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Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.336 by root, Mon Oct 25 11:10:10 2010 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	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floatingpoint value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
		145
		146	=head1 ERROR HANDLING
		147
		148	Libev knows three classes of errors: operating system errors, usage errors
		149	and internal errors (bugs).
		150
		151	When libev catches an operating system error it cannot handle (for example
		152	a system call indicating a condition libev cannot fix), it calls the callback
		153	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		154	abort. The default is to print a diagnostic message and to call C<abort
		155	()>.
		156
		157	When libev detects a usage error such as a negative timer interval, then
		158	it will print a diagnostic message and abort (via the C<assert> mechanism,
		159	so C<NDEBUG> will disable this checking): these are programming errors in
		160	the libev caller and need to be fixed there.
		161
		162	Libev also has a few internal error-checking C<assert>ions, and also has
		163	extensive consistency checking code. These do not trigger under normal
		164	circumstances, as they indicate either a bug in libev or worse.
		165
121		166
122	=head1 GLOBAL FUNCTIONS	167	=head1 GLOBAL FUNCTIONS
123		168
124	These functions can be called anytime, even before initialising the	169	These functions can be called anytime, even before initialising the
125	library in any way.	170	library in any way.
…		…
128		173
129	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
130		175
131	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
132	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
133	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
134		180
135	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
136		182
137	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	185	this is a sub-second-resolution C<sleep ()>.
140		186
141	=item int ev_version_major ()	187	=item int ev_version_major ()
142		188
143	=item int ev_version_minor ()	189	=item int ev_version_minor ()
144		190
…		…
155	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
156	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
157	not a problem.	203	not a problem.
158		204
159	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
161		208
162	assert (("libev version mismatch",	209	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
165		212
166	=item unsigned int ev_supported_backends ()	213	=item unsigned int ev_supported_backends ()
167		214
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	215	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	216	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	218	a description of the set values.
172		219
173	Example: make sure we have the epoll method, because yeah this is cool and	220	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	221	a must have and can we have a torrent of it please!!!11
175		222
176	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
178		225
179	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
180		227
181	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
182	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
184	most BSDs and will not be autodetected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
185	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
186	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
187		235
188	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
189		237
190	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
191	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
192	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
194	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
195		243
196	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
197		245
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		247
200	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	277	}
230		278
231	...	279	...
232	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
233		281
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		283
236	Set the callback function to call on a retryable syscall error (such	284	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	287	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	288	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	289	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	290	(such as abort).
243		291
244	Example: This is basically the same thing that libev does internally, too.	292	Example: This is basically the same thing that libev does internally, too.
…		…
253	...	301	...
254	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
255		303
256	=back	304	=back
257		305
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
259		307
260	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
261	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
262	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
263		315
264	=over 4	316	=over 4
265		317
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		319
268	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
269	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
270	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
271	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
272		330
273	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
274	function.	332	function (or via the C<EV_DEFAULT> macro).
275		333
276	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
278	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
279		338
280	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
281	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
282	for C<SIGCHLD>. If this is a problem for your app you can either	341	a problem for your application you can either create a dynamic loop with
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
285	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
286		363
287	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
289		366
290	The following flags are supported:	367	The following flags are supported:
…		…
296	The default flags value. Use this if you have no clue (it's the right	373	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	374	thing, believe me).
298		375
299	=item C<EVFLAG_NOENV>	376	=item C<EVFLAG_NOENV>
300		377
301	If this flag bit is ored into the flag value (or the program runs setuid	378	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	379	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	381	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
306	around bugs.	383	around bugs.
307		384
308	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
309		386
310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
311	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
312	enabling this flag.
313		389
314	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	394	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	395	C<pthread_atfork> which is even faster).
320		396
321	The big advantage of this flag is that you can forget about fork (and	397	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	398	forget about forgetting to tell libev about forking) when you use this
323	flag.	399	flag.
324		400
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	402	environment variable.
		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
327		423
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		425
330	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	429	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	430	usually the fastest backend for a low number of (low-numbered :) fds.
335		431
336	To get good performance out of this backend you need a high amount of	432	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	433	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	434	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	435	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	436	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	437	readiness notifications you get per iteration.
		438
		439	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		440	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		441	C<exceptfds> set on that platform).
342		442
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	443	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		444
345	And this is your standard poll(2) backend. It's more complicated	445	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	446	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	447	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	448	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	449	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	450	performance tips.
351		451
		452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		454
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
353		459
354	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	464
359	cases and requiring a syscall per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup and
		469	so on. The biggest issue is fork races, however - if a program forks then
		470	I<both> parent and child process have to recreate the epoll set, which can
		471	take considerable time (one syscall per file descriptor) and is of course
		472	hard to detect.
		473
		474	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		475	of course I<doesn't>, and epoll just loves to report events for totally
		476	I<different> file descriptors (even already closed ones, so one cannot
		477	even remove them from the set) than registered in the set (especially
		478	on SMP systems). Libev tries to counter these spurious notifications by
		479	employing an additional generation counter and comparing that against the
		480	events to filter out spurious ones, recreating the set when required. Last
		481	not least, it also refuses to work with some file descriptors which work
		482	perfectly fine with C<select> (files, many character devices...).
361		483
362	While stopping, setting and starting an I/O watcher in the same iteration	484	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	485	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	486	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	487	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	488	file descriptors might not work very well if you register events for both
367		489	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		490
372	Best performance from this backend is achieved by not unregistering all	491	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	492	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	493	i.e. keep at least one watcher active per fd at all times. Stopping and
		494	starting a watcher (without re-setting it) also usually doesn't cause
		495	extra overhead. A fork can both result in spurious notifications as well
		496	as in libev having to destroy and recreate the epoll object, which can
		497	take considerable time and thus should be avoided.
375		498
		499	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		500	faster than epoll for maybe up to a hundred file descriptors, depending on
		501	the usage. So sad.
		502
376	While nominally embeddeble in other event loops, this feature is broken in	503	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	504	all kernel versions tested so far.
		505
		506	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		507	C<EVBACKEND_POLL>.
378		508
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	509	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		510
381	Kqueue deserves special mention, as at the time of this writing, it	511	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	512	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	513	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	514	it's completely useless). Unlike epoll, however, whose brokenness
		515	is by design, these kqueue bugs can (and eventually will) be fixed
		516	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	517	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	518	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	519	system like NetBSD.
388		520
389	You still can embed kqueue into a normal poll or select backend and use it	521	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	522	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	523	the target platform). See C<ev_embed> watchers for more info.
392		524
393	It scales in the same way as the epoll backend, but the interface to the	525	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	526	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	527	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	528	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	529	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	530	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		531	cases
399		532
400	This backend usually performs well under most conditions.	533	This backend usually performs well under most conditions.
401		534
402	While nominally embeddable in other event loops, this doesn't work	535	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	536	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	537	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	538	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	539	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	540	also broken on OS X)) and, did I mention it, using it only for sockets.
		541
		542	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		543	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		544	C<NOTE_EOF>.
408		545
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	546	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		547
411	This is not implemented yet (and might never be, unless you send me an	548	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	549	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	553	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		554
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	555	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	556	it's really slow, but it still scales very well (O(active_fds)).
420		557
421	Please note that solaris event ports can deliver a lot of spurious	558	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	559	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	560	blocking when no data (or space) is available.
424		561
425	While this backend scales well, it requires one system call per active	562	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	563	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	564	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	565	might perform better.
429		566
430	On the positive side, ignoring the spurious readiness notifications, this	567	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	568	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	569	in all tests and is fully embeddable, which is a rare feat among the
		570	OS-specific backends (I vastly prefer correctness over speed hacks).
		571
		572	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		573	C<EVBACKEND_POLL>.
433		574
434	=item C<EVBACKEND_ALL>	575	=item C<EVBACKEND_ALL>
435		576
436	Try all backends (even potentially broken ones that wouldn't be tried	577	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	578	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		580
440	It is definitely not recommended to use this flag.	581	It is definitely not recommended to use this flag.
441		582
442	=back	583	=back
443		584
444	If one or more of these are ored into the flags value, then only these	585	If one or more of the backend flags are or'ed into the flags value,
445	backends will be tried (in the reverse order as listed here). If none are	586	then only these backends will be tried (in the reverse order as listed
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	587	here). If none are specified, all backends in C<ev_recommended_backends
447		588	()> will be tried.
448	The most typical usage is like this:
449
450	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452
453	Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:
455
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457
458	Use whatever libev has to offer, but make sure that kqueue is used if
459	available (warning, breaks stuff, best use only with your own private
460	event loop and only if you know the OS supports your types of fds):
461
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463
464	=item struct ev_loop *ev_loop_new (unsigned int flags)
465
466	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).
470
471	Note that this function I<is> thread-safe, and the recommended way to use
472	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.
474		589
475	Example: Try to create a event loop that uses epoll and nothing else.	590	Example: Try to create a event loop that uses epoll and nothing else.
476		591
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	592	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	593	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	594	fatal ("no epoll found here, maybe it hides under your chair");
480		595
		596	Example: Use whatever libev has to offer, but make sure that kqueue is
		597	used if available.
		598
		599	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		600
481	=item ev_default_destroy ()	601	=item ev_loop_destroy (loop)
482		602
483	Destroys the default loop again (frees all memory and kernel state	603	Destroys an event loop object (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	604	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	605	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	606	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	607	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	608	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	609	for example).
490		610
491	Note that certain global state, such as signal state, will not be freed by	611	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	612	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	613	as signal and child watchers) would need to be stopped manually.
494		614
495	In general it is not advisable to call this function except in the	615	This function is normally used on loop objects allocated by
496	rare occasion where you really need to free e.g. the signal handling	616	C<ev_loop_new>, but it can also be used on the default loop returned by
		617	C<ev_default_loop>, in which case it is not thread-safe.
		618
		619	Note that it is not advisable to call this function on the default loop
		620	except in the rare occasion where you really need to free it's resources.
497	pipe fds. If you need dynamically allocated loops it is better to use	621	If you need dynamically allocated loops it is better to use C<ev_loop_new>
498	C<ev_loop_new> and C<ev_loop_destroy>).	622	and C<ev_loop_destroy>.
499		623
500	=item ev_loop_destroy (loop)	624	=item ev_loop_fork (loop)
501		625
502	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.
504
505	=item ev_default_fork ()
506
507	This function sets a flag that causes subsequent C<ev_loop> iterations	626	This function sets a flag that causes subsequent C<ev_run> iterations to
508	to reinitialise the kernel state for backends that have one. Despite the	627	reinitialise the kernel state for backends that have one. Despite the
509	name, you can call it anytime, but it makes most sense after forking, in	628	name, you can call it anytime, but it makes most sense after forking, in
510	the child process (or both child and parent, but that again makes little	629	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
511	sense). You I<must> call it in the child before using any of the libev	630	child before resuming or calling C<ev_run>.
512	functions, and it will only take effect at the next C<ev_loop> iteration.	631
		632	Again, you I<have> to call it on I<any> loop that you want to re-use after
		633	a fork, I<even if you do not plan to use the loop in the parent>. This is
		634	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		635	during fork.
513		636
514	On the other hand, you only need to call this function in the child	637	On the other hand, you only need to call this function in the child
515	process if and only if you want to use the event library in the child. If	638	process if and only if you want to use the event loop in the child. If
516	you just fork+exec, you don't have to call it at all.	639	you just fork+exec or create a new loop in the child, you don't have to
		640	call it at all (in fact, C<epoll> is so badly broken that it makes a
		641	difference, but libev will usually detect this case on its own and do a
		642	costly reset of the backend).
517		643
518	The function itself is quite fast and it's usually not a problem to call	644	The function itself is quite fast and it's usually not a problem to call
519	it just in case after a fork. To make this easy, the function will fit in	645	it just in case after a fork.
520	quite nicely into a call to C<pthread_atfork>:
521		646
		647	Example: Automate calling C<ev_loop_fork> on the default loop when
		648	using pthreads.
		649
		650	static void
		651	post_fork_child (void)
		652	{
		653	ev_loop_fork (EV_DEFAULT);
		654	}
		655
		656	...
522	pthread_atfork (0, 0, ev_default_fork);	657	pthread_atfork (0, 0, post_fork_child);
523
524	=item ev_loop_fork (loop)
525
526	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.
529		658
530	=item int ev_is_default_loop (loop)	659	=item int ev_is_default_loop (loop)
531		660
532	Returns true when the given loop actually is the default loop, false otherwise.	661	Returns true when the given loop is, in fact, the default loop, and false
		662	otherwise.
533		663
534	=item unsigned int ev_loop_count (loop)	664	=item unsigned int ev_iteration (loop)
535		665
536	Returns the count of loop iterations for the loop, which is identical to	666	Returns the current iteration count for the event loop, which is identical
537	the number of times libev did poll for new events. It starts at C<0> and	667	to the number of times libev did poll for new events. It starts at C<0>
538	happily wraps around with enough iterations.	668	and happily wraps around with enough iterations.
539		669
540	This value can sometimes be useful as a generation counter of sorts (it	670	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	671	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	672	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		673	prepare and check phases.
		674
		675	=item unsigned int ev_depth (loop)
		676
		677	Returns the number of times C<ev_run> was entered minus the number of
		678	times C<ev_run> was exited, in other words, the recursion depth.
		679
		680	Outside C<ev_run>, this number is zero. In a callback, this number is
		681	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		682	in which case it is higher.
		683
		684	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		685	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		686	ungentleman-like behaviour unless it's really convenient.
543		687
544	=item unsigned int ev_backend (loop)	688	=item unsigned int ev_backend (loop)
545		689
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	690	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	691	use.
…		…
552	received events and started processing them. This timestamp does not	696	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	697	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	698	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	699	event occurring (or more correctly, libev finding out about it).
556		700
		701	=item ev_now_update (loop)
		702
		703	Establishes the current time by querying the kernel, updating the time
		704	returned by C<ev_now ()> in the progress. This is a costly operation and
		705	is usually done automatically within C<ev_run ()>.
		706
		707	This function is rarely useful, but when some event callback runs for a
		708	very long time without entering the event loop, updating libev's idea of
		709	the current time is a good idea.
		710
		711	See also L<The special problem of time updates> in the C<ev_timer> section.
		712
		713	=item ev_suspend (loop)
		714
		715	=item ev_resume (loop)
		716
		717	These two functions suspend and resume an event loop, for use when the
		718	loop is not used for a while and timeouts should not be processed.
		719
		720	A typical use case would be an interactive program such as a game: When
		721	the user presses C<^Z> to suspend the game and resumes it an hour later it
		722	would be best to handle timeouts as if no time had actually passed while
		723	the program was suspended. This can be achieved by calling C<ev_suspend>
		724	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		725	C<ev_resume> directly afterwards to resume timer processing.
		726
		727	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		728	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		729	will be rescheduled (that is, they will lose any events that would have
		730	occurred while suspended).
		731
		732	After calling C<ev_suspend> you B<must not> call I<any> function on the
		733	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		734	without a previous call to C<ev_suspend>.
		735
		736	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		737	event loop time (see C<ev_now_update>).
		738
557	=item ev_loop (loop, int flags)	739	=item ev_run (loop, int flags)
558		740
559	Finally, this is it, the event handler. This function usually is called	741	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	742	after you have initialised all your watchers and you want to start
561	events.	743	handling events. It will ask the operating system for any new events, call
		744	the watcher callbacks, an then repeat the whole process indefinitely: This
		745	is why event loops are called I<loops>.
562		746
563	If the flags argument is specified as C<0>, it will not return until	747	If the flags argument is specified as C<0>, it will keep handling events
564	either no event watchers are active anymore or C<ev_unloop> was called.	748	until either no event watchers are active anymore or C<ev_break> was
		749	called.
565		750
566	Please note that an explicit C<ev_unloop> is usually better than	751	Please note that an explicit C<ev_break> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	752	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	753	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	754	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	755	of relying on its watchers stopping correctly, that is truly a thing of
		756	beauty.
571		757
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	758	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	759	those events and any already outstanding ones, but will not wait and
574	case there are no events and will return after one iteration of the loop.	760	block your process in case there are no events and will return after one
		761	iteration of the loop. This is sometimes useful to poll and handle new
		762	events while doing lengthy calculations, to keep the program responsive.
575		763
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	764	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	765	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	766	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	767	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	768	user-registered callback will be called), and will return after one
		769	iteration of the loop.
		770
		771	This is useful if you are waiting for some external event in conjunction
		772	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	773	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	774	usually a better approach for this kind of thing.
583		775
584	Here are the gory details of what C<ev_loop> does:	776	Here are the gory details of what C<ev_run> does:
585		777
		778	- Increment loop depth.
		779	- Reset the ev_break status.
586	- Before the first iteration, call any pending watchers.	780	- Before the first iteration, call any pending watchers.
		781	LOOP:
587	* If EVFLAG_FORKCHECK was used, check for a fork.	782	- If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	783	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	784	- Queue and call all prepare watchers.
		785	- If ev_break was called, goto FINISH.
590	- If we have been forked, recreate the kernel state.	786	- If we have been forked, detach and recreate the kernel state
		787	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	788	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	789	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	790	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	791	(active idle watchers, EVRUN_NOWAIT or not having
595	any active watchers at all will result in not sleeping).	792	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	793	- Sleep if the I/O and timer collect interval say so.
		794	- Increment loop iteration counter.
597	- Block the process, waiting for any events.	795	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	796	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	797	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	798	- Queue all expired timers.
601	- Queue all outstanding periodics.	799	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	800	- Queue all idle watchers with priority higher than that of pending events.
603	- Queue all check watchers.	801	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	802	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	803	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	804	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	805	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
608	were used, or there are no active watchers, return, otherwise	806	were used, or there are no active watchers, goto FINISH, otherwise
609	continue with step *.	807	continue with step LOOP.
		808	FINISH:
		809	- Reset the ev_break status iff it was EVBREAK_ONE.
		810	- Decrement the loop depth.
		811	- Return.
610		812
611	Example: Queue some jobs and then loop until no events are outstanding	813	Example: Queue some jobs and then loop until no events are outstanding
612	anymore.	814	anymore.
613		815
614	... queue jobs here, make sure they register event watchers as long	816	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	817	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	818	ev_run (my_loop, 0);
617	... jobs done. yeah!	819	... jobs done or somebody called unloop. yeah!
618		820
619	=item ev_unloop (loop, how)	821	=item ev_break (loop, how)
620		822
621	Can be used to make a call to C<ev_loop> return early (but only after it	823	Can be used to make a call to C<ev_run> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	824	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	825	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	826	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
625		827
626	This "unloop state" will be cleared when entering C<ev_loop> again.	828	This "break state" will be cleared when entering C<ev_run> again.
		829
		830	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
627		831
628	=item ev_ref (loop)	832	=item ev_ref (loop)
629		833
630	=item ev_unref (loop)	834	=item ev_unref (loop)
631		835
632	Ref/unref can be used to add or remove a reference count on the event	836	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	837	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	838	count is nonzero, C<ev_run> will not return on its own.
635	a watcher you never unregister that should not keep C<ev_loop> from	839
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	840	This is useful when you have a watcher that you never intend to
		841	unregister, but that nevertheless should not keep C<ev_run> from
		842	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		843	before stopping it.
		844
637	example, libev itself uses this for its internal signal pipe: It is not	845	As an example, libev itself uses this for its internal signal pipe: It
638	visible to the libev user and should not keep C<ev_loop> from exiting if	846	is not visible to the libev user and should not keep C<ev_run> from
639	no event watchers registered by it are active. It is also an excellent	847	exiting if no event watchers registered by it are active. It is also an
640	way to do this for generic recurring timers or from within third-party	848	excellent way to do this for generic recurring timers or from within
641	libraries. Just remember to I<unref after start> and I<ref before stop>	849	third-party libraries. Just remember to I<unref after start> and I<ref
642	(but only if the watcher wasn't active before, or was active before,	850	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	851	before, respectively. Note also that libev might stop watchers itself
		852	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		853	in the callback).
644		854
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	855	Example: Create a signal watcher, but keep it from keeping C<ev_run>
646	running when nothing else is active.	856	running when nothing else is active.
647		857
648	struct ev_signal exitsig;	858	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	859	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	860	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	861	evf_unref (loop);
652		862
653	Example: For some weird reason, unregister the above signal handler again.	863	Example: For some weird reason, unregister the above signal handler again.
654		864
655	ev_ref (loop);	865	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	866	ev_signal_stop (loop, &exitsig);
657		867
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	868	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		869
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	870	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		871
662	These advanced functions influence the time that libev will spend waiting	872	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	873	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	874	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		875	latency.
665		876
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	877	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	878	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	879	to increase efficiency of loop iterations (or to increase power-saving
		880	opportunities).
669		881
670	The background is that sometimes your program runs just fast enough to	882	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	883	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	884	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	885	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	886	overhead for the actual polling but can deliver many events at once.
675		887
676	By setting a higher I<io collect interval> you allow libev to spend more	888	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	889	time collecting I/O events, so you can handle more events per iteration,
678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	890	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	891	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	892	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		893	sleep time ensures that libev will not poll for I/O events more often then
		894	once per this interval, on average.
681		895
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	896	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	897	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	898	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	899	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	900	value will not introduce any overhead in libev.
687		901
688	Many (busy) programs can usually benefit by setting the io collect	902	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	903	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	904	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	905	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	906	as this approaches the timing granularity of most systems. Note that if
		907	you do transactions with the outside world and you can't increase the
		908	parallelity, then this setting will limit your transaction rate (if you
		909	need to poll once per transaction and the I/O collect interval is 0.01,
		910	then you can't do more than 100 transactions per second).
693		911
		912	Setting the I<timeout collect interval> can improve the opportunity for
		913	saving power, as the program will "bundle" timer callback invocations that
		914	are "near" in time together, by delaying some, thus reducing the number of
		915	times the process sleeps and wakes up again. Another useful technique to
		916	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		917	they fire on, say, one-second boundaries only.
		918
		919	Example: we only need 0.1s timeout granularity, and we wish not to poll
		920	more often than 100 times per second:
		921
		922	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		923	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		924
		925	=item ev_invoke_pending (loop)
		926
		927	This call will simply invoke all pending watchers while resetting their
		928	pending state. Normally, C<ev_run> does this automatically when required,
		929	but when overriding the invoke callback this call comes handy. This
		930	function can be invoked from a watcher - this can be useful for example
		931	when you want to do some lengthy calculation and want to pass further
		932	event handling to another thread (you still have to make sure only one
		933	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		934
		935	=item int ev_pending_count (loop)
		936
		937	Returns the number of pending watchers - zero indicates that no watchers
		938	are pending.
		939
		940	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		941
		942	This overrides the invoke pending functionality of the loop: Instead of
		943	invoking all pending watchers when there are any, C<ev_run> will call
		944	this callback instead. This is useful, for example, when you want to
		945	invoke the actual watchers inside another context (another thread etc.).
		946
		947	If you want to reset the callback, use C<ev_invoke_pending> as new
		948	callback.
		949
		950	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		951
		952	Sometimes you want to share the same loop between multiple threads. This
		953	can be done relatively simply by putting mutex_lock/unlock calls around
		954	each call to a libev function.
		955
		956	However, C<ev_run> can run an indefinite time, so it is not feasible
		957	to wait for it to return. One way around this is to wake up the event
		958	loop via C<ev_break> and C<av_async_send>, another way is to set these
		959	I<release> and I<acquire> callbacks on the loop.
		960
		961	When set, then C<release> will be called just before the thread is
		962	suspended waiting for new events, and C<acquire> is called just
		963	afterwards.
		964
		965	Ideally, C<release> will just call your mutex_unlock function, and
		966	C<acquire> will just call the mutex_lock function again.
		967
		968	While event loop modifications are allowed between invocations of
		969	C<release> and C<acquire> (that's their only purpose after all), no
		970	modifications done will affect the event loop, i.e. adding watchers will
		971	have no effect on the set of file descriptors being watched, or the time
		972	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		973	to take note of any changes you made.
