly more complex timers, such as	966	They can also be used to implement vastly more complex timers, such as
487	triggering an event on eahc midnight, local time.	967	triggering an event on eahc midnight, local time.
488		968
		969	As with timers, the callback is guarenteed to be invoked only when the
		970	time (C<at>) has been passed, but if multiple periodic timers become ready
		971	during the same loop iteration then order of execution is undefined.
		972
489	=over 4	973	=over 4
490		974
491	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	975	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
492		976
493	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	977	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
494		978
495	Lots of arguments, lets sort it out... There are basically three modes of	979	Lots of arguments, lets sort it out... There are basically three modes of
496	operation, and we will explain them from simplest to complex:	980	operation, and we will explain them from simplest to complex:
497
498		981
499	=over 4	982	=over 4
500		983
501	=item * absolute timer (interval = reschedule_cb = 0)	984	=item * absolute timer (interval = reschedule_cb = 0)
502		985
…		…
516		999
517	ev_periodic_set (&periodic, 0., 3600., 0);	1000	ev_periodic_set (&periodic, 0., 3600., 0);
518		1001
519	This doesn't mean there will always be 3600 seconds in between triggers,	1002	This doesn't mean there will always be 3600 seconds in between triggers,
520	but only that the the callback will be called when the system time shows a	1003	but only that the the callback will be called when the system time shows a
521	full hour (UTC), or more correct, when the system time is evenly divisible	1004	full hour (UTC), or more correctly, when the system time is evenly divisible
522	by 3600.	1005	by 3600.
523		1006
524	Another way to think about it (for the mathematically inclined) is that	1007	Another way to think about it (for the mathematically inclined) is that
525	ev_periodic will try to run the callback in this mode at the next possible	1008	C<ev_periodic> will try to run the callback in this mode at the next possible
526	time where C<time = at (mod interval)>, regardless of any time jumps.	1009	time where C<time = at (mod interval)>, regardless of any time jumps.
527		1010
528	=item * manual reschedule mode (reschedule_cb = callback)	1011	=item * manual reschedule mode (reschedule_cb = callback)
529		1012
530	In this mode the values for C<interval> and C<at> are both being	1013	In this mode the values for C<interval> and C<at> are both being
531	ignored. Instead, each time the periodic watcher gets scheduled, the	1014	ignored. Instead, each time the periodic watcher gets scheduled, the
532	reschedule callback will be called with the watcher as first, and the	1015	reschedule callback will be called with the watcher as first, and the
533	current time as second argument.	1016	current time as second argument.
534		1017
535	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1018	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
536	periodic watcher, ever, or make any event loop modificstions>. If you need	1019	ever, or make any event loop modifications>. If you need to stop it,
537	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	1020	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		1021	starting a prepare watcher).
538		1022
539	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1023	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
540	ev_tstamp now)>, e.g.:	1024	ev_tstamp now)>, e.g.:
541		1025
542	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1026	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
543	{	1027	{
544	return now + 60.;	1028	return now + 60.;
…		…
547	It must return the next time to trigger, based on the passed time value	1031	It must return the next time to trigger, based on the passed time value
548	(that is, the lowest time value larger than to the second argument). It	1032	(that is, the lowest time value larger than to the second argument). It
549	will usually be called just before the callback will be triggered, but	1033	will usually be called just before the callback will be triggered, but
550	might be called at other times, too.	1034	might be called at other times, too.
551		1035
		1036	NOTE: I<< This callback must always return a time that is later than the
		1037	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1038
552	This can be used to create very complex timers, such as a timer that	1039	This can be used to create very complex timers, such as a timer that
553	triggers on each midnight, local time. To do this, you would calculate the	1040	triggers on each midnight, local time. To do this, you would calculate the
554	next midnight after C<now> and return the timestamp value for this. How you do this	1041	next midnight after C<now> and return the timestamp value for this. How
555	is, again, up to you (but it is not trivial).	1042	you do this is, again, up to you (but it is not trivial, which is the main
		1043	reason I omitted it as an example).
556		1044
557	=back	1045	=back
558		1046
559	=item ev_periodic_again (loop, ev_periodic *)	1047	=item ev_periodic_again (loop, ev_periodic *)
560		1048
561	Simply stops and restarts the periodic watcher again. This is only useful	1049	Simply stops and restarts the periodic watcher again. This is only useful
562	when you changed some parameters or the reschedule callback would return	1050	when you changed some parameters or the reschedule callback would return
563	a different time than the last time it was called (e.g. in a crond like	1051	a different time than the last time it was called (e.g. in a crond like
564	program when the crontabs have changed).	1052	program when the crontabs have changed).
565		1053
		1054	=item ev_tstamp interval [read-write]
		1055
		1056	The current interval value. Can be modified any time, but changes only
		1057	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1058	called.
		1059
		1060	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1061
		1062	The current reschedule callback, or C<0>, if this functionality is
		1063	switched off. Can be changed any time, but changes only take effect when
		1064	the periodic timer fires or C<ev_periodic_again> is being called.
		1065
566	=back	1066	=back
567		1067
		1068	Example: call a callback every hour, or, more precisely, whenever the
		1069	system clock is divisible by 3600. The callback invocation times have
		1070	potentially a lot of jittering, but good long-term stability.
