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Revision 1.71 by root, Fri Dec 7 20:13:09 2007 UTC vs.
Revision 1.202 by root, Fri Oct 24 08:30:01 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
317	While stopping and starting an I/O watcher in the same iteration will	394	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	395	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	396	(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	397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	398	very well if you register events for both fds.
322		399
323	Please note that epoll sometimes generates spurious notifications, so you	400	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	401	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	402	(or space) is available.
326		403
		404	Best performance from this backend is achieved by not unregistering all
		405	watchers for a file descriptor until it has been closed, if possible,
		406	i.e. keep at least one watcher active per fd at all times. Stopping and
		407	starting a watcher (without re-setting it) also usually doesn't cause
		408	extra overhead.
		409
		410	While nominally embeddable in other event loops, this feature is broken in
		411	all kernel versions tested so far.
		412
		413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		414	C<EVBACKEND_POLL>.
		415
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		417
329	Kqueue deserves special mention, as at the time of this writing, it	418	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	419	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	420	anything but sockets and pipes, except on Darwin, where of course it's
332	completely useless). For this reason its not being "autodetected"	421	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	422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
334	C<EVBACKEND_KQUEUE>).	423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		424
		425	You still can embed kqueue into a normal poll or select backend and use it
		426	only for sockets (after having made sure that sockets work with kqueue on
		427	the target platform). See C<ev_embed> watchers for more info.
335		428
336	It scales in the same way as the epoll backend, but the interface to the	429	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	430	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	431	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	432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	433	two event changes per incident. Support for C<fork ()> is very bad and it
		434	drops fds silently in similarly hard-to-detect cases.
		435
		436	This backend usually performs well under most conditions.
		437
		438	While nominally embeddable in other event loops, this doesn't work
		439	everywhere, so you might need to test for this. And since it is broken
		440	almost everywhere, you should only use it when you have a lot of sockets
		441	(for which it usually works), by embedding it into another event loop
		442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		443	using it only for sockets.
		444
		445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		447	C<NOTE_EOF>.
341		448
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	449	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		450
344	This is not implemented yet (and might never be).	451	This is not implemented yet (and might never be, unless you send me an
		452	implementation). According to reports, C</dev/poll> only supports sockets
		453	and is not embeddable, which would limit the usefulness of this backend
		454	immensely.
345		455
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	456	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		457
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	458	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)).	459	it's really slow, but it still scales very well (O(active_fds)).
350		460
351	Please note that solaris ports can result in a lot of spurious	461	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	462	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	463	blocking when no data (or space) is available.
		464
		465	While this backend scales well, it requires one system call per active
		466	file descriptor per loop iteration. For small and medium numbers of file
		467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		468	might perform better.
		469
		470	On the positive side, with the exception of the spurious readiness
		471	notifications, this backend actually performed fully to specification
		472	in all tests and is fully embeddable, which is a rare feat among the
		473	OS-specific backends.
		474
		475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		476	C<EVBACKEND_POLL>.
354		477
355	=item C<EVBACKEND_ALL>	478	=item C<EVBACKEND_ALL>
356		479
357	Try all backends (even potentially broken ones that wouldn't be tried	480	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	481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	482	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		483
		484	It is definitely not recommended to use this flag.
		485
361	=back	486	=back
362		487
363	If one or more of these are ored into the flags value, then only these	488	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	489	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	490	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		491
368	The most typical usage is like this:	492	Example: This is the most typical usage.
369		493
370	if (!ev_default_loop (0))	494	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
372		496
373	Restrict libev to the select and poll backends, and do not allow	497	Example: Restrict libev to the select and poll backends, and do not allow
374	environment settings to be taken into account:	498	environment settings to be taken into account:
375		499
376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
377		501
378	Use whatever libev has to offer, but make sure that kqueue is used if	502	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	503	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):	504	private event loop and only if you know the OS supports your types of
		505	fds):
381		506
382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
383		508
384	=item struct ev_loop *ev_loop_new (unsigned int flags)	509	=item struct ev_loop *ev_loop_new (unsigned int flags)
385		510
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	511	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	512	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	513	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).	514	undefined behaviour (or a failed assertion if assertions are enabled).
390		515
		516	Note that this function I<is> thread-safe, and the recommended way to use
		517	libev with threads is indeed to create one loop per thread, and using the
		518	default loop in the "main" or "initial" thread.
		519
391	Example: Try to create a event loop that uses epoll and nothing else.	520	Example: Try to create a event loop that uses epoll and nothing else.
392		521
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	523	if (!epoller)
395	fatal ("no epoll found here, maybe it hides under your chair");	524	fatal ("no epoll found here, maybe it hides under your chair");
396		525
397	=item ev_default_destroy ()	526	=item ev_default_destroy ()
398		527
399	Destroys the default loop again (frees all memory and kernel state	528	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	529	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	530	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>	531	responsibility to either stop all watchers cleanly yourself I<before>
403	calling this function, or cope with the fact afterwards (which is usually	532	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	533	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	534	for example).
		535
		536	Note that certain global state, such as signal state, will not be freed by
		537	this function, and related watchers (such as signal and child watchers)
		538	would need to be stopped manually.
		539
		540	In general it is not advisable to call this function except in the
		541	rare occasion where you really need to free e.g. the signal handling
		542	pipe fds. If you need dynamically allocated loops it is better to use
		543	C<ev_loop_new> and C<ev_loop_destroy>).
406		544
407	=item ev_loop_destroy (loop)	545	=item ev_loop_destroy (loop)
408		546
409	Like C<ev_default_destroy>, but destroys an event loop created by an	547	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	548	earlier call to C<ev_loop_new>.
411		549
412	=item ev_default_fork ()	550	=item ev_default_fork ()
413		551
		552	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	553	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	554	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	555	the child process (or both child and parent, but that again makes little
417	again makes little sense).	556	sense). You I<must> call it in the child before using any of the libev
		557	functions, and it will only take effect at the next C<ev_loop> iteration.
418		558
419	You I<must> call this function in the child process after forking if and	559	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	560	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.	561	you just fork+exec, you don't have to call it at all.
422		562
423	The function itself is quite fast and it's usually not a problem to call	563	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	564	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>:	565	quite nicely into a call to C<pthread_atfork>:
426		566
427	pthread_atfork (0, 0, ev_default_fork);	567	pthread_atfork (0, 0, ev_default_fork);
428		568
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)	569	=item ev_loop_fork (loop)
434		570
435	Like C<ev_default_fork>, but acts on an event loop created by	571	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	572	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.	573	after fork that you want to re-use in the child, and how you do this is
		574	entirely your own problem.
		575
		576	=item int ev_is_default_loop (loop)
		577
		578	Returns true when the given loop is, in fact, the default loop, and false
		579	otherwise.
438		580
439	=item unsigned int ev_loop_count (loop)	581	=item unsigned int ev_loop_count (loop)
440		582
441	Returns the count of loop iterations for the loop, which is identical to	583	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	584	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		597
456	Returns the current "event loop time", which is the time the event loop	598	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	599	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	600	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	601	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).	602	event occurring (or more correctly, libev finding out about it).
		603
		604	=item ev_now_update (loop)
		605
		606	Establishes the current time by querying the kernel, updating the time
		607	returned by C<ev_now ()> in the progress. This is a costly operation and
		608	is usually done automatically within C<ev_loop ()>.
		609
		610	This function is rarely useful, but when some event callback runs for a
		611	very long time without entering the event loop, updating libev's idea of
		612	the current time is a good idea.
		613
		614	See also "The special problem of time updates" in the C<ev_timer> section.
461		615
462	=item ev_loop (loop, int flags)	616	=item ev_loop (loop, int flags)
463		617
464	Finally, this is it, the event handler. This function usually is called	618	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	619	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	622	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.	623	either no event watchers are active anymore or C<ev_unloop> was called.
470		624
471	Please note that an explicit C<ev_unloop> is usually better than	625	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	626	relying on all watchers to be stopped when deciding when a program has
473	finished (especially in interactive programs), but having a program that	627	finished (especially in interactive programs), but having a program
474	automatically loops as long as it has to and no longer by virtue of	628	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.	629	of relying on its watchers stopping correctly, that is truly a thing of
		630	beauty.
476		631
477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	632	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	633	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.	634	process in case there are no events and will return after one iteration of
		635	the loop.
480		636
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	637	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	638	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	639	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	640	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	641	user-registered callback will be called), and will return after one
		642	iteration of the loop.
		643
		644	This is useful if you are waiting for some external event in conjunction
		645	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	646	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.	647	usually a better approach for this kind of thing.
488		648
489	Here are the gory details of what C<ev_loop> does:	649	Here are the gory details of what C<ev_loop> does:
490		650
491	* If there are no active watchers (reference count is zero), return.	651	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	652	* If EVFLAG_FORKCHECK was used, check for a fork.
		653	- If a fork was detected (by any means), queue and call all fork watchers.
		654	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	655	- If we have been forked, detach and recreate the kernel state
		656	as to not disturb the other process.
494	- Update the kernel state with all outstanding changes.	657	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	658	- Update the "event loop time" (ev_now ()).
496	- Calculate for how long to block.	659	- Calculate for how long to sleep or block, if at all
		660	(active idle watchers, EVLOOP_NONBLOCK or not having
		661	any active watchers at all will result in not sleeping).
		662	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	663	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	664	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
500	- Queue all outstanding timers.	666	- Queue all expired timers.
501	- Queue all outstanding periodics.	667	- Queue all expired periodics.
502	- If no events are pending now, queue all idle watchers.	668	- Unless any events are pending now, queue all idle watchers.
503	- Queue all check watchers.	669	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	670	- 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	671	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	672	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	674	were used, or there are no active watchers, return, otherwise
		675	continue with step *.
509		676
510	Example: Queue some jobs and then loop until no events are outsanding	677	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	678	anymore.
512		679
513	... queue jobs here, make sure they register event watchers as long	680	... 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..)	681	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	682	ev_loop (my_loop, 0);
516	... jobs done. yeah!	683	... jobs done or somebody called unloop. yeah!
517		684
518	=item ev_unloop (loop, how)	685	=item ev_unloop (loop, how)
519		686
520	Can be used to make a call to C<ev_loop> return early (but only after it	687	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	688	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	689	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.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
524		691
		692	This "unloop state" will be cleared when entering C<ev_loop> again.
		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
525	=item ev_ref (loop)	696	=item ev_ref (loop)
526		697
527	=item ev_unref (loop)	698	=item ev_unref (loop)
528		699
529	Ref/unref can be used to add or remove a reference count on the event	700	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	701	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	702	count is nonzero, C<ev_loop> will not return on its own.
		703
532	a watcher you never unregister that should not keep C<ev_loop> from	704	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	705	from returning, call ev_unref() after starting, and ev_ref() before
		706	stopping it.
		707
534	example, libev itself uses this for its internal signal pipe: It is not	708	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	709	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	710	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	711	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>.	712	libraries. Just remember to I<unref after start> and I<ref before stop>
		713	(but only if the watcher wasn't active before, or was active before,
		714	respectively).
539		715
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	717	running when nothing else is active.
542		718
543	struct ev_signal exitsig;	719	ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	722	evf_unref (loop);
547		723
548	Example: For some weird reason, unregister the above signal handler again.	724	Example: For some weird reason, unregister the above signal handler again.
549		725
550	ev_ref (loop);	726	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	727	ev_signal_stop (loop, &exitsig);
		728
		729	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		730
		731	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		732
		733	These advanced functions influence the time that libev will spend waiting
		734	for events. Both time intervals are by default C<0>, meaning that libev
		735	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		736	latency.
		737
		738	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		739	allows libev to delay invocation of I/O and timer/periodic callbacks
		740	to increase efficiency of loop iterations (or to increase power-saving
		741	opportunities).
		742
		743	The idea is that sometimes your program runs just fast enough to handle
		744	one (or very few) event(s) per loop iteration. While this makes the
		745	program responsive, it also wastes a lot of CPU time to poll for new
		746	events, especially with backends like C<select ()> which have a high
		747	overhead for the actual polling but can deliver many events at once.
		748
		749	By setting a higher I<io collect interval> you allow libev to spend more
		750	time collecting I/O events, so you can handle more events per iteration,
		751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		752	C<ev_timer>) will be not affected. Setting this to a non-null value will
		753	introduce an additional C<ev_sleep ()> call into most loop iterations.
		754
		755	Likewise, by setting a higher I<timeout collect interval> you allow libev
		756	to spend more time collecting timeouts, at the expense of increased
		757	latency/jitter/inexactness (the watcher callback will be called
		758	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		759	value will not introduce any overhead in libev.
		760
		761	Many (busy) programs can usually benefit by setting the I/O collect
		762	interval to a value near C<0.1> or so, which is often enough for
		763	interactive servers (of course not for games), likewise for timeouts. It
		764	usually doesn't make much sense to set it to a lower value than C<0.01>,
		765	as this approaches the timing granularity of most systems.
		766
		767	Setting the I<timeout collect interval> can improve the opportunity for
		768	saving power, as the program will "bundle" timer callback invocations that
		769	are "near" in time together, by delaying some, thus reducing the number of
		770	times the process sleeps and wakes up again. Another useful technique to
		771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		772	they fire on, say, one-second boundaries only.
		773
		774	=item ev_loop_verify (loop)
		775
		776	This function only does something when C<EV_VERIFY> support has been
		777	compiled in, which is the default for non-minimal builds. It tries to go
		778	through all internal structures and checks them for validity. If anything
		779	is found to be inconsistent, it will print an error message to standard
		780	error and call C<abort ()>.
		781
		782	This can be used to catch bugs inside libev itself: under normal
		783	circumstances, this function will never abort as of course libev keeps its
		784	data structures consistent.
552		785
553	=back	786	=back
554		787
555		788
556	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
557		794
558	A watcher is a structure that you create and register to record your	795	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	796	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:	797	become readable, you would create an C<ev_io> watcher for that:
561		798
562	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
563	{	800	{
564	ev_io_stop (w);	801	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
566	}	803	}
567		804
568	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
569	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
570	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
573	ev_loop (loop, 0);	813	ev_loop (loop, 0);
574		814
575	As you can see, you are responsible for allocating the memory for your	815	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,	816	watcher structures (and it is I<usually> a bad idea to do this on the
577	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
578		821
579	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	823	(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	824	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	825	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	826	is readable and/or writable).
584		827
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	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	829	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	830	is also a macro to combine initialisation and setting in one call: C<<
588	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
589		832
590	To make the watcher actually watch out for events, you have to start it	833	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	834	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	835	*) >>), and you can stop watching for events at any time by calling the
593	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
594		837
595	As long as your watcher is active (has been started but not stopped) you	838	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	839	must not touch the values stored in it. Most specifically you must never
597	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
598		841
599	Each and every callback receives the event loop pointer as first, the	842	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	843	registered watcher structure as second, and a bitset of received events as
601	third argument.	844	third argument.