		974
		975	In theory, threads executing C<ev_run> will be async-cancel safe between
		976	invocations of C<release> and C<acquire>.
		977
		978	See also the locking example in the C<THREADS> section later in this
		979	document.
		980
		981	=item ev_set_userdata (loop, void *data)
		982
		983	=item ev_userdata (loop)
		984
		985	Set and retrieve a single C<void *> associated with a loop. When
		986	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		987	C<0.>
		988
		989	These two functions can be used to associate arbitrary data with a loop,
		990	and are intended solely for the C<invoke_pending_cb>, C<release> and
		991	C<acquire> callbacks described above, but of course can be (ab-)used for
		992	any other purpose as well.
		993
694	=item ev_loop_verify (loop)	994	=item ev_verify (loop)
695		995
696	This function only does something when C<EV_VERIFY> support has been	996	This function only does something when C<EV_VERIFY> support has been
697	compiled in. It tries to go through all internal structures and checks	997	compiled in, which is the default for non-minimal builds. It tries to go
698	them for validity. If anything is found to be inconsistent, it will print	998	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	999	is found to be inconsistent, it will print an error message to standard
		1000	error and call C<abort ()>.
700		1001
701	This can be used to catch bugs inside libev itself: under normal	1002	This can be used to catch bugs inside libev itself: under normal
702	circumstances, this function will never abort as of course libev keeps its	1003	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	1004	data structures consistent.
704		1005
705	=back	1006	=back
706		1007
707		1008
708	=head1 ANATOMY OF A WATCHER	1009	=head1 ANATOMY OF A WATCHER
709		1010
		1011	In the following description, uppercase C<TYPE> in names stands for the
		1012	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1013	watchers and C<ev_io_start> for I/O watchers.
		1014
710	A watcher is a structure that you create and register to record your	1015	A watcher is an opaque structure that you allocate and register to record
711	interest in some event. For instance, if you want to wait for STDIN to	1016	your interest in some event. To make a concrete example, imagine you want
712	become readable, you would create an C<ev_io> watcher for that:	1017	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1018	for that:
713		1019
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1020	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	1021	{
716	ev_io_stop (w);	1022	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	1023	ev_break (loop, EVBREAK_ALL);
718	}	1024	}
719		1025
720	struct ev_loop *loop = ev_default_loop (0);	1026	struct ev_loop *loop = ev_default_loop (0);
		1027
721	struct ev_io stdin_watcher;	1028	ev_io stdin_watcher;
		1029
722	ev_init (&stdin_watcher, my_cb);	1030	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1031	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	1032	ev_io_start (loop, &stdin_watcher);
		1033
725	ev_loop (loop, 0);	1034	ev_run (loop, 0);
726		1035
727	As you can see, you are responsible for allocating the memory for your	1036	As you can see, you are responsible for allocating the memory for your
728	watcher structures (and it is usually a bad idea to do this on the stack,	1037	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	1038	stack).
730		1039
		1040	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1041	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1042
731	Each watcher structure must be initialised by a call to C<ev_init	1043	Each watcher structure must be initialised by a call to C<ev_init (watcher
732	(watcher *, callback)>, which expects a callback to be provided. This	1044	*, callback)>, which expects a callback to be provided. This callback is
733	callback gets invoked each time the event occurs (or, in the case of io	1045	invoked each time the event occurs (or, in the case of I/O watchers, each
734	watchers, each time the event loop detects that the file descriptor given	1046	time the event loop detects that the file descriptor given is readable
735	is readable and/or writable).	1047	and/or writable).
736		1048
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1049	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
738	with arguments specific to this watcher type. There is also a macro	1050	macro to configure it, with arguments specific to the watcher type. There
739	to combine initialisation and setting in one call: C<< ev_<type>_init	1051	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	1052	ev_TYPE_init (watcher *, callback, ...) >>.
741		1053
742	To make the watcher actually watch out for events, you have to start it	1054	To make the watcher actually watch out for events, you have to start it
743	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1055	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
744	*) >>), and you can stop watching for events at any time by calling the	1056	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1057	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		1058
747	As long as your watcher is active (has been started but not stopped) you	1059	As long as your watcher is active (has been started but not stopped) you
748	must not touch the values stored in it. Most specifically you must never	1060	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	1061	reinitialise it or call its C<ev_TYPE_set> macro.
750		1062
751	Each and every callback receives the event loop pointer as first, the	1063	Each and every callback receives the event loop pointer as first, the
752	registered watcher structure as second, and a bitset of received events as	1064	registered watcher structure as second, and a bitset of received events as
753	third argument.	1065	third argument.
754		1066
…		…
763	=item C<EV_WRITE>	1075	=item C<EV_WRITE>
764		1076
765	The file descriptor in the C<ev_io> watcher has become readable and/or	1077	The file descriptor in the C<ev_io> watcher has become readable and/or
766	writable.	1078	writable.
767		1079
768	=item C<EV_TIMEOUT>	1080	=item C<EV_TIMER>
769		1081
770	The C<ev_timer> watcher has timed out.	1082	The C<ev_timer> watcher has timed out.
771		1083
772	=item C<EV_PERIODIC>	1084	=item C<EV_PERIODIC>
773		1085
…		…
791		1103
792	=item C<EV_PREPARE>	1104	=item C<EV_PREPARE>
793		1105
794	=item C<EV_CHECK>	1106	=item C<EV_CHECK>
795		1107
796	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1108	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
797	to gather new events, and all C<ev_check> watchers are invoked just after	1109	to gather new events, and all C<ev_check> watchers are invoked just after
798	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1110	C<ev_run> has gathered them, but before it invokes any callbacks for any
799	received events. Callbacks of both watcher types can start and stop as	1111	received events. Callbacks of both watcher types can start and stop as
800	many watchers as they want, and all of them will be taken into account	1112	many watchers as they want, and all of them will be taken into account
801	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1113	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
802	C<ev_loop> from blocking).	1114	C<ev_run> from blocking).
803		1115
804	=item C<EV_EMBED>	1116	=item C<EV_EMBED>
805		1117
806	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1118	The embedded event loop specified in the C<ev_embed> watcher needs attention.
807		1119
808	=item C<EV_FORK>	1120	=item C<EV_FORK>
809		1121
810	The event loop has been resumed in the child process after fork (see	1122	The event loop has been resumed in the child process after fork (see
811	C<ev_fork>).	1123	C<ev_fork>).
812		1124
		1125	=item C<EV_CLEANUP>
		1126
		1127	The event loop is about to be destroyed (see C<ev_cleanup>).
		1128
813	=item C<EV_ASYNC>	1129	=item C<EV_ASYNC>
814		1130
815	The given async watcher has been asynchronously notified (see C<ev_async>).	1131	The given async watcher has been asynchronously notified (see C<ev_async>).
816		1132
		1133	=item C<EV_CUSTOM>
		1134
		1135	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1136	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1137
817	=item C<EV_ERROR>	1138	=item C<EV_ERROR>
818		1139
819	An unspecified error has occured, the watcher has been stopped. This might	1140	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	1141	happen because the watcher could not be properly started because libev
821	ran out of memory, a file descriptor was found to be closed or any other	1142	ran out of memory, a file descriptor was found to be closed or any other
		1143	problem. Libev considers these application bugs.
		1144
822	problem. You best act on it by reporting the problem and somehow coping	1145	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	1146	watcher being stopped. Note that well-written programs should not receive
		1147	an error ever, so when your watcher receives it, this usually indicates a
		1148	bug in your program.
824		1149
825	Libev will usually signal a few "dummy" events together with an error,	1150	Libev will usually signal a few "dummy" events together with an error, for
826	for example it might indicate that a fd is readable or writable, and if	1151	example it might indicate that a fd is readable or writable, and if your
827	your callbacks is well-written it can just attempt the operation and cope	1152	callbacks is well-written it can just attempt the operation and cope with
828	with the error from read() or write(). This will not work in multithreaded	1153	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	1154	programs, though, as the fd could already be closed and reused for another
		1155	thing, so beware.
830		1156
831	=back	1157	=back
832		1158
833	=head2 GENERIC WATCHER FUNCTIONS	1159	=head2 GENERIC WATCHER FUNCTIONS
834
835	In the following description, C<TYPE> stands for the watcher type,
836	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
837		1160
838	=over 4	1161	=over 4
839		1162
840	=item C<ev_init> (ev_TYPE *watcher, callback)	1163	=item C<ev_init> (ev_TYPE *watcher, callback)
841		1164
…		…
847	which rolls both calls into one.	1170	which rolls both calls into one.
848		1171
849	You can reinitialise a watcher at any time as long as it has been stopped	1172	You can reinitialise a watcher at any time as long as it has been stopped
850	(or never started) and there are no pending events outstanding.	1173	(or never started) and there are no pending events outstanding.
851		1174
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1175	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	1176	int revents)>.
854		1177
		1178	Example: Initialise an C<ev_io> watcher in two steps.
		1179
		1180	ev_io w;
		1181	ev_init (&w, my_cb);
		1182	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1183
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1184	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
856		1185
857	This macro initialises the type-specific parts of a watcher. You need to	1186	This macro initialises the type-specific parts of a watcher. You need to
858	call C<ev_init> at least once before you call this macro, but you can	1187	call C<ev_init> at least once before you call this macro, but you can
859	call C<ev_TYPE_set> any number of times. You must not, however, call this	1188	call C<ev_TYPE_set> any number of times. You must not, however, call this
860	macro on a watcher that is active (it can be pending, however, which is a	1189	macro on a watcher that is active (it can be pending, however, which is a
861	difference to the C<ev_init> macro).	1190	difference to the C<ev_init> macro).
862		1191
863	Although some watcher types do not have type-specific arguments	1192	Although some watcher types do not have type-specific arguments
864	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1193	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		1194
		1195	See C<ev_init>, above, for an example.
		1196
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1197	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		1198
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1199	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
869	calls into a single call. This is the most convinient method to initialise	1200	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	1201	a watcher. The same limitations apply, of course.
871		1202
		1203	Example: Initialise and set an C<ev_io> watcher in one step.
		1204
		1205	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1206
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1207	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
873		1208
874	Starts (activates) the given watcher. Only active watchers will receive	1209	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	1210	events. If the watcher is already active nothing will happen.
876		1211
		1212	Example: Start the C<ev_io> watcher that is being abused as example in this
		1213	whole section.
		1214
		1215	ev_io_start (EV_DEFAULT_UC, &w);
		1216
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1217	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
878		1218
879	Stops the given watcher again (if active) and clears the pending	1219	Stops the given watcher if active, and clears the pending status (whether
		1220	the watcher was active or not).
		1221
880	status. It is possible that stopped watchers are pending (for example,	1222	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1223	non-repeating timers are being stopped when they become pending - but
882	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1224	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
883	you want to free or reuse the memory used by the watcher it is therefore a	1225	pending. If you want to free or reuse the memory used by the watcher it is
884	good idea to always call its C<ev_TYPE_stop> function.	1226	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1227
886	=item bool ev_is_active (ev_TYPE *watcher)	1228	=item bool ev_is_active (ev_TYPE *watcher)
887		1229
888	Returns a true value iff the watcher is active (i.e. it has been started	1230	Returns a true value iff the watcher is active (i.e. it has been started
889	and not yet been stopped). As long as a watcher is active you must not modify	1231	and not yet been stopped). As long as a watcher is active you must not modify
…		…
905	=item ev_cb_set (ev_TYPE *watcher, callback)	1247	=item ev_cb_set (ev_TYPE *watcher, callback)
906		1248
907	Change the callback. You can change the callback at virtually any time	1249	Change the callback. You can change the callback at virtually any time
908	(modulo threads).	1250	(modulo threads).
909		1251
910	=item ev_set_priority (ev_TYPE *watcher, priority)	1252	=item ev_set_priority (ev_TYPE *watcher, int priority)
911		1253
912	=item int ev_priority (ev_TYPE *watcher)	1254	=item int ev_priority (ev_TYPE *watcher)
913		1255
914	Set and query the priority of the watcher. The priority is a small	1256	Set and query the priority of the watcher. The priority is a small
915	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1257	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
916	(default: C<-2>). Pending watchers with higher priority will be invoked	1258	(default: C<-2>). Pending watchers with higher priority will be invoked
917	before watchers with lower priority, but priority will not keep watchers	1259	before watchers with lower priority, but priority will not keep watchers
918	from being executed (except for C<ev_idle> watchers).	1260	from being executed (except for C<ev_idle> watchers).
919		1261
920	This means that priorities are I<only> used for ordering callback
921	invocation after new events have been received. This is useful, for
922	example, to reduce latency after idling, or more often, to bind two
923	watchers on the same event and make sure one is called first.
924
925	If you need to suppress invocation when higher priority events are pending	1262	If you need to suppress invocation when higher priority events are pending
926	you need to look at C<ev_idle> watchers, which provide this functionality.	1263	you need to look at C<ev_idle> watchers, which provide this functionality.
927		1264
928	You I<must not> change the priority of a watcher as long as it is active or	1265	You I<must not> change the priority of a watcher as long as it is active or
929	pending.	1266	pending.
930		1267
		1268	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1269	fine, as long as you do not mind that the priority value you query might
		1270	or might not have been clamped to the valid range.
		1271
931	The default priority used by watchers when no priority has been set is	1272	The default priority used by watchers when no priority has been set is
932	always C<0>, which is supposed to not be too high and not be too low :).	1273	always C<0>, which is supposed to not be too high and not be too low :).
933		1274
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1275	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
935	fine, as long as you do not mind that the priority value you query might	1276	priorities.
936	or might not have been adjusted to be within valid range.
937		1277
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1278	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1279
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1280	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
941	C<loop> nor C<revents> need to be valid as long as the watcher callback	1281	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1282	can deal with that fact, as both are simply passed through to the
		1283	callback.
943		1284
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1285	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1286
946	If the watcher is pending, this function returns clears its pending status	1287	If the watcher is pending, this function clears its pending status and
947	and returns its C<revents> bitset (as if its callback was invoked). If the	1288	returns its C<revents> bitset (as if its callback was invoked). If the
948	watcher isn't pending it does nothing and returns C<0>.	1289	watcher isn't pending it does nothing and returns C<0>.
949		1290
		1291	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1292	callback to be invoked, which can be accomplished with this function.
		1293
		1294	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1295
		1296	Feeds the given event set into the event loop, as if the specified event
		1297	had happened for the specified watcher (which must be a pointer to an
		1298	initialised but not necessarily started event watcher). Obviously you must
		1299	not free the watcher as long as it has pending events.
		1300
		1301	Stopping the watcher, letting libev invoke it, or calling
		1302	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1303	not started in the first place.
		1304
		1305	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1306	functions that do not need a watcher.
		1307
950	=back	1308	=back
951		1309
952
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1310	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
954		1311
955	Each watcher has, by default, a member C<void *data> that you can change	1312	Each watcher has, by default, a member C<void *data> that you can change
956	and read at any time, libev will completely ignore it. This can be used	1313	and read at any time: libev will completely ignore it. This can be used
957	to associate arbitrary data with your watcher. If you need more data and	1314	to associate arbitrary data with your watcher. If you need more data and
958	don't want to allocate memory and store a pointer to it in that data	1315	don't want to allocate memory and store a pointer to it in that data
959	member, you can also "subclass" the watcher type and provide your own	1316	member, you can also "subclass" the watcher type and provide your own
960	data:	1317	data:
961		1318
962	struct my_io	1319	struct my_io
963	{	1320	{
964	struct ev_io io;	1321	ev_io io;
965	int otherfd;	1322	int otherfd;
966	void *somedata;	1323	void *somedata;
967	struct whatever *mostinteresting;	1324	struct whatever *mostinteresting;
968	}	1325	};
		1326
		1327	...
		1328	struct my_io w;
		1329	ev_io_init (&w.io, my_cb, fd, EV_READ);
969		1330
970	And since your callback will be called with a pointer to the watcher, you	1331	And since your callback will be called with a pointer to the watcher, you
971	can cast it back to your own type:	1332	can cast it back to your own type:
972		1333
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1334	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
974	{	1335	{
975	struct my_io *w = (struct my_io *)w_;	1336	struct my_io *w = (struct my_io *)w_;
976	...	1337	...
977	}	1338	}
978		1339
979	More interesting and less C-conformant ways of casting your callback type	1340	More interesting and less C-conformant ways of casting your callback type
980	instead have been omitted.	1341	instead have been omitted.
981		1342
982	Another common scenario is having some data structure with multiple	1343	Another common scenario is to use some data structure with multiple
983	watchers:	1344	embedded watchers:
984		1345
985	struct my_biggy	1346	struct my_biggy
986	{	1347	{
987	int some_data;	1348	int some_data;
988	ev_timer t1;	1349	ev_timer t1;
989	ev_timer t2;	1350	ev_timer t2;
990	}	1351	}
991		1352
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1353	In this case getting the pointer to C<my_biggy> is a bit more
993	you need to use C<offsetof>:	1354	complicated: Either you store the address of your C<my_biggy> struct
		1355	in the C<data> member of the watcher (for woozies), or you need to use
		1356	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1357	programmers):
994		1358
995	#include <stddef.h>	1359	#include <stddef.h>
996		1360
997	static void	1361	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1362	t1_cb (EV_P_ ev_timer *w, int revents)
999	{	1363	{
1000	struct my_biggy big = (struct my_biggy *	1364	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1365	(((char *)w) - offsetof (struct my_biggy, t1));
1002	}	1366	}
1003		1367
1004	static void	1368	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1369	t2_cb (EV_P_ ev_timer *w, int revents)
1006	{	1370	{
1007	struct my_biggy big = (struct my_biggy *	1371	struct my_biggy big = (struct my_biggy *)
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1372	(((char *)w) - offsetof (struct my_biggy, t2));
1009	}	1373	}
		1374
		1375	=head2 WATCHER STATES
		1376
		1377	There are various watcher states mentioned throughout this manual -
		1378	active, pending and so on. In this section these states and the rules to
		1379	transition between them will be described in more detail - and while these
		1380	rules might look complicated, they usually do "the right thing".
		1381
		1382	=over 4
		1383
		1384	=item initialiased
		1385
		1386	Before a watcher can be registered with the event looop it has to be
		1387	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1388	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1389
		1390	In this state it is simply some block of memory that is suitable for use
		1391	in an event loop. It can be moved around, freed, reused etc. at will.
		1392
		1393	=item started/running/active
		1394
		1395	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1396	property of the event loop, and is actively waiting for events. While in
		1397	this state it cannot be accessed (except in a few documented ways), moved,
		1398	freed or anything else - the only legal thing is to keep a pointer to it,
		1399	and call libev functions on it that are documented to work on active watchers.
		1400
		1401	=item pending
		1402
		1403	If a watcher is active and libev determines that an event it is interested
		1404	in has occurred (such as a timer expiring), it will become pending. It will
		1405	stay in this pending state until either it is stopped or its callback is
		1406	about to be invoked, so it is not normally pending inside the watcher
		1407	callback.
		1408
		1409	The watcher might or might not be active while it is pending (for example,
		1410	an expired non-repeating timer can be pending but no longer active). If it
		1411	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1412	but it is still property of the event loop at this time, so cannot be
		1413	moved, freed or reused. And if it is active the rules described in the
		1414	previous item still apply.
		1415
		1416	It is also possible to feed an event on a watcher that is not active (e.g.
		1417	via C<ev_feed_event>), in which case it becomes pending without being
		1418	active.
		1419
		1420	=item stopped
		1421
		1422	A watcher can be stopped implicitly by libev (in which case it might still
		1423	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1424	latter will clear any pending state the watcher might be in, regardless
		1425	of whether it was active or not, so stopping a watcher explicitly before
		1426	freeing it is often a good idea.
		1427
		1428	While stopped (and not pending) the watcher is essentially in the
		1429	initialised state, that is it can be reused, moved, modified in any way
		1430	you wish.
		1431
		1432	=back
		1433
		1434	=head2 WATCHER PRIORITY MODELS
		1435
		1436	Many event loops support I<watcher priorities>, which are usually small
		1437	integers that influence the ordering of event callback invocation
		1438	between watchers in some way, all else being equal.
		1439
		1440	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1441	description for the more technical details such as the actual priority
		1442	range.
		1443
		1444	There are two common ways how these these priorities are being interpreted
		1445	by event loops:
		1446
		1447	In the more common lock-out model, higher priorities "lock out" invocation
		1448	of lower priority watchers, which means as long as higher priority
		1449	watchers receive events, lower priority watchers are not being invoked.
		1450
		1451	The less common only-for-ordering model uses priorities solely to order
		1452	callback invocation within a single event loop iteration: Higher priority
		1453	watchers are invoked before lower priority ones, but they all get invoked
		1454	before polling for new events.
		1455
		1456	Libev uses the second (only-for-ordering) model for all its watchers
		1457	except for idle watchers (which use the lock-out model).
		1458
		1459	The rationale behind this is that implementing the lock-out model for
		1460	watchers is not well supported by most kernel interfaces, and most event
		1461	libraries will just poll for the same events again and again as long as
		1462	their callbacks have not been executed, which is very inefficient in the
		1463	common case of one high-priority watcher locking out a mass of lower
		1464	priority ones.
		1465
		1466	Static (ordering) priorities are most useful when you have two or more
		1467	watchers handling the same resource: a typical usage example is having an
		1468	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1469	timeouts. Under load, data might be received while the program handles
		1470	other jobs, but since timers normally get invoked first, the timeout
		1471	handler will be executed before checking for data. In that case, giving
		1472	the timer a lower priority than the I/O watcher ensures that I/O will be
		1473	handled first even under adverse conditions (which is usually, but not
		1474	always, what you want).
		1475
		1476	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1477	will only be executed when no same or higher priority watchers have
		1478	received events, they can be used to implement the "lock-out" model when
		1479	required.
		1480
		1481	For example, to emulate how many other event libraries handle priorities,
		1482	you can associate an C<ev_idle> watcher to each such watcher, and in
		1483	the normal watcher callback, you just start the idle watcher. The real
		1484	processing is done in the idle watcher callback. This causes libev to
		1485	continuously poll and process kernel event data for the watcher, but when
		1486	the lock-out case is known to be rare (which in turn is rare :), this is
		1487	workable.
		1488
		1489	Usually, however, the lock-out model implemented that way will perform
		1490	miserably under the type of load it was designed to handle. In that case,
		1491	it might be preferable to stop the real watcher before starting the
		1492	idle watcher, so the kernel will not have to process the event in case
		1493	the actual processing will be delayed for considerable time.
		1494
		1495	Here is an example of an I/O watcher that should run at a strictly lower
		1496	priority than the default, and which should only process data when no
		1497	other events are pending:
		1498
		1499	ev_idle idle; // actual processing watcher
		1500	ev_io io; // actual event watcher
		1501
		1502	static void
		1503	io_cb (EV_P_ ev_io *w, int revents)
		1504	{
		1505	// stop the I/O watcher, we received the event, but
		1506	// are not yet ready to handle it.
		1507	ev_io_stop (EV_A_ w);
		1508
		1509	// start the idle watcher to handle the actual event.
		1510	// it will not be executed as long as other watchers
		1511	// with the default priority are receiving events.