		1071
		1072	static void
		1073	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1074	{
		1075	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1076	}
		1077
		1078	struct ev_periodic hourly_tick;
		1079	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1080	ev_periodic_start (loop, &hourly_tick);
		1081
		1082	Example: the same as above, but use a reschedule callback to do it:
		1083
		1084	#include <math.h>
		1085
		1086	static ev_tstamp
		1087	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1088	{
		1089	return fmod (now, 3600.) + 3600.;
		1090	}
		1091
		1092	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1093
		1094	Example: call a callback every hour, starting now:
		1095
		1096	struct ev_periodic hourly_tick;
		1097	ev_periodic_init (&hourly_tick, clock_cb,
		1098	fmod (ev_now (loop), 3600.), 3600., 0);
		1099	ev_periodic_start (loop, &hourly_tick);
		1100
		1101
568	=head2 ev_signal - signal me when a signal gets signalled	1102	=head2 C<ev_signal> - signal me when a signal gets signalled!
569		1103
570	Signal watchers will trigger an event when the process receives a specific	1104	Signal watchers will trigger an event when the process receives a specific
571	signal one or more times. Even though signals are very asynchronous, libev	1105	signal one or more times. Even though signals are very asynchronous, libev
572	will try its best to deliver signals synchronously, i.e. as part of the	1106	will try it's best to deliver signals synchronously, i.e. as part of the
573	normal event processing, like any other event.	1107	normal event processing, like any other event.
574		1108
575	You cna configure as many watchers as you like per signal. Only when the	1109	You can configure as many watchers as you like per signal. Only when the
576	first watcher gets started will libev actually register a signal watcher	1110	first watcher gets started will libev actually register a signal watcher
577	with the kernel (thus it coexists with your own signal handlers as long	1111	with the kernel (thus it coexists with your own signal handlers as long
578	as you don't register any with libev). Similarly, when the last signal	1112	as you don't register any with libev). Similarly, when the last signal
579	watcher for a signal is stopped libev will reset the signal handler to	1113	watcher for a signal is stopped libev will reset the signal handler to
580	SIG_DFL (regardless of what it was set to before).	1114	SIG_DFL (regardless of what it was set to before).
…		…
586	=item ev_signal_set (ev_signal *, int signum)	1120	=item ev_signal_set (ev_signal *, int signum)
587		1121
588	Configures the watcher to trigger on the given signal number (usually one	1122	Configures the watcher to trigger on the given signal number (usually one
589	of the C<SIGxxx> constants).	1123	of the C<SIGxxx> constants).
590		1124
		1125	=item int signum [read-only]
		1126
		1127	The signal the watcher watches out for.
		1128
591	=back	1129	=back
592		1130
		1131
593	=head2 ev_child - wait for pid status changes	1132	=head2 C<ev_child> - watch out for process status changes
594		1133
595	Child watchers trigger when your process receives a SIGCHLD in response to	1134	Child watchers trigger when your process receives a SIGCHLD in response to
596	some child status changes (most typically when a child of yours dies).	1135	some child status changes (most typically when a child of yours dies).
597		1136
598	=over 4	1137	=over 4
…		…
602	=item ev_child_set (ev_child *, int pid)	1141	=item ev_child_set (ev_child *, int pid)
603		1142
604	Configures the watcher to wait for status changes of process C<pid> (or	1143	Configures the watcher to wait for status changes of process C<pid> (or
605	I<any> process if C<pid> is specified as C<0>). The callback can look	1144	I<any> process if C<pid> is specified as C<0>). The callback can look
606	at the C<rstatus> member of the C<ev_child> watcher structure to see	1145	at the C<rstatus> member of the C<ev_child> watcher structure to see
607	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1146	the status word (use the macros from C<sys/wait.h> and see your systems
608	contains the pid of the process causing the status change.	1147	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1148	process causing the status change.
		1149
		1150	=item int pid [read-only]
		1151
		1152	The process id this watcher watches out for, or C<0>, meaning any process id.
		1153
		1154	=item int rpid [read-write]
		1155
		1156	The process id that detected a status change.
		1157
		1158	=item int rstatus [read-write]
		1159
		1160	The process exit/trace status caused by C<rpid> (see your systems
		1161	C<waitpid> and C<sys/wait.h> documentation for details).
609		1162
610	=back	1163	=back
611		1164
		1165	Example: try to exit cleanly on SIGINT and SIGTERM.
		1166
		1167	static void
		1168	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1169	{
		1170	ev_unloop (loop, EVUNLOOP_ALL);
		1171	}
		1172
		1173	struct ev_signal signal_watcher;
		1174	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1175	ev_signal_start (loop, &sigint_cb);
		1176
		1177
		1178	=head2 C<ev_stat> - did the file attributes just change?
		1179
		1180	This watches a filesystem path for attribute changes. That is, it calls
		1181	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1182	compared to the last time, invoking the callback if it did.
		1183
		1184	The path does not need to exist: changing from "path exists" to "path does
		1185	not exist" is a status change like any other. The condition "path does
		1186	not exist" is signified by the C<st_nlink> field being zero (which is
		1187	otherwise always forced to be at least one) and all the other fields of
		1188	the stat buffer having unspecified contents.
		1189
		1190	Since there is no standard to do this, the portable implementation simply
		1191	calls C<stat (2)> regulalry on the path to see if it changed somehow. You
		1192	can specify a recommended polling interval for this case. If you specify
		1193	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1194	unspecified default> value will be used (which you can expect to be around
		1195	five seconds, although this might change dynamically). Libev will also
		1196	impose a minimum interval which is currently around C<0.1>, but thats
		1197	usually overkill.
		1198
		1199	This watcher type is not meant for massive numbers of stat watchers,
		1200	as even with OS-supported change notifications, this can be
		1201	resource-intensive.
		1202
		1203	At the time of this writing, no specific OS backends are implemented, but
		1204	if demand increases, at least a kqueue and inotify backend will be added.
