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Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_TYPE
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
117		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
122	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	170	version of the library your program was compiled against.
127		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
128	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	178	not a problem.
132		179
133	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	181	version.
135		182
136	assert (("libev version mismatch",	183	assert (("libev version mismatch",
137	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
138	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
139		186
140	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
141		188
142	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
143	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
145	a description of the set values.	192	a description of the set values.
146		193
147	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
148	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
149		196
150	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
151	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
152		199
153	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
154		201
155	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
156	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
157	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
158	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
159	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
160	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
161		208
162	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
163		210
…		…
167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
168	recommended ones.	215	recommended ones.
169		216
170	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
171		218
172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
173		220
174	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
175	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
176	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
177	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
178	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
179	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
180		230
181	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
182	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
183	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
184		234
185	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
186	retries).	236	retries (example requires a standards-compliant C<realloc>).
187		237
188	static void *	238	static void *
189	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
190	{	240	{
191	for (;;)	241	for (;;)
…		…
200	}	250	}
201		251
202	...	252	...
203	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
204		254
205	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
206		256
207	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
208	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
209	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
210	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
211	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
212	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
213	(such as abort).	263	(such as abort).
214		264
215	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
226		276
227	=back	277	=back
228		278
229	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
230		280
231	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
232	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
233	events, and dynamically created loops which do not.	283	I<function>).
234		284
235	If you use threads, a common model is to run the default event loop	285	The library knows two types of such loops, the I<default> loop, which
236	in your main thread (or in a separate thread) and for each thread you	286	supports signals and child events, and dynamically created loops which do
237	create, you also create another event loop. Libev itself does no locking	287	not.
238	whatsoever, so if you mix calls to the same event loop in different
239	threads, make sure you lock (this is usually a bad idea, though, even if
240	done correctly, because it's hideous and inefficient).
241		288
242	=over 4	289	=over 4
243		290
244	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
245		292
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	296	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		297
251	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
252	function.	299	function.
253		300
		301	Note that this function is I<not> thread-safe, so if you want to use it
		302	from multiple threads, you have to lock (note also that this is unlikely,
		303	as loops cannot bes hared easily between threads anyway).
		304
		305	The default loop is the only loop that can handle C<ev_signal> and
		306	C<ev_child> watchers, and to do this, it always registers a handler
		307	for C<SIGCHLD>. If this is a problem for your application you can either
		308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		310	C<ev_default_init>.
		311
254	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		314
257	The following flags are supported:	315	The following flags are supported:
258		316
…		…
263	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
264	thing, believe me).	322	thing, believe me).
265		323
266	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
267		325
268	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
269	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
271	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
272	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
273	around bugs.	331	around bugs.
…		…
279	enabling this flag.	337	enabling this flag.
280		338
281	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
287		345
288	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
290	flag.	348	flag.
291		349
292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
293	environment variable.	351	environment variable.
294		352
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		354
297	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	356	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
		360
		361	To get good performance out of this backend you need a high amount of
		362	parallelism (most of the file descriptors should be busy). If you are
		363	writing a server, you should C<accept ()> in a loop to accept as many
		364	connections as possible during one iteration. You might also want to have
		365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
302		371
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		373
305	And this is your standard poll(2) backend. It's more complicated than	374	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	375	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	376	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	377	considerably with a lot of inactive fds). It scales similarly to select,
		378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		379	performance tips.
		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
309		383
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		385
312	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	387	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	388	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	389	epoll scales either O(1) or O(active_fds). The epoll design has a number
		390	of shortcomings, such as silently dropping events in some hard-to-detect
		391	cases and requiring a system call per fd change, no fork support and bad
		392	support for dup.
316		393
		394	Epoll is also notoriously buggy - embedding epoll fds should work, but
		395	of course doesn't, and epoll just loves to report events for totally
		396	I<different> file descriptors (even already closed ones) than registered
		397	in the set (especially on SMP systems). Libev tries to counter these
		398	spurious notifications by employing an additional generation counter and
		399	comparing that against the events to filter out spurious ones.
		400
317	While stopping and starting an I/O watcher in the same iteration will	401	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	402	will result in some caching, there is still a system call per such incident
319	(because the fd could point to a different file description now), so its	403	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	405	very well if you register events for both fds.
322		406
323	Please note that epoll sometimes generates spurious notifications, so you	407	Best performance from this backend is achieved by not unregistering all
324	need to use non-blocking I/O or other means to avoid blocking when no data	408	watchers for a file descriptor until it has been closed, if possible,
325	(or space) is available.	409	i.e. keep at least one watcher active per fd at all times. Stopping and
		410	starting a watcher (without re-setting it) also usually doesn't cause
		411	extra overhead.
		412
		413	While nominally embeddable in other event loops, this feature is broken in
		414	all kernel versions tested so far.
		415
		416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		417	C<EVBACKEND_POLL>.
326		418
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		420
329	Kqueue deserves special mention, as at the time of this writing, it	421	Kqueue deserves special mention, as at the time of this writing, it was
330	was broken on all BSDs except NetBSD (usually it doesn't work with	422	broken on all BSDs except NetBSD (usually it doesn't work reliably with
331	anything but sockets and pipes, except on Darwin, where of course its	423	anything but sockets and pipes, except on Darwin, where of course it's
332	completely useless). For this reason its not being "autodetected"	424	completely useless). For this reason it's not being "auto-detected" unless
333	unless you explicitly specify it explicitly in the flags (i.e. using	425	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
334	C<EVBACKEND_KQUEUE>).	426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		427
		428	You still can embed kqueue into a normal poll or select backend and use it
		429	only for sockets (after having made sure that sockets work with kqueue on
		430	the target platform). See C<ev_embed> watchers for more info.
335		431
336	It scales in the same way as the epoll backend, but the interface to the	432	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	433	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	434	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	435	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	436	two event changes per incident. Support for C<fork ()> is very bad and it
		437	drops fds silently in similarly hard-to-detect cases.
		438
		439	This backend usually performs well under most conditions.
		440
		441	While nominally embeddable in other event loops, this doesn't work
		442	everywhere, so you might need to test for this. And since it is broken
		443	almost everywhere, you should only use it when you have a lot of sockets
		444	(for which it usually works), by embedding it into another event loop
		445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		446	using it only for sockets.
		447
		448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		450	C<NOTE_EOF>.
341		451
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	452	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		453
344	This is not implemented yet (and might never be).	454	This is not implemented yet (and might never be, unless you send me an
		455	implementation). According to reports, C</dev/poll> only supports sockets
		456	and is not embeddable, which would limit the usefulness of this backend
		457	immensely.
345		458
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	459	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		460
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	461	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	462	it's really slow, but it still scales very well (O(active_fds)).
350		463
351	Please note that solaris ports can result in a lot of spurious	464	Please note that Solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	465	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	466	blocking when no data (or space) is available.
		467
		468	While this backend scales well, it requires one system call per active
		469	file descriptor per loop iteration. For small and medium numbers of file
		470	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		471	might perform better.
		472
		473	On the positive side, with the exception of the spurious readiness
		474	notifications, this backend actually performed fully to specification
		475	in all tests and is fully embeddable, which is a rare feat among the
		476	OS-specific backends.
		477
		478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		479	C<EVBACKEND_POLL>.
354		480
355	=item C<EVBACKEND_ALL>	481	=item C<EVBACKEND_ALL>
356		482
357	Try all backends (even potentially broken ones that wouldn't be tried	483	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	485	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		486
		487	It is definitely not recommended to use this flag.
		488
361	=back	489	=back
362		490
363	If one or more of these are ored into the flags value, then only these	491	If one or more of these are or'ed into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	492	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	493	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		494
368	The most typical usage is like this:	495	Example: This is the most typical usage.
369		496
370	if (!ev_default_loop (0))	497	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
372		499
373	Restrict libev to the select and poll backends, and do not allow	500	Example: Restrict libev to the select and poll backends, and do not allow
374	environment settings to be taken into account:	501	environment settings to be taken into account:
375		502
376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
377		504
378	Use whatever libev has to offer, but make sure that kqueue is used if	505	Example: Use whatever libev has to offer, but make sure that kqueue is
379	available (warning, breaks stuff, best use only with your own private	506	used if available (warning, breaks stuff, best use only with your own
380	event loop and only if you know the OS supports your types of fds):	507	private event loop and only if you know the OS supports your types of
		508	fds):
381		509
382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
383		511
384	=item struct ev_loop *ev_loop_new (unsigned int flags)	512	=item struct ev_loop *ev_loop_new (unsigned int flags)
385		513
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	514	Similar to C<ev_default_loop>, but always creates a new event loop that is
387	always distinct from the default loop. Unlike the default loop, it cannot	515	always distinct from the default loop. Unlike the default loop, it cannot
388	handle signal and child watchers, and attempts to do so will be greeted by	516	handle signal and child watchers, and attempts to do so will be greeted by
389	undefined behaviour (or a failed assertion if assertions are enabled).	517	undefined behaviour (or a failed assertion if assertions are enabled).
390		518
		519	Note that this function I<is> thread-safe, and the recommended way to use
		520	libev with threads is indeed to create one loop per thread, and using the
		521	default loop in the "main" or "initial" thread.
		522
391	Example: Try to create a event loop that uses epoll and nothing else.	523	Example: Try to create a event loop that uses epoll and nothing else.
392		524
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	525	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	526	if (!epoller)
395	fatal ("no epoll found here, maybe it hides under your chair");	527	fatal ("no epoll found here, maybe it hides under your chair");
396		528
397	=item ev_default_destroy ()	529	=item ev_default_destroy ()
398		530
399	Destroys the default loop again (frees all memory and kernel state	531	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	532	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	533	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	534	responsibility to either stop all watchers cleanly yourself I<before>
403	calling this function, or cope with the fact afterwards (which is usually	535	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	536	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	537	for example).
		538
		539	Note that certain global state, such as signal state (and installed signal
		540	handlers), will not be freed by this function, and related watchers (such
		541	as signal and child watchers) would need to be stopped manually.
		542
		543	In general it is not advisable to call this function except in the
		544	rare occasion where you really need to free e.g. the signal handling
		545	pipe fds. If you need dynamically allocated loops it is better to use
		546	C<ev_loop_new> and C<ev_loop_destroy>).
406		547
407	=item ev_loop_destroy (loop)	548	=item ev_loop_destroy (loop)
408		549
409	Like C<ev_default_destroy>, but destroys an event loop created by an	550	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	551	earlier call to C<ev_loop_new>.
411		552
412	=item ev_default_fork ()	553	=item ev_default_fork ()
413		554
		555	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	556	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	557	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	558	the child process (or both child and parent, but that again makes little
417	again makes little sense).	559	sense). You I<must> call it in the child before using any of the libev
		560	functions, and it will only take effect at the next C<ev_loop> iteration.
418		561
419	You I<must> call this function in the child process after forking if and	562	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	563	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	564	you just fork+exec, you don't have to call it at all.
422		565
423	The function itself is quite fast and it's usually not a problem to call	566	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	567	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	568	quite nicely into a call to C<pthread_atfork>:
426		569
427	pthread_atfork (0, 0, ev_default_fork);	570	pthread_atfork (0, 0, ev_default_fork);
428		571
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	572	=item ev_loop_fork (loop)
434		573
435	Like C<ev_default_fork>, but acts on an event loop created by	574	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	575	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	576	after fork that you want to re-use in the child, and how you do this is
		577	entirely your own problem.
		578
		579	=item int ev_is_default_loop (loop)
		580
		581	Returns true when the given loop is, in fact, the default loop, and false
		582	otherwise.
438		583
439	=item unsigned int ev_loop_count (loop)	584	=item unsigned int ev_loop_count (loop)
440		585
441	Returns the count of loop iterations for the loop, which is identical to	586	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	587	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		600
456	Returns the current "event loop time", which is the time the event loop	601	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	602	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	603	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	604	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	605	event occurring (or more correctly, libev finding out about it).
		606
		607	=item ev_now_update (loop)
		608
		609	Establishes the current time by querying the kernel, updating the time
		610	returned by C<ev_now ()> in the progress. This is a costly operation and
		611	is usually done automatically within C<ev_loop ()>.
		612
		613	This function is rarely useful, but when some event callback runs for a
		614	very long time without entering the event loop, updating libev's idea of
		615	the current time is a good idea.
		616
		617	See also "The special problem of time updates" in the C<ev_timer> section.
461		618
462	=item ev_loop (loop, int flags)	619	=item ev_loop (loop, int flags)
463		620
464	Finally, this is it, the event handler. This function usually is called	621	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	622	after you initialised all your watchers and you want to start handling
…		…
468	If the flags argument is specified as C<0>, it will not return until	625	If the flags argument is specified as C<0>, it will not return until
469	either no event watchers are active anymore or C<ev_unloop> was called.	626	either no event watchers are active anymore or C<ev_unloop> was called.
470		627
471	Please note that an explicit C<ev_unloop> is usually better than	628	Please note that an explicit C<ev_unloop> is usually better than
472	relying on all watchers to be stopped when deciding when a program has	629	relying on all watchers to be stopped when deciding when a program has
473	finished (especially in interactive programs), but having a program that	630	finished (especially in interactive programs), but having a program
474	automatically loops as long as it has to and no longer by virtue of	631	that automatically loops as long as it has to and no longer by virtue
475	relying on its watchers stopping correctly is a thing of beauty.	632	of relying on its watchers stopping correctly, that is truly a thing of
		633	beauty.
476		634
477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	635	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
478	those events and any outstanding ones, but will not block your process in	636	those events and any already outstanding ones, but will not block your
479	case there are no events and will return after one iteration of the loop.	637	process in case there are no events and will return after one iteration of
		638	the loop.
480		639
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	640	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
482	neccessary) and will handle those and any outstanding ones. It will block	641	necessary) and will handle those and any already outstanding ones. It
483	your process until at least one new event arrives, and will return after	642	will block your process until at least one new event arrives (which could
484	one iteration of the loop. This is useful if you are waiting for some	643	be an event internal to libev itself, so there is no guarentee that a
485	external event in conjunction with something not expressible using other	644	user-registered callback will be called), and will return after one
		645	iteration of the loop.
		646
		647	This is useful if you are waiting for some external event in conjunction
		648	with something not expressible using other libev watchers (i.e. "roll your
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	649	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	650	usually a better approach for this kind of thing.
488		651
489	Here are the gory details of what C<ev_loop> does:	652	Here are the gory details of what C<ev_loop> does:
490		653
491	* If there are no active watchers (reference count is zero), return.	654	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	655	* If EVFLAG_FORKCHECK was used, check for a fork.
		656	- If a fork was detected (by any means), queue and call all fork watchers.
		657	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	658	- If we have been forked, detach and recreate the kernel state
		659	as to not disturb the other process.
494	- Update the kernel state with all outstanding changes.	660	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	661	- Update the "event loop time" (ev_now ()).
496	- Calculate for how long to block.	662	- Calculate for how long to sleep or block, if at all
		663	(active idle watchers, EVLOOP_NONBLOCK or not having
		664	any active watchers at all will result in not sleeping).
		665	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	666	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	667	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
500	- Queue all outstanding timers.	669	- Queue all expired timers.
501	- Queue all outstanding periodics.	670	- Queue all expired periodics.
502	- If no events are pending now, queue all idle watchers.	671	- Unless any events are pending now, queue all idle watchers.
503	- Queue all check watchers.	672	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	673	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	674	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	675	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	677	were used, or there are no active watchers, return, otherwise
		678	continue with step *.
509		679
510	Example: Queue some jobs and then loop until no events are outsanding	680	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	681	anymore.
512		682
513	... queue jobs here, make sure they register event watchers as long	683	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	684	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	685	ev_loop (my_loop, 0);
516	... jobs done. yeah!	686	... jobs done or somebody called unloop. yeah!
517		687
518	=item ev_unloop (loop, how)	688	=item ev_unloop (loop, how)
519		689
520	Can be used to make a call to C<ev_loop> return early (but only after it	690	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	691	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	692	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
524		694
		695	This "unloop state" will be cleared when entering C<ev_loop> again.
		696
		697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		698
525	=item ev_ref (loop)	699	=item ev_ref (loop)
526		700
527	=item ev_unref (loop)	701	=item ev_unref (loop)
528		702
529	Ref/unref can be used to add or remove a reference count on the event	703	Ref/unref can be used to add or remove a reference count on the event
530	loop: Every watcher keeps one reference, and as long as the reference	704	loop: Every watcher keeps one reference, and as long as the reference
531	count is nonzero, C<ev_loop> will not return on its own. If you have	705	count is nonzero, C<ev_loop> will not return on its own.
		706
532	a watcher you never unregister that should not keep C<ev_loop> from	707	If you have a watcher you never unregister that should not keep C<ev_loop>
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	708	from returning, call ev_unref() after starting, and ev_ref() before
		709	stopping it.
		710
534	example, libev itself uses this for its internal signal pipe: It is not	711	As an example, libev itself uses this for its internal signal pipe: It is
535	visible to the libev user and should not keep C<ev_loop> from exiting if	712	not visible to the libev user and should not keep C<ev_loop> from exiting
536	no event watchers registered by it are active. It is also an excellent	713	if no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	714	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	715	libraries. Just remember to I<unref after start> and I<ref before stop>
		716	(but only if the watcher wasn't active before, or was active before,
		717	respectively).
539		718
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	720	running when nothing else is active.
542		721
543	struct ev_signal exitsig;	722	ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	723	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	724	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	725	evf_unref (loop);
547		726
548	Example: For some weird reason, unregister the above signal handler again.	727	Example: For some weird reason, unregister the above signal handler again.
549		728
550	ev_ref (loop);	729	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	730	ev_signal_stop (loop, &exitsig);
		731
		732	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		733
		734	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		735
		736	These advanced functions influence the time that libev will spend waiting
		737	for events. Both time intervals are by default C<0>, meaning that libev
		738	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		739	latency.
		740
		741	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		742	allows libev to delay invocation of I/O and timer/periodic callbacks
		743	to increase efficiency of loop iterations (or to increase power-saving
		744	opportunities).
		745
		746	The idea is that sometimes your program runs just fast enough to handle
		747	one (or very few) event(s) per loop iteration. While this makes the
		748	program responsive, it also wastes a lot of CPU time to poll for new
		749	events, especially with backends like C<select ()> which have a high
		750	overhead for the actual polling but can deliver many events at once.
		751
		752	By setting a higher I<io collect interval> you allow libev to spend more
		753	time collecting I/O events, so you can handle more events per iteration,
		754	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		755	C<ev_timer>) will be not affected. Setting this to a non-null value will
		756	introduce an additional C<ev_sleep ()> call into most loop iterations.
		757
		758	Likewise, by setting a higher I<timeout collect interval> you allow libev
		759	to spend more time collecting timeouts, at the expense of increased
		760	latency/jitter/inexactness (the watcher callback will be called
		761	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		762	value will not introduce any overhead in libev.
		763
		764	Many (busy) programs can usually benefit by setting the I/O collect
		765	interval to a value near C<0.1> or so, which is often enough for
		766	interactive servers (of course not for games), likewise for timeouts. It
		767	usually doesn't make much sense to set it to a lower value than C<0.01>,
		768	as this approaches the timing granularity of most systems.
