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Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	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	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
51		106
52	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
53		108
54	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
55	library in any way.	110	library in any way.
…		…
64		119
65	=item int ev_version_major ()	120	=item int ev_version_major ()
66		121
67	=item int ev_version_minor ()	122	=item int ev_version_minor ()
68		123
69	You can find out the major and minor version numbers of the library	124	You can find out the major and minor ABI version numbers of the library
70	you linked against by calling the functions C<ev_version_major> and	125	you linked against by calling the functions C<ev_version_major> and
71	C<ev_version_minor>. If you want, you can compare against the global	126	C<ev_version_minor>. If you want, you can compare against the global
72	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
73	version of the library your program was compiled against.	128	version of the library your program was compiled against.
74		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
75	Usually, it's a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	136	not a problem.
79		137
		138	Example: Make sure we haven't accidentally been linked against the wrong
		139	version.
		140
		141	assert (("libev version mismatch",
		142	ev_version_major () == EV_VERSION_MAJOR
		143	&& ev_version_minor () >= EV_VERSION_MINOR));
		144
		145	=item unsigned int ev_supported_backends ()
		146
		147	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		148	value) compiled into this binary of libev (independent of their
		149	availability on the system you are running on). See C<ev_default_loop> for
		150	a description of the set values.
		151
		152	Example: make sure we have the epoll method, because yeah this is cool and
		153	a must have and can we have a torrent of it please!!!11
		154
		155	assert (("sorry, no epoll, no sex",
		156	ev_supported_backends () & EVBACKEND_EPOLL));
		157
		158	=item unsigned int ev_recommended_backends ()
		159
		160	Return the set of all backends compiled into this binary of libev and also
		161	recommended for this platform. This set is often smaller than the one
		162	returned by C<ev_supported_backends>, as for example kqueue is broken on
		163	most BSDs and will not be autodetected unless you explicitly request it
		164	(assuming you know what you are doing). This is the set of backends that
		165	libev will probe for if you specify no backends explicitly.
		166
		167	=item unsigned int ev_embeddable_backends ()
		168
		169	Returns the set of backends that are embeddable in other event loops. This
		170	is the theoretical, all-platform, value. To find which backends
		171	might be supported on the current system, you would need to look at
		172	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		173	recommended ones.
		174
		175	See the description of C<ev_embed> watchers for more info.
		176
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		178
82	Sets the allocation function to use (the prototype is similar to the	179	Sets the allocation function to use (the prototype is similar - the
83	realloc C function, the semantics are identical). It is used to allocate	180	semantics is identical - to the realloc C function). It is used to
84	and free memory (no surprises here). If it returns zero when memory	181	allocate and free memory (no surprises here). If it returns zero when
85	needs to be allocated, the library might abort or take some potentially	182	memory needs to be allocated, the library might abort or take some
86	destructive action. The default is your system realloc function.	183	potentially destructive action. The default is your system realloc
		184	function.
87		185
88	You could override this function in high-availability programs to, say,	186	You could override this function in high-availability programs to, say,
89	free some memory if it cannot allocate memory, to use a special allocator,	187	free some memory if it cannot allocate memory, to use a special allocator,
90	or even to sleep a while and retry until some memory is available.	188	or even to sleep a while and retry until some memory is available.
		189
		190	Example: Replace the libev allocator with one that waits a bit and then
		191	retries).
		192
		193	static void *
		194	persistent_realloc (void *ptr, size_t size)
		195	{
		196	for (;;)
		197	{
		198	void *newptr = realloc (ptr, size);
		199
		200	if (newptr)
		201	return newptr;
		202
		203	sleep (60);
		204	}
		205	}
		206
		207	...
		208	ev_set_allocator (persistent_realloc);
91		209
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	210	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		211
94	Set the callback function to call on a retryable syscall error (such	212	Set the callback function to call on a retryable syscall error (such
95	as failed select, poll, epoll_wait). The message is a printable string	213	as failed select, poll, epoll_wait). The message is a printable string
…		…
97	callback is set, then libev will expect it to remedy the sitution, no	215	callback is set, then libev will expect it to remedy the sitution, no
98	matter what, when it returns. That is, libev will generally retry the	216	matter what, when it returns. That is, libev will generally retry the
99	requested operation, or, if the condition doesn't go away, do bad stuff	217	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	218	(such as abort).
101		219
		220	Example: This is basically the same thing that libev does internally, too.
		221
		222	static void
		223	fatal_error (const char *msg)
		224	{
		225	perror (msg);
		226	abort ();
		227	}
		228
		229	...
		230	ev_set_syserr_cb (fatal_error);
		231
102	=back	232	=back
103		233
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		235
106	An event loop is described by a C<struct ev_loop *>. The library knows two	236	An event loop is described by a C<struct ev_loop *>. The library knows two
…		…
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	249	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		250
121	This will initialise the default event loop if it hasn't been initialised	251	This will initialise the default event loop if it hasn't been initialised
122	yet and return it. If the default loop could not be initialised, returns	252	yet and return it. If the default loop could not be initialised, returns
123	false. If it already was initialised it simply returns it (and ignores the	253	false. If it already was initialised it simply returns it (and ignores the
124	flags).	254	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		255
126	If you don't know what event loop to use, use the one returned from this	256	If you don't know what event loop to use, use the one returned from this
127	function.	257	function.
128		258
129	The flags argument can be used to specify special behaviour or specific	259	The flags argument can be used to specify special behaviour or specific
130	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		261
132	It supports the following flags:	262	The following flags are supported:
133		263
134	=over 4	264	=over 4
135		265
136	=item C<EVFLAG_AUTO>	266	=item C<EVFLAG_AUTO>
137		267
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	276	override the flags completely if it is found in the environment. This is
147	useful to try out specific backends to test their performance, or to work	277	useful to try out specific backends to test their performance, or to work
148	around bugs.	278	around bugs.
149		279
		280	=item C<EVFLAG_FORKCHECK>
		281
		282	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		283	a fork, you can also make libev check for a fork in each iteration by
		284	enabling this flag.
		285
		286	This works by calling C<getpid ()> on every iteration of the loop,
		287	and thus this might slow down your event loop if you do a lot of loop
		288	iterations and little real work, but is usually not noticeable (on my
		289	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		290	without a syscall and thus I<very> fast, but my Linux system also has
		291	C<pthread_atfork> which is even faster).
		292
		293	The big advantage of this flag is that you can forget about fork (and
		294	forget about forgetting to tell libev about forking) when you use this
		295	flag.
		296
		297	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		298	environment variable.
		299
150	=item C<EVMETHOD_SELECT> (portable select backend)	300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		301
		302	This is your standard select(2) backend. Not I<completely> standard, as
		303	libev tries to roll its own fd_set with no limits on the number of fds,
		304	but if that fails, expect a fairly low limit on the number of fds when
		305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		306	the fastest backend for a low number of fds.
		307
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		309
154	=item C<EVMETHOD_EPOLL> (linux only)	310	And this is your standard poll(2) backend. It's more complicated than
		311	select, but handles sparse fds better and has no artificial limit on the
		312	number of fds you can use (except it will slow down considerably with a
		313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
155		314
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	315	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		316
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	317	For few fds, this backend is a bit little slower than poll and select,
		318	but it scales phenomenally better. While poll and select usually scale
		319	like O(total_fds) where n is the total number of fds (or the highest fd),
		320	epoll scales either O(1) or O(active_fds). The epoll design has a number
		321	of shortcomings, such as silently dropping events in some hard-to-detect
		322	cases and rewuiring a syscall per fd change, no fork support and bad
		323	support for dup:
159		324
160	=item C<EVMETHOD_PORT> (solaris 10 only)	325	While stopping, setting and starting an I/O watcher in the same iteration
		326	will result in some caching, there is still a syscall per such incident
		327	(because the fd could point to a different file description now), so its
		328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
		329	very well if you register events for both fds.
		330
		331	Please note that epoll sometimes generates spurious notifications, so you
		332	need to use non-blocking I/O or other means to avoid blocking when no data
		333	(or space) is available.
		334
		335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		336
		337	Kqueue deserves special mention, as at the time of this writing, it
		338	was broken on I<all> BSDs (usually it doesn't work with anything but
		339	sockets and pipes, except on Darwin, where of course it's completely
		340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
		341	is used by default there). For this reason it's not being "autodetected"
		342	unless you explicitly specify it explicitly in the flags (i.e. using
		343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		344	system like NetBSD.
		345
		346	It scales in the same way as the epoll backend, but the interface to the
		347	kernel is more efficient (which says nothing about its actual speed,
		348	of course). While stopping, setting and starting an I/O watcher does
		349	never cause an extra syscall as with epoll, it still adds up to two event
		350	changes per incident, support for C<fork ()> is very bad and it drops fds
		351	silently in similarly hard-to-detetc cases.
		352
		353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		354
		355	This is not implemented yet (and might never be).
		356
		357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		358
		359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
		360	it's really slow, but it still scales very well (O(active_fds)).
		361
		362	Please note that solaris event ports can deliver a lot of spurious
		363	notifications, so you need to use non-blocking I/O or other means to avoid
		364	blocking when no data (or space) is available.
		365
		366	=item C<EVBACKEND_ALL>
		367
		368	Try all backends (even potentially broken ones that wouldn't be tried
		369	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		371
		372	=back
161		373
162	If one or more of these are ored into the flags value, then only these	374	If one or more of these are ored into the flags value, then only these
163	backends will be tried (in the reverse order as given here). If one are	375	backends will be tried (in the reverse order as given here). If none are
164	specified, any backend will do.	376	specified, most compiled-in backend will be tried, usually in reverse
		377	order of their flag values :)
165		378
166	=back	379	The most typical usage is like this:
		380
		381	if (!ev_default_loop (0))
		382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		383
		384	Restrict libev to the select and poll backends, and do not allow
		385	environment settings to be taken into account:
		386
		387	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		388
		389	Use whatever libev has to offer, but make sure that kqueue is used if
		390	available (warning, breaks stuff, best use only with your own private
		391	event loop and only if you know the OS supports your types of fds):
		392
		393	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
167		394
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	395	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		396
170	Similar to C<ev_default_loop>, but always creates a new event loop that is	397	Similar to C<ev_default_loop>, but always creates a new event loop that is
171	always distinct from the default loop. Unlike the default loop, it cannot	398	always distinct from the default loop. Unlike the default loop, it cannot
172	handle signal and child watchers, and attempts to do so will be greeted by	399	handle signal and child watchers, and attempts to do so will be greeted by
173	undefined behaviour (or a failed assertion if assertions are enabled).	400	undefined behaviour (or a failed assertion if assertions are enabled).
174		401
		402	Example: Try to create a event loop that uses epoll and nothing else.
		403
		404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		405	if (!epoller)
		406	fatal ("no epoll found here, maybe it hides under your chair");
		407
175	=item ev_default_destroy ()	408	=item ev_default_destroy ()
176		409
177	Destroys the default loop again (frees all memory and kernel state	410	Destroys the default loop again (frees all memory and kernel state
178	etc.). This stops all registered event watchers (by not touching them in	411	etc.). None of the active event watchers will be stopped in the normal
179	any way whatsoever, although you cannot rely on this :).	412	sense, so e.g. C<ev_is_active> might still return true. It is your
		413	responsibility to either stop all watchers cleanly yoursef I<before>
		414	calling this function, or cope with the fact afterwards (which is usually
		415	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		416	for example).