		1205
		1206	=over 4
		1207
		1208	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1209
		1210	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1211
		1212	Configures the watcher to wait for status changes of the given
		1213	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1214	be detected and should normally be specified as C<0> to let libev choose
		1215	a suitable value. The memory pointed to by C<path> must point to the same
		1216	path for as long as the watcher is active.
		1217
		1218	The callback will be receive C<EV_STAT> when a change was detected,
		1219	relative to the attributes at the time the watcher was started (or the
		1220	last change was detected).
		1221
		1222	=item ev_stat_stat (ev_stat *)
		1223
		1224	Updates the stat buffer immediately with new values. If you change the
		1225	watched path in your callback, you could call this fucntion to avoid
		1226	detecting this change (while introducing a race condition). Can also be
		1227	useful simply to find out the new values.
		1228
		1229	=item ev_statdata attr [read-only]
		1230
		1231	The most-recently detected attributes of the file. Although the type is of
		1232	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1233	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1234	was some error while C<stat>ing the file.
		1235
		1236	=item ev_statdata prev [read-only]
		1237
		1238	The previous attributes of the file. The callback gets invoked whenever
		1239	C<prev> != C<attr>.
		1240
		1241	=item ev_tstamp interval [read-only]
		1242
		1243	The specified interval.
		1244
		1245	=item const char *path [read-only]
		1246
		1247	The filesystem path that is being watched.
		1248
		1249	=back
		1250
		1251	Example: Watch C</etc/passwd> for attribute changes.
		1252
		1253	static void
		1254	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1255	{
		1256	/* /etc/passwd changed in some way */
		1257	if (w->attr.st_nlink)
		1258	{
		1259	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1260	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1261	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1262	}
		1263	else
		1264	/* you shalt not abuse printf for puts */
		1265	puts ("wow, /etc/passwd is not there, expect problems. "
		1266	"if this is windows, they already arrived\n");
		1267	}
		1268
		1269	...
		1270	ev_stat passwd;
		1271
		1272	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1273	ev_stat_start (loop, &passwd);
		1274
		1275
612	=head2 ev_idle - when you've got nothing better to do	1276	=head2 C<ev_idle> - when you've got nothing better to do...
613		1277
614	Idle watchers trigger events when there are no other I/O or timer (or	1278	Idle watchers trigger events when there are no other events are pending
615	periodic) events pending. That is, as long as your process is busy	1279	(prepare, check and other idle watchers do not count). That is, as long
616	handling sockets or timeouts it will not be called. But when your process	1280	as your process is busy handling sockets or timeouts (or even signals,
617	is idle all idle watchers are being called again and again - until	1281	imagine) it will not be triggered. But when your process is idle all idle
		1282	watchers are being called again and again, once per event loop iteration -
618	stopped, that is, or your process receives more events.	1283	until stopped, that is, or your process receives more events and becomes
		1284	busy.
619		1285
620	The most noteworthy effect is that as long as any idle watchers are	1286	The most noteworthy effect is that as long as any idle watchers are
621	active, the process will not block when waiting for new events.	1287	active, the process will not block when waiting for new events.
622		1288
623	Apart from keeping your process non-blocking (which is a useful	1289	Apart from keeping your process non-blocking (which is a useful
…		…
633	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1299	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
634	believe me.	1300	believe me.
635		1301
636	=back	1302	=back
637		1303
638	=head2 prepare and check - your hooks into the event loop	1304	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1305	callback, free it. Alos, use no error checking, as usual.
639		1306
		1307	static void
		1308	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1309	{
		1310	free (w);
		1311	// now do something you wanted to do when the program has
		1312	// no longer asnything immediate to do.
		1313	}
		1314
		1315	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1316	ev_idle_init (idle_watcher, idle_cb);
		1317	ev_idle_start (loop, idle_cb);
		1318
		1319
		1320	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1321
640	Prepare and check watchers usually (but not always) are used in	1322	Prepare and check watchers are usually (but not always) used in tandem:
641	tandom. Prepare watchers get invoked before the process blocks and check	1323	prepare watchers get invoked before the process blocks and check watchers
642	watchers afterwards.	1324	afterwards.
643		1325
		1326	You I<must not> call C<ev_loop> or similar functions that enter
		1327	the current event loop from either C<ev_prepare> or C<ev_check>
		1328	watchers. Other loops than the current one are fine, however. The
		1329	rationale behind this is that you do not need to check for recursion in
		1330	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1331	C<ev_check> so if you have one watcher of each kind they will always be
		1332	called in pairs bracketing the blocking call.
		1333
644	Their main purpose is to integrate other event mechanisms into libev. This	1334	Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1335	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.	1336	variable changes, implement your own watchers, integrate net-snmp or a
		1337	coroutine library and lots more. They are also occasionally useful if
		1338	you cache some data and want to flush it before blocking (for example,
		1339	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1340	watcher).
647		1341
648	This is done by examining in each prepare call which file descriptors need	1342	This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1343	to be watched by the other library, registering C<ev_io> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1344	them and starting an C<ev_timer> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1345	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1346	any events that occured (by checking the pending status of all watchers
653	and call back into the library.	1347	and stopping them) and call back into the library. The I/O and timer
		1348	callbacks will never actually be called (but must be valid nevertheless,
		1349	because you never know, you know?).
654		1350
655	As another example, the perl Coro module uses these hooks to integrate	1351	As another example, the Perl Coro module uses these hooks to integrate
656	coroutines into libev programs, by yielding to other active coroutines	1352	coroutines into libev programs, by yielding to other active coroutines
657	during each prepare and only letting the process block if no coroutines	1353	during each prepare and only letting the process block if no coroutines
658	are ready to run.	1354	are ready to run (it's actually more complicated: it only runs coroutines
		1355	with priority higher than or equal to the event loop and one coroutine
		1356	of lower priority, but only once, using idle watchers to keep the event
		1357	loop from blocking if lower-priority coroutines are active, thus mapping
		1358	low-priority coroutines to idle/background tasks).