		769
		770	Setting the I<timeout collect interval> can improve the opportunity for
		771	saving power, as the program will "bundle" timer callback invocations that
		772	are "near" in time together, by delaying some, thus reducing the number of
		773	times the process sleeps and wakes up again. Another useful technique to
		774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		775	they fire on, say, one-second boundaries only.
		776
		777	=item ev_loop_verify (loop)
		778
		779	This function only does something when C<EV_VERIFY> support has been
		780	compiled in, which is the default for non-minimal builds. It tries to go
		781	through all internal structures and checks them for validity. If anything
		782	is found to be inconsistent, it will print an error message to standard
		783	error and call C<abort ()>.
		784
		785	This can be used to catch bugs inside libev itself: under normal
		786	circumstances, this function will never abort as of course libev keeps its
		787	data structures consistent.
552		788
553	=back	789	=back
554		790
555		791
556	=head1 ANATOMY OF A WATCHER	792	=head1 ANATOMY OF A WATCHER
		793
		794	In the following description, uppercase C<TYPE> in names stands for the
		795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		796	watchers and C<ev_io_start> for I/O watchers.
557		797
558	A watcher is a structure that you create and register to record your	798	A watcher is a structure that you create and register to record your
559	interest in some event. For instance, if you want to wait for STDIN to	799	interest in some event. For instance, if you want to wait for STDIN to
560	become readable, you would create an C<ev_io> watcher for that:	800	become readable, you would create an C<ev_io> watcher for that:
561		801
562	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
563	{	803	{
564	ev_io_stop (w);	804	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	805	ev_unloop (loop, EVUNLOOP_ALL);
566	}	806	}
567		807
568	struct ev_loop *loop = ev_default_loop (0);	808	struct ev_loop *loop = ev_default_loop (0);
		809
569	struct ev_io stdin_watcher;	810	ev_io stdin_watcher;
		811
570	ev_init (&stdin_watcher, my_cb);	812	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	814	ev_io_start (loop, &stdin_watcher);
		815
573	ev_loop (loop, 0);	816	ev_loop (loop, 0);
574		817
575	As you can see, you are responsible for allocating the memory for your	818	As you can see, you are responsible for allocating the memory for your
576	watcher structures (and it is usually a bad idea to do this on the stack,	819	watcher structures (and it is I<usually> a bad idea to do this on the
577	although this can sometimes be quite valid).	820	stack).
		821
		822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
578		824
579	Each watcher structure must be initialised by a call to C<ev_init	825	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	826	(watcher *, callback)>, which expects a callback to be provided. This
581	callback gets invoked each time the event occurs (or, in the case of io	827	callback gets invoked each time the event occurs (or, in the case of I/O
582	watchers, each time the event loop detects that the file descriptor given	828	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	829	is readable and/or writable).
584		830
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
586	with arguments specific to this watcher type. There is also a macro	832	macro to configure it, with arguments specific to the watcher type. There
587	to combine initialisation and setting in one call: C<< ev_<type>_init	833	is also a macro to combine initialisation and setting in one call: C<<
588	(watcher *, callback, ...) >>.	834	ev_TYPE_init (watcher *, callback, ...) >>.
589		835
590	To make the watcher actually watch out for events, you have to start it	836	To make the watcher actually watch out for events, you have to start it
591	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	837	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
592	*) >>), and you can stop watching for events at any time by calling the	838	*) >>), and you can stop watching for events at any time by calling the
593	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	839	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
594		840
595	As long as your watcher is active (has been started but not stopped) you	841	As long as your watcher is active (has been started but not stopped) you
596	must not touch the values stored in it. Most specifically you must never	842	must not touch the values stored in it. Most specifically you must never
597	reinitialise it or call its C<set> macro.	843	reinitialise it or call its C<ev_TYPE_set> macro.
598		844
599	Each and every callback receives the event loop pointer as first, the	845	Each and every callback receives the event loop pointer as first, the
600	registered watcher structure as second, and a bitset of received events as	846	registered watcher structure as second, and a bitset of received events as
601	third argument.	847	third argument.
602		848
…		…
656	=item C<EV_FORK>	902	=item C<EV_FORK>
657		903
658	The event loop has been resumed in the child process after fork (see	904	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	905	C<ev_fork>).
660		906
		907	=item C<EV_ASYNC>
		908
		909	The given async watcher has been asynchronously notified (see C<ev_async>).
		910
661	=item C<EV_ERROR>	911	=item C<EV_ERROR>
662		912
663	An unspecified error has occured, the watcher has been stopped. This might	913	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	914	happen because the watcher could not be properly started because libev
665	ran out of memory, a file descriptor was found to be closed or any other	915	ran out of memory, a file descriptor was found to be closed or any other
		916	problem. Libev considers these application bugs.
		917
666	problem. You best act on it by reporting the problem and somehow coping	918	You best act on it by reporting the problem and somehow coping with the
667	with the watcher being stopped.	919	watcher being stopped. Note that well-written programs should not receive
		920	an error ever, so when your watcher receives it, this usually indicates a
		921	bug in your program.
668		922
669	Libev will usually signal a few "dummy" events together with an error,	923	Libev will usually signal a few "dummy" events together with an error, for
670	for example it might indicate that a fd is readable or writable, and if	924	example it might indicate that a fd is readable or writable, and if your
671	your callbacks is well-written it can just attempt the operation and cope	925	callbacks is well-written it can just attempt the operation and cope with
672	with the error from read() or write(). This will not work in multithreaded	926	the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	927	programs, though, as the fd could already be closed and reused for another
		928	thing, so beware.
674		929
675	=back	930	=back
676		931
677	=head2 GENERIC WATCHER FUNCTIONS	932	=head2 GENERIC WATCHER FUNCTIONS
678
679	In the following description, C<TYPE> stands for the watcher type,
680	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
681		933
682	=over 4	934	=over 4
683		935
684	=item C<ev_init> (ev_TYPE *watcher, callback)	936	=item C<ev_init> (ev_TYPE *watcher, callback)
685		937
…		…
691	which rolls both calls into one.	943	which rolls both calls into one.
692		944
693	You can reinitialise a watcher at any time as long as it has been stopped	945	You can reinitialise a watcher at any time as long as it has been stopped
694	(or never started) and there are no pending events outstanding.	946	(or never started) and there are no pending events outstanding.
695		947
696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	948	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
697	int revents)>.	949	int revents)>.
		950
		951	Example: Initialise an C<ev_io> watcher in two steps.
		952
		953	ev_io w;
		954	ev_init (&w, my_cb);
		955	ev_io_set (&w, STDIN_FILENO, EV_READ);
698		956
699	=item C<ev_TYPE_set> (ev_TYPE *, [args])	957	=item C<ev_TYPE_set> (ev_TYPE *, [args])
700		958
701	This macro initialises the type-specific parts of a watcher. You need to	959	This macro initialises the type-specific parts of a watcher. You need to
702	call C<ev_init> at least once before you call this macro, but you can	960	call C<ev_init> at least once before you call this macro, but you can
…		…
705	difference to the C<ev_init> macro).	963	difference to the C<ev_init> macro).
706		964
707	Although some watcher types do not have type-specific arguments	965	Although some watcher types do not have type-specific arguments
708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	966	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		967
		968	See C<ev_init>, above, for an example.
		969
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	970	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		971
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	972	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
713	calls into a single call. This is the most convinient method to initialise	973	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	974	a watcher. The same limitations apply, of course.
		975
		976	Example: Initialise and set an C<ev_io> watcher in one step.
		977
		978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
715		979
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		981
718	Starts (activates) the given watcher. Only active watchers will receive	982	Starts (activates) the given watcher. Only active watchers will receive
719	events. If the watcher is already active nothing will happen.	983	events. If the watcher is already active nothing will happen.
720		984
		985	Example: Start the C<ev_io> watcher that is being abused as example in this
		986	whole section.
		987
		988	ev_io_start (EV_DEFAULT_UC, &w);
		989
721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
722		991
723	Stops the given watcher again (if active) and clears the pending	992	Stops the given watcher if active, and clears the pending status (whether
		993	the watcher was active or not).
		994
724	status. It is possible that stopped watchers are pending (for example,	995	It is possible that stopped watchers are pending - for example,
725	non-repeating timers are being stopped when they become pending), but	996	non-repeating timers are being stopped when they become pending - but
726	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	997	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
727	you want to free or reuse the memory used by the watcher it is therefore a	998	pending. If you want to free or reuse the memory used by the watcher it is
728	good idea to always call its C<ev_TYPE_stop> function.	999	therefore a good idea to always call its C<ev_TYPE_stop> function.
729		1000
730	=item bool ev_is_active (ev_TYPE *watcher)	1001	=item bool ev_is_active (ev_TYPE *watcher)
731		1002
732	Returns a true value iff the watcher is active (i.e. it has been started	1003	Returns a true value iff the watcher is active (i.e. it has been started
733	and not yet been stopped). As long as a watcher is active you must not modify	1004	and not yet been stopped). As long as a watcher is active you must not modify
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	1007	=item bool ev_is_pending (ev_TYPE *watcher)
737		1008
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1009	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	1010	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	1011	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	1012	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	1013	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1014	it).
743		1015
744	=item callback ev_cb (ev_TYPE *watcher)	1016	=item callback ev_cb (ev_TYPE *watcher)
745		1017
746	Returns the callback currently set on the watcher.	1018	Returns the callback currently set on the watcher.
747		1019
…		…
766	watchers on the same event and make sure one is called first.	1038	watchers on the same event and make sure one is called first.
767		1039
768	If you need to suppress invocation when higher priority events are pending	1040	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	1041	you need to look at C<ev_idle> watchers, which provide this functionality.
770		1042
		1043	You I<must not> change the priority of a watcher as long as it is active or
		1044	pending.
		1045
771	The default priority used by watchers when no priority has been set is	1046	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	1047	always C<0>, which is supposed to not be too high and not be too low :).
773		1048
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	1050	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	1051	or might not have been clamped to the valid range.
		1052
		1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1054
		1055	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1056	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1057	can deal with that fact, as both are simply passed through to the
		1058	callback.
		1059
		1060	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1061
		1062	If the watcher is pending, this function clears its pending status and
		1063	returns its C<revents> bitset (as if its callback was invoked). If the
		1064	watcher isn't pending it does nothing and returns C<0>.
		1065
		1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1067	callback to be invoked, which can be accomplished with this function.
777		1068
778	=back	1069	=back
779		1070
780		1071
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
782		1073
783	Each watcher has, by default, a member C<void *data> that you can change	1074	Each watcher has, by default, a member C<void *data> that you can change
784	and read at any time, libev will completely ignore it. This can be used	1075	and read at any time: libev will completely ignore it. This can be used
785	to associate arbitrary data with your watcher. If you need more data and	1076	to associate arbitrary data with your watcher. If you need more data and
786	don't want to allocate memory and store a pointer to it in that data	1077	don't want to allocate memory and store a pointer to it in that data
787	member, you can also "subclass" the watcher type and provide your own	1078	member, you can also "subclass" the watcher type and provide your own
788	data:	1079	data:
789		1080
790	struct my_io	1081	struct my_io
791	{	1082	{
792	struct ev_io io;	1083	ev_io io;
793	int otherfd;	1084	int otherfd;
794	void *somedata;	1085	void *somedata;
795	struct whatever *mostinteresting;	1086	struct whatever *mostinteresting;
796	}	1087	};
		1088
		1089	...
		1090	struct my_io w;
		1091	ev_io_init (&w.io, my_cb, fd, EV_READ);
797		1092
798	And since your callback will be called with a pointer to the watcher, you	1093	And since your callback will be called with a pointer to the watcher, you
799	can cast it back to your own type:	1094	can cast it back to your own type:
800		1095
801	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1096	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
802	{	1097	{
803	struct my_io *w = (struct my_io *)w_;	1098	struct my_io *w = (struct my_io *)w_;
804	...	1099	...
805	}	1100	}
806		1101
807	More interesting and less C-conformant ways of casting your callback type	1102	More interesting and less C-conformant ways of casting your callback type
808	instead have been omitted.	1103	instead have been omitted.
809		1104
810	Another common scenario is having some data structure with multiple	1105	Another common scenario is to use some data structure with multiple
811	watchers:	1106	embedded watchers:
812		1107
813	struct my_biggy	1108	struct my_biggy
814	{	1109	{
815	int some_data;	1110	int some_data;
816	ev_timer t1;	1111	ev_timer t1;
817	ev_timer t2;	1112	ev_timer t2;
818	}	1113	}
819		1114
820	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1115	In this case getting the pointer to C<my_biggy> is a bit more
821	you need to use C<offsetof>:	1116	complicated: Either you store the address of your C<my_biggy> struct
		1117	in the C<data> member of the watcher (for woozies), or you need to use
		1118	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1119	programmers):
822		1120
823	#include <stddef.h>	1121	#include <stddef.h>
824		1122
825	static void	1123	static void
826	t1_cb (EV_P_ struct ev_timer *w, int revents)	1124	t1_cb (EV_P_ ev_timer *w, int revents)
827	{	1125	{
828	struct my_biggy big = (struct my_biggy *	1126	struct my_biggy big = (struct my_biggy *
829	(((char *)w) - offsetof (struct my_biggy, t1));	1127	(((char *)w) - offsetof (struct my_biggy, t1));
830	}	1128	}
831		1129
832	static void	1130	static void
833	t2_cb (EV_P_ struct ev_timer *w, int revents)	1131	t2_cb (EV_P_ ev_timer *w, int revents)
834	{	1132	{
835	struct my_biggy big = (struct my_biggy *	1133	struct my_biggy big = (struct my_biggy *
836	(((char *)w) - offsetof (struct my_biggy, t2));	1134	(((char *)w) - offsetof (struct my_biggy, t2));
837	}	1135	}
838		1136
839		1137
840	=head1 WATCHER TYPES	1138	=head1 WATCHER TYPES
841		1139
842	This section describes each watcher in detail, but will not repeat	1140	This section describes each watcher in detail, but will not repeat
…		…
866	In general you can register as many read and/or write event watchers per	1164	In general you can register as many read and/or write event watchers per
867	fd as you want (as long as you don't confuse yourself). Setting all file	1165	fd as you want (as long as you don't confuse yourself). Setting all file
868	descriptors to non-blocking mode is also usually a good idea (but not	1166	descriptors to non-blocking mode is also usually a good idea (but not
869	required if you know what you are doing).	1167	required if you know what you are doing).
870		1168
871	You have to be careful with dup'ed file descriptors, though. Some backends	1169	If you cannot use non-blocking mode, then force the use of a
872	(the linux epoll backend is a notable example) cannot handle dup'ed file	1170	known-to-be-good backend (at the time of this writing, this includes only
873	descriptors correctly if you register interest in two or more fds pointing	1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
874	to the same underlying file/socket/etc. description (that is, they share
875	the same underlying "file open").
876
877	If you must do this, then force the use of a known-to-be-good backend
878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
879	C<EVBACKEND_POLL>).
880		1172
881	Another thing you have to watch out for is that it is quite easy to	1173	Another thing you have to watch out for is that it is quite easy to
882	receive "spurious" readyness notifications, that is your callback might	1174	receive "spurious" readiness notifications, that is your callback might
883	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1175	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
884	because there is no data. Not only are some backends known to create a	1176	because there is no data. Not only are some backends known to create a
885	lot of those (for example solaris ports), it is very easy to get into	1177	lot of those (for example Solaris ports), it is very easy to get into
886	this situation even with a relatively standard program structure. Thus	1178	this situation even with a relatively standard program structure. Thus
887	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1179	it is best to always use non-blocking I/O: An extra C<read>(2) returning
888	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1180	C<EAGAIN> is far preferable to a program hanging until some data arrives.
889		1181
890	If you cannot run the fd in non-blocking mode (for example you should not	1182	If you cannot run the fd in non-blocking mode (for example you should
891	play around with an Xlib connection), then you have to seperately re-test	1183	not play around with an Xlib connection), then you have to separately
892	whether a file descriptor is really ready with a known-to-be good interface	1184	re-test whether a file descriptor is really ready with a known-to-be good
893	such as poll (fortunately in our Xlib example, Xlib already does this on	1185	interface such as poll (fortunately in our Xlib example, Xlib already
894	its own, so its quite safe to use).	1186	does this on its own, so its quite safe to use). Some people additionally
		1187	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1188	indefinitely.
		1189
		1190	But really, best use non-blocking mode.
		1191
		1192	=head3 The special problem of disappearing file descriptors
		1193
		1194	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1195	descriptor (either due to calling C<close> explicitly or any other means,
		1196	such as C<dup2>). The reason is that you register interest in some file
		1197	descriptor, but when it goes away, the operating system will silently drop
		1198	this interest. If another file descriptor with the same number then is
		1199	registered with libev, there is no efficient way to see that this is, in
		1200	fact, a different file descriptor.
		1201
		1202	To avoid having to explicitly tell libev about such cases, libev follows
		1203	the following policy: Each time C<ev_io_set> is being called, libev
		1204	will assume that this is potentially a new file descriptor, otherwise
		1205	it is assumed that the file descriptor stays the same. That means that
		1206	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1207	descriptor even if the file descriptor number itself did not change.
		1208
		1209	This is how one would do it normally anyway, the important point is that
		1210	the libev application should not optimise around libev but should leave
		1211	optimisations to libev.
		1212
		1213	=head3 The special problem of dup'ed file descriptors
		1214
		1215	Some backends (e.g. epoll), cannot register events for file descriptors,
		1216	but only events for the underlying file descriptions. That means when you
		1217	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1218	events for them, only one file descriptor might actually receive events.
		1219
		1220	There is no workaround possible except not registering events
		1221	for potentially C<dup ()>'ed file descriptors, or to resort to
		1222	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1223
		1224	=head3 The special problem of fork
		1225
		1226	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1227	useless behaviour. Libev fully supports fork, but needs to be told about
		1228	it in the child.
		1229
		1230	To support fork in your programs, you either have to call
		1231	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1232	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1233	C<EVBACKEND_POLL>.
		1234
		1235	=head3 The special problem of SIGPIPE
		1236
		1237	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1238	when writing to a pipe whose other end has been closed, your program gets
		1239	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1240	this is sensible behaviour, for daemons, this is usually undesirable.
		1241
		1242	So when you encounter spurious, unexplained daemon exits, make sure you
		1243	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1244	somewhere, as that would have given you a big clue).
		1245
		1246
		1247	=head3 Watcher-Specific Functions
895		1248
896	=over 4	1249	=over 4
897		1250
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1251	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1252
900	=item ev_io_set (ev_io *, int fd, int events)	1253	=item ev_io_set (ev_io *, int fd, int events)
901		1254
902	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1255	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
903	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1256	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
904	C<EV_READ | EV_WRITE> to receive the given events.	1257	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
905		1258
906	=item int fd [read-only]	1259	=item int fd [read-only]
907		1260
908	The file descriptor being watched.	1261	The file descriptor being watched.
909		1262
910	=item int events [read-only]	1263	=item int events [read-only]
911		1264
912	The events being watched.	1265	The events being watched.
913		1266
914	=back	1267	=back
		1268
		1269	=head3 Examples
915		1270
916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1271	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
917	readable, but only once. Since it is likely line-buffered, you could	1272	readable, but only once. Since it is likely line-buffered, you could
918	attempt to read a whole line in the callback.	1273	attempt to read a whole line in the callback.