		1512	ev_idle_start (EV_A_ &idle);
		1513	}
		1514
		1515	static void
		1516	idle_cb (EV_P_ ev_idle *w, int revents)
		1517	{
		1518	// actual processing
		1519	read (STDIN_FILENO, ...);
		1520
		1521	// have to start the I/O watcher again, as
		1522	// we have handled the event
		1523	ev_io_start (EV_P_ &io);
		1524	}
		1525
		1526	// initialisation
		1527	ev_idle_init (&idle, idle_cb);
		1528	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1529	ev_io_start (EV_DEFAULT_ &io);
		1530
		1531	In the "real" world, it might also be beneficial to start a timer, so that
		1532	low-priority connections can not be locked out forever under load. This
		1533	enables your program to keep a lower latency for important connections
		1534	during short periods of high load, while not completely locking out less
		1535	important ones.
1010		1536
1011		1537
1012	=head1 WATCHER TYPES	1538	=head1 WATCHER TYPES
1013		1539
1014	This section describes each watcher in detail, but will not repeat	1540	This section describes each watcher in detail, but will not repeat
…		…
1038	In general you can register as many read and/or write event watchers per	1564	In general you can register as many read and/or write event watchers per
1039	fd as you want (as long as you don't confuse yourself). Setting all file	1565	fd as you want (as long as you don't confuse yourself). Setting all file
1040	descriptors to non-blocking mode is also usually a good idea (but not	1566	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1567	required if you know what you are doing).
1042		1568
1043	If you must do this, then force the use of a known-to-be-good backend	1569	If you cannot use non-blocking mode, then force the use of a
1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1570	known-to-be-good backend (at the time of this writing, this includes only
1045	C<EVBACKEND_POLL>).	1571	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1572	descriptors for which non-blocking operation makes no sense (such as
		1573	files) - libev doesn't guarantee any specific behaviour in that case.
1046		1574
1047	Another thing you have to watch out for is that it is quite easy to	1575	Another thing you have to watch out for is that it is quite easy to
1048	receive "spurious" readiness notifications, that is your callback might	1576	receive "spurious" readiness notifications, that is your callback might
1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1577	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1050	because there is no data. Not only are some backends known to create a	1578	because there is no data. Not only are some backends known to create a
1051	lot of those (for example solaris ports), it is very easy to get into	1579	lot of those (for example Solaris ports), it is very easy to get into
1052	this situation even with a relatively standard program structure. Thus	1580	this situation even with a relatively standard program structure. Thus
1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1581	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1054	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1055		1583
1056	If you cannot run the fd in non-blocking mode (for example you should not	1584	If you cannot run the fd in non-blocking mode (for example you should
1057	play around with an Xlib connection), then you have to seperately re-test	1585	not play around with an Xlib connection), then you have to separately
1058	whether a file descriptor is really ready with a known-to-be good interface	1586	re-test whether a file descriptor is really ready with a known-to-be good
1059	such as poll (fortunately in our Xlib example, Xlib already does this on	1587	interface such as poll (fortunately in our Xlib example, Xlib already
1060	its own, so its quite safe to use).	1588	does this on its own, so its quite safe to use). Some people additionally
		1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1590	indefinitely.
		1591
		1592	But really, best use non-blocking mode.
1061		1593
1062	=head3 The special problem of disappearing file descriptors	1594	=head3 The special problem of disappearing file descriptors
1063		1595
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1596	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1065	descriptor (either by calling C<close> explicitly or by any other means,	1597	descriptor (either due to calling C<close> explicitly or any other means,
1066	such as C<dup>). The reason is that you register interest in some file	1598	such as C<dup2>). The reason is that you register interest in some file
1067	descriptor, but when it goes away, the operating system will silently drop	1599	descriptor, but when it goes away, the operating system will silently drop
1068	this interest. If another file descriptor with the same number then is	1600	this interest. If another file descriptor with the same number then is
1069	registered with libev, there is no efficient way to see that this is, in	1601	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1602	fact, a different file descriptor.
1071		1603
…		…
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1634	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1103	C<EVBACKEND_POLL>.	1635	C<EVBACKEND_POLL>.
1104		1636
1105	=head3 The special problem of SIGPIPE	1637	=head3 The special problem of SIGPIPE
1106		1638
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1639	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1108	when reading from a pipe whose other end has been closed, your program	1640	when writing to a pipe whose other end has been closed, your program gets
1109	gets send a SIGPIPE, which, by default, aborts your program. For most	1641	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1642	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1643
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1644	So when you encounter spurious, unexplained daemon exits, make sure you
1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1645	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1115	somewhere, as that would have given you a big clue).	1646	somewhere, as that would have given you a big clue).
1116		1647
		1648	=head3 The special problem of accept()ing when you can't
		1649
		1650	Many implementations of the POSIX C<accept> function (for example,
		1651	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1652	connection from the pending queue in all error cases.
		1653
		1654	For example, larger servers often run out of file descriptors (because
		1655	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1656	rejecting the connection, leading to libev signalling readiness on
		1657	the next iteration again (the connection still exists after all), and
		1658	typically causing the program to loop at 100% CPU usage.
		1659
		1660	Unfortunately, the set of errors that cause this issue differs between
		1661	operating systems, there is usually little the app can do to remedy the
		1662	situation, and no known thread-safe method of removing the connection to
		1663	cope with overload is known (to me).
		1664
		1665	One of the easiest ways to handle this situation is to just ignore it
		1666	- when the program encounters an overload, it will just loop until the
		1667	situation is over. While this is a form of busy waiting, no OS offers an
		1668	event-based way to handle this situation, so it's the best one can do.
		1669
		1670	A better way to handle the situation is to log any errors other than
		1671	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1672	messages, and continue as usual, which at least gives the user an idea of
		1673	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1674	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1675	usage.
		1676
		1677	If your program is single-threaded, then you could also keep a dummy file
		1678	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1679	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1680	close that fd, and create a new dummy fd. This will gracefully refuse
		1681	clients under typical overload conditions.
		1682
		1683	The last way to handle it is to simply log the error and C<exit>, as
		1684	is often done with C<malloc> failures, but this results in an easy
		1685	opportunity for a DoS attack.
1117		1686
1118	=head3 Watcher-Specific Functions	1687	=head3 Watcher-Specific Functions
1119		1688
1120	=over 4	1689	=over 4
1121		1690
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1691	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1692
1124	=item ev_io_set (ev_io *, int fd, int events)	1693	=item ev_io_set (ev_io *, int fd, int events)
1125		1694
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1695	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1127	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1696	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1128	C<EV_READ | EV_WRITE> to receive the given events.	1697	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1698
1130	=item int fd [read-only]	1699	=item int fd [read-only]
1131		1700
1132	The file descriptor being watched.	1701	The file descriptor being watched.
1133		1702
…		…
1141		1710
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1711	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1143	readable, but only once. Since it is likely line-buffered, you could	1712	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1713	attempt to read a whole line in the callback.
1145		1714
1146	static void	1715	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1716	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1717	{
1149	ev_io_stop (loop, w);	1718	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1719	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1720	}
1152		1721
1153	...	1722	...
1154	struct ev_loop *loop = ev_default_init (0);	1723	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1724	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1725	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1726	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1727	ev_run (loop, 0);
1159		1728
1160		1729
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1730	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1731
1163	Timer watchers are simple relative timers that generate an event after a	1732	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1733	given time, and optionally repeating in regular intervals after that.
1165		1734
1166	The timers are based on real time, that is, if you register an event that	1735	The timers are based on real time, that is, if you register an event that
1167	times out after an hour and you reset your system clock to january last	1736	times out after an hour and you reset your system clock to January last
1168	year, it will still time out after (roughly) and hour. "Roughly" because	1737	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1738	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1739	monotonic clock option helps a lot here).
		1740
		1741	The callback is guaranteed to be invoked only I<after> its timeout has
		1742	passed (not I<at>, so on systems with very low-resolution clocks this
		1743	might introduce a small delay). If multiple timers become ready during the
		1744	same loop iteration then the ones with earlier time-out values are invoked
		1745	before ones of the same priority with later time-out values (but this is
		1746	no longer true when a callback calls C<ev_run> recursively).
		1747
		1748	=head3 Be smart about timeouts
		1749
		1750	Many real-world problems involve some kind of timeout, usually for error
		1751	recovery. A typical example is an HTTP request - if the other side hangs,
		1752	you want to raise some error after a while.
		1753
		1754	What follows are some ways to handle this problem, from obvious and
		1755	inefficient to smart and efficient.
		1756
		1757	In the following, a 60 second activity timeout is assumed - a timeout that
		1758	gets reset to 60 seconds each time there is activity (e.g. each time some
		1759	data or other life sign was received).
		1760
		1761	=over 4
		1762
		1763	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1764
		1765	This is the most obvious, but not the most simple way: In the beginning,
		1766	start the watcher:
		1767
		1768	ev_timer_init (timer, callback, 60., 0.);
		1769	ev_timer_start (loop, timer);
		1770
		1771	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1772	and start it again:
		1773
		1774	ev_timer_stop (loop, timer);
		1775	ev_timer_set (timer, 60., 0.);
		1776	ev_timer_start (loop, timer);
		1777
		1778	This is relatively simple to implement, but means that each time there is
		1779	some activity, libev will first have to remove the timer from its internal
		1780	data structure and then add it again. Libev tries to be fast, but it's
		1781	still not a constant-time operation.
		1782
		1783	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1784
		1785	This is the easiest way, and involves using C<ev_timer_again> instead of
		1786	C<ev_timer_start>.
		1787
		1788	To implement this, configure an C<ev_timer> with a C<repeat> value
		1789	of C<60> and then call C<ev_timer_again> at start and each time you
		1790	successfully read or write some data. If you go into an idle state where
		1791	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1792	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1793
		1794	That means you can ignore both the C<ev_timer_start> function and the
		1795	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1796	member and C<ev_timer_again>.
		1797
		1798	At start:
		1799
		1800	ev_init (timer, callback);
		1801	timer->repeat = 60.;
		1802	ev_timer_again (loop, timer);
		1803
		1804	Each time there is some activity:
		1805
		1806	ev_timer_again (loop, timer);
		1807
		1808	It is even possible to change the time-out on the fly, regardless of
		1809	whether the watcher is active or not:
		1810
		1811	timer->repeat = 30.;
		1812	ev_timer_again (loop, timer);
		1813
		1814	This is slightly more efficient then stopping/starting the timer each time
		1815	you want to modify its timeout value, as libev does not have to completely
		1816	remove and re-insert the timer from/into its internal data structure.
		1817
		1818	It is, however, even simpler than the "obvious" way to do it.
		1819
		1820	=item 3. Let the timer time out, but then re-arm it as required.
		1821
		1822	This method is more tricky, but usually most efficient: Most timeouts are
		1823	relatively long compared to the intervals between other activity - in
		1824	our example, within 60 seconds, there are usually many I/O events with
		1825	associated activity resets.
		1826
		1827	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1828	but remember the time of last activity, and check for a real timeout only
		1829	within the callback:
		1830
		1831	ev_tstamp last_activity; // time of last activity
		1832
		1833	static void
		1834	callback (EV_P_ ev_timer *w, int revents)
		1835	{
		1836	ev_tstamp now = ev_now (EV_A);
		1837	ev_tstamp timeout = last_activity + 60.;
		1838
		1839	// if last_activity + 60. is older than now, we did time out
		1840	if (timeout < now)
		1841	{
		1842	// timeout occurred, take action
		1843	}
		1844	else
		1845	{
		1846	// callback was invoked, but there was some activity, re-arm
		1847	// the watcher to fire in last_activity + 60, which is
		1848	// guaranteed to be in the future, so "again" is positive:
		1849	w->repeat = timeout - now;
		1850	ev_timer_again (EV_A_ w);
		1851	}
		1852	}
		1853
		1854	To summarise the callback: first calculate the real timeout (defined
		1855	as "60 seconds after the last activity"), then check if that time has
		1856	been reached, which means something I<did>, in fact, time out. Otherwise
		1857	the callback was invoked too early (C<timeout> is in the future), so
		1858	re-schedule the timer to fire at that future time, to see if maybe we have
		1859	a timeout then.
		1860
		1861	Note how C<ev_timer_again> is used, taking advantage of the
		1862	C<ev_timer_again> optimisation when the timer is already running.
		1863
		1864	This scheme causes more callback invocations (about one every 60 seconds
		1865	minus half the average time between activity), but virtually no calls to
		1866	libev to change the timeout.
		1867
		1868	To start the timer, simply initialise the watcher and set C<last_activity>
		1869	to the current time (meaning we just have some activity :), then call the
		1870	callback, which will "do the right thing" and start the timer:
		1871
		1872	ev_init (timer, callback);
		1873	last_activity = ev_now (loop);
		1874	callback (loop, timer, EV_TIMER);
		1875
		1876	And when there is some activity, simply store the current time in
		1877	C<last_activity>, no libev calls at all:
		1878
		1879	last_activity = ev_now (loop);
		1880
		1881	This technique is slightly more complex, but in most cases where the
		1882	time-out is unlikely to be triggered, much more efficient.
		1883
		1884	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1885	callback :) - just change the timeout and invoke the callback, which will
		1886	fix things for you.
		1887
		1888	=item 4. Wee, just use a double-linked list for your timeouts.
		1889
		1890	If there is not one request, but many thousands (millions...), all
		1891	employing some kind of timeout with the same timeout value, then one can
		1892	do even better:
		1893
		1894	When starting the timeout, calculate the timeout value and put the timeout
		1895	at the I<end> of the list.
		1896
		1897	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1898	the list is expected to fire (for example, using the technique #3).
		1899
		1900	When there is some activity, remove the timer from the list, recalculate
		1901	the timeout, append it to the end of the list again, and make sure to
		1902	update the C<ev_timer> if it was taken from the beginning of the list.
		1903
		1904	This way, one can manage an unlimited number of timeouts in O(1) time for
		1905	starting, stopping and updating the timers, at the expense of a major
		1906	complication, and having to use a constant timeout. The constant timeout
		1907	ensures that the list stays sorted.
		1908
		1909	=back
		1910
		1911	So which method the best?
		1912
		1913	Method #2 is a simple no-brain-required solution that is adequate in most
		1914	situations. Method #3 requires a bit more thinking, but handles many cases
		1915	better, and isn't very complicated either. In most case, choosing either
		1916	one is fine, with #3 being better in typical situations.
		1917
		1918	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1919	rather complicated, but extremely efficient, something that really pays
		1920	off after the first million or so of active timers, i.e. it's usually
		1921	overkill :)
		1922
		1923	=head3 The special problem of time updates
		1924
		1925	Establishing the current time is a costly operation (it usually takes at
		1926	least two system calls): EV therefore updates its idea of the current
		1927	time only before and after C<ev_run> collects new events, which causes a
		1928	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1929	lots of events in one iteration.
1171		1930
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1931	The relative timeouts are calculated relative to the C<ev_now ()>
1173	time. This is usually the right thing as this timestamp refers to the time	1932	time. This is usually the right thing as this timestamp refers to the time
1174	of the event triggering whatever timeout you are modifying/starting. If	1933	of the event triggering whatever timeout you are modifying/starting. If
1175	you suspect event processing to be delayed and you I<need> to base the timeout	1934	you suspect event processing to be delayed and you I<need> to base the
1176	on the current time, use something like this to adjust for this:	1935	timeout on the current time, use something like this to adjust for this:
1177		1936
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1937	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1938
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1939	If the event loop is suspended for a long time, you can also force an
1181	but if multiple timers become ready during the same loop iteration then	1940	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1941	()>.
		1942
		1943	=head3 The special problems of suspended animation
		1944
		1945	When you leave the server world it is quite customary to hit machines that
		1946	can suspend/hibernate - what happens to the clocks during such a suspend?
		1947
		1948	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1949	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1950	to run until the system is suspended, but they will not advance while the
		1951	system is suspended. That means, on resume, it will be as if the program
		1952	was frozen for a few seconds, but the suspend time will not be counted
		1953	towards C<ev_timer> when a monotonic clock source is used. The real time
		1954	clock advanced as expected, but if it is used as sole clocksource, then a
		1955	long suspend would be detected as a time jump by libev, and timers would
		1956	be adjusted accordingly.
		1957
		1958	I would not be surprised to see different behaviour in different between
		1959	operating systems, OS versions or even different hardware.
		1960
		1961	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1962	time jump in the monotonic clocks and the realtime clock. If the program
		1963	is suspended for a very long time, and monotonic clock sources are in use,
		1964	then you can expect C<ev_timer>s to expire as the full suspension time
		1965	will be counted towards the timers. When no monotonic clock source is in
		1966	use, then libev will again assume a timejump and adjust accordingly.
		1967
		1968	It might be beneficial for this latter case to call C<ev_suspend>
		1969	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1970	deterministic behaviour in this case (you can do nothing against
		1971	C<SIGSTOP>).
1183		1972
1184	=head3 Watcher-Specific Functions and Data Members	1973	=head3 Watcher-Specific Functions and Data Members
1185		1974
1186	=over 4	1975	=over 4
1187		1976
…		…
1206	This will act as if the timer timed out and restart it again if it is	1995	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	1996	repeating. The exact semantics are:
1208		1997
1209	If the timer is pending, its pending status is cleared.	1998	If the timer is pending, its pending status is cleared.
1210		1999
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	2000	If the timer is started but non-repeating, stop it (as if it timed out).
1212		2001
1213	If the timer is repeating, either start it if necessary (with the	2002	If the timer is repeating, either start it if necessary (with the
1214	C<repeat> value), or reset the running timer to the C<repeat> value.	2003	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		2004
1216	This sounds a bit complicated, but here is a useful and typical	2005	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1217	example: Imagine you have a tcp connection and you want a so-called idle	2006	usage example.
1218	timeout, that is, you want to be called when there have been, say, 60
1219	seconds of inactivity on the socket. The easiest way to do this is to
1220	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1221	C<ev_timer_again> each time you successfully read or write some data. If
1222	you go into an idle state where you do not expect data to travel on the
1223	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1224	automatically restart it if need be.
1225		2007
1226	That means you can ignore the C<after> value and C<ev_timer_start>	2008	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1227	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1228		2009
1229	ev_timer_init (timer, callback, 0., 5.);	2010	Returns the remaining time until a timer fires. If the timer is active,
1230	ev_timer_again (loop, timer);	2011	then this time is relative to the current event loop time, otherwise it's
1231	...	2012	the timeout value currently configured.
1232	timer->again = 17.;
1233	ev_timer_again (loop, timer);
1234	...
1235	timer->again = 10.;
1236	ev_timer_again (loop, timer);
1237		2013
1238	This is more slightly efficient then stopping/starting the timer each time	2014	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1239	you want to modify its timeout value.	2015	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2016	will return C<4>. When the timer expires and is restarted, it will return
		2017	roughly C<7> (likely slightly less as callback invocation takes some time,
		2018	too), and so on.
1240		2019
1241	=item ev_tstamp repeat [read-write]	2020	=item ev_tstamp repeat [read-write]
1242		2021
1243	The current C<repeat> value. Will be used each time the watcher times out	2022	The current C<repeat> value. Will be used each time the watcher times out
1244	or C<ev_timer_again> is called and determines the next timeout (if any),	2023	or C<ev_timer_again> is called, and determines the next timeout (if any),
1245	which is also when any modifications are taken into account.	2024	which is also when any modifications are taken into account.
1246		2025
1247	=back	2026	=back
1248		2027
1249	=head3 Examples	2028	=head3 Examples
1250		2029
1251	Example: Create a timer that fires after 60 seconds.	2030	Example: Create a timer that fires after 60 seconds.
1252		2031
1253	static void	2032	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2033	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	2034	{
1256	.. one minute over, w is actually stopped right here	2035	.. one minute over, w is actually stopped right here
1257	}	2036	}
1258		2037
1259	struct ev_timer mytimer;	2038	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2039	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	2040	ev_timer_start (loop, &mytimer);
1262		2041
1263	Example: Create a timeout timer that times out after 10 seconds of	2042	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	2043	inactivity.
1265		2044
1266	static void	2045	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2046	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	2047	{
1269	.. ten seconds without any activity	2048	.. ten seconds without any activity
1270	}	2049	}
1271		2050
1272	struct ev_timer mytimer;	2051	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2052	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	2053	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	2054	ev_run (loop, 0);
1276		2055
1277	// and in some piece of code that gets executed on any "activity":	2056	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	2057	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	2058	ev_timer_again (&mytimer);
1280		2059
1281		2060
1282	=head2 C<ev_periodic> - to cron or not to cron?	2061	=head2 C<ev_periodic> - to cron or not to cron?
1283		2062
1284	Periodic watchers are also timers of a kind, but they are very versatile	2063	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	2064	(and unfortunately a bit complex).
1286		2065
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2066	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1288	but on wallclock time (absolute time). You can tell a periodic watcher	2067	relative time, the physical time that passes) but on wall clock time
1289	to trigger after some specific point in time. For example, if you tell a	2068	(absolute time, the thing you can read on your calender or clock). The
1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2069	difference is that wall clock time can run faster or slower than real
1291	+ 10.>, that is, an absolute time not a delay) and then reset your system	2070	time, and time jumps are not uncommon (e.g. when you adjust your
1292	clock to january of the previous year, then it will take more than year	2071	wrist-watch).
1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1294	roughly 10 seconds later as it uses a relative timeout).
1295		2072
		2073	You can tell a periodic watcher to trigger after some specific point
		2074	in time: for example, if you tell a periodic watcher to trigger "in 10
		2075	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2076	not a delay) and then reset your system clock to January of the previous
		2077	year, then it will take a year or more to trigger the event (unlike an
		2078	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2079	it, as it uses a relative timeout).
		2080
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	2081	C<ev_periodic> watchers can also be used to implement vastly more complex
1297	such as triggering an event on each "midnight, local time", or other	2082	timers, such as triggering an event on each "midnight, local time", or
1298	complicated, rules.	2083	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2084	those cannot react to time jumps.
1299		2085
1300	As with timers, the callback is guarenteed to be invoked only when the	2086	As with timers, the callback is guaranteed to be invoked only when the
1301	time (C<at>) has passed, but if multiple periodic timers become ready	2087	point in time where it is supposed to trigger has passed. If multiple
1302	during the same loop iteration then order of execution is undefined.	2088	timers become ready during the same loop iteration then the ones with
		2089	earlier time-out values are invoked before ones with later time-out values
		2090	(but this is no longer true when a callback calls C<ev_run> recursively).
1303		2091
1304	=head3 Watcher-Specific Functions and Data Members	2092	=head3 Watcher-Specific Functions and Data Members
1305		2093
1306	=over 4	2094	=over 4
1307		2095
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2096	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1309		2097
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2098	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1311		2099
1312	Lots of arguments, lets sort it out... There are basically three modes of	2100	Lots of arguments, let's sort it out... There are basically three modes of
1313	operation, and we will explain them from simplest to complex:	2101	operation, and we will explain them from simplest to most complex:
1314		2102
1315	=over 4	2103	=over 4
1316		2104
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2105	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1318		2106
1319	In this configuration the watcher triggers an event after the wallclock	2107	In this configuration the watcher triggers an event after the wall clock
1320	time C<at> has passed and doesn't repeat. It will not adjust when a time	2108	time C<offset> has passed. It will not repeat and will not adjust when a
1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2109	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1322	run when the system time reaches or surpasses this time.	2110	will be stopped and invoked when the system clock reaches or surpasses
		2111	this point in time.
1323		2112
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2113	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1325		2114
1326	In this mode the watcher will always be scheduled to time out at the next	2115	In this mode the watcher will always be scheduled to time out at the next
1327	C<at + N * interval> time (for some integer N, which can also be negative)	2116	C<offset + N * interval> time (for some integer N, which can also be
1328	and then repeat, regardless of any time jumps.	2117	negative) and then repeat, regardless of any time jumps. The C<offset>
		2118	argument is merely an offset into the C<interval> periods.