602		845
…		…
656	=item C<EV_FORK>	899	=item C<EV_FORK>
657		900
658	The event loop has been resumed in the child process after fork (see	901	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	902	C<ev_fork>).
660		903
		904	=item C<EV_ASYNC>
		905
		906	The given async watcher has been asynchronously notified (see C<ev_async>).
		907
661	=item C<EV_ERROR>	908	=item C<EV_ERROR>
662		909
663	An unspecified error has occured, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	911	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	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
666	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
667	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
668		919
669	Libev will usually signal a few "dummy" events together with an error,	920	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	921	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	922	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	923	the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	924	programs, though, as the fd could already be closed and reused for another
		925	thing, so beware.
674		926
675	=back	927	=back
676		928
677	=head2 GENERIC WATCHER FUNCTIONS	929	=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		930
682	=over 4	931	=over 4
683		932
684	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
685		934
…		…
691	which rolls both calls into one.	940	which rolls both calls into one.
692		941
693	You can reinitialise a watcher at any time as long as it has been stopped	942	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.	943	(or never started) and there are no pending events outstanding.
695		944
696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	945	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
697	int revents)>.	946	int revents)>.
		947
		948	Example: Initialise an C<ev_io> watcher in two steps.
		949
		950	ev_io w;
		951	ev_init (&w, my_cb);
		952	ev_io_set (&w, STDIN_FILENO, EV_READ);
698		953
699	=item C<ev_TYPE_set> (ev_TYPE *, [args])	954	=item C<ev_TYPE_set> (ev_TYPE *, [args])
700		955
701	This macro initialises the type-specific parts of a watcher. You need to	956	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	957	call C<ev_init> at least once before you call this macro, but you can
…		…
705	difference to the C<ev_init> macro).	960	difference to the C<ev_init> macro).
706		961
707	Although some watcher types do not have type-specific arguments	962	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.	963	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		964
		965	See C<ev_init>, above, for an example.
		966
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	967	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		968
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	969	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	970	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	971	a watcher. The same limitations apply, of course.
		972
		973	Example: Initialise and set an C<ev_io> watcher in one step.
		974
		975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
715		976
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		978
718	Starts (activates) the given watcher. Only active watchers will receive	979	Starts (activates) the given watcher. Only active watchers will receive
719	events. If the watcher is already active nothing will happen.	980	events. If the watcher is already active nothing will happen.
720		981
		982	Example: Start the C<ev_io> watcher that is being abused as example in this
		983	whole section.
		984
		985	ev_io_start (EV_DEFAULT_UC, &w);
		986
721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
722		988
723	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
724	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
725	non-repeating timers are being stopped when they become pending), but	993	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	994	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	995	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.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
729		997
730	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
731		999
732	Returns a true value iff the watcher is active (i.e. it has been started	1000	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	1001	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)	1004	=item bool ev_is_pending (ev_TYPE *watcher)
737		1005
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1006	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	1007	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	1008	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	1009	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	1010	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1011	it).
743		1012
744	=item callback ev_cb (ev_TYPE *watcher)	1013	=item callback ev_cb (ev_TYPE *watcher)
745		1014
746	Returns the callback currently set on the watcher.	1015	Returns the callback currently set on the watcher.
747		1016
…		…
766	watchers on the same event and make sure one is called first.	1035	watchers on the same event and make sure one is called first.
767		1036
768	If you need to suppress invocation when higher priority events are pending	1037	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.	1038	you need to look at C<ev_idle> watchers, which provide this functionality.
770		1039
		1040	You I<must not> change the priority of a watcher as long as it is active or
		1041	pending.
		1042
771	The default priority used by watchers when no priority has been set is	1043	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 :).	1044	always C<0>, which is supposed to not be too high and not be too low :).
773		1045
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1046	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	1047	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.	1048	or might not have been clamped to the valid range.
		1049
		1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1051
		1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1053	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1054	can deal with that fact, as both are simply passed through to the
		1055	callback.
		1056
		1057	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1058
		1059	If the watcher is pending, this function clears its pending status and
		1060	returns its C<revents> bitset (as if its callback was invoked). If the
		1061	watcher isn't pending it does nothing and returns C<0>.
		1062
		1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1064	callback to be invoked, which can be accomplished with this function.
777		1065
778	=back	1066	=back
779		1067
780		1068
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
782		1070
783	Each watcher has, by default, a member C<void *data> that you can change	1071	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	1072	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	1073	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	1074	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	1075	member, you can also "subclass" the watcher type and provide your own
788	data:	1076	data:
789		1077
790	struct my_io	1078	struct my_io
791	{	1079	{
792	struct ev_io io;	1080	ev_io io;
793	int otherfd;	1081	int otherfd;
794	void *somedata;	1082	void *somedata;
795	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
796	}	1084	};
		1085
		1086	...
		1087	struct my_io w;
		1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
797		1089
798	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
799	can cast it back to your own type:	1091	can cast it back to your own type:
800		1092
801	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
802	{	1094	{
803	struct my_io *w = (struct my_io *)w_;	1095	struct my_io *w = (struct my_io *)w_;
804	...	1096	...
805	}	1097	}
806		1098
807	More interesting and less C-conformant ways of casting your callback type	1099	More interesting and less C-conformant ways of casting your callback type
808	instead have been omitted.	1100	instead have been omitted.
809		1101
810	Another common scenario is having some data structure with multiple	1102	Another common scenario is to use some data structure with multiple
811	watchers:	1103	embedded watchers:
812		1104
813	struct my_biggy	1105	struct my_biggy
814	{	1106	{
815	int some_data;	1107	int some_data;
816	ev_timer t1;	1108	ev_timer t1;
817	ev_timer t2;	1109	ev_timer t2;
818	}	1110	}
819		1111
820	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1112	In this case getting the pointer to C<my_biggy> is a bit more
821	you need to use C<offsetof>:	1113	complicated: Either you store the address of your C<my_biggy> struct
		1114	in the C<data> member of the watcher (for woozies), or you need to use
		1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1116	programmers):
822		1117
823	#include <stddef.h>	1118	#include <stddef.h>
824		1119
825	static void	1120	static void
826	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
827	{	1122	{
828	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
829	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
830	}	1125	}
831		1126
832	static void	1127	static void
833	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
834	{	1129	{
835	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
836	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
837	}	1132	}
838		1133
839		1134
840	=head1 WATCHER TYPES	1135	=head1 WATCHER TYPES
841		1136
842	This section describes each watcher in detail, but will not repeat	1137	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	1161	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	1162	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	1163	descriptors to non-blocking mode is also usually a good idea (but not
869	required if you know what you are doing).	1164	required if you know what you are doing).
870		1165
871	You have to be careful with dup'ed file descriptors, though. Some backends	1166	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	1167	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	1168	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		1169
881	Another thing you have to watch out for is that it is quite easy to	1170	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	1171	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	1172	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	1173	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	1174	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	1175	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	1176	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.	1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.
889		1178
890	If you cannot run the fd in non-blocking mode (for example you should not	1179	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	1180	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	1181	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	1182	interface such as poll (fortunately in our Xlib example, Xlib already
894	its own, so its quite safe to use).	1183	does this on its own, so its quite safe to use). Some people additionally
		1184	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1185	indefinitely.
		1186
		1187	But really, best use non-blocking mode.
		1188
		1189	=head3 The special problem of disappearing file descriptors
		1190
		1191	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1192	descriptor (either due to calling C<close> explicitly or any other means,
		1193	such as C<dup2>). The reason is that you register interest in some file
		1194	descriptor, but when it goes away, the operating system will silently drop
		1195	this interest. If another file descriptor with the same number then is
		1196	registered with libev, there is no efficient way to see that this is, in
		1197	fact, a different file descriptor.
		1198
		1199	To avoid having to explicitly tell libev about such cases, libev follows
		1200	the following policy: Each time C<ev_io_set> is being called, libev
		1201	will assume that this is potentially a new file descriptor, otherwise
		1202	it is assumed that the file descriptor stays the same. That means that
		1203	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1204	descriptor even if the file descriptor number itself did not change.
		1205
		1206	This is how one would do it normally anyway, the important point is that
		1207	the libev application should not optimise around libev but should leave
		1208	optimisations to libev.
		1209
		1210	=head3 The special problem of dup'ed file descriptors
		1211
		1212	Some backends (e.g. epoll), cannot register events for file descriptors,
		1213	but only events for the underlying file descriptions. That means when you
		1214	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1215	events for them, only one file descriptor might actually receive events.
		1216
		1217	There is no workaround possible except not registering events
		1218	for potentially C<dup ()>'ed file descriptors, or to resort to
		1219	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of fork
		1222
		1223	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1224	useless behaviour. Libev fully supports fork, but needs to be told about
		1225	it in the child.
		1226
		1227	To support fork in your programs, you either have to call
		1228	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1230	C<EVBACKEND_POLL>.
		1231
		1232	=head3 The special problem of SIGPIPE
		1233
		1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1235	when writing to a pipe whose other end has been closed, your program gets
		1236	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1237	this is sensible behaviour, for daemons, this is usually undesirable.
		1238
		1239	So when you encounter spurious, unexplained daemon exits, make sure you
		1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1241	somewhere, as that would have given you a big clue).
		1242
		1243
		1244	=head3 Watcher-Specific Functions
895		1245
896	=over 4	1246	=over 4
897		1247
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1248	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1249
900	=item ev_io_set (ev_io *, int fd, int events)	1250	=item ev_io_set (ev_io *, int fd, int events)
901		1251
902	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1252	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	1253	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.	1254	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
905		1255
906	=item int fd [read-only]	1256	=item int fd [read-only]
907		1257
908	The file descriptor being watched.	1258	The file descriptor being watched.
909		1259
910	=item int events [read-only]	1260	=item int events [read-only]
911		1261
912	The events being watched.	1262	The events being watched.
913		1263
914	=back	1264	=back
		1265
		1266	=head3 Examples
915		1267
916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	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	1269	readable, but only once. Since it is likely line-buffered, you could
918	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
919		1271
920	static void	1272	static void
921	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1273	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
922	{	1274	{
923	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
924	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
925	}	1277	}
926		1278
927	...	1279	...
928	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
929	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
930	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
931	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
932	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
933		1285
934		1286
935	=head2 C<ev_timer> - relative and optionally repeating timeouts	1287	=head2 C<ev_timer> - relative and optionally repeating timeouts
936		1288
937	Timer watchers are simple relative timers that generate an event after a	1289	Timer watchers are simple relative timers that generate an event after a
938	given time, and optionally repeating in regular intervals after that.	1290	given time, and optionally repeating in regular intervals after that.
939		1291
940	The timers are based on real time, that is, if you register an event that	1292	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	1293	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	1294	year, it will still time out after (roughly) one hour. "Roughly" because
943	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the
944	monotonic clock option helps a lot here).	1296	monotonic clock option helps a lot here).
		1297
		1298	The callback is guaranteed to be invoked only I<after> its timeout has
		1299	passed, but if multiple timers become ready during the same loop iteration
		1300	then order of execution is undefined.
		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
		1476
		1477	=head3 The special problem of time updates
		1478
		1479	Establishing the current time is a costly operation (it usually takes at
		1480	least two system calls): EV therefore updates its idea of the current
		1481	time only before and after C<ev_loop> collects new events, which causes a
		1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1483	lots of events in one iteration.
945		1484
946	The relative timeouts are calculated relative to the C<ev_now ()>	1485	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	1486	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	1487	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	1488	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:	1489	timeout on the current time, use something like this to adjust for this:
951		1490
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1491	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1492
954	The callback is guarenteed to be invoked only when its timeout has passed,	1493	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	1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update
956	order of execution is undefined.	1495	()>.
		1496
		1497	=head3 Watcher-Specific Functions and Data Members
957		1498
958	=over 4	1499	=over 4
959		1500
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1502
962	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1503	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
963		1504
964	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1505	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	1506	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	1507	reached. If it is positive, then the timer will automatically be
967	later, again, and again, until stopped manually.	1508	configured to trigger again C<repeat> seconds later, again, and again,
		1509	until stopped manually.
968		1510
969	The timer itself will do a best-effort at avoiding drift, that is, if you	1511	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	1512	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	1513	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	1514	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.	1515	do stuff) the timer will not fire more than once per event loop iteration.
974		1516
975	=item ev_timer_again (loop)	1517	=item ev_timer_again (loop, ev_timer *)
976		1518
977	This will act as if the timer timed out and restart it again if it is	1519	This will act as if the timer timed out and restart it again if it is
978	repeating. The exact semantics are:	1520	repeating. The exact semantics are:
979		1521
980	If the timer is pending, its pending status is cleared.	1522	If the timer is pending, its pending status is cleared.
981		1523
982	If the timer is started but nonrepeating, stop it (as if it timed out).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
983		1525
984	If the timer is repeating, either start it if necessary (with the	1526	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.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
986		1528
987	This sounds a bit complicated, but here is a useful and typical	1529	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	1530	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		1531
1012	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1013		1533
1014	The current C<repeat> value. Will be used each time the watcher times out	1534	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),	1535	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.	1536	which is also when any modifications are taken into account.
1017		1537
1018	=back	1538	=back
1019		1539
		1540	=head3 Examples
		1541
1020	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1021		1543
1022	static void	1544	static void
1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1545	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1024	{	1546	{
1025	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1026	}	1548	}
1027		1549
1028	struct ev_timer mytimer;	1550	ev_timer mytimer;
1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1030	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1031		1553
1032	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1033	inactivity.	1555	inactivity.
1034		1556
1035	static void	1557	static void
1036	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1558	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1037	{	1559	{
1038	.. ten seconds without any activity	1560	.. ten seconds without any activity
1039	}	1561	}
1040		1562
1041	struct ev_timer mytimer;	1563	ev_timer mytimer;
1042	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1043	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1044	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1045		1567
1046	// and in some piece of code that gets executed on any "activity":	1568	// and in some piece of code that gets executed on any "activity":
1047	// reset the timeout to start ticking again at 10 seconds	1569	// reset the timeout to start ticking again at 10 seconds
1048	ev_timer_again (&mytimer);	1570	ev_timer_again (&mytimer);
1049		1571
1050		1572
1051	=head2 C<ev_periodic> - to cron or not to cron?	1573	=head2 C<ev_periodic> - to cron or not to cron?
1052		1574
1053	Periodic watchers are also timers of a kind, but they are very versatile	1575	Periodic watchers are also timers of a kind, but they are very versatile
1054	(and unfortunately a bit complex).	1576	(and unfortunately a bit complex).
1055		1577
1056	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1578	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	1579	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	1580	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 ()	1581	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	1582	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1583	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	1584	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	1585	roughly 10 seconds later as it uses a relative timeout).