		417
		418	Note that certain global state, such as signal state, will not be freed by
		419	this function, and related watchers (such as signal and child watchers)
		420	would need to be stopped manually.
		421
		422	In general it is not advisable to call this function except in the
		423	rare occasion where you really need to free e.g. the signal handling
		424	pipe fds. If you need dynamically allocated loops it is better to use
		425	C<ev_loop_new> and C<ev_loop_destroy>).
180		426
181	=item ev_loop_destroy (loop)	427	=item ev_loop_destroy (loop)
182		428
183	Like C<ev_default_destroy>, but destroys an event loop created by an	429	Like C<ev_default_destroy>, but destroys an event loop created by an
184	earlier call to C<ev_loop_new>.	430	earlier call to C<ev_loop_new>.
…		…
188	This function reinitialises the kernel state for backends that have	434	This function reinitialises the kernel state for backends that have
189	one. Despite the name, you can call it anytime, but it makes most sense	435	one. Despite the name, you can call it anytime, but it makes most sense
190	after forking, in either the parent or child process (or both, but that	436	after forking, in either the parent or child process (or both, but that
191	again makes little sense).	437	again makes little sense).
192		438
193	You I<must> call this function after forking if and only if you want to	439	You I<must> call this function in the child process after forking if and
194	use the event library in both processes. If you just fork+exec, you don't	440	only if you want to use the event library in both processes. If you just
195	have to call it.	441	fork+exec, you don't have to call it.
196		442
197	The function itself is quite fast and it's usually not a problem to call	443	The function itself is quite fast and it's usually not a problem to call
198	it just in case after a fork. To make this easy, the function will fit in	444	it just in case after a fork. To make this easy, the function will fit in
199	quite nicely into a call to C<pthread_atfork>:	445	quite nicely into a call to C<pthread_atfork>:
200		446
201	pthread_atfork (0, 0, ev_default_fork);	447	pthread_atfork (0, 0, ev_default_fork);
202		448
		449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		450	without calling this function, so if you force one of those backends you
		451	do not need to care.
		452
203	=item ev_loop_fork (loop)	453	=item ev_loop_fork (loop)
204		454
205	Like C<ev_default_fork>, but acts on an event loop created by	455	Like C<ev_default_fork>, but acts on an event loop created by
206	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	456	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
207	after fork, and how you do this is entirely your own problem.	457	after fork, and how you do this is entirely your own problem.
208		458
		459	=item unsigned int ev_loop_count (loop)
		460
		461	Returns the count of loop iterations for the loop, which is identical to
		462	the number of times libev did poll for new events. It starts at C<0> and
		463	happily wraps around with enough iterations.
		464
		465	This value can sometimes be useful as a generation counter of sorts (it
		466	"ticks" the number of loop iterations), as it roughly corresponds with
		467	C<ev_prepare> and C<ev_check> calls.
		468
209	=item unsigned int ev_method (loop)	469	=item unsigned int ev_backend (loop)
210		470
211	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	471	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
212	use.	472	use.
213		473
214	=item ev_tstamp ev_now (loop)	474	=item ev_tstamp ev_now (loop)
215		475
216	Returns the current "event loop time", which is the time the event loop	476	Returns the current "event loop time", which is the time the event loop
217	got events and started processing them. This timestamp does not change	477	received events and started processing them. This timestamp does not
218	as long as callbacks are being processed, and this is also the base time	478	change as long as callbacks are being processed, and this is also the base
219	used for relative timers. You can treat it as the timestamp of the event	479	time used for relative timers. You can treat it as the timestamp of the
220	occuring (or more correctly, the mainloop finding out about it).	480	event occurring (or more correctly, libev finding out about it).
221		481
222	=item ev_loop (loop, int flags)	482	=item ev_loop (loop, int flags)
223		483
224	Finally, this is it, the event handler. This function usually is called	484	Finally, this is it, the event handler. This function usually is called
225	after you initialised all your watchers and you want to start handling	485	after you initialised all your watchers and you want to start handling
226	events.	486	events.
227		487
228	If the flags argument is specified as 0, it will not return until either	488	If the flags argument is specified as C<0>, it will not return until
229	no event watchers are active anymore or C<ev_unloop> was called.	489	either no event watchers are active anymore or C<ev_unloop> was called.
		490
		491	Please note that an explicit C<ev_unloop> is usually better than
		492	relying on all watchers to be stopped when deciding when a program has
		493	finished (especially in interactive programs), but having a program that
		494	automatically loops as long as it has to and no longer by virtue of
		495	relying on its watchers stopping correctly is a thing of beauty.
230		496
231	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	497	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
232	those events and any outstanding ones, but will not block your process in	498	those events and any outstanding ones, but will not block your process in
233	case there are no events and will return after one iteration of the loop.	499	case there are no events and will return after one iteration of the loop.
234		500
235	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	501	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
236	neccessary) and will handle those and any outstanding ones. It will block	502	neccessary) and will handle those and any outstanding ones. It will block
237	your process until at least one new event arrives, and will return after	503	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	504	one iteration of the loop. This is useful if you are waiting for some
		505	external event in conjunction with something not expressible using other
		506	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		507	usually a better approach for this kind of thing.
239		508
240	This flags value could be used to implement alternative looping
241	constructs, but the C<prepare> and C<check> watchers provide a better and
242	more generic mechanism.
243
244	Here are the gory details of what ev_loop does:	509	Here are the gory details of what C<ev_loop> does:
245		510
		511	- Before the first iteration, call any pending watchers.
246	1. If there are no active watchers (reference count is zero), return.	512	* If there are no active watchers (reference count is zero), return.
247	2. Queue and immediately call all prepare watchers.	513	- Queue all prepare watchers and then call all outstanding watchers.
248	3. If we have been forked, recreate the kernel state.	514	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	515	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	516	- Update the "event loop time".
251	6. Calculate for how long to block.	517	- Calculate for how long to block.
252	7. Block the process, waiting for events.	518	- Block the process, waiting for any events.
		519	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	520	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	521	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	522	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	523	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	524	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	525	- Call all queued watchers in reverse order (i.e. check watchers first).
		526	Signals and child watchers are implemented as I/O watchers, and will
		527	be handled here by queueing them when their watcher gets executed.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	529	were used, return, otherwise continue with step *.
		530
		531	Example: Queue some jobs and then loop until no events are outsanding
		532	anymore.
		533
		534	... queue jobs here, make sure they register event watchers as long
		535	... as they still have work to do (even an idle watcher will do..)
		536	ev_loop (my_loop, 0);
		537	... jobs done. yeah!
261		538
262	=item ev_unloop (loop, how)	539	=item ev_unloop (loop, how)
263		540
264	Can be used to make a call to C<ev_loop> return early (but only after it	541	Can be used to make a call to C<ev_loop> return early (but only after it
265	has processed all outstanding events). The C<how> argument must be either	542	has processed all outstanding events). The C<how> argument must be either
…		…
279	visible to the libev user and should not keep C<ev_loop> from exiting if	556	visible to the libev user and should not keep C<ev_loop> from exiting if
280	no event watchers registered by it are active. It is also an excellent	557	no event watchers registered by it are active. It is also an excellent
281	way to do this for generic recurring timers or from within third-party	558	way to do this for generic recurring timers or from within third-party
282	libraries. Just remember to I<unref after start> and I<ref before stop>.	559	libraries. Just remember to I<unref after start> and I<ref before stop>.
283		560
		561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		562	running when nothing else is active.
		563
		564	struct ev_signal exitsig;
		565	ev_signal_init (&exitsig, sig_cb, SIGINT);
		566	ev_signal_start (loop, &exitsig);
		567	evf_unref (loop);
		568
		569	Example: For some weird reason, unregister the above signal handler again.
		570
		571	ev_ref (loop);
		572	ev_signal_stop (loop, &exitsig);
		573
284	=back	574	=back
		575
285		576
286	=head1 ANATOMY OF A WATCHER	577	=head1 ANATOMY OF A WATCHER
287		578
288	A watcher is a structure that you create and register to record your	579	A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	580	interest in some event. For instance, if you want to wait for STDIN to
…		…
322	*) >>), and you can stop watching for events at any time by calling the	613	*) >>), and you can stop watching for events at any time by calling the
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	614	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		615
325	As long as your watcher is active (has been started but not stopped) you	616	As long as your watcher is active (has been started but not stopped) you
326	must not touch the values stored in it. Most specifically you must never	617	must not touch the values stored in it. Most specifically you must never
327	reinitialise it or call its set method.	618	reinitialise it or call its C<set> macro.
328
329	You can check whether an event is active by calling the C<ev_is_active
330	(watcher *)> macro. To see whether an event is outstanding (but the
331	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.
333		619
334	Each and every callback receives the event loop pointer as first, the	620	Each and every callback receives the event loop pointer as first, the
335	registered watcher structure as second, and a bitset of received events as	621	registered watcher structure as second, and a bitset of received events as
336	third argument.	622	third argument.
337		623
…		…
361	The signal specified in the C<ev_signal> watcher has been received by a thread.	647	The signal specified in the C<ev_signal> watcher has been received by a thread.
362		648
363	=item C<EV_CHILD>	649	=item C<EV_CHILD>
364		650
365	The pid specified in the C<ev_child> watcher has received a status change.	651	The pid specified in the C<ev_child> watcher has received a status change.
		652
		653	=item C<EV_STAT>
		654
		655	The path specified in the C<ev_stat> watcher changed its attributes somehow.
366		656
367	=item C<EV_IDLE>	657	=item C<EV_IDLE>
368		658
369	The C<ev_idle> watcher has determined that you have nothing better to do.	659	The C<ev_idle> watcher has determined that you have nothing better to do.
370		660
…		…
378	received events. Callbacks of both watcher types can start and stop as	668	received events. Callbacks of both watcher types can start and stop as
379	many watchers as they want, and all of them will be taken into account	669	many watchers as they want, and all of them will be taken into account
380	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	670	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
381	C<ev_loop> from blocking).	671	C<ev_loop> from blocking).
382		672
		673	=item C<EV_EMBED>
		674
		675	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		676
		677	=item C<EV_FORK>
		678
		679	The event loop has been resumed in the child process after fork (see
		680	C<ev_fork>).
		681
383	=item C<EV_ERROR>	682	=item C<EV_ERROR>
384		683
385	An unspecified error has occured, the watcher has been stopped. This might	684	An unspecified error has occured, the watcher has been stopped. This might
386	happen because the watcher could not be properly started because libev	685	happen because the watcher could not be properly started because libev
387	ran out of memory, a file descriptor was found to be closed or any other	686	ran out of memory, a file descriptor was found to be closed or any other
…		…
393	your callbacks is well-written it can just attempt the operation and cope	692	your callbacks is well-written it can just attempt the operation and cope
394	with the error from read() or write(). This will not work in multithreaded	693	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.	694	programs, though, so beware.
396		695
397	=back	696	=back
		697
		698	=head2 GENERIC WATCHER FUNCTIONS
		699
		700	In the following description, C<TYPE> stands for the watcher type,
		701	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		702
		703	=over 4
		704
		705	=item C<ev_init> (ev_TYPE *watcher, callback)
		706
		707	This macro initialises the generic portion of a watcher. The contents
		708	of the watcher object can be arbitrary (so C<malloc> will do). Only
		709	the generic parts of the watcher are initialised, you I<need> to call
		710	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		711	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		712	which rolls both calls into one.