1329		2119
1330	This can be used to create timers that do not drift with respect to system	2120	This can be used to create timers that do not drift with respect to the
1331	time, for example, here is a C<ev_periodic> that triggers each hour, on	2121	system clock, for example, here is an C<ev_periodic> that triggers each
1332	the hour:	2122	hour, on the hour (with respect to UTC):
1333		2123
1334	ev_periodic_set (&periodic, 0., 3600., 0);	2124	ev_periodic_set (&periodic, 0., 3600., 0);
1335		2125
1336	This doesn't mean there will always be 3600 seconds in between triggers,	2126	This doesn't mean there will always be 3600 seconds in between triggers,
1337	but only that the the callback will be called when the system time shows a	2127	but only that the callback will be called when the system time shows a
1338	full hour (UTC), or more correctly, when the system time is evenly divisible	2128	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	2129	by 3600.
1340		2130
1341	Another way to think about it (for the mathematically inclined) is that	2131	Another way to think about it (for the mathematically inclined) is that
1342	C<ev_periodic> will try to run the callback in this mode at the next possible	2132	C<ev_periodic> will try to run the callback in this mode at the next possible
1343	time where C<time = at (mod interval)>, regardless of any time jumps.	2133	time where C<time = offset (mod interval)>, regardless of any time jumps.
1344		2134
1345	For numerical stability it is preferable that the C<at> value is near	2135	For numerical stability it is preferable that the C<offset> value is near
1346	C<ev_now ()> (the current time), but there is no range requirement for	2136	C<ev_now ()> (the current time), but there is no range requirement for
1347	this value, and in fact is often specified as zero.	2137	this value, and in fact is often specified as zero.
1348		2138
1349	Note also that there is an upper limit to how often a timer can fire (cpu	2139	Note also that there is an upper limit to how often a timer can fire (CPU
1350	speed for example), so if C<interval> is very small then timing stability	2140	speed for example), so if C<interval> is very small then timing stability
1351	will of course detoriate. Libev itself tries to be exact to be about one	2141	will of course deteriorate. Libev itself tries to be exact to be about one
1352	millisecond (if the OS supports it and the machine is fast enough).	2142	millisecond (if the OS supports it and the machine is fast enough).
1353		2143
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2144	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1355		2145
1356	In this mode the values for C<interval> and C<at> are both being	2146	In this mode the values for C<interval> and C<offset> are both being
1357	ignored. Instead, each time the periodic watcher gets scheduled, the	2147	ignored. Instead, each time the periodic watcher gets scheduled, the
1358	reschedule callback will be called with the watcher as first, and the	2148	reschedule callback will be called with the watcher as first, and the
1359	current time as second argument.	2149	current time as second argument.
1360		2150
1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2151	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1362	ever, or make ANY event loop modifications whatsoever>.	2152	or make ANY other event loop modifications whatsoever, unless explicitly
		2153	allowed by documentation here>.
1363		2154
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2155	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2156	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	2157	only event loop modification you are allowed to do).
1367		2158
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2159	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	2160	*w, ev_tstamp now)>, e.g.:
1370		2161
		2162	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2163	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	2164	{
1373	return now + 60.;	2165	return now + 60.;
1374	}	2166	}
1375		2167
1376	It must return the next time to trigger, based on the passed time value	2168	It must return the next time to trigger, based on the passed time value
…		…
1396	a different time than the last time it was called (e.g. in a crond like	2188	a different time than the last time it was called (e.g. in a crond like
1397	program when the crontabs have changed).	2189	program when the crontabs have changed).
1398		2190
1399	=item ev_tstamp ev_periodic_at (ev_periodic *)	2191	=item ev_tstamp ev_periodic_at (ev_periodic *)
1400		2192
1401	When active, returns the absolute time that the watcher is supposed to	2193	When active, returns the absolute time that the watcher is supposed
1402	trigger next.	2194	to trigger next. This is not the same as the C<offset> argument to
		2195	C<ev_periodic_set>, but indeed works even in interval and manual
		2196	rescheduling modes.
1403		2197
1404	=item ev_tstamp offset [read-write]	2198	=item ev_tstamp offset [read-write]
1405		2199
1406	When repeating, this contains the offset value, otherwise this is the	2200	When repeating, this contains the offset value, otherwise this is the
1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2201	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2202	although libev might modify this value for better numerical stability).
1408		2203
1409	Can be modified any time, but changes only take effect when the periodic	2204	Can be modified any time, but changes only take effect when the periodic
1410	timer fires or C<ev_periodic_again> is being called.	2205	timer fires or C<ev_periodic_again> is being called.
1411		2206
1412	=item ev_tstamp interval [read-write]	2207	=item ev_tstamp interval [read-write]
1413		2208
1414	The current interval value. Can be modified any time, but changes only	2209	The current interval value. Can be modified any time, but changes only
1415	take effect when the periodic timer fires or C<ev_periodic_again> is being	2210	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	2211	called.
1417		2212
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2213	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		2214
1420	The current reschedule callback, or C<0>, if this functionality is	2215	The current reschedule callback, or C<0>, if this functionality is
1421	switched off. Can be changed any time, but changes only take effect when	2216	switched off. Can be changed any time, but changes only take effect when
1422	the periodic timer fires or C<ev_periodic_again> is being called.	2217	the periodic timer fires or C<ev_periodic_again> is being called.
1423		2218
1424	=back	2219	=back
1425		2220
1426	=head3 Examples	2221	=head3 Examples
1427		2222
1428	Example: Call a callback every hour, or, more precisely, whenever the	2223	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	2224	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	2225	potentially a lot of jitter, but good long-term stability.
1431		2226
1432	static void	2227	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2228	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1434	{	2229	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	2230	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	2231	}
1437		2232
1438	struct ev_periodic hourly_tick;	2233	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2234	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	2235	ev_periodic_start (loop, &hourly_tick);
1441		2236
1442	Example: The same as above, but use a reschedule callback to do it:	2237	Example: The same as above, but use a reschedule callback to do it:
1443		2238
1444	#include <math.h>	2239	#include <math.h>
1445		2240
1446	static ev_tstamp	2241	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2242	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	2243	{
1449	return fmod (now, 3600.) + 3600.;	2244	return now + (3600. - fmod (now, 3600.));
1450	}	2245	}
1451		2246
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2247	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		2248
1454	Example: Call a callback every hour, starting now:	2249	Example: Call a callback every hour, starting now:
1455		2250
1456	struct ev_periodic hourly_tick;	2251	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	2252	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	2253	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	2254	ev_periodic_start (loop, &hourly_tick);
1460		2255
1461		2256
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	2257	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		2258
1464	Signal watchers will trigger an event when the process receives a specific	2259	Signal watchers will trigger an event when the process receives a specific
1465	signal one or more times. Even though signals are very asynchronous, libev	2260	signal one or more times. Even though signals are very asynchronous, libev
1466	will try it's best to deliver signals synchronously, i.e. as part of the	2261	will try it's best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	2262	normal event processing, like any other event.
1468		2263
		2264	If you want signals to be delivered truly asynchronously, just use
		2265	C<sigaction> as you would do without libev and forget about sharing
		2266	the signal. You can even use C<ev_async> from a signal handler to
		2267	synchronously wake up an event loop.
		2268
1469	You can configure as many watchers as you like per signal. Only when the	2269	You can configure as many watchers as you like for the same signal, but
		2270	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2271	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2272	C<SIGINT> in both the default loop and another loop at the same time. At
		2273	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2274
1470	first watcher gets started will libev actually register a signal watcher	2275	When the first watcher gets started will libev actually register something
1471	with the kernel (thus it coexists with your own signal handlers as long	2276	with the kernel (thus it coexists with your own signal handlers as long as
1472	as you don't register any with libev). Similarly, when the last signal	2277	you don't register any with libev for the same signal).
1473	watcher for a signal is stopped libev will reset the signal handler to
1474	SIG_DFL (regardless of what it was set to before).
1475		2278
1476	If possible and supported, libev will install its handlers with	2279	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2280	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1478	interrupted. If you have a problem with syscalls getting interrupted by	2281	not be unduly interrupted. If you have a problem with system calls getting
1479	signals you can block all signals in an C<ev_check> watcher and unblock	2282	interrupted by signals you can block all signals in an C<ev_check> watcher
1480	them in an C<ev_prepare> watcher.	2283	and unblock them in an C<ev_prepare> watcher.
		2284
		2285	=head3 The special problem of inheritance over fork/execve/pthread_create
		2286
		2287	Both the signal mask (C<sigprocmask>) and the signal disposition
		2288	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2289	stopping it again), that is, libev might or might not block the signal,
		2290	and might or might not set or restore the installed signal handler.
		2291
		2292	While this does not matter for the signal disposition (libev never
		2293	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2294	C<execve>), this matters for the signal mask: many programs do not expect
		2295	certain signals to be blocked.
		2296
		2297	This means that before calling C<exec> (from the child) you should reset
		2298	the signal mask to whatever "default" you expect (all clear is a good
		2299	choice usually).
		2300
		2301	The simplest way to ensure that the signal mask is reset in the child is
		2302	to install a fork handler with C<pthread_atfork> that resets it. That will
		2303	catch fork calls done by libraries (such as the libc) as well.
		2304
		2305	In current versions of libev, the signal will not be blocked indefinitely
		2306	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2307	the window of opportunity for problems, it will not go away, as libev
		2308	I<has> to modify the signal mask, at least temporarily.
		2309
		2310	So I can't stress this enough: I<If you do not reset your signal mask when
		2311	you expect it to be empty, you have a race condition in your code>. This
		2312	is not a libev-specific thing, this is true for most event libraries.
1481		2313
1482	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1483		2315
1484	=over 4	2316	=over 4
1485		2317
…		…
1496		2328
1497	=back	2329	=back
1498		2330
1499	=head3 Examples	2331	=head3 Examples
1500		2332
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	2333	Example: Try to exit cleanly on SIGINT.
1502		2334
1503	static void	2335	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2336	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	2337	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	2338	ev_break (loop, EVBREAK_ALL);
1507	}	2339	}
1508		2340
1509	struct ev_signal signal_watcher;	2341	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2342	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	2343	ev_signal_start (loop, &signal_watcher);
1512		2344
1513		2345
1514	=head2 C<ev_child> - watch out for process status changes	2346	=head2 C<ev_child> - watch out for process status changes
1515		2347
1516	Child watchers trigger when your process receives a SIGCHLD in response to	2348	Child watchers trigger when your process receives a SIGCHLD in response to
1517	some child status changes (most typically when a child of yours dies). It	2349	some child status changes (most typically when a child of yours dies or
1518	is permissible to install a child watcher I<after> the child has been	2350	exits). It is permissible to install a child watcher I<after> the child
1519	forked (which implies it might have already exited), as long as the event	2351	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	2352	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2353	forking and then immediately registering a watcher for the child is fine,
		2354	but forking and registering a watcher a few event loop iterations later or
		2355	in the next callback invocation is not.
1521		2356
1522	Only the default event loop is capable of handling signals, and therefore	2357	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	2358	you can only register child watchers in the default event loop.
		2359
		2360	Due to some design glitches inside libev, child watchers will always be
		2361	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2362	libev)
1524		2363
1525	=head3 Process Interaction	2364	=head3 Process Interaction
1526		2365
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	2366	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	2367	initialised. This is necessary to guarantee proper behaviour even if the
1529	the first child watcher is started after the child exits. The occurance	2368	first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2369	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	2370	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	2371	children, even ones not watched.
1533		2372
1534	=head3 Overriding the Built-In Processing	2373	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	2377	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	2378	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	2379	default loop never gets destroyed. You are encouraged, however, to use an
1541	event-based approach to child reaping and thus use libev's support for	2380	event-based approach to child reaping and thus use libev's support for
1542	that, so other libev users can use C<ev_child> watchers freely.	2381	that, so other libev users can use C<ev_child> watchers freely.
		2382
		2383	=head3 Stopping the Child Watcher
		2384
		2385	Currently, the child watcher never gets stopped, even when the
		2386	child terminates, so normally one needs to stop the watcher in the
		2387	callback. Future versions of libev might stop the watcher automatically
		2388	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2389	problem).
1543		2390
1544	=head3 Watcher-Specific Functions and Data Members	2391	=head3 Watcher-Specific Functions and Data Members
1545		2392
1546	=over 4	2393	=over 4
1547		2394
…		…
1576	=head3 Examples	2423	=head3 Examples
1577		2424
1578	Example: C<fork()> a new process and install a child handler to wait for	2425	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	2426	its completion.
1580		2427
1581	ev_child cw;	2428	ev_child cw;
1582		2429
1583	static void	2430	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	2431	child_cb (EV_P_ ev_child *w, int revents)
1585	{	2432	{
1586	ev_child_stop (EV_A_ w);	2433	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2434	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	2435	}
1589		2436
1590	pid_t pid = fork ();	2437	pid_t pid = fork ();
1591		2438
1592	if (pid < 0)	2439	if (pid < 0)
1593	// error	2440	// error
1594	else if (pid == 0)	2441	else if (pid == 0)
1595	{	2442	{
1596	// the forked child executes here	2443	// the forked child executes here
1597	exit (1);	2444	exit (1);
1598	}	2445	}
1599	else	2446	else
1600	{	2447	{
1601	ev_child_init (&cw, child_cb, pid, 0);	2448	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	2449	ev_child_start (EV_DEFAULT_ &cw);
1603	}	2450	}
1604		2451
1605		2452
1606	=head2 C<ev_stat> - did the file attributes just change?	2453	=head2 C<ev_stat> - did the file attributes just change?
1607		2454
1608	This watches a filesystem path for attribute changes. That is, it calls	2455	This watches a file system path for attribute changes. That is, it calls
1609	C<stat> regularly (or when the OS says it changed) and sees if it changed	2456	C<stat> on that path in regular intervals (or when the OS says it changed)
1610	compared to the last time, invoking the callback if it did.	2457	and sees if it changed compared to the last time, invoking the callback if
		2458	it did.
1611		2459
1612	The path does not need to exist: changing from "path exists" to "path does	2460	The path does not need to exist: changing from "path exists" to "path does
1613	not exist" is a status change like any other. The condition "path does	2461	not exist" is a status change like any other. The condition "path does not
1614	not exist" is signified by the C<st_nlink> field being zero (which is	2462	exist" (or more correctly "path cannot be stat'ed") is signified by the
1615	otherwise always forced to be at least one) and all the other fields of	2463	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	2464	least one) and all the other fields of the stat buffer having unspecified
		2465	contents.
1617		2466
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	2467	The path I<must not> end in a slash or contain special components such as
		2468	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1619	relative and your working directory changes, the behaviour is undefined.	2469	your working directory changes, then the behaviour is undefined.
1620		2470
1621	Since there is no standard to do this, the portable implementation simply	2471	Since there is no portable change notification interface available, the
1622	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2472	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	2473	to see if it changed somehow. You can specify a recommended polling
1624	a polling interval of C<0> (highly recommended!) then a I<suitable,	2474	interval for this case. If you specify a polling interval of C<0> (highly
1625	unspecified default> value will be used (which you can expect to be around	2475	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	2476	(which you can expect to be around five seconds, although this might
1627	impose a minimum interval which is currently around C<0.1>, but thats	2477	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	2478	currently around C<0.1>, but that's usually overkill.
1629		2479
1630	This watcher type is not meant for massive numbers of stat watchers,	2480	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	2481	as even with OS-supported change notifications, this can be
1632	resource-intensive.	2482	resource-intensive.
1633		2483
1634	At the time of this writing, only the Linux inotify interface is	2484	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	2485	is the Linux inotify interface (implementing kqueue support is left as an
1636	reader, note, however, that the author sees no way of implementing ev_stat	2486	exercise for the reader. Note, however, that the author sees no way of
1637	semantics with kqueue). Inotify will be used to give hints only and should	2487	implementing C<ev_stat> semantics with kqueue, except as a hint).
1638	not change the semantics of C<ev_stat> watchers, which means that libev
1639	sometimes needs to fall back to regular polling again even with inotify,
1640	but changes are usually detected immediately, and if the file exists there
1641	will be no polling.
1642		2488
1643	=head3 ABI Issues (Largefile Support)	2489	=head3 ABI Issues (Largefile Support)
1644		2490
1645	Libev by default (unless the user overrides this) uses the default	2491	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	2492	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	2493	support disabled by default, you get the 32 bit version of the stat
1648	structure. When using the library from programs that change the ABI to	2494	structure. When using the library from programs that change the ABI to
1649	use 64 bit file offsets the programs will fail. In that case you have to	2495	use 64 bit file offsets the programs will fail. In that case you have to
1650	compile libev with the same flags to get binary compatibility. This is	2496	compile libev with the same flags to get binary compatibility. This is
1651	obviously the case with any flags that change the ABI, but the problem is	2497	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	2498	most noticeably displayed with ev_stat and large file support.
1653		2499
1654	=head3 Inotify	2500	The solution for this is to lobby your distribution maker to make large
		2501	file interfaces available by default (as e.g. FreeBSD does) and not
		2502	optional. Libev cannot simply switch on large file support because it has
		2503	to exchange stat structures with application programs compiled using the
		2504	default compilation environment.
1655		2505
		2506	=head3 Inotify and Kqueue
		2507
1656	When C<inotify (7)> support has been compiled into libev (generally only	2508	When C<inotify (7)> support has been compiled into libev and present at
1657	available on Linux) and present at runtime, it will be used to speed up	2509	runtime, it will be used to speed up change detection where possible. The
1658	change detection where possible. The inotify descriptor will be created lazily	2510	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	2511	watcher is being started.
1660		2512
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	2513	Inotify presence does not change the semantics of C<ev_stat> watchers
1662	except that changes might be detected earlier, and in some cases, to avoid	2514	except that changes might be detected earlier, and in some cases, to avoid
1663	making regular C<stat> calls. Even in the presence of inotify support	2515	making regular C<stat> calls. Even in the presence of inotify support
1664	there are many cases where libev has to resort to regular C<stat> polling.	2516	there are many cases where libev has to resort to regular C<stat> polling,
		2517	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2518	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2519	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2520	xfs are fully working) libev usually gets away without polling.
1665		2521
1666	(There is no support for kqueue, as apparently it cannot be used to	2522	There is no support for kqueue, as apparently it cannot be used to
1667	implement this functionality, due to the requirement of having a file	2523	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2524	descriptor open on the object at all times, and detecting renames, unlinks
		2525	etc. is difficult.
		2526
		2527	=head3 C<stat ()> is a synchronous operation
		2528
		2529	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2530	the process. The exception are C<ev_stat> watchers - those call C<stat
		2531	()>, which is a synchronous operation.
		2532
		2533	For local paths, this usually doesn't matter: unless the system is very
		2534	busy or the intervals between stat's are large, a stat call will be fast,
		2535	as the path data is usually in memory already (except when starting the
		2536	watcher).
		2537
		2538	For networked file systems, calling C<stat ()> can block an indefinite
		2539	time due to network issues, and even under good conditions, a stat call
		2540	often takes multiple milliseconds.
		2541
		2542	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2543	paths, although this is fully supported by libev.
1669		2544
1670	=head3 The special problem of stat time resolution	2545	=head3 The special problem of stat time resolution
1671		2546
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2547	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2548	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2549	still only support whole seconds.
1675		2550
1676	That means that, if the time is the only thing that changes, you can	2551	That means that, if the time is the only thing that changes, you can
1677	easily miss updates: on the first update, C<ev_stat> detects a change and	2552	easily miss updates: on the first update, C<ev_stat> detects a change and
1678	calls your callback, which does something. When there is another update	2553	calls your callback, which does something. When there is another update
1679	within the same second, C<ev_stat> will be unable to detect it as the stat	2554	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2555	stat data does change in other ways (e.g. file size).
1681		2556
1682	The solution to this is to delay acting on a change for slightly more	2557	The solution to this is to delay acting on a change for slightly more
1683	than a second (or till slightly after the next full second boundary), using	2558	than a second (or till slightly after the next full second boundary), using
1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2559	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2560	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2580	C<path>. The C<interval> is a hint on how quickly a change is expected to
1706	be detected and should normally be specified as C<0> to let libev choose	2581	be detected and should normally be specified as C<0> to let libev choose
1707	a suitable value. The memory pointed to by C<path> must point to the same	2582	a suitable value. The memory pointed to by C<path> must point to the same
1708	path for as long as the watcher is active.	2583	path for as long as the watcher is active.
1709		2584
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2585	The callback will receive an C<EV_STAT> event when a change was detected,
1711	to the attributes at the time the watcher was started (or the last change	2586	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2587	last change was detected).
1713		2588
1714	=item ev_stat_stat (loop, ev_stat *)	2589	=item ev_stat_stat (loop, ev_stat *)
1715		2590
1716	Updates the stat buffer immediately with new values. If you change the	2591	Updates the stat buffer immediately with new values. If you change the
1717	watched path in your callback, you could call this function to avoid	2592	watched path in your callback, you could call this function to avoid
…		…
1738		2613
1739	The specified interval.	2614	The specified interval.
1740		2615
1741	=item const char *path [read-only]	2616	=item const char *path [read-only]
1742		2617
1743	The filesystem path that is being watched.	2618	The file system path that is being watched.
1744		2619
1745	=back	2620	=back
1746		2621
1747	=head3 Examples	2622	=head3 Examples
1748		2623
1749	Example: Watch C</etc/passwd> for attribute changes.	2624	Example: Watch C</etc/passwd> for attribute changes.
1750		2625
1751	static void	2626	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2627	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2628	{
1754	/* /etc/passwd changed in some way */	2629	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2630	if (w->attr.st_nlink)
1756	{	2631	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2632	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2633	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2634	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2635	}
1761	else	2636	else
1762	/* you shalt not abuse printf for puts */	2637	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2638	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2639	"if this is windows, they already arrived\n");
1765	}	2640	}
1766		2641
1767	...	2642	...
1768	ev_stat passwd;	2643	ev_stat passwd;
1769		2644
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2645	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2646	ev_stat_start (loop, &passwd);
1772		2647
1773	Example: Like above, but additionally use a one-second delay so we do not	2648	Example: Like above, but additionally use a one-second delay so we do not
1774	miss updates (however, frequent updates will delay processing, too, so	2649	miss updates (however, frequent updates will delay processing, too, so
1775	one might do the work both on C<ev_stat> callback invocation I<and> on	2650	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2651	C<ev_timer> callback invocation).
1777		2652
1778	static ev_stat passwd;	2653	static ev_stat passwd;
1779	static ev_timer timer;	2654	static ev_timer timer;
1780		2655
1781	static void	2656	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2657	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2658	{
1784	ev_timer_stop (EV_A_ w);	2659	ev_timer_stop (EV_A_ w);
1785		2660
1786	/* now it's one second after the most recent passwd change */	2661	/* now it's one second after the most recent passwd change */
1787	}	2662	}
1788		2663
1789	static void	2664	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2665	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2666	{
1792	/* reset the one-second timer */	2667	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2668	ev_timer_again (EV_A_ &timer);
1794	}	2669	}
1795		2670
1796	...	2671	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2672	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2673	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2674	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2675
1801		2676
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2677	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2678
1804	Idle watchers trigger events when no other events of the same or higher	2679	Idle watchers trigger events when no other events of the same or higher
1805	priority are pending (prepare, check and other idle watchers do not	2680	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2681	as receiving "events").
1807		2682
1808	That is, as long as your process is busy handling sockets or timeouts	2683	That is, as long as your process is busy handling sockets or timeouts
1809	(or even signals, imagine) of the same or higher priority it will not be	2684	(or even signals, imagine) of the same or higher priority it will not be
1810	triggered. But when your process is idle (or only lower-priority watchers	2685	triggered. But when your process is idle (or only lower-priority watchers
1811	are pending), the idle watchers are being called once per event loop	2686	are pending), the idle watchers are being called once per event loop
…		…
1822		2697
1823	=head3 Watcher-Specific Functions and Data Members	2698	=head3 Watcher-Specific Functions and Data Members
1824		2699
1825	=over 4	2700	=over 4
1826		2701
1827	=item ev_idle_init (ev_signal *, callback)	2702	=item ev_idle_init (ev_idle *, callback)
1828		2703
1829	Initialises and configures the idle watcher - it has no parameters of any	2704	Initialises and configures the idle watcher - it has no parameters of any
1830	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2705	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1831	believe me.	2706	believe me.