1063	again).
1064		1586
1065	They can also be used to implement vastly more complex timers, such as	1587	C<ev_periodic>s can also be used to implement vastly more complex timers,
1066	triggering an event on eahc midnight, local time.	1588	such as triggering an event on each "midnight, local time", or other
		1589	complicated rules.
1067		1590
1068	As with timers, the callback is guarenteed to be invoked only when the	1591	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	1592	time (C<at>) has passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1593	during the same loop iteration, then order of execution is undefined.
		1594
		1595	=head3 Watcher-Specific Functions and Data Members
1071		1596
1072	=over 4	1597	=over 4
1073		1598
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1600
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1077		1602
1078	Lots of arguments, lets sort it out... There are basically three modes of	1603	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1604	operation, and we will explain them from simplest to most complex:
1080		1605
1081	=over 4	1606	=over 4
1082		1607
1083	=item * absolute timer (interval = reschedule_cb = 0)	1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1609
1085	In this configuration the watcher triggers an event at the wallclock time	1610	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,	1611	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	1612	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.	1613	only run when the system clock reaches or surpasses this time.
1089		1614
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1616
1092	In this mode the watcher will always be scheduled to time out at the next	1617	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	1618	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1619	and then repeat, regardless of any time jumps.
1095		1620
1096	This can be used to create timers that do not drift with respect to system	1621	This can be used to create timers that do not drift with respect to the
1097	time:	1622	system clock, for example, here is a C<ev_periodic> that triggers each
		1623	hour, on the hour:
1098		1624
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1625	ev_periodic_set (&periodic, 0., 3600., 0);
1100		1626
1101	This doesn't mean there will always be 3600 seconds in between triggers,	1627	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	1628	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	1629	full hour (UTC), or more correctly, when the system time is evenly divisible
1104	by 3600.	1630	by 3600.
1105		1631
1106	Another way to think about it (for the mathematically inclined) is that	1632	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	1633	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.	1634	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1635
		1636	For numerical stability it is preferable that the C<at> value is near
		1637	C<ev_now ()> (the current time), but there is no range requirement for
		1638	this value, and in fact is often specified as zero.
		1639
		1640	Note also that there is an upper limit to how often a timer can fire (CPU
		1641	speed for example), so if C<interval> is very small then timing stability
		1642	will of course deteriorate. Libev itself tries to be exact to be about one
		1643	millisecond (if the OS supports it and the machine is fast enough).
		1644
1110	=item * manual reschedule mode (reschedule_cb = callback)	1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1646
1112	In this mode the values for C<interval> and C<at> are both being	1647	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	1648	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1649	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1650	current time as second argument.
1116		1651
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1652	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,	1653	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		1654
		1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1657	only event loop modification you are allowed to do).
		1658
1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1123	ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1124		1661
		1662	static ev_tstamp
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1126	{	1664	{
1127	return now + 60.;	1665	return now + 60.;
1128	}	1666	}
1129		1667
1130	It must return the next time to trigger, based on the passed time value	1668	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	1669	(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	1670	will usually be called just before the callback will be triggered, but
1133	might be called at other times, too.	1671	might be called at other times, too.
1134		1672
1135	NOTE: I<< This callback must always return a time that is later than the	1673	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.	1674	equal to the passed C<now> value >>.
1137		1675
1138	This can be used to create very complex timers, such as a timer that	1676	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	1677	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	1678	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	1679	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).	1680	reason I omitted it as an example).
1143		1681
1144	=back	1682	=back
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1686	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1687	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	1688	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1689	program when the crontabs have changed).
1152		1690
		1691	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1692
		1693	When active, returns the absolute time that the watcher is supposed to
		1694	trigger next.
		1695
		1696	=item ev_tstamp offset [read-write]
		1697
		1698	When repeating, this contains the offset value, otherwise this is the
		1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1700
		1701	Can be modified any time, but changes only take effect when the periodic
		1702	timer fires or C<ev_periodic_again> is being called.
		1703
1153	=item ev_tstamp interval [read-write]	1704	=item ev_tstamp interval [read-write]
1154		1705
1155	The current interval value. Can be modified any time, but changes only	1706	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	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1708	called.
1158		1709
1159	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1160		1711
1161	The current reschedule callback, or C<0>, if this functionality is	1712	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	1713	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.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1164		1715
1165	=back	1716	=back
1166		1717
		1718	=head3 Examples
		1719
1167	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1170		1723
1171	static void	1724	static void
1172	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1173	{	1726	{
1174	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1175	}	1728	}
1176		1729
1177	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1179	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1180		1733
1181	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1182		1735
1183	#include <math.h>	1736	#include <math.h>
1184		1737
1185	static ev_tstamp	1738	static ev_tstamp
1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1187	{	1740	{
1188	return fmod (now, 3600.) + 3600.;	1741	return now + (3600. - fmod (now, 3600.));
1189	}	1742	}
1190		1743
1191	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1192		1745
1193	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1194		1747
1195	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1196	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1197	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1198	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1199		1752
1200		1753
1201	=head2 C<ev_signal> - signal me when a signal gets signalled!	1754	=head2 C<ev_signal> - signal me when a signal gets signalled!
1202		1755
1203	Signal watchers will trigger an event when the process receives a specific	1756	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	1757	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	1758	will try it's best to deliver signals synchronously, i.e. as part of the
1206	normal event processing, like any other event.	1759	normal event processing, like any other event.
1207		1760
		1761	If you want signals asynchronously, just use C<sigaction> as you would
		1762	do without libev and forget about sharing the signal. You can even use
		1763	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1764
1208	You can configure as many watchers as you like per signal. Only when the	1765	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	1766	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	1767	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	1768	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	1769	the last signal watcher for a signal is stopped, libev will reset the
1213	SIG_DFL (regardless of what it was set to before).	1770	signal handler to SIG_DFL (regardless of what it was set to before).
		1771
		1772	If possible and supported, libev will install its handlers with
		1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1774	interrupted. If you have a problem with system calls getting interrupted by
		1775	signals you can block all signals in an C<ev_check> watcher and unblock
		1776	them in an C<ev_prepare> watcher.
		1777
		1778	=head3 Watcher-Specific Functions and Data Members
1214		1779
1215	=over 4	1780	=over 4
1216		1781
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1782	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1783
…		…
1225		1790
1226	The signal the watcher watches out for.	1791	The signal the watcher watches out for.
1227		1792
1228	=back	1793	=back
1229		1794
		1795	=head3 Examples
		1796
		1797	Example: Try to exit cleanly on SIGINT.
		1798
		1799	static void
		1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1801	{
		1802	ev_unloop (loop, EVUNLOOP_ALL);
		1803	}
		1804
		1805	ev_signal signal_watcher;
		1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1807	ev_signal_start (loop, &signal_watcher);
		1808
1230		1809
1231	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1232		1811
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1812	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).	1813	some child status changes (most typically when a child of yours dies or
		1814	exits). It is permissible to install a child watcher I<after> the child
		1815	has been forked (which implies it might have already exited), as long
		1816	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1817	forking and then immediately registering a watcher for the child is fine,
		1818	but forking and registering a watcher a few event loop iterations later is
		1819	not.
		1820
		1821	Only the default event loop is capable of handling signals, and therefore
		1822	you can only register child watchers in the default event loop.
		1823
		1824	=head3 Process Interaction
		1825
		1826	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1827	initialised. This is necessary to guarantee proper behaviour even if
		1828	the first child watcher is started after the child exits. The occurrence
		1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1830	synchronously as part of the event loop processing. Libev always reaps all
		1831	children, even ones not watched.
		1832
		1833	=head3 Overriding the Built-In Processing
		1834
		1835	Libev offers no special support for overriding the built-in child
		1836	processing, but if your application collides with libev's default child
		1837	handler, you can override it easily by installing your own handler for
		1838	C<SIGCHLD> after initialising the default loop, and making sure the
		1839	default loop never gets destroyed. You are encouraged, however, to use an
		1840	event-based approach to child reaping and thus use libev's support for
		1841	that, so other libev users can use C<ev_child> watchers freely.
		1842
		1843	=head3 Stopping the Child Watcher
		1844
		1845	Currently, the child watcher never gets stopped, even when the
		1846	child terminates, so normally one needs to stop the watcher in the
		1847	callback. Future versions of libev might stop the watcher automatically
		1848	when a child exit is detected.
		1849
		1850	=head3 Watcher-Specific Functions and Data Members
1235		1851
1236	=over 4	1852	=over 4
1237		1853
1238	=item ev_child_init (ev_child *, callback, int pid)	1854	=item ev_child_init (ev_child *, callback, int pid, int trace)
1239		1855
1240	=item ev_child_set (ev_child *, int pid)	1856	=item ev_child_set (ev_child *, int pid, int trace)
1241		1857
1242	Configures the watcher to wait for status changes of process C<pid> (or	1858	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	1859	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	1860	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	1861	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	1862	C<waitpid> documentation). The C<rpid> member contains the pid of the
1247	process causing the status change.	1863	process causing the status change. C<trace> must be either C<0> (only
		1864	activate the watcher when the process terminates) or C<1> (additionally
		1865	activate the watcher when the process is stopped or continued).
1248		1866
1249	=item int pid [read-only]	1867	=item int pid [read-only]
1250		1868
1251	The process id this watcher watches out for, or C<0>, meaning any process id.	1869	The process id this watcher watches out for, or C<0>, meaning any process id.
1252		1870
…		…
1259	The process exit/trace status caused by C<rpid> (see your systems	1877	The process exit/trace status caused by C<rpid> (see your systems
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1878	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1879
1262	=back	1880	=back
1263		1881
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1882	=head3 Examples
1265		1883
		1884	Example: C<fork()> a new process and install a child handler to wait for
		1885	its completion.
		1886
		1887	ev_child cw;
		1888
1266	static void	1889	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1268	{	1891	{
1269	ev_unloop (loop, EVUNLOOP_ALL);	1892	ev_child_stop (EV_A_ w);
		1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1270	}	1894	}
1271		1895
1272	struct ev_signal signal_watcher;	1896	pid_t pid = fork ();
1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1897
1274	ev_signal_start (loop, &sigint_cb);	1898	if (pid < 0)
		1899	// error
		1900	else if (pid == 0)
		1901	{
		1902	// the forked child executes here
		1903	exit (1);
		1904	}
		1905	else
		1906	{
		1907	ev_child_init (&cw, child_cb, pid, 0);
		1908	ev_child_start (EV_DEFAULT_ &cw);
		1909	}
1275		1910
1276		1911
1277	=head2 C<ev_stat> - did the file attributes just change?	1912	=head2 C<ev_stat> - did the file attributes just change?
1278		1913
1279	This watches a filesystem path for attribute changes. That is, it calls	1914	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	1915	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.	1916	compared to the last time, invoking the callback if it did.
1282		1917
1283	The path does not need to exist: changing from "path exists" to "path does	1918	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	1919	not exist" is a status change like any other. The condition "path does
…		…
1287	the stat buffer having unspecified contents.	1922	the stat buffer having unspecified contents.
1288		1923
1289	The path I<should> be absolute and I<must not> end in a slash. If it is	1924	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.	1925	relative and your working directory changes, the behaviour is undefined.
1291		1926
1292	Since there is no standard to do this, the portable implementation simply	1927	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	1928	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	1929	it changed somehow. You can specify a recommended polling interval for
1295	a polling interval of C<0> (highly recommended!) then a I<suitable,	1930	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	1931	then a I<suitable, unspecified default> value will be used (which
1297	five seconds, although this might change dynamically). Libev will also	1932	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	1933	dynamically). Libev will also impose a minimum interval which is currently
1299	usually overkill.	1934	around C<0.1>, but thats usually overkill.
1300		1935
1301	This watcher type is not meant for massive numbers of stat watchers,	1936	This watcher type is not meant for massive numbers of stat watchers,
1302	as even with OS-supported change notifications, this can be	1937	as even with OS-supported change notifications, this can be
1303	resource-intensive.	1938	resource-intensive.
1304		1939
1305	At the time of this writing, only the Linux inotify interface is	1940	At the time of this writing, the only OS-specific interface implemented
1306	implemented (implementing kqueue support is left as an exercise for the	1941	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	1942	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	1943	of implementing C<ev_stat> semantics with kqueue).
1309	to fall back to regular polling again even with inotify, but changes are	1944
1310	usually detected immediately, and if the file exists there will be no	1945	=head3 ABI Issues (Largefile Support)
1311	polling.	1946
		1947	Libev by default (unless the user overrides this) uses the default
		1948	compilation environment, which means that on systems with large file
		1949	support disabled by default, you get the 32 bit version of the stat
		1950	structure. When using the library from programs that change the ABI to
		1951	use 64 bit file offsets the programs will fail. In that case you have to
		1952	compile libev with the same flags to get binary compatibility. This is
		1953	obviously the case with any flags that change the ABI, but the problem is
		1954	most noticeably disabled with ev_stat and large file support.
		1955
		1956	The solution for this is to lobby your distribution maker to make large
		1957	file interfaces available by default (as e.g. FreeBSD does) and not
		1958	optional. Libev cannot simply switch on large file support because it has
		1959	to exchange stat structures with application programs compiled using the
		1960	default compilation environment.
		1961
		1962	=head3 Inotify and Kqueue
		1963
		1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	only available with Linux 2.6.25 or above due to bugs in earlier
		1966	implementations) and present at runtime, it will be used to speed up
		1967	change detection where possible. The inotify descriptor will be created
		1968	lazily when the first C<ev_stat> watcher is being started.
		1969
		1970	Inotify presence does not change the semantics of C<ev_stat> watchers
		1971	except that changes might be detected earlier, and in some cases, to avoid
		1972	making regular C<stat> calls. Even in the presence of inotify support
		1973	there are many cases where libev has to resort to regular C<stat> polling,
		1974	but as long as the path exists, libev usually gets away without polling.
		1975
		1976	There is no support for kqueue, as apparently it cannot be used to
		1977	implement this functionality, due to the requirement of having a file
		1978	descriptor open on the object at all times, and detecting renames, unlinks
		1979	etc. is difficult.
		1980
		1981	=head3 The special problem of stat time resolution
		1982
		1983	The C<stat ()> system call only supports full-second resolution portably, and
		1984	even on systems where the resolution is higher, most file systems still
		1985	only support whole seconds.
		1986
		1987	That means that, if the time is the only thing that changes, you can
		1988	easily miss updates: on the first update, C<ev_stat> detects a change and
		1989	calls your callback, which does something. When there is another update
		1990	within the same second, C<ev_stat> will be unable to detect unless the
		1991	stat data does change in other ways (e.g. file size).