919		1274
920	static void	1275	static void
921	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1276	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
922	{	1277	{
923	ev_io_stop (loop, w);	1278	ev_io_stop (loop, w);
924	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1279	.. read from stdin here (or from w->fd) and handle any I/O errors
925	}	1280	}
926		1281
927	...	1282	...
928	struct ev_loop *loop = ev_default_init (0);	1283	struct ev_loop *loop = ev_default_init (0);
929	struct ev_io stdin_readable;	1284	ev_io stdin_readable;
930	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
931	ev_io_start (loop, &stdin_readable);	1286	ev_io_start (loop, &stdin_readable);
932	ev_loop (loop, 0);	1287	ev_loop (loop, 0);
933		1288
934		1289
935	=head2 C<ev_timer> - relative and optionally repeating timeouts	1290	=head2 C<ev_timer> - relative and optionally repeating timeouts
936		1291
937	Timer watchers are simple relative timers that generate an event after a	1292	Timer watchers are simple relative timers that generate an event after a
938	given time, and optionally repeating in regular intervals after that.	1293	given time, and optionally repeating in regular intervals after that.
939		1294
940	The timers are based on real time, that is, if you register an event that	1295	The timers are based on real time, that is, if you register an event that
941	times out after an hour and you reset your system clock to last years	1296	times out after an hour and you reset your system clock to January last
942	time, it will still time out after (roughly) and hour. "Roughly" because	1297	year, it will still time out after (roughly) one hour. "Roughly" because
943	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the
944	monotonic clock option helps a lot here).	1299	monotonic clock option helps a lot here).
		1300
		1301	The callback is guaranteed to be invoked only I<after> its timeout has
		1302	passed, but if multiple timers become ready during the same loop iteration
		1303	then order of execution is undefined.
		1304
		1305	=head3 Be smart about timeouts
		1306
		1307	Many real-world problems involve some kind of timeout, usually for error
		1308	recovery. A typical example is an HTTP request - if the other side hangs,
		1309	you want to raise some error after a while.
		1310
		1311	What follows are some ways to handle this problem, from obvious and
		1312	inefficient to smart and efficient.
		1313
		1314	In the following, a 60 second activity timeout is assumed - a timeout that
		1315	gets reset to 60 seconds each time there is activity (e.g. each time some
		1316	data or other life sign was received).
		1317
		1318	=over 4
		1319
		1320	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1321
		1322	This is the most obvious, but not the most simple way: In the beginning,
		1323	start the watcher:
		1324
		1325	ev_timer_init (timer, callback, 60., 0.);
		1326	ev_timer_start (loop, timer);
		1327
		1328	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1329	and start it again:
		1330
		1331	ev_timer_stop (loop, timer);
		1332	ev_timer_set (timer, 60., 0.);
		1333	ev_timer_start (loop, timer);
		1334
		1335	This is relatively simple to implement, but means that each time there is
		1336	some activity, libev will first have to remove the timer from its internal
		1337	data structure and then add it again. Libev tries to be fast, but it's
		1338	still not a constant-time operation.
		1339
		1340	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1341
		1342	This is the easiest way, and involves using C<ev_timer_again> instead of
		1343	C<ev_timer_start>.
		1344
		1345	To implement this, configure an C<ev_timer> with a C<repeat> value
		1346	of C<60> and then call C<ev_timer_again> at start and each time you
		1347	successfully read or write some data. If you go into an idle state where
		1348	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1349	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1350
		1351	That means you can ignore both the C<ev_timer_start> function and the
		1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1353	member and C<ev_timer_again>.
		1354
		1355	At start:
		1356
		1357	ev_timer_init (timer, callback);
		1358	timer->repeat = 60.;
		1359	ev_timer_again (loop, timer);
		1360
		1361	Each time there is some activity:
		1362
		1363	ev_timer_again (loop, timer);
		1364
		1365	It is even possible to change the time-out on the fly, regardless of
		1366	whether the watcher is active or not:
		1367
		1368	timer->repeat = 30.;
		1369	ev_timer_again (loop, timer);
		1370
		1371	This is slightly more efficient then stopping/starting the timer each time
		1372	you want to modify its timeout value, as libev does not have to completely
		1373	remove and re-insert the timer from/into its internal data structure.
		1374
		1375	It is, however, even simpler than the "obvious" way to do it.
		1376
		1377	=item 3. Let the timer time out, but then re-arm it as required.
		1378
		1379	This method is more tricky, but usually most efficient: Most timeouts are
		1380	relatively long compared to the intervals between other activity - in
		1381	our example, within 60 seconds, there are usually many I/O events with
		1382	associated activity resets.
		1383
		1384	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1385	but remember the time of last activity, and check for a real timeout only
		1386	within the callback:
		1387
		1388	ev_tstamp last_activity; // time of last activity
		1389
		1390	static void
		1391	callback (EV_P_ ev_timer *w, int revents)
		1392	{
		1393	ev_tstamp now = ev_now (EV_A);
		1394	ev_tstamp timeout = last_activity + 60.;
		1395
		1396	// if last_activity + 60. is older than now, we did time out
		1397	if (timeout < now)
		1398	{
		1399	// timeout occured, take action
		1400	}
		1401	else
		1402	{
		1403	// callback was invoked, but there was some activity, re-arm
		1404	// the watcher to fire in last_activity + 60, which is
		1405	// guaranteed to be in the future, so "again" is positive:
		1406	w->again = timeout - now;
		1407	ev_timer_again (EV_A_ w);
		1408	}
		1409	}
		1410
		1411	To summarise the callback: first calculate the real timeout (defined
		1412	as "60 seconds after the last activity"), then check if that time has
		1413	been reached, which means something I<did>, in fact, time out. Otherwise
		1414	the callback was invoked too early (C<timeout> is in the future), so
		1415	re-schedule the timer to fire at that future time, to see if maybe we have
		1416	a timeout then.
		1417
		1418	Note how C<ev_timer_again> is used, taking advantage of the
		1419	C<ev_timer_again> optimisation when the timer is already running.
		1420
		1421	This scheme causes more callback invocations (about one every 60 seconds
		1422	minus half the average time between activity), but virtually no calls to
		1423	libev to change the timeout.
		1424
		1425	To start the timer, simply initialise the watcher and set C<last_activity>
		1426	to the current time (meaning we just have some activity :), then call the
		1427	callback, which will "do the right thing" and start the timer:
		1428
		1429	ev_timer_init (timer, callback);
		1430	last_activity = ev_now (loop);
		1431	callback (loop, timer, EV_TIMEOUT);
		1432
		1433	And when there is some activity, simply store the current time in
		1434	C<last_activity>, no libev calls at all:
		1435
		1436	last_actiivty = ev_now (loop);
		1437
		1438	This technique is slightly more complex, but in most cases where the
		1439	time-out is unlikely to be triggered, much more efficient.
		1440
		1441	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1442	callback :) - just change the timeout and invoke the callback, which will
		1443	fix things for you.
		1444
		1445	=item 4. Wee, just use a double-linked list for your timeouts.
		1446
		1447	If there is not one request, but many thousands (millions...), all
		1448	employing some kind of timeout with the same timeout value, then one can
		1449	do even better:
		1450
		1451	When starting the timeout, calculate the timeout value and put the timeout
		1452	at the I<end> of the list.
		1453
		1454	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1455	the list is expected to fire (for example, using the technique #3).
		1456
		1457	When there is some activity, remove the timer from the list, recalculate
		1458	the timeout, append it to the end of the list again, and make sure to
		1459	update the C<ev_timer> if it was taken from the beginning of the list.
		1460
		1461	This way, one can manage an unlimited number of timeouts in O(1) time for
		1462	starting, stopping and updating the timers, at the expense of a major
		1463	complication, and having to use a constant timeout. The constant timeout
		1464	ensures that the list stays sorted.
		1465
		1466	=back
		1467
		1468	So which method the best?
		1469
		1470	Method #2 is a simple no-brain-required solution that is adequate in most
		1471	situations. Method #3 requires a bit more thinking, but handles many cases
		1472	better, and isn't very complicated either. In most case, choosing either
		1473	one is fine, with #3 being better in typical situations.
		1474
		1475	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1476	rather complicated, but extremely efficient, something that really pays
		1477	off after the first million or so of active timers, i.e. it's usually
		1478	overkill :)
		1479
		1480	=head3 The special problem of time updates
		1481
		1482	Establishing the current time is a costly operation (it usually takes at
		1483	least two system calls): EV therefore updates its idea of the current
		1484	time only before and after C<ev_loop> collects new events, which causes a
		1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1486	lots of events in one iteration.
945		1487
946	The relative timeouts are calculated relative to the C<ev_now ()>	1488	The relative timeouts are calculated relative to the C<ev_now ()>
947	time. This is usually the right thing as this timestamp refers to the time	1489	time. This is usually the right thing as this timestamp refers to the time
948	of the event triggering whatever timeout you are modifying/starting. If	1490	of the event triggering whatever timeout you are modifying/starting. If
949	you suspect event processing to be delayed and you I<need> to base the timeout	1491	you suspect event processing to be delayed and you I<need> to base the
950	on the current time, use something like this to adjust for this:	1492	timeout on the current time, use something like this to adjust for this:
951		1493
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1494	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1495
954	The callback is guarenteed to be invoked only when its timeout has passed,	1496	If the event loop is suspended for a long time, you can also force an
955	but if multiple timers become ready during the same loop iteration then	1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update
956	order of execution is undefined.	1498	()>.
		1499
		1500	=head3 Watcher-Specific Functions and Data Members
957		1501
958	=over 4	1502	=over 4
959		1503
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1504	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1505
962	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1506	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
963		1507
964	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1508	Configure the timer to trigger after C<after> seconds. If C<repeat>
965	C<0.>, then it will automatically be stopped. If it is positive, then the	1509	is C<0.>, then it will automatically be stopped once the timeout is
966	timer will automatically be configured to trigger again C<repeat> seconds	1510	reached. If it is positive, then the timer will automatically be
967	later, again, and again, until stopped manually.	1511	configured to trigger again C<repeat> seconds later, again, and again,
		1512	until stopped manually.
968		1513
969	The timer itself will do a best-effort at avoiding drift, that is, if you	1514	The timer itself will do a best-effort at avoiding drift, that is, if
970	configure a timer to trigger every 10 seconds, then it will trigger at	1515	you configure a timer to trigger every 10 seconds, then it will normally
971	exactly 10 second intervals. If, however, your program cannot keep up with	1516	trigger at exactly 10 second intervals. If, however, your program cannot
972	the timer (because it takes longer than those 10 seconds to do stuff) the	1517	keep up with the timer (because it takes longer than those 10 seconds to
973	timer will not fire more than once per event loop iteration.	1518	do stuff) the timer will not fire more than once per event loop iteration.
974		1519
975	=item ev_timer_again (loop)	1520	=item ev_timer_again (loop, ev_timer *)
976		1521
977	This will act as if the timer timed out and restart it again if it is	1522	This will act as if the timer timed out and restart it again if it is
978	repeating. The exact semantics are:	1523	repeating. The exact semantics are:
979		1524
980	If the timer is pending, its pending status is cleared.	1525	If the timer is pending, its pending status is cleared.
981		1526
982	If the timer is started but nonrepeating, stop it (as if it timed out).	1527	If the timer is started but non-repeating, stop it (as if it timed out).
983		1528
984	If the timer is repeating, either start it if necessary (with the	1529	If the timer is repeating, either start it if necessary (with the
985	C<repeat> value), or reset the running timer to the C<repeat> value.	1530	C<repeat> value), or reset the running timer to the C<repeat> value.
986		1531
987	This sounds a bit complicated, but here is a useful and typical	1532	This sounds a bit complicated, see "Be smart about timeouts", above, for a
988	example: Imagine you have a tcp connection and you want a so-called idle	1533	usage example.
989	timeout, that is, you want to be called when there have been, say, 60
990	seconds of inactivity on the socket. The easiest way to do this is to
991	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
992	C<ev_timer_again> each time you successfully read or write some data. If
993	you go into an idle state where you do not expect data to travel on the
994	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
995	automatically restart it if need be.
996
997	That means you can ignore the C<after> value and C<ev_timer_start>
998	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
999
1000	ev_timer_init (timer, callback, 0., 5.);
1001	ev_timer_again (loop, timer);
1002	...
1003	timer->again = 17.;
1004	ev_timer_again (loop, timer);
1005	...
1006	timer->again = 10.;
1007	ev_timer_again (loop, timer);
1008
1009	This is more slightly efficient then stopping/starting the timer each time
1010	you want to modify its timeout value.
1011		1534
1012	=item ev_tstamp repeat [read-write]	1535	=item ev_tstamp repeat [read-write]
1013		1536
1014	The current C<repeat> value. Will be used each time the watcher times out	1537	The current C<repeat> value. Will be used each time the watcher times out
1015	or C<ev_timer_again> is called and determines the next timeout (if any),	1538	or C<ev_timer_again> is called, and determines the next timeout (if any),
1016	which is also when any modifications are taken into account.	1539	which is also when any modifications are taken into account.
1017		1540
1018	=back	1541	=back
1019		1542
		1543	=head3 Examples
		1544
1020	Example: Create a timer that fires after 60 seconds.	1545	Example: Create a timer that fires after 60 seconds.
1021		1546
1022	static void	1547	static void
1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1548	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1024	{	1549	{
1025	.. one minute over, w is actually stopped right here	1550	.. one minute over, w is actually stopped right here
1026	}	1551	}
1027		1552
1028	struct ev_timer mytimer;	1553	ev_timer mytimer;
1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1554	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1030	ev_timer_start (loop, &mytimer);	1555	ev_timer_start (loop, &mytimer);
1031		1556
1032	Example: Create a timeout timer that times out after 10 seconds of	1557	Example: Create a timeout timer that times out after 10 seconds of
1033	inactivity.	1558	inactivity.
1034		1559
1035	static void	1560	static void
1036	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1561	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1037	{	1562	{
1038	.. ten seconds without any activity	1563	.. ten seconds without any activity
1039	}	1564	}
1040		1565
1041	struct ev_timer mytimer;	1566	ev_timer mytimer;
1042	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1043	ev_timer_again (&mytimer); /* start timer */	1568	ev_timer_again (&mytimer); /* start timer */
1044	ev_loop (loop, 0);	1569	ev_loop (loop, 0);
1045		1570
1046	// and in some piece of code that gets executed on any "activity":	1571	// and in some piece of code that gets executed on any "activity":
1047	// reset the timeout to start ticking again at 10 seconds	1572	// reset the timeout to start ticking again at 10 seconds
1048	ev_timer_again (&mytimer);	1573	ev_timer_again (&mytimer);
1049		1574
1050		1575
1051	=head2 C<ev_periodic> - to cron or not to cron?	1576	=head2 C<ev_periodic> - to cron or not to cron?
1052		1577
1053	Periodic watchers are also timers of a kind, but they are very versatile	1578	Periodic watchers are also timers of a kind, but they are very versatile
1054	(and unfortunately a bit complex).	1579	(and unfortunately a bit complex).
1055		1580
1056	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1057	but on wallclock time (absolute time). You can tell a periodic watcher	1582	but on wall clock time (absolute time). You can tell a periodic watcher
1058	to trigger "at" some specific point in time. For example, if you tell a	1583	to trigger after some specific point in time. For example, if you tell a
1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1584	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1060	+ 10.>) and then reset your system clock to the last year, then it will	1585	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1586	clock to January of the previous year, then it will take more than year
1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1062	roughly 10 seconds later and of course not if you reset your system time	1588	roughly 10 seconds later as it uses a relative timeout).
1063	again).
1064		1589
1065	They can also be used to implement vastly more complex timers, such as	1590	C<ev_periodic>s can also be used to implement vastly more complex timers,
1066	triggering an event on eahc midnight, local time.	1591	such as triggering an event on each "midnight, local time", or other
		1592	complicated rules.
1067		1593
1068	As with timers, the callback is guarenteed to be invoked only when the	1594	As with timers, the callback is guaranteed to be invoked only when the
1069	time (C<at>) has been passed, but if multiple periodic timers become ready	1595	time (C<at>) has passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1596	during the same loop iteration, then order of execution is undefined.
		1597
		1598	=head3 Watcher-Specific Functions and Data Members
1071		1599
1072	=over 4	1600	=over 4
1073		1601
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1603
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1077		1605
1078	Lots of arguments, lets sort it out... There are basically three modes of	1606	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1607	operation, and we will explain them from simplest to most complex:
1080		1608
1081	=over 4	1609	=over 4
1082		1610
1083	=item * absolute timer (interval = reschedule_cb = 0)	1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1612
1085	In this configuration the watcher triggers an event at the wallclock time	1613	In this configuration the watcher triggers an event after the wall clock
1086	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1614	time C<at> has passed. It will not repeat and will not adjust when a time
1087	that is, if it is to be run at January 1st 2011 then it will run when the	1615	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1088	system time reaches or surpasses this time.	1616	only run when the system clock reaches or surpasses this time.
1089		1617
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1619
1092	In this mode the watcher will always be scheduled to time out at the next	1620	In this mode the watcher will always be scheduled to time out at the next
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1621	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1622	and then repeat, regardless of any time jumps.
1095		1623
1096	This can be used to create timers that do not drift with respect to system	1624	This can be used to create timers that do not drift with respect to the
1097	time:	1625	system clock, for example, here is a C<ev_periodic> that triggers each
		1626	hour, on the hour:
1098		1627
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1628	ev_periodic_set (&periodic, 0., 3600., 0);
1100		1629
1101	This doesn't mean there will always be 3600 seconds in between triggers,	1630	This doesn't mean there will always be 3600 seconds in between triggers,
1102	but only that the the callback will be called when the system time shows a	1631	but only that the callback will be called when the system time shows a
1103	full hour (UTC), or more correctly, when the system time is evenly divisible	1632	full hour (UTC), or more correctly, when the system time is evenly divisible
1104	by 3600.	1633	by 3600.
1105		1634
1106	Another way to think about it (for the mathematically inclined) is that	1635	Another way to think about it (for the mathematically inclined) is that
1107	C<ev_periodic> will try to run the callback in this mode at the next possible	1636	C<ev_periodic> will try to run the callback in this mode at the next possible
1108	time where C<time = at (mod interval)>, regardless of any time jumps.	1637	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1638
		1639	For numerical stability it is preferable that the C<at> value is near
		1640	C<ev_now ()> (the current time), but there is no range requirement for
		1641	this value, and in fact is often specified as zero.
		1642
		1643	Note also that there is an upper limit to how often a timer can fire (CPU
		1644	speed for example), so if C<interval> is very small then timing stability
		1645	will of course deteriorate. Libev itself tries to be exact to be about one
		1646	millisecond (if the OS supports it and the machine is fast enough).
		1647
1110	=item * manual reschedule mode (reschedule_cb = callback)	1648	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1649
1112	In this mode the values for C<interval> and C<at> are both being	1650	In this mode the values for C<interval> and C<at> are both being
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1651	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1652	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1653	current time as second argument.
1116		1654
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1655	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118	ever, or make any event loop modifications>. If you need to stop it,	1656	ever, or make ANY event loop modifications whatsoever>.