		713
		714	You can reinitialise a watcher at any time as long as it has been stopped
		715	(or never started) and there are no pending events outstanding.
		716
		717	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		718	int revents)>.
		719
		720	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		721
		722	This macro initialises the type-specific parts of a watcher. You need to
		723	call C<ev_init> at least once before you call this macro, but you can
		724	call C<ev_TYPE_set> any number of times. You must not, however, call this
		725	macro on a watcher that is active (it can be pending, however, which is a
		726	difference to the C<ev_init> macro).
		727
		728	Although some watcher types do not have type-specific arguments
		729	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		730
		731	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		732
		733	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		734	calls into a single call. This is the most convinient method to initialise
		735	a watcher. The same limitations apply, of course.
		736
		737	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		738
		739	Starts (activates) the given watcher. Only active watchers will receive
		740	events. If the watcher is already active nothing will happen.
		741
		742	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		743
		744	Stops the given watcher again (if active) and clears the pending
		745	status. It is possible that stopped watchers are pending (for example,
		746	non-repeating timers are being stopped when they become pending), but
		747	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		748	you want to free or reuse the memory used by the watcher it is therefore a
		749	good idea to always call its C<ev_TYPE_stop> function.
		750
		751	=item bool ev_is_active (ev_TYPE *watcher)
		752
		753	Returns a true value iff the watcher is active (i.e. it has been started
		754	and not yet been stopped). As long as a watcher is active you must not modify
		755	it.
		756
		757	=item bool ev_is_pending (ev_TYPE *watcher)
		758
		759	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		760	events but its callback has not yet been invoked). As long as a watcher
		761	is pending (but not active) you must not call an init function on it (but
		762	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		763	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		764	it).
		765
		766	=item callback ev_cb (ev_TYPE *watcher)
		767
		768	Returns the callback currently set on the watcher.
		769
		770	=item ev_cb_set (ev_TYPE *watcher, callback)
		771
		772	Change the callback. You can change the callback at virtually any time
		773	(modulo threads).
		774
		775	=item ev_set_priority (ev_TYPE *watcher, priority)
		776
		777	=item int ev_priority (ev_TYPE *watcher)
		778
		779	Set and query the priority of the watcher. The priority is a small
		780	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		781	(default: C<-2>). Pending watchers with higher priority will be invoked
		782	before watchers with lower priority, but priority will not keep watchers
		783	from being executed (except for C<ev_idle> watchers).
		784
		785	This means that priorities are I<only> used for ordering callback
		786	invocation after new events have been received. This is useful, for
		787	example, to reduce latency after idling, or more often, to bind two
		788	watchers on the same event and make sure one is called first.
		789
		790	If you need to suppress invocation when higher priority events are pending
		791	you need to look at C<ev_idle> watchers, which provide this functionality.
		792
		793	You I<must not> change the priority of a watcher as long as it is active or
		794	pending.
		795
		796	The default priority used by watchers when no priority has been set is
		797	always C<0>, which is supposed to not be too high and not be too low :).
		798
		799	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		800	fine, as long as you do not mind that the priority value you query might
		801	or might not have been adjusted to be within valid range.
		802
		803	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		804
		805	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		806	C<loop> nor C<revents> need to be valid as long as the watcher callback
		807	can deal with that fact.
		808
		809	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		810
		811	If the watcher is pending, this function returns clears its pending status
		812	and returns its C<revents> bitset (as if its callback was invoked). If the
		813	watcher isn't pending it does nothing and returns C<0>.
		814
		815	=back
		816
398		817
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	818	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		819
401	Each watcher has, by default, a member C<void *data> that you can change	820	Each watcher has, by default, a member C<void *data> that you can change
402	and read at any time, libev will completely ignore it. This can be used	821	and read at any time, libev will completely ignore it. This can be used
…		…
420	{	839	{
421	struct my_io *w = (struct my_io *)w_;	840	struct my_io *w = (struct my_io *)w_;
422	...	841	...
423	}	842	}
424		843
425	More interesting and less C-conformant ways of catsing your callback type	844	More interesting and less C-conformant ways of casting your callback type
426	have been omitted....	845	instead have been omitted.
		846
		847	Another common scenario is having some data structure with multiple
		848	watchers:
		849
		850	struct my_biggy
		851	{
		852	int some_data;
		853	ev_timer t1;
		854	ev_timer t2;
		855	}
		856
		857	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		858	you need to use C<offsetof>:
		859
		860	#include <stddef.h>
		861
		862	static void
		863	t1_cb (EV_P_ struct ev_timer *w, int revents)
		864	{
		865	struct my_biggy big = (struct my_biggy *
		866	(((char *)w) - offsetof (struct my_biggy, t1));
		867	}
		868
		869	static void
		870	t2_cb (EV_P_ struct ev_timer *w, int revents)
		871	{
		872	struct my_biggy big = (struct my_biggy *
		873	(((char *)w) - offsetof (struct my_biggy, t2));
		874	}
427		875
428		876
429	=head1 WATCHER TYPES	877	=head1 WATCHER TYPES
430		878
431	This section describes each watcher in detail, but will not repeat	879	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	880	information given in the last section. Any initialisation/set macros,
		881	functions and members specific to the watcher type are explained.
433		882
		883	Members are additionally marked with either I<[read-only]>, meaning that,
		884	while the watcher is active, you can look at the member and expect some
		885	sensible content, but you must not modify it (you can modify it while the
		886	watcher is stopped to your hearts content), or I<[read-write]>, which
		887	means you can expect it to have some sensible content while the watcher
		888	is active, but you can also modify it. Modifying it may not do something
		889	sensible or take immediate effect (or do anything at all), but libev will
		890	not crash or malfunction in any way.
		891
		892
434	=head2 C<ev_io> - is this file descriptor readable or writable	893	=head2 C<ev_io> - is this file descriptor readable or writable?
435		894
436	I/O watchers check whether a file descriptor is readable or writable	895	I/O watchers check whether a file descriptor is readable or writable
437	in each iteration of the event loop (This behaviour is called	896	in each iteration of the event loop, or, more precisely, when reading
438	level-triggering because you keep receiving events as long as the	897	would not block the process and writing would at least be able to write
439	condition persists. Remember you can stop the watcher if you don't want to	898	some data. This behaviour is called level-triggering because you keep
440	act on the event and neither want to receive future events).	899	receiving events as long as the condition persists. Remember you can stop
		900	the watcher if you don't want to act on the event and neither want to
		901	receive future events.
441		902
442	In general you can register as many read and/or write event watchers per	903	In general you can register as many read and/or write event watchers per
443	fd as you want (as long as you don't confuse yourself). Setting all file	904	fd as you want (as long as you don't confuse yourself). Setting all file
444	descriptors to non-blocking mode is also usually a good idea (but not	905	descriptors to non-blocking mode is also usually a good idea (but not
445	required if you know what you are doing).	906	required if you know what you are doing).
446		907
447	You have to be careful with dup'ed file descriptors, though. Some backends	908	You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	909	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	910	descriptors correctly if you register interest in two or more fds pointing
450	to the same underlying file/socket etc. description (that is, they share	911	to the same underlying file/socket/etc. description (that is, they share
451	the same underlying "file open").	912	the same underlying "file open").
452		913
453	If you must do this, then force the use of a known-to-be-good backend	914	If you must do this, then force the use of a known-to-be-good backend
454	(at the time of this writing, this includes only EVMETHOD_SELECT and	915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	916	C<EVBACKEND_POLL>).
		917
		918	Another thing you have to watch out for is that it is quite easy to
		919	receive "spurious" readyness notifications, that is your callback might
		920	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		921	because there is no data. Not only are some backends known to create a
		922	lot of those (for example solaris ports), it is very easy to get into
		923	this situation even with a relatively standard program structure. Thus
		924	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		925	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		926
		927	If you cannot run the fd in non-blocking mode (for example you should not
		928	play around with an Xlib connection), then you have to seperately re-test
		929	whether a file descriptor is really ready with a known-to-be good interface
		930	such as poll (fortunately in our Xlib example, Xlib already does this on
		931	its own, so its quite safe to use).
		932
		933	=head3 The special problem of disappearing file descriptors
		934
		935	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		936	descriptor (either by calling C<close> explicitly or by any other means,
		937	such as C<dup>). The reason is that you register interest in some file
		938	descriptor, but when it goes away, the operating system will silently drop
		939	this interest. If another file descriptor with the same number then is
		940	registered with libev, there is no efficient way to see that this is, in
		941	fact, a different file descriptor.
		942
		943	To avoid having to explicitly tell libev about such cases, libev follows
		944	the following policy: Each time C<ev_io_set> is being called, libev
		945	will assume that this is potentially a new file descriptor, otherwise
		946	it is assumed that the file descriptor stays the same. That means that
		947	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		948	descriptor even if the file descriptor number itself did not change.
		949
		950	This is how one would do it normally anyway, the important point is that
		951	the libev application should not optimise around libev but should leave
		952	optimisations to libev.
		953
		954	=head3 Ths special problem of dup'ed file descriptors
		955
		956	Some backends (e.g. epoll), cannot register events for file descriptors,
		957	but only events for the underlying file descriptions. That menas when you
		958	have C<dup ()>'ed file descriptors and register events for them, only one
		959	file descriptor might actually receive events.
		960
		961	There is no workaorund possible except not registering events
		962	for potentially C<dup ()>'ed file descriptors or to resort to
		963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		964
		965	=head3 The special problem of fork
		966
		967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		968	useless behaviour. Libev fully supports fork, but needs to be told about
		969	it in the child.
		970
		971	To support fork in your programs, you either have to call
		972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		974	C<EVBACKEND_POLL>.
		975
		976
		977	=head3 Watcher-Specific Functions
456		978
457	=over 4	979	=over 4
458		980
459	=item ev_io_init (ev_io *, callback, int fd, int events)	981	=item ev_io_init (ev_io *, callback, int fd, int events)
460		982
461	=item ev_io_set (ev_io *, int fd, int events)	983	=item ev_io_set (ev_io *, int fd, int events)
462		984
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	985	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
464	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	986	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
465	EV_WRITE> to receive the given events.	987	C<EV_READ | EV_WRITE> to receive the given events.
		988
		989	=item int fd [read-only]
		990
		991	The file descriptor being watched.
		992
		993	=item int events [read-only]
		994
		995	The events being watched.
466		996
467	=back	997	=back
468		998
		999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		1000	readable, but only once. Since it is likely line-buffered, you could
		1001	attempt to read a whole line in the callback.
		1002
		1003	static void
		1004	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1005	{
		1006	ev_io_stop (loop, w);
		1007	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		1008	}
		1009
		1010	...
		1011	struct ev_loop *loop = ev_default_init (0);
		1012	struct ev_io stdin_readable;
		1013	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		1014	ev_io_start (loop, &stdin_readable);
		1015	ev_loop (loop, 0);
		1016
		1017
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	1018	=head2 C<ev_timer> - relative and optionally repeating timeouts
470		1019
471	Timer watchers are simple relative timers that generate an event after a	1020	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	1021	given time, and optionally repeating in regular intervals after that.
473		1022
474	The timers are based on real time, that is, if you register an event that	1023	The timers are based on real time, that is, if you register an event that
475	times out after an hour and you reset your system clock to last years	1024	times out after an hour and you reset your system clock to last years
476	time, it will still time out after (roughly) and hour. "Roughly" because	1025	time, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	1026	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	1027	monotonic clock option helps a lot here).