		1992
		1993	The solution to this is to delay acting on a change for slightly more
		1994	than a second (or till slightly after the next full second boundary), using
		1995	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1996	ev_timer_again (loop, w)>).
		1997
		1998	The C<.02> offset is added to work around small timing inconsistencies
		1999	of some operating systems (where the second counter of the current time
		2000	might be be delayed. One such system is the Linux kernel, where a call to
		2001	C<gettimeofday> might return a timestamp with a full second later than
		2002	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2003	update file times then there will be a small window where the kernel uses
		2004	the previous second to update file times but libev might already execute
		2005	the timer callback).
		2006
		2007	=head3 Watcher-Specific Functions and Data Members
1312		2008
1313	=over 4	2009	=over 4
1314		2010
1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	2011	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316		2012
…		…
1320	C<path>. The C<interval> is a hint on how quickly a change is expected to	2016	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	2017	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	2018	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.	2019	path for as long as the watcher is active.
1324		2020
1325	The callback will be receive C<EV_STAT> when a change was detected,	2021	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	2022	relative to the attributes at the time the watcher was started (or the
1327	last change was detected).	2023	last change was detected).
1328		2024
1329	=item ev_stat_stat (ev_stat *)	2025	=item ev_stat_stat (loop, ev_stat *)
1330		2026
1331	Updates the stat buffer immediately with new values. If you change the	2027	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	2028	watched path in your callback, you could call this function to avoid
1333	detecting this change (while introducing a race condition). Can also be	2029	detecting this change (while introducing a race condition if you are not
1334	useful simply to find out the new values.	2030	the only one changing the path). Can also be useful simply to find out the
		2031	new values.
1335		2032
1336	=item ev_statdata attr [read-only]	2033	=item ev_statdata attr [read-only]
1337		2034
1338	The most-recently detected attributes of the file. Although the type is of	2035	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	2036	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	2037	suitable for your system, but you can only rely on the POSIX-standardised
		2038	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.	2039	some error while C<stat>ing the file.
1342		2040
1343	=item ev_statdata prev [read-only]	2041	=item ev_statdata prev [read-only]
1344		2042
1345	The previous attributes of the file. The callback gets invoked whenever	2043	The previous attributes of the file. The callback gets invoked whenever
1346	C<prev> != C<attr>.	2044	C<prev> != C<attr>, or, more precisely, one or more of these members
		2045	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2046	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1347		2047
1348	=item ev_tstamp interval [read-only]	2048	=item ev_tstamp interval [read-only]
1349		2049
1350	The specified interval.	2050	The specified interval.
1351		2051
1352	=item const char *path [read-only]	2052	=item const char *path [read-only]
1353		2053
1354	The filesystem path that is being watched.	2054	The file system path that is being watched.
1355		2055
1356	=back	2056	=back
1357		2057
		2058	=head3 Examples
		2059
1358	Example: Watch C</etc/passwd> for attribute changes.	2060	Example: Watch C</etc/passwd> for attribute changes.
1359		2061
1360	static void	2062	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2063	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1362	{	2064	{
1363	/* /etc/passwd changed in some way */	2065	/* /etc/passwd changed in some way */
1364	if (w->attr.st_nlink)	2066	if (w->attr.st_nlink)
1365	{	2067	{
1366	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2068	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1367	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2069	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1368	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2070	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1369	}	2071	}
1370	else	2072	else
1371	/* you shalt not abuse printf for puts */	2073	/* you shalt not abuse printf for puts */
1372	puts ("wow, /etc/passwd is not there, expect problems. "	2074	puts ("wow, /etc/passwd is not there, expect problems. "
1373	"if this is windows, they already arrived\n");	2075	"if this is windows, they already arrived\n");
1374	}	2076	}
1375		2077
1376	...	2078	...
1377	ev_stat passwd;	2079	ev_stat passwd;
1378		2080
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2081	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	2082	ev_stat_start (loop, &passwd);
		2083
		2084	Example: Like above, but additionally use a one-second delay so we do not
		2085	miss updates (however, frequent updates will delay processing, too, so
		2086	one might do the work both on C<ev_stat> callback invocation I<and> on
		2087	C<ev_timer> callback invocation).
		2088
		2089	static ev_stat passwd;
		2090	static ev_timer timer;
		2091
		2092	static void
		2093	timer_cb (EV_P_ ev_timer *w, int revents)
		2094	{
		2095	ev_timer_stop (EV_A_ w);
		2096
		2097	/* now it's one second after the most recent passwd change */
		2098	}
		2099
		2100	static void
		2101	stat_cb (EV_P_ ev_stat *w, int revents)
		2102	{
		2103	/* reset the one-second timer */
		2104	ev_timer_again (EV_A_ &timer);
		2105	}
		2106
		2107	...
		2108	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2109	ev_stat_start (loop, &passwd);
		2110	ev_timer_init (&timer, timer_cb, 0., 1.02);
1381		2111
1382		2112
1383	=head2 C<ev_idle> - when you've got nothing better to do...	2113	=head2 C<ev_idle> - when you've got nothing better to do...
1384		2114
1385	Idle watchers trigger events when no other events of the same or higher	2115	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	2116	priority are pending (prepare, check and other idle watchers do not count
1387	count).	2117	as receiving "events").
1388		2118
1389	That is, as long as your process is busy handling sockets or timeouts	2119	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	2120	(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	2121	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	2122	are pending), the idle watchers are being called once per event loop
…		…
1399	Apart from keeping your process non-blocking (which is a useful	2129	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	2130	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	2131	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	2132	event loop has handled all outstanding events.
1403		2133
		2134	=head3 Watcher-Specific Functions and Data Members
		2135
1404	=over 4	2136	=over 4
1405		2137
1406	=item ev_idle_init (ev_signal *, callback)	2138	=item ev_idle_init (ev_signal *, callback)
1407		2139
1408	Initialises and configures the idle watcher - it has no parameters of any	2140	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,	2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1410	believe me.	2142	believe me.
1411		2143
1412	=back	2144	=back
1413		2145
		2146	=head3 Examples
		2147
1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1415	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1416		2150
1417	static void	2151	static void
1418	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2152	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1419	{	2153	{
1420	free (w);	2154	free (w);
1421	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1422	// no longer asnything immediate to do.	2156	// no longer anything immediate to do.
1423	}	2157	}
1424		2158
1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1426	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1427	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1428		2162
1429		2163
1430	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1431		2165
1432	Prepare and check watchers are usually (but not always) used in tandem:	2166	Prepare and check watchers are usually (but not always) used in pairs:
1433	prepare watchers get invoked before the process blocks and check watchers	2167	prepare watchers get invoked before the process blocks and check watchers
1434	afterwards.	2168	afterwards.
1435		2169
1436	You I<must not> call C<ev_loop> or similar functions that enter	2170	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>	2171	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,	2174	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	2175	C<ev_check> so if you have one watcher of each kind they will always be
1442	called in pairs bracketing the blocking call.	2176	called in pairs bracketing the blocking call.
1443		2177
1444	Their main purpose is to integrate other event mechanisms into libev and	2178	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	2179	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	2180	variable changes, implement your own watchers, integrate net-snmp or a
1447	coroutine library and lots more. They are also occasionally useful if	2181	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,	2182	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>	2183	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1450	watcher).	2184	watcher).
1451		2185
1452	This is done by examining in each prepare call which file descriptors need	2186	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	2187	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	2188	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	2189	libraries provide exactly this functionality). Then, in the check watcher,
1456	any events that occured (by checking the pending status of all watchers	2190	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	2191	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,	2192	I/O and timer callbacks will never actually be called (but must be valid
1459	because you never know, you know?).	2193	nevertheless, because you never know, you know?).
1460		2194
1461	As another example, the Perl Coro module uses these hooks to integrate	2195	As another example, the Perl Coro module uses these hooks to integrate
1462	coroutines into libev programs, by yielding to other active coroutines	2196	coroutines into libev programs, by yielding to other active coroutines
1463	during each prepare and only letting the process block if no coroutines	2197	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	2198	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	2199	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	2200	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	2201	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	2202	low-priority coroutines to idle/background tasks).
1469		2203
		2204	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2205	priority, to ensure that they are being run before any other watchers
		2206	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2207
		2208	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2209	activate ("feed") events into libev. While libev fully supports this, they
		2210	might get executed before other C<ev_check> watchers did their job. As
		2211	C<ev_check> watchers are often used to embed other (non-libev) event
		2212	loops those other event loops might be in an unusable state until their
		2213	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2214	others).
		2215
		2216	=head3 Watcher-Specific Functions and Data Members
		2217
1470	=over 4	2218	=over 4
1471		2219
1472	=item ev_prepare_init (ev_prepare *, callback)	2220	=item ev_prepare_init (ev_prepare *, callback)
1473		2221
1474	=item ev_check_init (ev_check *, callback)	2222	=item ev_check_init (ev_check *, callback)
1475		2223
1476	Initialises and configures the prepare or check watcher - they have no	2224	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>	2225	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.	2226	macros, but using them is utterly, utterly, utterly and completely
		2227	pointless.
1479		2228
1480	=back	2229	=back
1481		2230
1482	Example: To include a library such as adns, you would add IO watchers	2231	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	2232
		2233	There are a number of principal ways to embed other event loops or modules
		2234	into libev. Here are some ideas on how to include libadns into libev
		2235	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2236	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2237	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2238	Glib event loop).
		2239
		2240	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	2241	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	2242	is pseudo-code only of course. This requires you to either use a low
		2243	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2244	the callbacks for the IO/timeout watchers might not have been called yet.
1486		2245
1487	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
1488	static ev_timer tw;	2247	static ev_timer tw;
1489		2248
1490	static void	2249	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	2250	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1492	{	2251	{
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	}	2252	}
1499		2253
1500	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
1501	static void	2255	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2256	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1503	{	2257	{
1504	int timeout = 3600000;	2258	int timeout = 3600000;
1505	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
1506	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1508		2262
1509	/* the callback is illegal, but won't be called as we stop during check */	2263	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	2264	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	2265	ev_timer_start (loop, &tw);
1512		2266
1513	// create on ev_io per pollfd	2267	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	2268	for (int i = 0; i < nfd; ++i)
1515	{	2269	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	2270	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	2271	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2272	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		2273
1520	fds [i].revents = 0;	2274	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	2275	ev_io_start (loop, iow + i);
1523	}	2276	}
1524	}	2277	}
1525		2278
1526	// stop all watchers after blocking	2279	// stop all watchers after blocking
1527	static void	2280	static void
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2281	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1529	{	2282	{
1530	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
1531		2284
1532	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
		2286	{
		2287	// set the relevant poll flags
		2288	// could also call adns_processreadable etc. here
		2289	struct pollfd *fd = fds + i;
		2290	int revents = ev_clear_pending (iow + i);
		2291	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2292	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2293
		2294	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	2295	ev_io_stop (loop, iow + i);
		2296	}
1534		2297
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2298	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1536	}	2299	}
		2300
		2301	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2302	in the prepare watcher and would dispose of the check watcher.
		2303
		2304	Method 3: If the module to be embedded supports explicit event
		2305	notification (libadns does), you can also make use of the actual watcher
		2306	callbacks, and only destroy/create the watchers in the prepare watcher.
		2307
		2308	static void
		2309	timer_cb (EV_P_ ev_timer *w, int revents)
		2310	{
		2311	adns_state ads = (adns_state)w->data;
		2312	update_now (EV_A);
		2313
		2314	adns_processtimeouts (ads, &tv_now);
		2315	}
		2316
		2317	static void
		2318	io_cb (EV_P_ ev_io *w, int revents)
		2319	{
		2320	adns_state ads = (adns_state)w->data;
		2321	update_now (EV_A);
		2322
		2323	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2324	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2325	}
		2326
		2327	// do not ever call adns_afterpoll
		2328
		2329	Method 4: Do not use a prepare or check watcher because the module you
		2330	want to embed is not flexible enough to support it. Instead, you can
		2331	override their poll function. The drawback with this solution is that the
		2332	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2333	this approach, effectively embedding EV as a client into the horrible
		2334	libglib event loop.
		2335
		2336	static gint
		2337	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2338	{
		2339	int got_events = 0;
		2340
		2341	for (n = 0; n < nfds; ++n)
		2342	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2343
		2344	if (timeout >= 0)
		2345	// create/start timer
		2346
		2347	// poll
		2348	ev_loop (EV_A_ 0);
		2349
		2350	// stop timer again
		2351	if (timeout >= 0)
		2352	ev_timer_stop (EV_A_ &to);
		2353
		2354	// stop io watchers again - their callbacks should have set
		2355	for (n = 0; n < nfds; ++n)
		2356	ev_io_stop (EV_A_ iow [n]);
		2357
		2358	return got_events;
		2359	}
1537		2360
1538		2361
1539	=head2 C<ev_embed> - when one backend isn't enough...	2362	=head2 C<ev_embed> - when one backend isn't enough...
1540		2363
1541	This is a rather advanced watcher type that lets you embed one event loop	2364	This is a rather advanced watcher type that lets you embed one event loop
…		…
1547	prioritise I/O.	2370	prioritise I/O.
1548		2371
1549	As an example for a bug workaround, the kqueue backend might only support	2372	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	2373	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	2374	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	2375	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	2376	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	2377	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.	2378	C<kevent>, but at least you can use both mechanisms for what they are
		2379	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1556		2380
1557	As for prioritising I/O: rarely you have the case where some fds have	2381	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	2382	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	2383	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	2384	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.	2385	the rest in a second one, and embed the second one in the first.
1562		2386
1563	As long as the watcher is active, the callback will be invoked every time	2387	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	2388	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	2389	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	2390	their callbacks (you could also start an idle watcher to give the embedded
…		…
1574	interested in that.	2398	interested in that.
1575		2399
1576	Also, there have not currently been made special provisions for forking:	2400	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,	2401	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	2402	but you will also have to stop and restart any C<ev_embed> watchers
1579	yourself.	2403	yourself - but you can use a fork watcher to handle this automatically,
		2404	and future versions of libev might do just that.
1580		2405
1581	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
1582	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1583	portable one.	2408	portable one.
1584		2409
1585	So when you want to use this feature you will always have to be prepared	2410	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	2411	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	2412	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:	2413	create it, and if that fails, use the normal loop for everything.
1589		2414
1590	struct ev_loop *loop_hi = ev_default_init (0);	2415	=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		2416
1600	// if we got one, then embed it, otherwise default to loop_hi	2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
1601	if (loop_lo)	2418	automatically be applied to the embedded loop as well, so no special
1602	{	2419	fork handling is required in that case. When the watcher is not running,
1603	ev_embed_init (&embed, 0, loop_lo);	2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1604	ev_embed_start (loop_hi, &embed);	2421	as applicable.