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).
1121		1657
		1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1660	only event loop modification you are allowed to do).
		1661
1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1662	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1123	ev_tstamp now)>, e.g.:	1663	*w, ev_tstamp now)>, e.g.:
1124		1664
		1665	static ev_tstamp
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1666	my_rescheduler (ev_periodic *w, ev_tstamp now)
1126	{	1667	{
1127	return now + 60.;	1668	return now + 60.;
1128	}	1669	}
1129		1670
1130	It must return the next time to trigger, based on the passed time value	1671	It must return the next time to trigger, based on the passed time value
1131	(that is, the lowest time value larger than to the second argument). It	1672	(that is, the lowest time value larger than to the second argument). It
1132	will usually be called just before the callback will be triggered, but	1673	will usually be called just before the callback will be triggered, but
1133	might be called at other times, too.	1674	might be called at other times, too.
1134		1675
1135	NOTE: I<< This callback must always return a time that is later than the	1676	NOTE: I<< This callback must always return a time that is higher than or
1136	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1677	equal to the passed C<now> value >>.
1137		1678
1138	This can be used to create very complex timers, such as a timer that	1679	This can be used to create very complex timers, such as a timer that
1139	triggers on each midnight, local time. To do this, you would calculate the	1680	triggers on "next midnight, local time". To do this, you would calculate the
1140	next midnight after C<now> and return the timestamp value for this. How	1681	next midnight after C<now> and return the timestamp value for this. How
1141	you do this is, again, up to you (but it is not trivial, which is the main	1682	you do this is, again, up to you (but it is not trivial, which is the main
1142	reason I omitted it as an example).	1683	reason I omitted it as an example).
1143		1684
1144	=back	1685	=back
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1689	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1690	when you changed some parameters or the reschedule callback would return
1150	a different time than the last time it was called (e.g. in a crond like	1691	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1692	program when the crontabs have changed).
1152		1693
		1694	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1695
		1696	When active, returns the absolute time that the watcher is supposed to
		1697	trigger next.
		1698
		1699	=item ev_tstamp offset [read-write]
		1700
		1701	When repeating, this contains the offset value, otherwise this is the
		1702	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1703
		1704	Can be modified any time, but changes only take effect when the periodic
		1705	timer fires or C<ev_periodic_again> is being called.
		1706
1153	=item ev_tstamp interval [read-write]	1707	=item ev_tstamp interval [read-write]
1154		1708
1155	The current interval value. Can be modified any time, but changes only	1709	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1710	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1711	called.
1158		1712
1159	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1713	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1160		1714
1161	The current reschedule callback, or C<0>, if this functionality is	1715	The current reschedule callback, or C<0>, if this functionality is
1162	switched off. Can be changed any time, but changes only take effect when	1716	switched off. Can be changed any time, but changes only take effect when
1163	the periodic timer fires or C<ev_periodic_again> is being called.	1717	the periodic timer fires or C<ev_periodic_again> is being called.
1164		1718
1165	=back	1719	=back
1166		1720
		1721	=head3 Examples
		1722
1167	Example: Call a callback every hour, or, more precisely, whenever the	1723	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1724	system time is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1725	potentially a lot of jitter, but good long-term stability.
1170		1726
1171	static void	1727	static void
1172	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1173	{	1729	{
1174	... its now a full hour (UTC, or TAI or whatever your clock follows)	1730	... its now a full hour (UTC, or TAI or whatever your clock follows)
1175	}	1731	}
1176		1732
1177	struct ev_periodic hourly_tick;	1733	ev_periodic hourly_tick;
1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1734	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1179	ev_periodic_start (loop, &hourly_tick);	1735	ev_periodic_start (loop, &hourly_tick);
1180		1736
1181	Example: The same as above, but use a reschedule callback to do it:	1737	Example: The same as above, but use a reschedule callback to do it:
1182		1738
1183	#include <math.h>	1739	#include <math.h>
1184		1740
1185	static ev_tstamp	1741	static ev_tstamp
1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1742	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1187	{	1743	{
1188	return fmod (now, 3600.) + 3600.;	1744	return now + (3600. - fmod (now, 3600.));
1189	}	1745	}
1190		1746
1191	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1747	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1192		1748
1193	Example: Call a callback every hour, starting now:	1749	Example: Call a callback every hour, starting now:
1194		1750
1195	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1196	ev_periodic_init (&hourly_tick, clock_cb,	1752	ev_periodic_init (&hourly_tick, clock_cb,
1197	fmod (ev_now (loop), 3600.), 3600., 0);	1753	fmod (ev_now (loop), 3600.), 3600., 0);
1198	ev_periodic_start (loop, &hourly_tick);	1754	ev_periodic_start (loop, &hourly_tick);
1199		1755
1200		1756
1201	=head2 C<ev_signal> - signal me when a signal gets signalled!	1757	=head2 C<ev_signal> - signal me when a signal gets signalled!
1202		1758
1203	Signal watchers will trigger an event when the process receives a specific	1759	Signal watchers will trigger an event when the process receives a specific
1204	signal one or more times. Even though signals are very asynchronous, libev	1760	signal one or more times. Even though signals are very asynchronous, libev
1205	will try it's best to deliver signals synchronously, i.e. as part of the	1761	will try it's best to deliver signals synchronously, i.e. as part of the
1206	normal event processing, like any other event.	1762	normal event processing, like any other event.
1207		1763
		1764	If you want signals asynchronously, just use C<sigaction> as you would
		1765	do without libev and forget about sharing the signal. You can even use
		1766	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1767
1208	You can configure as many watchers as you like per signal. Only when the	1768	You can configure as many watchers as you like per signal. Only when the
1209	first watcher gets started will libev actually register a signal watcher	1769	first watcher gets started will libev actually register a signal handler
1210	with the kernel (thus it coexists with your own signal handlers as long	1770	with the kernel (thus it coexists with your own signal handlers as long as
1211	as you don't register any with libev). Similarly, when the last signal	1771	you don't register any with libev for the same signal). Similarly, when
1212	watcher for a signal is stopped libev will reset the signal handler to	1772	the last signal watcher for a signal is stopped, libev will reset the
1213	SIG_DFL (regardless of what it was set to before).	1773	signal handler to SIG_DFL (regardless of what it was set to before).
		1774
		1775	If possible and supported, libev will install its handlers with
		1776	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1777	interrupted. If you have a problem with system calls getting interrupted by
		1778	signals you can block all signals in an C<ev_check> watcher and unblock
		1779	them in an C<ev_prepare> watcher.
		1780
		1781	=head3 Watcher-Specific Functions and Data Members
1214		1782
1215	=over 4	1783	=over 4
1216		1784
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1785	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1786
…		…
1225		1793
1226	The signal the watcher watches out for.	1794	The signal the watcher watches out for.
1227		1795
1228	=back	1796	=back
1229		1797
		1798	=head3 Examples
		1799
		1800	Example: Try to exit cleanly on SIGINT.
		1801
		1802	static void
		1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1804	{
		1805	ev_unloop (loop, EVUNLOOP_ALL);
		1806	}
		1807
		1808	ev_signal signal_watcher;
		1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1810	ev_signal_start (loop, &signal_watcher);
		1811
1230		1812
1231	=head2 C<ev_child> - watch out for process status changes	1813	=head2 C<ev_child> - watch out for process status changes
1232		1814
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1815	Child watchers trigger when your process receives a SIGCHLD in response to
1234	some child status changes (most typically when a child of yours dies).	1816	some child status changes (most typically when a child of yours dies or
		1817	exits). It is permissible to install a child watcher I<after> the child
		1818	has been forked (which implies it might have already exited), as long
		1819	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1820	forking and then immediately registering a watcher for the child is fine,
		1821	but forking and registering a watcher a few event loop iterations later is
		1822	not.
		1823
		1824	Only the default event loop is capable of handling signals, and therefore
		1825	you can only register child watchers in the default event loop.
		1826
		1827	=head3 Process Interaction
		1828
		1829	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1830	initialised. This is necessary to guarantee proper behaviour even if
		1831	the first child watcher is started after the child exits. The occurrence
		1832	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1833	synchronously as part of the event loop processing. Libev always reaps all
		1834	children, even ones not watched.
		1835
		1836	=head3 Overriding the Built-In Processing
		1837
		1838	Libev offers no special support for overriding the built-in child
		1839	processing, but if your application collides with libev's default child
		1840	handler, you can override it easily by installing your own handler for
		1841	C<SIGCHLD> after initialising the default loop, and making sure the
		1842	default loop never gets destroyed. You are encouraged, however, to use an
		1843	event-based approach to child reaping and thus use libev's support for
		1844	that, so other libev users can use C<ev_child> watchers freely.
		1845
		1846	=head3 Stopping the Child Watcher
		1847
		1848	Currently, the child watcher never gets stopped, even when the
		1849	child terminates, so normally one needs to stop the watcher in the
		1850	callback. Future versions of libev might stop the watcher automatically
		1851	when a child exit is detected.
		1852
		1853	=head3 Watcher-Specific Functions and Data Members
1235		1854
1236	=over 4	1855	=over 4
1237		1856
1238	=item ev_child_init (ev_child *, callback, int pid)	1857	=item ev_child_init (ev_child *, callback, int pid, int trace)
1239		1858
1240	=item ev_child_set (ev_child *, int pid)	1859	=item ev_child_set (ev_child *, int pid, int trace)
1241		1860
1242	Configures the watcher to wait for status changes of process C<pid> (or	1861	Configures the watcher to wait for status changes of process C<pid> (or
1243	I<any> process if C<pid> is specified as C<0>). The callback can look	1862	I<any> process if C<pid> is specified as C<0>). The callback can look
1244	at the C<rstatus> member of the C<ev_child> watcher structure to see	1863	at the C<rstatus> member of the C<ev_child> watcher structure to see
1245	the status word (use the macros from C<sys/wait.h> and see your systems	1864	the status word (use the macros from C<sys/wait.h> and see your systems
1246	C<waitpid> documentation). The C<rpid> member contains the pid of the	1865	C<waitpid> documentation). The C<rpid> member contains the pid of the
1247	process causing the status change.	1866	process causing the status change. C<trace> must be either C<0> (only
		1867	activate the watcher when the process terminates) or C<1> (additionally
		1868	activate the watcher when the process is stopped or continued).
1248		1869
1249	=item int pid [read-only]	1870	=item int pid [read-only]
1250		1871
1251	The process id this watcher watches out for, or C<0>, meaning any process id.	1872	The process id this watcher watches out for, or C<0>, meaning any process id.
1252		1873
…		…
1259	The process exit/trace status caused by C<rpid> (see your systems	1880	The process exit/trace status caused by C<rpid> (see your systems
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1881	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1882
1262	=back	1883	=back
1263		1884
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1885	=head3 Examples
1265		1886
		1887	Example: C<fork()> a new process and install a child handler to wait for
		1888	its completion.
		1889
		1890	ev_child cw;
		1891
1266	static void	1892	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1893	child_cb (EV_P_ ev_child *w, int revents)
1268	{	1894	{
1269	ev_unloop (loop, EVUNLOOP_ALL);	1895	ev_child_stop (EV_A_ w);
		1896	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1270	}	1897	}
1271		1898
1272	struct ev_signal signal_watcher;	1899	pid_t pid = fork ();
1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1900
1274	ev_signal_start (loop, &sigint_cb);	1901	if (pid < 0)
		1902	// error
		1903	else if (pid == 0)
		1904	{
		1905	// the forked child executes here
		1906	exit (1);
		1907	}
		1908	else
		1909	{
		1910	ev_child_init (&cw, child_cb, pid, 0);
		1911	ev_child_start (EV_DEFAULT_ &cw);
		1912	}
1275		1913
1276		1914
1277	=head2 C<ev_stat> - did the file attributes just change?	1915	=head2 C<ev_stat> - did the file attributes just change?
1278		1916
1279	This watches a filesystem path for attribute changes. That is, it calls	1917	This watches a file system path for attribute changes. That is, it calls
1280	C<stat> regularly (or when the OS says it changed) and sees if it changed	1918	C<stat> regularly (or when the OS says it changed) and sees if it changed
1281	compared to the last time, invoking the callback if it did.	1919	compared to the last time, invoking the callback if it did.
1282		1920
1283	The path does not need to exist: changing from "path exists" to "path does	1921	The path does not need to exist: changing from "path exists" to "path does
1284	not exist" is a status change like any other. The condition "path does	1922	not exist" is a status change like any other. The condition "path does
…		…
1287	the stat buffer having unspecified contents.	1925	the stat buffer having unspecified contents.
1288		1926
1289	The path I<should> be absolute and I<must not> end in a slash. If it is	1927	The path I<should> be absolute and I<must not> end in a slash. If it is
1290	relative and your working directory changes, the behaviour is undefined.	1928	relative and your working directory changes, the behaviour is undefined.
1291		1929
1292	Since there is no standard to do this, the portable implementation simply	1930	Since there is no standard kernel interface to do this, the portable
1293	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1931	implementation simply calls C<stat (2)> regularly on the path to see if
1294	can specify a recommended polling interval for this case. If you specify	1932	it changed somehow. You can specify a recommended polling interval for
1295	a polling interval of C<0> (highly recommended!) then a I<suitable,	1933	this case. If you specify a polling interval of C<0> (highly recommended!)
1296	unspecified default> value will be used (which you can expect to be around	1934	then a I<suitable, unspecified default> value will be used (which
1297	five seconds, although this might change dynamically). Libev will also	1935	you can expect to be around five seconds, although this might change
1298	impose a minimum interval which is currently around C<0.1>, but thats	1936	dynamically). Libev will also impose a minimum interval which is currently
1299	usually overkill.	1937	around C<0.1>, but thats usually overkill.
1300		1938
1301	This watcher type is not meant for massive numbers of stat watchers,	1939	This watcher type is not meant for massive numbers of stat watchers,
1302	as even with OS-supported change notifications, this can be	1940	as even with OS-supported change notifications, this can be
1303	resource-intensive.	1941	resource-intensive.
1304		1942
1305	At the time of this writing, only the Linux inotify interface is	1943	At the time of this writing, the only OS-specific interface implemented
1306	implemented (implementing kqueue support is left as an exercise for the	1944	is the Linux inotify interface (implementing kqueue support is left as
1307	reader). Inotify will be used to give hints only and should not change the	1945	an exercise for the reader. Note, however, that the author sees no way
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1946	of implementing C<ev_stat> semantics with kqueue).
1309	to fall back to regular polling again even with inotify, but changes are	1947
1310	usually detected immediately, and if the file exists there will be no	1948	=head3 ABI Issues (Largefile Support)
1311	polling.	1949
		1950	Libev by default (unless the user overrides this) uses the default
		1951	compilation environment, which means that on systems with large file
		1952	support disabled by default, you get the 32 bit version of the stat
		1953	structure. When using the library from programs that change the ABI to
		1954	use 64 bit file offsets the programs will fail. In that case you have to
		1955	compile libev with the same flags to get binary compatibility. This is
		1956	obviously the case with any flags that change the ABI, but the problem is
		1957	most noticeably disabled with ev_stat and large file support.
		1958
		1959	The solution for this is to lobby your distribution maker to make large
		1960	file interfaces available by default (as e.g. FreeBSD does) and not
		1961	optional. Libev cannot simply switch on large file support because it has
		1962	to exchange stat structures with application programs compiled using the
		1963	default compilation environment.
		1964
		1965	=head3 Inotify and Kqueue
		1966
		1967	When C<inotify (7)> support has been compiled into libev (generally
		1968	only available with Linux 2.6.25 or above due to bugs in earlier
		1969	implementations) and present at runtime, it will be used to speed up
		1970	change detection where possible. The inotify descriptor will be created
		1971	lazily when the first C<ev_stat> watcher is being started.
		1972
		1973	Inotify presence does not change the semantics of C<ev_stat> watchers
		1974	except that changes might be detected earlier, and in some cases, to avoid
		1975	making regular C<stat> calls. Even in the presence of inotify support
		1976	there are many cases where libev has to resort to regular C<stat> polling,
		1977	but as long as the path exists, libev usually gets away without polling.
		1978
		1979	There is no support for kqueue, as apparently it cannot be used to
		1980	implement this functionality, due to the requirement of having a file
		1981	descriptor open on the object at all times, and detecting renames, unlinks
		1982	etc. is difficult.
		1983
		1984	=head3 The special problem of stat time resolution
		1985
		1986	The C<stat ()> system call only supports full-second resolution portably, and
		1987	even on systems where the resolution is higher, most file systems still
		1988	only support whole seconds.
		1989
		1990	That means that, if the time is the only thing that changes, you can
		1991	easily miss updates: on the first update, C<ev_stat> detects a change and
		1992	calls your callback, which does something. When there is another update
		1993	within the same second, C<ev_stat> will be unable to detect unless the
		1994	stat data does change in other ways (e.g. file size).
		1995
		1996	The solution to this is to delay acting on a change for slightly more
		1997	than a second (or till slightly after the next full second boundary), using
		1998	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1999	ev_timer_again (loop, w)>).
		2000
		2001	The C<.02> offset is added to work around small timing inconsistencies
		2002	of some operating systems (where the second counter of the current time
		2003	might be be delayed. One such system is the Linux kernel, where a call to
		2004	C<gettimeofday> might return a timestamp with a full second later than
		2005	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2006	update file times then there will be a small window where the kernel uses
		2007	the previous second to update file times but libev might already execute
		2008	the timer callback).
		2009
		2010	=head3 Watcher-Specific Functions and Data Members
1312		2011
1313	=over 4	2012	=over 4
1314		2013
1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	2014	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316		2015
…		…
1320	C<path>. The C<interval> is a hint on how quickly a change is expected to	2019	C<path>. The C<interval> is a hint on how quickly a change is expected to
1321	be detected and should normally be specified as C<0> to let libev choose	2020	be detected and should normally be specified as C<0> to let libev choose
1322	a suitable value. The memory pointed to by C<path> must point to the same	2021	a suitable value. The memory pointed to by C<path> must point to the same
1323	path for as long as the watcher is active.	2022	path for as long as the watcher is active.
1324		2023
1325	The callback will be receive C<EV_STAT> when a change was detected,	2024	The callback will receive an C<EV_STAT> event when a change was detected,
1326	relative to the attributes at the time the watcher was started (or the	2025	relative to the attributes at the time the watcher was started (or the
1327	last change was detected).	2026	last change was detected).
1328		2027
1329	=item ev_stat_stat (ev_stat *)	2028	=item ev_stat_stat (loop, ev_stat *)
1330		2029
1331	Updates the stat buffer immediately with new values. If you change the	2030	Updates the stat buffer immediately with new values. If you change the
1332	watched path in your callback, you could call this fucntion to avoid	2031	watched path in your callback, you could call this function to avoid
1333	detecting this change (while introducing a race condition). Can also be	2032	detecting this change (while introducing a race condition if you are not
1334	useful simply to find out the new values.	2033	the only one changing the path). Can also be useful simply to find out the
		2034	new values.