659		1359
660	=over 4	1360	=over 4
661		1361
662	=item ev_prepare_init (ev_prepare *, callback)	1362	=item ev_prepare_init (ev_prepare *, callback)
663		1363
664	=item ev_check_init (ev_check *, callback)	1364	=item ev_check_init (ev_check *, callback)
665		1365
666	Initialises and configures the prepare or check watcher - they have no	1366	Initialises and configures the prepare or check watcher - they have no
667	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1367	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
668	macros, but using them is utterly, utterly pointless.	1368	macros, but using them is utterly, utterly and completely pointless.
669		1369
670	=back	1370	=back
671		1371
		1372	Example: To include a library such as adns, you would add IO watchers
		1373	and a timeout watcher in a prepare handler, as required by libadns, and
		1374	in a check watcher, destroy them and call into libadns. What follows is
		1375	pseudo-code only of course:
		1376
		1377	static ev_io iow [nfd];
		1378	static ev_timer tw;
		1379
		1380	static void
		1381	io_cb (ev_loop *loop, ev_io *w, int revents)
		1382	{
		1383	// set the relevant poll flags
		1384	// could also call adns_processreadable etc. here
		1385	struct pollfd *fd = (struct pollfd *)w->data;
		1386	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1387	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1388	}
		1389
		1390	// create io watchers for each fd and a timer before blocking
		1391	static void
		1392	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1393	{
		1394	int timeout = 3600000;truct pollfd fds [nfd];
		1395	// actual code will need to loop here and realloc etc.
		1396	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1397
		1398	/* the callback is illegal, but won't be called as we stop during check */
		1399	ev_timer_init (&tw, 0, timeout * 1e-3);
		1400	ev_timer_start (loop, &tw);
		1401
		1402	// create on ev_io per pollfd
		1403	for (int i = 0; i < nfd; ++i)
		1404	{
		1405	ev_io_init (iow + i, io_cb, fds [i].fd,
		1406	((fds [i].events & POLLIN ? EV_READ : 0)
		1407	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1408
		1409	fds [i].revents = 0;
		1410	iow [i].data = fds + i;
		1411	ev_io_start (loop, iow + i);
		1412	}
		1413	}
		1414
		1415	// stop all watchers after blocking
		1416	static void
		1417	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1418	{
		1419	ev_timer_stop (loop, &tw);
		1420
		1421	for (int i = 0; i < nfd; ++i)
		1422	ev_io_stop (loop, iow + i);
		1423
		1424	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1425	}
		1426
		1427
		1428	=head2 C<ev_embed> - when one backend isn't enough...
		1429
		1430	This is a rather advanced watcher type that lets you embed one event loop
		1431	into another (currently only C<ev_io> events are supported in the embedded
		1432	loop, other types of watchers might be handled in a delayed or incorrect
		1433	fashion and must not be used).
		1434
		1435	There are primarily two reasons you would want that: work around bugs and
		1436	prioritise I/O.
		1437
		1438	As an example for a bug workaround, the kqueue backend might only support
		1439	sockets on some platform, so it is unusable as generic backend, but you
		1440	still want to make use of it because you have many sockets and it scales
		1441	so nicely. In this case, you would create a kqueue-based loop and embed it
		1442	into your default loop (which might use e.g. poll). Overall operation will
		1443	be a bit slower because first libev has to poll and then call kevent, but
		1444	at least you can use both at what they are best.
		1445
		1446	As for prioritising I/O: rarely you have the case where some fds have
		1447	to be watched and handled very quickly (with low latency), and even
		1448	priorities and idle watchers might have too much overhead. In this case
		1449	you would put all the high priority stuff in one loop and all the rest in
		1450	a second one, and embed the second one in the first.
		1451
		1452	As long as the watcher is active, the callback will be invoked every time
		1453	there might be events pending in the embedded loop. The callback must then
		1454	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1455	their callbacks (you could also start an idle watcher to give the embedded
		1456	loop strictly lower priority for example). You can also set the callback
		1457	to C<0>, in which case the embed watcher will automatically execute the
		1458	embedded loop sweep.
		1459
		1460	As long as the watcher is started it will automatically handle events. The
		1461	callback will be invoked whenever some events have been handled. You can
		1462	set the callback to C<0> to avoid having to specify one if you are not
		1463	interested in that.
		1464
		1465	Also, there have not currently been made special provisions for forking:
		1466	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1467	but you will also have to stop and restart any C<ev_embed> watchers
		1468	yourself.
		1469
		1470	Unfortunately, not all backends are embeddable, only the ones returned by
		1471	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1472	portable one.
		1473
		1474	So when you want to use this feature you will always have to be prepared
		1475	that you cannot get an embeddable loop. The recommended way to get around
		1476	this is to have a separate variables for your embeddable loop, try to
		1477	create it, and if that fails, use the normal loop for everything:
		1478
		1479	struct ev_loop *loop_hi = ev_default_init (0);
		1480	struct ev_loop *loop_lo = 0;
		1481	struct ev_embed embed;
		1482
		1483	// see if there is a chance of getting one that works
		1484	// (remember that a flags value of 0 means autodetection)
		1485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1487	: 0;
		1488
		1489	// if we got one, then embed it, otherwise default to loop_hi
		1490	if (loop_lo)
		1491	{
		1492	ev_embed_init (&embed, 0, loop_lo);
		1493	ev_embed_start (loop_hi, &embed);
		1494	}
		1495	else
		1496	loop_lo = loop_hi;
		1497
		1498	=over 4
		1499
		1500	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1501
		1502	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1503
		1504	Configures the watcher to embed the given loop, which must be
		1505	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1506	invoked automatically, otherwise it is the responsibility of the callback
		1507	to invoke it (it will continue to be called until the sweep has been done,
		1508	if you do not want thta, you need to temporarily stop the embed watcher).