1605	}	2422
1606	else	2423	=head3 Watcher-Specific Functions and Data Members
1607	loop_lo = loop_hi;
1608		2424
1609	=over 4	2425	=over 4
1610		2426
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2427	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1612		2428
…		…
1614		2430
1615	Configures the watcher to embed the given loop, which must be	2431	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	2432	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	2433	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,	2434	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).	2435	if you do not want that, you need to temporarily stop the embed watcher).
1620		2436
1621	=item ev_embed_sweep (loop, ev_embed *)	2437	=item ev_embed_sweep (loop, ev_embed *)
1622		2438
1623	Make a single, non-blocking sweep over the embedded loop. This works	2439	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	2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.	2441	appropriate way for embedded loops.
1626		2442
1627	=item struct ev_loop *loop [read-only]	2443	=item struct ev_loop *other [read-only]
1628		2444
1629	The embedded event loop.	2445	The embedded event loop.
1630		2446
1631	=back	2447	=back
		2448
		2449	=head3 Examples
		2450
		2451	Example: Try to get an embeddable event loop and embed it into the default
		2452	event loop. If that is not possible, use the default loop. The default
		2453	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2455	used).
		2456
		2457	struct ev_loop *loop_hi = ev_default_init (0);
		2458	struct ev_loop *loop_lo = 0;
		2459	ev_embed embed;
		2460
		2461	// see if there is a chance of getting one that works
		2462	// (remember that a flags value of 0 means autodetection)
		2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2465	: 0;
		2466
		2467	// if we got one, then embed it, otherwise default to loop_hi
		2468	if (loop_lo)
		2469	{
		2470	ev_embed_init (&embed, 0, loop_lo);
		2471	ev_embed_start (loop_hi, &embed);
		2472	}
		2473	else
		2474	loop_lo = loop_hi;
		2475
		2476	Example: Check if kqueue is available but not recommended and create
		2477	a kqueue backend for use with sockets (which usually work with any
		2478	kqueue implementation). Store the kqueue/socket-only event loop in
		2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2480
		2481	struct ev_loop *loop = ev_default_init (0);
		2482	struct ev_loop *loop_socket = 0;
		2483	ev_embed embed;
		2484
		2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2487	{
		2488	ev_embed_init (&embed, 0, loop_socket);
		2489	ev_embed_start (loop, &embed);
		2490	}
		2491
		2492	if (!loop_socket)
		2493	loop_socket = loop;
		2494
		2495	// now use loop_socket for all sockets, and loop for everything else
1632		2496
1633		2497
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2498	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2499
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2500	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,	2503	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	2504	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	2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2506	handlers will be invoked, too, of course.
1643		2507
		2508	=head3 Watcher-Specific Functions and Data Members
		2509
1644	=over 4	2510	=over 4
1645		2511
1646	=item ev_fork_init (ev_signal *, callback)	2512	=item ev_fork_init (ev_signal *, callback)
1647		2513
1648	Initialises and configures the fork watcher - it has no parameters of any	2514	Initialises and configures the fork watcher - it has no parameters of any
…		…
1650	believe me.	2516	believe me.
1651		2517
1652	=back	2518	=back
1653		2519
1654		2520
		2521	=head2 C<ev_async> - how to wake up another event loop
		2522
		2523	In general, you cannot use an C<ev_loop> from multiple threads or other
		2524	asynchronous sources such as signal handlers (as opposed to multiple event
		2525	loops - those are of course safe to use in different threads).
		2526
		2527	Sometimes, however, you need to wake up another event loop you do not
		2528	control, for example because it belongs to another thread. This is what
		2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2530	can signal it by calling C<ev_async_send>, which is thread- and signal
		2531	safe.
		2532
		2533	This functionality is very similar to C<ev_signal> watchers, as signals,
		2534	too, are asynchronous in nature, and signals, too, will be compressed
		2535	(i.e. the number of callback invocations may be less than the number of
		2536	C<ev_async_sent> calls).
		2537
		2538	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2539	just the default loop.
		2540
		2541	=head3 Queueing
		2542
		2543	C<ev_async> does not support queueing of data in any way. The reason
		2544	is that the author does not know of a simple (or any) algorithm for a
		2545	multiple-writer-single-reader queue that works in all cases and doesn't
		2546	need elaborate support such as pthreads.
		2547
		2548	That means that if you want to queue data, you have to provide your own
		2549	queue. But at least I can tell you how to implement locking around your
		2550	queue:
		2551
		2552	=over 4
		2553
		2554	=item queueing from a signal handler context
		2555
		2556	To implement race-free queueing, you simply add to the queue in the signal
		2557	handler but you block the signal handler in the watcher callback. Here is
		2558	an example that does that for some fictitious SIGUSR1 handler:
		2559
		2560	static ev_async mysig;
		2561
		2562	static void
		2563	sigusr1_handler (void)
		2564	{
		2565	sometype data;
		2566
		2567	// no locking etc.
		2568	queue_put (data);
		2569	ev_async_send (EV_DEFAULT_ &mysig);
		2570	}
		2571
		2572	static void
		2573	mysig_cb (EV_P_ ev_async *w, int revents)
		2574	{
		2575	sometype data;
		2576	sigset_t block, prev;
		2577
		2578	sigemptyset (&block);
		2579	sigaddset (&block, SIGUSR1);
		2580	sigprocmask (SIG_BLOCK, &block, &prev);
		2581
		2582	while (queue_get (&data))
		2583	process (data);
		2584
		2585	if (sigismember (&prev, SIGUSR1)
		2586	sigprocmask (SIG_UNBLOCK, &block, 0);
		2587	}
		2588
		2589	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2590	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2591	either...).
		2592
		2593	=item queueing from a thread context
		2594
		2595	The strategy for threads is different, as you cannot (easily) block
		2596	threads but you can easily preempt them, so to queue safely you need to
		2597	employ a traditional mutex lock, such as in this pthread example:
		2598
		2599	static ev_async mysig;
		2600	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2601
		2602	static void
		2603	otherthread (void)
		2604	{
		2605	// only need to lock the actual queueing operation
		2606	pthread_mutex_lock (&mymutex);
		2607	queue_put (data);
		2608	pthread_mutex_unlock (&mymutex);
		2609
		2610	ev_async_send (EV_DEFAULT_ &mysig);
		2611	}
		2612
		2613	static void
		2614	mysig_cb (EV_P_ ev_async *w, int revents)
		2615	{
		2616	pthread_mutex_lock (&mymutex);
		2617
		2618	while (queue_get (&data))
		2619	process (data);
		2620
		2621	pthread_mutex_unlock (&mymutex);
		2622	}
		2623
		2624	=back
		2625
		2626
		2627	=head3 Watcher-Specific Functions and Data Members
		2628
		2629	=over 4
		2630
		2631	=item ev_async_init (ev_async *, callback)
		2632
		2633	Initialises and configures the async watcher - it has no parameters of any
		2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2635	trust me.
		2636
		2637	=item ev_async_send (loop, ev_async *)
		2638
		2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2641	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2643	section below on what exactly this means).
		2644
		2645	This call incurs the overhead of a system call only once per loop iteration,
		2646	so while the overhead might be noticeable, it doesn't apply to repeated
		2647	calls to C<ev_async_send>.
		2648
		2649	=item bool = ev_async_pending (ev_async *)
		2650
		2651	Returns a non-zero value when C<ev_async_send> has been called on the
		2652	watcher but the event has not yet been processed (or even noted) by the
		2653	event loop.
		2654
		2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2656	the loop iterates next and checks for the watcher to have become active,
		2657	it will reset the flag again. C<ev_async_pending> can be used to very
		2658	quickly check whether invoking the loop might be a good idea.
		2659
		2660	Not that this does I<not> check whether the watcher itself is pending, only
		2661	whether it has been requested to make this watcher pending.
		2662
		2663	=back
		2664
		2665
1655	=head1 OTHER FUNCTIONS	2666	=head1 OTHER FUNCTIONS
1656		2667
1657	There are some other functions of possible interest. Described. Here. Now.	2668	There are some other functions of possible interest. Described. Here. Now.
1658		2669
1659	=over 4	2670	=over 4
1660		2671
1661	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1662		2673
1663	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
1664	callback on whichever event happens first and automatically stop both	2675	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	2676	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	2677	or timeout without having to allocate/configure/start/stop/free one or
1667	more watchers yourself.	2678	more watchers yourself.
1668		2679
1669	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	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	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1671	C<events> set will be craeted and started.	2682	the given C<fd> and C<events> set will be created and started.
1672		2683
1673	If C<timeout> is less than 0, then no timeout watcher will be	2684	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	2685	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	2686	repeat = 0) will be started. C<0> is a valid timeout.
1676	dubious value.
1677		2687
1678	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2688	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	2689	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>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1681	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
1682		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2696
1683	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
1684	{	2698	{
1685	if (revents & EV_TIMEOUT)
1686	/* doh, nothing entered */;
1687	else if (revents & EV_READ)	2699	if (revents & EV_READ)
1688	/* stdin might have data for us, joy! */;	2700	/* stdin might have data for us, joy! */;
		2701	else if (revents & EV_TIMEOUT)
		2702	/* doh, nothing entered */;
1689	}	2703	}
1690		2704
1691	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1692		2706
1693	=item ev_feed_event (ev_loop *, watcher *, int revents)	2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1694		2708
1695	Feeds the given event set into the event loop, as if the specified event	2709	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	2710	had happened for the specified watcher (which must be a pointer to an
1697	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
1698		2712
1699	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1700		2714
1701	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
1702	the given events it.	2716	the given events it.
1703		2717
1704	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1705		2719
1706	Feed an event as if the given signal occured (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
1707	loop!).	2721	loop!).
1708		2722
1709	=back	2723	=back
1710		2724
1711		2725
…		…
1727		2741
1728	=item * Priorities are not currently supported. Initialising priorities	2742	=item * Priorities are not currently supported. Initialising priorities
1729	will fail and all watchers will have the same priority, even though there	2743	will fail and all watchers will have the same priority, even though there
1730	is an ev_pri field.	2744	is an ev_pri field.
1731		2745
		2746	=item * In libevent, the last base created gets the signals, in libev, the
		2747	first base created (== the default loop) gets the signals.
		2748
1732	=item * Other members are not supported.	2749	=item * Other members are not supported.
1733		2750
1734	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1735	to use the libev header file and library.	2752	to use the libev header file and library.
1736		2753
1737	=back	2754	=back
1738		2755
1739	=head1 C++ SUPPORT	2756	=head1 C++ SUPPORT
1740		2757
1741	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2758	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	2759	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.	2760	the callback model to a model using method callbacks on objects.
1744		2761
1745	To use it,	2762	To use it,
1746		2763
1747	#include <ev++.h>	2764	#include <ev++.h>
1748		2765
1749	This automatically includes F<ev.h> and puts all of its definitions (many	2766	This automatically includes F<ev.h> and puts all of its definitions (many
1750	of them macros) into the global namespace. All C++ specific things are	2767	of them macros) into the global namespace. All C++ specific things are
1751	put into the C<ev> namespace. It should support all the same embedding	2768	put into the C<ev> namespace. It should support all the same embedding
1752	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2769	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1753		2770
1754	Care has been taken to keep the overhead low. The only data member added	2771	Care has been taken to keep the overhead low. The only data member the C++
1755	to the C-style watchers is the event loop the watcher is associated with	2772	classes add (compared to plain C-style watchers) is the event loop pointer
1756	(or no additional members at all if you disable C<EV_MULTIPLICITY> when	2773	that the watcher is associated with (or no additional members at all if
1757	embedding libev).	2774	you disable C<EV_MULTIPLICITY> when embedding libev).
1758		2775
1759	Currently, functions and static and non-static member functions can be	2776	Currently, functions, and static and non-static member functions can be
1760	used as callbacks. Other types should be easy to add as long as they only	2777	used as callbacks. Other types should be easy to add as long as they only
1761	need one additional pointer for context. If you need support for other	2778	need one additional pointer for context. If you need support for other
1762	types of functors please contact the author (preferably after implementing	2779	types of functors please contact the author (preferably after implementing
1763	it).	2780	it).
1764		2781
…		…
1819	your compiler is good :), then the method will be fully inlined into the	2836	your compiler is good :), then the method will be fully inlined into the
1820	thunking function, making it as fast as a direct C callback.	2837	thunking function, making it as fast as a direct C callback.
1821		2838
1822	Example: simple class declaration and watcher initialisation	2839	Example: simple class declaration and watcher initialisation
1823		2840
1824	struct myclass	2841	struct myclass
1825	{	2842	{
1826	void io_cb (ev::io &w, int revents) { }	2843	void io_cb (ev::io &w, int revents) { }
1827	}	2844	}
1828		2845
1829	myclass obj;	2846	myclass obj;
1830	ev::io iow;	2847	ev::io iow;
1831	iow.set <myclass, &myclass::io_cb> (&obj);	2848	iow.set <myclass, &myclass::io_cb> (&obj);
1832		2849
1833	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2850	=item w->set<function> (void *data = 0)
1834		2851
1835	Also sets a callback, but uses a static method or plain function as	2852	Also sets a callback, but uses a static method or plain function as
1836	callback. The optional C<data> argument will be stored in the watcher's	2853	callback. The optional C<data> argument will be stored in the watcher's
1837	C<data> member and is free for you to use.	2854	C<data> member and is free for you to use.
1838		2855
		2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2857
1839	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
		2859
		2860	Example: Use a plain function as callback.
		2861
		2862	static void io_cb (ev::io &w, int revents) { }
		2863	iow.set <io_cb> ();
1840		2864
1841	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
1842		2866
1843	Associates a different C<struct ev_loop> with this watcher. You can only	2867	Associates a different C<struct ev_loop> with this watcher. You can only
1844	do this when the watcher is inactive (and not pending either).	2868	do this when the watcher is inactive (and not pending either).
1845		2869
1846	=item w->set ([args])	2870	=item w->set ([arguments])
1847		2871
1848	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1849	called at least once. Unlike the C counterpart, an active watcher gets	2873	called at least once. Unlike the C counterpart, an active watcher gets
1850	automatically stopped and restarted when reconfiguring it with this	2874	automatically stopped and restarted when reconfiguring it with this
1851	method.	2875	method.
1852		2876
1853	=item w->start ()	2877	=item w->start ()
…		…
1857		2881
1858	=item w->stop ()	2882	=item w->stop ()
1859		2883
1860	Stops the watcher if it is active. Again, no C<loop> argument.	2884	Stops the watcher if it is active. Again, no C<loop> argument.
1861		2885
1862	=item w->again () C<ev::timer>, C<ev::periodic> only	2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1863		2887
1864	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2888	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1865	C<ev_TYPE_again> function.	2889	C<ev_TYPE_again> function.