1335		2035
1336	=item ev_statdata attr [read-only]	2036	=item ev_statdata attr [read-only]
1337		2037
1338	The most-recently detected attributes of the file. Although the type is of	2038	The most-recently detected attributes of the file. Although the type is
1339	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2039	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1340	suitable for your system. If the C<st_nlink> member is C<0>, then there	2040	suitable for your system, but you can only rely on the POSIX-standardised
		2041	members to be present. If the C<st_nlink> member is C<0>, then there was
1341	was some error while C<stat>ing the file.	2042	some error while C<stat>ing the file.
1342		2043
1343	=item ev_statdata prev [read-only]	2044	=item ev_statdata prev [read-only]
1344		2045
1345	The previous attributes of the file. The callback gets invoked whenever	2046	The previous attributes of the file. The callback gets invoked whenever
1346	C<prev> != C<attr>.	2047	C<prev> != C<attr>, or, more precisely, one or more of these members
		2048	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2049	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1347		2050
1348	=item ev_tstamp interval [read-only]	2051	=item ev_tstamp interval [read-only]
1349		2052
1350	The specified interval.	2053	The specified interval.
1351		2054
1352	=item const char *path [read-only]	2055	=item const char *path [read-only]
1353		2056
1354	The filesystem path that is being watched.	2057	The file system path that is being watched.
1355		2058
1356	=back	2059	=back
1357		2060
		2061	=head3 Examples
		2062
1358	Example: Watch C</etc/passwd> for attribute changes.	2063	Example: Watch C</etc/passwd> for attribute changes.
1359		2064
1360	static void	2065	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2066	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1362	{	2067	{
1363	/* /etc/passwd changed in some way */	2068	/* /etc/passwd changed in some way */
1364	if (w->attr.st_nlink)	2069	if (w->attr.st_nlink)
1365	{	2070	{
1366	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2071	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1367	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2072	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1368	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2073	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1369	}	2074	}
1370	else	2075	else
1371	/* you shalt not abuse printf for puts */	2076	/* you shalt not abuse printf for puts */
1372	puts ("wow, /etc/passwd is not there, expect problems. "	2077	puts ("wow, /etc/passwd is not there, expect problems. "
1373	"if this is windows, they already arrived\n");	2078	"if this is windows, they already arrived\n");
1374	}	2079	}
1375		2080
1376	...	2081	...
1377	ev_stat passwd;	2082	ev_stat passwd;
1378		2083
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2084	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	2085	ev_stat_start (loop, &passwd);
		2086
		2087	Example: Like above, but additionally use a one-second delay so we do not
		2088	miss updates (however, frequent updates will delay processing, too, so
		2089	one might do the work both on C<ev_stat> callback invocation I<and> on
		2090	C<ev_timer> callback invocation).
		2091
		2092	static ev_stat passwd;
		2093	static ev_timer timer;
		2094
		2095	static void
		2096	timer_cb (EV_P_ ev_timer *w, int revents)
		2097	{
		2098	ev_timer_stop (EV_A_ w);
		2099
		2100	/* now it's one second after the most recent passwd change */
		2101	}
		2102
		2103	static void
		2104	stat_cb (EV_P_ ev_stat *w, int revents)
		2105	{
		2106	/* reset the one-second timer */
		2107	ev_timer_again (EV_A_ &timer);
		2108	}
		2109
		2110	...
		2111	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2112	ev_stat_start (loop, &passwd);
		2113	ev_timer_init (&timer, timer_cb, 0., 1.02);
1381		2114
1382		2115
1383	=head2 C<ev_idle> - when you've got nothing better to do...	2116	=head2 C<ev_idle> - when you've got nothing better to do...
1384		2117
1385	Idle watchers trigger events when no other events of the same or higher	2118	Idle watchers trigger events when no other events of the same or higher
1386	priority are pending (prepare, check and other idle watchers do not	2119	priority are pending (prepare, check and other idle watchers do not count
1387	count).	2120	as receiving "events").
1388		2121
1389	That is, as long as your process is busy handling sockets or timeouts	2122	That is, as long as your process is busy handling sockets or timeouts
1390	(or even signals, imagine) of the same or higher priority it will not be	2123	(or even signals, imagine) of the same or higher priority it will not be
1391	triggered. But when your process is idle (or only lower-priority watchers	2124	triggered. But when your process is idle (or only lower-priority watchers
1392	are pending), the idle watchers are being called once per event loop	2125	are pending), the idle watchers are being called once per event loop
…		…
1399	Apart from keeping your process non-blocking (which is a useful	2132	Apart from keeping your process non-blocking (which is a useful
1400	effect on its own sometimes), idle watchers are a good place to do	2133	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	2134	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	2135	event loop has handled all outstanding events.
1403		2136
		2137	=head3 Watcher-Specific Functions and Data Members
		2138
1404	=over 4	2139	=over 4
1405		2140
1406	=item ev_idle_init (ev_signal *, callback)	2141	=item ev_idle_init (ev_signal *, callback)
1407		2142
1408	Initialises and configures the idle watcher - it has no parameters of any	2143	Initialises and configures the idle watcher - it has no parameters of any
1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2144	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1410	believe me.	2145	believe me.
1411		2146
1412	=back	2147	=back
1413		2148
		2149	=head3 Examples
		2150
1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2151	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1415	callback, free it. Also, use no error checking, as usual.	2152	callback, free it. Also, use no error checking, as usual.
1416		2153
1417	static void	2154	static void
1418	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2155	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1419	{	2156	{
1420	free (w);	2157	free (w);
1421	// now do something you wanted to do when the program has	2158	// now do something you wanted to do when the program has
1422	// no longer asnything immediate to do.	2159	// no longer anything immediate to do.
1423	}	2160	}
1424		2161
1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1426	ev_idle_init (idle_watcher, idle_cb);	2163	ev_idle_init (idle_watcher, idle_cb);
1427	ev_idle_start (loop, idle_cb);	2164	ev_idle_start (loop, idle_cb);
1428		2165
1429		2166
1430	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1431		2168
1432	Prepare and check watchers are usually (but not always) used in tandem:	2169	Prepare and check watchers are usually (but not always) used in pairs:
1433	prepare watchers get invoked before the process blocks and check watchers	2170	prepare watchers get invoked before the process blocks and check watchers
1434	afterwards.	2171	afterwards.
1435		2172
1436	You I<must not> call C<ev_loop> or similar functions that enter	2173	You I<must not> call C<ev_loop> or similar functions that enter
1437	the current event loop from either C<ev_prepare> or C<ev_check>	2174	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1440	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2177	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1441	C<ev_check> so if you have one watcher of each kind they will always be	2178	C<ev_check> so if you have one watcher of each kind they will always be
1442	called in pairs bracketing the blocking call.	2179	called in pairs bracketing the blocking call.
1443		2180
1444	Their main purpose is to integrate other event mechanisms into libev and	2181	Their main purpose is to integrate other event mechanisms into libev and
1445	their use is somewhat advanced. This could be used, for example, to track	2182	their use is somewhat advanced. They could be used, for example, to track
1446	variable changes, implement your own watchers, integrate net-snmp or a	2183	variable changes, implement your own watchers, integrate net-snmp or a
1447	coroutine library and lots more. They are also occasionally useful if	2184	coroutine library and lots more. They are also occasionally useful if
1448	you cache some data and want to flush it before blocking (for example,	2185	you cache some data and want to flush it before blocking (for example,
1449	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2186	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1450	watcher).	2187	watcher).
1451		2188
1452	This is done by examining in each prepare call which file descriptors need	2189	This is done by examining in each prepare call which file descriptors
1453	to be watched by the other library, registering C<ev_io> watchers for	2190	need to be watched by the other library, registering C<ev_io> watchers
1454	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2191	for them and starting an C<ev_timer> watcher for any timeouts (many
1455	provide just this functionality). Then, in the check watcher you check for	2192	libraries provide exactly this functionality). Then, in the check watcher,
1456	any events that occured (by checking the pending status of all watchers	2193	you check for any events that occurred (by checking the pending status
1457	and stopping them) and call back into the library. The I/O and timer	2194	of all watchers and stopping them) and call back into the library. The
1458	callbacks will never actually be called (but must be valid nevertheless,	2195	I/O and timer callbacks will never actually be called (but must be valid
1459	because you never know, you know?).	2196	nevertheless, because you never know, you know?).
1460		2197
1461	As another example, the Perl Coro module uses these hooks to integrate	2198	As another example, the Perl Coro module uses these hooks to integrate
1462	coroutines into libev programs, by yielding to other active coroutines	2199	coroutines into libev programs, by yielding to other active coroutines
1463	during each prepare and only letting the process block if no coroutines	2200	during each prepare and only letting the process block if no coroutines
1464	are ready to run (it's actually more complicated: it only runs coroutines	2201	are ready to run (it's actually more complicated: it only runs coroutines
1465	with priority higher than or equal to the event loop and one coroutine	2202	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	2203	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	2204	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	2205	low-priority coroutines to idle/background tasks).
1469		2206
		2207	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2208	priority, to ensure that they are being run before any other watchers
		2209	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2210
		2211	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2212	activate ("feed") events into libev. While libev fully supports this, they
		2213	might get executed before other C<ev_check> watchers did their job. As
		2214	C<ev_check> watchers are often used to embed other (non-libev) event
		2215	loops those other event loops might be in an unusable state until their
		2216	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2217	others).
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
1470	=over 4	2221	=over 4
1471		2222
1472	=item ev_prepare_init (ev_prepare *, callback)	2223	=item ev_prepare_init (ev_prepare *, callback)
1473		2224
1474	=item ev_check_init (ev_check *, callback)	2225	=item ev_check_init (ev_check *, callback)
1475		2226
1476	Initialises and configures the prepare or check watcher - they have no	2227	Initialises and configures the prepare or check watcher - they have no
1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2228	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478	macros, but using them is utterly, utterly and completely pointless.	2229	macros, but using them is utterly, utterly, utterly and completely
		2230	pointless.
1479		2231
1480	=back	2232	=back
1481		2233
1482	Example: To include a library such as adns, you would add IO watchers	2234	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	2235
		2236	There are a number of principal ways to embed other event loops or modules
		2237	into libev. Here are some ideas on how to include libadns into libev
		2238	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2239	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2240	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2241	Glib event loop).
		2242
		2243	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	2244	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	2245	is pseudo-code only of course. This requires you to either use a low
		2246	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2247	the callbacks for the IO/timeout watchers might not have been called yet.
1486		2248
1487	static ev_io iow [nfd];	2249	static ev_io iow [nfd];
1488	static ev_timer tw;	2250	static ev_timer tw;
1489		2251
1490	static void	2252	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	2253	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1492	{	2254	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd *fd = (struct pollfd *)w->data;
1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498	}	2255	}
1499		2256
1500	// create io watchers for each fd and a timer before blocking	2257	// create io watchers for each fd and a timer before blocking
1501	static void	2258	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2259	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1503	{	2260	{
1504	int timeout = 3600000;	2261	int timeout = 3600000;
1505	struct pollfd fds [nfd];	2262	struct pollfd fds [nfd];
1506	// actual code will need to loop here and realloc etc.	2263	// actual code will need to loop here and realloc etc.
1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1508		2265
1509	/* the callback is illegal, but won't be called as we stop during check */	2266	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	2267	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	2268	ev_timer_start (loop, &tw);
1512		2269
1513	// create on ev_io per pollfd	2270	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	2271	for (int i = 0; i < nfd; ++i)
1515	{	2272	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	2273	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	2274	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2275	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		2276
1520	fds [i].revents = 0;	2277	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	2278	ev_io_start (loop, iow + i);
1523	}	2279	}
1524	}	2280	}
1525		2281
1526	// stop all watchers after blocking	2282	// stop all watchers after blocking
1527	static void	2283	static void
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2284	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1529	{	2285	{
1530	ev_timer_stop (loop, &tw);	2286	ev_timer_stop (loop, &tw);
1531		2287
1532	for (int i = 0; i < nfd; ++i)	2288	for (int i = 0; i < nfd; ++i)
		2289	{
		2290	// set the relevant poll flags
		2291	// could also call adns_processreadable etc. here
		2292	struct pollfd *fd = fds + i;
		2293	int revents = ev_clear_pending (iow + i);
		2294	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2295	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2296
		2297	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	2298	ev_io_stop (loop, iow + i);
		2299	}
1534		2300
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2301	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1536	}	2302	}
		2303
		2304	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2305	in the prepare watcher and would dispose of the check watcher.
		2306
		2307	Method 3: If the module to be embedded supports explicit event
		2308	notification (libadns does), you can also make use of the actual watcher
		2309	callbacks, and only destroy/create the watchers in the prepare watcher.
		2310
		2311	static void
		2312	timer_cb (EV_P_ ev_timer *w, int revents)
		2313	{
		2314	adns_state ads = (adns_state)w->data;
		2315	update_now (EV_A);
		2316
		2317	adns_processtimeouts (ads, &tv_now);
		2318	}
		2319
		2320	static void
		2321	io_cb (EV_P_ ev_io *w, int revents)
		2322	{
		2323	adns_state ads = (adns_state)w->data;
		2324	update_now (EV_A);
		2325
		2326	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2327	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2328	}
		2329
		2330	// do not ever call adns_afterpoll
		2331
		2332	Method 4: Do not use a prepare or check watcher because the module you
		2333	want to embed is not flexible enough to support it. Instead, you can
		2334	override their poll function. The drawback with this solution is that the
		2335	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2336	this approach, effectively embedding EV as a client into the horrible
		2337	libglib event loop.
		2338
		2339	static gint
		2340	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2341	{
		2342	int got_events = 0;
		2343
		2344	for (n = 0; n < nfds; ++n)
		2345	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2346
		2347	if (timeout >= 0)
		2348	// create/start timer
		2349
		2350	// poll
		2351	ev_loop (EV_A_ 0);
		2352
		2353	// stop timer again
		2354	if (timeout >= 0)
		2355	ev_timer_stop (EV_A_ &to);
		2356
		2357	// stop io watchers again - their callbacks should have set
		2358	for (n = 0; n < nfds; ++n)
		2359	ev_io_stop (EV_A_ iow [n]);
		2360
		2361	return got_events;
		2362	}
1537		2363
1538		2364
1539	=head2 C<ev_embed> - when one backend isn't enough...	2365	=head2 C<ev_embed> - when one backend isn't enough...
1540		2366
1541	This is a rather advanced watcher type that lets you embed one event loop	2367	This is a rather advanced watcher type that lets you embed one event loop
…		…
1547	prioritise I/O.	2373	prioritise I/O.
1548		2374
1549	As an example for a bug workaround, the kqueue backend might only support	2375	As an example for a bug workaround, the kqueue backend might only support
1550	sockets on some platform, so it is unusable as generic backend, but you	2376	sockets on some platform, so it is unusable as generic backend, but you
1551	still want to make use of it because you have many sockets and it scales	2377	still want to make use of it because you have many sockets and it scales
1552	so nicely. In this case, you would create a kqueue-based loop and embed it	2378	so nicely. In this case, you would create a kqueue-based loop and embed
1553	into your default loop (which might use e.g. poll). Overall operation will	2379	it into your default loop (which might use e.g. poll). Overall operation
1554	be a bit slower because first libev has to poll and then call kevent, but	2380	will be a bit slower because first libev has to call C<poll> and then
1555	at least you can use both at what they are best.	2381	C<kevent>, but at least you can use both mechanisms for what they are
		2382	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1556		2383
1557	As for prioritising I/O: rarely you have the case where some fds have	2384	As for prioritising I/O: under rare circumstances you have the case where
1558	to be watched and handled very quickly (with low latency), and even	2385	some fds have to be watched and handled very quickly (with low latency),
1559	priorities and idle watchers might have too much overhead. In this case	2386	and even priorities and idle watchers might have too much overhead. In
1560	you would put all the high priority stuff in one loop and all the rest in	2387	this case you would put all the high priority stuff in one loop and all
1561	a second one, and embed the second one in the first.	2388	the rest in a second one, and embed the second one in the first.
1562		2389
1563	As long as the watcher is active, the callback will be invoked every time	2390	As long as the watcher is active, the callback will be invoked every time
1564	there might be events pending in the embedded loop. The callback must then	2391	there might be events pending in the embedded loop. The callback must then
1565	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2392	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1566	their callbacks (you could also start an idle watcher to give the embedded	2393	their callbacks (you could also start an idle watcher to give the embedded
…		…
1574	interested in that.	2401	interested in that.
1575		2402
1576	Also, there have not currently been made special provisions for forking:	2403	Also, there have not currently been made special provisions for forking:
1577	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2404	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1578	but you will also have to stop and restart any C<ev_embed> watchers	2405	but you will also have to stop and restart any C<ev_embed> watchers
1579	yourself.	2406	yourself - but you can use a fork watcher to handle this automatically,
		2407	and future versions of libev might do just that.
1580		2408
1581	Unfortunately, not all backends are embeddable, only the ones returned by	2409	Unfortunately, not all backends are embeddable: only the ones returned by
1582	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1583	portable one.	2411	portable one.
1584		2412
1585	So when you want to use this feature you will always have to be prepared	2413	So when you want to use this feature you will always have to be prepared
1586	that you cannot get an embeddable loop. The recommended way to get around	2414	that you cannot get an embeddable loop. The recommended way to get around
1587	this is to have a separate variables for your embeddable loop, try to	2415	this is to have a separate variables for your embeddable loop, try to
1588	create it, and if that fails, use the normal loop for everything:	2416	create it, and if that fails, use the normal loop for everything.
1589		2417
1590	struct ev_loop *loop_hi = ev_default_init (0);	2418	=head3 C<ev_embed> and fork
1591	struct ev_loop *loop_lo = 0;
1592	struct ev_embed embed;
1593
1594	// see if there is a chance of getting one that works
1595	// (remember that a flags value of 0 means autodetection)
1596	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1597	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1598	: 0;
1599		2419
1600	// if we got one, then embed it, otherwise default to loop_hi	2420	While the C<ev_embed> watcher is running, forks in the embedding loop will
1601	if (loop_lo)	2421	automatically be applied to the embedded loop as well, so no special
1602	{	2422	fork handling is required in that case. When the watcher is not running,
1603	ev_embed_init (&embed, 0, loop_lo);	2423	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1604	ev_embed_start (loop_hi, &embed);	2424	as applicable.
1605	}	2425
1606	else	2426	=head3 Watcher-Specific Functions and Data Members
1607	loop_lo = loop_hi;
1608		2427
1609	=over 4	2428	=over 4
1610		2429
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2430	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1612		2431
…		…
1614		2433
1615	Configures the watcher to embed the given loop, which must be	2434	Configures the watcher to embed the given loop, which must be
1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2435	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1617	invoked automatically, otherwise it is the responsibility of the callback	2436	invoked automatically, otherwise it is the responsibility of the callback
1618	to invoke it (it will continue to be called until the sweep has been done,	2437	to invoke it (it will continue to be called until the sweep has been done,
1619	if you do not want thta, you need to temporarily stop the embed watcher).	2438	if you do not want that, you need to temporarily stop the embed watcher).
1620		2439
1621	=item ev_embed_sweep (loop, ev_embed *)	2440	=item ev_embed_sweep (loop, ev_embed *)
1622		2441
1623	Make a single, non-blocking sweep over the embedded loop. This works	2442	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2443	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.	2444	appropriate way for embedded loops.