		1509
		1510	=item ev_embed_sweep (loop, ev_embed *)
		1511
		1512	Make a single, non-blocking sweep over the embedded loop. This works
		1513	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1514	apropriate way for embedded loops.
		1515
		1516	=item struct ev_loop *loop [read-only]
		1517
		1518	The embedded event loop.
		1519
		1520	=back
		1521
		1522
		1523	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1524
		1525	Fork watchers are called when a C<fork ()> was detected (usually because
		1526	whoever is a good citizen cared to tell libev about it by calling
		1527	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1528	event loop blocks next and before C<ev_check> watchers are being called,
		1529	and only in the child after the fork. If whoever good citizen calling
		1530	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1531	handlers will be invoked, too, of course.
		1532
		1533	=over 4
		1534
		1535	=item ev_fork_init (ev_signal *, callback)
		1536
		1537	Initialises and configures the fork watcher - it has no parameters of any
		1538	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1539	believe me.
		1540
		1541	=back
		1542
		1543
672	=head1 OTHER FUNCTIONS	1544	=head1 OTHER FUNCTIONS
673		1545
674	There are some other fucntions of possible interest. Described. Here. Now.	1546	There are some other functions of possible interest. Described. Here. Now.
675		1547
676	=over 4	1548	=over 4
677		1549
678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1550	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
679		1551
680	This function combines a simple timer and an I/O watcher, calls your	1552	This function combines a simple timer and an I/O watcher, calls your
681	callback on whichever event happens first and automatically stop both	1553	callback on whichever event happens first and automatically stop both
682	watchers. This is useful if you want to wait for a single event on an fd	1554	watchers. This is useful if you want to wait for a single event on an fd
683	or timeout without havign to allocate/configure/start/stop/free one or	1555	or timeout without having to allocate/configure/start/stop/free one or
684	more watchers yourself.	1556	more watchers yourself.
685		1557
686	If C<fd> is less than 0, then no I/O watcher will be started and events is	1558	If C<fd> is less than 0, then no I/O watcher will be started and events
687	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1559	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
688	will be craeted and started.	1560	C<events> set will be craeted and started.
689		1561
690	If C<timeout> is less than 0, then no timeout watcher will be	1562	If C<timeout> is less than 0, then no timeout watcher will be
691	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1563	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
692	= 0) will be started.	1564	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1565	dubious value.
693		1566
694	The callback has the type C<void (*cb)(int revents, void *arg)> and	1567	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
695	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1568	passed an C<revents> set like normal event callbacks (a combination of
696	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1569	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1570	value passed to C<ev_once>:
697		1571
698	static void stdin_ready (int revents, void *arg)	1572	static void stdin_ready (int revents, void *arg)
699	{	1573	{
700	if (revents & EV_TIMEOUT)	1574	if (revents & EV_TIMEOUT)
701	/* doh, nothing entered */	1575	/* doh, nothing entered */;
702	else if (revents & EV_READ)	1576	else if (revents & EV_READ)
703	/* stdin might have data for us, joy! */	1577	/* stdin might have data for us, joy! */;
704	}	1578	}
705		1579
706	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1580	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
707		1581
708	=item ev_feed_event (loop, watcher, int events)	1582	=item ev_feed_event (ev_loop *, watcher *, int revents)
709		1583
710	Feeds the given event set into the event loop, as if the specified event	1584	Feeds the given event set into the event loop, as if the specified event
711	has happened for the specified watcher (which must be a pointer to an	1585	had happened for the specified watcher (which must be a pointer to an
712	initialised but not necessarily active event watcher).	1586	initialised but not necessarily started event watcher).
713		1587
714	=item ev_feed_fd_event (loop, int fd, int revents)	1588	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
715		1589
716	Feed an event on the given fd, as if a file descriptor backend detected it.	1590	Feed an event on the given fd, as if a file descriptor backend detected
		1591	the given events it.
717		1592
718	=item ev_feed_signal_event (loop, int signum)	1593	=item ev_feed_signal_event (ev_loop *loop, int signum)
719		1594
720	Feed an event as if the given signal occured (loop must be the default loop!).	1595	Feed an event as if the given signal occured (C<loop> must be the default
		1596	loop!).
721		1597
722	=back	1598	=back
723		1599
		1600
		1601	=head1 LIBEVENT EMULATION
		1602
		1603	Libev offers a compatibility emulation layer for libevent. It cannot
		1604	emulate the internals of libevent, so here are some usage hints:
		1605
		1606	=over 4
		1607
		1608	=item * Use it by including <event.h>, as usual.
		1609
		1610	=item * The following members are fully supported: ev_base, ev_callback,
		1611	ev_arg, ev_fd, ev_res, ev_events.
		1612
		1613	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1614	maintained by libev, it does not work exactly the same way as in libevent (consider
		1615	it a private API).
		1616
		1617	=item * Priorities are not currently supported. Initialising priorities
		1618	will fail and all watchers will have the same priority, even though there
		1619	is an ev_pri field.
		1620
		1621	=item * Other members are not supported.
		1622
		1623	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1624	to use the libev header file and library.
		1625
		1626	=back
		1627
		1628	=head1 C++ SUPPORT
		1629
		1630	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1631	you to use some convinience methods to start/stop watchers and also change
		1632	the callback model to a model using method callbacks on objects.