1866		2890
1867	=item w->sweep () C<ev::embed> only	2891	=item w->sweep () (C<ev::embed> only)
1868		2892
1869	Invokes C<ev_embed_sweep>.	2893	Invokes C<ev_embed_sweep>.
1870		2894
1871	=item w->update () C<ev::stat> only	2895	=item w->update () (C<ev::stat> only)
1872		2896
1873	Invokes C<ev_stat_stat>.	2897	Invokes C<ev_stat_stat>.
1874		2898
1875	=back	2899	=back
1876		2900
1877	=back	2901	=back
1878		2902
1879	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
1880	the constructor.	2904	the constructor.
1881		2905
1882	class myclass	2906	class myclass
1883	{	2907	{
1884	ev_io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
1885	ev_idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1886		2910
1887	myclass ();	2911	myclass (int fd)
1888	}	2912	{
1889
1890	myclass::myclass (int fd)
1891	{
1892	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
1893	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
1894		2915
1895	io.start (fd, ev::READ);	2916	io.start (fd, ev::READ);
		2917	}
1896	}	2918	};
		2919
		2920
		2921	=head1 OTHER LANGUAGE BINDINGS
		2922
		2923	Libev does not offer other language bindings itself, but bindings for a
		2924	number of languages exist in the form of third-party packages. If you know
		2925	any interesting language binding in addition to the ones listed here, drop
		2926	me a note.
		2927
		2928	=over 4
		2929
		2930	=item Perl
		2931
		2932	The EV module implements the full libev API and is actually used to test
		2933	libev. EV is developed together with libev. Apart from the EV core module,
		2934	there are additional modules that implement libev-compatible interfaces
		2935	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
		2938
		2939	It can be found and installed via CPAN, its homepage is at
		2940	L<http://software.schmorp.de/pkg/EV>.
		2941
		2942	=item Python
		2943
		2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2945	seems to be quite complete and well-documented. Note, however, that the
		2946	patch they require for libev is outright dangerous as it breaks the ABI
		2947	for everybody else, and therefore, should never be applied in an installed
		2948	libev (if python requires an incompatible ABI then it needs to embed
		2949	libev).
		2950
		2951	=item Ruby
		2952
		2953	Tony Arcieri has written a ruby extension that offers access to a subset
		2954	of the libev API and adds file handle abstractions, asynchronous DNS and
		2955	more on top of it. It can be found via gem servers. Its homepage is at
		2956	L<http://rev.rubyforge.org/>.
		2957
		2958	=item D
		2959
		2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2962
		2963	=item Ocaml
		2964
		2965	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2967
		2968	=back
1897		2969
1898		2970
1899	=head1 MACRO MAGIC	2971	=head1 MACRO MAGIC
1900		2972
1901	Libev can be compiled with a variety of options, the most fundemantal is	2973	Libev can be compiled with a variety of options, the most fundamental
1902	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2974	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1903	callbacks have an initial C<struct ev_loop *> argument.	2975	functions and callbacks have an initial C<struct ev_loop *> argument.
1904		2976
1905	To make it easier to write programs that cope with either variant, the	2977	To make it easier to write programs that cope with either variant, the
1906	following macros are defined:	2978	following macros are defined:
1907		2979
1908	=over 4	2980	=over 4
…		…
1911		2983
1912	This provides the loop I<argument> for functions, if one is required ("ev	2984	This provides the loop I<argument> for functions, if one is required ("ev
1913	loop argument"). The C<EV_A> form is used when this is the sole argument,	2985	loop argument"). The C<EV_A> form is used when this is the sole argument,
1914	C<EV_A_> is used when other arguments are following. Example:	2986	C<EV_A_> is used when other arguments are following. Example:
1915		2987
1916	ev_unref (EV_A);	2988	ev_unref (EV_A);
1917	ev_timer_add (EV_A_ watcher);	2989	ev_timer_add (EV_A_ watcher);
1918	ev_loop (EV_A_ 0);	2990	ev_loop (EV_A_ 0);
1919		2991
1920	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1921	which is often provided by the following macro.	2993	which is often provided by the following macro.
1922		2994
1923	=item C<EV_P>, C<EV_P_>	2995	=item C<EV_P>, C<EV_P_>
1924		2996
1925	This provides the loop I<parameter> for functions, if one is required ("ev	2997	This provides the loop I<parameter> for functions, if one is required ("ev
1926	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2998	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1927	C<EV_P_> is used when other parameters are following. Example:	2999	C<EV_P_> is used when other parameters are following. Example:
1928		3000
1929	// this is how ev_unref is being declared	3001	// this is how ev_unref is being declared
1930	static void ev_unref (EV_P);	3002	static void ev_unref (EV_P);
1931		3003
1932	// this is how you can declare your typical callback	3004	// this is how you can declare your typical callback
1933	static void cb (EV_P_ ev_timer *w, int revents)	3005	static void cb (EV_P_ ev_timer *w, int revents)
1934		3006
1935	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3007	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1936	suitable for use with C<EV_A>.	3008	suitable for use with C<EV_A>.
1937		3009
1938	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3010	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1939		3011
1940	Similar to the other two macros, this gives you the value of the default	3012	Similar to the other two macros, this gives you the value of the default
1941	loop, if multiple loops are supported ("ev loop default").	3013	loop, if multiple loops are supported ("ev loop default").
		3014
		3015	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3016
		3017	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3018	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3019	is undefined when the default loop has not been initialised by a previous
		3020	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3021
		3022	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3023	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1942		3024
1943	=back	3025	=back
1944		3026
1945	Example: Declare and initialise a check watcher, utilising the above	3027	Example: Declare and initialise a check watcher, utilising the above
1946	macros so it will work regardless of whether multiple loops are supported	3028	macros so it will work regardless of whether multiple loops are supported
1947	or not.	3029	or not.
1948		3030
1949	static void	3031	static void
1950	check_cb (EV_P_ ev_timer *w, int revents)	3032	check_cb (EV_P_ ev_timer *w, int revents)
1951	{	3033	{
1952	ev_check_stop (EV_A_ w);	3034	ev_check_stop (EV_A_ w);
1953	}	3035	}
1954		3036
1955	ev_check check;	3037	ev_check check;
1956	ev_check_init (&check, check_cb);	3038	ev_check_init (&check, check_cb);
1957	ev_check_start (EV_DEFAULT_ &check);	3039	ev_check_start (EV_DEFAULT_ &check);
1958	ev_loop (EV_DEFAULT_ 0);	3040	ev_loop (EV_DEFAULT_ 0);
1959		3041
1960	=head1 EMBEDDING	3042	=head1 EMBEDDING
1961		3043
1962	Libev can (and often is) directly embedded into host	3044	Libev can (and often is) directly embedded into host
1963	applications. Examples of applications that embed it include the Deliantra	3045	applications. Examples of applications that embed it include the Deliantra
1964	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3046	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1965	and rxvt-unicode.	3047	and rxvt-unicode.
1966		3048
1967	The goal is to enable you to just copy the neecssary files into your	3049	The goal is to enable you to just copy the necessary files into your
1968	source directory without having to change even a single line in them, so	3050	source directory without having to change even a single line in them, so
1969	you can easily upgrade by simply copying (or having a checked-out copy of	3051	you can easily upgrade by simply copying (or having a checked-out copy of
1970	libev somewhere in your source tree).	3052	libev somewhere in your source tree).
1971		3053
1972	=head2 FILESETS	3054	=head2 FILESETS
1973		3055
1974	Depending on what features you need you need to include one or more sets of files	3056	Depending on what features you need you need to include one or more sets of files
1975	in your app.	3057	in your application.
1976		3058
1977	=head3 CORE EVENT LOOP	3059	=head3 CORE EVENT LOOP
1978		3060
1979	To include only the libev core (all the C<ev_*> functions), with manual	3061	To include only the libev core (all the C<ev_*> functions), with manual
1980	configuration (no autoconf):	3062	configuration (no autoconf):
1981		3063
1982	#define EV_STANDALONE 1	3064	#define EV_STANDALONE 1
1983	#include "ev.c"	3065	#include "ev.c"
1984		3066
1985	This will automatically include F<ev.h>, too, and should be done in a	3067	This will automatically include F<ev.h>, too, and should be done in a
1986	single C source file only to provide the function implementations. To use	3068	single C source file only to provide the function implementations. To use
1987	it, do the same for F<ev.h> in all files wishing to use this API (best	3069	it, do the same for F<ev.h> in all files wishing to use this API (best
1988	done by writing a wrapper around F<ev.h> that you can include instead and	3070	done by writing a wrapper around F<ev.h> that you can include instead and
1989	where you can put other configuration options):	3071	where you can put other configuration options):
1990		3072
1991	#define EV_STANDALONE 1	3073	#define EV_STANDALONE 1
1992	#include "ev.h"	3074	#include "ev.h"
1993		3075
1994	Both header files and implementation files can be compiled with a C++	3076	Both header files and implementation files can be compiled with a C++
1995	compiler (at least, thats a stated goal, and breakage will be treated	3077	compiler (at least, thats a stated goal, and breakage will be treated
1996	as a bug).	3078	as a bug).
1997		3079
1998	You need the following files in your source tree, or in a directory	3080	You need the following files in your source tree, or in a directory
1999	in your include path (e.g. in libev/ when using -Ilibev):	3081	in your include path (e.g. in libev/ when using -Ilibev):
2000		3082
2001	ev.h	3083	ev.h
2002	ev.c	3084	ev.c
2003	ev_vars.h	3085	ev_vars.h
2004	ev_wrap.h	3086	ev_wrap.h
2005		3087
2006	ev_win32.c required on win32 platforms only	3088	ev_win32.c required on win32 platforms only
2007		3089
2008	ev_select.c only when select backend is enabled (which is enabled by default)	3090	ev_select.c only when select backend is enabled (which is enabled by default)
2009	ev_poll.c only when poll backend is enabled (disabled by default)	3091	ev_poll.c only when poll backend is enabled (disabled by default)
2010	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3092	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2011	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3093	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2012	ev_port.c only when the solaris port backend is enabled (disabled by default)	3094	ev_port.c only when the solaris port backend is enabled (disabled by default)
2013		3095
2014	F<ev.c> includes the backend files directly when enabled, so you only need	3096	F<ev.c> includes the backend files directly when enabled, so you only need
2015	to compile this single file.	3097	to compile this single file.
2016		3098
2017	=head3 LIBEVENT COMPATIBILITY API	3099	=head3 LIBEVENT COMPATIBILITY API
2018		3100
2019	To include the libevent compatibility API, also include:	3101	To include the libevent compatibility API, also include:
2020		3102
2021	#include "event.c"	3103	#include "event.c"
2022		3104
2023	in the file including F<ev.c>, and:	3105	in the file including F<ev.c>, and:
2024		3106
2025	#include "event.h"	3107	#include "event.h"
2026		3108
2027	in the files that want to use the libevent API. This also includes F<ev.h>.	3109	in the files that want to use the libevent API. This also includes F<ev.h>.
2028		3110
2029	You need the following additional files for this:	3111	You need the following additional files for this:
2030		3112
2031	event.h	3113	event.h
2032	event.c	3114	event.c
2033		3115
2034	=head3 AUTOCONF SUPPORT	3116	=head3 AUTOCONF SUPPORT
2035		3117
2036	Instead of using C<EV_STANDALONE=1> and providing your config in	3118	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2037	whatever way you want, you can also C<m4_include([libev.m4])> in your	3119	whatever way you want, you can also C<m4_include([libev.m4])> in your
2038	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3120	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2039	include F<config.h> and configure itself accordingly.	3121	include F<config.h> and configure itself accordingly.
2040		3122
2041	For this of course you need the m4 file:	3123	For this of course you need the m4 file:
2042		3124
2043	libev.m4	3125	libev.m4
2044		3126
2045	=head2 PREPROCESSOR SYMBOLS/MACROS	3127	=head2 PREPROCESSOR SYMBOLS/MACROS
2046		3128
2047	Libev can be configured via a variety of preprocessor symbols you have to define	3129	Libev can be configured via a variety of preprocessor symbols you have to
2048	before including any of its files. The default is not to build for multiplicity	3130	define before including any of its files. The default in the absence of
2049	and only include the select backend.	3131	autoconf is documented for every option.
2050		3132
2051	=over 4	3133	=over 4
2052		3134
2053	=item EV_STANDALONE	3135	=item EV_STANDALONE
2054		3136
…		…
2059	F<event.h> that are not directly supported by the libev core alone.	3141	F<event.h> that are not directly supported by the libev core alone.
2060		3142
2061	=item EV_USE_MONOTONIC	3143	=item EV_USE_MONOTONIC
2062		3144
2063	If defined to be C<1>, libev will try to detect the availability of the	3145	If defined to be C<1>, libev will try to detect the availability of the
2064	monotonic clock option at both compiletime and runtime. Otherwise no use	3146	monotonic clock option at both compile time and runtime. Otherwise no use
2065	of the monotonic clock option will be attempted. If you enable this, you	3147	of the monotonic clock option will be attempted. If you enable this, you
2066	usually have to link against librt or something similar. Enabling it when	3148	usually have to link against librt or something similar. Enabling it when
2067	the functionality isn't available is safe, though, althoguh you have	3149	the functionality isn't available is safe, though, although you have
2068	to make sure you link against any libraries where the C<clock_gettime>	3150	to make sure you link against any libraries where the C<clock_gettime>
2069	function is hiding in (often F<-lrt>).	3151	function is hiding in (often F<-lrt>).
2070		3152
2071	=item EV_USE_REALTIME	3153	=item EV_USE_REALTIME
2072		3154
2073	If defined to be C<1>, libev will try to detect the availability of the	3155	If defined to be C<1>, libev will try to detect the availability of the
2074	realtime clock option at compiletime (and assume its availability at	3156	real-time clock option at compile time (and assume its availability at
2075	runtime if successful). Otherwise no use of the realtime clock option will	3157	runtime if successful). Otherwise no use of the real-time clock option will
2076	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2077	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2078	in the description of C<EV_USE_MONOTONIC>, though.	3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3161
		3162	=item EV_USE_NANOSLEEP
		3163
		3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3165	and will use it for delays. Otherwise it will use C<select ()>.
		3166
		3167	=item EV_USE_EVENTFD
		3168
		3169	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3170	available and will probe for kernel support at runtime. This will improve
		3171	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3172	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3173	2.7 or newer, otherwise disabled.
2079		3174
2080	=item EV_USE_SELECT	3175	=item EV_USE_SELECT
2081		3176
2082	If undefined or defined to be C<1>, libev will compile in support for the	3177	If undefined or defined to be C<1>, libev will compile in support for the
2083	C<select>(2) backend. No attempt at autodetection will be done: if no	3178	C<select>(2) backend. No attempt at auto-detection will be done: if no
2084	other method takes over, select will be it. Otherwise the select backend	3179	other method takes over, select will be it. Otherwise the select backend
2085	will not be compiled in.	3180	will not be compiled in.