1626		2445
1627	=item struct ev_loop *loop [read-only]	2446	=item struct ev_loop *other [read-only]
1628		2447
1629	The embedded event loop.	2448	The embedded event loop.
1630		2449
1631	=back	2450	=back
		2451
		2452	=head3 Examples
		2453
		2454	Example: Try to get an embeddable event loop and embed it into the default
		2455	event loop. If that is not possible, use the default loop. The default
		2456	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2457	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2458	used).
		2459
		2460	struct ev_loop *loop_hi = ev_default_init (0);
		2461	struct ev_loop *loop_lo = 0;
		2462	ev_embed embed;
		2463
		2464	// see if there is a chance of getting one that works
		2465	// (remember that a flags value of 0 means autodetection)
		2466	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2467	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2468	: 0;
		2469
		2470	// if we got one, then embed it, otherwise default to loop_hi
		2471	if (loop_lo)
		2472	{
		2473	ev_embed_init (&embed, 0, loop_lo);
		2474	ev_embed_start (loop_hi, &embed);
		2475	}
		2476	else
		2477	loop_lo = loop_hi;
		2478
		2479	Example: Check if kqueue is available but not recommended and create
		2480	a kqueue backend for use with sockets (which usually work with any
		2481	kqueue implementation). Store the kqueue/socket-only event loop in
		2482	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2483
		2484	struct ev_loop *loop = ev_default_init (0);
		2485	struct ev_loop *loop_socket = 0;
		2486	ev_embed embed;
		2487
		2488	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2489	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2490	{
		2491	ev_embed_init (&embed, 0, loop_socket);
		2492	ev_embed_start (loop, &embed);
		2493	}
		2494
		2495	if (!loop_socket)
		2496	loop_socket = loop;
		2497
		2498	// now use loop_socket for all sockets, and loop for everything else
1632		2499
1633		2500
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2501	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2502
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2503	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	2506	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	2507	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2508	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2509	handlers will be invoked, too, of course.
1643		2510
		2511	=head3 Watcher-Specific Functions and Data Members
		2512
1644	=over 4	2513	=over 4
1645		2514
1646	=item ev_fork_init (ev_signal *, callback)	2515	=item ev_fork_init (ev_signal *, callback)
1647		2516
1648	Initialises and configures the fork watcher - it has no parameters of any	2517	Initialises and configures the fork watcher - it has no parameters of any
…		…
1650	believe me.	2519	believe me.
1651		2520
1652	=back	2521	=back
1653		2522
1654		2523
		2524	=head2 C<ev_async> - how to wake up another event loop
		2525
		2526	In general, you cannot use an C<ev_loop> from multiple threads or other
		2527	asynchronous sources such as signal handlers (as opposed to multiple event
		2528	loops - those are of course safe to use in different threads).
		2529
		2530	Sometimes, however, you need to wake up another event loop you do not
		2531	control, for example because it belongs to another thread. This is what
		2532	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2533	can signal it by calling C<ev_async_send>, which is thread- and signal
		2534	safe.
		2535
		2536	This functionality is very similar to C<ev_signal> watchers, as signals,
		2537	too, are asynchronous in nature, and signals, too, will be compressed
		2538	(i.e. the number of callback invocations may be less than the number of
		2539	C<ev_async_sent> calls).
		2540
		2541	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2542	just the default loop.
		2543
		2544	=head3 Queueing
		2545
		2546	C<ev_async> does not support queueing of data in any way. The reason
		2547	is that the author does not know of a simple (or any) algorithm for a
		2548	multiple-writer-single-reader queue that works in all cases and doesn't
		2549	need elaborate support such as pthreads.
		2550
		2551	That means that if you want to queue data, you have to provide your own
		2552	queue. But at least I can tell you how to implement locking around your
		2553	queue:
		2554
		2555	=over 4
		2556
		2557	=item queueing from a signal handler context
		2558
		2559	To implement race-free queueing, you simply add to the queue in the signal
		2560	handler but you block the signal handler in the watcher callback. Here is
		2561	an example that does that for some fictitious SIGUSR1 handler:
		2562
		2563	static ev_async mysig;
		2564
		2565	static void
		2566	sigusr1_handler (void)
		2567	{
		2568	sometype data;
		2569
		2570	// no locking etc.
		2571	queue_put (data);
		2572	ev_async_send (EV_DEFAULT_ &mysig);
		2573	}
		2574
		2575	static void
		2576	mysig_cb (EV_P_ ev_async *w, int revents)
		2577	{
		2578	sometype data;
		2579	sigset_t block, prev;
		2580
		2581	sigemptyset (&block);
		2582	sigaddset (&block, SIGUSR1);
		2583	sigprocmask (SIG_BLOCK, &block, &prev);
		2584
		2585	while (queue_get (&data))
		2586	process (data);
		2587
		2588	if (sigismember (&prev, SIGUSR1)
		2589	sigprocmask (SIG_UNBLOCK, &block, 0);
		2590	}
		2591
		2592	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2593	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2594	either...).
		2595
		2596	=item queueing from a thread context
		2597
		2598	The strategy for threads is different, as you cannot (easily) block
		2599	threads but you can easily preempt them, so to queue safely you need to
		2600	employ a traditional mutex lock, such as in this pthread example:
		2601
		2602	static ev_async mysig;
		2603	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2604
		2605	static void
		2606	otherthread (void)
		2607	{
		2608	// only need to lock the actual queueing operation
		2609	pthread_mutex_lock (&mymutex);
		2610	queue_put (data);
		2611	pthread_mutex_unlock (&mymutex);
		2612
		2613	ev_async_send (EV_DEFAULT_ &mysig);
		2614	}
		2615
		2616	static void
		2617	mysig_cb (EV_P_ ev_async *w, int revents)
		2618	{
		2619	pthread_mutex_lock (&mymutex);
		2620
		2621	while (queue_get (&data))
		2622	process (data);
		2623
		2624	pthread_mutex_unlock (&mymutex);
		2625	}
		2626
		2627	=back
		2628
		2629
		2630	=head3 Watcher-Specific Functions and Data Members
		2631
		2632	=over 4
		2633
		2634	=item ev_async_init (ev_async *, callback)
		2635
		2636	Initialises and configures the async watcher - it has no parameters of any
		2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2638	trust me.
		2639
		2640	=item ev_async_send (loop, ev_async *)
		2641
		2642	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2643	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2644	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2646	section below on what exactly this means).
		2647
		2648	This call incurs the overhead of a system call only once per loop iteration,
		2649	so while the overhead might be noticeable, it doesn't apply to repeated
		2650	calls to C<ev_async_send>.
		2651
		2652	=item bool = ev_async_pending (ev_async *)
		2653
		2654	Returns a non-zero value when C<ev_async_send> has been called on the
		2655	watcher but the event has not yet been processed (or even noted) by the
		2656	event loop.
		2657
		2658	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2659	the loop iterates next and checks for the watcher to have become active,
		2660	it will reset the flag again. C<ev_async_pending> can be used to very
		2661	quickly check whether invoking the loop might be a good idea.
		2662
		2663	Not that this does I<not> check whether the watcher itself is pending, only
		2664	whether it has been requested to make this watcher pending.
		2665
		2666	=back
		2667
		2668
1655	=head1 OTHER FUNCTIONS	2669	=head1 OTHER FUNCTIONS
1656		2670
1657	There are some other functions of possible interest. Described. Here. Now.	2671	There are some other functions of possible interest. Described. Here. Now.
1658		2672
1659	=over 4	2673	=over 4
1660		2674
1661	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2675	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1662		2676
1663	This function combines a simple timer and an I/O watcher, calls your	2677	This function combines a simple timer and an I/O watcher, calls your
1664	callback on whichever event happens first and automatically stop both	2678	callback on whichever event happens first and automatically stops both
1665	watchers. This is useful if you want to wait for a single event on an fd	2679	watchers. This is useful if you want to wait for a single event on an fd
1666	or timeout without having to allocate/configure/start/stop/free one or	2680	or timeout without having to allocate/configure/start/stop/free one or
1667	more watchers yourself.	2681	more watchers yourself.
1668		2682
1669	If C<fd> is less than 0, then no I/O watcher will be started and events	2683	If C<fd> is less than 0, then no I/O watcher will be started and the
1670	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2684	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1671	C<events> set will be craeted and started.	2685	the given C<fd> and C<events> set will be created and started.
1672		2686
1673	If C<timeout> is less than 0, then no timeout watcher will be	2687	If C<timeout> is less than 0, then no timeout watcher will be
1674	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1675	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2689	repeat = 0) will be started. C<0> is a valid timeout.
1676	dubious value.
1677		2690
1678	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2691	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1679	passed an C<revents> set like normal event callbacks (a combination of	2692	passed an C<revents> set like normal event callbacks (a combination of
1680	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1681	value passed to C<ev_once>:	2694	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2695	a timeout and an io event at the same time - you probably should give io
		2696	events precedence.
1682		2697
		2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2699
1683	static void stdin_ready (int revents, void *arg)	2700	static void stdin_ready (int revents, void *arg)
1684	{	2701	{
1685	if (revents & EV_TIMEOUT)
1686	/* doh, nothing entered */;
1687	else if (revents & EV_READ)	2702	if (revents & EV_READ)
1688	/* stdin might have data for us, joy! */;	2703	/* stdin might have data for us, joy! */;
		2704	else if (revents & EV_TIMEOUT)
		2705	/* doh, nothing entered */;
1689	}	2706	}
1690		2707
1691	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1692		2709
1693	=item ev_feed_event (ev_loop *, watcher *, int revents)	2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1694		2711
1695	Feeds the given event set into the event loop, as if the specified event	2712	Feeds the given event set into the event loop, as if the specified event
1696	had happened for the specified watcher (which must be a pointer to an	2713	had happened for the specified watcher (which must be a pointer to an
1697	initialised but not necessarily started event watcher).	2714	initialised but not necessarily started event watcher).
1698		2715
1699	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1700		2717
1701	Feed an event on the given fd, as if a file descriptor backend detected	2718	Feed an event on the given fd, as if a file descriptor backend detected
1702	the given events it.	2719	the given events it.
1703		2720
1704	=item ev_feed_signal_event (ev_loop *loop, int signum)	2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1705		2722
1706	Feed an event as if the given signal occured (C<loop> must be the default	2723	Feed an event as if the given signal occurred (C<loop> must be the default
1707	loop!).	2724	loop!).
1708		2725
1709	=back	2726	=back
1710		2727
1711		2728
…		…
1727		2744
1728	=item * Priorities are not currently supported. Initialising priorities	2745	=item * Priorities are not currently supported. Initialising priorities
1729	will fail and all watchers will have the same priority, even though there	2746	will fail and all watchers will have the same priority, even though there
1730	is an ev_pri field.	2747	is an ev_pri field.
1731		2748
		2749	=item * In libevent, the last base created gets the signals, in libev, the
		2750	first base created (== the default loop) gets the signals.
		2751
1732	=item * Other members are not supported.	2752	=item * Other members are not supported.
1733		2753
1734	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2754	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1735	to use the libev header file and library.	2755	to use the libev header file and library.
1736		2756
1737	=back	2757	=back
1738		2758
1739	=head1 C++ SUPPORT	2759	=head1 C++ SUPPORT
1740		2760
1741	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2761	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1742	you to use some convinience methods to start/stop watchers and also change	2762	you to use some convenience methods to start/stop watchers and also change
1743	the callback model to a model using method callbacks on objects.	2763	the callback model to a model using method callbacks on objects.
1744		2764
1745	To use it,	2765	To use it,
1746		2766
1747	#include <ev++.h>	2767	#include <ev++.h>
1748		2768
1749	(it is not installed by default). This automatically includes F<ev.h>	2769	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2770	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2771	put into the C<ev> namespace. It should support all the same embedding
		2772	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2773
1753	It should support all the same embedding options as F<ev.h>, most notably	2774	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2775	classes add (compared to plain C-style watchers) is the event loop pointer
		2776	that the watcher is associated with (or no additional members at all if
		2777	you disable C<EV_MULTIPLICITY> when embedding libev).
		2778
		2779	Currently, functions, and static and non-static member functions can be
		2780	used as callbacks. Other types should be easy to add as long as they only
		2781	need one additional pointer for context. If you need support for other
		2782	types of functors please contact the author (preferably after implementing
		2783	it).
1755		2784
1756	Here is a list of things available in the C<ev> namespace:	2785	Here is a list of things available in the C<ev> namespace:
1757		2786
1758	=over 4	2787	=over 4
1759		2788
…		…
1775		2804
1776	All of those classes have these methods:	2805	All of those classes have these methods:
1777		2806
1778	=over 4	2807	=over 4
1779		2808
1780	=item ev::TYPE::TYPE (object *, object::method *)	2809	=item ev::TYPE::TYPE ()
1781		2810
1782	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2811	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2812
1784	=item ev::TYPE::~TYPE	2813	=item ev::TYPE::~TYPE
1785		2814
1786	The constructor takes a pointer to an object and a method pointer to	2815	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2816	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2817
1789	before starting it. If you do not specify a loop then the constructor	2818	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2819	C<set> method before starting it.
		2820
		2821	It will not set a callback, however: You have to call the templated C<set>
		2822	method to set a callback before you can start the watcher.
		2823
		2824	(The reason why you have to use a method is a limitation in C++ which does
		2825	not allow explicit template arguments for constructors).
1791		2826
1792	The destructor automatically stops the watcher if it is active.	2827	The destructor automatically stops the watcher if it is active.
		2828
		2829	=item w->set<class, &class::method> (object *)
		2830
		2831	This method sets the callback method to call. The method has to have a
		2832	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2833	first argument and the C<revents> as second. The object must be given as
		2834	parameter and is stored in the C<data> member of the watcher.
		2835
		2836	This method synthesizes efficient thunking code to call your method from
		2837	the C callback that libev requires. If your compiler can inline your
		2838	callback (i.e. it is visible to it at the place of the C<set> call and
		2839	your compiler is good :), then the method will be fully inlined into the
		2840	thunking function, making it as fast as a direct C callback.
		2841
		2842	Example: simple class declaration and watcher initialisation
		2843
		2844	struct myclass
		2845	{
		2846	void io_cb (ev::io &w, int revents) { }
		2847	}
		2848
		2849	myclass obj;
		2850	ev::io iow;
		2851	iow.set <myclass, &myclass::io_cb> (&obj);
		2852
		2853	=item w->set<function> (void *data = 0)
		2854
		2855	Also sets a callback, but uses a static method or plain function as
		2856	callback. The optional C<data> argument will be stored in the watcher's
		2857	C<data> member and is free for you to use.
		2858
		2859	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2860
		2861	See the method-C<set> above for more details.
		2862
		2863	Example: Use a plain function as callback.
		2864
		2865	static void io_cb (ev::io &w, int revents) { }
		2866	iow.set <io_cb> ();
1793		2867
1794	=item w->set (struct ev_loop *)	2868	=item w->set (struct ev_loop *)
1795		2869
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2870	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2871	do this when the watcher is inactive (and not pending either).
1798		2872
1799	=item w->set ([args])	2873	=item w->set ([arguments])
1800		2874
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2875	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2876	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2877	automatically stopped and restarted when reconfiguring it with this
		2878	method.
1804		2879
1805	=item w->start ()	2880	=item w->start ()
1806		2881
1807	Starts the watcher. Note that there is no C<loop> argument as the	2882	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2883	constructor already stores the event loop.
1809		2884
1810	=item w->stop ()	2885	=item w->stop ()
1811		2886
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2887	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2888
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2889	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2890
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2891	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2892	C<ev_TYPE_again> function.
1818		2893
1819	=item w->sweep () C<ev::embed> only	2894	=item w->sweep () (C<ev::embed> only)
1820		2895
1821	Invokes C<ev_embed_sweep>.	2896	Invokes C<ev_embed_sweep>.
1822		2897
1823	=item w->update () C<ev::stat> only	2898	=item w->update () (C<ev::stat> only)
1824		2899
1825	Invokes C<ev_stat_stat>.	2900	Invokes C<ev_stat_stat>.
1826		2901
1827	=back	2902	=back
1828		2903
1829	=back	2904	=back
1830		2905
1831	Example: Define a class with an IO and idle watcher, start one of them in	2906	Example: Define a class with an IO and idle watcher, start one of them in
1832	the constructor.	2907	the constructor.
1833		2908
1834	class myclass	2909	class myclass
1835	{	2910	{
1836	ev_io io; void io_cb (ev::io &w, int revents);	2911	ev::io io ; void io_cb (ev::io &w, int revents);
1837	ev_idle idle void idle_cb (ev::idle &w, int revents);	2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1838		2913
1839	myclass ();	2914	myclass (int fd)
1840	}	2915	{
		2916	io .set <myclass, &myclass::io_cb > (this);
		2917	idle.set <myclass, &myclass::idle_cb> (this);
1841		2918
1842	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{
1846	io.start (fd, ev::READ);	2919	io.start (fd, ev::READ);
		2920	}
1847	}	2921	};
		2922
		2923
		2924	=head1 OTHER LANGUAGE BINDINGS
		2925
		2926	Libev does not offer other language bindings itself, but bindings for a
		2927	number of languages exist in the form of third-party packages. If you know
		2928	any interesting language binding in addition to the ones listed here, drop
		2929	me a note.
		2930
		2931	=over 4
		2932
		2933	=item Perl
		2934
		2935	The EV module implements the full libev API and is actually used to test
		2936	libev. EV is developed together with libev. Apart from the EV core module,
		2937	there are additional modules that implement libev-compatible interfaces
		2938	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2939	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2940	and C<EV::Glib>).
		2941
		2942	It can be found and installed via CPAN, its homepage is at
		2943	L<http://software.schmorp.de/pkg/EV>.
		2944
		2945	=item Python
		2946
		2947	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2948	seems to be quite complete and well-documented. Note, however, that the
		2949	patch they require for libev is outright dangerous as it breaks the ABI
		2950	for everybody else, and therefore, should never be applied in an installed
		2951	libev (if python requires an incompatible ABI then it needs to embed
		2952	libev).
		2953
		2954	=item Ruby
		2955
		2956	Tony Arcieri has written a ruby extension that offers access to a subset
		2957	of the libev API and adds file handle abstractions, asynchronous DNS and
		2958	more on top of it. It can be found via gem servers. Its homepage is at
		2959	L<http://rev.rubyforge.org/>.
		2960
		2961	=item D
		2962
		2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2965
		2966	=item Ocaml
		2967
		2968	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2970
		2971	=back
1848		2972
1849		2973
1850	=head1 MACRO MAGIC	2974	=head1 MACRO MAGIC
1851		2975
1852	Libev can be compiled with a variety of options, the most fundemantal is	2976	Libev can be compiled with a variety of options, the most fundamental
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2977	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2978	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2979
1856	To make it easier to write programs that cope with either variant, the	2980	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2981	following macros are defined:
1858		2982
1859	=over 4	2983	=over 4
…		…
1862		2986
1863	This provides the loop I<argument> for functions, if one is required ("ev	2987	This provides the loop I<argument> for functions, if one is required ("ev
1864	loop argument"). The C<EV_A> form is used when this is the sole argument,	2988	loop argument"). The C<EV_A> form is used when this is the sole argument,
1865	C<EV_A_> is used when other arguments are following. Example:	2989	C<EV_A_> is used when other arguments are following. Example:
1866		2990
1867	ev_unref (EV_A);	2991	ev_unref (EV_A);
1868	ev_timer_add (EV_A_ watcher);	2992	ev_timer_add (EV_A_ watcher);
1869	ev_loop (EV_A_ 0);	2993	ev_loop (EV_A_ 0);
1870		2994
1871	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2995	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1872	which is often provided by the following macro.	2996	which is often provided by the following macro.