479		1028
480	The relative timeouts are calculated relative to the C<ev_now ()>	1029	The relative timeouts are calculated relative to the C<ev_now ()>
481	time. This is usually the right thing as this timestamp refers to the time	1030	time. This is usually the right thing as this timestamp refers to the time
482	of the event triggering whatever timeout you are modifying/starting. If	1031	of the event triggering whatever timeout you are modifying/starting. If
483	you suspect event processing to be delayed and you *need* to base the timeout	1032	you suspect event processing to be delayed and you I<need> to base the timeout
484	on the current time, use something like this to adjust for this:	1033	on the current time, use something like this to adjust for this:
485		1034
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1036
		1037	The callback is guarenteed to be invoked only when its timeout has passed,
		1038	but if multiple timers become ready during the same loop iteration then
		1039	order of execution is undefined.
		1040
		1041	=head3 Watcher-Specific Functions and Data Members
487		1042
488	=over 4	1043	=over 4
489		1044
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1045	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		1046
…		…
505	=item ev_timer_again (loop)	1060	=item ev_timer_again (loop)
506		1061
507	This will act as if the timer timed out and restart it again if it is	1062	This will act as if the timer timed out and restart it again if it is
508	repeating. The exact semantics are:	1063	repeating. The exact semantics are:
509		1064
		1065	If the timer is pending, its pending status is cleared.
		1066
510	If the timer is started but nonrepeating, stop it.	1067	If the timer is started but nonrepeating, stop it (as if it timed out).
511		1068
512	If the timer is repeating, either start it if necessary (with the repeat	1069	If the timer is repeating, either start it if necessary (with the
513	value), or reset the running timer to the repeat value.	1070	C<repeat> value), or reset the running timer to the C<repeat> value.
514		1071
515	This sounds a bit complicated, but here is a useful and typical	1072	This sounds a bit complicated, but here is a useful and typical
516	example: Imagine you have a tcp connection and you want a so-called idle	1073	example: Imagine you have a tcp connection and you want a so-called idle
517	timeout, that is, you want to be called when there have been, say, 60	1074	timeout, that is, you want to be called when there have been, say, 60
518	seconds of inactivity on the socket. The easiest way to do this is to	1075	seconds of inactivity on the socket. The easiest way to do this is to
519	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1076	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
520	time you successfully read or write some data. If you go into an idle	1077	C<ev_timer_again> each time you successfully read or write some data. If
521	state where you do not expect data to travel on the socket, you can stop	1078	you go into an idle state where you do not expect data to travel on the
522	the timer, and again will automatically restart it if need be.	1079	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1080	automatically restart it if need be.
		1081
		1082	That means you can ignore the C<after> value and C<ev_timer_start>
		1083	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1084
		1085	ev_timer_init (timer, callback, 0., 5.);
		1086	ev_timer_again (loop, timer);
		1087	...
		1088	timer->again = 17.;
		1089	ev_timer_again (loop, timer);
		1090	...
		1091	timer->again = 10.;
		1092	ev_timer_again (loop, timer);
		1093
		1094	This is more slightly efficient then stopping/starting the timer each time
		1095	you want to modify its timeout value.
		1096
		1097	=item ev_tstamp repeat [read-write]
		1098
		1099	The current C<repeat> value. Will be used each time the watcher times out
		1100	or C<ev_timer_again> is called and determines the next timeout (if any),
		1101	which is also when any modifications are taken into account.
523		1102
524	=back	1103	=back
525		1104
		1105	Example: Create a timer that fires after 60 seconds.
		1106
		1107	static void
		1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1109	{
		1110	.. one minute over, w is actually stopped right here
		1111	}
		1112
		1113	struct ev_timer mytimer;
		1114	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1115	ev_timer_start (loop, &mytimer);
		1116
		1117	Example: Create a timeout timer that times out after 10 seconds of
		1118	inactivity.
		1119
		1120	static void
		1121	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1122	{
		1123	.. ten seconds without any activity
		1124	}
		1125
		1126	struct ev_timer mytimer;
		1127	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1128	ev_timer_again (&mytimer); /* start timer */
		1129	ev_loop (loop, 0);
		1130
		1131	// and in some piece of code that gets executed on any "activity":
		1132	// reset the timeout to start ticking again at 10 seconds
		1133	ev_timer_again (&mytimer);
		1134
		1135
526	=head2 C<ev_periodic> - to cron or not to cron	1136	=head2 C<ev_periodic> - to cron or not to cron?
527		1137
528	Periodic watchers are also timers of a kind, but they are very versatile	1138	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	1139	(and unfortunately a bit complex).
530		1140
531	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1141	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
532	but on wallclock time (absolute time). You can tell a periodic watcher	1142	but on wallclock time (absolute time). You can tell a periodic watcher
533	to trigger "at" some specific point in time. For example, if you tell a	1143	to trigger "at" some specific point in time. For example, if you tell a
534	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1144	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
535	+ 10.>) and then reset your system clock to the last year, then it will	1145	+ 10.>) and then reset your system clock to the last year, then it will
536	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1146	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
537	roughly 10 seconds later and of course not if you reset your system time	1147	roughly 10 seconds later).
538	again).
539		1148
540	They can also be used to implement vastly more complex timers, such as	1149	They can also be used to implement vastly more complex timers, such as
541	triggering an event on eahc midnight, local time.	1150	triggering an event on each midnight, local time or other, complicated,
		1151	rules.
		1152
		1153	As with timers, the callback is guarenteed to be invoked only when the
		1154	time (C<at>) has been passed, but if multiple periodic timers become ready
		1155	during the same loop iteration then order of execution is undefined.
		1156
		1157	=head3 Watcher-Specific Functions and Data Members
542		1158
543	=over 4	1159	=over 4
544		1160
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1161	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		1162
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1163	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		1164
549	Lots of arguments, lets sort it out... There are basically three modes of	1165	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	1166	operation, and we will explain them from simplest to complex:
551		1167
552
553	=over 4	1168	=over 4
554		1169
555	=item * absolute timer (interval = reschedule_cb = 0)	1170	=item * absolute timer (at = time, interval = reschedule_cb = 0)
556		1171
557	In this configuration the watcher triggers an event at the wallclock time	1172	In this configuration the watcher triggers an event at the wallclock time
558	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
559	that is, if it is to be run at January 1st 2011 then it will run when the	1174	that is, if it is to be run at January 1st 2011 then it will run when the
560	system time reaches or surpasses this time.	1175	system time reaches or surpasses this time.
561		1176
562	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
563		1178
564	In this mode the watcher will always be scheduled to time out at the next	1179	In this mode the watcher will always be scheduled to time out at the next
565	C<at + N * interval> time (for some integer N) and then repeat, regardless	1180	C<at + N * interval> time (for some integer N, which can also be negative)
566	of any time jumps.	1181	and then repeat, regardless of any time jumps.
567		1182
568	This can be used to create timers that do not drift with respect to system	1183	This can be used to create timers that do not drift with respect to system
569	time:	1184	time:
570		1185
571	ev_periodic_set (&periodic, 0., 3600., 0);	1186	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
577		1192
578	Another way to think about it (for the mathematically inclined) is that	1193	Another way to think about it (for the mathematically inclined) is that
579	C<ev_periodic> will try to run the callback in this mode at the next possible	1194	C<ev_periodic> will try to run the callback in this mode at the next possible
580	time where C<time = at (mod interval)>, regardless of any time jumps.	1195	time where C<time = at (mod interval)>, regardless of any time jumps.
581		1196
		1197	For numerical stability it is preferable that the C<at> value is near
		1198	C<ev_now ()> (the current time), but there is no range requirement for
		1199	this value.
		1200
582	=item * manual reschedule mode (reschedule_cb = callback)	1201	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
583		1202
584	In this mode the values for C<interval> and C<at> are both being	1203	In this mode the values for C<interval> and C<at> are both being
585	ignored. Instead, each time the periodic watcher gets scheduled, the	1204	ignored. Instead, each time the periodic watcher gets scheduled, the
586	reschedule callback will be called with the watcher as first, and the	1205	reschedule callback will be called with the watcher as first, and the
587	current time as second argument.	1206	current time as second argument.
588		1207
589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1208	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
590	ever, or make any event loop modifications>. If you need to stop it,	1209	ever, or make any event loop modifications>. If you need to stop it,
591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1210	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
592	starting a prepare watcher).	1211	starting an C<ev_prepare> watcher, which is legal).
593		1212
594	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1213	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
595	ev_tstamp now)>, e.g.:	1214	ev_tstamp now)>, e.g.:
596		1215
597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1216	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
620	Simply stops and restarts the periodic watcher again. This is only useful	1239	Simply stops and restarts the periodic watcher again. This is only useful
621	when you changed some parameters or the reschedule callback would return	1240	when you changed some parameters or the reschedule callback would return
622	a different time than the last time it was called (e.g. in a crond like	1241	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	1242	program when the crontabs have changed).
624		1243
		1244	=item ev_tstamp offset [read-write]
		1245
		1246	When repeating, this contains the offset value, otherwise this is the
		1247	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1248
		1249	Can be modified any time, but changes only take effect when the periodic
		1250	timer fires or C<ev_periodic_again> is being called.
		1251
		1252	=item ev_tstamp interval [read-write]
		1253
		1254	The current interval value. Can be modified any time, but changes only
		1255	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1256	called.
		1257
		1258	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1259
		1260	The current reschedule callback, or C<0>, if this functionality is
		1261	switched off. Can be changed any time, but changes only take effect when
		1262	the periodic timer fires or C<ev_periodic_again> is being called.
		1263
		1264	=item ev_tstamp at [read-only]
		1265
		1266	When active, contains the absolute time that the watcher is supposed to
		1267	trigger next.
		1268
625	=back	1269	=back
626		1270
		1271	Example: Call a callback every hour, or, more precisely, whenever the
		1272	system clock is divisible by 3600. The callback invocation times have
		1273	potentially a lot of jittering, but good long-term stability.
		1274
		1275	static void
		1276	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1277	{
		1278	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1279	}
		1280
		1281	struct ev_periodic hourly_tick;
		1282	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1283	ev_periodic_start (loop, &hourly_tick);
		1284
		1285	Example: The same as above, but use a reschedule callback to do it:
		1286
		1287	#include <math.h>
		1288
		1289	static ev_tstamp
		1290	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1291	{
		1292	return fmod (now, 3600.) + 3600.;
		1293	}
		1294
		1295	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1296
		1297	Example: Call a callback every hour, starting now:
		1298
		1299	struct ev_periodic hourly_tick;
		1300	ev_periodic_init (&hourly_tick, clock_cb,
		1301	fmod (ev_now (loop), 3600.), 3600., 0);
		1302	ev_periodic_start (loop, &hourly_tick);
		1303
		1304
627	=head2 C<ev_signal> - signal me when a signal gets signalled	1305	=head2 C<ev_signal> - signal me when a signal gets signalled!
628		1306
629	Signal watchers will trigger an event when the process receives a specific	1307	Signal watchers will trigger an event when the process receives a specific
630	signal one or more times. Even though signals are very asynchronous, libev	1308	signal one or more times. Even though signals are very asynchronous, libev
631	will try it's best to deliver signals synchronously, i.e. as part of the	1309	will try it's best to deliver signals synchronously, i.e. as part of the
632	normal event processing, like any other event.	1310	normal event processing, like any other event.