1832		2707
…		…
1835	=head3 Examples	2710	=head3 Examples
1836		2711
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2712	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2713	callback, free it. Also, use no error checking, as usual.
1839		2714
1840	static void	2715	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2716	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2717	{
1843	free (w);	2718	free (w);
1844	// now do something you wanted to do when the program has	2719	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2720	// no longer anything immediate to do.
1846	}	2721	}
1847		2722
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2723	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2724	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2725	ev_idle_start (loop, idle_watcher);
1851		2726
1852		2727
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2728	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2729
1855	Prepare and check watchers are usually (but not always) used in tandem:	2730	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2731	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2732	afterwards.
1858		2733
1859	You I<must not> call C<ev_loop> or similar functions that enter	2734	You I<must not> call C<ev_run> or similar functions that enter
1860	the current event loop from either C<ev_prepare> or C<ev_check>	2735	the current event loop from either C<ev_prepare> or C<ev_check>
1861	watchers. Other loops than the current one are fine, however. The	2736	watchers. Other loops than the current one are fine, however. The
1862	rationale behind this is that you do not need to check for recursion in	2737	rationale behind this is that you do not need to check for recursion in
1863	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2738	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1864	C<ev_check> so if you have one watcher of each kind they will always be	2739	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2740	called in pairs bracketing the blocking call.
1866		2741
1867	Their main purpose is to integrate other event mechanisms into libev and	2742	Their main purpose is to integrate other event mechanisms into libev and
1868	their use is somewhat advanced. This could be used, for example, to track	2743	their use is somewhat advanced. They could be used, for example, to track
1869	variable changes, implement your own watchers, integrate net-snmp or a	2744	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2745	coroutine library and lots more. They are also occasionally useful if
1871	you cache some data and want to flush it before blocking (for example,	2746	you cache some data and want to flush it before blocking (for example,
1872	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2747	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2748	watcher).
1874		2749
1875	This is done by examining in each prepare call which file descriptors need	2750	This is done by examining in each prepare call which file descriptors
1876	to be watched by the other library, registering C<ev_io> watchers for	2751	need to be watched by the other library, registering C<ev_io> watchers
1877	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2752	for them and starting an C<ev_timer> watcher for any timeouts (many
1878	provide just this functionality). Then, in the check watcher you check for	2753	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2754	you check for any events that occurred (by checking the pending status
1880	and stopping them) and call back into the library. The I/O and timer	2755	of all watchers and stopping them) and call back into the library. The
1881	callbacks will never actually be called (but must be valid nevertheless,	2756	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2757	nevertheless, because you never know, you know?).
1883		2758
1884	As another example, the Perl Coro module uses these hooks to integrate	2759	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2760	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2761	during each prepare and only letting the process block if no coroutines
1887	are ready to run (it's actually more complicated: it only runs coroutines	2762	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1890	loop from blocking if lower-priority coroutines are active, thus mapping	2765	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2766	low-priority coroutines to idle/background tasks).
1892		2767
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2768	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1894	priority, to ensure that they are being run before any other watchers	2769	priority, to ensure that they are being run before any other watchers
		2770	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2771
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2772	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1896	too) should not activate ("feed") events into libev. While libev fully	2773	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2774	might get executed before other C<ev_check> watchers did their job. As
1898	did their job. As C<ev_check> watchers are often used to embed other	2775	C<ev_check> watchers are often used to embed other (non-libev) event
1899	(non-libev) event loops those other event loops might be in an unusable	2776	loops those other event loops might be in an unusable state until their
1900	state until their C<ev_check> watcher ran (always remind yourself to	2777	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2778	others).
1902		2779
1903	=head3 Watcher-Specific Functions and Data Members	2780	=head3 Watcher-Specific Functions and Data Members
1904		2781
1905	=over 4	2782	=over 4
1906		2783
…		…
1908		2785
1909	=item ev_check_init (ev_check *, callback)	2786	=item ev_check_init (ev_check *, callback)
1910		2787
1911	Initialises and configures the prepare or check watcher - they have no	2788	Initialises and configures the prepare or check watcher - they have no
1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2789	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1913	macros, but using them is utterly, utterly and completely pointless.	2790	macros, but using them is utterly, utterly, utterly and completely
		2791	pointless.
1914		2792
1915	=back	2793	=back
1916		2794
1917	=head3 Examples	2795	=head3 Examples
1918		2796
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2805	and in a check watcher, destroy them and call into libadns. What follows
1928	is pseudo-code only of course. This requires you to either use a low	2806	is pseudo-code only of course. This requires you to either use a low
1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2807	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1930	the callbacks for the IO/timeout watchers might not have been called yet.	2808	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2809
1932	static ev_io iow [nfd];	2810	static ev_io iow [nfd];
1933	static ev_timer tw;	2811	static ev_timer tw;
1934		2812
1935	static void	2813	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2814	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2815	{
1938	}	2816	}
1939		2817
1940	// create io watchers for each fd and a timer before blocking	2818	// create io watchers for each fd and a timer before blocking
1941	static void	2819	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2820	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2821	{
1944	int timeout = 3600000;	2822	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2823	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2824	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2825	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2826
1949	/* the callback is illegal, but won't be called as we stop during check */	2827	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2828	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1951	ev_timer_start (loop, &tw);	2829	ev_timer_start (loop, &tw);
1952		2830
1953	// create one ev_io per pollfd	2831	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2832	for (int i = 0; i < nfd; ++i)
1955	{	2833	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2834	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2835	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2836	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2837
1960	fds [i].revents = 0;	2838	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2839	ev_io_start (loop, iow + i);
1962	}	2840	}
1963	}	2841	}
1964		2842
1965	// stop all watchers after blocking	2843	// stop all watchers after blocking
1966	static void	2844	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2845	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2846	{
1969	ev_timer_stop (loop, &tw);	2847	ev_timer_stop (loop, &tw);
1970		2848
1971	for (int i = 0; i < nfd; ++i)	2849	for (int i = 0; i < nfd; ++i)
1972	{	2850	{
1973	// set the relevant poll flags	2851	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2852	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2853	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2854	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2855	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2856	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2857
1980	// now stop the watcher	2858	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2859	ev_io_stop (loop, iow + i);
1982	}	2860	}
1983		2861
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2862	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2863	}
1986		2864
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2865	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1988	in the prepare watcher and would dispose of the check watcher.	2866	in the prepare watcher and would dispose of the check watcher.
1989		2867
1990	Method 3: If the module to be embedded supports explicit event	2868	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2869	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2870	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2871
1994	static void	2872	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2873	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2874	{
1997	adns_state ads = (adns_state)w->data;	2875	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2876	update_now (EV_A);
1999		2877
2000	adns_processtimeouts (ads, &tv_now);	2878	adns_processtimeouts (ads, &tv_now);
2001	}	2879	}
2002		2880
2003	static void	2881	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2882	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2883	{
2006	adns_state ads = (adns_state)w->data;	2884	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2885	update_now (EV_A);
2008		2886
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2887	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2888	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2889	}
2012		2890
2013	// do not ever call adns_afterpoll	2891	// do not ever call adns_afterpoll
2014		2892
2015	Method 4: Do not use a prepare or check watcher because the module you	2893	Method 4: Do not use a prepare or check watcher because the module you
2016	want to embed is too inflexible to support it. Instead, youc na override	2894	want to embed is not flexible enough to support it. Instead, you can
2017	their poll function. The drawback with this solution is that the main	2895	override their poll function. The drawback with this solution is that the
2018	loop is now no longer controllable by EV. The C<Glib::EV> module does	2896	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2897	this approach, effectively embedding EV as a client into the horrible
		2898	libglib event loop.
2020		2899
2021	static gint	2900	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2901	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2902	{
2024	int got_events = 0;	2903	int got_events = 0;
2025		2904
2026	for (n = 0; n < nfds; ++n)	2905	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2906	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2907
2029	if (timeout >= 0)	2908	if (timeout >= 0)
2030	// create/start timer	2909	// create/start timer
2031		2910
2032	// poll	2911	// poll
2033	ev_loop (EV_A_ 0);	2912	ev_run (EV_A_ 0);
2034		2913
2035	// stop timer again	2914	// stop timer again
2036	if (timeout >= 0)	2915	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2916	ev_timer_stop (EV_A_ &to);
2038		2917
2039	// stop io watchers again - their callbacks should have set	2918	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2919	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2920	ev_io_stop (EV_A_ iow [n]);
2042		2921
2043	return got_events;	2922	return got_events;
2044	}	2923	}
2045		2924
2046		2925
2047	=head2 C<ev_embed> - when one backend isn't enough...	2926	=head2 C<ev_embed> - when one backend isn't enough...
2048		2927
2049	This is a rather advanced watcher type that lets you embed one event loop	2928	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2934	prioritise I/O.
2056		2935
2057	As an example for a bug workaround, the kqueue backend might only support	2936	As an example for a bug workaround, the kqueue backend might only support
2058	sockets on some platform, so it is unusable as generic backend, but you	2937	sockets on some platform, so it is unusable as generic backend, but you
2059	still want to make use of it because you have many sockets and it scales	2938	still want to make use of it because you have many sockets and it scales
2060	so nicely. In this case, you would create a kqueue-based loop and embed it	2939	so nicely. In this case, you would create a kqueue-based loop and embed
2061	into your default loop (which might use e.g. poll). Overall operation will	2940	it into your default loop (which might use e.g. poll). Overall operation
2062	be a bit slower because first libev has to poll and then call kevent, but	2941	will be a bit slower because first libev has to call C<poll> and then
2063	at least you can use both at what they are best.	2942	C<kevent>, but at least you can use both mechanisms for what they are
		2943	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2944
2065	As for prioritising I/O: rarely you have the case where some fds have	2945	As for prioritising I/O: under rare circumstances you have the case where
2066	to be watched and handled very quickly (with low latency), and even	2946	some fds have to be watched and handled very quickly (with low latency),
2067	priorities and idle watchers might have too much overhead. In this case	2947	and even priorities and idle watchers might have too much overhead. In
2068	you would put all the high priority stuff in one loop and all the rest in	2948	this case you would put all the high priority stuff in one loop and all
2069	a second one, and embed the second one in the first.	2949	the rest in a second one, and embed the second one in the first.
2070		2950
2071	As long as the watcher is active, the callback will be invoked every time	2951	As long as the watcher is active, the callback will be invoked every
2072	there might be events pending in the embedded loop. The callback must then	2952	time there might be events pending in the embedded loop. The callback
2073	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2953	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2074	their callbacks (you could also start an idle watcher to give the embedded	2954	sweep and invoke their callbacks (the callback doesn't need to invoke the
2075	loop strictly lower priority for example). You can also set the callback	2955	C<ev_embed_sweep> function directly, it could also start an idle watcher
2076	to C<0>, in which case the embed watcher will automatically execute the	2956	to give the embedded loop strictly lower priority for example).
2077	embedded loop sweep.
2078		2957
2079	As long as the watcher is started it will automatically handle events. The	2958	You can also set the callback to C<0>, in which case the embed watcher
2080	callback will be invoked whenever some events have been handled. You can	2959	will automatically execute the embedded loop sweep whenever necessary.
2081	set the callback to C<0> to avoid having to specify one if you are not
2082	interested in that.
2083		2960
2084	Also, there have not currently been made special provisions for forking:	2961	Fork detection will be handled transparently while the C<ev_embed> watcher
2085	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2962	is active, i.e., the embedded loop will automatically be forked when the
2086	but you will also have to stop and restart any C<ev_embed> watchers	2963	embedding loop forks. In other cases, the user is responsible for calling
2087	yourself.	2964	C<ev_loop_fork> on the embedded loop.
2088		2965
2089	Unfortunately, not all backends are embeddable, only the ones returned by	2966	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2967	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	2968	portable one.
2092		2969
2093	So when you want to use this feature you will always have to be prepared	2970	So when you want to use this feature you will always have to be prepared
2094	that you cannot get an embeddable loop. The recommended way to get around	2971	that you cannot get an embeddable loop. The recommended way to get around
2095	this is to have a separate variables for your embeddable loop, try to	2972	this is to have a separate variables for your embeddable loop, try to
2096	create it, and if that fails, use the normal loop for everything.	2973	create it, and if that fails, use the normal loop for everything.
2097		2974
		2975	=head3 C<ev_embed> and fork
		2976
		2977	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2978	automatically be applied to the embedded loop as well, so no special
		2979	fork handling is required in that case. When the watcher is not running,
		2980	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2981	as applicable.
		2982
2098	=head3 Watcher-Specific Functions and Data Members	2983	=head3 Watcher-Specific Functions and Data Members
2099		2984
2100	=over 4	2985	=over 4
2101		2986
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2987	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		2990
2106	Configures the watcher to embed the given loop, which must be	2991	Configures the watcher to embed the given loop, which must be
2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2992	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2108	invoked automatically, otherwise it is the responsibility of the callback	2993	invoked automatically, otherwise it is the responsibility of the callback
2109	to invoke it (it will continue to be called until the sweep has been done,	2994	to invoke it (it will continue to be called until the sweep has been done,
2110	if you do not want thta, you need to temporarily stop the embed watcher).	2995	if you do not want that, you need to temporarily stop the embed watcher).
2111		2996
2112	=item ev_embed_sweep (loop, ev_embed *)	2997	=item ev_embed_sweep (loop, ev_embed *)
2113		2998
2114	Make a single, non-blocking sweep over the embedded loop. This works	2999	Make a single, non-blocking sweep over the embedded loop. This works
2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3000	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2116	apropriate way for embedded loops.	3001	appropriate way for embedded loops.
2117		3002
2118	=item struct ev_loop *other [read-only]	3003	=item struct ev_loop *other [read-only]
2119		3004
2120	The embedded event loop.	3005	The embedded event loop.
2121		3006
…		…
2123		3008
2124	=head3 Examples	3009	=head3 Examples
2125		3010
2126	Example: Try to get an embeddable event loop and embed it into the default	3011	Example: Try to get an embeddable event loop and embed it into the default
2127	event loop. If that is not possible, use the default loop. The default	3012	event loop. If that is not possible, use the default loop. The default
2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3013	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3014	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	3015	used).
2131		3016
2132	struct ev_loop *loop_hi = ev_default_init (0);	3017	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	3018	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	3019	ev_embed embed;
2135		3020
2136	// see if there is a chance of getting one that works	3021	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	3022	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3023	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3024	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	3025	: 0;
2141		3026
2142	// if we got one, then embed it, otherwise default to loop_hi	3027	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	3028	if (loop_lo)
2144	{	3029	{
2145	ev_embed_init (&embed, 0, loop_lo);	3030	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	3031	ev_embed_start (loop_hi, &embed);
2147	}	3032	}
2148	else	3033	else
2149	loop_lo = loop_hi;	3034	loop_lo = loop_hi;
2150		3035
2151	Example: Check if kqueue is available but not recommended and create	3036	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	3037	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	3038	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3039	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		3040
2156	struct ev_loop *loop = ev_default_init (0);	3041	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	3042	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	3043	ev_embed embed;
2159		3044
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3045	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3046	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	3047	{
2163	ev_embed_init (&embed, 0, loop_socket);	3048	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	3049	ev_embed_start (loop, &embed);
2165	}	3050	}
2166		3051
2167	if (!loop_socket)	3052	if (!loop_socket)
2168	loop_socket = loop;	3053	loop_socket = loop;
2169		3054
2170	// now use loop_socket for all sockets, and loop for everything else	3055	// now use loop_socket for all sockets, and loop for everything else
2171		3056
2172		3057
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3058	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		3059
2175	Fork watchers are called when a C<fork ()> was detected (usually because	3060	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2178	event loop blocks next and before C<ev_check> watchers are being called,	3063	event loop blocks next and before C<ev_check> watchers are being called,
2179	and only in the child after the fork. If whoever good citizen calling	3064	and only in the child after the fork. If whoever good citizen calling
2180	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3065	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2181	handlers will be invoked, too, of course.	3066	handlers will be invoked, too, of course.
2182		3067
		3068	=head3 The special problem of life after fork - how is it possible?
		3069
		3070	Most uses of C<fork()> consist of forking, then some simple calls to set
		3071	up/change the process environment, followed by a call to C<exec()>. This
		3072	sequence should be handled by libev without any problems.
		3073
		3074	This changes when the application actually wants to do event handling
		3075	in the child, or both parent in child, in effect "continuing" after the
		3076	fork.
		3077
		3078	The default mode of operation (for libev, with application help to detect
		3079	forks) is to duplicate all the state in the child, as would be expected
		3080	when I<either> the parent I<or> the child process continues.
		3081
		3082	When both processes want to continue using libev, then this is usually the
		3083	wrong result. In that case, usually one process (typically the parent) is
		3084	supposed to continue with all watchers in place as before, while the other
		3085	process typically wants to start fresh, i.e. without any active watchers.
		3086
		3087	The cleanest and most efficient way to achieve that with libev is to
		3088	simply create a new event loop, which of course will be "empty", and
		3089	use that for new watchers. This has the advantage of not touching more
		3090	memory than necessary, and thus avoiding the copy-on-write, and the
		3091	disadvantage of having to use multiple event loops (which do not support
		3092	signal watchers).
		3093
		3094	When this is not possible, or you want to use the default loop for
		3095	other reasons, then in the process that wants to start "fresh", call
		3096	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3097	Destroying the default loop will "orphan" (not stop) all registered
		3098	watchers, so you have to be careful not to execute code that modifies
		3099	those watchers. Note also that in that case, you have to re-register any
		3100	signal watchers.
		3101
2183	=head3 Watcher-Specific Functions and Data Members	3102	=head3 Watcher-Specific Functions and Data Members
2184		3103
2185	=over 4	3104	=over 4
2186		3105
2187	=item ev_fork_init (ev_signal *, callback)	3106	=item ev_fork_init (ev_fork *, callback)
2188		3107
2189	Initialises and configures the fork watcher - it has no parameters of any	3108	Initialises and configures the fork watcher - it has no parameters of any
2190	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3109	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2191	believe me.	3110	really.
2192		3111
2193	=back	3112	=back
2194		3113
2195		3114
		3115	=head2 C<ev_cleanup> - even the best things end
		3116
		3117	Cleanup watchers are called just before the event loop is being destroyed
		3118	by a call to C<ev_loop_destroy>.
		3119
		3120	While there is no guarantee that the event loop gets destroyed, cleanup
		3121	watchers provide a convenient method to install cleanup hooks for your
		3122	program, worker threads and so on - you just to make sure to destroy the
		3123	loop when you want them to be invoked.
		3124
		3125	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3126	all other watchers, they do not keep a reference to the event loop (which
		3127	makes a lot of sense if you think about it). Like all other watchers, you
		3128	can call libev functions in the callback, except C<ev_cleanup_start>.
		3129
		3130	=head3 Watcher-Specific Functions and Data Members
		3131
		3132	=over 4
		3133
		3134	=item ev_cleanup_init (ev_cleanup *, callback)
		3135
		3136	Initialises and configures the cleanup watcher - it has no parameters of
		3137	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3138	pointless, I assure you.
		3139
		3140	=back
		3141
		3142	Example: Register an atexit handler to destroy the default loop, so any
		3143	cleanup functions are called.
		3144
		3145	static void
		3146	program_exits (void)
		3147	{
		3148	ev_loop_destroy (EV_DEFAULT_UC);
		3149	}
		3150
		3151	...
		3152	atexit (program_exits);
		3153
		3154
2196	=head2 C<ev_async> - how to wake up another event loop	3155	=head2 C<ev_async> - how to wake up an event loop
2197		3156
2198	In general, you cannot use an C<ev_loop> from multiple threads or other	3157	In general, you cannot use an C<ev_run> from multiple threads or other
2199	asynchronous sources such as signal handlers (as opposed to multiple event	3158	asynchronous sources such as signal handlers (as opposed to multiple event
2200	loops - those are of course safe to use in different threads).	3159	loops - those are of course safe to use in different threads).
2201		3160
2202	Sometimes, however, you need to wake up another event loop you do not	3161	Sometimes, however, you need to wake up an event loop you do not control,
2203	control, for example because it belongs to another thread. This is what	3162	for example because it belongs to another thread. This is what C<ev_async>
2204	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3163	watchers do: as long as the C<ev_async> watcher is active, you can signal
2205	can signal it by calling C<ev_async_send>, which is thread- and signal	3164	it by calling C<ev_async_send>, which is thread- and signal safe.
2206	safe.
2207		3165
2208	This functionality is very similar to C<ev_signal> watchers, as signals,	3166	This functionality is very similar to C<ev_signal> watchers, as signals,
2209	too, are asynchronous in nature, and signals, too, will be compressed	3167	too, are asynchronous in nature, and signals, too, will be compressed
2210	(i.e. the number of callback invocations may be less than the number of	3168	(i.e. the number of callback invocations may be less than the number of
2211	C<ev_async_sent> calls).	3169	C<ev_async_sent> calls).
…		…
2216	=head3 Queueing	3174	=head3 Queueing
2217		3175
2218	C<ev_async> does not support queueing of data in any way. The reason	3176	C<ev_async> does not support queueing of data in any way. The reason
2219	is that the author does not know of a simple (or any) algorithm for a	3177	is that the author does not know of a simple (or any) algorithm for a
2220	multiple-writer-single-reader queue that works in all cases and doesn't	3178	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	3179	need elaborate support such as pthreads or unportable memory access
		3180	semantics.
2222		3181
2223	That means that if you want to queue data, you have to provide your own	3182	That means that if you want to queue data, you have to provide your own
2224	queue. But at least I can tell you would implement locking around your	3183	queue. But at least I can tell you how to implement locking around your
2225	queue:	3184	queue:
2226		3185
2227	=over 4	3186	=over 4
2228		3187
2229	=item queueing from a signal handler context	3188	=item queueing from a signal handler context
2230		3189
2231	To implement race-free queueing, you simply add to the queue in the signal	3190	To implement race-free queueing, you simply add to the queue in the signal
2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3191	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	3192	an example that does that for some fictitious SIGUSR1 handler:
2234		3193
2235	static ev_async mysig;	3194	static ev_async mysig;
2236		3195
2237	static void	3196	static void
2238	sigusr1_handler (void)	3197	sigusr1_handler (void)
…		…
2304	=over 4	3263	=over 4
2305		3264
2306	=item ev_async_init (ev_async *, callback)	3265	=item ev_async_init (ev_async *, callback)
2307		3266
2308	Initialises and configures the async watcher - it has no parameters of any	3267	Initialises and configures the async watcher - it has no parameters of any
2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3268	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	3269	trust me.
2311		3270
2312	=item ev_async_send (loop, ev_async *)	3271	=item ev_async_send (loop, ev_async *)
2313		3272
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3273	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3274	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2316	C<ev_feed_event>, this call is safe to do in other threads, signal or	3275	C<ev_feed_event>, this call is safe to do from other threads, signal or
2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3276	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2318	section below on what exactly this means).	3277	section below on what exactly this means).
2319		3278
		3279	Note that, as with other watchers in libev, multiple events might get
		3280	compressed into a single callback invocation (another way to look at this
		3281	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3282	reset when the event loop detects that).
		3283
2320	This call incurs the overhead of a syscall only once per loop iteration,	3284	This call incurs the overhead of a system call only once per event loop
2321	so while the overhead might be noticable, it doesn't apply to repeated	3285	iteration, so while the overhead might be noticeable, it doesn't apply to
2322	calls to C<ev_async_send>.	3286	repeated calls to C<ev_async_send> for the same event loop.