1873		2997
1874	=item C<EV_P>, C<EV_P_>	2998	=item C<EV_P>, C<EV_P_>
1875		2999
1876	This provides the loop I<parameter> for functions, if one is required ("ev	3000	This provides the loop I<parameter> for functions, if one is required ("ev
1877	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3001	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1878	C<EV_P_> is used when other parameters are following. Example:	3002	C<EV_P_> is used when other parameters are following. Example:
1879		3003
1880	// this is how ev_unref is being declared	3004	// this is how ev_unref is being declared
1881	static void ev_unref (EV_P);	3005	static void ev_unref (EV_P);
1882		3006
1883	// this is how you can declare your typical callback	3007	// this is how you can declare your typical callback
1884	static void cb (EV_P_ ev_timer *w, int revents)	3008	static void cb (EV_P_ ev_timer *w, int revents)
1885		3009
1886	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3010	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1887	suitable for use with C<EV_A>.	3011	suitable for use with C<EV_A>.
1888		3012
1889	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3013	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1890		3014
1891	Similar to the other two macros, this gives you the value of the default	3015	Similar to the other two macros, this gives you the value of the default
1892	loop, if multiple loops are supported ("ev loop default").	3016	loop, if multiple loops are supported ("ev loop default").
		3017
		3018	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3019
		3020	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3021	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3022	is undefined when the default loop has not been initialised by a previous
		3023	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3024
		3025	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3026	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1893		3027
1894	=back	3028	=back
1895		3029
1896	Example: Declare and initialise a check watcher, utilising the above	3030	Example: Declare and initialise a check watcher, utilising the above
1897	macros so it will work regardless of whether multiple loops are supported	3031	macros so it will work regardless of whether multiple loops are supported
1898	or not.	3032	or not.
1899		3033
1900	static void	3034	static void
1901	check_cb (EV_P_ ev_timer *w, int revents)	3035	check_cb (EV_P_ ev_timer *w, int revents)
1902	{	3036	{
1903	ev_check_stop (EV_A_ w);	3037	ev_check_stop (EV_A_ w);
1904	}	3038	}
1905		3039
1906	ev_check check;	3040	ev_check check;
1907	ev_check_init (&check, check_cb);	3041	ev_check_init (&check, check_cb);
1908	ev_check_start (EV_DEFAULT_ &check);	3042	ev_check_start (EV_DEFAULT_ &check);
1909	ev_loop (EV_DEFAULT_ 0);	3043	ev_loop (EV_DEFAULT_ 0);
1910		3044
1911	=head1 EMBEDDING	3045	=head1 EMBEDDING
1912		3046
1913	Libev can (and often is) directly embedded into host	3047	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	3048	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3049	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	3050	and rxvt-unicode.
1917		3051
1918	The goal is to enable you to just copy the neecssary files into your	3052	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	3053	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	3054	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	3055	libev somewhere in your source tree).
1922		3056
1923	=head2 FILESETS	3057	=head2 FILESETS
1924		3058
1925	Depending on what features you need you need to include one or more sets of files	3059	Depending on what features you need you need to include one or more sets of files
1926	in your app.	3060	in your application.
1927		3061
1928	=head3 CORE EVENT LOOP	3062	=head3 CORE EVENT LOOP
1929		3063
1930	To include only the libev core (all the C<ev_*> functions), with manual	3064	To include only the libev core (all the C<ev_*> functions), with manual
1931	configuration (no autoconf):	3065	configuration (no autoconf):
1932		3066
1933	#define EV_STANDALONE 1	3067	#define EV_STANDALONE 1
1934	#include "ev.c"	3068	#include "ev.c"
1935		3069
1936	This will automatically include F<ev.h>, too, and should be done in a	3070	This will automatically include F<ev.h>, too, and should be done in a
1937	single C source file only to provide the function implementations. To use	3071	single C source file only to provide the function implementations. To use
1938	it, do the same for F<ev.h> in all files wishing to use this API (best	3072	it, do the same for F<ev.h> in all files wishing to use this API (best
1939	done by writing a wrapper around F<ev.h> that you can include instead and	3073	done by writing a wrapper around F<ev.h> that you can include instead and
1940	where you can put other configuration options):	3074	where you can put other configuration options):
1941		3075
1942	#define EV_STANDALONE 1	3076	#define EV_STANDALONE 1
1943	#include "ev.h"	3077	#include "ev.h"
1944		3078
1945	Both header files and implementation files can be compiled with a C++	3079	Both header files and implementation files can be compiled with a C++
1946	compiler (at least, thats a stated goal, and breakage will be treated	3080	compiler (at least, thats a stated goal, and breakage will be treated
1947	as a bug).	3081	as a bug).
1948		3082
1949	You need the following files in your source tree, or in a directory	3083	You need the following files in your source tree, or in a directory
1950	in your include path (e.g. in libev/ when using -Ilibev):	3084	in your include path (e.g. in libev/ when using -Ilibev):
1951		3085
1952	ev.h	3086	ev.h
1953	ev.c	3087	ev.c
1954	ev_vars.h	3088	ev_vars.h
1955	ev_wrap.h	3089	ev_wrap.h
1956		3090
1957	ev_win32.c required on win32 platforms only	3091	ev_win32.c required on win32 platforms only
1958		3092
1959	ev_select.c only when select backend is enabled (which is enabled by default)	3093	ev_select.c only when select backend is enabled (which is enabled by default)
1960	ev_poll.c only when poll backend is enabled (disabled by default)	3094	ev_poll.c only when poll backend is enabled (disabled by default)
1961	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3095	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1962	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3096	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1963	ev_port.c only when the solaris port backend is enabled (disabled by default)	3097	ev_port.c only when the solaris port backend is enabled (disabled by default)
1964		3098
1965	F<ev.c> includes the backend files directly when enabled, so you only need	3099	F<ev.c> includes the backend files directly when enabled, so you only need
1966	to compile this single file.	3100	to compile this single file.
1967		3101
1968	=head3 LIBEVENT COMPATIBILITY API	3102	=head3 LIBEVENT COMPATIBILITY API
1969		3103
1970	To include the libevent compatibility API, also include:	3104	To include the libevent compatibility API, also include:
1971		3105
1972	#include "event.c"	3106	#include "event.c"
1973		3107
1974	in the file including F<ev.c>, and:	3108	in the file including F<ev.c>, and:
1975		3109
1976	#include "event.h"	3110	#include "event.h"
1977		3111
1978	in the files that want to use the libevent API. This also includes F<ev.h>.	3112	in the files that want to use the libevent API. This also includes F<ev.h>.
1979		3113
1980	You need the following additional files for this:	3114	You need the following additional files for this:
1981		3115
1982	event.h	3116	event.h
1983	event.c	3117	event.c
1984		3118
1985	=head3 AUTOCONF SUPPORT	3119	=head3 AUTOCONF SUPPORT
1986		3120
1987	Instead of using C<EV_STANDALONE=1> and providing your config in	3121	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1988	whatever way you want, you can also C<m4_include([libev.m4])> in your	3122	whatever way you want, you can also C<m4_include([libev.m4])> in your
1989	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3123	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1990	include F<config.h> and configure itself accordingly.	3124	include F<config.h> and configure itself accordingly.
1991		3125
1992	For this of course you need the m4 file:	3126	For this of course you need the m4 file:
1993		3127
1994	libev.m4	3128	libev.m4
1995		3129
1996	=head2 PREPROCESSOR SYMBOLS/MACROS	3130	=head2 PREPROCESSOR SYMBOLS/MACROS
1997		3131
1998	Libev can be configured via a variety of preprocessor symbols you have to define	3132	Libev can be configured via a variety of preprocessor symbols you have to
1999	before including any of its files. The default is not to build for multiplicity	3133	define before including any of its files. The default in the absence of
2000	and only include the select backend.	3134	autoconf is documented for every option.
2001		3135
2002	=over 4	3136	=over 4
2003		3137
2004	=item EV_STANDALONE	3138	=item EV_STANDALONE
2005		3139
…		…
2010	F<event.h> that are not directly supported by the libev core alone.	3144	F<event.h> that are not directly supported by the libev core alone.
2011		3145
2012	=item EV_USE_MONOTONIC	3146	=item EV_USE_MONOTONIC
2013		3147
2014	If defined to be C<1>, libev will try to detect the availability of the	3148	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	3149	monotonic clock option at both compile time and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	3150	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	3151	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	3152	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	3153	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	3154	function is hiding in (often F<-lrt>).
2021		3155
2022	=item EV_USE_REALTIME	3156	=item EV_USE_REALTIME
2023		3157
2024	If defined to be C<1>, libev will try to detect the availability of the	3158	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	3159	real-time clock option at compile time (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	3160	runtime if successful). Otherwise no use of the real-time clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3161	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3162	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	3163	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3164
		3165	=item EV_USE_NANOSLEEP
		3166
		3167	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3168	and will use it for delays. Otherwise it will use C<select ()>.
		3169
		3170	=item EV_USE_EVENTFD
		3171
		3172	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3173	available and will probe for kernel support at runtime. This will improve
		3174	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3175	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3176	2.7 or newer, otherwise disabled.
2030		3177
2031	=item EV_USE_SELECT	3178	=item EV_USE_SELECT
2032		3179
2033	If undefined or defined to be C<1>, libev will compile in support for the	3180	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	3181	C<select>(2) backend. No attempt at auto-detection will be done: if no
2035	other method takes over, select will be it. Otherwise the select backend	3182	other method takes over, select will be it. Otherwise the select backend
2036	will not be compiled in.	3183	will not be compiled in.
2037		3184
2038	=item EV_SELECT_USE_FD_SET	3185	=item EV_SELECT_USE_FD_SET
2039		3186
2040	If defined to C<1>, then the select backend will use the system C<fd_set>	3187	If defined to C<1>, then the select backend will use the system C<fd_set>
2041	structure. This is useful if libev doesn't compile due to a missing	3188	structure. This is useful if libev doesn't compile due to a missing
2042	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3189	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2043	exotic systems. This usually limits the range of file descriptors to some	3190	exotic systems. This usually limits the range of file descriptors to some
2044	low limit such as 1024 or might have other limitations (winsocket only	3191	low limit such as 1024 or might have other limitations (winsocket only
2045	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3192	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2046	influence the size of the C<fd_set> used.	3193	influence the size of the C<fd_set> used.
2047		3194
…		…
2053	be used is the winsock select). This means that it will call	3200	be used is the winsock select). This means that it will call
2054	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3201	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2055	it is assumed that all these functions actually work on fds, even	3202	it is assumed that all these functions actually work on fds, even
2056	on win32. Should not be defined on non-win32 platforms.	3203	on win32. Should not be defined on non-win32 platforms.
2057		3204
		3205	=item EV_FD_TO_WIN32_HANDLE
		3206
		3207	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3208	file descriptors to socket handles. When not defining this symbol (the
		3209	default), then libev will call C<_get_osfhandle>, which is usually
		3210	correct. In some cases, programs use their own file descriptor management,
		3211	in which case they can provide this function to map fds to socket handles.
		3212
2058	=item EV_USE_POLL	3213	=item EV_USE_POLL
2059		3214
2060	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3215	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2061	backend. Otherwise it will be enabled on non-win32 platforms. It	3216	backend. Otherwise it will be enabled on non-win32 platforms. It
2062	takes precedence over select.	3217	takes precedence over select.
2063		3218
2064	=item EV_USE_EPOLL	3219	=item EV_USE_EPOLL
2065		3220
2066	If defined to be C<1>, libev will compile in support for the Linux	3221	If defined to be C<1>, libev will compile in support for the Linux
2067	C<epoll>(7) backend. Its availability will be detected at runtime,	3222	C<epoll>(7) backend. Its availability will be detected at runtime,
2068	otherwise another method will be used as fallback. This is the	3223	otherwise another method will be used as fallback. This is the preferred
2069	preferred backend for GNU/Linux systems.	3224	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3225	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2070		3226
2071	=item EV_USE_KQUEUE	3227	=item EV_USE_KQUEUE
2072		3228
2073	If defined to be C<1>, libev will compile in support for the BSD style	3229	If defined to be C<1>, libev will compile in support for the BSD style
2074	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3230	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2087	otherwise another method will be used as fallback. This is the preferred	3243	otherwise another method will be used as fallback. This is the preferred
2088	backend for Solaris 10 systems.	3244	backend for Solaris 10 systems.
2089		3245
2090	=item EV_USE_DEVPOLL	3246	=item EV_USE_DEVPOLL
2091		3247
2092	reserved for future expansion, works like the USE symbols above.	3248	Reserved for future expansion, works like the USE symbols above.
2093		3249
2094	=item EV_USE_INOTIFY	3250	=item EV_USE_INOTIFY
2095		3251
2096	If defined to be C<1>, libev will compile in support for the Linux inotify	3252	If defined to be C<1>, libev will compile in support for the Linux inotify
2097	interface to speed up C<ev_stat> watchers. Its actual availability will	3253	interface to speed up C<ev_stat> watchers. Its actual availability will
2098	be detected at runtime.	3254	be detected at runtime. If undefined, it will be enabled if the headers
		3255	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3256
		3257	=item EV_ATOMIC_T
		3258
		3259	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3260	access is atomic with respect to other threads or signal contexts. No such
		3261	type is easily found in the C language, so you can provide your own type
		3262	that you know is safe for your purposes. It is used both for signal handler "locking"
		3263	as well as for signal and thread safety in C<ev_async> watchers.
		3264
		3265	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3266	(from F<signal.h>), which is usually good enough on most platforms.
2099		3267
2100	=item EV_H	3268	=item EV_H
2101		3269
2102	The name of the F<ev.h> header file used to include it. The default if	3270	The name of the F<ev.h> header file used to include it. The default if
2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3271	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3272	used to virtually rename the F<ev.h> header file in case of conflicts.
2105		3273
2106	=item EV_CONFIG_H	3274	=item EV_CONFIG_H
2107		3275
2108	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3276	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2109	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3277	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2110	C<EV_H>, above.	3278	C<EV_H>, above.
2111		3279
2112	=item EV_EVENT_H	3280	=item EV_EVENT_H
2113		3281
2114	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3282	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2115	of how the F<event.h> header can be found.	3283	of how the F<event.h> header can be found, the default is C<"event.h">.
2116		3284
2117	=item EV_PROTOTYPES	3285	=item EV_PROTOTYPES
2118		3286
2119	If defined to be C<0>, then F<ev.h> will not define any function	3287	If defined to be C<0>, then F<ev.h> will not define any function
2120	prototypes, but still define all the structs and other symbols. This is	3288	prototypes, but still define all the structs and other symbols. This is
…		…
2141	When doing priority-based operations, libev usually has to linearly search	3309	When doing priority-based operations, libev usually has to linearly search
2142	all the priorities, so having many of them (hundreds) uses a lot of space	3310	all the priorities, so having many of them (hundreds) uses a lot of space
2143	and time, so using the defaults of five priorities (-2 .. +2) is usually	3311	and time, so using the defaults of five priorities (-2 .. +2) is usually
2144	fine.	3312	fine.
2145		3313
2146	If your embedding app does not need any priorities, defining these both to	3314	If your embedding application does not need any priorities, defining these
2147	C<0> will save some memory and cpu.	3315	both to C<0> will save some memory and CPU.
2148		3316
2149	=item EV_PERIODIC_ENABLE	3317	=item EV_PERIODIC_ENABLE
2150		3318
2151	If undefined or defined to be C<1>, then periodic timers are supported. If	3319	If undefined or defined to be C<1>, then periodic timers are supported. If
2152	defined to be C<0>, then they are not. Disabling them saves a few kB of	3320	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2159	code.	3327	code.
2160		3328
2161	=item EV_EMBED_ENABLE	3329	=item EV_EMBED_ENABLE
2162		3330
2163	If undefined or defined to be C<1>, then embed watchers are supported. If	3331	If undefined or defined to be C<1>, then embed watchers are supported. If
2164	defined to be C<0>, then they are not.	3332	defined to be C<0>, then they are not. Embed watchers rely on most other
		3333	watcher types, which therefore must not be disabled.
2165		3334
2166	=item EV_STAT_ENABLE	3335	=item EV_STAT_ENABLE
2167		3336
2168	If undefined or defined to be C<1>, then stat watchers are supported. If	3337	If undefined or defined to be C<1>, then stat watchers are supported. If
2169	defined to be C<0>, then they are not.	3338	defined to be C<0>, then they are not.
…		…
2171	=item EV_FORK_ENABLE	3340	=item EV_FORK_ENABLE
2172		3341
2173	If undefined or defined to be C<1>, then fork watchers are supported. If	3342	If undefined or defined to be C<1>, then fork watchers are supported. If
2174	defined to be C<0>, then they are not.	3343	defined to be C<0>, then they are not.
2175		3344
		3345	=item EV_ASYNC_ENABLE
		3346
		3347	If undefined or defined to be C<1>, then async watchers are supported. If
		3348	defined to be C<0>, then they are not.
		3349
2176	=item EV_MINIMAL	3350	=item EV_MINIMAL
2177		3351
2178	If you need to shave off some kilobytes of code at the expense of some	3352	If you need to shave off some kilobytes of code at the expense of some
2179	speed, define this symbol to C<1>. Currently only used for gcc to override	3353	speed, define this symbol to C<1>. Currently this is used to override some
2180	some inlining decisions, saves roughly 30% codesize of amd64.	3354	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3355	much smaller 2-heap for timer management over the default 4-heap.
2181		3356
2182	=item EV_PID_HASHSIZE	3357	=item EV_PID_HASHSIZE
2183		3358
2184	C<ev_child> watchers use a small hash table to distribute workload by	3359	C<ev_child> watchers use a small hash table to distribute workload by
2185	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3360	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2186	than enough. If you need to manage thousands of children you might want to	3361	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	3362	increase this value (I<must> be a power of two).
2188		3363
2189	=item EV_INOTIFY_HASHSIZE	3364	=item EV_INOTIFY_HASHSIZE
2190		3365
2191	C<ev_staz> watchers use a small hash table to distribute workload by	3366	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3367	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	3368	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	3369	watchers you might want to increase this value (I<must> be a power of
2195	two).	3370	two).
2196		3371
		3372	=item EV_USE_4HEAP
		3373
		3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3377	faster performance with many (thousands) of watchers.
		3378
		3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3380	(disabled).
		3381
		3382	=item EV_HEAP_CACHE_AT
		3383
		3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3388	but avoids random read accesses on heap changes. This improves performance
		3389	noticeably with many (hundreds) of watchers.
		3390
		3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3392	(disabled).
		3393
		3394	=item EV_VERIFY
		3395
		3396	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3397	be done: If set to C<0>, no internal verification code will be compiled
		3398	in. If set to C<1>, then verification code will be compiled in, but not
		3399	called. If set to C<2>, then the internal verification code will be
		3400	called once per loop, which can slow down libev. If set to C<3>, then the
		3401	verification code will be called very frequently, which will slow down
		3402	libev considerably.