…		…
636	with the kernel (thus it coexists with your own signal handlers as long	1314	with the kernel (thus it coexists with your own signal handlers as long
637	as you don't register any with libev). Similarly, when the last signal	1315	as you don't register any with libev). Similarly, when the last signal
638	watcher for a signal is stopped libev will reset the signal handler to	1316	watcher for a signal is stopped libev will reset the signal handler to
639	SIG_DFL (regardless of what it was set to before).	1317	SIG_DFL (regardless of what it was set to before).
640		1318
		1319	=head3 Watcher-Specific Functions and Data Members
		1320
641	=over 4	1321	=over 4
642		1322
643	=item ev_signal_init (ev_signal *, callback, int signum)	1323	=item ev_signal_init (ev_signal *, callback, int signum)
644		1324
645	=item ev_signal_set (ev_signal *, int signum)	1325	=item ev_signal_set (ev_signal *, int signum)
646		1326
647	Configures the watcher to trigger on the given signal number (usually one	1327	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1328	of the C<SIGxxx> constants).
649		1329
		1330	=item int signum [read-only]
		1331
		1332	The signal the watcher watches out for.
		1333
650	=back	1334	=back
651		1335
		1336
652	=head2 C<ev_child> - wait for pid status changes	1337	=head2 C<ev_child> - watch out for process status changes
653		1338
654	Child watchers trigger when your process receives a SIGCHLD in response to	1339	Child watchers trigger when your process receives a SIGCHLD in response to
655	some child status changes (most typically when a child of yours dies).	1340	some child status changes (most typically when a child of yours dies).
		1341
		1342	=head3 Watcher-Specific Functions and Data Members
656		1343
657	=over 4	1344	=over 4
658		1345
659	=item ev_child_init (ev_child *, callback, int pid)	1346	=item ev_child_init (ev_child *, callback, int pid)
660		1347
…		…
665	at the C<rstatus> member of the C<ev_child> watcher structure to see	1352	at the C<rstatus> member of the C<ev_child> watcher structure to see
666	the status word (use the macros from C<sys/wait.h> and see your systems	1353	the status word (use the macros from C<sys/wait.h> and see your systems
667	C<waitpid> documentation). The C<rpid> member contains the pid of the	1354	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1355	process causing the status change.
669		1356
		1357	=item int pid [read-only]
		1358
		1359	The process id this watcher watches out for, or C<0>, meaning any process id.
		1360
		1361	=item int rpid [read-write]
		1362
		1363	The process id that detected a status change.
		1364
		1365	=item int rstatus [read-write]
		1366
		1367	The process exit/trace status caused by C<rpid> (see your systems
		1368	C<waitpid> and C<sys/wait.h> documentation for details).
		1369
670	=back	1370	=back
671		1371
		1372	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1373
		1374	static void
		1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1376	{
		1377	ev_unloop (loop, EVUNLOOP_ALL);
		1378	}
		1379
		1380	struct ev_signal signal_watcher;
		1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1382	ev_signal_start (loop, &sigint_cb);
		1383
		1384
		1385	=head2 C<ev_stat> - did the file attributes just change?
		1386
		1387	This watches a filesystem path for attribute changes. That is, it calls
		1388	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1389	compared to the last time, invoking the callback if it did.
		1390
		1391	The path does not need to exist: changing from "path exists" to "path does
		1392	not exist" is a status change like any other. The condition "path does
		1393	not exist" is signified by the C<st_nlink> field being zero (which is
		1394	otherwise always forced to be at least one) and all the other fields of
		1395	the stat buffer having unspecified contents.
		1396
		1397	The path I<should> be absolute and I<must not> end in a slash. If it is
		1398	relative and your working directory changes, the behaviour is undefined.
		1399
		1400	Since there is no standard to do this, the portable implementation simply
		1401	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1402	can specify a recommended polling interval for this case. If you specify
		1403	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1404	unspecified default> value will be used (which you can expect to be around
		1405	five seconds, although this might change dynamically). Libev will also
		1406	impose a minimum interval which is currently around C<0.1>, but thats
		1407	usually overkill.
		1408
		1409	This watcher type is not meant for massive numbers of stat watchers,
		1410	as even with OS-supported change notifications, this can be
		1411	resource-intensive.
		1412
		1413	At the time of this writing, only the Linux inotify interface is
		1414	implemented (implementing kqueue support is left as an exercise for the
		1415	reader). Inotify will be used to give hints only and should not change the
		1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1417	to fall back to regular polling again even with inotify, but changes are
		1418	usually detected immediately, and if the file exists there will be no
		1419	polling.
		1420
		1421	=head3 Watcher-Specific Functions and Data Members
		1422
		1423	=over 4
		1424
		1425	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1426
		1427	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1428
		1429	Configures the watcher to wait for status changes of the given
		1430	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1431	be detected and should normally be specified as C<0> to let libev choose
		1432	a suitable value. The memory pointed to by C<path> must point to the same
		1433	path for as long as the watcher is active.
		1434
		1435	The callback will be receive C<EV_STAT> when a change was detected,
		1436	relative to the attributes at the time the watcher was started (or the
		1437	last change was detected).
		1438
		1439	=item ev_stat_stat (ev_stat *)
		1440
		1441	Updates the stat buffer immediately with new values. If you change the
		1442	watched path in your callback, you could call this fucntion to avoid
		1443	detecting this change (while introducing a race condition). Can also be
		1444	useful simply to find out the new values.
		1445
		1446	=item ev_statdata attr [read-only]
		1447
		1448	The most-recently detected attributes of the file. Although the type is of
		1449	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1450	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1451	was some error while C<stat>ing the file.
		1452
		1453	=item ev_statdata prev [read-only]
		1454
		1455	The previous attributes of the file. The callback gets invoked whenever
		1456	C<prev> != C<attr>.
		1457
		1458	=item ev_tstamp interval [read-only]
		1459
		1460	The specified interval.
		1461
		1462	=item const char *path [read-only]
		1463
		1464	The filesystem path that is being watched.
		1465
		1466	=back
		1467
		1468	Example: Watch C</etc/passwd> for attribute changes.
		1469
		1470	static void
		1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1472	{
		1473	/* /etc/passwd changed in some way */
		1474	if (w->attr.st_nlink)
		1475	{
		1476	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1477	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1478	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1479	}
		1480	else
		1481	/* you shalt not abuse printf for puts */
		1482	puts ("wow, /etc/passwd is not there, expect problems. "
		1483	"if this is windows, they already arrived\n");
		1484	}
		1485
		1486	...
		1487	ev_stat passwd;
		1488
		1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1490	ev_stat_start (loop, &passwd);
		1491
		1492
672	=head2 C<ev_idle> - when you've got nothing better to do	1493	=head2 C<ev_idle> - when you've got nothing better to do...
673		1494
674	Idle watchers trigger events when there are no other events are pending	1495	Idle watchers trigger events when no other events of the same or higher
675	(prepare, check and other idle watchers do not count). That is, as long	1496	priority are pending (prepare, check and other idle watchers do not
676	as your process is busy handling sockets or timeouts (or even signals,	1497	count).
677	imagine) it will not be triggered. But when your process is idle all idle	1498
678	watchers are being called again and again, once per event loop iteration -	1499	That is, as long as your process is busy handling sockets or timeouts
		1500	(or even signals, imagine) of the same or higher priority it will not be
		1501	triggered. But when your process is idle (or only lower-priority watchers
		1502	are pending), the idle watchers are being called once per event loop
679	until stopped, that is, or your process receives more events and becomes	1503	iteration - until stopped, that is, or your process receives more events
680	busy.	1504	and becomes busy again with higher priority stuff.
681		1505
682	The most noteworthy effect is that as long as any idle watchers are	1506	The most noteworthy effect is that as long as any idle watchers are
683	active, the process will not block when waiting for new events.	1507	active, the process will not block when waiting for new events.
684		1508
685	Apart from keeping your process non-blocking (which is a useful	1509	Apart from keeping your process non-blocking (which is a useful
686	effect on its own sometimes), idle watchers are a good place to do	1510	effect on its own sometimes), idle watchers are a good place to do
687	"pseudo-background processing", or delay processing stuff to after the	1511	"pseudo-background processing", or delay processing stuff to after the
688	event loop has handled all outstanding events.	1512	event loop has handled all outstanding events.
689		1513
		1514	=head3 Watcher-Specific Functions and Data Members
		1515
690	=over 4	1516	=over 4
691		1517
692	=item ev_idle_init (ev_signal *, callback)	1518	=item ev_idle_init (ev_signal *, callback)
693		1519
694	Initialises and configures the idle watcher - it has no parameters of any	1520	Initialises and configures the idle watcher - it has no parameters of any
695	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1522	believe me.
697		1523
698	=back	1524	=back
699		1525
		1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1527	callback, free it. Also, use no error checking, as usual.
		1528
		1529	static void
		1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1531	{
		1532	free (w);
		1533	// now do something you wanted to do when the program has
		1534	// no longer asnything immediate to do.
		1535	}
		1536
		1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1538	ev_idle_init (idle_watcher, idle_cb);
		1539	ev_idle_start (loop, idle_cb);
		1540
		1541
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1542	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
701		1543
702	Prepare and check watchers are usually (but not always) used in tandem:	1544	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1545	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1546	afterwards.
705		1547
		1548	You I<must not> call C<ev_loop> or similar functions that enter
		1549	the current event loop from either C<ev_prepare> or C<ev_check>
		1550	watchers. Other loops than the current one are fine, however. The
		1551	rationale behind this is that you do not need to check for recursion in
		1552	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1553	C<ev_check> so if you have one watcher of each kind they will always be
		1554	called in pairs bracketing the blocking call.
		1555
706	Their main purpose is to integrate other event mechanisms into libev. This	1556	Their main purpose is to integrate other event mechanisms into libev and
707	could be used, for example, to track variable changes, implement your own	1557	their use is somewhat advanced. This could be used, for example, to track
708	watchers, integrate net-snmp or a coroutine library and lots more.	1558	variable changes, implement your own watchers, integrate net-snmp or a
		1559	coroutine library and lots more. They are also occasionally useful if
		1560	you cache some data and want to flush it before blocking (for example,
		1561	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1562	watcher).
709		1563
710	This is done by examining in each prepare call which file descriptors need	1564	This is done by examining in each prepare call which file descriptors need
711	to be watched by the other library, registering C<ev_io> watchers for	1565	to be watched by the other library, registering C<ev_io> watchers for
712	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1566	them and starting an C<ev_timer> watcher for any timeouts (many libraries
713	provide just this functionality). Then, in the check watcher you check for	1567	provide just this functionality). Then, in the check watcher you check for
…		…
723	with priority higher than or equal to the event loop and one coroutine	1577	with priority higher than or equal to the event loop and one coroutine
724	of lower priority, but only once, using idle watchers to keep the event	1578	of lower priority, but only once, using idle watchers to keep the event
725	loop from blocking if lower-priority coroutines are active, thus mapping	1579	loop from blocking if lower-priority coroutines are active, thus mapping
726	low-priority coroutines to idle/background tasks).	1580	low-priority coroutines to idle/background tasks).