2323		3287
2324	=item bool = ev_async_pending (ev_async *)	3288	=item bool = ev_async_pending (ev_async *)
2325		3289
2326	Returns a non-zero value when C<ev_async_send> has been called on the	3290	Returns a non-zero value when C<ev_async_send> has been called on the
2327	watcher but the event has not yet been processed (or even noted) by the	3291	watcher but the event has not yet been processed (or even noted) by the
2328	event loop.	3292	event loop.
2329		3293
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3294	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2331	the loop iterates next and checks for the watcher to have become active,	3295	the loop iterates next and checks for the watcher to have become active,
2332	it will reset the flag again. C<ev_async_pending> can be used to very	3296	it will reset the flag again. C<ev_async_pending> can be used to very
2333	quickly check wether invoking the loop might be a good idea.	3297	quickly check whether invoking the loop might be a good idea.
2334		3298
2335	Not that this does I<not> check wether the watcher itself is pending, only	3299	Not that this does I<not> check whether the watcher itself is pending,
2336	wether it has been requested to make this watcher pending.	3300	only whether it has been requested to make this watcher pending: there
		3301	is a time window between the event loop checking and resetting the async
		3302	notification, and the callback being invoked.
2337		3303
2338	=back	3304	=back
2339		3305
2340		3306
2341	=head1 OTHER FUNCTIONS	3307	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	3311	=over 4
2346		3312
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3313	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		3314
2349	This function combines a simple timer and an I/O watcher, calls your	3315	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	3316	callback on whichever event happens first and automatically stops both
2351	watchers. This is useful if you want to wait for a single event on an fd	3317	watchers. This is useful if you want to wait for a single event on an fd
2352	or timeout without having to allocate/configure/start/stop/free one or	3318	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	3319	more watchers yourself.
2354		3320
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	3321	If C<fd> is less than 0, then no I/O watcher will be started and the
2356	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3322	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	3323	the given C<fd> and C<events> set will be created and started.
2358		3324
2359	If C<timeout> is less than 0, then no timeout watcher will be	3325	If C<timeout> is less than 0, then no timeout watcher will be
2360	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3326	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2361	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3327	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		3328
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3329	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2365	passed an C<revents> set like normal event callbacks (a combination of	3330	passed an C<revents> set like normal event callbacks (a combination of
2366	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2367	value passed to C<ev_once>:	3332	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3333	a timeout and an io event at the same time - you probably should give io
		3334	events precedence.
2368		3335
		3336	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3337
2369	static void stdin_ready (int revents, void *arg)	3338	static void stdin_ready (int revents, void *arg)
2370	{	3339	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	3340	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	3341	/* stdin might have data for us, joy! */;
		3342	else if (revents & EV_TIMER)
		3343	/* doh, nothing entered */;
2375	}	3344	}
2376		3345
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		3347
2379	=item ev_feed_event (ev_loop *, watcher *, int revents)
2380
2381	Feeds the given event set into the event loop, as if the specified event
2382	had happened for the specified watcher (which must be a pointer to an
2383	initialised but not necessarily started event watcher).
2384
2385	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3348	=item ev_feed_fd_event (loop, int fd, int revents)
2386		3349
2387	Feed an event on the given fd, as if a file descriptor backend detected	3350	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	3351	the given events it.
2389		3352
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	3353	=item ev_feed_signal_event (loop, int signum)
2391		3354
2392	Feed an event as if the given signal occured (C<loop> must be the default	3355	Feed an event as if the given signal occurred (C<loop> must be the default
2393	loop!).	3356	loop!).
2394		3357
2395	=back	3358	=back
2396		3359
2397		3360
…		…
2426	=back	3389	=back
2427		3390
2428	=head1 C++ SUPPORT	3391	=head1 C++ SUPPORT
2429		3392
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3393	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2431	you to use some convinience methods to start/stop watchers and also change	3394	you to use some convenience methods to start/stop watchers and also change
2432	the callback model to a model using method callbacks on objects.	3395	the callback model to a model using method callbacks on objects.
2433		3396
2434	To use it,	3397	To use it,
2435		3398
2436	#include <ev++.h>	3399	#include <ev++.h>
2437		3400
2438	This automatically includes F<ev.h> and puts all of its definitions (many	3401	This automatically includes F<ev.h> and puts all of its definitions (many
2439	of them macros) into the global namespace. All C++ specific things are	3402	of them macros) into the global namespace. All C++ specific things are
2440	put into the C<ev> namespace. It should support all the same embedding	3403	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3404	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2475		3438
2476	=over 4	3439	=over 4
2477		3440
2478	=item ev::TYPE::TYPE ()	3441	=item ev::TYPE::TYPE ()
2479		3442
2480	=item ev::TYPE::TYPE (struct ev_loop *)	3443	=item ev::TYPE::TYPE (loop)
2481		3444
2482	=item ev::TYPE::~TYPE	3445	=item ev::TYPE::~TYPE
2483		3446
2484	The constructor (optionally) takes an event loop to associate the watcher	3447	The constructor (optionally) takes an event loop to associate the watcher
2485	with. If it is omitted, it will use C<EV_DEFAULT>.	3448	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2508	your compiler is good :), then the method will be fully inlined into the	3471	your compiler is good :), then the method will be fully inlined into the
2509	thunking function, making it as fast as a direct C callback.	3472	thunking function, making it as fast as a direct C callback.
2510		3473
2511	Example: simple class declaration and watcher initialisation	3474	Example: simple class declaration and watcher initialisation
2512		3475
2513	struct myclass	3476	struct myclass
2514	{	3477	{
2515	void io_cb (ev::io &w, int revents) { }	3478	void io_cb (ev::io &w, int revents) { }
2516	}	3479	}
2517		3480
2518	myclass obj;	3481	myclass obj;
2519	ev::io iow;	3482	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	3483	iow.set <myclass, &myclass::io_cb> (&obj);
		3484
		3485	=item w->set (object *)
		3486
		3487	This is a variation of a method callback - leaving out the method to call
		3488	will default the method to C<operator ()>, which makes it possible to use
		3489	functor objects without having to manually specify the C<operator ()> all
		3490	the time. Incidentally, you can then also leave out the template argument
		3491	list.
		3492
		3493	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3494	int revents)>.
		3495
		3496	See the method-C<set> above for more details.
		3497
		3498	Example: use a functor object as callback.
		3499
		3500	struct myfunctor
		3501	{
		3502	void operator() (ev::io &w, int revents)
		3503	{
		3504	...
		3505	}
		3506	}
		3507
		3508	myfunctor f;
		3509
		3510	ev::io w;
		3511	w.set (&f);
2521		3512
2522	=item w->set<function> (void *data = 0)	3513	=item w->set<function> (void *data = 0)
2523		3514
2524	Also sets a callback, but uses a static method or plain function as	3515	Also sets a callback, but uses a static method or plain function as
2525	callback. The optional C<data> argument will be stored in the watcher's	3516	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		3518
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3519	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		3520
2530	See the method-C<set> above for more details.	3521	See the method-C<set> above for more details.
2531		3522
2532	Example:	3523	Example: Use a plain function as callback.
2533		3524
2534	static void io_cb (ev::io &w, int revents) { }	3525	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	3526	iow.set <io_cb> ();
2536		3527
2537	=item w->set (struct ev_loop *)	3528	=item w->set (loop)
2538		3529
2539	Associates a different C<struct ev_loop> with this watcher. You can only	3530	Associates a different C<struct ev_loop> with this watcher. You can only
2540	do this when the watcher is inactive (and not pending either).	3531	do this when the watcher is inactive (and not pending either).
2541		3532
2542	=item w->set ([args])	3533	=item w->set ([arguments])
2543		3534
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3535	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2545	called at least once. Unlike the C counterpart, an active watcher gets	3536	method or a suitable start method must be called at least once. Unlike the
2546	automatically stopped and restarted when reconfiguring it with this	3537	C counterpart, an active watcher gets automatically stopped and restarted
2547	method.	3538	when reconfiguring it with this method.
2548		3539
2549	=item w->start ()	3540	=item w->start ()
2550		3541
2551	Starts the watcher. Note that there is no C<loop> argument, as the	3542	Starts the watcher. Note that there is no C<loop> argument, as the
2552	constructor already stores the event loop.	3543	constructor already stores the event loop.
2553		3544
		3545	=item w->start ([arguments])
		3546
		3547	Instead of calling C<set> and C<start> methods separately, it is often
		3548	convenient to wrap them in one call. Uses the same type of arguments as
		3549	the configure C<set> method of the watcher.
		3550
2554	=item w->stop ()	3551	=item w->stop ()
2555		3552
2556	Stops the watcher if it is active. Again, no C<loop> argument.	3553	Stops the watcher if it is active. Again, no C<loop> argument.
2557		3554
2558	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3555	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2570		3567
2571	=back	3568	=back
2572		3569
2573	=back	3570	=back
2574		3571
2575	Example: Define a class with an IO and idle watcher, start one of them in	3572	Example: Define a class with two I/O and idle watchers, start the I/O
2576	the constructor.	3573	watchers in the constructor.
2577		3574
2578	class myclass	3575	class myclass
2579	{	3576	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	3577	ev::io io ; void io_cb (ev::io &w, int revents);
		3578	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	3579	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		3580
2583	myclass (int fd)	3581	myclass (int fd)
2584	{	3582	{
2585	io .set <myclass, &myclass::io_cb > (this);	3583	io .set <myclass, &myclass::io_cb > (this);
		3584	io2 .set <myclass, &myclass::io2_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	3585	idle.set <myclass, &myclass::idle_cb> (this);
2587		3586
2588	io.start (fd, ev::READ);	3587	io.set (fd, ev::WRITE); // configure the watcher
		3588	io.start (); // start it whenever convenient
		3589
		3590	io2.start (fd, ev::READ); // set + start in one call
2589	}	3591	}
2590	};	3592	};
2591		3593
2592		3594
2593	=head1 OTHER LANGUAGE BINDINGS	3595	=head1 OTHER LANGUAGE BINDINGS
2594		3596
2595	Libev does not offer other language bindings itself, but bindings for a	3597	Libev does not offer other language bindings itself, but bindings for a
2596	numbe rof languages exist in the form of third-party packages. If you know	3598	number of languages exist in the form of third-party packages. If you know
2597	any interesting language binding in addition to the ones listed here, drop	3599	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	3600	me a note.
2599		3601
2600	=over 4	3602	=over 4
2601		3603
2602	=item Perl	3604	=item Perl
2603		3605
2604	The EV module implements the full libev API and is actually used to test	3606	The EV module implements the full libev API and is actually used to test
2605	libev. EV is developed together with libev. Apart from the EV core module,	3607	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	3608	there are additional modules that implement libev-compatible interfaces
2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3609	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3610	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3611	and C<EV::Glib>).
2609		3612
2610	It can be found and installed via CPAN, its homepage is found at	3613	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	3614	L<http://software.schmorp.de/pkg/EV>.
2612		3615
		3616	=item Python
		3617
		3618	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3619	seems to be quite complete and well-documented.
		3620
2613	=item Ruby	3621	=item Ruby
2614		3622
2615	Tony Arcieri has written a ruby extension that offers access to a subset	3623	Tony Arcieri has written a ruby extension that offers access to a subset
2616	of the libev API and adds filehandle abstractions, asynchronous DNS and	3624	of the libev API and adds file handle abstractions, asynchronous DNS and
2617	more on top of it. It can be found via gem servers. Its homepage is at	3625	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	3626	L<http://rev.rubyforge.org/>.
2619		3627
		3628	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3629	makes rev work even on mingw.
		3630
		3631	=item Haskell
		3632
		3633	A haskell binding to libev is available at
		3634	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3635
2620	=item D	3636	=item D
2621		3637
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3638	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3639	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3640
		3641	=item Ocaml
		3642
		3643	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3644	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3645
		3646	=item Lua
		3647
		3648	Brian Maher has written a partial interface to libev for lua (at the
		3649	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3650	L<http://github.com/brimworks/lua-ev>.
2624		3651
2625	=back	3652	=back
2626		3653
2627		3654
2628	=head1 MACRO MAGIC	3655	=head1 MACRO MAGIC
2629		3656
2630	Libev can be compiled with a variety of options, the most fundamantal	3657	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3658	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	3659	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		3660
2634	To make it easier to write programs that cope with either variant, the	3661	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	3662	following macros are defined:
…		…
2640		3667
2641	This provides the loop I<argument> for functions, if one is required ("ev	3668	This provides the loop I<argument> for functions, if one is required ("ev
2642	loop argument"). The C<EV_A> form is used when this is the sole argument,	3669	loop argument"). The C<EV_A> form is used when this is the sole argument,
2643	C<EV_A_> is used when other arguments are following. Example:	3670	C<EV_A_> is used when other arguments are following. Example:
2644		3671
2645	ev_unref (EV_A);	3672	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	3673	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	3674	ev_run (EV_A_ 0);
2648		3675
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3676	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	3677	which is often provided by the following macro.
2651		3678
2652	=item C<EV_P>, C<EV_P_>	3679	=item C<EV_P>, C<EV_P_>
2653		3680
2654	This provides the loop I<parameter> for functions, if one is required ("ev	3681	This provides the loop I<parameter> for functions, if one is required ("ev
2655	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3682	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2656	C<EV_P_> is used when other parameters are following. Example:	3683	C<EV_P_> is used when other parameters are following. Example:
2657		3684
2658	// this is how ev_unref is being declared	3685	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	3686	static void ev_unref (EV_P);
2660		3687
2661	// this is how you can declare your typical callback	3688	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	3689	static void cb (EV_P_ ev_timer *w, int revents)
2663		3690
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3691	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	3692	suitable for use with C<EV_A>.
2666		3693
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3694	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		3710
2684	Example: Declare and initialise a check watcher, utilising the above	3711	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	3712	macros so it will work regardless of whether multiple loops are supported
2686	or not.	3713	or not.
2687		3714
2688	static void	3715	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	3716	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	3717	{
2691	ev_check_stop (EV_A_ w);	3718	ev_check_stop (EV_A_ w);
2692	}	3719	}
2693		3720
2694	ev_check check;	3721	ev_check check;
2695	ev_check_init (&check, check_cb);	3722	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	3723	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	3724	ev_run (EV_DEFAULT_ 0);
2698		3725
2699	=head1 EMBEDDING	3726	=head1 EMBEDDING
2700		3727
2701	Libev can (and often is) directly embedded into host	3728	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	3729	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	3736	libev somewhere in your source tree).
2710		3737
2711	=head2 FILESETS	3738	=head2 FILESETS
2712		3739
2713	Depending on what features you need you need to include one or more sets of files	3740	Depending on what features you need you need to include one or more sets of files
2714	in your app.	3741	in your application.
2715		3742
2716	=head3 CORE EVENT LOOP	3743	=head3 CORE EVENT LOOP
2717		3744
2718	To include only the libev core (all the C<ev_*> functions), with manual	3745	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	3746	configuration (no autoconf):
2720		3747
2721	#define EV_STANDALONE 1	3748	#define EV_STANDALONE 1
2722	#include "ev.c"	3749	#include "ev.c"
2723		3750
2724	This will automatically include F<ev.h>, too, and should be done in a	3751	This will automatically include F<ev.h>, too, and should be done in a
2725	single C source file only to provide the function implementations. To use	3752	single C source file only to provide the function implementations. To use
2726	it, do the same for F<ev.h> in all files wishing to use this API (best	3753	it, do the same for F<ev.h> in all files wishing to use this API (best
2727	done by writing a wrapper around F<ev.h> that you can include instead and	3754	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	3755	where you can put other configuration options):
2729		3756
2730	#define EV_STANDALONE 1	3757	#define EV_STANDALONE 1
2731	#include "ev.h"	3758	#include "ev.h"
2732		3759
2733	Both header files and implementation files can be compiled with a C++	3760	Both header files and implementation files can be compiled with a C++
2734	compiler (at least, thats a stated goal, and breakage will be treated	3761	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	3762	as a bug).
2736		3763
2737	You need the following files in your source tree, or in a directory	3764	You need the following files in your source tree, or in a directory
2738	in your include path (e.g. in libev/ when using -Ilibev):	3765	in your include path (e.g. in libev/ when using -Ilibev):
2739		3766
2740	ev.h	3767	ev.h
2741	ev.c	3768	ev.c
2742	ev_vars.h	3769	ev_vars.h
2743	ev_wrap.h	3770	ev_wrap.h
2744		3771
2745	ev_win32.c required on win32 platforms only	3772	ev_win32.c required on win32 platforms only
2746		3773
2747	ev_select.c only when select backend is enabled (which is enabled by default)	3774	ev_select.c only when select backend is enabled (which is enabled by default)
2748	ev_poll.c only when poll backend is enabled (disabled by default)	3775	ev_poll.c only when poll backend is enabled (disabled by default)
2749	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3776	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2750	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3777	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2751	ev_port.c only when the solaris port backend is enabled (disabled by default)	3778	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		3779
2753	F<ev.c> includes the backend files directly when enabled, so you only need	3780	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	3781	to compile this single file.
2755		3782
2756	=head3 LIBEVENT COMPATIBILITY API	3783	=head3 LIBEVENT COMPATIBILITY API
2757		3784
2758	To include the libevent compatibility API, also include:	3785	To include the libevent compatibility API, also include:
2759		3786
2760	#include "event.c"	3787	#include "event.c"
2761		3788
2762	in the file including F<ev.c>, and:	3789	in the file including F<ev.c>, and:
2763		3790
2764	#include "event.h"	3791	#include "event.h"
2765		3792
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	3793	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		3794
2768	You need the following additional files for this:	3795	You need the following additional files for this:
2769		3796
2770	event.h	3797	event.h
2771	event.c	3798	event.c
2772		3799
2773	=head3 AUTOCONF SUPPORT	3800	=head3 AUTOCONF SUPPORT
2774		3801
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	3802	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2776	whatever way you want, you can also C<m4_include([libev.m4])> in your	3803	whatever way you want, you can also C<m4_include([libev.m4])> in your
2777	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3804	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	3805	include F<config.h> and configure itself accordingly.
2779		3806
2780	For this of course you need the m4 file:	3807	For this of course you need the m4 file:
2781		3808
2782	libev.m4	3809	libev.m4
2783		3810
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	3811	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		3812
2786	Libev can be configured via a variety of preprocessor symbols you have to	3813	Libev can be configured via a variety of preprocessor symbols you have to
2787	define before including any of its files. The default in the absense of	3814	define before including (or compiling) any of its files. The default in
2788	autoconf is noted for every option.	3815	the absence of autoconf is documented for every option.
		3816
		3817	Symbols marked with "(h)" do not change the ABI, and can have different
		3818	values when compiling libev vs. including F<ev.h>, so it is permissible
		3819	to redefine them before including F<ev.h> without breaking compatibility
		3820	to a compiled library. All other symbols change the ABI, which means all
		3821	users of libev and the libev code itself must be compiled with compatible
		3822	settings.
2789		3823
2790	=over 4	3824	=over 4
2791		3825
		3826	=item EV_COMPAT3 (h)
		3827
		3828	Backwards compatibility is a major concern for libev. This is why this
		3829	release of libev comes with wrappers for the functions and symbols that
		3830	have been renamed between libev version 3 and 4.
		3831
		3832	You can disable these wrappers (to test compatibility with future
		3833	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3834	sources. This has the additional advantage that you can drop the C<struct>
		3835	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3836	typedef in that case.
		3837
		3838	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3839	and in some even more future version the compatibility code will be
		3840	removed completely.
		3841
2792	=item EV_STANDALONE	3842	=item EV_STANDALONE (h)
2793		3843
2794	Must always be C<1> if you do not use autoconf configuration, which	3844	Must always be C<1> if you do not use autoconf configuration, which
2795	keeps libev from including F<config.h>, and it also defines dummy	3845	keeps libev from including F<config.h>, and it also defines dummy
2796	implementations for some libevent functions (such as logging, which is not	3846	implementations for some libevent functions (such as logging, which is not
2797	supported). It will also not define any of the structs usually found in	3847	supported). It will also not define any of the structs usually found in
2798	F<event.h> that are not directly supported by the libev core alone.	3848	F<event.h> that are not directly supported by the libev core alone.
2799		3849
		3850	In standalone mode, libev will still try to automatically deduce the
		3851	configuration, but has to be more conservative.
		3852
2800	=item EV_USE_MONOTONIC	3853	=item EV_USE_MONOTONIC
2801		3854
2802	If defined to be C<1>, libev will try to detect the availability of the	3855	If defined to be C<1>, libev will try to detect the availability of the
2803	monotonic clock option at both compiletime and runtime. Otherwise no use	3856	monotonic clock option at both compile time and runtime. Otherwise no
2804	of the monotonic clock option will be attempted. If you enable this, you	3857	use of the monotonic clock option will be attempted. If you enable this,
2805	usually have to link against librt or something similar. Enabling it when	3858	you usually have to link against librt or something similar. Enabling it
2806	the functionality isn't available is safe, though, although you have	3859	when the functionality isn't available is safe, though, although you have
2807	to make sure you link against any libraries where the C<clock_gettime>	3860	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	3861	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2809		3862
2810	=item EV_USE_REALTIME	3863	=item EV_USE_REALTIME
2811		3864
2812	If defined to be C<1>, libev will try to detect the availability of the	3865	If defined to be C<1>, libev will try to detect the availability of the
2813	realtime clock option at compiletime (and assume its availability at	3866	real-time clock option at compile time (and assume its availability
2814	runtime if successful). Otherwise no use of the realtime clock option will	3867	at runtime if successful). Otherwise no use of the real-time clock
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3868	option will be attempted. This effectively replaces C<gettimeofday>
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3869	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3870	correctness. See the note about libraries in the description of
		3871	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3872	C<EV_USE_CLOCK_SYSCALL>.
		3873
		3874	=item EV_USE_CLOCK_SYSCALL
		3875
		3876	If defined to be C<1>, libev will try to use a direct syscall instead
		3877	of calling the system-provided C<clock_gettime> function. This option
		3878	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3879	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3880	programs needlessly. Using a direct syscall is slightly slower (in
		3881	theory), because no optimised vdso implementation can be used, but avoids
		3882	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3883	higher, as it simplifies linking (no need for C<-lrt>).
2818		3884
2819	=item EV_USE_NANOSLEEP	3885	=item EV_USE_NANOSLEEP
2820		3886
2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3887	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2822	and will use it for delays. Otherwise it will use C<select ()>.	3888	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2830	2.7 or newer, otherwise disabled.	3896	2.7 or newer, otherwise disabled.
2831		3897
2832	=item EV_USE_SELECT	3898	=item EV_USE_SELECT
2833		3899
2834	If undefined or defined to be C<1>, libev will compile in support for the	3900	If undefined or defined to be C<1>, libev will compile in support for the
2835	C<select>(2) backend. No attempt at autodetection will be done: if no	3901	C<select>(2) backend. No attempt at auto-detection will be done: if no
2836	other method takes over, select will be it. Otherwise the select backend	3902	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	3903	will not be compiled in.
2838		3904
2839	=item EV_SELECT_USE_FD_SET	3905	=item EV_SELECT_USE_FD_SET
2840		3906
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	3907	If defined to C<1>, then the select backend will use the system C<fd_set>
2842	structure. This is useful if libev doesn't compile due to a missing	3908	structure. This is useful if libev doesn't compile due to a missing
2843	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3909	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2844	exotic systems. This usually limits the range of file descriptors to some	3910	on exotic systems. This usually limits the range of file descriptors to
2845	low limit such as 1024 or might have other limitations (winsocket only	3911	some low limit such as 1024 or might have other limitations (winsocket
2846	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3912	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2847	influence the size of the C<fd_set> used.	3913	configures the maximum size of the C<fd_set>.