2086		3181
2087	=item EV_SELECT_USE_FD_SET	3182	=item EV_SELECT_USE_FD_SET
2088		3183
2089	If defined to C<1>, then the select backend will use the system C<fd_set>	3184	If defined to C<1>, then the select backend will use the system C<fd_set>
2090	structure. This is useful if libev doesn't compile due to a missing	3185	structure. This is useful if libev doesn't compile due to a missing
2091	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2092	exotic systems. This usually limits the range of file descriptors to some	3187	exotic systems. This usually limits the range of file descriptors to some
2093	low limit such as 1024 or might have other limitations (winsocket only	3188	low limit such as 1024 or might have other limitations (winsocket only
2094	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2095	influence the size of the C<fd_set> used.	3190	influence the size of the C<fd_set> used.
2096		3191
…		…
2102	be used is the winsock select). This means that it will call	3197	be used is the winsock select). This means that it will call
2103	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3198	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2104	it is assumed that all these functions actually work on fds, even	3199	it is assumed that all these functions actually work on fds, even
2105	on win32. Should not be defined on non-win32 platforms.	3200	on win32. Should not be defined on non-win32 platforms.
2106		3201
		3202	=item EV_FD_TO_WIN32_HANDLE
		3203
		3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3205	file descriptors to socket handles. When not defining this symbol (the
		3206	default), then libev will call C<_get_osfhandle>, which is usually
		3207	correct. In some cases, programs use their own file descriptor management,
		3208	in which case they can provide this function to map fds to socket handles.
		3209
2107	=item EV_USE_POLL	3210	=item EV_USE_POLL
2108		3211
2109	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2110	backend. Otherwise it will be enabled on non-win32 platforms. It	3213	backend. Otherwise it will be enabled on non-win32 platforms. It
2111	takes precedence over select.	3214	takes precedence over select.
2112		3215
2113	=item EV_USE_EPOLL	3216	=item EV_USE_EPOLL
2114		3217
2115	If defined to be C<1>, libev will compile in support for the Linux	3218	If defined to be C<1>, libev will compile in support for the Linux
2116	C<epoll>(7) backend. Its availability will be detected at runtime,	3219	C<epoll>(7) backend. Its availability will be detected at runtime,
2117	otherwise another method will be used as fallback. This is the	3220	otherwise another method will be used as fallback. This is the preferred
2118	preferred backend for GNU/Linux systems.	3221	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3222	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2119		3223
2120	=item EV_USE_KQUEUE	3224	=item EV_USE_KQUEUE
2121		3225
2122	If defined to be C<1>, libev will compile in support for the BSD style	3226	If defined to be C<1>, libev will compile in support for the BSD style
2123	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3227	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2136	otherwise another method will be used as fallback. This is the preferred	3240	otherwise another method will be used as fallback. This is the preferred
2137	backend for Solaris 10 systems.	3241	backend for Solaris 10 systems.
2138		3242
2139	=item EV_USE_DEVPOLL	3243	=item EV_USE_DEVPOLL
2140		3244
2141	reserved for future expansion, works like the USE symbols above.	3245	Reserved for future expansion, works like the USE symbols above.
2142		3246
2143	=item EV_USE_INOTIFY	3247	=item EV_USE_INOTIFY
2144		3248
2145	If defined to be C<1>, libev will compile in support for the Linux inotify	3249	If defined to be C<1>, libev will compile in support for the Linux inotify
2146	interface to speed up C<ev_stat> watchers. Its actual availability will	3250	interface to speed up C<ev_stat> watchers. Its actual availability will
2147	be detected at runtime.	3251	be detected at runtime. If undefined, it will be enabled if the headers
		3252	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3253
		3254	=item EV_ATOMIC_T
		3255
		3256	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3257	access is atomic with respect to other threads or signal contexts. No such
		3258	type is easily found in the C language, so you can provide your own type
		3259	that you know is safe for your purposes. It is used both for signal handler "locking"
		3260	as well as for signal and thread safety in C<ev_async> watchers.
		3261
		3262	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3263	(from F<signal.h>), which is usually good enough on most platforms.
2148		3264
2149	=item EV_H	3265	=item EV_H
2150		3266
2151	The name of the F<ev.h> header file used to include it. The default if	3267	The name of the F<ev.h> header file used to include it. The default if
2152	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3268	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2153	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3269	used to virtually rename the F<ev.h> header file in case of conflicts.
2154		3270
2155	=item EV_CONFIG_H	3271	=item EV_CONFIG_H
2156		3272
2157	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2158	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3274	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2159	C<EV_H>, above.	3275	C<EV_H>, above.
2160		3276
2161	=item EV_EVENT_H	3277	=item EV_EVENT_H
2162		3278
2163	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2164	of how the F<event.h> header can be found.	3280	of how the F<event.h> header can be found, the default is C<"event.h">.
2165		3281
2166	=item EV_PROTOTYPES	3282	=item EV_PROTOTYPES
2167		3283
2168	If defined to be C<0>, then F<ev.h> will not define any function	3284	If defined to be C<0>, then F<ev.h> will not define any function
2169	prototypes, but still define all the structs and other symbols. This is	3285	prototypes, but still define all the structs and other symbols. This is
…		…
2190	When doing priority-based operations, libev usually has to linearly search	3306	When doing priority-based operations, libev usually has to linearly search
2191	all the priorities, so having many of them (hundreds) uses a lot of space	3307	all the priorities, so having many of them (hundreds) uses a lot of space
2192	and time, so using the defaults of five priorities (-2 .. +2) is usually	3308	and time, so using the defaults of five priorities (-2 .. +2) is usually
2193	fine.	3309	fine.
2194		3310
2195	If your embedding app does not need any priorities, defining these both to	3311	If your embedding application does not need any priorities, defining these
2196	C<0> will save some memory and cpu.	3312	both to C<0> will save some memory and CPU.
2197		3313
2198	=item EV_PERIODIC_ENABLE	3314	=item EV_PERIODIC_ENABLE
2199		3315
2200	If undefined or defined to be C<1>, then periodic timers are supported. If	3316	If undefined or defined to be C<1>, then periodic timers are supported. If
2201	defined to be C<0>, then they are not. Disabling them saves a few kB of	3317	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2208	code.	3324	code.
2209		3325
2210	=item EV_EMBED_ENABLE	3326	=item EV_EMBED_ENABLE
2211		3327
2212	If undefined or defined to be C<1>, then embed watchers are supported. If	3328	If undefined or defined to be C<1>, then embed watchers are supported. If
2213	defined to be C<0>, then they are not.	3329	defined to be C<0>, then they are not. Embed watchers rely on most other
		3330	watcher types, which therefore must not be disabled.
2214		3331
2215	=item EV_STAT_ENABLE	3332	=item EV_STAT_ENABLE
2216		3333
2217	If undefined or defined to be C<1>, then stat watchers are supported. If	3334	If undefined or defined to be C<1>, then stat watchers are supported. If
2218	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not.
…		…
2220	=item EV_FORK_ENABLE	3337	=item EV_FORK_ENABLE
2221		3338
2222	If undefined or defined to be C<1>, then fork watchers are supported. If	3339	If undefined or defined to be C<1>, then fork watchers are supported. If
2223	defined to be C<0>, then they are not.	3340	defined to be C<0>, then they are not.
2224		3341
		3342	=item EV_ASYNC_ENABLE
		3343
		3344	If undefined or defined to be C<1>, then async watchers are supported. If
		3345	defined to be C<0>, then they are not.
		3346
2225	=item EV_MINIMAL	3347	=item EV_MINIMAL
2226		3348
2227	If you need to shave off some kilobytes of code at the expense of some	3349	If you need to shave off some kilobytes of code at the expense of some
2228	speed, define this symbol to C<1>. Currently only used for gcc to override	3350	speed, define this symbol to C<1>. Currently this is used to override some
2229	some inlining decisions, saves roughly 30% codesize of amd64.	3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3352	much smaller 2-heap for timer management over the default 4-heap.
2230		3353
2231	=item EV_PID_HASHSIZE	3354	=item EV_PID_HASHSIZE
2232		3355
2233	C<ev_child> watchers use a small hash table to distribute workload by	3356	C<ev_child> watchers use a small hash table to distribute workload by
2234	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2235	than enough. If you need to manage thousands of children you might want to	3358	than enough. If you need to manage thousands of children you might want to
2236	increase this value (I<must> be a power of two).	3359	increase this value (I<must> be a power of two).
2237		3360
2238	=item EV_INOTIFY_HASHSIZE	3361	=item EV_INOTIFY_HASHSIZE
2239		3362
2240	C<ev_staz> watchers use a small hash table to distribute workload by	3363	C<ev_stat> watchers use a small hash table to distribute workload by
2241	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3364	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2242	usually more than enough. If you need to manage thousands of C<ev_stat>	3365	usually more than enough. If you need to manage thousands of C<ev_stat>
2243	watchers you might want to increase this value (I<must> be a power of	3366	watchers you might want to increase this value (I<must> be a power of
2244	two).	3367	two).
2245		3368
		3369	=item EV_USE_4HEAP
		3370
		3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3374	faster performance with many (thousands) of watchers.
		3375
		3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3377	(disabled).
		3378
		3379	=item EV_HEAP_CACHE_AT
		3380
		3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3385	but avoids random read accesses on heap changes. This improves performance
		3386	noticeably with many (hundreds) of watchers.
		3387
		3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3389	(disabled).
		3390
		3391	=item EV_VERIFY
		3392
		3393	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3394	be done: If set to C<0>, no internal verification code will be compiled
		3395	in. If set to C<1>, then verification code will be compiled in, but not
		3396	called. If set to C<2>, then the internal verification code will be
		3397	called once per loop, which can slow down libev. If set to C<3>, then the
		3398	verification code will be called very frequently, which will slow down
		3399	libev considerably.
		3400
		3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3402	C<0>.
		3403
2246	=item EV_COMMON	3404	=item EV_COMMON
2247		3405
2248	By default, all watchers have a C<void *data> member. By redefining	3406	By default, all watchers have a C<void *data> member. By redefining
2249	this macro to a something else you can include more and other types of	3407	this macro to a something else you can include more and other types of
2250	members. You have to define it each time you include one of the files,	3408	members. You have to define it each time you include one of the files,
2251	though, and it must be identical each time.	3409	though, and it must be identical each time.
2252		3410
2253	For example, the perl EV module uses something like this:	3411	For example, the perl EV module uses something like this:
2254		3412
2255	#define EV_COMMON \	3413	#define EV_COMMON \
2256	SV *self; /* contains this struct */ \	3414	SV *self; /* contains this struct */ \
2257	SV *cb_sv, *fh /* note no trailing ";" */	3415	SV *cb_sv, *fh /* note no trailing ";" */
2258		3416
2259	=item EV_CB_DECLARE (type)	3417	=item EV_CB_DECLARE (type)
2260		3418
2261	=item EV_CB_INVOKE (watcher, revents)	3419	=item EV_CB_INVOKE (watcher, revents)
2262		3420
2263	=item ev_set_cb (ev, cb)	3421	=item ev_set_cb (ev, cb)
2264		3422
2265	Can be used to change the callback member declaration in each watcher,	3423	Can be used to change the callback member declaration in each watcher,
2266	and the way callbacks are invoked and set. Must expand to a struct member	3424	and the way callbacks are invoked and set. Must expand to a struct member
2267	definition and a statement, respectively. See the F<ev.v> header file for	3425	definition and a statement, respectively. See the F<ev.h> header file for
2268	their default definitions. One possible use for overriding these is to	3426	their default definitions. One possible use for overriding these is to
2269	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3427	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2270	method calls instead of plain function calls in C++.	3428	method calls instead of plain function calls in C++.
		3429
		3430	=back
		3431
		3432	=head2 EXPORTED API SYMBOLS
		3433
		3434	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3435	exported symbols, you can use the provided F<Symbol.*> files which list
		3436	all public symbols, one per line:
		3437
		3438	Symbols.ev for libev proper
		3439	Symbols.event for the libevent emulation
		3440
		3441	This can also be used to rename all public symbols to avoid clashes with
		3442	multiple versions of libev linked together (which is obviously bad in
		3443	itself, but sometimes it is inconvenient to avoid this).
		3444
		3445	A sed command like this will create wrapper C<#define>'s that you need to
		3446	include before including F<ev.h>:
		3447
		3448	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3449
		3450	This would create a file F<wrap.h> which essentially looks like this:
		3451
		3452	#define ev_backend myprefix_ev_backend
		3453	#define ev_check_start myprefix_ev_check_start
		3454	#define ev_check_stop myprefix_ev_check_stop
		3455	...
2271		3456
2272	=head2 EXAMPLES	3457	=head2 EXAMPLES
2273		3458
2274	For a real-world example of a program the includes libev	3459	For a real-world example of a program the includes libev
2275	verbatim, you can have a look at the EV perl module	3460	verbatim, you can have a look at the EV perl module
…		…
2280	file.	3465	file.
2281		3466
2282	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2283	that everybody includes and which overrides some configure choices:	3468	that everybody includes and which overrides some configure choices:
2284		3469
2285	#define EV_MINIMAL 1	3470	#define EV_MINIMAL 1
2286	#define EV_USE_POLL 0	3471	#define EV_USE_POLL 0
2287	#define EV_MULTIPLICITY 0	3472	#define EV_MULTIPLICITY 0
2288	#define EV_PERIODIC_ENABLE 0	3473	#define EV_PERIODIC_ENABLE 0
2289	#define EV_STAT_ENABLE 0	3474	#define EV_STAT_ENABLE 0
2290	#define EV_FORK_ENABLE 0	3475	#define EV_FORK_ENABLE 0
2291	#define EV_CONFIG_H <config.h>	3476	#define EV_CONFIG_H <config.h>
2292	#define EV_MINPRI 0	3477	#define EV_MINPRI 0
2293	#define EV_MAXPRI 0	3478	#define EV_MAXPRI 0
2294		3479
2295	#include "ev++.h"	3480	#include "ev++.h"
2296		3481
2297	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2298		3483
2299	#include "ev_cpp.h"	3484	#include "ev_cpp.h"
2300	#include "ev.c"	3485	#include "ev.c"
2301		3486
		3487	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2302		3488
		3489	=head2 THREADS AND COROUTINES
		3490
		3491	=head3 THREADS
		3492
		3493	All libev functions are reentrant and thread-safe unless explicitly
		3494	documented otherwise, but libev implements no locking itself. This means
		3495	that you can use as many loops as you want in parallel, as long as there
		3496	are no concurrent calls into any libev function with the same loop
		3497	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3498	of course): libev guarantees that different event loops share no data
		3499	structures that need any locking.