727		1581
		1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1583	priority, to ensure that they are being run before any other watchers
		1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1585	too) should not activate ("feed") events into libev. While libev fully
		1586	supports this, they will be called before other C<ev_check> watchers did
		1587	their job. As C<ev_check> watchers are often used to embed other event
		1588	loops those other event loops might be in an unusable state until their
		1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1590	others).
		1591
		1592	=head3 Watcher-Specific Functions and Data Members
		1593
728	=over 4	1594	=over 4
729		1595
730	=item ev_prepare_init (ev_prepare *, callback)	1596	=item ev_prepare_init (ev_prepare *, callback)
731		1597
732	=item ev_check_init (ev_check *, callback)	1598	=item ev_check_init (ev_check *, callback)
…		…
734	Initialises and configures the prepare or check watcher - they have no	1600	Initialises and configures the prepare or check watcher - they have no
735	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
736	macros, but using them is utterly, utterly and completely pointless.	1602	macros, but using them is utterly, utterly and completely pointless.
737		1603
738	=back	1604	=back
		1605
		1606	There are a number of principal ways to embed other event loops or modules
		1607	into libev. Here are some ideas on how to include libadns into libev
		1608	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1609	use for an actually working example. Another Perl module named C<EV::Glib>
		1610	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1611	into the Glib event loop).
		1612
		1613	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1614	and in a check watcher, destroy them and call into libadns. What follows
		1615	is pseudo-code only of course. This requires you to either use a low
		1616	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1617	the callbacks for the IO/timeout watchers might not have been called yet.
		1618
		1619	static ev_io iow [nfd];
		1620	static ev_timer tw;
		1621
		1622	static void
		1623	io_cb (ev_loop *loop, ev_io *w, int revents)
		1624	{
		1625	}
		1626
		1627	// create io watchers for each fd and a timer before blocking
		1628	static void
		1629	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1630	{
		1631	int timeout = 3600000;
		1632	struct pollfd fds [nfd];
		1633	// actual code will need to loop here and realloc etc.
		1634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1635
		1636	/* the callback is illegal, but won't be called as we stop during check */
		1637	ev_timer_init (&tw, 0, timeout * 1e-3);
		1638	ev_timer_start (loop, &tw);
		1639
		1640	// create one ev_io per pollfd
		1641	for (int i = 0; i < nfd; ++i)
		1642	{
		1643	ev_io_init (iow + i, io_cb, fds [i].fd,
		1644	((fds [i].events & POLLIN ? EV_READ : 0)
		1645	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1646
		1647	fds [i].revents = 0;
		1648	ev_io_start (loop, iow + i);
		1649	}
		1650	}
		1651
		1652	// stop all watchers after blocking
		1653	static void
		1654	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1655	{
		1656	ev_timer_stop (loop, &tw);
		1657
		1658	for (int i = 0; i < nfd; ++i)
		1659	{
		1660	// set the relevant poll flags
		1661	// could also call adns_processreadable etc. here
		1662	struct pollfd *fd = fds + i;
		1663	int revents = ev_clear_pending (iow + i);
		1664	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1665	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1666
		1667	// now stop the watcher
		1668	ev_io_stop (loop, iow + i);
		1669	}
		1670
		1671	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1672	}
		1673
		1674	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1675	in the prepare watcher and would dispose of the check watcher.
		1676
		1677	Method 3: If the module to be embedded supports explicit event
		1678	notification (adns does), you can also make use of the actual watcher
		1679	callbacks, and only destroy/create the watchers in the prepare watcher.
		1680
		1681	static void
		1682	timer_cb (EV_P_ ev_timer *w, int revents)
		1683	{
		1684	adns_state ads = (adns_state)w->data;
		1685	update_now (EV_A);
		1686
		1687	adns_processtimeouts (ads, &tv_now);
		1688	}
		1689
		1690	static void
		1691	io_cb (EV_P_ ev_io *w, int revents)
		1692	{
		1693	adns_state ads = (adns_state)w->data;
		1694	update_now (EV_A);
		1695
		1696	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1697	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1698	}
		1699
		1700	// do not ever call adns_afterpoll
		1701
		1702	Method 4: Do not use a prepare or check watcher because the module you
		1703	want to embed is too inflexible to support it. Instead, youc na override
		1704	their poll function. The drawback with this solution is that the main
		1705	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1706	this.
		1707
		1708	static gint
		1709	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1710	{
		1711	int got_events = 0;
		1712
		1713	for (n = 0; n < nfds; ++n)
		1714	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1715
		1716	if (timeout >= 0)
		1717	// create/start timer
		1718
		1719	// poll
		1720	ev_loop (EV_A_ 0);
		1721
		1722	// stop timer again
		1723	if (timeout >= 0)
		1724	ev_timer_stop (EV_A_ &to);
		1725
		1726	// stop io watchers again - their callbacks should have set
		1727	for (n = 0; n < nfds; ++n)
		1728	ev_io_stop (EV_A_ iow [n]);
		1729
		1730	return got_events;
		1731	}
		1732
		1733
		1734	=head2 C<ev_embed> - when one backend isn't enough...
		1735
		1736	This is a rather advanced watcher type that lets you embed one event loop
		1737	into another (currently only C<ev_io> events are supported in the embedded
		1738	loop, other types of watchers might be handled in a delayed or incorrect
		1739	fashion and must not be used). (See portability notes, below).
		1740
		1741	There are primarily two reasons you would want that: work around bugs and
		1742	prioritise I/O.
		1743
		1744	As an example for a bug workaround, the kqueue backend might only support
		1745	sockets on some platform, so it is unusable as generic backend, but you
		1746	still want to make use of it because you have many sockets and it scales
		1747	so nicely. In this case, you would create a kqueue-based loop and embed it
		1748	into your default loop (which might use e.g. poll). Overall operation will
		1749	be a bit slower because first libev has to poll and then call kevent, but
		1750	at least you can use both at what they are best.
		1751
		1752	As for prioritising I/O: rarely you have the case where some fds have
		1753	to be watched and handled very quickly (with low latency), and even
		1754	priorities and idle watchers might have too much overhead. In this case
		1755	you would put all the high priority stuff in one loop and all the rest in
		1756	a second one, and embed the second one in the first.
		1757
		1758	As long as the watcher is active, the callback will be invoked every time
		1759	there might be events pending in the embedded loop. The callback must then
		1760	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1761	their callbacks (you could also start an idle watcher to give the embedded
		1762	loop strictly lower priority for example). You can also set the callback
		1763	to C<0>, in which case the embed watcher will automatically execute the
		1764	embedded loop sweep.
		1765
		1766	As long as the watcher is started it will automatically handle events. The
		1767	callback will be invoked whenever some events have been handled. You can
		1768	set the callback to C<0> to avoid having to specify one if you are not
		1769	interested in that.
		1770
		1771	Also, there have not currently been made special provisions for forking:
		1772	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1773	but you will also have to stop and restart any C<ev_embed> watchers
		1774	yourself.
		1775
		1776	Unfortunately, not all backends are embeddable, only the ones returned by
		1777	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1778	portable one.
		1779
		1780	So when you want to use this feature you will always have to be prepared
		1781	that you cannot get an embeddable loop. The recommended way to get around
		1782	this is to have a separate variables for your embeddable loop, try to
		1783	create it, and if that fails, use the normal loop for everything:
		1784
		1785	struct ev_loop *loop_hi = ev_default_init (0);
		1786	struct ev_loop *loop_lo = 0;
		1787	struct ev_embed embed;
		1788
		1789	// see if there is a chance of getting one that works
		1790	// (remember that a flags value of 0 means autodetection)
		1791	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1792	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1793	: 0;
		1794
		1795	// if we got one, then embed it, otherwise default to loop_hi
		1796	if (loop_lo)
		1797	{
		1798	ev_embed_init (&embed, 0, loop_lo);
		1799	ev_embed_start (loop_hi, &embed);
		1800	}
		1801	else
		1802	loop_lo = loop_hi;
		1803
		1804	=head2 Portability notes
		1805
		1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1807	tried, in various ways. Usually the embedded event loop will simply never
		1808	receive events, sometimes it will only trigger a few times, sometimes in a
		1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1810	will always eport the epoll fd as ready, even when no events are pending.
		1811
		1812	While libev allows embedding these backends (they are contained in
		1813	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1814	work.
		1815
		1816	When in doubt, create a dynamic event loop forced to use sockets (this
		1817	usually works) and possibly another thread and a pipe or so to report to
		1818	your main event loop.
		1819
		1820	=head3 Watcher-Specific Functions and Data Members
		1821
		1822	=over 4
		1823
		1824	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1825
		1826	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1827
		1828	Configures the watcher to embed the given loop, which must be
		1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1830	invoked automatically, otherwise it is the responsibility of the callback
		1831	to invoke it (it will continue to be called until the sweep has been done,
		1832	if you do not want thta, you need to temporarily stop the embed watcher).
		1833
		1834	=item ev_embed_sweep (loop, ev_embed *)
		1835
		1836	Make a single, non-blocking sweep over the embedded loop. This works
		1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1838	apropriate way for embedded loops.
		1839
		1840	=item struct ev_loop *other [read-only]
		1841
		1842	The embedded event loop.
		1843
		1844	=back
		1845
		1846
		1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1848
		1849	Fork watchers are called when a C<fork ()> was detected (usually because
		1850	whoever is a good citizen cared to tell libev about it by calling
		1851	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1852	event loop blocks next and before C<ev_check> watchers are being called,
		1853	and only in the child after the fork. If whoever good citizen calling
		1854	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1855	handlers will be invoked, too, of course.
		1856
		1857	=head3 Watcher-Specific Functions and Data Members
		1858
		1859	=over 4
		1860
		1861	=item ev_fork_init (ev_signal *, callback)
		1862
		1863	Initialises and configures the fork watcher - it has no parameters of any
		1864	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1865	believe me.
		1866
		1867	=back
		1868
739		1869
740	=head1 OTHER FUNCTIONS	1870	=head1 OTHER FUNCTIONS
741		1871
742	There are some other functions of possible interest. Described. Here. Now.	1872	There are some other functions of possible interest. Described. Here. Now.
743		1873
…		…
773	/* stdin might have data for us, joy! */;	1903	/* stdin might have data for us, joy! */;
774	}	1904	}
775		1905
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1906	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		1907
778	=item ev_feed_event (loop, watcher, int events)	1908	=item ev_feed_event (ev_loop *, watcher *, int revents)
779		1909
780	Feeds the given event set into the event loop, as if the specified event	1910	Feeds the given event set into the event loop, as if the specified event
781	had happened for the specified watcher (which must be a pointer to an	1911	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	1912	initialised but not necessarily started event watcher).
783		1913
784	=item ev_feed_fd_event (loop, int fd, int revents)	1914	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		1915
786	Feed an event on the given fd, as if a file descriptor backend detected	1916	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	1917	the given events it.
788		1918
789	=item ev_feed_signal_event (loop, int signum)	1919	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		1920
791	Feed an event as if the given signal occured (loop must be the default loop!).	1921	Feed an event as if the given signal occured (C<loop> must be the default
		1922	loop!).
792		1923
793	=back	1924	=back
		1925
794		1926
795	=head1 LIBEVENT EMULATION	1927	=head1 LIBEVENT EMULATION
796		1928
797	Libev offers a compatibility emulation layer for libevent. It cannot	1929	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	1930	emulate the internals of libevent, so here are some usage hints:
…		…
819		1951
820	=back	1952	=back
821		1953
822	=head1 C++ SUPPORT	1954	=head1 C++ SUPPORT
823		1955
824	TBD.	1956	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1957	you to use some convinience methods to start/stop watchers and also change
		1958	the callback model to a model using method callbacks on objects.