2848		3914
2849	=item EV_SELECT_IS_WINSOCKET	3915	=item EV_SELECT_IS_WINSOCKET
2850		3916
2851	When defined to C<1>, the select backend will assume that	3917	When defined to C<1>, the select backend will assume that
2852	select/socket/connect etc. don't understand file descriptors but	3918	select/socket/connect etc. don't understand file descriptors but
…		…
2854	be used is the winsock select). This means that it will call	3920	be used is the winsock select). This means that it will call
2855	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3921	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2856	it is assumed that all these functions actually work on fds, even	3922	it is assumed that all these functions actually work on fds, even
2857	on win32. Should not be defined on non-win32 platforms.	3923	on win32. Should not be defined on non-win32 platforms.
2858		3924
2859	=item EV_FD_TO_WIN32_HANDLE	3925	=item EV_FD_TO_WIN32_HANDLE(fd)
2860		3926
2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3927	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2862	file descriptors to socket handles. When not defining this symbol (the	3928	file descriptors to socket handles. When not defining this symbol (the
2863	default), then libev will call C<_get_osfhandle>, which is usually	3929	default), then libev will call C<_get_osfhandle>, which is usually
2864	correct. In some cases, programs use their own file descriptor management,	3930	correct. In some cases, programs use their own file descriptor management,
2865	in which case they can provide this function to map fds to socket handles.	3931	in which case they can provide this function to map fds to socket handles.
		3932
		3933	=item EV_WIN32_HANDLE_TO_FD(handle)
		3934
		3935	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3936	using the standard C<_open_osfhandle> function. For programs implementing
		3937	their own fd to handle mapping, overwriting this function makes it easier
		3938	to do so. This can be done by defining this macro to an appropriate value.
		3939
		3940	=item EV_WIN32_CLOSE_FD(fd)
		3941
		3942	If programs implement their own fd to handle mapping on win32, then this
		3943	macro can be used to override the C<close> function, useful to unregister
		3944	file descriptors again. Note that the replacement function has to close
		3945	the underlying OS handle.
2866		3946
2867	=item EV_USE_POLL	3947	=item EV_USE_POLL
2868		3948
2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3949	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2870	backend. Otherwise it will be enabled on non-win32 platforms. It	3950	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2897	otherwise another method will be used as fallback. This is the preferred	3977	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	3978	backend for Solaris 10 systems.
2899		3979
2900	=item EV_USE_DEVPOLL	3980	=item EV_USE_DEVPOLL
2901		3981
2902	reserved for future expansion, works like the USE symbols above.	3982	Reserved for future expansion, works like the USE symbols above.
2903		3983
2904	=item EV_USE_INOTIFY	3984	=item EV_USE_INOTIFY
2905		3985
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	3986	If defined to be C<1>, libev will compile in support for the Linux inotify
2907	interface to speed up C<ev_stat> watchers. Its actual availability will	3987	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2914	access is atomic with respect to other threads or signal contexts. No such	3994	access is atomic with respect to other threads or signal contexts. No such
2915	type is easily found in the C language, so you can provide your own type	3995	type is easily found in the C language, so you can provide your own type
2916	that you know is safe for your purposes. It is used both for signal handler "locking"	3996	that you know is safe for your purposes. It is used both for signal handler "locking"
2917	as well as for signal and thread safety in C<ev_async> watchers.	3997	as well as for signal and thread safety in C<ev_async> watchers.
2918		3998
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	3999	In the absence of this define, libev will use C<sig_atomic_t volatile>
2920	(from F<signal.h>), which is usually good enough on most platforms.	4000	(from F<signal.h>), which is usually good enough on most platforms.
2921		4001
2922	=item EV_H	4002	=item EV_H (h)
2923		4003
2924	The name of the F<ev.h> header file used to include it. The default if	4004	The name of the F<ev.h> header file used to include it. The default if
2925	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4005	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2926	used to virtually rename the F<ev.h> header file in case of conflicts.	4006	used to virtually rename the F<ev.h> header file in case of conflicts.
2927		4007
2928	=item EV_CONFIG_H	4008	=item EV_CONFIG_H (h)
2929		4009
2930	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4010	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2931	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4011	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2932	C<EV_H>, above.	4012	C<EV_H>, above.
2933		4013
2934	=item EV_EVENT_H	4014	=item EV_EVENT_H (h)
2935		4015
2936	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4016	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2937	of how the F<event.h> header can be found, the default is C<"event.h">.	4017	of how the F<event.h> header can be found, the default is C<"event.h">.
2938		4018
2939	=item EV_PROTOTYPES	4019	=item EV_PROTOTYPES (h)
2940		4020
2941	If defined to be C<0>, then F<ev.h> will not define any function	4021	If defined to be C<0>, then F<ev.h> will not define any function
2942	prototypes, but still define all the structs and other symbols. This is	4022	prototypes, but still define all the structs and other symbols. This is
2943	occasionally useful if you want to provide your own wrapper functions	4023	occasionally useful if you want to provide your own wrapper functions
2944	around libev functions.	4024	around libev functions.
…		…
2963	When doing priority-based operations, libev usually has to linearly search	4043	When doing priority-based operations, libev usually has to linearly search
2964	all the priorities, so having many of them (hundreds) uses a lot of space	4044	all the priorities, so having many of them (hundreds) uses a lot of space
2965	and time, so using the defaults of five priorities (-2 .. +2) is usually	4045	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	4046	fine.
2967		4047
2968	If your embedding app does not need any priorities, defining these both to	4048	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	4049	both to C<0> will save some memory and CPU.
2970		4050
2971	=item EV_PERIODIC_ENABLE	4051	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4052	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4053	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2972		4054
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	4055	If undefined or defined to be C<1> (and the platform supports it), then
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	4056	the respective watcher type is supported. If defined to be C<0>, then it
2975	code.	4057	is not. Disabling watcher types mainly saves code size.
2976		4058
2977	=item EV_IDLE_ENABLE	4059	=item EV_FEATURES
2978
2979	If undefined or defined to be C<1>, then idle watchers are supported. If
2980	defined to be C<0>, then they are not. Disabling them saves a few kB of
2981	code.
2982
2983	=item EV_EMBED_ENABLE
2984
2985	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.
2987
2988	=item EV_STAT_ENABLE
2989
2990	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.
2992
2993	=item EV_FORK_ENABLE
2994
2995	If undefined or defined to be C<1>, then fork watchers are supported. If
2996	defined to be C<0>, then they are not.
2997
2998	=item EV_ASYNC_ENABLE
2999
3000	If undefined or defined to be C<1>, then async watchers are supported. If
3001	defined to be C<0>, then they are not.
3002
3003	=item EV_MINIMAL
3004		4060
3005	If you need to shave off some kilobytes of code at the expense of some	4061	If you need to shave off some kilobytes of code at the expense of some
3006	speed, define this symbol to C<1>. Currently this is used to override some	4062	speed (but with the full API), you can define this symbol to request
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	4063	certain subsets of functionality. The default is to enable all features
3008	much smaller 2-heap for timer management over the default 4-heap.	4064	that can be enabled on the platform.
		4065
		4066	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4067	with some broad features you want) and then selectively re-enable
		4068	additional parts you want, for example if you want everything minimal,
		4069	but multiple event loop support, async and child watchers and the poll
		4070	backend, use this:
		4071
		4072	#define EV_FEATURES 0
		4073	#define EV_MULTIPLICITY 1
		4074	#define EV_USE_POLL 1
		4075	#define EV_CHILD_ENABLE 1
		4076	#define EV_ASYNC_ENABLE 1
		4077
		4078	The actual value is a bitset, it can be a combination of the following
		4079	values:
		4080
		4081	=over 4
		4082
		4083	=item C<1> - faster/larger code
		4084
		4085	Use larger code to speed up some operations.
		4086
		4087	Currently this is used to override some inlining decisions (enlarging the
		4088	code size by roughly 30% on amd64).
		4089
		4090	When optimising for size, use of compiler flags such as C<-Os> with
		4091	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4092	assertions.
		4093
		4094	=item C<2> - faster/larger data structures
		4095
		4096	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4097	hash table sizes and so on. This will usually further increase code size
		4098	and can additionally have an effect on the size of data structures at
		4099	runtime.
		4100
		4101	=item C<4> - full API configuration
		4102
		4103	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4104	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4105
		4106	=item C<8> - full API
		4107
		4108	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4109	details on which parts of the API are still available without this
		4110	feature, and do not complain if this subset changes over time.
		4111
		4112	=item C<16> - enable all optional watcher types
		4113
		4114	Enables all optional watcher types. If you want to selectively enable
		4115	only some watcher types other than I/O and timers (e.g. prepare,
		4116	embed, async, child...) you can enable them manually by defining
		4117	C<EV_watchertype_ENABLE> to C<1> instead.
		4118
		4119	=item C<32> - enable all backends
		4120
		4121	This enables all backends - without this feature, you need to enable at
		4122	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4123
		4124	=item C<64> - enable OS-specific "helper" APIs
		4125
		4126	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4127	default.
		4128
		4129	=back
		4130
		4131	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4132	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4133	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4134	watchers, timers and monotonic clock support.
		4135
		4136	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4137	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4138	your program might be left out as well - a binary starting a timer and an
		4139	I/O watcher then might come out at only 5Kb.
		4140
		4141	=item EV_AVOID_STDIO
		4142
		4143	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4144	functions (printf, scanf, perror etc.). This will increase the code size
		4145	somewhat, but if your program doesn't otherwise depend on stdio and your
		4146	libc allows it, this avoids linking in the stdio library which is quite
		4147	big.
		4148
		4149	Note that error messages might become less precise when this option is
		4150	enabled.
		4151
		4152	=item EV_NSIG
		4153
		4154	The highest supported signal number, +1 (or, the number of
		4155	signals): Normally, libev tries to deduce the maximum number of signals
		4156	automatically, but sometimes this fails, in which case it can be
		4157	specified. Also, using a lower number than detected (C<32> should be
		4158	good for about any system in existence) can save some memory, as libev
		4159	statically allocates some 12-24 bytes per signal number.
3009		4160
3010	=item EV_PID_HASHSIZE	4161	=item EV_PID_HASHSIZE
3011		4162
3012	C<ev_child> watchers use a small hash table to distribute workload by	4163	C<ev_child> watchers use a small hash table to distribute workload by
3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4164	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3014	than enough. If you need to manage thousands of children you might want to	4165	usually more than enough. If you need to manage thousands of children you
3015	increase this value (I<must> be a power of two).	4166	might want to increase this value (I<must> be a power of two).
3016		4167
3017	=item EV_INOTIFY_HASHSIZE	4168	=item EV_INOTIFY_HASHSIZE
3018		4169
3019	C<ev_stat> watchers use a small hash table to distribute workload by	4170	C<ev_stat> watchers use a small hash table to distribute workload by
3020	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4171	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3021	usually more than enough. If you need to manage thousands of C<ev_stat>	4172	disabled), usually more than enough. If you need to manage thousands of
3022	watchers you might want to increase this value (I<must> be a power of	4173	C<ev_stat> watchers you might want to increase this value (I<must> be a
3023	two).	4174	power of two).
3024		4175
3025	=item EV_USE_4HEAP	4176	=item EV_USE_4HEAP
3026		4177
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4178	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4179	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3029	to C<1>. The 4-heap uses more complicated (longer) code but has	4180	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	4181	faster performance with many (thousands) of watchers.
3031		4182
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4183	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3033	(disabled).	4184	will be C<0>.
3034		4185
3035	=item EV_HEAP_CACHE_AT	4186	=item EV_HEAP_CACHE_AT
3036		4187
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4188	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3038	timer and periodics heap, libev can cache the timestamp (I<at>) within	4189	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4190	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4191	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3041	but avoids random read accesses on heap changes. This improves performance	4192	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	4193	noticeably with many (hundreds) of watchers.
3043		4194
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4195	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3045	(disabled).	4196	will be C<0>.
3046		4197
3047	=item EV_VERIFY	4198	=item EV_VERIFY
3048		4199
3049	Controls how much internal verification (see C<ev_loop_verify ()>) will	4200	Controls how much internal verification (see C<ev_verify ()>) will
3050	be done: If set to C<0>, no internal verification code will be compiled	4201	be done: If set to C<0>, no internal verification code will be compiled
3051	in. If set to C<1>, then verification code will be compiled in, but not	4202	in. If set to C<1>, then verification code will be compiled in, but not
3052	called. If set to C<2>, then the internal verification code will be	4203	called. If set to C<2>, then the internal verification code will be
3053	called once per loop, which can slow down libev. If set to C<3>, then the	4204	called once per loop, which can slow down libev. If set to C<3>, then the
3054	verification code will be called very frequently, which will slow down	4205	verification code will be called very frequently, which will slow down
3055	libev considerably.	4206	libev considerably.
3056		4207
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4208	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3058	C<0.>	4209	will be C<0>.
3059		4210
3060	=item EV_COMMON	4211	=item EV_COMMON
3061		4212
3062	By default, all watchers have a C<void *data> member. By redefining	4213	By default, all watchers have a C<void *data> member. By redefining
3063	this macro to a something else you can include more and other types of	4214	this macro to something else you can include more and other types of
3064	members. You have to define it each time you include one of the files,	4215	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	4216	though, and it must be identical each time.
3066		4217
3067	For example, the perl EV module uses something like this:	4218	For example, the perl EV module uses something like this:
3068		4219
3069	#define EV_COMMON \	4220	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	4221	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	4222	SV *cb_sv, *fh /* note no trailing ";" */
3072		4223
3073	=item EV_CB_DECLARE (type)	4224	=item EV_CB_DECLARE (type)
3074		4225
3075	=item EV_CB_INVOKE (watcher, revents)	4226	=item EV_CB_INVOKE (watcher, revents)
3076		4227
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	4232	definition and a statement, respectively. See the F<ev.h> header file for
3082	their default definitions. One possible use for overriding these is to	4233	their default definitions. One possible use for overriding these is to
3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4234	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3084	method calls instead of plain function calls in C++.	4235	method calls instead of plain function calls in C++.
3085		4236
		4237	=back
		4238
3086	=head2 EXPORTED API SYMBOLS	4239	=head2 EXPORTED API SYMBOLS
3087		4240
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	4241	If you need to re-export the API (e.g. via a DLL) and you need a list of
3089	exported symbols, you can use the provided F<Symbol.*> files which list	4242	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	4243	all public symbols, one per line:
3091		4244
3092	Symbols.ev for libev proper	4245	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	4246	Symbols.event for the libevent emulation
3094		4247
3095	This can also be used to rename all public symbols to avoid clashes with	4248	This can also be used to rename all public symbols to avoid clashes with
3096	multiple versions of libev linked together (which is obviously bad in	4249	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	4250	itself, but sometimes it is inconvenient to avoid this).
3098		4251
3099	A sed command like this will create wrapper C<#define>'s that you need to	4252	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	4253	include before including F<ev.h>:
3101		4254
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4255	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	4272	file.
3120		4273
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4274	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3122	that everybody includes and which overrides some configure choices:	4275	that everybody includes and which overrides some configure choices:
3123		4276
3124	#define EV_MINIMAL 1	4277	#define EV_FEATURES 8
3125	#define EV_USE_POLL 0	4278	#define EV_USE_SELECT 1
3126	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	4279	#define EV_PREPARE_ENABLE 1
		4280	#define EV_IDLE_ENABLE 1
3128	#define EV_STAT_ENABLE 0	4281	#define EV_SIGNAL_ENABLE 1
3129	#define EV_FORK_ENABLE 0	4282	#define EV_CHILD_ENABLE 1
		4283	#define EV_USE_STDEXCEPT 0
3130	#define EV_CONFIG_H <config.h>	4284	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0
3133		4285
3134	#include "ev++.h"	4286	#include "ev++.h"
3135		4287
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4288	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		4289
3138	#include "ev_cpp.h"	4290	#include "ev_cpp.h"
3139	#include "ev.c"	4291	#include "ev.c"
3140		4292
		4293	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3141		4294
3142	=head1 THREADS AND COROUTINES	4295	=head2 THREADS AND COROUTINES
3143		4296
3144	=head2 THREADS	4297	=head3 THREADS
3145		4298
3146	Libev itself is completely threadsafe, but it uses no locking. This	4299	All libev functions are reentrant and thread-safe unless explicitly
		4300	documented otherwise, but libev implements no locking itself. This means
3147	means that you can use as many loops as you want in parallel, as long as	4301	that you can use as many loops as you want in parallel, as long as there
3148	only one thread ever calls into one libev function with the same loop	4302	are no concurrent calls into any libev function with the same loop
3149	parameter.	4303	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4304	of course): libev guarantees that different event loops share no data
		4305	structures that need any locking.
3150		4306
3151	Or put differently: calls with different loop parameters can be done in	4307	Or to put it differently: calls with different loop parameters can be done
3152	parallel from multiple threads, calls with the same loop parameter must be	4308	concurrently from multiple threads, calls with the same loop parameter
3153	done serially (but can be done from different threads, as long as only one	4309	must be done serially (but can be done from different threads, as long as
3154	thread ever is inside a call at any point in time, e.g. by using a mutex	4310	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	4311	a mutex per loop).
3156		4312
3157	If you want to know which design is best for your problem, then I cannot	4313	Specifically to support threads (and signal handlers), libev implements
		4314	so-called C<ev_async> watchers, which allow some limited form of
		4315	concurrency on the same event loop, namely waking it up "from the
		4316	outside".
		4317
		4318	If you want to know which design (one loop, locking, or multiple loops
		4319	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	4320	help you, but here is some generic advice:
3159		4321
3160	=over 4	4322	=over 4
3161		4323
3162	=item * most applications have a main thread: use the default libev loop	4324	=item * most applications have a main thread: use the default libev loop
3163	in that thread, or create a seperate thread running only the default loop.	4325	in that thread, or create a separate thread running only the default loop.
3164		4326
3165	This helps integrating other libraries or software modules that use libev	4327	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	4328	themselves and don't care/know about threading.
3167		4329
3168	=item * one loop per thread is usually a good model.	4330	=item * one loop per thread is usually a good model.
3169		4331
3170	Doing this is almost never wrong, sometimes a better-performance model	4332	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	4333	exists, but it is always a good start.
3172		4334
3173	=item * other models exist, such as the leader/follower pattern, where one	4335	=item * other models exist, such as the leader/follower pattern, where one
3174	loop is handed through multiple threads in a kind of round-robbin fashion.	4336	loop is handed through multiple threads in a kind of round-robin fashion.
3175		4337
3176	Chosing a model is hard - look around, learn, know that usually you cna do	4338	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	4339	better than you currently do :-)
3178		4340
3179	=item * often you need to talk to some other thread which blocks in the	4341	=item * often you need to talk to some other thread which blocks in the
		4342	event loop.
		4343
3180	event loop - C<ev_async> watchers can be used to wake them up from other	4344	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	4345	(or from signal contexts...).
		4346
		4347	An example use would be to communicate signals or other events that only
		4348	work in the default loop by registering the signal watcher with the
		4349	default loop and triggering an C<ev_async> watcher from the default loop
		4350	watcher callback into the event loop interested in the signal.
3182		4351
3183	=back	4352	=back
3184		4353
		4354	=head4 THREAD LOCKING EXAMPLE
		4355
		4356	Here is a fictitious example of how to run an event loop in a different
		4357	thread than where callbacks are being invoked and watchers are
		4358	created/added/removed.
		4359
		4360	For a real-world example, see the C<EV::Loop::Async> perl module,
		4361	which uses exactly this technique (which is suited for many high-level
		4362	languages).
		4363
		4364	The example uses a pthread mutex to protect the loop data, a condition
		4365	variable to wait for callback invocations, an async watcher to notify the
		4366	event loop thread and an unspecified mechanism to wake up the main thread.
		4367
		4368	First, you need to associate some data with the event loop:
		4369
		4370	typedef struct {
		4371	mutex_t lock; /* global loop lock */
		4372	ev_async async_w;
		4373	thread_t tid;
		4374	cond_t invoke_cv;
		4375	} userdata;
		4376
		4377	void prepare_loop (EV_P)
		4378	{
		4379	// for simplicity, we use a static userdata struct.
		4380	static userdata u;
		4381
		4382	ev_async_init (&u->async_w, async_cb);
		4383	ev_async_start (EV_A_ &u->async_w);
		4384
		4385	pthread_mutex_init (&u->lock, 0);
		4386	pthread_cond_init (&u->invoke_cv, 0);
		4387
		4388	// now associate this with the loop
		4389	ev_set_userdata (EV_A_ u);
		4390	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4391	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4392
		4393	// then create the thread running ev_loop
		4394	pthread_create (&u->tid, 0, l_run, EV_A);
		4395	}
		4396
		4397	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4398	solely to wake up the event loop so it takes notice of any new watchers
		4399	that might have been added:
		4400
		4401	static void
		4402	async_cb (EV_P_ ev_async *w, int revents)
		4403	{
		4404	// just used for the side effects
		4405	}
		4406
		4407	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4408	protecting the loop data, respectively.
		4409
		4410	static void
		4411	l_release (EV_P)
		4412	{
		4413	userdata *u = ev_userdata (EV_A);
		4414	pthread_mutex_unlock (&u->lock);
		4415	}
		4416
		4417	static void
		4418	l_acquire (EV_P)
		4419	{
		4420	userdata *u = ev_userdata (EV_A);
		4421	pthread_mutex_lock (&u->lock);
		4422	}
		4423
		4424	The event loop thread first acquires the mutex, and then jumps straight
		4425	into C<ev_run>:
		4426
		4427	void *
		4428	l_run (void *thr_arg)
		4429	{
		4430	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4431
		4432	l_acquire (EV_A);
		4433	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4434	ev_run (EV_A_ 0);
		4435	l_release (EV_A);
		4436
		4437	return 0;
		4438	}
		4439
		4440	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4441	signal the main thread via some unspecified mechanism (signals? pipe
		4442	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4443	have been called (in a while loop because a) spurious wakeups are possible
		4444	and b) skipping inter-thread-communication when there are no pending
		4445	watchers is very beneficial):
		4446
		4447	static void
		4448	l_invoke (EV_P)
		4449	{
		4450	userdata *u = ev_userdata (EV_A);
		4451
		4452	while (ev_pending_count (EV_A))
		4453	{
		4454	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4455	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4456	}
		4457	}
		4458
		4459	Now, whenever the main thread gets told to invoke pending watchers, it
		4460	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4461	thread to continue:
		4462
		4463	static void
		4464	real_invoke_pending (EV_P)
		4465	{
		4466	userdata *u = ev_userdata (EV_A);
		4467
		4468	pthread_mutex_lock (&u->lock);
		4469	ev_invoke_pending (EV_A);
		4470	pthread_cond_signal (&u->invoke_cv);
		4471	pthread_mutex_unlock (&u->lock);
		4472	}
		4473
		4474	Whenever you want to start/stop a watcher or do other modifications to an
		4475	event loop, you will now have to lock:
		4476
		4477	ev_timer timeout_watcher;
		4478	userdata *u = ev_userdata (EV_A);
		4479
		4480	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4481
		4482	pthread_mutex_lock (&u->lock);
		4483	ev_timer_start (EV_A_ &timeout_watcher);
		4484	ev_async_send (EV_A_ &u->async_w);
		4485	pthread_mutex_unlock (&u->lock);
		4486
		4487	Note that sending the C<ev_async> watcher is required because otherwise
		4488	an event loop currently blocking in the kernel will have no knowledge
		4489	about the newly added timer. By waking up the loop it will pick up any new
		4490	watchers in the next event loop iteration.