		1633
		1634	To use it,
		1635
		1636	#include <ev++.h>
		1637
		1638	(it is not installed by default). This automatically includes F<ev.h>
		1639	and puts all of its definitions (many of them macros) into the global
		1640	namespace. All C++ specific things are put into the C<ev> namespace.
		1641
		1642	It should support all the same embedding options as F<ev.h>, most notably
		1643	C<EV_MULTIPLICITY>.
		1644
		1645	Here is a list of things available in the C<ev> namespace:
		1646
		1647	=over 4
		1648
		1649	=item C<ev::READ>, C<ev::WRITE> etc.
		1650
		1651	These are just enum values with the same values as the C<EV_READ> etc.
		1652	macros from F<ev.h>.
		1653
		1654	=item C<ev::tstamp>, C<ev::now>
		1655
		1656	Aliases to the same types/functions as with the C<ev_> prefix.
		1657
		1658	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1659
		1660	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1661	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1662	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1663	defines by many implementations.
		1664
		1665	All of those classes have these methods:
		1666
		1667	=over 4
		1668
		1669	=item ev::TYPE::TYPE (object *, object::method *)
		1670
		1671	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1672
		1673	=item ev::TYPE::~TYPE
		1674
		1675	The constructor takes a pointer to an object and a method pointer to
		1676	the event handler callback to call in this class. The constructor calls
		1677	C<ev_init> for you, which means you have to call the C<set> method
		1678	before starting it. If you do not specify a loop then the constructor
		1679	automatically associates the default loop with this watcher.
		1680
		1681	The destructor automatically stops the watcher if it is active.
		1682
		1683	=item w->set (struct ev_loop *)
		1684
		1685	Associates a different C<struct ev_loop> with this watcher. You can only
		1686	do this when the watcher is inactive (and not pending either).
		1687
		1688	=item w->set ([args])
		1689
		1690	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1691	called at least once. Unlike the C counterpart, an active watcher gets
		1692	automatically stopped and restarted.
		1693
		1694	=item w->start ()
		1695
		1696	Starts the watcher. Note that there is no C<loop> argument as the
		1697	constructor already takes the loop.
		1698
		1699	=item w->stop ()
		1700
		1701	Stops the watcher if it is active. Again, no C<loop> argument.
		1702
		1703	=item w->again () C<ev::timer>, C<ev::periodic> only
		1704
		1705	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1706	C<ev_TYPE_again> function.
		1707
		1708	=item w->sweep () C<ev::embed> only
		1709
		1710	Invokes C<ev_embed_sweep>.
		1711
		1712	=item w->update () C<ev::stat> only
		1713
		1714	Invokes C<ev_stat_stat>.
		1715
		1716	=back
		1717
		1718	=back
		1719
		1720	Example: Define a class with an IO and idle watcher, start one of them in
		1721	the constructor.
		1722
		1723	class myclass
		1724	{
		1725	ev_io io; void io_cb (ev::io &w, int revents);
		1726	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1727
		1728	myclass ();
		1729	}
		1730
		1731	myclass::myclass (int fd)
		1732	: io (this, &myclass::io_cb),
		1733	idle (this, &myclass::idle_cb)
		1734	{
		1735	io.start (fd, ev::READ);
		1736	}
		1737
		1738
		1739	=head1 MACRO MAGIC
		1740
		1741	Libev can be compiled with a variety of options, the most fundemantal is
		1742	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1743	callbacks have an initial C<struct ev_loop *> argument.
		1744
		1745	To make it easier to write programs that cope with either variant, the
		1746	following macros are defined:
		1747
		1748	=over 4
		1749
		1750	=item C<EV_A>, C<EV_A_>
		1751
		1752	This provides the loop I<argument> for functions, if one is required ("ev
		1753	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1754	C<EV_A_> is used when other arguments are following. Example:
		1755
		1756	ev_unref (EV_A);
		1757	ev_timer_add (EV_A_ watcher);
		1758	ev_loop (EV_A_ 0);
		1759
		1760	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1761	which is often provided by the following macro.
		1762
		1763	=item C<EV_P>, C<EV_P_>
		1764
		1765	This provides the loop I<parameter> for functions, if one is required ("ev
		1766	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1767	C<EV_P_> is used when other parameters are following. Example:
		1768
		1769	// this is how ev_unref is being declared
		1770	static void ev_unref (EV_P);
		1771
		1772	// this is how you can declare your typical callback
		1773	static void cb (EV_P_ ev_timer *w, int revents)
		1774
		1775	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1776	suitable for use with C<EV_A>.
		1777
		1778	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1779
		1780	Similar to the other two macros, this gives you the value of the default
		1781	loop, if multiple loops are supported ("ev loop default").
		1782
		1783	=back
		1784
		1785	Example: Declare and initialise a check watcher, working regardless of
		1786	wether multiple loops are supported or not.
		1787
		1788	static void
		1789	check_cb (EV_P_ ev_timer *w, int revents)
		1790	{
		1791	ev_check_stop (EV_A_ w);
		1792	}
		1793
		1794	ev_check check;
		1795	ev_check_init (&check, check_cb);
		1796	ev_check_start (EV_DEFAULT_ &check);
		1797	ev_loop (EV_DEFAULT_ 0);
		1798
		1799
		1800	=head1 EMBEDDING
		1801
		1802	Libev can (and often is) directly embedded into host
		1803	applications. Examples of applications that embed it include the Deliantra
		1804	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1805	and rxvt-unicode.
		1806
		1807	The goal is to enable you to just copy the neecssary files into your
		1808	source directory without having to change even a single line in them, so
		1809	you can easily upgrade by simply copying (or having a checked-out copy of
		1810	libev somewhere in your source tree).