		3500
		3501	Or to put it differently: calls with different loop parameters can be done
		3502	concurrently from multiple threads, calls with the same loop parameter
		3503	must be done serially (but can be done from different threads, as long as
		3504	only one thread ever is inside a call at any point in time, e.g. by using
		3505	a mutex per loop).
		3506
		3507	Specifically to support threads (and signal handlers), libev implements
		3508	so-called C<ev_async> watchers, which allow some limited form of
		3509	concurrency on the same event loop, namely waking it up "from the
		3510	outside".
		3511
		3512	If you want to know which design (one loop, locking, or multiple loops
		3513	without or something else still) is best for your problem, then I cannot
		3514	help you, but here is some generic advice:
		3515
		3516	=over 4
		3517
		3518	=item * most applications have a main thread: use the default libev loop
		3519	in that thread, or create a separate thread running only the default loop.
		3520
		3521	This helps integrating other libraries or software modules that use libev
		3522	themselves and don't care/know about threading.
		3523
		3524	=item * one loop per thread is usually a good model.
		3525
		3526	Doing this is almost never wrong, sometimes a better-performance model
		3527	exists, but it is always a good start.
		3528
		3529	=item * other models exist, such as the leader/follower pattern, where one
		3530	loop is handed through multiple threads in a kind of round-robin fashion.
		3531
		3532	Choosing a model is hard - look around, learn, know that usually you can do
		3533	better than you currently do :-)
		3534
		3535	=item * often you need to talk to some other thread which blocks in the
		3536	event loop.
		3537
		3538	C<ev_async> watchers can be used to wake them up from other threads safely
		3539	(or from signal contexts...).
		3540
		3541	An example use would be to communicate signals or other events that only
		3542	work in the default loop by registering the signal watcher with the
		3543	default loop and triggering an C<ev_async> watcher from the default loop
		3544	watcher callback into the event loop interested in the signal.
		3545
		3546	=back
		3547
		3548	=head3 COROUTINES
		3549
		3550	Libev is very accommodating to coroutines ("cooperative threads"):
		3551	libev fully supports nesting calls to its functions from different
		3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3553	different coroutines, and switch freely between both coroutines running the
		3554	loop, as long as you don't confuse yourself). The only exception is that
		3555	you must not do this from C<ev_periodic> reschedule callbacks.
		3556
		3557	Care has been taken to ensure that libev does not keep local state inside
		3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3559	they do not clal any callbacks.
		3560
		3561	=head2 COMPILER WARNINGS
		3562
		3563	Depending on your compiler and compiler settings, you might get no or a
		3564	lot of warnings when compiling libev code. Some people are apparently
		3565	scared by this.
		3566
		3567	However, these are unavoidable for many reasons. For one, each compiler
		3568	has different warnings, and each user has different tastes regarding
		3569	warning options. "Warn-free" code therefore cannot be a goal except when
		3570	targeting a specific compiler and compiler-version.
		3571
		3572	Another reason is that some compiler warnings require elaborate
		3573	workarounds, or other changes to the code that make it less clear and less
		3574	maintainable.
		3575
		3576	And of course, some compiler warnings are just plain stupid, or simply
		3577	wrong (because they don't actually warn about the condition their message
		3578	seems to warn about). For example, certain older gcc versions had some
		3579	warnings that resulted an extreme number of false positives. These have
		3580	been fixed, but some people still insist on making code warn-free with
		3581	such buggy versions.
		3582
		3583	While libev is written to generate as few warnings as possible,
		3584	"warn-free" code is not a goal, and it is recommended not to build libev
		3585	with any compiler warnings enabled unless you are prepared to cope with
		3586	them (e.g. by ignoring them). Remember that warnings are just that:
		3587	warnings, not errors, or proof of bugs.
		3588
		3589
		3590	=head2 VALGRIND
		3591
		3592	Valgrind has a special section here because it is a popular tool that is
		3593	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3594
		3595	If you think you found a bug (memory leak, uninitialised data access etc.)
		3596	in libev, then check twice: If valgrind reports something like:
		3597
		3598	==2274== definitely lost: 0 bytes in 0 blocks.
		3599	==2274== possibly lost: 0 bytes in 0 blocks.
		3600	==2274== still reachable: 256 bytes in 1 blocks.
		3601
		3602	Then there is no memory leak, just as memory accounted to global variables
		3603	is not a memleak - the memory is still being refernced, and didn't leak.
		3604
		3605	Similarly, under some circumstances, valgrind might report kernel bugs
		3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3607	although an acceptable workaround has been found here), or it might be
		3608	confused.
		3609
		3610	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3611	make it into some kind of religion.
		3612
		3613	If you are unsure about something, feel free to contact the mailing list
		3614	with the full valgrind report and an explanation on why you think this
		3615	is a bug in libev (best check the archives, too :). However, don't be
		3616	annoyed when you get a brisk "this is no bug" answer and take the chance
		3617	of learning how to interpret valgrind properly.
		3618
		3619	If you need, for some reason, empty reports from valgrind for your project
		3620	I suggest using suppression lists.
		3621
		3622
		3623	=head1 PORTABILITY NOTES
		3624
		3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3626
		3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3628	requires, and its I/O model is fundamentally incompatible with the POSIX
		3629	model. Libev still offers limited functionality on this platform in
		3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3631	descriptors. This only applies when using Win32 natively, not when using
		3632	e.g. cygwin.
		3633
		3634	Lifting these limitations would basically require the full
		3635	re-implementation of the I/O system. If you are into these kinds of
		3636	things, then note that glib does exactly that for you in a very portable
		3637	way (note also that glib is the slowest event library known to man).
		3638
		3639	There is no supported compilation method available on windows except
		3640	embedding it into other applications.
		3641
		3642	Not a libev limitation but worth mentioning: windows apparently doesn't
		3643	accept large writes: instead of resulting in a partial write, windows will
		3644	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3645	so make sure you only write small amounts into your sockets (less than a
		3646	megabyte seems safe, but this apparently depends on the amount of memory
		3647	available).
		3648
		3649	Due to the many, low, and arbitrary limits on the win32 platform and
		3650	the abysmal performance of winsockets, using a large number of sockets
		3651	is not recommended (and not reasonable). If your program needs to use
		3652	more than a hundred or so sockets, then likely it needs to use a totally
		3653	different implementation for windows, as libev offers the POSIX readiness
		3654	notification model, which cannot be implemented efficiently on windows
		3655	(Microsoft monopoly games).
		3656
		3657	A typical way to use libev under windows is to embed it (see the embedding
		3658	section for details) and use the following F<evwrap.h> header file instead
		3659	of F<ev.h>:
		3660
		3661	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3662	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3663
		3664	#include "ev.h"
		3665
		3666	And compile the following F<evwrap.c> file into your project (make sure
		3667	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3668
		3669	#include "evwrap.h"
		3670	#include "ev.c"
		3671
		3672	=over 4
		3673
		3674	=item The winsocket select function
		3675
		3676	The winsocket C<select> function doesn't follow POSIX in that it
		3677	requires socket I<handles> and not socket I<file descriptors> (it is
		3678	also extremely buggy). This makes select very inefficient, and also
		3679	requires a mapping from file descriptors to socket handles (the Microsoft
		3680	C runtime provides the function C<_open_osfhandle> for this). See the
		3681	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3682	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3683
		3684	The configuration for a "naked" win32 using the Microsoft runtime
		3685	libraries and raw winsocket select is:
		3686
		3687	#define EV_USE_SELECT 1
		3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3689
		3690	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3691	complexity in the O(n²) range when using win32.
		3692
		3693	=item Limited number of file descriptors
		3694
		3695	Windows has numerous arbitrary (and low) limits on things.
		3696
		3697	Early versions of winsocket's select only supported waiting for a maximum
		3698	of C<64> handles (probably owning to the fact that all windows kernels
		3699	can only wait for C<64> things at the same time internally; Microsoft
		3700	recommends spawning a chain of threads and wait for 63 handles and the
		3701	previous thread in each. Great).
		3702
		3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3704	to some high number (e.g. C<2048>) before compiling the winsocket select
		3705	call (which might be in libev or elsewhere, for example, perl does its own
		3706	select emulation on windows).
		3707
		3708	Another limit is the number of file descriptors in the Microsoft runtime
		3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3710	or something like this inside Microsoft). You can increase this by calling
		3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3712	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3713	libraries.
		3714
		3715	This might get you to about C<512> or C<2048> sockets (depending on
		3716	windows version and/or the phase of the moon). To get more, you need to
		3717	wrap all I/O functions and provide your own fd management, but the cost of
		3718	calling select (O(n²)) will likely make this unworkable.
		3719
		3720	=back
		3721
		3722	=head2 PORTABILITY REQUIREMENTS
		3723
		3724	In addition to a working ISO-C implementation and of course the
		3725	backend-specific APIs, libev relies on a few additional extensions:
		3726
		3727	=over 4
		3728
		3729	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3730	calling conventions regardless of C<ev_watcher_type *>.
		3731
		3732	Libev assumes not only that all watcher pointers have the same internal
		3733	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3734	assumes that the same (machine) code can be used to call any watcher
		3735	callback: The watcher callbacks have different type signatures, but libev
		3736	calls them using an C<ev_watcher *> internally.
		3737
		3738	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3739
		3740	The type C<sig_atomic_t volatile> (or whatever is defined as
		3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3742	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3743	believed to be sufficiently portable.
		3744
		3745	=item C<sigprocmask> must work in a threaded environment
		3746
		3747	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3748	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3749	pthread implementations will either allow C<sigprocmask> in the "main
		3750	thread" or will block signals process-wide, both behaviours would
		3751	be compatible with libev. Interaction between C<sigprocmask> and
		3752	C<pthread_sigmask> could complicate things, however.
		3753
		3754	The most portable way to handle signals is to block signals in all threads
		3755	except the initial one, and run the default loop in the initial thread as
		3756	well.
		3757
		3758	=item C<long> must be large enough for common memory allocation sizes
		3759
		3760	To improve portability and simplify its API, libev uses C<long> internally
		3761	instead of C<size_t> when allocating its data structures. On non-POSIX
		3762	systems (Microsoft...) this might be unexpectedly low, but is still at
		3763	least 31 bits everywhere, which is enough for hundreds of millions of
		3764	watchers.
		3765
		3766	=item C<double> must hold a time value in seconds with enough accuracy
		3767
		3768	The type C<double> is used to represent timestamps. It is required to
		3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3770	enough for at least into the year 4000. This requirement is fulfilled by
		3771	implementations implementing IEEE 754 (basically all existing ones).
		3772
		3773	=back
		3774
		3775	If you know of other additional requirements drop me a note.
		3776
		3777
2303	=head1 COMPLEXITIES	3778	=head1 ALGORITHMIC COMPLEXITIES
2304		3779
2305	In this section the complexities of (many of) the algorithms used inside	3780	In this section the complexities of (many of) the algorithms used inside
2306	libev will be explained. For complexity discussions about backends see the	3781	libev will be documented. For complexity discussions about backends see
2307	documentation for C<ev_default_init>.	3782	the documentation for C<ev_default_init>.
2308		3783
2309	All of the following are about amortised time: If an array needs to be	3784	All of the following are about amortised time: If an array needs to be
2310	extended, libev needs to realloc and move the whole array, but this	3785	extended, libev needs to realloc and move the whole array, but this
2311	happens asymptotically never with higher number of elements, so O(1) might	3786	happens asymptotically rarer with higher number of elements, so O(1) might
2312	mean it might do a lengthy realloc operation in rare cases, but on average	3787	mean that libev does a lengthy realloc operation in rare cases, but on
2313	it is much faster and asymptotically approaches constant time.	3788	average it is much faster and asymptotically approaches constant time.
2314		3789
2315	=over 4	3790	=over 4
2316		3791
2317	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3792	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2318		3793
2319	This means that, when you have a watcher that triggers in one hour and	3794	This means that, when you have a watcher that triggers in one hour and
2320	there are 100 watchers that would trigger before that then inserting will	3795	there are 100 watchers that would trigger before that, then inserting will
2321	have to skip those 100 watchers.	3796	have to skip roughly seven (C<ld 100>) of these watchers.
2322		3797
2323	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3798	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2324		3799
2325	That means that for changing a timer costs less than removing/adding them	3800	That means that changing a timer costs less than removing/adding them,
2326	as only the relative motion in the event queue has to be paid for.	3801	as only the relative motion in the event queue has to be paid for.
2327		3802
2328	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3803	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2329		3804
2330	These just add the watcher into an array or at the head of a list.	3805	These just add the watcher into an array or at the head of a list.
		3806
2331	=item Stopping check/prepare/idle watchers: O(1)	3807	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2332		3808
2333	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3809	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2334		3810
2335	These watchers are stored in lists then need to be walked to find the	3811	These watchers are stored in lists, so they need to be walked to find the
2336	correct watcher to remove. The lists are usually short (you don't usually	3812	correct watcher to remove. The lists are usually short (you don't usually
2337	have many watchers waiting for the same fd or signal).	3813	have many watchers waiting for the same fd or signal: one is typical, two
		3814	is rare).
2338		3815
2339	=item Finding the next timer per loop iteration: O(1)	3816	=item Finding the next timer in each loop iteration: O(1)
		3817
		3818	By virtue of using a binary or 4-heap, the next timer is always found at a
		3819	fixed position in the storage array.
2340		3820
2341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3821	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2342		3822
2343	A change means an I/O watcher gets started or stopped, which requires	3823	A change means an I/O watcher gets started or stopped, which requires
2344	libev to recalculate its status (and possibly tell the kernel).	3824	libev to recalculate its status (and possibly tell the kernel, depending
		3825	on backend and whether C<ev_io_set> was used).
2345		3826
2346	=item Activating one watcher: O(1)	3827	=item Activating one watcher (putting it into the pending state): O(1)
2347		3828
2348	=item Priority handling: O(number_of_priorities)	3829	=item Priority handling: O(number_of_priorities)
2349		3830
2350	Priorities are implemented by allocating some space for each	3831	Priorities are implemented by allocating some space for each
2351	priority. When doing priority-based operations, libev usually has to	3832	priority. When doing priority-based operations, libev usually has to
2352	linearly search all the priorities.	3833	linearly search all the priorities, but starting/stopping and activating
		3834	watchers becomes O(1) with respect to priority handling.
		3835
		3836	=item Sending an ev_async: O(1)
		3837
		3838	=item Processing ev_async_send: O(number_of_async_watchers)
		3839
		3840	=item Processing signals: O(max_signal_number)
		3841
		3842	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3843	calls in the current loop iteration. Checking for async and signal events
		3844	involves iterating over all running async watchers or all signal numbers.
2353		3845
2354	=back	3846	=back
2355		3847
2356		3848
2357	=head1 AUTHOR	3849	=head1 AUTHOR

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