		1959
		1960	To use it,
		1961
		1962	#include <ev++.h>
		1963
		1964	This automatically includes F<ev.h> and puts all of its definitions (many
		1965	of them macros) into the global namespace. All C++ specific things are
		1966	put into the C<ev> namespace. It should support all the same embedding
		1967	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1968
		1969	Care has been taken to keep the overhead low. The only data member the C++
		1970	classes add (compared to plain C-style watchers) is the event loop pointer
		1971	that the watcher is associated with (or no additional members at all if
		1972	you disable C<EV_MULTIPLICITY> when embedding libev).
		1973
		1974	Currently, functions, and static and non-static member functions can be
		1975	used as callbacks. Other types should be easy to add as long as they only
		1976	need one additional pointer for context. If you need support for other
		1977	types of functors please contact the author (preferably after implementing
		1978	it).
		1979
		1980	Here is a list of things available in the C<ev> namespace:
		1981
		1982	=over 4
		1983
		1984	=item C<ev::READ>, C<ev::WRITE> etc.
		1985
		1986	These are just enum values with the same values as the C<EV_READ> etc.
		1987	macros from F<ev.h>.
		1988
		1989	=item C<ev::tstamp>, C<ev::now>
		1990
		1991	Aliases to the same types/functions as with the C<ev_> prefix.
		1992
		1993	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1994
		1995	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1996	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1997	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1998	defines by many implementations.
		1999
		2000	All of those classes have these methods:
		2001
		2002	=over 4
		2003
		2004	=item ev::TYPE::TYPE ()
		2005
		2006	=item ev::TYPE::TYPE (struct ev_loop *)
		2007
		2008	=item ev::TYPE::~TYPE
		2009
		2010	The constructor (optionally) takes an event loop to associate the watcher
		2011	with. If it is omitted, it will use C<EV_DEFAULT>.
		2012
		2013	The constructor calls C<ev_init> for you, which means you have to call the
		2014	C<set> method before starting it.
		2015
		2016	It will not set a callback, however: You have to call the templated C<set>
		2017	method to set a callback before you can start the watcher.
		2018
		2019	(The reason why you have to use a method is a limitation in C++ which does
		2020	not allow explicit template arguments for constructors).
		2021
		2022	The destructor automatically stops the watcher if it is active.
		2023
		2024	=item w->set<class, &class::method> (object *)
		2025
		2026	This method sets the callback method to call. The method has to have a
		2027	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2028	first argument and the C<revents> as second. The object must be given as
		2029	parameter and is stored in the C<data> member of the watcher.
		2030
		2031	This method synthesizes efficient thunking code to call your method from
		2032	the C callback that libev requires. If your compiler can inline your
		2033	callback (i.e. it is visible to it at the place of the C<set> call and
		2034	your compiler is good :), then the method will be fully inlined into the
		2035	thunking function, making it as fast as a direct C callback.
		2036
		2037	Example: simple class declaration and watcher initialisation
		2038
		2039	struct myclass
		2040	{
		2041	void io_cb (ev::io &w, int revents) { }
		2042	}
		2043
		2044	myclass obj;
		2045	ev::io iow;
		2046	iow.set <myclass, &myclass::io_cb> (&obj);
		2047
		2048	=item w->set<function> (void *data = 0)
		2049
		2050	Also sets a callback, but uses a static method or plain function as
		2051	callback. The optional C<data> argument will be stored in the watcher's
		2052	C<data> member and is free for you to use.
		2053
		2054	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2055
		2056	See the method-C<set> above for more details.
		2057
		2058	Example:
		2059
		2060	static void io_cb (ev::io &w, int revents) { }
		2061	iow.set <io_cb> ();
		2062
		2063	=item w->set (struct ev_loop *)
		2064
		2065	Associates a different C<struct ev_loop> with this watcher. You can only
		2066	do this when the watcher is inactive (and not pending either).
		2067
		2068	=item w->set ([args])
		2069
		2070	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2071	called at least once. Unlike the C counterpart, an active watcher gets
		2072	automatically stopped and restarted when reconfiguring it with this
		2073	method.
		2074
		2075	=item w->start ()
		2076
		2077	Starts the watcher. Note that there is no C<loop> argument, as the
		2078	constructor already stores the event loop.
		2079
		2080	=item w->stop ()
		2081
		2082	Stops the watcher if it is active. Again, no C<loop> argument.
		2083
		2084	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2085
		2086	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2087	C<ev_TYPE_again> function.
		2088
		2089	=item w->sweep () (C<ev::embed> only)
		2090
		2091	Invokes C<ev_embed_sweep>.
		2092
		2093	=item w->update () (C<ev::stat> only)
		2094
		2095	Invokes C<ev_stat_stat>.
		2096
		2097	=back
		2098
		2099	=back
		2100
		2101	Example: Define a class with an IO and idle watcher, start one of them in
		2102	the constructor.
		2103
		2104	class myclass
		2105	{
		2106	ev_io io; void io_cb (ev::io &w, int revents);
		2107	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2108
		2109	myclass ();
		2110	}
		2111
		2112	myclass::myclass (int fd)
		2113	{
		2114	io .set <myclass, &myclass::io_cb > (this);
		2115	idle.set <myclass, &myclass::idle_cb> (this);
		2116
		2117	io.start (fd, ev::READ);
		2118	}
		2119
		2120
		2121	=head1 MACRO MAGIC
		2122
		2123	Libev can be compiled with a variety of options, the most fundamantal
		2124	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2125	functions and callbacks have an initial C<struct ev_loop *> argument.
		2126
		2127	To make it easier to write programs that cope with either variant, the
		2128	following macros are defined:
		2129
		2130	=over 4
		2131
		2132	=item C<EV_A>, C<EV_A_>
		2133
		2134	This provides the loop I<argument> for functions, if one is required ("ev
		2135	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2136	C<EV_A_> is used when other arguments are following. Example:
		2137
		2138	ev_unref (EV_A);
		2139	ev_timer_add (EV_A_ watcher);
		2140	ev_loop (EV_A_ 0);
		2141
		2142	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2143	which is often provided by the following macro.
		2144
		2145	=item C<EV_P>, C<EV_P_>
		2146
		2147	This provides the loop I<parameter> for functions, if one is required ("ev
		2148	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2149	C<EV_P_> is used when other parameters are following. Example:
		2150
		2151	// this is how ev_unref is being declared
		2152	static void ev_unref (EV_P);
		2153
		2154	// this is how you can declare your typical callback
		2155	static void cb (EV_P_ ev_timer *w, int revents)
		2156
		2157	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2158	suitable for use with C<EV_A>.
		2159
		2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2161
		2162	Similar to the other two macros, this gives you the value of the default
		2163	loop, if multiple loops are supported ("ev loop default").
		2164
		2165	=back
		2166
		2167	Example: Declare and initialise a check watcher, utilising the above
		2168	macros so it will work regardless of whether multiple loops are supported
		2169	or not.
		2170
		2171	static void
		2172	check_cb (EV_P_ ev_timer *w, int revents)
		2173	{
		2174	ev_check_stop (EV_A_ w);
		2175	}
		2176
		2177	ev_check check;
		2178	ev_check_init (&check, check_cb);
		2179	ev_check_start (EV_DEFAULT_ &check);
		2180	ev_loop (EV_DEFAULT_ 0);
		2181
		2182	=head1 EMBEDDING
		2183
		2184	Libev can (and often is) directly embedded into host
		2185	applications. Examples of applications that embed it include the Deliantra
		2186	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2187	and rxvt-unicode.
		2188
		2189	The goal is to enable you to just copy the necessary files into your
		2190	source directory without having to change even a single line in them, so
		2191	you can easily upgrade by simply copying (or having a checked-out copy of
		2192	libev somewhere in your source tree).
		2193
		2194	=head2 FILESETS
		2195
		2196	Depending on what features you need you need to include one or more sets of files
		2197	in your app.
		2198
		2199	=head3 CORE EVENT LOOP
		2200
		2201	To include only the libev core (all the C<ev_*> functions), with manual
		2202	configuration (no autoconf):
		2203
		2204	#define EV_STANDALONE 1
		2205	#include "ev.c"
		2206
		2207	This will automatically include F<ev.h>, too, and should be done in a
		2208	single C source file only to provide the function implementations. To use
		2209	it, do the same for F<ev.h> in all files wishing to use this API (best
		2210	done by writing a wrapper around F<ev.h> that you can include instead and
		2211	where you can put other configuration options):
		2212
		2213	#define EV_STANDALONE 1
		2214	#include "ev.h"
		2215
		2216	Both header files and implementation files can be compiled with a C++
		2217	compiler (at least, thats a stated goal, and breakage will be treated
		2218	as a bug).
		2219
		2220	You need the following files in your source tree, or in a directory
		2221	in your include path (e.g. in libev/ when using -Ilibev):
		2222
		2223	ev.h
		2224	ev.c
		2225	ev_vars.h
		2226	ev_wrap.h
		2227
		2228	ev_win32.c required on win32 platforms only
		2229
		2230	ev_select.c only when select backend is enabled (which is enabled by default)
		2231	ev_poll.c only when poll backend is enabled (disabled by default)
		2232	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2233	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2234	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2235
		2236	F<ev.c> includes the backend files directly when enabled, so you only need
		2237	to compile this single file.
		2238
		2239	=head3 LIBEVENT COMPATIBILITY API
		2240
		2241	To include the libevent compatibility API, also include:
		2242
		2243	#include "event.c"
		2244
		2245	in the file including F<ev.c>, and:
		2246
		2247	#include "event.h"
		2248
		2249	in the files that want to use the libevent API. This also includes F<ev.h>.
		2250
		2251	You need the following additional files for this:
		2252
		2253	event.h
		2254	event.c
		2255
		2256	=head3 AUTOCONF SUPPORT
		2257
		2258	Instead of using C<EV_STANDALONE=1> and providing your config in
		2259	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2260	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2261	include F<config.h> and configure itself accordingly.
		2262
		2263	For this of course you need the m4 file:
		2264
		2265	libev.m4
		2266
		2267	=head2 PREPROCESSOR SYMBOLS/MACROS
		2268
		2269	Libev can be configured via a variety of preprocessor symbols you have to define
		2270	before including any of its files. The default is not to build for multiplicity
		2271	and only include the select backend.
		2272
		2273	=over 4
		2274
		2275	=item EV_STANDALONE
		2276
		2277	Must always be C<1> if you do not use autoconf configuration, which
		2278	keeps libev from including F<config.h>, and it also defines dummy
		2279	implementations for some libevent functions (such as logging, which is not
		2280	supported). It will also not define any of the structs usually found in
		2281	F<event.h> that are not directly supported by the libev core alone.
		2282
		2283	=item EV_USE_MONOTONIC
		2284
		2285	If defined to be C<1>, libev will try to detect the availability of the
		2286	monotonic clock option at both compiletime and runtime. Otherwise no use
		2287	of the monotonic clock option will be attempted. If you enable this, you
		2288	usually have to link against librt or something similar. Enabling it when
		2289	the functionality isn't available is safe, though, although you have
		2290	to make sure you link against any libraries where the C<clock_gettime>
		2291	function is hiding in (often F<-lrt>).