		1811
		1812	=head2 FILESETS
		1813
		1814	Depending on what features you need you need to include one or more sets of files
		1815	in your app.
		1816
		1817	=head3 CORE EVENT LOOP
		1818
		1819	To include only the libev core (all the C<ev_*> functions), with manual
		1820	configuration (no autoconf):
		1821
		1822	#define EV_STANDALONE 1
		1823	#include "ev.c"
		1824
		1825	This will automatically include F<ev.h>, too, and should be done in a
		1826	single C source file only to provide the function implementations. To use
		1827	it, do the same for F<ev.h> in all files wishing to use this API (best
		1828	done by writing a wrapper around F<ev.h> that you can include instead and
		1829	where you can put other configuration options):
		1830
		1831	#define EV_STANDALONE 1
		1832	#include "ev.h"
		1833
		1834	Both header files and implementation files can be compiled with a C++
		1835	compiler (at least, thats a stated goal, and breakage will be treated
		1836	as a bug).
		1837
		1838	You need the following files in your source tree, or in a directory
		1839	in your include path (e.g. in libev/ when using -Ilibev):
		1840
		1841	ev.h
		1842	ev.c
		1843	ev_vars.h
		1844	ev_wrap.h
		1845
		1846	ev_win32.c required on win32 platforms only
		1847
		1848	ev_select.c only when select backend is enabled (which is by default)
		1849	ev_poll.c only when poll backend is enabled (disabled by default)
		1850	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1851	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1852	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1853
		1854	F<ev.c> includes the backend files directly when enabled, so you only need
		1855	to compile this single file.
		1856
		1857	=head3 LIBEVENT COMPATIBILITY API
		1858
		1859	To include the libevent compatibility API, also include:
		1860
		1861	#include "event.c"
		1862
		1863	in the file including F<ev.c>, and:
		1864
		1865	#include "event.h"
		1866
		1867	in the files that want to use the libevent API. This also includes F<ev.h>.
		1868
		1869	You need the following additional files for this:
		1870
		1871	event.h
		1872	event.c
		1873
		1874	=head3 AUTOCONF SUPPORT
		1875
		1876	Instead of using C<EV_STANDALONE=1> and providing your config in
		1877	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1878	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1879	include F<config.h> and configure itself accordingly.
		1880
		1881	For this of course you need the m4 file:
		1882
		1883	libev.m4
		1884
		1885	=head2 PREPROCESSOR SYMBOLS/MACROS
		1886
		1887	Libev can be configured via a variety of preprocessor symbols you have to define
		1888	before including any of its files. The default is not to build for multiplicity
		1889	and only include the select backend.
		1890
		1891	=over 4
		1892
		1893	=item EV_STANDALONE
		1894
		1895	Must always be C<1> if you do not use autoconf configuration, which
		1896	keeps libev from including F<config.h>, and it also defines dummy
		1897	implementations for some libevent functions (such as logging, which is not
		1898	supported). It will also not define any of the structs usually found in
		1899	F<event.h> that are not directly supported by the libev core alone.
		1900
		1901	=item EV_USE_MONOTONIC
		1902
		1903	If defined to be C<1>, libev will try to detect the availability of the
		1904	monotonic clock option at both compiletime and runtime. Otherwise no use
		1905	of the monotonic clock option will be attempted. If you enable this, you
		1906	usually have to link against librt or something similar. Enabling it when
		1907	the functionality isn't available is safe, though, althoguh you have
		1908	to make sure you link against any libraries where the C<clock_gettime>
		1909	function is hiding in (often F<-lrt>).
		1910
		1911	=item EV_USE_REALTIME
		1912
		1913	If defined to be C<1>, libev will try to detect the availability of the
		1914	realtime clock option at compiletime (and assume its availability at
		1915	runtime if successful). Otherwise no use of the realtime clock option will
		1916	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1917	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1918	in the description of C<EV_USE_MONOTONIC>, though.
		1919
		1920	=item EV_USE_SELECT
		1921
		1922	If undefined or defined to be C<1>, libev will compile in support for the
		1923	C<select>(2) backend. No attempt at autodetection will be done: if no
		1924	other method takes over, select will be it. Otherwise the select backend
		1925	will not be compiled in.
		1926
		1927	=item EV_SELECT_USE_FD_SET
		1928
		1929	If defined to C<1>, then the select backend will use the system C<fd_set>
		1930	structure. This is useful if libev doesn't compile due to a missing
		1931	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1932	exotic systems. This usually limits the range of file descriptors to some
		1933	low limit such as 1024 or might have other limitations (winsocket only
		1934	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1935	influence the size of the C<fd_set> used.
		1936
		1937	=item EV_SELECT_IS_WINSOCKET
		1938
		1939	When defined to C<1>, the select backend will assume that
		1940	select/socket/connect etc. don't understand file descriptors but
		1941	wants osf handles on win32 (this is the case when the select to
		1942	be used is the winsock select). This means that it will call
		1943	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1944	it is assumed that all these functions actually work on fds, even
		1945	on win32. Should not be defined on non-win32 platforms.
		1946
		1947	=item EV_USE_POLL
		1948
		1949	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1950	backend. Otherwise it will be enabled on non-win32 platforms. It
		1951	takes precedence over select.
		1952
		1953	=item EV_USE_EPOLL
		1954
		1955	If defined to be C<1>, libev will compile in support for the Linux
		1956	C<epoll>(7) backend. Its availability will be detected at runtime,
		1957	otherwise another method will be used as fallback. This is the
		1958	preferred backend for GNU/Linux systems.