		3403
		3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3405	C<0>.
		3406
2197	=item EV_COMMON	3407	=item EV_COMMON
2198		3408
2199	By default, all watchers have a C<void *data> member. By redefining	3409	By default, all watchers have a C<void *data> member. By redefining
2200	this macro to a something else you can include more and other types of	3410	this macro to a something else you can include more and other types of
2201	members. You have to define it each time you include one of the files,	3411	members. You have to define it each time you include one of the files,
2202	though, and it must be identical each time.	3412	though, and it must be identical each time.
2203		3413
2204	For example, the perl EV module uses something like this:	3414	For example, the perl EV module uses something like this:
2205		3415
2206	#define EV_COMMON \	3416	#define EV_COMMON \
2207	SV *self; /* contains this struct */ \	3417	SV *self; /* contains this struct */ \
2208	SV *cb_sv, *fh /* note no trailing ";" */	3418	SV *cb_sv, *fh /* note no trailing ";" */
2209		3419
2210	=item EV_CB_DECLARE (type)	3420	=item EV_CB_DECLARE (type)
2211		3421
2212	=item EV_CB_INVOKE (watcher, revents)	3422	=item EV_CB_INVOKE (watcher, revents)
2213		3423
2214	=item ev_set_cb (ev, cb)	3424	=item ev_set_cb (ev, cb)
2215		3425
2216	Can be used to change the callback member declaration in each watcher,	3426	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	3427	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	3428	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	3429	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3430	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	3431	method calls instead of plain function calls in C++.
		3432
		3433	=back
		3434
		3435	=head2 EXPORTED API SYMBOLS
		3436
		3437	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3438	exported symbols, you can use the provided F<Symbol.*> files which list
		3439	all public symbols, one per line:
		3440
		3441	Symbols.ev for libev proper
		3442	Symbols.event for the libevent emulation
		3443
		3444	This can also be used to rename all public symbols to avoid clashes with
		3445	multiple versions of libev linked together (which is obviously bad in
		3446	itself, but sometimes it is inconvenient to avoid this).
		3447
		3448	A sed command like this will create wrapper C<#define>'s that you need to
		3449	include before including F<ev.h>:
		3450
		3451	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3452
		3453	This would create a file F<wrap.h> which essentially looks like this:
		3454
		3455	#define ev_backend myprefix_ev_backend
		3456	#define ev_check_start myprefix_ev_check_start
		3457	#define ev_check_stop myprefix_ev_check_stop
		3458	...
2222		3459
2223	=head2 EXAMPLES	3460	=head2 EXAMPLES
2224		3461
2225	For a real-world example of a program the includes libev	3462	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	3463	verbatim, you can have a look at the EV perl module
…		…
2231	file.	3468	file.
2232		3469
2233	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3470	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2234	that everybody includes and which overrides some configure choices:	3471	that everybody includes and which overrides some configure choices:
2235		3472
2236	#define EV_MINIMAL 1	3473	#define EV_MINIMAL 1
2237	#define EV_USE_POLL 0	3474	#define EV_USE_POLL 0
2238	#define EV_MULTIPLICITY 0	3475	#define EV_MULTIPLICITY 0
2239	#define EV_PERIODIC_ENABLE 0	3476	#define EV_PERIODIC_ENABLE 0
2240	#define EV_STAT_ENABLE 0	3477	#define EV_STAT_ENABLE 0
2241	#define EV_FORK_ENABLE 0	3478	#define EV_FORK_ENABLE 0
2242	#define EV_CONFIG_H <config.h>	3479	#define EV_CONFIG_H <config.h>
2243	#define EV_MINPRI 0	3480	#define EV_MINPRI 0
2244	#define EV_MAXPRI 0	3481	#define EV_MAXPRI 0
2245		3482
2246	#include "ev++.h"	3483	#include "ev++.h"
2247		3484
2248	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2249		3486
2250	#include "ev_cpp.h"	3487	#include "ev_cpp.h"
2251	#include "ev.c"	3488	#include "ev.c"
2252		3489
		3490	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2253		3491
		3492	=head2 THREADS AND COROUTINES
		3493
		3494	=head3 THREADS
		3495
		3496	All libev functions are reentrant and thread-safe unless explicitly
		3497	documented otherwise, but libev implements no locking itself. This means
		3498	that you can use as many loops as you want in parallel, as long as there
		3499	are no concurrent calls into any libev function with the same loop
		3500	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3501	of course): libev guarantees that different event loops share no data
		3502	structures that need any locking.
		3503
		3504	Or to put it differently: calls with different loop parameters can be done
		3505	concurrently from multiple threads, calls with the same loop parameter
		3506	must be done serially (but can be done from different threads, as long as
		3507	only one thread ever is inside a call at any point in time, e.g. by using
		3508	a mutex per loop).
		3509
		3510	Specifically to support threads (and signal handlers), libev implements
		3511	so-called C<ev_async> watchers, which allow some limited form of
		3512	concurrency on the same event loop, namely waking it up "from the
		3513	outside".
		3514
		3515	If you want to know which design (one loop, locking, or multiple loops
		3516	without or something else still) is best for your problem, then I cannot
		3517	help you, but here is some generic advice:
		3518
		3519	=over 4
		3520
		3521	=item * most applications have a main thread: use the default libev loop
		3522	in that thread, or create a separate thread running only the default loop.
		3523
		3524	This helps integrating other libraries or software modules that use libev
		3525	themselves and don't care/know about threading.
		3526
		3527	=item * one loop per thread is usually a good model.
		3528
		3529	Doing this is almost never wrong, sometimes a better-performance model
		3530	exists, but it is always a good start.
		3531
		3532	=item * other models exist, such as the leader/follower pattern, where one
		3533	loop is handed through multiple threads in a kind of round-robin fashion.
		3534
		3535	Choosing a model is hard - look around, learn, know that usually you can do
		3536	better than you currently do :-)
		3537
		3538	=item * often you need to talk to some other thread which blocks in the
		3539	event loop.
		3540
		3541	C<ev_async> watchers can be used to wake them up from other threads safely
		3542	(or from signal contexts...).
		3543
		3544	An example use would be to communicate signals or other events that only
		3545	work in the default loop by registering the signal watcher with the
		3546	default loop and triggering an C<ev_async> watcher from the default loop
		3547	watcher callback into the event loop interested in the signal.
		3548
		3549	=back
		3550
		3551	=head3 COROUTINES
		3552
		3553	Libev is very accommodating to coroutines ("cooperative threads"):
		3554	libev fully supports nesting calls to its functions from different
		3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3556	different coroutines, and switch freely between both coroutines running the
		3557	loop, as long as you don't confuse yourself). The only exception is that
		3558	you must not do this from C<ev_periodic> reschedule callbacks.
		3559
		3560	Care has been taken to ensure that libev does not keep local state inside
		3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3562	they do not clal any callbacks.
		3563
		3564	=head2 COMPILER WARNINGS
		3565
		3566	Depending on your compiler and compiler settings, you might get no or a
		3567	lot of warnings when compiling libev code. Some people are apparently
		3568	scared by this.
		3569
		3570	However, these are unavoidable for many reasons. For one, each compiler
		3571	has different warnings, and each user has different tastes regarding
		3572	warning options. "Warn-free" code therefore cannot be a goal except when
		3573	targeting a specific compiler and compiler-version.
		3574
		3575	Another reason is that some compiler warnings require elaborate
		3576	workarounds, or other changes to the code that make it less clear and less
		3577	maintainable.
		3578
		3579	And of course, some compiler warnings are just plain stupid, or simply
		3580	wrong (because they don't actually warn about the condition their message
		3581	seems to warn about). For example, certain older gcc versions had some
		3582	warnings that resulted an extreme number of false positives. These have
		3583	been fixed, but some people still insist on making code warn-free with
		3584	such buggy versions.
		3585
		3586	While libev is written to generate as few warnings as possible,
		3587	"warn-free" code is not a goal, and it is recommended not to build libev
		3588	with any compiler warnings enabled unless you are prepared to cope with
		3589	them (e.g. by ignoring them). Remember that warnings are just that:
		3590	warnings, not errors, or proof of bugs.
		3591
		3592
		3593	=head2 VALGRIND
		3594
		3595	Valgrind has a special section here because it is a popular tool that is
		3596	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3597
		3598	If you think you found a bug (memory leak, uninitialised data access etc.)
		3599	in libev, then check twice: If valgrind reports something like:
		3600
		3601	==2274== definitely lost: 0 bytes in 0 blocks.
		3602	==2274== possibly lost: 0 bytes in 0 blocks.
		3603	==2274== still reachable: 256 bytes in 1 blocks.
		3604
		3605	Then there is no memory leak, just as memory accounted to global variables
		3606	is not a memleak - the memory is still being refernced, and didn't leak.
		3607
		3608	Similarly, under some circumstances, valgrind might report kernel bugs
		3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3610	although an acceptable workaround has been found here), or it might be
		3611	confused.
		3612
		3613	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3614	make it into some kind of religion.
		3615
		3616	If you are unsure about something, feel free to contact the mailing list
		3617	with the full valgrind report and an explanation on why you think this
		3618	is a bug in libev (best check the archives, too :). However, don't be
		3619	annoyed when you get a brisk "this is no bug" answer and take the chance
		3620	of learning how to interpret valgrind properly.
		3621
		3622	If you need, for some reason, empty reports from valgrind for your project
		3623	I suggest using suppression lists.
		3624
		3625
		3626	=head1 PORTABILITY NOTES
		3627
		3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3629
		3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3631	requires, and its I/O model is fundamentally incompatible with the POSIX
		3632	model. Libev still offers limited functionality on this platform in
		3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3634	descriptors. This only applies when using Win32 natively, not when using
		3635	e.g. cygwin.
		3636
		3637	Lifting these limitations would basically require the full
		3638	re-implementation of the I/O system. If you are into these kinds of
		3639	things, then note that glib does exactly that for you in a very portable
		3640	way (note also that glib is the slowest event library known to man).
		3641
		3642	There is no supported compilation method available on windows except
		3643	embedding it into other applications.
		3644
		3645	Not a libev limitation but worth mentioning: windows apparently doesn't
		3646	accept large writes: instead of resulting in a partial write, windows will
		3647	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3648	so make sure you only write small amounts into your sockets (less than a
		3649	megabyte seems safe, but this apparently depends on the amount of memory
		3650	available).
		3651
		3652	Due to the many, low, and arbitrary limits on the win32 platform and
		3653	the abysmal performance of winsockets, using a large number of sockets
		3654	is not recommended (and not reasonable). If your program needs to use
		3655	more than a hundred or so sockets, then likely it needs to use a totally
		3656	different implementation for windows, as libev offers the POSIX readiness
		3657	notification model, which cannot be implemented efficiently on windows
		3658	(Microsoft monopoly games).
		3659
		3660	A typical way to use libev under windows is to embed it (see the embedding
		3661	section for details) and use the following F<evwrap.h> header file instead
		3662	of F<ev.h>:
		3663
		3664	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3665	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3666
		3667	#include "ev.h"
		3668
		3669	And compile the following F<evwrap.c> file into your project (make sure
		3670	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3671
		3672	#include "evwrap.h"
		3673	#include "ev.c"
		3674
		3675	=over 4
		3676
		3677	=item The winsocket select function
		3678
		3679	The winsocket C<select> function doesn't follow POSIX in that it
		3680	requires socket I<handles> and not socket I<file descriptors> (it is
		3681	also extremely buggy). This makes select very inefficient, and also
		3682	requires a mapping from file descriptors to socket handles (the Microsoft
		3683	C runtime provides the function C<_open_osfhandle> for this). See the
		3684	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3685	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3686
		3687	The configuration for a "naked" win32 using the Microsoft runtime
		3688	libraries and raw winsocket select is:
		3689
		3690	#define EV_USE_SELECT 1
		3691	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3692
		3693	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3694	complexity in the O(n²) range when using win32.
		3695
		3696	=item Limited number of file descriptors
		3697
		3698	Windows has numerous arbitrary (and low) limits on things.
		3699
		3700	Early versions of winsocket's select only supported waiting for a maximum
		3701	of C<64> handles (probably owning to the fact that all windows kernels
		3702	can only wait for C<64> things at the same time internally; Microsoft
		3703	recommends spawning a chain of threads and wait for 63 handles and the
		3704	previous thread in each. Great).
		3705
		3706	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3707	to some high number (e.g. C<2048>) before compiling the winsocket select
		3708	call (which might be in libev or elsewhere, for example, perl does its own
		3709	select emulation on windows).
		3710
		3711	Another limit is the number of file descriptors in the Microsoft runtime
		3712	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3713	or something like this inside Microsoft). You can increase this by calling
		3714	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3715	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3716	libraries.
		3717
		3718	This might get you to about C<512> or C<2048> sockets (depending on
		3719	windows version and/or the phase of the moon). To get more, you need to
		3720	wrap all I/O functions and provide your own fd management, but the cost of
		3721	calling select (O(n²)) will likely make this unworkable.
		3722
		3723	=back
		3724
		3725	=head2 PORTABILITY REQUIREMENTS
		3726
		3727	In addition to a working ISO-C implementation and of course the
		3728	backend-specific APIs, libev relies on a few additional extensions:
		3729
		3730	=over 4
		3731
		3732	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3733	calling conventions regardless of C<ev_watcher_type *>.
		3734
		3735	Libev assumes not only that all watcher pointers have the same internal
		3736	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3737	assumes that the same (machine) code can be used to call any watcher
		3738	callback: The watcher callbacks have different type signatures, but libev
		3739	calls them using an C<ev_watcher *> internally.
		3740
		3741	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3742
		3743	The type C<sig_atomic_t volatile> (or whatever is defined as
		3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3745	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3746	believed to be sufficiently portable.
		3747
		3748	=item C<sigprocmask> must work in a threaded environment
		3749
		3750	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3751	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3752	pthread implementations will either allow C<sigprocmask> in the "main
		3753	thread" or will block signals process-wide, both behaviours would
		3754	be compatible with libev. Interaction between C<sigprocmask> and
		3755	C<pthread_sigmask> could complicate things, however.
		3756
		3757	The most portable way to handle signals is to block signals in all threads
		3758	except the initial one, and run the default loop in the initial thread as
		3759	well.
		3760
		3761	=item C<long> must be large enough for common memory allocation sizes
		3762
		3763	To improve portability and simplify its API, libev uses C<long> internally
		3764	instead of C<size_t> when allocating its data structures. On non-POSIX
		3765	systems (Microsoft...) this might be unexpectedly low, but is still at
		3766	least 31 bits everywhere, which is enough for hundreds of millions of
		3767	watchers.
		3768
		3769	=item C<double> must hold a time value in seconds with enough accuracy
		3770
		3771	The type C<double> is used to represent timestamps. It is required to
		3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3773	enough for at least into the year 4000. This requirement is fulfilled by
		3774	implementations implementing IEEE 754 (basically all existing ones).
		3775
		3776	=back
		3777
		3778	If you know of other additional requirements drop me a note.
		3779
		3780
2254	=head1 COMPLEXITIES	3781	=head1 ALGORITHMIC COMPLEXITIES
2255		3782
2256	In this section the complexities of (many of) the algorithms used inside	3783	In this section the complexities of (many of) the algorithms used inside
2257	libev will be explained. For complexity discussions about backends see the	3784	libev will be documented. For complexity discussions about backends see
2258	documentation for C<ev_default_init>.	3785	the documentation for C<ev_default_init>.
2259		3786
2260	All of the following are about amortised time: If an array needs to be	3787	All of the following are about amortised time: If an array needs to be
2261	extended, libev needs to realloc and move the whole array, but this	3788	extended, libev needs to realloc and move the whole array, but this
2262	happens asymptotically never with higher number of elements, so O(1) might	3789	happens asymptotically rarer with higher number of elements, so O(1) might
2263	mean it might do a lengthy realloc operation in rare cases, but on average	3790	mean that libev does a lengthy realloc operation in rare cases, but on
2264	it is much faster and asymptotically approaches constant time.	3791	average it is much faster and asymptotically approaches constant time.
2265		3792
2266	=over 4	3793	=over 4
2267		3794
2268	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3795	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2269		3796
2270	This means that, when you have a watcher that triggers in one hour and	3797	This means that, when you have a watcher that triggers in one hour and
2271	there are 100 watchers that would trigger before that then inserting will	3798	there are 100 watchers that would trigger before that, then inserting will
2272	have to skip those 100 watchers.	3799	have to skip roughly seven (C<ld 100>) of these watchers.
2273		3800
2274	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3801	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2275		3802
2276	That means that for changing a timer costs less than removing/adding them	3803	That means that changing a timer costs less than removing/adding them,
2277	as only the relative motion in the event queue has to be paid for.	3804	as only the relative motion in the event queue has to be paid for.
2278		3805
2279	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3806	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2280		3807
2281	These just add the watcher into an array or at the head of a list.	3808	These just add the watcher into an array or at the head of a list.
		3809
2282	=item Stopping check/prepare/idle watchers: O(1)	3810	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2283		3811
2284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3812	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2285		3813
2286	These watchers are stored in lists then need to be walked to find the	3814	These watchers are stored in lists, so they need to be walked to find the
2287	correct watcher to remove. The lists are usually short (you don't usually	3815	correct watcher to remove. The lists are usually short (you don't usually
2288	have many watchers waiting for the same fd or signal).	3816	have many watchers waiting for the same fd or signal: one is typical, two
		3817	is rare).
2289		3818
2290	=item Finding the next timer per loop iteration: O(1)	3819	=item Finding the next timer in each loop iteration: O(1)
		3820
		3821	By virtue of using a binary or 4-heap, the next timer is always found at a
		3822	fixed position in the storage array.
2291		3823
2292	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3824	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2293		3825
2294	A change means an I/O watcher gets started or stopped, which requires	3826	A change means an I/O watcher gets started or stopped, which requires
2295	libev to recalculate its status (and possibly tell the kernel).	3827	libev to recalculate its status (and possibly tell the kernel, depending
		3828	on backend and whether C<ev_io_set> was used).
2296		3829
2297	=item Activating one watcher: O(1)	3830	=item Activating one watcher (putting it into the pending state): O(1)
2298		3831
2299	=item Priority handling: O(number_of_priorities)	3832	=item Priority handling: O(number_of_priorities)
2300		3833
2301	Priorities are implemented by allocating some space for each	3834	Priorities are implemented by allocating some space for each
2302	priority. When doing priority-based operations, libev usually has to	3835	priority. When doing priority-based operations, libev usually has to
2303	linearly search all the priorities.	3836	linearly search all the priorities, but starting/stopping and activating
		3837	watchers becomes O(1) with respect to priority handling.
		3838
		3839	=item Sending an ev_async: O(1)
		3840
		3841	=item Processing ev_async_send: O(number_of_async_watchers)
		3842
		3843	=item Processing signals: O(max_signal_number)
		3844
		3845	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3846	calls in the current loop iteration. Checking for async and signal events
		3847	involves iterating over all running async watchers or all signal numbers.
2304		3848
2305	=back	3849	=back
2306		3850
2307		3851
2308	=head1 AUTHOR	3852	=head1 AUTHOR

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