		4491
3185	=head2 COROUTINES	4492	=head3 COROUTINES
3186		4493
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	4494	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	4495	libev fully supports nesting calls to its functions from different
3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4496	coroutines (e.g. you can call C<ev_run> on the same loop from two
3190	different coroutines and switch freely between both coroutines running the	4497	different coroutines, and switch freely between both coroutines running
3191	loop, as long as you don't confuse yourself). The only exception is that	4498	the loop, as long as you don't confuse yourself). The only exception is
3192	you must not do this from C<ev_periodic> reschedule callbacks.	4499	that you must not do this from C<ev_periodic> reschedule callbacks.
3193		4500
3194	Care has been invested into making sure that libev does not keep local	4501	Care has been taken to ensure that libev does not keep local state inside
3195	state inside C<ev_loop>, and other calls do not usually allow coroutine	4502	C<ev_run>, and other calls do not usually allow for coroutine switches as
3196	switches.	4503	they do not call any callbacks.
3197		4504
		4505	=head2 COMPILER WARNINGS
3198		4506
3199	=head1 COMPLEXITIES	4507	Depending on your compiler and compiler settings, you might get no or a
		4508	lot of warnings when compiling libev code. Some people are apparently
		4509	scared by this.
3200		4510
3201	In this section the complexities of (many of) the algorithms used inside	4511	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	4512	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	4513	warning options. "Warn-free" code therefore cannot be a goal except when
		4514	targeting a specific compiler and compiler-version.
3204		4515
3205	All of the following are about amortised time: If an array needs to be	4516	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	4517	workarounds, or other changes to the code that make it less clear and less
3207	happens asymptotically never with higher number of elements, so O(1) might	4518	maintainable.
3208	mean it might do a lengthy realloc operation in rare cases, but on average
3209	it is much faster and asymptotically approaches constant time.
3210		4519
3211	=over 4	4520	And of course, some compiler warnings are just plain stupid, or simply
		4521	wrong (because they don't actually warn about the condition their message
		4522	seems to warn about). For example, certain older gcc versions had some
		4523	warnings that resulted in an extreme number of false positives. These have
		4524	been fixed, but some people still insist on making code warn-free with
		4525	such buggy versions.
3212		4526
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4527	While libev is written to generate as few warnings as possible,
		4528	"warn-free" code is not a goal, and it is recommended not to build libev
		4529	with any compiler warnings enabled unless you are prepared to cope with
		4530	them (e.g. by ignoring them). Remember that warnings are just that:
		4531	warnings, not errors, or proof of bugs.
3214		4532
3215	This means that, when you have a watcher that triggers in one hour and
3216	there are 100 watchers that would trigger before that then inserting will
3217	have to skip roughly seven (C<ld 100>) of these watchers.
3218		4533
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4534	=head2 VALGRIND
3220		4535
3221	That means that changing a timer costs less than removing/adding them	4536	Valgrind has a special section here because it is a popular tool that is
3222	as only the relative motion in the event queue has to be paid for.	4537	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		4538
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4539	If you think you found a bug (memory leak, uninitialised data access etc.)
		4540	in libev, then check twice: If valgrind reports something like:
3225		4541
3226	These just add the watcher into an array or at the head of a list.	4542	==2274== definitely lost: 0 bytes in 0 blocks.
		4543	==2274== possibly lost: 0 bytes in 0 blocks.
		4544	==2274== still reachable: 256 bytes in 1 blocks.
3227		4545
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4546	Then there is no memory leak, just as memory accounted to global variables
		4547	is not a memleak - the memory is still being referenced, and didn't leak.
3229		4548
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4549	Similarly, under some circumstances, valgrind might report kernel bugs
		4550	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4551	although an acceptable workaround has been found here), or it might be
		4552	confused.
3231		4553
3232	These watchers are stored in lists then need to be walked to find the	4554	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3233	correct watcher to remove. The lists are usually short (you don't usually	4555	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		4556
3236	=item Finding the next timer in each loop iteration: O(1)	4557	If you are unsure about something, feel free to contact the mailing list
		4558	with the full valgrind report and an explanation on why you think this
		4559	is a bug in libev (best check the archives, too :). However, don't be
		4560	annoyed when you get a brisk "this is no bug" answer and take the chance
		4561	of learning how to interpret valgrind properly.
3237		4562
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	4563	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	4564	I suggest using suppression lists.
3240		4565
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		4566
3243	A change means an I/O watcher gets started or stopped, which requires	4567	=head1 PORTABILITY NOTES
3244	libev to recalculate its status (and possibly tell the kernel, depending
3245	on backend and wether C<ev_io_set> was used).
3246		4568
3247	=item Activating one watcher (putting it into the pending state): O(1)	4569	=head2 GNU/LINUX 32 BIT LIMITATIONS
3248		4570
3249	=item Priority handling: O(number_of_priorities)	4571	GNU/Linux is the only common platform that supports 64 bit file/large file
		4572	interfaces but I<disables> them by default.
3250		4573
3251	Priorities are implemented by allocating some space for each	4574	That means that libev compiled in the default environment doesn't support
3252	priority. When doing priority-based operations, libev usually has to	4575	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3253	linearly search all the priorities, but starting/stopping and activating
3254	watchers becomes O(1) w.r.t. priority handling.
3255		4576
3256	=item Sending an ev_async: O(1)	4577	Unfortunately, many programs try to work around this GNU/Linux issue
		4578	by enabling the large file API, which makes them incompatible with the
		4579	standard libev compiled for their system.
3257		4580
3258	=item Processing ev_async_send: O(number_of_async_watchers)	4581	Likewise, libev cannot enable the large file API itself as this would
		4582	suddenly make it incompatible to the default compile time environment,
		4583	i.e. all programs not using special compile switches.
3259		4584
3260	=item Processing signals: O(max_signal_number)	4585	=head2 OS/X AND DARWIN BUGS
3261		4586
3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4587	The whole thing is a bug if you ask me - basically any system interface
3263	calls in the current loop iteration. Checking for async and signal events	4588	you touch is broken, whether it is locales, poll, kqueue or even the
3264	involves iterating over all running async watchers or all signal numbers.	4589	OpenGL drivers.
3265		4590
3266	=back	4591	=head3 C<kqueue> is buggy
3267		4592
		4593	The kqueue syscall is broken in all known versions - most versions support
		4594	only sockets, many support pipes.
3268		4595
3269	=head1 Win32 platform limitations and workarounds	4596	Libev tries to work around this by not using C<kqueue> by default on this
		4597	rotten platform, but of course you can still ask for it when creating a
		4598	loop - embedding a socket-only kqueue loop into a select-based one is
		4599	probably going to work well.
		4600
		4601	=head3 C<poll> is buggy
		4602
		4603	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4604	implementation by something calling C<kqueue> internally around the 10.5.6
		4605	release, so now C<kqueue> I<and> C<poll> are broken.
		4606
		4607	Libev tries to work around this by not using C<poll> by default on
		4608	this rotten platform, but of course you can still ask for it when creating
		4609	a loop.
		4610
		4611	=head3 C<select> is buggy
		4612
		4613	All that's left is C<select>, and of course Apple found a way to fuck this
		4614	one up as well: On OS/X, C<select> actively limits the number of file
		4615	descriptors you can pass in to 1024 - your program suddenly crashes when
		4616	you use more.
		4617
		4618	There is an undocumented "workaround" for this - defining
		4619	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4620	work on OS/X.
		4621
		4622	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4623
		4624	=head3 C<errno> reentrancy
		4625
		4626	The default compile environment on Solaris is unfortunately so
		4627	thread-unsafe that you can't even use components/libraries compiled
		4628	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4629	defined by default. A valid, if stupid, implementation choice.
		4630
		4631	If you want to use libev in threaded environments you have to make sure
		4632	it's compiled with C<_REENTRANT> defined.
		4633
		4634	=head3 Event port backend
		4635
		4636	The scalable event interface for Solaris is called "event
		4637	ports". Unfortunately, this mechanism is very buggy in all major
		4638	releases. If you run into high CPU usage, your program freezes or you get
		4639	a large number of spurious wakeups, make sure you have all the relevant
		4640	and latest kernel patches applied. No, I don't know which ones, but there
		4641	are multiple ones to apply, and afterwards, event ports actually work
		4642	great.
		4643
		4644	If you can't get it to work, you can try running the program by setting
		4645	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4646	C<select> backends.
		4647
		4648	=head2 AIX POLL BUG
		4649
		4650	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4651	this by trying to avoid the poll backend altogether (i.e. it's not even
		4652	compiled in), which normally isn't a big problem as C<select> works fine
		4653	with large bitsets on AIX, and AIX is dead anyway.
		4654
		4655	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4656
		4657	=head3 General issues
3270		4658
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4659	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3272	requires, and its I/O model is fundamentally incompatible with the POSIX	4660	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	4661	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4662	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3275	descriptors. This only applies when using Win32 natively, not when using	4663	descriptors. This only applies when using Win32 natively, not when using
3276	e.g. cygwin.	4664	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4665	as every compielr comes with a slightly differently broken/incompatible
		4666	environment.
3277		4667
3278	Lifting these limitations would basically require the full	4668	Lifting these limitations would basically require the full
3279	re-implementation of the I/O system. If you are into these kinds of	4669	re-implementation of the I/O system. If you are into this kind of thing,
3280	things, then note that glib does exactly that for you in a very portable	4670	then note that glib does exactly that for you in a very portable way (note
3281	way (note also that glib is the slowest event library known to man).	4671	also that glib is the slowest event library known to man).
3282		4672
3283	There is no supported compilation method available on windows except	4673	There is no supported compilation method available on windows except
3284	embedding it into other applications.	4674	embedding it into other applications.
		4675
		4676	Sensible signal handling is officially unsupported by Microsoft - libev
		4677	tries its best, but under most conditions, signals will simply not work.
		4678
		4679	Not a libev limitation but worth mentioning: windows apparently doesn't
		4680	accept large writes: instead of resulting in a partial write, windows will
		4681	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4682	so make sure you only write small amounts into your sockets (less than a
		4683	megabyte seems safe, but this apparently depends on the amount of memory
		4684	available).
3285		4685
3286	Due to the many, low, and arbitrary limits on the win32 platform and	4686	Due to the many, low, and arbitrary limits on the win32 platform and
3287	the abysmal performance of winsockets, using a large number of sockets	4687	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	4688	is not recommended (and not reasonable). If your program needs to use
3289	more than a hundred or so sockets, then likely it needs to use a totally	4689	more than a hundred or so sockets, then likely it needs to use a totally
3290	different implementation for windows, as libev offers the POSIX readiness	4690	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	4691	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	4692	(due to Microsoft monopoly games).
3293		4693
3294	=over 4	4694	A typical way to use libev under windows is to embed it (see the embedding
		4695	section for details) and use the following F<evwrap.h> header file instead
		4696	of F<ev.h>:
3295		4697
		4698	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4699	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4700
		4701	#include "ev.h"
		4702
		4703	And compile the following F<evwrap.c> file into your project (make sure
		4704	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4705
		4706	#include "evwrap.h"
		4707	#include "ev.c"
		4708
3296	=item The winsocket select function	4709	=head3 The winsocket C<select> function
3297		4710
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	4711	The winsocket C<select> function doesn't follow POSIX in that it
3299	socket I<handles> and not socket I<file descriptors>. This makes select	4712	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	4713	also extremely buggy). This makes select very inefficient, and also
3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4714	requires a mapping from file descriptors to socket handles (the Microsoft
3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4715	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	4716	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4717	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		4718
3305	The configuration for a "naked" win32 using the microsoft runtime	4719	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	4720	libraries and raw winsocket select is:
3307		4721
3308	#define EV_USE_SELECT 1	4722	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4723	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		4724
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	4725	Note that winsockets handling of fd sets is O(n), so you can easily get a
3312	complexity in the O(n²) range when using win32.	4726	complexity in the O(n²) range when using win32.
3313		4727
3314	=item Limited number of file descriptors	4728	=head3 Limited number of file descriptors
3315		4729
3316	Windows has numerous arbitrary (and low) limits on things.	4730	Windows has numerous arbitrary (and low) limits on things.
3317		4731
3318	Early versions of winsocket's select only supported waiting for a maximum	4732	Early versions of winsocket's select only supported waiting for a maximum
3319	of C<64> handles (probably owning to the fact that all windows kernels	4733	of C<64> handles (probably owning to the fact that all windows kernels
3320	can only wait for C<64> things at the same time internally; microsoft	4734	can only wait for C<64> things at the same time internally; Microsoft
3321	recommends spawning a chain of threads and wait for 63 handles and the	4735	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	4736	previous thread in each. Sounds great!).
3323		4737
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4738	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3325	to some high number (e.g. C<2048>) before compiling the winsocket select	4739	to some high number (e.g. C<2048>) before compiling the winsocket select
3326	call (which might be in libev or elsewhere, for example, perl does its own	4740	call (which might be in libev or elsewhere, for example, perl and many
3327	select emulation on windows).	4741	other interpreters do their own select emulation on windows).
3328		4742
3329	Another limit is the number of file descriptors in the microsoft runtime	4743	Another limit is the number of file descriptors in the Microsoft runtime
3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4744	libraries, which by default is C<64> (there must be a hidden I<64>
3331	or something like this inside microsoft). You can increase this by calling	4745	fetish or something like this inside Microsoft). You can increase this
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4746	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3333	arbitrary limit), but is broken in many versions of the microsoft runtime	4747	(another arbitrary limit), but is broken in many versions of the Microsoft
3334	libraries.
3335
3336	This might get you to about C<512> or C<2048> sockets (depending on	4748	runtime libraries. This might get you to about C<512> or C<2048> sockets
3337	windows version and/or the phase of the moon). To get more, you need to	4749	(depending on windows version and/or the phase of the moon). To get more,
3338	wrap all I/O functions and provide your own fd management, but the cost of	4750	you need to wrap all I/O functions and provide your own fd management, but
3339	calling select (O(n²)) will likely make this unworkable.	4751	the cost of calling select (O(n²)) will likely make this unworkable.
3340		4752
3341	=back
3342
3343
3344	=head1 PORTABILITY REQUIREMENTS	4753	=head2 PORTABILITY REQUIREMENTS
3345		4754
3346	In addition to a working ISO-C implementation, libev relies on a few	4755	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	4756	backend-specific APIs, libev relies on a few additional extensions:
3348		4757
3349	=over 4	4758	=over 4
3350		4759
		4760	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4761	calling conventions regardless of C<ev_watcher_type *>.
		4762
		4763	Libev assumes not only that all watcher pointers have the same internal
		4764	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4765	assumes that the same (machine) code can be used to call any watcher
		4766	callback: The watcher callbacks have different type signatures, but libev
		4767	calls them using an C<ev_watcher *> internally.
		4768
		4769	=item pointer accesses must be thread-atomic
		4770
		4771	Accessing a pointer value must be atomic, it must both be readable and
		4772	writable in one piece - this is the case on all current architectures.
		4773
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	4774	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		4775
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	4776	The type C<sig_atomic_t volatile> (or whatever is defined as
3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4777	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3355	threads. This is not part of the specification for C<sig_atomic_t>, but is	4778	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	4779	believed to be sufficiently portable.
3357		4780
3358	=item C<sigprocmask> must work in a threaded environment	4781	=item C<sigprocmask> must work in a threaded environment
3359		4782
…		…
3368	except the initial one, and run the default loop in the initial thread as	4791	except the initial one, and run the default loop in the initial thread as
3369	well.	4792	well.
3370		4793
3371	=item C<long> must be large enough for common memory allocation sizes	4794	=item C<long> must be large enough for common memory allocation sizes
3372		4795
3373	To improve portability and simplify using libev, libev uses C<long>	4796	To improve portability and simplify its API, libev uses C<long> internally
3374	internally instead of C<size_t> when allocating its data structures. On	4797	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4798	systems (Microsoft...) this might be unexpectedly low, but is still at
3376	is still at least 31 bits everywhere, which is enough for hundreds of	4799	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	4800	watchers.
3378		4801
3379	=item C<double> must hold a time value in seconds with enough accuracy	4802	=item C<double> must hold a time value in seconds with enough accuracy
3380		4803
3381	The type C<double> is used to represent timestamps. It is required to	4804	The type C<double> is used to represent timestamps. It is required to
3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4805	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3383	enough for at least into the year 4000. This requirement is fulfilled by	4806	good enough for at least into the year 4000 with millisecond accuracy
		4807	(the design goal for libev). This requirement is overfulfilled by
3384	implementations implementing IEEE 754 (basically all existing ones).	4808	implementations using IEEE 754, which is basically all existing ones. With
		4809	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3385		4810
3386	=back	4811	=back
3387		4812
3388	If you know of other additional requirements drop me a note.	4813	If you know of other additional requirements drop me a note.
3389		4814
3390		4815
3391	=head1 VALGRIND	4816	=head1 ALGORITHMIC COMPLEXITIES
3392		4817
3393	Valgrind has a special section here because it is a popular tool that is	4818	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	4819	libev will be documented. For complexity discussions about backends see
		4820	the documentation for C<ev_default_init>.
3395		4821
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	4822	All of the following are about amortised time: If an array needs to be
3397	in libev, then check twice: If valgrind reports something like:	4823	extended, libev needs to realloc and move the whole array, but this
		4824	happens asymptotically rarer with higher number of elements, so O(1) might
		4825	mean that libev does a lengthy realloc operation in rare cases, but on
		4826	average it is much faster and asymptotically approaches constant time.
3398		4827
3399	==2274== definitely lost: 0 bytes in 0 blocks.	4828	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		4829
3403	then there is no memory leak. Similarly, under some circumstances,	4830	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3404	valgrind might report kernel bugs as if it were a bug in libev, or it
3405	might be confused (it is a very good tool, but only a tool).
3406		4831
3407	If you are unsure about something, feel free to contact the mailing list	4832	This means that, when you have a watcher that triggers in one hour and
3408	with the full valgrind report and an explanation on why you think this is	4833	there are 100 watchers that would trigger before that, then inserting will
3409	a bug in libev. However, don't be annoyed when you get a brisk "this is	4834	have to skip roughly seven (C<ld 100>) of these watchers.
3410	no bug" answer and take the chance of learning how to interpret valgrind
3411	properly.
3412		4835
3413	If you need, for some reason, empty reports from valgrind for your project	4836	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.
3415		4837
		4838	That means that changing a timer costs less than removing/adding them,
		4839	as only the relative motion in the event queue has to be paid for.
		4840
		4841	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4842
		4843	These just add the watcher into an array or at the head of a list.
		4844
		4845	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4846
		4847	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4848
		4849	These watchers are stored in lists, so they need to be walked to find the
		4850	correct watcher to remove. The lists are usually short (you don't usually
		4851	have many watchers waiting for the same fd or signal: one is typical, two
		4852	is rare).
		4853
		4854	=item Finding the next timer in each loop iteration: O(1)
		4855
		4856	By virtue of using a binary or 4-heap, the next timer is always found at a
		4857	fixed position in the storage array.
		4858
		4859	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4860
		4861	A change means an I/O watcher gets started or stopped, which requires
		4862	libev to recalculate its status (and possibly tell the kernel, depending
		4863	on backend and whether C<ev_io_set> was used).
		4864
		4865	=item Activating one watcher (putting it into the pending state): O(1)
		4866
		4867	=item Priority handling: O(number_of_priorities)
		4868
		4869	Priorities are implemented by allocating some space for each
		4870	priority. When doing priority-based operations, libev usually has to
		4871	linearly search all the priorities, but starting/stopping and activating
		4872	watchers becomes O(1) with respect to priority handling.
		4873
		4874	=item Sending an ev_async: O(1)
		4875
		4876	=item Processing ev_async_send: O(number_of_async_watchers)
		4877
		4878	=item Processing signals: O(max_signal_number)
		4879
		4880	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4881	calls in the current loop iteration. Checking for async and signal events
		4882	involves iterating over all running async watchers or all signal numbers.
		4883
		4884	=back
		4885
		4886
		4887	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4888
		4889	The major version 4 introduced some incompatible changes to the API.
		4890
		4891	At the moment, the C<ev.h> header file provides compatibility definitions
		4892	for all changes, so most programs should still compile. The compatibility
		4893	layer might be removed in later versions of libev, so better update to the
		4894	new API early than late.
		4895
		4896	=over 4
		4897
		4898	=item C<EV_COMPAT3> backwards compatibility mechanism
		4899
		4900	The backward compatibility mechanism can be controlled by
		4901	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4902	section.
		4903
		4904	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4905
		4906	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4907
		4908	ev_loop_destroy (EV_DEFAULT_UC);
		4909	ev_loop_fork (EV_DEFAULT);
		4910
		4911	=item function/symbol renames
		4912
		4913	A number of functions and symbols have been renamed:
		4914
		4915	ev_loop => ev_run
		4916	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4917	EVLOOP_ONESHOT => EVRUN_ONCE
		4918
		4919	ev_unloop => ev_break
		4920	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4921	EVUNLOOP_ONE => EVBREAK_ONE
		4922	EVUNLOOP_ALL => EVBREAK_ALL
		4923
		4924	EV_TIMEOUT => EV_TIMER
		4925
		4926	ev_loop_count => ev_iteration
		4927	ev_loop_depth => ev_depth
		4928	ev_loop_verify => ev_verify
		4929
		4930	Most functions working on C<struct ev_loop> objects don't have an
		4931	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4932	associated constants have been renamed to not collide with the C<struct
		4933	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4934	as all other watcher types. Note that C<ev_loop_fork> is still called
		4935	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4936	typedef.
		4937
		4938	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4939
		4940	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4941	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4942	and work, but the library code will of course be larger.
		4943
		4944	=back
		4945
		4946
		4947	=head1 GLOSSARY
		4948
		4949	=over 4
		4950
		4951	=item active
		4952
		4953	A watcher is active as long as it has been started and not yet stopped.
		4954	See L<WATCHER STATES> for details.
		4955
		4956	=item application
		4957
		4958	In this document, an application is whatever is using libev.
		4959
		4960	=item backend
		4961
		4962	The part of the code dealing with the operating system interfaces.
		4963
		4964	=item callback
		4965
		4966	The address of a function that is called when some event has been
		4967	detected. Callbacks are being passed the event loop, the watcher that
		4968	received the event, and the actual event bitset.
		4969
		4970	=item callback/watcher invocation
		4971
		4972	The act of calling the callback associated with a watcher.
		4973
		4974	=item event
		4975
		4976	A change of state of some external event, such as data now being available
		4977	for reading on a file descriptor, time having passed or simply not having
		4978	any other events happening anymore.
		4979
		4980	In libev, events are represented as single bits (such as C<EV_READ> or
		4981	C<EV_TIMER>).
		4982
		4983	=item event library
		4984
		4985	A software package implementing an event model and loop.
		4986
		4987	=item event loop
		4988
		4989	An entity that handles and processes external events and converts them
		4990	into callback invocations.
		4991
		4992	=item event model
		4993
		4994	The model used to describe how an event loop handles and processes
		4995	watchers and events.
		4996
		4997	=item pending
		4998
		4999	A watcher is pending as soon as the corresponding event has been
		5000	detected. See L<WATCHER STATES> for details.
		5001
		5002	=item real time
		5003
		5004	The physical time that is observed. It is apparently strictly monotonic :)
		5005
		5006	=item wall-clock time
		5007
		5008	The time and date as shown on clocks. Unlike real time, it can actually
		5009	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5010	clock.
		5011
		5012	=item watcher
		5013
		5014	A data structure that describes interest in certain events. Watchers need
		5015	to be started (attached to an event loop) before they can receive events.
		5016
		5017	=back
3416		5018
3417	=head1 AUTHOR	5019	=head1 AUTHOR
3418		5020
3419	Marc Lehmann <libev@schmorp.de>.	5021	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5022	Magnusson and Emanuele Giaquinta.
3420		5023

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