		1959
		1960	=item EV_USE_KQUEUE
		1961
		1962	If defined to be C<1>, libev will compile in support for the BSD style
		1963	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1964	otherwise another method will be used as fallback. This is the preferred
		1965	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1966	supports some types of fds correctly (the only platform we found that
		1967	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1968	not be used unless explicitly requested. The best way to use it is to find
		1969	out whether kqueue supports your type of fd properly and use an embedded
		1970	kqueue loop.
		1971
		1972	=item EV_USE_PORT
		1973
		1974	If defined to be C<1>, libev will compile in support for the Solaris
		1975	10 port style backend. Its availability will be detected at runtime,
		1976	otherwise another method will be used as fallback. This is the preferred
		1977	backend for Solaris 10 systems.
		1978
		1979	=item EV_USE_DEVPOLL
		1980
		1981	reserved for future expansion, works like the USE symbols above.
		1982
		1983	=item EV_H
		1984
		1985	The name of the F<ev.h> header file used to include it. The default if
		1986	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1987	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1988
		1989	=item EV_CONFIG_H
		1990
		1991	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1992	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		1993	C<EV_H>, above.
		1994
		1995	=item EV_EVENT_H
		1996
		1997	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		1998	of how the F<event.h> header can be found.
		1999
		2000	=item EV_PROTOTYPES
		2001
		2002	If defined to be C<0>, then F<ev.h> will not define any function
		2003	prototypes, but still define all the structs and other symbols. This is
		2004	occasionally useful if you want to provide your own wrapper functions
		2005	around libev functions.
		2006
		2007	=item EV_MULTIPLICITY
		2008
		2009	If undefined or defined to C<1>, then all event-loop-specific functions
		2010	will have the C<struct ev_loop *> as first argument, and you can create
		2011	additional independent event loops. Otherwise there will be no support
		2012	for multiple event loops and there is no first event loop pointer
		2013	argument. Instead, all functions act on the single default loop.
		2014
		2015	=item EV_PERIODIC_ENABLE
		2016
		2017	If undefined or defined to be C<1>, then periodic timers are supported. If
		2018	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2019	code.
		2020
		2021	=item EV_EMBED_ENABLE
		2022
		2023	If undefined or defined to be C<1>, then embed watchers are supported. If
		2024	defined to be C<0>, then they are not.
		2025
		2026	=item EV_STAT_ENABLE
		2027
		2028	If undefined or defined to be C<1>, then stat watchers are supported. If
		2029	defined to be C<0>, then they are not.
		2030
		2031	=item EV_FORK_ENABLE
		2032
		2033	If undefined or defined to be C<1>, then fork watchers are supported. If
		2034	defined to be C<0>, then they are not.
		2035
		2036	=item EV_MINIMAL
		2037
		2038	If you need to shave off some kilobytes of code at the expense of some
		2039	speed, define this symbol to C<1>. Currently only used for gcc to override
		2040	some inlining decisions, saves roughly 30% codesize of amd64.
		2041
		2042	=item EV_PID_HASHSIZE
		2043
		2044	C<ev_child> watchers use a small hash table to distribute workload by
		2045	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2046	than enough. If you need to manage thousands of children you might want to
		2047	increase this value.
		2048
		2049	=item EV_COMMON
		2050
		2051	By default, all watchers have a C<void *data> member. By redefining
		2052	this macro to a something else you can include more and other types of
		2053	members. You have to define it each time you include one of the files,
		2054	though, and it must be identical each time.
		2055
		2056	For example, the perl EV module uses something like this:
		2057
		2058	#define EV_COMMON \
		2059	SV *self; /* contains this struct */ \
		2060	SV *cb_sv, *fh /* note no trailing ";" */
		2061
		2062	=item EV_CB_DECLARE (type)
		2063
		2064	=item EV_CB_INVOKE (watcher, revents)
		2065
		2066	=item ev_set_cb (ev, cb)
		2067
		2068	Can be used to change the callback member declaration in each watcher,
		2069	and the way callbacks are invoked and set. Must expand to a struct member
		2070	definition and a statement, respectively. See the F<ev.v> header file for
		2071	their default definitions. One possible use for overriding these is to
		2072	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2073	method calls instead of plain function calls in C++.
		2074
		2075	=head2 EXAMPLES
		2076
		2077	For a real-world example of a program the includes libev
		2078	verbatim, you can have a look at the EV perl module
		2079	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2080	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2081	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2082	will be compiled. It is pretty complex because it provides its own header
		2083	file.
		2084
		2085	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2086	that everybody includes and which overrides some autoconf choices:
		2087
		2088	#define EV_USE_POLL 0
		2089	#define EV_MULTIPLICITY 0
		2090	#define EV_PERIODICS 0
		2091	#define EV_CONFIG_H <config.h>
		2092
		2093	#include "ev++.h"
		2094
		2095	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2096
		2097	#include "ev_cpp.h"
		2098	#include "ev.c"
		2099
		2100
		2101	=head1 COMPLEXITIES
		2102
		2103	In this section the complexities of (many of) the algorithms used inside
		2104	libev will be explained. For complexity discussions about backends see the
		2105	documentation for C<ev_default_init>.
		2106
		2107	=over 4
		2108
		2109	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2110
		2111	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2112
		2113	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2114
		2115	=item Stopping check/prepare/idle watchers: O(1)
		2116
		2117	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		2118
		2119	=item Finding the next timer per loop iteration: O(1)
		2120
		2121	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2122
		2123	=item Activating one watcher: O(1)
		2124
		2125	=back
		2126
		2127
724	=head1 AUTHOR	2128	=head1 AUTHOR
725		2129
726	Marc Lehmann <libev@schmorp.de>.	2130	Marc Lehmann <libev@schmorp.de>.
727		2131

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