		2292
		2293	=item EV_USE_REALTIME
		2294
		2295	If defined to be C<1>, libev will try to detect the availability of the
		2296	realtime clock option at compiletime (and assume its availability at
		2297	runtime if successful). Otherwise no use of the realtime clock option will
		2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2301
		2302	=item EV_USE_SELECT
		2303
		2304	If undefined or defined to be C<1>, libev will compile in support for the
		2305	C<select>(2) backend. No attempt at autodetection will be done: if no
		2306	other method takes over, select will be it. Otherwise the select backend
		2307	will not be compiled in.
		2308
		2309	=item EV_SELECT_USE_FD_SET
		2310
		2311	If defined to C<1>, then the select backend will use the system C<fd_set>
		2312	structure. This is useful if libev doesn't compile due to a missing
		2313	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2314	exotic systems. This usually limits the range of file descriptors to some
		2315	low limit such as 1024 or might have other limitations (winsocket only
		2316	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2317	influence the size of the C<fd_set> used.
		2318
		2319	=item EV_SELECT_IS_WINSOCKET
		2320
		2321	When defined to C<1>, the select backend will assume that
		2322	select/socket/connect etc. don't understand file descriptors but
		2323	wants osf handles on win32 (this is the case when the select to
		2324	be used is the winsock select). This means that it will call
		2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2326	it is assumed that all these functions actually work on fds, even
		2327	on win32. Should not be defined on non-win32 platforms.
		2328
		2329	=item EV_USE_POLL
		2330
		2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2332	backend. Otherwise it will be enabled on non-win32 platforms. It
		2333	takes precedence over select.
		2334
		2335	=item EV_USE_EPOLL
		2336
		2337	If defined to be C<1>, libev will compile in support for the Linux
		2338	C<epoll>(7) backend. Its availability will be detected at runtime,
		2339	otherwise another method will be used as fallback. This is the
		2340	preferred backend for GNU/Linux systems.
		2341
		2342	=item EV_USE_KQUEUE
		2343
		2344	If defined to be C<1>, libev will compile in support for the BSD style
		2345	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2346	otherwise another method will be used as fallback. This is the preferred
		2347	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2348	supports some types of fds correctly (the only platform we found that
		2349	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2350	not be used unless explicitly requested. The best way to use it is to find
		2351	out whether kqueue supports your type of fd properly and use an embedded
		2352	kqueue loop.
		2353
		2354	=item EV_USE_PORT
		2355
		2356	If defined to be C<1>, libev will compile in support for the Solaris
		2357	10 port style backend. Its availability will be detected at runtime,
		2358	otherwise another method will be used as fallback. This is the preferred
		2359	backend for Solaris 10 systems.
		2360
		2361	=item EV_USE_DEVPOLL
		2362
		2363	reserved for future expansion, works like the USE symbols above.
		2364
		2365	=item EV_USE_INOTIFY
		2366
		2367	If defined to be C<1>, libev will compile in support for the Linux inotify
		2368	interface to speed up C<ev_stat> watchers. Its actual availability will
		2369	be detected at runtime.
		2370
		2371	=item EV_H
		2372
		2373	The name of the F<ev.h> header file used to include it. The default if
		2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2376
		2377	=item EV_CONFIG_H
		2378
		2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2381	C<EV_H>, above.
		2382
		2383	=item EV_EVENT_H
		2384
		2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2386	of how the F<event.h> header can be found.
		2387
		2388	=item EV_PROTOTYPES
		2389
		2390	If defined to be C<0>, then F<ev.h> will not define any function
		2391	prototypes, but still define all the structs and other symbols. This is
		2392	occasionally useful if you want to provide your own wrapper functions
		2393	around libev functions.
		2394
		2395	=item EV_MULTIPLICITY
		2396
		2397	If undefined or defined to C<1>, then all event-loop-specific functions
		2398	will have the C<struct ev_loop *> as first argument, and you can create
		2399	additional independent event loops. Otherwise there will be no support
		2400	for multiple event loops and there is no first event loop pointer
		2401	argument. Instead, all functions act on the single default loop.
		2402
		2403	=item EV_MINPRI
		2404
		2405	=item EV_MAXPRI
		2406
		2407	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2408	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2409	provide for more priorities by overriding those symbols (usually defined
		2410	to be C<-2> and C<2>, respectively).
		2411
		2412	When doing priority-based operations, libev usually has to linearly search
		2413	all the priorities, so having many of them (hundreds) uses a lot of space
		2414	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2415	fine.
		2416
		2417	If your embedding app does not need any priorities, defining these both to
		2418	C<0> will save some memory and cpu.
		2419
		2420	=item EV_PERIODIC_ENABLE
		2421
		2422	If undefined or defined to be C<1>, then periodic timers are supported. If
		2423	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2424	code.
		2425
		2426	=item EV_IDLE_ENABLE
		2427
		2428	If undefined or defined to be C<1>, then idle watchers are supported. If
		2429	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2430	code.
		2431
		2432	=item EV_EMBED_ENABLE
		2433
		2434	If undefined or defined to be C<1>, then embed watchers are supported. If
		2435	defined to be C<0>, then they are not.
		2436
		2437	=item EV_STAT_ENABLE
		2438
		2439	If undefined or defined to be C<1>, then stat watchers are supported. If
		2440	defined to be C<0>, then they are not.
		2441
		2442	=item EV_FORK_ENABLE
		2443
		2444	If undefined or defined to be C<1>, then fork watchers are supported. If
		2445	defined to be C<0>, then they are not.
		2446
		2447	=item EV_MINIMAL
		2448
		2449	If you need to shave off some kilobytes of code at the expense of some
		2450	speed, define this symbol to C<1>. Currently only used for gcc to override
		2451	some inlining decisions, saves roughly 30% codesize of amd64.
		2452
		2453	=item EV_PID_HASHSIZE
		2454
		2455	C<ev_child> watchers use a small hash table to distribute workload by
		2456	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2457	than enough. If you need to manage thousands of children you might want to
		2458	increase this value (I<must> be a power of two).
		2459
		2460	=item EV_INOTIFY_HASHSIZE
		2461
		2462	C<ev_staz> watchers use a small hash table to distribute workload by
		2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2464	usually more than enough. If you need to manage thousands of C<ev_stat>
		2465	watchers you might want to increase this value (I<must> be a power of
		2466	two).
		2467
		2468	=item EV_COMMON
		2469
		2470	By default, all watchers have a C<void *data> member. By redefining
		2471	this macro to a something else you can include more and other types of
		2472	members. You have to define it each time you include one of the files,
		2473	though, and it must be identical each time.
		2474
		2475	For example, the perl EV module uses something like this:
		2476
		2477	#define EV_COMMON \
		2478	SV *self; /* contains this struct */ \
		2479	SV *cb_sv, *fh /* note no trailing ";" */
		2480
		2481	=item EV_CB_DECLARE (type)
		2482
		2483	=item EV_CB_INVOKE (watcher, revents)
		2484
		2485	=item ev_set_cb (ev, cb)
		2486
		2487	Can be used to change the callback member declaration in each watcher,
		2488	and the way callbacks are invoked and set. Must expand to a struct member
		2489	definition and a statement, respectively. See the F<ev.h> header file for
		2490	their default definitions. One possible use for overriding these is to
		2491	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2492	method calls instead of plain function calls in C++.
		2493
		2494	=head2 EXPORTED API SYMBOLS
		2495
		2496	If you need to re-export the API (e.g. via a dll) and you need a list of
		2497	exported symbols, you can use the provided F<Symbol.*> files which list
		2498	all public symbols, one per line:
		2499
		2500	Symbols.ev for libev proper
		2501	Symbols.event for the libevent emulation
		2502
		2503	This can also be used to rename all public symbols to avoid clashes with
		2504	multiple versions of libev linked together (which is obviously bad in
		2505	itself, but sometimes it is inconvinient to avoid this).
		2506
		2507	A sed command like this will create wrapper C<#define>'s that you need to
		2508	include before including F<ev.h>:
		2509
		2510	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2511
		2512	This would create a file F<wrap.h> which essentially looks like this:
		2513
		2514	#define ev_backend myprefix_ev_backend
		2515	#define ev_check_start myprefix_ev_check_start
		2516	#define ev_check_stop myprefix_ev_check_stop
		2517	...
		2518
		2519	=head2 EXAMPLES
		2520
		2521	For a real-world example of a program the includes libev
		2522	verbatim, you can have a look at the EV perl module
		2523	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2524	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2525	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2526	will be compiled. It is pretty complex because it provides its own header
		2527	file.
		2528
		2529	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2530	that everybody includes and which overrides some configure choices:
		2531
		2532	#define EV_MINIMAL 1
		2533	#define EV_USE_POLL 0
		2534	#define EV_MULTIPLICITY 0
		2535	#define EV_PERIODIC_ENABLE 0
		2536	#define EV_STAT_ENABLE 0
		2537	#define EV_FORK_ENABLE 0
		2538	#define EV_CONFIG_H <config.h>
		2539	#define EV_MINPRI 0
		2540	#define EV_MAXPRI 0
		2541
		2542	#include "ev++.h"
		2543
		2544	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2545
		2546	#include "ev_cpp.h"
		2547	#include "ev.c"
		2548
		2549
		2550	=head1 COMPLEXITIES
		2551
		2552	In this section the complexities of (many of) the algorithms used inside
		2553	libev will be explained. For complexity discussions about backends see the
		2554	documentation for C<ev_default_init>.
		2555
		2556	All of the following are about amortised time: If an array needs to be
		2557	extended, libev needs to realloc and move the whole array, but this
		2558	happens asymptotically never with higher number of elements, so O(1) might
		2559	mean it might do a lengthy realloc operation in rare cases, but on average
		2560	it is much faster and asymptotically approaches constant time.
		2561
		2562	=over 4
		2563
		2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2565
		2566	This means that, when you have a watcher that triggers in one hour and
		2567	there are 100 watchers that would trigger before that then inserting will
		2568	have to skip those 100 watchers.
		2569
		2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2571
		2572	That means that for changing a timer costs less than removing/adding them
		2573	as only the relative motion in the event queue has to be paid for.
		2574
		2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2576
		2577	These just add the watcher into an array or at the head of a list.
		2578	=item Stopping check/prepare/idle watchers: O(1)
		2579
		2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2581
		2582	These watchers are stored in lists then need to be walked to find the
		2583	correct watcher to remove. The lists are usually short (you don't usually
		2584	have many watchers waiting for the same fd or signal).
		2585
		2586	=item Finding the next timer per loop iteration: O(1)
		2587
		2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2589
		2590	A change means an I/O watcher gets started or stopped, which requires
		2591	libev to recalculate its status (and possibly tell the kernel).
		2592
		2593	=item Activating one watcher: O(1)
		2594
		2595	=item Priority handling: O(number_of_priorities)
		2596
		2597	Priorities are implemented by allocating some space for each
		2598	priority. When doing priority-based operations, libev usually has to
		2599	linearly search all the priorities.
		2600
		2601	=back
		2602
825		2603
826	=head1 AUTHOR	2604	=head1 AUTHOR
827		2605
828	Marc Lehmann <libev@schmorp.de>.	2606	Marc Lehmann <libev@schmorp.de>.
829		2607

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